Yes, we know high blood pressure can be bad. Over the long term, it can accelerate atherosclerotic heart disease and pound away at the kidneys and brain. And when it is acutely elevated to critical levels, it can lead to stroke.
But is it always bad in trauma? Trauma hurts like hell, so it’s no wonder than many of our patients (not suffering blood loss of course) are hypertensive. But how often have you seen this scenario occur:
An elderly patient fell from standing, striking her head. She is brought to your ED by ground EMS. She has a GCS of 8 (E1 V3 M4) with a BP of 200/130 and pulse of 56. This meets your trauma activation criteria and the team assembles to meet the patient.
As you move her onto the bed, one of your colleagues calls out for some nicardipine to control the pressure. Is this a wise move? Remember the First Law of Trauma:
Any anomaly in your trauma patient is due to trauma, no matter how unlikely it may seem.
What else can cause hypertension and bradycardia in your trauma patient? In this case, certainly a subdural or epidural hematoma.
And why is that happening? Because the intracranial pressure is elevated from the space-occupying lesion. Remember the formula for cerebral perfusion pressure (CPP):
CPP = MAP – ICP
Where MAP = mean arterial pressure and ICP = intracranial pressure. Normally the MAP is around 90 torr and ICP is about 10 torr. Thus, the normal CPP is approximately 80. The range is 60 to well over 100 torr, and flow autoregulation keeps brain perfusion constant over this range.
But let’s say that we are psychic and know the ICP of our patient to be 60 because of a large subdural hematoma. Her current CPP is 150 – 60 or about 90 torr. What happens if we start her on a nicardipine drip or some other antihypertensive medication? We can certainly normalize the blood pressure to 120/80. But now her CPP drops to 90 – 60 = 30 torr!
Congratulations, you have just shut down circulation to her brain!
Bottom line: Think first before calling for antihypertensive medications in patients who may have increased intracranial pressure. You may be sabotaging the only mechanism protecting their brain while you are calling your neurosurgeon for help. Your top priority is to get them to the CT scanner while permitting that pressure. If it turns out that there is no evidence for pathology that would lead to increased ICP, then turn to the antihypertensive agents to help protect against stroke.