Prehospital trauma care: Influence of emergency medical services on trauma center patient outcomes

Golden hour or golden opportunity?

“There is a golden hour between life and death. If you are critically injured, you have less than 60 minutes to survive.” And hence was born the much-quoted dogma of the golden hour of trauma, in a simple interview with Dr. R. Adams Cowley, in 1976.

Many Vietnam surgeons have consistently stated that the “golden hour” was born through the 1.04 hours that it took for a wounded soldier to arrive in a surgical hospital in Vietnam due to the great efforts of the “dustoff” medical helicopters otherwise known as MEDEVAC.

Although there was no scientific evidence to support that statement, it was intuitively obvious to most that the essence of the statement was true. But the blanket acceptance of that concept has not been without cost and risk, and more recent science has brought that concept into question.

Much of our current trauma system structure is based upon the golden hour concept, with patients transported to trauma centers as rapidly as possible, even if that includes helicopter and lights-and-siren ground ambulance transport. Helicopter evacuation of combat casualties became synonymous with the Korean and Vietnam wars with the help of the television, movie, and news industries.

The call sign “Dustoff” for the MEDEVAC unit helicopters was originally chosen in 1963 by Major Lloyd E. Spencer, then Commander of the U.S. Army 57th medical/detachment in Vietnam. MEDEVAC dustoff flights transported all wounded with a 3.3 times greater risk of helicopter losses from enemy fire.

Translation to civilian trauma use was easy, with a marked increase of helicopter emergency medical service providers in recent decades. In 1980, 32 helicopter emergency medical service programs with 39 helicopters were flying more than 17,000 patients a year. The 2017 Atlas and Database of Air Medical Services reported over 300 air ambulance services, 1000 bases, and 1400 registered aircraft now providing aeromedical transport.

The justification, of course, is the more rapid transport of trauma victims from the scene to the trauma center. But helicopter transport has been deadly for some. In one 2-year period of the Vietnam War, 39 crew members were killed and 210 were wounded in unarmed medical evacuation missions. Four decades later, 217 people died in 81 fatal civilian EMS helicopter accidents, with 28 of those in 2008 alone. Several National Transportation Safety Board and Federal Aviation Administration actions have resulted, with ongoing safety modifications addressing and enhancing the overall safety of both fixed and rotor wing medical patient evacuation.

Ground transport introduces its own set of risks to patients, providers, and the public. The highest risk of on-duty fatality for EMS personnel is associated with vehicle crashes. However, not all ambulance crash-related injuries are isolated to EMS providers. In a 10-year study conducted by the National Institute for Occupational Safety and Health, in 300 fatal ambulance crashes, 27 EMS workers perished, as did 55 other ambulance occupants and 275 pedestrians and occupants of other vehicles. Not surprisingly, the majority of ambulance accidents occurred during emergency calls. The most common explanation of fatal injuries to EMS providers is the fact that EMS workers providing active patient care during transport believe they are unable to provide that care effectively while restrained with seatbelts. However, 40% of the ambulance occupant fatalities were riding in the rear patient compartment, with the vast majority of these being unrestrained. Extensive work has been done to study this problem, but the solutions are not universal. Interestingly, although the Federal Aviation Administration attributes up to 80% of all aircraft accidents to pilot error, 60% of the ambulance crashes seen in the National Institute for Occupational Safety and Health study were due to driver error. None of these studies delineated the reason for patient transport, but one can extrapolate these findings to the stress and perceived need for rapid transport of a trauma victim, under the guise of the golden hour.

In one study, neither time of transport nor expertise of responding personnel affected the outcome of trauma patients with severe physiologic derangement. One hundred forty-six EMS agencies, including air and ground, transported 3656 trauma patients to 51 U.S. and Canadian Level I and II trauma centers. Study patients were severely injured, as evidenced by inclusion criteria of either a systolic blood pressure less than or equal to 90, Glasgow Coma Scale score less than or equal to 12, respiratory rate less than 10 or greater than 29 breaths per minute, or need for an advanced airway intervention. Median response times (4 minutes), on-scene times (19 minutes), and transport times (10 minutes) resulted in total times ranging from 28 minutes to 47 minutes, with a median total time of 36 minutes. In all variations of time analysis, no mortality difference could be found based on prehospital times. These findings persisted not only with prehospital times, but also for mode of transport, level of first responding EMS provider, patient age, and mechanism of injury.

On the other hand, it would make empiric sense that patients such as those actively bleeding from injuries to the spleen, liver, or pelvis would do better with rapid transport and definitive treatment. Early studies showed an increase in fatality when more than 60 minutes were spent in the prehospital arena. In Trunkey’s early description of trauma deaths in 1983, a trimodal distribution of death was identified. More recently, a bimodal distribution has been described, with near elimination of late deaths and a shift in the time of early deaths. Early deaths in the study by Gunst et al occurred with a median time of 52 minutes (compared with Trunkey’s 120 minutes), and patients arrived to a trauma center at a median time of 42 minutes from the time of injury. With 24% of patients having potentially survivable injuries, yet succumbing in less than an hour after injury, the golden hour may indeed be real.

One must consider that helicopter transport does not always mean faster arrival to a trauma center. The decision on the ground to call for a helicopter and await its arrival might save minutes, but could also cost minutes.

In the end, there is little disagreement that the likelihood of an improved outcome is probably greater the sooner a severely injured patient can begin definitive care. This was definitely the Vietnam experience. Dr. Cowley likely was very aware that he was making a scientifically unproven statement, but if his intent was to teach a valuable lesson in the early days of civilian trauma care, for that he has been wildly successful. Most importantly, the trauma victim should arrive to definitive care without incident and with the safety of the patient, the transporting prehospital crew, and innocent bystanders of foremost concern.

Prehospital fluids

The debate over whether field paramedics should establish venous access for fluid resuscitation in trauma is not new. For years, Prehospital Trauma Life Support, in cooperation with the American College of Surgeons, has emphasized the importance of field intravenous (IV) access and fluid resuscitation, though that concept is now changing. But what practice is the safest for trauma victims?

Placement of venous lines early in the care of trauma patients has long been considered important, both for fluid and drug administration and while vein diameter still permitted cannulation before hypovolemia was severe enough to collapse peripheral access. However, few drugs are indicated in the prehospital environment of the trauma victim, and ready availability of intraosseous access devices enable venous access in even the most severely volume-depleted patient. Placement of lines should never delay transport to a trauma center. So the question then becomes, does fluid resuscitation during transport affect the outcome in an injured victim?

Animal studies in the early 1990s suggested that though saline resuscitation increased blood loss, mortality rate was not affected. And Advanced Trauma Life Support doctrine has historically advocated a 2-L bolus of lactated Ringer’s solution as needed. This concept was subsequently carried into the prehospital environment and became common practice, but with few options for monitoring adequacy of resuscitation. Concerns for underresuscitation included the risks of diffuse organ ischemia, especially in the brain-injured patient. Additionally, at what point would hypovolemia turn from acceptable to lethal?

Despite these concerns, the overwhelming current consensus favors limited to no field resuscitation, even in the emergency department, until control of active, or potentially active, bleeding sites can be obtained. Arguments against normotensive resuscitation with crystalloid include dilution of clotting factors, increase in bleeding and hemoglobin loss, dislodgement of established clot, extravascular fluid overload, and the potential to worsen hypothermia with room temperature fluids. A large 2011 National Trauma Data Bank review showed that patients with a prehospital IV line had a significantly higher mortality rate than those who did not. Though one might argue that a selection bias existed, the increase in mortality rate was seen in nearly all subsets of patients. This cohort included both blunt and penetrating injuries, though the mortality rate increase was more pronounced in the latter. Mortality rate was not affected in normotensive patients, but was significantly increased in the hypotensive ones, and severely brain-injured patients had a 34% increase in risk of death. Low injury-severity patients did not exhibit a difference in mortality rate. It is now recognized that overuse of crystalloids before the use of blood products during resuscitation leads to dilutional coagulopathy, pulmonary edema, and interstitial edema resulting in abdominal compartment syndrome. Changes in Advanced Trauma Life Support 10 now reflect these issues and limit the suggested crystalloid volume to 1 L, given with a judicious approach.

Recent combat experience has further supported the abandonment of normotensive field resuscitation. Though injury patterns are admittedly different in the civilian versus battlefield setting, hemorrhage control is paramount in both. Judicious rather than overzealous use of resuscitation fluids is now recommended.

If the concept of limited fluid resuscitation, or permissive hypotension, is to be embraced by prehospital personnel, what is the limit of permissive? In patients with hemorrhagic shock, in whom bleeding has temporarily ceased, Israeli Defense Force guidelines recommend fluids aimed at restoration of a radial pulse, sensorium, or a systolic blood pressure of 80 mm Hg. Because of the concern for cerebral perfusion in the setting of central nervous system injuries, a systolic blood pressure of 100 mm Hg is recommended. The U.S. Department of Defense Tactical Combat Casualty Care Fluid Resuscitation Guidelines 2019, now adopted by all services in the Department of Defense, recommend no IV fluids in patients not in shock, and fluid resuscitation of those in uncontrolled hemorrhagic shock, with shock determined by the absence of a palpable radial pulse.

Despite decades of publications refuting prehospital fluid administration in the prehospital setting, the practice continues. The administration of crystalloid, with “normal” vital signs being the goal, should be abandoned. Although crossing the line of permissive hypotension to death is not a desirable outcome, evidence of adequate, albeit not normal, resuscitation should be the desired end point. Measures of adequate perfusion include a palpable radial artery pulse and systolic blood pressure of 80–90 mm Hg (90–100 mm Hg in suspected traumatic brain injury patients) and should be the preferred end point of field resuscitation. This goal should be accomplished with low-volume (500 mL) boluses, rather than the previous practice of 2-L boluses. Though seldom part of standard EMS supplies, blood product resuscitation (whole blood, plasma, or red blood cells, plasma, and platelets in a 1:1:1 ratio) is preferred over crystalloid solutions (lactated Ringer’s, normal saline, Plasma-Lyte A). Fluid resuscitation should be discontinued once resuscitation end points have been reached.