Benchmarking Outcomes in the Critically Injured Burn Patient
Benchmarking Outcomes in the Critically Injured Burn Patient
Five hundred forty-one patients (300 adults and 241 children) were enrolled in the study. Table 1 shows the baseline and injury characteristics, resuscitation data, outcomes, and complications for the adults (age ≥17 years). In general, adult survivors were younger with smaller burn sizes. When comparing the 2 adult age categories, the mortality rate in those patients aged 55 years or more was greater (38.5% vs 14.1%, P = 0.0001). In these adults, survival was not affected by sex, race, ethnicity, number of comorbidities, or mechanism of injury. Initial base deficit, lactate, and APACHE II scores were all significantly lower for those who survived. Fluid resuscitation volumes were greater than 6 mL/kg/% TBSA and comparable between survivors and nonsurvivors. Even at discharge, the adult patients remained seriously debilitated in that only 52% went directly home. Complications including pneumonia (47%), sepsis (10%), and nosocomial infections (70.7%) were common in these patients who experienced extended lengths of stay and numerous ventilator days. Presence of inhalation injury was associated with mortality (P = 0.0023) in this univariate analysis.
Table 2 shows the baseline and injury characteristics, resuscitation data, outcomes, and complications for children (age <17 years). There was a trend, with females having a higher mortality rate (12.8% vs 5.5%, P = 0.0712). There was a strong statistical difference in mortality related to race (P = 0.0052). Ethnicity, comorbidities, and burn mechanism did not influence the likelihood of survival. Initial base deficit, lactate, and APACHE II scores were lower in those children who survived. As with the adults, average resuscitation fluid volumes exceeded 4 mL/kg/% TBSA, and the presence of inhalation injury was associated with mortality in children (P = 0.008).
As expected, there were multiple differences observed when comparing children and adults. When compared with adults, mortality (7.9% in children vs 14.1% in adults), frequency of complications, and frequency of comorbidities were all substantially lower despite a larger average burn size for the children, 57.8 ± 18.2 versus 41.2 ± 18.3% TBSA. Compared with adults, children had a shorter length of stay (32.2 ± 25.1 vs 51.8 ± 48.1 days) and fewer ventilator days (8.6 ± 14.1 vs 18.7 ± 24.2). The volumes of resuscitation fluid on a 1-mL/kg/% TBSA basis were comparable between children and adults and were not related to the mortality rates (Table 1 and Table 2).
Regarding minimal urinary output, the fluid resuscitation SOP requires that average urinary output be 0.3 mL/kg/h or more. To be compliant, patients with urinary outputs of less than 0.3 mL/kg/h should have received 2 mL/kg/% TBSA or more over the first 24 hours. Compliance was excellent in that 97% of patients met the protocol criterion for both the first and second 24-hour time periods. However, compliance with the requirement of total fluid resuscitation volumes of 2 to 4 mL/kg/% TBSA was poor. Patients received more than the recommended fluid volumes for resuscitation, with 46% of patients receiving greater than 4 mL/kg/% TBSA over the first 24 hours. These compliance values remained stable over the course of the study.
Only 1% of the patients had a recorded mean arterial pressure of 60 mm Hg or less at any time during the first 24 hours postinjury in the settings of the prehospital setting, emergency department(s), transferring facility, or in the participating burn center.
With respect to the protocol for prevention of hyperglycemia, blood glucose levels could have been on-target (<180 mg/dL) or off-target (≥180 mg/dL) if the patient was receiving insulin. Approximately 22.9% of the patients had recorded blood glucose values off-target (≥180 mg/dL) and were not receiving insulin. Compliance with this SOP did not seem to change over the course of the study.
It has been well described that 3 factors strongly affect the probability of death from burn injuries—age, overall burn size, and presence of inhalation injury. Figure 1A shows a gradual, monotonic effect of age up to approximately 50 years with an inflection point between 50 and 60, indicating that the effect of age becomes more dominant. Similarly, Figure 1B shows a gradual, monotonic effect of burn size of 20% up to approximately 70% TBSA beyond which burn size seems to provide an even stronger effect. With respect to burn size, the LA50 (Lethal Area 50, burn area lethal in 50% of patients) is approximately 90% TBSA. When the adult and pediatric databases were combined, mortality was 19.5% for those with inhalation injury and 8.9% for those without. This difference in mortality has a calculated P < 0.0001 that is unadjusted for potential imbalances other than inhalation injury.
(Enlarge Image)
Figure 1.
Mortality versus age and % TBSA mortality rates were plotted versus age (panel A) and % TBSA (panel B). The Lethal Area 50 (LA50) is shown for each.
Figure 2A shows an invariant mortality rate of approximately 14% over the course of our 7-year study. Figure 2B shows the comparison of mortality in TBSA quintiles of burn size for patients younger than versus older than 50 years in the NBR versus the current study, which suggests that there might be survival improvements in patients younger than 50 years with larger burns. In patients 50 years of age and older, there might be survival improvements in the smaller burns, but there does not seem to be any survival differences in older patients with very large burn injuries.
(Enlarge Image)
Figure 2.
Mortality for Glue Grant study patients compared with the NBR in panel A shows the mortality rate by year for those patients in the Glue Grant study. Comparisons of mortality rates by TBSA quintile and age group (<50 years of age vs ≥50 years of age) for those patients in the Glue Grant with those in the NBR are shown in panel B.
In a comparison of the data in this study versus patients in the NBR after excluding those with burn sizes less than 20% TBSA, a logistic regression stratified on age, burn size, and presence of inhalation injury was performed. Following these adjustments, there was a lower risk of mortality for patients in our current study [odds ratio (OR) = 0.71 (95% confidence interval: 0.53–0.97), P = 0.03]. An analysis of the mortality rate in the Glue cohort alone was based upon a model that predicts expected mortality rate in patients admitted to the Massachusetts General Hospital and Shriners Hospitals for Children—Boston, from 1990 to 1994. The result of this model was highly consistent with the outcomes in this study and predicted that 74.09 deaths would occur versus the 74 deaths that actually occurred (Flora's score Z = -0.01, P = 0.9895).
Figure 3A shows 4 groups of patients categorized by Denver MOF score: 0 (blue), 1 to 3 (red), ≥4 (brighter red), and nonsurvival (black). Note that approximately 30% of the patients demonstrated a score of 0 for all components of the Denver score throughout their entire hospital course. Most patients showed waxing and waning of component Denver scores with occasional scores of 4 or more, consistent with MOF, for periods up to 180 days postinjury. Deaths occurred soon after admission but continued to occur as many as 100 days postadmission. To the left of Figure 3A, there is a scatter plot of both age and burn size for each of the patients shown top to bottom. A smooth curve plots the centroids for each. Figure 3A shows that the average age increased from approximately 25 to 40 years and burn size increased from 40% to 70% TBSA from top to bottom of the figure. These findings are consistent with the finding that those patients with organ failure scores of 0 are younger and with more moderate-sized injuries. Figure 3B identifies 4 categories of patients that show that there were deaths occurring up to 90 to 100 days postinjury. There was gradual recovery for those patients with Denver scores of 1 to 3 and 4 or more (MOF) over the 180-day period. All patients had died or were recovered from organ failure or MOF by 180 days.
(Enlarge Image)
Figure 3.
Time to recovery (A) to the left of panel A, the age and burn size were plotted for each of the 541 patients in the Glue Grant study. From top to bottom, the centroid was plotted for age and burn size. To the right of panel B, the Denver organ failure scores were plotted for each time period up to 200 days. The patients can be considered as having no organ failure, in organ failure, or dead. There are 4 categories shown by Denver organ failure scores: no organ failure: 0 (blue), organ failure: 1 to 3 (red), multiple organ failure: ≥4 (brighter red), and dead (black). (B) The Kaplan-Meyer mortality curves and the organ recovery curves over the year postinjury are shown. At each time point, there are 4 patient possibilities plotted as the proportion of the total population: multiple organ failure (below dashed curve), organ failure (above dashed curve and below dotted curve), fully recovered (above dotted curve and below solid curve), or dead (above solid curve).
Table 3 tabulates the values for organ component scores. Overall rate for MOF was substantial, with 27% of patients demonstrating MOF. Pulmonary dysfunction was the most common organ failure after burn injury, with nearly 63% of patients demonstrating some degree of pulmonary failure within the first 3 weeks (early organ failure) after admission and 31.0% after 3 weeks (late organ failure). During the early organ failure phase, cardiac failure was the second most common organ failure, with 29.9% of patients showing abnormal values. Hepatic and renal dysfunctions were uncommon, with only 13% (hepatic) and 16% (renal) of the patients demonstrating any abnormal values during the first 3 weeks. In comparison between adults and children, organ function values were different for each of the organs evaluated. There appeared to be greater cardiac (P = 0.0003), pulmonary (P = 0.0189), and hepatic (P = 0.00002) organ dysfunction and less renal (P = 0.0001) dysfunction in children than in adults. Given the greater degree of organ failure in children, it is surprising that the mortality rate was significantly different compared with adults. ARDS was diagnosed far more commonly in adults (P < 0.0001).
Results
Study Population
Five hundred forty-one patients (300 adults and 241 children) were enrolled in the study. Table 1 shows the baseline and injury characteristics, resuscitation data, outcomes, and complications for the adults (age ≥17 years). In general, adult survivors were younger with smaller burn sizes. When comparing the 2 adult age categories, the mortality rate in those patients aged 55 years or more was greater (38.5% vs 14.1%, P = 0.0001). In these adults, survival was not affected by sex, race, ethnicity, number of comorbidities, or mechanism of injury. Initial base deficit, lactate, and APACHE II scores were all significantly lower for those who survived. Fluid resuscitation volumes were greater than 6 mL/kg/% TBSA and comparable between survivors and nonsurvivors. Even at discharge, the adult patients remained seriously debilitated in that only 52% went directly home. Complications including pneumonia (47%), sepsis (10%), and nosocomial infections (70.7%) were common in these patients who experienced extended lengths of stay and numerous ventilator days. Presence of inhalation injury was associated with mortality (P = 0.0023) in this univariate analysis.
Table 2 shows the baseline and injury characteristics, resuscitation data, outcomes, and complications for children (age <17 years). There was a trend, with females having a higher mortality rate (12.8% vs 5.5%, P = 0.0712). There was a strong statistical difference in mortality related to race (P = 0.0052). Ethnicity, comorbidities, and burn mechanism did not influence the likelihood of survival. Initial base deficit, lactate, and APACHE II scores were lower in those children who survived. As with the adults, average resuscitation fluid volumes exceeded 4 mL/kg/% TBSA, and the presence of inhalation injury was associated with mortality in children (P = 0.008).
As expected, there were multiple differences observed when comparing children and adults. When compared with adults, mortality (7.9% in children vs 14.1% in adults), frequency of complications, and frequency of comorbidities were all substantially lower despite a larger average burn size for the children, 57.8 ± 18.2 versus 41.2 ± 18.3% TBSA. Compared with adults, children had a shorter length of stay (32.2 ± 25.1 vs 51.8 ± 48.1 days) and fewer ventilator days (8.6 ± 14.1 vs 18.7 ± 24.2). The volumes of resuscitation fluid on a 1-mL/kg/% TBSA basis were comparable between children and adults and were not related to the mortality rates (Table 1 and Table 2).
Standard Operating Procedure Compliance
Regarding minimal urinary output, the fluid resuscitation SOP requires that average urinary output be 0.3 mL/kg/h or more. To be compliant, patients with urinary outputs of less than 0.3 mL/kg/h should have received 2 mL/kg/% TBSA or more over the first 24 hours. Compliance was excellent in that 97% of patients met the protocol criterion for both the first and second 24-hour time periods. However, compliance with the requirement of total fluid resuscitation volumes of 2 to 4 mL/kg/% TBSA was poor. Patients received more than the recommended fluid volumes for resuscitation, with 46% of patients receiving greater than 4 mL/kg/% TBSA over the first 24 hours. These compliance values remained stable over the course of the study.
Only 1% of the patients had a recorded mean arterial pressure of 60 mm Hg or less at any time during the first 24 hours postinjury in the settings of the prehospital setting, emergency department(s), transferring facility, or in the participating burn center.
With respect to the protocol for prevention of hyperglycemia, blood glucose levels could have been on-target (<180 mg/dL) or off-target (≥180 mg/dL) if the patient was receiving insulin. Approximately 22.9% of the patients had recorded blood glucose values off-target (≥180 mg/dL) and were not receiving insulin. Compliance with this SOP did not seem to change over the course of the study.
Comparative Outcomes
It has been well described that 3 factors strongly affect the probability of death from burn injuries—age, overall burn size, and presence of inhalation injury. Figure 1A shows a gradual, monotonic effect of age up to approximately 50 years with an inflection point between 50 and 60, indicating that the effect of age becomes more dominant. Similarly, Figure 1B shows a gradual, monotonic effect of burn size of 20% up to approximately 70% TBSA beyond which burn size seems to provide an even stronger effect. With respect to burn size, the LA50 (Lethal Area 50, burn area lethal in 50% of patients) is approximately 90% TBSA. When the adult and pediatric databases were combined, mortality was 19.5% for those with inhalation injury and 8.9% for those without. This difference in mortality has a calculated P < 0.0001 that is unadjusted for potential imbalances other than inhalation injury.
(Enlarge Image)
Figure 1.
Mortality versus age and % TBSA mortality rates were plotted versus age (panel A) and % TBSA (panel B). The Lethal Area 50 (LA50) is shown for each.
Figure 2A shows an invariant mortality rate of approximately 14% over the course of our 7-year study. Figure 2B shows the comparison of mortality in TBSA quintiles of burn size for patients younger than versus older than 50 years in the NBR versus the current study, which suggests that there might be survival improvements in patients younger than 50 years with larger burns. In patients 50 years of age and older, there might be survival improvements in the smaller burns, but there does not seem to be any survival differences in older patients with very large burn injuries.
(Enlarge Image)
Figure 2.
Mortality for Glue Grant study patients compared with the NBR in panel A shows the mortality rate by year for those patients in the Glue Grant study. Comparisons of mortality rates by TBSA quintile and age group (<50 years of age vs ≥50 years of age) for those patients in the Glue Grant with those in the NBR are shown in panel B.
In a comparison of the data in this study versus patients in the NBR after excluding those with burn sizes less than 20% TBSA, a logistic regression stratified on age, burn size, and presence of inhalation injury was performed. Following these adjustments, there was a lower risk of mortality for patients in our current study [odds ratio (OR) = 0.71 (95% confidence interval: 0.53–0.97), P = 0.03]. An analysis of the mortality rate in the Glue cohort alone was based upon a model that predicts expected mortality rate in patients admitted to the Massachusetts General Hospital and Shriners Hospitals for Children—Boston, from 1990 to 1994. The result of this model was highly consistent with the outcomes in this study and predicted that 74.09 deaths would occur versus the 74 deaths that actually occurred (Flora's score Z = -0.01, P = 0.9895).
Figure 3A shows 4 groups of patients categorized by Denver MOF score: 0 (blue), 1 to 3 (red), ≥4 (brighter red), and nonsurvival (black). Note that approximately 30% of the patients demonstrated a score of 0 for all components of the Denver score throughout their entire hospital course. Most patients showed waxing and waning of component Denver scores with occasional scores of 4 or more, consistent with MOF, for periods up to 180 days postinjury. Deaths occurred soon after admission but continued to occur as many as 100 days postadmission. To the left of Figure 3A, there is a scatter plot of both age and burn size for each of the patients shown top to bottom. A smooth curve plots the centroids for each. Figure 3A shows that the average age increased from approximately 25 to 40 years and burn size increased from 40% to 70% TBSA from top to bottom of the figure. These findings are consistent with the finding that those patients with organ failure scores of 0 are younger and with more moderate-sized injuries. Figure 3B identifies 4 categories of patients that show that there were deaths occurring up to 90 to 100 days postinjury. There was gradual recovery for those patients with Denver scores of 1 to 3 and 4 or more (MOF) over the 180-day period. All patients had died or were recovered from organ failure or MOF by 180 days.
(Enlarge Image)
Figure 3.
Time to recovery (A) to the left of panel A, the age and burn size were plotted for each of the 541 patients in the Glue Grant study. From top to bottom, the centroid was plotted for age and burn size. To the right of panel B, the Denver organ failure scores were plotted for each time period up to 200 days. The patients can be considered as having no organ failure, in organ failure, or dead. There are 4 categories shown by Denver organ failure scores: no organ failure: 0 (blue), organ failure: 1 to 3 (red), multiple organ failure: ≥4 (brighter red), and dead (black). (B) The Kaplan-Meyer mortality curves and the organ recovery curves over the year postinjury are shown. At each time point, there are 4 patient possibilities plotted as the proportion of the total population: multiple organ failure (below dashed curve), organ failure (above dashed curve and below dotted curve), fully recovered (above dotted curve and below solid curve), or dead (above solid curve).
Table 3 tabulates the values for organ component scores. Overall rate for MOF was substantial, with 27% of patients demonstrating MOF. Pulmonary dysfunction was the most common organ failure after burn injury, with nearly 63% of patients demonstrating some degree of pulmonary failure within the first 3 weeks (early organ failure) after admission and 31.0% after 3 weeks (late organ failure). During the early organ failure phase, cardiac failure was the second most common organ failure, with 29.9% of patients showing abnormal values. Hepatic and renal dysfunctions were uncommon, with only 13% (hepatic) and 16% (renal) of the patients demonstrating any abnormal values during the first 3 weeks. In comparison between adults and children, organ function values were different for each of the organs evaluated. There appeared to be greater cardiac (P = 0.0003), pulmonary (P = 0.0189), and hepatic (P = 0.00002) organ dysfunction and less renal (P = 0.0001) dysfunction in children than in adults. Given the greater degree of organ failure in children, it is surprising that the mortality rate was significantly different compared with adults. ARDS was diagnosed far more commonly in adults (P < 0.0001).
Source...