The effect of different norepinephrine administration methods on hypotension after spinal anesthesia in caesarean sections

Abstract

We aimed to evaluate the effect of different routes of norepinephrine (NE) administration on maternal hypotension in pregnant females undergoing spinal anesthesia for caesarean section. 208 pregnant women were divided randomly into 4 groups (n=52). Bolus 4 µg/ml NE was administered intravenous (iv) immediately after spinal anesthesia in Group PB (Prophylactic Bolus). In Group PI (Prophylactic Infusion), 1 ml of saline solution was applied promptly after spinal anesthesia and then the NE infusion was started at 1 ml/min. In Group TB (Treatment Bolus), 1 ml Physiological Saline (PS) was administered after 1 ml/min infusion of PS immediately after spinal anesthesia and then 1 ml/min NE bolus when blood pressure decreased by 20% after the entry. In Group TBI (Treatment Bolus Infusion), 1 ml PS was administered after 1 ml/min infusion of PS immediately after spinal anesthesia, 1 ml NE and then 1 ml/min NE infusion was initiated when blood pressure decreased by 20% after the entry. At the 4th, 6th, and 8th minutes, the PI Group exhibited higher systolic and mean blood pressures than the other groups (p<.001). Additionally, hypotension was statistically lower in the PI Group than in PB, TB, TBI groups (p<.001), and episodes of hypotension, ephedrine required and extra NE boluses given were statistically lower in the PI Group than in the other groups (p<.001). Umbilical vein (UV) pH values were lower in the TBI Group at compared to the other groups (p<.001). It is suggested that a prophylactic infusion of 4 µg/min of NE in the prevention of hypotension following spinal anesthesia for cesarean section will reduce the possibility of maternal hypotension and better maintain fetal well-being than a prophylactic bolus, a treatment bolus or a post-treatment bolus infusion at the same dose.