Anesthesia Coding Alert

Stedman's Medical Dictionary defines "hypothermia" as "A body temperature significantly below 98.6 degrees Fahrenheit," and "total body hypothermia" as "The deliberate reduction of total body temperature in order to reduce tissue metabolism." Hypothermia commonly accompanies procedures such as CABG and can also be used during procedures to treat other conditions such as traumatic brain injury, cerebral aneurysm or other neurological problems.

Hypothermia is induced by setting the heat exchanger on the cardiopulmonary bypass machine (CPB) to the desired setting. Body core temperature is routinely reduced to 20-28 degrees Celsius for procedures.

States and organizations have different guidelines regarding the actual temperature that is considered hypothermia level and what temperature ranges are considered mild, moderate or severe. A few examples include:

California Guidelines from the 1974 California Relative Value Study stated that hypothermia is considered to be a total body temperature of less than 30 degrees Celsius (with normal body temperatures being 34-37 degrees Celsius). Today's description reads, "lower full body temperature to decrease blood flow." Coders often look for body temperatures around 28 degrees or less that last for a long time.

The "Hypothermia Clinical Guidelines" for the American Society of Peri-Anesthesia Nurses based in Cherry Hill, N.J., state that hypothermia exists when the patient's core body temperature is less than 36 degrees Celsius.

The level of hypothermia is often classified as mild, moderate or severe. General ranges for each category are 32-35 degrees Celsius for mild hypothermia, 28-32 degrees Celsius for moderate, and less than 28 degrees Celsius for severe. Profound hypothermia, which may be used for total circulatory arrest up to one hour during complex surgeries, is about 15-18 degrees Celsius.