The effectiveness of low-dose intravenous ketamine on postoperative pain management in arthroscopic knee surgery under spinal anesthesia

Aims: This study aimed to determine the efficacy of intraoperative low-dose intravenous ketamine on postoperative analgesia in patients who were underwent arthroscopic knee surgery under spinal anesthesia.
Methods: Forty patients were equally classified as control and ketamine groups. In the ketamine group, 0.15 mg/kg intravenous ketamine was administered between 35-45. minutes of the surgery, whereas the patients in the control group received no medication. Postoperative pain was assessed using a visual analogue score. An analgesic, intravenous tramadol, was administered if the patients showed a value of at least 5 on the VAS. The need of first analgesic drug, the time to first analgesic drug administration, and additional (second and third) analgesic requirement during the postoperative period were compared between the groups.
Results: All patients in the control group and 8 (40%) patients in the ketamine group required first analgesic drug (p<0.001) postoperatively. The mean time to first analgesic drug administration was longer in the ketamine group (8.5 hours) than in the control group (4.2 hours) (p=0.008). Ten patients in the control group needed second analgesic drug whereas only one patient needed the second analgesic in the ketamine group. Third analgesic drug was required in three patients of the control group while none of the patients in the ketamine group needed third analgesic. For patient satisfaction, 11 (55%) patients marked “good” and 9 (45%) marked “very good” in the control group whereas all patients in the ketamine group marked “very good” (p<0.001).
Conclusion: Intraoperative subanesthetic dose IV ketamine prolongs the duration of postoperative analgesia and reduces the need for analgesics in elective arthroscopic knee surgery, with an acceptable side effect rates.

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