Dexmedetomidine and alfaxalone intravenous co-administration for the induction of general anaesthesia in bitches undergoing C-section: impact on newborn viability and pharmacokinetics

The study aims to evaluate the impact of dexmedetomidine (DEX) and alfaxalone (AFX) on the viability of pups and to determine the pharmacokinetic profile of both drugs following intravenous (IV) co-administration for general anaesthesia induction in bitches undergoing cesarean section (C-section).

Fourteen client-owned bitches, scheduled for elective or emergency C-section, received IV co-administration of AFX (1.2 mg/kg) and DEX (2 μg/kg) for anaesthesia induction. Newborns were assessed within 5 min after birth using the Apgar score (range 0–14). Quantification of drugs from maternal serum and placental tissue was performed with mass spectrometry analysis. Associations between Apgar scores and either placental/serum drug concentrations or clinical variables were evaluated using separate univariate regression models. The pharmacokinetic profiles of DEX and AFX were determined in bitches.

Of the 68 pups delivered, 88.2 % were vigorous at birth (Apgar score 10–14), and no stillbirths occurred. Placental concentrations of DEX (range 1.12–7.79 ng/g) and AFX (range 91.12–583.14 ng/g) were positively correlated and significantly influenced by the timing of pups’ delivery (p < 0.05). Higher AFX placental concentrations were associated with increased neonatal body temperature (p < 0.05). For DEX, C_max was 0.37 ± 0.14 ng/mL, at a T_max of 16 ± 8 min; AFX showed a C_max of 187.84 ± 154.42 ng/mL at a T_max of 18 ± 10 min. The half-lives λ_z were 47.36 ± 30.61 min for DEX and 55.82 ± 33.06 min for AFX.

The IV co-administration of DEX and AFX appeared to be safe for anaesthesia induction in dogs undergoing C-sections, yielding favorable neonatal clinical outcomes.