What are the possible causes of a code blue (life-threatening emergency)?

Complete List of Causes of Code Blue

Code blue events are triggered by cardiac arrest, respiratory arrest, or life-threatening medical emergencies requiring immediate resuscitation, with the most common underlying causes being cardiac arrhythmias, respiratory failure, septic shock, pulmonary embolism, opioid overdose, and severe electrolyte disturbances. 1

Primary Cardiac Causes

Cardiac arrest rhythms are the most frequent triggers for code blue activation:

• Ventricular fibrillation (VF) and pulseless ventricular tachycardia (pVT) - shockable rhythms requiring immediate defibrillation 1
• Asystole and pulseless electrical activity (PEA) - account for 92.4% of cardiac arrest rhythms in hospitalized patients 2
• Acute myocardial infarction - coronary thrombosis causing sudden cardiac death 1
• Cardiac arrhythmias - including torsades de pointes from methadone or propoxyphene, and other life-threatening dysrhythmias 1
• Cardiac tamponade - one of the reversible "H's and T's" causes 1

Respiratory Causes

Respiratory failure progressing to respiratory arrest is a major trigger:

• Severe hypoxia - from any cause leading to inadequate oxygenation 1
• Bronchospasm - severe airway constriction preventing ventilation 1
• Pneumothorax (especially tension pneumothorax) - one of the reversible causes 1
• Airway obstruction - including choking, accidental extubation, or selective intubation 1
• Severe asthma - can progress to respiratory arrest and death 1
• Patient-ventilator desynchronization - in mechanically ventilated patients 1

Toxicologic and Overdose Causes

Opioid overdose has become the leading cause of unintentional injurious death in people aged 25-60 years in the United States:

• Prescription opioid toxicity - caused 16,235 deaths in 2013 in the US 1
• Heroin overdose - caused 8,257 deaths in 2013 in the US 1
• CNS and respiratory depression from opioids - progressing to respiratory and cardiac arrest 1
• Drug overdose (non-opioid) - various substances causing cardiovascular collapse 1
• Toxins - listed as one of the reversible "H's and T's" causes 1

Thromboembolic Causes

Pulmonary embolism (PE) can result in sudden cardiovascular collapse:

• Massive PE - causing cardiac arrest, often presenting as PEA 1
• Coronary thrombosis - acute myocardial infarction from coronary artery occlusion 1

Metabolic and Electrolyte Causes

Severe electrolyte disturbances are potentially lethal and frequently cause cardiac arrest:

• Hyperkalemia (>6.5 mmol/L) - causes cardiac arrhythmias and arrest, most commonly from renal failure 1
• Hypokalemia - can trigger life-threatening arrhythmias 1
• Hydrogen ion excess (severe acidosis) - one of the reversible "H's and T's" 1
• Hypoglycemia and hyperglycemia - severe glucose abnormalities 1
• Hypothermia - one of the reversible causes 1

Infectious and Septic Causes

Septic shock is a medical emergency that can progress to cardiac arrest:

• Sepsis with cardiovascular collapse - combination of infection with inadequate tissue perfusion 3
• Severe infections - including those requiring emergency source control 1, 3

Hypovolemic and Hemorrhagic Causes

Severe volume depletion leading to cardiovascular collapse:

• Hypovolemia - from hemorrhage or severe dehydration, one of the reversible "H's and T's" 1
• Hemorrhagic shock - from trauma or internal bleeding 1

Neurologic Causes

Central nervous system emergencies can trigger code blue:

• Intracranial hypertension - causing brainstem herniation and cardiorespiratory arrest 1
• Severe agitation - requiring emergency intervention 1
• Altered level of responsiveness - as a presenting sign of life-threatening emergency 1

Trauma-Related Causes

Injuries cause more childhood deaths than all other diseases combined:

• Blunt trauma - with respiratory failure or hemorrhagic shock 1
• Penetrating trauma - causing direct cardiac or vascular injury 1
• Cervical spine injury - with secondary spinal cord injury causing respiratory arrest 1

Anaphylactic Causes

Severe allergic reactions can rapidly progress to cardiovascular collapse:

• Anaphylaxis - severe allergic reaction causing airway compromise and shock 1

Thermal and Environmental Causes

Temperature-related emergencies:

• Heatstroke - causing multiorgan failure and cardiac arrest 1
• Hypothermia - severe cold exposure 1

Electrical Causes

Electrocution can cause immediate cardiac arrest:

• Electric shock - causing ventricular fibrillation, asystole, or ventricular tachycardia 1
• Respiratory arrest from electrical injury - from CNS injury or respiratory muscle paralysis 1

Equipment and Iatrogenic Causes

Hospital-related complications during patient care:

• Equipment malfunction - including ventilator failure, oxygen failure, or monitoring line problems 1
• Accidental extubation - loss of airway control 1
• Medication errors - including unadapted emergency treatment 1

Special Pediatric Considerations

Unique causes in children requiring code blue activation:

• Brief Resolved Unexplained Events (BRUE) - formerly ALTEs, though most are not truly life-threatening 1
• Child abuse - can present as apparent life-threatening event 1
• Congenital abnormalities - causing acute decompensation 1
• Inborn errors of metabolism - presenting with acute crisis 1

The Reversible "H's and T's" Framework

A systematic approach to identifying treatable causes during resuscitation 1:

The H's:

• Hypovolemia
• Hypoxia
• Hydrogen ion (acidosis)
• Hypo-/hyperkalemia
• Hypothermia

The T's:

• Tension pneumothorax
• Tamponade, cardiac
• Toxins
• Thrombosis, pulmonary
• Thrombosis, coronary

Common Misuse of Code Blue

Not all code blue activations represent true emergencies - studies show significant misuse:

• Change in mental status (not cardiac arrest) - 18% of activations in one study 4
• Presyncope - 11% of activations 4
• Chest pain (without arrest) - 12% of activations 4
• Conversive disorder - 18% of activations 4
• Staff worry for the patient - 22% of activations without objective criteria 4

True cardiac or respiratory arrest accounts for only 8-68% of code blue calls depending on the institution, with cardiopulmonary arrest representing the minority of activations in some hospitals 5, 4, 2

High-Risk Patient Populations

Certain patient groups have higher code blue risk:

• Patients in infectious disease wards - 22.3% of code blues 6
• Hematology/oncology patients - 21.6% of code blues, with cancer as significant comorbidity for mortality 6, 2
• Cardiology ward patients - 10.8% of code blues 6
• Emergency department patients - 27.8% of code blues occur here 7
• Elderly patients (70-89 years) - 43% of code blue patients, with age as independent risk factor for mortality 7, 2