Comparative efficacy of different routes of administration of lignocaine on hemodynamic stress response during endotracheal intubation- a prospective randomized controlled trial

Airway management is a cornerstone of safe anesthetic practice.Among the techniques employed, direct laryngoscopy and endotracheal intubation remain the gold standard for securing the airway during general anesthesia.However, despite its widespread use and clinical effectiveness, this procedure stimulates a sympathetic response.The underlying mechanism is the intense nociceptive stimulation of the upper airway, including the pharynx, larynx, and trachea.This leads to activation of the sympathoadrenal axis, resulting in tachycardia, hypertension, increased intracranial and intraocular pressures and elevated myocardial oxygen demand, especially concerning in patients with underlying comorbidities such as ischemic heart disease or cerebrovascular disorders.The hemodynamic changes associated with laryngoscopy and intubation occur rapidly—within 5 seconds of laryngoscopy, peaking at around 1–2 minutes, and typically resolving within 5 minutes. During this period, however, substantial physiological disturbances may occur.Studies have reported that heart rate can increase by 20–25 beats per minute, blood pressure by as much as 50– 55 mmHg, and left ventricular ejection fraction may transiently fall by up to 20%.

Over the years, multiple pharmacologic interventions have been employed to reduce the pressor response associated with intubation.These include opioids (e.g, fentanyl, alfentanil, remifentanil), vasodilators (e.g. nitroglycerine, nifedipine), beta-blockers (e.g, esmolol, labetalol), centrally acting alpha-2 agonists (e.g., clonidine, dexmedetomidine), magnesium sulphate, gabapentin, and local anesthetics such as lignocaine.Among these, lignocaine stands out due to its versatility, low cost, wide safety margin, and multiple routes of administration.Lignocaine acts by blocking voltage-gated sodium channels in neuronal membranes, thus inhibiting the initiation and propagation of nerve impulses.Lignocaine can be administered through three primary routes for airway anesthesia: Intravenous (IV): Systemically administered lignocaine has been shown to blunt sympathetic responses and reduce intraoperative awareness, but it has minimal local anesthetic effect on the airway mucosa. Nebulization (4%): This non-invasive technique distributes lignocaine aerosol throughout the airway, including the oropharynx, larynx, and proximal trachea, providing widespread mucosal anesthesia. Topical spray (10%): Offers rapid onset and localized anesthesia, typically applied to the posterior pharyngeal wall and laryngeal inlet. It is highly effective for short-term suppression of airway reflexes but may have limited reach in deeper structures.

In the current study, we aim to evaluate and compare the efficacy of three commonly used methods of lignocaine administration—2% intravenous lignocaine, 4% nebulized lignocaine, and 10% topical lignocaine spray—in suppressing airway reflexes and mitigating hemodynamic responses during endotracheal intubation