Thesis (M.Sc)--Chulalongkorn University, 2010

Objective: To determine effect of noise block using earplugs on reducing propofol infusion needed to maintain a constant bispectral index (BIS) values in patients undergoing extracorporeal shock wave lithotripsy (ESWL). Design: Randomized double- blinded controlled trial. Material and method: Fifty-eight patients (18-65 years) with nephrolithiasis undergoing ESWL, having ASA physical status I or II and have normal hearing function tested by audiometry were enrolled in this randomized, double-blind, controlled trial. Patients were randomized and allocated into two groups: noise blocked group (earplugs inserted into both ears) and control group (earplugs not inserted). Sedation by target-controlled infusion was started with 1.2 mcg/mL of propofol and propofol target concentration was adjusted gradually by 0.2 mcg/ml every 5 minutes intraoperatively to achieve and maintain bispectral index (BIS) values within 75-80% until the procedure finished. Total amount of propofol (mg), BIS values (%), ambient noise level (dB) and patient satisfaction (1-5) were measured. Results: The amount of propofol infusion needed to maintain a constant BIS index value in patients undergoing ESWL in the noise blocked group was significantly lower than that in the control group (6.91+2.05 vs 8.23+2.16 mg/kg/m2/hr, p=0.021, 95%CI=0.21-2.42).Patient satisfaction was similar in both groups (4[1] vs 4[1], p=0.929). Conclusion: Noise elimination in ambient operating room can reduce the amount of propofol needed to maintain light sedation during ESWL.