Cardiopulmonary resuscitation (CPR) is a life-saving intervention performed when a person experiences cardiac arrest. The procedure involves rhythmically compressing the chest to manually circulate blood and providing rescue breaths to supply oxygen. CPR itself does not cause brain damage. Instead, it is the primary action taken to prevent the severe brain damage that cardiac arrest would otherwise guarantee, maintaining minimal brain function until advanced medical care can restore circulation.
The Actual Source of Brain Injury: Oxygen Deprivation
Brain injury following cardiac arrest begins the moment the heart stops pumping blood, leading to global cerebral ischemia. This lack of blood flow immediately deprives brain cells of the necessary oxygen and glucose. Because the brain uses about 20% of the body’s total oxygen consumption, it is highly sensitive to any interruption in this supply.
Without circulation, the brain’s vulnerable neurons begin to die within the first five minutes. Unconsciousness typically occurs within seconds of the heart stopping, and irreversible damage can start to accumulate around the four-to-six-minute mark. The longer the brain goes without effective perfusion, the more extensive the damage becomes, making the time to resuscitation the main determinant of the long-term neurological outcome.
How CPR Limits Neurological Damage
The physiological goal of chest compressions is to create an artificial circulation that delivers oxygenated blood to the brain and heart. During high-quality CPR, rhythmic force on the chest compresses the heart between the sternum and the spine, forcing blood to circulate. This manual pumping action restores a partial flow of blood, typically achieving approximately 20% of normal blood flow to the brain.
While this minimal flow is not sufficient for normal brain function, it delays the rapid death of brain cells. The oxygen supplied through rescue breaths is carried by this manually circulated blood to the brain tissue. CPR effectively extends the brief window of opportunity for a patient to be successfully resuscitated. By mechanically sustaining minimal perfusion, CPR buys the time necessary for emergency personnel to arrive and administer advanced life support measures.
Common Physical Injuries Caused By CPR
Although CPR is a life-saving procedure, mechanical injuries are a frequent and expected consequence due to the forceful application of pressure. The chest wall must be compressed deeply to effectively circulate blood. The most common injury reported in patients who undergo CPR is rib fracture, with prevalence often exceeding 50%.
Fractured ribs and sternal fractures are often detected after resuscitation. Other less common, though more serious, injuries include internal bruising or lacerations to organs like the liver or spleen. While these injuries can be severe, they are considered an acceptable trade-off when the alternative is death or irreversible brain damage. The presence of these non-neurological injuries confirms the necessary force was applied to sustain life.
Assessing Brain Function After Resuscitation
Once a patient achieves a Return of Spontaneous Circulation (ROSC), the focus shifts to minimizing the secondary brain injury that can occur in the hours following the event. Post-resuscitation care often includes therapeutic hypothermia, where the patient’s core body temperature is deliberately cooled for about 24 hours. This cooling slows the brain’s metabolic rate and lessens the inflammation and chemical reactions that exacerbate neurological damage.
Assessing the full extent of neurological injury is a gradual process, as sedatives and cooling can temporarily mask true brain function. Clinicians use various tools to monitor the patient. These include electroencephalography (EEG) to detect electrical brain activity and brain imaging like computed tomography (CT) scans. The Glasgow Coma Scale (GCS) and observations of brainstem reflexes are used to evaluate consciousness and motor response.
A definitive long-term prognosis is rarely determined immediately after ROSC. It is often assessed after the patient has been fully rewarmed, typically 48 to 72 hours post-arrest. Many patients who survive cardiac arrest may experience some degree of cognitive impairment, ranging from mild memory deficits to severe functional disability. Recovery is a protracted process that may require extensive rehabilitation.