Respiratory and antinociceptive effects of dexmedetomidine and doxapram in ball pythons (Python regius)

OBJECTIVE To determine the effects of dexmedetomidine, doxapram, and dexmedetomidine plus doxapram on ventilation (e), breath frequency, and tidal volume (Vt) in ball pythons (Python regius) and of doxapram on the thermal antinociceptive efficacy of dexmedetomidine. ANIMALS 14 ball pythons. PROCEDURES Respiratory effects of dexmedetomidine and doxapram were assessed with whole-body, closed-chamber plethysmography, which allowed for estimates of e and Vt. In the first experiment of this study with a complete crossover design, snakes were injected, SC, with saline (0.9% NaCl) solution, dexmedetomidine (0.1 mg/kg), doxapram (10 mg/kg), or dexmedetomidine and doxapram, and breath frequency, e, and Vt were measured before and every 30 minutes thereafter, through 240 minutes. In the second experiment, antinociceptive efficacy of saline solution, dexmedetomidine, and dexmedetomidine plus doxapram was assessed by measuring thermal withdrawal latencies before and 60 minutes after SC injection. RESULTS Dexmedetomidine significantly decreased breath frequency and increased Vt but did not affect e at all time points, compared with baseline. Doxapram significantly increased e, breath frequency, and Vt at 60 minutes after injection, compared with saline solution. The combination of dexmedetomidine and doxapram, compared with dexmedetomidine alone, significantly increased e at 30 and 60 minutes after injection and did not affect breath frequency and Vt at all time points. Thermal withdrawal latencies significantly increased when snakes received dexmedetomidine or dexmedetomidine plus doxapram, versus saline solution. CONCLUSIONS AND CLINICAL RELEVANCE Concurrent administration of doxapram may mitigate the dexmedetomidine-induced reduction of breathing frequency without disrupting thermal antinociceptive efficacy in ball pythons.