Lurie et al 2016 - Physiology of CPR

Question 1

Give an overview of Lurie et al 2106

Answer 1

Published in ‘Anaesthesia and Analgesia’

Review of developments in resuscitation science

Main take home: success likely comes from a set of interventions done well

Identifies multiple gaps and unmet needs:
1. Need to achieve better blood flow than with closed chest compressions
2. Need for tools
3. Reduced potential for brain injury
4. Prevent reperfusion injury
5. Post ROSC care

Covers:
Compression phase and its errors
Decompression phase and its errors

Ventilation and its errors, with the effects of gasping and coughing

Limitations of conventional CPR

Intrathoracic pressure regulation therapy using an ITD

Head-up CPR

Reperfusion injury protection

The resuscitation bundle

Is there a benefit to CPR

Considerations in paediatric patients

Future implications

Question 2

Discuss the compression phase of CPR

Answer 2

Heart compressed between the sternum and the spine

Aortic AND right sided pressures increase

Close relationship between intrathoracic pressure and ICP
Higher the ICP, less cerebral perfusion

High right atrial pressure also limits coronary perfusion

Errors:
Too slow/too fast
Too much/too little
Interruptions

Better survival with 5cm compression at 100-120 beats/min

Question 3

Discuss the decompression phase of CPR

Answer 3

Heart is refilled, extremely inefficient
Relies on passive chest recoil only - problem in chest trauma

ICP reduces during decompression

Errors:
Not allowing full recoil

Question 4

Discuss ventilation during CPR

Answer 4

Inflation oxygenates the blood and opens up pulmonary vasculature

Too little - not enough oxygenation
Too much - increases pulmonary vascular resistance

Positive pressure:
- decreases venous return to right side
- temporarily increases LV stroke volume

Also increases ICP

No good evidence for compressions only

600mls, 10 breaths

Errors:
- Too much/too little harmful
- Too much - decreased cerebral and myocardial perfusion pressure
- Too little - bronchiolar and vasculature collapse

Gasping/coughing:
- Decreases intrathoracic pressure
- Improves cerebral perfusion
- Cough CPR demonstrates this - seen in angio

Question 5

What are the limitations of conventional CPR?

Answer 5

Relies on:
- Correct rate and depth
- Full recoil
- Lack of interruptions
- Proper ventilation technique

Only provides 15-25% of normal cardiac output when done perfectly

Question 6

Discuss regulation of intrathoracic pressure in CPR

Answer 6

• Suction to aid in chest recoil, decreases intrathoracic pressure
• Use of impedance threshold device transiently prevents airflow into the chest during recoil - reduces ITP
• Improves venous return to the right side
• PRIMED showed no benefit of ITD versus sham unless good quality CPR
• Even better when combined with Device CPR
• Device even for active generating negative pressure

Question 7

Discuss head-up CPR

Answer 7

Pig studies show profound benefit to cerebral blood flow

Uses gravity to improve venous drainage of the head

30 degrees

But only in conjunction with an impedance threshold device

Question 8

How can reperfusion injury be reduced or prevented following ROSC?

Answer 8

Intentional pauses
Administration of volatile gases
Synthetic surfactants

Question 9

How does paediatric cardiac arrest differ to adults?

Answer 9

Presenting rhythm usually asystole or severe bradycardia

Younger children more likely to survive.
Might be due to better CPR-induced blood flow secondary to greater thoracic cage compliance