Ketamine versus magnesium sulphate as an adjuvant to local anesthetics in the peribulbar block for posterior segment surgeries: a randomized controlled study.

Background: The use of an adjuvant to local anesthetics in the peribulbar block may improve block characteristics. The aim of this double-blinded, parallel-group, randomized, controlled trial was to evaluate the safety and efficacy of ketamine versus magnesium sulphate as adjuvants to the local anesthetic mixture of peribulbar block in patients scheduled for vitreoretinal surgeries.

Methods: A total of 126 patients scheduled for vitreoretinal surgery were randomly allocated as either ketamine (GK, N.=42), magnesium sulphate (GM, N.=42), or control (GC, N.=42) groups. The primary outcomes were the onset and duration of globe akinesia, duration of lid akinesia, and onset of sensory block. Secondary outcomes included time to start surgery, duration of analgesia, intraocular pressure, and patient and surgeon satisfaction.

Results: The use of either ketamine or magnesium significantly shortened the onset of globe akinesia, enhanced the onset of sensory block, prolonged the duration of globe and lid akinesia, minimized the time required to start surgery, and increased the total analgesic time. The effect of magnesium was significantly more pronounced on durations of globe and lid akinesia as well as analgesia, whereas ketamine significantly shortened the time required to start surgery. Both patient and surgeon satisfaction were significantly improved with the use of either drug.

Conclusions: In vitreoretinal surgeries the use of either ketamine or magnesium sulphate as adjuvants to the local anesthetic mixture of peribulbar block improved the onset, duration, and quality of the block, offered better patient and surgeon satisfaction, and was not associated with drug adverse effects or surgical complications.