A comparison of conservative versus early excision. Therapies in severely burned patients.

Early excision and grafting of small burn wounds is a generally accepted treatment. Early excision of burn injuries greater than 30% total body surface area (TBSA) in adults, however, has not been universally accepted. In this study, 85 patients whose ages ranged from 17 to 55 years with greater than 30% total body surface area (TBSA) burns were randomly assigned to either early excision or topical antimicrobial therapy and skin grafting after spontaneous eschar separation. Mortality from burns without inhalation injury was significantly decreased by early excision from 45% to 9% in patients who were 17 to 30 years of age (p less than 0.025). No differences in mortality could be demonstrated between therapies in adult patients older than 30 years of age or with a concomitant inhalation injury. Children (n = 259) with similar large burns treated by early excision showed a significant increase in mortality with increasing burn size and with concomitant inhalation injury (p less than 0.05). The mean length of hospital stay of survivors was less than one day per per cent of TBSA burn in both children and adults.     

The role of inhalation injury in burn trauma. A Canadian experience.

From 1977 to 1987, 1705 thermally injured patients were admitted to the Firefighters' Burn Center at the University of Alberta Hospitals. Thirteen hundred forty-four were male (78.8%) and 361 were female (21.2%), with a mean total burn surface area (TBSA) of 15.1 (SEM +/- 0.4%) and a range of 1% to 99% TBSA. Sixteen hundred thirty-five patients survived to be discharged from hospital, with an overall survival rate of 95.9%. One hundred twenty-four burn patients (7.3%) suffered concomitant inhalation injury diagnosed by bronchoscopy. Patients with inhalation injury suffered from larger TBSA (39.7% +/- 2.8% versus 12.2% +/- 0.3%; p less than 0.01) than those without inhalation injury. Inhalation injury increased the number of deaths from burn injury (34.7% versus 1.7%; p less than 0.01) independent of age and TBSA. Inhalation injury was associated with a threefold prolongation of hospital stay (23.7 +/- 0.7 versus 74.4 +/- 6.2 days; p less than 0.01) and was independent of age and TBSA. Multifactorial probit analysis was performed for both inhalation- and noninhalation-injured burned patients to allow TBSA and age adjusted rates of mortality for the burn population presented. The maximum detrimental effects of inhalation injury in burn patient outcome occurred when it coexisted with moderate (15% to 29% TBSA) to large (30% to 69% TBSA) thermal injuries. These data demonstrate that inhalation injury is an important comorbid factor in burn injury that increases the number of deaths substantially. Most importantly such injuries also independently prolong the duration of hospitalization in a highly unpredictable fashion as compared to patients with cutaneous burns only. As such our data illustrate the extreme importance of inhalation injury as a comorbid factor following thermal injury and reveal the present limitations for accurate quantification of the magnitude of respiratory tract injury accompanying thermal trauma.     

Burns in motor vehicle accidents

Burns received as a result of motor vehicle accidents (MVA's) create special problems in their care, as they are frequently severe and are often associated with other injuries. One hundred seventy-eight consecutive patients with burns sustained in an MVA were studied. The mean TBSA burn was 33.9%. The mortality was 24.7%, but the mean burn size in this fatal group was almost doubled at 63.9%. The injury most commonly associated with death was inhalation injury (in 36.3%). Thirty-six per cent of the patients sustained other injuries in addition to their burn, the most frequent of which was to the musculoskeletal system (67 injuries). Multiple trauma had little effect on mortality unless severe, but fractures especially complicated burn wound care unless surgically stabilized. Current methods of management are presented along with our approach to multiply injured burn patients.     

Mortality following combined burn and traumatic brain injuries: An analysis of the national trauma data bank of the American College of Surgeons

BackgroundSevere burn and traumatic brain injuries (TBI) lead to significant mortality, and combined burn-TBI injuries may predispose towards even worse outcomes. The purpose of this study was to investigate the mortality of patients with burn, burn with non-TBI trauma, and combined burn/TBI to determine if combined injury portends a worse outcome.MethodsWe obtained the National Trauma Data Bank from 2007 to 2012, identifying 32,334 patients with burn related injuries, dividing this cohort into three injury types: BURN ONLY, BURN with TRAUMA/NO TBI, and BURN with TBI. For each patient, demographic data was obtained, including age, gender, presence of trauma, TBI, or inhalation injury, burn total body surface area (TBSA), Glasgow Coma Scale, Injury Severity Score, and mortality. Multivariable logistic regression was performed.ResultsAge, gender, and TBSA were similar across the three injury groups, but the incidence of inhalation injury was doubled in the BURN with TRAUMA/NO TBI (15.4 %) and BURN with TBI (15.3 %) groups when compared to the BURN ONLY (7.2 %) group. Mortality differed across injury categories after adjusting for age, TBSA, and inhalation injury. Increased mortality was seen in BURN with TRAUMA/NO TBI versus BURN ONLY (OR = 1.27 [1.06, 1.53]) and was higher when comparing BURN with TBI versus BURN ONLY (OR = 4.22 [2.85, 6.18]). BURN with TBI also had higher mortality when compared to BURN with TRAUMA/NO TBI (OR = 3.33 [2.30, 4.82]). The logs odds of mortality also increased with increasing age, TBSA and presence of inhalation injury.DiscussionThis analysis of the NTDB suggests that mortality following burn-related injuries may be higher when burn injury is combined with TBI when compared to burns with other trauma, even after correcting for age, TBSA, and inhalation injury. Further clinical and laboratory research is needed to validate these findings and better understand how to optimize combined TBI and burn injury treatment.     

Severe burns in Australian and New Zealand adults: Epidemiology and burn centre care

IntroductionStudies describing the epidemiology of severe burns (>20% total body surface area) in adults are limited despite the extensive associated morbidity and mortality. This study aimed to describe the epidemiology of severe burn injuries admitted to burn centres in Australia and New Zealand.Materials and methodsData from the Burns Registry of Australia and New Zealand (BRANZ) were used in this study. Patients were eligible for inclusion if they were admitted between August 2009 and June 2013, were adults (18-years or older), and had burns of 20% total body surface area (TBSA) or greater. Demographics, burn characteristics and in-hospital mortality risk factors were investigated using multivariable Cox proportional hazards analysis.ResultsThere were 496 BRANZ registered patients who met the inclusion criteria. Over half of the patients were aged 18–40 years and most were male. The median (IQR) TBSA was 31 (25–47). Most (75%) patients had burns involving <50% TBSA, 58% sustained their burn injury at home, and 86% had sustained flame burns. Leisure activities, working for income and preparing food together accounted for over 48% of the activities undertaken at the time of injury. The in-hospital mortality rate was 17% and the median (IQR) length of stay was 24 (12–44) days. Seventy-two percent were admitted to an intensive care unit (ICU) and 40% of patients had an associated inhalation injury. Alcohol and/or drug involvement was suspected in 25% of cases.ConclusionThis study describes the demographics, burn injury characteristics and in-hospital outcomes of severe burn injuries in adults whilst also identifying key predictors of inpatient mortality. Key findings included the over-representation of young males, intentional self-harm injuries and flame as a cause of burns and highlights high risk groups to help aid in the development of targeted prevention strategies.     

Mortality in paediatric burns at the Women’s and Children’s Hospital (WCH), Adelaide,South Australia: 1960–2017

BackgroundBurn injuries are the third leading cause of preventable death in children worldwide, resulting in over 100 000 annual hospitalisations. In the paediatric population, scalds are the commonest mechanism and burn injuries of greater than 40% total burn surface area (TBSA) are associated with a high mortality and morbidity rate.AimsThe aim of this study was to review mortality in paediatric burns in a tertiary burns centre over a 60-year period, providing an understanding of local causes of mortality and directing future clinical research.MethodsWe reviewed data collected prospectively from patients treated for burn injuries at the WCH from 1960 to 2017. Data of age, gender, mechanism of injury and TBSA were collected. TBSA of 40% and greater were included in the study.ResultsAll patients with total burn surface area (TBSA) less than 40% survived. There were a total of 75 patients who sustained burns of or greater than 40% TBSA. Overall mortality was 34% (26 of 75) of which 24 occurred in the 1960s. Of the 21 patients who died of flame burn injuries, 12 of them were described as clothes catching alight from being in close proximity to the source of flame. Average length of stay for patients who did not survive was 7 days (1–26).ConclusionMortality has since declined and the prognosis for survival good, even in TBSA of greater than 90%. The investigations in fabric flammability led by Dr Thomas Pressley and Mr Murray Clarke prompted the rewriting of Australian standards for production of children’s clothing. This, in combination with advances in paediatric resuscitation, surgical techniques as well as wound care has improved survival rates and outcomes in extensive burn injuries. Future studies focus to see not only better survival rates, but also better aesthetic and functional outcomes in burn survivors.     

An epidemiological study of 1063 hospitalized burn patients in a tertiary burns centre in Hong Kong

A total of 1063 acute burn patients were admitted to the Burns Unit of Prince of Wales Hospital, Hong Kong between March 1993 and February 1999. There were 678 males and 385 females with a male to female ratio of 1.76:1. The median age was 13.1 year-old and the median burn size was 6% total body surface area (TBSA). Pediatric patients under the age of 15 year-old accounted for 550 (51.7%) admissions and 235 (42.7%) of them were toddlers <2 year-old, while adult patients of age above 15 year-old accounted for the other 513 (48.3%) admissions. There was no seasonal variation in admission. Domestic burns resulted in 756 (71.1%) injuries followed by industrial burns that caused 175 (16.5%) admissions. The median hospital stay was 9 days and 54 patients (5.1%) had inhalation injury requiring intubation and ventilatory support. Twenty-four patients died in this series which yielded a mortality rate of 2.3%. The median age for this mortality group was 46.6 year-olds with a median extent of burns of 68% TBSA. There were 16 males and 8 females with a male to female ratio of 2:1. Eighteen (75%) patients had flame burns and 15 (83.3%) of them had inhalation injury. The mortality group had significantly larger burn size (P<0.001), higher incidence of inhalation injury (P<0.001) and older age (P<0.001) compared to the survivors.     

Burns in pregnancy

A 9-year prospective study of burns in pregnant women hospitalized at the Sina hospital burn center was conducted to determine the etiology and outcome of pregnant patients. Fifty-one patients (27.45% self-inflicted, 72.55% unintentional) were identified and stratified by age, burn size, presence or absence of inhalation injury, trimester of pregnancy, maternal and fetal mortality, and cause of burn. The mean patient age was 24.2 years. There were 20 maternal deaths and 23 fetal deaths. The majority of which (maternal: 13 and fetal: 13) were among self-inflicted burned pregnant women. The mean burn size was 37.7%, and was significantly larger for nonsurvivors of mother than survivors (68.8% versus 17.6%; p<0.001). In the 51 pregnant women, as the total burned body surface area exceeds 40%, both maternal and fetal mortality reaches 100%. Inhalation injuries were strongly associated with large burns, and were presents in all suicide patients. Kerosene ignition (68.6% of all patients, 100% of self-inflicted patients) was the most common type of burn. Large burn size was the strongest predictor of mortality of mother and fetus followed by the presence of inhalation injury.     

A three decade analysis of factors affecting burn mortality in the elderly

This study's objective was to identify variables that affect the mortality of elderly burn patients and to assess their changes over time. A retrospective review was conducted on all patients 75 or older (n = 201) admitted to a university-based burn center between 1972 and 2000. Variables examined were age, sex, TBSA, ABSI, inhalation injury, timing from burn to operative intervention, the number of surgical procedures, the number of pre-morbid conditions, and mortality. There were 95 fatalities. TBSA strongly correlated with mortality (p < 0.0001). Adjusting for TBSA and inhalation injury, mortality significantly decreased (p = 0.04, odds ratio = 0.58). Mortality significantly increased with inhalation injury (p < 0.01). Fatality risk increased by 400% with inhalation injury. Absence of inhalation injury was not significant with respect to mortality in the 1970s, however there was a significant decrease (p = 0.02) in mortality without an inhalation injury in the 1980s and 1990s. ABSI was strongly predictive of mortality (p < 0.0001). On average there was a 200% increase in mortality per unit increase of ABSI. The elderly are 58% less likely to die from burns now as compared to the 1970s. Although mortality rose with increasing TBSA equally in each decade, the absolute risk of mortality decreased over time. This data suggests major strides have been made in burn care, however similar success has not been achieved with inhalation injuries.     

Etiology and outcome of pediatric burns in Tabriz, Iran

A 3-year prospective study of burn victims hospitalized at a major burn center was conducted to determine the etiology and outcome of pediatric burns. One thousand one hundred sixty patients under the age of 14 years identified and stratified by age, sex, burn size, presence or absence of inhalation injury, and cause of burn. The mean patient age was 2.2 years, and the male:female ratio was 1.6:1. There were 74 deaths overall (6.4%), the majority of which (44) were among children under 5 years of age. Except for burn incidence, there were no significant differences between males and females. The mean burn size was 19%, and was significantly larger for nonsurvivors than survivors (50.3% versus 16.8%; P<0.001). Inhalation injuries were strongly associated with large burns, and were present in all flame-burn fatalities. Scalds were the most common type of burn among children under 5 years of age; flame burns predominated in older children. There were 39 deaths related to scalds. Large burn size was the strongest predictor of mortality followed by the presence of inhalation injury and the length of time to intravenous access.     

Influence of demographics and inhalation injury on burn mortality in children

BACKGROUND: Pulmonary failure has emerged as one of the leading causes of mortality in burned children due, in part, to the success in reducing the incidence of sepsis, early surgery and fluid resuscitation, and new advances in nutritional support. To evaluate the effect of pulmonary injury, age, gender, race, and burn size on mortality, the records of 3179 burned children admitted to our burn center from 1985 to 2001 were reviewed. In this population, 1246 were admitted within 14 days of injury with burns greater than 20% of their total body surface area (TBSA). METHODS: Lethal burn areas (LAs) for a thermal injury only or burn plus inhalation injury were estimated from best fit probit curve within 95% confidence limits. Data analysis was by chi(2)-test, t-test, or Fisher's exact test where appropriate. RESULTS: The lethal burn area for a 10% mortality rate with and without concomitant inhalation injury was a 50 and 73% TBSA burn, respectively. Children up to the age of 3 with >/=20% TBSA burns had a higher rate of mortality (9.9%) compared to those 3-12 years of age (4.9%) and 13-18 years of age (4.2%). Children with 21-80% TBSA burns showed a significant difference in mortality (P<0.05) between those with burn plus inhalation injury (13.9%) and burn only (2.9%), while those with 81-100% TBSA burns showed no significant difference between burn only and burn plus inhalation injury. CONCLUSION: Inhalation injury remains one of the primary contributors to burn mortality. Children under the age of 3 years, however, are at a higher risk both with and without inhalation injury.     

Trends and risk factors for mortality in elderly burns patients: A retrospective review

IntroductionThe elderly experience higher mortality rates and poorer outcomes compared to younger burn survivors with similar injuries.MethodsThis epidemiological study reviewed records of all admitted elderly burn patients collected from five burns facilities in Israel between 1997–2016. Collected data was limited to the population aged 20+, focused on the population aged 60+.ResultsMortality rates for elderly patients increased with TBSA and increases with age. Regression analyses demonstrated a decrease in mortality of 2.9% (p = 0.013) per 5 years, an overall decrease of 11.6% over the 20-year study period, with the decline more significant for older age groups. This decrease in mortality was much larger than that observed for all burns patients over this period. The most common cause of injury in the elderly population was fire, with mortality rate highest for this cause. There was no effect of gender on mortality rate. Mortality increased when smoke inhalation was present for TBSA<20%, with mortality unaffected by the presence of smoke inhalation for higher TBSA. The need for surgery correlates with high mortality rates.ConclusionThis study identified key factors that impact mortality and demonstrated a large decrease in mortality in the elderly patients over the study period.     

Paediatric burn injuries in Enugu,South-East Nigeria: A 7-year multi-centre retrospective review

Burn injuries contribute significantly to childhood morbidity and mortality. This study was designed to document the pattern of presentation and outcome of pediatric burn injury in Enugu.MethodsAll children with burn injuries over a 7-year period (June 2011 to May 2018) and were managed at three tertiary health institutions, were studied. Information including their socio-demographics, clinical features and treatment outcome were obtained and analyzed using the Statistical Package for Social Sciences (SPSS) version 17.0.Results198 out of 201 records were available for analysis. Most (186; 93.9%) burn injuries occurred at home. Hot liquid (112; 56.7%) was the commonest cause of burn injury. A lot of substances were used topically for first aid, raw eggs (52; 31%) being the commonest. The outcome had significant association with cause of injury, depth of injury, total burn surface area (TBSA), and inhalation injury. Most were safely discharged home while a total of thirteen (6.6%) children died. LA₅₀ was 54.87%, while the maximum TBSA salvaged was 65%.ConclusionBurn injuries in children in this environment remain a serious challenge in the face of widespread lack of awareness regarding safe practices in handling hot and flammable items at home.     

Radiological manifestation of pulmonary complications in deceased intensive care burn patients

The chest radiographs of 46 burn patients who died in the burn intensive care unit (BICU) were retrospectively analyzed to study the spectrum of pulmonary complications and their contribution to patient's mortality. There were 25 male and 21 female patients and their mean ages were 34 and 30 years, respectively. Forty-three patients had flame burns, two chemical, and one scald with a mean total burn surface area (TBSA) of 71%. Thirty-six of them had inhalation injury and of these 25 patients developed septicaemia. Out of these 46 patients, 39 had a total of 60 pulmonary complications on various postburn days. The commonest complications were consolidation (28.3%) and adult respiratory distress syndrome (ARDS) (26.7%) mainly due to inhalation injury and/or following septicaemia. The majority of these complications (46.7%) occurred in the late phase (postburn day 5 onwards). Forty-one (89.2%) patients died due to multi-organ failure (MOF) and a good number of them had secondary respiratory failure. The flame burn patients with large TBSA, presence of inhalation injury, and occurrence of septicaemia, are at risk for pulmonary complications that equally affect adult males and females. Pulmonary complications irrespective of the cause significantly contribute to the mortality. This study suggests that serial chest X-rays done in BICU form an important diagnostic tool for pulmonary complications from postburn day 1 onwards, and is useful for subsequent monitoring of the treatment. All burn intensive care units may not be privileged to have a full time radiologist, and intensivist. Therefore, the burn surgeon needs to metamorphose into an intensivist and double as a burn radiologist for early detection and quick treatment if his surgical skills are to be adequately rewarded.     

Thermal injury in the elderly: when is comfort care the right choice?

The factors contributing to a higher mortality rate in elderly thermal injury victims are not well delineated. The purpose of this study is to determine the impact of the initial injury, medical comorbidities, and burn size on patient outcome and to determine a level of injury in this population when comfort care is an appropriate first choice. Individual medical records of patients over 65 years of age admitted to our burn center over a 10-year interval were reviewed for patient demographics, mechanism of injury, total body surface area (TBSA) burned, medical comorbidities, use of Swan-Ganz catheters, evidence of inhalation injury, level of support, and patient outcome. The mechanisms of thermal injury were flame (68%), scald (21%) and electrical or chemical contact (11%). Twenty-six preventable bathing, cooking, and smoking-related injuries were seen (33%). The average TBSA was 25 per cent. Average length of stay varied depending on outcome. The overall mortality rate for this group was 45 per cent. Patients older than 80 years with 40 per cent or greater TBSA burned had a 100 per cent mortality rate despite aggressive treatment. Burn wound size correlated better with probability of poor outcome than age. Thermal injuries in the elderly are becoming more important with the aging of our population. Underlying medical problems--specifically chronic obstructive pulmonary disease--do play a role in increased patient morbidity and mortality. This study shows that age greater than 80 years in combination with burns greater than 40 per cent TBSA are uniformly fatal despite aggressive therapy. We believe that delaying the start of comfort-only measures in this situation only prolongs the pain and suffering for the patient, the family, and the physician.     

Racial And Socioeconomic Differences Affect Outcomes in Elderly Burn Patients

BackgroundRace and socioeconomic status influence outcomes for adult and pediatric burn patients, yet the impact of these factors on elderly patients (Medicare eligible, 65 years of age) remains unknown.MethodsData pooled from three verified burn centers from 2004 to 2014 were reviewed retrospectively. Age, race, gender, percent total body surface area (%TBSA) burn, mortality, length of stay (LOS), LOS per %TBSA burn, and zip code which provided Census data on race, poverty, and education levels within a community were collected. Data were analyzed using logistic and generalized linear models in SAS version 9.4 (SAS Institute, Cary, NC, USA).ResultsOur population was mainly Caucasian (63%), African American (18%), Hispanic (7.6%), and Asian (3.5%). Mean age was 76.3 ± 8.3 years, 52.5% were male. Mean %TBSA was 9 ± 13.8%; 15% of the patients sustained an inhalation injury. The mortality rate was 14.4%. Inhalation injury was significantly associated with mortality and discharge to a skilled nursing facility (SNF) (p < 0.05). Race was significantly associated with socioeconomic disparities and affected LOS/TBSA, but not discharge to SNF or mortality on univariate analysis. Poverty level, education level, and insurance status (others vs. public) independently predicted SNF discharge, while median income and insurance type independently predicted LOS/TBSA.ConclusionIn this elderly cohort, race did not predict standard markers of burn outcome (mortality and discharge to SNF). Socioeconomic status independently predicted LOS and discharge to SNF, suggesting a relationship between socioeconomic status and recovery from a burn injury. Better understanding of racial and socioeconomic disparities is necessary to provide equitable treatment of all patients.     

A study of burn injuries in the elderly in a regional burn centre

We evaluated the epidemiology and outcome of 94 elderly burn patients of age 60 years or older treated in a local burn centre over a period of 6 years. There were 44 males and 50 females with a male to female ratio of 0.88 and an average age of 73.8+/-9 years. The mean extent of burn was 13.3+/-18.4% total body surface area (TBSA) with 14 patients (15%) suffering from a burn size >20% TBSA. The vast majority of injuries (90%) occurred at home. Scalds resulted in 62 admissions (66%) and flame burns accounted for another 29 admissions (31%). The burns predominantly involved the extremities and the trunk. Four patients had inhalation injuries and required admission to the Intensive Care Unit for ventilatory support. The majority of patients (60%) did not require any operations. The mean hospital stay of the survivors was 30.1+/-34.1 days and 35% of them stayed less than 2 weeks. Fifty-five patients (59%) had at least one pre-existing medical problem requiring long-term medication and 41 patients (44%) were living alone. Sixty-three patients (67%) presented more than 8 h after the burn injuries and 34 patients (36.2%) had no first aid treatment of their burn wounds. In addition, 40 patients (42.5%) had their wounds treated inappropriately. Seven patients died in this series which yielded a mortality rate of 7.4%. The outcomes of early versus late excision and grafting were also analyzed.     

Severity score for predicting pneumonia in inhalation injury patients

Inhalation injuries contribute significantly to morbidity and mortality in both children and adults with burns. Pneumonia is a major compromising factor in these patients. The purpose of this article was to evaluate the characteristics, impact factors, incidence, morbidity, and mortality of pneumonia in inhalation injuries. Furthermore, a severity score has been formulated to help predict the probability of developing pneumonia following inhalation injuries. A retrospective study was performed of 214 patients, treated for inhalation injuries from 1999 to 2009 at the Burn Center in Chang Gung Memorial Hospital, Linkou, Taiwan. Patients' characteristics, length of hospitalization, total burn surface area, initial PaO2:FiO2 ratio, number of intubated days, bronchoscope grade, initial carboxyhemoglobin level (COHb) and mortality rate were recorded. A Student's t-test was used for comparison of inhalation injury patients with and without pneumonia and was also used for comparing a TBSA of >20% to those with a TBSA of ≤20% in patients with inhalation injury and pneumonia. Logistic regression analyses were utilized to create a severity score related to pneumonia. 129 patients with inhalation injury were included in the analysis. Overall, 38% (49/129) patients developed pneumonia. Pneumonia associated with inhalation injury occurred more often in patients with a TBSA>20% (P<0.05). The intubation days, bronchoscope grade and COHb level of pneumonia patients were significantly longer (P<0.05). Initial PaO2:FiO2 ratio (PaO2/FiO2) was significantly lower in patients with pneumonia (P<0.05). Mortality following pneumonia was increased sevenfold (P<0.05). Hospitalization days and intubation days were significantly longer in TBSA>20%. Logistic regression analysis was performed to find out the impact factors of pneumonia in inhalation injury patients and to set a severity score. Patients age >60 years, TBSA >20%, bronchoscope grade is 3 or 4, initial PaO2/FiO2≦300 and initial COHb level>10% showed a significant difference (P<0.05). The total severity scale was set at 5 points. Each impact factor was given one point and when the score ≥2 it means patients have high risk of development of pneumonia. This study had identified the significant risk factors for potential development of pneumonia in a group of inhalation injury patients. The impact of these risk factors should be validated in further prospective trials to improve outcome or at least reduce the incidence of the surrogate diagnosis of pneumonia.