RESUMEN
This study was carried out on 39 patients undergoing day-case surgeries to evaluate the efficacy for the selection of a proper dose of fentanyl. They were randomly divided to three groups: Group I injected intrathecally with 5 ml of 0.125% bupivacaine; in group II, 10 mug fentanyl was added to the solution and in group III, 20 mug fentany1 was added to the solution. The highest level of block was T7, T8 and T8 in group I, II and III, respectively. The time to highest level of block was 11, 10 and 10 minutes, respectively. A small dose diluted bupivacaine was inadequate and the addition of 10 mug fentanyl made it reliable. With 20 mug fentanyl, there was no more improvement in the quality of anesthesia, but there was an increase in the time to discharge and the percentage of the side effects of fentanyl