Speed and Time in Prehospital Trauma Care
One of the most fundamental tenets of EMS has been the attempt to get the patient to the hospital as quickly as possible. This concept was bolstered by R. Adams Cowley with his "Golden Hour" scheme. The trauma folks soon developed catchy phrases like "load and go" and "scoop and run." But, several recent studies have shown that total out-of-hospital time has little or no impact on most subsequent patient outcomes and mortality.
In a soon-to-be-published study in Annals of Emergency Medicine, Newgard and colleagues looked at outcomes of prehospital trauma patients and correlated these with various out-of-hospital time intervals. The study included a total of 3,565 trauma patients transported by 146 EMS agencies to 51 Level I and II trauma hospitals in 10 sites across North America from December 1, 2005, through March 31, 2007. The inclusion criteria were a systolic blood pressure less than or equal to 90 mm Hg, respiratory rate less than 10 or greater than 29 breaths/min, a Glasgow Coma Scale score less than or equal to 12, or the need for an advanced airway intervention.
They looked at various defined prehospital time intervals (activation interval, response interval, on-scene interval, transport interval, and total EMS interval). The study concluded, "Among injured patients with physiologic abnormality prospectively sampled from a diverse group of sites and EMS systems across North America, there was no association between EMS intervals and mortality."1 This was the largest study with the greatest validity on this topic conducted thus far.
Several other studies have come to the same conclusion. In a Denver study, which included all types of EMS response, Dr. Peter Pons and colleagues found that a paramedic response time less than eight minutes was not associated with improved survival to hospital discharge after controlling for several important confounders, including level of illness severity. However, a survival benefit was identified when the response time was within four minutes for patients with intermediate or high risk of mortality. They concluded that adherence to an eight-minute response time guideline in most patients who access out-of-hospital emergency services was not supported by the results of the study.2
In a study of 1,877 prehospital trauma patents, six percent (116) did not survive. The following parameters were found to be predictors of mortality: CUPS (critical, unstable, potentially unstable, stable) status, patient age, Injury Severity Score (ISS), and Revised Trauma Score (RTS). The total out-of-hospital time was the only variable NOT found to be a significant predictor of mortality.3 A Norwegian study found that longer prehospital scene times by medical helicopter crews were not associated with worsened outcomes.4
Now, I am not naïve enough to say that we should not make every possible effort to minimize out-of-hospital time. But, we should not do so at the peril of the providers and the public. All of the pseudoscientific response time standards and rapid deployment schemes (e.g., system status management) do little to improve patient outcomes (other than customer satisfaction) and torture employees in the process. Helicopter EMS (HEMS) is almost totally based upon the perceived need for speed and decreased out-of-hospital times. But, will they react to evolving evidence that seems to show that out-of-hospital times have little or no impact on patient outcomes and negates the main reason for their existence? The whole HEMS industry is out of control and all EMS providers share the blame for the problem and overuse. The needs of the patient have given way to the need to make a profit. Ground EMS personnel and physicians must start limiting use of this expensive and dangerous technology to patients who really stand to derive benefit (which are actually few and far between). Is a patient's life really worth a helicopter pin for your cap, a coffee cup, or a pizza dinner?
Perhaps EMS needs what the aviation industry calls a "stand down." We need to stop, catch our breath, and critically analyze the things that we do. Can any EMS system (except the casinos in Las Vegas) provide a response time of four minutes or less (the only response interval scientifically associated with improved patient survival? Are our artificial response time guidelines truly beneficial and sustainable? As I get older I find more and more things that I do because of ritual or misinformed beliefs. Changing these has made my life easier and safer. Think about it.
1. Newgard CD, Schmicker RH, Hedges JR. at al. Emergency Medical Services Intervals and Survival in Trauma: Assessment of the "Golden Hour" in a North American Prospective Cohort. Ann Emerg Med. 2009;(in press)
2. Pons PT, Haukoos JS, Bludworth W, Cribley T, Pons KA, Markovchick VJ. Paramedic response time: does it affect patient survival? Acad Emerg Med. 2005;12:594-600.
3. Lerner EB, Billittier AJ, Dorn JM, Wu WY. Is total out-of-hospital time a significant predictor of trauma patient mortality? Acad Emerg Med. 2003;10:949-54.
4. Ringburg AN, Spanjersberg WR, Frankema SP, Steyerberg EW, Patka P, Schipper IB. Helicopter emergency medical services (HEMS): impact on on-scene times. J Trauma. 2007;63:258-262.