Left ventricular failure complicating severe pediatric burn injuries

Burn-Induced Cardiac Dysfunction: A Brief Review and Long-Term Consequences for Cardiologists in Clinical Practice

BACKGROUND

Severe burn injury is a specific type of trauma, which induces a unique complex of responses in the body and leads to an extreme increase in stress hormones and proinflammatory cytokines. These hypermetabolic and stress responses are desirable in the acute phase but can persist for several years and lead - due to several mechanisms - to many late complications, including myocardial dysfunction.

METHODS

The databases of PubMed, ScienceDirect, National Institutes of Health (NIH) of the United States, and Google Scholar were searched. Studies relevant to the topic of late cardiovascular dysfunction after burn injury were compiled using key words.

RESULTS

Burn-induced heart disease significantly increases morbidity and mortality and contributes to the reduction in the quality of life of patients after severe burn trauma. A variety of mechanisms causing myocardial dysfunction after burn trauma have been detailed but understanding all of the exact consequences is limited, especially regarding chronic cardiovascular changes.

CONCLUSION

A detailed understanding of the pathophysiology of chronic cardiac changes can contribute to a comprehensive and preventive treatment plan and improve long-term outcomes of burn patients.

Burn Injury May Have Age-Dependent Effects on Strength and Aerobic Exercise Capacity in Males

Whether burn injury affects boys and men differently is currently unknown. To test the hypothesis that burned boys have lower exercise capacity and exercise training-induced responses compared with burned men, 40 young boys (12 ± 4 years, 149 ± 20 cm, 46 ± 18 kg) were matched to 35 adult men (33 ± 9 years, 174 ± 10 cm, 84 ± 16 kg) based on extent of burn injury (total body surface area burned, boys 46 ± 14% vs men 47 ± 30, P = .85) and length of hospital stay (boys 33 ± 23 vs men 41 ± 32 days, P = .23). Strength (peak torque) and cardiorespiratory fitness (peak VO2) were normalized to kg of lean body mass for group comparisons. Each group was also compared with normative age-sex matched values at discharge and after an aerobic and resistance exercise training (RET) program. A two-way factorial analysis of covariance assessed interaction and main effects of group and time. We found that boys and men showed similar pre-RET to post-RET increases in total lean (~4%) and fat (7%) mass (each P ≤ .008). Both groups had lower age-sex matched norm values at discharge for peak torque (boys 36%; men 51% of normative values) and peak VO2 (boys: 44; men: 59%; each P ≤ .0001). Boys strength were 13-15 per cent lower than men at discharge and after RET (main effect for group, P < .0001). Cardiorespiratory fitness improved to a greater extent in men (19%) compared with boys (10%) after the RET (group × time interaction, P = .011). These results show that at discharge and after RET, burn injury may have age-dependent effects and should be considered when evaluating efficacy and progress of the exercise program.

Short-term metformin and exercise training effects on strength, aerobic capacity, glycemic control, and mitochondrial function in children with burn injury

Severely burned children experience a chronic state of sympathetic nervous system activation that is associated with hypermetabolic/cardiac stress and muscle wasting. Metformin, a diabetes medication, helps control hyperglycemia in obese diabetic populations, and exercise has been shown to improve exercise strength and aerobic exercise capacity after severe burns. However, whether exercise improves glycemic control in burned children and whether combining exercise and metformin improves outcomes to a greater degree than exercise alone are unknown. We tested the hypothesis that a 6-wk exercise program combined with short-term metformin administration (E + M) improves aerobic and strength exercise capacity to a greater degree than exercise and placebo (E), while improving glucose tolerance and muscle metabolic function. We found that, before exercise training, the metformin group compared with the placebo group had attenuated mitochondrial respiration (pmol·s^-1·mg^-1) for each state: state 2 (-22.5 ± 3), state 3 (-42.4 ± 13), and oxphos (-58.9 ± 19) ( P ≤ 0.02, M vs. E + M group for each state). However, in the E + M group, exercise increased mitochondrial respiration in each state ( P ≤ 0.05), with respiration being comparable to that in the E group (each P > 0.05). In both groups, exercise induced comparable improvements in strength (change from preexercise, Δ1.6 ± 0.6 N-M·kg^LBM) and V̇o_2peak (Δ9 ± 7 mlO₂·kg^LBM) as well as fasting glucose (Δ19.3 ± 13 mg·dl) and glucose AUC (Δ3402 ± 3674 mg·dl^-1·min^-1), as measured by a 75-g OGTT (all P ≤ 0.03). Exercise reduced resting energy expenditure in E + M (Δ539 ± 480 kcal/24 h, P < 0.01) but not E subjects ( P = 0.68). Both groups exhibited reduced resting heart rate (Δ30 ± 23 beats/min, P ≤ 0.02). These data indicate that short-term metformin combined with exercise provides no further improvement beyond that of exercise alone for strength, exercise capacity, and glycemic control.

Burn Shock and Resuscitation: Proceedings of a Symposium Conducted at the Meeting of the American Burn Association, Chicago, IL, 21 April 2015

The Special Interest Groups of the American Burn Association provide a forum for interested members of the multidisciplinary burn team to congregate and discuss matters of mutual interest. At the 47th Annual Meeting of the American Burn Association in Chicago, IL, the Fluid Resuscitation Special Interest Group sponsored a special symposium on burn resuscitation. The purpose of the symposium was to review the history, current status, and future direction of fluid resuscitation of patients with burn shock. The reader will note several themes running through the following presentations. One is the perennial question of the proper role for albumin or other fluid-sparing strategies. Another is the unique characteristics of the pediatric burn patient. A third is the need for multicenter trials of burn resuscitation, while recognizing the obstacles to conducting randomized controlled trials in this setting.

Children with Burn Injury Have Impaired Cardiac Output during Submaximal Exercise

INTRODUCTION

Burn trauma damages resting cardiac function; however, it is currently unknown if the cardiovascular response to exercise is likewise impaired. We tested the hypothesis that, in children, burn injury lowers cardiac output (Q˙) and stroke volume (SV) during submaximal exercise.

METHODS

Five children with 49% ± 4% total body surface area (BSA) burned (two female, 11.7 ± 1 yr, 40.4 ± 18 kg, 141.1 ± 9 cm) and eight similar nonburned controls (five female, 12.5 ± 2 yr, 58.0 ± 17 kg, 147.3 ± 12 cm) with comparable exercise capacity (peak oxygen consumption [peak V˙O2]: 31.9 ± 11 vs 36.8 ± 8 mL O2·kg·min, P = 0.39) participated. The exercise protocol entailed a preexercise (pre-EX) rest period followed by 3-min exercise stages at 20 W and 50 W. V˙O2, HR, Q˙ (via nonrebreathing), SV (Q˙/HR), and arteriovenous O2 difference ([a-v]O2diff, Q˙/ V˙O2) were the primary outcome variables.

RESULTS

Using a 2-way factorial ANOVA (group [G] × exercise [EX]), we found that Q˙ was approximately 27% lower in the burned than the nonburned group at 20 W of exercise (burned 5.7 ± 1.0 vs nonburned: 7.9 ± 1.8 L·min) and 50 W of exercise (burned 6.9 ± 1.6 vs nonburned 9.2 ± 3.2 L·min) (G-EX interaction, P = 0.012). SV did not change from rest to exercise in burned children but increased by approximately 24% in the nonburned group (main effect for EX, P = 0.046). Neither [a-v] O2diff nor V˙O2 differed between groups at rest or exercise, but HR response to exercise was reduced in the burn group (G-EX interaction, P = 0.004). When normalized to BSA, SV (index) was similar between groups; however, Q˙ (index) remained attenuated in the burned group (G-EX interaction, P < 0.008).

CONCLUSIONS

Burned children have an attenuated cardiovascular response to submaximal exercise. Further investigation of hemodynamic function during exercise will provide insights important for cardiovascular rehabilitation in burned children.

Children with severe burns display no sex differences in exercise capacity at hospital discharge or adaptation after exercise rehabilitation training

BACKGROUND AND OBJECTIVE

Females have a 50% increased risk of death from burn injury compared to males. However, whether exercise capacity and exercise induced training adaptations differ between burned boys and girls is unknown. This project tested the hypothesis that girls with burns have lower exercise capacity and different exercise induced training adaptations.

METHODS

Twenty-five girls were matched to 26 boys (mean, 95%CI; years 13 [12,14], cm 151 [143,161], kg 54 [45,63]; each P>0.05) for burn injury (% total body surface area burn, 54 [45,62]; P=0.82). Lean body mass (LBM), strength (peak torque) and cardiorespiratory fitness (peak VO₂) were normalized to kg LBM and compared as a percentage of age-sex matched non-burned children (n=26 boys, years 13 [12,14]; n=25 girls, years 13 [12,14]) at discharge (DC) and after aerobic and resistance rehabilitation exercise training (RET).

RESULTS

Using a 2-way factorial ANOVA (group×time), we found both groups had similar 11% change in LBM (87.3% of non-burned values [82.2,92.3]) and after the RET (92.8% [87.2,98.3]; main effect, time P<0.0001). Peak torque increased similarly by 16% in both groups (% of age-sex matched non-burned DC, 55.9 [51.3,60.5]; after RET, 77.5 [72.1,82.9]; main effect, time P<0.0001). Likewise, peak VO₂ increased in both groups by 15% (% of age-sex matched non-burned DC, 56.8 [52.4,61.2] to RET, 72.2 [67.6,76.8]; main effect, time; P<0.0001). Burned children exercise at greater percentage of their peak VO₂ and peak HR compared to non-burned children (Interaction, group×time, P<0.0001).

CONCLUSION

The burn injury does not have sex-dependent effects on LBM or exercise capacity in severely burn injured children. Differences in relative peak VO₂ and peak HR suggest the need for burn specific exercise programs for improving the efficacy of a rehabilitation program.

American College of Critical Care Medicine Clinical Practice Parameters for Hemodynamic Support of Pediatric and Neonatal Septic Shock

OBJECTIVES

The American College of Critical Care Medicine provided 2002 and 2007 guidelines for hemodynamic support of newborn and pediatric septic shock. Provide the 2014 update of the 2007 American College of Critical Care Medicine "Clinical Guidelines for Hemodynamic Support of Neonates and Children with Septic Shock."

DESIGN

Society of Critical Care Medicine members were identified from general solicitation at Society of Critical Care Medicine Educational and Scientific Symposia (2006-2014). The PubMed/Medline/Embase literature (2006-14) was searched by the Society of Critical Care Medicine librarian using the keywords: sepsis, septicemia, septic shock, endotoxemia, persistent pulmonary hypertension, nitric oxide, extracorporeal membrane oxygenation, and American College of Critical Care Medicine guidelines in the newborn and pediatric age groups.

MEASUREMENTS AND MAIN RESULTS

The 2002 and 2007 guidelines were widely disseminated, translated into Spanish and Portuguese, and incorporated into Society of Critical Care Medicine and American Heart Association/Pediatric Advanced Life Support sanctioned recommendations. The review of new literature highlights two tertiary pediatric centers that implemented quality improvement initiatives to improve early septic shock recognition and first-hour compliance to these guidelines. Improved compliance reduced hospital mortality from 4% to 2%. Analysis of Global Sepsis Initiative data in resource rich developed and developing nations further showed improved hospital mortality with compliance to first-hour and stabilization guideline recommendations.

CONCLUSIONS

The major new recommendation in the 2014 update is consideration of institution-specific use of 1) a "recognition bundle" containing a trigger tool for rapid identification of patients with septic shock, 2) a "resuscitation and stabilization bundle" to help adherence to best practice principles, and 3) a "performance bundle" to identify and overcome perceived barriers to the pursuit of best practice principles.

Sepsis in Pediatric Cardiac Intensive Care

OBJECTIVES

In this review, we will discuss risk factors for developing sepsis; the role of biomarkers in establishing an early diagnosis, in monitoring therapeutic efficacy, in stratification, and for the identification of sepsis endotypes; and the pathophysiology and management of severe sepsis and septic shock, with an emphasis on the impact of sepsis on cardiovascular function.

DATA SOURCE

MEDLINE and PubMed.

CONCLUSIONS

There is a lot of excitement in the field of sepsis research today. Scientific advances in the diagnosis and clinical staging of sepsis, as well as a personalized approach to the treatment of sepsis, offer tremendous promise for the future. However, at the same time, it is also evident that sepsis mortality has not improved enough, even with progress in our understanding of the molecular pathophysiology of sepsis.

Burn-induced cardiac dysfunction increases length of stay in pediatric burn patients

The aim of this study was to evaluate cardiac function and clinical outcomes in perioperative pediatric burn patients. Transesophageal echocardiography data were collected on 40 patients from 2004 to 2007. Of the 40 patients who received exams, a complete set of cardiac parameters and outcome variables was obtained in 26 patients. The mean age of the patients was 9.7 ± 0.9 years, and the mean TBSA burn size was 64 ± 3%. Patients were divided into two groups based on systolic function. One group represented patients with ejection fractions of >50% and the other ≤50%. Clinical variables were then compared among the groups. In our cohort, systolic dysfunction was observed in 62% of patients (EF ≤ 50%). Systolic dysfunction was associated with a statistically significant increase in number of surgeries, ventilator days, and length of stay in the intensive care unit. The length of stay in patients with preserved systolic function and those with systolic dysfunction was 34.3 ± 3.3 days and 67.2 ± 4.0 days, respectively. Diastolic function measurements were obtained in 65%, and 88% had evidence of diastolic dysfunction. Diastolic dysfunction was not associated with any statistically significant correlations. This study lends evidence to the well-supported basic science models showing cardiac dysfunction after burns. Additionally, it shows that cardiac dysfunction can have clinical consequences. To our knowledge, this is the first study that shows the clinical sequelae of systolic dysfunction in the perioperative pediatric burn population.

Combination of ketamine and xylazine exacerbates cardiac dysfunction in severely scalded rats during the shock stage

Cardiac inhibition due to burn injury and anesthetics have been documented previously. However, little is known about their combined effects on cardiac function. The aim of the present study was to observe the effects of a ketamine/xylazine (K/X) combination on the cardiac function of rats with severe scalds and compare them with those of avertin. Adult rats were randomly distributed into four groups: the KXB group (scalds anesthetized with K/X, n=10), the KXC group (sham scalds anesthetized with K/X, n=10), the AVB group (scalds anesthetized with avertin, n=10) and the AVC group (sham scalds anesthetized with avertin, n=10). Ketamine and xylazine were administered at 25 and 6 mg/kg, respectively, and avertin at 200 mg/kg before full-thickness scalds or sham scalds of 30% total body surface area (TBSA) were produced. Echocardiographic parameters were assessed following injury. The heart rate (HR) in the KXB group was fatally low during the study period. Fractional shortening (FS%) and ejection fraction (EF) in the KXB group were extremely low initially and remained low. The left ventricular end-diastolic volume (LVEDV) and left ventricular end-systolic volume (LVESV) were reduced in the burned rats. Serum levels of cardiac troponin I (cTnI) were significantly higher in the KXB group than in the AVB group (1.66±0.28 vs. 1.16±0.34 ng/ml, P<0.01). The highest lung wet/dry weight ratio was observed in the KXB group. However, no evident heart tissue pathological changes were observed in these groups. The apoptotic index of myocardial cells and caspase 3 expression level were highest in the KXB group (P<0.01). In conclusion, K/X exacerbated cardiac inhibition in severely scalded rats during the shock stage by a mechanism which may involve mitochondrial apoptosis.

Pediatric Sepsis - Part I: "Children are not small adults!"

The recognition, diagnosis, and management of sepsis remain among the greatest challenges in pediatric critical care medicine. Sepsis remains among the leading causes of death in both developed and underdeveloped countries and has an incidence that is predicted to increase each year. Unfortunately, promising therapies derived from preclinical models have universally failed to significantly reduce the substantial mortality and morbidity associated with sepsis. There are several key developmental differences in the host response to infection and therapy that clearly delineate pediatric sepsis as a separate, albeit related, entity from adult sepsis. Thus, there remains a critical need for well-designed epidemiologic and mechanistic studies of pediatric sepsis in order to gain a better understanding of these unique developmental differences so that we may provide the appropriate treatment. Herein, we will review the important differences in the pediatric host response to sepsis, highlighting key differences at the whole-organism level, organ system level, and cellular and molecular level.

Pulmonary artery catheters

BACKGROUND

After its introduction in 1970, the use of the pulmonary artery catheter became a central part of the management of critically ill patients in adult and pediatric intensive care units. However, because it was introduced as a class II device, efficacy for its safety and clinical benefit did not exist during the early years of use. This review describes the pulmonary artery catheter and reviews the literature supporting its use.

METHODOLOGY

A search of MEDLINE, PubMed, and the Cochrane Database was made to find literature about pulmonary artery catheter use. Literature for both adult and pediatric patients was reviewed. Guidelines published by the Society for Critical Care Medicine and the American Heart Association were reviewed, including further review of references cited.

RESULTS AND CONCLUSIONS

The evidence supporting the use of the pulmonary artery catheter is mostly limited to level IV (nonrandomized, historical controls, and expert opinion) and level V (case series, uncontrolled studies, and expert opinion). A higher level of evidence supports the use of the pulmonary artery catheter in selected pediatric patients, especially those with pulmonary arterial hypertension and shock refractory to standard fluid resuscitation and vasoactive agents. There are no data to suggest that use of the pulmonary artery catheter increases mortality in children.

Fluid resuscitation protocols for burn patients at intensive care units of the United Kingdom and Ireland

Introduction: The objective of this study was to determine the thermal injury fluid resuscitation protocols at intensive care units (ICUs) in the United Kingdom and Ireland.

Materials and methods: A telephone questionnaire was designed to survey the fluid resuscitation protocols of ICUs at all hospitals with plastic/burn surgery departments in the British Isles in 2010. The feedback from the questionnaire was from the senior nurse in charge of the ICUs.

Results: 32/64 (50%) of these ICUs had provided care to burns patients. A 100% response from these 32 units was obtained. 71.4% commence fluid resuscitation at 15% total body surface area burn (TBSA), 21.4% at 20% TBSA and 7.1% at 10% TBSA in adults. The estimated resuscitation volume was most often calculated using the Parkland/Modified Parkland formula (87.5%) or the Muir and Barclay formula (12.5%). Interestingly, of the ICUs using formulae, two had recently moved from using the Muir and Barclay formula to Parkland formula and one had recently moved from using the Parkland formula to Muir and Barclay formula. Despite this, 37.5% of ICUs using a formula did not rigidly follow it exactly. The most commonly used resuscitation fluid was Ringer’s lactate solution (46.9%) and Human Albumin Solution was used in 12.5%. No ICU used red cell concentrate as a first line fluid. 18.8% used a central line. 40.6% ICUs considered changing the IV solution during resuscitation. 78.1% ICUs consider urine output to be the most important factor in modifying resuscitation volumes. 59.4% ICUs calculate a maintenance fluid rate after completion of resuscitation. The endpoint for resuscitation was at 24 h in 46.9% ICUs and at 36 h in 9.4%. 5/32 (16%) felt their protocol gave too little and 6/32 (19%) felt their protocol gave too much. 59.3% ICUs gave oral/enteral fluids by naso-gastric or naso-jejenal tubes. 21.9% felt that oral/enteral resuscitation worked. Exactly half of the units believed that the formula that they used provided approximately the right amount of fluid, with 25% believing that it provided too much and 21.9% that it provided too little.

Discussion and conclusion: There is substantial variation in the fluid resuscitation protocols for burns of ICUs in the British Isles. The different practices demonstrated in this survey may have important consequences as inadequate fluid resuscitation can limit perfusion to potentially recoverable burns, grafted tissue and body organs not directly injured.

The host response to sepsis and developmental impact

Invasion of the human by a pathogen necessitates an immune response to control and eradicate the microorganism. When this response is inadequately regulated, systemic manifestations can result in physiologic changes described as "sepsis." Recognition, diagnosis, and management of sepsis remain among the greatest challenges shared by the fields of neonatology and pediatric critical care medicine. Sepsis remains among the leading causes of death in both developed and underdeveloped countries and has an incidence that is predicted to increase each year. Despite these sobering statistics, promising therapies derived from preclinical models have universally failed to obviate the substantial mortality and morbidity associated with sepsis. Thus, there remains a need for well-designed epidemiologic and mechanistic studies of neonatal and pediatric sepsis to improve our understanding of the causes (both early and late) of deaths attributed to the syndrome. In reviewing the definitions and epidemiology, developmental influences, and regulation of the host response to sepsis, it is anticipated that an improved understanding of this host response will assist clinician-investigators in identifying improved therapeutic strategies.

Anesthetic considerations for major burn injury in pediatric patients

Major burn injury remains a significant cause of morbidity and mortality in pediatric patients. With advances in burn care and with the development of experienced multi-disciplinary teams at regionalized burn centers, many children are surviving severe burn injury. As members of the multi-disciplinary care team, anesthesia providers are called upon to care for these critically ill children. These children provide several anesthetic challenges, such as difficult airways, difficult vascular access, fluid and electrolyte imbalances, altered temperature regulation, sepsis, cardiovascular instability, and increased requirements of muscle relaxants and opioids. The anesthesia provider must understand the physiologic derangements that occur with severe burn injury as well as the subsequent anesthetic implications.

Clinical practice parameters for hemodynamic support of pediatric and neonatal septic shock: 2007 update from the American College of Critical Care Medicine

BACKGROUND

The Institute of Medicine calls for the use of clinical guidelines and practice parameters to promote "best practices" and to improve patient outcomes.

OBJECTIVE

2007 update of the 2002 American College of Critical Care Medicine Clinical Guidelines for Hemodynamic Support of Neonates and Children with Septic Shock.

PARTICIPANTS

Society of Critical Care Medicine members with special interest in neonatal and pediatric septic shock were identified from general solicitation at the Society of Critical Care Medicine Educational and Scientific Symposia (2001-2006).

METHODS

The Pubmed/MEDLINE literature database (1966-2006) was searched using the keywords and phrases: sepsis, septicemia, septic shock, endotoxemia, persistent pulmonary hypertension, nitric oxide, extracorporeal membrane oxygenation (ECMO), and American College of Critical Care Medicine guidelines. Best practice centers that reported best outcomes were identified and their practices examined as models of care. Using a modified Delphi method, 30 experts graded new literature. Over 30 additional experts then reviewed the updated recommendations. The document was subsequently modified until there was greater than 90% expert consensus.

RESULTS

The 2002 guidelines were widely disseminated, translated into Spanish and Portuguese, and incorporated into Society of Critical Care Medicine and AHA sanctioned recommendations. Centers that implemented the 2002 guidelines reported best practice outcomes (hospital mortality 1%-3% in previously healthy, and 7%-10% in chronically ill children). Early use of 2002 guidelines was associated with improved outcome in the community hospital emergency department (number needed to treat = 3.3) and tertiary pediatric intensive care setting (number needed to treat = 3.6); every hour that went by without guideline adherence was associated with a 1.4-fold increased mortality risk. The updated 2007 guidelines continue to recognize an increased likelihood that children with septic shock, compared with adults, require 1) proportionally larger quantities of fluid, 2) inotrope and vasodilator therapies, 3) hydrocortisone for absolute adrenal insufficiency, and 4) ECMO for refractory shock. The major new recommendation in the 2007 update is earlier use of inotrope support through peripheral access until central access is attained.

CONCLUSION

The 2007 update continues to emphasize early use of age-specific therapies to attain time-sensitive goals, specifically recommending 1) first hour fluid resuscitation and inotrope therapy directed to goals of threshold heart rates, normal blood pressure, and capillary refill 70% and cardiac index 3.3-6.0 L/min/m.

Cardiovascular distribution of the calcium sensing receptor before and after burns

Due to up-regulation of the parathyroid gland calcium-sensing receptor (CaR), burned children have hypocalcemic hypoparathyroidism, and decreased myocardial contractility. Our aim was to localize the CaR in the heart and measure receptor density changes due to burns. Heart and aorta samples from sheep subjected to 40% burn or sham conditions were probed for CaR via fluorescence microscopy. CaR was localized to endocardial endothelium, myocardial microvasculature, and fibroblasts and vessels of the aortic adventitia. CaR was not found in cardiomyocytes or smooth muscle cells. No differences in density of CaR or beta-adrenergic receptors were noted. No differences in CaR distribution were seen in the myocardium or aorta, in contrast to the parathyroid where burn injury up-regulates CaR. We suggest that CaR has a local, tissue-specific role, and functions in vascular calcium sensing for intravascular calcium deposition or regulation of other calcium channels after trauma or burn.

Role of p38 mitogen-activated protein kinase pathway on heart failure in the infant rat after burn injury

We examined the hypothesis that post-burn activation of the p38 mitogen-activated protein kinase (MAPK) pathway is one aspect of the signalling cascade culminating in post-burn secretion of tumour necrosis factor (TNF)-alpha which contributes to post-burn myocardial apoptosis. Studies were designed to determine the time course of the induction of p38MAPK, TNF-alpha and myocardial apoptosis after burn injury. Our quantitative bacterial culture data demonstrated that viable bacteria reached the heart, and Western blotting data identified the increase in the phosphorylation of p38MAPK at an early time after burn. The peak incidence of myocardial apoptosis was also seen at an early time after burn. The expression of TNF-alpha mRNA, infiltrated neutrophils and serum creatine phosphokinase myocardial band data peaked at a late time after burn. FR167653, a specific inhibitor of p38MAPK, prevented the induction of myocardial apoptosis, TNF-alpha expression and myocardial injury after burn. Presumably, the bacterial LPS-induced activation of p38MAPK pathway occurring at an early time after burn induced the subsequent myocardial apoptosis. The p38MAPK-induced activation of pro-inflammatory cytokine appeared to promote the degenerative myocardial injury at a late time after burn. Our present data provided evidence for the hypothesis that the p38MAPK pathway controls both myocardial apoptosis and the pro-inflammatory mediator.

Small skin burn injury reduces cardiac tolerance to ischemia via a tumor necrosis factor alpha-dependent pathway

BACKGROUND

Large burns cause systemic inflammation and myocardial depression. We hypothesized that small burns affect cardiac tolerance to ischemia, and that tumor necrosis factor alpha (TNFalpha) signaling through endothelin-1 (ET) and nuclear factor kappa B (NF kappaB) are associated.

METHODS

Mice were randomly assigned to four groups: burn (caused by boiling water on <2% of the body surface area), sham, burn+etanercept (TNFalpha blocker) treatment and sham+etanercept treatment. Twenty-four hours later, hearts were isolated and subjected to global ischemia followed by reperfusion. Additional hearts and burned skin lesions were sampled to evaluate expression of TNFalpha (immunoblotting) and endothelin-1 (radioimmunoassay). A NF kappaB-luciferase reporter mouse was used to evaluate NF kappaB activation.

RESULTS

Baseline cardiac function before ischemia (BI) was only negligibly influenced by burn or etanercept, but was reduced by burn+etanercept. Burn markedly impaired post-ischemic left ventricular function and increased infarct size in comparison with sham-treated mice. Cardiac, but nut cutaneous, expression of TNFalpha was increased in burned mice, while cardiac NF kappaB and endothelin-1 were not influenced. TNFalpha blockade reduced the detrimental effects of burn on cardiac tolerance to ischemia.

CONCLUSIONS

Small cutaneous burns, that did not influence baseline heart function, impaired the tolerance to ischemia. This effect may be mediated through TNFalpha, but does not involve signaling through NF kappaB or endothelin-1.

Continuous noninvasive monitoring of cardiac performance and tissue perfusion in pediatric trauma patients

PURPOSE

The aim of this study was to assess the accuracy of a continuous survival probability prediction using noninvasive measures of cardiac performance and tissue perfusion in severely injured pediatric patients.

METHODS

Review of all patients entered into a prospective noninvasive monitoring protocol. Cardiac index (CI) was measured using a thoracic bioimpedance device and tissue perfusion was assessed by transcutaneous carbon dioxide (Ptcco(2)) tension and oxygen tension indexed to the fraction of inspired oxygen (Ptco(2)/Fio(2)). Survival probability (SP) was continuously calculated using a stochastic analysis program.

RESULTS

There were 45 patients with a total of 953 data sets. The mean age was 11 years (range, 1-16 years) with a mean Injury Severity Score of 24 (+/-16). There was no difference between survivors (n = 32) and nonsurvivors (n = 13) at study entry for heart rate, blood pressure, CI, or pulse oximetry (all P > .05). However, survivors demonstrated higher Ptcco(2) (45 vs 35), higher Ptco(2)/Fio(2) (236 vs 156), and higher predicted SP (89% vs 62%) compared with nonsurvivors at study entry and throughout the monitoring period (all P < .01). For the entire data set, the strongest independent predictors of survival were Ptco(2)/Fio(2) and SP. The area under the receiver operating characteristic curve for mortality prediction was 0.83 for SP and 0.71 for Ptco(2)/Fio(2), compared with 0.6 for heart rate, 0.51 for blood pressure, and 0.53 for CI. Similar hemodynamic patterns were observed for all injury patterns with the exception of those with severe brain injury.

CONCLUSIONS

Thoracic bioimpedance and transcutaneous monitoring give critical real-time hemodynamic and tissue perfusion data that can provide early identification of pathologic flow patterns and accurately predict survival.

Macrophage migration inhibitory factor mediates late cardiac dysfunction after burn injury

We have recently demonstrated that macrophage migration inhibitory factor (MIF) is a myocardial depressant protein and that MIF mediates late, prolonged cardiac dysfunction after endotoxin challenge in mice. Because many factors, including endotoxin, have been implicated in the pathogenesis of cardiac dysfunction after burn injury, we tested the hypothesis that MIF might also be the mediator of prolonged cardiac dysfunction in this model. At 4 h after 40% total body surface area burn in anesthetized mice, serum MIF levels increased significantly compared with baseline (2.2-fold). This increase was accompanied by a significant decrease in cardiac tissue MIF levels (2.1-fold decrease compared with controls). This pattern was consistent with MIF release from preformed cytoplasmic stores in the heart and other organs. To determine whether MIF mediates cardiac dysfunction after burn injury, mice were pretreated with anti-MIF neutralizing monoclonal antibodies or isotype control antibodies. Beginning 4 h after burn injury (and continuing through 48 h), burned mice demonstrated a significantly depressed left ventricular shortening fraction of 38.6 +/- 1.8%, compared with the normal controls (56.0 +/- 2.6%). Mice treated with anti-MIF displayed an initial depression of cardiac function similar to nontreated animals but then showed rapid restoration of cardiac function with complete recovery by 24 h, which persisted for the duration of the protocol. This study is the first to demonstrate that MIF mediates late, prolonged cardiac dysfunction after burn injury and suggests that MIF blockade should be considered a therapeutic target for the treatment of burn injury.

Myocardial function and haemodynamics in extensive burn trauma: evaluation by clinical signs, invasive monitoring, echocardiography and cytokine concentrations. A prospective clinical study

BACKGROUND

The objectives of this study were to (1). describe the haemodynamic profile of patients with extensive burns during the early fluid resuscitation phase, (2). evaluate myocardial performance by invasive monitoring and echocardiography and (3). analyze the relations between serum cytokine (IL-6, IL-8, TNF) and natriuretic peptide (ANP, BNP) concentrations and myocardial function in these patients.

METHODS

Prospective, clinical study in a tertiary care burn centre. Invasive haemodynamic measurements including a pulmonary artery catheter, echocardiography, blood samples for cytokine and atriopeptide analyses. The follow-up time was up to 72 h postinjury.

RESULTS

According to echocardiography, patients were hypovolaemic despite aggressive (median 7,9 ml kg(-1) h(-1), range 3.3-11.7) fluid resuscitation and adequate urine output (median 0.9 ml kg(-1) h(-1), range 0.46-1.35) during the first day postinjury. There were no consistent findings of hyperlactatemia, metabolic acidosis or low mixed venous oxygen saturations. Daily highest and lowest values of cardiac index and stroke volume index increased and the lowest and highest values of systemic vascular resistance decreased. Cardiac performance (stroke volume index) improved during the study period even though there were no initial signs of myocardial depression in echocardiography. Three patients received a dobutamine infusion based on clinical judgement. There was no consistent association between haemodynamic changes and plasma cytokine concentrations.

CONCLUSION

Persisting hypovolaemia is evident in the resuscitation phase of extensive burns despite aggressive fluid therapy and the lack of classic signs of hypoperfusion. Cardiac performance improves during the first days after extensive burn injury without association with plasma cytokine profile.

Nitric oxide, inflammation and acute burn injury

Nitric oxide (NOz.rad;) is a diatomic mediator liberated on oxidation of L-arginine by the nitric oxide synthase (NOS) family of enzymes. It has complex and wide ranging functions in vivo and has been implicated in the development of the profound inflammatory response that occurs as a result of cutaneous burn injury. In addition, dysregulation of NOS activity has been associated with multiple organ failure in human burn patients and may therefore represent a novel therapeutic target in such circumstances. This review focuses on the role of NOz.rad; in inflammation, with particular emphasis on the acute post-burn inflammatory response. Specific areas of discussion include the maintenance of microvascular haemostasis, leukocyte recruitment and remote organ dysfunction following thermal injury.

Burns

During the past 20 yrs, as burn care has evolved as a specialty of surgery, survival and outcome quality have soared. Public expectations for survival and long-term outcomes are at previously unprecedented levels. These changes are the result of a number of advances in aspects of burn care that have occurred in parallel and have fostered increasing regionalization of this resource-intensive activity into fewer specialized centers. These are complex hospitalizations and can be divided into four phases: initial evaluation and resuscitation, initial wound excision and biological closure, definitive wound closure, and rehabilitation and reconstruction.

TLR4 inactivation and rBPI(21) block burn-induced myocardial contractile dysfunction

Both large burns and severe gram-negative sepsis are associated with acute myocardial contractile dysfunction. Because others have reported that burn injury may be followed by transient endotoxemia, we hypothesized that bacterial endotoxin induces contractile impairment after burn trauma. We tested this hypothesis in two rodent models. In each model, postburn myocardial contractility was assessed using Langendorff preparations of excised hearts. In the first model, mice expressing either a mutant form of or no Toll-like receptor 4 (TLR4), a critical element of the mammalian endotoxin receptor, were resistant to postburn myocardial contractile dysfunction. In the second model, starting 30 min or 4 h after burn injury, rats were infused with recombinant bactericidal/permeability-increasing protein (rBPI(21)), a protein that binds and neutralizes endotoxin. Hearts from rBPI(21)-treated animals were completely protected from postburn contractile impairment. Because burn-induced contractile dysfunction can be prevented either by blocking signaling through the endotoxin receptor or by neutralizing circulating LPS, bacterial endotoxin may contribute to impaired myocardial contractility after burn injury.

Correlation between QT dispersion and burn severity

QT dispersion, defined as the maximal-minus-minimal QT interval on a 12-lead electrocardiogram, has emerged as a non-invasive measurement for quantifying the spatial inhomogeneity of ventricular repolarization under various conditions, including acute stress. Because burn injuries elicit acute stress reactions, it was hypothesized that QT dispersion increases with the severity of the burn injury. To test the hypothesis, 13 burned patients (age range of 22-76 years, nine males, ranging from 4.0 to 75.0% of total body surface area burned) in whom a measurable 12-lead electrocardiogram had been obtained within 4h after arrival at the emergency department were identified retrospectively, and their QTc intervals, i.e. QT intervals corrected for heart rate by the standard Bazett formula, were measured. QTc dispersion (QTcd) was then calculated, and correlations were assessed with burn severity (burn index, BI; prognostic burn index, PBI). Of the 13 patients, nine patients had a prolonged QTcd (>40 ms), and linear correlation analyses showed significant positive correlations between QTcd and both BI and PBI (r=0.61 and 0.62, respectively). In conclusion, QT dispersion was greater in the burned patients, and although the pathophysiology was unclear from the present study, the findings suggested that acute stress contributed to the spatial inhomogeneity of ventricular repolarization.

Reversible myocardial dysfunction in critically ill, noncardiac patients: a review

OBJECTIVE

To review reversible myocardial dysfunction affecting critically ill patients without cardiac pathology.

DATA SOURCES

The bibliography for the study was compiled through a search of different databases for the period 1966-2001. References cited in the selected articles also were reviewed.

STUDY SELECTION

The selection criteria included all articles published on reversible myocardial dysfunction in critically ill patients.

CONCLUSIONS

Reversible myocardial dysfunction may develop in a situation of critical pathology, but the etiology of reversible myocardial dysfunction is not fully understood. This dysfunction may be accompanied by increases in enzyme concentrations and electrocardiographic changes. Reversible myocardial dysfunction probably is underdiagnosed, although its presence is associated with a worsening of the prognosis and with more specific therapeutic options. Further studies are necessary to define its true incidence and clinical implications.

Clinical practice parameters for hemodynamic support of pediatric and neonatal patients in septic shock

BACKGROUND

The Institute of Medicine has called for the development of clinical guidelines and practice parameters to develop "best practice" and potentially improve patient outcome.

OBJECTIVE

To provide American College of Critical Care Medicine clinical guidelines for hemodynamic support of neonates and children with septic shock.

SETTING

Individual members of the Society of Critical Care Medicine with special interest in neonatal and pediatric septic shock were identified from literature review and general solicitation at Society of Critical Care Medicine Educational and Scientific Symposia (1998-2001).

METHODS

The MEDLINE literature database was searched with the following age-specific keywords: sepsis, septicemia, septic shock, endotoxemia, persistent pulmonary hypertension, nitric oxide, and extracorporeal membrane oxygenation. More than 30 experts graded literature and drafted specific recommendations by using a modified Delphi method. More than 30 more experts then reviewed the compiled recommendations. The task-force chairman modified the document until <10% of experts disagreed with the recommendations.

RESULTS

Only four randomized controlled trials in children with septic shock could be identified. None of these randomized trials led to a change in practice. Clinical practice has been based, for the most part, on physiologic experiments, case series, and cohort studies. Despite relatively low American College of Critical Care Medicine-graded evidence in the pediatric literature, outcomes in children have improved from 97% mortality in the 1960s to 60% in the 1980s and 9% mortality in 1999. U.S. hospital survival was three-fold better in children compared with adults (9% vs. 27% mortality) in 1999. Shock pathophysiology and response to therapies is age specific. For example, cardiac failure is a predominant cause of death in neonates and children, but vascular failure is a predominant cause of death in adults. Inotropes, vasodilators (children), inhaled nitric oxide (neonates), and extracorporeal membrane oxygenation can be more important contributors to survival in the pediatric populations, whereas vasopressors can be more important contributors to adult survival.

CONCLUSION

American College of Critical Care Medicine adult guidelines for hemodynamic support of septic shock have little application to the management of pediatric or neonatal septic shock. Studies are required to determine whether American College of Critical Care Medicine guidelines for hemodynamic support of pediatric and neonatal septic shock will be implemented and associated with improved outcome.

[Initial shock from burns. Physiopathology: therapeutic principles]

Widespread destruction of the skin induces a large necrotic mass and a break of the skin barrier. It also leads to an intense inflammatory reaction. This activates keratinocytes, endothelial cells and neutrophils. Certain mediators (e.g. endothelin, histamine, bradykinin, serotonin, catecholamines, vasopressin, prostaglandins, cytokines and nitrogen monoxide) are thus released in large quantities and act both at the site of the burns and at a distance. The abnormally high level of albumin in the capillary wall and the increased capacity of absorption of the interstitial areas around the burns are the main abnormalities observed. This results in a hypovolemia associated with a hemoconcentration, hyponatremia, hypoalbuminemia, systemic vasoconstriction and myocardial malfunction, which is difficult to evidence. During the initial phase, the major risk is the appearance of hypovolemic shock, which is rapidly irreversible if early treatment is not administered. Vascular filling with iso- or hyper-osmolar sodium crystalloids, associated with buffer solutions, is the first line. There is still debate regarding the best moment at which to give albumin. A hyperkinetic shock may occur after several hours and despite the filling. The symptoms are tachycardia, increased heart rate and a dramatic decrease in systemic vascular resistance. This may lead to metabolic acidosis and multi-organ failure. Study of the hemodynamic profile of the patient allows the rational use of pressor amines and haemodialysis.

Role of nitric oxide in myocardial dysfunction after combined burn and smoke inhalation injury

This study tested the hypothesis that nitric oxide (NO) synthesized from inducible NO synthase (iNOS) is responsible for the cardiac dysfunction observed after burn and smoke inhalation injury. Twelve sheep received 40% third-degree burn and smoke inhalation under halothane anesthesia. The animals were divided into two groups: a MEG group [iNOS was inhibited with mercaptoethylguanidine (MEG), a selective inhibitor of iNOS, n=6] and a control group (n=6). The control group showed a significant increase in NO(2)(-)/NO(3)(-) (NO(x)) concentration, metabolite of NO, in plasma after 24 h, whereas the MEG group did not. In the control group, cardiac depression was observed immediately after injury associated with hemoconcentration. Cardiac function returned to a normal level within 6 h following injury. In the control group cardiac dysfunction was observed again after 24 h although the hemoconcentration peaked at 24 h after injury and then began to resolve. In the MEG group, cardiac depression and hemoconcentration were not observed. The present data suggest that cardiac depression seen with this combination injury consists of two phases and that the later phase is mediated by iNOS-NO.

Septic shock

Infection is problematic because it affects many patients (adults and children), is a major cause of death in intensive care units (ICU) worldwide, and uses a large amount of hospital resources. The mortality rate among patients with septic shock varies but approximates 40% in infected patients admitted to ICUs. Because of the large number of adults dying of sepsis, many resources are expended. Children are physiologically different from adults, but nonetheless, many similarities exist with respect to the response to septic shock.

Cardiac apoptosis in burned rats with delayed fluid resuscitation

Clinical and experimental studies have shown that delayed fluid resuscitation postburn decreases heart function. We hypothesized that apoptosis occurs in the cardiomyocyte in this condition. To investigate this hypothesis, rats were burned, fluid resuscitation was delayed, and the integrity of cardiac genomic DNA in the burned rats was determined with an LM-PCR Ladder Assay kit. DNA fragmentation shown as DNA ladders on gels, the hallmark of apoptosis, was found in the heart tissue of these rats. In the early phase of delayed fluid resuscitation, the nuclear factor kappa B (NF-kappa B) was examined using an electrophoretic mobility shift assay and was found to be activated. In comparison with burned rats with immediate fluid resuscitation, nitric oxide levels in hearts from burned rats with delayed fluid resuscitation were significantly lower (P<0.01). These results suggest that apoptosis may be an important pathway for cardiac injury, which may result from the activation of NF-kappa B and decreased nitric oxide levels.

Cardiac compromise in a patient with Down's Syndrome: a lesson learnt

A 49 year old burn victim with Down's Syndrome (Trisomy 21) was admitted with 15% body surface area (BSA) superficial burns. This was complicated by a large atrioseptal defect. Her course was stormy with difficulties encountered in managing her fluid status. Adequate fluid resuscitation was difficult to maintain with a fragile compromise between pulmonary insufficiency and renal impairment. She expired 12 days post-injury. Cardiac anomalies are not uncommon in the subgroup of patients with major burns who respond poorly to fluid resuscitation.

Long-term outcomes of burned children after in-hospital cardiac arrest

OBJECTIVE

Cardiopulmonary resuscitation (CPR) in severely burned patients experiencing cardiac arrest (CA) has been considered by some as futile. The objective of this article is to report predisposing factors and the outcomes of burned children experiencing in-hospital CA at our institution.

DESIGN

The records of 595 children admitted from 1985 to 1998 with burns covering >35% of their total body surface area were reviewed. Thirty-four children receiving CPR after in-hospital CA were studied for predisposing factors and long-term outcomes.

SETTING AND PATIENTS

Shriners Burns Hospital. Burned children of both genders, 0.5-19 yrs of age, who experienced in-hospital CA and received CPR.

INTERVENTION

Standard burn care and CPR.

MEASUREMENTS AND MAIN RESULTS

Predisposing factors of CA, mortality, and long-term outcomes were measured. The incidence of CA in burned children with burns on >35% total body surface area was 5.7%. No significant difference in age or burn size could be shown between long-term CA survivors (n = 17) and nonsurvivors (n = 17). CPR was successful (defined as survival for at least 1 day after CA) in 22 of 34 children (65%), with 17 of the 22 survivors (77%) experiencing long-term survival, currently from 2-14 yrs. Significant predisposing factors of CA were sepsis, identified in 53% of the nonsurvivors vs. 12% of the survivors (p<.05), and delayed fluid resuscitation (>2 hrs after burn injury), identified in 82% of the nonsurvivors vs. 6% of the survivors (p<.001). There was only one morbid long-term survivor. This survivor was diagnosed as having anoxic brain injury with persistent neurologic deficiencies.

CONCLUSION

In this study, 50% of the burned children experiencing CA are long-term survivors. We suggest that all burned children with CA should be afforded cardiopulmonary resuscitation.

[Management of severe burns during the 1st 72 hours]

Early and efficient management of severely burned patients facilitates outcome improvement. Pre-hospital care includes fluid loading with 2 mL.kg-1/% burn over the first six hours, sedation and analgesia, prevention of hypothermia and ventilatory support for either critically burned patients or facial, cervical or pulmonary burn injury. The transient stay in a general hospital before transfer to a burn centre allows extension of initial care, the critical investigation for associated injuries (intoxication, multiple trauma) and to perform initial local treatment with sterile coverage or vaseline gauze after a revised assessment of the burned skin area, and possibly escharotomies. The main aim of care in the burn centre is to control hypovolaemia and to obtain maximal tissue perfusion and oxygen delivery to burned tissues, as well as to healthy organs. To manage the burn shock (initially hypovolemic and later on hyperdynamic) catecholamines are often indicated when appropriate fluid loading remains insufficient. Mechanical ventilation is indicated in case of either a deep extensive burn over 60% of total body surface area, or facial and cervical burns or severe pulmonary burn injury from smoke inhalation, carbon monoxide intoxication, tracheobronchial thermal injury and blast injury. Because of the severity of burn-related pain, and the stimulus linked to intensive care, continuous sedation is usually required. Early surgical treatment such as escharotomies, excision and grafting, which cause significant pain as well as blood loss, and hydrotherapy, often require general anaesthesia. Burn injury can modify the volume of distribution and the pharmacokinetics of anaesthetic agents. Finally, chemical or electrical burn, radiation, associated CO intoxication or multiple trauma, as well as burn injury in infants, raise specific problems. With improvement in early intensive care, the survival rate of the most severely burned patients is obviously improving. New techniques in skin substitution will probably further improve the final outcome.

Hemodynamic support in fluid-refractory pediatric septic shock

OBJECTIVE

Assess outcome in children treated with inotrope, vasopressor, and/or vasodilator therapy for reversal of fluid-refractory and persistent septic shock.

DESIGN

Survey; case series.

SETTING

Three pediatric hospitals.

PATIENTS

Fifty consecutive patients with fluid-refractory septic shock with a pulmonary artery catheter within 6 hours of resuscitation.

INTERVENTIONS

Patients were categorized according to hemodynamic state and use of inotrope, vasopressor, and/or vasodilator therapy to maintain cardiac index (CI) >3.3 L/min/m2 and systemic vascular resistance >800 dyne-sec/cm/m to reverse shock.

OUTCOME MEASURES

Hemodynamic state, response to class of cardiovascular therapy, and mortality.

RESULTS

After fluid resuscitation, 58% of the children had a low CI and responded to inotropic therapy with or without a vasodilator (group I), 20% had a high CI and low systemic vascular resistance and responded to vasopressor therapy alone (group II), and 22% had both vascular and cardiac dysfunction and responded to combined vasopressor and inotropic therapy (group III). Shock persisted in 36% of the children. Of the children in group I, 50% needed the addition of a vasodilator, and in group II, 50% of children needed the addition of an inotrope for evolving myocardial dysfunction. Four children showed a complete change in hemodynamic state and responded to a switch from inotrope to vasopressor therapy or vice versa. The overall 28-day survival rate was 80% (group I, 72%; group II, 90%; group III, 91%).

CONCLUSIONS

Unlike adults, children with fluid-refractory shock are frequently hypodynamic and respond to inotrope and vasodilator therapy. Because hemodynamic states are heterogeneous and change with time, an incorrect cardiovascular therapeutic regimen should be suspected in any child with persistent shock. Outcome can be improved compared with historical literature.