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MEDEVAC: Survival and Physiological Parameters Improved With Higher Level of Flight Medic Training [Military Medicine]
[June 29, 2013]

MEDEVAC: Survival and Physiological Parameters Improved With Higher Level of Flight Medic Training [Military Medicine]


(Military Medicine Via Acquire Media NewsEdge) ABSTRACT Objective: Determine if a higher level of Army flight medic (AFM) training was associated with improved physiological state on arrival to a combat support hospital (CSH). Methods: A retrospective study comparing casualties who were evacuated by two AFM units with only Emergency Medical Technicians-Basic (EMT-Bs) to an Army National Guard unit with Critical Care Flight Paramedics (CCFPs) in Afghanistan with an injury severity score >16 in different time periods looking at their 48-hour mortality, hematocrit (HCT), base deficit (BD), oxygen saturation (SpO2), and physiological parameters on arrival to the CSH. Results: The CCFP group had better HCT [36.5 (8.8)] than the EMT-B group [33.1 (11.4); p £ 0.001]. BD and SpO2 were better in the CCFP group [-3.2 (4.7)]/[97.8 (4.8)] than the EMT-B group [-4.4 (5.5)]/[96.3 (10.9)] [p £ 0.014]. The CCFP group had a 72% lower estimated risk ratio of mortality with an associated improvement in 48-hour survivability of 4.9% versus 15.8% for the EMT-B-group. Conclusions: There is a statistically significant improvement in the HCT, BD, SpO2, and 48-hour survivability at the CSH in the cohort transported by the CCFP group when compared to the cohort transported by the EMT-B group.



INTRODUCTION We compared combat casualties on arrival to a combat support hospital (CSH), who were transported by a higher trained Civilian Critical Care Flight Paramedic (CCFP), in an Army National Guard unit, to a regular Army trained Emergency Medical Technicians-Basic (EMT-B) flight medic. We hypothesized that combat casualties who were evacuated by helicopter and transported to the CSH by a higher level of training and experience would be associated with improved physiological parameters, such as systolic blood pressure (SBP), diastolic blood pressure (DBP), heart rate (HR), oxygen saturation (SpO2), hematocrit (HCT), base deficit (BD), temperature (Temp), and improved 48-hour survivability.

In Iraq and Afghanistan, air medical evacuation (MEDEVAC) has been instrumental in saving the lives of personnel injured in battle. Currently, the U.S. Army uses a single Combat Healthcare Specialist Flight Medic (Military Occupational Specialty Code 68WF3) trained to the level of an EMT-B with additional training onboard a UH-60 MEDEVAC helicopter to transport injured personnel during combat. Casualties can be transported from different levels of care: from the point of injury (POI) to CSHs, from the POI to forward surgical teams (FSTs), or from the FST to a CSH. Each one of these levels of care provides its own unique challenges: from acute hemorrhage control, airway problems, and head injuries at POI to transporting postsurgical patients who are intubated on ventilators and with multiple medication drips for pain control/sedation and antibiotics.


The current prerequisite for Army flight medic (AFM) EMT-B training is at least 1 year of experience as an Army medic. Next, the AFM is required to attend a two-phase training program. The first phase of the program is distance learning during which the medic is required to complete 33 hours of aeromedical and aviation classes relevant to performing tasks as a member of the helicopter crew. After completing phase I, the medic attends a 4-week course (phase II) that covers advanced cardiac life support, flight medic pharmacology, drug dosage calculations, international trauma life support, pediatric education for prehospital professionals, critical care management of a patient in a MEDEVAC aircraftplatform, rapid sequence induction, helicopter underwater egress training, high-altitude chamber, personal recovery operations, survival training, and canine trauma management. There is a capstone training exercise during the last week of the course in which the AFMstudent will have to apply all the knowledge and skills taught over the past 3 weeks.1 Training is entirely didactic and simulation based. There is no "hands-on" clinical application of the new skills in an intensive care unit (ICU), nor is there a field apprenticeship with an experienced flight medic. AFMs can go straight from training to immediate deployment without having any clinical experience.

The civilian flight helicopter emergency medical system (HEMS) operates differently from the Army system. Civilians use a two-person critical care flight team to transport injured or sick patients. The civilian flight team generally consists of a critical care flight nurse (CCFN) and a CCFP. The CCFN is a registered nurse who, after working 3 to 5 years in an ICU or in an emergency room (ER), attends a flight nurse program. To become a CCFP, a paramedic must be a graduate of an accredited paramedic program and have a minimum of 3 to 5 years of experience in critical care or in a high-call-volume 911 service. Some HEMS systems also require 2 years of experience as a medic working in a medical intensive care unit (MICU). The International Association of Flight Paramedics recommends that civilian flight medics take one of the two certifying tests: the Flight Paramedic Certified Exam (FP-C) or the Critical Care Paramedic Certified Exam (CCP-C). The goal for CCFPs is to be certified using one of the two mentioned tests within the first 3 years of being hired as a flight medic. Currently, there is no national requirement for CCFPs to be certified in either of the two certifying examinations; taking the examinations is only a recommendation.2 The CCFPs receive the following training: Trauma Casualty Management; Transport fundamentals, safety, and survival; Advance Airway Management Techniques; and treatment of the following types of patients: neurologic, cardiac, respiratory, toxic exposure, obstetrical, neonatal, pediatric, burn, general medical, and environmental. They are also trained in specialty areas and advanced procedures (Table I).2,3 Some HEMS companies require CCFP clinical training that also includes 5 hours in critical care with an emphasis on hemodynamic and ventilator management; 5 hours in the emergency room with a concentration on patient assessment and rapid treatment; 2 hours in obstetrics concentrating on high-risk obstetrics patients; and 16 hours of prehospital training with a concentration on the proper transport of patients, proper equipment use, and preparation and handling.4 A Certified Intensive Care Provider course, a 128-hour critical care program to prepare candidates for the FP-C or CCP-C, is also available. A criterion for entering this course is being a paramedic for a minimum of 1 year. The course consists of 96 hours of classroom didactics and 32 hours of experience in a critical care setting. 5 Depending on the state and the HEMS companies, the clinical training hours before becoming a flight paramedic vary. The International Association of Flight Paramedics "Critical Care Paramedic Position Statement" does not specify how many clinical hours are required for becoming a flight paramedic. But it does state that flight paramedics will successfully complete a critical care education program that has didactic sessions, practical sessions, demonstrable skill proficiency, and clinical rotations.2 With the large discrepancy in training, it seems obvious that CCFP transporting casualties via helicopters would have better outcomes compared to AFMs trained to the level of an EMT-B. However, there is conflicting evidence in the civilian literature on the effectiveness of HEMS.6-8 Some of the military literature advocates the use of more highly skilled/ trained critical care practitioners in a combat environment, but there is no outcomes-based evidence in the literature, such as comparing the level of training with the patient's physiology status on arrival to the hospital.8-17 The studies currently in the literature often focus on the cost versus the benefit of the civilian HEMS or in the context of injuries, generally blunt vehicular trauma, of casualties who are generally transported by the civilian HEMS.8,17-23 Most civilian HEMS studies are probably not a suitable comparison to the combat environment. In general, the civilian HEMS have shorter evacuation times, whereas casualties routinely transported in combat have longer evacuation times complicated by multiple penetrating injuries often with associated blast trauma, head injuries, and airway insufficiency.

METHODS This study was a retrospective cohort study with a protocol approved by the U.S. Army Institute of Surgical Research Institutional Review Board. The data used were obtained from the Joint Theater Trauma Registry to compare the physiological parameters of casualties (soldiers and host national personnel) who were transported by conventional Army air MEDEVAC EMT-B trained units from December 2007 to November 2008 and November 2010 to August 2010 to an Army National Guard CCFP-trained air MEDEVAC unit from December 2008 to October 2009. Both the EMT-B units and the Army National Guard CCFP unit were deployed in the same areas in Afghanistan.

All cases included in the study were United States, coalition, and host national civilian patients who were evacuated by the air MEDEVAC units with an injury severity score (ISS) equal to or greater than 16. Casualties were excluded from the study if they had an ISS of less than 16, if they were nontrauma (e.g., psychological health), or if they were prisoners or detainees.

The following physiological parameters were obtained once the casualties arrived to the CSH: vitals SBP, DBP, HR, Temp, Respiration Rate (RR), SpO2, HCT, and BD. The disposition of the casualties transported (i.e., died on arrival, died of wounds) at 48 hours was also obtained.

The data analysis was performed using SAS 9.2 software (Cary, North Carolina), and continuous variables were evaluated using a Student's t-test. All categorical variables were compared using a c2 test, and for covariates with less than five samples per field, a Fisher's exact test was used. Differences were determined to be significant at p < 0.05.

RESULTS The number of cases who met criteria for inclusion in the study was 788. The EMT-B group had 546 cases, and the CCFP group had 242 cases. Of these cases, 97 were excluded from the EMT-B group and 20 from the CCFP because of inadequate documentation to make a determination for analysis. These exclusions left449 cases in the EMT-B group and 222 cases in the CCFP group for evaluation and analysis (Fig. 1).

A Student's t-test (2-tailed) for independent samples was performed; it revealed that three of the physiological parameters, HCT, BD, and SpO2, were statistically significant ( p < 0.05).

The rest of the physiological parameters (SBP, DBP, HR, Temp, and RR) were not statistically significant (Table II).

Of the 671 cases that met the criteria, data were missing on two cases, leaving 669 for analysis. The parameter, 48-hour mortality (dead versus alive) for the EMT-B and the CCFP group was compared, and it was found that the CCFP group had a lower mortality rate than the EMT-B group. Out of 222 patients transported by the CCFP group, 11 (5%) died at 48 hours, whereas of 447 patients transported by the EMT-B group, 71 (16%) died at 48 hours. A c2 test revealed a statistical significance between the CCFP group and the EMT-B group [c2 (1, N = 669) = 16.47, p < 0.001] with a Cramer's V = 0.16, p < 0.001 with an odds ratio of 0.28 [95% confidence interval (CI) (0.14) (0.53)], which is a 72% reduction in mortality for casualties who were transported by CCFP (Table III).

To minimize bias, the ISS was analyzed to see whether there was a difference in the ISS between the two groups, which would account for the outcomes at 48 hours. The analysis showed that 671 cases met the criteria, but 659 cases were used for analysis because of missing ISS data. The EMT-B group (N = 4 42) had a mean of 25.00 (SD = 9.67) and the CCFP group (N = 219) a mean of 25.34 (SD = 9.28). Student's independent samples t-test was performed; it revealed that there was no statistical significance between the means t(659) = 0.43, p = 0.66 with a mean difference of 0.34 [95% CI (-1.89) (1.21)].

DISCUSSION To our knowledge, this study is the first of its type to compare MEDEVAC outcomes-physiological parameters and survival as a function of the level of training (EMT-B versus CCFP). This retrospective study suggests that casualties who had an ISS greater than 16 and who were transported by the CCFP group had a statistically significant improvement in HCT, BD, and SpO2 and 48-hour survivability when compared to the EMT-B group. There was no statistically significant change between the vitals (SBP/DBP/HR/Temp/RR) of the two groups.

The HCT by far was the most statistically significant parameter between the groups with a p < 0.001. The mean HCT for the EMT-B group was 33.1 (SD = 11.4) compared to the mean HCT of the CCFP group of 36.5 (SD = 4.8). The change in HCT was also clinically significant because there is a mean difference of 3.35, which correlates to the amount of change that one unit of blood administered would change the HCT. There are two possible explanations as to why the CCFP group had a better HCT than the EMT-B group. First, it is possible that with the CCFPs' more extensive training and experience, they reduced overall blood loss, either by controlling bleeding more quickly or more effectively, when compared to the EMT-B group. Martin et al24 discovered that 47% of patients transported in Iraq from January 2007 to January 2008 had delays in hemorrhage control during transport. The Defense Health Board concluded in a document titled "Tactical Evacuation Care Improvements within Department of Defense 2011-03" that trauma training and experience play a critical role in survival outcomes especially in instances of polytrauma. 25 Part of the training of a CCFP is hands-on training in an ICU setting where the CCFP is required to undergo hemodynamic monitoring and management. This specific hands-on training of hemodynamic monitoring and management is not part of the AFM EMT-B training program.

Another reason for lower HCT is significant volume expansion with crystalloid fluid causing dilutional anemia. A recent process improvement project that was conducted in theater among evacuation units in Afghanistan showed that nearly all casualties transported received a routine infusion of crystalloids and that less than 10% of those with significant hemorrhage received the appropriate fluid therapy in accordance with tactical combat casualty care (TCCC) guidelines.26 According to Alam et al,27 infusion of large amount of crystalloids can result in significant lactic acidosis, dilutional anemia, and thrombocytopenia. Also according to Alam et al,27 large doses of hetastarch fluid in trauma patients could result in worsening coagulopathy. Another reason for a discrepancy in the fluid management is that the CCFP group not only had formalized certification, didactics, and hands-on training, but also had 9 years of trauma experience.

A confounder to the HCT is the fluid resuscitation. During the time frame that this study looks at, there is a discrepancy between the AFM's standard operating procedures (SOPs) and the recommended algorithm of fluid resuscitation for combat casualties published by the U.S. Special Operations Command, TCCC Committee (August 2002)26 (Table IV) and the AFM's SOPs. The AFM's SOPs advocate a hypotensive resuscitation but does not completely follow the TCCC committee's guidelines for fluids. The AFM's SOPs advocate that a crystalloid bolus of 1 L could be used first and up to 2 to 3 times or a 500 mL bolus of colloid 1 to 2 times (Figure 2).28 Unfortunately, there were no CCFP group's SOPs that were available for comparison in this study.

Another statistically significant physiological parameter was the BD (p = 0.012). The mean BD in the EMT-B group at -4.38 (SD = 5.5) was worse than the mean BD in the CCFP group at -3.2 (SD = 4.7). A BD >-4 could be clinically significant. Kincaid et al29 noted that patients who maintained a BD >-4 had an increase in mortality and lower oxygen consumption at 48 hours. Smith et al30 noted that patients with a BD > -4 and lactate > 1.5 on admission to the ICU had a sensitivity of 80.3% and a specificity of 58.7% for mortality. Niles et al31 showed that soldiers injured in combat who present to the emergency department of the CSH with an ISS >15 and a BD > -6 and who were coagulopathic were known to have an increased mortality rate.

The mean SpO2 was also statistically significant between the EMT-B group and the CCFP group but not clinically significant. The CCFP group SpO2 mean of 97.83 (SD = 4.8) was higher than the EMT-B group mean of 96.25 (SD = 10.9).

There was no difference between the average vital parameters (SBP, DBP, HR, RR, and Temp) between the CCFP group and the EMT-B group. The reason could be that soldiers are generally younger and have better health; therefore, they have a better physiological reserve. This ability to preserve their physiological status makes it difficult to assess their level of shock. Their vitals do not necessarily show the amount of tissue ischemia that is ongoing. Young patients can essentially have approximately 40% blood loss of their normal circulating volume before they reach vascular collapse.32 The 48-hour survivability was 95% in the CCFP group versus 85% for the EMT-B group. The CCFP group had an odds ratio of 0.28 [95% CI (0.14) (0.53)], which is a 72% reduction in mortality for casualties who were transported by CCFP group.

A look at the ISS score showed that there was no statistical significance in the injured who were transported between the two groups (p = 0.66). The mean ISS score for the CCFP group was 25.34 (SD = 9.28), and the mean ISS score of the EMT-B group was 25.00 (SD = 9.67). Based on this score, there is no evidence that the EMT-B group was transporting more seriously injured patients that could be accounting for the differences in outcomes.

LIMITATIONS Since this study was retrospective, some constraints limited data collection. Currently, there is not a system or a prehospital database to obtain data from which to compare the casualties' vitals from the POI through the transport to arrival to the emergency department. There were not adequate data from which to determine what treatments were performed at the POI and which treatments were conducted in transport. This lack of data hinders the study because there is currently no way to determine what treatments were provided enroute (amount of crystalloid/colloid or blood products given) or what level of training and experience of the individual who provided care to the wounded enroute to the CSH. In January 2010, the Army started to have a physician, physician assistants, and nurses to provide care while en route. This change could have altered the data for the EMT-B group and the CCFP group, which could have potentially improved the physiological parameters and the 48-hour survivability.

The main reason that we used BD over blood lactate as a measure to assess physiology is that the blood lactate was not available in the Joint Theater Trauma Registry. Elliot states that in young trauma patients, the BD and the blood lactate are essentially the same and have the same correlation as to a state of shock.33 The other reason is to keep in line with other studies that have used BD as an indicator of shock to help validate the findings in this research.31,34 The other parameter that we used was HCT. We did not look at hemoglobin because there was no utility in obtaining both. According to Nijboer et al,35 HCT and hemoglobin respond the same in the trauma patient, and there is no need to evaluate ongoing blood loss using both. The standard vitals (SBP/DBP/ HR/RR/SpO2/Temp) were chosen for evaluation because they are generally measured in all of the cases we looked at, and also because it was important to know whether there were any significant changes between the two groups that could have resulted in an improved outcome.

The ISS between the groups was compared, but evacuation times were not compared to see whether they could have made a difference. Since each EMT-B group and the CCFP group operated in the same area of operations, flight times would be the same. According to McLeod et al,36 the average evacuation time for Afghanistan is approximately 2 hours; therefore, evaluating evacuation times would not have made a difference in outcome.

Data were also not obtained about physiological parameters through the 48-hour period once casualties arrived to the CSH because outcome would be more associated with the treatment that the casualty received from the CSH than with the treatment received from the EMT-B or the CCFP.

CONCLUSION This study suggests that in Afghanistan, air MEDEVAC from field to CSH showed improvements in 48-hour survival, and clinically significant differences in HCT and BD, when using medics with a higher level of training and experience (CCFP versus EMT-B). This study supports the 40 after-action reviews that have been written since 2002 for Operation Enduring Freedom and Operation Iraqi Freedom that have called for AFMs to have paramedic training and more experience.37,38 Even when it has been proposed to place a provider on board a helicopter to transport patients, the provider needs to be appropriately trained in emergency medicine and/or critical care and have the necessary experience to transport the casaulty.39-43 Training and experience appear to be key to improved outcomes.

There is very little literature about prehospital care, particularly prehospital care in combat. Currently, most civilian prehospital guidelines are not based on scientific evidence, therefore making it difficult to fully evaluate treatments and/or even establish scientifically based clinical practice guidelines for prehospital care.43 Even though experience and training appear to be influential components to improved outcome, future research needs to be performed by collecting prehospital data better and looking at multiple factors such as vital signs, interventions used at the POI and enroute, the level of training/experience of the person providing care, lab values, and a 48-hour survivability window. If trauma research is looked at as a continuum from the POI to discharge from the hospital, better clinical practice guidelines could be established to improve training and outcomes in casualties.

ACKNOWLEDGMENTS The authors thank the faculty of the Department of General Surgery at Brook Army Medical Center and the U.S. Army Institute for Surgical Research for their critical feedback of this work.

TABLE IV. U.S. Special Operations Command, TCCC Committee Fluid Resuscitation for Combat Casualties (August 2002) 1. Superficial wounds (50% of injured): No immediate Intravenous (IV) access or fluid resuscitation is required.

2. Any significant extremity or truncal wound (neck, chest, abdomen, or pelvis) with or without obvious blood loss and irrespective of pulse character: (a) If the soldier is coherent and has a palpable radial pulse, blood loss has likely stopped. (b) Start a saline lock; hold fluids; reevaluate as frequently as situation allows.

3. Significant blood loss from any wound and the soldier either has no palpable radial pulse or is not coherent (note: mental status changes resulting from blood loss only, not head injury): A. Stop the Bleeding: Direct pressure/hands and gauze rolls, with or without adjuncts such as Ace bandages are the primary methods. In addition, various advanced hemostatic dressings will soon be available. Extremity injuries may require temporary use of an effective arterial tourniquet. However, 90% of hypotensive casualties suffer from truncal injuries, not amendable to either of these strategies.

B. After hemorrhage is controlled to the extent obviously possible, obtain IV access and start 500 mL Hextend (1 bag).

1. If the casualty's mental status improves and a palpable radial pulse returns (a positive response), hold fluids.

2. If no response is seen, give an additional 500 mL Hextend. If a positive response is obtained, stop fluids.

C. Titrating fluids is desirable but may not be possible, given the tactical situation. Likewise, the rate of infusion is likely to be difficult to control. On the basis of the effective volume of Hextend versus lactated Ringer's, no more than 1,000 mL of Hextend should be given to any one casualty (approximately 10 mL/kg). This amount is intravascularly equivalent to 6 L of lactated Ringer's. If the casualty is still unresponsive and without a radial pulse after 1,000 mL of Hextend, consideration should be given to triaging supplies and attention to more salvageable casualties.

4. Based on response to fluids, casualties will separate themselves into responders, transient responders, and nonresponders.

A. Casualties with a sustained response to fluids probably have had significant blood loss but have stopped bleeding. These casualties should be evacuated at a time that is tactically judicious.

B. Transient- and nonresponders are most likely continuing to bleed. They need evacuation and surgical intervention as soon as tactically feasible. If rapid evacuation is not possible, the medic may need to triage his attention, equipment, and supplies to other casualties as determined by the tactical situation. No more than 1,000 mL Hextend should be given to any one casualty.

5. Head injuries impose special considerations. Hypotension (SBP 90 mm Hg) and hypoxia (SpO2 90%) are known to exacerbate secondary brain injury. Both are exceedingly difficult to control in the initial phases of combat casualty care. Given current recommendations on the care of head injury, hypotensive resuscitation as outlined above for the soldier with obvious head injuries cannot be recommended.

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CPT Seth R. Holland, SP USA*; Amy Apodaca, PhD*; LTC Robert L. Mabry, MC USA* *U.S. Army Institute for Surgical Research, 3698 Chambers Pass, Building 3611, Fort Sam Houston, TX 78234-6315.

The authors have no financial or proprietary interest in the subject matter and no other identifiable conflict of interest. This work was conducted under a protocol approved by the institutional review board at the U.S. Army Medical Research and Materiel Command, Fort Detrick, Maryland.

doi: 10.7205/MILMED-D-12-00286 (c) 2013 Association of Military Surgeons of the United States

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