In the ASA Relative Value Guide (RVG), every anesthetic service has a base unit value assigned. Currently, the base units range from 3 units to 30 units, and the base units reflect the amount of work involved in the pre-anesthetic evaluation, the postanesthetic management, the administration of fluids and blood, intraoperative monitoring, and the overall complexity and intensity of the anesthetic service. Table 209.1 provides examples of base unit values for various anesthetics.

The creators of the anesthesia relative value system understood that the time involved in providing anesthesia care was not in the control of the anesthesiologist. They also understood that time could be highly variable between surgical procedures that were otherwise identical in anesthetic complexity. Therefore, the anesthesia relative value system explicitly identifies time as part of the payment formula. Each time unit represents a defined period of anesthesia care, most typically 15 minutes. According to the ASA, anesthesia time begins when the anesthesiologist begins to prepare the patient for anesthesia in the operating room or equivalent area and ends when the patient is safely placed under postanesthesia care. One can think of this as “hands on to hand-off.”