Comparison between transtracheal and intravenous 2% lignocaine in attenuating hemodynamic stress response following direct laryngoscopy and endotracheal intubation

Patients undergoing general anesthesia are required to be intubated for the purpose of maintaining a patent airway and mechanical ventilation. Direct laryngoscopy and endotracheal intubation are associated with increased sympathetic and adrenomedullary catecholamine activity resulting in a surge in heart rate and blood pressure. In the vulnerable group of patients, this sudden rise though for a brief period may cause adverse events like arrhythmias, myocardial infarction, cardiac failure, intracerebral hemorrhage, and raised intracranial pressure.

Over the years various methods have been in use to attenuate hemodynamic stress response during laryngoscopy and intubation. Lignocaine is one such agent which has been proven to be effective in the attenuation of a hemodynamic surge in response to laryngoscopy and endotracheal intubation. It has been used as an oral topical viscous solution, aerosolized/nebulized solution, laryngotracheal spray, and intravenous (IV) injection and found to be effective in previous studies.

During awake fiberoptic intubation, transtracheal application of lignocaine is routinely practiced to facilitate intubation. This topical application anesthetizes the infraglottic larynx and upper trachea and facilitates the prevention of hemodynamic surge during awake intubation. Though common during awake fiberoptic intubation, their use in post-induction endotracheal intubation has not been documented.

Disadvantages with oral topical viscous solution are additional preoperative preparation time, decreased effectiveness when oral secretions are present, and patient acceptance of oral anesthesia. Aerosolization with lignocaine is not routinely practiced as it often causes patient discomfort due to nebulization itself and the feeling of throat heaviness happens as anesthesia develops. It also requires extra preparation time. During laryngotracheal spray, after induction of general anesthesia, under direct vision with a standard Macintosh laryngoscope lignocaine is sprayed 2 minutes prior to intubation to allow its adequate effect to come. It requires lighter airway manipulation for this purpose prior to the actual intubation.

In our institute intravenous 2% lignocaine, 1.5mg/kg 3 minutes prior to endotracheal intubation is often administered to attenuate the hemodynamic response of laryngoscopy and intubation. The attenuating effect of intravenous lignocaine has been attributed to the arteriolar vasodilatation [10], blunting of the autonomic response, cough suppression, and increased depth of general anesthesia. In this study, we will administer transtracheal 2% lignocaine, 1.5 mg/kg following induction of general anesthesia and 3 minutes prior to endotracheal intubation. Transtracheal lignocaine causes reversible blockade of nerve fiber impulse propagation hence anesthetizes infraglottic laryngeal and upper tracheal mucosa.

As it will be performed following induction of general anesthesia it will cause no patient discomfort. It will not require any preoperative preparation and it will not involve any airway manipulation. Potential complications of transtracheal injection include subcutaneous and intratracheal bleeding, infection, subcutaneous emphysema, pneumomediastinum, pneumothorax, vocal cord trauma, and esophageal perforation. But these complications are rare, which was illustrated by a review of 17,500 cases of translaryngeal puncture that documented an incidence of complications of less than 0.01%. In our study, we hypothesize that post-induction transtracheal 2% lignocaine, 1.5 mg/kg will produce a similar effect as intravenous 2% lignocaine, 1.5 mg/kg and can be used as an alternative to attenuate the hemodynamic stress response of laryngoscopy and endotracheal intubation.