基本生命支持： 心肺复苏和除颤

High-quality cardiopulmonary resuscitation, or CPR, is the single most important determinant of intact survival in cardiac arrest, and it is critical that all healthcare workers are able to effectively perform this basic life support technique. Despite the conceptual simplicity of CPR, the reality is that many providers perform it incorrectly, resulting in suboptimal survival outcomes for their patients.

This video looks at the essential elements of high-quality CPR, discusses the physiologic basis for each step, and describes how to optimize them in order to enhance survival outcomes.

The first step of CPR is to assess the patient’s responsiveness by speaking loudly and stimulating the patient. If the patient is unresponsive, the diagnosis is cardiac arrest until proven otherwise. Next, assess circulation by palpating the carotid artery. Do this for no more than 10 seconds, as longer assessment time will delay the initiation of resuscitation. While palpating the pulse, assess the patient’s airway and breathing by observing for respiratory effort. This process is called “CAB Assessment” because the emphasis is on circulation, while airway and breathing are secondary considerations.

As soon as you confirm that the patient is unresponsive, call for assistance, and ask for emergency equipment, mainly a defibrillator.

Position the patient for chest compressions by rolling them onto their back. Make the bed flat and get railings out of the way.

Next, place a backboard under the patient. This is critical as chest compressions performed on a soft surface like a bed are not effective. Since mechanical energy flows down the path of least resistance, your compression will deform the most compressible object under it; for a patient in bed, this will be the mattress. Therefore, placing a backboard under the patient prevents compression of the mattress and ensures that the force applied by your arm deforms the chest wall and heart instead, resulting in a better cardiac output.

Next, position yourself, for which you may need a step stool to be at an appropriate height above the patient. This is also important, as you should be able to position such that elbows are locked and directly over the wrists, and the shoulders are directly over the elbows, which warrants that the compressions are more ergonomic and effective.

If you are not able to position yourself correctly and lock your elbows, it means you are too low relative to the patient and this may lead to less effective compressions and greater rescuer fatigue.

After ensuring that you are in correct position, begin with chest compressions.

Place the heel of one hand directly over the patient’s sternum at the nipple line. Make sure that this hand is in the midline of the patient’s body and not off to one side. Next, place the other hand over the first hand and interlace the fingers. Lock the elbows and position yourself as described previously. Then, moving your entire body downward like a piston, depress the patient’s sternum at least 2-2.5 inches. Adequate compression depth is essential in order to provide sufficient stroke volume to perfuse the heart and brain. Shallow compressions might lead to decreased stroke volume, thus causing reduced cardiac output.

Recall, is you’re too low relative to the patient then you wont be able to lock your elbows and the compressions might be less effective.

Completely releasing pressure on the sternum between compressions is equally important. As, under normal circumstances, negative intrathoracic pressure causes blood to fill the heart, which contributes to the stroke volume. Therefore, leaning on the sternum and not releasing the pressure entirely would raise the intrathoracic pressure and decrease cardiac filling, thereby reducing stroke volume.

Aim to perform 100-120 compressions per minute. The correct rate is vital, as compressing too slowly directly reduces cardiac output, while compressing too quickly impairs filling and decreases stroke volume. Continue compressions without interruption until resuscitation equipment arrives, as CPR continuity is a major determinant of survival. Under no circumstances should the CPR be stopped.

This procedure can be exhausting, and if the quality of your CPR is suboptimal due to fatigue, have another rescuer step in. Be sure to coordinate switches, so that there are no pauses in between compressions.

The next step following effective CPR is defibrillation.

Start by attaching a set of pads to the defibrillator cable. The positions are illustrated on the pads themselves. The most common pad positions are: the antero-lateral position — in which the pads are placed over the right sternal border and apex of the heart, and the antero-posterior position — in which the pads are placed on the left precordium and left back upper back. When the pads are secure, turn on the defibrillator. The machine shown here is in the manual mode. For automated defibrillators, follow the manufacture’s instructions.

Stop chest compressions to reveal the underlying rhythm. This is important as compressions create electrical interference that will make it impossible to interpret the pattern. Determine if the waveform is shockable. The two shockable arrest rhythms are: ventricular fibrillation – a randomly fluctuating pattern without organized QRS complexes. There is no predictability or pattern to it whatsoever. And ventricular tachycardia – a rapid, wide-complex rhythm, usually more than 150 beats per minute. The QRS complexes are so wide that one just segues into the next without discernible T-waves. If the rhythm is not the one that can be shocked by the defibrillator, resume chest compressions for two minutes, at which time the rhythm should be rechecked. If it is the one that may be shocked, resume chest compressions while preparing to deliver the shock.

Verify the defibrillator is set to the correct dose of electricity – 200 Joules for adults, and press the charge button. Wait until the defibrillator is fully charged. The high-pitched charging tone will get louder when the defibrillator is ready. Clear all personnel away and make sure that no one is in physical contact with the patient. Then press the shock button. The high-pitched tone will stop, and the patient will “jump”, indicating that electricity was delivered successfully.

Resume CPR immediately after delivering the shock, and continue for two minutes before pausing again to reassess the rhythm. Notice that there has been no mention of ventilation, vascular access, or drugs up to this point. That is because these are lower-priority interventions, with less impact on cardiac arrest survival. In the first few minutes of resuscitation, the priorities are rapid recognition of cardiac arrest, initiation of high-quality chest compressions, and performance of defibrillation when indicated.

Quality CPR is absolutely essential to cardiac arrest survival, and must be perfected by all healthcare providers. Ideally, the first compression should be delivered in the first 30 seconds of the arrest. Regrettably, suboptimal CPR is quite common, and leads to poor survival outcomes. Pausing CPR inappropriately is a common mistake, and is particularly likely when providers incorrectly prioritize advanced interventions like intubation and vascular access over basic life support. Other common mistakes include inappropriate compression rate, inadequate compression depth, leaning on the chest between compressions, ventilating ineffectively, and hyperventilating.

Even with perfect CPR, outcomes from cardiac arrest aren’t great — with less than 10% survival among out-of-hospital adult arrest victims and less than 33% in-hospital. However, quality CPR and rapid defibrillation are absolute prerequisites to survival, and widespread improvement of resuscitation performance by providers could potentially increase survival rates.

You have just watched a JoVE video detailing the CPR and rapid defibrillation procedure. You should now understand the essential steps of this technique and also the rationale behind these steps. As always, thanks for watching!