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Pain Following Battlefield Injury and Evacuation: A Survey of 110 Casualties from the Wars in Iraq and Afghanistan

Chester C. Buckenmaier III MD, Col., Christine Rupprecht RN, MSN, Geselle McKnight CRNA, MSN, Brian McMillan DO, Maj., Ronald L. White MD, Maj., Rollin M. Gallagher MD, MPH, Rosemary Polomano PhD, RN, FAAN
DOI: http://dx.doi.org/10.1111/j.1526-4637.2009.00731.x 1487-1496 First published online: 1 November 2009

ABSTRACT

Objective. Advances in regional anesthesia, specifically continuous peripheral nerve blocks (CPNBs), have greatly improved pain outcomes for wounded soldiers in Iraq and Afghanistan. Pain management practice variations, however, do exist, depending on the availability of pain-trained military professionals deployed to combat support hospitals. An exploratory study was undertaken to examine pain and other outcomes during evacuation and at Landstuhl Regional Medical Center (LRMC), Germany.

Design. A mixed-methods, semistructured interview survey design was conducted on a convenience sample of wounded U.S. soldiers evacuated from Iraq and Afghanistan to LRMC.

Setting and Patients. A total of 110 wounded soldiers evacuated from Iraq and Afghanistan from July 2007 to February 2008 completed a pain survey at LRMC. Data were collected on demographics, injury mechanism, last 24-hour average, least, and worst, and pain now by using a 0–10 scale, and percent pain relief (from 0% [No relief] to 100% [Complete relief]). Similar items and measures of anxiety, distress, and worry during flight transport were measured (from 0 [None] to 10 [Extreme]). Responses were analyzed by using descriptive and correlational statistics, multiple linear regression, Mann–Whitney U-tests, and t-tests. The Walter Reed Army Medical Center, Human Use Committee approved this investigation.

Results. Participants were typically male (99.1%), Caucasian (80%), and injured from improvised explosive devices (60%) and gunshots (21.8%). Average and worst pain scores were inversely correlated with pain relief during transport (r = −0.58 and r = −0.46, respectively; P < 0.001), and low to moderately positively correlated with increased anxiety, distress, and worry during transport (P < 0.05). Average percent pain relief achieved was 45.2% ± 26.6% during transport and 64.5% ± 23.5% while at LRMC (P < 0.001). Participants with CPNB catheters placed at LRMC reported significantly less pain right now (P = 0.031) and better pain relief (P = 0.029) than soldiers without CPNBs.

Conclusions. Our findings underscore the value of early aggressive pain management after major combat injuries. Increased pain was associated with increased anxiety, distress, and worry during transport, suggesting the need for psychological management along with analgesia. Regional anesthesia techniques while at LRMC contributed to better pain outcomes.

  • Combat Casualty Care
  • Pain
  • Continuous Peripheral Nerve Block
  • Pain Outcomes

Introduction

The discovery of morphine by Wilhelm Sertürner in 1804 coupled with Alexander Wood's development of the syringe and needle for subcutaneous injection forever changed the management of pain on the battlefield. These miraculous advances allowed, on demand, pain control that led to the liberal use of opiates by Civil War surgeons to treat combat casualties. Archives tracing history of the Civil War noted that opioid dependency rose among the war wounded, which was known as the “Soldier's Disease”[1]. Following the Civil War, little attention was paid to the problem of pain from combat injuries, and it was not until World War II that a landmark study of pain was carried out during 1943 and 1944 [2]. The motivation for this investigation was sparked by the increasing numbers of casualties with obvious clinical manifestations of morphine overdose leading, in many cases, to death. Importantly, this study was the first to heighten awareness of the concerning prevalence of pain caused by combat injuries. A prevailing assumption at the time was that most injured soldiers did not require analgesia prior to the arrival at the field hospital [3]. Subsequently, pain care of the wounded was essentially restricted to those who were hospitalized, and intravenous morphine became the mainstay for therapy. In conflicts that followed World War II, military pain management regimens remained predominately opioid based, with practice that is essentially static. Casualties continued to be managed within the war theater until they were “stable” enough for transport.

Attitudes about military pain management have only recently been transformed, with the striking realities of 21st century warfare in the Iraq and Afghanistan conflicts. While the lethality of weapons and severity of wounds have continued to increase, paradoxically, casualty survival from the current conflicts approaches 90%. The significance of this achievement is appreciated when compared with survival rates from previous conflicts, where 76% survived during the Vietnam War (1961–1973), 67% survived during the Civil War (1861–1865), and only 58% survived during the Revolutionary War (1775–1783) [4]. Increased survival noted in the current conflicts is attributable to many factors, such as advanced surgical care far-forward, improved surgical and critical care techniques, availability of blood products, body armor advances, and rapid air evacuation to major medical facilities outside of the war zone [5]. Speedy air transport, in particular, has placed greater emphasis on the need for improved pain management processes and technology, as traditional opioid-based pain management fails in the challenging air-evacuation environment [6].

Pain management in wounded soldiers from the Iraq and Afghanistan Wars has improved significantly from previous conflicts, with the introduction of continuous peripheral nerve block (CPNB) techniques and advances in medication delivery technologies [7–9]. However, currently, the application of specialized pain care for combat casualties is inconsistent and challenging due to insufficient numbers of trained military medical personnel available to specifically manage pain. Less than 10% of active duty anesthesiologists have been trained in pain medicine fellowship programs [10]. The delivery of pain care immediately following battlefield injuries is further complicated in the austere and dangerous combat environment by the lack of available equipment and supplies, prolonged evacuation times, and the need to prioritize life-saving measures [11]. An analysis of the types of procedures performed in the battlefield surroundings indicates that major surgical interventions are accomplished prior to evacuation to Landstuhl Regional Medical Center (LRMC) [12]. Of 290 orthopedic surgeries, 114 (40%) involved amputation and another 40% of vascular procedures (32 of 82) were considered major repairs. Despite these challenges, there is still urgency for early aggressive pain treatment to prevent or minimize the potential for the development of central changes that ensue in the initial phase of severe tissue injury and pain and contribute to many chronic pain syndromes [13–15].

Few studies have evaluated pain outcomes immediately after combat injuries and during evacuation. Presenting symptoms and mechanisms for pain have been reported for soldiers (N = 162) seeking medical care after evacuation from the battlefield in Iraq and Afghanistan, but only a small subset (17%) of the sample sustained injuries in combat [16]. A significant void currently exists in the literature regarding self-reported information on pain intensity levels, perceptions of pain relief, and psychological experiences early on following major combat trauma. The specific aim of this investigation was to determine the severity of pain and extent to which pain affected emotional status in soldiers who were evacuated to and treated at LRMC, Germany.

Materials and Methods

A mixed-methods, semi-structured interview survey design was conducted on a convenience sample of 110 wounded U.S. soldiers evacuated from Iraq and Afghanistan to LRMC from July 2007 to February 2008. During the study period, when clinician-coinvestigators were available at various times for 2- to 8-week tours of duty, eligible participants were approached to complete the survey. Of those approached, all agreed to participate. Participants were eligible for the study if they 1) sustained a major injury to one or more limbs; 2) arrived at LRMC by air transport; 3) were alert and capable of reporting current pain levels and recalling events during air transport from combat support hospitals; and 4) were experiencing pain and receiving analgesics. Injured soldiers are routinely screened for traumatic brain injury (TBI) at LRMC [17].

Those diagnosed with severe TBI were, for obvious reasons, excluded from the study. However, soldiers with mild TBI meeting the eligibility criteria were surveyed in our study. Soldiers who could not verbalize answers or understand questions about their pain were not approached to participate. Potential participants were identified for the study during routine pain rounds at LRMC. However, not all of them were being followed up by the anesthesiology pain service. A pain management clinical nurses specialist and anesthesiology pain fellows from the Walter Reed Army Medical Center (WRAMC) recruited and administered all study procedures. The study was approval by the WRAMC, Department of Clinical Investigation, Human Use Committee. The research met criteria for waiver of informed consent. All research procedures were in accordance and compliance with the Health Insurance Portability and Accountability Act regulations and WRAMC's policies and guidelines for the protection of human subjects. This included provisions for deidentifying all survey forms and avoiding the collection of any personal identifiers at the time of participant recruitment. All participants agreeing to participate were informed of the purpose for the study and of how the information would be used and disseminated to improve the pain care to soldiers sustaining injuries in combat.

Each participant completed a brief survey quantitating several pain outcomes and provided narratives about their pain and psychological experiences by interview techniques conducted by those collecting the data (Appendix). Demographic data, mechanisms of and circumstances surrounding the injury, and type of analgesic therapies received were recorded. The patient-reported survey form was developed by the investigators for the purposes of testing the tool in the context of this study.

The Pain Outcomes for Warriors Experiences Research (POWER) survey form includes dimensions of pain intensity (pain right now, average pain, and worst pain) measured by a numeric rating scale (0 = no pain, 10 = worst pain imagined), percent pain relief, and ratings for levels of anxiety, distress, and worry also captured by a numeric rating scale (0 = none, 10 = extreme). Various pain-related and emotional outcomes were measured by recall during their air transport experience. Additional information was collected to capture pain-related outcomes shortly after they were hospitalized at LRMC. This information included the type of analgesic therapy patients were receiving at the time of the interview, for example, systemic opioid analgesia with or without CPNB. Pain therapy with systemic multimodal analgesia (e.g., anticonvulsants or antidepressants) is rarely initiated in the early course of the treatment at LRMC. A global measure of pain control on a five-point scale (1 [poor] to 5 [excellent]) was also obtained to capture the perceived quality of pain management efforts. Opportunities were also provided for participants to write short narratives about their concerns, fears and worries during air evacuation and to comment on what could have been carried out to improve care on the aircraft. The results of these qualitative data are summarized in an abstract [18].

Responses to the survey were analyzed by using descriptive and correlational statistics and multiple linear regression to identify significant predictors for specific pain outcomes. Students' t-test for dependent groups was used to detect a significant difference in mean scores for perceptions of pain relief during transport and while at LRMC. By using the Mann–Whitney U-test, dimensions of pain intensity and pain relief were compared between participants receiving early CPNB catheters and those treated with systemic opioids alone. Internal consistency reliability for the POWER survey was assessed by using Cronbach's alpha, and construct validity was evaluated with principal component factor analyses. All statistics were performed by using SPSS v15.0 software (SPSS Inc., Chicago, IL).

Results

Participants' ages ranged from 19 to 43 years (average: 25 years ± 5). They were typically male (99.1%), Caucasian (80%), and most often wounded from an improvised explosive device (60%), gunshots (21.8%), or motor vehicle accident (5.4%). The majority, 93%, was hospitalized at LRMC for less than 8 days at the time the survey was administered, 85% of the sample was surveyed within 5 days of arriving to LRMC, and, for 93%, the length of stay was <8 days. All participants sustained limb injuries, with 39 (35.5%) having an injury to one arm, 5 (4.5%) having an injury to both arms, 55 (50%) with an injury to one leg, and 24 (21.8%) with an injury to both legs. Nine (8.1%) of these injured soldiered had significant trauma to both legs and an arm. At the time of the survey, seven had one or two limb amputations.

Soldiers' ratings of pain, anxiety, distress, and worry experienced during air evacuation by plane to LRMC are presented in Figure 1. Average (r = −0.58) and worst pain scores (r = −0.46) were negatively correlated with pain relief during transport (P < 0.001) and low to moderately positively correlated with increased anxiety, distress, and worry during transport (P < 0.01). Greater worry during transport (P < 0.05) and higher worst pain scores (P < 0.001) explained 71% (P < 0.001) of the variance in average pain levels during transport. Of the sample, 65% (N = 69) reported 50% or less pain relief during transport. No meaningful or statistically significant correlations were noted between pain relief, and each of the emotional components measured in the POWER survey for both participants with pain relief levels less than or equal to 50% and for those greater than 50%.

Figure 1

Recall of pain levels and psychological outcomes during transport to Landstuhl Regional Medical Center. NRS = numeric rating scale; SD = standard deviation of the mean.

Pain intensity scores at LRMC for pain right now and recall for average, worst, and least pain for the past 24 hours are provided in Figure 2. As expected, average pain in the last 24 hours significantly improved from recall during transport to reports when soldiers were surveyed at LRMC (mean 5.3 ± 2.3, 4.1 ± 1.8, respectively; P < 0.001). Percent pain relief scores (achieved by any means of pain treatment) also increased from the perceptions during transport (45.2 ± 26.6%) to the time while they are hospitalized at LRMC (64.5 ± 23.5%; P < 0.001). One-third of the soldiers indicated percent pain relief less than or equal to 50%.

Figure 2

Mean and median pain scores at Landstuhl Regional Medical Center. NRS = numeric rating scale; SD = standard deviation of the mean.

A comparison of pain levels during hospitalization between patients who did not have CPNB catheters (N = 83) and those who did (N = 27) is shown in Figure 3. Patients with CPNB catheters placed at LRMC had less pain right now than soldiers without CPNB catheters (P = 0.031). At LRMC, patients with CPNB catheters reported 74.0 ± 18.9% relief of pain compared with 61.7 ± 24.1% without CPNB (P = 0.029) (Figure 4). Patients who received CPNB at LRMC reported significantly better percent pain relief than those who did not, despite higher worst pain intensity scores at LRMC in the CPNB group (P = 0.012). No difference was found for global pain control (P = 0.182) between these two treatment groups.

Figure 3

Mean pain scores for patients who did not have continuous peripheral nerve block (CPNB) vs those received a CPNB at Landstuhl Regional Medical Center. Statistically significant differences are noted. NRS = numeric rating scale; SD = standard deviation of the mean.

Figure 4

Mean percent pain relief scores since arriving at Landstuhl Regional Medical Center for patients receiving CPNB vs no CPNB. CPNB = continuous peripheral nerve block.

Psychometric Testing of the POWER Survey

Psychometric properties for the POWER survey were analyzed in the context of this study. The ability for items in the instrument to detect differences to a degree supports construct validity. A principal component varimax rotation factor analysis was also performed to identify factor structures or item clusters. Three factor structures were identified with Eigen values >1, and, collectively, the 11 items explained a considerable amount of the variance in the measure, 70.7%. Factor loadings were considered acceptable to assignment on a factor if >0.40 [19]. Table 1 shows the mean values and standard deviations for each item along with the factor loading.

View this table:
Table 1

Mean (SD) numeric rating scale (NRS) scores, principal component factor loadings, and internal consistency reliability for items and/or subscales for the POWER survey

NRS Mean ± SDFactor Loading
LRMC pain outcomes (Cronbach's alpha: 0.79)
  Worst pain in the last 24 hours7.4 ± 2.40.731
  Least pain in the last 24 hours2.3 ± 1.80.770
  Average pain in the last 24 hours4.0 ± 1.80.876
  Pain right now3.4 ± 2.10.870
  Percent pain relief while in the hospital64.5% ± 23.5%0.578
Psychological outcomes during transport (Cronbach's alpha: 0.82)
  Anxiety during transport3.5 ± 3.40.872
  Distress during transport3.6 ± 3.40.897
  Worry during transport4.1 ± 3.50.763
Transport pain outcomes (Cronbach's alpha: 0.62)
  Average pain during transport5.3 ± 2.30.908
  Worst pain during transport6.8 ± 2.30.865
  Percent pain relief during transport45.2% ± 26.6%0.803
  • LRMC = Landstuhl Regional Medical Center; POWER = Pain Outcomes for Warriors Experiences Research; SD = standard deviation.

Internal consistency reliability was assessed for the instrument and subscales by using Cronbach's formula for coefficient alpha. Cronbach's alpha values of >0.70 were considered acceptable [19]. However, slightly lower alphas may be evident with small numbers of items in a cluster or subscale. Cronbach's alpha for the 11 items (excluding the global pain rating) was 0.81. Individual Cronbach's alphas for item clusters from the factor analysis are reported in Table 1. Item analyses were also conducted. Item-to-total correlations are generally considered good if above 0.3 [19]. All items except for the “percent pain relief” during transport and hospitalization, which were 0.28 and 0.20, respectively, were greater than 0.4. All items except for percent pain relief during transport lowered the overall Cronbach's alpha if deleted by as much as 0.037. If deleted, “percent pain relief during transport” only raised the alpha by 0.012. Consequently, all items were considered acceptable for internal consistency reliability.

Discussion

This survey is the first study to quantitate pain in combat casualties arriving by air transport from the battlefields in Iraq and Afghanistan. To our knowledge, this is also the first demonstration of a study on casualty acute pain levels and the impact of treatment in soldiers since World War II.

Rapid evacuation of critically wounded soldiers has been identified as a key factor in the improved survival of wounded soldiers in the current conflicts [20]. Despite recent advances in pain technology available to the soldiers, pain scores among the wounded who responded to this survey were high during air transport (>4 on a numeric rating scale) (Table 1). Pain intensity scores of 4 or less (mild pain) on an 11-point scale [21] are generally considered an acceptable goal of pain management in American military polytrauma patients. The lower mean percent relief of pain during transport, compared with the percent relief achieved at LRMC, confirms the conviction of many health care providers in the military concerning the difficulties of achieving successful pain management during medical evacuation flights. In fact, during transport, patients in this survey failed to achieve at least a 50% reduction in their pain. This suggests that more effective pain medicine strategies are needed in preparing injured soldiers for long evacuation flights. Moreover, it will be critical to design treatment approaches that not only alleviate constant pain but also provide more reliable relief from intense episodic or breakthrough pains encountered from turbulence, movement, or paroxysmal ectopic discharge from injured nerves. An earlier investigation of the use of oral transmucosal fentanyl citrate showed that rapid delivery and onset of action with those injured soldiers who are hemodynamically stable may be beneficial in treating pain in the combat or austere environments [22].

Average pain scores were significantly improved once the soldier arrived at LRMC. However, the samples' mean “worst pain” intensity score actually increased possibly as a result of higher pain intensity following surgical procedures at LRMC although the influence of this variable was not evaluated in the context of this study. These data support the conclusion that acute pain services are needed throughout the military evacuation chain. The ability to provide effective acute pain services assumes that designated personnel who are responsible for and trained to provide regular pain assessments and effective pain management are available [23].

Participants receiving CPNBs during their hospitalization at LRMC, despite higher “worst pain” intensity, reported significantly better percent pain relief (P < 0.05) since arriving there than those who did not receive CPNB. Patients with CPNB also had significantly less “pain right now” (P < 0.05) than patients without catheters. It is not clear why there was no significant difference in average pain levels between the treatment groups, given that the mean score for perceptions of pain relief was higher with CPNBs. Nonetheless, these findings indicate that CPNBs may play an important role in early aggressive management of pain following major limb injuries sustained in combat.

As expected, higher pain intensity scores correlated with higher anxiety, distress, and worry scores during transport. It is well known that acute pain is associated with psychological distress. Consequently, it is not surprising that soldiers with higher “worst pain” during transport might also be more worried about their pain control and its meaning in terms of injury severity and outcome. The contextual component of the concept of worry is examined more fully in a subsequent article in progress, describing the qualitative arm of the investigation with this sample of injured soldiers [18].

The impacts of preinjury psychological characteristics on the experience of acute pain in such dangerous conditions and psychological distress experienced during acute pain following injury are subjects of great importance for future research. Anxiety plays an important role as a mediating variable for increasing the perception of acute pain in experimental and clinical conditions [24–26]. Data from this study show considerable variations in emotional experiences and relationships to pain intensity, which underscore the importance of psychological preparation to reduce distress prior to and during transport as a helpful component of pain control. Further exploration of these psychological factors on soldier health, rehabilitation, and posttraumatic stress represents critical areas for future study.

Our survey methods do have limitations. First, the sample of survey participants is relatively small, and there was no consistency in the timing of offering the survey to soldiers as they arrived at LRMC. Clearly, not only was this a function of our ability to actively identify potential participants but also this was related to the readiness of soldiers who required medical and surgical interventions. Second, the survey was brief and included only measurement components believed to be critical to our understanding of their experiences. In the absence of instruments validated specifically for this population and environment, brevity, reduction of burden to participants during a difficult adjustment to life-altering injuries, and tolerability in completing an instrument to elucidate pain and psychological experiences remained a priority. Consequently, it was not possible to incorporate more specific measures of emotional and cognitive aspects of the pain experience. We did, however, obtain qualitative data, which will be useful in directing subsequent instrument development to evaluate the soldiers' experiences during transport [18]. Third, researcher resources to accomplish this investigation were limited by the responsibilities for also providing and coordinating pain care to this population. Last, surveys were offered to as many new patients that were identified as part of routine acute pain team visits during the times that clinician-coinvestigators were at LRMC and were available to recruit patients and conduct the study. Thus, a sampling bias may have existed with periodic data collection and exclusion of more severely wounded polytrauma soldiers who were critically ill and unable to participate early on during their hospitalization but may have been capable of doing so at a later time. This may have contributed to the underestimation of the severity of pain and psychological outcomes.

Notwithstanding these limitations, our data do suggest that there is opportunity to improve pain management of soldiers wounded in Iraq and Afghanistan. Importantly, our study highlights the need for better-designed, resourced, and administered surveys of wounded soldiers. It is somewhat surprising and concerning that work of this type has not been undertaken since the Second World War. The impact of poorly treated pain on the recovery and psychosocial function of wounded soldiers remains unknown. Without data immediately following combat injuries in the early treatment phase, it will not be possible to fully understand the benefits of early aggressive pain control on subsequent outcomes. Based on studies of the impact of early effective management of acute postoperative pain on preventing chronic pain syndromes and psychological morbidity in those at risk for these long-term problems [27–29], it is reasonable to assume that there are also significant advantages to implementing prompt successful pain interventions to avoid the long-lasting effects of combat injuries.

The POWER survey was easy to administer and complete, and this instrument should be considered as a measure to obtain information about soldiers' pain experiences. Future research must focus on ways to facilitate effective and efficient pain care in the austere combat environment and evacuation aircraft. More immediately, practice changes must occur to respond to pain and psychological distress. One suggestion for improving the pain care of wounded soldiers prior to evacuation flights would be the establishment of an acute pain service, with personnel at combat air staging facilities within the theaters of war whose primary roles would be to evaluate and treat pain and psychological distress in preparation for air-evacuation flights. Our data confirm the need for such a service, especially to control episodic or worst pains during the 6-hour air transport to LRMC. Another recommendation is the examination of the effects of ground and air interventions such as greater use of technology-supported pain care (e.g., patient-controlled analgesia), multimodal analgesia, and regional anesthesia/analgesia.

Footnotes

  • The opinions or assertions contained herein are the private views of the authors and are not to be construed as official or reflecting the views of the Department of the Army or the Department of Defense.

  • Financial Support: John P. Murtha Neuroscience & Pain Institute and Departmental

References

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