Determination of the ED50 and ED95 of intravenous bolus of norepinephrine for the treatment of hypotension during spinal anesthesia for cesarean delivery

Abstract

Norepinephrine is considered as a potential alternative for blood pressure stabilization during spinal anesthesia for cesarean delivery, as it maintains a better maternal heart rate and cardiac output compared with phenylephrine. However, its use as a bolus dose for hypotension treatment remains largely unexplored. Therefore, the present study investigated the ED 50 and ED 95 of norepinephrine as a bolus for maternal hypotension during cesarean delivery. In the present prospective trial, 42 patients were enrolled for elective delivery under spinal anesthesia. The dose of norepinephrine was decided by the up-and-down sequential allocation method (UDM) with an initial dose of 0.075 µg/kg and a 0.025 µg/kg increment. The 42 patients received a bolus of norepinephrine when systolic blood pressure fell to <80% of baseline. The ED 50 was calculated by the sequential method and the probit regression model. The ED 95 was then calculated using the probit regression model. The ED 50 of norepinephrine, which was determined by the UDM, was 0.067 µg/kg (95% CI, 0.056-0.081). The probit regression model calculated an ED 50 of 0.072 µg/kg (95% CI, 0.056-0.088) and an ED 95 of 0.121 µg/kg (95% CI, 0.1-0.207). In summary, the present results suggested the ED 50 of a bolus norepinephrine for preventing hypotension in elective CD is 0.067 µg/kg (95% CI, 0.056-0.081), with an ED 95 of 0.121 µg/kg (95% CI, 0.1-0.207).

Prophylactic norepinephrine infusion for postspinal anesthesia hypotension in patients undergoing cesarean section: A randomized, controlled, dose‐finding trial

“…Similar result was also found by Wang et al 17 In the current study, a 6 μg loading bolus of norepinephrine was given immediately following spinal anesthesia before a maintenance dose of norepinephrine.…”

“…Onwochei et al 8 carried out a sequential allocation dose‐finding study and demonstrated that the ED90 of intermittent boluses of norepinephrine to prevent postspinal anesthesia hypotension was 5.8 μg (95% CI: 5.01–6.59). Similar result was also found by Wang et al 17 In the current study, a 6 μg loading bolus of norepinephrine was given immediately following spinal anesthesia before a maintenance dose of norepinephrine. To some extent, this lowered the incidence of subsequent hypotension and hypotension‐related nausea and vomiting (without a higher proportion of reflex hypertension, however).…”

Preventing Spinal Hypotension During Cesarean Birth With Two Initial Boluses of Norepinephrine in Chinese Parturients: A Randomized, Double-Blind, Controlled Trial

“…This is the most common definition. [14][15][16] Compared to SBP at baseline, nausea or vomiting is increased when SBP decreases by 80% to 90%. 17 In our study, the 0.10 μg/ kg group had a lower frequency of nausea and vomiting, which may be explained by the low incidence of hypotension.…”