Physiological and sedative responses in Phrynops geoffroanus (Schweigger, 1812): Comparison of two anesthetic protocols using dexmedetomidine and ketamine

Abstract

Abstract This study evaluated the anesthetic combination of dexmedetomidine and ketamine in free-ranging Phrynops geoffroanus , assessing cardiopulmonary and sedative variables, as well as pharmacological reversal with atipamezole. Twenty-five adult individuals were allocated into two groups: HG (dexmedetomidine 0.1 mg/kg + ketamine 10 mg/kg; n = 13) and LG (dexmedetomidine 0.05 mg/kg + ketamine 10 mg/kg; n = 12). Heart rate, respiratory rate, and cloacal temperature, along with motor and behavioral reflexes and venous blood gas analysis, were evaluated at baseline, during chemical restraint, and throughout recovery. No significant differences were observed between groups at the same time points for heart rate, respiratory rate, or cloacal temperature, indicating physiological stability at both dosages. In the HG group, respiratory rate progressively decreased from baseline (39 ± 13 [12–64]) to 7 ± 12 [0–42] between 35 and 45 min after drug administration, with recovery to 36 ± 10 [17–56] fifteen minutes following atipamezole administration. Reflex assessment demonstrated deeper sedation in the HG group, with significant differences in head tone, limb tone, righting reflex, and palpebral reflex, whereas cloacal reflex and jaw tone did not differ between doses. Pharmacological reversal restored physiological parameters to near-baseline values within 25 min. Venous blood gas analysis revealed mild and transient changes in pH and pCO₂ in both groups, without clinically relevant consequences. In conclusion, dexmedetomidine at doses of 0.1 mg/kg and 0.05 mg/kg, combined with ketamine (10 mg/kg) and administered at an ambient temperature of 28 °C, is safe for P. geoffroanus . The higher dose was associated with deeper sedation, making it suitable for field procedures and clinical handling.