Summary of Key Points for OSCEs
The Algorithm
The key to doing well in this station is following the Resuscitation Council (UK) algorithms to the letter. For advanced life support (ALS), this is included in Figure 69.1.
Figure 69.1 The adult Advanced Life Support Algorithm. PEA, pulseless electrical activity; VF, ventricular fibrillation; VT, ventricular tachycardia.
Reproduced with kind permission of the Resuscitation Council (UK)
Reversible Causes
Any resuscitation effort should not stop until and unless all reversible causes have been excluded. These can be broadly classified into ‘the 4Hs and the 4 Ts’.
| H | T |
| Hypoxia | Tamponade |
| Hypovolaemia | Tension pneumothorax |
| Hypo/hyperkalaemia or other metabolic cause | Thromboembolism |
| Hypothermia | Toxins |
You are likely to be given a scenario, and that should allow you to establish the most likely cause. For example, if you are told that your patient has been rescued from submersion in a river, the most likely causes are hypothermia or hypoxia. If you then get further details, such as that the patient had consumed unknown pills before jumping in the river, ‘toxins’ becomes a possible cause. Suppose your patient had been thrown into the river by means of a road traffic accident as the cyclist hit by a car. This would lead to suspicion of tamponade, tension pneumothorax and hypovolaemia (as for any other trauma scenario) in addition to all the above.
In each case, the key is to begin good quality CPR and work through each of these possible causes. It should be reiterated that resuscitation should not stop until each of them has been addressed.
Cardiac Arrest Rhythms
Figure 69.2 illustrates the cardiac arrest rhythms you will encounter. Learn what they look like. It is highly likely that you will be asked to recognise them in the exam.
Figure 69.2 The following ECG rhythm strips demonstrate the shockable and non-shockable rhythms of a cardiac arrest: ventricular fibrillation (VF), ventricular tachycardia (VT), asystole and pulseless electrical activity (PEA)
Defibrillation
The ventricular fibrillation/ventricular tachycardia (VF/VT) side of the algorithm is the side that is ‘shockable’ and associated with a better outcome (although a good outcome post-cardiac arrest is rare).
Good defibrillation needs good technique. Applying the defibrillation pads in such a manner that the maximum possible voltage reaches the myocardium through thoracic wall tissues is vital. This means applying pads in a position of maximum contact, and using gel-based pads to reduce the impedance of the chest wall to the voltage delivered. In older machines, paddles and gel pads came as separate pieces. More modern machines use disposable self-adhesive paddles, with gel included.
Getting good access to the chest wall may mean cutting off the patient’s shirt/blouse, jacket, etc. All medication patches should be removed as these will explode when shock is delivered. Oxygen must be taken away at the time of the shock. It is prudent to check that no member of the resuscitation team is touching the patient or the bed before delivering the current. A ‘visual sweep’ (i.e. looking around the bed to ensure nobody is touching any part of it) must be exaggerated in the exam to show the examiner that you know how to defibrillate safely.
Correct placement of the paddles is illustrated in Figure 69.3. One paddle is placed to the right of the sternum, below the clavicle, the other in the left mid-axillary line in the V6 position. If the patient has a permanent pacemaker, the paddles must be placed at least 15 cm away from any part of it or it may malfunction, or burn and cause tissue damage.
Figure 69.3 The diagram illustrates where on the thorax the defibrillation paddles should be placed. One should be placed to the right of the sternum under the clavicle, the other should be placed in the left mid-axillary line
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