Intra-abdominal pressure, vertebral column length, and spread of spinal anesthesia in parturients undergoing cesarean section: An observational study

BACKGROUND: In parturients with increased physiologically intra-abdominal pressure (IAP) and a short stature, a greater cephalad spread of spinal anesthesia is often observed after a fixed amount of plain bupivacaine is administered. Therefore, we designed this prospective study to test whether IAP and vertebral column length (VCL) were predictors of spinal spread in parturients undergoing a cesarean section. METHODS: A total of 113 parturients, all undergoing elective cesarean sections with single-shot spinal anesthesia, were enrolled. The L3-L4 interspace was entered, and 2 mL of 0.5% plain bupivacaine was injected into the subarachnoid space. Upon loss of temperature sensation at the T4 level, IAP was measured through a bladder catheter while the patient was in the supine position with a 10°left lateral tilt. Parturient demographic variables, including age, height, weight, IAP, and VCL were recorded. Linear regressions and multiple regressions were performed to analyze the relationships between parturient variables and the spread of spinal anesthesia. RESULTS: A total of 109 parturients were included in the analysis. Linear regression analysis showed a significant univariate correlation of height, weight, body mass index (BMI), IAP, and VCL with cephalad spread (all P< 0.004). Multiple linear regression analysis showed that IAP and VCL were the key determinants of spinal spread (both P < 0.0001), where as exclusion of age, weight, and height did not change the result (all P> 0.209). CONCLUSIONS: Our data indicated that IAP and VCL were significant predictors of intrathecal spread of plain bupivacaine, and there was a positive association between IAP and abdominal girth in term parturients.