Comparison of bispectral index guided propofol, etomidate and etofol infusion for supraglottic airway device insertion in paediatric patients: a randomised controlled trial

Propofol is the most common inducing agent for general anaesthesia. Propofol obtunds the airway reflexes and provides good conditions for airway management. However though titrated to effect, propofol causes hypotension and a decreased heart rate on induction. This hypotension and bradycardia may be pronounced in paediatric population, with a parasympathetic predominance. Etomidate, another inducing agent is known to provide a better haemodynamic stability compared to propofol. However, both propofol and etomidate cause pain on injection and myoclonus.

The aim of our study is to compare the haemodynamic stability between induction doses of propofol, etomidate and propofol-etomidate combination (titrated using bispectral index monitoring) in paediatric patients. We aim to see which drug provides the best conditions for insertion of supraglottic airway device (SAD)  with least side-effects. The primary objective of our study is to compare the change in the mean arterial pressure with propofol, etomidate and etofol to achieve BIS value of 50 for SAD insertion in paediatric patients aged 6 to 10 years. Our secondary objectives are 1. To determine the time taken to achieve BIS value of 50 2. Change in heart rate between the study groups 3. Other side effects of intravenous study drugs (such as myoclonus, pain on injection etc. 4. SAD related parameters (insertion summed score, number of attempts taken, time taken for insertion, additional study drug boluses required).

Institute ethics committee approval was sought for. A written informed consent/assent will be obtained from all patients. We conducted a pilot study to calculate the sample size.  Assuming the power as 90% at alpha error of 5 %, 44 patients will be recruited in each group. One hundred and thirty two patients with ASA physical status I/II scheduled for surgery under general anaesthesia aged between 6 to 10 years will be included in our study. The exclusion criteria are 1. Patients with anticipated difficult airway 2. Known allergy to study drugs 3. History of seizure disorder 4. Contraindications to the placement of SAD 5. Refusal to participate.

Patients will be randomly allocated into 3 groups based on computer generated random number table with group allocation using sealed opaque envelopes- Group P (Propofol), group E (Etomidate) and group EP (etofol i.e. etomidate and propofol). The patients and investigator will be blinded to the study groups. On the day of surgery, patients will be premedicated with midazolam in a dose of 20mcg/kg IV. In the operating room, after attaching standard ASA monitors and bispectral (BIS) index electrode, baseline vital parameters (heart rate, systolic blood pressure, diastolic blood pressure, mean arterial blood pressure and oxygen saturation on room air) will be recorded. All patients will receive fentanyl @ 1mcg/kg IV. The study drugs will be prepared in a 20ml syringe while will be injected using a infusion pump. Patient in group P and E will receive propofol (10mg/ml) and etomidate (2mg/ml) while the patient in group PE will receive the 1:1 combination of the propofol (10mg/ml) and etomidate (2mg/ml) at an infusion rate of 50 ml/hour. The infusion will continue will till BIS value of 50 is achieved thereafter the infusion will be stopped. Once a BIS value of 50 is attained, SAD of adequate size as per the weight of the patient will be inserted.

The haemodynamic parameters will be monitored at following time points namely the baseline parameters, after the induction of anaesthesia when BIS reaches 50,during placement of SAD, 1, 2 and 5 minutes after placement of SAD. A difference of more than 20% from the baseline will be considered significant. The other parameters observed will include: time to attain BIS of 50, pain during injection of study drugs using four-graded scale, Myoclonus severity (0-3), total number of attempts and time taken to successfully place SAD, insertion conditions terms of mouth opening, coughing, swallowing, movements, laryngospasm and ease of SAD insertion.