the initial response to a cardiac arrest?
The initial response to a witnessed cardiac
arrest is to confirm the diagnosis. Patients in arrest are unresponsive,
apneic, and pulseless. Assistance should be called for immediately prior to any
intervention. In the past, it was recommended to call for assistance after the
initiation of cardiopulmonary resuscitation (CPR), but since 80–90% of patients
with sudden cardiac arrest have ventricular fibrillation (VF), which is the
most treatable dysrhythmia but which requires urgent defibrillation, the
rescuer is advised to call first so that a defibrillator can be brought to the
scene. The only exception is in the case of children less than 8 years of age,
who usually arrest because of airway problems. In that case, an attempt at securing
the airway should first be made.
Monitored patients should be treated according
to the Advanced Cardiac Life Support (ACLS) protocol devised for their
dysrhythmia. This includes basic life support (BLS), usually in the form of
CPR, as well as adjunctive equipment for airway control, dysrhythmia detection
and treatment, and post-resuscitation care. Unmonitored, unre-sponsive patients
should have their airway assessed first followed by two breaths and a pulse
check. In a witnessed cardiac arrest, a precordial thump may be indicated but
CPR must be started immediately if the patient remains pulseless. As soon as
possible, paddles or electrocardiogram (ECG) leads should be placed on the
patient to determine the rhythm. If pulseless ventricular tachycardia (VT) or
VF is the initial rhythm, the patient should receive up to three uniphasic
countershocks of increasing power: 200 joules (J), 200-300 J, and 360 J,
respectively. Biphasic equivalents are approximately half that of uniphasic
doses. If VF or pulse-less VT is not the initial rhythm, or if the
countershocks are unsuccessful, then chest compressions and ventilation should
be continued and the patient treated accordingly (Figure 1.1).
The essential element in treating cardiac
arrest is rapid identification and treatment. The goal of CPR is to provide
oxygenated blood to the heart and brain until ACLS proce-dures are initiated.
The best results (survival of approxi-mately 40%) are achieved in patients
receiving CPR within 4 minutes and ACLS within 8 minutes of arrest, whereas
survival is less than 6% when CPR and ACLS are started after 9 minutes.
The groups of patients most likely to be
resuscitated include patients outside the hospital with witnessed arrests due
to VF, hospitalized patients with VF secondary to ischemic heart disease,
arrests not associated with coexisting life-threatening conditions, and
patients who are hypother-mic or intoxicated. Patients with severe multisystem
disease, metastatic cancer, or oliguria do not often survive CPR.