preoperative measurement of maternal abdominal circumference relates the initial sensory block level of spinal anesthesia for cesarean section: an observational study

Objective: Lumbosacral cerebrospinal fluid volume is decreased as the enlarging uterus compresses the inferior vena cava during pregnancy. A subsequent greater cephalad spread of sensory blockade is observed. Gravid uterus plays a crucial role in affecting the spinal anesthesia level. We hypothesized that maternal abdominal circumference can reflect compressive effect of the uterus and investigated the relationship between abdominal circumference and the level of sensory blockade, and incidence of hypotension following spinal anesthesia with hyperbaric bupivacaine in term parturients. Materials and Methods: Forty-two term parturients scheduled for elective cesarean section were studied. Abdominal circumference was measured before spinal anesthesia; 0.5% hyperbaric bupivacaine (2 mL, 2.2 mL, or 2.4 mL) was injected in to the subarachnoid space at the L3–L4 intervertebral level according to the parturient's height. The level of sensory blockade was assessed using an ice cube 1 minute, 5 minutes, 10 minutes, and 15 minutes after the spinal injection. The level of sensory blockade at the 15th minute was defined as the level of maximum sensory blockade. Statistical correlation coefficients were evaluated with Spearman's rank correlation. Results: The correlation coefficient between the abdominal circumference and spinal level measured by cold sensation loss at 5 minutes after spinal anesthesia was significantly positive (right side ρ=0.43, p=0.005; left side ρ=0.46, p=0.003). No significant correlation was found between abdominal circumference and the level of maximum sensory blockade, the incidence of hypotension, ephedrine dosage, nausea, and vomiting after spinal anesthesia. Conclusion: Parturients with greater abdominal circumference value have a higher level of sensory blockade at 5 minutes after spinal anesthesia. Abdominal circumference cannot predict the maximum sensory blockade level and the incidence of hypotension.