Kelly Kreuter

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.

Intramuscular Cobinamide Sulfite in a Rabbit Model of Sublethal Cyanide Toxicity

STUDY OBJECTIVE Exposure to cyanide in fires and industrial exposures and intentional cyanide poisoning by terrorists leading to mass casualties is an ongoing threat. Current treatments for cyanide poisoning must be administered intravenously, and no rapid treatment methods are available for mass casualty cyanide exposures. Cobinamide is a cobalamin (vitamin B(12)) analog with an extraordinarily high affinity for cyanide that is more water-soluble than cobalamin. We investigate the use of intramuscular cobinamide sulfite to reverse cyanide toxicity-induced physiologic changes in a sublethal cyanide exposure animal model and determine the ability of an intramuscular cobinamide sulfite injection to rapidly reverse the physiologic effects of cyanide toxicity. METHODS New Zealand white rabbits were given 10 mg sodium cyanide intravenously over 60 minutes. Quantitative diffuse optical spectroscopy and continuous-wave near-infrared spectroscopy monitoring of tissue oxyhemoglobin and deoxyhemoglobin concentrations were performed concurrently with blood cyanide level measurements and cobinamide levels. Immediately after completion of the cyanide infusion, the rabbits were injected intramuscularly with cobinamide sulfite (n=6) or inactive vehicle (controls, n=5). RESULTS Intramuscular administration led to rapid mobilization of cobinamide and was extremely effective at reversing the physiologic effects of cyanide on oxyhemoglobin and within deoxyhemoglobin extraction. Recovery time to 63% of their baseline values in the central nervous system occurred within a mean of 1,032 minutes in the control group and 9 minutes in the cobinamide group, with a difference of 1,023 minutes (95% confidence interval 116 to 1,874 minutes). In muscle tissue, recovery times were 76 and 24 minutes, with a difference of 52 minutes (95% confidence interval 7 to 98 minutes). RBC cyanide levels returned toward normal significantly faster in cobinamide sulfite-treated animals than in control animals. CONCLUSION Intramuscular cobinamide sulfite rapidly and effectively reverses the physiologic effects of cyanide poisoning, suggesting that a compact cyanide antidote kit can be developed for mass casualty cyanide exposures.

In vivo three-dimensional imaging of normal tissue and tumors in the rabbit pleural cavity using endoscopic swept source optical coherence tomography with thoracoscopic guidance

The purpose of this study was to develop a dynamic tunable focal distance graded-refractive-index lens rod-based high-speed 3-D swept-source (SS) optical coherence tomography (OCT) endoscopic system and demonstrate real-time in vivo, high-resolution (10-microm) imaging of pleural-based malignancies in an animal model. The GRIN lens-based 3-D SS OCT system, which images at 39 fps with 512 A-lines per frame, was able to capture images of and detect abnormalities during thoracoscopy in the thoracic cavity, including the pleura, chest wall, pericardium, and the lungs. The abnormalities were confirmed by histological evaluation and compared to OCT findings. The dynamic tunable focal distance range and rapid speed of the probe and SS prototype OCT system enabled this first-reported application of in vivo 3-D thoracoscopic imaging of pleural-based malignancies. The imaging probe of the system was found to be easily adaptable to various sites within the thoracic cavity and can be readily adapted to other sites, including rigid airway endoscopic examinations.

In vivo optical coherence tomography detection of differences in regional large airway smoke inhalation induced injury in a rabbit model.

Smoke inhalation injury causes acute airway injury that may result in airway compromise with significant morbidity and mortality. We investigate the ability of high resolution endobronchial optical coherence tomography (OCT) to obtain real-time images for quantitatively assessing regional differences between upper tracheal versus lower tracheal and bronchial airway injury responses to smoke inhalation in vivo using a prototype spectral domain (SLD)-OCT system we constructed, and flexible fiber optic probes. 33 New Zealand White rabbits are intubated and mechanically ventilated. The treatment groups are exposed to inhaled smoke. The OCT probe is introduced through the endotracheal tube and maintained in place for 5 to 6 h. Images of airway mucosa and submucosa are obtained at baseline and at specified intervals postexposure. Starting within less than 15 min after smoke inhalation, there is significant airway thickening in the smoke-exposed animals. This is maintained over 5 h of imaging studies. The lower tracheal airway changes, correlating closely with carboxyhemoglobin levels, are much greater than upper tracheal changes. Significant differences are seen in lower trachea and bronchi after acute smoke inhalation compared to upper trachea as measured in vivo by minimally invasive OCT. OCT is capable of quantitatively detecting regional changes in airway swelling following inhalation injury.

Detection of acute smoke-induced airway injury in a New Zealand white rabbit model using optical coherence tomography

Optical coherence tomography (OCT) is a micron scale high-resolution optical technology that can provide real-time in vivo images noninvasively. The ability to detect airway mucosal and submucosal injury rapidly will be valuable for a range of pulmonary applications including assessment of acute inhalation smoke and burn injury. OCT has the potential ability to monitor the progression of airway injury changes including edema, hyperemia, and swelling, which are critical clinical components of smoke-inhalation injury. New Zealand white male rabbits exposed to cold smoke from standardized unbleached burned cotton administered during ventilation were monitored for 6 h using a 1.8-mm diameter flexible fiberoptic longitudinal probe that was inserted through the endotracheal tube. The thickness of the epithelial, mucosal, and submucosal layers of the rabbit trachea to the tracheal cartilage was measured using a prototype superluminescent diode OCT system we constructed. OCT was able to detect significant smoke-injury-induced increases in the thickness of the tracheal walls of the rabbit beginning very shortly after smoke administration. Airway wall thickness increased to an average of 120% (+/-33%) of baseline values by 5 h following exposure. OCT is capable of providing real-time, noninvasive images of airway injury changes following smoke exposure. These studies suggest that OCT may have the ability to provide information on potential early indicators of impending smoke-inhalation-induced airway compromise.

Broadband diffuse optical spectroscopy assessment of hemorrhage- and hemoglobin-based blood substitute resuscitation

Hemoglobin-based oxygen carriers (HBOCs) are solutions of cell-free hemoglobin (Hb) that have been developed for replacement or augmentation of blood transfusion. It is important to monitor in vivo tissue hemoglobin content, total tissue hemoglobin [THb], oxy- and deoxy-hemoglobin concentrations ([OHb], [RHb]), and tissue oxygen saturation (S(t)O(2)=[OHb][THb]x100%) to evaluate effectiveness of HBOC transfusion. We designed and constructed a broadband diffuse optical spectroscopy (DOS) prototype system to measure bulk tissue absorption and scattering spectra between 650 and 1000 nm capable of accurately determining these tissue hemoglobin component concentrations in vivo. Our purpose was to assess the feasibility of using DOS to optically monitor tissue [OHb], [RHb], S(t)O(2), and total tissue hemoglobin concentration ([THb]=[OHb]+[RHb]) during HBOC infusion using a rabbit hypovolemic shock model. The DOS prototype probe was placed on the shaved inner thigh muscle of the hind leg to assess concentrations of [OHb], [RHb], [THb], as well as S(t)O(2). Hemorrhagic shock was induced in intubated New Zealand white rabbits (N=6) by withdrawing blood via a femoral arterial line to 20% blood loss (10-15 cckg). Hemoglobin glutamer-200 (Hb-200) 1:1 volume resuscitation was administered following the hemorrhage. These values were compared against traditional invasive measurements, serum hemoglobin concentration (sHGB), systemic blood pressure, heart rate, and blood gases. DOS revealed increases of [THb], [OHb], and tissue hemoglobin oxygen saturation after Hb-200 infusion, while blood total hemoglobin values continued did not increase; we speculate, due to hyperosmolality induced hemodilution. DOS enables noninvasive in vivo monitoring of tissue hemoglobin and oxygenation parameters during shock and volume expansion with HBOC and potentially enables the assessment of efficacy of resuscitation efforts using artificial blood substitutes.

Detection and monitoring of early airway injury effects of half-mustard (2-chloroethylethylsulfide) exposure using high-resolution optical coherence tomography

Optical coherence tomography (OCT) is a noninvasive, high-resolution imaging technology capable of delivering real-time, near-histologic images of tissues. Mustard gas is a vesicant-blistering agent that can cause severe and lethal damage to airway and lungs. The ability to detect and assess airway injury in the clinical setting of mustard exposure is currently limited. The purpose of this study is to assess the ability to detect and monitor progression of half-mustard [2-chloroethylethylsulfide (CEES)] airway injuries with OCT techniques. A ventilated rabbit mustard exposure airway injury model is developed. A flexible fiber optic OCT probe is introduced into the distal trachea to image airway epithelium and mucosa in vivo. Progression of airway injury is observed over eight hours with OCT using a prototype time-domain superluminescent diode OCT system. OCT tracheal images from CEES exposed animals are compared to control rabbits for airway mucosal thickening and other changes. OCT detects the early occurrence and progression of dramatic changes in the experimental group after exposure to CEES. Histology and immunofluorescence staining confirms this finding. OCT has the potential to be a high resolution imaging modality capable of detecting, assessing, and monitoring treatment for airway injury following mustard vesicant agent exposures.

REAL-TIME HIGH-RESOLUTION COMPARISON OF TRACHEAL AND BRONCHIAL INJURY CHANGES DURING SMOKE INHALATION IN RABBITS USING OPTICAL COHERENCE TOMOGRAPHY.: 150

Background Smoke inhalation injury causes acute airway swelling that results in significant morbidity and mortality. There are currently no available modalities for early detection of this edema. We performed high-resolution endobronchial optical coherence tomography (OCT) using a prototype SLD-OCT system and flexible fiberoptic probes we constructed to obtain novel real-time images of inhalation at near histologic levels showing differences between tracheal and bronchial responses to smoke in vivo. Method Nineteen New Zealand rabbits (four controls, seven tracheal, and eight bronchial) were intubated and mechanically ventilated. The experimental group was exposed to inhaled smoke. The OCT probe was introduced through the endotracheal tube. Images of airway mucosa and submucosa were obtained at baseline and at set time intervals. The mucosal and submucosal thickness was measured and compared between the three groups. The images were also compared to histologic sections of the trachea. Results Starting at 30 minutes after smoke inhalation, there was significant bronchial airway thickening. This was maintained through 360 minutes. No significant tracheal thickening was detected. Conclusions OCT is capable of detecting changes in airway swelling following inhalation injury and may be very useful for inhalation injury assessment. Significant differences were seen between bronchial and tracheal effects of acute smoking inhalation. Further studies will be needed to determine the causes for these differences.

489 NONINVASIVE IN VIVO MONITORING OF TISSUE HEMOGLOBIN CONTENTS AFTER HEMOGLOBIN-BASED OXYGEN CARRIER INFUSION IN RABBIT HYPOVOLEMIC SHOCK MODEL.

Introduction Despite their oxygen carrying capacities, the efficacy of hemoglobin-based oxygen carrier (HBOC) transfusion has been complicated by several side effects including hemodilution due to high oncotic properties and vasoconstriction from nitric oxide scavenging. Therefore, it is important to monitor in vivo tissue hemoglobin contents (oxy- and deoxyhemoglobin concentrations ([OxyHb], [DeOxyHb]), and tissue oxygen saturation (StO2) to evaluate the physiologic effects of HBOC transfusion. In this study, the feasibility of a noninvasive diffuse optical spectroscopy (DOS) system to monitor in vivo tissue hemoglobin concentrations during HBOC infusion is demonstrated using a rabbit hypovolemic shock model. Material and Methods Hemorrhage and fluid replacement in intubated New Zealand White rabbits (N = 6) was accomplished by 20% blood loss and slow infusion of Hb glutamer-200 (Hb-200) (Oxyglobin, Biopure, 0.5 mL/min). The DOS prototype probe was placed on the right inner thigh muscle of the hind leg to assess concentrations of [OxyHb], [DeOxyHb], total tissue hemoglobin concentration (THC = [OxyHb] + [DeOxyHb]) as well as StO2 during bloodletting and volume expansion. These values were compared against traditional invasive measurements. Serum hemoglobin concentration (sHgb), systemic blood pressure, heart rate, and blood gas were monitored at regular intervals throughout the experiment. Results THC and sHgb during shock and HBOC infusion (Figure 1) demonstrate that DOS was able to detect the restoration of THC in tissue after Hb-200 infusion, while systemic sHgb continued to decrease due to significant hemodilution. DOS also enables measurements of tissue hemoglobin oxygen saturation status from quantification of [OxyHb] and [DeOxyHb]. Conclusion DOS enables noninvasive in vivo monitoring of oxygen carrying capacity during shock and volume expansion with HBOC and renders insight on distribution of artificial blood substitute at the tissue level. FIGURE 1 Fractional changes of THC and sHgb from baseline during hemorrhage and resuscitation using oxyglobin.

490 VALIDATION OF NONINVASIVE IN VIVO DIAGNOSIS OF METHEMOGLOBINEMIA USING DIFFUSE OPTICAL SPECTROSCOPY IN A NEW ZEALAND RABBIT MODEL.

Introduction Broadband diffuse optical spectroscopy (DOS) 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 1,000 nm wavelength. Simultaneous determination of absorption and scattering provides the capability for accurate noninvasive direct measurement of tissue metabolite composition and concentrations. DOS could potentially be used to monitor changes in various metabolic solutes such as methemoglobin (MetHb) and methylene blue concentrations during treatment in vivo. The purposes of this study are to evaluate the feasibility of DOS to noninvasively monitor metabolic events during methemoglobinemia and treatment using methylene blue (MB) in vivo and to validate DOS measurements with on-site co-oximetry. Material and Methods In vivo diagnosis of methemoglobinemia was evaluated in a New Zealand Rabbit model via intravascular injection of sodium nitrite, and the effects were assessed using DOS monitoring with a prototype device constructed in our laboratory. The DOS data were then compared to standard arterial blood measurements of %MetHb using an on-site co-oximeter. Results In vivo MetHb concentration was quantitatively measured by DOS and was compared to %MetHb obtained through arterial blood from an on-site co-oximetry. %MetHb values from DOS and co-oximetry showed a close correlation (r 2 = .902, p < .0001, N = 4) and the quantification of %MetHb by DOS was not influenced by the cross-talk from oxy- and deoxyhemoglobin concentrations (as demonstrated by varying arterial and venous oxygenation). Conclusion Our results demonstrate the feasibility and robustness of noninvasive in vivo optical quantization of methemoglobinemia in tissue using DOS. FIGURE 1 Comparison between %MetHb vaues from DOS and co-oximetry. N = 4. FIGURE 2 Comparison of %MetHb values from DOS and co-oximetry at different doses of NaNO2 and different FiO2.