Inhaled anesthetics INDEX

The efficacy and safety of new inhalation anesthetics has to be evaluated in pharmacological experiments. Robbins (1946) defined the anesthetic AD50 as the concentration of anesthetic at which 50 % of mice failed to right themselves for 15 s when placed in a rotating bottle with a known concentration of anesthetic. The concentration of the anesthetic that caused apnea in 50 % of the mice in 10 min was defined as the LD50 and the ratio LD50IAD50 as and an index of safety. 

Regan MJ, Eger El II (1967) Effect of hypothermia in dogs on anesthetizing and apneic doses of inhalation agents. Determination of the anesthetic index (Apnea/MAC). Anesthesiol 28 689-700... 

In ponies, desflurane (MAC) caused a decrease in arterial blood pressure and systemic vascular resistance while heart rate and cardiac index were not changed significantly (Clarke et al 1996). Increasing the concentration of desflurane to 1.3 times MAC resulted in further depression of the arterial blood pressure and a significant decrease in the cardiac index, attributed to the onset of cardiac depression at higher concentrations (Clarke et al 1996). Desflurane also results in respiratory depression there is a significant increase in PaC02 at MAC (Clarke et al 1996). In other species, the cardiopulmonary effects of desflurane are considered to be approximately equal to those of isoflurane, but a direct comparison of desflurane and other inhalation anesthetics has not yet been carried out in the horse. 

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