Prophylactic hemodialysis in the treatment of acute renal failure. Annals of Internal Medicine, 53:992-1016, 1960.

Prophylactic hemodialysis has been employed in the treatment of 15 patients with acute renal failure due to acute tubular necrosis (12), bilateral renal cortical necrosis (two), and poststreptococcal glomerulonephritis (one). Dialyses, usually lasting six hours each, were begun before clinical evidence of uremia developed in each patient and/or before the nonprotein nitrogen reached 200 mg.%, and were repeated daily or often enough to maintain the nonprotein nitrogen below 150 mg.%. The hypothesis underlying this technic postulates (1) that wasting, sepsis and impaired wound healing in these patients may reflect tissue injury by the same dialyzable toxic agents which produce the uremic symptoms that are readily reversible by dialysis, and (2) that repeated dialyses should therefore prevent both clinical uremia and the later, often lethal sequelae. The results contrast dramatically with our own past experience in treating patients with acute renal failure with a carefully executed medical regimen together with hemodialysis on conventional indications. Except in one instance of crush injury with progressive intracerebral damage, and one brief occasion in another individual, these patients experienced a stable, convalescent clinical course, remained free of uremic symptoms or chemical imbalances, ate at least three meals daily which were unrestricted in amount and composition, and were ambulatory between dialyses unless confined to bed by associated disease. Wounds healed well. Infection either did not occur, or subsided after appropriate therapy. Fluid restriction was liberalized by means of ultrafiltration with dialysis. Regional heparinization of only the extracorporeal circuit eliminated actual or impending bleeding as a contraindication to dialysis. Chronic vessel cannulation made the frequent dialyses possible, but may have provided the route for repeated, transient bacterial contamination of the blood stream in the first hour of many dialyses. Marked anemia, despite reticulocytosis, moderate to mild weight loss and some mental deficit persisted in spite of the general clinical improvement and well-being. Three patients with tubular necrosis died after seven, 11 and 26 days of oliguria; both patients with bilateral renal cortical necrosis also succumbed, on the seventy-third and ninety-second days of renal failure, and after 29 and 40 dialyses, respectively. At autopsy, evidence of sepsis was conspicuously absent. The remaining 10 patients survived. Thus some, but not all, clinical manifestations of acute renal failure appear to be favorably influenced by prophylactic dialysis treatment. Our initial experience in this group of 15 patients does not of course prove that freedom from complications and a significantly better outlook for survival can be assured to patients with acute renal failure by these methods. However, it seems to offer a reasonable hope of this possibility which we cannot attach to management by medical measures alone, or by dialysis on conventional indications. If this hope is realized in greatly extended, subsequent series, then it seems inevitable that some form of prophylactic dialysis, or some equally effective alternative, should be adopted in treating the majority of patients with acute renal failure.

Skin burn injury and oxidative stress in liver and lung tissues of rabbit models.

The effects of burn injury (30% of total body surface area) on the levels of oxidized and reduced glutathione, malondialdehyde, and on the activities of certain glutathione-dependent enzymes, have been determined in tissues of rabbit models. Thus, the malondialdehyde, glutathione (GSH), glutathione disulfide (GSSG) concentrations and the specific activities of glutathione peroxidase, glutathione S-transferase, and glutathione reductase were measured in liver and lung of 24-h burn rabbit models and compared to the corresponding values in 24-h sham burn (medicated, anesthetic/analgesic) rabbit models. It was found that the concentrations of malondialdehyde in liver and lung of burn models were increased by 17% and 29% respectively. Glutathione concentrations were decreased by 29% in liver and 13% in lung, and glutathione disulfide concentrations were increased by 35% in liver and 33% in lung, in burn versus sham burn models. It was also found that the specific activities of glutathione peroxidase decreased significantly, resultant to burn injury, by an average of 35% and 27% in liver and lung, respectively. Burn injury also decreased glutathione S-transferase specific activities by 14% in liver and 23% in lung tissues. In contrast, glutathione reductase specific activity was increased in liver tissues (22%), but was decreased (19%), as with the other enzymes studied, in lung tissues of burn models. Control model studies (no medication, no sham burn) show that these effects of burn injury are additional to effects elicited by medication associated with sham burn models. The data of this study are indicative of a major oxidative stress in liver and lung tissues due to burn injury at a remote site.

Effects of omega-3 and omega-6 fatty acid-rich oils on the cardiovascular system of thermally injured rabbits: changes in plasma triglycerides, plasma cholesterol, relative blood viscosity, platelet count, and bleeding time.

New Zealand white male rabbits were studied to determine how supplements of soybean oil, soybean + MaxEPA oil, or MaxEPA oil affected their cardiovascular status when they were burned. Plasma triglyceride concentrations increased at 2 hours after burn injury (28 days after supplement administration) and declined by the end of the study in all three experimental groups of rabbits. These same animals showed no noticeable differences in the plasma concentrations of total cholesterol or in the high-density lipoprotein cholesterol subfractions. Plasma low-density/very-low-density lipoprotein cholesterol levels remained unchanged at 2 hours after burn injury/sham treatment but increased by the end of the study in all three experimental groups of rabbits. The mean platelet number was significantly higher in burned/sham treated rabbits given soybean oil supplement as compared with numbers in those given either soybean oil + MaxEPA oil or MaxEPA oil supplement. Plasma relative viscosity was highest in the soybean oil-supplemented rabbits, decreased in animals fed soybean oil + MaxEPA, and lowest in MaxEPA oil-supplemented rabbits. Mean bleeding time was lowest in soybean oil-fed rabbits. The bleeding time was higher in rabbits fed soybean oil+MaxEPA oil and highest in MaxEPA oil-supplemented animals. Platelet number and plasma viscosity were highest in the soybean oil-supplemented rabbits and lowest in the MaxEPA oil-supplemented group. The reverse pattern occurred when bleeding time was established. Overall results obtained suggest that supplementation with oils rich in omega-3 and omega-6 fatty acids may have significant effects on the cardiovascular health of burned male New Zealand white rabbits.

Effects of supplemented omega-3 and omega-6 fatty acid rich oils on the cardiovascular system of thermally injured rabbits: changes in plasma and platelet fatty acids.

The effects of omega-3 fatty acid rich oil (MaxEPA oil), omega-6 fatty acid rich oil (soybean oil), and a combination of omega-3 and omega-6 oils (MaxEPA oil + soybean oil) on cardiovascular health-related parameters of thermally injured and control (sham) rabbits were determined. Plasma and platelet analyses of burned rabbits fed with MaxEPA oil revealed significantly higher concentrations of eicosapentaenoic acid and docosahexaenoic acid + myristic acid. Linolenic acid concentrations declined in animals supplemented with soybean oil + MaxEPA oil. At the end of this study the lowest concentrations of linoleic acid and arachidonic acid were found in the sham and burned groups supplemented with soybean oil + MaxEPA oil. Overall, favorable significant differences in plasma and platelet fatty acids concentrations were found in burned or sham groups supplemented with MaxEPA when compared with those of groups supplemented with soybean oil. These favorable changes in plasma and platelet lipids may have an impact on the risk of cardiovascular disease in thermally injured patients.

Guidelines for preventing "dilution false negatives" in in vitro laboratory testing of the donor population.

In this article we develop a calculation or formula for use in determining the potential dilution effect of fluids administered during patient treatment on serologic testing parameters. The formula uses basic principles of (a) fluid distribution over time from administration; (b) ratios of plasma and extravascular fluid volumes to body weight; and (c) common practices of fluid resuscitation. A dilution threshold of 50% was set using data from enzyme-linked immunosorbent assay human immunodeficiency virus antibody determinations performed on in vitro diluted seropositive serum samples. These data respond to issues raised by guidelines from the Centers for Disease Control and the U.S. Food and Drug Administration to achieve recipient safety without unnecessarily restricting the potential donor pool.

Dipeptidyl peptidase IV and aminopeptidase in burn wound exudates: implications for wound healing.

Two catalytically active proteases, dipeptidyl peptidase IV (DP IV) and aminopeptidase (AP), not previously reported as present in burn wound exudates, have been identified by substrate specificity and susceptibility to known enzyme inhibitors. The ratio of the two enzymes in exudates is significantly different from the ratio in plasma collected from the same patient during the same time interval, suggesting that measurement of exudate components may be more significant than plasma activities in evaluating local conditions in the wound. A number of biologically significant substances are DP IV substrates, and the list can be considerably extended by the sequential action of AP and DP IV. Some polypeptides are converted to their biologically active form by DP IV action, while others are degraded to inactive forms. Either action generates X-Pro dipeptides, which have a demonstrably beneficial effect on wound healing. Although not resolved by molecular sizing or anion exchange chromatography, DP IV and AP in a burn wound exudate were purified by affinity chromatography.

Liposome encapsulation: a method for enhancing the effectiveness of local antibiotics.

BACKGROUND: Treatment of contaminated surgical wounds is often complicated by the failure of local or systemic antibiotic treatment and prophylaxis. Locally administered liposome-encapsulated antimicrobials may offer advantages over free antibiotics, including an increase in efficacy, ease of administration, and safety. The therapeutic advantages, as well as the absorption and distribution of locally administered liposome-encapsulated antibiotics, were compared with those of locally applied unencapsulated antibiotics in a contaminated wound model. METHODS: Anesthetized rats had a 1 cm incision over the midback that was inoculated with 10(8) colony-forming units Pseudomonas aeruginosa (group 1; n = 102) or left uninfected (group 2; n = 35). Before wound closure, infected animals were treated with a local application of 0.3 ml saline solution (untreated; n = 30), 5.5 mg tobramycin in 0.3 ml saline solution (free tobramycin; n = 30), or 0.3 ml liposome-encapsulated tobramycin (LET; n = 42). Animals were killed 24, 48, and 72 hours after operation; serum and tissue tobramycin concentrations and tissue quantitative cultures were studied. Liposomes were radiolabeled to examine organ distribution. RESULTS: The data show that LET produced sustained local concentrations of antibiotic compared with free drug; sustained concentration prolonged the antimicrobial effect despite a single dose of antibiotic. LET reduced tissue bacterial counts to a greater extent and for a longer period of time than free tobramycin. The presence of infection further reduced clearance of LET from the infected site. CONCLUSIONS: The liposomal delivery of local antibiotics in this model of surgical wound infection reduced the number of organisms more effectively than locally applied free drug. Animals treated with LET had consistently less than the 10(5) organisms per gm tissue considered critical for invasive infection, suggesting that liposomal antibiotics may be clinically useful in surgical wound prophylaxis.

Proteolytic activity in burn wound exudates and comparison of fibrin degradation products and protease inhibitors in exudates and sera.

Proteolytic (caseinolytic) activity in burn wound exudates was screened over the range pH 5.3 to 8.4. Although activity was greatest at pH 8.4 in four of seven exudates, individual differences indicated that different proteases predominate in the local environment of the wound. Paired exudate and serum samples were compared with regard to fibrin degradation products and three protease inhibitors: antithrombin III, a1-protease inhibitor, and a2-antiplasmin. Fibrin degradation products concentration was higher in exudates than in paired sera, indicating the wound as the source of circulating fibrin degradation products rather than intravascular coagulation followed by fibrinolysis. In contrast, all three protease inhibitors exhibited higher concentrations in serum than in the paired exudate. The serum/exudate ratio for AT III differed significantly from that for a1-protease inhibitor and a2-antiplasmin, and the ratio of two inhibitors in serum differed from the ratio of the same two inhibitors in the exudate in two of three comparisons. These findings emphasize the importance of exudate examinations as a reflection of events in the wound itself. The importance of microenvironments is invoked to account for the significant exudate fibrin degradation products titers, which are seen despite the presence of antithrombin III, which could inhibit coagulation, and the presence of a2-antiplasmin, which could inhibit fibrin degradation.

Local macromolecular extravasation in thermal burns quantified by fluorescent video microscopy and computer vision.

A dorsal skin flap chamber model was developed for analysis of the microvascular response to moderate intensity local thermal burns. Fluorescein isothiocyanate tagged 70,000 d dextran was introduced to visualize the extravasation and interstitial transport of macromolecules at the burn site. Contact burns 0.5 cm in diameter were affected by touching a thermostated metal rod onto the exposed epidermal side of the chamber preparation. All burns were of 5-second duration at temperatures between 55 degrees C and 70 degrees C. Postburn leakage of the fluorescein-labeled probed was monitored at numerous sites in the preparation on a fluorescent microscope equipped with a low-light-level intensified silicon intensified target video camera and recorded on tape for subsequent quantitative analysis. Selected scenes were digitized and subjected to a sequence of computer-image processing operations to extract quantitative information about the concentration distribution and net accumulation of dextran in the interstitial space as a function of postburn time. A diffusion model based on cylindrical geometry was fit to the concentration profile data at each site analyzed, and an apparent diffusion coefficient describing the interstitial transport process was determined. The interstitial transport increased with burn temperature up to a threshold of 70 degrees C, where other factors resulted in significant reduction in the loss of fluorescent macromolecule from the vasculature.

Immunologic reactions in chronic wounds.

Although, healing is initiated by local inflammation, excessive or prolonged inflammation may delay healing and increase scar potential. Inflammatory cascades in the wound's microenvironment are triggered by complement degradation products; polymorphonuclear leukocyte products; oxygen free radicals; enzymes, particularly proteinases; and microbial products. Infection, ischemia, necrotic or severely damaged tissue, or foreign matter propel and prolong inflammation and challenge host defenses, leaving the patient susceptible to further microbial invasion. Occlusion dressings can minimize necrotic tissue by preventing desiccation, aiding debridement, and providing a barrier against exogenous pathogenic organisms, thus limiting the resulting inflammatory cascade.

Burn-induced alterations in vasoactive function of the peripheral cutaneous microcirculation.

Alterations in the cutaneous vasomotion function caused by scald burns to a large area on the flank were observed and quantified in a dorsal skin flap window with a hamster model. Subsequent to chronic implantation of the window chamber to provide direct microscopic observation of blood flow for an entire thickness of skin, control measurements of vasoactivity in a defined network of arterioles were taken by means of a digital video image splitter over a period of several days. A 100 degrees C, 5-second water scald was then effected over 17% to 55% of the total body surface area, and the vasoactivity was remeasured in the targeted set of sites at serial time intervals for 2 to 4 days. Data were acquired directly into a computer and analyzed for both the magnitude and time pattern of diameter fluctuations during 3-minute observation periods. Average and standard deviations of diameters were computed, and the Prony power spectral analysis method was applied to identify the presence and strength of fluctuation frequencies. In general, vasomotion was suppressed for several hours subsequent to the burn, and the activity was dominated by much slower contractions than control. No direction of vessel diameter changes prevailed uniformly throughout the peripheral microcirculation. Large alternate constrictions and dilations were also observed for some arteriolar and venular components, but others exhibited no significant change at all. The incidence and magnitude of peripheral microvascular response was proportional to the size of the injured area.

Management of burn wounds.

The pathophysiology of thermal injury is described and applied to the clinical diagnosis of the depth of the injury. The basis of the selection of the type of nonoperative therapy for moderate depth second-degree burns is outlined for optimizing healing time. The importance of early tangential (sequential) excision of deep second-degree burns and third-degree burns in reducing functional and cosmetic residual is emphasized.

Detection of the actin scavenger system in burn wound fluid.

The intravascular actin scavenger system depolymerizes and sequesters actin released after tissue injury. Studies were carried out to determine if this system is active in the extracellular space during wound repair. Using burn wound fluid as a noninvasive means for analyzing the wound environment, we measured actin accumulation and actin complex formation with the plasma proteins responsible for scavenger function. Actin at concentrations as high as 0.25 mg/ml ( approximately 5 micromol/L) was found in burn wound fluid samples from 9 of 11 patients. Wound fluid also contained the two plasma proteins that bind actin-gelsolin (both plasma and cytoplasmic forms) and Gc protein. Because actin in wound fluid was complexed with gelsolin and Gc protein, we conclude that the components of the actin scavenger system are functional in wound tissue. In addition, proteolysis of gelsolin, but not actin or Gc protein, appeared to occur at the wound site. Gelsolin proteolysis was accompanied by the appearance of 49 kd gelsolin fragments, and wound fluid samples lacking intact gelsolin also contained high metalloproteinase levels.

The effects of epinephrine, ibuprofen, and tetrachlorodecaoxide on cutaneous microcirculation in thermally injured hamsters.

Fluctuations in the diameter of selected arterioles in the cutaneous microcirculation of Syrian golden hamster dorsal skin flap chambers, which ranged in size from 10 to 70 microns at different branching order sites, were measured before burn, at the same sites after burn and after injection of the drug. Three different drugs epinephrine (administered intravenously), ibuprofen (administered intravenously), and tetrachlorodecaoxide (administered intravenously and topically) were evaluated. Results show that the response to thermal injury in the control group involved extensive vasodilation in the arterioles, prolonged flow irregularities including flow obstructions and stasis, and a decrease in the level of vasoactivity of the microvessels. In two treatment groups, the ibuprofen and tetrachlorodecaoxide groups, significant improvement as indicated by reduced vasodilation and edema and improved microcirculatory blood flow after injury were observed. Further testing of tetrachlorodecaoxide as a topically applied wound dressing is indicated.

Equations for the estimation of energy expenditures in patients with burns with special reference to ventilatory status.

There are advantages to the use of easily assessed variables for the prediction of energy expenditures of patients with burns. The purpose of this study was to determine whether height, age, sex, weight, ventilatory status, and diagnosis could be correlated with measured energy expenditures of hospitalized patients. With the use of data from 200 patients, stepwise, multivariate regression analysis derived the following equations: EEE(v) = 1925 - 10(A) + 5(W) + 281(S) + 292(T) + 851(B) (R2 = 0.43); EEE(s) = 629 - 11(A) + 25(W) - 609(O) (R2 = 0.50); where EEE = estimated energy expenditure (kcal/day), v = ventilatory dependency, s = spontaneously breathing, A = age (yr), W = body weight (kg), S = sex (male = 1, female = 0), diagnosis of T = trauma, B = burn, O = obesity present = 1, absent = 0). The equations were tested on 100 patients. Measured energy expenditures were not significantly different from calculated EEE(s) or EEE(v) (paired t test, p greater than 0.25). Energy expenditures can be accurately estimated in a variety of patients, including those with major burns with the use of easily attained information.

Liposome delivery of aminoglycosides in burn wounds.

The current study evaluated the pharmacodynamics of topically applied antimicrobials incorporated into radiolabeled liposomes. Radiolabeled 125I-phenyldecanoic acid was used in the formulation of small unilamellar liposomes. Sephadex (cross-linked dextran beads) G-50 columns were run to determine the per cent of radioactivity incorporated into liposomes and persistence of radioactive tag on the liposome after two weeks (greater than 95 per cent) remained incorporated. On the day of the experiment, 31 adult Sprague Dawley rats were subjected to a 10 per cent total body surface area full thickness burn (Walker burn model). All rats were treated with topical application of 0.3 milliliters of tobramycin entrapped in 125I-liposomes, and burn wounds were covered with Opsite (Winfield Laboratories). This formulation resulted in each rat receiving 14 milligrams per kilogram of tobramycin with a specific activity of 10.41 microcuries. Rats were sacrificed at several time periods after burn injury (nine after 24 hours, 12 after 48 hours, 11 after 72 hours). At these time intervals, serum and tissue tobramycin levels were measured, burn dressing, burn tissue and splanchnic organs were harvested and radioactivity was assessed with a gamma scintillation counter to determine tissue concentration of 125I-liposome tobramycin. Concentration of tobramycin in the serum was negligible at 24, 48 and 72 hours postburn, but was significant in the burn tissues at these times. The radioactive recovery data demonstrated that the majority (greater than 90 per cent) of the recovered liposomes remained at the site of application (the burn wound). No splanchnic organs had greater than 2 per cent of the recovered 125I-liposomes at any time period. These data suggest that, in burn wounds, tobramycin incorporated into liposomes remain at the site of initial application, resulting in high local concentrations with little systemic absorption and confirm that liposomes provide an effective vehicle for delivery of antimicrobials at the site of the burn injury.