Trigemino-Vagal Recalibration in Pediatric Anesthesia: A Prospective Cohort Study on the "60-Minute Autonomic Cliff,"...

Background: The trigeminocardiac reflex (TCR) is a potent brainstem response often underrecognized during pediatric dental procedures. We aimed to quantify TCR dynamics, identifying procedural and temporal predictors of occurrence and resolution. Methods: We conducted a prospective observational study (NCT07240688) in pediatric patients undergoing dental procedures under standardized sevoflurane anesthesia. TCR was defined as a ≥10% (mild) or ≥20% (severe) abrupt decrease in heart rate (HR) and/or mean arterial blood pressure (MABP). Data were analyzed using Generalized Estimating Equations (GEE) and hierarchical logistic regression to identify procedural risk factors and recovery dynamics. Results: The study included 85 pediatric patients (aged 2-9 years) undergoing 1115 monitored dental procedures. The overall TCR incidence was 82.3% (n = 70). Operative duration was the strongest predictor of occurrence; each 1 min increase raised TCR odds by 6.7% (aOR: 1.067, p < 0.001). A landmark "60-min Autonomic Cliff" was identified: the probability of rapid spontaneous recovery dropped from 97.1% before 60 min to 0.0% thereafter (p < 0.001). Pulpal involvement was associated with a 3.37-fold increase in odds of severe TCR (Cramer's V = 0.747). While lingual manipulation was strongly associated with rapid resolution (OR: 650.04), deep pulpal maneuvers led to a state of "Vagal Lock-in"-a sustained bradycardic response with reduced spontaneous recovery-effectively neutralized by atropine (97.0% success). Conclusions: Pediatric TCR is a time-dependent autonomic phenomenon in which operative duration influences reflex susceptibility and recovery dynamics, without affecting reflex severity. Beyond the "60-min Autonomic Cliff," spontaneous recovery becomes unlikely, marking a transition to a refractory physiological state rather than an increase in reflex severity. This threshold provides a clinically actionable signal for anesthesiologists to intensify monitoring and consider early vagolytic intervention, supporting anticipatory, time-guided intraoperative management.