Effect of Dexmedetomidine on Improving Intubating Conditions Without the Use of Muscle Relaxant

Tracheal intubation is usually facilitated by the administration of anesthetic drugs including a muscle relaxant. Over the past few years, several factors have led researchers to consider omitting neuromuscular blocking agents for tracheal intubation. (1, 2) Despite the frequent use of NMBAs in clinical practice, side effects associated with NMBA use can be particularly concerning such as anaphylaxis, cardiovascular effects related to histamine release or sympathomimetic properties, Bronchospasm, and prolonged paralysis. (3) Therefore, many studies (4, 5) focused on the possibility of performing tracheal intubation without the use of neuromuscular blocking agents. The challenge was to find the correct choice and dose of induction agent, opioid, or adjuvant drug to produce adequate intubating conditions without cardiovascular side effects. Dexmedetomidine is a potent and highly selective alpha-2 receptor agonist with sympatholytic, sedative, amnestic, and analgesic properties. It inhibits sympathetic activity thus terminating the pain signals and thereby blunts the pressor response associated with laryngoscopy and endotracheal intubation.

Methods: the study is designed to be prospective randomized double blinded study. 74 ASA I, II patients will be divided into 2 groups group D and group C, 37 patients in each group. Group D will receive single dose of dexmedetomidine 1.5 mcg /kg in 50 ml normal saline over 10 min IV infusion and Group C will receive 50 ml normal saline over 10 min IV infusion. Intravenous induction of anesthesia will be done using propofol (2 mg/Kg), fentanyl (1 mcg/Kg) and atracurium (0.5 mg/Kg) in the control group versus propofol (2 mg/Kg), fentanyl (1 mg/kg) and normal saline in the dexmedetomidine group. After 2 minutes of mask ventilation with 2% sevoflurane, endotracheal intubation (ETI) with 7.5mm endotracheal tube for male patients and a 7mm endotracheal tube for female patients will be performed by an experienced anesthiolgist Base line readings including heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP),) will be recorded and continuous measurements will be recorded till 5 minutes after intubation. Scoring of Intubation Conditions as follows: Intubation conditions will be evaluated using a scoring system, which includes 5 factors:

score 1 2 3 4 Laryngoscope: Easy Fair Difficult Impossible Vocal cords: Open Moving Closing Closed Coughing: None Slight Moderate Severe Jaw Relaxation: Complete Slight Stiff Rigid Limb movement: None Slight Moderate Severe

The score was interpreted into 3 categories: excellent, acceptable and poor conditions:

* Excellent conditions: received a score of 1 for all the 5 factors.
* Acceptable conditions: received a score of 2 for any of the 5 factors.
* Poor conditions received a score \>2 for any of the 5 factors. Both excellent and acceptable conditions was defined as successful intubations. Poor conditions was defined as failed intubations.

Eligibility Criteria:
Inclusion Criteria:

* ASA physical status I, II.
* Age 18- 60 years old of both sexes.
* Mallampati I, II
* Patients undergoing elective surgery under general anesthesia and tracheal intubation.

Exclusion Criteria:

* Age \< 18 years and ≥ 60 years
* Pregnancy
* Emergency surgery or full stomach
* Mallampati III , IV
* Renal or Hepatic patients
* Patients with any cardiac condition
* Patients with suspected difficult airway; e.g., high neck circumference, high body mass index (≥30 kg/m2), airway masses, mouth scars, neck scars, limited neck extension or history of snoring.
* Any patient on regular intake of beta blockers or calcium channel blockers
* Patients with any known hypersensitivity or contraindication to dexmedetomidine,
* Patients with significant neurological, psychiatric, or neuromuscular disorders.