Risk prediction score for high spinal block in patients undergoing cesarean delivery: a retrospective cohort study

High spinal block is a serious complication of spinal anesthesia. However, findings regarding its associated risk factors are inconsistent, and no studies have reported a relevant risk prediction score. We aimed to determine the risk prediction score for high spinal block in patients who were induced spinal anesthesia for cesarean delivery.

This retrospective cohort study was conducted at a hospital in Southern Thailand between 2019 and 2020. We recorded demographic characteristics, gestational age (GA), hyperbaric bupivacaine dose, sensory block level, pre- and post-procedure blood pressure, and birth weight. High spinal block was defined as a decrease in pinprick sensation > T4. Risk scores, adjusted odds ratios (OR), and 95% confidence intervals (CI) were determined. Risk scores were derived from the coefficients of the final multivariate logistic regression model.

The incidence of high spinal block was 22.4% among the 1003 parturients. Our risk prediction tool for high spinal block had a sensitivity and specificity of 76% and 49%, respectively, and was classified into high (> 21), intermediate (15-21), and low (≤ 14) risk groups. The patient-related predictors were a GA < 35 weeks (OR [95% CI]: 2.31 [1.13, 4.71], score of 8), height < 150 cm (2.21 [1.11, 4.38], score of 8), and post-pregnancy body mass index > 27.5 kg/m² (2.68 [1.33, 5.41], score of 10). The anesthesia-related predictors were a hyperbaric bupivacaine dose > 11 mg (2.56 [1.34, 4.87], score of 9) and induction by a first-year resident (1.48 [1.05, 2.09], score of 4). The surgery-related predictors were previous cesarean delivery in labor (1.83 [1.2, 2.78], score of 6) and elective cesarean delivery (2.53 [1.57, 4.07], score of 9) compared to indication by cephalopelvic disproportion. The incidence of intraoperative hypotension was significantly higher in the high-block group than in the control group (46% vs. 25%, p < 0.001).

The combination of patient- and anesthesia-related predictors played an important role in the intermediate- and high-risk groups for high sensory spinal block. Addressing the modifiable risk factors-a GA < 35 weeks, an optimal dose of bupivacaine, and the experience level of the spinal block performer-could minimize the risk of high spinal block during cesarean delivery.