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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Interesting post. Trying to put myself in that scenario. How would you prepare this for a physician to utilize? We only carry the 4mg/4ml vials/ampules. In a pinch, I would probably dilute 1ml in 100ml of NS to try and make a 10mcg/ml concentration. Any better ideas?
Hi John! I would prefer to draw out of an existing IV bag and dilute further if needed in a 10 mL saline flush syringe. Using your concentration of 10 mcg/mL I might add 20-30 mcg in the saline flush and qs to 10 mL for a final 2 or 3mcg/mL concentration.