Anatomical Dimensions of the Lumbar Dural Sac Predict the Sensory Block Level of Continuous Epidural Analgesia during Labor

Abstract

Background: The anatomical dimensions of the lumbar dural sac determine the sensory block level of spinal anesthesia; however, whether they show the same predictive value during continuous epidural anesthesia (CEA) remains undetermined. We designed the present study to verify the efficacy of the anatomical dimensions of the lumbar dural sac in predicting the sensory block level during labor analgesia. Methods: A total of 122 parturients with singleton pregnancies requesting labor analgesia were included in this study. The lumbar dural sac diameter (DSD), lumbar dural sac length (DSL), lumbar dural sac surface area (DSA) , and lumbar dural sac volume (DSV) were measured with an ultrasound color Doppler diagnostic apparatus. CEA was performed at the L2-L3 interspace. After epidural cannulation, an electronic infusion pump containing 0.08% ropivacaine and sufentanil 0.4 µg/ml was connected. The sensory block level was determined with alcohol-soaked cotton, a cotton swab, and a pinprick. The analgesic efficacy of CEA was determined with a visual analog scale (VAS). Divided the parturients into two groups: "ideal analgesia" and "non-ideal analgesia", and compared the groups by t test. Pearson's correlation was performed to evaluate the association between the anatomical dimensions of the lumbar dural sac and sensory block level. Multiple linear regression analysis was used to create a model for predicting the sensory block level. Results: In the "ideal analgesia" group, the height, DSL, DSA, DSV and DSD were significantly smaller, and the BMI was significantly larger (P<0.05) (Table 1). In addition, the DSL demonstrated the strongest correlation with the peak level of pain block (r=-0.816, P<0.0001; Figure 2A), temperature block (r=-0.874, P<0.0001; Figure 3A) and tactile block (r=-0.727, P<0.0001; Figure 4A). Finally, multiple linear regression analysis revealed that the DSL and BMI contributed to predicting the peak sensory block level. Conclusion: In conclusion, our study shows that the sensory block level of CEA is higher when the DSL, DSA, DSV and DSD of puerpera are lower. The DSL and BMI can be treated as predictors of the peak sensory block level in CEA during labor analgesia.