Chapter 11 – Anesthesia for Craniofacial Surgery

Chapter 11 Anesthesia for Craniofacial Surgery

Elaina E. Lin and Paul A. Stricker

Introduction

Anesthetic management of children undergoing craniofacial reconstruction surgery represents an important domain of neuroanesthesia that is specific to the pediatric anesthesiologist. Craniofacial surgical procedures as discussed herein refer to reconstructive surgical procedures of the bones of the head and face most commonly performed to treat craniofacial deformity secondary to craniosynostosis. These procedures are generally performed at tertiary pediatric medical centers, as the incidence of craniosynostosis is only approximately 1 in 2,000 live births. The goals of these operations are twofold: to normalize skull shape and appearance and to prevent neurocognitive sequelae that can occur secondary to increased intracranial pressure (ICP) associated with craniosynostosis.

In those children at risk for neurodevelopmental disturbances arising from elevated ICP due to craniosynostosis, the benefit of cranial vault remodeling and expansion is easily appreciated. However, what is often underappreciated is the profound, positive, lifelong effect normalization of appearance can have for all children with skull deformities from craniosynostosis. Taken together with the myriad challenges of providing safe anesthetic care, it is unsurprising that many pediatric anesthesiologists derive great satisfaction in ensuring a safe perioperative course for children undergoing these surgeries.

Preoperative Assessment and Preparation

Patients undergoing craniofacial surgery require a thorough history and physical as well as laboratory testing prior to their procedure. The majority of infants presenting with craniosynostosis (80–95%) present with isolated forms of craniosynostosis; that is, they present as a premature fusion of one or more sutures not in association with a constellation of other abnormalities. Most of these children with isolated craniosynostosis are otherwise healthy.

In the remaining cases, craniosynostosis occurs as syndromic craniosynostosis. These forms of craniosynostosis are less common and are associated with typical associated physical features depending on the syndrome. Syndromic forms of craniosynostosis (and their associated incidence) include but are not limited to Apert syndrome (1 per 65,000), Crouzon syndrome (1 per 60,000), Pfeiffer syndrome (1 per 100,000), Saethre-Chotzen syndrome (1 per 25,000–50,000), and Muenke syndrome (1 per 10,000). Syndromic forms of craniosynostosis may have associated abnormalities such as midface hypoplasia and retrusion. These children may occasionally be difficult to intubate, and appropriate difficult airway preparation may be required. The more common respiratory challenge in children with syndromic forms of craniosynostosis is upper airway obstruction and obstructive sleep apnea. Preexisting upper airway obstruction and sleep apnea may necessitate postoperative tracheal intubation and mechanical ventilation in some children. In severe cases, some children require tracheostomy in infancy, which may ultimately be removed following midface advancement procedures performed when these children reach school age.

Preoperative laboratory evaluation should include a complete blood count (hemoglobin, hematocrit, platelet count) and a specimen for type and screen at a minimum. In most cases, cross matching of blood is warranted. Young infants tolerate only small volumes of blood loss and may be present for surgery at their physiologic red blood cell nadir. Even in procedures associated with low rates of transfusion, there is often the potential for unanticipated significant hemorrhage. Many centers routinely obtain a preoperative coagulation profile (prothrombin time [PT], international normalized ratio [INR], partial thromboplastin time [PTT]). Other centers reserve such testing for patients with a history or family history of bleeding disorders.

Patients with craniosynostosis may have elevated ICP. Elevated ICP may be diagnosed by ophthalmic exam or computed tomography (CT) scan or inferred from nonspecific findings like headaches in older children. However, many children with elevated ICP are asymptomatic. The incidence of elevated ICP in multiple suture craniosynostosis was 47% and in isolated single-suture craniosynostosis was 14%.¹ Although there is a relatively high incidence of elevated ICP, most children can safely be induced with an inhalational induction .

Surgical Procedures

Modified Pi Procedure

The modified pi procedure (so named for the similarity of the shape of the cut bone to the Greek letter pi) and its variants are open surgical procedures most commonly performed for sagittal craniosynostosis in infants 2–4 months old. These procedures do not involve bone grafting or complex reconstruction and are much shorter in duration as compared to complex cranial vault reconstruction procedures. Owing to the large scalp incision, extensive calvarial osteotomies, small size of patients, and time of surgery coincident with the nadir physiologic anemia of infancy, these surgeries carry risks of significant blood loss and transfusion is common. Open surgical techniques represent the traditional surgical approach to sagittal synostosis and remain the primary procedure at many centers. The principal advantage of the open approach is that the procedure is completed in a single operation and postoperative helmeting is not required.

Neuroendoscopic Surgery

The surgical technique of neuroendoscopically resecting a strip of the synostotic sagittal suture through two small scalp incisions followed by parietal barrel stave osteotomies was pioneered by Drs. Jimenez and Barone between 1996 and 1998.² The limited scalp incisions and reduced extent of cranial osteotomies allow for these procedures to commonly be performed without blood transfusion. However, owing to the difference in surgical technique, postoperative helmeting is required for up to 6 months to achieve the desired remodeling of skull shape.

Spring-Mediated Cranioplasty

Spring-mediated cranioplasty was first performed in infants during the same time period that neuroendoscopic approaches to craniosynostosis were developed. In spring-mediated cranioplasty, a more limited scalp incision is performed than with an open procedure, and the synostotic suture is cut free along its length and calibrated pretensioned springs are positioned between the cut edges of bone on either side of the released suture. The incision is then closed, and over the ensuing months the springs cause cranial expansion perpendicular to the affected suture and remodel skull shape. Once the desired remodeling is achieved, the springs are removed in a brief procedure a few months following the initial surgery. Like neuroendoscopic procedures, spring-mediated cranioplasty has the advantage of significantly reduced blood loss and transfusion compared to open procedures. Postoperative helmet therapy is also not required. The main drawback of this approach is the need for a second operation to remove the springs.

Complex Cranial Vault Reconstruction

Complex cranial vault reconstruction (CCVR) is typically performed in infants 6–12 months old to treat a wider array of cranial vault deformities, including those arising from metopic synostosis, unicoronal synostosis, multisuture craniosysnostosis, and syndromic craniosynostosis (Figure 11.1). These are open surgical procedures that involve wide scalp incisions, extensive craniotomies, and reconstruction of large areas of the cranial vault, often with bone grafting. Consequently, these are longer operations with greater amounts of blood loss and transfusion. Broadly, these procedures fall into three categories: fronto-orbital advancement/anterior cranial vault reconstruction, mid- and posterior cranial vault reconstruction, and total cranial vault reconstruction. In contrast to the other surgical procedures outlined above, CCVR is performed in older children as well as in infants.