HYPOBARIC SPINAL-ANESTHESIA WITH BUPIVACAINE (0.1-PERCENT) GIVES SELECTIVE SENSORY BLOCK FOR ANORECTAL SURGERY

Twenty adult male patients undergoing anorectal surgery in the jackkni fe position under spinal anaesthesia were studied for the anaesthetic properties of 5 ml hypobaric 0.1% bupivacaine. The patients were posit ioned in the prone, jack-knife position with a pillow under the hips a nd with an operating table break angulation of 30 degrees with head do wn tilt of 20 degrees. In this position a 25-gauge Qincke spinal needl e was inserted intrathecally through L(3-4) and 5 ml solution, prepare d by mixing 1 ml bupivacaine 0.5% with 4 ml of distilled water with a specific gravity of 1.001 at 20 degrees C, was given over 15-20 sec. O nset time, progression and upper level of sensory blockade evaluated b y pin prick, and the extent of motor block (I full motor movement al a nkle and knee joint, 2 = restricted motor movements, 3 = full motor bl ock, no movements) were measured at one minute intervals for the first five minutes, then every five minutes for 30 min. The number of derma tomes blocked was also noted. The median level of cephalad sensory blo ckage was of L(1), with a range from T-10-L(3). On average, nine derma tomes were blocked (range 7-12). Motor blockade was not observed in an y patient. Changes in heart rate and blood pressure were minimal. The average duration of postoperative analgesia was 339.5 +/- 182.9 min. P ost-spinal headache was not observed in any patients. In conclusion, 5 ml intrathecal hypobaric bupivacaine, 0.1%, provided excellent periop erative analgesia without motor blockade and haemodynamic stability in patients undergoing anorectal surgery in jackknife position.