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Resuscitation Success With Chest Compressions Only
Abstract & Commentary
By John P. DiMarco, MD, PhD, Professor of Medicine, Division of Cardiology, University of Virginia, Charlottesville. Dr. DiMarco is a consultant for Novartis, and does research for Medtronic and Guidant.
Source: SOS-KANTO Study Group. Cardiopulmonary Resuscitation by Bystanders With Chest Compression Only (SOS-KANTO): An Observational Study. Lancet. 2007;369:920-926.
The SOS-Kanto study is a survey of survivors of out-of-hospital cardiac arrest in the Kanto region of Japan. In this paper, the SOS-Kanto investigators analyzed outcomes in patients with an out-of-hospital cardiac arrest that was witnessed by bystanders between September 1, 2002, and December 31, 2003. Emergency Medical Service (EMS) paramedics observed the technique of bystander resuscitation and asked additional standardized questions of witnesses. The technique was classified as: cardiac-only resuscitation (chest compressions only), conventional CPR (chest compressions plus breathing), pulmonary-only resuscitation (breathing only) and unidentified or not documented. In addition, the person attempting bystander resuscitation was classified as either a layperson with basic CPR training, a layperson assisted by a dispatcher, a layperson without training or assistance, or an off-duty health worker. The primary endpoint was a favorable neurological outcome defined as a Glasgow-Pittsburgh cerebral performance category of either 1 or 2 when measured 30 days after cardiac arrest. The secondary endpoint was survival 30 days after cardiac arrest.
During the study period, 9,592 patients received advanced life-support by EMS paramedics in the Kanto region. Of these, 4,068 adult patients had a bystander witnessed cardiac arrest outside the hospital and are included in this report. In this group, 1,151 (28%) received some form of bystander resuscitation, including 439 (11%) who received cardiac-only resuscitation, and 712 (18%) who received conventional CPR. There were 2,917 (72%) witnessed cardiac-arrest victims who did not receive any bystander resuscitation. The patients who received bystander resuscitation were more likely to have their cardiac arrest occur in a public place and to have either gasping breathing or ventricular fibrillation or pulseless VT at the time of EMS arrival. When the cardiac-resuscitation only vs conventional CPR groups were compared, the baseline characteristics were similar except that conventional CPR was more likely to be performed by off-duty medical staff while cardiac-only resuscitation was more likely to be performed by laypersons without formal CPR training.
Compared to the no-bystander resuscitation group, patients who had any resuscitation attempt were significantly more likely to have a favorable neurological outcome (5% vs 2%; p = less than 0.001). Subgroup analysis showed consistent improvement in patients with a cardiac cause for their arrest, apnea at the time of EMS arrival, ventricular fibrillation or pulseless VT as the initial cardiac rhythm. Any bystander resuscitation also showed benefit for patients with both short and long EMS response times. When the cardiac-resuscitation only vs conventional CPR groups were compared, cardiac-only resuscitation resulted in a higher proportion of patients with a favorable neurological outcome. This was due to improved neurological outcomes in patients with apnea, ventricular fibrillation or tachycardia as the initial rhythm or with resuscitation starting within 4 minutes of collapse. Multiple logistic regression analysis showed that cardiac-only resuscitation resulted in higher proportions of favorable neurological outcome than with conventional CPR with an adjusted odds ratio of 2.22 (1.17-4.21). Of note, the 2 bystander resuscitation groups did not show differences in total survival at 30 days or in survival until hospital admission despite the improvement in neurological outcomes.
The authors conclude that cardiac-only resuscitation should be the preferred approach to bystander resuscitation for adult patients with witnessed out-of-hospital cardiac arrest. Improvements in neurological outcome are more marked in those with apnea, a shockable cardiac rhythm or short periods of untreated arrests.
The standard method for cardiopulmonary resuscitation for many years has been a combination of chest compression and ventilation. Recently, the importance of ventilation during CPR has been questioned. There are a number of reasons for this. Most importantly, many bystanders are reluctant to perform mouth-to-mouth ventilation. This decreases the number of cardiac arrest victims who receive any bystander resuscitation at all. Conventional CPR is a complex technique, is difficult to teach and its complexity intimidates many. There are many reasons why ventilation may not be necessary. Mouth-to-mouth ventilation causes interruptions in chest compression and this can decrease cardiac outputs. Mouth-to-mouth or positive ventilation may also change intrathoracic pressures in a deleterious fashion. At the onset of a primary cardiac arrest, the blood in the lungs should be fully oxygenated and enough oxygenation to maintain organ function will be maintained for several minutes of chest compression. These concepts have been supported by data from experimental laboratory preparations showing that ventilation is not beneficial in the early stages of resuscitation. The SOS-KANTOS Study now has demonstrated this to be also true in an observational study in a clinical population. Adoption of this finding into ACLS guidelines should simplify our ability to train people in CPR and also benefit outcomes. Victims of drowning, drug overdose or asphyxia will still require ventilation, but chest-compression-only CRP should become the standard for most cardiac arrest victims.