EFFECT OF LATE POSTURE CHANGE ON THE LEVEL OF SPINAL ANAESTHESIA WITH PLAIN BUPIVACAINE

We studied 40 patients, 18–60 yr, undergoing orthopaedicsurgery of the lower limb under spinal anaesthesia. A midilnelumbar puncture was performed in the L3–4 interspace usinga 27-gaugeneedle with the patient in the lateral horizontalposition. Plain bupivacaine 3 ml at room temperature was injected.The cephalad level of an algesia was assessed by pinprick 60min after injection of local anaesthetic, at the end of surgeryand again after the patient was moved into bed. All patientshad a segmental level of the block of L1-T5 at the beginningof the study. The upper half of the patient's body was thentilted to a 30° head-up position. Segmental spread was subsequentlyassessed by pinprick at 5-min intervals for 30 min. In six ofthe 40 patients (15%), increased cephalad spread of spinal analgesiaoccurred. The mean time from induction of spinal anaesthesiawas shorter in these six patients (mean 92 min, range 80–115min) than in the patients whose block did not change or wasdecreasing during the 30-min test (mean 119 mm, range 83–210min) (P <0.05). We conclude that the patient should remainin the supine horizontal position until recovery from the spinalblock. (Br. J. Anaesth. 1993; 71: 807–809)