Hemodynamic response to endotracheal intubation with C-MAC® video laryngoscope versus C-MAC® video stylet in patients with controlled hypertension scheduled for elective surgery under general anesthesia -A randomized controlled trial

METHODOLOGY

The study will be conducted only after approval from the Institutional Ethical Committee (IEC) and will be registered with Clinical Trials Registry India (CTRI). A detailed pre-anesthetic check-up will be done for all patients. A written voluntary informed consent will be obtained for anaesthesia, surgery and participation in the study.

An anaesthesiologist with an experience of at least 20 successful endotracheal intubations with both the devices will perform the intubations. Patients will be randomised to one of the two groups: Group VL: Intubation using the C-MAC video laryngoscope

Group VS: Intubation using the C-MAC video stylet

Patients will be kept nil per oral (NPO) for 6 hours for solid foods, prior to surgery as per standard guidelines. Tablet alprazolam 0.25 mg will be given to all patients orally the night before surgery. Hypertensive patients shall receive the antihypertensive medication in the night before the surgery or on the morning of surgery as prescribed by the treating physician. After arrival in the operating room, an 18G or 20G peripheral intravenous catheter will be inserted.

Standard monitoring will be applied, including non-invasive blood pressure (NIBP), electrocardiograph (ECG) with heart rate (HR) and pulse oximetry (SpO2) and baseline parameters will be recorded. A venous blood sample shall be obtained pre induction for baseline serum cortisol levels estimation.

The appropriate device for intubation will be prepared.

In group VL, the endotracheal tube shall be loaded with a stylet shaped in a hockey stick fashion while in group VS, the appropriately sized endotracheal tube shall be loaded on the well lubricated C-MAC VS.

Patients will be pre-oxygenated with 100% oxygen via a facemask for 3 minutes and anaesthesia will be induced intravenously with slow administration of injection (inj.) fentanyl 2 µg/Kg and inj. propofol 2 mg/Kg. After confirming adequate mask ventilation, inj. rocuronium 0.6 mg/Kg will be administered for neuromuscular blockade. Intermittent positive pressure ventilation will be continued with oxygen in air and 2% sevoflurane for 3 minutes. A venous sample will be obtained to estimate the serum cortisol levels pre intubation (which will be considered as baseline). The neuromuscular blockade will be monitored by the loss of the train of four (TOF) stimulation of the peripheral nerve, and intubation with a weight appropriate cuffed endotracheal tube will be done when a fully relaxed status is achieved (TOF 0/4).

Group VL: The VL will be positioned in the midline of the mouth, and the tip guided under vision towards the base of the tongue, then under monitor view towards the vallecula, allowing visibility of the glottic opening. Subsequently, close to the blade edge, the endotracheal tube over stylet will be advanced under direct vision, taking care to maintain the tube tip visibility at all times. The endotracheal tube will be advanced over the stylet immediately in front of the arytenoid cartilages with the assistance of monitor guidance

Group VS: The video stylet will be inserted into the endotracheal tube, and the tracheal tube will be fixed at the upper end to prevent the lens from sticking out of the tracheal tube and avoid contamination of the lens with secretions. After 11–12 cm (at the level of the upper larynx), the lens will be aimed to the left and middle of the neck while the screen is observed to locate the glottic opening. If required a jaw-thrust technique will be employed to create a pharyngeal space for visualization of laryngeal structures. The endotracheal tube will be advanced into the trachea, the core will be pulled out, the video stylet will be withdrawn.

The cuff of the endotracheal tube will be slowly inflated with air so that there is no leak at a peak airway pressure of 20 cmH2O. Adequate ventilation will be confirmed by bilateral chest movements and capnographic waveforms.

The hemodynamic parameters such as HR, SBP, DBP will be recorded at following time intervals: baseline, immediately pre intubation and 1-, 3- and 5-minutes post intubation. Percentage of glottic opening (POGO) score-(100% is Visualisation of entire glottis from anterior commissure of vocal cords to arytenoids and 0% is No glottic opening visualised) will be recorded. Any OELM required for successful intubation and the number of patients requiring application of OELM will be recorded. Time taken for tracheal intubation will be measured (in seconds) as the time from introduction of intubating device into the mouth to till the appearance of first square wave capnograph. Any evidence of orodental trauma in terms of injury to lips, teeth, gums, and mucosa of the oropharynx shall be observed while withdrawing the device after the endotracheal intubation is achieved.

Failure of intubation shall be defined if more than three attempts are required to secure the airway. In such a situation, the airway will be secured as per the anesthesiologist discretion and the patient will be excluded from the study.

Second venous blood sample shall be collected for estimation of serum cortisol levels at 2 minutes post intubation in plain red capped vacutainer. Both the sample tubes collected at pre induction and 2 minutes post intubation will be labelled appropriately and sample will be sent to lab for further processing. After clot formation, sample will be centrifuged at 1500 rpm for 5 minutes. The separated serum will be pipetted in labelled aliquots for storing at -20 degrees in deep freeze. Batch analysis of samples will be performed on DXI 800 immunoassay analyzer using kit method for estimation of serum cortisol levels.

After successful intubation the patients’ lungs will be ventilated with a mixture of oxygen in air with sevoflurane maintaining a minimum alveolar concentration (MAC) of 1.0-1.2, with the patient on controlled mechanical ventilation to maintain normocarbia. Electrocardiograph with HR, NIBP, SpO2, end tidal carbon dioxide (EtCO2), end tidal anaesthetic gas concentration, MAC and temperature will be monitored for all patients throughout. In case of severe hemodynamic response, the plane of anaesthesia will be deepened by increasing the concentration of inhalational anaesthetic agent and if required injection propofol will be administered intravenously in small aliquots of 10-20mg, if the hemodynamic response does not settle, then inj. labetalol 20mg intravenous bolus shall be administered slowly. The patient would be subsequently handed over for surgery.

At the end of the surgery, anaesthesia will be terminated, neuromuscular blockade will be reversed and the patient’s trachea will be extubated. The patient will be then transferred to the post-anaesthesia care unit (PACU).

WHY IS THIS RESEARCH WORK NECESSARY?

This study aims to fill this gap by comparing the hemodynamic responses and change in serum cortisol levels elicited by VL and VS when used for endotracheal intubation in patients with well-controlled hypertension undergoing elective surgery. By identifying the technique that produces a lesser pressor response, our study may support safer airway management strategies in hypertensive patients, ultimately contributing to improved perioperative outcomes.