RESUMO
With the advent of such systems as the airborne laser and advanced tactical laser, high-energy lasers that use 1315-nm wavelengths in the near-infrared band will soon present a new laser safety challenge to armed forces and civilian populations. Experiments in nonhuman primates using this wavelength have demonstrated a range of ocular injuries, including corneal, lenticular, and retinal lesions as a function of pulse duration. American National Standards Institute (ANSI) laser safety standards have traditionally been based on experimental data, and there is scant data for this wavelength. We are reporting minimum visible lesion (MVL) threshold measurements using a porcine skin model for two different pulse durations and spot sizes for this wavelength. We also compare our measurements to results from our model based on the heat transfer equation and rate process equation, together with actual temperature measurements on the skin surface using a high-speed infrared camera. Our MVL-ED50 thresholds for long pulses (350 micros) at 24-h postexposure are measured to be 99 and 83 J cm(-2) for spot sizes of 0.7 and 1.3 mm diam, respectively. Q-switched laser pulses of 50 ns have a lower threshold of 11 J cm(-2) for a 5-mm-diam top-hat laser pulse.
Assuntos
Queimaduras/fisiopatologia , Raios Infravermelhos/efeitos adversos , Lasers/efeitos adversos , Modelos Biológicos , Lesões por Radiação/fisiopatologia , Temperatura Cutânea/efeitos da radiação , Pele/lesões , Animais , Queimaduras/etiologia , Queimaduras/patologia , Simulação por Computador , Limiar Diferencial/efeitos da radiação , Relação Dose-Resposta à Radiação , Técnicas In Vitro , Doses de Radiação , Lesões por Radiação/etiologia , Lesões por Radiação/patologia , Medição de Risco/métodos , Fatores de Risco , Pele/patologia , Pele/efeitos da radiação , SuínosRESUMO
The kinetics of tritiated metoprolol and its metabolites have been determined after intravenous and oral administration in dialysis patients. The kinetic behaviour of metoprolol in these patients does not differ from that in healthy volunteers, since its elimination depends on hepatic metabolism. The pharmacologically less active metabolite alpha-hydroxymetoprolol is formed to an individually varying degree and its half-life is prolonged. The concentration of the total radioactivity, which represents the sum of all metabolites, does not decline in the dialysis interval. During haemodialysis, however, its concentration decreases with a half-life of 5h. It might be assumed, that dialysis of these polar compounds is rather nonspecific and that it depends essentially on the dialysis technique.