Thursday, October 06, 2011

Approach to the patient with severely elevated blood pressure

So you're called by the ER doc, saying “I've got this previously healthy patient” (maybe he was seen for a minor injury) “and he had a blood pressure of 190/120, asymptomatic. I've given him a couple of doses of clonidine. He's been here for over four hours and I can't get it below 180/100, so I think he needs to come in to be observed and treated overnight.” We've all been there. That seems to be the knee jerk approach. But is it the best approach? How can the best evidence guide us?

It's all nicely outlined in a review published in American Family Physician, linked from a post at The Kidney Doctor. The review is concise, practical and evidence based, and one of those few full text articles from AFP freely available on line (BTW, AFP now has the most restrictive access policy of any journal I know. You normally can't even get the abstract unless you are a subscriber).

According to the review the first thing you need to do is to classify the patient's elevated blood pressure. That can be confusing. Although JNC 7 (JNC 8 is supposed to come out next year) gives the traditional hypertension classification of prehypertension and stages 1 and 2 hypertension it does not define the terms for patients who present with severely elevated blood pressure. To make matters worse the terms out there right now are widely misused. Terms like “hypertensive crisis” are applied to so many different clinical circumstances they have become meaningless. “Malignant hypertension” used to mean something specific but has suffered the same fate in recent years. Even worse is the clinically inappropriate terminology in the ICD 9 codes we're forced to use (those are, what, 40 years out of date now?).

The terms are defined and the classification is succinctly presented in the review. Severely elevated blood pressure of any classification is defined as being greater than 180/100. If it is entirely uncomplicated without historical risk factors (heart disease, renal disease) or acute organ damage it's called severe asymptomatic hypertension or severe uncontrolled hypertension. If it is associated with historic cardiovascular risk factors or renal disease it is called hypertensive urgency. Finally, the term hypertensive emergency is reserved for individuals with evidence of acute organ damage. (Now when the latter are present they may trump the absolute level of blood pressure in defining a hypertensive emergency, e.g. aortic dissection, acute decompensated heart failure).

So that's step 1. Classify the patient using current terminology. How often is that done?

The article goes a little into pathophysiology. For our purposes I'll just mention the most important core concept: autoregulation. A graphic of the autoregulation curve is provided in the article. It's a familiar concept to most of you. If not, get it emblazoned in your hippocampus. Raise BP above the autoregulatory zone and you've got hypertensive encephalopathy. Go below, and perfusion of vital organs is proportional to blood pressure and may drop below critical levels. Acute “normalization” of blood pressure in the ER may take the patient into that zone.

As far as treatment is concerned go to the article, but here is the Cliff Notes version. In general the recommendations for starting patients on meds or admitting them to the hospital are a lot more conservative than what is commonly done. If it is really a HT emergency they go to the ICU. In HT emergency the BP target, the specific agent and route are specific to the underlying condition and are beyond the scope of this post as they are for the article.

For HT urgency or severe asymptomatic HT there appears to be no specific evidence that you should treat them in the ER or send them out with a prescription. Of course then the approach may be dictated by the patient's social situation. If non compliance, poor social connections or lack of a PCP complicate the situation it may be wise to have the patient spend the night in the hospital. But if the patient is better situated, according to the best evidence s/he could be sent home without meds with plans for very early PCP follow up (24-48 hrs if HT urgency, a week if severe asymptomatic HT) at which time the PCP would further evaluate the patient and initiate oral medication.

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