Magnesium sulfate inhibits sufentanil-induced cough during anesthetic induction

Sufentanil-induced cough is a common phenomenon during the induction of anesthesia. This double-blind, randomized, and placebo-controlled study was designed to investigate the effects of prophylactic magnesium sulfate (MgSO4) on the incidence and severity of sufentanil-induced cough. A total of 165 patients who were scheduled for elective surgery under general anesthesia were allocated into three groups (I, II, and III; n = 55 each) that were injected with either 50 ml of normal saline, 30 or 50 mg/kg of MgSO4 (diluted with normal saline into 50 ml). One minute following the injection, all patients were injected with 1.0 μg/kg of sufentanil within 5 s. The incidence and severity of cough were recorded 30 s after the sufentanil injection. The hemodynamic parameters and plasma magnesium concentration of the patients were also noted. Three patients dropped out the study due to an obvious burning sensation during the injection of 50 mg/kg of MgSO4. Although the injection of 50 mg/kg of MgSO4 increased the plasma magnesium level, the increase remained within the therapeutic range (2-4 mmol/L). The incidence of cough was much higher in group I than in groups II and III (47.1% vs. 16.4% and 7.6%, respectively, P < 0.05). Compared with group I, group III had the lowest incidence of mild cough and both groups II and III had lower incidence of moderate and severe cough (P < 0.05). There were no differences in the hemodynamic data at three timepoints among the three groups. In conclusion, sufentanil-induced cough may be suppressed effectively and safely by prophylactic use of 30 mg/kg of MgSO4 during anesthetic induction.