Deep hypothermic circulatory arrest (DHCA) is a surgical technique in which the temperature of the body falls significantly (between 20 °C (68 °F) to 25 °C (77 °F)) and blood circulation is stopped for up to one hour.
[7][2] The use of hypothermia for medical purposes dates back to Hippocrates, who advocated packing snow and ice into wounds to reduce hemorrhage.
The first heart surgery using hypothermia to provide a longer time that blood circulation through the whole body could be safely stopped was performed by F. John Lewis and Mansur Taufic at the University of Minnesota in 1952.
[13] In this procedure, the first successful open heart surgery, Lewis repaired an atrial septal defect in a 5-year-old girl during 5 minutes of total circulatory arrest at 28 °C.
Cardiopulmonary bypass machines allow blood circulation and cooling to continue below the temperature at which the heart stops working.
[13] Randall B. Griepp, in 1975, is generally credited with demonstrating DHCA as a safe and practical approach for aortic arch surgery.
Cold therefore extends the length of time that cells can maintain homeostasis and avoid damaging hypoxia and anaerobic glycolysis by conserving local resources when blood circulation is stopped and unable to deliver fresh oxygen and glucose to make more energy.
[26] A key principle of DHCA is total inactivation of the brain by cooling, as verified by "flatline" isoelectric EEG, also called electrocerebral silence (ECS).
Similar low temperatures are expected to be reached in emergency preservation and resuscitation (EPR) clinical trials described in the Research section of this article.
[8] This method would fall under conventional cooling techniques, in which cold saline and crushed ice are used to induce a state of hypothermia to the patient.
[30] Hospitals and emergency medical services commonly use surface cooling systems that circulate cold air or water around blankets or pads.
Advantages of this method are accuracy of cooling due to auto-regulating temperature control, feedback probes, applicable in non-hospital settings, and non-complexity of use.
[8] People who are to undergo DHCA surgery are placed on cardiopulmonary bypass (CPB), a procedure that uses an external heart-lung machine that can artificially replace the function of the heart and lungs.
[42] Except for the period of complete inactivation just prior to and during the circulatory arrest interval, barbiturate infusion is used to keep the brain in a state of burst suppression for the entirety of the DHCA procedure until emergence from anesthesia.
[30] Virtually all patients who undergo DHCA develop impaired glucose metabolism and require insulin to control blood sugars.
[2] Although DHCA is necessary for some procedures, the use of anesthesia can provide optimum operation time and organ protection but can also have serious impacts on cellular demand, brain cells, and serious systemic inflammatory results.
[45] Possible disadvantages of DHCA includes alteration in organ functions of the liver, kidney, brain, pancreas, intestines and smooth muscles due to cellular damage.
[30] Cases of partial or complete limb motor loss, impaired language, visual defects, and cognitive decline have all been reported as consequences of DHCA.
[45] Other neurological complications are increase risk for seizures postoperative due to delayed return of cellular blood flow to the brain.
[45] Longer recovery time postoperatively have been noted with DHCA as compared to Moderate Hypothermia, but the length of hospital stay and death has no correlated difference.
[2] One of the anticipated medical uses of long circulatory arrest times, or so-called clinical suspended animation, is treatment of traumatic injury.
In 1984 CPR pioneer Peter Safar and U.S. Army surgeon Ronald Bellamy proposed suspended animation by hypothermic circulatory arrest as a way of saving people who had exsanguinated from traumatic injuries to the trunk of the body.
Traditional treatments such as CPR and fluid replacement or blood transfusion are not effective when cardiac arrest has already occurred and bleeding remains uncontrolled.