Transthoracic echocardiography and hemodynamic effects of isoflurane in dexmedetomidine-ketamine-immobilized free-ranging capybaras (Hydrochoerus hydrochaeris).

This study reports transthoracic echocardiographic values and hemodynamic responses to isoflurane anesthesia in adult immobilized capybaras (Hydrochoerus hydrochaeris). Animals (median weight: 52.1 kg; range: 35–67 kg) were immobilized with intramuscular dexmedetomidine (7 µg/kg) and ketamine (6 mg/kg) (n = 20), followed by induction with intravenous propofol (2 mg/kg) for inhalant anesthesia (n = 15). Echocardiographic and cardiovascular variables were assessed 40 min after immobilization (TIMMO), and during 20-minute exposures to 0.7% (TISO−0.7) and 0.9% (TISO−0.9) end-expired isoflurane. Cardiac imaging followed small animal echocardiographic guidelines. Time point comparisons used ANOVA followed by Tukey’s test or Friedman’s test with Dunn’s post hoc (p < 0.05). Trivial mitral valve insufficiencies were common during both restraint (65%) and anesthesia (60%). Isoflurane reduced MAP by 29 ± 12% at TISO−0.7 and 30 ± 13% at TISO−0.9 (p ≤ 0.001), with hypotension (MAP < 60 mmHg) observed in 3/15 animals at 0.9% end-expired isoflurane. Heart rate dropped at TISO−0.9 (61 [49–63] beats/minute) compared to TISO−0.7 (65 [56–68] beats/minute) (p = 0.042) and TIMMO (74 [66–79] beats/minute) (p < 0.001). Cardiac index differed across all time points (p = 0.003 to 0.024), from highest at TIMMO (56.4 ± 15.3 mL/kg/minute) to lowest at TISO−0.9 (42.6 ± 9.7 mL/kg/minute). Peak velocities of aortic and pulmonary blood flow also decreased at TISO−0.7 and TISO−0.9, while late diastolic transmitral flow decreased only at TISO−0.9. Cardiac structure and function can be assessed in capybaras using standard transthoracic echocardiography, with isoflurane-related cardiovascular depression evident below FE’Iso 1.0% after dexmedetomidine-ketamine immobilization.