Viper’s Bite Triggered aHUS, Case Report Says

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by Patricia Inacio PhD |

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A 57-year old man developed atypical hemolytic uremic syndrome (aHUS) after being bitten by a pit viper belonging to the Bothrops aspe species, a recent case report suggests.

According to its authors, this is the first report describing an association between aHUS and this viper species, likely triggered by venom-induced thrombotic microangiopathy (TMA), a condition that causes blood clots to form in tiny blood vessels, particularly those of the kidneys. The patient recovered within 14 days following plasma exchange therapy.

The report, “Atypical Hemolytic Uremic Syndrome in a Patient With Bothrops asper Envenomation,” was published in the journal Wilderness & Environmental Medicine.

The man, a military professional stationed on southwestern Colombia, was bitten on his left foot by an adult B. asper pit viper. He was admitted to the hospital within eight hours after being bitten. His medical history included mild high blood pressure, for which he was being treated with hydrochlorothiazide and losartan.

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Upon admission, he was in good condition with a blood pressure of 135/82 millimeters of mercury (mm Hg) and a heart rate of 78 beats per minute. Further examination, including cardiac, respiratory and neurological tests all came back normal.

Blood analysis revealed abnormally high creatinine levels and high urea nitrogen — both  indicative of poorer kidney function. But other parameters, namely the number of blood-circulating immune cells, were normal.

More tests revealed the patient had an impairment in his ability to form blood clots, a condition triggered by the snakebite called venom-induced consumption coagulopathy (VICC). VICC is induced by the consumption and exhaustion of blood coagulation factors due to the presence of venom toxins.

He had to receive a total of 15 vials of polyvalent antivenom — seven more  vials than standard guidelines recommend — until his coagulation test was normalized. It took 18 hours to control his VICC.

Within two days after his admission, however, he developed oliguria, a condition in which there is a marked reduction in urine volume. He also was pale and developed jaundice, or yellowing of the skin and eyes.

The back of his left foot, where he was bitten by the viper, turned red and hot. This indicated a potential infection, so he began treatment with piperacillin and tazobactam, an antibiotic combo with broad spectrum antibacterial activity. Dosing was adjusted to his kidney function.

An MRI scan of his left foot showed no fluid accumulation, but blood tests revealed signs of hemolytic anemia, a condition in which red blood cells are destroyed faster than they can be replaced, and low platelet counts.

These findings, together with poor kidney function, suggested a TMA diagnosis.

Due to abnormally high potassium levels in his blood, a frequent finding in patients with chronic kidney disease, increased acidity in his blood and edema (swelling), the patient began daily hemodialysis and hemofiltration as needed. In hemodialysis and hemofiltration, blood flows out of the body into a machine to be “cleaned,” removing waste material and replacing important electrolytes like sodium.

Physicians suspected of aHUS due to the combination of acute kidney disease, low platelet counts, and hemolytic anemia. As a result, he started plasma exchange (plasmapheresis), a form of treatment which involves replacing a person’s plasma — the non-cellular parts of blood.

In total, he underwent four plasma exchange sessions. His anemia was resolved and his platelet counts gradually increased. Twenty days after being admitted to the hospital, the bite injury to his left foot improved significantly and his urine volume normalized, as did other blood parameters.

“To the best of our knowledge, this is the first case of B. asper envenomation in which the patient presented with hemolytic uremic syndrome after VICC,” the authors wrote.

“Although our patient had an adequate response with fresh frozen plasma and TPE, further studies need to be performed to assess the significance of these treatments in these types of patients,” they wrote.