Post-Cardiac Arrest Syndrome

Post-cardiac arrest syndrome is the multi-system injury after return of spontaneous circulation, comprising post-arrest brain injury, post-arrest myocardial dysfunction, the systemic ischaemia reperfusion response and persistent precipitating pathology. It determines outcome in resuscitated patients.

Epidemiology. Survival to hospital discharge is about 8 to 10% after out-of-hospital arrest and 20 to 25% after in hospital arrest. Brain injury is the cause of death in two thirds of patients dying after out-of-hospital arrest. Cardiovascular failure is the main cause of death in the first 3 days.

Components.

• Brain injury: coma, seizures, myoclonus, cognitive impairment, brain death.
• Myocardial dysfunction: low output, arrhythmia and shock, usually peaking at 8 hours and recovering by 72 hours.
• Systemic ischaemia reperfusion: vasoplegia, capillary leak, adrenal impairment, coagulopathy, immune suppression and infection.
• Persistent cause: coronary occlusion, pulmonary embolism, sepsis, toxins, haemorrhage and lung disease.

Pathophysiology. Whole body ischaemia then reperfusion activates oxidative injury, inflammation and endothelial damage, causing sepsis like physiology. Cerebral autoregulation is impaired, so brain perfusion depends on systemic pressure and oxygen content.

Presentation is coma or reduced consciousness, hypotension, arrhythmia, hypoxia, acidosis, high lactate and fever. Myoclonus and seizures occur in a minority.

Red flags.

• Persistent shock or recurrent arrhythmia.
• ST elevation on the 12-lead ECG.
• Seizure or status myoclonus.
• Temperature over 37.7 °C.

12-lead ECG at once, then echocardiography, arterial gas with lactate, glucose, electrolytes (potassium, magnesium, calcium), troponin, creatinine, liver tests, coagulation, cultures and toxicology. CT head and chest (and CT pulmonary angiography when pulmonary embolism is suspected). Continuous EEG for unexplained coma and suspected seizures.

Differential diagnosis. The cause of the arrest (acute coronary syndrome, pulmonary embolism, intracranial haemorrhage, sepsis, overdose, hypoxia, hypothermia, electrolyte disturbance), and sedative drug effect.

Airway and breathing. Intubate when the patient is unconscious. Oxygen to saturation 94 to 98% (avoid hyperoxia and hypoxia). Aim for normal PaCO2 (4.7 to 6.0 kPa or 35 to 45 mmHg). Use lung protective ventilation (6 to 8 mL/kg).

Circulation. Mean arterial pressure at least 65 mmHg (some centres aim for 70 to 80 mmHg), using noradrenaline 0.05 to 0.5 microgram/kg/min, with fluid directed by echocardiography. Add dobutamine 2.5 to 10 microgram/kg/min for low output. Treat arrhythmia.

Coronary angiography. Urgent for ST elevation (and consider for shockable rhythm without ST elevation, electrical or haemodynamic instability), with intervention for culprit lesions.

Temperature control. Prevent fever (over 37.7 °C) for at least 72 hours in unconscious patients. Use a target between 32 °C and 37.5 °C for at least 24 hours, with active devices and feedback control. Treat shivering with magnesium, buspirone, paracetamol or sedation and short term neuromuscular blockade.

Sedation and seizures. Short acting sedation (propofol 1 to 4 mg/kg/h with an opioid). Treat seizures with levetiracetam 60 mg/kg IV (maximum 4500 mg) or valproate. Prophylactic anti-seizure drugs are not advised.

Metabolic control. Glucose 7.8 to 10 mmol/L (avoid hypoglycaemia), potassium 4.0 to 5.0 mmol/L, magnesium over 1.0 mmol/L.

Infection. Treat aspiration pneumonia when present. Prophylactic antibiotics are not advised.

Prognostication. Not before 72 hours after return of circulation or after normothermia, after exclusion of sedation, neuromuscular blockade and metabolic confounders. Use multimodal assessment, with two or more concordant indicators.

Stress ulcer prophylaxis and thromboprophylaxis. Omeprazole 40 mg IV daily or pantoprazole 40 mg IV daily for ventilated patients at risk. Enoxaparin 40 mg SC daily (20 mg with creatinine clearance under 30 mL/min).

Monitoring. Continuous arterial pressure, ECG, temperature, oxygenation, lactate every 2 to 4 hours, glucose, urine output and neurological examination.

Referral and escalation. Cardiology, intensive care, neurology and rehabilitation. Mechanical circulatory support for refractory cardiogenic shock.

Special groups. In pregnancy, left lateral tilt and obstetric input. In children, dosing is weight based and fever is avoided.