What are the steps to check for reversible causes during Advanced Cardiovascular Life Support (ACLS)?

Checking Reversible Causes During ACLS

During cardiac arrest resuscitation, systematically check for the "H's and T's" - the potentially reversible causes of cardiac arrest - while maintaining high-quality CPR and following the appropriate ACLS algorithm. 1

The H's and T's Framework

The H's:

• Hypovolemia: Look for signs of blood loss, dehydration, or third-spacing. Use bedside cardiac ultrasound (BCU) to identify small, hyperdynamic left ventricle and collapsed IVC. 2
• Hypoxia: Check airway patency, ventilation adequacy, and oxygen saturation. Look for low SpO2 and low PETCO2 despite adequate CPR. 2
• Hydrogen ion (acidosis): Obtain arterial blood gas to check pH (<7.2 suggests acidosis). Ensure adequate ventilation. 2
• Hypo/Hyperkalemia: Look for ECG changes and obtain serum electrolytes. For hyperkalemia, administer calcium, insulin/glucose, and sodium bicarbonate. For hypokalemia, provide potassium replacement. 2
• Hypothermia: Measure core temperature. If severe hypothermia is present, consider specialized rewarming techniques. 1, 3

The T's:

• Tension pneumothorax: Examine for absent breath sounds, tracheal deviation, and distended neck veins. Use BCU to identify absence of lung sliding, absence of B-lines, and lung point sign. Perform immediate needle decompression if suspected. 2
• Tamponade, cardiac: Look for distended neck veins, muffled heart sounds, and pulsus paradoxus (if pulse present). Use BCU to identify pericardial effusion with right atrial/ventricular diastolic collapse. Perform pericardiocentesis if identified. 2
• Toxins: Review history for potential ingestions or exposures. Consider specific antidotes when toxin is known. 1
• Thrombosis, pulmonary: Consider in patients with risk factors for PE. Use BCU to identify right ventricular dilation and dysfunction. Consider fibrinolytic therapy when PE is suspected. 1, 2
• Thrombosis, coronary: Consider in patients with risk factors for ACS. Obtain ECG when possible. Consider emergency coronary angiography for patients with STEMI or high suspicion of cardiac etiology. 2

Diagnostic Tools for Identifying Reversible Causes

Bedside Cardiac Ultrasound (BCU)

• Perform BCU during cardiac arrest with minimal interruption to chest compressions (≤10 seconds). 2
• Views should include subcostal four-chamber, parasternal long-axis, and apical four-chamber. 2
• Use BCU to differentiate true PEA from pseudo-PEA. 2, 4

Laboratory Tests

• Obtain arterial blood gas to assess oxygenation, ventilation, and acid-base status.
• Check serum electrolytes, particularly potassium.
• Consider toxicology screening when appropriate.
• Check blood glucose (hypoglycemia is a potential reversible cause). 5

Clinical Assessment

• Review patient history for clues to potential causes.
• Perform focused physical examination during pulse checks.
• Monitor capnography (PETCO2) to assess CPR quality and potential ROSC. 1

Implementation During Resuscitation

1. Continue high-quality CPR while searching for reversible causes. 1, 2
2. Minimize interruptions in chest compressions to maintain cerebral and coronary perfusion. 1
3. Delegate tasks to team members to simultaneously address potential reversible causes.
4. Administer appropriate medications per ACLS protocol while investigating causes. 2
5. Consider empiric treatments when high suspicion exists (e.g., fluid bolus for suspected hypovolemia, needle decompression for suspected tension pneumothorax). 2

Special Considerations

• In traumatic cardiac arrest, prioritize control of external hemorrhage, airway management, and chest decompression before standard ACLS interventions. 6
• In hypothermic cardiac arrest, the saying "not dead until warm and dead" applies - continue resuscitation efforts until the patient is rewarmed. 3
• Consider hypoglycemia as a potential cause of cardiac arrest, especially in diabetic patients. 5

Common Pitfalls to Avoid

• Focusing solely on the algorithm without addressing reversible causes.
• Interrupting CPR unnecessarily during diagnostic procedures.
• Delaying critical interventions while waiting for diagnostic confirmation.
• Failing to reassess for reversible causes throughout the resuscitation.
• Overlooking less common causes that may be specific to the patient's history or presentation.

By systematically evaluating and addressing these potential reversible causes during ACLS, you can significantly improve the chances of successful resuscitation and patient survival.