Is the bulbocavernosus reflex reliable under dexmedetomidine administration in children? -An analysis during tethered cord surgery.

OBJECTIVE

Dexmedetomidine (DEX) is increasingly utilized in pediatric anesthesia; however, its impact on the bulbocavernosus reflex (BCR) remains unclear. The objective of this study was to elucidate the suppressive effects of DEX on the BCR and to establish a safe therapeutic window for its administration during pediatric spinal untethering surgery.

METHODS

A retrospective two-stage investigation was conducted, enrolling 66 children. Cohort 1 (exploratory, n = 46) aimed to identify independent risk factors for BCR attenuation under standard anesthesia where DEX was initiated before dural opening. Multivariate analysis was performed to distinguish DEX effects from other variables. Cohort 2 (pharmacodynamic, n = 20) was designed to validate findings and define the safety threshold; DEX was administered after dural closure to isolate pharmacological effects from surgical manipulation. We analyzed the correlation between predicted plasma DEX concentrations (Potts model) and BCR amplitude using logistic regression.

RESULTS

Cohort 1 identified DEX administration as the sole independent risk factor associated with BCR amplitude decline (p = 0.01), whereas others showed no significant impact. Cohort 2 confirmed a specific concentration-dependent suppression. A statistically significant amplitude reduction was observed starting 12 min after initiation. Logistic regression identified a critical inflection point at 0.67 ng/mL in predicted plasma concentration, around which BCR reliability was significantly compromised (p = 0.005).

CONCLUSIONS

DEX suppresses BCR monitoring in a concentration-dependent manner during pediatric spinal untethering surgery. A predicted plasma concentration of approximately 0.67 ng/mL may represent a critical threshold for reliable BCR monitoring, although prospective validation using direct blood sampling is required.