Laryngoscopy and endotracheal intubation are considered potent noxious stimuli which provoke haemodynamic responses leading to a marked increase in heart rate and blood pressure. These events are especially detrimental in individuals who have limited myocardial reserve due to coronary artery disease, cardiac dysrhythmias, congestive heart failure, hypertension, cardiomyopathy and in the geriatric age group. Hence, it is mandatory to take measures to attenuate these pressor responses.
The mechanisms of these haemodynamic alterations are reflexes due to sympathetic stimulation. During intubation of trachea, the laryngeal and tracheal sensory receptors are stimulated which result in the release of endogenous catecholamines resulting in tachycardia and hypertension. Since the invention of laryngoscopy and endotracheal intubation, various drug regimens and techniques have been used from time to time to attenuate these stress responses. Some of these agents being opioids (fentanyl, alfentanil), calcium channel blockers (verapamil, diltiazem), sympatholytics (clonidine, dexmedetomidine and methyldopa), beta blockers (esmolol, propranolol), benzodiazepines (midazolam, alprazolam), barbiturates, propofol, pregabalin and peripheral vasodilators (sodium nitroprusside, nitroglycerine). However, each agent has its own limitations such as respiratory depression with opioids and benzodiazepines, hypotension and bradycardia with sympatholytics and beta blockers and so on. Hence, there is always been a search for a ideal agent.
Melatonin (Nacetyl5methoxytryptamine) is an endogenous sleepregulating hormone secreted by pineal gland. Exogenous administration of melatonin facilitates sleep onset and improves the quality of sleep. It is different from benzodiazepines and their derivatives in that it produces natural sleep pattern and does not lead to impairment of cognitive functions. Various researchers have used this drug in different dose patterns as premedication in both adults as well as children. Based on this we hypothesised that melatonin when given before the procedure can provide haemodynamic stability during laryngoscopy and intubation. The primary objective is to assess the efficacy of melatonin to attenuate the changes in blood pressure to laryngoscopy and intubation.
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