Popliteal artery injuries. Less ischemic time may lead to improved outcomes

BACKGROUND

Popliteal artery injuries are rare. They have high amputation rates.

OBJECTIVES

To report our experience, identify predictors of outcome; mechanism of injury (MOI), Mangled Extremity Severity Score (MESS) score and length of ischemic time. We hypothesized that ischemic time as close to six hours results in improved outcomes.

METHODS

Retrospective 132-month study. All popliteal artery injuries. Urban Level I Trauma Center.

OUTCOME MEASURES

MOI, ISS, MESS, ischemic time, risk factors for amputation, role of popliteal venous injuries, and limb salvage.

STATISTICAL ANALYSIS

univariate and multivariate.

RESULTS

76 patients - 59 (76.1%) males and 17 (22.4%) females. MOI: penetrating - 54 (71%). MESS for penetrating injuries - 5.8 ± 1.5, blunt injuries - 5.6 ± 1.8. Admission-perfusion restoration (n = 76) - 5.97 hours (358 minutes). Ischemic time was not predictive of outcome (p = 0.79). Ischemic time penetrating (n = 58) 5.9 hours (354 ± 209 minutes), blunt 6.1 hours (371 ± 201 minutes). Popliteal arterial repairs: RSVG 44 (58%), primary repair 21 (26%), PTFE 3 (4%), vein patch 2 (2%), ligation 2 (3%), exsanguinated 4 (6%). No patients underwent stenting. Popliteal Vein: Repair 19 (65%), ligation 10 (35%). Fasciotomies 45 patients (59%).

OUTCOMES

Limb salvage - 90% (68/76). Adjusted limb salvage excluding intraoperative deaths - 94% (68/72). Selected patient characteristics; MOI: penetrating vs. blunt - age (p <0.0005). Amputated vs. non-amputated patients, age (p < 0.05). ISS (p < 0.005) predicted amputation, MESS (p = 0.98) did not. Mean ischemic time (p = 0.79) did not predict amputation. Relative risk of amputation, MOI - blunt (p = 0.26, RR 4.67, 95% CI: 1.11 - 14.1), popliteal artery ligation (p = 0.06, RR 3.965, 95% CI: 1.11 - 14.1) as predictors of outcome. Combined artery and vein injuries (p = 0.25) did not predict amputation.

CONCLUSIONS

Decreasing ischemic time from arrival to restoration of perfusion may lead to improved outcomes and increased limb salvage. MESS is not predictive for amputation. Blunt MOI is a risk factor for amputation. Maintaining ischemic times as close to six hours as possible may lead to improved outcomes.

Seeing the forest beyond the trees: Predicting survival in burn patients with machine learning

BACKGROUND

This study aims to identify predictors of survival for burn patients at the patient and hospital level using machine learning techniques.

METHODS

The HCUP SID for California, Florida and New York were used to identify patients admitted with a burn diagnosis and merged with hospital data from the AHA Annual Survey. Random forest and stochastic gradient boosting (SGB) were used to identify predictors of survival at the patient and hospital level from the top performing model.

RESULTS

We analyzed 31,350 patients from 670 hospitals. SGB (AUC 0.93) and random forest (AUC 0.82) best identified patient factors such as age and absence of renal failure (p < 0.001) and hospital factors such as full time residents (p < 0.001) and nurses (p = 0.004) to be associated with increased survival.

CONCLUSIONS

Patient and hospital factors are predictive of survival in burn patients. It is difficult to control patient factors, but hospital factors can inform decisions about where burn patients should be treated.

Age-related anabolic resistance after endurance-type exercise in healthy humans

Age-related skeletal muscle loss is thought to stem from suboptimal nutrition and resistance to anabolic stimuli. Impaired microcirculatory (nutritive) blood flow may contribute to anabolic resistance by reducing delivery of amino acids to skeletal muscle. In this study, we employed contrast-enhanced ultrasound, microdialysis sampling of skeletal muscle interstitium, and stable isotope methodology, to assess hemodynamic and metabolic responses of older individuals to endurance type (walking) exercise during controlled amino acid provision. We hypothesized that older individuals would exhibit reduced microcirculatory blood flow, interstitial amino acid concentrations, and amino acid transport when compared with younger controls. We report for the first time that aging induces anabolic resistance following endurance exercise, manifested as reduced (by ∼40%) efficiency of muscle protein synthesis. Despite lower (by ∼40-45%) microcirculatory flow in the older than in the younger participants, circulating and interstitial amino acid concentrations and phenylalanine transport into skeletal muscle were all equal or higher in older individuals than in the young, comprehensively refuting our hypothesis that amino acid availability limits postexercise anabolism in older individuals. Our data point to alternative mediators of age-related anabolic resistance and importantly suggest correction of these impairments may reduce requirements for, and increase the efficacy of, dietary protein in older individuals.

Emerging infections in burns

BACKGROUND

Patients who suffer severe burns are at higher risk for local and systemic infections. In recent years, emerging resistant pathogens have forced burn care providers world wide to search for alternative forms of treatment. Multidrug-resistant Staphylococcus aureus, Pseudomonas aeruginosa, Acinetobacter spp., and various fungal strains have been the major contributors to the increase in morbidity and mortality rates. Multi-drug-resistant S. aureus remains the major cause of gram-positive burn wound infections world wide. Treatment strategies include rigorous isolation protocols and new types of antibiotics where necessary.

METHODS

We reviewed 398 severely burned patients (burns >40% total body surface area [TBSA]) admitted to our hospital between 2000 and 2006. Patients who did not contract multi-drug-resistant gram-negative organisms during their hospital course and received our standard antibiotic regimen-vancomycin and piperacillin/tazobactam-served as controls (piperacillin/tazobactam; n = 280). The treatment group consisted of patients who, during their acute hospital stay, developed infections with multi-drug-resistant gram-negative pathogens and were treated with vancomycin and colistin for at least three days (colistin; n = 118).

RESULTS

Gram-negative organisms continue to cause the most severe infections in burn patients. Colistin has re-emerged as a highly effective antibiotic against multiresistant Pseudomonas and Acinetobacter infections of burns. Patients who required colistin therapy had a significantly larger average total and full-thickness burn than patients treated with piperacillin/tazobactam and vancomycin, and the mortality rate was significantly higher in the colistin group (p < 0.05). However, there was no significant difference between the colistin and piperacillin/tazobactam groups in the incidence of neurotoxicity, hepatic toxicity, or nephrotoxicity. The main fungal pathogens in burn patients are Candida spp., Aspergillus spp., and Fusarium spp. A definitive diagnosis is more difficult to obtain than in bacterial infections. Amphotericin B and voriconazole remain the two most important anti-fungal substances in our practice.

CONCLUSIONS

Innovations in fluid management, ventilatory support, surgical care, and antimicrobial therapy have contributed to a significant reduction in morbidity and mortality rates in burn patients. Vancomycin and clindamycin are the two most important reserve antibiotics for methicillin-resistant Staphylococcus aureus infection. Oxazolidinones and streptogramins have showed high effectiveness against gram-positive infections. Colistin has re-emerged as a highly effective antibiotic against multiresistant Pseudomonas and Acinetobacter infections. Current challenges include Candida, Aspergillus, and molds. The development of new agents, prudent and appropriate use of antibiotics, and better infection control protocols are paramount in the ongoing battle against multi-resistant organisms.

Amino acid supplementation increases lean body mass, basal muscle protein synthesis, and insulin-like growth factor-I expression in older women

CONTEXT

Inadequate dietary protein intake has been implicated in sarcopenia.

OBJECTIVE AND DESIGN

The objectives of this study were to determine whether: 1) chronic essential amino acid (EAA) supplementation improves postabsorptive muscle protein fractional synthesis rate (FSR), lean body mass (LBM), and one-repetition maximum muscle strength, and androgen receptor and IGF-I muscle protein expression; and 2) the acute anabolic response to EAA ingestion is preserved after a 3-month supplementation period. Using a randomized, double-blinded, placebo-controlled design, older women (68 +/- 2 yr) were assigned to receive either placebo (n = 7), or 15 g EAA/d [supplemented treatment group (SUP)] (n = 7) for 3 months. Metabolic outcomes were assessed in association with stable isotope studies conducted at 0 and 3 months.

SETTING

The study was performed at The University of Texas Medical Branch General Clinical Research Center.

RESULTS

Ingestion of 7.5 g EAA acutely stimulated FSR in both groups at 0 months (P < 0.05). Basal FSR at 3 months was increased in SUP only. The magnitude of the acute response to EAA was unaltered after 3 months in SUP. LBM increased in SUP only (P < 0.05). One-repetition maximum strength remained unchanged in both groups. Basal IGF-I protein expression increased in SUP after 3 months (P = 0.05), with no changes in androgen receptor or total and phosphorylated Akt, mammalian target of rapamycin, S6 kinase, and 4E-binding protein.

CONCLUSIONS

EAA improved LBM and basal muscle protein synthesis in older individuals. The acute anabolic response to EAA supplementation is maintained over time and can improve LBM, possibly offsetting the debilitating effects of sarcopenia.

Longitudinal assessment of Integra in primary burn management: A randomized pediatric clinical trial*

BACKGROUND

Early excision with autograft-allograft closure is standard in severe burn management. Cadaver skin is associated with risks such as antigenicity, infection, and limited availability and shelf life. Previous studies have shown that Integra is safe to use in burns of <20% total body surface area. However, the suitability of its use in large burns (>50% total body surface area), its effects on postburn hypermetabolism, and the long-term cosmetic and functional results have not yet been evaluated.

MATERIALS AND METHODS

Twenty children with an average burn size of 73 +/- 15% total body surface area (71 +/- 15% full-thickness burn) were randomized to be treated with either Integra or with autograft-allograft technique. Outcome measures such as length of hospital stay, mortality, incidence of infection and sepsis, acute phase protein levels, and muscle fractional synthetic rate were compared between and within groups during the acute stay (admission to discharge). Outcome measures such as resting energy expenditure, body composition data (measured by dual-energy radiograph absorptiometry), cardiac function indexes, and number of reconstructive procedures were compared during acute hospital stay and at long-term follow-up (up to 2 yrs postinjury). Scar evaluation was performed at long-term follow-up.

RESULTS

There were no significant differences between Integra and controls in burn size (70 +/- 5% vs. 74 +/- 4% total body surface area), mortality (40% vs. 30%), and length of stay (41 +/- 4 vs. 39 +/- 4 days). In the short term, resting energy expenditure significantly decreased (p < .01), and serum levels of constitutive proteins significantly increased (p < .03) in the Integra group compared with controls. Long-term follow-up revealed a significant increase in bone mineral content and density (24 months postburn, p < .05), as well as improved scarring in terms of height, thickness, vascularity, and pigmentation (12 months and 18-24 months, p < .01) in the Integra group.

CONCLUSION

Integra can be used for immediate wound coverage in children with severe burns without the associated risks of cadaver skin.

Amino acid metabolism and inflammatory burden in ovarian cancer patients undergoing intense oncological therapy

BACKGROUND & AIMS

Cancer and oncological therapy are associated with a progressive physical deterioration, malnutrition, and enhanced inflammatory burden. Our considerable data showing the strong anabolic potential of amino acids (AA) led us to test whether AA can acutely stimulate muscle protein synthesis in cancer patients (CA) undergoing intense chemotherapy.

METHODS

Mixed muscle fractional synthesis rate (FSR), rates of phenylalanine appearance and disappearance (Ra and Rd), and net phenylalanine balance (NB) were measured during a primed constant infusion of L-[ring-(2)H(5)]phenylalanine. Blood and muscle tissue samples were collected in the basal state and following ingestion of 40 g of AA given in 30 mL boluses every 10 min for 3h. Serum and tissue cytokines and NF-kappaB expression in skeletal muscle were measured and compared to normative, healthy older controls (OC).

RESULTS

Skeletal muscle TNF-alpha, IL-6, and NF-kappaB were elevated in CA. FSR and model-derived protein synthesis (Rd) increased significantly from basal to AA (FSR: 0.052+/-0.009 vs. 0.120+/-0.008%h(-1), P<0.001; Rd: 23.1+/-4.1 vs. 36.4+/-5.0 nmol min(-1) 100 mL leg(-1), P0.05). Model-derived protein breakdown (Ra) remained unchanged from basal to AA. Phenylalanine NB improved from a negative basal value (-16+/-2) to zero (0.8+/-6 nmol min(-1) 100 ml leg(-1), P0.05) following AA.

CONCLUSION

Despite advanced cancer, ongoing therapy, and an enhanced inflammatory burden, AA were capable of acutely stimulating muscle protein synthesis in these patients.

Insulin sensitivity and mitochondrial function are improved in children with burn injury during a randomized controlled trial of fenofibrate

OBJECTIVE

To determine some of the mechanisms involved in insulin resistance immediately following burn trauma, and to determine the efficacy of PPAR-alpha agonism for alleviating insulin resistance in this population.

SUMMARY BACKGROUND DATA

Hyperglycemia following trauma, especially burns, is well documented. However, the underlying insulin resistance is not well understood, and there are limited treatment options.

METHODS

Twenty-one children 4 to 16 years of age with >40% total body surface area burns were enrolled in a double-blind, prospective, placebo-controlled randomized trial. Whole body and liver insulin sensitivity were assessed with a hyperinsulinemic-euglycemic clamp, and insulin signaling and mitochondrial function were measured in muscle biopsies taken before and after approximately 2 weeks of either placebo (PLA) or 5 mg/kg of PPAR-alpha agonist fenofibrate (FEN) treatment, within 3 weeks of injury.

RESULTS

The change in average daily glucose concentrations was significant between groups after treatment (146 +/- 9 vs. 161 +/- 9 mg/dL PLA and 158 +/- 7 vs. 145 +/- 4 FEN; pretreatment vs. posttreatment; P = 0.004). Insulin-stimulated glucose uptake increased significantly in FEN (4.3 +/- 0.6 vs. 4.5 +/- 0.7 PLA and 5.2 +/- 0.5 vs. 7.6 +/- 0.6 mg/kg per minute FEN; pretreatment vs. posttreatment; P = 0.003). Insulin trended to suppress hepatic glucose release following fenofibrate treatment (P = 0.06). Maximal mitochondrial ATP production from pyruvate increased significantly after fenofibrate (P = 0.001) and was accompanied by maintained levels of cytochrome C oxidase and citrate synthase activity levels. Tyrosine phosphorylation of the insulin receptor and insulin receptor substrate-1 in response to insulin increased significantly following fenofibrate treatment (P = 0.04 for both).

CONCLUSIONS

Fenofibrate treatment started within 1 week postburn and continued for 2 weeks significantly decreased plasma glucose concentrations by improving insulin sensitivity, insulin signaling, and mitochondrial glucose oxidation. Fenofibrate may be a potential new therapeutic option for treating insulin resistance following severe burn injury.

Stimulation of net muscle protein synthesis by whey protein ingestion before and after exercise

Timing of nutrient ingestion has been demonstrated to influence the anabolic response of muscle following exercise. Previously, we demonstrated that net amino acid uptake was greater when free essential amino acids plus carbohydrates were ingested before resistance exercise rather than following exercise. However, it is unclear if ingestion of whole proteins before exercise would stimulate a superior response compared with following exercise. This study was designed to examine the response of muscle protein balance to ingestion of whey proteins both before and following resistance exercise. Healthy volunteers were randomly assigned to one of two groups. A solution of whey proteins was consumed either immediately before exercise (PRE; n = 8) or immediately following exercise (POST; n = 9). Each subject performed 10 sets of 8 repetitions of leg extension exercise. Phenylalanine concentrations were measured in femoral arteriovenous samples to determine balance across the leg. Arterial amino acid concentrations were elevated by approximately 50%, and net amino acid balance switched from negative to positive following ingestion of proteins at either time. Amino acid uptake was not significantly different between PRE and POST when calculated from the beginning of exercise (67 +/- 22 and 27 +/- 10 for PRE and POST, respectively) or from the ingestion of each drink (60 +/- 17 and 63 +/- 15 for PRE and POST, respectively). Thus the response of net muscle protein balance to timing of intact protein ingestion does not respond as does that of the combination of free amino acids and carbohydrate.

Quantification of protein metabolism in vivo for skin, wound, and muscle in severe burn patients

BACKGROUND

In response to injury, muscle catabolism can be extensive, and in theory, the wound consumes amino acids to support healing. The purpose of this study is to assess a technique by which in vivo protein kinetics of muscle, wound, and normal skin can be quantified in burn-injured patients.

METHODS

Study protocol consisting of infusion of d5 phenylalanine; biopsies of skeletal muscle, skin, and donor-site wound on the leg; quantification of blood flow to total leg, wound, and skin; and sequential blood sampling from the femoral artery and vein. Five-compartment modeling was used to quantify the rates of protein synthesis, breakdown, and phenylalanine transport between muscle, wound, and skin.

RESULTS

The study results demonstrated a net release of phenylalanine from muscle yet a net consumption of phenylalanine by the wound. Compared with skin, the wound had a substantially increased rate of protein synthesis and a reduced rate of protein breakdown (p < .01). Transport rates into and out of muscle were significantly higher than those for wound (p < .01).

CONCLUSIONS

This novel methodology enables in vivo quantification of the integrated response of muscle, wound, and skin protein/amino acid metabolism and confirms the long-held theory of a net catabolism of muscle and a net anabolism of wound protein in patients after injury. This methodology can be used to assess the metabolic impact of such measures as nutrition, pharmacologic agents, and surgical procedures.

Effects of oxandrolone on outcome measures in the severely burned: a multicenter prospective randomized double-blind trial

Severe burns induce pathophysiologic problems, among them catabolism of lean mass, leading to protracted hospitalization and prolonged recovery. Oxandrolone is an anabolic agent shown to decrease lean mass catabolism and improve wound healing in the severely burned patients. We enrolled 81 adult subjects with burns 20% to 60% TBSA in a multicenter trial testing the effects of oxandrolone on length of hospital stay. Subjects were randomized between oxandrolone 10 mg every 12 hours or placebo. The study was stopped halfway through projected enrollment because of a significant difference between groups found on planned interim analysis. We found that length of stay was shorter in the oxandrolone group (31.6 +/- 3.1 days) than placebo (43.3 +/- 5.3 days; P < .05). This difference strengthened when deaths were excluded and hospital stay was indexed to burn size (1.24 +/- 0.15 days/% TBSA burned vs 0.87 +/- 0.05 days/% TBSA burned, P < .05). We conclude that treatment using oxandrolone should be considered for use in the severely burned while hepatic transaminases are monitored.

Body composition changes with time in pediatric burn patients

BACKGROUND

Major trauma and burns are associated with whole body catabolism which can persist for 1 or more years after injury. This study investigates body composition in massively burned children for up to 2 years.

METHODS

Twenty-five pediatric patients with greater than 40% total body surface area burns were studied. At discharge, 6, 12, 18, and 24 months after burn height, weight, body composition, resting energy expenditure (REE), serum growth hormone, insulin-like growth factor-I (IGF-I), IGF binding protein-3 (IGFBP-3), insulin, cortisol, parathyroid hormone, and thyroid hormones were measured. Tukey's test was used for analysis. Significance was accepted at p < 0.05.

RESULTS

Lean body mass, fat mass, bone mineral content, height, and weight increased significantly during the second year after burn. Percent predicted REE decreased significantly, whereas IGFBP-3 and parathyroid hormone levels increased significantly over time. Insulin and T3 uptake were significantly higher at discharge.

CONCLUSIONS

Body composition of severely burned children significantly improved in the second year compared with the first year after injury. This demonstrates a need for long-term rehabilitation in these burn patients.

Milk ingestion stimulates net muscle protein synthesis following resistance exercise

PURPOSE

Previous studies have examined the response of muscle protein to resistance exercise and nutrient ingestion. Net muscle protein synthesis results from the combination of resistance exercise and amino acid intake. No study has examined the response of muscle protein to ingestion of protein in the context of a food. This study was designed to determine the response of net muscle protein balance following resistance exercise to ingestion of nutrients as components of milk.

METHOD

Three groups of volunteers ingested one of three milk drinks each: 237 g of fat-free milk (FM), 237 g of whole milk (WM), and 393 g of fat-free milk isocaloric with the WM (IM). Milk was ingested 1 h following a leg resistance exercise routine. Net muscle protein balance was determined by measuring amino acid balance across the leg.

RESULTS

Arterial concentrations of representative amino acids increased in response to milk ingestion. Threonine balance and phenylalanine balance were both > 0 following milk ingestion. Net amino acid uptake for threonine was 2.8-fold greater (P < 0.05) for WM than for FM. Mean uptake of phenylalanine was 80 and 85% greater for WM and IM, respectively, than for FM, but not statistically different. Threonine uptake relative to ingested was significantly (P < 0.05) higher for WM (21 +/- 6%) than FM (11 +/- 5%), but not IM (12 +/- 3%). Mean phenylalanine uptake/ingested also was greatest for WM, but not significantly.

CONCLUSIONS

Ingestion of milk following resistance exercise results in phenylalanine and threonine uptake, representative of net muscle protein synthesis. These results suggest that whole milk may have increased utilization of available amino acids for protein synthesis.

Thermoregulation during exercise in severely burned children

INTRODUCTION

Severe burns result in skeletal muscle catabolism and weakness, which is worsened by prolonged physical inactivity. Exercise would be an ideal tool in the rehabilitation of burned children. However, it has been postulated that burned children may have an excessive rise in body temperature during exercise compared to non-burned children, partly due to the reduced area available for heat dissipation, thereby questioning the safety of exercise in burned children.

METHODS

Children (n = 15) with >40% total body surface area (TBSA) burns and non-burned children (n = 13) successfully completed this study. All subjects completed 20 minutes of treadmill exercise at approximately 75% of their peak aerobic power. Tympanic temperature (Ttym), burned and unburned skin temperature were recorded pre-exercise, every 2 minutes during exercise and during recovery.

RESULTS

Within burned children, significant differences between the temperature of unburned skin and burned skin, during later stages of sub-maximal exercise (minutes 12-20) were present. However, there were no significant differences between burned and non-burned children in Ttym or unburned skin temperature indicating that severely burned children do not demonstrate an impaired thermoregulatory response to 20 minutes of sub-maximal exercise at room temperatures.

CONCLUSION

It is concluded that exercise at moderate intensities conducted at room temperature is safe in burned children with <75% TBSA burns.

Metabolic and hormonal changes of severely burned children receiving long-term oxandrolone treatment

OBJECTIVE

When given to children for 1 year after a severe burn, oxandrolone significantly improves lean body mass, bone mineral content, and muscle strength. The beneficial effects of oxandrolone on height and weight were observed 1 year after treatment was discontinued. To study the efficacy of oxandrolone in severely burned children for 12 months after burn and 12 months after the drug was discontinued.

SUMMARY BACKGROUND DATA

Oxandrolone attenuates body catabolism during the acute phase after burn. It is unclear whether oxandrolone would have any beneficial effects during long-term treatment or if there were any effects after the drug was stopped.

METHODS

Sixty-one children with 40% total body surface area burns were enrolled in this study. Patients were randomized into those to receive oxandrolone (n = 30) or placebo (n = 31) for the first 12 months. Treatment was discontinued after 12 months, and the patients were studied without the drug for the following 12 months. At discharge and 6, 12, 18, and 24 months after burn, height, weight, body composition, resting energy expenditure, muscle strength, and serum human growth hormone, insulin-like growth factor-I (IGF-1), IGF binding protein-3, insulin, cortisol, parathyroid hormone, tri-iodothyronine uptake (T3 uptake), and free thyroxine index (FTI) were measured. Statistical analysis used Tukey multiple comparison test. Significance was accepted at P < 0.05.

RESULTS

Oxandrolone improved lean body mass, bone mineral content and muscle strength compared with controls during treatment, P < 0.05. Serum IGF-1, T3 uptake, and FTI were significantly higher during drug treatment compared with controls, P < 0.05. Significant increases in height and weight with oxandrolone were observed after the end of treatment.

CONCLUSIONS

Oxandrolone improved body composition and strength in severely burned children during the 12 months of treatment. Its effect on height and weight continued after treatment was discontinued.

The efficacy of acute administration of pamidronate on the conservation of bone mass following severe burn injury in children: a double-blind, randomized, controlled study

Bone loss is a known complication of severe burn injury. It is, in part, due to increased endogenous glucocorticoids that contribute to the reduction in bone formation and osteoblast differentiation, hypercalciuria secondary to hypoparathyroidism, and vitamin D deficiency. In this study we attempted to prevent post-burn bone loss by acute intravenous administration of the bisphosphonate pamidronate. We enrolled 43 children, with burns of > 40% total body surface area, in a randomized, double-blind, placebo-controlled study, administering the study drug within 10 days of burn injury and again 1 week later. Dual energy X-ray absorptiometry was performed prior to drug therapy, at hospital discharge and at 6 months post-burn. Urine specimens were obtained at baseline and discharge for determination of calcium and free deoxypyridinoline. Blood was obtained along with the urine specimens for measurement of intact parathyroid hormone (iPTH) and ionized calcium (Ca) levels. Following doxycycline labeling, intra-operative iliac crest bone biopsies were obtained, and bone histomorphometry was determined. At time of discharge there were no differences in total body bone mineral content (BMC), but lumbar spine BMC was significantly higher in the pamidronate group (P < 0.005). By 6 months post-burn the differences in lumbar spine BMC persisted, but, now, total body BMC was significantly higher in the pamidronate group (P < 0.05). Bone histomorphometry and levels of urine Ca and free deoxypyridinoline failed to show significant increases in bone formation or decreases in bone resorption. Pamidronate did not exacerbate the hypocalcemia in burn patients. In summary, acute intravenous pamidronate administration following burns may help to preserve bone mass, perhaps by inhibiting the glucocorticoid-induced apoptosis of osteoblasts and osteocytes.

Mixed muscle and hepatic derived plasma protein metabolism is differentially regulated in older and younger men following resistance exercise

We sought to determine whether exercise-induced muscle protein turnover alters the subsequent production of hepatically derived acute-phase plasma proteins, and whether age affects how these proteins are regulated. We measured arteriovenous (a-v) balance and the synthesis of mixed muscle protein, albumin (A) and fibrinogen (F) before exercise (REST) and from the beginning of exercise to 10, 60, and 180 min following a single bout of moderate-intensity leg extension exercise (POST-EX) in postabsorptive untrained older (n = 6) and younger (n = 6) men using L-[ring-2H5]phenylalanine (Phe). Subjects performed 6 sets of 8 repetitions of leg extension at 80% of their 1-RM (one-repetition maximum). All data are presented as the difference from REST (Delta from REST at 10, 60, and 180 min POST-EX). Mixed muscle fractional synthesis rate (FSR-M) increased significantly from the beginning of exercise until 10 min POST-EX in the older men (DeltaFSR-M: 0.044%/h), whereas FSR-M in the younger men was not elevated until 180 min POST-EX (DeltaFSR-M: 0.030%/h). FSR-A and FSR-F increased at all POST-EX periods in the older men (DeltaFSR-A = 10 min: 1.90%/day; 60 min: 2.72%/day; 180 min: 2.78%/day; DeltaFSR-F = 10 min: 1.00%/day; 60 min: 3.01%/day; 180 min: 3.73%/day). No change occurred in FSR-A in the younger men, but FSR-F was elevated from the beginning of exercise until 10 and 180 min POST-EX (10 min: 3.07%/day and 180 min: 3.96%/day). Net balance of Phe was positive in the older men in the immediate POST-EX period. Our data indicate that mixed muscle and hepatic derived protein synthesis is differentially regulated in younger and older men in response to a single bout of moderate-intensity leg extension exercise. Moreover, our data suggest that with age may come a greater need to salvage or make available amino acids from exercise-induced muscle protein breakdown to mount an acute-phase response.

Ingestion of casein and whey proteins result in muscle anabolism after resistance exercise

PURPOSE

Determination of the anabolic response to exercise and nutrition is important for individuals who may benefit from increased muscle mass. Intake of free amino acids after resistance exercise stimulates net muscle protein synthesis. The response of muscle protein balance to intact protein ingestion after exercise has not been studied. This study was designed to examine the acute response of muscle protein balance to ingestion of two different intact proteins after resistance exercise.

METHODS

Healthy volunteers were randomly assigned to one of three groups. Each group consumed one of three drinks: placebo (PL; N = 7), 20 g of casein (CS; N = 7), or whey proteins (WH; N = 9). Volunteers consumed the drink 1 h after the conclusion of a leg extension exercise bout. Leucine and phenylalanine concentrations were measured in femoral arteriovenous samples to determine balance across the leg.

RESULTS

Arterial amino acid concentrations were elevated by protein ingestion, but the pattern of appearance was different for CS and WH. Net amino acid balance switched from negative to positive after ingestion of both proteins. Peak leucine net balance over time was greater for WH (347 +/- 50 nmol.min(-1).100 mL(-1) leg) than CS (133 +/- 45 nmol.min(-1).100 mL(-1) leg), but peak phenylalanine balance was similar for CS and WH. Ingestion of both CS and WH stimulated a significantly larger net phenylalanine uptake after resistance exercise, compared with the PL (PL -5 +/- 15 mg, CS 84 +/- 10 mg, WH 62 +/- 18 mg). Amino acid uptake relative to amount ingested was similar for both CS and WH (approximately 10-15%).

CONCLUSIONS

Acute ingestion of both WH and CS after exercise resulted in similar increases in muscle protein net balance, resulting in net muscle protein synthesis despite different patterns of blood amino acid responses.

Essential amino acid and carbohydrate supplementation ameliorates muscle protein loss in humans during 28 days bedrest

We determined whether essential amino acid and carbohydrate supplementation could offset the catabolic response to prolonged inactivity. Major outcome measures included mixed muscle fractional synthetic rate (FSR), phenylalanine net balance, lean leg mass, and leg extension strength. On d 1 and 28, vastus lateralis muscle biopsies and femoral arterio-venous blood samples were obtained during a primed constant infusion of l-[ring-(2)H(5)]phenylalanine. Net balance and FSR were calculated over 16 h, during which the control group (CON) received a nutritionally mixed meal every 5 h (0830, 1330, and 1830 h). The experimental group (EXP) also consumed 16.5 g essential amino acids and 30 g carbohydrate (1100, 1600, and 2100 h). The dietary regimen was maintained during bedrest. FSR was higher in the EXP group on d 1 (EXP, 0.099 +/- 0.008%/h; CON: 0.075 +/- 0.005%/h) and d 28 (EXP, 0.093 +/- 0.006%/h; CON, 0.055 +/- 0.007%/h). Lean leg mass was maintained throughout bedrest in the EXP group (+0.2 +/- 0.3 kg), but fell in the CON group (-0.4 +/- 0.1 kg). Strength loss was more pronounced in the CON group (EXP, -8.8 +/- 1.4 kg; CON, -17.8 +/- 4.4 kg). Essential amino acid and carbohydrate supplementation may represent a viable intervention for individuals at risk of sarcopenia due to immobility or prolonged bedrest.

Growth hormone effects on hypertrophic scar formation: a randomized controlled trial of 62 burned children

The hypercatabolism after massive pediatric burns has been effectively treated with recombinant human growth hormone, an anabolic agent that stimulates protein synthesis and abrogates growth arrest. While experimental studies have shown increased potential for fibrosis induced by growth hormone therapy, adverse effects on human scars have not been investigated. Our aim was to evaluate hypertrophic scar formation in 62 patients randomized to receive injections of 0.05 mg/kg/day of recombinant human growth hormone or placebo, from discharge until 1 year after burn. Scar scales were used to evaluate scar-severity at discharge, 6, 9, 12, and 18-24 months after burn, by three observers blinded to treatment. Computer-assisted planimetry allowed quantification of percentage of hypertrophic scar formation. Types I and III collagens were localized and quantified in scars and normal skin of patients from both groups, using immunohistochemistry with confocal laser microscopy analysis. Insulin-like growth factor-1 blood levels helped assess compliance. Statistical analysis showed that scar hypertrophy significantly increased from 6 to 12 months after injury in both groups, while decreasing at 18-24 months postburn. Types I and III collagens were statistically increased in the reticular layer of scars from both groups when compared to paired normal skin. Insulin-like growth factor-1 was significantly increased in the recombinant human growth factor-treated group. No differences were seen when recombinant human growth factor and control groups were compared using the scar scales, planimetry, or immunohistochemistry. We concluded that recombinant human growth hormone therapy did not adversely affect scar formation and should not contraindicate the administration of recombinant human growth hormone as a therapeutic approach to severely burned children.

Extremity hyperinsulinemia stimulates muscle protein synthesis in severely injured patients

Insulin has a well-recognized anabolic effect on muscle protein, yet critically ill, severely injured patients are often considered "resistant" to the action of insulin. The purpose of this study was to assess the in vivo effects of hyperinsulinemia on human skeletal muscle in severely injured patients. To accomplish this goal, 14 patients with burns encompassing >40% of their body surface area underwent metabolic evaluation utilizing isotopic dilution of phenylalanine, femoral artery and vein blood sampling, and sequential muscle biopsies of the leg. After baseline metabolic measurements were taken, insulin was infused into the femoral artery at 0.45 mIU.min(-1).100 ml leg volume(-1) to create a local hyperinsulinemia but with minimal systemic perturbations. Insulin administration increased femoral venous concentration of insulin (P < 0.01) but with only a 4% (insignificant) decrease in the arterial glucose concentration and a 7% (insignificant) decrease in the arterial concentration of phenylalanine. Extremity hyperinsulinemia significantly increased leg blood flow (P < 0.05) and the rate of muscle protein synthesis (P < 0.05). Neither the rate of muscle protein breakdown nor the rate of transmembrane transport of phenylalanine was significantly altered with extremity hyperinsulinemia. In conclusion, this study demonstrates that insulin directly stimulates muscle protein synthesis in severely injured patients.

Insulin decreases hepatic acute phase protein levels in severely burned children

BACKGROUND

Severe burn induces the hepatic acute phase response. In this study, we wondered whether continuous insulin treatment decreases acute phase protein levels in the severely burned.

METHODS

Eighteen children aged 2 to 17 years with burns >40% of total body surface area were randomized to receive either insulin (n=9) or no treatment (n=9) within 72 hours after injury until the wounds were 95% healed. Insulin was given at a continuous rate of > or =1.5 microU/kg/min to maintain euglycemia (serum glucose 100-140 microg/dL). Plasma was examined at days 7, 14, 21, and 28 for acute phase protein levels including C-reactive protein, C3 complement, alpha1-acid glycoprotein, haptoglobin, alpha2-macroglobulin, prealbumin, transferrin, and retinol-binding protein. Statistical analysis was by ANOVA and t test.

RESULTS

With insulin treatment, alpha1-acid glycoprotein, C3 complement, alpha2-macroglobulin, and haptoglobin levels decreased (P<.05) after a severe burn compared with control, especially at days 21 and 28. Additionally, the hepatic constitutive proteins (prealbumin, transferrin, and retinol-binding protein) were lower in the insulin-treatment group than those of the control group at day 21 (P<.05).

CONCLUSIONS

Continuous insulin treatment decreases acute phase protein levels after a severe burn. The results suggest insulin downregulation of the hepatic acute phase response to injury.

Hypercortisolemia alters muscle protein anabolism following ingestion of essential amino acids

Debilitating injury is accompanied by hypercortisolemia, muscle wasting, and disruption of the normal anabolic response to food. We sought to determine whether acute hypercortisolemia alters muscle protein metabolism following ingestion of a potent anabolic stimulus: essential amino acids (EAA). A 27-h infusion (80 microg. kg(-1). h(-1)) of hydrocortisone sodium succinate mimicked cortisol (C) levels accompanying severe injury (>30 microg/dl), (C + AA; n = 6). The control group (AA) received intravenous saline (n = 6). Femoral arteriovenous blood samples and muscle biopsies were obtained during a primed (2.0 micromol/kg) constant infusion (0.05 micromol. kg(-1). min(-1)) of l-[ring-(2)H(5)]phenylalanine before and after ingestion of 15 g of EAA. Hypercortisolemia [36.5 +/- 2.1 (C + AA) vs. 9.0 +/- 1.0 microg/dl (AA)] increased postabsorptive arterial, venous, and muscle intracellular phenylalanine concentrations. Hypercortisolemia also increased postabsorptive and post-EAA insulin concentrations. Net protein balance was blunted (40% lower) following EAA ingestion but remained positive for a greater period of time (60 vs. 180 min) in the C + AA group. Thus, although differences in protein metabolism were evident, EAA ingestion improved muscle protein anabolism during acute hypercortisolemia and may help minimize muscle loss following debilitating injury.

Prediction of mortality from catastrophic burns in children

BACKGROUND

We previously developed a model to predict survival in massive paediatric burns (>80% total body surface area [TBSA]). This model included not only demographic variables, but also variables obtained throughout the hospital course. We aimed to prospectively validate our model for accuracy of outcome prediction.

METHODS

We admitted 33 paediatric burn patients with burns greater than 80% TBSA. We recorded age, burn size, inhalation injury, resuscitation, packed-cell volume at admission, base deficit, serum osmolarity, sepsis, inotropic support, platelet count, creatinine, and ventilator dependency. We entered these data into our previous models.

RESULTS

20 male and 13 female children with mean age 7.6 (SD 1) years with TBSA burns of 88% (SD 1; full thickness 86% [SD 1]) were admitted. Mortality was 39.4% (13 of 30). When all variables were integrated into our final model, we predicted outcome with 97% accuracy. When we used a model based only on demographic characteristics of age, burn size, and presence of inhalation injury, outcome was correctly predicted in only 51% of patients.

CONCLUSION

We show prospectively that mortality in severely burned children can be reliably estimated at a burn centre, and that outcome cannot be reliably predicted on the basis of demographic and injury characteristics alone. These data suggest that all severely burned children should be given a course of treatment before consideration of treatment futility.

Acute response of net muscle protein balance reflects 24-h balance after exercise and amino acid ingestion

The purpose of this study was to determine if the acute anabolic muscle response to resistance exercise and essential amino acids (EAA) reflects the response over 24 h. Seven subjects participated in the following two 24-h studies: 1) resting (REST) and 2) rest plus resistance exercise and consumption of EAA (ES). Net balance (NB) across the leg was determined for four amino acids. [(13)C(6)]phenylalanine was infused to determine mixed muscle fractional synthetic rate (FSR). Twenty-four-hour FSR was significantly greater for ES than for REST (P = 0.003). Exchange of phenylalanine across the leg was -194 +/- 74 (SE) mg for ES and -371 +/- 88 mg for REST (P = 0.07) over 24 h and 229 +/- 42 mg (ES) and 28 +/- 15 mg (REST; P < 0.01) over 3 h corresponding to exercise and EAA consumption for ES. The difference in phenylalanine exchange between REST and ES was not different for measurements over 24 and 3 h. Increases in NB during ES were primarily the result of increases in protein synthesis. Results for other amino acids were similar. The acute anabolic response of muscle to EAA intake and exercise is additive to the response at rest and thus reflects the 24-h response.

The use of abdominal computed tomography scan decreases the frequency of misdiagnosis in cases of suspected appendicitis

BACKGROUND

Despite considerable experience the reported frequency of misdiagnosis in patients undergoing appendectomy continues in the range of 20% to 40% in some populations.

METHODS

We developed a clinical guideline that recommended abdominal computed tomography (CT) for all nonpregnant adults in whom the diagnosis of appendicitis was suspected unless the diagnosis could be ruled out clinically. The records of adult patients that underwent appendectomy from July 1998 through October 2001 were reviewed. The clinical guideline was developed in July 2000.

RESULTS

There were 194 appendectomies performed, 114 prior to the guideline and 80 after the development of the guideline. The rate of misdiagnosis decreased from 25% to 6% (P <0.05), the rate of CT use increased from 32% to 84% (P <0.05), and the perforation rate remained unchanged.

CONCLUSIONS

These results support the effectiveness of a clinical guideline that encourage the use of abdominal CT in decreasing the frequency of misdiagnosis in cases of suspected appendicitis.

Hyperglycemia exacerbates muscle protein catabolism in burn-injured patients

OBJECTIVE

The purpose of this study was to assess if hyperglycemia influences energy expenditure or the extent of muscle protein catabolism in severely burned adults.

DESIGN

Retrospective study.

SETTING

Burn intensive care unit at a university hospital.

PATIENTS

Adults with burns on >/=40% of their body surface area.

INTERVENTIONS

Simultaneous measurement of indirect calorimetry and leg net balance of phenylalanine (as an index of muscle protein catabolism). Patients were stratified by plasma glucose values at the time of metabolic measurements (i.e., normal, glucose at </=130 mg/dL; mild hyperglycemia, glucose at 130-200 mg/dL; severe hyperglycemia, glucose at >200 mg/dL).

MEASUREMENTS AND MAIN RESULTS

Normal (n = 9; plasma glucose, 109 +/- 13 mg/dL [mean +/- sd]), mildly hyperglycemic (n = 13l plasma glucose, 156 +/- 17 mg/dL), and severely hyperglycemic subjects (n = 7, glucose 231 +/- 32 mg/dL) were similar in age, body weight, extent of burn area, and daily caloric intake. Severe hyperglycemia was associated with significantly higher arterial concentrations of phenylalanine (normal, 0.079 +/- 0.027 micromol/L; severe hyperglycemia, 0.116 +/- 0.028; p <.05) and a significantly greater net efflux of phenylalanine from the leg (normal, -0.067 +/- 0.072 micromol.min(-1).100 mL(-1) leg volume; severe hyperglycemia, -0.151 +/- 0.080 micromol.min(-1).100 mL(-1) leg volume; p <.05). Resting energy expenditure and respiratory quotient were similar between patient groups.

CONCLUSIONS

These findings demonstrate an association between hyperglycemia and an increased rate of muscle protein catabolism in severely burned patients. This suggests a possible link between resistance of muscle to the action of insulin for both glucose clearance and muscle protein catabolism.

An increase in the susceptibility of burned patients to infectious complications due to impaired production of macrophage inflammatory protein 1 alpha

Sepsis is a major mortality concern with burned patients, who have an increased susceptibility to infectious complications. PBMC from 41 of 45 severely burned patients (91%) failed to produce macrophage inflammatory protein 1alpha (MIP-1alpha) in cultures, while 2355-6900 pg/ml MIP-1alpha were produced by healthy donor PBMC, stimulation with anti-human CD3 mAb. Healthy chimeras (SCID mice inoculated with healthy donor PBMC) treated with anti-human MIP-1alpha mAb and patient chimeras (SCID mice reconstituted with burned patient PBMC) were susceptible (0% survival) to infectious complications induced by well-controlled cecal ligation and puncture. In contrast, patient chimeras treated with human recombinant MIP-1alpha and healthy chimeras were resistant ( approximately 77-81% survival). Similarly, after anti-mouse CD3 mAb stimulation, splenic mononuclear cells from burned mice (6 h to 3 days after thermal injury) did not produce significant amounts of MIP-1alpha in their culture fluids. Normal mice treated with anti-murine MIP-1alpha mAb and burned mice were susceptible to cecal ligation- and puncture-induced infectious complications, while burned mice treated with murine recombinant MIP-1alpha and normal mice were resistant. Burned patients seemed to be more susceptible to infectious complications when the production of MIP-1alpha was impaired.

Effects of delayed wound excision and grafting in severely burned children

HYPOTHESIS

Advances in burn treatment including early excision of the wound have increased survival in patients treated at specialized burn centers. We hypothesized that the patients with delayed wound excision and grafting would experience deleterious outcomes.

METHODS

From 1995 to 1999, 157 children with acute burns covering 40% or more of total body surface area and having more than 10% of full-thickness burns were admitted to our institution within 2 weeks of injury. Among them, 86, 42, and 29 patients underwent first operation on days 0 to 2, days 3 to 6, and days 7 to 14 after burn, respectively. Outcomes observed were mortality, number of operative procedures, length of hospitalization, blood transfused, incidence of wound bacterial and fungal contamination, invasive wound infection, and sepsis.

RESULTS

Demographic data for the groups showed no differences in sex or total body surface area burned. Mortality and number of operative procedures and blood transfusions were not different between groups. Hospitalizations were longer in the delayed groups, which was associated with a higher incidence of significant wound contamination (P =.008). Invasive wound infection also increased significantly with delay of excision (P<.001). An increased incidence of sepsis was seen in patients with delayed wound excision and grafting (P =.04).

CONCLUSIONS

Delays in excision were associated with longer hospitalization and delayed wound closure, as well as increased rates of invasive wound infection and sepsis. Our data indicate that early excision within 48 hours is optimal for pediatric patients with massive burns.

Treatment of extensive toxic epidermal necrolysis in children

OBJECTIVE

Toxic epidermal necrolysis (TEN) is a rare but life-threatening disease of the skin and mucous membranes. We report our experience in the treatment of pediatric TEN patients with early debridement of necrotic skin and coverage with human allograft skin.

METHODS

From 1984 to 2000, 15 children (6 girls, 9 boys, 7.2 +/- 1.5 years) with a histologic diagnosis of TEN and involvement of >30% total body surface area were treated at the Shriners Hospitals for Children in Galveston. All were treated in a specialized pediatric burn intensive care unit after our standard treatment protocol, including operative debridement of sloughing skin and allografting within 24 hours of admission. Outcome parameters were mortality, length of hospital stay, wound healing, clinical complications, causative drugs, corticosteroid use, and delay in referral to a burn center.

RESULTS

Taking a new medication (antibiotics, anticonvulsive drugs) was associated with all cases of TEN. Patients who were treated with early debridement and coverage with allograft skin showed no wound infection, and overall mortality was 7%. Total length of hospital stay was 26 +/- 3 days. Long-term sequelae were changes in skin pigmentation (100%), ophthalmologic problems (40%), and diffuse itching early after wound healing (53%).

CONCLUSION

Although a rare disease in children, TEN was managed successfully in a burn center environment, using early debridement and wound coverage with allograft skin as a biological dressing. The use of corticosteroids and referral patterns seems unchanged during the past 2 decades, indicating an additional need for information and education about the disease.