How ETCO2 may inform vasopressor use!
Consider the following scenario. While in the emergency department a man suffers a witnessed cardiac arrest, for which he receives prompt high quality CPR, 200 joules defibrillation for an initial rhythm of V-Tach. The defibrillation is followed by a further 2 minute round of high quality CPR during which time an advanced airway with minimal interruptions in chest compressions. ETCO2 monitoring is initiated and shows 12mm/Hg. From this resuscitators can see that patient remains without pulmonary circulation and that the quality of CPR is satisfactory. After the 2 minutes, a quick pause in CPR reveals persistent V-Tach on the monitor. Chest compressions are resumed while the defibrillator is charged, the patient is cleared, 200 joules are delivered chest compressions are immediately resumed.
Let’s now consider two different paths that the scenario can take from here:
- The defibrillation is unsuccessful, and during the 2 minutes of high quality CPR that follow the ETCO2 hovers around 7 mm/Hg. Seeing this low number, the team changes chest compression providers, and a new clinician is able to get the waveform up to 12mm/Hg. In this case, there is no ETCO2 indication of return of spontaneous circulation, and since there remain no signs of life, CPR is continued and as the code progresses the clinicians consider giving IV epinephrine.
- Alternatively, the defibrillation is successful, and during the 2 minutes of high quality CPR that follow the ETCO2 jumps to 40mm/Hg. In this case there is ETCO2 indication of return of spontaneous circulation, and the team searches for other signs of life, which may include a pulse. Finding none: high quality CPR is continued however this time the decision is made to withhold the IV epinephrine.
The above scenario illustrates how continuous ETCO2 can not only serve to confirm ongoing placement of advanced airways, but can also be used to inform the quality of CPR, illuminate ROSC and help guide vasopressor use during resuscitation attempts. This being said there still remains no evidence that using epinephrine in this way contributes to neurological intact survival to hospital discharge.
Lastly, this practice of ETCO2 monitoring during resuscitation attempts relies on placement of advanced airways, which have been deemphasized in the ACLS Guidelines since 2005. As such we can see how with increased emphasis on ETCO2, the latest Guidelines may result in an increased use of advanced airways. This unto itself is not necessarily a bad thing, as long as we do not do so to the detriment of our patients. When using advanced airways there is an increase in responsibility to not interrupting chest compressions for too long, and to avoid the hyperventilation of our patients with tidal volumes that are too large and ventilation rates that are too excessive.
Darin Abbey RN
Clinical Nurse Educator
Nanaimo Regional General Hospital