2016/03/22 - Medical Tidbits: The value of Orthostatic Blood Pressure

This past January we sat down with the new guidelines and made a number of corrections / changes. One of these changes is dealing specifically with obtaining orthostatic blood pressure on patients. Should we be doing this? Who is the correct patient that we should be doing it on? The patient is already complaining of feeling dizzy, do we really need to do this?

From EMRAP November 2013

This if from EMRAP (emergency medicine reviews and perspectives November 2013). The Orthostatics Myth was presented by Anand Swaminathan MD. In this presentation he talks about assessing volume status, aspect that elderly patients will have normal volume status, but still have orthostatic blood pressure.

  • Why is this important? We see patients with possible volume depletion, dehydration or bleeding every day. Orthostatic measures are what we have been taught to do to assess volume status. The GI bleeder with a variceal bleed is going to get blood and a procedure regardless of the orthostatics. But when you are trying to assess how dehydrated a little old lady with a UTI and a few episodes of vomiting is, you want an easy beside test that doesn’ttake long and assesses volume status. We want to know about moderate volume depletion or moderate blood loss.

  • The history of orthostatics seems to be drawn from studies with healthy volunteers after blood draws.

  • What is a positive test by numbers? A drop in systolic blood pressure by 20mmHg or an increase in heart rate by 30 beats per minute when they stand up from the supine position.

  • What does the literature say? Changes in systolic blood pressure are actually pretty common. Approximately 10% of completely healthy patients under the age of 65 will have orthostatics at baseline. Over 65 years old, approximately 11-50% will have orthostatics by numbers when they are completely asymptomatic.

  • Ooi WL et al. Patterns of orthostatic blood pressure change and their clinical correlates in a frail, elderly population. JAMA. 1997 Apr 23-30;277(16):1299-304 • PMID 9109468. Took a bunch of elderly patients who lived in a nursing home and checked orthostatics at baseline. They found about 50-60% were orthostatic at baseline despite being asymptomatic.

  • Witting MD et al. Defining the positive tilt test: a study of healthy adults with moderate acute blood loss. Ann Emerg Med. 1994 Jun;23(6):1320-3 • PMID 8198307.

    • Checked the blood pressure and heart rate after blood donations in healthy volunteers.

    • When they looked at just the heart rate in patients over 65, they found the sensitivity and specificity of an increase in heart rate of 20 beats per minute were 25% and 100%. That means that if they didn’t have a change, it didn’t tell you anything. Many of the patients did have an increase in heart rate which was expected. The change in heart rate was increased to 25 beats per minute in the group under 65 but sensitivity remained poor (33%) and specificity was 94%.

    • When they looked at blood pressure with a drop of 20mmHg, it wasn’t useful at all.

    • hey concluded that heart rate was kind of useful but you can’t use it to rule out blood loss. Remember that this was done in healthy volunteers and it is unknown how it translates to the sick or semi-sick patients in the ED.

  • McGee S et al. The rational clinical examination. Is this patient hypovolemic? JAMA. 1999 Mar 17;281(11):1022-9 • PMID 10086438.

    • Postural pulse change was present with a sensitivity of 22% in patients with moderate blood loss. Postural blood pressure changes had a sensitivity ranging from 7 to 27%. Again, pretty poor.

    • The study did show postural pulse change had a sensitivity of 97% with severe blood loss. However, if you can’t tell who has severe blood loss, you probably shouldn’t be doing this job.

  • How about orthostatics with dehydration? The literature on this is scant. Johnson DR et al. Dehydration and orthostatic vital signs in women with hyperemesis gravidarum. Acad Emerg Med. 1995 Aug;2(8):692-7 • PMID 7584747.

    • Included 23 patients with hyperemesis.

    • They concluded vital sign changes were not helpful in assessing volume status.

  • In the McGee article above (which put all the literature together but was not quite a meta-analysis as the papers varied so much), they also found that there was not much help from assessing pulse or blood pressure in dehydration.

    • They found a pulse change of 30 beats per minute had an overall sensitivity of 43% and specificity of 75%.

    • Blood pressure changes had a sensitivity of 29% and specificity of 81%.

  • How about children? There are a few articles looking at children. The adult cutoffs are used for children. The researchers looked at whether these cutoffs were useful.

    • Skinner JE et al. Orthostatic heart rate and blood pressure in adolescents: reference ranges. J Child Neurol. 2010 Oct;25(10):1210-5 • PMID 20197269. Included children 15-17 years old (which are practically adults). Heart rate change had a sensitivity of 61% and a specificity of 56%.

    • Stewart JM et al. Transient orthostatic hypotension is common in adolescents. J Pediatr. 2002 Apr;140(4):418-24 • PMID 12006955. Took healthy adolescents and performed tilt table testing. Found 44% had orthostatic heart rate changes at baseline. These kids weren’t dehydrated or with blood loss.

  • There isn’t much literature to defend the use of orthostatics. Overall, it doesn’t seem very helpful to determine who has moderate hypovolemia due to dehydration or blood loss. The change in blood pressure is clearly useless. If you are going to check orthostatics you should limit it to pulse change alone. Better yet, don’t check the numbers at all. Just stand the patient up and ask them if they feel light-headed or dizzy; if they have symptoms, they are orthostatic.

At the end of the day … if a patient is complaining of feeling light-headed, dizzy then make sure an IV is in place and the patient is receiving some IV fluids (of course always take into consideration the other medical co-morbidities / complaints). Avoid having the patient perform tests that are not evidence based and scientifically unsound.

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