The solubility of halothane in canine blood and tissues

In vitro measurements were made of the solubility of halothane (about 1%, carried in 5% carbon dioxide in air) in tissues taken from dogs, mostly Alsatians, and usually after about 8 hr anaesthesia with pentobarbitone and halothane. The mean Ostwald solubility coefficient lambda in atm- minus 1 at 37 degrees C, for seven to 21 animals, were: brain 6.03, gut 4.23, cardiac muscle 4.88, kidney 4.95, liver 6.64, skeletal muscle (psoas) 5.45. For the gracilis muscle solubilities up to 20 atm- minus 1 were obtained. Solubility in blood was shown to increase significantly with haematocrit and haemoglobin and to be significantly higher in blood from unanaesthetized than from anaesthetized animals. The best-estimate equations were lambda-2.38 + 0.042H for the unanaesthetized condition and lambda-1.69+0.049 H for the anaesthetized condition, where H is haematocrit %. Combining the present results with those for other species showed that the solubility of halothane increased fairly systematically from blood to kidney to brain to liver, and from ox to man to dog to rabbit.