الفهرس 
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Abstract
Laryngoscopy and intubation are associated with cardiovascular changes such as hypertension, tachycardia, dysrhythmias and even myocardial ischemia, as well as increased circulating catecholamines and may lead to cerebral hemorrhage.
Endotracheal intubation is one of the most invasive stimuli in anesthesia, particularly during induction and after tracheal intubation. It is usually well tolerated by normotensive patients, but even short-lasting stimulation has been associated with increased morbidity and mortality in patients with recent myocardial infarction, hypertension, pre-eclampsia, and cerebro-vascular pathology such as tumors, aneurysms or increased intracranial pressure.
Several techniques have been proposed to prevent or attenuate the hemodynamic responses following laryngoscopy and intubation, such as deepening of anesthesia, omitting cholinergic premedication, pretreatment with vasodilators such as nitroglycerin, beta-blockers, calcium channel blockers and opioids.
Melatonin is secreted by the pineal gland in a circadian fashion at night. The use of exogenous melatonin is widespread in the general public. Melatonin use is reported to be greater than the consumption of vitamin C tablets. Melatonin has been linked to improved sleep, prevention of jet lag, enhanced immune response, antioxidant actions, and prevention of tumor growth. In addition, data suggests that melatonin affects cardiovascular function. Melatonin has been reported to reduce arterial blood pressure in normal and hypertensive rats.
Several studies reported that melatonin has analgesic potential in addition to anxiolytic and sedative effects without disturbances of the cognitive and psychomotor skills, and thus improves the quality of recovery.
In this study, the effect of melatonin as a premedication on the stress response to laryngoscopy and endotracheal intubation was measured.
In our study Patients were randomly allocated according to computer-generated randomization into 3 groups each group consists of 30 patients of ASA physical status I & II of both sexes scheduled for any elective surgery under general anesthesia with endotracheal intubation. Exclusion criteria were refusal of participation in the study, history of hypersensitivity to any used drug or drug abuse, presence of other associated problems that may cause pain preoperative. In addition, patients with expected difficult intubation or Raynaud’s disease, sickle cell anemia, chronic pain syndromes, depression or schizophrenia, epilepsy, leukemia, autoimmune disease, diabetes, those who used any analgesic or sedative 24 hours before surgery, or breast-feeding women were also excluded.
Group I patients’ age rangd between ”18-39”, males represented 46.6% while females represented 53.4% of the group size. Group II patients’ age ranged between ”18-38”. Males represented 46.6% while females represented 53.4% of the group size. Group III patients’ age ranged between ”18-39”. Males represented 50% while females represented 50% of the group size.
Evaluation of the patients was carried out through proper history taking and clinical examination- routine laboratory investigations including; CBC, FBS, renal function test, liver enzymes, hemostatic profile. History of difficult intubation in previous operations was recorded and considered.
The first group which was considered the control group received placebo 1 hour prior the operation. The second and third group received 6 mg and 9 mg melatonin 1 hour prior the operation consecutively.
Primary outcome measures include; HR, SBP, DBP, MBP and perfusion index were recorded before drug premedication, pre-induction, pre-intubation, 1, 2, 3, 5 and 10 minutes after laryngoscopy and intubation. Moreover perioperative anxiety was evaluated by recording the preoperative and postoperative verbal anxiety score (VAS) of the sample patients.
In the present study, the baseline “before premedication” value of mean SBP, DBP and MBP significantly decreased following the administration of the melatonin 6 mg or 9 mg one hour prior to surgery. In addition, it further decreased significantly after the induction of anesthesia. Besides, although these values increased significantly at 1, 2 and 3 minutes following endotracheal intubation compared to the “pre-intubation” value, it did not increase significantly mostly more than the “before premedication” value following endotracheal intubation as in the control group. However, the arterial blood pressure values were significantly lower in the 6 mg melatonin and 9 mg melatonin groups than in the control group at “before intubation” period as well as mostly from 1 minute interval till 10 minutes period following endotracheal intubation. Nonetheless, only at 1 minute period following intubation, the SBP, DBP and MBP values were significantly lower in the 9 mg melatonin group compared to the 6 mg melatonin group.
As regard the heart rate changes, there were no significant differences between the mean values of HR in the three groups at the “before premedication”, “before induction” and “before intubation” periods. However, the HR values were transiently lower in the 6 mg melatonin and 9 mg melatonin groups than in the control group only at 1 minute period following endotracheal intubation. Otherwise, no significant differences were detected between the three groups at other time intervals.
In the current study, the PI increased significantly after the induction of anesthesia. Furthermore, the PI values decreased significantly at 1, 2 and 3 minutes following endotracheal intubation compared to the “pre-intubation” value in all groups. However, the PI values were significantly higher in the 9 mg melatonin and 6 mg melatonin groups than in the control group at the “before induction” period. In addition, the PI values were significantly higher in the 6 mg melatonin and 9 mg melatonin groups than in the control group at 1 minute interval thereafter following endotracheal intubation. Nonetheless, at 1, 3, 5 and minutes periods following intubation, the PI values significantly increased in the 9 mg melatonin group compared to the 6 mg melatonin group.
Lastly, there was a significant decrease in the anxiety scores in the patients who received 6 mg and 9 mg melatonin tablets relative to the placebo group. Moreover, the anxiety scores were significantly lower in those who received 9 mg melatonin tablets compared to those who received 6 mg melatonin tablets.
Our study proved that preoperative administration of melatonin one hour before surgery provided a significant clinical benefit, by decreasing stress response of direct laryngoscopy and tracheal intubation as regard to blood pressure. Moreover it showed that preoperative melatonin has a significant anxiolytic effect for patients undergoing surgery.