General anesthetics and therapeutic gases

Publisher Summary Although anesthetists have a series of agents that are highly effective and useful, they do not possess an ideal agent. Cost is an important factor in choosing an anesthetic. The relative cost of administering the newer and less soluble anesthetic desflurane can be less than, greater than, or the same as the cost of administering isoflurane, depending on the background rate of the gas inflow used. So, the manner in which inhaled anesthetics are used and the differences in their pharmacokinetics are important determinants of relative cost. The effect of intravenous anesthetics on the heart has been assessed in an isolated rat heart-lung preparation. The results suggested that the cardio-depressant effects of intravenous anesthetics may be due to their effects on the central nervous system. Intravenous anesthetic agents act differently on pulmonary vascular resistance. To determine their actions, thiopental, ketamine, etomidate, propofol, and midazolam were injected into the endothelium of intact isolated rat lungs, which were either unconstricted or constricted with angiotensin, and into lungs with endothelial injury produced by electrolysis. Thiopental and etomidate were shown to be direct pulmonary vasoconstrictors, ketamine and propofol were direct pulmonary vasodilators, and midazolam was neither. These effects did not vary with baseline pulmonary vascular resistance, and only propofol appeared to have endothelium-dependent effects.