Hormonal and metabolic responses of controlled hypotensive anaesthesia for functional endoscopic sinus surgery: A comparison between magnesium sulfate and nitroglycerin

Abstract

Hypotensive anaesthesia is essential during functional endoscopic sinus surgery (FESS) for better visualization of the surgical field. In a prospective, randomized, double-blind study, we compared the hormonal and metabolic changes that evoked during FESS performed under general anaesthesia with deliberate hypotensive technique using either magnesium sulfate or nitroglycerin. Sixty patients aged 18-50 years, scheduled for FESS under general anaesthesia were enrolled. After induction of anaesthesia, patients were randomized to receive a slow loading dose of either magnesium sulfate 30 mg/ kg, followed by continuous infusion of 10-30 mg /kg/h (Magnesium group; n= 30), or saline followed by infusion of nitroglycerin 1-3 µg/ kg/min (Nitroglycerin group; n= 30), to maintain mean arterial pressure between 60-65 mmHg throughout the surgery. Perioperative serum cortisol, blood glucose, triiodothyronine (T3), thyroxine (T4), serum uric acid and fibrinogen concentrations were measured. Postoperative pain and sedation scores were also measured. Patients in nitroglycerin group had statistically higher cortisol level compared to magnesium group, and higher glucose level at the postoperative hour , with no significant difference in T3, T4, uric acid and fibrinogen levels .There was no difference in the levels of serum cortisol, blood glucose, T3, T4, serum uric acid and fibrinogen between pre- and 24 hour postoperative assessments in both groups .Pain scores were significantly lower in magnesium group till 90 min postoperatively with higher sedation scores. In this study, Induced hypotension and proper quality of the operative field had been achieved effectively by both magnesium sulfate and nitroglycerin administration during FESS performed under general anaesthesia represented by remarkable decrease in MAP during the surgery. However, the patients treated with magnesium had a more favorable postoperative course regarding attenuation of the surgical stress response estimated by observed lower levels of cortisol and glucose postoperatively and improvement of postoperative analgesia detected by lower pain scores recorded postoperatively, observed lower analgesics consumption and remarkable reduction of the time needed for the first analgesic demand.