Heat loss: Prevention
Basic, Clinical Sciences: Anesthesia Procedures, Methods, and Techniques
Hypothermia is often defined as a core body temperature of less than 36 degrees Celsius. In an normal individual not under anesthesia, the hypothalamus tightly regulates core body temperature through warming or cooling processes. While under anesthesia, the ability of the hypothalamus to regulate core body temperature is blunted. Without intervention the core body temperature will drop 1 to 2 degrees Celsius in the first hour of anesthesia and then drop less precipitously over the next 3 to 4 hours until reaching a new homeostatic range well below 36 degrees.
The deleterious effects of hypothermia on the surgical patient are well known and include cardiac arrhythmias and ischemia, a reversible coagulopathy brought on by platelet dysfunction, a left shift of the oxygen-hemoglobin dissociation curve which decreased oxygen delivery to end organs, increased peripheral vascular resistance, decreased renal function, decreased drug metabolism, decreased wound healing, increased post-op protein catabolism and stress response, and increased risk of infection. Thus, it is imperative that the anesthesia provider prevent hypothermia.
Methods of preventing heat loss while under anesthesia include pre-warming with a forced air warming blanket before surgery, use of a forced air warming blanket during surgery, heated humidification of inhaled gases, warming of IV fluids, and increasing the temperature of the operating room. Of these methods, the most effective is forced air warming.