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

We studied 40 patients, 18-60 yr, undergoing orthopaedic surgery of th e lower limb under spinal anaesthesia. A midline lumbar puncture was p erformed in the L3-4 interspace using a 27-gauge needle with the patie nt in the lateral horizontal position. Plain bupivacaine 3 ml at room temperature was injected. The cephalad level of analgesia was assessed by pinprick 60 min after injection of local anaesthetic, at the end o f surgery and again after the patient was moved into bed. All patients had a segmental level of the block of L1-T5 at the beginning of the s tudy. The upper half of the patient's body was then tilted to a 30-deg rees head-up position. Segmental spread was subsequently assessed by p inprick at 5-min intervals for 30 min. In six of the 40 patients (15%) , increased cephalad spread of spinal analgesia occurred. The mean tim e from induction of spinal anaesthesia was shorter in these six patien ts (mean 92 min, range 80-115 min) than in the patients whose block di d not change or was decreasing during the 30-min test (mean 119 min, r ange 83-210 min) (P < 0.05). We conclude that the patient should remai n in the supine horizontal position until recovery from the spinal blo ck.