Without fail, every time I teach a lecture on spinal injuries at least one student uses a phrase something along the lines of, “I can’t believe I have never heard of this before.”
They are not the only ones who are surprised. I am equally puzzled. In fact, the first time I learned of autonomic dysreflexia was from a paraplegic patient.
She told me she felt worried because she felt dizzy and needed nitroglycerine. She had a broken tibia and I was unsure how a nitrate would help. Somewhere between memorizing the cranial nerves and remembering Brown Sequard Syndrome causes ipsilateral temperature sensation, I missed out on this crucial bit of knowledge.
Autonomic dysreflexia is a medical emergency. It’s maddening I didn’t know this because, unlike cranial nerves, you don’t even need a pneumonic to remember it.
Hypertension in a patient with a spinal injury is autonomic dysreflexia until proven otherwise. See, super simple stuff.
Firstly, let’s define autonomic dysreflexia
Autonomic dysreflexia is a phenomenon experienced by about 20% to 70% of people who have a spinal injury above T6, according to a StatPearls book. Additionally, it is almost always an old spinal injury.
Essentially, autonomic dysreflexia is an out-of-control autonomic response to an unfelt painful stimulus. Patients with complete spinal injuries are unable to sense pain below the site of their injury. But, that doesn’t mean that they lack the receptors for pain, the impulse is just unable to travel to the brain.
In a natural response to painful stimuli, vasoconstriction happens below the injury site. Receptors above the site recognize there is an increase in blood pressure and tell the parasympathetic system to take over because there is no reason for the hypertension.
After all, the pain impulse doesn’t move beyond the level of spinal injury. Above the injury site, the parasympathetic system attempts to reduce blood pressure which results in sweating, nasal congestion and flushing above the site. But, this is ineffective and the patient’s blood pressure can reach catastrophic levels.
Under serious pressure
Our body is constantly working to keep all our organs adequately perfused. But it also doesn’t want to create a situation where pressure is too high.
Hypertensive crisis can cause all kinds of adverse outcomes, some that can cause permanent harm, according to the Annals of Translational Medicine. For example, in autonomic dysreflexia the uncontrolled sympathetic response can result in:
- Acute myocardial infarction
- Hypertensive encephalopathy
- Cerebrovascular accident
- Acute pulmonary edema
- Other undesirable conditions
These complications make it important to interrupt the continuous feedback loop that the autonomic system is stuck in.
In order to stop uncontrolled hypertensive emergencies, you need to address the instigator of the situation. If you can find the cause, you can break the cycle and the patient will return to a baseline blood pressure.
In the majority of autonomic dysreflexia cases, the cause is from a distended bladder. The patient is unable to void or a foley catheter is kinked. Or perhaps they have a bowel obstruction. These are the common causes.
But since we often respond to uncommon calls, other things to consider are decubitus ulcers, belts or shoes that are too tight and even menstrual cramps.
If we are on the scene of a call where the patient’s blood pressure is a secondary finding, look toward the patient’s reason for the call. Maybe they have an unrecognized broken bone or a burn. It’s imperative to find the cause and treat it immediately.
How to treat autonomic dysreflexia
What if the source of the stimulus cannot be readily found? This is where it gets tricky. There isn’t a consensus of what the best treatment should be.
Obviously, reducing blood pressure should be beneficial. But, like everything else we do, it’s not a completely benign endeavor.
And if the source is found after the patient is treated pharmacologically for hypertension, the patient could have profound hypotension. Nifedipine, hydralazine and nitroglycerine are potential agents for reducing blood pressure.
It’s unlikely your protocols account for autonomic dysreflexia. So, what do you do? If you have a protocol for hypertensive crisis, great! Use that.
But, if not, it is probably worth a call to the receiving physician or your medical director. Let them know what your options are for anti-hypertensives and let them make the decision.
The next time you are treating a patient with a spinal cord injury, think about autonomic dysreflexia. Be on the lookout for upward trending blood pressures. If your patient is hypertensive, be a sleuth and go looking for the cause.
Remember, it is almost always the patient’s gastrointestinal or genitourinary systems. If you can treat the cause quickly, you can prevent some diseases that have high associated morbidity and mortality rates.
Now you have the knowledge to recognize and treat autonomic dysreflexia. And it was easier than memorizing the cranial nerves and, arguably, more valuable.