Sunday, February 23, 2020

Blood Pressure Measurements: Arterial Line vs Oscillometric Cuffs

We all do this every single day. We measure target many of our interventions in the critically ill patients to blood pressure. Whether it’s fluids, vasopressors, or blood pressure lowering agents, we obsess over these parameters. We feel warm and fuzzy if it’s okay. But are we using the right tool to find out these numbers?

I’ve always harped on arterial lines, although invasive, being the most reliable method of evaluating the blood pressure in our patients. If someone is critically ill on jet fuel, they’re getting an a-line. This is a fun study where they compared the oscillometric BP cuffs to a-lines in 736 patients.

When you look at the mean differences they obtained, the numbers weren’t too bad.
Systolic: 0.8mmHg
Diastolic: -2.9mmHg
Mean Arterial pressure: -1mmHg

This wouldn’t drive any of us crazy, right? We’d be cool with these differences if it avoids invasive (painful) interventions on our patients. But wait, there’s more. There was a large amount of variability which could lead to additional interventions.
Systolic: ± 15.7mmHg
Diastolic: ± 11mmHg
MAP: ± 10.2mmHg

The article goes as far as to say that BP cuffs would not pass the Association for the Advancement of Medical Instrumentation standards. There’s no data as to how this changes outcomes.

This was a post hoc analysis (after the fact). This shouldn’t be too challenging to accomplish a prospective study looking at this in our critically ill patients. We have many patients who have a BP cuffs and an a-line in place. Why not just record cuff pressures every 15 minutes and obtain some data? Obviously it’s more complicated than that.

A hat tip to the authors.

T. Kaufmann, E.G.M. Cox, R. Wiersema, et al., Non-invasive oscillometric versus invasive arterial blood pressure measurements in critically ill patients: A post hoc analysis of a prospective observational study, Journal of Critical Care(2019)

Link to full article (not free)

Although great care has been taken to ensure that the information in this post is accurate, eddyjoemd, LLC shall not be held responsible or in any way liable for the continued accuracy of the information, or for any errors, omissions or inaccuracies, or for any consequences arising therefrom.

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