Backgroud：This study aims to discuss the risk factors to hypotension for caesarean parturients with scarred uterus when low dose of bupivacaine and sulfentanyl are used in spinal anesthesia. Methods：A total of 322 singleton-pregnancy parturients with scarred uterus who had been scheduled for caesarean spinal anesthesia were randomly sampled. The data about the basic information of the parturients, the gestation, the fetus and the anesthesia has been recorded and filed according to the clinical questionnaires about hypotension in caesarean section. The parturients whose systolic pressure drops below 90mmHG or decreases by 20% during the time from the completion of anesthesia until the delivery of infant were classified to be Group Hypotension (Group H) and the rest are in Group non-hypotension (Group N). This study analyzes the correlation of 39 factors to the occurrence of hypotension and then further analyzes the statistically significant factors through binary classification logistic regression.Results：Of the 322 sampled parturients, 148 parturients suffered hypotension. The incidence of hypotension in this study is 45.96%. The result of univariate analysis shows that the differences in the factors including height (p=0.005), post-pregnancy Body Mass Index (BMI) (p=0.00), weight gain in gestation (p=0.000), fundal height(p=0.047), fasting time (p=0.031), exercise history in gestation (p=0.006) and dermatomal level of analgesia (p=0.000) between two groups are statistically significant. The variables with statistical significance are analyzed by multivariate logistic regression model. The result shows that BMI in gestation (OR=1.146 95%, CI 1.041-1.262, p <0.05), weight gain in gestation (OR = 1.126 95%, CI 1.060-1.198, p <0.001), exercise history in gestation (OR = 0.399, 95% CI 0.205-0.778, p = 0.007), dermatomal level of analgesia (OR = 2.248, 95% CI 1.645-3.074, p <0.001) are risk factors to hypotension occurrence after caesarean spinal anesthesia for parturients with scarred uterus. Conclusion：The incidence of hypotension occurring after caesarean spinal anesthesia for parturients with scarred uterus is relatively high. Factors including post-pregnancy BMI, weight gain in gestation, exercise history in gestation and dermatomal level of analgesia after anesthesia are risk factors to hypotension occurring after caesarean spinal anesthesia for parturients with scarred uterus. The result plays an important role in predicting the occurrence of hypotension after spinal anesthesia by parturients with scarred uterus in clinic. Trial registration：Chinese Clinical Trial Registry(chiCTR-ROC-17011251)

Background：This study examined the risk factors for hypotension after caesarean spinal anesthesia with low dose of bupivacaine and sulfentanyl in parturients with scarred uterus. Methods：A total of 322 singleton-pregnancy parturients with scarred uterus who had been scheduled for caesarean spinal anesthesia were randomly sampled. The data on the basic information of the parturients, the gestation, the fetus and the anesthesia were recorded and filed according to the clinical questionnaires on hypotension in caesarean section. The parturients whose systolic blood pressure dropped below 90 mmHg or decreased by 20% during the time from the completion of anesthesia until the delivery of infant were classified as Group hypotension (Group H) and the rest were in Group non-hypotension (Group N). This study analyzed the correlation of 39 factors to the occurrence of hypotension, and further analyzed the statistically significant factors through binary classification logistic regression.Results：Of the 322 sampled parturients, 148 parturients suffered hypotension. The incidence of hypotension in this study was 45.96%. The result of univariate analysis showed statistically significant differences in the factors including height (p=0.005), post-pregnancy Body Mass Index (BMI) (p=0.00), fasting time (p=0.031),weight gain in gestation (p=0.000), fundal height (p=0.047), exercise history in gestation (p=0.006) and dermatomal level of analgesia (p=0.000) between the two groups. The variables with statistical significance were analyzed by multivariate logistic regression model. The result showed that BMI in gestation (OR=1.146, 95% CI 1.041-1.262, p <0.05), weight gain in gestation (OR = 1.126, 95% CI 1.060-1.198, p <0.001), exercise history in gestation (OR = 0.399, 95% CI 0.205-0.778, p = 0.007), and dermatomal level of analgesia (OR = 2.248, 95% CI 1.645-3.074, p <0.001) were risk factors for hypotension after caesarean spinal anesthesia in parturients with scarred uterus. Conclusion：The incidence of hypotension after caesarean spinal anesthesia in parturients with scarred uterus was relatively high. The post-pregnancy BMI, weight gain in gestation, exercise history in gestation and dermatomal level of analgesia after anesthesia were risk factors for hypotension after caesarean spinal anesthesia in parturients with scarred uterus. These findings play an important role in predicting the occurrence of hypotension after caesarean spinal anesthesia in parturients with scarred uterus. Trial registration：Chinese Clinical Trial Registry (chiCTR-ROC-17011251)