Introduction Currently, there are no reliable non-invasive methods of monitoring the severity of in vivo cyanide (CN) toxicity and the resulting physiological changes. A non-invasive technique to monitor CN toxicity would allow for the rapid detection and triage of those exposed to CN. We developed a Broadband Diffuse Optical Spectroscopy (DOS) prototype system that combines multi-frequency domain photon migration (FDPM) with time-independent near infrared (NIR) spectroscopy to accurately measure bulk tissue absorption and scattering spectra between 600 and 1000 nm. This study shows the feasibility of using DOS to optically monitor CN toxicity and treatment with sodium nitrite (NaNO2) by simultaneously quantifying oxy, deoxy, and Met Hemoglobin, and the redox state changes of cytochrome-c oxidase.
Material and Methods New Zealand White (NZW) rabbits were used in this study. The DOS prototype probe was placed on the shaved right inner thigh muscle of the hind leg. Sodium cyanide solution of 6mg in 60cc saline was infused through a femoral venous line for 40 minutes. DOS measurements, arterial and venous blood gases, blood pressure, heart rate, and oxygen saturation were monitored at 10 minute intervals. After completion of CN induction, 6mg/cc NaNO2 was introduced intravenously at a rate of 1.4cc per minute in order to reverse CN toxicity.
Results After induction of CN, blood gas measurements showed a rise in venous pO2 values steadily increased from 46.4 to 52.2. During reversal with NaNO2, venous pO2 values decreased to 22.1. DOS measurements showed the corresponding changes in redox states of cytochrome-c oxidase during CN injection and NaNO2 treatment. DOS successfully monitored the concentration of Met-hemoglobin induced from sodium NaNO2 infusion. (figure)
Conclusion DOS enables non-invasive detection of CN toxicity and treatment with NaNO2. DOS technology has the potential for quantitative non-invasive monitoring for a range of clinical conditions where specific solute concentration measurements may be important.