ABSTRACT
MAC is in effect the ED50 (see Chapter 19) of the inhaled agent, i.e. half the patients will be adequately anaesthetized and half not. The ED95 is probably a more useful measure and in data published to date has always been less than 1.5 MAC. (ED50 is the dose required to produce 50% of the maximum response and ED95 is that required to produce 95% of the maximum response.) The full explanation of ED50 and ED95 as pharmacological concepts is given in Chapter 19, Figure 19.20. In some of the published literature, the ED50 and ED95 are called the AD50 and AD95 when applied to volatile agents. An example of the type of plot used to determine the ED50 and ED95 for sevoflurane in oxygen and N2O is shown in Figure 33.9. Examples of the ED50 and ED95 for some inhalational and intravenous agents and their confidence limits are given in Table 33.7. This table is not complete for all the agents in current use, but represents the information that could be found in the current literature. The intravenous equivalent of MAC is the minimum infusion rate (MIR) defined in the same way in response to a standard incision. (See Chapter 19 for details of this.)
