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

What an AED Save Really Looks Like

I am sure you have read the stats before, but here they are again:

  • In Canada, 35,000 to 45,000 people die of sudden cardiac arrest each year. 
  • Early defibrillation is the only effective treatment for Sudden Cardiac Arrest (SCA). 
  • For every one minute delay in defibrillation, the survival rate of a cardiac arrest victim decrease by 7 to 10%
  • After more than 12 minutes of ventricular fibrillation, the survival rate of adults is less than 5%.

These statistics do not paint a pretty picture, and even now, with all the technology at our disposal, AED saves are frighteningly rare. There is no “good time” to have an SCA, but when an individual does survive, it is usually a combination of having an SCA at the “right place and the right time.”

At Iridia, it is one of our goals to increase access to Automated External Defibrillators (AEDs), as well as create more awareness of these devices. Again, the only cure for SCA is early defibrillation.

It’s one thing to hear about a statistic, it’s another to see it in action:

[youtube=http://www.youtube.com/watch?v=ICODRFoWZkw]

With increased access and widespread awareness, hopefully we will see an increase in  similar outcomes.

 

 

AED Shopping Tips

When buying an automated external defibrillator (AED), choosing a model can be a daunting task. When evaluating a defibrillator, you don’t need an exhaustive background in electronics or cardiac medicine, but with a growing number of manufacturers and a plethora of models and features, how can you know which type of AED will suit your needs?

Keep in mind that all defibrillators do one fundamental thing: they deliver an electric shock that resets the heart’s natural pacemaker and converts an irregular, unstable heart rhythm to a sustainable one. To accomplish this, all AED’s possess three basic elements: a battery that provides energy for the cardiac shock; a main unit that analyzes heart rhythms and generates the electrical charge; and the electrodes, or pads, that deliver the shock to the patient.

These similarities lead some to believe that all AED’s are the same, but there are differences. The features that distinguish defibrillators are component quality, user interface, and innovations in technology.

AED Shopping Tips

Components

Getting to know a few simple details will quickly determine the overall quality of an AED:

  • Better quality AEDs use medical-grade, lithium-ion batteries and do not rely on any secondary source of power to run self-checks or power the unit.
  • Many units use a diagram to show the proper placement for electrodes and the polarity (positive or negative) of each.  The best public-use AED’s simplify this process and use non-polarized electrodes that can be placed interchangeably.
  • Most Health-Canada approved AEDs have been drop tested to just over a meter and are designed to survive rough treatment.

A product specification associated with durability of any electronic equipment is the IPX rating.  The IP Code is an International (or Ingress) Protection Rating and is expressed as IP followed by a two-digit number. The first digit indicates the level of protection against particles such as dust or dirt; the second gives the level of protection from water. The higher the number, the greater the resistance. Every AED has an IP Code which can usually be found in the user’s manual.

Usability

The most visible features that differentiate AED’s are those that indicated ease of use and quality of performance.  As public access defibrillation programs become more commonplace, simplicity in design and use become paramount.  There are a few factors to consider when purchasing an AED:

  • How many buttons (if any) do I have to push for a shock?
  • Are there voice prompts and a display to guide me during a rescue?
  • Will the unit’s prompts assist me with delivering CPR to the victim?

Many units run daily, weekly and monthly self checks.  It is important to purchase a unit that checks issues such as the presence of electrodes, pad connectivity, battery life and wire conductivity as they increase the potential life of your unit.

Time spent remembering or figuring out how an AED works and how to apply the pads can make the difference between a save and a non-save when using a defibrillator.  Features that limit this time are invaluable.

Technology

The most important component of an AED’s design is the technology used to deliver a shock.

There are two methods of shock delivery:  fixed energy and escalating energy. With fixed energy, a shock is delivered once at a given level measured in joules (J), and then subsequently redelivered until there is a correction in the heart’s rhythm. With escalating energy, if the first shock is unsuccessful, the AED progressively increases the energy of subsequent shocks until reaching the maximum allowable number of joules and redelivers shocks at that level.

When purchasing an AED, it is important to find a unit that is not only capable of escalating the shock energy, but of doing so beyond 200J. While an initial shock of 200J is usually successful in an out-of-hospital environment, there are exceptions and escalation above 200J is necessary to maintain success for multi-shock patients. In cases of sudden cardiac arrest (SCA), refibrillation is not just common, it is expected… as long as the AED is up to the task.

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There are some costs associated with buying and setting up an AED. Making an informed purchase decision ensures that the hard-earned money you to spend will give a potential SCA victim the very best chance of survival.