Search

We studied the effect of water-soluble antioxidants geared at restoring glutathione levels on oxygen consumption, cell energetics as measured by energy charge potential (ECP), glutathione levels, and mortality, in response to a 20% total body surface area (TBSA) third degree burn injury combined with endotoxemia, five days after burn in a rat model. The 20% TBSA third degree burn injury was not fatal for the six day study period. Oxygen consumption as well as red blood cell ECP remained unchanged from control values. Liver ECP was significantly reduced; however, liver glutathione was significantly increased. The 20% TBSA burn injury combined with endotoxemia produced a 60% mortality rate. Twenty-four hour survivors (40%) demonstrated a significant decrease in oxygen consumption, red blood cell ECP, and liver ECP. Liver glutathione was significantly decreased compared with burn but was not significantly decreased compared with control. Nonsurvivors of the burn injury combined with endotoxin (60%) demonstrated a significant reduction in liver glutathione levels compared with survivors. Oxygen consumption and ECP could not be measured in the nonsurvivors due to the rapid loss of ATP in the moribund state that occurred by 4 h postinjury. Antioxidants produced 100% survival, attenuated in the fall in liver ECP, and restored red blood cell ECP and liver glutathione levels to normal values. We conclude that a modest burn injury combined with endotoxemia produces a liver glutathione debt, oxygen debt, an energy deficit, and 60% mortality. The mechanism of injury is oxidant related as antioxidants prevented mortality restored liver glutathione levels, and prevented or attenuated the decrease in ECP. A decrease in ECP and glutathione levels appear to be more sensitive indicators of outcome than the presence of an oxygen debt. The survivors, in both burn plus endotoxin groups treated with or without antioxidants was comparable, indicating a critical value for oxygen consumption exists before death occurs.

We studied the effect of the oral administration of a water-soluble antioxidant solution containing ascorbic acid, glutathione, and a precursor for glutathione synthesis, N-Acetyl-L-cysteine, on liver antioxidant activity, liver cell energetics, and mortality in rats in response to a 20% third-degree burn injury challenged 5 days later with an intraperitoneal injection of 30 mg/kg endotoxin. Rats with burns were fluid-resuscitated with subcutaneous Ringer's lactate solution according to the Parkland formula (4 cc/kg/%burn). Rats challenged with endotoxin 5 days after burn were given an additional 100 ml/kg of subcutaneous Ringer's lactate solution immediately after the injection of endotoxin. A group of rats with burns challenged with endotoxin 5 days after burn were given an oral antioxidant solution beginning after burn injury. Liver cell energetics were measured as tissue energy charge potential (ECP), adenosine triphosphate (ATP) content, and total adenine nucleotides. The levels of endogenous liver glutathione, catalase, vitamin C, and vitamin E were measured to monitor antioxidant status. We found that burn injury alone did not produce any mortality over the 6-day period despite a 35% decrease in liver energy charge potential resulting from a decrease in ATP, a 34% decrease in liver catalase activity, and a 20% decrease in liver vitamin C. It was interesting that glutathione increased and vitamin E remained unchanged. We found that endotoxin injury combined with burn injury produced a 61% mortality rate with a 63% decrease in liver energy charge potential, again resulting from a decrease in ATP, a 74% decrease in liver catalase activity, a 16% decrease in vitamin C, and a 29% decrease in vitamin E. Glutathione was significantly decreased compared with burn alone. We compared the liver antioxidant status of survivors with that of nonsurvivors who were killed when appearing moribund and found that glutathione was decreased by 51% and vitamin C by 73% in nonsurvivors over that in survivors, whereas catalase and vitamin E levels were comparable between the two groups. The oral administration of the antioxidants prevented mortality and the decrease in antioxidant activity and attenuated the decrease in energy charge potential. We conclude that a 20% burn produces a modest decrease in liver energy charge potential and antioxidant defenses without producing mortality. The addition of endotoxin further decreases liver antioxidant defenses, liver energy charge potential, and markedly increases mortality. Antioxidants, given post-burn, restored antioxidant defenses, attenuated the altered cell energetics, and prevented mortality, indicating oxidants to be the cause of mortality. This data also suggests that a critical value of decreases in antioxidant defenses and ATP exists, resulting in mortality.

We studied the effect of water-soluble antioxidants on the cell energetics in multiple organs in rats in response to a 20% total body surface area third-degree burn injury. Liver, lung, and heart tissue were studied. Cell energetics were measured as tissue energy charge potential (ECP), adenosine triphosphate (ATP) content, and total adenine nucleotides. The enzymatic antioxidant catalase was used as a marker of endogenous cell antioxidant activity, especially to hydrogen peroxide. The water-soluble antioxidants glutathione, N-acetylcysteine, and vitamin C were given orally beginning at the time of burn injury and for the 6-day study period. All rats were fluid resuscitated according to the Parkland formula. The mortality rate was 0% for this size burn. The ECP in lung, liver, and heart, was normal on day 1 after the burn injury. However, the ECP was significantly decreased from the controls in the liver by day 3, with a peak decrease at day 6 as inflammation increased. A decrease in the heart ECP occurred between day 3 and day 6. Total adenine nucleotides did not decrease, indicating the decrease in ECP to be the result of a decrease in ATP. ECP remained normal in the lung. Catalase was also decreased in the liver and the heart and remained at normal levels in the lung. The decrease in the liver and heart ECP and ATP was eliminated with the oral antioxidant administration after the burn injury. We conclude that a modest burn injury decreases cellular energy charge in the heart and liver not immediately after burn but 3 to 6 days later. The decrease in antioxidant activity precedes the decrease in ECP. The lung appears to be protected. Water-soluble antioxidants, given after burn injury, prevent the altered cell energetics-strongly suggesting a cause-and-effect relationship between increased oxidant release with inflammation, decreased antioxidant activity, and altered cell energetics.

Objective: To study the early (first 24 hrs) effect of increasing lung exposure to smoke on the hemodynamic response to a modest body burn., Design: A prospective randomized study., Setting: Laboratory at a university medical center., Subjects: Thirty-two adult yearling female sheep., Interventions: Adult sheep (n = 32) were given an 18% of body surface burn; 24 sheep were then exposed to cotton toweling smoke using 12 breaths of a tidal volume of 5, 10, or 20 mL/kg. Animals were awakened, resuscitated to baseline oxygen delivery, and then killed at 24 hrs., Measurements and Main Results: Vascular pressure, cardiac output, and oxygen consumption and delivery were measured, as well as blood gases, lung and soft tissue lymph flow, and fluid balance. We found that a 5-mL/kg tidal volume smoke exposure x 12 breaths did not produce significant airway inflammation or alter the cardiopulmonary response to a burn alone. Oxygen consumption (VO2) remained at baseline and the net 24-hr positive fluid balance of 1.5 L was comparable to a burn alone. Increasing the smoke exposure to 10 mL/kg tidal volume, which produced a moderate airway injury, resulted in a significant increase in early fluid requirements, a 40% early increase in VO2, a doubling of positive fluid balance, as well as a marked increase in burn edema. However, gas exchange was not impaired. The 20-mL/kg tidal volume exposure resulted in an early 100% increase in VO2, a three-fold increase in fluid requirements at 1 to 4 hrs, compared with burn alone, in addition to a severe airway inflammation with mucosal slough and resulting impaired gas exchange., Conclusions: The addition of a smoke exposure which produces airway inflammation and injury significantly increases early post burn systemic metabolic demands and fluid requirements, as well as the degree of burn edema and positive fluid balance compared with a burn alone. The magnitude of the accentuated response appears to correspond with the degree of airway inflammation and not with alveolar dysfunction.

Objective: We compared the effect of a modest smoke inhalation injury, a burn injury alone, and a smoke inhalation injury plus a body burn, on the degree of lung oxidant-induced lipid peroxidation and lung injury., Design: Prospective animal study with concurrent controls., Setting: An animal laboratory., Subjects: Forty-four adult yearling female sheep (weight range 45 to 50 kg)., Interventions: Forty-four sheep were prepared with lung and prefemoral (soft tissue) lymph fistulas. Twelve breaths of cooled smoke with tidal volume of 10 mL/kg body weight were given to 24 sheep, producing a peak blood carboxyhemoglobin of 25% to 30%. Twelve sheep also received a 15% total body surface third-degree burn. Sheep were killed at 4 or 24 hrs., Measurements and Main Results: Circulating lipid peroxidation was monitored as conjugated dienes and tracheobronchial mucosal and lung parenchyma as malondialdehyde. Antioxidant defenses were monitored by catalase activity. Lung physiologic and histologic changes were compared. We noted intense airways inflammation in both smoke inhalation groups and lung parenchymal inflammation in all groups. Lung lymph flow was modestly increased (two-fold) in the smoke inhalation groups. Alveolar water content was not significantly increased after any injury. PaO2 was decreased at 24 hrs after the smoke insult alone. Parenchymal malondialdehyde content did not increase with the smoke insult alone, but did increase from a control value of 110 +/- 20 to 270 +/- 24 nmol/g tissue by 4 hrs in the combined burn and smoke injury group, while catalase activity decreased. Airway mucosal malondialdehyde did not increase in any group., Conclusions: We conclude that alveolar capillary permeability is not increased early after a moderate smoke injury or smoke injury with burn. Lipid peroxidation is not increased in large airway or lung parenchyma with early after-smoke exposure. The addition of a burn significantly increases lung parenchymal lipid peroxidation, but the oxidant changes do not correspond with the degree of early lung dysfunction.

We determined the lung and systemic response of a moderate smoke inhalation injury combined with a 15% total body surface third-degree burn compared with a burn alone and inhalation alone. Adult sheep were prepared with chronic lung and bilateral prefemoral soft tissue lymph fistula. The burn was confined to one side. Physiologic parameters, lymph flow (QL), and lymph/plasma protein ratio were monitored. Oxidant changes were measured as lipid peroxidation by circulating and lymph-conjugated dienes and lung tissue malondialdehyde. Animals were resuscitated with lactated Ringer's solution during the 24-hour study period to restore and maintain vascular filling pressures and cardiac index. We found net 24-hour fluid balance for burn-inhalation injuries to be 4.1 +/- 1.2 L compared with burn alone of 2.9 +/- 0.9 L and inhalation alone of 2.4 +/- 0.5 L, a significant difference. Protein-rich burn tissue QL increased by fivefold to sixfold with burn alone compared with more than tenfold with burn-inhalation injury. A twofold increase in both lung and nonburn soft tissue QL was also seen in the combined injury not seen with burn alone. Arterial blood gases decreased only at 12 hours. Plasma conjugated dienes were increased in all groups, whereas burn lymph values were increased only in combined insult. In addition, lung malondialdehyde content at 24 hours was 155 +/- 11 nmol/gm with burn-inhalation injury compared with 62 +/- 8 nmol/L for burn alone, 55 +/- 9 nmol/L in inhalation alone, and 45 +/- 4 nmol/L for controls. However, no alveolar flooding was noted in any group. We conclude that a modest smoke inhalation (carboxyhemoglobin of 25%) added to a 15% total body surface burn markedly increases the degree of burn edema, as well as nonburn soft tissue and lung QL, compared with burn alone, indicating increased plasma to interstitial fluid transport in these tissues as well. Increased burn tissue lipid peroxidation products corresponded with the increased burn fluid losses. The increased lung lipid peroxidation also indicates further lung oxidant activity as well.

Objectives: To determine the effect of a body burn on effective or nutrient liver blood flow and the relationship between blood flow and oxidant-induced lipid peroxidation., Design: Anesthetized sheep were given a 40% of total body surface, third-degree burn, after which animals were fluid resuscitated to return ventricular filling pressures and cardiac output to baseline values. Animals, for the 6-hr study period, were resuscitated with lactated Ringer's solution alone or lactated Ringer's solution plus 1500 mL of 5% hydroxyethyl starch or lactated Ringer's solution plus hydroxyethyl starch on which was complexed the iron chelator deferoxamine to prevent oxidant release. Effective liver blood flow was measured using the galactose infusion technique. Liver tissue lipid peroxidation was monitored using malondialdehyde content., Results: We found that effective liver blood flow was decreased by 50% in the 4- to 5-hr postburn period, even when animals were resuscitated to baseline cardiac output values with lactated Ringer's solution. Tissue malondialdehyde content increased in the group treated with lactated Ringer's solution from a control value of 110 +/- 7 to 202 +/- 59 nmol/g of tissue. Resuscitation with hydroxyethyl starch restored postburn effective liver blood flow to control values, but malondialdehyde content was still increased two-fold. Resuscitation with hydroxyethyl starch and deferoxamine resulted in an increase in effective liver blood flow postburn to a value 80% above controls. In addition, lipid peroxidation was prevented., Conclusions: Effective liver blood flow is markedly decreased after burn injury, even with apparently adequate volume resuscitation, when using lactated Ringer's solution. Liver lipid peroxidation persists even when effective liver blood flow is maintained, indicating that the oxidant process is not solely related to blood flow. Infusion of the antioxidant deferoxamine during resuscitation not only prevents the lipid peroxidation, most likely by a nonblood-flow-related process, but also results in an increase in blood flow above normal rates, suggesting that postburn liver oxygen needs exceed normal values.

We determined the relationship between oxygen delivery, DO2, and oxygen consumption, VO2, in sheep after a moderate smoke inhalation injury and 15% TBSA third-degree burn compared with burn alone and controls. Comparison was made beginning three hours after injury when carboxyhemoglobin levels were back to baseline values. We decreased DO2 between three and eight hours by 25% by either removing blood (controls) or decreasing the resuscitation fluid infusion rate. Lung oxidant, measured as tissue malondialdehyde (MDA) levels, and histologic changes were also assessed. Animals were killed at 24 hours. We found that in controls and animals with a burn alone, a 25% decrease in DO2 was compensated for by an increase in O2 extraction, maintaining VO2 constant. Correlation of DO2 to VO2 was r2 = 0.3, indicating independence of VO2 from DO2. With the combined injury, VO2 decreased in proportion to DO2, since O2 extraction did not increase. The correlation of DO2 to VO2 was r2 = 0.9, indicating delivery-dependent consumption, a pathologic process most likely caused by increased inflammatory mediators from the combined injury. Lung lipid peroxidation was markedly increased in the combined injury, 148 +/- 18 nmol MDA/gram of tissue compared with burn alone, 64 +/- 5 nmol/g, or controls, 45 +/- 4 nmol/g. However, no decrease in arterial O2 tension or increase in lung water was noted, i.e., the sheep did not have ARDS, which is known to impair O2 extraction. We conclude that a pathologic O2 delivery-dependent consumption develops with the combination of burn and inhalation injury, increasing the potential for tissue hypoxemia. This change corresponds with increased lung tissue oxidant change.

Inflammatory mediators play a major role in both the local burn wound and the systemic response to burn injury. Oxidant and arachidonic acid metabolites are involved in the initial burn edema process. The mediators as well as the cytokines released from activated macrophages also result in an early generalized inflammatory response. The later postburn hyper-metabolism is initiated and perpetuated by these same mediators, especially the cytokines, tumor necrosis factor, interleukin-1, and interleukin-2. Circulating endotoxin from the wound or the gut also appears to be involved. The postburn septic response is now recognized to be the result of inflammation; infection is not necessary. Mediator induced priming of the inflammatory cells by the burn itself results in an exaggerated response to infection in the postburn period. Defining the specific mechanism of injury and mediators involved can result in a major improvement in burn care, especially since many mediator inhibitors are already available for clinical use. It is essential that the clinician understand this pharmacologic manipulation in order to be able to optimally utilize these future advances.

A skin burn is a common traumatic injury that results in both local tissue damage and a systemic mediator-induced response. There is evidence of both local and systemic oxidant changes manifested by lipid peroxidation in animal burn models and also in burned man. Both increased xanthine oxidase and neutrophil activation appear to be the oxidant sources. Animal studies have also demonstrated decreased burn edema, and also decreased distant organ dysfunction with the use of antioxidants, suggesting a cause-and-effect relationship, which needs to be tested in man. Smoke inhalation injury, a chemical injury to the airways caused by incomplete products of combustion, is frequently seen in conjunction with a body burn. Lipid peroxidation, both in lung and in distant organs, is also seen with this injury. The combined body burn and smoke inhalation injury lead to a marked increase in mortality rate and also an increase in the degree of generalized oxidant release and lipid peroxidation. Although data in man are limited, the available information, along with that from animal research on burns and smoke inhalation, indicates oxidants may well play a key role, and antioxidants may be of clinical therapeutic use.

We studied the effect of the topical application of the nonsteroidal anti-inflammatory agent, flurbiprofen, on postburn hypermetabolism and systemic lipid peroxidation. Twelve sheep with a 15% total body surface third-degree burn were monitored over a 4-day postburn period. In six sheep, a single application of a 5% flurbiprofen cream was placed on the burn wound on day 3. Data were compared to both burned and nonburned controls (n = 6). All animals were killed on day 4. Oxygen consumption was increased at day 3 by 28% +/- 10% over the preburn value in all animals. Flurbiprofen significantly attenuated the increase in oxygen consumption, returning the value essentially to baseline by 12 hours after application. Lung and liver peroxidation, as measured by malondialdehyde, was significantly increased in the burned, nontreated sheep at day 4 from a control value of 45 +/- 9 and 110 +/- 12 to 60 +/- 6 and 310 +/- 71 nmol/gm tissue, respectively. In flurbiprofen-treated animals, values were 42 +/- 8 and 160 +/- 18 nmol/gm at day 4, significantly attenuated from burn alone. Protein-rich burn lymph flow remained fourfold increased in both groups, indicating a persistent increase in burn tissue vascular permeability, not modified by flurbiprofen. Burn wound biopsies revealed bacterial contents of less than 10(4) organisms/gram tissue in all animals. We conclude that topical flurbiprofen significantly decreases burn wound-induced systemic hypermetabolism and oxidant-induced lipid peroxidation seen at 3 days after burn injury, but does not attenuate the remaining local burn-wound vascular permeability.

We studied the effect of deferoxamine (DFO) infused after burns on hemodynamic stability as well as local and systemic inflammation and oxidant-induced lipid peroxidation. Eighteen anesthetized sheep were given a 40% of total body surface burn and fluid resuscitated to restore oxygen delivery (DO2) and filling pressures to baseline values. Animals were resuscitated with lactated Ringer's (LR) alone or LR plus 1,500 ml of a 5% hetastarch complexed with DFO (8 mg/ml). Animals were killed 6 hours postburn. The sheep resuscitated with LR and LR plus hetastarch demonstrated significant lung inflammation and significant increases in lung and liver malondialdehyde (MDA) from controls of 47 +/- 6 and 110 +/- 7 nMol/gm to 63 +/- 13 and 202 +/- 59 for LR and 67 +/- 4 and 211 +/- 9 for LR + hetastarch, respectively. The group resuscitated with hetastarch alone required 15% less fluid. VO2 returned to baseline values in both groups by 2 hours. Resuscitation with the 5% hetastarch-DFO decreased total fluids by 30% over LR and prevented the increase in lung and liver MDA. In addition, postburn VO2 increased by 25% above baseline values. Burn tissue edema, measured as protein-rich lymph flow, was significantly increased with the administration of DFO compared with the other groups. We conclude that DFO used for burn resuscitation prevents systemic lipid peroxidation and decreases the vascular leak in nonburn tissues while also increasing O2 utilization. Resuscitation with hetastarch-DFO may accentuate burn tissue edema, possibly by increased perfusion of burn tissue.

Both endotoxin and a burn alone produce oxidant-induced tissue lipid peroxidation. The endotoxin response is due in large part to hydrogen peroxide. The combination of endotoxin after a burn results in an increased liver, but not lung, oxidant injury. Our purpose was to determine whether the burn oxidant injury inactivated endogenous liver tissue catalase, thereby amplifying a subsequent H2O2 insult. Twenty-six adult sheep were studied. Twelve sheep had a 15% TBS burn. Tissue catalase activity, measured in lung and liver 3 days postburn, was significantly decreased from a control of 3.58 +/- 1.8 and 193 +/- 63, respectively, to 1.72 +/- 0.63 and 148 +/- 33 k(sec-1)/0.5 gram tissue. The addition of endotoxin 3 days postburn resulted in an increase in liver malondialdehyde, MDA, a measure of lipid peroxidation, from a control of 110 +/- 80 to 450 +/- 54 nmol/gram tissue. This value was significantly greater than the 210 +/- 80 nmol/gram tissue seen after endotoxin alone. Lung tissue MDA with burn and endotoxin was 65 +/- 8 compared to 42 +/- 7 for control and 80 +/- 6 nmol/gram for endotoxin alone. We conclude that a decrease in liver catalase activity occurs after a burn. The decrease corresponds to an accentuated oxidant-induced lipid peroxidation after an added endotoxin insult where H2O2 is known to be an etiologic agent. The catalase activity also decreases in postburn lung, but accentuated lung damage was not seen, indicating a variable tissue response from the burn-induced decrease in antioxidant activity.(ABSTRACT TRUNCATED AT 250 WORDS)

The lung and systemic physiologic response to endotoxin is markedly accentuated in the presence of a body burn. Our purpose was to determine whether early burn excision and closure would decrease this response. We compared the endotoxin (2 micrograms/kg)-induced response in 10 adult sheep with lung and soft-tissue lymph fistulas 3 days after a 15% total-body surface full-thickness burn that was excised immediately with that of sheep without burn excision and nonburned sheep. No infection was present in the burn wound. Early excision prevented the ongoing postburn lipid peroxidation and lung inflammation seen 3 days after burn before endotoxemia in animals with 15% total body surface burn wound not excised. Sheep that underwent excision demonstrated significantly less pulmonary hypertension and hypoxia after endotoxin than did either endotoxin-treated and intact burned sheep or endotoxin-treated nonburned sheep. Lung inflammatory changes as determined by neutrophil content of lung tissue and the increase in lung tissue malondialdehyde in the group that underwent burn excision after endotoxin were comparable to those seen with endotoxin alone, as was the lung lymph-flow response. Also, the systemic response was nearly identical to that seen with endotoxin alone with no increase in soft-tissue permeability as measured by lymph flow. Oxygen consumption (VO2) remained unchanged from baseline. In contrast, VO2 doubled in burn-intact animals initially after endotoxin, after which VO2 decreased to levels below baseline. An increase in soft-tissue vascular permeability was also noted. We can conclude that early burn excision and closure prevent the accentuated response to endotoxin that is seen when the burn wound is left intact, even if it is uninfected.

We determined the effect of a 15% total body surface (TBS), full-thickness burn on the physiologic, histologic, and oxidant-induced lipid peroxidation changes produced by endotoxin. The endotoxin-burn response was compared with that of endotoxin alone. Twenty-two adult sheep with chronic lung and flank lymph fistulas were studied. In 11 sheep a burn was produced under anesthesia and 3 days later they were given 2 micrograms/kg of endotoxin. Data were also compared with those of control sheep and those that were given burns alone. Circulating conjugated dienes increased with endotoxin alone but remained at baseline with endotoxin and burn injury. The lung lymph flow response was increased significantly in the endotoxin-burn group (sixfold) compared with that of endotoxin alone (fourfold). Histologic quantitation of lung neutrophil count was comparable in both groups 6 hours after injury, although mononuclear cells were much more evident in lungs in the endotoxin-burn group. Lipid peroxidation measured by malondialdehyde was significantly increased in the endotoxin group compared with the endotoxin-burn group, despite the greater increase in lymph flow and lung water in the burned group. Oxygen consumption (VO2) remained constant after endotoxin alone compared with baseline. However, VO2 increased twofold immediately after endotoxin in the endotoxin-burn group. This marked increase was followed by a significant decrease in VO2 from baseline. Flank soft-tissue nonburned increased lung lymph flow twofold to threefold with endotoxin and burn, indicating increased soft-tissue permeability, whereas it remained unchanged with endotoxin alone. Liver malondialdehyde increased from a control of 110 +/- 20 to 210 +/- 80 mmol/gm tissue with endotoxin alone and to 450 +/- 54 nmol/gm tissue with endotoxin and burn. We can conclude that burn injury accentuates both the pulmonary and systemic physiologic response to endotoxin, possibly as a result of mediators released from mononuclear cells already activated in the presence of the burn. The increased lung physiologic response does not appear to be caused by greater oxidant-induced lipid peroxidation, as was seen in the liver with the combined injury.

We measured lipid peroxidation of plasma, lung, and liver in anaesthetized sheep after third-degree burns involving 30% of total body surface. Animals were resuscitated to baseline filling pressures with lactated Ringer's solution and killed 10 hours after burn. Six sheep were pretreated with ibuprofen (12.5 mg/kg) and five with allopurinol (50 mg/kg). We used conjugated dienes and malondialdehyde as measures of lipid peroxidation. Circulating conjugated dienes increased from a baseline of 0.48 +/- 0.06 to 0.64 +/- 0.05 after burn, while protein-rich burn tissue lymph flow increased up to eightfold. We also noted a significant increase in lung tissue malondialdehyde from 45 +/- 4 to 60 +/- 6 nmol/gm and liver malondialdehyde from 110 +/- 20 to 271 +/- 34 nmol/gm along with increased tissue neutrophil sequestration. Ibuprofen attenuated lung-tissue malondialdehyde but had no effect on lung inflammation, circulating lipid peroxides or burn edema, indicating that ibuprofen most likely decreased O2 radical release in lung tissue by the already-sequestered neutrophils. Allopurinol, possibly via xanthine oxidase inhibition, markedly attenuated burn QL and circulating lipid peroxides and prevented all pulmonary lipid peroxidation and inflammation, indicating that release of oxidant from burn tissue was in part responsible for local burn edema, as well as distant inflammation and oxidant release, the latter most likely from complement activation. Neither antioxidant decreased lipid peroxidation in the liver; this indicates that its mechanism of production was different from that seen in burn tissue, in plasma, or in the lung. An ischemic event resulting from a selective decrease in splanchnic blood flow may be the cause of the liver changes.

We determined the time course of the oxidant-induced systemic lipid peroxidation seen after burn injury. Twelve sheep were given a 15% of total body surface third-degree burn and monitored for 3 or 5 days. Circulating lipid peroxides were monitored by both malondialdehyde (MDA) and conjugated dienes (CD). Lung and liver tissue MDA was also measured and compared to controls. A significant but transient increase in circulating MDA and CD was noted several hours after burn. Venous plasma levels increased again 3-5 days postburn with onset of wound inflammation. Oxygen consumption, VO2, also increased by 35 +/- 12% at this time. Lung MDA, which increased to 64 +/- 5 from a control of 45 +/- 4 nMol/gm, at 12 hours after burn was still increased 3 days after injury. Marked lung inflammation was present early after injury and persisted for the 5-day study period. Liver MDA also increased from control value of 110 +/- 20 to 252 +/- 25 at 12 hours and remained increased over the 5-day period. Serum alkaline phosphatase was also increased. Burn biopsies revealed no infection to explain the ongoing lipid peroxidation process, i.e., bacterial content was less than 10(5) organisms/gram burn tissue. We conclude that an initial system lipid peroxidation occurs immediately after burn injury, and that this process continues well into the post-resuscitation period, corresponding in time with increased VO2, lung inflammation, and evidence of liver dysfunction. The ongoing oxidant changes with the presence of a burn may explain the accentuated organ dysfunction seen with an additional septic insult in burned patients.

The cardiopulmonary effects of a third-degree scald burn involving the anterolateral chest wall was compared with a burn of equal size (30% of total body surface) to the flanks in anesthetized sheep with lung lymph fistulas. The chest-burn group was characterized by immediate decreases in cardiac output (6.5 to 3.0 L/min), central venous pressure (5 mm Hg to 0 mm Hg), pulmonary wedge pressure (10 mm Hg to 6 mm Hg), and urine output 1.5 ml/kg/hr to less than 0.5 ml/kg/hr. The temperature of pulmonary artery blood increased from 38 to 42 degrees C and plasma prostacyclin increased from 20 to 200 pg/ml. These changes were significantly different from those seen in the body sheep with burns. Initial fluid requirements necessary to restore filling pressures were 50% greater in the sheep with chest burns than in the sheep with body burns. An early decrease in static lung compliance was also seen after chest burn that was not the result of increased lung edema. A progressive decrease in compliance, urine output, and stroke output was also seen in the later postburn period (6 to 7 hours), which was significantly improved by a chest wall escharotomy. Postmortem analysis in the chest-burn group revealed a significantly increased malondialdehyde content, a reflection of increased oxygen radical-induced lipid peroxidation relative to the body burn. Pretreatment of the chest burn with ibuprofen, 12.5 mg/kg, prevented the initial vasodilator and lung compliance changes so that early cardiopulmonary status was identical to that seen with a body burn alone. Ibuprofen also decreased the lung tissue malondialdehyde content. We conclude that a burn involving the chest wall results in cardiopulmonary abnormalities, not seen after a body burn of a comparable size, which appear to be due to hyperthermia and an increased release of prostacyclin and O2 radicals.

We injected Escherichia coli endotoxin, 2 micrograms/kg, beneath the eschar of sheep with 25% total body surface full-thickness burns to determine whether burn tissue in the presence of endotoxin releases prostanoids, particularly thromboxane A2, (TxA2), and if increased local TxA2 production can lead to distant lung dysfunction. We compared this response to the lung injury produced by the same dose given intravenously. We noted a marked increase in burn tissue TxA2 production after subeschar endotoxin as reflected in significant increases in burn lymph and pulmonary artery TxB2 levels. Pulmonary artery pressure increased from 22 to 38 mm Hg and PaO2 decreased from 89 to 71 torr while lung lymph flow (QL) increased only modestly with no evidence of increased lung permeability. The TxA2 production and the lung response were prevented by the subeschar injection of ibuprofen, 12.5 mg/kg. Circulating endotoxin was noted in only one of five sheep. After intravenous (endotoxin), a significant increase in lung TxA2 production was noted and a characteristic two-phase lung injury was seen with an initial phase basically identical to that seen with the subeschar injection followed by an increase in lung protein permeability. Burn tissue endotoxin can stimulate local TxA2 production leading to distant lung dysfunction without the need for circulating endotoxin. The source of the TxA2 is the burn, while with endotoxemia the source is the lung.

The pulmonary and systemic response to a full-thickness burn (15% of total body surface area) was determined in 15 adult sheep. Also compared was the effect of wound bacterial content and prostanoid release on this response. Burn wound thromboxane A2, measured as TxB2, and prostacyclin, measured as 6-keto-PGF1 alpha, were measured in burn wound lymph. Animals were monitored for 7 days. On the final day, a full-thickness biopsy specimen of burn tissue was obtained for quantitative bacteriology. Wounds with 10(4) or less organisms per gram of burn tissue were considered colonized, whereas those with 10(5) or more organisms per gram of burn tissue indicated wound infection. Seven sheep had 10(4) or less bacteria and the remaining eight sheep had 10(6) or greater bacteria. We noted a significant mean increase in cardiac index from a baseline of 5 to 6.2 L/min/m2, a decrease in systemic vascular resistance from 16 to 12 mm Hg/L/min, and a mean increase in oxygen consumption from a baseline of 135 to 165 ml/min/m2 during the 7-day study period. There were no differences in these responses between the colonized and the infected wounds. Pulmonary artery pressure increased from a mean baseline of 19 to 24 mm Hg and arterial oxygen tension (PaO2) decreased from a baseline of 90 to 80 mm Hg in the infected wound group, with values remaining at baseline in the colonized wound group. These changes corresponded with an increase in lymph and plasma TxB2 from a baseline of 200 to 210 pg/ml to 1000 +/- 250 and 600 +/- 190 pg/ml, respectively. Values in the animals with colonized wounds were not significantly increased.(ABSTRACT TRUNCATED AT 250 WORDS)

Pulmonary dysfunction is a well-recognized complication of burn wound excision. It remains unclear whether this is caused by bacteria or inflammatory mediators released during excision of the wound. We produced a 15% full-thickness burn in 18 sheep, and between days 5 and 7 completely excised the wound under general anesthesia. Pulmonary parameters of static and dynamic lung compliance (CSTAT and CDYN), PaO2/FiO2, and pulmonary artery pressure (Ppa) were measured, as well as burn lymph, venous and aortic thromboxane B2 (TxB2), chemotactic index (chemotaxis/chemikinesis), and oxygen radical activity reflected in the level of lipid peroxidation in lung tissue. We noted a transient increase in burn lymph and venous TxB2 during excision, increasing from a preburn value of 200 and 220 +/- 50 pg/ml to 950 +/- 210 and 980 +/- 280 pg/ml, respectively. In 13 of 18 sheep, chemotactic activity and lung tissue lipid peroxidation, measured as malondialdehyde (MDA) content, were not increased. In this group only a very transient decrease in CDYN, PaO2/FiO2, and a 3 mm Hg increase in mean Ppa was seen with excision, with these parameters returning rapidly to baseline. Five of the 13 sheep had wound biopsy specimens that were greater than 10(6) organisms/gm tissue. In the remaining five sheep, plasma chemotactic index was also significantly increased with excision, as was lung MDA content, while decreases in CDYN, CSTAT, and PaO2/FiO2 and an increase in Ppa were more protracted. Three of these five sheep had wound biopsy specimens greater than 10(6) organisms/gm. We conclude that a release of thromboxane occurs during excision, which corresponds in time to transient lung dysfunction. If there is also a release of chemotactic factors, a more protracted pulmonary response occurs with evidence of O2 radical-induced lung changes.

We studied the effect of partial excision and wound closure on the postburn hypermetabolic state. A 25% of total body surface burn was produced in seven sheep. Oxygen consumption (VO2) was significantly increased to 215 +/- 44 ml/min/M2 by day 3 compared with baseline of 125 +/- 21 ml/min/M2. The calculated increase was the result of the increased cardiac index as the average oxygen (AvO2) difference remained relatively constant. Body temperature was not significantly increased. Plasma and burn lymph thromboxane B2 were significantly increased. On day 7, 60% of the burn was completely excised to fascia and covered with a full-thickness graft from a donor animal. The VO2 decreased to below preburn levels during the period of anesthesia but returned completely to the preexcision hypermetabolic state by 2 hours after anesthesia and remained at this level for the remaining 2-day postexcision period. Quantitative cultures of burn hide at day 7 postburn and of the remaining 10% of total body surface burn at 2 days after excision revealed values less than 10(5) bacteria/gram eschar. No positive blood cultures were evident. We conclude that postburn hypermetabolism, once developed, may be perpetuated by a burn of lesser size. Partial excision, therefore, does not appear to significantly decrease the hypermetabolic state if a substantial inflammatory wound remains. Infection is not necessary to perpetuate the increased VO2.

A full-thickness burn wound in adult sheep releases prostanoids when they are injected locally with E. coli endotoxin, 2 micrograms/kg, resulting in an increase in pulmonary artery pressure (Ppa) from 20 +/- 3 to 34 +/- 5 mm Hg, and a decrease in mean arterial oxygen tension (PaO2) from 88 +/- 6 to 70 +/- 5 torr; this corresponds to an increase in venous plasma TxB2 content from a baseline of 220 +/- 79 pg/ml to 440 +/- 90 pg/ml. Burn prostanoid production, measured in lymph, increased ten- to fifteen-fold for both thromboxane A2, measured as TxB2, and prostacyclin, 6-keto-PGF1 alpha. The intravenous administration of ibuprofen, 12.5 mg/kg, eliminated both the increase in Ppa and decrease in PaO2 as well as the increase in burn lymph prostanoids. However, plasma prostanoids were also decreased below baseline, a potentially deleterious effect. A topical ibuprofen cream, 5% ibuprofen in a water-soluble ester, was applied to the burn hide every 6 hrs x 4 after which endotoxin was again injected below the hide. The pulmonary dysfunction was prevented as was the increase in plasma TxB2 with the value remaining at baseline. Burn lymph levels were only increased three- to five fold. Ibuprofen levels in burn lymph were maintained at 1-2 mcg/ml. The addition of the cream to the burn, however, did increase the wound bacterial content to 10(5)-10(7) bacteria/gram of tissue compared to 10(2)-10(3) for the dry, untreated burn, probably due to softening of the burn. Topically applied ibuprofen, therefore, can decrease burn wound prostanoid production from local endotoxin, preventing lung dysfunction.(ABSTRACT TRUNCATED AT 250 WORDS)

We studied the relationship between oxygen delivery (DO2) and oxygen consumption (VO2) in the early post-burn period. Unanesthetized sheep with a 15% total body surface (TBS) third-degree burn were resuscitated back to baseline VO2 and vascular pressures. DO2 was adjusted further by infusion and removal of whole blood. The response was compared to the same maneuver in nonburned sheep. We found that increasing DO2 after burns resulted in a 32% increase in VO2, while the same maneuver in controls produced no change in VO2. We then determined whether the increase in VO2, caused by volume loading, resulted in a further increase in postburn oxidant release and lipid peroxidation measured as conjugated dienes. Plasma conjugated dienes increased significantly and equally by 30% in burns maintained at baseline VO2 vs. the increased VO2. Therefore, the increased oxygen used is not simply resulting in further oxidant damage. VO2 was maintained equally in both burned animals and controls with a decrease in DO2 by increased oxygen extraction from Hgb. We conclude that standard burn resuscitation does not restore adequate DO2 for oxygen demands. The 30% increase in VO2 achieved by increasing DO2 does not lead to a further release of oxidants from burn tissue and is therefore potentially beneficial for cell function.

We determined the effect of topically applied ibuprofen on formation of second-degree burn edema and prostanoid production, a possible causative factor. Six adult sheep were given second-degree burns on both flanks with water at 80 degrees C while they were under general anesthesia. Lymph (QL), draining the flank areas, was used to monitor edema formation and prostanoid production. A 5% ibuprofen cream was applied at 2 and 5 hours after the burn and full-thickness biopsy specimens of burned hide were obtained at 8 hours for determination of water content. The QL increased sixfold in nontreated and 2.5 times in treated burn tissue. The lymph/plasma (L/P) protein ratio increased from 0.4 to 0.58 in both sides. Lymph TxB2 was increased from baseline of 200 pg/ml to 500 +/- 100 and 310 +/- 90 pg/ml in untreated and treated sides, respectively. Lymph 6-keto-PGF1 alpha increased from a baseline of 50 +/- 10 to 150 +/- 40 and 90 +/- 80 pg/ml in untreated and treated sides. The difference between PG content of lymph in treated and untreated sides was significant. Plasma prostanoids, except for a transient early rise, remained at preburn baseline. Lymph ibuprofen content on the treated side rose to 1.9 +/- 0.8 mcg/ml with no detectable plasma level. Water content of hide increased from a control value of 74 +/- 2% to 84 +/- 2% in untreated burn, while the value in the treated side was 76 +/- 4%, a significant difference between the two sides. We conclude that topically applied ibuprofen decreases both local edema and prostanoid production in burn tissue without altering systemic production.

Thromboxane A2 production is increased early after burn. We studied the effect of inhibiting thromboxane synthetase, using dazmegrel, on postburn hemodynamic stability and edema formation, the latter monitored by burn tissue lymph flow. Dazmegrel (3.4 mg/kg) was given to six anesthetized sheep, and a 40% of total-body-surface third-degree burn was produced. Lactated Ringer's solution was infused at a rate to restore filling pressures during a 12-hour study period. Data were compared to burn alone (n = 8), anesthesia alone (n = 6), and dazmegrel alone (n = 5) groups. The latter two groups showed no physiologic changes. Dazmegrel pretreatment prevented increased thromboxane A2, measured as thromboxane B2, but resulted in a significant increase in plasma prostacyclin, measured as 6-keto-PGF1 alpha. In addition, a marked vasodilatation and decrease in systemic vascular resistance were noted, as well as a 30% increase in fluid requirements and an increase in lymph flow compared with burn alone. The increase in prostacyclin more than likely accentuated the burn-induced permeability change. Of interest was that oxygen consumption was better maintained with dazmegrel postburn, even with the relative hypovolemia, indicating that postburn vasoconstriction impairs adequate O2 delivery to tissues and that thromboxane synthetase inhibition attenuates this process.

We studied the intraoperative and postoperative effects of anesthesia and wound excision on oxygen delivery and oxygen consumption after burn injury. Twenty adult sheep were studied: six had halothane anesthesia alone and 14 had anesthesia and third-degree burns over 15% of the total body surface. Body temperatures were maintained within 1 degree C of baseline value during the operations. The burns on six sheep were totally excised and hide from donor sheep was grafted 3 hours after injury; in eight sheep, excision and grafting were done 5 days after injury. We found that 3 hours of anesthesia in controls decreased oxygen delivery (DO2) by 22% +/- 6% and oxygen consumption (VO2) by 30% +/- 7% from waking baseline values primarily because of a decrease in cardiac output as oxygen (O2) extraction from hemoglobin also decreased. However, no base deficit developed. DO2 and (VO2) transiently increased to 9% +/- 3% above baseline value on the sheeps' return to the waking state. Anesthesia and wound excision, which began 3 hours after the burns were formed, decreased DO2 and VO2 by 25% +/- 4% and 32% +/- 4%, respectively, despite baseline filling pressures. However, a base deficit of -3 +/- 1 mEq/L developed during the two-hour operations, which began with the administration of anesthesia alone. Oxygen consumption increased to 25% +/- 6% above the waking baseline value upon each subject's return to the waking state. In the sheep treated 5 days after burn injury, DO2 decreased by 35% +/- 6% and VO2 decreased by 42% +/- 6% below the value during the waking hypermetabolic state when the sheep were under anesthesia.(ABSTRACT TRUNCATED AT 250 WORDS)

We determined the effect of complete excision and closure of the burn wound on the postburn increase in oxygen consumption. Twelve sheep were given a 15% of total body surface full-thickness burn and were monitored for 7 days. By the third day, a 50% increase in O2 consumption, VO2, was noted, as was a significant increase in cardiac index and decrease in mixed venous PO2, compared to baseline. The hypermetabolic process persisted for the 7-day pre-excision period. On the seventh postburn day all sheep were anesthetized for 2 hours with halothane and placed on positive pressure ventilation, and then one half of these sheep underwent excision and closure. During anesthesia, VO2 decreased to 76 +/- 15 ml/min/M2, a value significantly lower than even the preburn awake baseline of 122 +/- 14 ml/min/M2 and the 7-day postburn value of 180 +/- 18 ml/min/M2. Quantitative cultures, before excision, revealed the wounds to be noninfected (less than 10(5) organisms per gram). In six animals, the burns were totally excised to fascia and closed with full-thickness defatted hide from other sheep obtained at the same time under sterile conditions. In these animals, the VO2 returned to preburn baseline by 24 hours postexcision and remained there for the 3-day postexcision study period. In the other six burned sheep, the 15% full-thickness burns remained. The hypermetabolic state returned to the 7-day postburn level on return to the awake state and persisted for the remainder of the study. We conclude that complete excision and wound closure can reverse the postburn increase in O2 consumption.

Our purpose was to determine the effect of anesthesia and positive pressure ventilation, PPV, on early postburn (1-12 hr) cardiopulmonary changes. Adult sheep were given a 40% full-thickness TBS burn not involving chest wall. Halothane anesthesia and PPV alone decreased cardiac output by 20% but also decreased oxygen demands by 30% from the awake state. Systemic vascular resistance, SVR, was increased by 40% over the awake state in the first several hours postburn: cardiac output was decreased despite baseline filling pressures. Low molecular weight dextran, LMWD, prevented the increased SVR by decreasing resistance to flow. A continued decrease in cardiac output was evident during the next 6-12 hr postburn with anesthesia while awake sheep values returned to baseline. Fluid requirements to maintain filling pressures also increased by 30% over the awake state. Static lung compliance, CSTAT, decreased from a baseline of 43 +/- 5 to 32 +/- 4 ml/cm H2O with anesthesia and ventilation. This was due to nonburn chest wall edema: lung water was normal. The 7-cm H2O increase in inspiratory pressure necessary to maintain constant volume was the cause of the decreased cardiac output, because maintaining pressure constant resulted in no decrease in cardiac output. VO2 remained relatively constant due to increased O2 extraction. LMWD prevented the CSTAT changes and, in turn, the decreased output. We conclude that both the increase in SVR and decrease in CSTAT postburn resulted in a significant decrease in cardiac output with anesthesia not seen in the awake burn state. The decreased output was, however, in large part compensated for by decreased O2 demands and increased O2 extraction.

We determined the effect of a body burn on pulmonary function. Full-thickness burns varying in size from 25 to 70% of total body surface (TBS), were produced in sheep. Resuscitation was performed with lactated Ringer's. We noted an increase in lung transvascular fluid flux as measured by lymph flow, Q1, during the resuscitation period, varying from one- to threefold over baseline with the degree of increase directly proportional to the burn size. The increase in QL could be totally explained by the degree of hypoproteinemia which was also proportional to burn size. Transient pulmonary hypertension 20 +/- 4 to 26 +/- 5 mm Hg and a decrease in PaO2 from 90 +/- 5 to 83 +/- 6 torr occurred in the 50 and 70% burns as well as a significant decrease in lung compliance. These alterations were not due to pulmonary edema as there was no increase in measured lung water. Also, the increase in QL could be prevented by using a combination of Dextran and protein for resuscitation but this had no effect on the hypertension or hypoxia. Burn lymph and venous plasma thromboxane levels were increased during this period of lung dysfunction. Ibuprofen 12.5 mg/kg preburn and 12.5 mg/kg every 2 hours postburn decreased the degree of dysfunction suggesting a cause and effect relationship.

We studied whether changes in lung function after burns (1- to 12-h period) were due to changes in lung water or airways resistance and the relationship of the changes to prostanoid and O2 radical activity (measured as lipid peroxidation). Twenty-five anesthetized mechanically ventilated adult sheep were given a 40% of body surface scald burn and resuscitated to restore and maintain base-line filling pressures. Dynamic lung compliance (Cdyn) decreased by 40% from 38 +/- 5 to 24 +/- 4 ml/cmH2O at 12 h. Venous thromboxane B2 transiently increased from 210 +/- 40 to 1,100 +/- 210 pg/ml, and the value in lung lymph increased from 180 +/- 80 to 520 +/- 80 pg/ml. Prostacyclin levels in lung lymph and plasma remained at base line. Protein-poor lung lymph flow increased two- to threefold, but postmortem lung analysis revealed no increase in lung water from the control of 3.5 +/- 0.3 g H2O/g dry wt. No increase in protein permeability was seen. However, the lipid peroxidation of lung tissue measured as malondialdehyde was significantly increased from the control value of 56 +/- 4 nmol/g lung to a value of 69 +/- 6. Ibuprofen pretreatment (12.5 mg/kg) markedly attenuated the decrease in Cdyn, with the value at 12 h being 90% of base line. Ibuprofen also decreased the amount of lung lipid peroxidation but did not decrease the lung lymph response. We conclude that the decrease in Cdyn seen early postburn is not due to increased lung water, but, rather, is due to a mediator-induced bronchoconstriction, attenuated by ibuprofen; the mediator being either thromboxane or a byproduct of O2 radicals as evidenced by increased lipid peroxide production in lung tissue.

We studied the effect of a body burn on lung physiologic, biochemical, and histologic changes in a 2-day postburn period. A 15% of total-body-surface third-degree burn was produced in 24 adult sheep with lung and burn lymph fistulas. Eight sheep were killed at 12 hours and eight at 48 hours. At 12 hours we noted increased lung tissue lipid peroxidation, lung congestion, and neutrophil sequestration, in addition to a 30% decrease in lung compliance. Lung permeability and water content were not increased. Increased release of lipid peroxides and prostanoids were noted from burn tissue, as evidenced by increased plasma levels of malondialdehyde and conjugated dienes that remained elevated for about 8 hours and were decreased with wound removal. The lung inflammatory response was still present at 48 hours, the cells being primarily neutrophils. Nevertheless, the lipid peroxidation process, as measured by lung tissue malondialdehyde, had resolved. There was no evidence of burn tissue infection, measured by quantitative culture, to explain the persistent increase in lung inflammatory cells. Excision and closure of the burn wound at 3 hours postburn in eight sheep attenuated the lipid peroxidation and compliance changes but did not decrease the neutrophil sequestration. We conclude that burn injury results in a local wound oxidant release that leads to lipid peroxidation, both in wounds and in lung, as well as lung inflammation. The lipid peroxidation process may be attenuated by removal of the wound. The neutrophil sequestration is not altered, however, indicating this response occurs very early after injury, probably as a result of oxidant-initiated complement activation.