Prediction of the oculocardiac reflex from pre-operative linear and nonlinear heart rate dynamics in children

This study was aimed to determine whether pre-operatively measured linear and nonlinear analysis of heart rate variability might predict the occurrence of the oculocardiac reflex (OCR) or other arrhythmia during strabismus surgery in children (n = 185, mean (SD) age = 8.09 (3.31) years). We compared time- and frequency-domain, and nonlinear dynamic indices of pre-operatively measured RR interval data between the OCR-positive group (maximum heart rate decrement = 20 beat.min-1 during the traction of extraocular muscle, n = 54), OCR-negative group (< 20 beat x min(-1), n = 78) and arrhythmia-positive group (all other arrhythmias; n = 53). pNN50, rMSSD, high-frequency power and nonlinear prediction error were significantly lower in the OCR-positive and arrhythmia-positive groups than in the OCR-negative group. Discriminant analysis using these indices could correctly identify 39/54 (72.2%) OCR-positive patients. Some pre-operatively measured indices of linear and nonlinear heart rate variability, especially when used in combination, are valuable for predicting significant bradycardia during strabismus surgery in children.