Triage and trauma workload in mass casualty: a computer model.

BACKGROUND: The aim of this study was to quantitatively analyze the impact of hospital triage on the workload of trauma teams in the Emergency Department during a mass casualty incident, using a computer model. METHODS: The inflow and triage of casualties into an Emergency Department with 5 trauma teams was modeled using the Monte Carlo method. Triage was represented as a binary classification task performed in one or two sequential steps. The input variables were triage accuracy (specificity and sensitivity) and casualty load, and the key output variable was the time to saturation (TTS) of the trauma teams, which was computed from the available and needed team minutes. RESULTS: The relationship between an increasing casualty load and the TTS describes a sigmoid-shaped curve. Improving triage accuracy extends the TTS and shifts the curve to the right. Switching to sequential competent triage (80% accuracy) results in TTS that is similar to perfect single-step triage (100% accuracy) but at the cost of investing less team time in urgent casualties. The optimal ratio of trauma teams to urgent casualties in sequential mode is 1:8, indicating that the treatment of urgent casualties must be delegated to reinforcement staff. CONCLUSIONS: This study introduces innovative tools for quantitative analysis of hospital triage in mass casualty incidents and shows how triage accuracy and mode affect the ability of trauma teams to cope with heavy casualty loads. These tools can be used to optimize the hospital response to future threats.

Comparison of conservative and operative treatment for blunt carotid injuries: analysis of the National Trauma Data Bank.

OBJECTIVES: Blunt carotid injury (BCI) is uncommon but potentially devastating. The best treatment modality for this injury remains undetermined. We conducted this study to better understand the hospital course and treatment outcomes for patients with BCI who received different interventions. METHODS: BCI and related vascular procedures were identified by ICD-9-CM codes from the National Trauma Data Bank(1) using data gathered from 2002 to 2006. Conservative and operative treatment groups were compared by variables of patient demographics, initial assessment in the emergency department (ED), hospital course, and treatment outcomes. Open surgical and endovascular interventions were further compared. RESULTS: A total of 842 BCI were identified from 1,633,126 discharged blunt trauma patients (0.05%). Of these, 762 (90.5%) were treated conservatively and 80 (9.5%) received operative intervention. No differences in demographics were observed between these treatment groups. On initial assessment, no differences between conservative and operative treatment groups were noted with regard to vital signs, Glasgow coma scale, presence of drugs or alcohol in blood, or Trauma Related Injury Severity Score survival probability. Significant differences were seen in terms of the presence of a base deficit (-3.1 +/- 6.8 vs -7.6 +/- 8.3; P = .01), likelihood of a positive head computed tomography (CT) scan (58.6% vs 26.1%; P = .003), and total Injury Severity Score (29.8 +/- 13.3 vs 26.1 +/- 14.1; P = .02). Hospital course and treatment outcomes were comparable, with no differences in hospital length of stay (13.4 +/- 15.3 days vs 13.7 +/- 13.6 days; P = .86), total Functional Independence Measure (8.8 +/- 3.3 vs 9.3 +/- 3.1; P = .38), progression of original neurologic insult (7.5% vs 4.6%; P = .61) or mortality (28.1% vs 19%; P = .08). When comparing open surgical to endovascular interventions (46 open, 34 endovascular, including 3 combined), the only significant differences were in the total Injury Severity Score (22.4 +/- 12.2 vs 31.4 +/- 15.4; P = .01) and length of intensive care unit (ICU) and hospital stay (5.0 +/- 6.0 days vs 10.7 +/- 10.4 days; P = .01, and 10.3 +/- 9.2 days vs 19.3 +/- 17.7 days; P = .01). Multivariate regression analysis confirmed that neither Functional Independence Measure (FIM) nor mortality was associated with conservative or operative treatment. CONCLUSION: BCI is rare and carries a poor prognosis. Operative intervention is not associated with functional improvement or a survival advantage. This study was unable to support that less invasive endovascular treatment improves treatment outcome when compared to open surgery.

Disasters and mass casualties: II. explosive, biologic, chemical, and nuclear agents.

Terrorists' use of explosive, biologic, chemical, and nuclear agents constitutes the potential for catastrophic events. Understanding the unique aspects of these agents can help in preparing for such disasters with the intent of mitigating injury and loss of life. Explosive agents continue to be the most common weapons of terrorists and the most prevalent cause of injuries and fatalities. Knowledge of blast pathomechanics and patterns of injury allows for improved diagnostic and treatment strategies. A practical understanding of potential biologic, chemical, and nuclear agents, their attendant clinical symptoms, and recommended management strategies is an important prerequisite for optimal preparation and response to these less frequently used agents of mass casualty. Orthopaedic surgeons should be aware of the principles of management of catastrophic events. Stress is less an issue when one is adequately prepared. Decontamination is essential both to manage victims and prevent further spread of toxic agents to first responders and medical personnel. It is important to assess the risk of potential threats, thereby allowing disaster planning and preparation to be proportional and aligned with the actual casualty event.

Disasters and mass casualties: I. General principles of response and management.

Disaster planning and response to a mass casualty incident pose unique demands on the medical community. Because they would be required to confront many casualties with bodily injury and surgical problems, surgeons in particular must become better educated in disaster management. Compared with routine practice, triage principles in disasters require an entirely different approach to evaluation and care and often run counter to training and ethical values. An effective response to disaster and mass casualty events should focus on an "all hazards" approach, defined as the ability to adapt and apply fundamental disaster management principles universally to any mass casualty incident, whether caused by people or nature. Organizational tools such as the Incident Command System and the Hospital Incident Command System help to effect a rapid and coordinated response to specific situations. The United States federal government, through the National Response Plan, has the responsibility to respond quickly and efficiently to catastrophic incidents and to ensure critical life-saving assistance. International medical surgical response teams are capable of providing medical, surgical, and intensive care services in austere environments anywhere in the world.

Timing of fluid resuscitation shapes the hemodynamic response to uncontrolled hemorrhage: analysis using dynamic modeling.

BACKGROUND: Timing of fluid resuscitation with respect to intrinsic hemostasis is an unexplored aspect of uncontrolled hemorrhage, because most animal models do not allow direct monitoring of blood loss. The aim of this study was to define how timing of crystalloid administration affects the bleeding patient's hemodynamic response to fluids, using a computer model of blood volume changes during uncontrolled hemorrhage. METHODS: A multi-compartment lumped-parameter deterministic model of intravascular volume changes in a bleeding adult patient was developed and implemented. The model incorporates empirical mathematical descriptions of intrinsic hemostasis and rebleeding. RESULTS: The predicted hemodynamic response to uncontrolled hemorrhage closely corresponds to that seen in animal studies. A 2-L crystalloid bolus given during ongoing hemorrhage increases blood loss by 4 to 29%, an effect that is inversely related to the initial bleeding rate. A similar bolus given after intrinsic hemostasis may trigger rebleeding if given when the hemostatic clot is mechanically vulnerable. This period of clot vulnerability (ranging from 0-34 minutes) changes with both the initial bleeding rate and the rate of fluid administration. CONCLUSIONS: The timing of crystalloid administration with respect to intrinsic hemostasis shapes the bleeding patient's hemodynamic response. An early bolus delays hemostasis and increases blood loss, while a late bolus may trigger rebleeding. These observations provide valuable insight into the hemodynamic response to fluid resuscitation.

Early aggressive closure of the open abdomen.

BACKGROUND: The aim of this series is to describe a new and aggressive approach to definitive closure of the open abdomen. METHODS: A retrospective review of 37 patients who underwent definitive abdominal closure using a combination of vacuum pack, vacuum-assisted wound management and human acellular dermal matrix (HADM). RESULTS: All patients' open abdomens were maintained with vacuum assisted wound management in attempts for primary closure. Once it was determined that the abdomen would not close primarily; it was closed with HADM and skin advancement. The mean duration of the open abdomen was 21.7 days (range 6-45), with an average of 127.78 cm of HADM, the largest number being 800 cm, with decreasing use of product later in the series. No major complications were seen with the repair. Superficial wound infection occurred with two patients that were easily treated with wet to dry dressing changes. No intraabdominal complications such as fistula or graft loss were seen. All patients left the hospital with an intact abdominal wall and skin. All 37 patients survived to discharge and were seen in follow-up within one month. No early hernia formation was seen at the one month follow up with the longest at three years. No abdominal wall complications were seen in subsequent follow up patients. CONCLUSIONS: Early aggressive closure of the open abdomen is possible with a combination of vacuum pack, vacuum-assisted wound management and HADM. Short term results are promising and warrant further study.

Impact of the 80-hour work week on resident emergency operative experience.

BACKGROUND: The goal of this study was to analyze the impact of the 80-hour work week on the emergency operative experience of surgical residents. METHODS: A 2-year retrospective comparison of the operative experience in emergency abdominal procedures of postgraduate year 4 and 5 residents in a city hospital before (group 1) and after (group 2) duty hour restriction. RESULTS: There was no difference between groups in the mean number of procedures performed as the primary surgeon, but group 2 showed a 40% decrease in technically advanced procedures with a 44% increase in basic procedures. The study also demonstrated a 54% decrease in the operative volume as first assistant. Operative continuity of care by residents decreased from 60% to 26% of cases. CONCLUSIONS: The ACGME regulatory environment is adversely affecting the emergency operative experience of surgical residents. Our findings underscore the need to develop alternative methods to augment the residents' operative experience.

How does casualty load affect trauma care in urban bombing incidents? A quantitative analysis.

BACKGROUND: The aim of this modeling study was to examine how casualty load affects the level of trauma care in multiple casualty incidents and to define the surge capacity of the hospital trauma assets. METHODS: The disaster plan of a U.S. Level I trauma center was translated into a computer model and challenged with simulated casualties based on 223 patients from 22 bombing incidents treated at an Israeli hospital. The model assigns providers and facilities to casualties and computes the level of care for each critical casualty from six variables that reflect the composition of the trauma team and access to facilities. RESULTS: The model predicts a sigmoid-shaped relationship between casualty load and the level of care, with the upper flat portion of the curve corresponding to the surge capacity of the trauma assets of the hospital. This capacity is 4.6 critical patients per hour using immediately available assets. A fully deployed disaster plan shifts the curve to the right, increasing the surge capacity to 7.1. Overtriage rates of 50% and 75% shift the curve to the left, decreasing the surge capacity to 3.8 and 2.7, respectively. CONCLUSION: This model defines the quantitative relationship between an increasing casualty load and gradual degradation of the level of trauma care in multiple casualty incidents, and defines the surge capacity of the hospital trauma assets as a rate of casualty arrival rather than a number of beds. The study demonstrates the value of dynamic computer modeling as an important tool in disaster planning.

Patterns of microbiology in intra-abdominal packing for trauma.

INTRODUCTION: This study tracks the microbiology of packs and infections in damage-control trauma patients to determine whether the packs cause infections. METHODS: The peritoneum and abdominal packs were cultured in patients who survived to re-operation. The study recorded all positive cultures, pack count, packing duration, number of operations, and infections. RESULTS: Thirty-five patients were studied. Twenty-eight patients survived; seven died. Packs were cultured in 29 patients. Data for 291 cultures collected. Pack cultures were positive in 20 patients and negative in nine. Positive pack cultures grew skin and gut flora. Twenty-one patients had infections, 14 did not. Organisms from positive pack cultures did not contribute to subsequent infections or mortality. Microbes and sites of infections were consistent with SICU patients. CONCLUSIONS: Intra-abdominal packs are contaminated with skin and gut flora. These contaminants, however, do not contribute to subsequent infections. Pathogens from subsequent infections were typical for ICU infections.

Minimizing dilutional coagulopathy in exsanguinating hemorrhage: a computer simulation.

BACKGROUND: Current massive transfusion guidelines are derived from washout equations that may not apply to bleeding trauma patients. Our aim was to analyze these guidelines using a computer simulation. METHODS: A combined hemodilution and hemodynamic model of an exsanguinating patient was developed to calculate the changes in prothrombin time (PT), fibrinogen, and platelets with bleeding. The model was calibrated to data from 44 patients. Time intervals to subhemostatic values of each coagulation test were calculated for a range of replacement options. RESULTS: Prolongation of PT is the sentinel event of dilutional coagulopathy and occurs early in the operation. The key to preventing coagulopathy is plasma infusion before PT becomes subhemostatic. The optimal replacement ratios were 2:3 for plasma and 8:10 for platelets. Concurrent transfusion of plasma with blood is another effective strategy for minimizing coagulopathy. CONCLUSION: Existing protocols underestimate the dilution of clotting factors in severely bleeding patients. The model presents an innovative approach to optimizing component replacement in exsanguinating hemorrhage.