Heart rate response to a caudal block in children anesthetized with sevoflurane after ultrasound confirmation of placement

INTRODUCTION:Previous studies identified decreasing heart rate (HR) as a predictor of successful caudal placement in children using halothane and isoflurane. No changes were found in HR in the one study using sevoflurane. We documented HR changes in children following a caudal block during sevoflurane anesthesia utilizing ultrasound to confirm successful caudal placement. METHODS:Seventy-one children (1-82 months) were anesthetized with sevoflurane. A caudal block was placed with confirmation by ultrasound. Four aliquots of bupivacaine 0.2% with epinephrine 5 μg·cc(-1) were administered for a total volume of 1 cc·kg(-1) with HR recorded for 4 min. The outcomes measured were HR changes from the initial baseline and during each 1-min interval. The age-related differences in HR were also analyzed. RESULTS:Heart rate change from the initial baseline after placing the caudal needle and allowing for equilibration ranged from -10.2% to +8.9% and the HR change from the baseline at the start of each aliquot injection ranged from -9.5% to +8.9%. Most participants (n = 60, 84.5%) experienced at least one HR reduction over the observation period. For patients <36 months, the HR change ranged from -11 to +12 b·min(-1) (mean -0.3); for patients aged ≥36 months, the HR change ranged from -10 to +6 b·min(-1) (mean -1.1). CONCLUSIONS:Heart rate changes following a caudal block in children ≤82 months of age anesthetized with sevoflurane is not a reliable indicator of a successful block. Despite 100% caudal success, many children had no decrease in HR, and in those that did, the decline was of a magnitude indeterminate from beat-to-beat variability.