Comparison of STOP-BANG and BERLIN questionnaire in the prediction of overweight and obese patients developing desaturation during induction of general anaesthesia

Following approval from the Institutional Ethical Committee, informed consent will be taken from 100 patients satisfying the inclusion criteria will be allocated by Randomization using shuffled Sealed Envelope Technique. Patients will be allotted into 2 groups namely Group 1 (assessed by the Berlin Questionnaire) and Group 2 (assessed by the STOP-BANG Questionnaire).

Total number of patients 100, with 50 patients in each group.

1. Group 1 (n=50) : screened by the Berlin Questionnaire

2. Group 2 (n=50) : screened by the STOP-BANG Questionnaire

All patients will be admitted before the surgery and pre anaesthetic evaluation will be done. Fasting of 6 hours for solids and 2 hours for clear liquids will be ensured.

After obtaining written informed consent, patients between the ages of 18 years up to the age of 60 years belonging to ASA grade of I–II of either gender, with BMI greater than or equal to 25 posted for elective surgery under general endotracheal anaesthesia will be included in the study. Patients less than the age of 18 years or greater than 60 years, belonging to ASA grades III and above, having BMI less than 25, undergoing emergency surgeries, with contraindications to any of the general anaesthetics or muscle relaxants (such as succinylcholine), allergy to anaesthetics, already diagnosed cases of OSA who are on treatment (such as CPAP) will be excluded from the study.

On the day of surgery Intravenous (IV) access will be secured. In the operation theatre standard monitoring devices will be attached, including noninvasive arterial blood pressure, ECG and peripheral oxygen saturation probe using the GE Medical Systems Information Technologies, Inc. B125M Patient Monitor. Baseline readings will be recorded.

With the patient in supine position, patients will be appropriately premedicated with premedicants Inj. Ondansetron (4mg), Inj. Midazolam (1mg), Inj. Glycopyrrolate (0.2mg) and Inj. Fentanyl (1mcg/kg body wt). Patients from both the groups will be preoxygenated for three minutes with 100% oxygen, using closed circuit keeping total fresh gas flow at 10 litres. After this, patients will be administered 1.5mg/kg/body weight of IV lidocaine (preservative free), followed by induction with 1% Propofol 2 mg/kg, till there is loss of eye lash reflexes.

After trial ventilation and assessing for demonstrable bag and mask ventilation, depolarising muscle relaxant Inj. Succinylcholine 1.5 mg/Kg is administered for facilitating laryngoscopy & intubation. If bag and mask ventilation was difficult, patients were excluded from the study. Upon induction bag and mask ventilation is withdrawn briefly. Airway is maintained by triple manoeuvre (Head tilt, chin lift and jaw thrust).

Thereafter, the investigator will assess and record the time taken for the oxygen saturation to reach upto 93%. Intraoperative and postoperative desaturation events and other airway complications will also be observed and documented. (SpO2 cut-off: upto 93% in Room Air via peripheral oxygen saturation i.e., pulse oximetry).

The parameters assessed will be -

1. Desaturation onset time : Desaturation onset time will be considered after induction (loss of eyelash reflex) as the time taken from the administration of Succinylcholine till the first sign of fall in saturation from maximum saturation.

2. Period of desaturation : Period of desaturation will be considered after induction (loss of eyelash reflex) and administration of succinylcholine as the time taken for the saturation to drop to 93% on RA from the desaturation onset time.

3. Difficult Airway Events : Difficulty airway events including use of advanced airway, number of intubation attempts, need for reintubation after extubation and airway trauma.

Bag and mask ventilation will be resumed immediately followed by endotracheal intubation with mechanical ventilation. The peripheral oxygen saturation will be recorded heart rate and arterial pressure will be recorded at 0 and then at 3min intervals for the first 15 mins and then every 10 mins till end of surgery.

Hypotension (20% or more decrease in mean arterial blood pressure [MAP] from the baseline value) will be treated with boluses of IV Mephentermine (6 mg) and crystalloid infusion until the normotensive state is achieved. Bradycardia (20% or more decrease in heart rate [HR] from the baseline value) will be treated with 0.6 mg IV atropine.

On extubation, patient will be observed for any desaturation (SpO2 less than 92% on Room Air). Patient will be observed for any desaturation and will be managed with O2 mask and or side effects such as nausea and vomiting in the post operative period.