Post Cardiac Arrest Syndrome (PCAS)

Introduction

Post–Cardiac Arrest Syndrome (PCAS) refers to the complex pathophysiological state that develops after Return of Spontaneous Circulation (ROSC) following cardiac arrest. It is a multisystem disorder characterized by global ischemia-reperfusion injury, systemic inflammation, and organ dysfunction.

👉 Mortality after ROSC remains high (≈50–70%)
👉 Neurological injury is the most common cause of death in survivors.

PCAS is analogous to sepsis + ischemia-reperfusion injury + postcardiotomy syndrome occurring simultaneously.

Post-cardiac arrest syndrome includes four major components:

1. Post-cardiac arrest brain injury
2. Post-cardiac arrest myocardial dysfunction
3. Systemic ischemia-reperfusion response
4. Persistent precipitating pathology

Timeline of PCAS

Pathophysiology of PCAS

Global Ischemia–Reperfusion Injury

Cardiac arrest causes complete cessation of blood flow, resulting in:

During Cardiac Arrest

• ATP depletion
• Cellular ion pump failure
• Intracellular calcium overload
• Lactic acidosis
• Membrane instability

After ROSC (Reperfusion Phase)

• Oxygen free radical generation
• Mitochondrial dysfunction
• Cytokine storm
• Endothelial injury
• Microvascular thrombosis

👉 This resembles sepsis-like syndrome

Component 1 – Post-Cardiac Arrest Brain Injury

Pathogenesis

Brain is extremely vulnerable to ischemia.

Mechanisms

1. Excitotoxicity (glutamate release)
2. Calcium-mediated neuronal injury
3. Cerebral edema
4. Microcirculatory dysfunction
5. Delayed apoptosis

Clinical Features

Early

• Coma
• Seizures
• Myoclonus
• Loss of brainstem reflexes

Late

• Persistent vegetative state
• Cognitive deficits

Neurological Prognostic Factors

Assessment recommended ≥72 hours after ROSC or after rewarming from TTM.

Poor prognostic indicators:

• Absent pupillary reflex
• Bilateral absent N20 SSEP
• High neuron-specific enolase
• Diffuse cerebral edema
• Malignant EEG patterns

Immediately after ROSC, coma and absent brainstem reflexes usually represent transient post-ischemic brain dysfunction — not brain death — hence Brain Stem Death protocol must be delayed

Component 2 – Post-Cardiac Arrest Myocardial Dysfunction

Characteristics

• Reversible myocardial stunning
• Occurs within hours after ROSC
• Peaks 8–24 hrs
• Usually resolves within 48–72 hrs

Pathophysiology

Mechanisms:

• Calcium overload
• Free radical injury
• Mitochondrial damage
• Microvascular dysfunction

Clinical Manifestations

• Low cardiac output state
• Hypotension
• Arrhythmias
• Elevated troponin (without acute MI necessarily)

Management

Guideline-based approach:

Hemodynamic Targets

• MAP ≥ 65 mmHg
• Urine output ≥ 0.5 mL/kg/hr
• Lactate clearance

Pharmacologic Therapy

• Fluids (balanced crystalloids)
• Vasopressors (Norepinephrine – first line)
• Inotropes (Dobutamine if low cardiac output)

Component 3 – Systemic Ischemia-Reperfusion Response

Sepsis-Like Syndrome

Features resemble SIRS:

Mechanisms

• Cytokine release (IL-6, TNF-α)
• Endothelial activation
• Capillary leak
• Coagulopathy
• Mitochondrial dysfunction

Clinical Consequences

• Vasoplegic shock
• ARDS
• Acute kidney injury
• Liver dysfunction
• Coagulopathy

Component 4 – Persistent Precipitating Cause

Common causes include:

Post Cardiac Arrest Care Bundle (AHA/ERC Guideline)

1. Oxygenation & Ventilation

Oxygen Targets

• Avoid hyperoxia
• Maintain SpO₂ = 92–98%

Ventilation Targets

• Maintain PaCO₂ 35–45 mmHg
• Avoid hypocapnia → reduces cerebral blood flow

2. Hemodynamic Optimization

Goals:

• MAP ≥ 65 mmHg
• ScvO₂ > 70%
• Lactate clearance

Use:

• Fluid resuscitation
• Vasopressors
• Inotropes

3. Targeted Temperature Management (TTM)

Indications

• Comatose patients after ROSC

Temperature Targets

Modern guidelines recommend:

👉 Maintain 32–36°C
👉 Avoid fever (>37.7°C)

Duration

• Maintain ≥24 hrs
• Controlled rewarming

Mechanisms of Benefit

• Reduces cerebral metabolism
• Reduces excitotoxicity
• Reduces inflammation
• Stabilizes blood–brain barrier

4. Coronary Reperfusion

Indications

• STEMI → Immediate PCI
• Suspected coronary cause with shock/arrhythmia

5. Neurological Monitoring

Tools

• Continuous EEG
• SSEP
• Neuroimaging
• Biomarkers

6. Glycemic Control

Target: 140–180 mg/dL-Avoid hypoglycemia.

7. Seizure Management

• Common after ROSC
• Treat with benzodiazepines → levetiracetam/valproate

8. Prognostication Strategy

Multimodal approach after:
👉 ≥72 hours
👉 After sedative washout
👉 After rewarming

Includes:

• Clinical exam
• EEG
• Imaging
• Biomarkers

Complications of PCAS

Determinants of Outcome

Cardiac Arrest Factors

• Witnessed arrest
• Early CPR
• Initial shockable rhythm
• Short downtime

Post-ROSC Factors

• Quality of ICU care
• Temperature control
• Hemodynamic optimization

Post-Cardiac Arrest Outcome Categories