Cardiac arrest (CA) is a sudden, unexpected loss of heart function, breathing, and consciousness, occurring when the heart’s electrical system malfunctions. The immediate goal is the return of spontaneous circulation (ROSC) through resuscitation. Survival leads immediately into post-cardiac arrest syndrome (PCAS).
PCAS is a state of whole-body injury resulting from oxygen deprivation and subsequent ischemia-reperfusion injury when blood flow returns. This syndrome involves four major components: brain injury, heart muscle dysfunction, a systemic inflammatory response, and the persistent underlying cause of the arrest. Post-CA care is a specialized, multi-system approach designed to manage these complex injuries and maximize functional recovery.
Immediate Critical Care and Hemodynamic Support
The moment ROSC is achieved, the patient is transferred to an Intensive Care Unit (ICU) to begin acute stabilization. The immediate focus is securing the airway and optimizing oxygen delivery while preventing further injury from excessive oxygen. Intubation and mechanical ventilation are standard for comatose patients. Clinicians carefully titrate oxygen to maintain blood oxygen saturation (SpO2) between 94% and 98%, deliberately avoiding hyperoxia, which can be harmful.
Ventilation rates are managed precisely to maintain carbon dioxide (CO2) levels within a normal range, typically targeting an end-tidal CO2 between 35 and 40 mmHg. Hyperventilation, which lowers CO2 too much, can constrict blood vessels in the brain, potentially reducing blood flow and worsening neurological damage. Simultaneously, the care team works to stabilize the patient’s circulation, a process referred to as hemodynamic support. The heart muscle often suffers temporary weakness, known as post-cardiac arrest myocardial dysfunction, which leads to low blood pressure.
Physicians aim to maintain a Mean Arterial Pressure (MAP) of at least 65 mmHg, and often higher, sometimes targeting over 80 mmHg, to ensure adequate blood flow to the brain and other organs. This is accomplished through initial fluid resuscitation using intravenous crystalloid solutions and the use of vasopressor medications, such as norepinephrine, which constrict blood vessels to raise blood pressure. The initial phase also includes correcting severe metabolic imbalances, such as acidosis or electrolyte disturbances, that occurred during the arrest period.
Targeted Temperature Management for Neuroprotection
The most critical intervention for comatose survivors is Targeted Temperature Management (TTM), which is employed to protect the brain from extensive damage after the return of circulation. The brain is susceptible to a cascade of cellular events, including inflammation and the production of toxic free radicals, triggered when oxygen-rich blood returns to oxygen-starved tissue. TTM works by gently lowering the body’s core temperature, slowing the brain’s metabolic rate, reducing oxygen demand, and minimizing the destructive effects of reperfusion injury.
The process is divided into three phases: induction, maintenance, and rewarming. For unresponsive patients, the target temperature is typically maintained within a range of 32°C to 36°C for a maintenance period of at least 24 hours. Cooling is achieved using specialized equipment, such as surface cooling pads, water-circulating blankets, or intravenous cold fluids. Throughout this phase, patients require sedation and often muscle relaxants to prevent shivering, which would counteract the cooling efforts.
After maintenance, the patient is gradually rewarmed to a normal body temperature, ideally at a slow, controlled rate of about 0.25°C to 0.5°C per hour. Rapid rewarming is avoided because it can reverse the neuroprotective benefits and potentially increase the risk of complications. Following TTM, it remains important to actively prevent fever for at least 72 hours, as even a mild fever can significantly worsen the neurological outcome.
Identifying and Treating the Underlying Cause
While life support stabilizes the patient, a simultaneous effort diagnoses the specific event that caused the cardiac arrest. Failure to identify and treat this underlying trigger leaves the patient at high risk for a recurrent arrest. The most common causes are acute cardiac events, such as a myocardial infarction (heart attack) or a severe, life-threatening arrhythmia.
A 12-lead electrocardiogram (ECG) is one of the first and most informative diagnostic tests, quickly revealing patterns indicative of an ongoing heart attack, specifically an ST-elevation myocardial infarction (STEMI). If a STEMI is identified, the patient is immediately rushed to the cardiac catheterization lab for urgent angiography and percutaneous coronary intervention (PCI). During this procedure, a blocked coronary artery is located and reopened with a stent to restore blood flow to the heart muscle, an intervention that is performed even if the patient is still receiving TTM.
Beyond coronary issues, physicians investigate other reversible causes, often categorized by the mnemonic “H’s and T’s.” These include imbalances like severe low blood volume (hypovolemia), low oxygen levels (hypoxia), or a massive pulmonary embolism. Targeted laboratory tests and imaging studies are used to confirm or rule out these possibilities. Providing the best chance for long-term survival without a relapse requires treating the cause.
Long-Term Recovery and Rehabilitation
Once the patient is stabilized in the ICU and TTM is complete, the focus shifts to assessing neurological injury and planning long-term recovery. Neurological prognosis is determined through a multimodal approach, including clinical examination, brain imaging such as MRI, and electroencephalogram (EEG) monitoring. These assessments predict the potential for functional recovery and guide the need for specialized rehabilitation.
Many survivors experience cognitive deficits, including issues with short-term memory, attention, and executive functions like planning and organization. Physical recovery can be marked by fatigue, muscle weakness, and difficulties with fine motor skills. Consequently, discharge planning almost always includes a referral to a comprehensive rehabilitation program.
Cardiac rehabilitation is a structured, medically supervised program that typically lasts three to six months and focuses on supervised exercise, nutritional counseling, and stress management. Patients with significant brain injury may also require neurorehabilitation, which addresses cognitive and physical impairments to help them regain independence. The overall recovery process is long and often involves managing emotional challenges, such as anxiety and depression, which require ongoing support for both the survivor and their family.