Postoperative analgesic efficacy of intrathecal Nalbuphine with Bupivacaine in

INTERVENTION: 0.5% hyperbaric bupivacaine 1.5‐2ml (7.5‐10 mg) mixed with Nalbuphine 0.3 mg intrathecal (intervention) intrathecal by anesthetist or anesthesia resident once only just before surgery (dose based on Gudaityte J, Marchertiene I, Pavalkis D, Saladzinskas Z, Tamelis A, Toker I. Minimal effective dose of spinal hyperbaric bupivacaine for adult anorectal surgery: a prospective, double‐blinded, randomized study: A‐362. European Journal of Anaesthesiology | EJA. 2005;22:96.)) CONDITION: Anaesthesiology ‐ Pain management Postoperative pain after anorectal surgery; ; Postoperative pain after anorectal surgery PRIMARY OUTCOME: postoperative pain score at rest [visual analogue scale 12 hours after administration of spinal anesthesia] postoperative pain score on motion [visual analogue scale 12 hours after administration of spinal anesthesia] SECONDARY OUTCOME: possible adverse effects from spinal Nalbuphine (composite outcome)[record possible signs and symptoms of adverse effects such as hypotension (systolic blood pressure < 90 mmHg or decrease more than 20% of baseline blood pressure), nausea and vomitting (score 0‐3 from none to severe), pruritus (score 0‐3 from none to severe), sedation score (Ramsay sedation scale from 1‐6), urinary retention (time to first spontaneous voiding, urinary retention symptoms and time when catheterization if occur) from medical records From administration of spinal anaesthesia to 24 hours after spinal anaesthesia] time to first analgesia required[record the first time that patient ask for other pain medication after spinal anesthesia (as hours) From administration of spinal anaesthesia to 24 hours after spinal anaesthesia] types and amount of analgesia required after spinal anesthesia[record type, amount and timing of analgesia require after spinal anesthesia from medical records From administration of spinal anaesthesia to 24 hours after spinal anaesthesia] INCLUSION CRITERIA: 1. patients under going elective anorectal surgery under spinal anesthesia at King Chulalongkorn Memorial Hospital age from 18 to 65 year old 2. American Society of Anesthesiologists Physical Status I to II 3. patients consented to participate in our research