Toxicology Brief: Sodium hypochlorite bleach ingestion in two dogs - Veterinary Medicine
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Toxicology Brief: Sodium hypochlorite bleach ingestion in two dogs

While fatalities in people are rare, they have occurred in adults who ingested as little as 250 to 500 ml of bleach at higher concentrations (e.g. 12.5% sodium hypochlorite).3 It should be noted that bleach ingestion in adults is often associated with intentional poisoning (suicide), and death may be hastened by the consumption of other toxins, chemicals, or pharmacologic agents.1,3 In children, death may occur with smaller doses, but the exact amount ingested is often unknown. Defining a lethal dose in people is difficult since there are few cases in the literature, sodium hypochlorite concentrations in bleach vary, and cases of intentional poisonings may involve multiple toxins.

In this case, the exact volume of bleach ingested by each animal was unknown since copious amounts of clear fluid were noted in multiple areas near the dogs on initial discovery. This fluid may have been bleach, urine, or a mixture of both. Also, the fluid on the skin and coat of both dogs smelled like urine and bleach. It was speculated that each dog ingested at least several hundred milliliters of the estimated 2.12 L in the bottle.

While a lethal dose of sodium hypochlorite in dogs is not established in the veterinary literature, extrapolation from a reported lethal dose of sodium chloride of 3.7 g/kg in dogs may be considered.5 For example, a 40-lb (18-kg) dog would have to ingest about 67 g of sodium chloride to attain this lethal dose. The consumption of 1 L of 6.15% sodium hypochlorite bleach containing 19.1 mg/ml of sodium and 30 mg/ml of chloride would equal the ingestion of 49.1 g of sodium chloride. Assuming the animals only ingested several hundred milliliters of bleach, this amount would not have been sufficient to attain the lethal dose of sodium chloride. However, corrosive injury to the gastrointestinal tract and the development of other metabolic derangements and secondary complications, such as aspiration pneumonia, likely contributed to the severity of the toxicosis. Therefore, it is reasonable to suspect that ingestion of at least several hundred milliliters of bleach resulted in the severe morbidity of these dogs, which led to their euthanasia.

Toxic effects

The severe metabolic derangements and complications noted in these two dogs are comparable to those that occur in fatal cases in people.

Increased serum osmolality. A common finding in fatal cases of sodium hypochlorite bleach ingestion in people is altered consciousness resulting from acute elevations of serum sodium concentrations and osmolality.1 These elevations may cause central nervous system lesions such as intracranial hemorrhage, cerebral edema, and cerebral or cerebellar herniation.1

The calculated serum osmolality for these dogs was approximately 391 mOsm/L in the female and 340 mOsm/L in the male (reference interval = 290 to 310 mOsm/L). Both animals were poorly responsive, which was attributed to the acute hypernatremia and elevated osmolality. In addition, the hypernatremia likely initiated the shifting of solutes within the erythrocytes in an attempt to equilibrate with the hypertonic plasma. When the erythrocytes were exposed to the isotonic diluent used by the hematology analyzer, cell swelling resulted in the detection of an increased MCV (macrocytosis), a decreased MCHC (hypochromasia), and a higher calculated hematocrit.

In dogs, macrocytosis and hypochromasia are most commonly associated with a regenerative anemia, which would be unexpected in this case since both dogs had either a high normal or an elevated hematocrit. Cell swelling may also explain the discrepancies noted between the calculated and spun hematocrit in our patients since the hematology analyzer calculates the hematocrit based on the measured MCV value and the red blood cell count. In this case, an artifactual elevation of the MCV due to in vitro red blood cell swelling would have led to an increase in the calculated hematocrit. The spun hematocrit for both animals was in the high normal range, which was attributed to dehydration.

Hemostatic abnormalities. The slight elevation of the prothrombin time and markedly elevated D-dimer concentration in the female may have indicated developing hemostatic abnormalities and fibrinolysis associated with disseminated intravascular coagulation, given the severity of the dog's clinical condition.


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