Neuraxial analgesia for labor & delivery

What the Anesthesiologist Should Know before the Operative Procedure

Neuraxial analgesia is the preferred method of providing analgesia for labor and vaginal delivery. If needed, the epidural catheter will usually provide anesthesia for cesarean section and other surgical procedures related to pregnancy.

1. What is the urgency of the surgery?

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

Labor analgesia is elective, although ethically and in the interest of good customer service, parturients expect their request for pain medication to be responded to in an expeditious way. The obstetrician can usually tell the anesthesiologist if there are medical issues that might complicate or preclude provision of neuraxial analgesia for labor. Cesarean section may be emergent, urgent or elective depending on the condition of the mother and of the fetus. Obstetrical anesthesia requires balancing these considerations; however, the life and well-being of the mother should come before that of the fetus. In reality, with good planning and communication, such dire decisions are seldom necessary.

Emergent: Instrumented vaginal delivery or cesarean section must occur within minutes to ensure the well-being of the mother and/or fetus. Examples of situations that would require emergent delivery are a prolapsed umbilical cord, massive hemorrhage with maternal instability, or prolonged fetal bradycardia. Some anesthesiologists prefer general anesthesia for the emergent cesarean section, while others, depending on the patient’s airway exam and bony landmarks on the back, believe that a spinal can be quicker. The decision depends on the anatomy of the patient, her physical condition, and the skill and experience of the operator.

Urgent: Urgent delivery should not be delayed unnecessarily, but need not occur within minutes. Indications for urgent vaginal or cesarean delivery would be a fetal heart rate tracing with repetitive variable decelerations and minimal baseline variability remote from delivery or labor in a patient with prior cesarean section who refuses a trial of labor. Most urgent cesarean sections can be done with spinal, epidural, or general anesthesia as indicated by the patient’s condition. Instrumented vaginal delivery can be accomplished with a spinal anesthetic or extension of an existing epidural block.

Elective: Elective surgery is normally scheduled for the convenience of the patient and practitioners. There is no special urgency. Elective cesarean sections are usually done with regional anesthesia when not medically contraindicated. Neuraxial analgesia for labor is always elective, although the discomfort and anxiety of the parturient will give a sense of urgency, especially late in labor.

2. Preoperative evaluation

It is imperative to ensure adequate clotting function prior to regional analgesia or anesthesia.

Thrombocytopenia is not rare in pregnancy; however, it is rarely severe (i.e., less than 50,000). The ASA Task Force on Guidelines for Obstetrical Anesthesia has suggested that in healthy women, obtaining a routine platelet count does not reduce complications of neuraxial anesthesia. On the other hand, in patients with known or suspected platelet abnormalities (e.g., preeclampsia, ITP, TTP), the platelet count should be followed at regular intervals. In patients receiving heparin for more than 4 doses, at least a single platelet count should be measured to rule out HIT (heparin-induced thrombocytopenia). The platelet count can be decreased in patients receiving even low dose heparin (5000 U BID). The number of normal platelets that are necessary for hemostasis within the neuraxis if the large venous plexuses are interrupted is unknown. There is extensive experience with neuraxial anesthesia in parturients with at least 100,000 platelets. There are many case series that support the safety of neuraxial anesthesia in parturients with greater than 75,000 platelets.

There are rare, often genetic syndromes that result in specific factor deficiencies. The safety of regional anesthesia in these patients should be guided individually with hematological consultation.

Medically unstable conditions warranting further evaluation include symptomatic maternal cardiac, respiratory, and hematological disease. The normal physiological changes of pregnancy can exacerbate these conditions and make a previously asymptomatic patient decompensate.

Delaying surgery may be indicated if the medical condition is not optimal and the surgery is not urgent. Analgesia for labor is always elective and the provider should not proceed if further evaluation is deemed necessary.

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

b. Cardiovascular system

Medically unstable conditions warranting further evaluation include symptomatic maternal cardiac, respiratory and hematological disease. The normal physiological changes of pregnancy can exacerbate these conditions and make a previously asymptomatic patient decompensate. For example, pregnancy is a thrombophilic state, and conditions such as protein C or S deficiency or factor V Leiden mutation may be diagnosed during pregnancy because of a DVT or pulmonary embolus requiring anticoagulation.

Delaying surgery may be indicated if the medical condition is not optimal and the surgery is not urgent. Although labor cannot be delayed, analgesia can be provided with intravenous opioids if necessary while further work-up for neuraxial block occurs.

Acute/unstable conditions: Although unusual, parturients with any preexisting cardiac disease that are New York Heart Association Class II or higher require special consideration. In particular, patients with stenotic valvular heart disease often cannot tolerate the increased intravascular volume and cardiac output associating with increasing gestation. Careful management requires balancing diuresis with adequate preload. Neuraxial analgesia may also decrease preload and afterload with adverse consequences. In contrast, regurgitant lesions are often well tolerated because the regurgitant fraction is reduced in the setting of high preload and low afterload that accompanies pregnancy. Neuraxial techniques also decrease afterload and are well tolerated with regurgitant lesions. In general, reducing catecholamines by treating labor pain will benefit the parturient with cardiac disease, although associated drops in preload and afterload must be managed carefully depending on the physiology.

Baseline coronary artery disease or cardiac dysfunction – Goals of management: Preexisting coronary artery disease is uncommon in parturients and usually the result of coronary artery dissection or long-standing diabetes. Parturients can be maintained on nitrates and beta blockade, but angiotensin converting enzyme inhibitors are contraindicated in pregnancy. Preexisting myocardial insufficiency is concerning, particularly when it is due to peripartum cardiomyopathy which can recur or worsen in subsequent pregnancies. Management requires diuresis with inotropy as needed. Cardiac medications including digoxin, dobutamine, and milrinone can be used when needed as a bridge to delivery and further treatment. Neuraxial analgesia for labor is beneficial in patients with myocardial ischemia or reduced ejection fraction because it reduces catecholamines and maternal heart rate while reducing afterload and preload.

Many cardiac lesions will benefit from a passive second stage of labor without pushing, and an assisted vaginal delivery. Neuraxial blocks can provide excellent perineal analgesia to block the perineal reflex and remove the urge to push.

c. Pulmonary

COPD is rare in parturients, but obstructive pulmonary disease is managed with the full array of inhaled beta-agonists and corticosteroids that are used in women who are not pregnant. Patients with respiratory insufficiency will benefit from neuraxial analgesia in labor that reduces their respiratory requirements by relieving pain and anxiety and preventing hyperventilation.

Reactive airway disease (Asthma): Asthma is managed with inhaled beta agonists and steroids as in the nonpregnant state. It is relatively uncommon to have a severe asthma exacerbation in the setting of labor because maternal catecholamines are high. In the setting of an acute exacerbation, the mother should be treated with beta-agonists and oxygen to improve both maternal and fetal oxygen supply. By providing neuraxial analgesia in labor, work of breathing is reduced. If deemed beneficial, perineal anesthesia can be provided during the second stage of labor to allow passive descent and assisted vaginal delivery.

d. Renal-GI:

i. Patients with severe renal dysfunction seldom have successful pregnancies because significant uremia prevents ovulation. After transplantation or with good dialysis treatment (hemo- or peritoneal), ovulation may resume and pregnancy is possible. In the setting of pregnancy the need for dialysis is increased and care is required to avoid significant fluid shifts during dialysis. Severe anemia may be treated with erythropoietic stimulating drugs or transfusion. Patients who are severely uremic can have platelet dysfunction, and there are no guidelines for managing neuraxial anesthesia in that setting.

Nausea and vomiting is a common complication of pregnancy, represented in its most extreme case as hyperemesis gravidarum early in gestation. In severe cases, parenteral feeding may be required. Biliary obstruction is relatively common in pregnancy and requires surgery in 1:6000 pregnancies. Surgery is best planned for the second trimester when possible. During labor, relief of pain with neuraxial techniques usually improves nausea.

e. Neurologic:

Common neurological issues that occur in young women who may become pregnant include multiple sclerosis, lumbar disc disease and peripheral nerve dysfunction including carpal tunnel syndrome and sciatica. Headache is a common problem that occurs in pregnancy and can be associated with preeclampsia or post dural puncture headache. The patient may be particularly anxious about how neuraxial analgesia might affect her underlying condition. In virtually all cases they can be reassured that neuraxial techniques are not associated with exacerbations, and may even be beneficial by reducing stress and helping manage chronic pain patients who have opioid tolerance.

Acute issues: Severe headache: The anesthesiologist is often the first physician consulted for a parturient’s headache, particularly post-partum. Headache is very common and the most common etiologies are muscular tension, migraine or caffeine withdrawal. However, headache can be a sign of severe preeclampsia and impending seizure. Dural puncture headache is normally positional with exacerbation on standing and relief when supine. It usually has a gradual onset. The more concerning etiologies of headache postpartum include sagittal sinus thrombosis, an intracerebral bleed, or a subarachnoid hemorrhage. These headaches are usually accompanied by other neurological signs, which may include seizures. The headache is usually severe and sudden. In this setting, neurological consultation should be requested and imaging obtained prior to consideration of epidural blood patch, although dural puncture headache may be considered in the differential diagnosis.

Chronic disease: Multiple sclerosis is rare, but may be seen in young women in their child-bearing years. It is generally agreed that neuraxial anesthesia is safe in parturients with multiple sclerosis. There are many case series of successful epidural analgesia in patients with multiple sclerosis. There are theoretical concerns that direct application of local anesthetic to demyelinated nerves in spinal anesthesia may cause toxicity. However, there are many case reports of successful spinal anesthesia in parturients with multiple sclerosis. The patient’s neurologic deficits should be well-documented preoperatively and she should be counseled that postpartum exacerbations are common, but occur with or without use of neuraxial analgesia for labor.

It is safe to give neuraxial analgesia in the setting of disc disease. However it is important to warn the patient that they will not have pain feedback while the epidural is running, so they should be careful with positioning. If she is on chronic opioids for back pain, she may have a high tolerance to narcotics. She will benefit from neuraxial analgesia during labor, as it will be extremely difficult to provide adequate analgesia through intravenous opioids. The same is true for providing postoperative analgesia if cesarean delivery becomes necessary.

f. Endocrine:

Pregnancy is a common time for diabetes to be diagnosed or exacerbated. It is important to have good glucose control in the first trimester to avoid an increased incidence of birth defects. In later pregnancy it is important that blood sugar be well controlled to excessive fetal growth, promote lung maturity, and prevent hypoglycemia after birth. During labor and delivery, good analgesia with neuraxial techniques will help control blood sugar elevations by reducing catecholamines and other stress hormones.

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

Gestational thrombocytopenia, or thrombocytopenia of pregnancy, occurs in 6%-8% of parturients, but is usually benign and self-limited with normal platelet function. Therefore it is not necessary to check laboratory tests before offering neuraxial analgesia in healthy women who are not on any medications. Heparin 5000 units twice a day is not a contraindication to regional anesthesia. However, patients who have been on heparin for more than 4 days should have a platelet count checked to rule out heparin induced thrombocytopenia. Higher heparin doses are often used in pregnancy because the volume of distribution is increased and there is heparin resistance. PTT should be checked in this situation before neuraxial analgesia.

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

Pregnant women rarely take medications other than vitamins and iron supplementation. Most other medications should be continued in the peripartum period. Anticoagulation is the exception, as delivery can be complicated by excessive hemorrhage in the setting of full anticoagulation, and neuraxial techniques will be contraindicated.

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

Heparin should be discontinued prior to labor and delivery in all but the highest risk cases (e.g., mechanical heart valves, recent pulmonary embolism). Warfarin is being used more commonly in late pregnancy for patients with mechanical heart valves and needs to be transitioned to heparin before delivery. Newer longer-acting anticoagulants are problematic when considering neuraxial techniques in labor, as is the question of proper transition from antiplatelet therapies for pregnant women with drug eluting stents. A multidisciplinary team should make recommendations in these complex patients. Follow the recommendations in the ASRA consensus statement on regional anesthesia and anticoagulation.

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

Cardiac: Beta-blockers, calcium channel blockers, and most blood pressure medications should be continued during labor and delivery when the release of catecholamines can cause exacerbation of hypertension. Angiotensin-converting enzyme inhibitors are contraindicated in pregnancy due to teratogenicity. Anticoagulation must be at least partially reversed for delivery and fully reversed to allow for neuraxial anesthesia.

Pulmonary:Continue all medications peripartum.

Renal: Continue medications, but diuretics must be carefully monitored by her nephrologist and obstetrician.

Neurologic: Continue all medications peripartum, especially antiseizure drugs.

Antiplatelet: Nonsteroidal anti-inflammatory medications are not commonly used in labor and delivery because they are tocolytics and have the potential to cause premature closure of the ductus arteriosus. Low-dose aspirin may be used in women at high risk for preeclampsia or those with recurrent miscarriages.

Psychiatric: There is controversy about the effect of certain medications for depression on fetal development and outcome. However, the definite risk to the mother of untreated severe depression must be weighed against the potential and not well-defined risk to the fetus.

j. How To modify care for patients with known allergies –

True anesthetic allergies are uncommon. Patients with known drug allergies should be given drugs from another class.

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

Latex allergy is becoming more prevalent, particularly in health care workers who are sensitized. Equipment for neuraxial blocks will be latex-free. In cases of anaphylaxis of unknown etiology, latex should be considered. Treatment is the same as with other allergic reactions with small doses of epinephrine (20 μg) initially. This is often effective to terminate the reaction and stabilize hemodynamics and respiratory function. Corticosteroids are useful to prevent mast cell degranulation. The most important action is to remove the offending agent.

l. Does the patient have any antibiotic allergies- [Tier 2- Common antibiotic allergies and alternative antibiotics]

No antibiotics are routinely given in labor unless she requires penicillin for prematurity or culture-proved group B Streptococcus colonization. Cefazolin is the most commonly used prophylactic antibiotic for cesarean delivery as it has good coverage for skin flora. Older studies suggested that cross reactivity with penicillin allergy was as common as 13%; however, the cephalosporins that were used at that time may have been contaminated with penicillins as they were produced in the same facility. Likely the cross reactivity is significantly lower.

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

Malignant hyperthermia (MH)

Documented: Use neuraxial anesthesia and avoid all trigger agents such as succinylcholine and inhalational agents. Neuraxial techniques are an excellent option for labor analgesia in MH-susceptible patients since local anesthetics and opioids are not triggering agents, and epidural analgesia can be extended for cesarean delivery if needed.

Proposed general anesthetic plan: Induction with propofol and high-dose rocuronium for rapid sequence intubation with propofol and opioids or ketamine for TIVA maintenance. The neonatology service must be aware of potential need for neonatal resuscitation.

Ensure MH cart available: Family history or risk factors for MH: Patients with family history of MH or potential personal history of MH should be treated with a nontriggering technique involving neuraxial anesthesia. TIVA can be used if general anesthesia becomes necessary.

Local anesthetics/ muscle relaxants: If the patient has a documented or suspected allergy to local anesthetics (e.g., an ester), neuraxial analgesia can be provided using an agent from the other class (e.g., an amide).

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

For planned labor in a healthy woman, no laboratory tests are required prior to placement of neuraxial anesthesia. In patients with comorbidities by history or physical exam, the appropriate laboratory tests should be ordered to ensure optimal medical management of the patient’s condition.

Hematocrit will be lower beginning in the second trimester due to plasma volume increases and dilution: the “physiologic anemia of pregnancy”. Creatinine should be lower (0.6 mg/dL or less) due to increased renal blood flow and GFR. A normal creatinine is concerning in a pregant woman at term.

Hemoglobin levels: Stable and > 10

PLT > 75,000 for regional anesthesia depending on the diagnosis of the thrombocytopenia and the risk for platelet dysfunction.

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

Neuraxial analgesia is preferred for labor analgesia as it is the most effective and least depressant analgesic technique that gives the flexibility to convert to surgical anesthesia if cesarean delivery is required. Regional anesthesia is preferred over general anesthesia for cesarean delivery because regional anesthesia lets her participate in the birth and see her newborn, it avoids manipulation of the maternal airway which may be more difficult to secure when compared with a airway of a nonpregnant woman, and it provides superior postoperative pain relief. However, most pregnant women do not have difficult airways and intubation should not be delayed when it can be potentially lifesaving for the mother or the child if there is no indication of difficult airway.

a. Regional anesthesia

Continuous lumbar epidural analgesia is commonly used to treat labor pain. A small dose of subarachnoid local anesthetic (e.g., isobaric bupivacaine 1.25-2.5 mg) and/or opioid (e.g., sufentanil 2.5-5 mcg or fentanyl 10-25 mcg) can be placed as a needle-through-needle technique at the time of epidural placement for combined spinal-epidural (CSE) analgesia. The benefits of the combined technique are more rapid onset of analgesia within 5 minutes, better sacral analgesia, and potentially a smaller incidence of patchy or inadequate epidural blocks because the epidural needle placement has been verified by detecting CSF distal to the tip. The increase in reliability of an epidural catheter placed as part of a CSE technique was surprising, because when the technique was developed there were fears that an untested epidural catheter might be less reliable if conversion to anesthesia for cesarean section was required.

Neuraxial

Benefits: Less placental passage of drug to the fetus compared with intravenous techniques.

Drawbacks: Invasive and resource intensive. More expensive for the patient because of equipment and pharmacy charges and professional fees to the anesthesiologist.

Issues: Epidural analgesia provides the most effective pain relief for labor. However, some women do not desire an injection in their back or do not like the “numb sensation”. It is very expensive to provide a full coverage for an obstetric anesthesia service around the clock, and not all hospitals have the necessary resources.

Other options: Intravenous opioids, particularly fentanyl and remifentanil have been used as patient-controlled techniques for labor analgesia with reasonable patient acceptance. Continuous infusion remifentanil can induce effective pain relief for the mother without risking severe neonatal depression. Remifentanil has unique pharmacokinetics with an ester bond that is metabolized by tissue esterases. The UA:UV ratio is approximately 0.3. If a remifentanil infusion is discontinued just prior to vaginal delivery, neonatal depression is uncommon but pediatric presence at delivery is recommended.

Peripheral nerve block

Benefits: Pudendal nerve block may be used for second stage analgesia if the obstetrician is familiar with the technique.

Drawbacks This technique is somewhat difficult because the fetal head is in close proximity to the injection and intracranial injection can have dire consequences for the fetus.

Lumbar plexus block may be useful for the first stage of labor but has not been studied extensively.

b. General Anesthesia

Benefits: Sedation has been used for labor analgesia but the main issue is pain not anxiety. General anesthesia can be used for instrumented vaginal delivery, but requires intubation of the potentially more difficult maternal airway.

Drawbacks: The patient is asleep and misses the birth experience. The baby is exposed to general anesthetic medications and may need resuscitation.

Airway concerns:The maternal airway is more likely to be more difficult than the nonpregnant woman’s airway; however, the vast majority of pregnant woman are not difficult to intubate. The normal considerations for airway evaluation apply including Malampati score, thyromental distance, mouth opening and neck mobility. Being unable to intubate or ventilate is the most common cause of anesthesia-related maternal mortality.

c. Monitored anesthesia care

MAC or sedation is rarely indicated for labor or vaginal delivery and never indicated for cesarean section. Medications such as ketamine may be used for short painful procedures such as urgent forceps delivery or manual removal of retained placenta.

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

Epidural analgesia is preferred for labor analgesia if not contraindicated. Combined spinal-epidural is used when I believe the parturient would benefit from the rapid onset of a spinal dose. If a spinal dose is not given, the epidural is initially bolused in an incremental fashion with 10-15 ml 0.125-0.25% bupivacaine (or comparable concentrations of ropivacaine) plus 50 mcg fentanyl or 10 mcg sufentanil. Once the patient is comfortable, an epidural infusion is started with a patient-controlled (PCEA) option. For example, 0.0625-0.1% bupivacaine (or equivalent concentrations of ropivacaine) with 2 mcg/mL fentanyl will run at 5-10 mL/hr with up to four patient-controlled increments of 5 ml with a 10-minute lockout. The use of PCEA improves patient satisfaction and reduces workload for the anesthesia provider. Explain to the patient that the goal is adequate analgesia for her with minimal motor block. She should notify her nurse if her legs become heavy so the PCEA pump can be adjusted accordingly.

If a combined spinal-epidural is chosen, instead of the epidural bolus, a spinal dose of 10-25 mcg fentanyl or 2.5-5 mcg sufentanil is injected into the CSF. If she is in the active phase of labor, local anesthetic can be added as well, for example 0.5-1 mL or 0.25% bupivacaine. The epidural infusion and PCEA pump are set up as described previously.

What prophylactic antibiotics should be administered?

No antibiotics are routinely indicated for labor and vaginal delivery. If cesarean delivery is necessary, current SCIP guidelines recommend treatment with prophylactic antibiotics within 1 hour before skin incision. Recent studies have shown that there is no risk of masking neonatal sepsis, and that there is a benefit to treating the mother before incision rather than waiting until cord clamp. Women should be treated with1-2 gm cefazolin depending on weight. Beta-lactam allergic mothers should be treated with clindamycin 900 mg or metronidazole 500 mg IV and ciprofloxacin 400 mg IV.

Routine episiotomy for vaginal delivery is strongly discouraged. Skin incision for cesarean delivery may be vertical or horizontal depending on surgeon and patient preference. A low horizontal incision on the uterus is lower risk for uterine rupture in future pregnancies, but a vertical incision may be required in the setting of extreme prematurity or back-down transverse lie.

What can I do intraoperatively to assist the surgeon and optimize patient care?

To facilitate vaginal delivery, motor block should be minimized throughout labor so she can push effectively when completely dilated. This requires dilute solutions of local anesthetic in the epidural infusion, and may be facilitated by a patient-controlled technique. If cesarean delivery is required, in order to deliver the fetus the surgeon may request uterine relaxation. Intubation with high dose volatile anesthetic was used in the past, but this practice has been replaced by intravenous terbutaline or nitroglycerin during regional anesthesia. Nitroglycerin 50-500 mcg is shorter acting than terbutaline and causes less uterine atony.

The most common intrapartum complications are hemorrhage, thrombosis, and amniotic fluid embolism. The pregnant woman is at risk of both bleeding and clotting. If there is inadequate uterine contraction after delivery, vessels in the placental bed will not close, unlike bleeding in other tissues where platelets and coagulation factors are most important. The risk of thrombosis is addressed prophylactically with sequential compression stockings.

Complications

Cardiac: Maternal tachycardia is common during delivery and usually benign. ST-segment depression may occur and is usually not related to chest pain or apparent cardiac ischemia.

Pulmonary:Amniotic fluid embolism (AFE) or anaphalactoid syndrome of pregnancy can initially present with shortness of breath, but quickly progresses to cardiovascular collapse, coagulopathy, and often seizures. Treatment is resuscitation and supportive care. Thrombosis and pulmonary embolism should always be considered if the patient is dyspneic or has low oxygen saturations.

Neurologic: Seizures can be a sign of eclampsia, AFE, or, less commonly, intracranial hemorrhage.

a. Neurologic:

N/A

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

Rarely applicable to labor analgesia. After cesarean delivery using general anesthesia, the patient should be awake and following commands before extubation because of GE reflux and potential for aspiration of gastric contents.

c. Postoperative management

Pain management after vaginal delivery is usually accomplished with NSAIDs. If there was extensive perineal injury, 2-3 mg of preservative free morphine provides excellent analgesia, or the epidural infusion can be continued using 0.0625%-0.08% bupivacaine or 0.1% ropivacaine with fentanyl 2 mcg/mL. These patients should be ambulating immediately after vaginal delivery to avoid postpartum thrombotic complications and to care for their baby, so motor block must be avoided.

What level bed acuity is appropriate?

The postpartum L&D floor is appropriate for most healthy parturients. No special monitoring is required after epidural analgesia for labor and vaginal delivery.

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

Common complications are hemorrhage and thrombosis. Patients must resume ambulating immediately postpartum. If they cannot, compression stockings should be used.

What's the Evidence?

Anesthesiology. vol. 106. 2007. pp. 843-63. Practice guidelines for obstetric anesthesia: an updated report by the American Society of Anesthesiologists Task Force on Obstetric Anesthesia. (These are the ASA Practice Guidelines that cover analgesia for labor.)

Reg Anesth Pain Med. vol. 35. 2010. pp. 64-101. Regional anesthesia in the patient receiving antithrombotic or thrombolytic therapy: American Society of Regional Anesthesia and Pain Medicine Evidence-Based Guidelines (Third Edition). (ASRA has evidence-based guidelines for providing neuraxial techniques in parturients who are taking anticoagulant medications.)

Anesth Analg. vol. 109. 2009. pp. 648-60. Neuraxial techniques in obstetric and non-obstetric patients with common bleeding diatheses. (This review uses ASRA and other society guidelines to make recommendations for neuraxial techniques in patients with coagulopathies.)

Anesth Analg. vol. 112. 2011. pp. 648-52. The unanticipated difficult intubation in obstetrics. (An excellent algorithm for preparing for the difficult airway in parturients.)

N Engl J Med. vol. 362. 2010. pp. 1503-10. Epidural analgesia for labor and delivery. (An evidence-based review of the risks and benefits of epidural analgesia for labor.)

Anesth Analg. vol. 108. 2009. pp. 921-8. Patient-controlled epidural analgesia for labor. (A review of PCEA regimens for labor analgesia.)

Anesthesiology. vol. 111. 2009. pp. 165-72. Success of spinal and epidural labor analgesia. (This RCT compares loss of resistance to air versus saline during CSE placement and finds no difference in efficacy of labor analgesia.)

Anesth Analg. vol. 113. 2011. pp. 559-64. Ultrasound assessment of the vertebral level of the intercristal line in pregnancy. (In term pregnant women, clinical estimates of vertebral level were higher than that determined by ultrasound in 40% of patients.)

Anesth Analg. vol. 113. 2011. pp. 826-31. Programmed intermittent epidural bolus versus continuous epidural infusion for labor analgesia: the effects on maternal motor function and labor outcome. A randomized double-blind study in nulliparous women. (A programmed intermittent bolus of epidural local anesthetic provided better analgesia than a continuous infusion.)

Acta Anaesthesiol Scand. vol. 55. 2011. pp. 910-7. Neuraxial techniques in patients with pre-existing back impairment or prior spine interventions: a topical review with special reference to obstetrics. (Current evidence is mostly reassuring with respect to the risks of neuraxial blocks, and they may even be recommendable in some conditions. Ultrasound technology may be of additional help to increase the success rate.)

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