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Background: The co-administration of intrathecal ketamine and bupivacaine resulted in a substantial improvement in the time elapsed before the initial request for analgesics. A range of doses, spanning from 0.05 to 0.7 mg/kg, has been utilized in previous studies. We aimed to compare three doses to ascertain the optimal dosage that delivers the most effective pain relief while minimizing potential side effects.Methods: One hundred and five patients aged 18-70 years, with a body mass index (BMI) of 20-30 kg/m2 and planned for knee arthroscopy were randomly allocated to receive intrathecal heavy bupivacaine 0.5% in addition to intrathecal ketamine at a dose of either 0.1 mg/kg (n = 35), 0.2 mg/kg (n = 35), or 0.3 mg/kg (n = 35). Our primary outcome was the time elapsed to first rescue analgesia.Results: All groups exhibited comparable time intervals until the first rescue analgesic was requested (11.4 ± 3.99 vs 11.2 ± 4.65 vs 11.63 ± 5.11, p = 0.93). The groups examined also demonstrated similar numeric rating scale (NRS) scores during the 6th, 12th, and 24th postoperative hours. However, a statistically significant difference was observed among the groups regarding the incidence of confusion and dizziness (p = 0.001), with a higher occurrence in the 0.2 and 0.3 mg groups compared to the 0.1 mg group.Conclusion: Based on our findings, it can be inferred that an intrathecal ketamine dose of 0.1 mg/kg exhibits analgesic efficacy comparable to higher doses while having the fewest side effects
Abbas et al. (Mon,) studied this question.