Epinephrine to Prevent Postintubation Collapse in Shocked ICU Patients

patients will receive epinephrine prepared as 10 ml syringe filled with 10 ml of epinephrine 10 mcg/ml. prepared by drawing 1ml epinephrine 1mg ampule into 9 ml saline then discarding 9 ml and adding another 9 ml saline. now the investigators have 10 ml of epinephrine 10 mcg/ ml (1:100,000), then 10 µg will be given intravenously every 2-minute starting before intubation and continue during and after intubation for 4 times or until the systolic blood pressure (SBP) will be at least 90 mmHg or the mean arterial pressure (MAP) 65 mmHg or greater or after 4th dose of epinephrine and still hypotensive vasopressor (norepinephrine 30 ng /kg/min.) will be added or increased.

patients will receive IV bolus isotonic fluid 500 ml