Changes in the tissue and plasma superoxide dismutase (SOD) levels in a burned rat model.

To examine whether thermal injury alters the superoxide dismutase (SOD) concentrations in various types of tissue or plasma, we studied the plasma and tissue Mn- and Cu/Zn-SOD levels in a rodent burn model. The animals were resuscitated with saline (50 mg/kg, i.p.) immediately following thermal injury and thereafter were sacrificed at either 6 or 24 hours post-burn. The Mn- and Cu/Zn-SOD levels were measured using an enzyme-linked immunosorbent assay (ELISA). The plasma Mn- and Cu/Zn-SOD concentrations significantly increased 6 hours after the injury and positively correlated with the burn size. The kidney Mn-SOD concentrations were significantly higher 24 hours after the injury in the animals with 30% burns than in those with either sham or 50% burn injuries. The lung Cu/Zn-SOD concentrations were also significantly higher 6 hours after the injury in animals with 30% burns than in the other two types above. These findings suggest that the changes in the SOD concentrations after burn injury vary according to the type of SOD and also the type of tissue. As a result, the SOD concentrations may play some role in the early response to thermal trauma.

Appendicitis: why so complicated? Analysis of 5755 consecutive appendectomies.

A perceived high rate of complicated (gangrenous or perforated) appendicitis, despite advances in laboratory and radiographic diagnostic modalities, prompted a review of our experience with appendicitis followed by a prospective analysis that examined the time course from presentation to definitive treatment in 218 consecutive patients. In 5755 appendectomies, our overall rate of complicated appendicitis was 32 per cent; higher in males, in the young, and in the elderly; and relatively stable over each year reviewed. Prospectively, we determined that of the various time intervals, the time from the onset of symptoms to first seeking medical attention is the only significant predictor of complicated appendicitis (39.8 vs 16.5 hours for acute appendicitis). On the other hand, the time from surgical evaluation to operative intervention was significantly shorter for complicated appendicitis (3.8 vs 4.7 hours for acute appendicitis). The high rate of complicated appendicitis with its subsequent sequelae of increased morbidity and resource expenditure is primarily the direct result of patient delay in seeking medical attention and not the result of diagnostic dilemma or surgical delay. Public education, specifically targeting those groups at risk, may provide a substantial and significant solution to the complicated appendix.

Accelerated healing with a mesh autograft/allodermal composite skin graft treated with silver nylon dressings with and without direct current in rats.

PURPOSE: Evaluation of the healing and persistence of a meshed composite skin graft applied without immunosuppression. METHODS: The contraction of wounds grafted with 9:1 split-thickness autograft/1.5:1 allodermal mesh composite skin grafts (auto/allo MCSGs) was investigated. No immunosuppressive agent was applied. Male ACI rats and female Lewis rats reciprocally served as allodermis graft donors and recipients. Autograft/dermal autograft and allograft/dermal allograft MCSGs were the controls. RESULTS: AT 3 months after grafting, when epithelized auto/allo MCSG wounds were measured by computerized morphometric analysis, the silver nylon (SN) dressing group displayed less contraction than the Vaseline (petroleum jelly) dressing group (p < 0.003), and direct current treatment (SNDC) was more effective than SN (p < 0.005). The histologic structures of the hair follicles appear to confine the rejection process to the allogeneic follicles of the graft. The focal nature of the rejection process and the relatively low antigenicity of the dermal matrix allowed the survival of the allodermis layer. Although direct current significantly enhanced MCSG healing, SN and SNDC were not the immunosuppressive agents that were confirmed. CONCLUSION: This type of MCSG can heal without immunosuppressive treatment.

Half-life of blood carboxyhemoglobin after short-term and long-term exposure to carbon monoxide.

BACKGROUND: In models of smoke inhalation injury and carbon monoxide poisoning blood carboxy-hemoglobin (COHb) levels decrease faster than predicted by the generally recognized half-life of COHb. We studied the effects of duration of exposure to carbon monoxide (CO) on the subsequent CO elimination. METHODS: Each of four sheep were insufflated with CO gas mixtures either for a few minutes (short-term exposure) or for several hours (long-term exposure), then ventilated with air for 3 hours. Serial COHb concentrations were analyzed by using a two-compartment, single central outlet mathematical model. RESULTS: Short-term exposures exhibited biphasic decreases of COHb concentration compatible with a two-compartment model; an initial rapid decrease (half-life 5.7 +/- 1.4 minutes) was followed by a slower phase (103 +/- 20.5 minutes). Long-term exposures exhibited almost monophasic decreases, which were nevertheless compatible with the model (half-life, 21.5 +/- 2.1 and 118 +/- 11.2 minutes). CONCLUSION: This study demonstrated different patterns of CO elimination curve, which suggests distribution of CO to two compartments having different rates of equilibration.

Blunt splenic injuries: dedicated trauma surgeons can achieve a high rate of nonoperative success in patients of all ages.

BACKGROUND: Selective nonoperative management (NOM) of blunt splenic injuries is becoming a more prevalent practice. Inclusion criteria for NOM, which have been a source of controversy, continue to evolve. Age > or = 55 years has been proposed as a predictor for failure of and even a contraindication to NOM of blunt splenic trauma. Additionally, the high rate of NOM in children (up to 79%) has been attributed to their management by pediatric surgeons. We evaluated our experience with NOM of blunt splenic injury with special attention to these age groups. METHODS: By using our trauma registry, all patients with blunt splenic injuries (documented by computed tomography, operative findings, or both) cared for over a 36-month period, at a single American College of Surgeons verified Level I trauma center were reviewed. Detailed chart reviews were performed to examine admission demographics, laboratory data, radiologic findings, outcome measures, and patient management strategy. All patients were managed by nonpediatric trauma surgeons. We then compared our adult data with that in the recent literature and our pediatric data with that of the National Pediatric Trauma Registry over the same time period. RESULTS: We identified 251 consecutive patients with blunt splenic injuries. Eighteen patients who expired in the immediate postinjury period were excluded from statistical evaluation. No deaths occurred as a result of splenic injury. Of the remaining 233 patients, 73 patients (31%) required early celiotomy, 160 patients (69%) were selected for NOM, with 151 patients (94%) being successfully managed without operation. Blunt splenic injury occurred in 23 patients age 55 years or older. Eighteen patients (78%) were selected for NOM and 17 patients (94%) were successfully treated without operation. Blunt splenic injury occurred in 35 patients less than 16 years of age. Thirty-two patients (91%) were selected for NOM. Thirty-one patients (89% of all pediatric patients) were successfully treated without operation. CONCLUSION: Age > or = 55 years is not a contraindication to nonoperative management of blunt splenic injuries. Children with blunt splenic injuries can be successfully managed nonoperatively by nonpediatric trauma surgeons.

Effects of heme proteins on nitric oxide levels and cell viability in isolated PMNs: a mechanism of toxicity.

Isolated human PMNs served as a model to determine oxyhemoglobin (oxyHb) binding and the effects of oxymyoglobin (oxyMb) or oxyHb on production of both nitric oxide (NO*) and superoxide (O2*-) and the resulting cytotoxicity. Physiologically relevant concentrations of NO* and H2O2 oxidized, to a similar extent, 2,7-dichlorodihydrofluorescein (DCFH) loaded into polymorphonuclear neutrophils (PMNs). Activation of PMNs with phorbol 12-myristate 13-acetate (PMA) markedly increased the internalization of extracellular oxyHb (10-250 microg/mL). OxyMb (10-300 microg/mL) or oxyHb (30-300 microg/mL) enhanced DCFH oxidation by a concentration-dependent mechanism in unstimulated, lipopolysaccharide (LPS) and tumor necrosis factor alpha (TNF-alpha)-, and PMA-stimulated PMNs. This increased DCFH oxidation was eliminated by NO* synthase inhibitors, glutathione and ascorbate, and was reduced by albumin. Nitrite accumulation in PMN filtrates mirrored NO*-induced DCF fluorescence. OxyMb-induced increases in NO* levels paralleled alterations in DNA and cell membrane damage and ATP levels in PMNs and co-cultured lymphocytes, and were attenuated by NO* synthase inhibitors. OxyMb eliminated extracellular O2*- at protein concentrations 100- to 1000-fold above those of superoxide dismutase. These results suggest that heme proteins bind and internalize into PMNs and increase NO*-induced damage in neighboring cells by inhibiting O2*(-)-scavenging of NO*. We propose a mechanism whereby heme protein-induced NO* levels may contribute to immunosuppression and increased infection rates associated with transfusions and cellular damage during inflammation.

Direct current reduces accumulation of Evans Blue albumin in full-thickness burns.

BACKGROUND: Application of direct current (DC) to a burn wound limits extension of the zone-of-stasis and reduces wound tissue edema. OBJECTIVE: To study the effects of DC on extravasation of plasma proteins after burn by using Evans blue (EB) as a marker of plasma albumin. MATERIALS AND METHODS: Male Sprague-Dawley rats with 20% total body surface area full-thickness scalds (100 degrees C/10 sec) were used as the experimental model. Burn wounds were treated with plain nylon, silver-nylon, silver-nylon and 40 microA DC, or no dressing. EB (30 mg/kg) was injected immediately or at variably delayed postburn (PB) times and accompanied by DC application at various time intervals PB. Tissue content of Evans blue was assessed at different times after injection of the dye or infliction of burn injury. RESULTS: Evans blue albumin (EBA) concentration in untreated burn wounds (307.7 microg/g tissue) was nine times greater than in unburned skin (36.5 microg/g tissue) at 48 hours PB. When animals received a DC and EB injection immediately PB, DC treatment reduced EBA concentration by 60% at any time point PB. When EB was injected immediately PB, or at variably delayed times PB, accompanied by DC immediately PB, or at variably delayed times PB, DC reduced EBA accumulation at all examined times PB by more the 50% (p < 0.001). CONCLUSION: EBA and edema fluid accumulation in burn wound change in concert after injury and show similar response to DC treatment.

Selectin blockade worsened lipopolysaccharide-induced lung injury in a swine model.

BACKGROUND: Polymorphonuclear leukocytes have been reported to play an important role in various acute lung injuries. Neutrophil recruitment into tissues is a multistep process involving sequential engagement of adhesion molecules. The objective of this study was to determine the effect of selectin inactivation with Sulfo Lewis C (SO3-3betaGal1-3betaGlcNAc-O(CH2)8-COOMe) on the pulmonary response to lipopolysaccharide (LPS) infusion. METHODS: All animals (n = 11) were pretreated with an intramuscular injection of a priming dose of Escherichia coli LPS (10 microg/kg). Eighteen hours later, animals received an intravenous infusion of LPS (20 microg/kg) over 20 minutes. All animals were resuscitated with a lactated Ringer's solution. Group I (G1; n = 5) received no additional treatment. Group II (G2; n = 6) received a bolus injection of Sulfo Lewis C (10 mg/kg) 10 minutes before LPS insult followed by a continuous infusion (1 mg/kg per hour) for the rest of the study. Animals were observed for 5 hours from initiation of the LPS infusion and killed. Cardiopulmonary variables and blood gases were measured serially. The multiple inert gas elimination technique (MIGET) was used to evaluate the matching of air flow and blood flow in the lung 5 hours after LPS infusion. Histologic evaluation of the parenchymal injury was performed by using light microscopy. The number of polymorphonuclear leukocytes and red blood cells in the alveolar spaces per field at 400x magnification were counted in 10 randomly selected fields. RESULTS: Hypoxemia, indexed as Pao2/FIO2, was exacerbated by the administration of Sulfo Lewis C (G1:437+/-33 vs. G2: 241+/-63 mm Hg at 5 hours, p<0.03). This finding is supported by the multiple inert gas elimination technique analysis, which demonstrated significantly greater blood flow to true shunt in G2 (G1:4.42+/-1.75 vs. G2:23.2+/-5.69, p<0.02). There was no difference between the two groups in red blood cell counts in the alveolar spaces. However, polymorphonuclear leukocyte counts were significantly greater in G2 (G1:1.8+/-0.58 vs. G2:9.9+/-2.34, p<0.01). CONCLUSION: Selectin blockade significantly worsened lung injury induced by LPS infusion, and greater numbers of neutrophils were observed in alveolar spaces in the group treated with Sulfo Lewis C. These findings are supported by the multiple inert gas elimination technique analysis, which demonstrated significantly greater blood flow to the true shunt compartment in treated animals. Further studies are required to determine the role of selectins in sepsis-induced lung injury.

Effects of long-term hemofiltration on circulating mediators and superoxide production during continuous endotoxin administration.

BACKGROUND: The purpose of this study was to test whether continuous hemofiltration eliminates cytokines and eicosanoids, or stimulates granulocyte function. METHODS: Nineteen pigs were divided into a control group (n = 7), a hemofiltration group (n = 7), and an extracorporeal circuit only group (n = 5). All animals received the same amount of intravenous endotoxin and resuscitation fluid. Zero-balanced hemofiltration was started 30 minutes after initiation of endotoxemia and continued throughout the experiment. Plasma endotoxin, tumor necrosis factor-alpha, eicosanoids, superoxide production, and other physiologic parameters were measured before challenge and at scheduled intervals thereafter. RESULTS: Eicosanoids were filtered but plasma concentrations were not reduced. Tumor necrosis factor-alpha was not filtered or adsorbed. There were no significant differences between groups in any measured parameters. CONCLUSION: Continuous hemofiltration could not efficiently remove tumor necrosis factor-alpha or eicosanoids. Also, continuous hemofiltration did not stimulate production of the proinflammatory mediators measured, nor improve respiratory distress.

Biphasic changes in left ventricular function during hyperdynamic endotoxemia.

Cardiac contractility was studied in a clinically relevant conscious swine model simulating human hemodynamics during endotoxemia. The slope of the end-systolic pressure-volume relationship [end-systolic elastance (EES)] was used as a load-independent contractility index. Chronic instrumentation in 10 pigs included two pairs of endocardial ultrasonic crystals for measuring internal major and minor axial dimensions of the left ventricle, a micromanometer for left ventricular pressure measurement, and a thermodilution pulmonary artery catheter. After a 10-day recovery period, control measurements of cardiac hemodynamic function were obtained. The following week, Escherichia coli endotoxin (10 micrograms . kg-1. h-1) was administered intravenously for 24 h. EES increased 1 h after endotoxin infusion and decreased beyond 7 h. The later hemodynamic changes resembled human cardiovascular performance during endotoxemia more closely than the changes during the acute phase. EES decreased in the later phase. A similar biphasic response of EES has been reported during a tumor necrosis factor-alpha (TNF) challenge. Even though plasma TNF was highest at 1 h and declined thereafter in this study, no consistent relationship between TNF and EES was identified, and TNF levels did not correlate directly with the changes in EES.

Inhaled nitric oxide prevents left ventricular impairment during endotoxemia.

We evaluated the effect of long-term inhalation of nitric oxide (NO) on cardiac contractility after endotoxemia by using the end-systolic elastance of the left ventricle (LV) as a load-independent contractility index. Chronic instrumentation in 12 pigs included implantation of two pairs of endocardial dimension transducers to measure LV volume and a micromanometer to measure LV pressure. One week later, the animals were divided into a control group (n = 6) or a NO group (n = 6). All animals received intravenous Escherichia coli endotoxin (10 micrograms. kg-1. h-1) and equivalent lactated Ringer solution. NO inhalation (20 parts/million) was begun 30 min after the initiation of endotoxemia and was continued for 24 h. In both groups, tachycardia, pulmonary hypertension, and systemic hyperdynamic changes were noted. The end-systolic elastance in the control group was significantly decreased beyond 7 h. NO inhalation maintained the end-systolic elastance at baseline levels and prevented its impairment. These findings indicate that NO exerts a protective effect on LV contractility in this model of endotoxemia.

Observations on the risk of resistance with the extended use of vancomycin.

OBJECTIVE: To document the risk of the development of vancomycin-resistant bacteria in a population of seriously burned patients during a 10-year period of common vancomycin hydrochloride use. DESIGN: Retrospective study. SETTING: The US Army Institute of Surgical Research, Burn Center, Fort Sam Houston, Tex. POPULATION AND METHODS: Microbiology, infection, and antibiotic use records collected during the hospitalization of 2266 consecutively admitted seriously burned patients were reviewed. Vancomycin was the primary therapeutic agent used for gram-positive infections and was also used as a perioperative prophylactic antibiotic during burn wound excision. This policy was established prior to this review because of a high incidence of methicillin-resistant Staphylococcus aureus colonization and an anecdotal association of increased beta-lactam resistance in endemic gram-negative pathogens associated with the use of penicillinase-resistant penicillins and cephalosporins. MAIN OUTCOME MEASURES: Isolation of vancomycin-resistant enterococci (VRE) or other gram-positive organisms resistant to vancomycin. RESULTS: Examinations of 15 125 gram-positive isolates, including 957 enterococci, for in vitro sensitivity to vancomycin yielded 3 VRE isolates in 3 patients. Vancomycin was used prior to VRE isolation in one of these patients. Resistance was found in 3 other organisms (2 Corynebacterium species, 1 Lactobacillus species). Vancomycin was used prior to these isolations in 2 of 3 patients. None of the vancomycin-resistant organisms was associated with infection and all 6 patients survived. Vancomycin-resistant enterococci or other vancomycin-resistant gram-positive organisms were not found in 663 patients treated with vancomycin for documented gram-positive infections or in 1027 patients where perioperative vancomycin was used. CONCLUSION: Use of vancomycin as the primary therapeutic agent in seriously burned patients was not associated with increased risk of VRE isolation or VRE infection.

Factors contributing to delayed extremity amputation in burn patients.

BACKGROUND: Previous series of traumatic amputations have noted that delay in amputation results in prolonged hospital stay and delayed rehabilitation. A series of major extremity amputations after burn injury was analyzed to identify the frequency of delayed amputation and to identify factors resulting in the delay. METHODS: Chart review of burn admissions between January of 1991 and December of 1995. RESULTS: Twenty-eight patients underwent a total of 44 major extremity amputations. Thirty-five amputations in 22 patients were performed by postburn day 16 (mean 4.3). Nine amputations in six patients were delayed beyond postburn day 26 (mean, 48.3). Delayed amputations occurred in the subgroups of deep thermal burns with extensive necrosis and thermal burns complicated by infections. Early amputation was associated with a 13.6% mortality rate, delayed amputation with a 50% mortality rate. CONCLUSION: There is a bimodal distribution of time to amputation determined by mechanism of injury, severity of burn, and infectious complications. Earlier identification of nonsalvageable limbs may decrease infectious complications and improve the chances of patient survival.

Effect of Sulfo Lewis C on smoke inhalation injury in an ovine model.

OBJECTIVE: To evaluate the effect of Sulfo Lewis C (SO3-3âGal1-3GlcNAc-O(CH2)8-COOMe), a putative ligand of selectins, on smoke inhalation injury. DESIGN: Prospective animal study with concurrent controls. SETTING: An animal laboratory. SUBJECTS: Twelve 1-yr-old female sheep, weighing 24 to 33 kg. INTERVENTIONS: Twelve sheep received nine exposure units of smoke generated by thermolysis of pine woodchips (80 g). Group 1 (n = 6) was untreated. Group 2 (n = 6) was treated with an intravenous infusion of Sulfo Lewis C after smoke exposure. Animals were killed 48 hrs after injury. MEASUREMENTS AND MAIN RESULTS: Cardiopulmonary variables and blood gases were measured serially. Granulocyte free-radical production was measured before smoke exposure and at 4 and 48 hrs after injury. Ventilation/perfusion distribution (VA/Q) was analyzed using the multiple inert gas elimination technique. Granulocyte free-radical production was increased after smoke exposure in both groups. Oxygenation was significantly improved by the administration of Sulfo Lewis C. VA/Q analysis demonstrated significantly less blood flow to low VA/Q lung segments in treated animals. CONCLUSIONS: Selectin blockade attenuated lung injury after smoke exposure. These data support the hypothesis that neutrophils play a pivotal role in smoke inhalation injury.

Burn wound infections: current status.

The burn wound represents a susceptible site for opportunistic colonization by organisms of endogenous and exogenous origin. Patient factors such as age, extent of injury, and depth of burn in combination with microbial factors such as type and number of organisms, enzyme and toxin production, and motility determine the likelihood of invasive burn wound infection. Burn wound infections can be classified on the basis of the causative organism, the depth of invasion, and the tissue response. Diagnostic procedures and therapy must be based on an understanding of the pathophysiology of the burn wound and the pathogenesis of the various forms of burn wound infection. The time-related changes in the predominant flora of the burn wound from gram-positive to gram-negative recapitulate the history of burn wound infection. Proper clinical and culture surveillance of the burn wound permits early diagnosis of gram-positive cellulitis, and the stable susceptibility of beta-hemolytic streptococci to penicillin has eliminated the threat of this once common burn wound pathogen. Selection and dissemination of intrinsic and acquired resistance mechanisms increase the probability of burn wound colonization by resistant species such as Pseudomonas aeruginosa. Even so, effective topical antimicrobial chemotherapy and early burn wound excision have significantly reduced the overall occurrence of invasive burn wound infections. Individual patients, usually those with extensive burns in whom wound closure is difficult to achieve, may still develop a variety of bacterial and nonbacterial burn wound infections. Consequently, the entirety of the burn wound must be examined on a daily basis by the attending surgeon. Any change in wound appearance, with or without associated clinical changes, should be evaluated by biopsy. Quantitative cultures of the biopsy sample may identify predominant organisms but are not useful for making the diagnosis of invasive burn wound infection. Histologic examination of the biopsy specimen, which permits staging the invasive process, is the only reliable means of differentiating wound colonization from invasive infection. Identification of the histologic changes characteristic of bacterial, fungal, and viral infections facilitates the selection of appropriate therapy. A diagnosis of invasive burn wound infection necessitates change of both local and systemic therapy and, in the case of bacterial and fungal infections, prompt surgical removal of the infected tissue. Even after the wounds of extensively burned patients have healed or been grafted, burn wound impetigo, commonly caused by Staphylococcus aureus, may occur in the form of multifocal, small superficial abscesses that require surgical debridement. Current techniques of burn wound care have significantly reduced the incidence of invasive burn wound infection, altered the organisms causing the infections that do occur, increased the interval between injury and the onset of infection, reduced the mortality associated with infection, decreased the overall incidence of infection in burn patients, and increased burn patient survival.

Optimized mesh expansion of composite skin grafts in rats treated with direct current.

BACKGROUND: The purpose of this study was to determine the optimum autoepidermal and allodermal expansion ratio of each component of a meshed composite skin graft (MCSG) that would lead to successful healing. METHODS: Male Sprague-Dawley rats were used as hosts of the MCSG and donors of autologous tissue. Male ACI rats were used as donors of allodermis. MCSGs with open meshed area (autoepidermal/allodermal) of 9:1/1.5:1, 9:1/3:1, 9:1/6:1, or 6:1/6:1 were applied to full-thickness skin defects and treated with a silver nylon dressing (SN) or SN with direct current (DC). Wound size, hair regrowth, and thickness of dermal layer were evaluated at 3 months. RESULTS: MCSGs of 9:1/1.5:1, 9:1/3:1, and 6:1/6:1 mesh ratios healed completely within 3 months with no difference in wound size between SN dressing groups or DC-treated groups. Application of DC reduced MCSG contraction and stimulated regrowth of hair. CONCLUSION: Fresh autoepidermis can be expanded 6:1 on a 6:1 allodermis or 9:1 on a 3:1 allodermis and achieve successful wound healing.