Clinical Study Of The Bracket For Preventing Supine Hypotension During Cesarean Section

Background and ObjectiveSupine hypotension syndrome is a common adverse reaction during cesarean section after anesthesia. Anesthesia causes blood vessels dilate and blood vessels reflux disorder of lower body blood vessels.Severe hypotension may lead to maternal nausea, vomiting and even loss of consciousness.Hypotension can cause rapid decline of the utero-placental blood flow with the rapid decline, exchange of impede the placenta blood gas and serious consequences of fetal hypoxia, acidosis even the central nervous system injury.Spinal anesthesia becomes more and more common in cesarean section surgery. However, the incidence of hypotension is usually 55%～90% during spinal anesthesia. At the present time, there are many kinds of methods for preventing maternal supine hypotension syndrome after spinal anesthesia, such as changing maternal posture, preload. However, these methods have poor results.Therefore, how to prevent hypotension in cesarean section surgery after spinal anesthesia is extremely important. The objective of this study is to analyze the effect of self-made bracket (Patent No. ZL 2007 2 0092454.1)for preventing supine hypotension syndrome on maternal hemodynamics and neonatal umbilical cord blood gas during cesarean section under spinal anesthesia, and therefore to evaluate the safety and the efficacy of self-made bracket.Materials and Methods1.SubjectsOne hundred and twenty ASAⅠorⅡpatients, aged 24-35 yr, weighting 52-80Kg,37-41 weeks of pregnant, singl pregnant, undergoing selective cesarean section with spinal anesthesia were randomly divided into 2 groups (n=60 each):bracket groups (groupⅠ),control group (groupⅡ).Exclusion criteria includ the following: multiple pregnancy, pregnancy complications, fetal abnormalities, cardiovascular and cerebrovascular diseases, diabetes, the weight of the newborn is less than 2.5 kg.2.AnesthesiaAll subjects were lying on the left-lateral position, punctured at L3～4 Subarachnoid space, given 0.75% bupivacaine 12.5mg. The operation began after the pregnant woman was satisfied with Anesthetic effect.20U oxytocin was given immediately after the fetus was partused. None of the sedative drug was used before parturient had the operation. All pragnat women were given oxygen with mask after they entered into the operation room. If the systolic blood pressure below 90mmHg or below 25% of the basal blood pressure 3～12mg of ephedrine was given intravenously.3.Blood sampleBefore the newborn breathe after he was delivered, a section of umbilical cord was clamped with two vascular clamp.Then 2ml of umbilical arterial blood and umbilical venous blood was extrcted with heparinized syringe and done blood gas analys immediately. PH value, partial pressure of oxygen (PO2), partial pressure of carbon dioxide(PCO2),bicarbonate ions(HCO3),and base excess(BE)value were analyzed.4. Monitoring indicators4.1 HemodynamicsThe hemodynamic change was consecutively monitored by the BioZ.com system. Hemodynamic parameters including systolic blood pressure(SBP), diastolic blood pressure (DBP), heart rate (HR), stroke volume (SV), cardiac output (CO), thoracic fluid content(TFC), cardiac acceleration Index (ACI), systemic vascular resistance (SVR)were recorded before (T1)and 1 minute (T2),3minutes(T3),5minutes (T4),10 minutes (T5) after anesthesia,1minute before (T6) and 3minutes(T7) after the cesarean section, and completion of the procedure (T8). Adverse reactions, the operation time, blood loss and liquid infusion were recorded. 4.2 umbilical cord blood gasPH, partial pressure of oxygen (PO2), partial pressure of carbon dioxide (PCO2), bicarbonate ions(HCO3),and base excess(BE)values of umbilical arterial and umbilical venous blood were recorded,1min Apgar score and 5min Apgar score of the newborns were recorded.5. Statistics AnalysisStatistical software package (SPSS13.0) was used for processing data, the numerical data variables expressed as mean±standard deviation. The factor within-subject was analysized with variance for repeated measures data.The factor between-subject was analysized with indenpent-samples t test. The count data was used Chi-square test.The statistical significance test criterion is a=0.05.Results1.GeneraL informationThere were no significant differences between two groups in age [(27.62±2.07) yr vs (27.27±2.19)yr],weight [(70.05±5.14) kg vs (70.83±3.90)kg],height[(159.27±3.35)cm vs(159.87±3.33)cm], gestational age [(38.90±0.90)w vs (39.02±0.81)w], time from anaesthesia to operation starting (6.58±1.00min vs 6.68±1.00min), time from operation starting to fetus parturition [(3.10±1.00)min vs (3.27±0.94)min], liquid infusion[(1215.00±114.35)ml vs(1239.17±82.90)ml],blood loss [(240.17±22.13)ml vs (245.33±20.02)ml],and operation time [(36.77±3.21)min vs (37.57±3.11) min] (P>0.05).2. Hemodynamics.There were no significant differences between two groups in heart rate (HR), thoracic fluid content (TFC) of the pregnant women at all tinme points (P>0.05). In the bracket group (groupⅠ)systolic blood pressure(SBP) was higher than that of the control group (groupⅡ)at 3 minutes,5 minutes after anesthesia, the difference was statistically significant (P<0.05). At 3 minutes(T3),5 minutes(T4) after anesthesia,3 minutes (T7) after the cesarean section, and completion of the procedure (T8), diastolic blood pressure(DBP) of the Bracket group was higher than that of the control group, the difference was statistically significant (P<0.05).At 3 minutes(T3), 5 minutes (T4), 10minutes (T5) after anesthesia,1 minute before (T6) cesarean delivery,3 minutes (T7) after cesarean delivery, and completion of the procedure (T8), stroke volume (SV) of the bracket group was higher than that of the control group, the difference was statistically significant (P<0.05).At 3 minutes(T3),5 minutes(T4), 10minutes(T5) after anesthesia,1 minute before (T6) cesarean delivery,3 minutes(T7) after cesarean delivery, cardiac output(CO)of the bracket group was higher than that of the control group, the difference was statistically significant (P<0.05). At 5 minutes(T4),10minutes (T5) after anesthesia, cardiac acceleration Index(ACI) of the bracket group was higher than that of the control group, the difference was statistically significant (P<0.05).At 10minutes(T5) after anesthesia,1 minute before (T6) cesarean delivery, systemic vascular resistance(SVR) of the bracket group was lower than that of the control group, the difference was statistically significant (P<0.05).3. Maternal adverse reactionsThere were 29 cases with hypotension in the control group, with the incidence of 49.3%.Compared with 6 cases with hypotension in the bracket group, with the incidence of 10.0%, difference between the two groups was statistically significant (P<0.05).10 puerperas had nausea and vomiting in the control group, with the incidence of 16.7%. However, none of the puerperas feels nausea or has vomiting in the bracket group. Difference between the two groups was statistically significant (P<0.05).The use of ephedrine in the control group (2.42±3.15mg) was more than that of the bracket group (0.37±1.15mg). Difference between two groups was statistically significant (P<0.05).4. Comparison of umbilical cord blood gasThere were no significant differences between two groups in PO2, PCO2, HCO3-of umbilical cord blood gas (P>0.05). Difference of PH, BE in umbilical arterial blood and umbilical veinblood, between two groups was statistically significant [(7.28±0.06vs7.24±0.08,(-4.05±2.50)mmol/ml vs(-5.03±2.00)mmol/ml,or 7.31±0.06 vs 7.28±0.08,(-4.73±1.93)mmol/ml vs(-5.57±1.75)mmol/ml)](P<0.05). 5.Neonatal acidosis and the Apgar scoreThere were 7 newborns with acidosis in the control group (PH<7.15), with the incidence of 11.7%, compared with no acidosis in bracket group, the difference has statistical significance (P<0.05).lmin Apgar score (9.60±0.62) min,5min Apgar score(10.00±0.00)min of the bracket group were higher than that of the control group[(8.58±1.64)min, (9.63±0.71 min)],difference between the two groups was statistically significant (P<0.05). the lmin Apgar scores of 13 newborns is less than 7, with the incidence of 21.7%. However, lmin Apgar scores of the all newborns is no less than 7 in bracket group. The difference was statistically significant (P<0.05).Conclusion1.The bracket is effective to prevent severe hypotension after spinal anesthesia.It can decrease the incidence of maternal hypotension significantly and can guarantee a stable maternal hemodynamics.2.The bracket can prevent neonatal acidosis, asphyxia, raise Apgar score and guarantee their safety.3.The bracket don't cause any injury on the pregnant women and fetus. It is simple and convenient to operate the bracket. It has no any impact on the operation.