Fig. 3. Normogram for minimum alveolar concentration (MAC) as a function of age. The MACs for desflurane (Des), sevoflurane (Sev), and Isoflurane (Iso) can be determined by placing a ruler on the dot at left and drawing a line through the age of the patient. Where the line crosses the respective MAC normogram line yields the MAC value for that age. The dotted line shows an example for MAC in a 75-yr-old patient. As an approximation, MACawake(the concentration that produces unconsciousness in 50% of patients) can be determined by dividing the MAC by 3. The normograms are based on the formula: MAC fraction = 1.32 · 10−0.00303 · age, where MAC is the MAC fraction based on 1 MAC = MAC at age 40 yr. We assumed MAC at age 40 yr for desflurane, sevoflurane, and isoflurane to be 6.45, 1.9, and 1.2 vol%, respectively. Data and formula are from Eger. 11