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Biomedical subjects

A D Mason

Publications and source records attributed to A D Mason.

At least 73 records · Page 4Linked to original sources
PubMed1988

Chemical burns.

In chemical skin injuries, reduction of the time of exposure to the causative agent and recognition of systemic toxicity are necessary to lessen the severity of the insult, reduce morbidity, and maximize survival. During a 17-year period (1969 through 1985), 87 (2.1%) of the 4,212 burned patients admitted to the U.S. Army Institute of Surgical Research sustained chemical burns. Twelve of 87 patients died (13.8%). White phosphorous, the most common causative agent, produced cutaneous injury in 49 patients. Acids (13 patients), alkalies (ten patients), and organic solvents (five patients) were the other common causes of injury. Initial treatment consisted of water lavage. Later wound management was carried out with topical antibiotic therapy and excision and grafting as necessary. Systemic toxicity due to phenol, nitrate, and formate absorption occurred, as did acute tubular necrosis following copper sulfate treatment of white phosphorus burns. Inhalation injury occurred in five patients. A decrease in hospital stay for chemically injured patients was observed. To minimize chemical injury, clothing should be removed promptly and water lavage begun. Systemic toxicity and inhalation injury are rare but often severe and increase mortality.

Adolescent↗
PubMed1988

Therapeutic effects of silver nylon dressings with weak direct current on Pseudomonas aeruginosa-infected burn wounds.

The therapeutic and prophylactic effects of nylon dressings coated with metallic silver in a direct current circuit have been examined in a rat model of fatal burn wound sepsis. Male Sprague-Dawley rats weighing 325 +/- 25 grams with 20% full-thickness scald injuries were used. Therapeutic effects were examined at 4 or 24 hours after surface inoculation with a lethal dose of Pseudomonas aeruginosa (Strain 59-1244). When used as a surface anode with an implanted silver needle cathode, the silver nylon was therapeutic at currents between 0.4 and 40 microA when applied at either test time and continued for 5 days (p less than 0.001). When used as a cathode, silver nylon was not effective. Nylon cloth without a silver metal coating was not effective without applied current or when used as an anode. Silver nylon dressings placed at 4 hours after inoculation but without applied current showed significant effectiveness (p less than 0.01). This effect, however, was significantly less than that seen with silver nylon used as an anode (p less than 0.001). Barrier prophylactic effects were examined by placing silver nylon or uncoated nylon on burn wounds before inoculation with Pseudomonas aeruginosa. The uncoated nylon had no barrier effect. Silver nylon was found protective but applied current was not required for significant (p less than 0.001) barrier effect. These results indicate silver nylon dressings may be a valuable antimicrobial burn wound covering device.

Animals↗
PubMed1988

Fluid resuscitation of infants and children with massive thermal injury.

Age-related limitations of physiologic reserve in burned children make adequacy of intravenous fluid resuscitation critical. To quantify fluid requirements, the medical records of all children admitted to the Army Institute of Surgical Research from 1980 to 1986 whose weight was 25 kilograms or less and burn size was 25% or greater were reviewed to quantify fluid requirements. Forty-three children ranging in age from 1.5-108 months (means 26 +/- 22 m), with 25-89% total body surface burned (TBSB) (means 41.7% +/- 14.6%), met inclusion criteria. The average total volume of fluid received during the first 24 hours was 6.3 +/- 2.2 cc/kg/% TBSB. The net volume of resuscitation fluid, total volume less the calculated maintenance fluid requirements, was 3.91 +/- 2.2 cc/kg/% TBSB. Univariate analysis and linear regression of independent variables including age, weight, per cent full thickness, and inhalation injury revealed each had no significant influence on the volume of resuscitation. We recommend supplying maintenance volume and initiating burn resuscitation at 3 cc/kg/% TBSB.

Body Surface Area↗
PubMed1988

The effect of burn injury and zinc nutriture on fecal endogenous zinc, tissue zinc distribution, and T-lymphocyte subset distribution using a murine model.

The interrelationship among burn injury, zinc metabolism, and circulating T-lymphocyte distribution was studied using a rat model. Sixty Sprague-Dawley male rats were fed a zinc-deficient (less than 0.5 ppm) semipurified diet and given daily subcutaneous injections of 1 mg Zn/kg body wt for 14 days. On Day 15, 24 of the rats were subjected to a full-thickness dorsal scald injury of 30% of the total body surface. Half of the burned rats were continued on the zinc supplementation (BS) while the other half were maintained on the zinc-deficient (BD) regimen by injecting physiological saline. Feces and urine were collected for 10 days postburn and subsequently analyzed for zinc content. On Day 10 postburn all the rats were sacrificed. Zinc bound to cytosol proteins in hepatic and intestinal mucosal tissue was determined by gel column chromatography procedures and T-lymphocyte subset distributions were determined by flow cytometry. No significant difference (P less than 0.05) in total endogenous zinc excretion was seen among treatment groups. A dramatic increase was seen in zinc bound to a 12,000 mol wt protein in hepatic tissue from the BS group only. The only significant (P less than 0.05) change in T-lymphocyte populations was an increase in T-suppressor cells in the BD group.

Animals↗
PubMed1988

Suppurative chondritis: its incidence, prevention, and treatment in burn patients.

A retrospective study of 317 cases of suppurative otochondritis occurring in a population of 4794 burned patients successively admitted to one institution between 1967 and 1984 is presented. During the study interval, the incidence of the disease decreased from 20 percent to less than 3 percent in patients with burns of one or both ears. The bacterial species associated with chondritis, principally Pseudomonas aeruginosa and Staphylococcus species, did not change. Patients admitted later than the second postburn day exhibited a significantly greater incidence of chondritis. The crucial factors in prevention of this complication appear to be avoidance of pressure on burned ears and topical chemotherapeutic control of local Pseudomonas infection. Systemic antibiotic prophylaxis did not appear to influence the incidence in the studied population. Several approaches to clinical management of suppurative chondritis are reviewed.

Adult↗
PubMed1987

Comparison of quantitative microbiology and histopathology in divided burn-wound biopsy specimens.

We examined the association between quantitative microbiologic results and histopathologic findings in divided biopsy specimens from 200 burned patients. Microbiologic counts were determined as log10 colony-forming units per gram of disrupted tissue. Histopathologic results were scored on a scale of 1 to 6, values of 4 or greater indicating microbial invasion of viable tissue. Agreement of 96.1% was found between negative cultures, arbitrarily identified as those with fewer than 5 logs/g, and histologic absence of invasive infection. In sharp contrast, however, histologic invasion occurred in only 36% of specimens with positive cultures. Though low tissue counts are essentially synonymous with negative histologic findings, quantitative microbiology is not a diagnostic substitute for histologic examination, since high tissue counts quite commonly do not indicate invasion. The principal value of quantitative burn-wound biopsies is the demonstration of predominant burn-wound flora.

Adolescent↗
PubMed1987

Design and conduct of antibiotic trials. A report of the Scientific Studies Committee of the Surgical Infection Society.

Several recent publications have identified important methodologic problems in the design and conduct of antimicrobial trials in surgery. Developed by consensus of the members of the Scientific Studies Committee of the Surgical Infection Society, this report provides broad guidelines for the construction of antimicrobial trials. The central issues identified include pretrial definition of study purpose, entry criteria, assignment device, and statistical analysis. These issues are fundamental in designing studies with an acceptable likelihood of finding differences among those antimicrobial regimens at least risk to the study subjects. The importance of stratifying patients on the basis of background condition, disease, and severity of illness is stressed. The inclusion in a study of variables that enhance the statistical power and, therefore, the believability of this study is stressed as an important means of clarifying substantial differences between therapies.

Abdomen↗
PubMed1987

Flow cytometric measurement of rat lymphocyte subpopulations after burn injury and burn injury with infection.

Increased infection rates in burned patients may result from a disproportionate increase in the suppressor subpopulations. Measurement of lymphocyte subpopulations is difficult in burned patients because gradient-purified cells are contaminated by nonlymphoid cells. The accuracy of flow cytometric subpopulation analysis was improved by restricting (gating) the analysis to cells with light-scatter intensity typical of lymphocytes. Blood was obtained 48 hours after burn from rats receiving no burns, 30% scald burns, or burns seeded with Pseudomonas aeruginosa to induce infection. Subpopulations were identified by monoclonal antibodies to T-lymphocyte antigens. Gating increased the values obtained for most subpopulations, but the relative differences between groups were unchanged. Burned and infected animals, but not animals burned only, had a decreased ratio of helper to suppressor lymphocytes (HSR) relative to control. A decreased HSR correlated with sepsis, but not with infection susceptibility. This suggests that a decrease in HSR may be a result of infection rather than a cause of susceptibility to infection.

Animals↗
PubMed1987

Nyctohemeral rhythm in melatonin response to isoproterenol in vitro: comparison of rats and Syrian hamsters.

The in vitro response of melatonin synthesis was assessed by incubation of individual whole pineal glands for 4 hr without or with different concentrations of isoproterenol in the medium. Pineals were taken either at the end of the 14-hr light phase (day), or at 6 1/2 hr into the 10-hr dark phase (night) after a 30-min exposure of the animals to light just before sacrifice at night. The response was greater in pineals taken at night than in those taken at the end of the light phase in rats, but was absent at the end of the light phase in Syrian hamsters. Hamster pineals taken at night responded, though higher isoproterenol concentrations were required than in the rats. Unresponsiveness of hamster pineals during the day may explain previous failure of isoproterenol administration to stimulate pineal MEL content in this species.

Animals↗
PubMed1987

The influence of inhalation injury and pneumonia on burn mortality.

In order to assess the specific effects of inhalation injury and pneumonia on mortality in burn patients, the records of 1058 patients treated at a single institution over a five-year period, 1980-1984, were reviewed. Of these patients, 373 (35%) had inhalation injury diagnosed by bronchoscopy and/or ventilation perfusion lung scan. Of the 373 patients, 141 (38%) had subsequent pneumonia. Among the patients without inhalation injury, pneumonia occurred in 60 of 685 (8.8%). A multiple logistic equation was developed to estimate expected mortality at any age and burn size for patients without either inhalation injury or pneumonia, with either alone, or with both. Subtraction of the expected mortality without either inhalation injury or pneumonia from the expected mortality in the presence of either or both permitted the estimation of additional mortality attributable to these complications. Inhalation injury alone increased mortality by a maximum of 20% and pneumonia by a maximum of 40%, with a maximum increase of approximately 60% when both were present. The influence on mortality was maximal in the midrange of expected mortality without these complications for any age group. These data indicate that inhalation injury and pneumonia have significant, independent, additive effects on burn mortality and that these effects vary with age and burn size in a predictable manner.

Adolescent↗
PubMed1987

A dose-responsive model of smoke inhalation injury. Severity-related alteration in cardiopulmonary function.

The dose responsiveness of selected physiologic indices was studied in a sheep model of smoke inhalation injury. In this model, graded severity of injury was achieved by changing the contact time with smoke (defined by "unit"), whereas other variables were kept constant. Blood gas and cardiopulmonary indices were measured in 70 sheep, including 12 controls, either 24 or 72 hours after exposure to 3, 6, 9, 12, 15, or 18 units of smoke. A 12-unit dose of smoke was fatal within 72 hours and an 18-unit dose was fatal within 24 hours. The best correlation between smoke dose and response was observed in arterial oxygen tension 24 hours after exposure. At 24 hours, most of the cardiopulmonary indices showed significant change only after a 12-unit exposure. Although the exact shape of the dose-response curve could not be defined, sigmoid or curved linear shape was suggested, reflecting the progressive deterioration.

Animals↗
PubMed1987

Central hypogonadism in burned men.

Serum samples were obtained from 30 burned men at different times up to the fourth month after injury. Mean concentrations of estradiol (E2) were elevated above those for healthy control subjects. Mean serum total testosterone (T), sex hormone-binding globulin (SHBG), bioassayable luteinizing hormone (LH), thyroxine (T4), triiodothyronine (T3) and their free indices (FT4I and FT3I) were depressed below those of controls during the first postburn week. Mean values for T and LH were progressively higher in samples taken from later time periods but remained depressed. Mean SHBG and thyroid hormones rose and were not significantly different from control values during later periods of the study. Calculated non-SHBG-bound T (NSBT) was below normal in each time period. The close correlation of SHBG values with those of T3 and FT3I in the patients suggests that SHBG responds to the altered thyroid hormone milieu of burn injury. It is postulated that elevated serum E2 perhaps from adrenal precursors promotes an alteration of hypothalamic function resulting in a markedly reduced secretion of bioactive LH and diminished Leydig cell function.

Adolescent↗
PubMed1987

Clinical trial of imipenem/cilastatin in severely burned and infected patients.

Imipenem/cilastatin was examined for safety and efficacy in a population of 20 seriously burned patients with acute bacterial infections. The study was made up of 18 males and two females with an average age of 38 years and average burn size of 52 per cent of the total body surface area. Inhalation injury was present in 14 patients. The infections treated included 16 pulmonary, two urinary tract, one wound and one bacteremia. Treatment was clinically successful in 13 patients; five patients had no improvement and the clinical response could not be determined in two in whom multisystem organ failure preceded the treated infection. All of the clinical failures were in the pulmonary infection group. No serious toxicity or side effects were noted. No patient died while receiving the drug or as a consequence of known failure of the drug. Microbiologic success was noted in 12. Resistant organisms developed in eight of whom five were in the clinical failure group. Pseudomonas aeruginosa resistant to imipenem/cilastatin was isolated from seven patients and occurred at an average of 3.6 days after treatment was begun.

Adult↗
PubMed1986

Effects of environment on infection in burn patients.

Burn patients in an early cohort (n = 173) treated in an intensive care ward without separate enclosures were compared with a later cohort (n = 213) treated in a renovated unit with separate bed enclosures. The number of patients developing infection was significantly reduced in the late group. Observed mortality was compared with mortality predicted on the basis of burn size and age alone. Reduction in observed compared with predicted mortality, inapparent in the early group, was seen in the late group and was restricted to the subgroup of patients with predicted mortality of 25% to 75%, in which the observed mortality of 28.3% was less than the predicted mortality of 48.7%. The incidence of infected patients was reduced from 58.1% in the early cohort to 30.4% in the late cohort. In comparison of the early cohort with the late cohort, the overall proportion of patients with bacteremia was reduced from 20.1% to 9.4%, while the incidences of both pneumonia and burn wound invasion remained unchanged. Providencia and Pseudomonas species, endemic in the early cohort, were eliminated in the late cohort. Reduction of infection by environmental manipulation in burn patients was possible and was associated with improved survival.

Adult↗
PubMed1986

Association of burn mortality and bacteremia. A 25-year review.

The relationship between bacteremia and mortality was studied in 5882 burn patients consecutively admitted to one burn center between 1959 and 1983. Among 5877 patients with adequate data, 1481 had one or more positive blood cultures; 1529 patients died. A predictor of mortality was developed, based on data from the 4396 patients without positive blood cultures, and used to assign a discrete probability of death in the absence of bacteremia to all the patients. Comparisons were then made between observed and predicted mortality in subsets of patients with bacteremia due to enteric organisms, Pseudomonas species, gram-positive organisms, or yeastlike organisms, or without bacteremia. These comparisons indicate significantly increased mortality in patients with gram-negative bacteremia, an equivocal increase in patients with blood cultures positive for yeastlike organisms, and no increase attributable to gram-positive bacteremia.

Adolescent↗
PubMed1986

Effects of infection on oxygen consumption and core temperature in experimental thermal injury.

Oxygen consumption (VO2) and colonic temperature (Tc) were measured in groups of rats before and after 30% total body surface, full thickness burns. Some wounds were seeded with Pseudomonas aeruginosa or Staphylococcus epidermidis, and some seeded wounds were treated with Sulfamylon or Silvadene. Three groups became bacteremic (B) during the 2-3 week period of observation. At an ambient temperature (Ta) of 32 C, VO2 of the B group rose from 0.83 +/- 0.01 to 1.20 +/- 0.01 ml/hr/g (mean +/- S.E., p less than 0.001) versus 0.81 +/- 0.01 to 0.99 +/- 0.02 for nine nonbacteremic (NB) groups (p less than 0.001). Tc increased only in the B groups--from 36.8 +/- 0.1 to 37.7 +/- 0.1 C (p less than 0.001). In the second or third week postinjury, VO2 of the NB rats was reduced when Ta was increased to 34 C; Tc followed changes in Ta. Sulfamylon lowered VO2 of P. aeruginosa seeded, NB rats. The metabolic cost of wound contamination appeared to vary with bacterial strain. The metabolic effects of infection appear to be a continuum, beginning with a modest rise in VO2 and progressing to greater increases in VO2 and Tc with wound invasion and systemic infection.

Animals↗