An in-hospital cardiac arrest (IHCA) is a cardiac arrest that occurs within a hospital, as distinct from an out-of-hospital cardiac arrest (OHCA), which occurs in the community. The distinction is clinically and epidemiologically important because the two settings differ in the speed of response, resources available, and outcomes achieved.
In-hospital cardiac arrests benefit from the immediate availability of trained clinical staff, resuscitation equipment, and cardiac arrest teams. Response times are typically seconds to a few minutes rather than the longer delays inherent in community emergencies. Despite these advantages, IHCA carries significant mortality, partly because in-hospital patients are often already severely ill from the underlying condition that precipitated their admission, and partly because IHCA is frequently non-shockable (asystole or pulseless electrical activity rather than ventricular fibrillation), which carries a worse prognosis.
Unlike most out-of-hospital arrests, many in-hospital cardiac arrests are preceded by a period of physiological deterioration that can be identified and acted upon before arrest occurs. This has led to the development of Medical Emergency Teams (METs) and early warning scores (such as NEWS2) aimed at identifying and treating deteriorating patients before they reach cardiac arrest.
The overall survival rate from in-hospital cardiac arrest is approximately 20 to 25% to hospital discharge in the UK, compared to around 10 to 12% for out-of-hospital arrest. This reflects the faster response times and availability of specialist care in the hospital setting, though outcomes vary considerably with the initial cardiac rhythm, the patient’s underlying condition, and the speed of recognition and treatment.
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