What are the target EtCO2 (end-tidal carbon dioxide) goals post Return Of Spontaneous Circulation (ROSC)?

Target EtCO2 Goals Post Return of Spontaneous Circulation (ROSC)

After return of spontaneous circulation (ROSC), clinicians should target normocapnia with an EtCO2 of 35-40 mmHg (4.7-5.3 kPa), while recognizing that there is a significant arterial to end-tidal CO2 gradient in post-cardiac arrest patients. 1

Understanding EtCO2 in Post-ROSC Care

Normal Ranges and Targets

• The 2024 International Consensus on Cardiopulmonary Resuscitation recommends:
  • Avoiding hypocapnia (weak recommendation, low-certainty evidence) 1
  • Targeting normocapnia (PaCO2 35-45 mmHg) 1, 2
  • There is insufficient evidence to suggest for or against targeting mild hypercapnia compared with normocapnia 1

Arterial to End-Tidal CO2 Gradient

• A critical consideration in post-ROSC patients is the significant gradient between arterial CO2 (PaCO2) and end-tidal CO2 (EtCO2)
• Recent research shows this gradient averages 32 ± 18 mmHg in post-ROSC patients, which is much higher than physiologic ranges 3
• This means EtCO2 values significantly underestimate actual arterial CO2 levels

Clinical Application and Monitoring

Ventilation Strategy

• Use EtCO2 monitoring to guide ventilation rate and volume to maintain EtCO2 between 35-40 mmHg 1
• Titrate ventilation to avoid:
  • Hyperventilation (which can cause cerebral vasoconstriction and worsen brain ischemia) 1
  • Hypoventilation (which can cause hypercapnia)
  • Excessive tidal volumes (which can increase intrathoracic pressure and compromise hemodynamics) 1

Monitoring Recommendations

1. Initial monitoring: Use continuous capnography in intubated patients 1
2. Target adjustment: Due to the significant PaCO2-EtCO2 gradient, obtain arterial blood gas measurements to calibrate EtCO2 targets 3
3. Ongoing assessment: Continue to monitor EtCO2 trends rather than absolute values

Clinical Significance of EtCO2 Post-ROSC

Indicator of ROSC

• An abrupt sustained increase in EtCO2 during CPR is a reliable indicator of ROSC 1, 4
• This is often the first clinical sign that ROSC has occurred 4

Prognostic Value

• EtCO2 values correlate with cardiac output during and after CPR 4, 5
• Higher EtCO2 values post-ROSC generally indicate better cardiac output and systemic perfusion 6, 5

Pitfalls and Considerations

Common Pitfalls

1. Relying solely on EtCO2 without arterial blood gas correlation

   • The large and variable PaCO2-EtCO2 gradient makes EtCO2 alone unreliable for precise ventilation management 3

2. Hyperventilation

   • Routine hyperventilation with hypocapnia should be avoided as it may worsen global brain ischemia through excessive cerebral vasoconstriction 1

3. Misinterpreting transient EtCO2 changes

   • Transient rises in EtCO2 after sodium bicarbonate administration should not be misinterpreted as improved CPR quality or ROSC 1

Special Considerations

• In patients with pulmonary pathology (e.g., COPD, pulmonary edema), the PaCO2-EtCO2 gradient may be even larger 3
• Hemodynamic instability may affect the reliability of EtCO2 measurements 1

Conclusion

While targeting an EtCO2 of 35-40 mmHg post-ROSC is recommended, clinicians must recognize the significant arterial to end-tidal CO2 gradient in these patients. Arterial blood gas analysis should be performed to correlate with EtCO2 readings and guide ventilation management. Avoiding both hypocapnia and severe hypercapnia is important to optimize neurological outcomes after cardiac arrest.