ORIGINAL ARTICLES
National Trends in Burn and Inhalation Injury in Burn Patients: Results of Analysis of the Nationwide Inpatient Sample Database Anand Veeravagu, MD,* Byung C. Yoon, MD, PhD,* Bowen Jiang, MD,* Carla M. Carvalho, MD,† Fred Rincon, MD, MSc, FACP, FCCP, FAHA,‡ Mitchell Maltenfort, PhD,§ Jack Jallo, MD, PhD, FACS,‡ and John K. Ratliff, MD, FACS*
The aim of this study was describe national trends in prevalence, demographics, hospital length of stay (LOS), hospital charges, and mortality for burn patients with and without inhalational injury and to compare to the National Burn Repository. Burns and inhalation injury cause considerable mortality and morbidity in the United States. There remains insufficient reporting of the demographics and outcomes surrounding such injuries. The National Inpatient Sample database, the nation’s largest all-payer inpatient care data repository, was utilized to select 506,628 admissions for burns from 1988 to 2008 based on ICD-9-CM recording. The data were stratified based on the extent of injury (%TBSA) and presence or absence of inhalational injury. Inhalation injury was observed in only 2.2% of burns with 18 years with primary diagnosis code of burns (ICD-9-CM 940–949, 948.0–948.9 for BSA, 692.71, 692.76–692.77; see Table, Supplemental Digital Content, http://links. lww.com/BCR/A19). Inhalation injury was defined by ICD-9-CM 506, 947.0, 947.1, and 947.9. Medical comorbidities such as hyperglycemia and diabetes were coded using ICD-9-CM 790.29, 249.0–249.9, 250, and surgical complications were coded using ICD9-CM 996–999 and e878-e879. A total 506,628 cases were identified and further stratified. Other demographics such as age, sex, and race were also obtained. Hospitals were divided by type into urban-academic, urban-private, and rural. Hospital sizes were categorized as small to medium (500 beds). Patients were excluded from the analysis if no disposition was recorded. The exposure variable of interest was inhalation injury, coded in binary. The primary outcome measure was in-hospital mortality.
Statistical Analysis The NIS is based on national surveys, including discharge weights, stratification over various hospital and regional factors, and clustering around individual hospitals; the purpose of this complex survey design is to achieve more accurate national estimates from the 20% sample of U.S. hospital discharges. The χ2 test and the Wilcoxon rank test were used to determine differences in demographics, hospital characteristics, comorbidities, in-hospital complications, and outcomes. Multivariate analysis was first used to identify significant risk factors from candidate variables. Then, multivariable logistic regression modeling was used to calculate odds ratios (ORs) and 95% confidence interval (95% CI). In all multivariate analyses, all factors of interest were included, systematically removing the least significant factor and recalculating the model found in parsimonious models. For the validation study we calculated sensitivity, positive predictive value, and receiver operator characteristic curve. The analysis was conducted using Structured Query Language and the LME-4 package (ver. 0.99) in the R programming language for statistical computing (ver. 2.11). Statistical significance was judged when P < .05.
RESULTS Between 1988 and 2008, there were more than 750 million hospitalizations nationwide; 506,628 fulfilled
260 Veeravagu et al
our primary inclusion criteria. As much as 70% of the burn patients were men. The mean age for all cases was 30 years. Among the admissions, 312,815 or 62% suffered a burn with TBSA of less than 10%. Patients with burns more than 30% TBSA composed only 8.3% of the cohort. More extensive burns tend to have greater likelihood of inhalation effect. Inhalation injury was observed in only 2.2% of burns with 10 to 19% TBSA but 14% of burns with 80 to 99% TBSA (Figure 1). Overall, inhalation injury was seen in approximately 3.5% of total burn cases. Mortality information was available for 489,025 patients. The mortality rate from burn injuries has remained steady between 1988 and 2008, with a mean of 3.7% (range, 2.0–4.5%). The overall mean mortality from inhalation injury was 16%, which has trended down from as high as 27% in 1989 to 5.5% in 2006 (Figure 2). Mortality and demographic information are reviewed on Table 1. In terms of mortality demographics, African– American patients were slightly more likely to expire in-hospital from burn injury than their Caucasian counterparts (OR, 1.37; 95% CI, 1.19–1.58; P < .001). Females were also more likely to expire inhospital compared to males (OR, 1.32; 95% CI, 1.17–1.48; P < .001). Advancing age was associated with increased risk of inpatient mortality (OR, 1.07; 95% CI, 1.07–1.07; P < .001) per year. Compared to the urban academic setting, burn patients treated at an urban private center were four times more likely to expire in-hospital (OR, 4.18; 95% CI, 3.29–5.30; P < .001). Patients treated at rural medical centers (OR, 0.31; 95% CI, 0.16–0.60; P < .001) and patients with hyperglycemia (OR, 0.77; 95%
Journal of Burn Care & Research March/April 2015
CI, 0.63–0.93; P = .007) were less likely to expire in-hospital. Impact of individual factors on patient mortality is reviewed in Table 2. The rate of in-hospital deaths correlated linearly with the extent of burns. Only 0.4% of patients with burns involving
National Trends in Burn and Inhalation Injury in Burn Patients: Results of Analysis of the Nationwide Inpatient Sample Database Anand Veeravagu, MD,* Byung C. Yoon, MD, PhD,* Bowen Jiang, MD,* Carla M. Carvalho, MD,† Fred Rincon, MD, MSc, FACP, FCCP, FAHA,‡ Mitchell Maltenfort, PhD,§ Jack Jallo, MD, PhD, FACS,‡ and John K. Ratliff, MD, FACS*
The aim of this study was describe national trends in prevalence, demographics, hospital length of stay (LOS), hospital charges, and mortality for burn patients with and without inhalational injury and to compare to the National Burn Repository. Burns and inhalation injury cause considerable mortality and morbidity in the United States. There remains insufficient reporting of the demographics and outcomes surrounding such injuries. The National Inpatient Sample database, the nation’s largest all-payer inpatient care data repository, was utilized to select 506,628 admissions for burns from 1988 to 2008 based on ICD-9-CM recording. The data were stratified based on the extent of injury (%TBSA) and presence or absence of inhalational injury. Inhalation injury was observed in only 2.2% of burns with 18 years with primary diagnosis code of burns (ICD-9-CM 940–949, 948.0–948.9 for BSA, 692.71, 692.76–692.77; see Table, Supplemental Digital Content, http://links. lww.com/BCR/A19). Inhalation injury was defined by ICD-9-CM 506, 947.0, 947.1, and 947.9. Medical comorbidities such as hyperglycemia and diabetes were coded using ICD-9-CM 790.29, 249.0–249.9, 250, and surgical complications were coded using ICD9-CM 996–999 and e878-e879. A total 506,628 cases were identified and further stratified. Other demographics such as age, sex, and race were also obtained. Hospitals were divided by type into urban-academic, urban-private, and rural. Hospital sizes were categorized as small to medium (500 beds). Patients were excluded from the analysis if no disposition was recorded. The exposure variable of interest was inhalation injury, coded in binary. The primary outcome measure was in-hospital mortality.
Statistical Analysis The NIS is based on national surveys, including discharge weights, stratification over various hospital and regional factors, and clustering around individual hospitals; the purpose of this complex survey design is to achieve more accurate national estimates from the 20% sample of U.S. hospital discharges. The χ2 test and the Wilcoxon rank test were used to determine differences in demographics, hospital characteristics, comorbidities, in-hospital complications, and outcomes. Multivariate analysis was first used to identify significant risk factors from candidate variables. Then, multivariable logistic regression modeling was used to calculate odds ratios (ORs) and 95% confidence interval (95% CI). In all multivariate analyses, all factors of interest were included, systematically removing the least significant factor and recalculating the model found in parsimonious models. For the validation study we calculated sensitivity, positive predictive value, and receiver operator characteristic curve. The analysis was conducted using Structured Query Language and the LME-4 package (ver. 0.99) in the R programming language for statistical computing (ver. 2.11). Statistical significance was judged when P < .05.
RESULTS Between 1988 and 2008, there were more than 750 million hospitalizations nationwide; 506,628 fulfilled
260 Veeravagu et al
our primary inclusion criteria. As much as 70% of the burn patients were men. The mean age for all cases was 30 years. Among the admissions, 312,815 or 62% suffered a burn with TBSA of less than 10%. Patients with burns more than 30% TBSA composed only 8.3% of the cohort. More extensive burns tend to have greater likelihood of inhalation effect. Inhalation injury was observed in only 2.2% of burns with 10 to 19% TBSA but 14% of burns with 80 to 99% TBSA (Figure 1). Overall, inhalation injury was seen in approximately 3.5% of total burn cases. Mortality information was available for 489,025 patients. The mortality rate from burn injuries has remained steady between 1988 and 2008, with a mean of 3.7% (range, 2.0–4.5%). The overall mean mortality from inhalation injury was 16%, which has trended down from as high as 27% in 1989 to 5.5% in 2006 (Figure 2). Mortality and demographic information are reviewed on Table 1. In terms of mortality demographics, African– American patients were slightly more likely to expire in-hospital from burn injury than their Caucasian counterparts (OR, 1.37; 95% CI, 1.19–1.58; P < .001). Females were also more likely to expire inhospital compared to males (OR, 1.32; 95% CI, 1.17–1.48; P < .001). Advancing age was associated with increased risk of inpatient mortality (OR, 1.07; 95% CI, 1.07–1.07; P < .001) per year. Compared to the urban academic setting, burn patients treated at an urban private center were four times more likely to expire in-hospital (OR, 4.18; 95% CI, 3.29–5.30; P < .001). Patients treated at rural medical centers (OR, 0.31; 95% CI, 0.16–0.60; P < .001) and patients with hyperglycemia (OR, 0.77; 95%
Journal of Burn Care & Research March/April 2015
CI, 0.63–0.93; P = .007) were less likely to expire in-hospital. Impact of individual factors on patient mortality is reviewed in Table 2. The rate of in-hospital deaths correlated linearly with the extent of burns. Only 0.4% of patients with burns involving
