Certain physiological and pathological states may alter MAC. MAC is higher in infants and lower in the elderly. Also, MAC increases with hyperthermia, hypernatremia and chronic alcohol ingestion. Likewise, hypothermia, hypotension (MAP < 40 mmHg), and pregnancy seem to decrease MAC. Duration of anesthesia, gender, height and weight seem to have little effect on MAC. Opioid analgesics and sedative-hypnotics, often used as adjuvants to anesthesia, decrease MAC. It should also be noted that MAC values are additive. For instance, when applying MAC of drug X and 1 MAC of drug Y the total MAC achieved is MAC. In this way nitrous oxide is often used as a "carrier" gas to decrease the anesthetic requirement of other drugs.