Use of nitrous oxide is contraindicated in animals with pneumothorax, pneumoperitoneum, or intestinal obstruction with gaseous distension. Because nitrous oxide is 20-30 times more soluble in blood or tissues than nitrogen, any air bubbles within the body will be greatly expanded from diffusion of N2O into it. Oxygen administration must be continued for five minutes after nitrous oxide is discontinued in order to prevent hypoxia. Major advantage of halothane is that induction of anesthesia is easily accomplished using a facemask, the level of anesthesia can be changed rapidly, the patient rapidly recovers consciousness, and the organ function returns to normal relatively quickly. Halothane causes a dose dependent decrease in cardiac output and blood pressure by depression of the myocardium, bradycardia, and peripheral vasodilation.
Halothane sensitizes the myocardium to epinephrine.
Use of epinephrine for hemostasis or circulatory stimulation is contraindicated. Increased respiratory rate may occur in both light and deep anesthesia. Respiratory arrest usually precedes cardiac asystole by a reasonable margin. Blood and brain levels drop to negligible levels within minutes. The preservative, thymol, in halothane often causes the vaporizer dial to stick.