This prospective observational study aims to determine, if an tracheal intubation-related decrease in heart rate is associated with intraoperative reflex bradycardia in patients undergoing microlaryngoscopy (MLS) in general anesthesia.

Small studies and case series reported precipitous bradycardia or even asystole due to reflex vagal activity during tracheal intubation and/or laryngoscopy attributable to a so called laryngocardiac reflex (reflex bradycardia); however, larger systematic trials are still lacking. For the purpose of MLS, ENT surgeons frequently apply suspension laryngoscopy (Kleinsasser laryngoscope) in order to visualize the glottis and to enable surgery. Severe bradycardia has been reported during MLS that has been suspected to be induced by reflex vagal activity possibly promoted by the superior laryngeal nerve.

It is still unknown, which patients are at risk for relevant intraoperative bradycardia and moreover, which patients might benefit from preemptive measures such as prophylactic application of positive chronotropic drugs like atropine sulfate, epinephrine or glycopyrrolate. Predictive factors for MLS-induced intraoperative bradycardia have not systematically been investigated yet.

In particularly, it is unknown, if patients that present with a preoperative tracheal intubation-related decrease in heart rate have a predisposition for intraoperative reflex bradycardia during MLS.

This prospective observational study aims to determine, if an tracheal intubation-related decrease in heart rate is associated with intraoperative reflex bradycardia in patients undergoing microlaryngoscopy (MLS) in general anesthesia. Moreover, if we find a positive association, we further aim to determine the predictive value of intubation-relatd bradycardia.

Inclusion Criteria:

• Patients requiring general anesthesia with tracheal intubation for elective MLS
• Age ≥ 18

Exclusion Criteria:

• Pregnant or breastfeeding women
• Confirmed indications for awake fiberoptic intubation
• Planned endotracheal intubation without deep anesthesia or neuromuscular blocking agents (e.g. awake videolaryngoscopy)
• Patients at risk for pulmonary aspiration who qualify for rapid sequence induction
• Cardiac pacemaker
• Atrial fibrillation
• Denial of consent

Adult patients requiring general anesthesia with tracheal intubation for elective MLS in a tertiary care hospital who consent to participate within the study period.