The effect of anthropometric characteristics on the spread of hyperbaric bupivacaine spinal anaesthesia in patients undergoing lower abdominal or lower extremity surgery.

Background:Several factors have been described to effect the spread of spinal anesthesia. Clinical sense says that patients with a larger hip size and a narrow shoulder size have a relative trendelenburg position on a horizontal operation table that results in more cephalad spread of the hyperbaric local anesthetic solution although there is no clinical study reporting the effect of hip/shoulder size ratio on the spread of spinal anesthesia.We hypothesized that the increase in cephalad spread is strongly correlated with the increased hip/shoulder size ratio. Methods: Age, weight, height, body mass index, hip size, shoulder size, hip/shoulder size ratio, vertebral column length were recorded for 75 patients. The L4-L5 interspace was introduced at lateral position on a horizontal operation table with a 25G spinal needle and 3ml 0.5% hyperbaric bupivacaine was injected intrathecal in 15 seconds without barbotage and patient was turned supine 5 minutes after intrathecal injection. Pearson and Sperman’sRho Correlation Tests were performed for the relation between age, height, weight, body mass index, hip size, hip/shoulder size ratio, shoulder size and vertebral column length and the multiple regression analysis was used to test the combined contribution of the above variables on cephalad spread of spinal anesthesia. Results:We determined a positive correlation with hip/shoulder size ratio (r = 0, 40; p = 0,002), and a negative correlation with the height (r= -0, 29; p=0,026), and the shoulder size (r= -0, 31; p= 0,017) of the patients with the cephalad spread ofspinal anesthesia. Multiple regression analysis showed that hip size and the hip/shoulder size ratio were the important determinants for the cephalad spread of spinal anesthesia and the other variables had no effect. Conclusions: The cephalad spread of spinal anesthesia with a fixed dose of hyperbaric bupivacaine is affected by the ratio of hip/shoulder size, shoulder size and the height of the patient. Vertebral column length has no effect on spinal anesthesia spread.