Intravenous magnesium-fentanyl sedation versus midazolam-fentanyl sedation before local anesthesia for eye surgery: a comparative study

Background
Phacoemulsification operation is a common practice nowadays, and it is usually done under local anesthesia in elderly patients who have multiple comorbidities. Sedation is important in these patients to eliminate intraoperative anxiety and stress response. The aim of this study is to compare the effect of single dose of intravenous magnesium sulfate to a single dose of 2 mg midazolam in patients receiving local anesthesia to the eye for phacoemulsification operation as regards the sedative effect, cardiovascular and respiratory stability.
Method
In this study, 100 patients (American physical status II-III, 50–75 years) were randomized to receive either intravenous magnesium sulfate 20 mg/kg IV bolus together with 25 μg fentanyl (M group) or 2 mg midazolam together with 25 μg fentanyl IV bolus (D group) during cataract surgery performed under peribulbar block. The study groups were compared with respect to hemodynamic variables, perception of pain during local anesthetic injection by using a numeric rating scale, intraoperative Ramsay Sedation Score, incidence of intraoperative complications, and patient and surgeon satisfaction by using a numeric rating scale.
Results
Intraoperative mean heart rate, systolic and diastolic blood pressures, and respiratory rate were found to be lower in the M group, while arterial oxygen saturation was significantly higher. The level of sedation was also better in the M group. The midazolam group showed also adequate sedation; however, three patients were agitated. Patients in the M group were more satisfied with the procedure and did not experience pain during application of local anesthetic to the eye, whereas surgeons were equally satisfied with both types of sedation given.
Conclusions
This study demonstrates that both combinations of drugs were effective in providing adequate level of sedation. However, intravenous magnesium sulfate 20 mg/kg IV bolus, together with 25 μg fentanyl, decreased pain on injection and provided effective sedation without causing respiratory depression.