usmle文件克氏外科学19版chapter

1、 CHAPTER 25THE SURGEONS ROLE IN MASS CASUALTY INCIDENTSAsher Hirshberg and Michael Steinmedical response to civilian mass casualty incidents and disasters from the perspective of the clinical surgeon practicing in a hos- pital that is part of a modern trauma system.KEY CONCEPTSClassification of Disa

2、sters and Implications for Trauma CareIn a mass casualty incident (MCI), a medical system is suddenly confronted by a large number of casualties needing care within a short period of time. This unexpected surge creates a discrep- ancy between the number of patients and the resources available to tre

3、at them. An MCI can be classified by cause (natural versus man-made), duration, location, and many other characteristics, but there is no single universally accepted classification of disas- ters. From the clinical perspective of medical care, it is important to distinguish among three classes of di

4、saster scenarios and understand the implications for trauma care (Table 25-1).1,2Multiple Casualty IncidentsThese involve dozens of casualties and can be effectively managed using local hospital resources. In other words, the arriving casu- alties strain the hospital resources beyond normal daily op

5、era- tions, but do not overwhelm them.Mass Casualty IncidentsThese involve hundreds of casualties arriving at a single institu- tion. Despite an effective disaster response, this number exceeds the capacity of the emergency department (ED) and the hospi- tal. As a result, some severely wounded patie

6、nts will not receive the level of care they require, and others will experience signifi- cant delays. Therefore, the term mass casualty implies some degree of failure to provide optimal trauma care to all severe casualties.Major Medical DisastersThese typically result in many thousands of casualties

7、 and destruction of organized commu support systems. In this scenario, the resources to treat critically injured casualties have been largely destroyed. External medical teams supported by appropriate logistic envelopes can make a difference in the man- agement of severely injured survivors, althoug

8、h help usually arrives late and deals primarily with delayed complications.In this chapter, MCI is used as a generic term describing a large-scale event. When referring to a specific disaster class or scenario (e.g., multiple casualty incident), it is fully spelled out.In the past decade, there has

9、been a surge of interest among surgeons in the medical consequences of mass casualty incidents and civilian disasters. The megaterrorist acts of 9/11 focused attention on the wave of urban terrorism that is sweeping across the globe, causing tens of thousands of casualties each year and challenging

10、trauma and emergency systems from New York to Bali and from Madrid to Mumbai. At the same time, a series of large-scale natural disasters, such as the 2004 tsunami in South- east Asia, which claimed almost 250,000 lives in 10 countries, and Hurricane Katrina, which devastated New Orleans in August 2

11、005, helped focus public attention on the medical consequences of natural catastrophes. As this chapter is being written, the horrible consequences of the Haiti earthquake in January 2010 are becoming clear and the unique challenges facing medical teams and other relief workers are the center of muc

12、h media attention.Until recently, the medical response to mass casualty inci- dents and disasters has not been part of the traditional body of knowledge of general surgery. However, as growing numbers of surgeons are involved in their institutions disaster planning, and treating casualties of urban

13、bombings, school shootings, train accidents, or natural disasters, interest in this topic has grown. Despite this increased interest, many surgeons remain unsure about their role in mass casualty incidents because they think of disasters primarily as logistic rather than medical chal- lenges. The pr

14、evailing view has always been that trauma care in disasters is similar to that in normal daily practice, only more of the same. This is a dangerous misconception. A mass casualty incident is a unique challenge to surgeons and trauma systems because the large number of casualties affects how individu

15、al patients are treated inside and outside the hospital. Furthermore, urban terrorism and natural disasters confront surgeons with unusual injury patterns and unique clinical problems not seen in their daily practice. Preparing for these challenges requires, therefore, not only special planning and

16、training but, most importantly, a different way of thinking about trauma care. The aim of this chapter is to provide a concise overview of the604key conceptsmass casualty and modern trauma systems clinical aspects of hospital disaster plans surgeons role in natural disastersblast trauma: clinical pa

17、tterns and system implicationsThe SurgeonS role in MaSS CaSualTy inCidenTS Chapter 25 6050%Probability of occurring within a year 100%FIGURE 25-1 graphic depiction of the inverse relationship between the magnitude of disaster scenarios and their frequency. although most surgeons will not encounter a

18、 major natural disaster during their careers, busy Friday nights are a regular feature in most urban trauma centers.The magnitude of a MCI is inversely related to its fre- quency (Fig. 25-1). The overwhelming majority of practicing surgeons will not encounter a major medical disaster in their commun

19、ities, whereas most hospitals occasionally face limited multiple casualty incidents. In fact, busy Friday nights, a single trauma team on call coping with a cluster of severely injured patients arriving together is situation that occurs frequently in every urban trauma center. It represents the lowe

20、rmost end of a spectrum of magnitudes, with a major earthquake or a devastat- ing Tsunami at the other extreme. The sad paradox of disaster preparedness is that the most time and effort is spent on prepar- ing and training for the largest and least likely doomsday sce- narios instead of improving th

21、e response to limited but more realistic threats.Injury Severity DistributionA key feature of every MCI is the injury severity distribution of the casualties. Regardless of the cause or magnitude of the MCI, only about 10% to 15% of survivors presenting to a hospital will be severely wounded, of who

22、m roughly one third will have immediate life-threatening injuries (Fig. 25-2). Most others sustain minor trauma or nonurgent injuries.3 For example, during the London subway bombings in July 2005, the Royal London Hospital received 194 casualties within 3 hours, but only 27 (14%) were severely injur

23、ed. Of these, only 8 casualties (4% of the total) were critically wounded.4 Although the death toll at the scene depends on the cause of the MCI, and is very high when structural collapse is involved, the injury severity distribution is a constant feature of MCIs. This means that even though the tot

24、al number of casualties may be high, the over- whelming majority will not require a high level of trauma care and are not urgent. These considerations form the rationale for planning an effective medical response.MASS CASUALTY AND MODERN TRAUMA SYSTEMSGoal of the Hospital Disaster ResponsesA well-kn

25、own underlying principle of medical disaster response is to do the greatest good for the greatest number of casualties, but it is crucial to understand the precise clinical implications of this principle for trauma care.Bearing in mind the injury severity distribution, a MCI is “a needle in a haysta

26、ck” situation in which a small group ofFIGURE 25-2 generic injury severity distribution for disaster scenar- ios. of all survivors arriving in the hospital, the overwhelming majority (85%) will have only minor injuries. of the severely injured (iSS > 9), only one third, or 1 in 20 arrivals, will

27、be critically injured with life- threatening injuries. This injury severity distribution forms the basis for planning the hospital disaster response.severely injured patients who require immediate high-level trauma care is immersed within a much larger group of casualties with minor injuries, who ca

28、n tolerate delays and even subopti- mal care without adversely affecting their outcome.1 The ulti- mate goal of the entire hospital disaster response is, therefore, to provide this small group of critically injured patients with a level of care that approximates the care provided to similarly injure

29、d patients on a normal working day. This goal has never been formally declared by the American College of Surgeons2 or any other professional organization, but it has always been implicitly understood by surgeons and trauma care providers and is certainly an expectation of the public. In a multiple

30、casu- alty incident, this goal can be achieved by effective triage and priority-driven trauma care. In a mass casualty incident, it can still be achieved by diverting trauma assets and resources from the less severely injured to the critically woundedbut at a cost. Contrary to popular belief, the ca

31、sualties whose management is delayed and compromised in a mass casualty scenario are not the mild ones but the severely injured patients with nonlife- threatening injuries.SECTION III TrauMa and CriTiCal CareMagnitude of eventMildSevere non- criticalCriticalMAJOR DISASTERMASS CASUALTYMultiple casual

32、ty“Busy Friday night”table 25-1 Classification of Disasters and Implications for trauma CaretOtaL NUMBer OFIMpLICatIONS FOr DISaSter CLaSSCaSUaLtIeStraUMa CareMultiple casualtyless than edStandards of care arecapacitymaintained for all severe casualties.Mass casualtyMore than edCare of some severeca

33、pacitycasualties is delayed or suboptimal.Major disastered and hospitalMost severely injuredoverwhelmedpatients die or survive without any medical care.606 SeCtION III TrauMa and CriTiCal Care100EDCTORICUSurge capacity80FIGURE 25-3 Schematic depiction of the trauma service line of a hospital. The se

34、rvice line consists of resource, assets, and facilities in which trauma care providers treat severely injured patients. The typical flow of a severely injured patient is from the trauma resuscita- tion bay of the ed to imaging, usually the CT scanner, then to the or, and finally to a surgical iCu be

35、d. Preserving this service line in the face of a large influx of severe casualties is the true goal of the hospital disaster response.604020005101520The Trauma Service Line in DisastersThere is a strange dissociation between the dramatic advances in trauma systems in the past 30 years and current di

36、saster plan- ning. The U.S. National Response Framework (NRF), which lays out the guiding principles for all levels of a unified national response to disasters, does not acknowledge the existence of trauma systems in the United States. Furthermore, most hospital disaster plans (including those of le

37、vel 1 trauma centers) do not refer specifically to the hospital trauma service or system, even though any effective disaster response must necessarily rely on them. Simply put, hospitals with 21st century trauma services and facilities have disaster plans that are still based on concepts of trauma c

38、are from the 1970s.Every modern trauma center establishes and maintains a dedicated trauma service line for severely injured patients during normal daily operations (Fig. 25-3). This service line includes trauma teams, assets, and facilities (e.g., resuscitation bays and operating rooms), all readil

39、y available to treat seriously injured patients. The trauma service line of a hospital provides the resources for optimal care of individual patients, but has limited capabilities to treat multiple badly injured patients simultane- ously. The goal of an effective disaster response is therefore to pr

40、eserve the hospital trauma service line in the face of an unusu- ally large number of casualties. From the trauma care perspec- tive, success in dealing with an MCI is not streamlining the flow of 40 or 60 casualties through the ED, but rather preserving the capability to pro ptimal trauma care to t

41、he three or four critically injured (but salvageable) casualties among them.5Casualty Load and Surge CapacityMany hospital administrators have an exaggerated view of the capacity of their institutions because hospital disaster planning is typically based on counting ED gurneys and hospital beds, rat

42、her than on the rate at which casualties are treated (or pro- cessed) by the hospital trauma system. In reality, as the MCI unfolds and progressively more casualties arrive, finding an avail- able resuscitation bay and staffing it with experienced trauma teams becomes increasingly difficult.1From th

43、e trauma care perspective, the arrival rate of severe casualties is a more meaningful metric of the burden on a trauma system than the absolute number of casualties. The casualty load is the arrival rate of severe casualties per hour, and an increasing casualty load eventually leads to degradation o

44、f trauma care as severely injured patients compete for the limited assets and resources. An intact trauma service line provides each severe casualty with a trauma team, resuscitation bay, and otherCritical casualty load (patients/hour)FIGURE 25-4 graphic depiction of the results of a computer simula

45、- tion of the flow of casualties of urban bombing through the trauma service line of the Ben Taub general hospital, a level 1 trauma centerin houston. The mpredicts a sigmoid-shaped relationshipbetween the casualty load and global level of trauma care. The level of care for a single patient on a nor

46、mal working day is defined as 100%. The upper flat portion of the curve corresponds to a multiple casualty incident, the steep portion represents a mass casualty situa- tion, and the lower flat portion represents a major medical disaster.The surge capacity of the hospital trauma service line is thea

47、lcritical casualty load that can be managed without a precipitous drop in the level of care. This simulation is based on clinical profiles of casualties treated at the rabin Medical Center in Petach Tikva, israel.(From hirshberg a, Scott Bg, granchi T,: how does casualty loadaffect trauma care in ur

48、ban bombing incidents? a quantitative analy- sis. J Trauma 58:686693, 2005.)resources, such as an available computed tomography (CT) scanner, operating room, and intensive care bed. The point beyond which this level of care cannot be maintained for new arrivals represents the surge capacity of the t

49、rauma service line of the hospital.6 Surge capacity is, therefore, a dynamic measure of the processing capacity of the trauma service line, and cannot be derived from static calculations of ED gurneys and staff. Using a similar definition, a surge capacity can also be defined separately for each tra

50、uma-related facility in the hospital.An increasing casualty load adversely affects the quality of trauma care for the severely injured because many casualties compete for the same limited trauma assets and resources. Anal- ysis using a computer m describes this relationship as a sigmoid-shaped curve

51、 (Fig. 25-4). The upper flat portion of the curve represents an intact trauma service line, where the level of care for severe casualties approximates the care given to a single patient on a normal working day. This is a multiple casualty incident. The steep portion represents a gradually failing tr

52、auma service line, corresponding to a mass casualty scenario. The lower flat portion represents a failed (or nonexistent) service line over- whelmed by a major medical disaster.The surge capacity of the trauma service line is the point beyond which the level of care begins to drop. An effective disa

53、ster response shifts the curve to the right, increasing the surge capacity and resulting in a more gradual degradation of the level of care. An empirical estimate7 puts the surge capacity6Level of trauma care (%)The SurgeonS role in MaSS CaSualTy inCidenTS Chapter 25 607at one severely injured patie

54、nt per hour for every 100 hospital beds, providing a practical yardstick that can be used in disaster planning.Mass Casualty and Modern Trauma SystemsThe overwhelming majority of urban terrorist bombings are multiple casualty incidents that do not exceed the surge capacity of individual hospitals. H

55、owever, in the past decade, terrorist groups have made repeated attempts to increase the magnitude of these MCIs by coordinated multiple simultaneous bombings. The two best documented examples were the Madrid trains bombing (March 2004)8 and the London subway bombing (July 2005).4 However, these inc

56、idents clearly demonstrated that modern emergency medical services (EMS) and trauma systems in large metropolitan areas serve as effective buffers that mitigate the medical impact of a large-scale event by distributing casual- ties among hospitals. With 2253 casualties in Madrid and more than 700 in

57、 London, rapid dispersion of the casualties among several hospitals resulted in each participating hospital facing only a multiple casualty incident with a handful of critical patients. This strong buffering mechanism was, however, con- spicuously absent in the U.S. Embassy bombing in Nairobi, Kenya

58、, in 1998, where more than 4000 casualties flooded the Kenyatta National Hospital.9 This inadequately documented MCI is the only truly overwhelming urban mass casualty inci- dent in recent history. This is a key point that is worth reem- phasizing: no hospital in a metropolitan area that has a funct

59、ioning EMS system has ever been overwhelmed by a MCI. A major difficulty in trying to learn useful lessons from past incidents is the paucity of clinical data. Most published reports pronly global statistics, such as the total number of casual- ties and the mortality among the critically injured (critical mor- tality), with f