Energy charge potential and glutathione levels as predictors of outcome following burn injury complicated by endotoxemia.

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.

Plasma catalase and glutathione levels are decreased in response to inhalation injury.

We determined the effect of a severe smoke exposure on plasma oxidant and antioxidant activity. Adult sheep were given a smoke exposure while under anesthesia that produced a carboxyhemoglobin level of 45% +/- 3%. Twelve sheep were studied; six were given smoke alone and volume-resuscitated with sufficient lactated Ringer's solution to maintain baseline hemodynamics. This response was compared with six control sheep during a 6-hour period. The smoke inhalation injury produced a significant increase in plasma hydrogen peroxide and a significant decrease in plasma lipid peroxidation. Circulating lipid peroxidation did not correlate with tissue lipid peroxidation because lung and liver lipid peroxidation were significantly increased. The plasma antioxidants glutathione, catalase, and vitamin E were significantly reduced in response to the injury. Vitamin C remained unchanged from control. Circulatory failure is not a key element in this study, because lactate levels were controlled with volume resuscitation. The degree of smoke inhalation to the airway produced distant organ lipid peroxidation and a decrease in circulating antioxidants--without producing an increase in circulating lipid peroxidation. Maintaining circulating antioxidants may prevent distant organ lipid peroxidation and may be of clinical use in devising treatment strategies for smoke inhalation injury with the availability of antioxidants.

Excessive liver oxidant stress causes mortality in response to burn injury combined with endotoxin and is prevented with antioxidants.

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.

Antioxidants prevent the cellular deficit produced in response to burn injury.

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.