In this episode, I’ll discuss differences in heart rate in patients with sepsis and AFib between phenylephrine and norepineprhine.
Phenylephrine, unlike norepinephrine, does not stimulate beta receptors and therefore should not raise a patient’s heart rate. This is often used as a reason to administer phenylephrine to patients with rapid afib and hypotension from septic shock.
However norepinephrine is associated with better patient outcomes when used in septic shock. The Sepsis Guidelines do not suggest that phenylephrine be used in any circumstance – in fact that drug is not even mentioned in the guidelines.
A group of researchers recently published in the journal Chest a retrospective review to determine among patients with sepsis and AF, what is the difference in heart rate after phenylephrine initiation versus norepinephrine initiation?
The review analyzed a patient database of over 1800 patients with septic shock and Afib, about half of which received phenylephrine and half norepinephrine.
After multivariable adjustment, phenylephrine was associated with a statistically significantly lower heart rate at 1 and 6 hours but only by 4 beats per minute.
Patients who had a higher heart rate prior to vasopressor administration were more likely to have a larger heart rate reduction with the use of phenylephrine. There were no significant differences found in any of the secondary outcomes including conversion to sinus rhythm, bradycardia, vasopressor duration, intensive care unit (ICU) and hospital length of stay, and hospital mortality.
While the difference in heart rate was statistically significant, there is no reason currently to believe that a difference of 4 beats per minute would result in a clinically meaningful effect on patients with rapid afib and sepsis. This data can be used to highlight the small difference in heart rate between these vasopressors in the setting of afib, which is likely not a reason to deviate from Sepsis Guideline recommendations even if patients have afib and hypotension from sepsis.
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