Closed-circuit liquid injection isoflurane anesthesia in the horse.

The research focuses on examining the efficacy of administering anesthesia to horses through liquid injection into a closed-breathing apparatus, specifically using the anesthetic isoflurane and guided by a prediction model known as the square root of time model.

Research Methodology

• A total of six horses were taken as study subjects to investigate the effect of a specific anesthesia administration method.
• The anesthetic isoflurane was administered through liquid injection into a closed breathing circuit system, a method that is different from conventional inhalation.
• This administration followed a model known as the square root of time model, which predicts the uptake of anesthetic by the body over time.
• The dosage of isoflurane prescribed to the horses, known as the unit dose (UD), was carefully calculated using Lowe’s formula, a mathematical model, aiming for an end-tidal concentration of 1.3%, which considered the minimum alveolar concentration or the minimum effective concentration needed to prevent motor response in 50% of patients to a stimulus.

Findings and Conclusions

• The average UD administered resulted at around 4.2 +/- 0.2 mL, and the study found that, from the second injection onwards, the end-tidal isoflurane concentration (ETiso) did not change significantly.
• This steadiness in concentration indicated that the square root of time model was accurate in its predictions of isoflurane uptake by the horse’s body.
• In the initial stages, after the first injection, the measured ETiso was 0.68 +/- 0.06%, significantly lower than the mean concentration after subsequent injections, which stood at around 1.1 +/- 0.1%.
• Peak ETiso was at about 1.1 +/- 0.25% after the first injection, with subsequent injections leading to a higher average of 1.7 +/- 0.26%.
• Despite these variations, the mean minimum end-tidal concentration throughout all the injections remained consistent at 0.77 +/- 0.13%.
• In conclusion, the research affirmed that isoflurane anesthesia administration following the square root of time model and using a closed-circuit liquid injection is a reliable method for horses.