KNEE-CHEST VS HORIZONTAL SIDE POSITION DURING INDUCTION OF SPINAL-ANESTHESIA IN PATIENTS UNDERGOING LUMBAR DISC SURGERY

In the prone knee-chest position the spread of plain 0.5% bupivacaine in the cerebrospinal fluid and associated haemodynamic changes may be different compared with the horizontal position. A randomized comparis on was performed in 40 ASA I-II patients, aged 24-61 yr, undergoing lu mbar disc surgery. Subarachnoid injection (27-gauge needle) at the L2- 3 interspace with 3 ml of 0.5% bupivacaine was performed with the pati ent in the operative knee-chest position (prone knee-chest group, n=20 ) or in the horizontal side position (supine side horizontal group, n= 20). Patients in the supine side horizontal group were turned into the horizontal supine position for 20 min, and subsequently they were pla ced in the operative knee-chest position. In three patients in the pro ne knee-chest group, the spinal needle was replaced by a larger needle (25-gauge). The final cephalad extension of sensory analgesia on skin tested by pinprick was T5 (median) in the prone knee-chest group and T6 in the supine side horizontal group. Recovery was also similar, on average 210 min from injection in both groups. The mean decrease in sy stolic arterial pressure was somewhat greater in the prone knee-chest group (30 mm Hg) than in the supine side horizontal group (13 mm Hg). The need for ephedrine occurred earlier in the supine side horizontal group (three patients, all within 10 min from local anaesthetic inject ion) than in the prone knee-chest group (six patients, all after 15 mi n). Four of the latter patients also required administration of an ant icholinergic for bradycardia compared with two patients in the supine side horizontal group. Light sedation was given to five patients in th e prone knee-chest group and to four in the supine side horizontal gro up because of numbness and aching in the shoulders. We conclude that s pinal block was similar in the two groups but there was a tendency to more frequent episodes of haemodynamic deterioration in the knee-chest position.