The Malignant Hyperthermia-Susceptible Parturient and Other Neuromuscular Disorders during Pregnancy

What the Anesthesiologist Should Know before the Operative Procedure

The malignant hyperthermia-susceptible (MHS) parturient

Prior to labor and vaginal delivery or cesarean delivery, whether it is emergent, urgent, or elective, the anesthesiologist should always be aware of any anesthetic history relating to malignant hyperthermia (MH). Specifically, the anesthesiologist should know of any personal or family history of MH susceptibility (MHS), including any previous episodes of MH or conclusive diagnostic testing for MH. Such testing could include muscle biopsy for caffeine-halothane contracture test and/or possible genetic testing. The anesthesiologist must also investigate any possibility of MHS with regard to the father of the fetus since MH is autosomal dominant. Although rare, potential risks of MHS in the newborn can exist and pose a problem following delivery. The anesthesiologist should also be aware of any maternal history of neuromuscular disorders or myopathies that might carry an increased risk for MHS or MH-like syndromes. These disorders include certain muscular dystrophies, Central Core disease, Multiminicore disease, or King-Denborough syndrome.

Parturient with Multiple Sclerosis

Most anesthesiologists believe that the use of epidural anesthesia/analgesia is acceptable and often preferred in these patients; while the risk of disease exacerbation is increased in the postpartum period, it does not appear to be related to epidural use. Spinal anesthesia has been used successfully in patients with Multiple Sclerosis; however, spinal anesthesia has been implicated in postoperative exacerbations in some studies. Even mild increases in temperature can lead to an exacerbation.

Parturient with Myasthenia Gravis

During pregnancy, approximately one-third of women have an improvement in myasthenia symptoms, one-third develop worsening symptoms, and the other third remain stable. Maternal mortality and morbidity as well as preterm labor are increased in parturients with myasthenia gravis. Neuraxial anesthesia/analgesia is usually preferred for labor and cesarean delivery. Assisted vaginal delivery (forceps, vacuum) may be recommended to prevent skeletal muscle fatigue during the second stage of labor. These patients have increased sensitivity to nondepolarizing neuromuscular blocking agents. The response to succinylcholine can be unpredictable. Resistance may occur, but its duration of action may be prolonged. Postoperative ventilation is sometimes required in patients who undergo general anesthesia.

Parturient with Guillain-Barre syndrome

There are several reports of successful use of neuraxial analgesia/anesthesia in these patients. Major anesthetic concerns in these patients include respiratory compromise, bulbar and autonomic dysfunction, and an increased risk of thromboembolism. Succinylcholine must be avoided to prevent a hyperkalemic response. There has even been a report of hyperkalemia when succinylcholine was administered to a patient who had recently recovered from the disease. These patients frequently require an instrument-assisted vaginal delivery as expulsive efforts are inadequate due to muscle weakness or, in severe cases, flaccid paralysis.

Parturient with Myotonic Dystrophy

Anesthetic concerns in these patients include respiratory compromise due to muscle weakness and the avoidance of a myotonic episode. Neuraxial analgesia/anesthesia is usually preferred. Succinylcholine must be avoided because fasciculation can precipitate a myotonic episode. These patients have a normal response to nondepolarizing neuromuscular blocking drugs. Shivering can also trigger myotonia, so maintenance of normothermia is crucial. Uterine smooth muscle is affected by the disease, and these patients may be at risk for prolonged labor, uterine atony, and associated postpartum hemorrhage.

1. What is the urgency of the surgery?

What is the risk of delay in order to obtain additional preoperative information?

The malignant hyperthermia-susceptible (MHS) parturient

The urgency for labor analgesia and/or cesarean delivery is generally not affected by the presence of MHS. Initiation of epidural analgesia early in labor is recommended to avoid the need for general anesthesia if an emergent situation should arise. Regardless of the urgency of a cesarean delivery, proper preoperative preventive measures must be taken to minimize the risk of an MH episode occurring in the parturient or the newborn if MHS exists.

Parturient with Multiple Sclerosis

The urgency for labor analgesia and/or cesarean delivery is generally not affected by the presence of multiple sclerosis. Rather, urgency will be determined by fetal status and the presence of obstetric complications.

Parturient with Myasthenia Gravis

The urgency for labor analgesia and/or cesarean delivery is generally not affected by the presence of myasthenia gravis. Rather, urgency will be determined by fetal status and the presence of obstetric complications.

Parturient with Guillain-Barre syndrome

Acute deterioration of a patient’s respiratory status may necessitate an urgent delivery if the fetal status is adversely affected by the mother’s condition. Otherwise, urgency will be determined by fetal status and the presence of obstetric complications.

Parturient with Myotonic Dystrophy

The urgency for labor analgesia and/or cesarean delivery is generally not affected by the presence of myotonic dystrophy. Rather, urgency will be determined by fetal status and the presence of obstetric complications.

2. Preoperative evaluation

The MHS parturient

The most important component of the preoperative evaluation is obtaining any personal or family history of MH. This is significant even if the parturient has had uneventful general anesthesia with triggering agents, as this does not completely negate the possibility of MHS. In addition, any past medical history of heat stroke or exercise-induced rhabdomyolysis could be concerning for MHS. Ideally, all MHS parturients should be seen in consultation with an obstetric anesthesiologist prior to their admission to the hospital for labor and delivery.

Parturient with Multiple Sclerosis

A thorough history that includes information regarding onset of disease, frequency of exacerbations, and current symptoms and disability should be elicited. A physical examination that includes a thorough neurological examination should be performed. Complete documentation of all pre-existing neurologic deficits is recommended. The patient’s pulmonary status should be carefully assessed with an emphasis on detecting any pulmonary compromise related to the patient’s multiple sclerosis.

During the pre-anesthetic evaluation, the anesthesiologist should discuss with the patient that the risk of an exacerbation of her multiple sclerosis is increased during the postpartum period. Precipitating factors may include stress, fatigue, and decreases in estrogen and progesterone levels, but the limited data that are available suggest neuraxial analgesia/anesthesia is an unlikely factor.

Parturient with Myasthenia Gravis

A thorough history that includes information regarding the onset and duration of the disease as well as current symptoms should be elicited. Particular emphasis should be focused on bulbar and respiratory involvement. The patient should be questioned about her ability to cough and clear secretions as well as previous episodes of aspiration.

Assessment of the adequacy of current therapy is important. Physical examination should include a thorough evaluation of current muscle weakness as well as pulmonary and cardiac status. In patients with significant respiratory compromise, antepartum pulmonary function testing, especially vital capacity, is recommended. This information may help predict whether a patient who undergoes general anesthesia will require postoperative mechanical ventilation. Focal myocardial necrosis leading to heart block does occur in some patients, so one should consider obtaining an ECG.

During the pre-anesthetic evaluation, the anesthesiologist should discuss with the patient the potential need for an instrument-assisted vaginal delivery and the recommendation of initiating neuraxial analgesia during labor. It should also be explained to the patient that if general anesthesia is used during cesarean delivery, short-term postoperative mechanical ventilation might be necessary.

Parturient with Guillain-Barre syndrome

A thorough history that includes information regarding onset and progression of the disorder as well as any improvement in symptoms that has occurred should be elicited. Attention to signs of bulbar or respiratory compromise and hemodynamic lability is important. Physical examination should include a complete neurologic examination with documentation of all deficits. Bulbar and respiratory function must be carefully assessed. Measurement of vital capacity helps determine whether respiratory support is indicated.

During the pre-anesthetic evaluation, the anesthesiologist should discuss with the patient the potential need for an instrument-assisted vaginal delivery. Women with severe disease should also be advised that general anesthesia may be required in the event of cesarean delivery with the potential for postoperative mechanical ventilation.

Parturient with Myotonic Dystrophy

A thorough history that focuses on muscle weakness and respiratory and cardiac involvement should be elicited. Symptoms of dysphagia and delayed gastric emptying should be determined as this would place the patient at increased risk for aspiration. Precipitating events and frequency of myotonic episodes should also be determined.

Evidence of the following disorders that occur with increased frequency in these patients should be determined: diabetes, hypothyroidism, adrenal insufficiency, and central sleep apnea. Physical examination should include a thorough pulmonary and cardiac examination as well as an assessment of muscle weakness and wasting. Pulmonary function testing to determine the extent of restrictive lung disease and an ECG to assess for the presence of conduction abnormalities or dysrhythmias should be included in the pre-anesthetic evaluation.

• Medically unstable conditions warranting further evaluation: These conditions include myasthenic or cholinergic crisis in parturients with myasthenia gravis; acute respiratory decompensation in patients with Guillain-Barre syndrome.

• Delaying surgery: If a cesarean delivery is not urgent or emergent and the proper drugs, equipment, monitoring, and/or properly trained anesthesia staff are not available to manage a potential episode of MH, the parturient should be transferred to an appropriate facility for specialized care. The presence of multiple sclerosis should not play a role in delaying cesarean delivery or the initiation of labor analgesia. In the setting of elective labor induction or cesarean delivery, delay should be considered in parturients with myasthenia gravis if it is determined that treatment of the disease is not currently optimized. If a parturient with Guillain-Barre syndrome experiences an acute respiratory deterioration, delay of delivery to initiate therapy with intravenous immunoglobulin or plasmapheresis should be considered, provided fetal status is stable. In an elective situation, development of a myotonic episode would justify delay of labor and delivery until it has resolved.

3. What are the implications of co-existing disease on perioperative care?

General considerations

Parturient with Multiple Sclerosis

1. Perioperative evaluation: Most patients require only routine noninvasive monitoring during labor and delivery. Careful attention should be paid to maternal temperature in all patients and oxygen saturation in those patients with pulmonary compromise.

2. Perioperative risk reduction strategies: Close monitoring of temperature is essential. Cooling strategies should be initiated with temperature increases as small as 0.5°C since exacerbations have been associated with mild temperature increases. When using neuraxial analgesia/anesthesia, an epidural technique may be preferred over a spinal technique as concerns have been raised about the potential neurotoxic effects of local anesthetics on demyelinated areas of the spinal cord. However, spinal anesthesia has been used successfully without adverse effects in parturients with multiple sclerosis. It is also recommended that the lowest possible concentration of local anesthetic be used during epidural labor analgesia, as one study reported that multiple sclerosis exacerbations occurred only in women who received higher concentrations of local anesthetic.

Parturient with Myasthenia Gravis

1. Perioperative evaluation: Most patients require only routine noninvasive monitoring. Continuous ECG monitoring is not routinely used during labor at most institutions. If a patient does have cardiac involvement, ECG monitoring is warranted. In patients with pulmonary compromise or those who begin to exhibit significant progression in muscle weakness during labor, oxygen saturation monitoring should be initiated.

2. Perioperative risk reduction strategies: To avoid muscle weakness associated with pushing during the second stage of labor, an instrument-assisted vaginal delivery may be performed. In patients with significant bulbar or pulmonary compromise, intubation and general anesthesia are advisable for cesarean delivery to prevent aspiration or respiratory decompensation.

Parturient with Guillain-Barre syndrome

1. Perioperative evaluation: In patients exhibiting autonomic dysfunction and hemodynamic lability, continuous blood pressure monitoring with an intra-arterial catheter and ECG monitoring may be indicated during labor and delivery. Oxygen saturation monitoring should be used in patients with respiratory or bulbar compromise.

2. Perioperative risk reduction strategies: When cesarean delivery is required in patients with significant respiratory or bulbar compromise, general anesthesia should be used to prevent aspiration or further deterioration of the women’s pulmonary status.

Parturient with myotonic dystrophy

1. Perioperative evaluation: Maternal temperature must be monitored closely during labor and delivery. If the patient has a cardiac conduction abnormality or a history of dysrhythmias, ECG monitoring is indicated during labor. In women with cardiomyopathy, additional invasive monitoring should be considered based on the patient’s current cardiac status. Oxygen saturation monitoring should be used in women with significant respiratory muscle weakness.

2. Perioperative risk reduction strategies: Prevention of myotonic episodes during labor and delivery is an important component of anesthetic management. Shivering is a common precipitating event. Maintenance of normothermia and the administration of epidural opioids are strategies for prevention. When general anesthesia is used, succinylcholine must be avoided to prevent myotonia.

b. Cardiovascular system

The MHS parturient

Aortocaval compression from the gravid uterus causes a decrease in cardiac output which can lead to hypotension and decreased uteroplacental perfusion. This in turn may worsen or hasten the acidosis should an episode of MH occur. In such a situation, efficient delivery of the fetus and placenta may diminish or alleviate this risk. This would also facilitate cardiac resuscitative efforts should the need arise.

Parturient with Guillain-Barre syndrome

These patients may experience significant hemodynamic lability due to autonomic dysfunction. Treatment of serious hypertension, hypotension, bradycardia, or tachycardia may be required. Indirect-acting vasopressors should be used cautiously to treat hypotension as these patients may have an exaggerated response; usually direct-acting agents are preferred. The pain of labor can precipitate autonomic dysfunction. Epidural analgesia is recommended to prevent this response.

Parturient with Myotonic Dystrophy

These patients may have cardiac conduction abnormalities, dysrhythmias, or cardiomyopathy that can lead to cardiac decompensation during labor and delivery. The anesthesiologist must be prepared to respond to these potential cardiac emergencies.

c. Pulmonary

The MHS parturient

Pulmonary maternal physiologic changes can complicate the signs and symptoms associated with MH. Because of increases in oxygen consumption, basal metabolic rate, minute ventilation (both tidal volume and respiratory rate), and decreased PaCO₂, the parturient typically has a compensated respiratory alkalosis owing to a decrease in serum bicarbonate and buffering capacity. This already altered buffering capacity could adversely affect the pregnant patient during an MH event compared to a non-pregnant patient.

Parturient with Multiple Sclerosis

In patients with severe disease that includes respiratory compromise, epidural analgesia is a preferred technique for labor pain relief, as it avoids the use of systemic opioids that could lead to respiratory depression. The high (T4 – T6) sensory and motor level of blockade that is required to perform cesarean delivery under neuraxial anesthesia could result in further pulmonary compromise in those patients with preexisting pulmonary involvement. When this technique is used, careful monitoring of pulmonary status is required, with the understanding that endotracheal intubation and mechanical ventilation could be required if acute respiratory decompensation occurs. In patients with severe respiratory involvement, general endotracheal anesthesia may be the preferred technique for cesarean delivery.

Parturient with Myasthenia Gravis

In patients with respiratory compromise, opioids should be avoided due to their respiratory depressant effects. For labor analgesia or postcesarean analgesia in these patients, epidural analgesia with local anesthesia only is recommended. Patients with severe bulbar or respiratory involvement may not tolerate the high sensory and motor level of blockade that is necessary to perform cesarean delivery under neuraxial anesthesia. For these patients, it is advisable to use general endotracheal anesthesia. The use of neuromuscular blocking drugs should be avoided or the lowest possible dose should be administered. Extubation should not be attempted until maximal muscle strength has been achieved. The anesthesiologist should not hesitate to maintain postoperative mechanical ventilation if any signs of muscle weakness remain after completion of surgery.

Parturient with Guillain-Barre syndrome

In women with respiratory compromise, epidural analgesia is a preferred labor analgesia technique because it avoids systemic opioids and their associated respiratory depressant effects. General anesthesia should be considered for cesarean delivery in patients with serious respiratory or bulbar dysfunction to prevent further deterioration intraoperatively. Postoperative mechanical ventilation may be required in these patients. Patients with paralysis that involves the intercostal muscles may require ventilatory support throughout labor and delivery.

Parturient with Myotonic Dystrophy

These patients, especially those with associated sleep apnea, may have increased sensitivity to the respiratory depressant effects of opioids, sedatives, and other anesthetic drugs. Neuraxial analgesia/anesthesia is usually preferred to avoid the use of these medications. Patients with serious respiratory compromise due to weakness and wasting of the accessory respiratory muscles may experience respiratory deterioration with the high sensory and motor level of blockade that is needed to perform cesarean delivery under neuraxial anesthesia; general endotracheal anesthesia may be recommended in these patients.

d. Renal-GI:

The MHS parturient

The pregnant patient should be well hydrated with crystalloids both to help prevent hypotension, often associated with neuraxial anesthesia/analgesia, and to combat potential acute renal failure or damage resulting from rhabdomyolysis during an episode of MH. Renal perfusion can be further augmented with mannitol and furosemide should the need arise during acute treatment of MH. Although recent data have challenged the need for preemptive volume loading prior to neuraxial anesthesia, it is probably a reasonable option for fluid management in the setting of a potential MH complication.

Parturient with Myotonic Dystrophy

Pharmacologic aspiration prophylaxis should be initiated during labor and delivery in women with symptoms of pharyngeal muscle weakness or delayed gastric emptying that can occur with this disease.

e. Neurologic:

Acute issues

Parturient with Multiple Sclerosis: The patient should be monitored for any signs or symptoms of an acute exacerbation during labor, delivery, and the postpartum period. If there is evidence of an exacerbation, consultation should occur with the patient’s neurologist to determine if any acute treatment should be initiated.

Parturient with Guillain-Barre syndrome: Symptoms of this disorder can progress rapidly over a few days. A patient who experienced lower extremity weakness just a few days earlier could present for delivery with full motor paralysis and respiratory failure requiring ventilation.

Chronic disease

Parturient with Multiple Sclerosis: Preexisting neurologic deficits must be documented so these can be differentiated from any new deficits that could occur as a result of the anesthetic or an acute exacerbation.

Parturient with Guillain-Barre syndrome: Preexisting neurologic deficits must be documented before providing analgesia or anesthesia for labor and delivery. The time course of the disease should also be determined because patients who have recently had resolution of their symptoms could still be at risk for a hyperkalemic response to succinylcholine.

f. Endocrine:

Parturient with Myasthenia Gravis

Approximately 10% to 15% of patients also have hyperthyroidism. Ideally, thyroid function is assessed in the antepartum period and a euthyroid state is achieved before labor and delivery to prevent the risk of thyroid storm. If a patient presents with signs of thyrotoxicosis and delivery must proceed, prompt initiation of beta-blocker and propylthiouracil (PTU) therapy is indicated.

Parturient with Myotonic Dystrophy

Associated disorders of diabetes, adrenal insufficiency, and hypothyroidism should be identified and treated appropriately in the antepartum period. Treatment should be continued during the peripartum period.

g. Additional systems/conditions that may be of concern in a patient undergoing this procedure and are relevant for the anesthetic plan (e.g., musculoskeletal in orthopedic procedures, hematologic in a cancer patient)

Musculoskeletal

Parturient with Myasthenia Gravis: Careful attention must be paid to the patient’s skeletal muscle weakness. Pharmacologic therapy should be optimized before labor and delivery. If there are signs of myasthenic crisis (worsening muscle weakness, including respiratory weakness), plasmapheresis should be considered before proceeding with delivery. Plasmapheresis can be performed in pregnancy.

Parturient with Guillain-Barre syndrome: Careful attention must be paid to the patient’s muscle weakness. This weakness increases the likelihood that a parturient will require an instrument-assisted delivery due to inadequate maternal pushing during the second stage of labor. Paralysis of the intercostal muscles in a patient with severe disease could lead to respiratory failure during labor and delivery, requiring mechanical ventilation.

Parturient with Myotonic Dystrophy: Prevention of myotonic episodes during labor and delivery is an important goal. Avoiding shivering by maintaining normothermia and warm ambient temperatures as well as avoiding succinylcholine administration are crucial. If generalized myotonic contractures occur, quinine, procainamide, or phenytoin are effective therapies. Neuraxial anesthesia or peripheral nerve blocks will not treat this condition. High concentrations of halogenated volatile anesthetics are a treatment option if an episode occurs during general anesthesia, but the myocardial depressant effects may not be tolerated, especially in patients with cardiomyopathy. If a localized myotonic contracture develops, injection of local anesthetic into the affected muscle is an effective treatment.

Hematologic

Parturient with Guillain-Barre syndrome: These patients are at increased risk for pulmonary embolism, and prophylactic anticoagulation is often used. During labor and delivery, these medications should be discontinued, but sequential compression stockings could be used to minimize thromboembolic risk.

4. What are the patient's medications and how should they be managed in the perioperative period?

The MHS parturient

Most of the medications commonly used in obstetrics and anesthesia outside and inside of the operating room pose no significant risk for the development of fulminant MH. However, there are a few drugs used in the treatment of obstetric patients that could be problematic with regard to the diagnosis of an MH reaction. Then there are triggering agents that cause an MH event and are, therefore, absolutely contraindicated.

a. The beta-sympathomimetic agents used for tocolysis (terbutaline) can produce tachycardia and anxiety in some patients. These symptoms can be confused with signs of MH, but these drugs are considered safe in MHS parturients. Other adrenergic agonists such as epinephrine, norepinephrine, and ephedrine, although not triggering agents for MH, could cause similar symptoms. These are also considered safe to use in MHS patients.

b. Magnesium sulfate, also a tocolytic agent, has been postulated to somewhat inhibit the development of MH, but it does not prevent it. Magnesium sulfate is considered safe in the MHS parturient.

c. Calcium channel blockers such as nifedipine or diltiazem have been theorized to have adverse reactions with dantrolene, potentially worsening the hyperkalemia associated with an MH episode. The use of these drugs during treatment of an MH event should be avoided.

d. Oxytocin is safe to use in MHS parturients for the treatment of uterine atony. The other commonly used agents for uterine atony include the ergot alkaloids (methylergonovine) and 15-methyl prostaglandin F2α (carboprost). These drugs, although probably safe, can produce effects that mimic the signs and symptoms of MH. The ergot preparations can cause tachycardia, dysrhythmias, and vasoconstriction, leading to possible lactic acidosis. The prostaglandins can cause changes in blood pressure and arterial oxygen saturation while potentially increasing temperature. These agents are probably best avoided if possible but should be used if severe postpartum hemorrhage occurs that is refractory to oxytocin.

e. Nitroglycerin, sometimes used when a short period of uterine relaxation is needed, can be safely use in MHS parturients.

f. All anti-emetics, including metoclopramide and ondansetron, are safe.

g. All local anesthetics, with, or without epinephrine are safe to use for neuraxial anesthesia/analgesia. Lidocaine can also be safely used intravenously.

h. All induction agents, including propofol, etomidate, and ketamine, are safe to use in MHS parturients.

i. Nitrous oxide is safe for use.

j. All opioids (IV and neuraxial) and benzodiazepines are safe.

k. Reversal drugs, including neostigmine and edrophonium are safe. The anticholinergic agents, administered in combination with reversal agents (atropine, glycopyrrolate), cause tachycardia. In addition, atropine can cause temperature elevation. These effects could confuse the clinical picture during an MH event.

l. All nondepolarizing neuromuscular blocking drugs are safe for use in MHS patients.

m. The depolarizing neuromuscular blocking agent succinylcholine is a triggering agent for MH and is absolutely contraindicated.

n. The halogenated volatile anesthetic agents, including desflurane, sevoflurane, isoflurane, and halothane, are triggering agents for MH and are absolutely contraindicated.

Parturients with Multiple Sclerosis

These patients may be taking any of the following medications for their disease: corticosteroids, interferon-beta, glatiramer acetate, and other immunosuppressive drugs such as methotrexate, azothioprine, and cyclophosphamide.

Parturients with Myasthenia Gravis

These patients will almost certainly be taking an anticholinesterase drug, most commonly pyridostigmine. They may also be taking an immunosuppressive drug such as a corticosteroid, azathioprine, or cyclosporine if symptoms are not adequately controlled with the anticholinesterase therapy.

Parturients with Guillain-Barre syndrome

These patients receive primarily supportive care, and there are no drugs used to treat or ameliorate symptoms. They may be receiving low molecular-weight or unfractionated heparin for prophylaxis or treatment of thromboembolism.

h. Are there medications commonly seen in patients undergoing this procedure and for which should there be greater concern?

Parturients with Multiple Sclerosis

Patients receiving corticosteroids may develop hyperglycemia. Bone marrow suppression can occur with azathioprine, and electrolyte abnormalities have been reported with cyclophosphamide therapy.

Parturients with Myasthenia Gravis

Patients taking anticholinesterase medications may develop a cholinergic crisis due to excess muscarinic effects of the drug. This is characterized by respiratory distress, miosis, and increased muscle weakness, salivation, and sweating. Anticholinesterase drugs do have uterotonic effects, which could lead to premature labor or uterine tachysystole during labor. Because of the many physiologic changes occurring during pregnancy, frequent dosage adjustments of anticholinesterase drugs may be necessary. Many drugs that might be used during labor and delivery can exacerbate muscle weakness in these patients and could result in myasthenic crisis. They should be avoided, if possible. These include tocolytic drugs, such as terbutaline, magnesium sulfate, and nifedipine, neuromuscular blocking drugs, aminoglycoside antibiotics, and beta-blockers.

Parturients with Guillain-Barre syndrome

Due to autonomic dysfunction, these patients are more likely to require treatment for hypotension associated with neuraxial anesthesia. They may have an exaggerated response to indirect-acting vasopressors.

Parturients with Myotonic Dystrophy

Beta-agonists used for tocolysis, such as terbutaline and succinylcholine, can precipitate myotonic episodes.

i. What should be recommended with regard to continuation of medications taken chronically?

i. Neurologic: (a) Medications for multiple sclerosis should be continued during labor and delivery. Patients receiving chronic steroid therapy should receive a stress dose of hydrocortisone or another corticosteroid if cesarean delivery is performed. (b) Anticholinesterase therapy for myasthenia gravis must be continued during labor and delivery. Because gastrointestinal absorption can be unreliable during labor (delayed gastric emptying due to pain, etc.), intravenous administration should be considered. Patients receiving chronic steroid therapy should receive a stress dose of hydrocortisone or another corticosteroid if cesarean delivery is performed.

ii. Anticoagulant: Low molecular-weight and unfractionated heparin should be discontinued in patients with Guillain-Barre syndrome before planned labor induction or cesarean delivery. American Society of Regional Anesthesia and Pain Medicine (ASRA) guidelines should be followed regarding the timing of neuraxial procedures in women who have been taking these medications.

j. How to modify care for patients with known allergies

N/A

k. Latex allergy- If the patient has a sensitivity to latex (e.g., rash from gloves, underwear, etc.) versus anaphylactic reaction, prepare the operating room with latex-free products.

N/A

l. Does the patient have any antibiotic allergies- Common antibiotic allergies and alternative antibiotics

N/A

m. Does the patient have a history of allergy to anesthesia?

While not a true allergy, MH is often described by patients as an “allergy” to anesthesia. Therefore, any mention of broad anesthesia allergy should be investigated for the possibility of MH.

5. What laboratory tests should be obtained, and has everything been reviewed?

While there are no specific laboratory tests available to monitor for MH, it is reasonable to obtain additional baseline laboratory values for comparison in case an MH event should occur during labor and delivery in an MHS parturient. The laboratory tests commonly ordered for normal labor and delivery include hemoglobin, hematocrit, platelet count, and basic electrolytes such as potassium, sodium, bicarbonate, BUN, and creatinine. Additional baseline laboratory tests that may be useful for MHS patients include a creatine kinase level, arterial blood gas, and coagulation studies.

• Hemoglobin levels: Patients with multiple sclerosis or myasthenia gravis who are taking immunosuppressant drugs that could lead to bone marrow suppression should have a complete blood count performed.

• Electrolytes: Electrolyte and/or glucose levels should be measured in patients taking multiple sclerosis or myasthenia gravis drugs that are associated with abnormalities in these values.

• Coagulation panel: Partial thromboplastin time (PTT) be measured in women with Guillain-Barre syndrome who are currently receiving unfractionated heparin. No coagulation testing is recommended for patients receiving low molecular-weight heparin.

• Other tests: Other than those laboratory tests described above, additional laboratory tests besides those routinely performed for labor and delivery are generally not required for women with multiple sclerosis. One possible exception is the patient with severe pulmonary compromise, in whom a baseline arterial blood gas and/or pulmonary function tests might be considered. In the patient with myasthenia gravis with pulmonary compromise, pulmonary function testing, especially vital capacity, is indicated. An ECG should also be considered. If the patient has associated hyperthyroidism, thyroid function tests are recommended to confirm a euthyroid state before delivery. Due to the potential for rapid pulmonary deterioration in women with a recent onset of Guillain-Barre syndrome, pulmonary function tests, especially vital capacity and arterial blood gas, are recommended. Pulmonary function testing is recommended in parturients with myotonic dystrophy to assess the extent of restrictive lung disease. An ECG should also be obtained to assess for conduction abnormalities and dysrhythmias. If the patient with myotonic dystrophy has signs suggestive of cardiomyopathy, an antepartum echocardiogram should be performed. Thyroid functions tests are also recommended to evaluate for hypothyroidism.

Intraoperative Management: What are the options for anesthetic management and how do I determine the best technique?

The MHS parturient

MH in pregnancy is rare, possibly due to some protective mechanism associated with pregnancy, but more likely secondary to the widespread use of neuraxial anesthesia/analgesia for labor and vaginal or cesarean delivery. Therefore, the best option for successful anesthetic and analgesic management of MHS parturients for labor and delivery remains neuraxial anesthesia. This can be an epidural, spinal, or combined spinal-epidural (CSE) technique. Regardless of the rarity of an MH crisis in pregnancy, an anesthetic plan must always be in place for the management of MHS patients. The emergent need for general anesthesia for cesarean delivery could arise at any time. This could be due to patient refusal, contraindication for neuraxial anesthesia (e.g., maternal hemorrhage), or inadequate time to perform a neuraxial procedure in an emergent situation (prolonged, severe fetal bradycardia).

Parturient with Multiple Sclerosis

Neuraxial analgesia provides the best quality analgesia for labor and is a preferred technique in women with multiple sclerosis. Systemic analgesia is another option for labor pain management when a patient wants to avoid neuraxial procedures. Neuraxial and general anesthesia are both acceptable techniques for cesarean delivery. There is no documented evidence showing an association between any anesthetic technique or drug and an increased risk of disease exacerbation.

Parturient with Myasthenia Gravis

Neuraxial analgesia provides the best quality analgesia for labor and is a preferred technique in women with myasthenia gravis. Neuraxial anesthesia is usually the preferred anesthetic technique for cesarean delivery, but general anesthesia can be safely performed and may be preferred in patients with severe bulbar or respiratory involvement.

Parturient with Guillain-Barre syndrome

Epidural and CSE analgesia have been used successfully for labor analgesia. Some authors have suggested neuraxial analgesia/anesthesia could exacerbate symptoms; however, no causal relationship has been determined, and these assertions are based on isolated cases. Neuraxial and general anesthesia are both acceptable techniques for cesarean delivery. The preferred technique is determined by each patient’s neurologic and respiratory status.

Parturient with Myotonic Dystrophy

Neuraxial analgesia/anesthesia is recommended for labor analgesia and cesarean delivery in most patients. In women with severe respiratory compromise or significant aspiration risk due to pharyngeal muscle weakness, general endotracheal may be preferred for cesarean delivery.

Regional anesthesia

Neuraxial anesthesia in MHS parturient

a. Benefits

i. Epidural analgesia provides excellent pain control for labor and vaginal delivery.

ii. All local anesthetics and opioids commonly used for epidural analgesia are safe for MHS parturients.

iii. Early placement of an epidural minimizes the need for general anesthesia and the possible development of an MH episode if an urgent or emergent cesarean delivery is required.

iv. Pain relief during labor and delivery lowers maternal stress and the hormones associated with the stress response. Maternal metabolism and oxygen consumption are also minimized.

b. Drawbacks

i. Risks of the procedure, although rare, such as epidural hematoma and epidural abscess.

ii. Possibility of failure of the neuraxial technique prior to operative delivery requiring general anesthesia, thereby increasing the risk of an MH event.

c. Issues

i. Upon admission and during labor and delivery, the parturient should be adequately and periodically monitored for temperature, heart rate, ECG, and blood pressure.

ii. The risks of general anesthesia are minimized but not eliminated when analgesia when neuraxial analgesia is used. Therefore, measures should always be taken to ensure an OR is available with an MH trigger-free atmosphere. This includes an anesthesia machine that has been adequately flushed with oxygen (10 liters with ventilator on for 20 min) with no vaporizers attached, fresh carbon dioxide absorbent, and new anesthesia circuit. Specialized activated charcoal filters that are attached to the inspiratory and expiratory limbs of the breaking circuit are also available. With the use of these filters, the machine is adequately prepared after the machine is flushed for less than 2 minutes. Appropriate induction drugs and intubating supplies should be readily available. Succinylcholine should be removed from the drug tray to minimize the risk of inadvertent administration should the use of general anesthesia be necessary. An adequate supply of dantrolene and resuscitation drugs should also be readily available.

Neuraxial anesthesia in Multiple Sclerosis

a. Benefits

i. Superior analgesia for labor.

ii. For cesarean delivery, avoids known risks of general anesthesia in parturients, including aspiration and difficult or failed intubation.

iii. Allows mother to be alert and involved in delivery of her infant.

b. Drawbacks

i. Limited data on use of neuraxial analgesia/anesthesia in multiple sclerosis.

ii. Few case reports implicating spinal anesthesia in exacerbations but no evidence for a causal relationship.

iii. Limited data suggesting use of higher concentrations of local anesthetic could be associated with greater risk of postpartum exacerbations.

iv. High sensory and motor blockade level required for adequate anesthesia during cesarean delivery may not be well tolerated in patients with significant pulmonary compromise resulting from multiple sclerosis.

c. Issues

i. Epidural analgesia is preferred over CSE analgesia for labor by some anesthesiologists, as it minimizes theoretical concern about potential neurotoxic effects of local anesthetic on demyelinated areas of spinal cord. However, available data have not supported this theoretical concern, and spinal analgesia/anesthesia has been used successfully in many parturients, without the development of disease exacerbation.

ii. In non-urgent situations, epidural anesthesia may be preferred over CSE or spinal anesthesia for cesarean delivery by some anesthesiologists for the same reason discussed above.

iii. Lowest concentration and dose of local anesthetic that provides adequate epidural analgesia for labor and epidural anesthesia for cesarean delivery should be used since one small study did report that only patients receiving higher concentrations of epidural local anesthetic experienced postpartum exacerbations of their multiple sclerosis

iv. Neuraxial anesthesia is not contraindicated in women with multiple sclerosis, and there is no evidence supporting a significant association between these procedures and the development of a disease exacerbation

Neuraxial anesthesia in Myasthenia Gravis

a. Benefits

i. Superior labor analgesia.

ii. Optimal anesthesia for instrument-assisted vaginal delivery that is frequently used in these patients.

iii. Avoids respiratory depressant effects of systemic opioids.

iv. For cesarean delivery avoids known risks of general anesthesia in parturients, including aspiration and difficult or failed intubation.

v. Allows mother to be alert and involved in delivery of her infant.

b. Drawbacks

i. Dense motor block not desirable in patient with preexisting muscle weakness.

ii. High sensory and motor blockade level required for adequate anesthesia during cesarean delivery may not be well tolerated in patients with significant bulbar or pulmonary compromise resulting from myasthenia gravis.

c. Issues

i. Use lowest possible concentration of local anesthetic to minimize motor block as patients may have preexisting muscle weakness.

ii. In patients without significant pulmonary involvement, CSE might be preferred for labor to further minimize local anesthetic dose.

iii. In patients without significant pulmonary dysfunction, epidural, or spinal anesthesia are equally desirable for cesarean delivery.

iv. In patients with significant respiratory compromise, should consider avoiding neuraxial opioids due to potential respiratory depressant effects. Consider using local anesthetic only.

v. For epidural analgesia/anesthesia in patients taking anticholinesterase drugs, amide local anesthetics should be used to avoid local anesthetic toxicity or excessive block. Plasma cholinesterase activity is decreased by these drugs, leading to a prolonged half-life for the ester local anesthetics

Neuraxial anesthesia in Guillain-Barre syndrome

a. Benefits

i. Superior labor analgesia.

ii. Optimal anesthesia for instrument-assisted vaginal delivery that is frequently needed.

iii. Prevents autonomic instability due to pain.

iv. Avoids respiratory depressant effects of systemic opioids.

v. Avoids risks of general anesthesia for cesarean delivery.

vi. Allows mother to be alert and involved in delivery of her infant.

b. Drawbacks

i. Some reports suggesting exacerbation of disease with neuraxial anesthesia (based only on case reports with no convincing evidence).

ii. Autonomic dysfunction can lead to exaggerated hypotension related to neuraxial block.

iii. High sensory and motor block required for cesarean delivery may not be well tolerated in patients with significant bulbar or pulmonary compromise.

iv. Risk of epidural hematoma in setting of recent anticoagulant therapy for thromboembolism may contraindicate procedure in some patients.

c. Issues

i. Use lowest possible concentration of local anesthetic to minimize motor block in these patients who have preexisting weakness.

ii. In patients with significant respiratory compromise, consider avoiding neuraxial opioids due to potential respiratory depressant effects.

iii. Direct-acting vasopressors should be used for block-induced hypotension.

iv. Follow ASRA guidelines for women who have recently received low molecular or unfractionated heparin.

Neuraxial anesthesia in Myotonic Dystrophy

a. Benefits

i. Superior labor analgesia.

ii. Avoids respiratory depressant effects of systemic opioids and other anesthetic drugs.

iii. Avoids risks of general anesthesia for cesarean delivery.

iv. Epidural opioids useful to reduce shivering.

v. Allows mother to be alert and involved in delivery of her infant.

b. Drawbacks

i. High sensory and motor block required for cesarean delivery may not be well tolerated in patients with significant pulmonary compromise.

c. Issues

i. Administration of epidural opioids can help reduce the incidence and severity of shivering.

Peripheral nerve block

There is a limited role for these procedures in obstetrics. A pudendal nerve block can be used to provide analgesia in the second stage of labor, and there is no contraindication to its use in patients with neuromuscular disorders. The transversus abdominis plane block can be used to provide postoperative analgesia for cesarean delivery and is especially useful in patients who did not receive neuraxial anesthesia. It can be safely performed in patients with any of these diseases.

General anesthesia

General anesthesia for the MHS parturient

General anesthesia for cesarean delivery should be avoided, if at all possible.

a. Benefits

i. There are no benefits to using general anesthesia for cesarean delivery in these patients.

ii. If the need for general anesthesia arises, a non-triggering technique will provide appropriate anesthesia.

b. Drawbacks

i. High risk of MH event.

c. Issues

i. If general anesthesia is required, the OR suite should be prepared as previously described.

ii. Unless a difficult airway is anticipated, the anesthesiologist should plan a modified rapid sequence induction with an appropriate induction agent and non-depolarizing neuromuscular blocking drug.

iii. The patient should be maintained on a propofol infusion and a 50:50 nitrous oxide:oxygen mixture. Opioids and benzodiazepines may be used to decrease the likelihood of awareness.

iv. The parturient should be closely monitored with standard monitoring. A processed EEG monitor may also be beneficial in this setting since there is a higher potential for awareness.

v. The neuromuscular block can be reversed with any reversal agent as all are safe.

General anesthesia for Multiple Sclerosis

a. Benefits

i. Avoids controversy associated with neuraxial anesthesia in the patient with multiple sclerosis.

ii. May be preferred over neuraxial anesthesia in patients with severe pulmonary compromise.

b. Drawbacks

i. Exposes patient to increased risks of general anesthesia in pregnancy, including risks of aspiration and difficult intubation.

ii. Most studies have found that anesthesia-related maternal mortality is higher with general anesthesia than with neuraxial anesthesia in the general obstetric population.

c. Other issues

i. In patients with significant neuromuscular weakness due to multiple sclerosis, the anesthesiologist should consider avoiding succinylcholine administration, as it could result in a hyperkalemic response.

ii. The response to non-depolarizing neuromuscular blocking drugs appears to be variable. Some patients seem to experience a prolonged effect, whereas others exhibit resistance to these drugs, possibly due to an increase in extrajunctional cholinergic receptors.

General anesthesia for Myasthenia Gravis

a. Benefits

i. Allows airway to be secured, and aspiration prevented in patients with serious bulbar involvement.

ii. May be preferred over neuraxial anesthesia in patients with severe pulmonary compromise.

b. Drawbacks

i. Exquisite sensitivity to nondepolarizing neuromuscular blocking drugs.

ii. Volatile halogenated anesthetic agents can further potentiate muscle weakness.

iii. Postoperative mechanical ventilation may be required.

iv. Exposes patient to increased risks of general anesthesia in pregnancy, including risks of aspiration and difficult intubation.

c. Issues

i. Resistance to the effective dose of succinylcholine may exist. This is not considered clinically significant because the commonly used dose for intubation is 3 to 5 times greater than its ED95. Its duration of action may be prolonged due to the decreased plasma cholinesterase activity associated with anticholinesterase drug therapy.

ii. If possible, non-depolarizing neuromuscular blocking drugs should be avoided. When they are needed, a short to intermediate-acting drug, such as rocuronium or vecuronium, should be used. The initial dose should be one-tenth to one-fifth the usual dose, and careful monitoring of the neuromuscular block is mandatory.

iii. If reversal of neuromuscular blockade with cholinesterase inhibitor and anticholinergic is desired, only small doses should be administered. Reversal with the selective relaxant binding agent sugammadex may be used in lieu of cholinesterase inhibitor and anticholinergic to reverse rocuronium or vecuronium. No matter the reversal method, extubation should not be attempted until the patient has reached her baseline muscle strength.

iv. Postoperative mechanical ventilation may be necessary, especially if a patient’s daily pyridostigmine dose is large and she has a significantly reduced vital capacity.

General anesthesia for Guillain-Barre syndrome

a. Benefits

i. Securing of airway in patient with bulbar dysfunction can prevent aspiration.

ii. Provides ventilatory support for patients with complete paralysis and respiratory compromise.

iii. Avoids potential respiratory deterioration due to blockade of accessory respiratory muscles associated with neuraxial anesthesia for cesarean delivery.

b. Drawbacks

i. Must perform modified rapid sequence induction with non-depolarizing neuromuscular blocking drug.

ii. Increased sensitivity to neuromuscular blocking drugs can lead to prolonged blockade and need for postoperative ventilation.

iii. Potential exists for hemodynamic instability during induction and maintenance of anesthesia due to autonomic dysfunction.

c. Issues

i. Avoid succinylcholine in patients with current deficits or recent recovery due to potential for hyperkalemic response.

ii. Consider placement of intra-arterial catheter for close blood pressure monitoring.

iii. Be prepared to treat significant blood pressure fluctuations.

General anesthesia for Myotonic Dystrophy

a. Benefits

i. Securing of airway in patient at risk for aspiration due to pharyngeal muscle weakness and/or delayed gastric emptying.

ii. In patients with preexisting pulmonary compromise, avoids potential respiratory deterioration due to blockade of accessory respiratory muscles during neuraxial anesthesia for cesarean delivery.

b. Drawbacks

i. Must avoid succinylcholine.

ii. Increased sensitivity to respiratory depressant effects of anesthetic drugs.

iii. Residual effects of nondepolarizing neuromuscular blocking drugs could lead to postoperative pulmonary complications or need for postoperative mechanical ventilation.

iv. Reversal agents for neuromuscular blockade could theoretically cause myotonia although no evidence this is a significant clinical problem.

c. Issues

i. Modified rapid sequence induction with short-to-intermediate acting nondepolarizing neuromuscular blocking drug must be performed.

ii. Patients have normal response to nondepolarizing neuromuscular blocking drugs.

iii. Use smallest possible doses of all anesthetic drugs to minimize adverse respiratory effects.

iv. Utilize forced-air warming blanket, warm IV fluids, and increased room temperature to prevent shivering.

Monitored anesthesia care

If the patient with multiple sclerosis chooses to avoid neuraxial procedures for labor analgesia, pain relief can be provided with systemic opioids. This would be discouraged in other neuromuscular diseases due to the potential for respiratory complications related to underlying respiratory compromise. Monitored anesthesia care (MAC) is not an option for cesarean delivery.

Drawbacks

i. Poorer quality of analgesia compared to epidural technique.

ii. Opioid-induced respiratory depression is a concern, especially in patients with preexisting respiratory compromise.

6. What is the author's preferred method of anesthesia technique and why?

The MHS parturient

Because an MH event can be catastrophic, neuraxial analgesia/anesthesia is always our preferred anesthetic technique in these patients for labor analgesia and cesarean delivery, if no contraindications exist. Early placement of an epidural during labor is recommended to minimize the chance that an emergent obstetric situation would mandate general anesthesia. The patient should be followed closely for adequacy of the epidural block throughout labor. If there is any concern that the epidural is not functioning appropriately at any time during labor, it should be replaced.

Parturient with multiple sclerosis

For labor analgesia, our preferred technique is epidural analgesia. Since there is some limited data suggesting use of higher-concentration epidural local anesthetics could be associated with a higher risk of postpartum exacerbation, we utilize strategies to decrease local anesthesia requirements. We add an opioid to the local anesthetic solution, as that has been shown to have a local anesthesia-sparing effect, and we use the lowest concentration of local anesthesia that will provide the patient with adequate pain relief.

Most of our patients receive a solution of 0.0625% bupivacaine + fentanyl 2 mcg/mL. We also use programmable intermittent bolus with patient-controlled epidural analgesia (PIB-PCEA). Studies have reported that patients receive equivalent analgesia while utilizing less local anesthetic with PIB-PCEA compared to either standard PCEA or physician-controlled continuous epidural infusion.

We choose to avoid CSE analgesia in parturients with multiple sclerosis for two reasons. (1) Intuitively, attenuates the possibility of local anesthetic neurotoxicity to demyelinated areas of the spinal cord when the drug is administered directly into the subarachnoid space rather than the epidural space. (2) There is also more controversy within the medical literature regarding a potential association between spinal anesthesia and disease exacerbation compared to epidural anesthesia. Since epidural analgesia provides excellent analgesia, we see no significant advantage of CSE and thus avoid it for labor analgesia in these patients.

In most situations, we choose neuraxial anesthesia for cesarean delivery. Due to increased risks of difficult/failed intubation and aspiration in obstetric patients receiving general anesthesia, neuraxial anesthesia is considered the preferred anesthetic technique in the general obstetric population. Data are lacking to support an association between neuraxial anesthesia and an increased risk of exacerbation in patients with multiple sclerosis. Therefore, we believe it is prudent to use neuraxial anesthesia for cesarean delivery in women with multiple sclerosis whenever the clinical scenario would support its use in healthy obstetric patients.

We generally prefer epidural anesthesia for the same reasons discussed above for labor analgesia. However, in urgent situations where there is insufficient time to perform epidural anesthesia and the anesthesiologist must choose between inducing general anesthesia or rapidly performing single-shot spinal anesthesia, we would choose spinal anesthesia in the parturient with multiple sclerosis. When a patient does have serious preexisting pulmonary compromise due to her multiple sclerosis, we may choose general anesthesia for a cesarean delivery.

Parturient with Myasthenia Gravis

For labor analgesia, our preferred technique for most women with myasthenia gravis is epidural or CSE analgesia. Both techniques provide superior analgesia compared to systemic opioids. Due to preexisting muscle weakness, we use the lowest local anesthetic doses possible to provide adequate pain relief.

Typically, we use a solution of 0.0625% bupivacaine + fentanyl 2 mcg/mL as part of a PIB-PCEA technique for epidural analgesia. We avoid ester local anesthetics, such as 2-chloroprocaine, due to the potential toxicity and excessive block that could result from the effect of anticholinesterase therapy on plasma cholinesterase activity. When an assisted vaginal delivery is planned, we administer 2% lidocaine epidurally to achieve a denser sensory block for the procedure.

One advantage of CSE labor analgesia is the ability to provide excellent pain relief with less local anesthetic than is required with epidural analgesia. This does require the administration of intrathecal opioid, which is tolerated without adverse effect by most parturients with myasthenia gravis. However, for women with significant bulbar and pulmonary compromise, we prefer to use epidural analgesia with only local anesthetic.

For most patients, our choice of anesthesia for cesarean delivery is based on obstetric considerations, including indication for and urgency of the surgery. The majority of our patients with myasthenia gravis who undergo cesarean delivery will receive a neuraxial anesthetic that could include epidural, CSE, or single-shot spinal anesthesia.

For patients with severe bulbar or pulmonary compromise due to the disease, however, we usually prefer to use general anesthesia. This allows the airway to be secured, avoiding aspiration risk related to bulbar dysfunction, and adequate ventilation to be achieved, avoiding potential respiratory difficulty related to the effect of a high neuraxial block on the intercostal muscles. When general anesthesia is administered, careful attention must be paid to the use and dosing of neuromuscular blocking drugs.

Parturient with Guillain-Barre syndrome

For labor analgesia, our preferred technique is epidural or CSE analgesia. There are several reports of the safe use of these techniques, and we do not believe there is reliable evidence suggesting risk of disease exacerbation when these procedures are performed. Due to the preexisting muscle weakness, we use the lowest local anesthetic doses possible to provide adequate analgesia.

One advantage of CSE analgesia is the ability to provide excellent pain relief with less local anesthetic than is required with epidural analgesia. This does require the administration of intrathecal opioid so we do avoid this technique in patients with severe bulbar or respiratory compromise. For epidural analgesia, we generally use PIB-PCEA with bupivacaine 0.0625% + fentanyl 2 mcg/mL.

For cesarean delivery, our choice of anesthetic technique is based on each patient’s overall condition. If we believe a patient can tolerate neuraxial anesthesia without significant respiratory deterioration, we prefer this technique. It avoids the need for general anesthesia, which poses increased challenges in these patients. In patients with severe bulbar or respiratory compromise, we do choose general anesthesia. The patient is monitored closely for weakness, and we have a low threshold for maintaining mechanical ventilation postoperatively.

Parturient with Myotonic Dystrophy

For labor analgesia, our preferred technique is epidural or CSE analgesia. In addition to providing excellent analgesia, these techniques avoid the problem in myotonic dystrophy of increased sensitivity to the respiratory depressant effects of systemic opioids. We usually administer epidural analgesia using PIB-PCEA with a solution of 0.0625% bupivacaine + fentanyl 2 mcg/mL. Another advantage of epidural analgesia is the ability to administer epidural opioids, which can reduce the risk of shivering.

Throughout labor and delivery, it is essential that all measures are taken to maintain normothermia and prevent shivering, which can precipitate myotonia. The room temperature in the patient’s room must be kept warm, a fluid warmer should be used for administering IV fluids, and use of a forced-air warming blanket should be considered.

For most patients with myotonic dystrophy undergoing cesarean delivery, we prefer neuraxial anesthesia. Obstetric and patient factors, such as urgency and estimated duration of surgery, determine whether we choose epidural, CSE, or single-shot spinal anesthesia. Whenever possible, we want to avoid general anesthesia in these patients.

The inability to administer succinylcholine significantly complicates the induction of general anesthesia in a parturient who requires a rapid sequence induction. We would prefer general anesthesia in the few patients with myotonic dystrophy who have severe respiratory compromise or markedly increased aspiration risk due to pharyngeal muscle dysfunction.

When general anesthesia is required, we use rocuronium for intubation. We try to avoid administering any additional neuromuscular blocking drugs. We also use the lowest doses possible of induction, opioid, and volatile anesthetic drugs to minimize the increased sensitivity to their respiratory depressant effects. We use all available strategies to maintain normothermia intraoperatively.

What can I do intraoperatively to optimize patient care?

The MHS parturient: Patient care can be optimized by appropriate communication with the obstetrician indicating any signs or symptoms of MH. Should an MH episode develop, the anesthesia and obstetric staff need to work together to efficiently expedite completion of the surgery while managing the MH crisis simultaneously.

What are the most common intraoperative complications and how can they be avoided/treated?

The MHS parturient

i. In an MHS parturient the most severe intraoperative complication during cesarean delivery or one that could theoretically occur from the stress of labor and vaginal delivery is that of an MH episode.

ii. MH episodes can present as masseter spasm only, masseter spasm with other metabolic derangements, unexplained cardiac arrest, isolated rhabdomyolysis, or mild to fulminant MH crisis.

iii. Fulminant MH crisis can involve signs and symptoms that include mixed or metabolic acidosis, hyperthermia, dysrhythmias, hyperkalemia, hypercalcemia, hyperphosphatemia, rhabdomyolysis with elevated creatine kinase levels and myoglobinuria, tachycardia, tachypnea and increases in minute ventilation (if breathing spontaneously), muscle rigidity, cyanosis, elevated end-tidal carbon dioxide concentration, and abnormal coagulation studies.

iv. Agents responsible for triggering MH include all halogenated volatile anesthetic gases and succinylcholine.

v. Management of any possible MH reaction, whether it occurs in a parturient with known MH susceptibility or in an unsuspected patient, includes:

(i) Calling for help.

(ii) Discontinuing any triggering agent and hyperventilating the patient with 100% oxygen at high flows

(iii) Administering dantrolene 2.5mg/kg IV repeated until resolution of symptoms or up to 10 mg/kg has been administered

(iv) Treating the metabolic acidosis and hyperkalemia that develops with appropriate drugs, such as insulin, calcium, and sodium bicarbonate.

(v) Treating any dysrhythmia according to advance cardiac life support guidelines. Dantrolene treatment should also help alleviate dysrhythmias.

(vi) Maintaining urine output with crystalloids, colloids, mannitol, and furosemide to combat rhabdomyolysis.

(vii) Cooling the patient with all possible strategies, including cooling blankets, cold IV crystalloid fluids, ice packs, and cold gastric lavage.

(viii) Calling the MH Hotline for assistance, if needed.

Parturient with Multiple Sclerosis: The most common problem during labor and delivery specific to the patient with multiple sclerosis is the development of even mild hyperthermia since this increases the risk of a disease exacerbation. The woman’s temperature should be closely monitored. If she develops even a small increase in body temperature, cooling strategies should be implemented.

With the prevention of hypothermia now a major goal in surgical patients, the use of forced air heating devices has become routine in the operating room. However, these should only be used in parturients with multiple sclerosis if hypothermia has been documented. When they are used, maternal temperature must be monitored very closely to prevent the development of iatrogenic hyperthermia.

Parturient with Myasthenia Gravis: The most common complication during labor and delivery specific to the patient with myasthenia gravis is the development of worsening muscle weakness, which could impede vaginal delivery and lead to respiratory difficulty if the accessory respiratory muscles are involved. The performance of an assisted vaginal delivery to shorten the second stage of labor and to minimize patient effort from pushing can minimize this risk.

When general anesthesia is utilized for cesarean delivery, a potential complication is prolonged neuromuscular blockade. This can best be prevented by using succinylcholine for rapid sequence induction and avoiding other neuromuscular blocking drugs. When non-depolarizing drugs are required intraoperatively, a very small initial dose of a short-to-intermediate acting drug should be used, and the patient’s response must be monitored closely with a peripheral nerve stimulator.

Parturient with Guillain-Barre syndrome: The patient may have inadequate strength to push effectively during the second stage of labor. An instrument-assisted vaginal delivery can be performed to avoid cesarean delivery. This procedure is facilitated by neuraxial anesthesia. Patients with bulbar dysfunction are at increased risk for aspiration. When they require cesarean delivery, general endotracheal anesthesia is recommended to avoid this complication. Non-depolarizing neuromuscular blocking drugs must be used for induction of general anesthesia in these patients. Prolonged neuromuscular block may result. Maintenance of mechanical ventilation until the patient exhibits adequate strength will prevent complications associated with residual neuromuscular block.

Parturient with Myotonic Dystrophy: Development of myotonia during labor and delivery is a feared complication in these patients. Preventing shivering by maintaining normothermia is the most important strategy for avoiding this complication. Terbutaline for tocolyis and succinylcholine during rapid sequence induction of general anesthesia must also be avoided as they can precipitate a myotonic episode. Respiratory depression from opioids, sedatives, and other anesthetic drugs is another concern as these patients have an increased sensitivity to the drugs’ effects. The use of neuraxial analgesia/anesthesia allows the use of these drugs to be minimized.

a. Neurologic:

N/A

b. If the patient is intubated, are there any special criteria for extubation?

N/A

c. Postoperative management

The MHS parturient

In the unlikely event that an MH event occurs, the patient should be closely monitored postoperatively in an intensive care unit. Dantrolene 1 mg/kg should be administered every 4 to 6 hours for 1 to 2 days along with continued assessment and management of any remaining acidosis, electrolyte, temperature, and ECG abnormalities as well as renal damage from rhabdomyolysis. The patient’s family should be counseled about MH and potential testing. After recovery, referral of the patient for muscle biopsy and caffeine-halothane contracture test for formal definitive diagnosis should be considered.

What analgesic modalities can I implement?

Parturient with Multiple Sclerosis: For post-cesarean analgesia, women with multiple sclerosis are usually candidates for the same analgesic techniques used by healthy parturients. This could include intravenous patient controlled analgesia, intermittent dosing of systemic opioids, PCEA, neuraxial morphine, nonsteroidal anti-inflammatory drugs (NSAIDs), and transversus abdominis blockade. In patients with significant pulmonary compromise, close post-operative monitoring is recommended when systemic or neuraxial opioids are used.

Parturient with Myasthenia Gravis: For post-cesarean analgesia, women with myasthenia gravis are usually candidates for the same analgesic techniques used by healthy parturients. This could include intravenous patient controlled analgesia, intermittent dosing of systemic opioids, PCEA, neuraxial morphine, NSAIDs, and transversus abdominis blockade. In patients with significant bulbar or respiratory compromise as well as those who develop worsening weakness during labor and delivery, the use of systemic and neuraxial opioids should be minimized to prevent the risk of respiratory depression.

Parturient with Guillain-Barre syndrome: For post-cesarean analgesia, the preferred technique will depend on the patient’s condition. Women without bulbar or respiratory involvement are candidates for all analgesic options. In patients with respiratory or bulbar compromise, systemic and neuraxial opioids should be used sparingly and with close respiratory monitoring. Epidural analgesia with local anesthesia only or NSAIDs may be better options in these patients.

Parturient with myotonic dystrophy: Due to an increased sensitivity to the respiratory depressant effects of opioids, epidural analgesia and/or NSAIDs are preferred for post-cesarean analgesia.

What bed acuity level is appropriate?

The MHS parturient: Any patient who experiences an MH event requires postoperative ICU care.

Parturient with Multiple Sclerosis: Patients with severe pulmonary involvement may require post-delivery care in a more intensive setting, but most women can be cared for safely on the routine postpartum floor.

Parturients with Myasthenia Gravis:In the immediate postpartum period (3–4 hours), these women should be monitored in a more acute setting since this a common time for an exacerbation with worsening of muscle weakness. It is advisable to keep the patient on the labor and delivery unit with a low nurse-patient ratio rather than transferring her to the routine postpartum floor. Patients with serious pre-existing bulbar or pulmonary dysfunction or who develop worsening muscle weakness postpartum do require post-delivery care in a more intensive setting. Patients requiring postoperative mechanical ventilation after cesarean delivery need to be cared for in an ICU setting.

Parturients with Guillain-Barre syndrome: Patients with significant bulbar or respiratory dysfunction should be cared for in a more intensive environment with a low nurse-patient ratio in the immediate postpartum period. Patients requiring postoperative mechanical ventilation will require ICU care.

Parturient with Myotonic Dystrophy: Most women can be cared for safely on the routine postpartum floor. Patients with serious respiratory compromise should be monitored in a more intensive setting with a lower nurse-patient ratio.

What are common postoperative complications, and ways to prevent and treat them?

Parturient with multiple sclerosis: These women are at increased risk of developing a disease exacerbation in the first three postpartum months. There is currently limited evidence supporting specific management strategies to prevent a postpartum exacerbation. Efforts should be made to minimize contributing factors for an exacerbation, such as stress, fatigue, infection, and temperature increases, although it is difficult to eliminate some of these in a new mother. Administration of immunosuppressive drugs during the postpartum period might help decrease relapse rates.

Parturient with Myasthenia Gravis:Patients may develop worsening muscle weakness postpartum due to the fatigue associated with labor. Rest is advised. It is crucial that dose adjustments in anticholinesterase therapy be made postpartum to ensure optimal treatment. If symptoms progress to myasthenic crisis, plasmapheresis should be considered. Maternal antibodies do cross the placenta, and 16% of infants will exhibit signs of myasthenia gravis. The pediatrician must be alert for this potential complication and initiate prompt treatment if the neonate exhibits hypotonia, feeding problems, or respiratory difficult.

Parturient with Guillain-Barre syndrome: These patients are at risk for postpartum thromboembolism. Sequential compression stockings and anticoagulant prophylaxis should be considered. In women who received neuraxial anesthesia, ASRA guidelines should be followed for determining the appropriate time to begin anticoagulant therapy.

Parturient with Myotonic Dystrophy: Postoperative pulmonary complications are increased in these patients. There are many contributing factors, including respiratory depressant effects of opioids and other anesthetic drugs, residual neuromuscular blockade, preexisting central sleep apnea, and aspiration risk secondary to pharyngeal muscle weakness and/or delayed gastric emptying. The use of neuraxial anesthesia rather than general anesthesia can minimize or eliminate these factors.

Myotonia is another potential postoperative complication. Maintenance of normothermia and prevention of shivering will decrease this risk. If a generalized myotonic episode occurs, quinine, procainamide, or phenytoin are effective treatments. A localized myotonic contracture can be treated with injection of local anesthesia into the affected muscle.

Due to effects of the disease on uterine muscle, these patients have an increased risk for uterine atony and postpartum hemorrhage. Pharmacologic therapies for uterine atony are the first line of treatment. If this treatment is ineffective, more invasive techniques, either surgical (B-Lynch compression suture, arterial ligation, etc.) or interventional radiologic (arterial embolization) techniques are warranted.

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