A Randomised Controlled Trial to Compare Etomidate and Propofol for Induction of General Anesthesia in Adults

Introduction: Anaesthetic induction techniques are based on haemodynamic stability, rapid clearance, minimal intubation stress response respiratory side effects and ease of administration. Etomidate and Propofol are rapid acting and safe induction agents however both drugs have different induction characteristics.Aim of this study was to compare haemodynamic parameters, myoclonus, pain on injection and other side effects during induction of anaesthesia with Propofol and Etomidate. Method: Single centered, double blinded, prospective randomised study done on 100 ASA grade I and II patients of age group 18-60 years scheduled for elective surgeries requiring general anesthesia. Patients were randomly divided into two groups of 50 each, group P and group E, receiving Propofol (2 mg/kg,) and Etomidate (0.3 mg/kg) respectively as an induction agent. Haemodynamic parameters, myoclonus and pain on injection at induction were recorded for comparison. Quantitative data were analysed using student’s t test with help of INDOSTAT software. p and t values were obtained. P values less than 0.05 were considered significant. Results: Both groups were comparable in terms of demographic and baseline haemodynamic characteristics. The fall in MAP at times T2 (one min post induction) and T3 (three min post induction) was much sharper and significant for Propofol group (12.50 and 18.57 mm of Hg respectively) as compared to Etomidate group (3.82 and 6.26 mm of Hg respectively), p values 0.004 and 0.001 respectively. The stimulus of laryngoscopy and intubation (time T4) failed to bring the MAP above baseline levels in Propofol group (8.33 mm of Hg below baseline) while in Etomidate group there was 3.62 mm of Hg rise in MAP above baseline after laryngoscopy( p value 0.001). Myoclonus was graded as mild in 22%, moderate in 10% and severe in 2% patients in Etomidate group. Myoclonus was not observed with Propofol. Incidence of pain on injection was 4% in Etomidate group and 34% in Propofol group. Conclusion – Etomidate is a better alternative to Propofol as an induction agent because of haemodynamic stability and less pain on injection. However, use of appropriate premedications is required for decreasing incidence and severity of myoclonus with Etomidate. Key wordsAnesthesia, Anesthesiology, Anesthetics, Intravenous, Etomidate. Hemodynamics, Humans, Intubation, Myoclonus, Pain, Propofol, Prospective Studies. Indian Journal of Basic and Applied Medical Research; December 2016: Vol.-6, Issue1, P. 769-777 769 www.ijbamr.com P ISSN: 2250-284X , E ISSN : 2250-2858 Introduction: An ideal induction agent for general anaesthesia should have haemodynamic stability, minimal respiratory side effects, minimal intubation stress response and rapid clearance. Over years there has been a continuous search for better and safer intravenous agent. Presently Etomidate and Propofol are popular, rapid acting and safe induction agent however these two drugs have different induction characteristics. Propofol is one of the most commonly used drug, has rapid onset, satisfactory recovery, short halflife and rapid elimination from the blood circulation. The most important side-effect of this drug is haemodynamic instability. Propofol causes reduction of heart's preload and after load, which are not synchronized with compensatory responses and would be intensified by high doses and high speed injection of the drug. Propofol decreases blood pressure, cardiac output and systemic vascular resistance due to inhibition of sympathetic vasoconstriction and impairment of baroreceptor reflex. These effects may be exaggerated in hypovolemic and elderly patients with compromised left ventricular function. Induction of anaesthesia with Propofol is frequently associated with apnoea in both adult and paediatric patients. A major problem with the use of Propofol is high incidence of pain on injection, though reduced by adding lignocaine to Propofol solution, still the incidence remain unacceptably high. [3] Haemodynamic stability of Etomidate is unique among the rapid onset induction agents. Stability of cardiovascular function suggests lack of effect on sympathetic nervous system and baroreceptor reflex regulatory system. It also does not have significant effect either on the peripheral and pulmonary vascular bed or on myocardium itself. Therefore Etomidate is most appropriate in patients with cardiovascular compromise particularly with poor left ventricular function as it does not cause hypotension. Etomidate is also preferred in patients with respiratory airway disease, [4] intracranial hypertension and in patients with shock. Common side effects of Etomidate are nausea and vomiting that may lead to aspiration in patients. Etomidate also induces spontaneous movement or myoclonic activity and can increase focal epileptogenic activity in patients with epilepsy. The incidence of myoclonus can be reduced by various agents including Benzodiazepines, Magnesium Sulphate, Rocuronium and Opioids. [5-8] Pain on injection is another side effect of the drug. [9] Pain on injection, venous irritation and haemolysis have been abolished by new fat emulsion of Etomidate, but the new solvent has not reduced the incidence of myoclonus after Etomidate injection. One of the most important, but rare side effect of this drug is the reversible inhibition of 11-betahydroxylase enzyme, causing reduction in serum cortisol level even after a single dose for upto twenty four hours [10] . Considering the common use of Propofol and Etomidate for induction of anaesthesia and the importance of patient’s haemodynamic stability during the surgery, this study was conducted with primary objective to compare the effects of these drugs for the induction of general anaesthesia with reference to haemodynamic parameters, myoclonus and pain at the site of injection while safety, recovery time and complications were the secondary objectives. Method: After approval by the Institute Ethical Committee., this study was carried out as a double–blind randomized prospective study on patients between the age group of 18 and 60 years belonging to