Anesthesia Management

Introduction

Craniosynostosis surgery presents a unique set of challenges to the anesthesiology team caring for the patient, particularly when surgery is done on young infants. Amongst a number of potential problems and concerns, the two most prominent are extensive blood losses and venous air emboli (VAE). As each child is different and presents with unique characteristics and concerns, the preoperative assessment needs to be tailored to each individual patient. Airway evaluation and appraisal is essential, particularly in cases where craniofacial syndromes are present. The same applies to cardiac assessment in association with syndromes. Historically, treatment has evolved and nowadays, most craniofacial programs in large children’s hospitals perform the type of procedures commonly known as calvarial vault remodeling (CVR). These operations are extensive, invasive, traumatic in nature, and typically associated with large blood losses. For this type of procedure, baseline blood work needs to be collected preoperatively and should include hematological values, electrolytes, and coagulation studies. Given the concern for possible sudden large volume blood loss, blood products should be ordered and be available at time of induction. Craniosynostosis vault surgery is perhaps one of the only surgeries where the anesthesiology team gives the patient blood products prior to skin incision. This is particularly the case when the patient presents with low blood volumes and values. Careful monitoring of the patient during the surgery requires placement and insertion of arterial peripheral lines, a central venous line, multiple large bore intravenous lines, and Foley catheter.

With the introduction of minimally invasive endoscopic-assisted techniques in 1998, the overall anesthetic management of patients afflicted with craniosynostosis has evolved significantly. In this chapter we will present our team’s approach to the successful application of anesthetic management principles to minimally invasive craniosynostosis techniques.

Preoperative Evaluation and Assessment

A careful history is imperative to ascertain possible intraoperative risks and complications as well as to properly prepare for unexpected events. Salient points to consider include preterm versus term birth, congenital cardiac/pulmonary defects, history of increased intracranial pressure, and/or any other factors that required admission to the neonatal intensive care unit (NICU). The physical examination should be focused on the airway assessment, breath sounds, and cardiac examination. Patients with a history of heart murmur should have a cardiology consult and an echocardiogram performed prior to surgery. A final critical consideration is the physiologic anemia of the newborn. At the nadir of anemia, in full-term infants, hemoglobin levels may be as low as 9 to 10 g/100 mL at 6 weeks of age. Given the short anesthetic time and minimal blood losses associated with endoscopic craniosynostosis procedures, we do not routinely obtain extensive preoperative blood work but simply rely on a hemoglobin/hematocrit (H/H) level and a type and screen, which is obtained after the patient is induced under general anesthesia. We do not type and cross our patients as the need of a blood transfusion (postoperatively) has been very rare during the last 10 years.

Positioning Issues

Depending on the type of suture involved, the patient positioning will vary. In all circumstances, following intubation, the table will be rotated 180 degrees away from the anesthesia provider. This requires a heightened level of attention on the part of the anesthesia team. The length of the circuit is increased and there are more potential opportunities for circuit disconnect ( Fig. 6.1 ). For correction of metopic and coronal craniosynostosis, the patients are placed in neutral position, supine, the head resting on a cerebellar horseshoe headrest. The stability of this positioning affords a lessened chance for endotracheal (ET) tube movement or dislodgement. Patients presenting with lambdoid synostosis can be placed with head turned fully to the contralateral side resting on a cerebellar horseshoe headrest or can be placed on the lateral decubitus position, with the head also on a cerebellar headrest. Patients presenting with bilateral craniosynostosis are placed prone on a cerebellar headrest. Care must be taken that the eyes are fully protected and free of pressure ( Fig. 6.2 ). The most challenging of all positions in the modified prone (sphinx) position that is used to treat sagittal craniosynostosis. The sphinx mandates prone positioning with the neck in full extension. This type of positioning can cause migration of the ET tube in a cephalad direction. For this reason, it is recommended that the ET tube be placed 1 to 2 cm past the usual depth because, as the neck is hyperextended, the ET tube will migrate 1 to 2 cm above the carina for proper ventilation ( Fig. 6.3 ). It is critical that the presence of equal and bilateral breath sounds is confirmed after final positioning to avoid alterations in patient oxygenation and, ultimately, interruption of the case. Additionally, care should be taken to place a throat pack in order to minimize tube movement as well as make sure that the tube is securely taped to the face. Use of Mastisol and Tegaderm after adequate taping minimizes the chance of tube dislodgement ( Fig. 6.4 ). All pressure points should be adequately padded and include the shoulders, axillae, chest, wrists, knees, and ankles ( Fig. 6.5 ).