Chronotropic Response to Intratracheal versus Intravenous Atropine in Anesthetized Adult Patients: A Randomized Controlled Trial

Atropine is a commonly used anticholinergic agent in anesthetic practice, administered primarily to counteract bradycardia. Rapid treatment of intraoperative bradycardia is clinically critical, as delays may lead to hemodynamic compromise. This study aimed to compare the onset, magnitude, and duration of the chronotropic response to atropine administered via the intravenous (IV) versus intratracheal (IT) route in anesthetized adult patients. A prospective, single-blind, randomized controlled study was conducted on 60 adult patients classified as American Society of Anesthesiologists (ASA) physical status I-II, scheduled for elective peripheral surgery under general anesthesia. Patients were randomly allocated into three equal groups (n = 20 each). Group A received 0.6 mg atropine intratracheally; Group B received 0.6 mg atropine intravenously with 1 mL saline instilled intratracheally; Group C (control) received 1 mL of 0.9% saline intratracheally. The primary outcome was onset of chronotropic effect (time to 10% increase in heart rate from baseline). Heart rate (HR) was recorded at 15-second intervals for the first minute, then every minute for 15 minutes. Both Groups A and B showed a statistically significant increase in heart rate (p < 0.01). The maximum HR increase was comparable between groups (Group A: +28.15 bpm; Group B: +29.15 bpm; p > 0.05), confirming equivalent efficacy. Onset of action was significantly faster in Group A (21 sec vs. 46.5 sec; p < 0.01), as was time to peak effect (49.5 sec vs. 267 sec; p < 0.01). Group C showed no significant chronotropic change. Intratracheal atropine produces a chronotropic response equivalent in magnitude but significantly faster in onset than the intravenous route, and may be considered as an effective alternative route, particularly when intravenous access is unavailable or delayed.