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. It is used when blood circulation to the brain must be stopped because of delicate surgery within the brain, or because of surgery on large blood vessels that lead to or from the brain. DHCA is used to provide a better visual field during surgery due to the cessation of blood flow.[1] DHCA is a form of carefully managed clinical death in which heartbeat and all brain activity cease.
When blood circulation stops at normal body temperature (37 °C), permanent damage occurs in only a few minutes. More damage occurs after circulation is restored. Reducing body temperature extends the time interval that such stoppage can be survived.[2] At a brain temperature of 14 °C, blood circulation can be safely stopped for 30 to 40 minutes.[3] There is an increased incidence of brain injury at times longer than 40 minutes, but sometimes circulatory arrest for up to 60 minutes is used if life-saving surgery requires it.[4][5] Infants tolerate longer periods of DHCA than adults.[6]
Applications of DHCA include repairs of the aortic arch, repairs to head and neck great vessels, repair of large cerebral aneurysms, repair of cerebral arteriovenous malformations, pulmonary thromboendarterectomy, and resection of tumors that have invaded the vena cava.[7][2]
- ^ Bhalala US, Appachi E, Mumtaz MA (2016). "Neurologic Injury Associated with Rewarming from Hypothermia: Is Mild Hypothermia on Bypass Better than Deep Hypothermic Circulatory Arrest?". Frontiers in Pediatrics. 4: 104. doi:10.3389/fped.2016.00104. PMC 5039167. PMID 27734011.
- ^ a b Conolly S, Arrowsmith JE, Klein AA (July 2010). "Deep hypothermic circulatory arrest". Continuing Education in Anaesthesia, Critical Care & Pain. 10 (5): 138–142. doi:10.1093/bjaceaccp/mkq024.
- ^ Yan TD, Bannon PG, Bavaria J, Coselli JS, Elefteriades JA, Griepp RB, Hughes GC, LeMaire SA, Kazui T, Kouchoukos NT, Misfeld M, Mohr FW, Oo A, Svensson LG, Tian DH (March 2013). "Consensus on hypothermia in aortic arch surgery". Annals of Cardiothoracic Surgery. 2 (2): 163–8. doi:10.3978/j.issn.2225-319X.2013.03.03. PMC 3741830. PMID 23977577.
HCA at 14 °C is also reported to provide at least 30-40 minutes of safe HCA time.
- ^ Conolly S, Arrowsmith JE, Klein AA (July 2010). "Deep hypothermic circulatory arrest". Continuing Education in Anaesthesia, Critical Care & Pain. 10 (5): 138–142. doi:10.1093/bjaceaccp/mkq024.
Most patients tolerate 30 min of DHCA without significant neurological dysfunction, but when this is extended to longer than 40 min, there is a marked increase in the incidence of brain injury. Above 60 min, the majority of patients will suffer irreversible brain injury, although there are still a small number of patients who can tolerate this.
- ^ "Cerebral ischemia: deep hypothermia". Open Anesthesia. Retrieved 14 April 2016.
45 to 60 minutes is upper limit of safe time period.
- ^ Conolly S, Arrowsmith JE, Klein AA (July 2010). "Deep hypothermic circulatory arrest". Continuing Education in Anaesthesia, Critical Care & Pain. 10 (5): 138–142. doi:10.1093/bjaceaccp/mkq024.
Longer periods of DHCA are tolerated in neonates and infants compared with adults.
- ^ Anton JM, Kanchuger M. "Anesthetic Management for Deep Hypothermic Circulatory Arrest" (PDF). Society of Cardiovascular Anesthesiologists. Retrieved 14 April 2016.
DHCA is used for open heart procedures where the ability to perfuse the brain through the head vessels is not possible with standard proximal aorta cannulation. Repairs of the aortic arch, congenital repairs involving the aortic arch, repairs to the head and neck great vessels, or neurosurgical and pulmonary endarterectomies may require DHCA. Inability to clamp the distal arch, secondary to severe aortic atheromas, may also require DHCA to minimize stroke risk.