WHAT ARE THE TOXIC EFFECTS OF CONCENTRATED HYDROGEN PEROXIDE?
Injury from concentrated H2O2 consumption is primarily from either direct caustic injury or the embolic obstruction of blood flow. Following ingestion, the enzyme catalase metabolizes the breakdown of H2O2 in accordance with the following equation: 2H2O2(aq) → 2H2O(l) + O2(g) + heat. A single milliliter of 35% H2O2 results in the liberation of 100 mL of O2. (The more common 3% household solution generates 10 mL of oxygen per 1 mL of H2O2.) The creation of a large intragastric pressure gradient from the liberation of gas, coupled with the caustic and exothermic injury of the bowel mucosa, may contribute to the movement of oxygen through epithelial interstices into the circulation.
In addition, and perhaps more importantly, absorption of intact H2O2 with subsequent metabolism by catalase in the blood liberates oxygen directly within the vasculature. Oxygen bubbles may coalesce in blood circulation and occlude vascular flow. In canine studies, elevated oxygen tension in the portal venous system led to cessation of mesenteric flow in arteries and veins, though the mechanism of action is unclear.4 Furthermore, coalescence of bubbles can lead to disruption of bowel-cell architecture, fibrin plugging of capillaries, venous thrombosis, and infarction of tissues.4
Cases of cardiac and cerebral gas embolism have been reported and present similarly to patients with diving-related decompression injuries (eg, stroke-like syndromes).5,6 The proposed mechanism for these latter effects involves the metabolism of H2O2 in the systemic circulation with production of oxygen bubbles. In the presence of an atrial septal defect, bubbles may move from the right atrium to the arterial circulation.7
Toxicity and death from H2O2 exposure associated with the historical treatment of inspissated meconium,4 as well as the irrigation of wounds,8 has been reported in the medical literature. Ingestion of a 3% solution is generally benign, resulting at worst in gastrointestinal symptoms or throat irritation.9 Rarely does significant toxicity occur at this low concentration,5 with the vast majority of such cases involving concentrated solutions of 35%.
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