The most important hypertension blog???

There was a small but (I think) important study showing that blood pressure measurement technique by medical students was strikingly inaccurate (see doi:10.1001/jama.2017.11255 ). This was a quite brief report without a lot of details about their methodology.

 

Details:

--159 medical students were asked to check the blood pressure on a simulated patient

--they were assessed for the 11 elements identified as necessary to get an accurate blood pressure measurement, which included:

    --using the correct cuff size, correctly placing the cuff over a bare arm, asking patient not to talk during the measurement, having patients uncross their legs, making sure that the patient's feet were flat on the floor, asking patient not to use their cellphones or read during the measurement, supporting the arm, checking the BP in both arms, noting which arm had the higher BP, correctly answering which arm should be used for future measurements, and having the patient rest for 5 minutes prior to checking the BP.

 

Results:

--the average student  performed 4.1 of the 11 elements

--more than ½ the students correctly placed the cuff over a bare arm, used the correct cuff size, supported the arm, asked patients not to talk during the measurement, and had patients uncross their legs

--fewer than ½ of students had the patient put their feet flat on the ground, asked them not to use cellphones or read, checked the BP in both arms, noted which arm had higher BP, and correctly answered the question of which are should be used in future measurements

--only 11 of the 159 students had the patient rest for 5 minutes in a chair before the measurement

--and, only 1 of the 159 correctly performed all 11 elements

 

Commentary:

--there are several quite disturbing issues raised by this study:

    --we are basing treatment for hypertension on accurate measurement of BP, with the potential significant iatrogenic problems of either overtreating it (adverse events from the unnecessary meds, hypotension and falls etc), or undertreating (not preventing preventable cardiovascular events)

    --accurate clinic-based blood pressure measurement involves the above 11 elements. This is what the hypertension studies have used in assessing the blood pressure and the treatment, and deviation from this methodology leads to blood pressure readings that should not really be evaluated/treated as found in these studies

    --some of these deviations can lead to substantial difference in the recorded blood pressure: they comment (without reference) that crossing legs raises the systolic by 3-8 mmHg; incorrect arm placement raises both systolic and diastolic BP by 10 mmHg

    --I would add, from my pretty considerable experience (ie, I always check manual blood pressures on my patients who are hypertensive or prehypertensive, and do so at least yearly on those who are normotensive, and have done so for decades):

        --using too small a blood pressure cuff can be associated with up to 20+ mmHg higher systolic blood pressure reading

        --not letting the patient sit still on the exam table for at least a few minutes can lead to shockingly higher blood pressure (not uncommonly in the 30+ mmHg range): I find this when I check the blood pressure as soon as the patient moves even the small distance of about 5 feet from the exam room chair to the exam table vs sitting on the table for a few minutes

        --at least in my clinical setting, the automatic blood pressure measurements by the medical assistants are often unreliable. I believe this is because the patient walks from the waiting room to the vital signs room and gets their blood pressure checked right away.  But, I have seen pretty dramatic differences in both directions: a recorded blood pressure of 118/79 actually being 190/120 (happens infrequently, but does happen), and the more common recorded 163/101 actually being 128/68 (which I really do find pretty often).

        --there are concerns about many of the automated cuffs having very inaccurate BP recordings in those with significant arrhythmias (eg atrial fib)

        --my general technique for measuring blood pressure in a very, very busy clinic setting is to speak with the patient when he/she is in the chair next to my desk, ask the patient to sit on the exam table, ask them to relax and think pleasant thoughts, often turn off the overhead light when the ambient light is glaring, go into my office to write the history part of the note/do referrals/order meds and labs, then go back into the room and check the blood pressure without talking with/disturbing the patient

    --an additional concern: this study was done with medical students, who tend to be more by-the-books than the rest of us.  Raises the issue that they are modeling what they see in actual clinical practice (BP measured in hurried fashion in the ER, clinic, etc) vs what they are taught in the classroom.

--I should also bring in the perspective here that even with accurate measurement of clinic-based blood pressure, there are pretty compelling arguments that ambulatory or home-based blood pressure readings are more predictive of actual clinical cardiovascular events than clinic-based ones, leading to many organizations (NICE in the UK in 2011, USPSTF in 2015) to recommend their use over clinic-based measurements, especially if the blood pressure is close to the cutpoint for treatment and, per the USPSTF, prior to starting meds. see prior blogs at http://blogs.bmj.com/ebm/page/2/?s=ambulatory+blood+pressure&submit=Search , and for the USPSTF recommendations https://www.uspreventiveservicestaskforce.org/Page/Document/RecommendationStatementFinal/high-blood-pressure-in-adults-screening  and my commentary on that at http://blogs.bmj.com/ebm/2015/01/15/primary-care-corner-with-geoffrey-modest-md-uspstf-recs-on-ambulatory-blood-pressure-monitoring/​ 

--that being noted, we clinicians still often use office-based blood pressures to guide therapy, so I think it is really important to get readings that reflect the guidelines and recommendations, which are based on studies which use the above recommended method for checking blood pressure.

so, 

 

--one relevant recent example of the importance of an accurate assessment of blood pressure is the highly-touted and perhaps game-changing SPRINT trial. As noted in the blog  http://blogs.bmj.com/ebm/2017/02/27/primary-care-corner-with-geoffrey-modest-md-blood-pressure-guidelines-for-older-adults/  : "For example, in the SPRINT study, which did achieve lower blood pressure in the tight control group than often found in other trials (123/62, in the elderly subgroup), they measured the blood pressure as follows: the staff person would tell a patient that they needed to rest for 5 minutes before taking the blood pressure, would leave the room completely, would return but not speak a word with the patient and immediately take the blood pressure. Argument has been raised in the literature that the blood pressure measured in randomized controlled trials is typically 5 to 10 mmHg lower than the clinic-based blood pressure (i.e. a randomized trial with an achieved systolic blood pressure of 123, as above, may be equivalent to a clinic-based blood pressure of 130 or so)". So, strictly following the SPRINT study BP goal could lead to overtreatment using even accurately determined clinic blood pressures.

--bottom line: if we are going to diagnose and treat hypertension accurately, it is important to get a correct blood pressure reading. we would not treat hypokalemia if the potassium were actually normal....

--and, perhaps the most general issue: us practicing clinicians really need to understand the methodology of all potentially relevant clinical trials: generalizing their results can be very problematic unless we can replicate how the study was done, and also the extent to which the patient in front of us fits into their inclusion/exclusion criteria and the general demographics of their patient population (eg: age, ethnicity/race, baseline comorbidites/meds/lab values, etc). [this really is the challenge of evidence-based medicine: the most well-executed, pristine study which produces a very clear conclusion may be totally irrelevant to the actual care of the vast majority of actual patients, yet still gets the highest "randomized controlled trial" moniker. Not all RCTs are created equal..., though they tend to get the highest ranking in the pyramid of high-quality studies]