Comparison of norepinephrine bolus versus infusion for prevention of post-spinal hypotension in parturients with preeclampsia undergoing cesarean section

Background: Currently, spinal anesthesia for cesarean section is the anesthetic technique of choice for women with preeclampsia in the absence of contraindications to neuraxial anesthesia. Recently, norepinephrine has been introduced for prevention and treatment of hypotension associated with spinal anesthesia; however, only a couple of studies have compared norepinephrine infusion and bolus. Aims: This study aims to compare primarily the efficacy and safety of norepinephrine bolus given therapeutically and norepinephrine infusion given prophylactically for management of hypotension and effects on other hemodynamic parameters in parturients with preeclampsia undergoing cesarean section under spinal anesthesia and secondarily to determine the effects of study drugs on neonatal Apgar score and arterial blood gas analysis of neonatal blood. Methods: In this prospective randomized study, 100 singleton full-term pregnant females of ASA grade II, aged 18–35 years, diagnosed with preeclampsia (controlled on single antihypertensive drug with BP ≤140/90), scheduled for elective cesarean section under spinal anesthesia were randomly divided into two groups. Group A: Received therapeutic norepinephrine bolus (4 μg) only when hypotension (fall in SBP to ≤20% of baseline) was detected after spinal anesthesia. Group B: Received prophylactic intravenous norepinephrine infusion (4 μg/min) immediately after induction of spinal anesthesia. Results: Heart rate, systolic, diastolic, and mean blood pressure had statistically significant difference at 3,4,5,6,7,8,9, and 10 mins of surgery. Number of episodes of hypotension and number of norepinephrine boluses used in Group A were higher and statistically significant (p-value < 0.001) than Group B. Apgar score at 1 and 5 minutes as well as umbilical artery parameters in two groups was comparable and statistically insignificant (p-value 0.301 for Apgar at 1 min and P value 0.562 for Apgar at 5 mins). Conclusion: Although both norepinephrine bolus and infusion doses are an effective way to treat spinal anesthesia-related hypotension in patients with preeclampsia undergoing cesarean section with comparable maternal and fetal side effects, infusion dose of norepinephrine is better in maintaining hemodynamics of parturients with insignificant changes in neonatal outcomes.