Effects of Magnesium Sulphate in Delibrated Hypotension for Mastoidectomy Surgery

BACKGROUND:
Deliberated hypotension and administration of vasoconstrictive drugs such as epinephrine during ear microsurgery are of the most important aids for reducing blood loss and improving the surgical field. One of the important challenges in selecting the appropriate method of deliberated hypotension is to easily reach to desired blood pressure and to have the least interaction to anesthetic drugs and the function of vital organs. This study aimed to assess the efficacy of magnesium sulphate for deliberated hypotension during ear microsurgery.

METHODS:
In this clinical trial, 55 patients candidate for mastoidectomy surgery, and aged 15-65 yrs, were randomly assigned to receive placebo (n=27) or magnesium sulphate (n=28) infuse 60 mg/Kg over 15 minute followed by a maintenance dose of 10 mg/Kg/h until 30 minutes prior to the end of surgery. Intra-operative bleeding, the surgery duration, surgeon satisfaction, serum magnesium level, recovery time, anesthetic drug requirements (atracurium-halothane), and vasodilator (TNG) were measured in both groups and then compared with independent t and Mann-Whitney statistical tests.

FINDINGS:
Patients receiving magnesium sulphate had less blood loss than controls (59.46±27.19 vs. 97.57±31.41 ml, respectively, p<0.01)). Serum magnesium levels were in the therapeutic range (3.1±0.78 meq/L). Patients had no significant arrhythmia, received lower doses of T.N.G (101.71±56.69 vs. 1107±450.45 µg)], and muscle relaxant (45.89±14.08 vs. (60.17±9.76 mg, respectively,p<0.01) but not significant difference in Halothane [(3.1±0.64 MAC/hr) vs. (3.45±0.6 MAC/hr)]. Also surgeon satisfaction was better in magnesium group (p<0.001). There were not statistically difference in surgical time [(155.71±27.27 min) vs. (157.50±33.62 min)] and recovery time [(44.64±7.92 min) vs. (45.71±8.99 min)] between two groups.

CONCLUSION:
Administration of intravenous magnesium sulphate as a hypotensive drug in mastoidectomy surgery may be effective in decreasing intra-operative bleeding, using atracurium and TNG drugs,however in spite of improvement of the surgeon satisfaction, it had no effect on reducing the duration of surgery and recovery time. Overall, its administration is recommended for deliberate hypotension is a feasible method in mastoidectomy surgery.

KEY WORDS:
Magnesium sulphate, deliberated hypotension, mastoidectomy surgery.