What the Anesthesiologist Should Know before the Operative Procedure
Myelodysplasia includes all the following conditions with varying degrees of spinal dysraphism (i.e., abnormal fusion of the posterior neuropore or failure of the neural tube to fuse):
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Encephalocoele – a relatively rare defect involving the cranium
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Meningocoele – contains CSF and no neural tissue
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Myelomeningocoele – contains CSF with neural tissue
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Rachischisis – open neural tissue no sac
Others include lipomeningocoele, lipomyelomeningocoele, and lipomyeloschisis. All defects are associated with spina bifida – defects in vertebrae. Mostly occurs in the lumbar sacral region (80%) and less commonly in the thoracic or cervical regions. Thoracic or cervical lesions usually associated with defects of the thoracic cage, diaphragm, or cardiac defects.
Associated conditions
a) Hydrocephalus 80% – particularly when paralysis below lesion occurs
b) Arnold Chiari type II malformation – almost always coexists
Classified as Type I-IV depending on the bony abnormality in the posterior fossa and upper cervical spine
Varying degrees of herniation of neural tissue though the foramen magnum may result in
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Cranial nerve involvement
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Medullary cord compression
c) Aqueductal stenosis
d) Short trachea described – care with ET tube
e) Inspiratory stridor secondary to cranial nerve involvement
1. What is the urgency of the surgery?
What is the risk of delay in order to obtain additional preoperative information?
Aim to restore re-convolution within spinal canal and restore the continuity of dural sac around reconstituted spinal cord by meticulous closure in layers. Some surgeons may require to do this using a microscope. Multidisciplinary team may be involved with closure – neurosurgery, plastic surgery, and, on occasion, spinal cord monitoring technicians.
Can be done electively when prenatal diagnosis (ultrasound and detection of alpha-fetoprotein in amniotic fluid) has been made.
Fetal surgery has been performed in some units with the hope of improving outcome. It is too soon to tell whether this is a real benefit. The balance of risks of premature labor is a major consideration: hydrocephalus remains an issue.
Aim for early closure within 24-48 hours of birth because of the risk of infection and to prevent further damage to neural tissue.
Often combined with VP shunt or ventriculostomy to prevent/reduce hydrocephalus, which may be hastened by closure.
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Performed at same sitting or within 48 hours.
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Deferred based on ultrasound evidence.
2. Preoperative evaluation
Neonatal condition and all the implications related to neonatal anesthesia pertain. In particular, temperature control and fluid balance are important. Infant may be born prematurely.
Delay in presentation/surgery may increase the risk of infection, meningitis, and sepsis.
Fluid balance particularly in the presence of sepsis important and the coagulation status should be checked (check that Vitamin K was given at birth).
3. What are the implications of co-existing disease on perioperative care?
Neonatal condition and all the implications related to neonatal anesthesia pertain.
Infant may be premature, which compounds the risk of immature respiratory control.
Arnold-Chiari malformation is associated with varying degrees of herniation of neural tissue (brainstem), which may cause medullary cord compression and involve cranial nerve.
Aqueductal stenosis
Inspiratory stridor secondary to cranial nerve involvement or even vocal cord paralysis
Short trachea has been described but is not common based on the authors’s experience.
Maintain temperature, caloric, fluid and electrolyte balance.
Prevent infection and protect the lesion from further damage.
Surgery performed in prone position – Recheck tube after positioning.
Intubation may be difficult in presence of large hydrocephalus.
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Protect defect on towels or “doughnut” sponge.
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Avoid pressure on open defect: keep covered and clean.
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Additional padding may be required beneath head and shoulders to facilitate intubation.
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Suxamethonium is not a problem – no increase in vitamin K is to be expected as in acquired forms of spinal cord paralysis.
Pressure points must be protected during prolonged surgery in particular attention must be paid to the eyes, the supraorbital ridge, knees, and feet. The abdomen should be free to move without any increase of abdominal pressure that can increase venous pressure — congestion — bleeding at time of surgery.
Blood loss is usually minimal, but with large lesions may be significant, particularly if skin needs to be undermined for closure.
May consider arterial catheter in this situation but usually not indicated.
Avoid extreme flexion to avoid the risk of brainstem compression particularly with Arnold-Chiari malformation.
Determine whether nerve monitoring/stimulation will be used to identify nerve roots? If so, avoid muscle relaxants, which will negate the value of the nerve monitor.
Body temperature may be difficult to maintain: warm OR, use overhead heater, use forced air warmers, and warm IV fluids
Latex precautions. because of subsequent risk of latex allergy in view of repeated catheterizations and surgery exposure.
Spinal anesthesia administered into the dural sac has been described (see Abaijan).
b. Cardiovascular system
A small percentage may have a congenital cardiac lesion (ASD, VSD, PDA, tetralogy of Fallot, or any other abnormality).
c. Pulmonary
Prematurity or aspiration, particularly when cranial nerves are involved or vocal cords are paralyzed
d. Renal-GI:
Unusual
e. Neurologic:
May be paralyzed below the lesion; uydrocephalus common
f. Endocrine:
N/A
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)
N/A
4. What are the patient's medications and how should they be managed in the perioperative period?
None specific; always worth checking that Vitamin K was administered after birth.
h. Are there medications commonly seen in patients undergoing this procedure and for which should there be greater concern?
Antibiotic therapy
i. What should be recommended with regard to continuation of medications taken chronically?
N/A
j. How To modify care for patients with known allergies –
Latex precautions, because of subsequent risk of latex allergy in view of repeated catheterizations and surgical exposure.
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 precautions, because of subsequent risk of latex allergy in view of repeated catheterizations and surgery exposure.
l. Does the patient have any antibiotic allergies- [Tier 2- Common antibiotic allergies and alternative antibiotics]
N/A
m. Does the patient have a history of allergy to anesthesia?
N/A
5. What laboratory tests should be obtained and has everything been reviewed?
Baseline levels
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Hemoglobin
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Electrolytes
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Coagulation
Intraoperative Management: What are the options for anesthetic management and how to determine the best technique?
Positioning for intubation is important as this may be difficult in the presence of large lesion, hydrocephalus, or encephalocoele
Protect defect on towels or “doughnut” sponge with aim of avoiding pressure on open defect which should be kept covered and clean to reduce the risk of infection.
Additional padding beneath head and shoulders may be needed to facilitate intubation.
Suxamethonium is not a problem since no significant increase in potassium levels are to be expected.
Surgery is performed in the prone position – after turning prone recheck the endotracheal tube position.
Protect pressure points – eyes, supraorbital ridge, abdomen free, knees, feet, etc
Blood loss is usually minimal but with large lesions may be significant particularly if skin needs to be undermined for closure.
Arterial catheter may be considered but is usually not indicated.
Avoid extreme flexion, which may contribute to brainstem compression particularly in those with Arnold-Chiari malformation.
Avoid the use of muscle relaxants when nerve monitoring/stimulation is to be used to identify nerve roots.
Body temperature may be difficult to maintain therefore all precautions to maintain normothermia is particularly important. This includes warming the OR, warming IV fluids, and using an overhead heating device for catheter placement and a forced air warmer intraoperatively.
Latex precautions are essential because of subsequent risk of latex allergy in view of repeated catheterizations and surgery exposure in the future.
Postoperatively
Risk of respiratory difficulties is high and may be due to stridor, ventilatory depression/apnea, or an abnormal response to hypoxia/hypocarbia particularly with Arnold-Chiari malformation or cranial nerve palsy or abnormal ventilatory control and abnormal swallowing.
Vocal cord paralysis may be present and there may be an associated risk of pulmonary aspiration.
Tight closure may affect ventilation – less likely.
Analgesia may not be necessary if sensory deficit exists.
Monitor for wound infection/cellulitis, CSF leakage, wound dehiscence, and hydrocephalus.
a. Regional anesthesia –
Spinal anesthesia has been described by Abaijan et al . Direct injection into the CSF through the meningocoele is possible but not generally supported since the newborn is operated on prone and it is therefore difficult to manage the airway in the event of problems.
6. What is the author's preferred method of anesthesia technique and why?
N/A
a. Neurologic: *** Type Here.
N/A
b. If the patient is intubated, are there any special criteria for extubation?
N/A
c. Postoperative management
Analgesia may not be necessary if sensory deficit exists.
Monitor for:
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Wound infection/cellulitis
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CSF leakage
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Wound dehiscence
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Hydrocephalus
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CT scan, MRI
What's the Evidence?
Jones, KL. “Smith's Recognizable Patterns in Human Malformation”. 2006.
Davis, PJ, Cladis, FP, Motoyama, EK. “Smith's Anesthesia for Infants and Children”. 2011.
Cote, C, Lerman, J, Todres, D, Frei, F, Erb, T, Jonmarker, C, Sumpelmann, R, Werner, O. “A Practice of Anesthesia for Infants and Children”. 2009.
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