Comparison of prophylactic norepinephrine bolus dose and infusion to prevent hypotension due to spinal anesthesia in cesarean section

Spinal anesthesia is a method that can be applied rapidly and simple neuraxial anesthesia method commonly used in pregnant women undergoing elective cesarean section. Sympathetic block, which may cause hypotension, occurs in addition to sensory and motor block. Complications caused by hypotension occurring following spinal anesthesia such as nausea, vomiting, decreased placental and umbilical blood flow and fetal acidosis may be seen in pregnant women and the incidence varies between 60-80%. In cesarean section, left uterine position is recommended for prevention of hypotension related with aortacaval compression and low dose spinal anesthesia and additional fluid support and prophylactic vasopressors is recommended to prevent sympathetic block induced hypotension. Norepinephrine (NE) is administered when hypotension develops or prophylactically to prevent hypotension after spinal anesthesia. In this study, we aimed to compare the incidence of hypotension and maternal and fetal hemodynamic side effects of prophylactic NE bolus or infusion applications in two groups of 40 randomly selected pregnant women between 18 and 40 years of age, ASA II, term (between 37-42 gestational weeks) and with systolic arterial pressure (SAB) values between 100-140 mmHg in a total of 80 pregnant women scheduled for elective cesarean section with spinal anesthesia. After administering 6 µg prophylactic NE in bolus group following spinal anesthesia, 4 µg if SAB decreases less than 90% of the baseline value, 6 mcg was administered in case it decreased less than 80%. In the infusion group, we administered prophylactic NE at a rate of 0 to 5 µg/min and titrated according to the severity of hypotension. In the bolus group, the incidence of 90-80% of baseline SAB was 92.5% and 80-60% was 57.5%, while in the infusion group, the incidence of 90-80% of baseline SAB was 62.5% and 80-60% was 32.5%. There are a statistically significant difference between the groups for incidence of hypotension. Hypotension episodes of 90-80% and below 80% of baseline SAB were significantly higher in the bolus group than in the infusion group (p0.05). Total consumed norepinephrin were 25 µg in bolus group while 45 µg in infusion group which were significantly higher. The incidence of hypertension, tachycardia, bradycardia and maternal nausea and vomiting were similar in both groups. The 1st minute APGAR score was significantly higher in the bolus group compared to the infusion group. The 5th minute APGAR and umbilical blood gas pH, PO2 and PCO2 values were similar between both groups. Base excess (BE) value in the infusion group was statistically different with higher negativity compared to the bolus dose. Although 1st minute APGAR scores and base excess were statistically different, the clinical difference was not imported. In conclusion, the infusion group provided more effective hemodynamic stability in preventing hypotension and clinical interventions were high in both groups. Key words: elective cesarean section, spinal anesthesia, norepinephrine