Magnesium Sulphate, Lidocaine or Nitroglycerin for Controlled Hypotension and Quality of the Surgical Field in Patients Undergoing Tympanoplasty

Background: Intraoperative bleeding impairs surgical field visibility during tympanoplasty; several methods have been used to decrease blood loss and improve the quality of the surgical field, one of them is usage of hypotensive anesthetic agents.
Objective: This study aimed to compare the effect of magnesium sulphate, lidocaine or nitroglycerin  for controlled hypotension on hemodynamics, quality of the surgical field and blood loss  in patients undergoing tympanoplasty.
Patients and methods: A prospective double blind randomized clinical study included 45 patients of both genders, ASA I&II undergoing  tympanoplasty were allocated into Three groups ( 15 patients each )  group (M) received magnesium sulphate by giving loading dose 40 mg/kg then the maintenance dose 15 mg/kg/hr, group (L) received lidocaine by giving  an infusion dose of 2 mg/kg/hr and group (N) received nitroglycerin by giving  an infusion dose of 5-10 μg/kg/min. For each group ( mean arterial blood pressure "MABP", heart rate "HR", quality of the surgical field, total IV fluids given, total blood loss, intraoperative complications, duration of the surgery and the extubation time) were recorded.
Results: The studied doses of the drugs achieved the target mean arterial pressure (50–65 mmHg) with superior hemodynamic stability in the lidocaine group. Group L showed a statistically significant decrease in blood loss (p < 0.05) , a statistically significant better quality of the surgical field (p < 0.05) and a statistically significant less complications (p < 0.05) compared to the other studied groups.
Conclusion: It was showed that using any of these three drugs can be effective for controlled hypotension in patients undergoing tympanoplasty but lidocaine has the priority for the achieving stablility of the hemodynamics, the best quality of the surgical field and the least blood loss.