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Biomedical subjects

R C Dart

Publications and source records attributed to R C Dart.

16 recordsLinked to original sources
PubMed1992

Effects of constriction bands on rattlesnake venom absorption: a pharmacokinetic study.

STUDY OBJECTIVE: To determine whether the use of a constriction band alters systemic absorption of rattlesnake venom in pigs and whether constriction band use alters local swelling. DESIGN: Using a crossover design, five pigs were studied with and without the use of a constriction band. 125I-Labeled Western Diamondback rattlesnake (Crotalus atrox) venom was injected subcutaneously into one foreleg. The protocol was repeated using the opposite foreleg six days later. The constriction band was applied at the time of injection and removed four hours later. Plasma radioactivity and leg circumference were measured serially. RESULTS: Maximum plasma venom concentration and area under the venom concentration-time curve were compared in trials with and without constriction band. Within the initial four hours, application of a constriction band decreased maximum plasma venom concentration by 25% and area under the venom concentration-time curve by 33% (P less than .05). After the constriction band removal at four hours, maximum plasma venom concentration and the area under the venom concentration-time curve were not significantly different between groups. Application of a constriction band did not result in a statistically significant increase in maximum leg circumference as compared with trials without a constriction band. CONCLUSION: The use of a constriction band was effective in reducing venom absorption while it was in place (reduced area under the venom concentration-time curve and maximum plasma venom concentration in the cuffed group), and constriction band removal did not result in a significant increase in maximum plasma venom concentration. Leg swelling was not affected by constriction band use. Because constriction band use delayed venom absorption without causing increased swelling, it may prove to be a useful first aid measure in human beings.

Absorption↗
PubMed1992

Urinary mercury after administration of 2,3-dimercaptopropane-1-sulfonic acid: correlation with dental amalgam score.

There is considerable controversy as to whether dental amalgams may cause systemic health effects in humans because they liberate elemental mercury. Most such amalgams contain as much as 50% metallic mercury. To determine the influence of dental amalgams on the mercury body burden of humans, we have given volunteers, with and without amalgams in their mouth, the sodium salt of 2,3-dimercaptopropane-1-sulfonic acid (DMPS), a chelating agent safely used in the Soviet Union and West Germany for a number of years. The diameters of dental amalgams of the subjects were determined to obtain the amalgam score. Administration of 300 mg DMPS by mouth increased the mean urinary mercury excretion of the amalgam group from 0.70 to 17.2 micrograms and that of the nonamalgam group from 0.27 to 5.1 micrograms over a 9-h period. Two-thirds of the mercury excreted in the urine of those with dental amalgams appears to be derived originally from the mercury vapor released from their amalgams. Linear regression analysis indicated a highly significant positive correlation between the mercury excreted in the urine 2 h after DMPS administration and the dental amalgam scores. DMPS can be used to increase the urinary excretion of mercury and thus increase the significance and reliability of this measure of mercury exposure or burden, especially in cases of micromercurialism.

Adolescent↗
PubMed1992

Human studies with the chelating agents, DMPS and DMSA.

Meso-2,3-dimercaptosuccinic acid (DMSA) is bound to plasma albumin in humans and appears to be excreted in the urine as the DMSA-cysteine mixed disulfide. The pharmacokinetics of DMSA have been determined after its administration to humans po. For the blood, the tmax and t1/2 were 3.0 h + 0.45 SE and 3.2 h + 0.56 SE, respectively. The Cmax was 26.2 microM + 4.7 SE. To determine whether dental amalgams influence the human body burden of mercury, we gave volunteers the sodium salt of 2,3-dimercaptopropane-1-sulfonic acid (DMPS). The diameters of dental amalgams of the subjects were determined to obtain the amalgam score. Administration of 300 mg DMPS by mouth increased the mean urinary mercury excretion of subjects over a 9 h period. There was a positive correlation between the amount of mercury excreted and the amalgam score. DMPS might be useful for increasing the urinary excretion of mercury and thus increasing the significance and reliability of this measure of mercury exposure. DMSA analogs have been designed and synthesized in attempts to increase the uptake by cell membranes of the DMSA prototype chelating agents. The i.v. administration of the monomethyl ester of DMSA, the dimethyl ester of DMSA or the zinc chelate of dimethyl DMSA increases the biliary excretion of platinum and cadmium in rats.

Adult↗
PubMed1991

Snake venom coagulopathy: use and abuse of blood products in the treatment of pit viper envenomation.

Coagulopathies are commonly encountered in victims of pit viper envenomation. In the majority of patients these defects improve with administration of antivenin. However, blood products are often transfused based on arbitrary criteria and with significant risk to the patient. This article documents the effectiveness and risks of antivenin administration and the risks of blood product transfusion. We recommend that blood products not be used except for clearly defined clinical indications.

Aged↗
PubMed1991

Failure of electric shock treatment for rattlesnake envenomation.

The use of high-voltage electric shock therapy for the treatment of snake venom poisoning has recently gained popularity in the United States. We present a case that documents the dangerous, ineffective application of electric shock to the face of a patient envenomated by a Great Basin rattlesnake (Crotalus viridis lutosus). The successful use of antivenin in this critically ill, antivenin-allergic patient is described.

Adult↗
PubMed1991

Effect of inadequate antivenin stores on the medical treatment of crotalid envenomation.

The case of a 27-y-old male with a serious Crotalus atrox envenomation is presented. His medical care was compromised by the lack of readily available polyvalent Crotalidae antivenin. An investigation of antivenin stocking by health care facilities in Arizona was undertaken. Failure to stock sufficient quantities of antivenin to initiate treatment of a single patient with a severe envenomation was found in 43.5% of urban hospitals, 41.2% of rural hospitals within 25 miles of another hospital, 52.9% of rural hospitals greater than 25 miles from another hospital, and 41.7% of Indian Health Service hospitals. Current antivenin stocking was related to antivenin use during the previous year. Reliance on recent antivenin use to guide current antivenin stocking leaves many hospitals with insufficient antivenin stores and may seriously compromise the medical care of patients suffering from rattlesnake envenomations.

Adult↗
PubMed1991

Determination and metabolism of dithiol chelating agents. XII. Metabolism and pharmacokinetics of sodium 2,3-dimercaptopropane-1-sulfonate in humans.

The sodium salt of 2,3-dimercaptopropane-1-sulfonic acid (DMPS) is used p.o. for the treatment of chronic lead and Hg intoxication in humans. The metabolism and pharmacokinetics of DMPS were determined after p.o. administration of 300 mg of DMPS to each of 10 normal young men. The absorbed DMPS was metabolized rapidly and extensively to a disulfide form(s). By 24 hr after DMPS administration, the area under the blood concentration-time curve of unaltered DMPS was 3.9 compared to 143 for altered DMPS. Altered DMPS is the difference between total DMPS and unaltered DMPS. Unaltered DMPS is the unbound, parent compound;, total DMPS consists of unaltered DMPS plus oxidized [disulfide] DMPS which is determined after reduction with dithiothreitol. In blood the altered form was confined to plasma. By 15 hr, only 3.7% of the administered DMPS was excreted in the urine as unaltered DMPS and 38.7% as altered DMPS. The unaltered and altered DMPS represented 9 and 91%, respectively, of the total amount of DMPS in the urine. Altered DMPS was converted to unaltered DMPS by treatment with dithiothreitol, which indicates that the altered DMPS is a disulfide(s). There was a high correlation between the urinary excretion of Hg and the urinary excretion of unaltered DMPS (r = 0.920 +/- 0.022 S.E.).

Adult↗
PubMed1989

Apparent coral snake envenomation in a patient without visible fang marks.

Envenomation by the North American coral snake is an uncommon entity in the United States. In most cases fang marks will be present, although they may be quite small and difficult to see. The case of a young man who demonstrated evidence of envenomation following the bite of a Texas coral snake (Micrurus fulvius tenere), despite the absence of any apparent fang marks on close examination, is reported. The problems associated with coral snake envenomation in terms of diagnosis and management are reviewed.

Adult↗
PubMed1989

Urinary excretion of meso-2,3-dimercaptosuccinic acid in human subjects.

The urinary excretion of meso-2,3-dimercaptosuccinic acid (DMSA), which is an effective chelating agent for lead, was determined after the oral administration of 10 mg DMSA/kg to six normal young men. The DMSA that was absorbed was extensively biotransformed. After 14 hours only 2.53% of the administered DMSA was excreted in the urine as unaltered DMSA and 18.1% as altered forms. The unaltered DMSA was 12% of the total DMSA found in the urine. The altered form(s) of DMSA was 88% of the total urinary DMSA. The altered DMSA can be converted to unaltered DMSA by electrolytic reduction, which indicates that the altered forms of DMSA are disulfides. The excretion of altered DMSA reached a peak between 2 and 4 hours after DMSA administration. There were small but statistically significant increases in the excretion of zinc, copper, and lead after DMSA administration. DMSA did not influence the urinary excretion of 27 other metals and elements.

Adult↗
PubMed1988

Efficacy of delayed administration of crotalid antivenom and crystalloid fluids.

Clinical and research reports suggest that the efficacy of antivenom declines when its administration is delayed after envenomation. A controlled sequential trial was performed comparing the efficacy of three treatments to untreated controls when applied 1 hr after subcutaneous injection of rats with Crotalus atrox venom. Survival was decreased in all groups when treatment was delayed for 1 hr. Survival was highest in animals treated with both antivenom and saline, followed by antivenom alone, saline alone and then untreated animals.

Animals↗
PubMed1988

Oxygen free radicals and myocardial reperfusion injury.

Diseases involving tissue reperfusion following ischemia are gaining significance in emergency medicine. The significance of reperfusion injury and the probable role of oxygen-derived free radicals has been described in many tissues, particularly the heart. During myocardial reperfusion a burst of oxygen-derived free radicals overwhelms normal cellular defenses. These radicals may have several detrimental effects. They can oxidize lipids, leading to membrane dysfunction. They can also alter nucleic and other proteins. Cellular dysfunction and death may ensue. Prevention of oxygen-derived free radical injury appears possible and may be feasible for several disease processes, including myocardial reperfusion after infarction.

Animals↗
PubMed1987

Tissue decorporation of polonium-210 in rats by DMPA.

Polonium-210 exposures, although rare, have occurred due to accidents in nuclear working environments. This alpha emitting radioactive element can bind thiols and thiol-containing proteins in vivo. Since thiol-containing chelating agents compete with many thiols for heavy metals, a number of these chelating agents have been investigated as protective agents against the lethal effects of 210Po and as tissue decorporating agents for it. Rats given 210Po (40 microCi/kg) ip had a median survival time (mst) of 39 days. The mst was increased to 106 days when N-(2,3-dimercaptopropyl)phthalamidic acid (DMPA), meso-dimercaptosuccinic acid (DMSA) or the Na salt of 2,3-dimercapto-1-propanesulfonic acid (DMPS) was administered sc (p less than .002). Decorporation studies were performed by giving rats 210Po (0.4 microCi) sc, followed by a series of thiol injections beginning one hour later. After 21 days, kidney levels of 210Po in rats given DMPA were only 28% of those of the untreated controls and significantly lower than those receiving DMSA, DMPS, N-acetyl-L-cysteine, or WR2721. After DMPA treatment, the 210Po levels of the spleen were 25% of the saline-treated control. DMPA appears to be a new and consistent decorporating agent for polonium-210.

Animals↗
PubMed1985

Liquid crystal thermometry for continuous temperature measurement in emergency department patients.

A single temperature measurement recorded on admission to the emergency department provides no information about temperature alterations occurring during the course of evaluation. Continuous monitoring of patients' temperatures in the ED, however, may alter management and decrease morbidity. Our study evaluated the reliability of liquid crystal thermometers (LCTs) and the clinical benefit of continuous temperature monitoring in the ED. Commercially available LCTs (corrected 4 degrees F to reflect core temperature) were applied to the foreheads of randomly selected patients. Serial oral electronic thermometer readings were compared to those obtained by LCT. Fever was defined as a temperature higher than 99.5 F orally or 100 F by LCT. One hundred two patients underwent simultaneous LCT and oral temperature measurements, with a correlation coefficient of 0.661. Hypothermia was not encountered. Eighty-four patients were afebrile, and 18 were febrile by oral measurement on admission. Of the afebrile patients, 13 (15.5%) became febrile while in the ED. The temperature course was identified correctly by LCT in 83.3% of cases. The LCT correctly identified all patients who were febrile on admission, as well as 92.3% of those who developed fever while in the ED. The latter fevers would have been missed by routine single-temperature determination on ED admission. Detection of fever stimulated more aggressive clinical evaluation of these patients. Eight of nine patients who defervesced in response to antipyretic therapy were identified correctly by LCT.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗