A comparative study between magnesium sulphate and dexmedetomidine for deliberate hypotension during middle ear surgery

Background
This study was designed to compare magnesium sulphate with dexmedetomidine, regarding their efficiency in inducing deliberate hypotension and providing a better surgical field exposure during middle ear surgery. It also compared the influence of their use on postoperative pain and recovery time.
Methods
Eighty-eight adult patients undergoing middle ear surgery were included. Patients were randomly divided into two equal groups. Patients were assigned to receive either magnesium sulphate (M group) or dexmedetomidine (D group). Anaesthesia was induced by propofol 2 mg/kg iv and fentanyl 1 μg/kg. Patients in the M group received an iv bolus of magnesium sulphate 50 mg/kg in a total of 100 ml saline over 10 min followed by infusion of 15 mg/kg/h until the end of surgery. Similarly, patients in the D group received dexmedetomidine 1 μg/kg over 10 min followed by 0.4–0.8 μg/kg/h until the end of operation. The target MAP during operation was between 60 and 70 mmHg. The surgeon who was blinded of the selected hypotensive agent was asked to assess the quality of the surgical field. In the postanaesthesia care unit (PACU), postoperative pain was assessed and recovery time was recorded.
Results
Both study drugs succeeded to reach the target MAP. The quality of the surgical field was not different between the two groups. Postoperative pain was not different between the two group and only eight patients in the M group and seven patients in the D group required analgesics. Recovery time was significantly longer for the patients in group D ( < 0.05).
Conclusion
We concluded that both magnesium sulphate and dexmedetomidine successfully induced deliberate hypotension in patients undergoing middle ear surgery but magnesium sulphate was associated with shorter recovery time and earlier discharge from the PACU.