A Clinical Study To Predict The Carotid Artery-Corrected Flow Time For Hypotension After Spinal Anesthesia In Patients Undergoing Cesarean Section

Objective:We measured the carotid artery flow time by ultrasound before surgery,calculated the corrected flow time(FTc)of the carotid artery to determine the volume responsiveness in patients undergoing cesarean section,and took individualized prophylaxis measures,prophylactic colloidal expansion or prophylactic norepinephrine infusion,to explore the most appropriate preventive measures to prevent hypotension after spinal anesthesia in women undergoing cesarean section;meanwhile,we observed the effects of both prophylaxis measures on the neonatal outcome and maternal outcome to further improve the safety of maternal and infant during the perioperative period.Methods:After the puerpera entered the operating room,routine ECG monitoring was performed,the carotid artery blood flow time(FT)and heart rate(HR)were measured by ultrasound,and FTc was calculated to determine volume reactivity.According to whether they had volume responsiveness,they were divided into the group with volume reactivity(R group):FTc<326.9ms,121 cases;the group without volume reactivity(NR group):FTc≥326.9ms,124 cases.According to the random number table method,each group was divided into two groups for pretreatment,and there were four groups in total:volume-responsive rehydration group(RH group,62 cases),volume-responsive norepinephrine group(RN group,59 cases),non-volume-responsive rehydration group(NRH group,64 cases),and non-volume-responsive norepinephrine group(NRN group,60 cases).Treatment in the rehydration group(RH group and NRH group):8ml/kg of hydroxy ethyl starch 130/0.4 NaCl injection was administered within 30min before surgery.Treatment in the norepinephrine group(RN group and NRN group):intravenous infusion of 4μg+0.05μg/kg/min with loading 20min before surgery was continued until the fetus was taken out,then gradually reduced to stop.The systolic blood pressure(SBP),diastolic blood pressure(DBP),heart rate(HR),and pulse oximetry(SpO2)of the four groups were recorded before pretreatment(T0)and after pretreatment(T1),lmin after lumbar anesthesia(T2),3min after lumbar anesthesia(T3),5min after lumbar anesthesia(T4),and at the time of skin resection(T5),during fetal extraction(T6).Adverse events such as hypotension,reactive hypertension,bradycardia,tachycardia,chest tightness,nausea,and vomiting were recorded during the operation.Apgar scores of 1min and 5min and blood gas analysis of umbilical cord blood were recorded.The number of adverse events including ventilation time and time to get out of bed,nausea,vomiting,dizziness,and headache were recorded.Results:A total of 245 women who underwent cesarean section under spinal anesthesia were enrolled.They were single pregnancy,aged 18-48 years,body mass index(BMI)20-40kg/m2,ASA grade I-II,gestational≥37 weeks.1、Incidence of hypotensionThe incidence of hypotension was 17.74%in the RH group,35.94%in the NRH group,16.95%in the RN group,and 15%in the NRN group.In the R group,there was no statistical difference between the RH group and the RN group in the incidence of hypotension after spinal anesthesia(P>0.05).In the NR group,the incidence of hypotension after spinal anesthesia was significantly lower in the NRN group compared with the NRH group(P<0.05).2、Comparison of MAP and HRIn R group,there was no statistically significant difference between groups in MAP at each time point in the RH and RN groups(P>0.05).In the NR group,MAP was significantly higher in the NRN group than in the NRH group at T2,T3,T4(P<0.05).In the comparison of the magnitude of maternal MAP changes in the four groups,the NRN group had the smallest MAP change amplitude and smoother fluctuations compared to the remaining three groups(P<0.05).There was no significant difference between the groups in HR among the four groups at each time point(P>0.05).In the comparison of the magnitude of HR changes in the four groups,the norepinephrine group showed smaller HR changes and smoother fluctuations compared to the rehydration group(P<0.05).3、Intraoperative adverse maternal eventsThere were no significant differences in the occurrence of intraoperative adverse events such as reactive hypertension,bradycardia,tachycardia,and chest tightness among the four groups(P>0.05).The incidence of intraoperative nausea and vomiting was significantly different among the four groups(P<0.05),and the incidence of intraoperative nausea and vomiting in the NRH group was significantly higher than the other three groups(P<0.05).4、Neonatal outcomes and maternal outcomesThere was no significant difference in the basic indexes of blood gas analysis of neonatal cord blood between the four groups(P>0.05),including PH,lac,BE,HCO3-,GLU,Apgarl min,and Apgar5 min.There were no significant differences in the incidence of ventilation time,time to get out of bed,postoperative nausea,postoperative vomiting,postoperative dizziness,and postoperative headache among the four groups(P>0.05).Conclusion:For women with volume-responsive caesarean section,preoperative prophylactic colloidal expansion can effectively prevent hypotension after spinal anesthesia.Pregnant women with preoperative prophylactic norepinephrine infusion for caesarean section,with or without volume responsiveness,are effective in preventing hypotension after spinal anesthesia.Preoperative prophylactic colloidal expansion or prophylactic norepinephrine infusion to prevent the occurrence of hypotension after spinal anesthesia did not have significant adverse effects on maternal and neonatal outcomes.