Comparison of hemodynamic response to laryngoscopy and tracheal intubation following combination of dexmedetomidine as premedicant with three different induction agents: propofol, etomidate and thiopentone

Laryngoscopy and tracheal intubation is particularly challenging in patients with raised intracranial pressure (ICP) as the resultant tachycardia and hypertension must be avoided to prevent further rise of intracranial pressure. The role of ideal combination of anesthetic drugs plays the key role in this. Various drugs have been tried in different combinations. However, an ideal combination of drugs for induction of anesthesia to perform laryngoscopy and tracheal intubation still to be found in neurosurgical patients with raised intracranial pressure. Dexmedetomidine is an alpha 2 agonist, a novel sedative with analgesic properties that controls stress, anxiety and pain. It decreases the level of stress hormones such as epinephrine, norepinephrine which are raised as a response to laryngoscopy and intubation. From various studies the attenuation of hemodynamic response to laryngoscopy and tracheal intubation by dexmedetomidine has been established. However, most of the studies documented this effect using single induction agent. For induction of anesthesia propofol, etomidate and thiopentone are the most commonly used three different induction agents. However each of them produces different cardiovascular effects when used alone or with other drugs such opioids or muscle relaxants. Therefore, it is no surprise that each of them will produce different cardiovascular effects when combined with dexmedetomidine for induction of anesthesia. This study will examine the cardiovascular response to laryngoscopy and tracheal intubation after combining dexmedetomidine with three different induction agents. This is a prospective, double blinded, randomized study where 90 ASA grade I and II patients aged between 14 to 60 years who will be posted for various type of elective neurosurgery procedures in the neurosurgery operation theater of Calcutta National Medical College and Hospital, will be randomly allocated into three groups of 30 patients each namely group P, group E, and group T. The anesthetic agent for induction will be different for the groups. Patients of group P, group E and group T will be induced by propofol 2 mg/kg, etomidate 0.3 mg/kg and thiopentone 5 mg/kg respectively. Rest of the anesthetic procedure will be same for all the groups. All the patients shall go through pre-anesthetic check-up. They will be fully explained about the nature of anesthesia and surgery. The patients will receive tablet alprazolam (0.25 mg for female and 0.5 mg for male patients) at the night before operation. Upon arrival in the operation theatre, they will be equipped with standard anesthesia monitoring viz. SpO2, NIBP, EtCO2, ECG, Temp (core), neuromuscular monitoring. CVP and IBP will be monitored in selective cases if required. Patients will be given injection (Inj) ondansetron (0.1 mg/kg) and Inj fentanyl (2 microg/kg) prior to dexmedetomidine infusion. Bolus dose of dexmedetomidine (1 µg/kg) will be infused over 10 minutes followed by maintenance (0.5 µg/kg/min) infusion. Patients will be given oxygen through face-mask. After the infusion of bolus dose of dexmedetomidine over 10 minutes, induction will be started. Patients will be induced by the different study drugs (i.e. thiopentone, etomidate, propofol) on a titration basis. Vecuronium (0.1 mg/kg) will be used as the muscle relaxant in all the patients. Patients will be assisted with bag and mask ventilation with 100% oxygen. The intubation procedure should start 3 min after the injection of vecuronium. Intubation shall be done with armored tube with stylet by an expert anesthetist with at least 2 years of experiences. The medication and observation of the study parameters will be done by separate anesthetists. Anesthesia will be maintained using N2O, O2, and propofol infusion or isoflurane.