The Impact of BMI on Heart Rate During Suspension Laryngoscopy Operation in Patients With Laryngeal Lesions: A Prospective Cohort Study.

Objectives: Suspension laryngoscopy can trigger vagal reflexes, leading to a decrease in heart rate, a phenomenon that is more common in patients with a high body mass index (BMI). This study aims to systematically evaluate the effect of BMI on heart rate during suspension laryngoscopy (SL-HR) in patients with laryngeal lesions.

Methods: We employed univariate generalized linear regression and stratified analyses to assess the relationship between BMI and changes in SLHR, adjusting for confounders such as age, gender, intubation type, and depth. A generalized additive model with spline smoothing was utilized to evaluate the BMI-HR relationship, with piecewise linear regression to identify specific cutoff points.

Results: We conducted a prospective study of 205 patients who underwent general anesthesia for suspension laryngoscopy. Multivariate linear regression analysis indicated that, after adjusting for covariates, each one-unit increase in BMI was associated with a decrease of 1.04 beats per minute in SL-HR (β = -1.04 [95% CI, -1.85 to -0.23]). Curve fitting revealed a gradual decline in SL-HR with increasing BMI, plateauing at around 60 beats per minute. The decrease in SL-HR became more pronounced as BMI approached 30 kg/m², with further analysis revealing an inflection point at a BMI of 28.8 kg/m², where each additional unit of BMI correlated with a 6.5 beats per minute decrease in heart rate (β = -6.5 [95% CI, -10.1 to -2.8], P < 0.001).

Conclusions: Patients with high BMI are more prone to vagal reflexes during suspension laryngoscopy, resulting in significant reductions in heart rate, especially when BMI exceeds 28.8 kg/m². Therefore, close monitoring of heart rate changes is crucial in this patient demographic, along with considering prophylactic anticholinergic agents to mitigate vagal reflex effects.