A comparison of two ketamine doses for field anaesthesia in horses undergoing castration.

This research investigates the comparative effects of two different doses of ketamine used in field anaesthesia for Icelandic horse castration, revealing that the higher dosage provided better surgical conditions but the lower dose offered improved recovery quality.

Study Objectives and Methodology

• The main purpose of this study was to determine the efficiency and effectiveness of two different ketamine dosages (5mg/kg and 2.2mg/kg) used in the anaesthesia given to horses before their castration.
• This was conducted as a prospective, randomised, blinded clinical study. Seventy-seven Icelandic horses that were brought for castration under field conditions were involved in the study.
• Each horse was given a pre-anaesthetic medication comprising of xylazine (0.7mg/kg), butorphanol (25 μg/kg), and acepromazine (50 μg/kg) via an intravenous injection.
• Following pre-medication, anaesthesia was induced with either 2.2mg/kg (K2.2) or 5mg/kg (K5) of intravenously injected ketamine, combined with 30 μg/kg of diazepam.

Comparative Measures and Results

• Various attributes, including the quality of induction, surgery conditions, and recovery, were evaluated using both objective and subjective measures. The number of additional ketamine doses required was also recorded and compared.
• The research found that the usage of 5mg/kg dosage of ketamine yielded more rapid induction and better surgical conditions, compared to the lower 2.2mg/kg dosage.
• However, the recovery quality seemed to be subjectively better in the case of the lower dosage group (K2.2), though this is subjective and no adverse events were observed during recovery with either dose.
• The necessity of additional ketamine doses was observed in five horses who received the lower dose (K2.2) and in two horses who received the higher dose (K5).

Conclusions

• While the pre-anaesthetic sedation and the benzodiazepine doses were consistent among the horses, the sedation level and muscle relaxation achieved varied.
• The study concludes that a ketamine dose of 5mg/kg can effectively enhance the quality of field anaesthesia for castration in Icelandic horses.
• Despite the subjective opinion that recovery quality is better with a lower dose of 2.2mg/kg, no negative occurrences were noted during recovery with either dose.