Review of:Liu JM, Yang Q, Pirrallo RG. "Hospital variability of out-of-hospital cardiac arrest survival." Prehospital Emergency Care. 12(3)339-346, 2008.
This Milwaukee County EMS study examined the hospital variables that may impact cardiac arrest victim survival. Of the 1,702 prehospital cardiac arrest patients who survived to 12 hospitals in the county, the survival rates varied from 29 to 40% more than the 10-year period that was examined. Although this variability wasn't statistically significant, the authors did find that that survival was associated with hospitals with higher levels of nurse staffing (more than one nurse per cardiac arrest victim).
There wasn't survival advantage for hospitals with larger emergency room (ER) volumes, total number of beds, presence of primary heart catheterization capability, myocardial infarction (MI) diagnosis or physician staffing.
Their data confirmed patients who survived to hospital admission had a greater likelihood of survival to discharge if they had a witnessed arrest (twice as likely), were aged less than 55 (twice as likely), presented rhythm V Fib (6.77 times as likely).
I would like to congratulate the authors on attempting to address a fundamental issue of cardiac arrest care that has frustrated EMS providers for years. We've been provided guidelines for improved care in the streets with the primary goal of improving survival, yet paper after paper has shown little evidence of an increase in survival. Unfortunately, these papers have failed to provide us the important information necessary to help us recognize that we are actually making a difference. They've lumped all cardiac arrests into one large group failing to recognize that the survival rates are very different for asystole than they are for V Fib/V Tach.
Furthermore, many adverse events that we have no control over can occur in the hospital. This paper has identified one variable, nurse-to-bed ratio, which appears to influence cardiac arrest survival.
I suspect there are others, such as rates of victims who are taken off life support by families because of pre-existing DNR/DNI or pre-existing conditions and hospital complications, such as infections and MI that go un-noticed or untreated. Another variable not examined in this study was the capability of the intensive care units. Did they have intensivists?
Further analysis of the study, as was recognized by the authors, the survival rates rose significantly during 2001 and 2004 following the institution of the 2000 AHA guidelines. Was this a result of increased awareness of the role of chest compression and other factors in the Milwaukee County EMS system? These issues further support the need to investigate the merits of cardiac arrest centers, particularly as we begin to explore the role of post-resuscitation hypothermia.