AUTONOMIC DYSREFLEXIA

Autonomic dysreflexia — Patients with high spinal cord injury are at risk for autonomic dysreflexia (AD) and may require deep general anesthesia or regional anesthesia, even without sensory function at the surgical site.

Occurring in 20 to 70 percent of patients with SCI above T6, AD is an exaggerated sympathetic response to a stimulus below the SCI level. AD is manifested by diffuse vasoconstriction below the level of SCI and hypertension producing headache, diaphoresis, brady- or tachycardia, and other symptoms. The noxious stimulus is most commonly a distended viscus, usually the bladder; however, constipation, pain from pressure sores, and other stimuli may be problematic in some patients. SCI lesions lower than T6 do not produce this complication.

ANESTHESIA MANAGEMENT

Choice of anesthetic technique — The choice of anesthetic technique depends on the level of SCI, remaining sensory function, and the surgical procedure. In particular, both general and spinal anesthesia can effectively prevent autonomic dysreflexia (AD) in response to surgery.

General anesthesia may be preferable for patients who cannot tolerate lying flat, who have upper extremity muscle spasms, contractures that make positioning difficult, or high anxiety.

●For patients at risk for, or with a history of, AD, or for those with lower extremity muscle spasms, either general or regional anesthesia may be used.

●For patients without sensation at the surgical site and who are not at risk for AD (ie, SCI below T6 and no history of AD), monitored anesthesia care with or without sedation is an option.

●For patients with incomplete sensory loss without risk for AD or spasms, local anesthesia or peripheral nerve block may be adequate for surgery.

Management of intraoperative autonomic dysreflexia — AD may occur intraoperatively, despite what appears to be adequate anesthesia, and should be treated rapidly. Signs and symptoms of AD may include the following:

●Sudden hypertension – Systolic BP can rapidly rise to >200 mmHg.

●Dysrhythmias – Bradycardia, tachycardia, heart block, and sinus arrest are all possible.

●Cutaneous changes – Typically, vasoconstriction occurs with blanching below the spinal lesion and with vasodilation, flushing, and sweating above the lesion.

●Headache and nasal congestion – Awake patients may complain of headache and nasal congestion.

●Cardiovascular effects – With severe AD – especially in patients with cardiovascular comorbidities – myocardial ischemia, myocardial infarction, and acute left heart failure can occur.

●Neurologic complications – Intracranial hemorrhage and seizures are possible.

Treatment includes the following:

●Remove inciting stimulus – Surgery should be paused; if appropriate, relieve distention of hollow viscus (ie, the bladder should be emptied, endoscope removed).

●Deepen anesthesia – For patients under general anesthesia, administer a bolus of propofol or deepen the inhalation agent.

●Position head up – Tip the operating table head-up to take advantage of orthostatic BP drop.

●Administer 100 percent oxygen – Increase the fraction of inspired oxygen (FiO2) until AD is resolved.

●Administer a vasodilator – Administer a rapid-onset, short-acting vasodilator to avoid hypotension when AD resolves:

•Nicardipine 0.2 to 0.5 mg IV bolus with nicardipine infusion (2.5 to 15 mg/hour), or

•Nitroglycerin infusion (5 mcg/minute to 200 to 500 mcg/minute), or

•For severe hypertension, nitroprusside infusion (0.2 to 10 mcg/kg/minute). The hypotensive effects of nitrates (ie, nitroglycerin and nitroprusside) may be exaggerated in patients who are using sildenafil for erectile dysfunction.

Longer acting vasodilators may be administered cautiously; hypotension may occur once the AD event resolves. Options include:

•Hydralazine 5 mg IV every 10 minutes, titrated to effect, up to 20 mg total dose

or

•Labetalol 5 mg every 5 minutes, titrated to effect, up to 50 mg total dose; beta blockers may exacerbate AD related bradycardia

●Treat arrhythmias – Treat arrhythmias as necessary with beta blockers, anticholinergics, and advanced cardiac life support (ACLS) medications.

●Treat myocardial ischemia – Treat ST and T-wave changes on electrocardiogram (ECG) as necessary (eg, with nitroglycerin infusion).

●Invasive monitoring – An arterial catheter should be placed for continuous BP monitoring if AD does not resolve quickly.

In most cases, rapid treatment, pause in surgery, and deepening anesthesia resolves the AD event quickly. However, severe complications such as intracranial hemorrhage, acute heart failure, and death can occur.

Temperature control — Patients with SCI are at risk for hypothermia during anesthesia and in a cold operating room (OR) or, less commonly, hyperthermia with overly aggressive warming measures. Temperature should be monitored during and after anesthesia. Warm air blankets and fluid warming should be used intraoperatively and may be continued into the recovery period.

Source:

Anesthesia for adults with chronic spinal cord injury. Letha Mathews, MBBS, FFARCS (I)Koffi Kla, MD.