By: Nellie Nguyen
Hypothermia is a state where a significant, dangerous drop in body temperature is caused by exposure to extreme cold. Oftentimes, hypothermia can be fatal when left untreated, because it leads to a complete failure of the heart and respiratory system, resulting in death. However, purposefully induced and carefully monitored hypothermia has led to astounding advancements in medical techniques, especially for cardiac surgery purposes.
Deep hypothermic circulatory arrest (DHCA) is a technique involving clinical death, and it is when a patient’s body temperature is greatly lowered and blood flow is reduced through the blood vessels, which can last up to 40 minutes. Clinical death is a term referring to the cessation of blood circulation and breathing, but this does not necessarily mean a person is truly dead; clinical death is reversible, and if handled carefully, it is extremely useful in surgical operations. The safest temperature range for DHCA is between 20º C, or 68º F, and 25º C, or 77º F; this is a major drop, considering that the average human body temperature is approximately 36.1º C to 37.2º C or 97º F to 99º F. The earliest documentation of using this technique dates back to 1959 when it was done on children undergoing repair of a condition caused by four heart defects, called Tetralogy of Fallot.