Attenuation Of Hemodynamic Response To Laryngoscopy. Role Of Dexmedetomidine. A Dose Finding Study

Two doses of Dexmedetomidine (0.5 µ/kg and 0.75 µ/kg) will be used to attenuate the stress response to laryngoscopy in American Society of Anesthesiology, physical class I patients which will be compared with the placebo-controlled group.

A randomized, double-blind controlled trial will be conducted to determine the attenuation of stress response caused by laryngoscopy and tracheal intubation (LTI). After the Institutional Ethics Committee approval, (Sindh Institute of Urology and Transplantation, Pakistan), written informed consent will be obtained from 105 adult patients.

Randomization will be done using a computer-generated random number table. Patients will be divided into three groups. Group A "Placebo group", will receive 20 mL of normal saline (NS), Group B "dexmedetomidine 0.5", will receive dexmedetomidine 0.5 μ/kg, whereas, Group C "dexmedetomidine 0.75", will receive dexmedetomidine 0.75 μ/kg, all as a 20mL infusion through a syringe pump over 10 minutes followed by induction of general anesthesia.

No premedication will be given in the ward. Once the patients will arrive in the operating room, routine monitoring (electrocardiogram, pulse oximetry, non-invasive blood pressure) will be started. After recording the baseline vitals and Ramsay sedation score, the study drug or normal saline (according to randomization) will be given in a look-alike syringe over 10 minutes. The study drug will be prepared as a 20 mL solution in a 25 mL syringe. An independent co-investigator (anaesthesiologist) who will not be involved in administering general anesthesia or recording the study parameters will prepare the study drug(s) according to the body weight or NS using identical-looking syringes. Study drug infusion will be started once the patient is taken to the operating table. Vitals and sedation scores will be recorded at 0,1,3,5 and 10 minutes during infusion. Investigators will keep the atropine drawn in a syringe and ready to be given in case of heart rate goes below 40 beats/min. Ephedrine (5mg/ml) and adrenaline 10µ/ml will also be ready for use.

Once completing the infusion, general anesthesia will be administered using a standard protocol (Nalbuphine 0.15 mg/kg, Propofol 2.5 mg/kg, Atracurium 0.6 mg/kg after assessing easy bag-mask ventilation in all patients. After 3-minute bag-mask ventilation with Isoflurane at 1.5% in 100% oxygen, the trachea will be intubated by one of three senior anaesthesiologists involved in this study. The intubating duration will be kept below 15 seconds. Hemodynamic monitoring will be continued for another 10 minutes at 1, 3, 5 and 10 minutes after intubating the trachea.

Eligibility Criteria:
Inclusion Criteria:

* Age between 18 to 55 years
* ASA I or II patients undergoing surgery under general anaesthesia with endotracheal intubation.
* Patients with Mallampati class I or II.

Exclusion Criteria:

* ASA III \& IV patients
* Anticipated or unanticipated difficult intubations which requires more than 15 seconds or more than one attempt.
* Patients with Mallampati class III, IV or with loose teeth.
* Patients with inotropes infusion.
* Patients with known allergy to any anaesthetic agents
* Patients with a heart rate of 60 beats/min or less
* Patients with known hypertension, incidental finding of hypertension while on operating table, diabetes, ischemic heart disease or peripheral vascular disease.
* Pregnant and lactating mothers.