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.


ECTO2

Let’s now consider two different paths that the ETCO2 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
Emergency Department
Nanaimo Regional General Hospital

Resuscitation and ETCO2: So what’s the use?

Resuscitation and ETCO2

Remember back in 2005 when it became ACLS Guideline directed practice to resume CPR immediately after defibrillation. Did that freak you out? Do you still pause after defibrillation, and try to sneak a quick peak at the monitor to check for a life sustaining rhythm?  Do you delay chest compressions to quickly feel for a pulse? If you answered, “yes” to either or both of these questions, perhaps you are doing so propelled by a combination of hope and or fear. Hope that your efforts at defibrillation were successful, and fear that your ongoing resuscitation efforts will cause harm. Indeed after defibrillation, the curious practitioner is left to wonder “what if our shock was successful and we obtained return of spontaneous circulation [ROSC], could we cause harm with chest compressions or by pushing IV epinephrine?”  At first glance delaying a rhythm and pulse check can feel like a great leap of faith, and for some members of the resuscitation community this leap represents a significant clinical hurdle to overcome. The 2010 ACLS Guidelines have given us a way to jump over that hurdle and keep on running safely through our resuscitations. In this latest iteration, emphasis has been placed on continuous waveform or capnometric ETCO2 monitoring. Achieved in cardiac arrest by inserting a line onto an advanced airway to a receiving monitor, this metric is used not only for ongoing confirmation of advanced airways, but also provides real time breath-by-breath physiological evaluation of patients. The study of capnography is multi-faceted and as a simplified statement normal values are 35-45 mm/Hg. The waveform below shows a patient with an ETCO2 of 34 mm/Hg: ETCO2 Naturally a pulseless patient, who has no pulmonary circulation, will in turn have no ETCO2. However when high quality CPR is performed, the exhaled ETCO2 jumps from 0 mm/Hg to greater than 10mm/Hg.  If during compressions, the ETCO2 lowers; code team members should turn their attention to the quality of the CPR being given. Rescuer fatigue for instance can dramatically decrease chest compression efficiency. The waveform below shows a patient receiving CPR with an ETCO2 rising from around 10 to 16 mm/Hg: ETCO2 If during high quality CPR there is a return of spontaneous circulation then the ETCO2 will display “an abrupt sustained increase” and as shown below will jump into the 35-45 mm/Hg range. ETCO2 This is how employing the use of continuous ETCO2 monitoring during CPR, that resuscitators are provided with insight into the outcome of their defibrillation attempts and with a window to ROSC. Indeed it is this information that allows clinicians to jump over the hurdle described above, and to gain an increased sense of comfort with the decision to resume chest compressions immediately after defibrillation. CPR

    Darin Abbey RN Clinical Nurse Educator Emergency Department Nanaimo Regional General Hospital