Resident - Cardiology The Ohio State University Columbus, Ohio, United States
Abstract:
Background: Medetomidine-vatinoxan (Zenalpha®) combines a selective alpha-2-agonist with a peripherally acting alpha-2-antagonist. Compared to sole alpha-2 agonists, Zenalpha® has been shown to be more cardiac-sparing due to attenuative effects of vatinoxan.
Hypothesis/
Objectives: Determine if Zenalpha® results in less cardiac dilation and ventricular dysfunction, with less impact on heart rate and blood pressure, compared with dexmedetomidine.
Animals:Twenty healthy client-owned dogs.
Methods: Double-blind, randomized crossover study; dogs received dexmedetomidine (10 mcg/kg) or Zenalpha® (20 mcg/kg) intramuscularly with a one-week washout period. Four timepoints were examined: baseline (T0), 15 (T15), 30 (T30), and 45 minutes (T45) following drug injection. At each time point, the following was performed: sedation score, vital monitoring, electrocardiogram, and echocardiogram. Paired t-tests were used to determine differences between groups/time points (significance P< 0.05).
Results: Both drugs caused significant reductions in systolic function from baseline (P < 0.0001). Dexmedetomidine resulted in more pronounced systolic dysfunction than Zenalpha® at T30 and T45 (T45 EF 45% vs 52%, P= 0.0001; LVIDsN 0.96 vs 0.84, P= 0.0001). There was no difference in presence of valvular regurgitation or spontaneous echocardiographic contrast. Blood pressure was higher with dexmedetomidine (P= 0.0099). Zenalpha® was less likely to result in second-degree atrioventricular block and prolonged pauses (T45 OR 0.14, 0.04, respectively), but average heart rates were similar and both significantly less than baseline.
Conclusions and Clinical Importance: The cardiovascular effects of dexmedetomidine were more pronounced and prolonged than Zenalpha®. Both drugs caused significant hemodynamic alterations from baseline. Cardiac diagnostics performed under sedation with Zenalpha® should be interpreted with caution.
