Sudden cardiac arrest (SCA) refers to the abrupt cessation of the heart's pumping function due to various causes, including cardiovascular diseases, trauma, electric shock, drowning, poisoning, and anesthesia, among others. Patients experiencing SCA immediately present with loss of consciousness, absence of a pulse, and cessation of breathing. SCA is the most common cause of sudden cardiac death, with an annual incidence of 55–120 cases per 100,000 people in out-of-hospital settings in developed countries, where the average survival rate is merely 10.6%.
"Cardiopulmonary resuscitation" (CPR) is an emergency medical intervention for SCA, aimed at sustaining circulation and breathing through manual and/or mechanical methods to maintain perfusion of vital organs and achieve a return of spontaneous circulation (ROSC) as quickly as possible. Successful CPR not only restores autonomous heartbeat and breathing but also seeks to minimize global cerebral ischemic injury following cardiac arrest. Consequently, the concept of "cardiopulmonary cerebral resuscitation" (CPCR) has been introduced, emphasizing various brain protection strategies to reduce post-resuscitation neurological deficits in surviving patients. The complete resuscitation process consists of three stages: initial resuscitation, advanced resuscitation, and post-resuscitation care.
Initial Resuscitation
Initial resuscitation is the critical, life-saving intervention administered immediately after cardiac arrest. It is primarily performed on-site and includes a rapid assessment of the patient's condition and the early initiation of CPR, defibrillation, and other rescue measures. The key components of initial resuscitation for adults include the following:
Early Recognition of Cardiac Arrest and Activation of Emergency Medical Services (EMS)
Rapid identification of cardiac arrest is of paramount importance. Any hesitation could result in a loss of valuable rescue time. To prevent delays in diagnosing cardiac arrest, the 2020 American Heart Association (AHA) resuscitation guidelines recommend that non-medical personnel assume cardiac arrest if the victim is unresponsive or does not react, coupled with abnormal or absent breathing, and proceed to initiate CPR. For healthcare professionals, the assessment involves confirming the absence of patient responsiveness and breathing, combined with a pulse check (not exceeding 10 seconds). If a pulse is not detected, cardiac arrest is presumed, and CPR is started.
In single-rescuer scenarios, while assessing for cardiac arrest, it is crucial to immediately call for help from nearby people, dial emergency services, and activate the EMS to secure expert assistance and access to a defibrillator. In cases involving two or more rescuers, one rescuer starts CPR immediately while another contacts EMS for assistance.
Early Initiation of CPR
The initiation of CPR as promptly as possible remains the cornerstone of initial resuscitation efforts. CPR should begin immediately alongside the activation of EMS. Chest compressions take precedence in CPR, as they provide the primary mechanism for systemic tissue perfusion until ROSC is achieved. International resuscitation guidelines have established a sequence for adult CPR as compressions-airway-breathing (C-A-B), whereby chest compressions are performed 30 times first, followed by airway opening and assisted breathing during on-site resuscitation.
To promote timely intervention, the 2020 AHA guidelines recommend compression-only CPR for bystanders without medical training. It is recognized that during the initial phase of cardiac arrest, oxygen is still present within the patient's lungs and bloodstream. Initiating chest compressions early facilitates the establishment of blood circulation, ensuring that oxygen is delivered to the brain and heart in the critical early moments.
Chest Compressions
Chest compressions refer to the application of indirect or direct pressure to the heart, enabling it to maintain filling and ejection functions, while also promoting the recovery of spontaneous cardiac rhythm. There are two methods for administering chest compressions: external chest compression and open chest cardiac compression.
External Chest Compression
External chest compression is a method of indirectly compressing the heart by applying pressure to the chest wall. There are two mechanisms proposed to explain how external chest compressions facilitate blood ejection:
- Cardiac Pump Mechanism: During chest compressions, direct pressure is applied to the heart between the sternum and the spine, increasing intraventricular pressure and propelling blood circulation.
- Thoracic Pump Mechanism: Chest compressions raise intrathoracic pressure, transmitting this increase to the heart and intrathoracic vessels, and subsequently to large extracardiac vessels, thereby driving blood flow. Upon release of compressions, the intrathoracic pressure decreases, facilitating venous blood return to the heart.
High-Quality Manual External Chest Compression
Positioning: Patients are best positioned lying flat on a firm surface, such as a board or the ground.
Compression Site: The compression site is the lower half of the sternum, located at the midpoint of a line between the two nipples.
Compression Technique: Rescuers should stand or kneel beside the patient, place the heel of one hand at the compression site, and position the other hand on top of it, with fingers interlocked and elevated. The rescuer should lean slightly forward, with straightened arms and aligned shoulders, elbows, and wrists, applying vertical pressure to the sternum using body weight.
Compression Depth and Rate: A depth of at least 5 cm (but not exceeding 6 cm) is recommended, with a rate of 100–120 compressions per minute.
Compression and Recoil Time: Full chest recoil after each compression is essential, with a 1:1 ratio of compression to relaxation time.
Compression-to-Breath Ratio: For adult CPR, the ratio is 30 compressions to 2 breaths, with one cycle consisting of 5 sets and lasting approximately 2 minutes.
Rescuer Rotation: During two-person (or more) CPR, rotation every 2 minutes is necessary to avoid rescuer fatigue, which can lower compression quality. Transitions should be swift to minimize interruptions in compressions.
External Compression Assist Devices
To enhance the quality of chest compressions and conserve human resources during prolonged resuscitation efforts or challenging conditions (e.g., rescuer wearing lead aprons, infectious disease protocols), chest compression assist devices can be used. These include mechanical compression devices and active compression-decompression devices. Prior to using these devices, personnel training is required to ensure proper operation, and strict management is necessary to limit interruptions during device setup and removal.
Open Chest Cardiac Compression (OCCC)
Open chest cardiac compression involves directly compressing the heart by opening the chest wall. Directly compressing the heart generates coronary and cerebral blood flow levels significantly higher than those achieved by external chest compressions. It is more likely to restore spontaneous circulation and reduce ischemic brain injury. However, OCCC demands advanced technical conditions and cannot be immediately initiated. Risks include delayed resuscitation and increased infection rates, making OCCC unsuitable for routine use. It may be considered in cases of cardiac arrest occurring during open-heart surgery or in patients with severe open chest trauma.
Airway Management
Maintaining airway patency is a prerequisite for assisted ventilation. Unconscious patients are prone to airway obstruction, commonly due to tongue retraction, secretions, vomitus, or foreign bodies in the airway. Before assisted ventilation, clearing any foreign objects from the airway is necessary. Airway patency can then be achieved using a head-tilt/chin-lift technique unless the patient has cervical spine or spinal cord injuries, in which case a jaw thrust technique is recommended. Adjuncts such as oropharyngeal or nasopharyngeal airways, esophageal occlusion airways, or endotracheal tubes can also be used to maintain airway patency when available.
Assisted Ventilation
As CPR progresses, blood oxygen levels decline. Assisted ventilation is therefore essential during CPR to increase blood oxygen content. However, ventilation can interrupt chest compressions and increase the risks of gastric inflation and regurgitation. The principle for assisted ventilation involves ensuring adequate oxygen delivery while minimizing its negative impact on compression efficiency. According to the 2020 AHA guidelines, the tidal volume for assisted ventilation should be 500–600 mL, sufficient to observe visible chest rise. Each ventilation should last more than 1 second. During mouth-to-mouth resuscitation, breathing should be steady rather than deep prior to exhalation into the patient. Over-ventilation (excessive rate or volume) should be avoided. The compression-to-ventilation ratio for adult CPR remains 30:2, with 30 compressions followed by 2 breaths. When an advanced airway (e.g., endotracheal tube) is in place, continuous chest compressions can be combined with ventilation at a rate of 10 breaths per minute.
Mouth-to-Mouth Ventilation
During mouth-to-mouth resuscitation, one hand is used to tilt the patient’s head back while pinching their nostrils closed, and the other hand lifts the chin. After a normal inhalation, the rescuer seals their lips over the patient’s mouth, delivering a breath. Following each breath, the rescuer withdraws, allowing the patient’s chest elasticity to facilitate passive exhalation.
Mouth-to-Nose Ventilation
This method is appropriate for patients with facial injuries or locked jaws. The rescuer elevates the patient’s chin to close the mouth and exhales air into the patient’s nose after a normal breath.
Bag-Valve-Mask Ventilation
Professional emergency personnel can use a bag-valve-mask for on-site ventilation, consisting of a mask, a one-way valve, and a squeezable bag. The mask is placed over the patient’s nose and mouth, secured using the EC technique while lifting the chin. The bag is then squeezed to deliver air into the lungs. Releasing the bag allows air to passively exit through the one-way valve into the atmosphere. The bag may also be connected to an oxygen source to increase the oxygen concentration of inhaled air.
Early Initiation of Defibrillation
Defibrillation is a method of terminating ventricular fibrillation by delivering an electrical shock to the heart. Direct current defibrillation is the most widely used technique. The most common arrhythmias in adult cardiac arrest are ventricular fibrillation (VF) and pulseless ventricular tachycardia (PVT), the latter of which can rapidly deteriorate into VF and is treated similarly. Defibrillation is the most effective means of terminating shockable rhythms (VF and PVT) and promptly restoring spontaneous circulation. Early defibrillation demonstrates a high success rate and significantly improves the prognosis of cardiac arrest patients. Consequently, timely activation of EMS and initiation of defibrillation are critical to successful resuscitation.
Principles for Using a Defibrillator
For out-of-hospital cardiac arrest, CPR is continued until a defibrillator becomes available. If VF or PVT is detected, one defibrillation attempt is performed, followed by 5 cycles of CPR; afterwards, heart rhythm and pulse are reassessed, and additional defibrillation is administered as needed. Biphasic defibrillators are considered superior to monophasic defibrillators. In cases of suspected refractory arrhythmias, defibrillation energy should be selected based on the manufacturer's recommendations for the device. If no recommendations are provided, the maximum energy is used as the initial setting (200 joules for biphasic defibrillators and 360 joules for monophasic defibrillators).
Method for Using an External Defibrillator
Positioning for Defibrillation
Patients are positioned supine with their head flat and removed of pillows. The chest is exposed while the left arm is abducted.
Pre-Defibrillation Preparation
The chest is inspected for implanted pacemakers, the chest skin is dried, and any metallic objects are removed.
Device Setup
The defibrillator is powered on, and the asynchronous mode is selected.
Electrode Placement and Rhythm Assessment
The placement of the two electrodes ensures that as much electrical current as possible passes through the myocardial tissue. In external defibrillation, the most common electrode placement is the "anterolateral position," where one electrode is positioned at the right sternal edge of the second intercostal space (near the cardiac base), and the other is placed at the fifth intercostal space along the left midaxillary line (near the cardiac apex). The defibrillator’s monitor is used to confirm whether a shockable rhythm exists.
Defibrillation Procedure
Conductive gel is evenly applied to the electrodes. The defibrillation energy is adjusted to the recommended level (up to 200 joules for biphasic and 360 joules for monophasic defibrillators). The device is charged, and once ready, the rescuer loudly announces “Prepare for defibrillation; everyone stand clear.” After confirming proper electrode placement and the presence of a shockable rhythm, a force of 10 kg is applied to the electrodes before simultaneously pressing both discharge buttons to deliver the shock.
Post-Defibrillation Management
Immediately after defibrillation, 5 cycles of CPR are performed. Heart rhythm and pulse are reassessed, and defibrillation is repeated as necessary.
Other Types of Defibrillators
During open-chest surgery, electrodes can be directly applied to the ventricular wall for defibrillation, commonly referred to as internal defibrillation. For adult internal defibrillation, the energy typically starts at 10 joules and does not exceed 40 joules. Automated external defibrillators (AEDs) are often available in public settings such as airports. These devices come equipped with self-adhesive electrodes that are placed near the cardiac base and apex. AEDs automatically analyze rhythms, charge, and deliver shocks, making them suitable for use by non-professional rescuers and enhancing survival rates for out-of-hospital cardiac arrest patients.
Indicators for Terminating Initial Resuscitation
Determining the appropriate time to terminate resuscitation during CPR is essential to identify patients with treatment potential while minimizing futile rescue efforts. According to the 2020 AHA resuscitation guidelines, initial resuscitation may be considered for termination, especially before emergency transport, if all of the following criteria are met:
- No emergency responder or first witness was present at the time of cardiac arrest.
- Spontaneous circulation is not restored despite active resuscitation efforts.
- Defibrillation was not performed due to the absence of a shockable rhythm.
Clinical evidence indicates that when all these criteria are satisfied, the likelihood of survival or recovery with good neurological function is extremely low.
Advanced Resuscitation
Advanced resuscitation serves as a continuation of initial resuscitation, focusing on achieving optimal outcomes and prognosis through high-quality techniques, specialized equipment, and pharmacological interventions. It includes the following components:
Respiratory Support
Advanced airway management is a critical method for maintaining airway patency and stability. However, establishing an advanced airway may present risks such as interruptions in chest compressions, airway injuries, and aspiration due to regurgitation. During the advanced resuscitation phase, the rapid establishment of an artificial airway and the implementation of mechanical ventilation by well-trained professionals ensures oxygen delivery, promoting the restoration of spontaneous circulation.
Establishment of an Artificial Airway
Artificial airways should be established as early as possible while minimizing interruptions to chest compressions. These airways include esophageal-tracheal combitubes, laryngeal masks, and endotracheal intubation, with endotracheal intubation being the most commonly used and reliable method.
Implementation of Mechanical Ventilation
Mechanical ventilation involves the use of ventilators to replace, control, or modify spontaneous breathing and is considered an effective and reliable respiratory support measure in clinical practice. During the advanced resuscitation phase, mechanical ventilation is typically set at a rate of 10 breaths per minute, with a tidal volume of 500–600 mL, avoiding hyperventilation.
Restoration and Maintenance of Spontaneous Circulation
The primary objective during the advanced resuscitation phase is the restoration and maintenance of spontaneous circulation. High-quality CPR and early defibrillation play vital roles in achieving this goal. For patients with ventricular fibrillation (VF), early CPR and defibrillation significantly increase survival rates. For non-VF patients, high-quality CPR combined with adjunctive pharmacological therapy supports faster restoration and stabilization of spontaneous circulation, improving clinical outcomes.
The workflow for advanced resuscitation includes considering defibrillation as soon as CPR is initiated. For shockable rhythms (VF or pulseless ventricular tachycardia, PVT), a single defibrillation is performed immediately, followed by 5 cycles of CPR. If the rhythm is deemed non-shockable (pulseless electrical activity or asystole), CPR is continued along with intravenous administration of 1 mg epinephrine, which can be repeated every 3–5 minutes. If the rhythm subsequently converts to a shockable rhythm, another defibrillation is performed, followed by 5 more cycles of CPR, accompanied by intravenous administration of 1 mg epinephrine every 3–5 minutes. These steps are repeated until spontaneous circulation is restored or criteria for terminating resuscitation are met.
Pharmacological Therapy
Medications used during resuscitation are primarily classified into vasoactive medications and non-vasoactive medications. Vasoactive medications assist in vasoconstriction to ensure perfusion of critical organs, while non-vasoactive medications, such as antiarrhythmic drugs, are primarily used to terminate VF or PVT.
Establishment of Administration Routes
Common administration routes during resuscitation include intravenous, intraosseous, and endotracheal delivery. Intravenous administration is the most commonly used method and can be performed via central or peripheral veins. When intravenous access is difficult, intraosseous administration is an effective alternative, often used in pediatric cases by puncturing the tibia or iliac bone, with effects similar to intravenous administration. If neither of these options is feasible, endotracheal drug delivery may be attempted by diluting 2–2.5 times the standard drug dose in 10 mL of saline and injecting it through the endotracheal tube.
Resuscitation Medications
Vasoactive Medications
These include epinephrine and vasopressin, which leverage their vasoconstrictive properties to increase coronary and cerebral perfusion pressure, aiding in the restoration of spontaneous circulation. Both medications are applicable for cardiac arrest caused by shockable and non-shockable rhythms.
Epinephrine
Epinephrine is the first-line drug for cardiopulmonary resuscitation. It enhances blood flow to the coronary and cerebral arteries, aiding the recovery of spontaneous rhythm and reducing ischemic brain injury. Additionally, it increases myocardial contractility and facilitates the conversion of fine VF waves to coarse VF waves, improving the success rate of defibrillation. Epinephrine is recommended at a dose of 1 mg administered intravenously every 3–5 minutes during CPR. For non-shockable rhythms, early use of epinephrine provides benefits. For shockable rhythms, epinephrine is considered after initial defibrillation attempts fail.
Vasopressin (VP)
Vasopressin can be used alone or in combination with epinephrine during cardiac arrest. However, compared to epinephrine, vasopressin provides no significant advantage in terms of restoring spontaneous circulation, improving survival rates, or enhancing neurological outcomes.
Antiarrhythmic Medications
These include amiodarone and lidocaine, which are used to terminate VF or PVT and achieve earlier restoration of spontaneous circulation.
Amiodarone
Amiodarone is the first-line antiarrhythmic medication during CPR and is effective for both supraventricular and ventricular arrhythmias. It improves the patient's response to defibrillation and enhances short-term survival rates. A loading dose of 300 mg is recommended via intravenous push, with an additional 150 mg administered if necessary. The total daily dose should not exceed 2 g. Due to its vasodilatory effect, precautions should be taken to prevent hypotension during use.
Lidocaine
Lidocaine is effective for ventricular arrhythmias but not for supraventricular arrhythmias. In patients experiencing recurrent VF, lidocaine can reduce recurrence rates. The initial dose is 1–1.5 mg/kg administered intravenously, followed by 0.5–0.75 mg/kg every 5–10 minutes as needed. The maximum cumulative dose is 3 mg/kg.
Medications Not Recommended for Routine Use in Cardiac Arrest
Atropine
Atropine is effective for sinus bradycardia and atrioventricular conduction block caused by vagal overactivity, but its routine use during CPR is no longer recommended by current AHA guidelines. Atropine is instead reserved for cases of bradycardia occurring after the restoration of spontaneous circulation.
Calcium
Calcium enhances myocardial contractility and ventricular automaticity, but its routine use during cardiac arrest is not recommended due to limited efficacy. It is reserved for cases of hypocalcemia, hyperkalemia, hypermagnesemia, or calcium channel blocker overdose.
Magnesium Sulfate (MgSO4)
Magnesium sulfate is only indicated for cardiac arrest associated with torsades de pointes (TdP) and prolonged QT intervals. Routine use is not recommended.
Sodium Bicarbonate
The routine use of sodium bicarbonate during resuscitation is not recommended. It may be considered in cases of pre-existing severe metabolic acidosis, hyperkalemia, or overdose of tricyclic antidepressants or barbiturates.
Real-Time Monitoring of CPR Quality
High-quality life support is at the core of CPR. Real-time monitoring of CPR quality helps to optimize its effectiveness and improve the success rate of resuscitation. Commonly used methods for CPR quality monitoring include audiovisual feedback devices, arterial blood pressure monitoring, electrocardiography (ECG), and end-tidal carbon dioxide (PETCO₂) monitoring.
Audiovisual Feedback Devices
These devices monitor parameters such as compression rate, depth, and recoil during CPR in real time, record the data, and provide corrective audio and visual feedback. As one of the most advanced CPR monitoring tools available, these devices can improve the quality of CPR and enhance the survival rate of patients discharged from the hospital.
Arterial Blood Pressure Monitoring
Diastolic blood pressure plays a critical role in maintaining coronary blood flow. Sustained diastolic pressures below 20 mmHg during chest compressions may result in inadequate myocardial perfusion, making the restoration of spontaneous circulation unlikely. Cerebral perfusion pressure correlates closely with mean arterial pressure. Maintaining sufficient mean arterial pressure can improve cerebral blood flow and support recovery of favorable neurological outcomes. Continuous arterial blood pressure monitoring is therefore vital for assessing CPR quality and organ perfusion.
Electrocardiographic (ECG) Monitoring
Various arrhythmias occur during cardiac arrest and throughout the resuscitation process. Continuous ECG monitoring enables accurate diagnosis and provides a basis for defibrillation and pharmacological therapy.
End-Tidal Carbon Dioxide (PETCO2) Monitoring
During CPR, carbon dioxide (CO2) elimination relies primarily on cardiac output and pulmonary perfusion. When cardiac output and lung perfusion are inadequate, PETCO2 levels remain low (<10 mmHg). As cardiac output increases and pulmonary perfusion improves, PETCO2 levels rise (>20 mmHg). The earliest sign of restored spontaneous circulation is often a sudden increase in PETCO2 to levels above 40 mmHg. Continuous PETCO2 monitoring can therefore assess the effectiveness of chest compressions. A PETCO₂ value exceeding 10 mmHg is indicative of effective CPR.
Extracorporeal Cardiopulmonary Resuscitation (ECPR)
ECPR involves the use of extracorporeal respiratory and circulatory support technologies during CPR. The primary method of ECPR currently involves the use of extracorporeal membrane oxygenation (ECMO) systems in out-of-hospital or in-hospital settings to provide extracorporeal respiratory and circulatory support. However, implementing ECPR requires highly specialized teams, advanced equipment, comprehensive management protocols, and significant financial resources, which limits its widespread use.
A large, multicenter clinical study conducted in France in 2020 reported that approximately 4% of out-of-hospital cardiac arrest patients received ECPR, but there was no improvement in survival rates among these patients. Based on this evidence, the 2020 AHA resuscitation guidelines state that there is currently insufficient evidence to support the routine use of ECPR in cardiac arrest cases. ECPR may, nonetheless, be considered in situations where cardiac arrest is potentially reversible with temporary respiratory and circulatory support.
Indicators for Termination of Advanced Resuscitation
The 2020 AHA resuscitation guidelines suggest that advanced resuscitation may be terminated if all of the following criteria are met:
- Cardiac arrest occurred without a witnessed event.
- No bystander initiated CPR.
- Spontaneous circulation was not restored despite aggressive treatments.
- Defibrillation was not performed due to the absence of a shockable rhythm.
Post-Resuscitation Care
Patients who achieve the return of spontaneous circulation (ROSC) after cardiac arrest require comprehensive medical interventions, including early life support, organ protection, rehabilitation therapy, and thorough prognostic assessment. Following ROSC, patients should be immediately transported to a medical facility with ICU resources for post-cardiac arrest care (PCAC). Post-resuscitation management focuses on respiratory and circulatory support, brain protection, and treatment of other complications. A systematic approach to post-resuscitation care not only improves survival rates but also enhances the quality of life for survivors.
Optimization of Oxygenation and Ventilation
After ROSC, the timely establishment of a reliable artificial airway, such as through endotracheal intubation, is important to maintain adequate oxygenation and ventilation. Both hypoxemia and hyperoxia can lead to further damage to critical organs such as the brain and heart. Additionally, abnormalities in ventilation, such as hypercapnia or hypocapnia, may cause vascular dysfunction and altered cerebral blood flow, potentially impairing organ function. Nonetheless, there is currently no universally accepted standard for optimal oxygenation and ventilation targets.
Based on current evidence, the 2021 European Resuscitation Guidelines make the following recommendations:
- Following ROSC, pure oxygen (100% FiO2`) may initially be administered until reliable data on arterial oxygen saturation (SaO2) or partial pressure of oxygen (PaO2) are obtained.
- Once reliable oxygenation data are available, oxygen concentration should be titrated to maintain an SpO2 of 94–98% or a PaO2 of 75–100 mmHg.
- Hypoxemia and hyperoxia should be avoided.
- For mechanically ventilated patients, lung-protective ventilation strategies should be adopted, with tidal volumes set at 6–8 mL/kg of ideal body weight.
- Mechanically ventilated patients should have their ventilation parameters adjusted to maintain an arterial carbon dioxide partial pressure (PaCO2) of 35–45 mmHg.
Circulatory Support
Maintaining hemodynamic stability is a fundamental element of supportive therapy for all critically ill patients. In patients with cardiac arrest, post-resuscitation hypotension is associated with lower survival rates and significant neurological deficits. Maintaining adequate arterial blood pressure is therefore crucial. An initial target of systolic blood pressure ≥90 mmHg or mean arterial pressure (MAP) ≥65 mmHg is commonly used. However, from the perspective of ensuring adequate perfusion of vital organs, optimal blood pressure targets require individualized adjustments. Determining the most appropriate blood pressure target entails consideration of the patient’s age and baseline blood pressure levels, along with comprehensive hemodynamic monitoring (e.g., preload, afterload, cardiac pump function, and oxygen metabolism) and perfusion assessments of critical organs (e.g., coronary and cerebral blood flow). Based on these evaluations, supportive therapies may include fluid resuscitation, the use of vasoactive agents to maintain organ perfusion, inotropic agents or implantable circulatory support devices to enhance cardiac pump function, and treatments targeting the underlying cause of cardiac arrest (such as coronary revascularization procedures).
Cerebral Resuscitation
Cerebral resuscitation refers to interventions aimed at preventing or mitigating hypoxic brain injury following cardiac arrest. Brain tissue is highly sensitive to ischemia and hypoxia, and irreversible morphological changes in the brain can occur after 5–7 minutes of complete cerebral ischemia. After the restoration of spontaneous circulation, cerebral reperfusion may cause brain congestion, cerebral edema, and sustained hypoperfusion, further exacerbating brain injury. The primary objectives of cerebral resuscitation are to maintain the balance between oxygen supply and demand in the brain, prevent cerebral edema and elevated intracranial pressure, reduce or avoid reperfusion injury, and restore brain cell function. Specific interventions include optimizing cerebral perfusion, targeted temperature management, seizure control, and other neuroprotection strategies.
Optimization of Cerebral Perfusion
Cerebral perfusion pressure (CPP) is defined as the difference between mean arterial pressure (MAP) and intracranial pressure (ICP). CPP is typically maintained at 60–70 mmHg. To ensure adequate cerebral perfusion while avoiding over-perfusion, reductions in ICP and determination of an optimal MAP are necessary.
Reduction of Intracranial Pressure (ICP)
Positioning
Positioning the head of the bed at 30° elevation with the neck in a neutral position facilitates jugular venous outflow.
Analgesia and Sedation
Adequate analgesia and moderate sedation reduce stress responses, lower cerebral oxygen consumption, and help decrease ICP.
Osmotherapy
Administration of hyperosmolar solutions, such as 20% mannitol or 3% hypertonic saline via rapid intravenous infusion, lowers ICP.
Surgical Intervention
For cases of refractory intracranial hypertension, decompressive craniectomy may be performed.
Titration of Optimal MAP
Cerebral blood flow is regulated by autoregulation mechanisms that maintain constant perfusion across MAP ranges between 50 and 150 mmHg under normal conditions. However, autoregulation may become impaired after ischemic brain injury, causing changes in MAP to directly affect cerebral perfusion. The development of multimodal brain monitoring technologies—integrating data on cerebral blood flow, brain tissue oxygen saturation, metabolism, electrical activity, and ICP—provides an opportunity to analyze autoregulatory function and guide individualized MAP targets for clinical management.
Targeted Temperature Management (TTM)
Targeted temperature management is an important component of cerebral resuscitation. Temperature control reduces cerebral blood flow and metabolism while assisting in lowering ICP. However, systemic hypothermia carries potential risks, including shivering, myocardial suppression, and coagulation dysfunction. According to the 2021 European Resuscitation Guidelines, TTM is recommended for patients who remain comatose after the return of spontaneous circulation. A target temperature of 32–36°C is maintained for at least 24 hours. For patients with persistent coma, body temperature is kept below 37.7°C within the first 72 hours after ROSC.
Seizure Control
Seizures, including epileptic-like activity, are a common clinical manifestation of brain injury. Early post-resuscitation seizure episodes are not uncommon. The 2020 AHA resuscitation guidelines recommend the use of electroencephalography (EEG) for diagnosing seizures in all comatose post-resuscitation patients. For seizures with clinical manifestations after cardiac arrest, treatment options include levetiracetam, valproic acid, or sedative medications. Prophylactic antiepileptic therapy is not recommended.
Other Neuroprotection Measures
Glucose Management
Brain cells rely heavily on glucose for energy metabolism. Maintaining glucose levels between 7.8–10 mmol/L supports neuronal recovery by ensuring energy supply.
Hemoglobin Levels
Adequate oxygen delivery to brain tissue requires a hemoglobin level of at least 70–90 g/L.
Additional Supportive Symptomatic Therapies
Routine use of proton pump inhibitors (PPIs) helps prevent stress-related ulceration.
Limb compression therapy and/or anticoagulant medications prevent the formation of deep vein thrombosis.
Adequate enteral nutrition is administered, with gastrointestinal tolerance closely evaluated.