Vertebral column length and spread of hyperbaric subarachnoid bupivacaine in the term parturient

Patient height is considered an important determinant of the dose of spinal anesthesia. However, the relationship between body height and the level of sensory anesthesia with a fixed dose of spinal anesthetic has not been clearly documented. Recent evidence suggests no correlation between height or weight of parturients and spread of spinal anesthesia. Vertebral column length rather than body height may be more important in determining anesthetic spread. We studied the correlation between vertebral length measured from C7 to the level of the iliac crest (IC) and to the sacral hiatus (SH) and the sensory anesthetic level after the subarachnoid administration of 12 mg hyperbaric bupivacaine in term pregnant patients. There was no correlation between patient height, weight or body mass index and sensory anesthesia level. However, a significant correlation existed between vertebral length measured from C7 to IC (r = 0.32, p = 0.025) or to SH (r = 0.38, p = 0.006) and the level of anesthesia.