1 Preoperative Evaluation and Optimization

10.1055/b-0038-162462

1 Preoperative Evaluation and Optimization

Michael P. Kelly and Scott J. Luhmann

Abstract

Pediatric neuromuscular spinal deformity surgeries are complex due to the multisystem involvement of the diseases commonly encountered. Complication rates may exceed 25%, in a stark contrast to adolescent idiopathic scoliosis. A multidisciplinary approach is mandatory to minimize the risk of complication. Furthermore, the perioperative team should be well versed in the care of these complex patients. Malnutrition is not uncommon and nutrition should be optimized before surgery, as these are generally elective and not performed on an emergent basis. Some comorbidities are “fixed” and not modifiable, such as cardiomyopathy or seizure disorders. Thus, knowledge of perioperative management of these comorbid conditions is required to avoid potentially common pitfalls. The physical examination helps define patient needs and assists with surgical planning, including patient positioning, which may not be overlooked. The radiographic evaluation helps indicate surgery and define the fusion levels through an examination of curve rigidity. Magnetic resonance imaging is sometimes needed to ensure there is no intraspinal pathology. Computed tomography scanning helps identify landmarks for fixation and reveals areas of dorsal bone deficiency, such as spina bifida or prior surgeries. Finally, anticipation of postoperative needs must occur at the preoperative visit so that families and caretakers are prepared at the time of discharge.

1.1 Introduction

Pediatric neuromuscular spinal deformity patients are among the most challenging faced due to the number of comorbid conditions that often exist, potentially affecting the intraoperative and postoperative course and outcomes. ¹ Complication rates approach 25%, and these patients are more prone to perioperative complications, especially infection, than adolescent idiopathic scoliosis patients. ² ^, ³ ^, ⁴ ^, ⁵ Careful preoperative evaluation and optimization will help minimize complications related to neuromuscular spinal surgery. Additionally, input from other specialists can be important contributions to risk stratification, surgical planning and decision making, and, ultimately, informed consent.

Neuromuscular scoliosis is a heterogeneous disease with a wide array of causes, each requiring different preoperative evaluations. Neuromuscular disease can present anywhere along the spectrum from high muscular tone (spastic) to low muscular tone (flaccid). In addition, there are varying levels of cognition. Cerebral palsy (CP) is a heterogeneous diagnosis itself, again requiring an understanding of the underlying disease state to allow for appropriate preoperative optimization. In the authors’ experience, a formulaic approach to the preoperative evaluation for all neuromuscular patients, with a standard checklist applied to all patients regardless of diagnosis, is helpful. A thorough standardized checklist will help minimize missed data, which may, in turn, improve outcomes in this complicated population.

Several groups treating adult spinal deformity have shown that preoperative, multidisciplinary conferences and standardized care protocols are able to reduce complications and improve outcomes. ⁶ ^, ⁷ ^, ⁸ At the foundation of these care pathways are evidence-based reviews of the literature. A multidisciplinary team consisting of neurological and orthopaedic spine surgeons, anesthesiologists, intensivists, internists, and internists, use the review to develop preoperative, intraoperative, and postoperative care protocols. ⁶ ^, ⁷ The institution of a preoperative multidisciplinary conference has been shown to reduce postoperative complications and 30-day readmissions. ⁶ Zeeni et al have shown that an intraoperative care protocol reduced operative time and the need for allogenic blood transfusion. ⁸ The “team” approach to care was emphasized, with protocol violations rarely reported (2.6%). While no published evidence exists, yet, for this approach in neuromuscular spinal deformity, it stands to reason that this is an approach that centers should consider. At a minimum, “virtual” conferences can be held via electronic mail, where the concerns of all may be addressed and the patients optimized for these complex surgeries.

1.2 History and Review of Systems

All preoperative evaluations begin with a comprehensive medical history and review of systems. Polypharmacy is common in neuromuscular scoliosis, and all medications, with dosages, must be recorded. Of particular importance are cardiac medications, such as B-blockers and calcium channel blockers. In addition to providing the impetus for a cardiology consultation, these medications should be discussed with the anesthesia team to ensure proper perioperative administration. Cessation of some antihypertensives is associated with rebound hypertension, which can be dangerous and cause delays with surgery. In some cases of muscular dystrophy, cardiac arrhythmias may be present and prophylactic anticoagulation may be required. Appropriate risk stratification of anticoagulation cessation versus a bridge to shorter acting agents, such as enoxaparin, will require multidisciplinary input. Postoperative anticoagulation plans should be made before surgery.

1.2.1 Cardiopulmonary System

The cardiopulmonary system review must be exhaustive. Respiratory disease, and thus pulmonary complications, is common in neuromuscular spinal. ⁴ A comprehensive history will include details regarding any prior history of sleep apnea and prior sleep studies. The surgeon must also know whether the patient has a history of pneumonia, asthma, prior aspiration events, and any history of prolonged intubation. Consultation of a pulmonologist is recommended for all children confined to a wheelchair with a vital capacity less than 80% of expected. ⁹ The benefit in engaging a pulmonologist goes beyond the preoperative workup of optimization. Additionally, the pulmonologist can familiarize themselves with the patients, their history, baseline conditions, and preoperative workup. This permits more rapid and appropriate postoperative pulmonary care. When possible, pulmonary function tests (PFTs), via spirometry, should be obtained. In some cases, these are not possible due to patient cognition or participation. Other methods of PFT include whole-body plethysmography, gas dilution, and diffusion capacity. These methods are more complicated than spirometry and their benefit in neuromuscular spinal has not been shown. At a minimum, when spirometry is not possible, oxyhemoglobin saturation should be assessed with pulse oximetry. The benefit of PFTs is that they allow for more accurate informed discussion with patients and caregivers, while also helping plan postoperative care. The need for prolonged ventilation, prolonged intensive care unit time, and, in some cases, tracheostomy should be anticipated prior to surgery. ¹⁰ While interventions to improve PFTs before surgery are unlikely to be successful, knowledge of current lung function is necessary to provide informed consent to the patient and caretakers, as there is an immediate decrement in lung function after scoliosis surgery. ¹¹ Low PFTs (forced vital capacity < 30%) are not an absolute contraindication to surgery. ¹² ^, ¹³ However, neuromuscular spinal patients with low PFTs may be more likely to sustain perioperative complications, such as pneumonia, prolonged ventilator times, and postoperative tracheostomy. ¹⁰ ^, ¹⁴ Noninvasive intermittent positive-pressure ventilation is useful in the postoperative period, after extubation, and may help avoid postoperative tracheostomy. ¹⁵ ^, ¹⁶

The “difficult airway” should be identified before the operating room and induction of anesthesia. This includes patients with severe cervicothoracic deformities and small facies/airways. In these cases, preoperative evaluation should include the otolaryngology (ear, nose, and throat [ENT]) service for possible postoperative tracheostomy needs. Patients deemed to have “difficult airways” are marked as such in their chart and in their hospital rooms, with signs, notifying caretakers of this status and providing the emergency number to alert a code team, ENT, and a trauma attending in the case of airway compromise.

As noted, cardiovascular abnormalities are common in some muscular dystrophies but are entirely uncommon in other forms of neuromuscular spinal, such as CP and myelomeningocele. ¹⁷ Muscular dystrophies, such as Duchenne’s muscular dystrophy and Becker’s muscular dystrophy are commonly associated with a cardiomyopathy. It is important to recognize this, as the cardiomyopathy may go unnoticed and can be a cause of mortality in these patients. Furthermore, the phenotype expressed by patients with muscular dystrophies varies and the cardiomyopathy may be worse than the exhibited skeletal muscle involvement. Beyond assisting with perioperative planning, early identification of the cardiomyopathy offers a chance for intervention with protective therapies. Historically, electrocardiogram (ECG) and echocardiography have been used to assess cardiac status. More recently, however, cardiac magnetic resonance imaging (MRI) has been shown effective in identifying cardiomyopathy before ECG or echocardiogram changes are present. ¹⁷

Duchenne’s and Becker’s Muscular Dystrophies

Identification of cardiomyopathy in these patients may be delayed due to the profound skeletal myopathy exhibited. In Duchenne’s muscular dystrophy (DMD), cardiomyopathy often begins at age 3 to 7 years, prior to a definitive spinal fusion surgery. All patients with DMD who survive to the third decade of life suffer from cardiomyopathy. Decreased cardiac output and arrhythmias are complications most commonly associated with DMD and Becker’s muscular dystrophy (BMD). Recommended screening for cardiomyopathy currently consists of biannual ECG and echocardiograms in boys until age 10, then yearly thereafter; in girls, ECG and echocardiograms are recommended every 5 years after the age of 16. Evidence of cardiomyopathy has been found in girls without DMD and BMD, but with relatives suffering from these diseases, and a cardiac evaluation must be performed in these patients as well. Current evidence supports the use of angiotensin-converting enzyme (ACE) inhibitors or, in those patients intolerant of ACE inhibitors, angiotensin receptor blockers (ARB).

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