Isabel Rangel Barón: Science-Based Medicine in the New Year

As 2018 ends, the managing editor of Science-Based Medicine comments on the future of SBM.

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Isabel Rangel Barón: Manual Versus Machine Blood Pressures

How do you want to be known as a Paramedic/EMT?

A. Reliable
B. Frequently wrong

According to a recent JEMS article, Ditch the Machine to Improve Accuracy in Blood Pressure Measurement and Diagnostics, “automated blood pressure readings are frequently inaccurate.”

Is this a surprise to anyone?

Yet, many of us continue to rely on automated BP cuff readings to direct our clinical actions.

A March 2016 research study in the Journal of Clinical and Diagnostic ResearchWhich is More Accurate in Measuring the Blood Pressure? A Digital or an Aneroid Sphygmomanometer  concluded:

The aneroid device had better accuracy than the digital device as compared to mercury sphygmomanometer and should be used for proper and better management.

The paper declared digital devices:

  1. should be used with caution, doubt and suspicion
  2. are not up to standard
  3. (can cause many people to be) wrongly or misdiagnosed
  4. may prove disastrous

Powerful words.

The JEMS article points out that even the operating instructions for the Physio-Control Lifepack 15 contains this warning:  

“shock may result in a blood pressure waveform that has a low amplitude, making it difficult for the monitor to accurately determine the systolic and diastolic pressures.”

Got that.  Your Lifepack 15 is not capable of providing reliable blood pressures if your patient is in shock.

Cardiogenic shock
Hypovolemic shock 
Anaphylactic shock 
Septic shock 
Neurogenic shock

Your machine BP is unreliable when addressing these conditions.  It is frequently wrong.

How are you going to make clinical decisions with bad data?

You need to take manual blood pressures.

As an EMS Coordinator, I see run forms with blood pressures like these:

158/71
210/190
143/84
95/87
170/119

All for the same patient.  With no explanation.  Paramedics just downloading the machine readings.  If you put the reading in you PCR without explanation, it assumes that you consider the reading reliable.

As a paramedic, I have had my patient in afib brought into a level one medical room because the triage BP machine said my patient (who had manual pressures in the 120’s) had a blood pressure of 79/40.   Why are we in here? the doctor asked as he looked at my calm, warm, dry patient.

Because the triage system at this hospital relies on digital blood pressures. 

Don’t relay on machines to take a blood pressure in patients with atrial fibrillation.

Here are my guidelines:

  • Make your first blood pressure manual
  • Treat your machine pressures as an inexperienced partner
  • Before making a critical clinical decision, take another manual pressure.

Make certain you know how to take a proper blood pressure.

Here are some good articles to help us improve our manual blood pressures:

Taking a Manual Blood Pressure: Techniques & Pitfalls

Blood pressure reading tips and tricks for EMS

I get it.  It is hard and nearly impossible sometimes in EMS to obtain optimal conditions for taking a blood pressure.

Just know that the blood pressure you obtain under those impossible conditions (using short cuts) may not be accurate.

Don’t let inaccurate and unreliable readings cloud your clinical judgement.

Take a manual, and if you can’t hear, palpate a blood pressure.

 

 

 

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