This prospective randomized, double blinded control study was done in a tertiary medical college hospital from August 2012 to August 2013 after getting institutional ethical committee approval. The patients were kept informed of the study and consent was obtained. Sixty patients undergoing elective surgical procedures under general anaesthesia with endotracheal intubation were selected for the study.

Inclusion Criteria: ASA Physical status I and II patients in the age group of 18 to 60, weighing between 50 to 100 kg and with airway of Modified Mallampati Grade I and II were included in the study.

Exclusion Criteria: The patients with hypertension, ischemic heart disease, pregnancy, full stomach and emergency surgery were excluded from the study. Patients with ASA Physical status III and above, suspected difficult airway and modified Mallampatti Grade III and IV were also excluded from the study. Patients who had Cormack Lahane score III and above and also those in which duration of laryngoscopy lasted more than 25 seconds were also removed from the study.

All the patients were assessed preoperatively and premedicated with Alprazolam 0.5mg orally on the night before and 2 hours before surgery. In preoperative room baseline parameters were observed and documented. A good intravenous access was secured and all patients were pre-hydrated with 500ml of Ringer’s lactate. Now patients were randomly divided by computer into two groups. Group A received 1 mcg/kg of Inj. Dexmedetomidine in 100 ml of normal saline over 10 minutes and 5ml of normal saline 3 minutes before induction. Group B received 100 ml of normal saline over 10 minutes and Inj. Fentanyl 2 mcg/kg diluted in 5 ml of normal saline 3 minutes before induction. These solutions of 100 ml and 5 ml were prepared by first anaesthesiologist and labeled them as group A and B accordingly. The second anaesthesiologist, who was not aware of the groups, administered the drug and monitored the patients recording vital parameters. The laryngoscopy and intubation were performed by the third anaesthesiologist who was also blinded to the drug given. If the patient develops any complications then it was planned to stop drug infusions immediately and treat complications accordingly. After preoxygenation patients were induced with Inj. Propofol in a dose of 2.5 mg/kg body weight over 30 seconds to all patients in both groups and followed by Inj. Vecuronium 0.1mg/kg body weight after confirming a lack of response to voice and a loss of the eyelid reflex. Patients were ventilated with 50% nitrous oxide and Sevoflurane 1% for 3 minutes. Endotracheal intubation was performed by an experienced anaesthesiologist with the appropriate size cuffed endotracheal tube. Anaesthesia was maintained with controlled ventilation with nitrous oxide 66% and oxygen 33% with Sevoflurane 1.6%. No surgical stimulation was allowed for 10 minutes after intubation.

The heart rate, systolic blood pressure and diastolic blood pressure were monitored before induction, after study drug, during laryngoscopy and intubation and thereafter for succeeding ten minutes at an interval of one minute and any complications noted. Results were tabulated. The data obtained were analysed statistically. Statistical analysis was carried out using student’s t-test and chi-square test. Demographic Data was analysed using students t-test and chi-square test was applied whenever there was a statistically significant difference between two different sets of data for each variable. Power analysis was perf ormed using SPSS version 15 for windows and for effective sample size on the basis of haemodynamic differences. The information collected regarding all the cases were recorded in master chart. The Mean, Standard Deviation, X², ‘P’ values were calculated. A p-value less than 0.05 was taken to denote significant relationship.

The demographic data were comparable in both the groups and are given in [Table/Fig-1]. There was no significant difference in basal heart rate and blood pressure and is given in [Table/Fig-2,3]. In dexmedetomidine group, the mean heart rate decreased after the administration of study drug and did not rise much beyond basal levels during or after intubation. In fentanyl group, the mean heart rate decreased after the administration of the study drug but it increased significantly beyond the basal values following intubation. The mean heart rate returned to basal levels only after 2 minutes but still it remained higher than the dexmedetomidine group. Only one patient developed bradycardia in the dexmedetomidine group which responded well to atropine. The variations in heart rate in both the groups are given in [Table/Fig-2,4]. The mean blood pressure decreased after dexmedetomidine infusion and after intubation, it did not increase beyond the basal levels. In fentanyl group though there was a slight reduction in blood pressure after drug administration blood pressure increased after intubation and returned to basal values after 1-2 minutes. The variations in blood pressure are given in [Table/Fig-2,3,5].

[Table/Fig-4]:

Changes in heart rate

[Table/Fig-5]:

Changes in blood pressure

The sympathomimetic stress response to laryngoscopy and intubation results in an increase in the myocardial oxygen demand and may lead to ischemia and acute heart failure in susceptible individuals. Hypertension and tachycardia during laryngoscopy can occur even in normotensive individuals and is rather surprising that complications have not been met very often probably because of its transient nature. Though numerous drugs have been tried to obtund haemodynamic response, none of them are totally satisfactory.

An advantage with dexmedetomidine is its ability to provide a dose dependent sedation allowing it to be useful for cooperative sedation in remote locations. Because of its pharmacological profile, dexmedetomidine can be used as an anaesthetic adjuvant and also for intensive care unit sedation [13]. Fentanyl acts on the opioid receptors, mainly μ receptors, for its analgesic action. Because of its ability to reduce sympathetic outflow, it brings about haemodynamic stability. Fentanyl is used routinely as part of general anaesthesia in a dose of 2 mcg/kg and this dose is effective for stress attenuation when given five minutes before laryngoscopy [14].

In the present study, heart rate was significantly decreased in the dexmedetomidine group when compared to fentanyl group immediately after study drug and there was statistically significant reduction in heart rate for up to 10 min after intubation in the dexmedetomidine group. In fentanyl group, heart rate increased following laryngoscopy and endotracheal intubation and returned back to normal only after 3 minutes. The attenuation in systolic, diastolic and mean arterial pressure was significantly better in the dexmedetomidine group than the fentanyl group. This finding was also observed by Laha et al., and Bloor et al., [7,19,20]. In dexmedetomidine group, systolic and diastolic blood pressure did not rise significantly following laryngoscopy and endotracheal intubation. With dexmedetomidine, mean systolic and diastolic blood pressure returned to baseline value within 1 minute after intubation, whereas in fentanyl group it was 2 minutes.

Laha et al., studied the effects of preinduction loading dose of dexmedetomidine 1 mcg/kg on attenuation of sympathoadrenal responses and requirements of anaesthetic agents [7]. They concluded that administration of dexmedetomidine not only attenuates the rise in mean heart rate, systolic blood pressure after intubation at 1, 2, 3 and 5 min but also significantly reduces the requirement of anaesthetic drugs. The dose of dexmedetomidine used and the results were similar to our study. Scheinin et al., performed a study on the effect of dexmedetomidine on tracheal intubation and dose of thiopentone and fentanyl needed for the surgery [12]. They observed that dexmedetomidine not only attenuates the haemodynamic responses to intubation but also reduces the doses of thiopentone and fentanyl. The plasma catecholamine concentration was measured in this study and it was found that the concentration of noradrenaline in mixed venous plasma was lesser in the dexmedetomidine group during all phases of induction. This study measured plasma catecholamine levels which was not possible in our study.

Sulaiman et al., studied the efficacy of dexmedetomidine on attenuation of stress response to endotracheal intubation in patients undergoing elective off pump coronary artery bypass grafting [13]. They concluded that administration of dexmedetomidine at a dose of 0.5mcg/kg over 10 min before induction of general anaesthesia decreases the heart rate and blood pressure following laryngoscopy and intubation for up to 5 minutes in patients undergoing myocardial revascularization. This study did not report any complications like hypotension or arrhythmias. Since this study was done on cardiac patients unlike normal patients in our study, they have used a lower dose than us.

Jaakola et al., did a study with dexmedetomidine in a dose of 0.6mcg/kg and observed that dexmedetomidine reduces the increase in heart rate and blood pressure during intubation [21]. The dosage used in these studies was less than the dose used by us. Lawrence et al., performed a study with a single dose of 2mcg/kg of dexmedetomidine before induction of anaesthesia and observed that it attenuated the haemodynamic response to both intubation and extubation [22]. Bradycardia was observed at the 1^st and 5^th min after administration and this might have been due to bolus administration of a large dose when compared to our study. Saraf et al., studied the effect of dexmedetomidine 0.6mcg/kg on stress response and found that bolus administration of 0.6mcg/kg administered 10 minutes before induction obtunds stress response in both adult and paediatric patients [23].

Gurulingappa et al., did a study comparing lignocaine and fentanyl for stress attenuation. They concluded that fentanyl at 4mcg/kg was more effective than lignocaine in attenuating the stress response [14]. Fentanyl was employed in a higher dose compared to our study. Since we felt fentanyl in a dose of 4mcg/kg could have an impact on postoperative recovery, we used the conventional dose of 2mcg/kg in our study. Gandhi et al., performed a study comparing dexmedetomidine in a dose of 0.6mcg/kg with fentanyl 2mcg/kg for stress attenuation. They observed that dexmedetomidine was effective in attenuating hear rate and blood pressure for up to 10 minutes after intubation [18]. In our study heart rate control was achieved for 10 minutes, but there was a statistically significant difference in blood pressure control for 1min only.

Several studies have highlighted that the use of dexmedetomidine in a dose of 0.5mcg/kg to 1mcg/kg is effective in obtunding haemodynamic stress response following laryngoscopy and intubation. The findings of all these studies were comparable to our study.

One of the limitations of our study is that we did not measure plasma catecholamine levels, which was not feasible in our institute.

It is concluded that bolus injection of dexmedetomidine 1mcg/kg given intravenously over 10 minutes prior to intubation provided consistent and reliable protection against the pressor response during laryngoscopy and endotracheal intubation when compared to fentanyl group and is devoid of any major complications.