OBJECTIVE: The addition of opioids to local anesthetics in spinal anesthesia modulates some aspects of anesthesia and analgesia. We evaluate the effect of adding different doses of intrathecal and subcutaneous sufentanil on propofol requirements for sedation during spinal anesthesia. MATERIAL AND METHODS: Prospective clinical trial randomizing patients undergoing knee arthroscopy to 4 groups. Group 1 received 12.5 mg of 0.75% hyperbaric bupivacaine (HBB); Group 2, 12.5 mg of HBB plus 2.5 microg of intrathecal sufentanil; Group 3, 12.5 mg of HBB plus 5 microg of intrathecal sufentanil; and Group 4, 12.5 mg of HBB plus 5 microg of subcutaneous sufentanil. When spinal anesthesia had been induced, a bispectral index (BIS) monitor was connected and baseline values were recorded for each patient. Sedation was then initiated with propofol at a dose of 2.5 microg/ml, using an effect-site target-controlled infusion system to maintain a BIS value between 60 and 75. BIS, vital signs, total propofol dose (TPD), mean infusion dose (MID), and awakening time were recorded. RESULTS: One hundred patients were included in the study. MID and TPD were lower in Groups 2 and 3 than in Groups 1 and 4 (P = .009). Consumption of propofol was 35.23% less in Group 2 and 37.50% less in Group 3 than in Group 1 (P = .001). CONCLUSIONS: The addition of 2.5 microg or 5 microg of intrathecal sufentanil to HBB reduces MID, TPD, and consumption of propofol in patients undergoing spinal anesthesia; the addition of 5 microg of subcutaneous sufentanil does not produce this effect.