In a cohort of more than 500,000 individuals who experienced out-of-hospital cardiac arrest in Japan, Akihito Hagihara and colleagues studied whether administration of lactated Ringer's solution was associated with survival and functional outcomes.
No studies have evaluated whether administering intravenous lactated Ringer's (LR) solution to patients with out-of-hospital cardiac arrest (OHCA) improves their outcomes, to our knowledge. Therefore, we examined the association between prehospital use of LR solution and patients' return of spontaneous circulation (ROSC), 1-month survival, and neurological or physical outcomes at 1 month after the event.
Methods and Findings
We conducted a prospective, non-randomized, observational study using national data of all patients with OHCA from 2005 through 2009 in Japan. We performed a propensity analysis and examined the association between prehospital use of LR solution and short- and long-term survival. The study patients were ≥18 years of age, had an OHCA before arrival of EMS personnel, were treated by EMS personnel, and were then transported to hospitals. A total of 531,854 patients with OHCA met the inclusion criteria. Among propensity-matched patients, compared with those who did not receive pre-hospital intravenous fluids, prehospital use of LR solution was associated with an increased likelihood of ROSC before hospital arrival (odds ratio [OR] adjusted for all covariates [95% CI] = 1.239 [1.146–1.339] [p<0.001], but with a reduced likelihood of 1-month survival with minimal neurological or physical impairment (cerebral performance category 1 or 2, OR adjusted for all covariates [95% CI] = 0.764 [0.589–0.992] [p = 0.04]; and overall performance category 1 or 2, OR adjusted for all covariates [95% CI] = 0.746 [0.573–0.971] [p = 0.03]). There was no association between prehospital use of LR solution and 1-month survival (OR adjusted for all covariates [95% CI] = 0.960 [0.854–1.078]).
In Japanese patients experiencing OHCA, the prehospital use of LR solution was independently associated with a decreased likelihood of a good functional outcome 1 month after the event, but with an increased likelihood of ROSC before hospital arrival. Prehospital use of LR solution was not associated with 1-month survival. Further study is necessary to verify these findings.
Please see later in the article for the Editors' Summary
Cardiac arrest, a condition in which the heart suddenly stops pumping, is caused by problems with the heart's internal electrical system, which controls the rate and rhythm of the heart contractions that pump blood around the body. If this electrical system malfunctions, an abnormal heartbeat or “arrhythmia” develops that, in some cases, causes cardiac arrest. Because blood is no longer being pumped around the body, the organs and tissues of the body do not receive the oxygen they need to function. Consciousness is lost immediately and, if medical attention is not provided quickly, death follows within a few minutes—about 95% of people who have a cardiac arrest die before they reach hospital or emergency medical help. Moreover, survivors of cardiac arrest are often left with permanent damage to the brain and other organs. Early cardiopulmonary resuscitation (CPR; chest compression to pump the heart and mouth-to-mouth resuscitation to inflate the lungs) and early defibrillation (delivery of an electric shock to the heart to restore its normal rhythm) reduce the risk of death and permanent organ damage after cardiac arrest.
Why Was This Study Done?
Another procedure that is sometimes used during pre-hospital resuscitation of cardiac arrest cases is intravenous fluid administration—delivering liquid into a vein through an intravenous needle. A solution that is often used for this purpose is lactated Ringer's (LR) solution, a mixture of inorganic salts and sodium lactate. However, the effects of intravenous LR solution on the outcomes of patients who have an out-of-hospital cardiac arrest have not been studied. In this prospective cohort analysis, the researchers examine the association between the pre-hospital use of LR solution and the return of spontaneous circulation, one-month survival, and neurological and physical outcomes at one month after cardiac arrest among patients in Japan who have had an out-of-hospital cardiac arrest. A prospective cohort analysis identifies a group of patients with a specific condition and examines how they subsequently fare.
What Did the Researchers Do and Find?
In Japan, the Fire and Disaster Management Agency records all out-of-hospital cardiac arrest cases in a nationwide database. The researchers used this database to identify more than half a million out-of-hospital cardiac arrest cases that occurred in Japan between 2005 and 2009. To examine the association between pre-hospital use of LR solution and short- and long-term survival, the researchers used a statistical technique called propensity analysis. This technique is used in observational studies to control for confounding—unknown differences between people who receive an intervention and those who do not receive an intervention that might affect outcomes and thus make it hard to draw conclusions about the intervention's true effects. By examining a large number of variables (for example, age, sex, and time taken for help to arrive), the researchers gave every patient a propensity score that indicated their probability of receiving pre-hospital LR solution, and then used this score to match each patient who received LR solution with a similar patient who did not receive LR solution. Among propensity-matched patients, pre-hospital use of LR solution was associated with a slightly increased chance of return of spontaneous circulation before arrival at a hospital and with a decreased chance of 1-month survival with minimal neurological or physical impairment. Among the whole cohort, pre-hospital use of LR solution was not associated with overall one-month survival.
What Do These Findings Mean?
These findings suggest that, among Japanese patients with out-of-hospital cardiac arrest, pre-hospital use of LR solution was associated with less chance of good functional outcomes at one month. However, the present study has several limitations. For example, data on in-hospital treatment following out-of-hospital cardiac arrest were not available, so the outcome differences between patients receiving and not receiving LR solution potentially could reflect differences in their in-hospital treatment. Moreover, although the researchers undertook a propensity analysis, this study, like all observational studies, can only partly control for selection bias and confounding factors. Thus, the observed associations between LR solution use and short- and long-term outcomes may actually reflect the effects of some unknown characteristic shared by the patients who received LR solution. Because of these and other limitations, it is essential that the findings of this study are verified before recommendations about the pre-hospital use of LR solution in patients with out-of-hospital cardiac arrest are made.
Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1001394.
The US National Heart Lung and Blood Institute provides information on sudden cardiac arrest and on heart arrhythmias
The American Heart Association also information in several languages on sudden cardiac death and on arrhythmias; a selection of personal stories about arrhythmia and cardiac arrest is also available
The not-for-profit Sudden Cardiac Arrest Foundation provides information on all aspects of cardiac arrest, including survivor stories
MedlinePlus provides links to other resources about cardiac arrest (in English and Spanish)