(P68) Successful Use of Hemato-polyvalent Anti Venom in the Management of Rhabdophis Subminiatus (red-necked Keelback) Envenomation: Is There Cross Neutralization Effects?

Chief Complaint : A 55-year-old man sustained snakebite to the left heel presenting to the emergency department with rapidly progressing pain and swelling over the bite site.

History of Present Illness : A 55-year-old man sustained snakebite to the left heel and presented to the emergency department with pain, swelling and bleeding at the bite site and foot. Intravenous opioids, antibiotics and anti-tetanus toxoid were initiated.
During observation, swelling progressed involving his leg and repeat blood investigations demonstrated coagulopathy.
Due to rapid progression, decision was made to administer 2 vials of hemato-polyvalent snake antivenom (HPAV) after pre-medication with hydrocortisone and diphenhydramine.
Although there was no overt bleeding manifestations and his lower limb swelling remained stable, coagulation profile showed initial improvement after HPAV administration followed by subsequent worsening attributed to venom-induced consumptive coagulopathy (VICC). A second dose of two vials HPAV was given 9 hours after the initial dose followed by cryoprecipitate infusion.
The patient's limb swelling subsided and coagulation profile improved following the second dose. He remained hemodynamically stable throughout the duration of treatment and was eventually discharged well 72 hours post-envenomation.

Pertinent Physical Exam: Initial examination, patient had stable vital signs. He had a single puncture wound over his heel. His left ankle and dorsum of his left foot appeared swollen and the area surrounding the bite wound appeared bruised and tender (Figure 1). The perfusion, temperature, colour, power and sensation of his lower limb were preserved. He had no systemic signs or symptoms or bleeding from other sites. After a period of observation, swelling worsened to involve his leg (Figure 2).

Pertinent Laboratory Data: Initial blood investigations performed were normal. X-rays of his left lower limb did not reveal any retained foreign bodies but soft tissue swelling was apparent. Repeat blood investigation when patient developed progression of leg swelling revealed coagulopathy which improved after 2 courses of HPAV and normalized prior to discharge at 72 hours post envenomation.

The snake was caught by the patient’s colleagues. Based on pictures of the captured snake (Figure 3), local herpetologist identified the snake as Rhabdophis subminiatus (red-necked keelback), a colubrid with rear fangs, generally thought to be non-venomous.

Case Discussion: Snake bites from Rhabdophis subminiatus, a rear fanged snake which belong to the Colubrid family are largely considered harmless to humans and many such snakes are kept as pets. There have been rare reports in the past of coagulopathy following bites by this species. Venom of these snakes, being procoagulant results in disseminated intravascular coagulation with enhanced fibrinolysis resulting in VICC. Progressive soft tissue inflammation and significant coagulopathy is demonstrated in this case which illustrates severe morbidity that can result from bites of this species of snake. It is also noted that use of hemato-polyvalent snake antivenom (HPAV) has helped clinical improvement in coagulopathy in our patient. HPAV has been shown to demonstrate cross neutralization with common Southeast Asian viperid venoms. However, the possible cross neutralization potential of HPAV for Rhabdophis a colubrid may suggest a possible common underlying structure and pathophysiology of venom protein shared amongst the different of species of snakes. As Rhabdophis specific antivenom are unavailable in most countries, the possible therapeutic role of HPAV in similar situations deserves further consideration and evaluation.

References and Acknowledgements (Optional): Acknowledgements

Emeritus Professor Ponnampalam Gopalakrishnakone, MBBS,PHD,FAMS,DSc, National University of Singapore (NUS) – Department of Anatomy, who helped with identification of the snake.

E/Prof Gopalakrishnakone P - Department of Anatomy (nus.edu.sg)