Evaluation of clinical and electrocardiographic changes during the euthanasia of horses.

The research study investigates if there’s a synchronization between clinical death and cardiac death in horses during euthanasia. It also studies changes that occur in EKG readings during this process. The results suggest that clinical signs of death appear before cardiac death, and the use of sedatives prior to euthanasia accelerates the cardiac death process.

Research Design and Methodology

• The study was a prospective field study that followed 29 horses to be euthanized with the use of pentobarbital at two different doses. Among these, 15 horses were also administered detomidine hydrochloride for sedation.
• The EKG readings of the horses were recorded prior to and during the euthanization process. Time of collapse, when reflexes stopped, the end of heart sounds, and asystole (end of cardiac activity) were documented.
• The EKG recordings were later analyzed to calculate intervals and amplitudes connected to different waves prior to and during euthanasia.
• Differences in groups and changes in EKG readings were evaluated with analysis of variance.

Observations and Findings

• The study found that clinical death occurred before cardiac death, meaning the horses exhibited signs of clinical death before their hearts completely stopped (asystole).
• Sedated horses took longer to collapse than unsedated ones, but their hearts stopped (asystole) faster.
• Although changes in QRS duration were not observed, RR, PQ, QTc, TpeakTend, and Tpeak were affected by both the dose of pentobarbital and sedation.

Conclusions

• The research concluded that sedating a horse prior to euthanasia can shorten the time to asystole, and thus, is recommended.
• Importantly, the study suggests that the clinical definition of death in horses may be premature compared to that in humans, signifying that clinically, horses may be declared dead before their hearts have completely stopped.