Blood cyanide concentrations after smoke inhalation

Noninvasive in vivo monitoring of cyanide toxicity and treatment using diffuse optical spectroscopy in a rabbit model

Currently, no reliable noninvasive methods exist for monitoring the severity of in vivo cyanide (CN) toxicity, treatment, and resulting physiological changes. We developed a broadband diffuse optical spectroscopy (DOS) system to measure bulk tissue absorption and scattering. DOS was used to optically monitor CN toxicity and treatment with sodium nitrite (NaNO2). To perform experiments, the DOS probe was placed on the hind leg of rabbits. A sodium CN solution was infused intravenously. DOS and concurrent physiologic measurements were obtained. After completion of CN infusion, NaNO2 was infused to induce methemoglobinemia (MetHb). During infusion of CN, blood gas measurements showed an increase in venous partial pressure of oxygen (pO2), and following reversal, venous pO2 values decreased. DOS measurements demonstrated corresponding changes in hemoglobin oxygenation states and redox states of cytochrome-c oxidase (CcO) during CN infusion and NaNO2 treatment. Therefore, DOS enables detection and monitoring of CN toxicity and treatment with NaNO2.

Comparison of cobinamide to hydroxocobalamin in reversing cyanide physiologic effects in rabbits using diffuse optical spectroscopy monitoring

Our purpose is to compare cobinamide to hydroxocobalamin in reversing cyanide (CN)-induced physiologic effects in an animal model using diffuse optical spectroscopy (DOS). Cyanide poisoning is a major threat worldwide. Cobinamide is a novel molecule that can bind two molecules of cyanide, has a much higher binding affinity than hydroxocobalamin, and is more water soluble. We investigated the ability of equimolar doses of cobinamide and hydroxocobalamin to reverse the effects of cyanide exposure in an animal model monitored continuously by DOS. Cyanide toxicity was induced in 16 New Zealand white rabbits by intravenous infusion. Animals were divided into three groups: controls (n=5) received saline following cyanide, hydroxocobalamin (N=6) following cyanide, and cobinamide (N=5) following cyanide. Cobinamide caused significantly faster and more complete recovery of oxy- and deoxyhemoglobin concentrations in cyanide-exposed animals than hydroxocobalamin- or saline-treated animals, with a recovery time constant of 13.8+/-7.1 min compared to 75.4+/-25.1 and 76.4+/-42.7 min, for hydroxocobalamin- and saline-treated animals, respectively (p<0.0001). This study indicates that cobinamide more rapidly and completely reverses the physiologic effects of cyanide than equimolar doses of cobalamin at the dose used in this study, and CN effects and response can be followed noninvasively using DOS.

Non-invasive in vivo diffuse optical spectroscopy monitoring of cyanide poisoning in a rabbit model

The objective of this study is to establish a cyanide toxicity animal model and to investigate the ability of broadband diffuse optical spectroscopy (DOS) to non-invasively monitor physiological changes that occur during the development of cyanide toxicity in a rabbit model. Broadband DOS combines multi-frequency frequency-domain photon migration (FDPM) with time-independent near-infrared spectroscopy (NIRS) to quantitatively measure bulk tissue absorption and scattering spectra between 600 nm and 1000 nm. Serum cyanide concentration and arterial and venous blood gas analysis at pre- and post-cyanide infusion were presented. To investigate the ability of DOS to non-invasively monitor physiologic changes occurring during development of CN toxicity, tissue concentrations of deoxyhemoglobin [Hb-R], oxyhemoglobin [Hb-O2], cytochrome c oxidase oxidized state [CcO_Ox] and reduced state [CcO_Re] were determined from absorption spectra acquired in 'real time' during cyanide infusions (NaCN 6 mg/60 ml normal saline) in six pathogen-free New Zealand white rabbits. During cyanide infusion, in vivo tissue oxygen saturation increased ( approximately 10%). In addition, broadband DOS was able to detect a concurrent increase in [CcO_Re] and decrease in [CcO_Ox]. Changes in tissue scattering properties in all six animals were detected during these events, confirming the need for DOS-based methods over traditional NIR spectroscopy to obtain accurate results.