Anesthesiology

Anterior Cervical Fusion

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What the Anesthesiologist Should Know before the Operative Procedure

Anterior cervical discectomy (ACD) or anterior cervical discectomy and fusion (ACDF) is used to treat compressive cervical radiculopathy due to either cervical spondylosis or disc herniation. At present there is little evidence that ACDF provides better long-term outcomes compared to conservative treatments. A recent review of neurosurgical cases performed in the United States between 1993 and 2007 found that the largest volume trend is for spinal fusion surgery. In light of these data, expectations for rapid increases in patients presenting for anterior cervical fusion should be expected. As with all surgical subspecialties, more minimally invasive techniques are being tried as a replacement for some of these procedures.

1. What is the urgency of the surgery?

What is the risk of delay in order to obtain additional preoperative information?

The urgency of surgery should always be discussed with your surgical colleague if there is any concern for perioperative morbidity. Most patients scheduled for anterior cervical fusion have failed conservative therapy and their symptoms may have been stable for some time

Emergent: Patients with signs of worsening radicular symptoms that are concerning for loss of limb function either due to trauma or a significant change in their clinical course should be considered emergent. Emergent repairs are rare in the nontrauma setting.

Urgent: Patients with ongoing signs of radicular dysfunction that are worsening and may lead to permanent upper extremity dysfunction may be considered urgent.

Elective: The majority of cases, by far, are of an elective nature. These include patients who have pain (with or without radicular dysfunction) of the upper extremity that have failed conservative treatments for their symptoms (i.e., systemic or epidural steroids, NSAIDs, physical therapy, etc.). It is appropriate to gather all necessary preoperative information on these patients as delaying their procedure should not affect overall outcome.

2. Preoperative evaluation

As most anterior cervical fusions are elective procedures, one must evaluate the nature of pain symptoms that patients have been experiencing. It is quite difficult for clinicians to always differentiate the arm pain associated with cervical radiculopathy and that associated with cardiac ischemia. For this reason, the focused evaluation should always focus on major organ systems to include neurologic, cardiac, and pulmonary issues as well as liver function and disorders of coagulation.

Medically unstable conditions warranting further evaluation include coronary or cerebrovascular disease, new heart murmur, and uncontrolled hypertension or diabetes mellitus. These conditions should be addressed and optimized prior to performing the procedure.

Delaying surgery may be indicated if evidence is found for cardiac or cerebral ischemia, signs of congestive heart failure are present, electrolyte or coagulation disturbances are present, or if the patient has clinical risk factors for cardiac morbidity (ischemic heart disease, prior congestive heart failure, diabetes mellitus, chronic kidney disease, cerebrovascular disease) and further testing would aid in your management.

3. What are the implications of co-existing disease on perioperative care?

b. Cardiovascular system

Recent chest pain consistent with cardiac ischemia should be worked up prior to proposed elective surgery. In the setting of urgent or emergent surgery, the risk of proceeding with surgery must be balanced against the benefit of a delay for medical diagnosis and management of a coronary lesion. This issue has become more difficult in the era of drug-eluting cardiac stents, which require at least 6 to 12 months of antiplatelet therapy. If a patient has a discovered lesion amenable to coronary revascularization, a discussion between the surgeon, cardiologist, and anesthesiologist should take place to determine the type of stent to be placed with its attendant anticoagulants in order to determine the optimal timing of cervical fusion.

Baseline coronary artery disease or cardiac dysfunction: Preserving or improving myocardial oxygen supply while decreasing oxygen demand is one of the mainstays of management in this population. Maintenance of blood pressure and enrichment of inspired oxygen are other goals.

c. Pulmonary

Chronic obstructive pulmonary disease (COPD)

The presence of COPD may predispose patients to postoperative pulmonary complications. Functional status should be ascertained as well as need for supplemental oxygen. Patients with sputum production should be interviewed as to the onset and duration to rule out acute bronchitis or pneumonia prior to surgery. Bronchodilators should be maintained throughout the perioperative period to maximize lung function in the setting of surgery. If a patient has had a recent pulmonary infection, elective procedures should be delayed until lung function is back to baseline.

Reactive airway disease (asthma)

The asthmatic patient should be interviewed for recent exacerbations and triggers. If a patient has had a recent asthma exacerbation requiring an increase in frequency and dose of bronchodilators, consider delaying surgery until symptoms are back to baseline.

Obstructive sleep apnea (OSA)

Patients with OSA should bring their CPAP machines on the day of surgery. Given the relatively short operative time for one or two level fusions and brief hospital stays, patients should be monitored closely in the postanesthesia care unit for oxygen desaturation. There is a theoretical risk of anterior neck inflammation following ACD and ACDF, which could potentially exacerbate obstructive symptoms in this population.

d. Renal-GI:

There are no specific renal issues with this surgery.

e. Neurologic:

Dysphonia and dysphagia following anterior cervical fusion are of concern to all involved with this procedure. The reported incidence of this complication varies from 0.1% to >50% with all of these data coming from small case series and questionnaires. Most of these cases are transient in nature but a significant number may still have symptoms at 2 months postprocedure. The causes of this problem may be multifactorial including surgical trauma to the recurrent or superior laryngeal nerve or anesthetic trauma due to intubation and endotracheal tube (ETT) pilot balloon pressure. A recent study suggests that intraoperative measurement of pilot balloon pressure may reduce postoperative hoarseness and cough. For this reason, techniques selected to secure the airway for patients undergoing anterior cervical fusion should be minimally traumatic and ETT cuff pressures should be measured to between 15 and 25 mm Hg if possible. If pilot balloon manometry is not available, cuffs should be inflated just to the point that a leak is not detectable by auscultation.

Somatosensory evoked potentials are used in some centers to prevent postoperative neurologic sequelae, but so far evidence is lacking that this improves outcome. One study looking at ACDF versus a less invasive implantable disc found a great reduction in dysphonia and dysphagia in the minimally invasive group. This may imply that most of these postoperative symptoms in ACD and ACDF patients are due to surgical denervation of the larynx and esophagus.

Acute issues: Patients undergoing anterior cervical fusion are usually experiencing pain and/or radicular dysfunction in one or both upper extremities depending on the mechanism of their disease. Cervical radiculopathy may be caused by either cervical spondylosis or disc herniation resulting in compression of cervical nerve roots. Imaging of the cervical spine is needed to correlate patient symptoms with spinal pathology.

Chronic disease: The major issue here is opioid dependency.

f. Endocrine

Diabetes mellitus should be managed conservatively during the perioperative period, with most of the focus on avoidance of hypoglycemia.

g. Additional systems/conditions which may be of concern in a patient undergoing this procedure and are relevant for the anesthetic plan (eg. musculoskeletal in orthopedic procedures, hematologic in a cancer patient)

N/A

4. What are the patient's medications and how should they be managed in the perioperative period?

h. Are there medications commonly seen in patients undergoing this procedure and for which should there be greater concern?

NSAIDs are commonly taken for pain control. These should be discontinued 7 to 10 days prior to surgery for normal platelet activity to recover.

Systemic steroids: Care should be taken to continue a patient's steroid dose (i.e., prednisone) in the perioperative period. As most of these procedures are done with only a minimal hospital stay in the postoperative period, it should not be difficult to continue these medications except in the event of severe postoperative dysphagia. In this event, doses greater than 5 to 10 mg of prednisone per day should be converted to an intravenous route.

Opioid analgesics: A thorough history should be obtained from the patient outlining any use of opioid analgesics to manage upper extremity pain or other pain symptoms prior to surgery. Postoperative analgesic regimens will be much more difficult in the patient who is not opioid naive (taking regular doses of opioids daily for >6 months to 1 year).

i. What should be recommended with regard to continuation of medications taken chronically?

Cardiac: All cardiac medications should be continued in the perioperative period. There is concern for perioperative hypotension for patients taking angiotensin-converting enzyme inhibitors or angiotensin receptor blockers. These medications may be held on the morning of surgery, especially for multilevel procedures, which may lead to greater blood loss. Also, patients on warfarin therapy for thromboprophylaxis should hold their doses 5 to 7 days prior to surgery and a PT/INR should be obtained on the morning of surgery. In patients at increased risk for thrombotic events, they may be bridged with low-molecular-weight heparin.

Pulmonary: Inhalers should be taken as usual; prior to surgery pulmonary status can be assessed and additional bronchodilators may be added for patients with obstructive disease.

Renal: Patients on chronic diuretic therapy should continue therapy if they have a history of congestive heart failure or have hypertension that is refractory to multiple agents.

Neurologic: Antidepressant, antianxiety, and antipsychotic medications should be continued in the perioperative period. Lithium may be held the day of surgery due to its interaction with anesthesia with very little change in patient symptoms.

Antiplatelet: See NSAIDs, per earlier discussion.

Psychiatric: Medication should be continued as appropriate.

j. How to modify care for patients with known allergies

Avoidance of medications to which patients have had a true or suspected allergic reaction is necessary. Avoidance of medications within the same class of chemical substances may be warranted if the reaction was fulminant.

k. Latex allergy- If the patient has a sensitivity to latex (eg. rash from gloves, underwear, etc.) versus anaphylactic reaction, prepare the operating room with latex-free products.

Do not use latex-based products for patients with a known or suspected latex allergy.

l. Does the patient have any antibiotic allergies? (common antibiotic allergies and alternative antibiotics)

A common allergy is to the beta-lactam antibiotics. The preferred antibiotic is cefazolin 1 to 2 g IV. If the patient has a beta-lactam allergy, then administer clindamycin 600 to 900 mg IV or vancomycin 1 g IV. If MRSA is a concern in a particular patient, then give vancomycin 1 g IV.

m. Does the patient have a history of allergy to anesthesia?

Malignant hyperthermia (MH)

Documented: Avoid all trigger agents such as succinylcholine and inhalational agents. Follow a proposed general anesthetic plan: total intravenous anesthesia with propofol ± opioid infusion ± nitrous oxide. Ensure an MH cart is available [MH protocol].

Local anesthetics/muscle relaxants: Recall that local anesthetics belong to two chemical classes (amides and esters). If a true allergy is present, it is most likely due to an ester class local anesthetic. Indeed, even in this rare situation the allergy may be from a local anesthetic metabolite such as para-amino-benzoic acid (PABA) or a preservative. If a true allergy is suspected, either a local anesthetic from another chemical class should be used or local anesthetic use should be withheld.

5. What laboratory tests should be obtained and has everything been reviewed?

Laboratory tests should be directed by the history and physical exam

Hematocrit is necessary in multilevel fusions where blood loss may be excessive. As most ACD and ACDF procedures are performed on one or two spinal levels, this is not necessary in patients that have no reason to have an abnormal finding.

Electrolytes should be obtained for patients on diuretic therapy or with known or suspected kidney disease

Coagulation studies should be obtained in those patients on chronic warfarin therapy prior to surgery. If a low-molecular-weight bridge has been used, it is important to note the last time of administration.

Common laboratory normal values will be same for all procedures, with a difference by age and gender.

Laboratory studies should be guided by the history and physical exam

Hemoglobin levels are only needed if excessive blood loss is anticipated. Electrolyte levels should be checked in the presence of kidney disease or in the patient who has recently been prescribed diuretic medications. Prothrombin time (PT) and international normalized ratio (INR) should be obtained if patients have been on chronic warfarin therapy prior to surgery. ECG should be obtained for patients at higher risk such as those with coronary or valvular heart disease, peripheral artery disease, congestive heart failure, history of cerebrovascular disease, diabetes mellitus, or chronic kidney disease.

Intraoperative Management: What are the options for anesthetic management and how to determine the best technique?

Due to patient positioning, intensity of surgical stimulation, and risk of airway injury, only a general anesthetic should be used for anterior cervical fusion.

a. Regional anesthesia

Regional anesthetic techniques would be suboptimal for this procedure. General anesthetics should be used to ensure patient safety and an optimal surgical field. Local anesthetics used at incision sites may aid in postoperative analgesia.

b. General anesthesia

Benefits: General anesthesia provides an optimal surgical field with a secured airway. This is particularly crucial given the surgical risk to vital structures in the anterior neck (carotid artery, internal jugular vein, recurrent laryngeal nerve, trachea, and esophagus).

Drawbacks: The side effects of general anesthetics are the only drawbacks of this technique, but this is the only manageable option.

Preoperative airway concerns: Due to the nature of the disease process, a careful airway exam including neck range of motion and its impact on neurologic symptoms should be obtained prior to induction. In general, the airway should be secured with the technique that is most familiar to the anesthetic team and least likely to cause airway trauma or worsen neurologic symptoms with extremes of positioning. This may be an awake fiberoptic intubation in a patient with a suspected difficult airway and severe gastroesophageal reflux disease or the use of video laryngoscopy or traditional direct laryngoscopy with minimal neck motion after induction in a patient without these concerns.

Postoperative concerns influenced by management: Dysphonia and dysphagia following anterior cervical fusion is of concern to all involved with this procedure. The reported incidence of this complication varies from 0.1% to >50% with all of this data coming from small case series and questionnaires. Most of these cases are transient in nature but a significant number may still have symptoms at 2 months post procedure. The causes of this problem may be multifactorial including surgical trauma to the recurrent or superior laryngeal nerve or anesthetic trauma due to intubation and ETT pilot balloon pressure. A recent study suggests that intraoperative measurement of pilot balloon pressure may reduce postoperative hoarseness and cough.

For this reason, techniques selected to secure the airway for patients undergoing anterior cervical fusion should be minimally traumatic and ETT cuff pressures should be measured to between 15 and 25 mm Hg if possible. If pilot balloon manometry is not available, cuffs should be inflated just to the point that a leak is not detectable by auscultation. Somatosensory evoked potentials are used in some centers to prevent postoperative neurologic sequelae, but so far evidence is lacking that this improves outcome. One study looking at ACDF versus a less invasive implantable disc found a great reduction in dysphonia and dysphagia in the minimally invasive group. This may imply that most of these postoperative symptoms in ACD and ACDF patients are due to surgical denervation of the larynx and esophagus.

c. Monitored anesthesia care (MAC)

MAC should not be used for this procedure due to the possibility of surgical airway injury.

6. What is the author's preferred method of anesthesia technique and why?

Preferred method of anesthesia: General anesthesia, as detailed above.

Preferred prophylactic antibiotic is cefazolin 1 to 2 g IV. If the patient has a beta-lactam allergy, then administer clindamycin 600 to 900 mg IV or vancomycin 1 g IV. If MRSA is a concern in a particular patient, then give vancomycin 1 g IV.

Several procedures for cervical radiculopathy are performed (posterior foraminotomy, ACD, and ACDF). This has implications for positioning and time of the procedure with anterior approaches being performed in the supine position. If fusion is performed, bone graft from the patient's iliac crest may be used, which creates a new area requiring postoperative analgesia. Other materials used for fusion include cadaveric bone, manufactured or resorbable cages, metal plates, or bone morphogenetic proteins (BMPs).

Dysphonia and dysphagia following anterior cervical fusion are of concern to all involved with this procedure. The reported incidence of this complication varies from 0.1% to >50% with data coming from small case series and questionnaires. Most of these cases are transient in nature but a significant number may still have symptoms at 2 months post procedure. The causes of this problem may be multifactorial including surgical trauma to the recurrent or superior laryngeal nerve or anesthetic trauma due to intubation and ETT pilot balloon pressure. A recent study suggests that intraoperative measurement of pilot balloon pressure may reduce postoperative hoarseness and cough. For this reason, techniques selected to secure the airway should be minimally traumatic and ETT cuff pressures should be measured between 15 and 25 mm Hg if possible. If pilot balloon manometry is not available, cuffs should be inflated just to the point that a leak is no longer detectable by auscultation. Somatosensory evoked potentials are used in some centers to prevent postoperative neurologic sequelae, but so far evidence is lacking that this improves outcome.

Common intraoperative complications

Surgical traumas to major structures of the anterior neck are the potential complications of this procedure. Disruption of the carotid artery or internal jugular vein would be one of the most serious, although its reported incidence in the literature is only on the level of the case report. Adequate volume resuscitation must be initiated immediately if major blood loss cannot be controlled by the surgical team. Assistance by other surgical consultants (i.e., vascular surgeons) should be initiated if they are available and communication with the blood bank regarding un–cross-matched blood should begin if blood products are needed. A sample should be drawn for emergency cross-match and if possible an arterial line should be placed to draw serial hematocrits and to evaluate the effectiveness of resuscitation. Disruption of the esophagus, recurrent, or superior laryngeal nerves is possible but the occurrence is fortunately rare.

Cardiac complications: Anterior cervical fusion is an intermediate risk procedure in terms of cardiac morbidity. There are no specific concerns for the procedure beyond the inherent risks to patients based on preoperative comorbidities.

Pulmonary complications: ACD and ACDF are low-risk procedures for pulmonary complications.

Neurologic complications: Unique to the procedure, worsening cervical radiculopathy is a potential surgical complication of ACD and ACDF but the incidence of this is not currently known from the literature. The more common neurologic complication is dysphonia and dysphagia due to trauma to the recurrent laryngeal or superior laryngeal nerves. Because endotracheal intubation can cause vocal cord dysfunction, caution should be taken when securing the airway. Techniques that are familiar to clinicians should be used and ETT cuff pressures should either be measured (15 to 25 mm Hg) or inflated until a leak is just sealed to auscultation.

a. Neurologic:

Unique to procedure: Worsening cervical radiculopathy is a potential surgical complication of ACD and ACDF, but the incidence of this is not currently known from the literature. The more common neurologic complication is dysphonia and dysphagia due to trauma to the recurrent laryngeal or superior laryngeal nerves. Because endotracheal intubation can cause vocal cord dysfunction, caution should be taken when securing the airway. Techniques that are familiar to clinicians should be used and ETT cuff pressures should either be measured (15 to 25 mm Hg) or inflated until a leak is just sealed by auscultation. There has been recent concern that BMPs may increase the risk for delayed airway swelling in this population.

b. If the patient is intubated, are there any special criteria for extubation?

In ACD and ACDF patients, the special concern for extubation would be in the event of a known or suspected injury to the recurrent laryngeal nerve or superior laryngeal nerve. In the case of a unilateral injury, patients may experience ipsilateral vocal cord dysfunction and hoarseness with or without respiratory compromise. In the rare case of a bilateral injury, vocal cord dysfunction may be severe with compromise of the airway requiring reintubation and mechanical support of ventilation.

c. Postoperative management

A multimodal approach should be implemented especially in the patient who is not opioid naive. A combination of scheduled NSAIDs (if acceptable to surgical colleagues), acetaminophen, and opioids should be used together in order to maximize analgesia and minimize opioid-related side effects. Discussion of the use of local anesthetics in the surgical field should be undertaken with surgeons. The risk of mechanical damage or neurotoxicity to anterior neck structures must be balanced with the benefits of analgesia.

Most ACD and ACDF patients should go to the floor after their procedure. Some centers send patients home after single level or more minimally invasive techniques.

Common postoperative complications: Upper airway obstruction due to edema, vocal cord dysfunction, or hematoma of the neck is a rare but serious postoperative complication that must be managed aggressively. If neck swelling is the major presenting feature, then a hematoma must be ruled out or drained and hemostasis achieved before tissue damage becomes irreversible. Reintubation of the trachea is certainly a judicious first step if airway compromise is evident, but the etiology is initially uncertain.

What's the Evidence?

Hughey, AB, Lesniak, MS, Ansari, SA, Roth, S. "What will anesthesiologists be anesthetizing? Trends in neurosurgical procedure usage". Anesth Analg. vol. 110. 2010. pp. 1686-97.

Bulger, RF, Rejowski, JE, Beatty, RA. "Vocal cord paralysis associated with anterior cervical fusion: considerations for prevention and treatment". J Neurosurg. vol. 62. 1985. pp. 657-61.

Winslow, CP, Winslow, TJ, Wax, MK. "Dysphonia and dysphagia following the anterior approach to the cervical spine". Arch Otolaryngol Head Neck Surg. vol. 127. 2001. pp. 51-5.

Liu, J, Zhang, X, Gong, W, Li, S, Wang, F, Fu, S, Zhang, M, Hang, Y. "Correlations between controlled endotracheal cuff pressure and postprocedural complications: a multicenter study". Anesth Analg. vol. 111. 2010. pp. 1133-7.

Smith, PN, Balzer, JR, Khan, MH, Davis, RA, Crammond, D, Welch, WC, Gerszten, p, Sclabassi, RJ, Kang, JD, Donaldson, WF. "Intraoperative somatosensory evoked potential monitoring during anterior cervical discectomy in nonmyelopathic patients: a review of 1,039 cases". Spine. vol. 7. 2007. pp. 83-7.

McAfee, PC, Cappuccino, A, Cunningham, BW, Devine, JG, Phillips, FM, Regan, JJ, Albert, TJ, Ahrens, JE. "Lower incidence of dysphagia with cervical arthroplasty compared with ACDF in a prospective randomized clinical trial". J Spinal Disord Techn. vol. 23. 2010. pp. 1-8.

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