Postoperative management and adverse events after spine surgery

1

What types of adverse events are encountered in the early postoperative period following spinal procedures?

In the postoperative period, adverse events (AEs) may involve the surgical site or arise due to systemic or medically related causes. Surgical site AEs include those related to the surgical approach, neural decompression, spinal instrumentation, bone graft site, wound healing, and wound infection. Systemic or medically related AEs include events that involve the cardiac, pulmonary, gastrointestinal, hematological, renal, and neurological systems, as well as AEs such as electrolyte abnormalities, medication-related side effects, and alcohol or narcotic withdrawal. A spine surgery focused AE classification system, the Spine Adverse Events Severity (SAVES) system, has been developed and validated to facilitate identification and recording of AEs related to spine surgery ( Table 23.1 ).

2

What is the rationale that supports a distinction between the terms “adverse event” and “complication”?

As noted by Rampersaud, (1), the terms “adverse event” and “complication” are often used interchangeably despite their different meanings. An AE is defined as “any event that is due to medical or surgical management, and not due to the underlying disease process or injury, which leads to harm of the patient or requires additional monitoring or treatment.” In contrast, complications are defined as “a disease or disorder, which, as a direct or indirect consequence of a surgical procedure, will change the expected outcome of the patient.” It has been documented that AEs occur frequently in association with spine surgery, but the majority of these events are not associated with clinical sequelae. To improve patient safety it is recommended to track all AEs regardless of clinical consequence to facilitate quality improvement, patient safety activities, and consistent AE reporting.

3

What are some factors that increase the risk for airway compromise following anterior cervical surgery and how do these factors influence postoperative airway management?

Acute airway compromise following anterior cervical procedures is associated with the need for reintubation and/or prolonged intubation, as well as additional sequellae, including pneumonia, prolonged intensive care admission, tracheostomy, and death. Postoperative airway compromise may develop following anterior cervical surgery due to hematoma, laryngopharyngeal edema, prevertebral soft tissue swelling, displacement of anterior spinal implants, or bone grafts or retropharyngeal abscess. Surgical risk factors associated with postoperative airway compromise following anterior cervical procedures include exposure of more than three vertebral bodies, blood loss >300 mL, exposures involving C2–C4, operative time >5 hours, combined anterior-posterior cervical surgery, and use of bone morphogenetic protein (BMP). Patient risk factors for development of postoperative airway compromise include morbid obesity, obstructive sleep apnea, pulmonary disease, spinal cord injury, cervical myelopathy, and previous anterior cervical surgery.

Various protocols are suggested for safe airway management following anterior cervical surgery based on surgical and patient-related risk factors. Lower risk patients are extubated following surgery. It is recommended that higher risk patients remain intubated overnight following surgery, with the head of the bed elevated 30°. Patients are evaluated for extubation based on weaning parameters obtained without sedation and following a cuff-leak test or fiber-optic bronchoscopy to verify airway patency. A cuff-leak test is performed in an awake patient by verifying air flow around the endotracheal tube after deflating the cuff and occluding the end of the endotracheal tube. The optimal time to extubate a high-risk patient following cervical surgery is controversial. Extubation should be attempted only when appropriate staff are available to manage a failed extubation. The peak time for development of airway compromise is 24–48 hours following surgery. Patients intubated beyond 1 week are considered for tracheostomy.

4

Describe the management of a patient who develops acute respiratory compromise following anterior cervical surgery.

An acute postoperative respiratory crisis in a patient who has been extubated following anterior cervical surgery is most commonly due to hematoma or laryngopharyngeal edema. Some general management guidelines related to management of patients with postoperative respiratory compromise include:

• The hospital’s emergency response system should be activated and additional staff called for assistance, including members of the anesthesia and surgical teams.

• If the patient’s status is noncritical and not life-threatening, the patient should be transported to an operating room as this is the optimal setting for securing an airway.

• For patients in respiratory arrest, ventilation is initiated with oxygen using a bag-valve mask system.

• If ventilation remains inadequate after 1 minute, oral intubation is attempted.

• If the initial intubation attempt is unsuccessful, the anterior surgical wound is opened and decompressed by removal of any hematoma if present.

• A second attempt at intubation is performed.

• If the second attempt at intubation is unsuccessful, the physician should perform a cricothyroidotomy.

5

What are some causes of dysphagia and dysphonia following anterior cervical spine surgery?

Dysphagia is defined as difficulty swallowing solids and/or liquids. The etiology of dysphagia following anterior cervical surgery is multifactorial and includes denervation, soft tissue swelling, and scar tissue formation. Risk factors for postoperative dysphagia include multilevel anterior surgical exposures, extended operating times, advanced age, use of rhBMP-2, prominent anterior cervical plates, and use of postoperative cervical immobilization. Swallowing is a complex multiphase activity, involving oral, pharyngeal, and esophageal phases, each phase controlled by different neurologic mechanisms. Important neurologic structures involved in swallowing that are placed at risk during anterior cervical procedures include the hypoglossal nerve (C3 level or above), superior laryngeal nerve, and pharyngeal plexus (C2–C5 levels) and the recurrent laryngeal nerve (C5–C7 levels). Postoperative dysphagia occurs in over half of patients who undergo anterior cervical spine surgery but the majority of patients experience improvement by 6 months. Persistent dysphagia after 1 year is reported in 12%–14% of patients. Evaluation of patients with severe and/or persistent dysphagia should include imaging of the operative site, speech pathology evaluation, swallowing studies, and evaluation for placement of a feeding tube.

Dysphonia is defined as hoarseness or alteration in the volume, pitch, or quality of the voice. Causes include nerve injury, vocal cord trauma, or postoperative edema, involving the larynx and vocal folds. Hoarseness is most commonly associated with injury to the recurrent laryngeal nerve. Injury to the superior laryngeal nerve during anterior cervical surgery can also produce hoarseness, as well as adversely affecting vocal quality, pitch elevation control, and vocal range. Dysphonia following anterior cervical surgery is less common than dysphagia, and has been reported in up to 30% of patients. Patients with severe and/or chronic dysphonia should be referred for evaluation by a speech therapist and/or otolaryngologist.

6

List some potential causes of neurologic deficits that are diagnosed following spinal procedures.

• Direct intraoperative neural trauma (e.g., during surgical exposure, related to decompression procedures, or as a result of neural impingement by spinal implants)

• Spinal deformity correction (e.g., L5 root injury during L5–S1 spondylolisthesis reduction)

• Acute vascular etiology (e.g., intraoperative hypotension, disruption of critical segmental blood vessels supplying the spinal cord during anterior surgical approaches)

• Subacute vascular etiology (neurologic deterioration may develop as late as 96 hours after spinal reconstructive surgery due to poor perfusion of the spinal cord and/or nerve roots)

• Patient positioning during surgery (e.g., brachial plexopathy, compressive neuropathy involving the ulnar or peroneal nerves, lower extremity compartment syndrome, cervical cord injury secondary to intraoperative neck positioning in a patient with cervical stenosis)

• Postoperative bleeding resulting in epidural hematoma and neural compromise

• Miscellaneous causes: cerebrovascular accident, transient ischemic attack, subarachnoid or intracerebral hemorrhage, and seizures

7

What basic elements comprise an adequate neurologic assessment of the postoperative spine patient?

Initial neurologic assessment after spine surgery should, at a minimum, include assessment of upper and lower extremity neurologic function (motor strength, sensation). It is not adequate to simply record that a patient was able to move their fingers or wiggle their toes as documentation of intact upper or lower extremity neurologic status. Documentation of function of the major motor groups in both upper and lower extremities is required. Neurologic examination is performed at regular intervals following surgery (i.e., every 2 hours for the first 24 hours, every 4 hours for the next 48 hours, and once every shift until discharge following major surgical procedures). When clinically appropriate, results of evaluation of voluntary anal contraction, deep anal pressure, perineal sensation, and bladder function are recorded. New-onset neurologic deficits require prompt imaging to rule out acute spinal cord or nerve root compression.

8

Describe the clinical presentation of a postoperative epidural hematoma.

Epidural hemorrhage involving the cervical or thoracic region may compress the spinal cord and classically produces an acute, painful myelopathy. Reports of pain unrelieved with narcotic analgesics, or atypical neurologic symptoms or findings (e.g., unexplained numbness, balance difficulty, mild weakness), require careful evaluation because such symptoms may represent early manifestations of an epidural hematoma. Epidural hematoma involving the lumbosacral region may manifest as a cauda equina syndrome. Risk factors include postoperative coagulopathy, multilevel laminectomies, intraoperative blood loss exceeding 1000 mL, spinal cord vascular malformations, previous spine surgery, advanced age, and preoperative use of nonsteroidal antiinflammatory medications (NSAIDs). Treatment of a symptomatic epidural hematoma is emergent spinal decompression.

9

What is cauda equina syndrome?

Cauda equina syndrome is a complex of low back pain, bilateral lower extremity pain and/or weakness, saddle anesthesia, and varying degrees of bowel and/or bladder dysfunction. Treatment is prompt surgical decompression. Inadequate decompression of lumbar spinal stenosis is a risk factor for developing cauda equina syndrome in the postoperative period.

10

After an uneventful posterior spinal instrumentation procedure for idiopathic scoliosis in a teenage patient, unilateral anterolateral thigh numbness and discomfort are noted. What is the most common cause of this problem?

Pressure injury to the lateral femoral cutaneous nerve (also known as meralgia paresthetica) secondary to intraoperative positioning. If there is no associated motor deficit and the sensory examination confirms a deficit limited to the distribution of the lateral femoral cutaneous nerve, the diagnosis is confirmed. The prognosis for recovery is good.

11

An adult patient with grade 1 L5–S1 isthmic spondylolisthesis undergoes L5–S1 posterior spinal instrumentation (pedicle fixation), decompression, and fusion. Before surgery, the patient experienced only right leg symptoms. After surgery, the patient reports relief of right leg pain but has a new left L5 radiculopathy, which was not present before surgery. What are the likely causes?

A problem related to the left L5 pedicle screw resulting in neural impingement must be ruled out. Rates of pedicle screw malposition range from 0% to 2%. However, most of these screw misplacements do not result in any long-term sequelae. Radiographs can be helpful in ruling out gross screw misplacement. However, a computed tomography (CT) scan is preferred because it can provide an axial view and depict the exact screw location in relation to the L5 nerve root. Other potential causes of new-onset left leg pain include intraoperative nerve root injury, inadequate L5 nerve root decompression, L5–S1 disc herniation, and postoperative hematoma.

12

A nurse taking care of your patient calls you and reports that this patient has developed a small amount of wound drainage 5 days after a posterior lumbar decompression and fusion procedure for spondylolisthesis. The discharge planner has already made arrangements to transfer this patient to a skilled nursing facility today. What should you advise?

The patient’s transfer should be postponed, and the patient should remain hospitalized to permit evaluation by the surgical team. As a general principle, postoperative spine patients with wound drainage should not be discharged if drainage persists past the fourth or fifth postsurgical day as surgical exploration is frequently indicated. The differential diagnosis of postoperative wound drainage includes superficial or deep wound infection, seroma, hematoma, wound dehiscence, suture abscess, and cerebrospinal fluid (CSF) leak. Expectant management and oral antibiotic treatment are not appropriate when infection is suspected.

The most common symptom in a patient with a postoperative spinal wound infection is pain at the surgical site. Clinical signs may include tenderness with palpation along the incision, erythema, induration, and wound drainage. Additional findings may include general malaise, pain out of proportion to the expected typical postoperative course, and a low-grade fever. Cultures of drainage from the superficial wound are unreliable due to potential for contamination with skin flora, and cultures obtained via aspiration of deeper layers of the wound are preferable, but are associated with a low diagnostic yield. Laboratory tests including complete blood count (CBC) with differential, erythrocyte sedimentation rate (ESR), C-reactive protein (CRP) levels, and blood cultures are obtained. CRP levels peak within 2–3 days postoperatively and generally decrease towards normal within 14 days, and are superior compared to monitoring of ESR or white blood cell counts for detection of early infection. If infection is suspected on a clinical basis, surgical exploration should be undertaken to allow for debridement, intraoperative wound cultures and gram stain, and initiation of broad-spectrum antibiotic therapy.

13

How is a surgical site infection defined?

The United States Center for Disease Control classifies a surgical site infection (SSI) as superficial, deep, or organ space. A superficial infection occurs within 30 days of surgery, involves only skin and subcutaneous tissues, and is associated with one of the following: purulent drainage; positive culture obtained aseptically; wound opened by surgeon or designee, and presence of signs or symptoms such as localized pain, swelling, erythema, or heat; or diagnosis as such by a surgeon or designee. A deep infection occurs within 30 or 90 days depending on procedure (laminectomy, 30 days; fusion, 90 days), and involves the fascia and muscles along with one of the following: purulent drainage from deep tissues; a dehiscence or opening or aspiration by the surgeon with positive identification of microorganisms; abscess or other histologic signs of infection; and the presence of at least one sign or symptom, including fever (>38 degrees C), localized pain, or tenderness. An organ space infection occurs deep to the muscles and fascia and has similar criteria as deep infection.