Extra Topic 5.4 -- Autonomic Hyper-reflexia Flashcards
Fifteen minutes into the procedure, the patient’s blood pressure is 210/98 mmHg, and his HR is 48.
What do you think is the cause?
(A 36-year-old paraplegic man is scheduled for cystoscopy. He was in a motor vehicle accident 4 years ago with complete spinal cord transection at the level of T6. He has complete sensory and motor loss below the level of the transection.)
The intraoperative occurrence of hypertension and bradycardia in this paraplegic patient with a high spinal cord lesion is consistent with autonomic hyperreflexia (AH).
Bladder distention or some other stimulus below the level of the spinal cord transection is probably the cause of his hypertension and bradycardia.
AH is also associated with – nasal stuffiness, headache, visual changes, dysrhythmias, nausea, confusion, and difficulty breathing.
Left untreated, sudden and sustained hypertension may lead to cerebral, retinal, or subarachnoid hemorrhage; loss of consciousness; seizures; myocardial ischemia; dysrhythmias; and pulmonary edema (left ventricular failure due to increased afterload).
While his symptomatology is likely the result of AH, I would also consider other potential causes of hypertension, such as – bladder perforation or inadequate anesthesia.
What is the pathophysiology of autonomic hyperreflexia (AH)?
(A 36-year-old paraplegic man is scheduled for cystoscopy. He was in a motor vehicle accident 4 years ago with complete spinal cord transection at the level of T6. He has complete sensory and motor loss below the level of the transection.)
Cutaneous (pain) or visceral (i.e. bladder or rectal distention) stimulus below the level of spinal cord injury results in a reflex sympathetic discharge.
Because the area of the body below the transaction is neurologically isolated, the sympathetic activity in this area is not modulated by inhibitory impulses from higher central nervous system centers.
This unopposed sympathetic activity leads to vasoconstriction below the level of the lesion, with reflex vasodilation above the level of the lesion.
When the lesion is above T7, vasodilation above the lesion is insufficient to prevent systemic hypertension, which then stimulates carotid sinus receptors, leading to reflex bradycardia.
Would you worry about autonomic hyperreflexia if his lesion were below T6?
(A 36-year-old paraplegic man is scheduled for cystoscopy. He was in a motor vehicle accident 4 years ago with complete spinal cord transection at the level of T6. He has complete sensory and motor loss below the level of the transection.)
Yes. While patients with transections below T7 rarely develop autonomic hyperreflexia, those with higher lesions are at risk.
With increasing height of the lesion, more of the splanchnic outflow tract is neurologically isolated from upper inhibitory modulation, leading to increasing risk of AH (65%-85% above T7; 85% above T5-T6).
Patients with transections above T7 are at risk for autonomic hyperreflexia when spinal cord reflexes return following spinal shock (usually 1 to 3 weeks post-injury, but may persist for up to 3 months).
Can autonomic hyperreflexia be prevented?
(A 36-year-old paraplegic man is scheduled for cystoscopy. He was in a motor vehicle accident 4 years ago with complete spinal cord transection at the level of T6. He has complete sensory and motor loss below the level of the transection.)
Autonomic hyperreflexia is an autonomic response that occurs independently of the patient’s ability to perceive pain.
So, even though patients with spinal cord injury may not perceive pain below the level of spinal cord injury, adequate anesthesia is essential to prevent an unopposed sympathetic response to cutaneous or visceral stimulation.
While adequate general and regional anesthesia effectively prevent AH, topical anesthesia has proven unreliable.
When it comes to neuraxial anesthesia, spinal anesthesia is more reliable than epidural anesthesia for labor, perineal surgery, or bladder surgery, presumably due to more reliable and complete blockade of sacral roots.
How would you treat this patient?
(A 36-year-old paraplegic man is scheduled for cystoscopy. He was in a motor vehicle accident 4 years ago with complete spinal cord transection at the level of T6. He has complete sensory and motor loss below the level of the transection.)
The best way to manage a patient who is at risk for AH is to prevent the reflex from occurring in the first place, by ensuring adequate anesthesia below the level of the transection (i.e. spinal or general).
Given this patient’s severe hypertension, I would first remove the inciting stimulus by asking the surgeon to stop operating and by reducing any bladder distention.
I would then place an arterial line for continuous blood pressure monitoring; administer a short acting direct vasodilator, such as sodium nitroprusside; and deepen the anesthetic.
Finally, I would cancel the case, monitor the patient closely for subsequent complications (myocardial ischemia, intracerebral hemorrhage, seizures, etc.), and allow for complete resolution of the autonomic hyperreflexia.
