Tra u m a R e s u s c i t a t i o n and Monitoring Military Lessons Learned Elizabeth J. Bridges, PhD, RN, CCNSa,*, Margaret M. McNeill, PhD, RN, APRN-CNS, CCRN, CCNS, NE-BC, CIPb,c KEYWORDS Monitoring/physiologic Combat casualty care Military medicine Wounds Injuries KEY POINTS Systolic blood pressure (SBP) and heart rate (HR) are not sensitive indicators of hypoperfusion. Hypoperfusion may begin with an SBP of 100 to 110 mm Hg. Shock index is a more sensitive and specific indicator of hypoperfusion than SBP or HR alone. New dynamic, noninvasive monitors may provide earlier and more sensitive indications of deterioration or occult hypoperfusion.
The management of a patient with a severe injury requires careful resuscitation and astute monitoring. The principles of trauma management have evolved over the past several years, partly due to the military experiences in the care of casualties in Iraq and Afghanistan.1 The United States and coalition partners have demonstrated an unprecedented reduction in combat-related deaths, despite an increase in injury severity. Within the context of a 7000-mile-long continuum of care from the point of injury to the United States and the new practices associated with damage-control resuscitation, this article draws on military research regarding the limitations of current vital sign monitoring and introduces innovative monitoring technologies that may be beneficial in severely injured patients.
The authors have nothing to disclose. a Biobehavioral Nursing and Health Systems, University of Washington School of Nursing, Box 357266, Seattle, WA 98195, USA; b University of Washington Medical Center, Seattle, WA, USA; c Department of Professional and Clinical Development, Frederick Memorial Hospital, 400 West Seventh Street, Frederick, MD 21701, USA * Corresponding author. E-mail address: [email protected] Crit Care Nurs Clin N Am 27 (2015) 199–211 http://dx.doi.org/10.1016/j.cnc.2015.02.003 ccnursing.theclinics.com 0899-5885/15/$ – see front matter Ó 2015 Elsevier Inc. All rights reserved.
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MILITARY TRAUMA CARE ACROSS THE CONTINUUM
The Joint Theater Trauma System (JTTS) was developed with the vision that every soldier, marine, sailor, and airman injured on the battlefield will have the optimal chance for survival and maximum potential for functional recovery. The military trauma care continuum begins at the point of injury and extends to definitive care in the United States (Fig. 1).2 In this system, medical capabilities are as close to the battlefield as possible,3 resulting in the need to provide critical care, including damage-control resuscitation, during transport for the patients.4,5 Global en route care and the Air Force Critical Care Air Transport Teams (CCATTs) have revolutionized combat critical care. The CCATTs, with a critical care physician, nurse, and respiratory therapist, transport patients in a cargo aircraft on missions that range from 1 to 18 hours, with most flights 6 to 8 hours long.6 During the Vietnam War, patients were evacuated from theater to a remote hospital in 21 days; with the CCATTs, the average time to transport after an injury is 28 hours, and often as little as 12 hours.3 Rapid movement of critically injured casualties (average Injury Severity Score 23.7) within hours of wounding is safe, with a minimal mortality during movement (0.02%). These patients have a 30-day mortality (2.1%) that is independent of the time from injury to arrival at definitive care.7 Among 1491 patients transported by CCATT, 69% suffered polytrauma, primarily due to explosions. The injuries are complex, including soft tissue trauma (64%), orthopedic (45%), thoracic (35%), skull fracture (27%), and brain injuries (25%).8 These patients, who may be stabilizing but not stable, require ongoing interventions and monitoring during the en route phase of care, which is challenging given the austere and dynamic conditions onboard an aircraft. The integration of new research and practice on the battlefield and during transport, and a system to support care across the 7000-mile continuum from the battlefield to the United States, has been instrumental in the unprecedented survival rate for combat casualties.9–12
Fig. 1. Military en route care continuum. The US military en route care system begins at the point of injury and extends to definitive care in the United States. Along the continuum, care is provided at military trauma hospitals and by highly specialized transport teams onboard military ground, sea, and air transports. (Adapted from Chairman Joint Chiefs of Staff (CJCS). Health service support (Joint Publication 4–02). 2012. Available at: http:// www.dtic.mil/doctrine/new_pubs/jp4_02.pdf. Accessed November 15, 2014.)
Trauma Resuscitation and Monitoring
THE GOAL OF TRAUMA RESUSCITATION: CONTROL THE TRAUMA TRIAD
Traumatic injuries may result in death or severe disability unless the trauma team is able to control life-threatening complications known as the Trauma Triad of Death: hypothermia, acidosis, and coagulopathy.13 In trauma patients, even after controlling for injury severity and other confounders, hypothermia remains an independent predictor of mortality (odds ratio [OR]1.19; 95% confidence interval [CI] 1.05–1.35),14 with mortality associated with hypothermia-associated coagulopathy and inflammatory effects.15 Severe acidosis (eg, pH 0.3 may indicate occult blood loss (ie, blood loss with hypoperfusion despite a normal SBP and HR) In patients with normal vital signs, the addition of the SI does not identify patients in need of life-saving interventions45 The SI may be attenuated in cases of moderate to severe traumatic brain injury46 Data from Refs.44–46
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was no significant difference in the mean arterial pressure (MAP) between survivors and nonsurvivors, and in both groups, the MAP was within normal limits. Both groups were tachycardic, with nonsurvivors having a higher HR. In contrast to the nonpredictive changes in the MAP and HR, there was a significant difference in tissue perfusion, as indicated by transcutaneous oxygen (PtcO2) and carbon dioxide levels (PtcCO2). The nonsurvivors had lower PtcO2 values and higher PtcCO2 compared with survivors. The survivors who developed organ failure had longer periods of hypoperfusion compared with survivors who did not develop organ failure (31 vs 5 minutes and 17 vs 1 minute, respectively). Patients with more than 60 minutes of decreased tissue perfusion had a mortality of 89% and a 100% incidence of organ failure or sepsis.50 This study highlights that even short periods of hypoperfusion increase the risk for multisystem organ failure and death and, given the limitations of standard vital signs and intermittent laboratory values, emphasizes the need for more sensitive, real-time measures to assess a patient’s perfusion status. Systolic Blood Pressure
A common assumption is that an SBP less than 90 mm Hg is the threshold for the onset of hypoperfusion. In a study of data from 870,634 patients in the National Trauma Data Bank, the onset of hypoperfusion, as indicated by an increase in base deficit above baseline, occurred when the SBP decreased below 118 mm Hg and mortality increased 6% for every 10 mm Hg decrease in SBP below 115 mm Hg.44 When the SBP was 90 mm Hg, the average base deficit was 8 mmol/L, indicating moderately severe occult hypoperfusion despite a “normal” SBP. Similar results were found in 7180 military combat trauma casualties.51 In these patients, the base deficit began to increase when the SBP decreased below 100 mm Hg, and the mortality increased by 4% with an admission SBP of 90 to 100 mm Hg compared with patients with an admission SBP of 101 to 110 mm Hg. Shock Index
The shock index (SI), which is the ratio of HR to SBP (SI 5 HR/BP), is inversely related to blood loss, cardiac index, stroke volume, MAP, left ventricular stroke work, and oxygen delivery.52 In general, an SI 0.9 is considered abnormal, thus any time the HR is greater than the SBP, the SI will be abnormal, and further evaluation of the patient is warranted. For example, if a patient has an HR of 120 and an SBP of 100 mm Hg, the SI is 1.2 beats per mm Hg. More specific SI ranges,53,54 which are consistent with increasing base deficit (sp) and lactate, are as follows:
SI SI SI SI
The management of a patient with a severe injury requires careful resuscitation and astute monitoring. The principles of trauma management have evolved over the past several years, partly due to the military experiences in the care of casualties in Iraq and Afghanistan.1 The United States and coalition partners have demonstrated an unprecedented reduction in combat-related deaths, despite an increase in injury severity. Within the context of a 7000-mile-long continuum of care from the point of injury to the United States and the new practices associated with damage-control resuscitation, this article draws on military research regarding the limitations of current vital sign monitoring and introduces innovative monitoring technologies that may be beneficial in severely injured patients.
The authors have nothing to disclose. a Biobehavioral Nursing and Health Systems, University of Washington School of Nursing, Box 357266, Seattle, WA 98195, USA; b University of Washington Medical Center, Seattle, WA, USA; c Department of Professional and Clinical Development, Frederick Memorial Hospital, 400 West Seventh Street, Frederick, MD 21701, USA * Corresponding author. E-mail address: [email protected] Crit Care Nurs Clin N Am 27 (2015) 199–211 http://dx.doi.org/10.1016/j.cnc.2015.02.003 ccnursing.theclinics.com 0899-5885/15/$ – see front matter Ó 2015 Elsevier Inc. All rights reserved.
200
Bridges & McNeill
MILITARY TRAUMA CARE ACROSS THE CONTINUUM
The Joint Theater Trauma System (JTTS) was developed with the vision that every soldier, marine, sailor, and airman injured on the battlefield will have the optimal chance for survival and maximum potential for functional recovery. The military trauma care continuum begins at the point of injury and extends to definitive care in the United States (Fig. 1).2 In this system, medical capabilities are as close to the battlefield as possible,3 resulting in the need to provide critical care, including damage-control resuscitation, during transport for the patients.4,5 Global en route care and the Air Force Critical Care Air Transport Teams (CCATTs) have revolutionized combat critical care. The CCATTs, with a critical care physician, nurse, and respiratory therapist, transport patients in a cargo aircraft on missions that range from 1 to 18 hours, with most flights 6 to 8 hours long.6 During the Vietnam War, patients were evacuated from theater to a remote hospital in 21 days; with the CCATTs, the average time to transport after an injury is 28 hours, and often as little as 12 hours.3 Rapid movement of critically injured casualties (average Injury Severity Score 23.7) within hours of wounding is safe, with a minimal mortality during movement (0.02%). These patients have a 30-day mortality (2.1%) that is independent of the time from injury to arrival at definitive care.7 Among 1491 patients transported by CCATT, 69% suffered polytrauma, primarily due to explosions. The injuries are complex, including soft tissue trauma (64%), orthopedic (45%), thoracic (35%), skull fracture (27%), and brain injuries (25%).8 These patients, who may be stabilizing but not stable, require ongoing interventions and monitoring during the en route phase of care, which is challenging given the austere and dynamic conditions onboard an aircraft. The integration of new research and practice on the battlefield and during transport, and a system to support care across the 7000-mile continuum from the battlefield to the United States, has been instrumental in the unprecedented survival rate for combat casualties.9–12
Fig. 1. Military en route care continuum. The US military en route care system begins at the point of injury and extends to definitive care in the United States. Along the continuum, care is provided at military trauma hospitals and by highly specialized transport teams onboard military ground, sea, and air transports. (Adapted from Chairman Joint Chiefs of Staff (CJCS). Health service support (Joint Publication 4–02). 2012. Available at: http:// www.dtic.mil/doctrine/new_pubs/jp4_02.pdf. Accessed November 15, 2014.)
Trauma Resuscitation and Monitoring
THE GOAL OF TRAUMA RESUSCITATION: CONTROL THE TRAUMA TRIAD
Traumatic injuries may result in death or severe disability unless the trauma team is able to control life-threatening complications known as the Trauma Triad of Death: hypothermia, acidosis, and coagulopathy.13 In trauma patients, even after controlling for injury severity and other confounders, hypothermia remains an independent predictor of mortality (odds ratio [OR]1.19; 95% confidence interval [CI] 1.05–1.35),14 with mortality associated with hypothermia-associated coagulopathy and inflammatory effects.15 Severe acidosis (eg, pH 0.3 may indicate occult blood loss (ie, blood loss with hypoperfusion despite a normal SBP and HR) In patients with normal vital signs, the addition of the SI does not identify patients in need of life-saving interventions45 The SI may be attenuated in cases of moderate to severe traumatic brain injury46 Data from Refs.44–46
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was no significant difference in the mean arterial pressure (MAP) between survivors and nonsurvivors, and in both groups, the MAP was within normal limits. Both groups were tachycardic, with nonsurvivors having a higher HR. In contrast to the nonpredictive changes in the MAP and HR, there was a significant difference in tissue perfusion, as indicated by transcutaneous oxygen (PtcO2) and carbon dioxide levels (PtcCO2). The nonsurvivors had lower PtcO2 values and higher PtcCO2 compared with survivors. The survivors who developed organ failure had longer periods of hypoperfusion compared with survivors who did not develop organ failure (31 vs 5 minutes and 17 vs 1 minute, respectively). Patients with more than 60 minutes of decreased tissue perfusion had a mortality of 89% and a 100% incidence of organ failure or sepsis.50 This study highlights that even short periods of hypoperfusion increase the risk for multisystem organ failure and death and, given the limitations of standard vital signs and intermittent laboratory values, emphasizes the need for more sensitive, real-time measures to assess a patient’s perfusion status. Systolic Blood Pressure
A common assumption is that an SBP less than 90 mm Hg is the threshold for the onset of hypoperfusion. In a study of data from 870,634 patients in the National Trauma Data Bank, the onset of hypoperfusion, as indicated by an increase in base deficit above baseline, occurred when the SBP decreased below 118 mm Hg and mortality increased 6% for every 10 mm Hg decrease in SBP below 115 mm Hg.44 When the SBP was 90 mm Hg, the average base deficit was 8 mmol/L, indicating moderately severe occult hypoperfusion despite a “normal” SBP. Similar results were found in 7180 military combat trauma casualties.51 In these patients, the base deficit began to increase when the SBP decreased below 100 mm Hg, and the mortality increased by 4% with an admission SBP of 90 to 100 mm Hg compared with patients with an admission SBP of 101 to 110 mm Hg. Shock Index
The shock index (SI), which is the ratio of HR to SBP (SI 5 HR/BP), is inversely related to blood loss, cardiac index, stroke volume, MAP, left ventricular stroke work, and oxygen delivery.52 In general, an SI 0.9 is considered abnormal, thus any time the HR is greater than the SBP, the SI will be abnormal, and further evaluation of the patient is warranted. For example, if a patient has an HR of 120 and an SBP of 100 mm Hg, the SI is 1.2 beats per mm Hg. More specific SI ranges,53,54 which are consistent with increasing base deficit (sp) and lactate, are as follows:
SI SI SI SI
