Third Effective Stratagem: Bag-valve-mask ventilations should be performed with precision; when used, the bag should be compressed with only one hand and delivered no faster than one breath every 3–5 seconds.
Fourth Effective Stratagem: In cases of pulseless electrical activity (PEA) or post-resuscitation hypotension, auto-PEEP should be considered foremost as a proximal cause.
Fifth Effective Stratagem: Ventilations in resuscitation should be viewed primarily as a means to oxygenate the patient rather than as a means to compensate from a systemic acidemia.
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Shocking Revelations
Even though patients in ventricular fibrillation (VF) and pulseless ventricular tachycardia (PVT) together only comprise about one–third of all inpatient cardiac arrests, they account for almost 70% of survivors of CA. Survival in these arrhythmias is predicated solely on rapid defibrillation: the simultaneous depolarization of a critical mass of myocytes by an electrical current with resultant resumption of normal cardiac conduction (36). Perhaps the best attestation to the importance of rapid defibrillation actually comes from the survival of patients with cardiac arrest at casinos: security cameras provided exact documentation of time of collapse and defibrillation. Survival to hospital discharge was cut in half when the time-from-collapse-to-defibrillation was greater than 3 minutes (74% vs. 49%)(37).
Sixth Effective Stratagem: Since patients in VF/PVT are the most likely to survive CA―and that rate is directly related to immediacy of defibrillation―all patients should be presumptively treated as if they are in VF/PVT and should be defibrillated within 3 minutes of collapse unless there are data to support another arrhythmia or cause of collapse.
Much of the electrical current delivered during a defibrillation attempt is either dissipated as heat or is conducted around the thorax without penetrating the myocardium; Lerman and Deale have shown that the amount of current reaching the heart may be as little as 4% during a defibrillation attempt (38). From Ohm’s Law, the current that reaches the heart is directly proportional to the voltage across the chest and inversely related to the resistance of the supervening tissues. Interestingly, increasing the voltage of a shock only increases the amount of heat produced without a commensurate increase in current delivered. Therefore, techniques that reduce thoracic resistance yield the highest current delivery: the use of manual defibrillator paddles (as opposed to self adhesive defibrillation pads), the amount of pressure applied to the paddles (>25 pounds), the correct placement (underneath, rather than on top of breast tissue), the use of a conduction material (gel or pads), and the rapid delivery of a stacked shock (resistance transiently decreases after a counter-shock) all improve current delivery and thus may improve defibrillation outcome (36).
Physician leadership during resuscitations is critical for maximizing likelihood of patient survival. Perhaps due to physicians’ lack of familiarity with defibrillators, the mechanics of defibrillation are often deferred unnecessarily to nursing staff. Unfortunately, this may have profoundly negative effects on the resuscitation. Since many hospitals reduce educational expenses by foregoing training nurses in ACLS unless they work in intensive care units, nurses on a code may have even less comfort in using defibrillators than physicians. One study showed nearly a 72.5% decrease in patient survival when the nurse who arrived first at the resuscitation was untrained in ACLS (37.5% vs. 10.3%); a difference that probably is related to delayed defibrillation though the study could not establish direct causality (39).
A separate study showed that 85% of patients on cardiac monitored wards were defibrillated in the target time of 3 minutes from collapse, while only 28% of patients on unmonitored wards were defibrillated within the target time; this led to an adjusted odds ratio for survival-to-discharge in patients on monitored versus non-monitored wards of 1.45 (95% CI, 0.95–2.20)(40). While at first these data seem to indicate faster responses on monitored wards, these data were specific to time-from-collapse-to-defibrillation and therefore should be location-independent once the need for resuscitation was identified. Instead, I interpret these data as showing the lower comfort nurses on non-monitored wards have with rapid defibrillation. Rather than serving as an indictment against nurses, these data in aggregate underscore the vital role physician responders have to ensure rapid defibrillation of patients in cardiac arrest.