Of what anesthetic significance is scoliosis? What longer-term comorbidities should you expect by adolescence? What is the significance of the 90° curve? Why? What specific laboratory tests will you order for the respiratory system? Why? With what specific tests will you evaluate the cardiovascular system? Why? What other systems are you concerned about in this patient? Why?

Of what significance is the myelomeningocele for preoperative evaluation of the patient? Why? How would you evaluate the functioning of the ventriculoperitoneal shunt? Do you need a shunt series preoperatively?

Scoliosis surgery involves prone positioning, extensive tissue trauma, considerable blood loss, and extensive bone dissection which may result in fat or air embolism. In addition, there is the potential for spinal cord ischemia. The significance of a high degree of curvature is that as the curvature increases above 65° it produces rotational spinal deformity, narrowing of the chest cavity, and maldistribution of ventilation and perfusion. Progression of the rotational deformity may predispose to spinal cord ischemia during the surgical correction. The restriction of lung volumes from the primary disease process has its greatest effect on vital capacity. The vital capacity is further diminished by 60 % on the first postoperative day and gradually recovers over the following 7 days. Further ventilatory compromise can occur from splinting of muscles due to inadequate pain control after surgery and diminished central respiratory drive from opioid analgesics. Therefore, many patients require postoperative ventilatory support. Respiratory function can be assessed by pulmonary function tests (PFT) and a room air arterial blood gas (ABG). PFTs assess the mechanical function of the lungs and chest wall. It is effort-dependent and can be useful in a cooperative patient. ABGs assess the adequacy of gas exchange. I would use an ECG to evaluate rhythm abnormalities and conduction system abnormalities, particularly in patients with significant clinical impairment of the cardiorespiratory system. Long-standing severe scoliosis can increase pulmonary vascular resistance by several mechanisms: reduced pulmonary vasculature, increased alveolar capillary pressure by compression from deformed ribs, hypoxemia, and hypercarbia. More advanced testing, when indicated by clinical findings, might include echocardiography for structural abnormalities as well as assessment of myocardial performance. A cardiac MRI would be useful if the chest is severely deformed and the echo imaging window is restrictive. Other organ systems and issues to be concerned about in this patient include chronic urinary tract infection, obstruction, and possible renal insufficiency, patency of the VP shunt, and a Chiari type II malformation, often associated with abnormalities of ventilatory control [1].

The preoperative evaluation of a child with myelomeningocele should include an assessment of overall cognitive function, autonomic function (depending on the level of the spinal cord lesion), symptoms of VP shunt malfunction, control of seizures if present, extent of the neurological deficit, lower extremity contractures, and history of latex allergy, to which these patients are often susceptible. Contractures of the lower extremities and obesity due to non-ambulation require extra care to avoid pressure injury. Attention to the VP shunt includes the avoidance of compression and avoidance of the insertion of a central line on the ipsilateral side. Brain stem compression may occur by hyperextension of the cervical spine if a Chiari malformation is uncorrected. In general, there is a decreased requirement for neuromuscular blockade due to reduced muscle mass in the lower extremities and a reduced analgesic and anesthetic requirement for lower extremity and perineal surgery because of impaired sensation. Standard doses of opioids and other CNS depressants may cause excessive sedation and respiratory depression due to an unfavorable shifting of the carbon dioxide/minute ventilation response curve. Brain stem compression by the Chiari malformation produces a rightward shift of the carbon dioxide response curve as well. The patient does not need a sleep study unless there is a history of sleep apnea. Malfunctioning of the VP shunt produces symptoms and signs of increased intracranial pressure such as unexplained abdominal pain, nausea and vomiting, decline in school performance, decreased mental status, and persistent or morning headaches. A head and neck radiograph may be helpful to visualize shunt catheter disconnection and migration. CSF pressure can be measured through the ventricular reservoir. In the absence of an abnormal mental status or other findings of elevated intracranial pressure, a shunt series is of no significant benefit. An MRI with a contrast injection can resolve remaining questions about shunt function.

How will you monitor this patient? Is an arterial line necessary? Why/why not? Where would you place a central venous line? Why? When would you consider a pulmonary artery catheter? Why? Will end-tidal CO2 sampling be accurate in this patient? Why/why not? Is it likely that evoked potentials will be used to monitor this patient? Why/why not? Are somatosensory (SSEP) as well as motor evoked potentials (MEP) indicated?

Having had numerous prior procedures, the patient is terrified of needles and requests a mask induction. Your response? Why? How do you justify it to the patient?

What anesthetic agents would you use for maintenance? Why? Would the use of somatosensory evoked potentials affect your answer? Why/why not?

During surgery the patient becomes progressively difficult to ventilate, with PIP increasing from 25 to 45 cm. H2O, blood pressure falling from 100/64 to 64/34, oxygen saturation decreasing to 92 % from 99 %, and wheezing noted. You also note hives on the forearms. Your considerations? Why? What is your differential diagnosis? Specific therapeutic interventions? Why? Would diphenhydramine help? Cimetidine? Why/why not?

The patient loses 750 mL. of blood during the first 1.5 h of the procedure. At what point would you begin transfusion? Why? Even with autologous blood? Why/why not? What is the role of hetastarch in this case? Is there a disadvantage to using it? Why? What other efforts can you direct to blood conservation?

The patient should be monitored with routine noninvasive monitors as well as an arterial line. A central venous line (peripherally inserted central catheter (PICC) or formal central line) may be placed for the appropriate clinical context (difficult vascular access with anticipated prolonged perioperative course, anticipated significant blood loss, e.g., >1 blood volume). The internal jugular or subclavian veins, using ultrasound guidance, are reasonable choices. Judgment should be exercised when considering this option in patients with a VA shunt. In addition, a central line placed in the superior vena cava close to the right atrial junction may impede cerebral venous drainage and be a conduit for potential contamination. A pulmonary artery catheter should be considered if there is preoperative evidence of severe pulmonary hypertension and/or ventricular dysfunction in order to monitor ventricular filling pressure and guide fluid and inotropic therapy. ETCO₂ sampling may not be accurate because of severe ventilation-perfusion mismatch and increased respiratory dead space. It is not likely that somatosensory evoked potentials would be useful for this patient if sensory impairment is severe, and even in the presence of some sensation and motor function, baselines will often not be normal and changes from baseline may be difficult to interpret. Anesthetic technique choices are affected if EP monitoring is chosen because the dose of inhalation anesthetic has to be tailored to minimizing its effect on amplitude and latency of signals on SSEPs and neuromuscular blockade must be avoided in order to allow monitoring of MEPs.