Spinal anaesthesia with glucose-free 2% lignocaine. Effect of different volumes

Spinal anaesthesia with 2, 3 or 4 ml of glucose-free 2% lignocaine was studied in 64 patients undergoing transurethral surgery of the bladder. Cephalad spread of analgesia, onset time, duration of analgesia, duration of motor block, quality of analgesia, and the cardiovascular effects were assessed. Two ml of 2% lignocaine was insufficient to produce reliable analgesia. Three ml provided sufficient analgesia in most of the patients, but 4 ml was needed to guarantee sufficient analgesia in all patients. Onset times for analgesia and motor block were 10-20 min. After 4 ml the median and interquartile values were: maximum cephalad spread: T8, (T10-T5); time from injection to regression of analgesia to T11: 84 min, (60-103 min); duration of complete motor block: 90 min, (60-120 min). All patients in the 3-ml and 4-ml groups developed complete motor block. There was a positive correlation between the dose and the duration of analgesia and motor block. A positive correlation, although weaker, was also seen between the dose and the maximum cephalad spread of analgesia. There was an inverse relationship between the cephalad spread of analgesia and the duration of motor block. Falls in systolic blood pressure greater than 30% were noted in seven patients in whom the cephalad spread of analgesia was higher than in the rest of the patients. Spinal anaesthesia with glucose-free 2% lignocaine in doses of 3-4 ml provides reliable analgesia for transurethral surgery of the bladder.