So, there ARE snakes in Thailand...

Green pit viper, commonly found in Thailand. 

Interesting case of the day: 

A 23 year old male presented at 6:00 this morning after being bit by a snake. He was bit twice just superior to the left medial malleolus. The bites occurred around midnight while he was walking in the woods (a lot of people work the night shift in the rubber plantations. Yes, terrifying). He presented with swelling and pain at the site of the bite, and also spreading proximally up to his left knee. He had no other symptoms.

On physical exam, his vitals were normal- no tachycardia, normal blood pressure. 

Left leg was markedly tender to palpation from his left calf into his foot. He had obvious swelling to the left foot and calf as well. His pulses and sensation were intact. There were no associated skin changes other than some focal ecchymosis isolated to the site of the bite. There was no blistering or associated erythema. He was able to move his ankle, but his range of motion was limited by the swelling and pain.

His exam was otherwise normal.

Luckily he was able to tell us that he had been bitten by a green pit viper, which I then promptly googled to figure out what I should do next. 

Venemous snake bites are thought to be the single most important cause of human injury from any kind of venemous or poisonous animal worldwide. The highest burden of deaths from envenomation are found in rural areas of South Asia, Southeast Asia, and sub-Saharan Africa. 

Coagulopathy or venom-induced consumption coagulopathy (VICC) is the most common and important clinical syndrome caused by snake envenomation and can lead to serious and life-threatening bleeding. Other, perhaps less serious, adverse effects of envenomation include local tissue injury and necrosis, severe pain and swelling, compartment syndrome and rhabdomyolysis.





The most important initial labs are a platelet count to assess for thrombocytopenia and measurement of hypofibrinogenemia, measured as prolonged PT/INR. But in most resource poor settings, including here at KRCH, we do not have access to PT/PTT/INR levels, unless we want to wait a couple of weeks. 

To identify VICC in a resource poor setting without PT/INR we obtain a "whole blood clotting time". The WBCT isn't 100% sensitive or specific, but it's a pretty good test. 

Sensitivity/specificity comparisons (VCT = venous clotting time): 

                                  Sensitivity                                  Specificity

INR >1.2                   85.7%                     95.6%

WBCT 20                 85.7%                    95.8%    I'd say that's pretty good!

VCT >30                   57.0%                     94.4%

So back to our patient. His initial CBC at 7:00 this morning was normal with a platelet count of 166 thousand--slightly low, but we did not know his baseline, so maybe normal? His WBCT however was not normal. His blood was "not coagulable". Two hours after his initial evaluation his pain was better with the power of morphine, but his left calf was more tense and much more swollen.

So what do we do with a leg at risk for compartment syndrome and a possible VICC??

ANTIVENOM

Indications for Viper Antivenom: 

1) Whole blood clotting time >20 minutes or PT/INR >1.2

2) Systemic bleeding

3) Severe thrombocytopenia (<50K?)

4) Impending compartment syndrome

**Repeat every 6 hours until the WBCT or PT normalize or bleeding has stopped. 

The problem with antivenom is it doesn't come without risks. Based on the literature I found, the risk of early adverse reactions ranges from 3.5-85% ?! What kind of statistic is this? The immediate risks  are basically anaphylaxis, so we had epi drawn up and ready to give to him. Patients can also develop serum sickness from days to weeks after administration. Before giving the antivenom we did a skin test to evaluate for any local reaction. But from the information I read, this doesn't even really predict the risk of anaphylaxis, so it's not universally recommended. 

The patient in the monitored hall bed during the antivenom

infusion. 

Around 11:00 we administered two vials of antivenom to the patient via slow infusion over approximately 20 minutes. He had no adverse reactions and remained hemodynamically stable. Four hours later we obtained a second CBC and WBCT. His platelets at this time had risen to 266K, so that was promising, however his whole blood remained "uncoagulable". His calf was tense and painful. We had one more vial of antivenom to give him, which was not enough for a full dose.










We then decided it was best to refer him to the Thai government hospital about 20 minutes away where they could do additional testing and might have more antivenom. We did not have the lab testing needed to confirm that he was in fact coagulopathic, and even if we did, we didn't have enough medicine to treat him. The problem is, I'm not sure that hospital will have enough antivenom either and he'll likely have to be sent further for definitive care. And because he's Karen, he won't have easy or affordable access to the Thai medical system, so it's likely to cost him a fortune. But losing a leg would be a bigger loss in the long run, so I hope it's all worth it.

Venomous snakebite is considered to be the single most

important cause of human injury from any kind of venomous or

poisonous animal worldwide. Envenoming and deaths resulting

from snakebite are a particularly important public health problem

in the tropical world, with the highest burden in rural areas of

South Asia, Southeast Asia, and sub-Saharan Africa [1].

Coagulopathy is the commonest important, systemic clinical

syndrome caused by snake envenoming in the world, and

venom-induced consumption coagulopathy (VICC) is the most

clinically important coagulopathy, because it can be complicated

by serious and life-threatening haemorrhage