Efficacy of preoperative oral midodrine as a prophylaxis against post induction hypotension in patients undergoing elective surgery under general anaesthesia

Post induction hypotension is defined as arterial hypotension which occurred within 20mins of anaesthesia induction or from anaesthesia induction till the beginning of surgical incision. Worldwide the incidence of post GA induction hypotension increased upto 66%. Hypotension was defined as either MAP decrease of >40% and MAP <70mmHg or MAP<60mmHg. Propofol causes hypotension by decreasing peripheral vascular resistance. Intraoperative hypotension compromises vital organ perfusion which consequently increase the risk of kidney injury, brain ischemia, cardiac ischemia and postop ICU admission. During this post induction hypotension alpha adrenoceptor agonist, such as ephedrine, phenylephrine and norepinephrine are used. In this study oral midodrine will be used as prophylaxis against post induction hypotension . Midodrine hydrochloride is another alpha Adrenoceptor agonist which has the advantage of being an oral drug with minimal CNS side effect and good oral bioavailability. Midodrine is a prodrug, metabolized to Desglymidodrine[DGM] by the process called deglycination. This DGM act on alpha 1 receptors in the arteriolar and venous system cause constriction of vessels. In this study we aimed to evaluate the incidence of post GA induction hypotension after preoperative medication with oral midodrine 5mg [60 min before Sx].

The study aims to evaluate the incidence of post induction hypotension with general anaesthesia after preoperative oral midodrine. Patients with hypertension, DM, cardiac issues, kidney and liver problems, pheochromocytoma , thyrotoxicosis will be excluded. We would randomize the patient 90 mins before procedure to receive either 5mg midodrine[group A] or placebo[group B].60 mins before the procedure we would ask the patient to take midodrine or placebo. After induction MAP & HR would be monitored every 2 mins for 20 mins after induction.