Prussian Blue Quiz

Of the presented structures, only the first answer choice correctly describes Radiogardase, which is an insoluble form of Prussian Blue. Other forms of Prussian Blue described in the other answer stems are soluble, but may also bind thallium and cesium, enhancing their elimination.

As the ionic radius of the cation increases, binding affinity increases. There is an important distinction between differences in atomic radii when comparing cations to the elemental form. In the cationic form Cs>Rb>Tl>K>Na; however, the order to elemental radii is different: Cs>Rb>K>Na>Tl. Yet, this is not clinically significant because the majority of exposure to thallium involve an ionic salt form.

The correct answer is that Prussian Blue binds Cesium and Thallium within the gut lumen and leads to fecal elimination. Furthermore, Cesium and Thallium that are excreted through the biliary tree also bind Prussian Blue within the gut, which leads to enhanced elimination and a decrease in total body Cesium and Thallium. All of the other answers are incorrect.

Activated charcoal has been shown bind cationic Thallium within the GI tract as effectively or even more effectively than Prussian Blue. It may also increase elimination by decreasing enterohepatic recirculation. Multiple animal in vitro studies and animal studies showed that activate charcoal may have superior toxicokinetic elimination of Thallium when compared to Prussian Blue. However, elimination of Thallium from tissues was consistently demonstrated to be superior with Prussian Blue. So, Prussian Blue is the treatment of choice, but until it is available to the patient MDAC is a reasonable choice as long as mental status allows for it.  Please note that this data does apply to Cesium exposed patients. None of the other answers are likely to increase elimination.

Prussian blue preferentially bind monovalent cations, eg Potassium, Cesium, Rubidium, Thallium, and Sodium. It is important to note that that it has the highest binding affinity for cationic forms of Cesium, Rubidium, and Thallium. Potassium falls closely behind these. Therefore, serum Potassium should be closely monitored, especially as chelator-target concentrations decrease. Potassium should be repleted as necessary. Sodium has a much lower binding affinity for Prussian Blue; therefore, one would expect Potassium to become depleted first. Magnesium and Calcium are divalent cations and do not have a significant binding affinity of Prussian Blue. Phosphate also doe not have a significant bind capacity for Prussian Blue.

Of the above answer choices, only constipation is the correct answer. In fact, treatment with Prussian Blue can lead to SBO, LBO and require NG GI decompression, even in the absence of pre-existing abdominal surgeries. Hypokalemia, not hyperkalemia, would be expected due to the binding affinity of Prussian Blue for monovalent cations. Diarrhea would not be expected. Hypochloremia would not be expected either.

The correct answer is daily urinary Thallium output less than 0.5 mg per day. Please note, that this measure is by historic convention only. If the patient is still symptomatic, treatment should continue. Fecal output is difficult to measure in most laboratories, and the reason why is relatively obvious. How does one collect all the stool?? Whole blood Thallium greater than 100 micrograms/L is associated with the initial range of toxicity. Whole blood Thallium greater than 300 micrograms/L is associated with severe toxicity. Neither of these markers are endpoints for cessation of treatment with Prussian Blue.

Even though it is not clearly demonstrated here via ECG tracing, the patients most likely etiology is Torsade de pointes. This has been shown to be induced by exogenous administration of Cesium salts. From a mechanistic point of view, this can be understood as competitively inhibiting K+ flow through the myocardial membrane, which thereby could cause increase in the QT interval and eventual degredation into Torsades de pointes. Therefore, the only answer that is correct is administration of Magnesium Sulfate. All of the other answers are incorrect because they treat hyperkalemia, which is not the problem here.

Out of the answer choices listed above, only insolubale Prussian Blue has been shown to be efficacious in reducing total body loads of of radioactive Cesium. Although, insoluable Prussian Blue has been shown to reduce total body radiaoactive Cesium, it is not as efficacious as insoluable Prussian Blue. All of the answer choices have not been shown to be efficacious.

Treatment of the mother for radioactitve Cesium may pose a risk to the developing neonate, although literature for this presumption is limited. Nonetheless, every effort to minimize risk to the neonate should be attempted. Continuance of breastfeeding may expose the neonate to Cesium, although data is limited. Therefore, the neonate should be converted to formula and bottled water. Tap water may be contaminated in the neraby area. Transitioning the child to a “wet-nurse” who is only 10 Km away may pose a similar risk of transmission of radioactive Cesium.

Out of all the answers above, only “9g for adults 3g for children under the age of 12 and 150-250 mg/kg for children under the age of 2” is correct, as per guidelines. All of the other answers are incorrect.