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<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<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<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<0.05) We conclude that magnesium sulfate attenuates the catecholamine mediated responses after tracheal intubation.