How many mcg of push-dose norepinephrine is needed to prevent hypotension?
Despite the popularity of push-dose vasopressors in emergency medicine and critical care scenarios, nearly all of the data supporting their use comes from women undergoing elective cesarean delivery under spinal anesthesia. Push-dose vasopressors are used in that setting to prevent the hypotension that can be expected from spinal anesthesia.
A group of investigators published a study of 42 women in Anesthesia & Analgesia in 2017. The women were undergoing elective cesarean delivery under spinal anesthesia.
Patients received intermittent norepinephrine boluses of either 3, 4, 5, 6, 7, or 8 mcg every time their systolic blood pressure fell to below 100% of baseline.
The authors determined that the minimum dose of norepinephrine to prevent postspinal hypotension in 90% of women undergoing elective cesarean delivery was 6 mcg.
The dose of phenylephrine IV push used in obstetric patients is 100-200 mcg, and this is the dose that is anecdotally effective in critically ill patients. It is just as reasonable to extrapolate the results of this trial to critically ill patients as it is the other trials of obstetric patients. Therefore if push-dose norepinephrine is used, the dose of 6mcg found in this study serves as a starting point.
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