Question 20

College answer

Syllabus topic/section:

2.1.4    Cardiovascular Intensive Care / Cardiopulmonary resuscitation: L1

Discussion:  

The majority of candidates were able to sensibly discuss this SAQ with a broad approach gaining the most marks. Answers which did not display the standard required failed to provide a valid rationale and detailed overview of advantages and disadvantages. Candidates are discouraged from “making up/ guessing” evidence to compensate for knowledge gaps. “Advantages” and “rationale” are two different questions and should be answered as such.
The answer to “clinical practice with rationale” needs more than a simple statement to gain the full marks. Candidates are advised to state WHEN they would use this, for WHICH patients, commenting on relative or absolute contraindications and indications. Detailing individual variations of practice and justifying the rationale for practice change will also demonstrate a mature clinical practice to the standard required.

Discussion

"“Advantages” and “rationale” are two different questions and should be answered as such" is an important point to make.  Rationale seems to be often conflated with advantages, in the sense that exam candidates tend to view it as a part of the answer where they note down the reasons for why the intervention being evaluated is being suggested. That is not what the rationale is; that is a list of advantages. The rationale is a description of how the proposed intervention is expected to achieve its desired effect. It is a reasoned logical basis for the intervention being proposed, rather than the  ways in which it is a proposed improvement on another system. Various positive features may come up in the course of the explanation but they are not the primary focus.

In this case:

Rationale:

• High quality CPR is important to resuscitation outcome
• Interruptions of CPR degrade the chance of successful defibrillation 
• Rescuer fatigue degrades the quality of CPR over time
• Chest compressions are a simple repetitive mechanical task, easily reproduced with simple machines
• Ergo, mechanical CPR devices should be able to offer better continuity of CPR of a reliable stable quality.

Advantages:

• CPR is of uniform (presumably, high) quality.
• CPR is not interrupted for defibrillation or radiation exposure (eg. in cath lab)
• ECMO cannulation may take place with CPR in progress.
• The device is more portable than a group of rescuers.
• Removes a rescuer from a manual role and allows more personnel to take part in higher order thinking and decisionmaking

Disadvantages:

• The device takes time to set up. this increases the no-flow time during the early stages of cardiac arrest
• An incorrectly aligned device might actually perform poorer compressions than a rescuer, because a rescuer corrects their own position.
• Injury may occur from incorrectly placed devices. Theoretical injury patterns include liver, lung,  spleen and stomach lacerations, as well as mediastinal or aortic trauma. 

Evidence:

• LINC - 2013 - LUCAS vs manual CPR. n=2589 in Europe. No difference in 4-hr survival (23.6% vs 23.7%).

• PARAMEDIC - LUCAS-2 vs manual CPR. n=4471 in the UK. No difference in 30-day survival (6 vs 7%), but only 60% of those randomised to LUCAS actually got LUCASed.

• CIRC - 2014 - AutoPulse vs manual CPR. n=4231 in US and Europe. No difference in 24-hour survival  (21.8% vs 25.0%). Plus the rate of rib fractures was almost doubled (from 31 to 69 of ~ 2100 patients), and the risk of pneumothorax increased by a third

• ASPIRE - 2010 - Paradis et al (2010) reported on the way in which this trial was stopped early, as the result of a prorocol

Own practice with rationale:

• Use where CPR will be prolonged, and consistent quality will be required
  • Cardiac arrest due to hypothermia
  • Cardiac arrest following thrombolysis for PE or MI
• Use where rescuers are few, or unskilled:
  • Pre-hospital setting
  • Rural and regional setting
• Use where space is limited
  • Aeromedical retrieval
  • Ambulance transport
  • Interventional radiology suite
• Use as a part of a larger ECPR bundle a'la CHEER, where ECMO cannulation and a trip to angio are essential parts of the Welcome to The Alfred package.