Craniosynostosis

3-Month-Old Boy With Sagittal Craniosynostosis : Learning Points


1. Preoperative workup of an infant undergoing craniofacial surgery.
2. Relative risks for performing the repair at an early age.
3. Different surgical approaches and respective anesthetic management of
sagittal craniosynostosis 4. Anesthetic management of the infant 5. Rationale for administering fluids and blood products in infants.
6. Management of venous air embolism in infants.


Case: 3-month-old boy with sagittal craniosynostosis is scheduled for a surgical
repair of his defect.

Preoperative Evaluation:

1. What significant preexisting issues in a 3 month old boy presenting for
craniofacial surgery?
2. What are the inherent risks of early versus late correction of sagittal
craniosynostosis?
3. What are the different types of sagittal craniosynostosis? What are the significant
issues affecting the conduct of anesthesia?

The surgeon decides to perform an anterior pi procedure.
Anesthetic management issues:

1. How would you induce anesthesia on this infant?
2. What monitors are essential for the pi procedure? Would you apply the same
monitors if an open or endoscopic-assisted strip craniectomy were performed?
3. What are your end-points for fluid administration?


After induction of anesthesia and placement of monitors, the infant’s vital sign are, BP 68/30, HR 120, esophageal temperature of 36.4°C. During the craniotomy the surgeon notes increased blood loss. At the same time the blood pressure falls to 42/20.


1. What is your differential diagnosis for this sudden change? How would you
confirm your diagnosis?
2. What would be your therapeutic maneuvers?
3. Your arterial catheter fails to provide an arterial trace and you are unable to draw
a blood sample for measuring the hematocrit. What will be your triggers for fluid
and blood administration?


The infant is now hemodynamically stable, however his hematocrit is now 24%.
After the closure of the scalp incision, the surgeon would like to perform a
neurological examination at the conclusion of the surgery.


1. Would you administer blood to this infant? If the hematocrit is 22% at the end of
the surgery would you administer blood before leaving the operating room?
2. What are you criteria for extubating the infant’s trachea?
3. Does this infant need to be admitted to the intensive care unit?Sagittal Craniosynostosis


Craniosynostosis results from premature fusion of one of or a combination of cranial sutures in an infant. Although majority of craniosynostosis are solitary deformities with an incidence of 1 in 2100 children, craniofacial syndromes include some form of premature fusion of cranial sutures. Sagittal craniosynostosis is the most common form and represents 40-60% of nonsyndromic craniosynostosis. Since brain growth occurs rapidly in the in utero to the third year of life, the restrictive nature of this defect can lead to; impaired brain growth1, increased intracranial pressure, and psychologically devastating craniofacial deformities.2,3 Since all three progressively worsens with age, repairs of craniosynostosis are likely to have the best result if done early in life.1
However, these procedures are associated with loss of a significant percentage of an
infant’s blood volume, with great losses occurring when more sutures are involved.4
However, the physiologic nadir of the infant’s hematocrit is around 3 month, thus
decreasing the reserve for blood loss and increasing the necessity for blood transfusions.
Furthermore, there appears to be increased morbidity and mortality associated with
younger infants undergoing surgery due to undiagnosed congenital anomalies and
inadvertent anesthetic overdoses.5 Several surgical approaches for repair of sagittal craniosynostosis have been advocated. The most common is a sagittal strip craniectomy where the fused sagittal suture is resected. Jimenez and Barone have recently modified this approach by applying endoscopic surgical techniques, thus minimizing blood loss and extensive surgical dissection and exposure.6,7 Jane and colleagues advocate a more extensive complex vault remodeling (CVR) by proposing a pi procedure, which entails a pi shape craniectomy with extensive remodeling of the adjacent cranial plates.
Perioperative Blood Loss
Several investigators have reported the effect of the surgical procedure on blood
loss. Kearney and colleagues reported that sagittal craniectomies were associated with a mean blood loss of 24% of the estimated blood volume (EBV) or 20 ml/kg. Meyer and colleagues estimated a mean blood loss of 60±24.5% of EBV in strip craniectomies and 170.6±10.3% of EBV in CVR.8 They also reported postoperative blood loss of
35.9±38.4% and 44.5±97.6% of EBV for strip craniotomies and CVR respectively.
Faberowski and Black confirmed that simple strip craniectomies have substantially less blood loss than more extensive strip craniectomies with osteotomies and remodeling of the adjacent cranial plates.9 Furthermore, they reported that 96.3% of their patients received a blood transfusion. Rapid blood transfusion in an infant can result in hyperkalemia and cardiac arrest, primary due to high concentration of potassium in stored blood.10,11 Furthermore, coagulopathy is associated with blood loss approaching 1.5 times EBV.12 Given the inherent risks of blood transfusion, several investigators have advocated the use of autologous blood transfusion and induced hypotension.13-16 However, induced hypotension may not be suitable in infants because of the potential for venous air embolism and sudden hemorrhage.
Venous Air Embolism
Venous air embolism (VAE) detected by echocardiography and precordial
Doppler occurred in 66% to 83% of open craniectomies in infants.4,17 A precordialDoppler ultrasound can detect minute VAE and should be routinely used in conjunction with an end-tidal carbon dioxide analyzer and arterial catheter in all craniotomies to detect VAE. The Doppler probe is best positioned on the anterior chest, usually just to the right of the sternum at the fourth intercostal space. An alternate site on the posterior thorax can be used in infants weighting approximately 6 kg or less.18 Other monitors for VAE include, sudden drops in end-tidal CO2 and dysrrhythmias and/or ischemic changes in the electrocardiogram. Fortunately, direct morbidity and mortality rarely occur and the issue of Doppler monitoring has been challenged by Meyer.19 Recently, Tobias reported an 8% incidence of VAE during endoscopic-assisted strip craniectomies.20 Standard neurosurgical techniques may elevate the head of the table to improve cerebral venous drainage, which can increase the risk for air entrainment into the venous system through open venous channels in bone and sinuses.21 Patients with cardiac defects and potential for left to right shunt, such as patent foramen ovale or ductus arteriosus are at risk for paradoxical air emboli through these defects. Venous air emboli can be minimized by early detection with continuous precordial Doppler ultrasound and maintaining euvolumia. Therefore, induced hypotension should be avoided. When hemodynamic instability does occur, the operating table can be placed in the Trendelenburg position, flooding the surgical field with warm saline and sealing the sites of egress with bone wax and direct pressure. These maneuvers will augment the patient’s blood pressure and prevent further entrainment of intravascular air. Routine insertion of central venous
catheters for withdrawal of air is limited by the diminutive size of the infant and catheter because the ability of rapidly aspirate air decreases with the size of the catheter.
Hemodynamic Monitoring
Infants undergoing major craniectomies and CVR are at risk of sudden
hemodynamic instability due to VAE and hemorrhage. The slope of the autoregulatory in
an infant and rises significantly at the lower and upper limits of the curve, respectively. This narrow range, with sudden hypotension and hypertension at either end of the autoregulatory curve, places the infant at risk for cerebral ischemia and intraventricular hemorrhage respectively. Another developmental difference between adults and infants is the larger percentage of cardiac output that is directed to the brain, since the head of the infant and child accounts for a large percentage of the body surface area and blood volume. These factors place the infant at risk for significant hemodynamic instability during neurosurgical procedures and emphasize the importance of continuous blood pressure monitoring. An arterial catheter will also provide access for sampling serial blood gases, electrolytes and hematocrit. The utility of central venous catheterization remains controversial. Cannulation of the jugular or subclavian veins with multi-orificed catheters in adults is preferred, particularly to treat VAE. However, these catheters are too large for infants and most children. Furthermore, monitoring of the central venous pressure may not accurately reflect intravascular volume in small children, particularly in
the prone position. Therefore the risks may outweigh the benefits of a central venous
catheter. In infants, central venous catheter used for aspirating venous air was only
successful 33% of the time, presumably because of the high resistance of the small gauge catheters used in these patients.22
Postoperative Issues
The decision to extubate the infant’s trachea and admission to the intensive care
unit depends on the severity of blood loss and duration of the surgery. Since most of the surgical procedure is localized to the cranium, the airway rarely becomes edematous. Certainly the ability to maintain spontaneous respirations and demonstrate purposeful movement dictates the removal of the endotracheal tube. Postoperative pain can be initially managed with intravenous morphine in monitored settings and rapidly changed to acetaminophen. The major issue in the postoperative period is ongoing blood loss through the drains and incision.8,9 Serial hematocrits should be measured in order to guide additional blood transfusions.


References

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craniectomy for craniosynostosis repair. Anesthesiology 2000; 92: 20-3
5. Morray JP, Geiduschek JM, Ramamoorthy C, et al. Anesthesia-related cardiac
arrest in children: initial findings of the Pediatric Perioperative Cardiac Arrest
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sagittal craniosynostosis. J.Neurosurg. 1998; 88: 77-81
7. Jimenez DF, Barone CM, Cartwright CC, et al. Early management of
craniosynostosis using endoscopic-assisted strip craniectomies and cranial
orthotic molding therapy. Pediatrics 2002; 110: 97-104
8. Meyer P, Renier D, Arnaud E, et al. Blood loss during repair of craniosynostosis.
Br.J.Anaesth. 1993; 71: 854-7
9. Faberowski LW, Black S, Mickle JP: Blood loss and transfusion practice in the
perioperative management of craniosynostosis repair. J Neurosurg Anesthesiol.
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10. Brown KA, Bissonnette B, MacDonald M, et al. Hyperkalaemia during massive
blood transfusion in paediatric craniofacial surgery. Can.J.Anaesth. 1990; 37:
401-8