Intravenous dexmedetomidine augments the oculocardiac reflex

BACKGROUND We reported that premedication with nasal dexmedetomidine was associated with a more intense oculocardiac reflex (OCR). In this study we performed an intrasubject, intravenous comparison to test our hypothesis that this alpha-adrenergic agonist potentiates the trigemino-vagal reflex. METHODS OCR (greatest change heart rate/baseline heart rate) was prospectively monitored with 10-second, square-wave 200 g tension on the inferior rectus or other muscles during strabismus surgery. Between the first and second muscle, intravenous dexmedetomidine 0.5 mu g/kg was delivered. RESULTS All patients had no anticholinergic agents. A total 842 historic control patients (median age, 5.5 years) with no dexmedetomidine between muscles experienced the first OCR of 75% +/- 24% (SD) and the second OCR of 77% +/- 22%. The 33 study patients (median age, 5.6 years) experienced the first OCR 84% +/- 16% and dexmedetomidine second OCR of 66% +/- 25% for a bradycardia augmentation of 18% +/- 19% (P < 0.01 [Mann-Whitney]). CONCLUSIONS Similar to the effect of fentanyl, intravenous fast-push dexmedetomidine augmented the bradycardia associated with extraocular muscle traction.