What the Anesthesiologist Should Know before the Operative Procedure
Vertebral fractures can be pathologic (metastatic cancer), degenerative (osteoporosis), or traumatic (motor vehicle accident, fall, sports, gunshot).
The most common sources for spinal metastatic disease are lung, breast, gastrointestinal, and prostate cancers.
In osteoporotic patients, vertebral fractures occur twice as often as fractures of other bones (hip, wrist).
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Traumatic vertebral fractures result from underlying mechanisms that often lead to concomitant injuries. Thus, the urgency of the repair must be balanced against the need to surgically address more pressing life-threatening issues (such as intracranial, intrathoracic, or intra-abdominal hemorrhage). Furthermore the decision to operate will also be dictated by the presence of a coexisting spinal cord injury.
Spinal cord injury can be complicated by neurogenic shock. Because of decreased sympathetic modulation from upper motor neurons, the latter is characterized by the presence of bradycardia and hypotension.
In the setting of spinal cord injury, high-dose methylprednisolone has been traditionally advocated (bolus dose = 30 mg/kg; infusion = 5.4 mg/kg/h for 24 hours if implemented within 3 hours of injury and for 48 hours if implemented within 8 hours of injury). Methylprednisolone was thought to provide minimal benefits if started more than 8 hours after the initial injury. However, citing methodological flaws of the NASCIS trials and potential side effects (hyperglycemia, increased risk of infection, delayed wound healing, gastrointestinal hemorrhage), multiple authors have questioned its use. Thus, the use of high-dose intravenous methylprednisolone should be discussed with the surgical team.
1. What is the urgency of the surgery?
What is the risk of delay in order to obtain additional preoperative information?
Repair of vertebral fractures are considered emergent in the presence of spinal cord injury. Animal data suggests that surgical intervention should take place within 3-6 hours in order to optimize neurological outcome.
In the absence of neural deficits, surgery can be delayed until additional preoperative information is obtained.
As with other emergent surgical procedures, the main issues pertain to the difficulty in obtaining a complete patient and medication history, the full stomach status as well as the limited time available to optimize the patient for surgery. Furthermore, the anesthesiologist should also be cognizant of the fact that, in the setting of traumatic fractures, coexisting injuries can be overlooked during the initial assessment.
When surgery can be safely delayed, a more thorough assessment can be obtained. Furthermore, fasting status can be implemented.
2. Preoperative evaluation
The most urgent medical conditions requiring immediate attention are coexisting intracranial, intrathoracic, or intra-abdominal trauma, possible spinal cord injury, and an unstable cervical spine.
Other anesthetic concerns stem from comorbidities (in geriatric patients) and iatrogenic complications (in cancer patients). See below.
In the setting of concomitant injuries, surgery should be temporarily delayed until life-threatening injuries are addressed and hemodynamic stabilization achieved.
3. What are the implications of co-existing disease on perioperative care?
The anesthetic implications related to repair of spinal fractures stem from coexisting diseases (for pathologic and osteoporotic fractures) and coexisting trauma (for traumatic fractures). Furthermore, coexisting treatment (such as chemotherapy) can also impact perioperative care.
b. Cardiovascular system
Preexisting cardiomyopathy can be due to chemotherapy treatment (such as doxorubicin, fluorouracil, anthracycline).
When present, neurogenic shock is characterized by the presence of bradycardia and hypotension (due to the decreased sympathetic outflow from upper motor neurons). It is usually treated with judicious fluid administration and vasopressors. In contrast, hemorrhagic shock, characterized by tachycardia and hypotension, is treated with fluids, blood products, and vasopressors. Distinction between the two conditions is paramount, as overly aggressive fluid therapy can lead to pulmonary edema in neurogenic shock.
In the setting of spinal cord injury, the goals of hemodynamic management revolve around the preservation of spinal cord perfusion pressure. This can be aided by the insertion of arterial and central venous as well as urinary catheters.
c. Pulmonary
Preexisting pulmonary fibrosis can be due to chemotherapy treatment (most notably bleomycin).
In the setting of polytrauma, rib fractures, pneumothoraces, and pulmonary contusions can lead to altered oxygenation and ventilation.
Acute fractures of the cervical spine may be associated with sufficient myelotrauma to cause acute respiratory insufficiency and inability to handle oropharyngeal secretions.
In the setting of a compromised airway or altered oxygenation and ventilation, endotracheal intubation with mechanical ventilation must be immediately implemented.
In the setting of spinal cord injury, the goals of ventilatory management revolve around the avoidance of hypoxemia and hypocapnia in order to preserve spinal cord perfusion pressure. Furthermore hypercapnia should also be avoided in the presence of a coexisting intracranial injury.
d. Renal-GI:
Preexisting renal/ bladder damage can result from chemotherapy treatment (such as methotrexate, cisplatin, cyclophosphamide, mitomycin-C). Hypotension should be actively treated to prevent the occurrence of acute prerenal failure.
The use of high-dose methylprednisolone can predispose the patient to gastric ulcers/hemorrhage.
e. Neurologic:
Preservation of cerebral perfusion pressure and control of intracranial pressure are paramount.
Vertebral fractures can lead to spinal cord injury. Preservation of spinal cord perfusion pressure, early surgical intervention, and, possibly, high-dose methylprednisolone should be implemented.
Preexisting peripheral neuropathy can result from chemotherapy treatment (such as cisplatin and vincristine).
f. Endocrine:
Paraneoplastic syndromes (such as Lambert-Eaton syndrome, Cushing’s syndrome, or SIADH) can be seen in patients with pathologic vertebral fractures.
When a methylprednisolone regimen is employed, blood glucose should be closely monitored to prevent the development of hyperglycemia.
g. Additional systems/conditions which may be of concern in a patient undergoing this procedure and are relevant for the anesthetic plan.
Airway: Securing the airway may be challenging in the presence of coexisting facial trauma. Cervical motion should be avoided in the presence of cervical spine fractures. Nasotracheal intubation should be avoided in the context of intracranial injury. Trauma patients should be considered at risk for aspiration.
Hematologic: Myelosuppression can result from prior chemotherapy treatment (such as azathioprine). In trauma patients, massive transfusion can lead to dilutional coagulopathy.
Metabolic: If spinal injury and paralysis have been present for more than 24 hours, succinylcholine can lead to hyperkalemia due to the proliferation of extrajunctional receptors on skeletal muscles. Thus a non depolarizing neuromuscular blocker should be used.
Musculoskeletal: Patients are at risk for pressure ulcers if positioned more than 2 hours on the backboard. For patients positioned prone during surgery, care must be taken to adequately pad pressure points.
Other: Isolated vertebral fractures occur most commonly in geriatric patients. The anesthesiologist should be cognizant of issues related to this patient population (decreased cardiopulmonary reserve, altered drug metabolism, polypharmacy, risk of hypothermia).
4. What are the patient's medications and how should they be managed in the perioperative period?
In a trauma setting, the anesthesiologist may not have full access to the patient’s complete list of medications. Typically, most medications are held until hemodynamic stabilization is achieved.
For elderly patients undergoing spinal fracture repair, a detailed medication history should be obtained. Pulmonary, antihypertensive and antianginal medications should be continued. As for anticoagulants, a discussion with the surgeon and the patient’s primary physician is warranted because of coexisting pathologies (metallic valves, coronary stents, history of cerebral vascular accidents). If required, bridging anticoagulant therapy can be implemented.
h. Are there medications commonly seen in patients undergoing this procedure and for which there should be greater concern?
In a trauma setting, antihypertensive agents and anticoagulants should be held.
i. What should be recommended with regard to continuation of medications taken chronically?
See above.
j. How to modify care for patients with known allergies
In a trauma setting, the anesthesiologist may not have full access to the patient’s history of allergies. However, if possible, the latter should queried out and trigger agents avoided.
k. Latex allergy- If the patient is known for sensitivity or allergy to latex (e.g., rash from gloves, underwear, etc.), prepare the operating room with latex-free products.
A history of latex allergy should be sought out and the latter avoided, if indicated.
l. Does the patient have any antibiotic allergies?
First- and second-generation cephalosporins are the most commonly used antibiotic for repairs of spinal fractures. If the patient is beta lactam-allergic, clindamycin and vancomycin can be used as alternatives.
m. Does the patient have a history of allergy to anesthesia?
In a trauma setting, the anesthesiologist may not have full access to the history of prior anesthetics. When possible, the patient should be queried about a history of malignant hyperthermia and pseudocholinesterase deficiency as well as known allergies to local anesthetics and muscle relaxants.
5. What laboratory tests should be obtained and has everything been reviewed?
Basic laboratory tests include a hemoglobin level, electrolytes and a coagulation panel. Additional tests depend on the patient’s age (electrocardiogram) and comorbidities (stress test, echocardiogram, chest radiograph, pulmonary function tests).
In the setting of polytrauma, imaging tests (CT scans of the head, thorax and abdomen) should be reviewed to rule out the presence of occult injuries. Communication with the hospital’s blood bank is paramount to ensure that the patient has been adequately cross matched and blood products are available.
Intraoperative Management: What are the options for anesthetic management and how to determine the best technique?
For the repair of vertebral fractures, because of the length of the surgery and the need for prompt postoperative neurologic assessment, general anesthesia (with endotracheal intubation) is preferred.
a. Regional anesthesia
Regional anesthesia is not indicated for this procedure.
b. General anesthesia
In addition to issues related to patient positioning (see above), the main drawback related to general anesthesia stems from hypotension. The latter can be compounded by the presence of concomitant injuries and hemorrhagic/neurogenic shock. Hypotension should be actively treated in order to maintain an adequate perfusion pressure to the spinal cord and to the eyes.
To optimize spinal cord perfusion, coagulopathy and anemia should also be avoided. Thus the patient’s coagulation status and hemoglobin level should be serially monitored and judiciously corrected with blood products. In the presence of a cervical spine fracture (or when the latter cannot be excluded by radiological or clinical examination), cervical motion should be avoided during endotracheal intubation. Furthermore nasotracheal intubation should be avoided in the presence of a coexisting intracranial injury.
c. Monitored anesthesia care
Monitored Anesthesia Care is not indicated for this procedure.
6. What is the author's preferred method of anesthesia technique and why?
Prophylactic antibiotics must be given before surgical incision. First and second generation cephalosporins (cefazolin or cefuroxime) constitute the first choice. In case of beta-lactam allergy, clindamycin or vancomycin can be used.
Repair of spinal fractures is most often performed with the patient prone. Thus attention must be paid to positioning in order to avoid kinking of the endotracheal tube, ocular injury, as well as compression of pressure points and peripheral nerves.
Bleeding constitutes the most common intraoperative complication. Careful positioning is paramount in order to prevent abdominal compression and engorgement of the epidural veins. A slight head-up position may also help to decrease venous congestion.
Although different blood-sparing strategies have been studied for spinal fusion, the literature remains scarce for repair of vertebral fractures. Caution must be exercised when drawing parallels between the two surgical procedures.
For multilevel spinal fusion, antifibrinolytic agents (tranexamic acid, aminocaproic acid) have been shown to decrease blood loss. Of note, aprotinin should be avoided because of its unfavorable profile of side effects (most notably renal dysfunction). For spinal fusion, the available literature does not support the use of controlled hypotension, normovolemic hemodilution and intraoperative blood salvage. Furthermore controlled hypotension should be avoided in the presence of spinal cord injury.
a. Neurologic
Neurologic impairment can be due to surgical instrumentation. Furthermore intraoperative hypotension, hypoxia, hypocapnea, hyperglycemia, and anemia can worsen a preexisting spinal cord injury.
b. If the patient is intubated, are there any special criteria for extubation?
For trauma patients, extubation should be delayed until the anesthesiologist is confident that the patient is hemodynamically stable and no additional surgical interventions are required.
In the setting of cervical fracture repair, the anesthesiologist should ensure that surgical hemostasis is adequate before attempting extubation. Because surgical fusion/ instrumentation will restrict cervical motion, emergent reintubation (due to cervical hematoma) is fraught with difficulties. In case of doubt, the patient should be kept intubated postoperatively and monitored for signs of airway compression. A prolonged prone position can lead to glottic edema. A leak test can be performed before attempting extubation. The leak test involves the demonstration of air passage around the endotracheal tube with the cuff deflated. The absence of a leak suggests the presence of glottic edema: thus the anesthesiologist should consider delaying extubation.
c. Postoperative management
Postoperatively, polytrauma patients should be transferred to the intensive care unit. If hemodynamically stable, patients undergoing repair of pathologic or osteoporotic fractures (without spinal cord injury) can be transferred to the ward.
Multimodal analgesia (acetaminophen, opioids, gabapentin, or pregabalin) can be used for postoperative pain control. Nonsteroidal anti-inflammatory drugs (NSAIDs) are often held to minimize the risk of postoperative bleeding and delayed bone healing. Alternatively, if NSAIDs are required for pain control, the issue can be discussed with the surgical team.
The most feared postoperative surgical complications include bleeding and neurologic deficits. Prompt assessment is paramount to assess the need for surgical reexploration. Airway compromise (due to cervical hematoma or glottic edema) can also occur postoperatively (see above). Another devastating complication after spine surgery is visual loss. The latter has been linked to a prolonged prone position (>6.5 hours) and large intraoperative blood loss (>45% of blood volume). Intraoperatively the anesthesiologist should avoid hypotension and anemia and ensure that ocular compression does not occur during (prone) positioning. A slight head up position may avoid ocular venous congestion. Dural laceration can also occur during repairs of spinal fractures. Less commonly, pneumothoraces have been reported after surgery of the cervical and thoracic spines.
For repairs of cervical fractures, other surgical complications include injury to the cervical sympathetic plexus (Horner’s syndrome), recurrent laryngeal nerve (hoarseness), and esophagus. In the setting of iliac bone graft harvesting, donor site problems include chronic pain, vascular injury and trauma to the lateral femoral cutaneous, and ilioinguinal nerves. Furthermore the medial branch of the superior cluneal nerve (terminal end of the posterior rami of the L1-2-3 spinal nerves) also passes over the iliac crest and thus can be damaged during bone harvest.
What's the Evidence?
SPINAL CORD INJURY:
Kirke Rogers, W, Todd, M.. “Acute spinal cord injury”. Best Pract Res Clin Anaesthesiol.. vol. 30. 2016. pp. 27-39. (An elegant and topical review)
HIGH-DOSE METHYLPREDNISOLONE:
Bracken, MB, Shepard, MJ, Collins, WF. “A randomized controlled trial of methylprednisolone or naloxone in the treatment of acute spinal cord injury: results of the Second National Acute Spinal Cord Injury Study”. N Engl J Med. vol. 322. 1990. pp. 1405-1411.
Bracken, MB, Sheard, MJ, Holford, TR. “Administration of methylprednisolone for 24 or 48 hours or tirilazad mesylate for 48 hours in the treatment of acute spinal cord injury: results of the Third National Acute Spinal Cord Injury Randomized Controlled Trial. National Acute Spinal Cord Injury Study”. JAMA. vol. 277. 1997. pp. 1597-1604.
Rozet, I.. “Methylprednisolone in acute spinal cord injury. Is there any other ethical choice?”. J Neurosurg Anesthesiol. vol. 20. 2008. pp. 137-139.
BLOOD-SPARING STRATEGIES FOR SPINAL SURGERY:
Theusinger, OM, Spahn, DR.. “Perioperative blood conservation strategies for major spine surgery”. Best Pract Res Clin Anaesthesiol.. vol. 30. 2016. pp. 41-52. (An elegant and topical review)
PERIOPERATIVE VISUAL LOSS
Kla, KM, Lee, LA.. “Perioperative visual loss”. Best Pract Res Clin Anaesthesiol.. vol. 30. 2016. pp. 69-77.
“Practice advisory for perioperative visual loss associated with spine surgery”. Anesthesiology. vol. 104. 2006. pp. 1319-1328.
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