Intravenous magnesium sulfate inhibits catecholamine release associated with tracheal intubation.

The effects of pre-treatment with 60 mg/kg body weight magnesium sulfate intravenous on cardiovascular responses and catecholamine release associated with tracheal intubation were measured in 15 normal patients and in 15 saline solution pre-treated controls. Magnesium pre-treatment increased heart rate by 13 +/- 3.9 beats/minute. After intubation, heart rate was unchanged in the magnesium group at 107.3 +/- 3.6 beats/minute but increased in the control group to 120.9 +/- 4.6 beats/minute (P less than 0.05). Systolic blood pressure increased after intubation from 106.8 +/- 3.1 to 121.0 +/- 4.4 mm Hg in patients given magnesium and from 106.4 +/- 3.12 to 145.1 +/- 5.6 mm Hg in the control group (P less than 0.05). Norepinephrine levels increased from 297.3 +/- 20.9 pg/ml to a peak of 532.5 +/- 30.1 pg/ml 2 minutes after intubation in the magnesium group. In controls, norepinephrine levels increased from 273.3 +/- 39.1 mg/ml to 944.6 +/- 68.7 pg/ml (P less than 0.05 for differences between groups). Epinephrine levels were unchanged from baseline after magnesium but in controls increased from 113.9 +/- 19.5 to 279.6 +/- 92.3 pg/ml (P less than 0.05). We conclude that magnesium sulfate attenuates the catecholamine mediated responses after tracheal intubation.