Cardiac arrest

Dr Daniel J Bell et al.

Cardiac arrest is the term used for the abrupt loss of cardiac pump function such that an adequate circulation cannot be maintained. Despite recent modest improvements in survival, it usually leads to death, if not immediately treated. Arrests may be in-hospital or out-of-hospital. 

The epidemiology of cardiac arrest varies markedly whether we are considering in- or out-of-hospital arrests.

Worldwide, the incidence of cardiac arrest is not known 1, however, studies in the US have shown that there are almost 300,000 in-hospital arrests per annum 1. Age-wise, cardiac arrests have a mean age of occurrence in the mid-sixties, with a small majority being men (58%) 1

Non-shockable rhythms are much more common, accounting for about 80% of arrests.

Patients may initially be awake, although once the heart stops, loss of consciousness rapidly ensues due to a critical lack of perfusion of the brain.

Cardiac arrest is usually straightforward to recognize, with classic signs and symptoms:

  • pallor
  • agonal/absent breathing
  • absent peripheral pulses
  • severe hypotension/unmeasurable blood pressure
  • poor oxygen saturations
  • unconscious (low GCS)

Over half of all cardiac arrests are secondary to a cardiac cause, with respiratory deterioration accounting for most of the remainder (up to 40%) 1. Many arrests will be multifactorial.

The so-called reversible causes should always be considered during the acute management of an arrest 1,6.

  • cerebral ischemia/hemorrhage: rare as cause of in-hospital arrest
  • hypovolemia, usually massive hemorrhage
  • hypothermia e.g. near drowning, exposure
  • metabolic e.g. hypo-/hyperkalemia, hypoglycemia, hypocalcemia, severe acidosis
  • toxins: includes carbon monoxide, opioids, methadone, benzodiazepines

"4 Hs and 4 Ts"

  • hypoxia
  • hypothermia
  • hypovolemia
  • hypo-/hyperkalemia, hypoglycemia, hypocalcemia, severe acidosis
  • thrombosis: pulmonary embolism or acute coronary syndrome
  • tension pneumothorax
  • tamponade
  • toxins
  • sepsis

Cardiac arrest can be classified according to whether the presenting arrhythmia can be successfully treated with a shock from a defibrillator or not. The majority of cardiac arrests are with non-shockable rhythms.

Point of care ultrasound (PoCUS) has been used to assess cardiac arrest patients in the Emergency Department.

Cardiac arrest is diagnosed clinically however occasionally a patient will be periarrest or have arrested just prior to, or even during, an imaging exam. Several case reports have described the findings on CT in this patient cohort 3,4:

Described CT features include:

Cardiopulmonary resuscitation (CPR) is the gold standard care performed for all patients in cardiac arrest 1. The algorithms have been modified somewhat over the years as the real-life evidence base has expanded. 

Successful CPR results in 'return of spontaneous circulation' (ROSC).

Survival post arrest remains grim, with a maximal 25% in-hospital cases reaching discharge 2 with the chance of survival outside-hospital being much worse.  Nevertheless, long term disability may still be an issue.

Poor prognostic factors for in-hospital arrests from a large meta-analysis 2:


  • male sex
  • older age
  • chronic renal disease
  • malignancy


  • prolonged resuscitation time
  • tracheal intubation

However, several conditions were correlated with improved outcomes for in-hospital arrests, including

  • witnessed arrest
  • arrest in a monitored environment
  • daytime arrest
  • shockable rhythm

It is also known that shockable rhythms are associated with a better prognosis in the out-of-hospital arrest scenario 2,5.

Article information

rID: 86743
System: Cardiac
Tag: cases3
Synonyms or Alternate Spellings:
  • Cardiorespiratory arrests
  • Cardiorespiratory arrest
  • Cardiac arrests

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