Neuroskeletal system
A Anterior cervical diskectomy or fusion
Anterior cervical diskectomy or fusion is most commonly performed for symptomatic nerve root or cord compression. Compression may occur from protrusion of an intervertebral disk or osteophytic bone into the spinal canal. An intervertebral disk usually herniates at the fifth or sixth cervical levels. A bone graft may be taken from the iliac crest or backbone may be used.
2. Preoperative assessment and patient preparation
a) Airway assessment should include thorough assessment of the range of motion of the neck. Neurologic deficits with limited neck movement may require intubation with the head in a neutral position. Intubation can be performed using passive immobilization or in-line traction with assistance of the GlideScope. Awake fiberoptic intubation with proper positioning is the safest option. Avoid flexion, extension, and lateral rotation of the head.
b) Neurologic deficits should be documented. Patients typically complain of neck pain radiating down one arm, which can progress to weakness and atrophy.
c) Diagnostic tests include type and screen, complete blood count, and other tests as the patient’s condition indicates.
d) Preoperative medication and intravenous (IV) therapy: Patients may have considerable pain preoperatively and require a narcotic with premedication. If a difficult airway is anticipated, premedication should be used sparingly. Use a 16- or 18-gauge IV catheter with minimal fluid replacement.
a) A standard tabletop setup is used.
b) The patient is in the supine position with the arms tucked at the sides; a small roll may be placed under the shoulders. Pad elbows to avoid ulnar compression and use slight knee flexion because many patients also have lumbar disease. A doughnut or foam headrest may be used.
c) Use a single, 18-gauge nonpositional IV catheter (arms tucked) with minimal fluid replacement.
4. Perioperative management and anesthetic technique
(1) General anesthesia with endotracheal intubation is used.
(2) Tape the endotracheal tube (ETT) to the side opposite of where the surgeon stands. Keep tape out of the sterile field.
(1) The trachea and esophagus are retracted laterally while the common carotid is retracted medially. The temporal artery can be palpated to monitor for carotid artery occlusion. There is the potential risk of damage to the recurrent laryngeal nerve, major arteries, veins, esophageal perforation, or pneumothorax.
(2) Blood loss is usually not significant, but epidural venous oozing can occur.
(3) Patients with spinal cord compression have an increased risk for decreased spinal cord perfusion and may not tolerate intraoperative hypotension. An arterial line is beneficial in these patients for close blood pressure monitoring.
(4) Spinal cord monitoring with somatosensory evoked potentials (SSEPs) may be performed. If SSEP is used, maintain the anesthetic using less than 1 minimum alveolar concentration (MAC) of inhalation agent IV narcotics and neuromuscular blocking agents.
(5) The absence of muscle relaxation is required for intraoperative motor evoked potentials (MEPs) testing.
(6) If a nerve stimulator is used on the face, limit twitch application to when the surgeon is not operating because the face may move during stimulation.
(1) Most patients are extubated in the operating room after the procedure.
(2) Coughing and bucking on the ETT should be avoided because they can dislodge the bone plug. IV lidocaine can be administered before extubation. The neck must remain in a neutral position. A neck brace may be applied.
(3) Extubate before application of the neck brace; a jaw lift may be required. The patient should be awake before leaving the operating room to allow the surgeon to assess neurologic function.
(4) Consider leaving the patient intubated if there is large blood loss or fluid replacement, difficult intubation, multilevel surgery, or difficult tracheal retraction that can lead to tracheal or airway edema.
(5) Assess the patient’s voice for recurrent laryngeal nerve damage, which rarely causes airway obstruction and usually resolves in a few days to 6 weeks.
B Lumbar laminectomy or fusion
Lumbar laminectomy is most commonly performed for symptomatic nerve root or spinal cord compression. Compression may occur from protrusion of an intervertebral disk or osteophyte bone into the spinal canal. An intervertebral disk usually herniates at the L4 to L5 or L5 to S1 intervertebral space. A laminectomy procedure involves the complete removal of lamina.
Lumbar fusion is performed when there is instability of the spine. This instability often leads to lower back pain. Bone graft material can be obtained from the patient’s iliac crest or from backbone. Back injuries account for a large percentage of work-related injuries and are a leading cause of work absences.
2. Preoperative assessment and patient preparation
a) History and physical examination: Assess and document neurologic deficits of the lower extremities.
b) Diagnostic tests: Type and screen blood and obtain a complete blood count.
a) General anesthesia is most commonly used; however, local infiltrations and regional blockade are other options.
b) Regional blockade: This reduces blood loss and shrinks epidural veins; analgesia to T7 to T8 is required, and regional anesthesia cannot be used if nerve function will be tested.
c) Spinal: Hypotension may be accentuated with position changes.
(1) If the prone or knee-chest position is used, anesthesia is induced while the patient is on the stretcher.
(2) Position changes may be done in stages to avoid hemodynamic compromise. It may be necessary to lighten the anesthetic and increase fluids before the position change. A vasopressor may be needed to treat hypotension.
(3) Tape the ETT to the side of the mouth that will be positioned upward. Confirm ETT placement after positioning.
(1) Question the surgeon regarding the use of muscle relaxants. If nerve function is to be tested, a single dose of an intermediate nondepolarizing muscle relaxant may be used for intubation.
(2) Pad all pressure points, and check for pressure on the face every 15 minutes during surgery.
(3) Blood loss is rarely sufficient to necessitate deliberate hypotension. The wound may be infiltrated with an epinephrine solution to decrease intraoperative blood loss.
(4) Sudden profound hypotension may indicate major intraabdominal vessel (iliac, aorta) damage with bleeding occurring in the retroperitoneal cavity, which may not be visible to the surgeon.
(5) Infiltration of the wound with a local anesthetic will decrease postoperative pain.
(6) If the patient is positioned prone, do not administer more than 40 mL/kg of crystalloid over the duration of the procedure. This helps decrease the incidence of the patient developing ischemic optic neuropathy.
c) Emergence: Extubation is performed when the patient is supine. The patient may need to be awake at the end of the procedure to allow the surgeon to assess for neurologic deficits. If the operation was long and airway edema is of concern, the patient may need to remain intubated.
The patient can usually be transported in any position because stability of the back is rarely compromised. Postoperative complications may include hemorrhage, neurologic deficits, and visual loss.
C Spinal cord injuries
Spinal cord transection is the description of spinal cord injury that is manifested as paralysis of the lower extremities (paraplegia) or of all extremities (quadriplegia). Spinal cord transection above the level of C2 to C4 is incompatible with survival because innervation to the diaphragm is likely to be destroyed.
The most common cause of spinal cord transection is the trauma associated with a motor vehicle or diving accident that results in fracture dislocation of cervical vertebrae. Occasionally, rheumatoid arthritis of the spine leads to spontaneous dislocation of the C1 vertebra on the C2 vertebra, producing progressive quadriparesis. These patients can suddenly become quadriplegic. The most frequent nontraumatic cause of spinal cord transection is multiple sclerosis. In addition, infections or vascular and developmental disorders may be responsible for permanent damage to the spinal cord.
Spinal cord transection initially produces flaccid paralysis with total absence of sensation below the level of injury. Temperature regulation and spinal cord reflexes are lost below the level of injury. The phase after the acute transection of the spinal cord is known as spinal shock and typically lasts 1 to 3 weeks. Several weeks after acute transection of the spinal cord, the spinal cord reflexes gradually return, and patients enter a chronic stage characterized by overactivity of the sympathetic nervous system and involuntary skeletal muscle spasms. Mental depression and pain are pressing problems after spinal cord injury.
a) History and physical examination
(1) Cardiovascular: Electrocardiograph abnormalities are common during the acute phase of spinal cord transection and include ventricular premature beats and ST–T-wave changes suggestive of myocardial ischemia. Decreased systemic blood pressure and bradycardia are also common secondary to a loss of sympathetic tone. Generally, this condition can be treated effectively with crystalloid and colloid infusion vasopressor and atropine to increase the heart rate. Around 85% of patients with spinal cord transection above T6 exhibit autonomic hyperreflexia, a disorder that appears after the resolution of spinal shock and in association with the return of the spinal cord reflexes.
(2) Respiratory: A transection between the levels of C2 and C4 may result in apnea from denervation of the diaphragm. The ability to cough and clear secretions from the airway is often impaired because of decreased expiratory reserve volume. Vital capacity also is significantly decreased if the transection of the spinal cord is at the cervical level. Furthermore, arterial hypoxemia is a consistent early finding during the period after cervical spinal cord injury. Tracheobronchial suctioning has been associated with bradycardia and cardiac arrest in these patients secondary to vasovagal reflex, a finding emphasizing the importance of establishing optimal arterial oxygenation before undertaking this maneuver. Acute respiratory insufficiency and the inability to handle oropharyngeal secretions necessitate immediate tracheal intubation. Before intubation is initiated, the neck must be stabilized.
(3) Neurologic: Whereas patients with spinal cord trauma at the T1 level are paraplegic, traumas above C5 may result in quadriplegia and loss of phrenic nerve function. Injuries between these two levels result in varying loss of motor and sensory functions in the upper extremities. Careful assessment and documentation of preoperative sensory and motor deficits are important.
(4) Musculoskeletal: Prolonged immobility leads to osteoporosis, skeletal muscle atrophy, and the development of decubitus ulcers. Pathologic fractures can occur when these patients are moved. Pressure points should be well protected and padded to minimize the likelihood of trauma to the skin and the development of ulcers.
(5) Renal: Renal failure is the leading cause of death in patients with chronic spinal cord transection. Chronic urinary tract infections and immobilization predispose to the development of renal calculi. Amyloidosis of the kidney can be manifested as proteinuria, leading to a decrease in the concentration of albumin in the plasma.
(1) Laboratory tests: Arterial blood gas analysis substantiates the degree of respiratory impairment. Urinalysis, complete blood count, coagulation profile, electrolytes, type and crossmatch, and other tests are as indicated by the history and physical examination.
(2) Diagnostic tests: Computed tomography, magnetic resonance imaging, radiography of the injured parts, and other tests are as indicated by the history and physical examination.
(3) Medications: Premedication is useful in this patient population and is individualized based on patient need. Patients with acute spinal cord injury often receive methylprednisolone, 30 mcg/kg loading dose over 15 minutes and then 5.4 mg/hr for 23 hours. The efficacy of steroid administration after spinal cord injury is controversial.
(1) Standard emergency drugs are used.
(2) A standard tabletop is used.
(3) IV fluids are infused through a 16- or 18-gauge IV line with normal saline at 4 to 6 mL/kg/hr with a fluid warmer.
(4) Regardless of the technique selected for anesthesia, a drug such as nitroprusside must be readily available to treat precipitous hypertension. Nitroprusside administration, 1 to 2 mcg/kg/min, is an effective method of treating sudden hypertension.
Use general endotracheal anesthesia. Management of anesthesia in the patient with transection of the spinal cord is largely determined by the duration of the injury. Regardless of the duration of spinal cord transection, preoperative hydration helps to prevent hypotension during the induction and maintenance of anesthesia.
a) Induction: All trauma patients are considered to have full stomachs, and rapid-sequence induction should be performed. Succinylcholine is avoided in patients with spinal cord injury after 24 hours because of the risk of hyperkalemia from potassium release from extrajunctional receptor sites. Furthermore, succinylcholine-induced fasciculations can exacerbate spinal cord injury. Ketamine can be used in hemodynamically unstable patients if head trauma is not suspected. The anesthesia provider should determine whether the cervical spine radiographs have been cleared before intubation. Avoid manipulating the head and neck during intubation and positioning, which can cause further injury. If the patient’s neck is unstable or if difficult intubation is anticipated secondary to a halo device or a body jacket, an awake fiberoptic intubation should be performed. The awake intubation has the advantage of preserving muscle tone, which may protect the unstable spine, and the patient’s neurologic status can be assessed after the procedure. Blind nasal, awake fiberoptic nasal, or oral intubations are possible options depending on the patient’s condition. A rigid laryngoscopy can be performed with in-line axial stabilization.
(1) Standard: A single dose of neuromuscular blocking drug (vecuronium 10 mg) may be administered to relax the neck muscles. Additional doses of relaxants are rarely necessary.
(2) Position: For the anterior approach, the patient is positioned supine with a roll under the shoulders, and the head is moderately hyperextended. Check and pad pressure points. A cervical strap may be placed below the chin to apply continuous cervical traction; avoid pressure on ears and facial nerves. Accidental extubation can result if the chin strap slips off the chin. For the posterior approach, the patient is positioned either prone with horseshoe headrest or three-point stabilization using a special frame or bolsters that allow the abdomen to hang freely to prevent venous engorgement. Occasionally, the sitting position is used, and this increases the risk of venous air embolism.
(3) Hypotension: The loss of sympathetic compensation response makes these patients more susceptible to hypotension from positioning, blood loss, and positive-pressure ventilation. One may need to treat with fluids and pressors. The goal is to maintain a systolic blood pressure of 90 mmHg. An arterial line should be placed before induction.
(4) Autonomic hyperreflexia: Patients with chronic spinal cord injury should be monitored for autonomic hyperreflexia. This condition is associated with injuries above the level of T6. It may be precipitated by cutaneous or visceral stimuli below the spinal cord lesion. Bladder, bowel, or intestinal distention is known to produce autonomic overactivity. An adequate level of general or spinal anesthesia is paramount. Symptoms are hypertension, bradycardia, dysrhythmias, headache, sweating, piloerection below the lesion, vasodilation above the lesion, hyperreflexia, convulsions, cerebral hemorrhage, and pulmonary edema. Treatment consists of eliminating the stimulus; deepening the anesthetic; raising the head of the bed; and administering vasodilators, α-antagonists, or ganglionic blockers.
(5) Hypothermia: Warming devices are necessary because the patient’s core temperature will approach room temperature because of the interruption in sympathetic pathways to the hypothalamus.
After a cervical fusion has been performed, the patient may have a halo device or body jacket. The patient should be fully awake and able to manage his or her airway before extubation. Lidocaine can be administered down the ETT or intravenously to prevent coughing and bucking. The patient should have a tidal volume of greater than 5 mL/kg, a negative inspiratory force of 20 to 25 cm H2O, and vital capacity of greater than 15 mL/kg. Airway patency can be tested by deflating the cuff to determine whether the patient can breathe around the tube before extubation. The patient should be assessed for airway obstruction secondary to soft tissue occlusion or superior laryngeal nerve damage after extubation.
a) Airway obstruction is usually caused by soft tissue against the posterior pharyngeal wall. The neck fusion or postoperative traction or stabilization device (halo or body jacket) may impair attempts to open the airway. An oral or nasal airway may be required.
b) Pneumonia may result postoperatively.
c) Respiratory insufficiency can result from the development of a tension pneumothorax from entrainment of air through the surgical wound; oropharyngeal laceration during tracheal intubation; or bleeding into the neck at the surgical site, with progressive compression and occlusion of the airway.
d) The patient should be assessed for the presence of neurologic deficits. Reversible causes such as a hematoma should be excluded.
e) Deep venous thrombosis can occur from decreased blood flow and venous stasis. Heparinization and sequential compression stockings should be instituted.
f) Urinary retention may require urinary catheterization.
g) Stress ulcers and gastric ileus can be treated with a nasogastric tube, antacids, and H2-receptor antagonists.
D Thoracic and lumbar spinal instrumentation and fusion
Anterolateral, posterior, or combined anteroposterior approaches can be used to treat pathologic processes of the thoracic and lumbar spine. Spinal instrumentation refers to implanted metal rods affixed to the spine to correct and internally splint a deformed spine. Originally designed for scoliosis, posterior spinal instrumentation is commonly performed simultaneously with spinal fusion for a variety of diagnoses, including fracture, tumor, degenerative changes, and developmental spinal deformity. The original Harrington rod is the simplest and still considered by many to be the standard. Other procedures, such as segmental spinal instrumentation, can distribute correctional forces by sublaminar wiring (Luque) or by hook or screw (Cotrel-Dubousset) procedures that apply multilevel corrective forces on the rods. Bone chips from the posterior iliac crest are placed over the site of fusion. Harrington rodding or similar extensive spinal instrumentation procedures to correct spinal column deformities put the spinal cord at risk for ischemia secondary to mechanical compression of its blood supply. This complication has been mitigated with methods to assess spinal cord function intraoperatively. These include intraoperative testing of neurologic function (wake-up test) and SSEP monitoring. Wake-up testing requires an informed cooperative patient and a practice trial of patient responses.
The anterior approach may use the Dwyer screw and cable apparatus or Zielke rod. It offers a limited fusion area and less blood loss and can correct significant lordosis. There is a greater risk of damage to the spinal cord compared with the Harrington rod procedure. The spinal cord can be damaged from the vertebral body screw, especially in the smaller thoracic vertebral bodies and larger number of segmental spinal arteries that require ligation. The patient is positioned laterally, and a transthoracic or retroperitoneal approach is used. The potential for respiratory compromise is significant when using the thoracoabdominal approach. Surgery above the level of T8 requires a double-lumen ETT to collapse the lung on the operative side. The procedure may require the removal of the tenth or sixth rib (or both) and diaphragmatic manipulation.
An anteroposterior fusion may be required for patients with unstable spines. Usually, the anterior procedure is performed first followed by posterior instrumentation after 1 to 2 weeks. Immediate posterior fusion is possible when the area to be fused is small and the primary curvature is below the diaphragm. The anteroposterior approach necessitates an intraoperative position change. Anesthetic considerations are similar to those required for posterior instrumentation. Anesthetic concerns for thoracic and lumbar spine procedures are positioning, replacing blood and fluid losses, maintaining spinal cord integrity, preventing venous air embolism, and avoiding hypothermia. The wake-up test and SSEPs are frequently used.
Patients requiring spinal reconstruction usually have either idiopathic or acquired scoliosis. Scoliosis is a deformity of the spine resulting in curvature and rotation of the vertebrae, as well as an associated deformity of the rib cage. Scoliosis can be classified as idiopathic, neuromuscular, myopathic, congenital, or trauma or tumor related or as part of mesenchymal disorders. Most cases are idiopathic, with a male-to-female ratio of 1:4. Surgery is indicated when the curvature is severe (the Cobb angle is greater than 50 degrees or rapidly progressing). Spinal instability requiring surgery may also result from trauma, cancer, or infection. Patients with scoliosis need careful preoperative evaluation of their cardiac, pulmonary, neuromuscular, and renal systems because associated anomalies occur frequently.
a) History and physical examination
(1) Cardiovascular: Patients have an increased incidence of congestive heart disease mitral valve prolapse, right ventricular hypertrophy, pulmonary hypertension, and cor pulmonale. Pulmonary vascular resistance is increased independent of the severity of scoliosis.
(2) Respiratory: Respiratory impairment is proportional to the angle of lateral curvature. Respiratory involvement is more likely when the Cobb angle is greater than 65 degrees. There may be a decreased total lung capacity and vital capacity (restrictive pattern). Ventilation–perfusion mismatch and alveolar hypoventilation may result in hypoxemia. If vital capacity is less than 40% of predicted, postoperative ventilation usually is required. Patients with neuromuscular disease may also have impaired protective airway mechanisms and weakness of respiratory musculature, making them prone to aspiration and respiratory failure.
(3) Neurologic: If an intraoperative wake-up test is planned, the patient should be informed preoperatively and assured that the procedure will involve minimal pain. A practice wake-up test helps to establish a baseline assessment and teaches the patient what to expect. Careful preoperative assessment and documentation of the patient’s neurologic status are essential.
(4) Musculoskeletal: Cardiomyopathy is a common finding in patients with muscular dystrophy. These patients are more sensitive to myocardial depression from anesthetic agents, changes in sympathetic tone, and hypercapnia. Patients with muscular dystrophy may require postoperative ventilation secondary to muscle weakness, impaired secretion removal, and atelectasis. The use of succinylcholine is contraindicated in patients with muscular dystrophy because it may lead to hyperkalemia and cardiac arrest. These patients may be at risk for developing malignant hyperthermia. The use of nontriggering anesthetic agents and careful observation for signs of malignant hyperthermia are essential.
(5) Hematologic: Discontinue platelet inhibitors for 2 to 3 weeks before surgery. Autologous blood donation is recommended. Consider the use of intraoperative hemodilution, controlled hypotension, and cell-saver devices.
(1) Laboratory tests: Complete blood count, international normalized ratio, prothrombin time, partial thromboplastin time, arterial blood gases, electrolytes, type and crossmatch, and other tests as indicated by the history and physical examination
(2) Diagnostic tests: Chest radiographs, pulmonary function test, spine studies, electrocardiography, and other tests as indicated by the history and physical examination
(1) Antibiotics, vasodilators if hypotensive technique
(2) Standard emergency drugs, tabletop
(3) IV fluids through one to two large-bore IV catheters with normal saline at 8 to 10 mL/kg/hr with a fluid warmer
(4) Blood loss possibly significant; at least 2 units of packed red blood cells need to be immediately available.
General endotracheal anesthesia is used. For pediatric cases, preheat the room to 72° F to 78° F.
a) Induction: Standard; for prone cases, induction is performed while the patient is on the stretcher.
(1) Standard: If SSEPs are monitored, a constant state of anesthesia is used; stable hemodynamics and normothermia are essential. Question the SSEP technician regarding the use of nitrous oxide. The concentration of inhalation agents should be kept below 1 MAC. A sufentanil infusion of 0.25 to 1 mcg/kg/hr provides a continuous state of anesthesia and lowers the MAC of volatile agents. Muscle relaxation is acceptable and should be kept constant (1 twitch).
(2) Position: The patient is prone on a spinal frame or bolster. Avoid abdominal compression, which impairs cardiac and pulmonary function and increases bleeding through epidural engorgement. Pressure points must be carefully padded and routinely assessed, especially during controlled hypotension. Anterior procedures are often performed with the patient in the lateral position; the dependent limb, ear, and eye should be checked frequently.
(3) Wake-up test: Performed after completion of spinal instrumentation and requires 40 to 60 minutes of advance notice from the surgeon. Avoid narcotic or muscle relaxant boluses; decrease inhalation agent; hand ventilate; reverse muscle relaxants and narcotics (naloxone [Narcan], 20-mcg increments) if necessary; monitor train-of-four; and request hand squeeze followed by bilateral foot movement. Uncontrolled patient movement during a wake-up test can result in accidental extubation or dislodgment of the spinal instrumentation. Forceful inspiratory efforts may provoke venous air embolism. If the patient moves the hands and not the feet, the surgeon will decrease the spinal distraction. If movement still does not occur, be prepared to increase the blood pressure and transfuse to increase spinal cord perfusion. The possibility of a hematoma should also be considered. After completion of the wake-up test, the anesthesia provider must be prepared to anesthetize the patient rapidly (have propofol ready). Intraoperative wake-up tests are infrequently performed if SSEP and MEP monitoring occurs.
(4) SSEP indications of spinal cord ischemia should be treated by notifying the surgeon, restoring normal blood pressure, and decreasing cord traction. Discontinue inhalation agents and ensure adequate oxygenation. Immediate transfusion may be necessary.
(5) Controlled hypotension may be used to decrease blood loss. Inhalation agents, vasodilators, nitroprusside, or nitroglycerin (or a combination) are usually used to achieve a mean arterial pressure of 65 mmHg in normotensive patients or lower the systolic blood pressure 20 mmHg from baseline in hypertensive patients. A major concern with hypotensive technique is compromising spinal cord blood supply. Blood pressure should be reduced slowly before the incision and allowed to gradually return to normal after surgery.
(6) Ischemic optic neuropathy can lead to blindness and is associated with deliberate hypotension, an increased length of surgery, pressure on the eyes, excessive fluid administration, and anemia. Consider the importance of early blood transfusion in patients undergoing hypotensive technique.
(7) Hypotensive technique requires an arterial line and Foley catheter to monitor urine output (0.5-1 mL/kg/hr).
(8) If a venous air embolism is suspected, the wound is packed, and nitrous oxide is discontinued if in use. Attempt to aspirate air using the central venous pressure catheter, use fluids and pressors, turn the patient supine, and institute cardiopulmonary resuscitation if necessary.
a) Pulmonary insufficiency: Postoperative ventilation may be required in patients with severe respiratory impairment. A patient with a preoperative vital capacity of less than 40% of predicted usually requires postoperative mechanical ventilation. Aggressive postoperative pulmonary care should be emphasized.
b) Neurologic sequelae are the most feared complications, and it is important to assess and document the postoperative neurologic examination.
c) Postoperative pain management allows for early ambulation and compliance with the pulmonary care regimen. Opioids can be administered by the intrathecal, epidural, or parenteral route.
