لخّصلي

A 55-year-old farmer presented to the emergency treatment unit with double vision and difficulty in speech. The patient said he was fine the day before and noticed these changes suddenly in the morning. The key features I noticed were petasos or drooping of the eyelids and drooling of saliva, which shows difficulty in swallowing. I at once checked his feet and saw a considerable swelling around the ankle. Now that I knew what I was looking for, I was able to spot the bite marks caused by the fangs of a snake. The swelling around the bite site and the neurological signs usually points towards a cobra bite in tropical countries. Though he is stable now, the victim will be paralyzed and go into respiratory failure if we don't treat him fast. People, today in our series about interesting medical cases, we'll learn about cobra bites. There are many species of cobra, like the famous king cobra tree cobras. Rink Hals. Et cetera. They are found in tropics and subtropics in Asia, Africa, Australia and America. All of them are highly venomous, while many can rear upwards and produce a hood when they are threatened. Cobra venom is highly toxic. Its first effects are usually seen around the bite site. The affected limb will become swollen and painful due to the heavy inflammation. The necrosis or cellular death will cause blisters and ulcers.

The presence of local effects alone is not a sign to administer anti-venom, because the traditional anti-venom itself is highly allergic and could result in a life-threatening allergic reaction called anaphylaxis. To give antivenom, the local effects should extend beyond half of the limb. However, we started the patient on antibiotics to prevent a secondary bacterial infection. Though the patient was stable when he was brought to the hospital. After a few minutes, it became obvious that he was breathing fast. The pulse oximeter showed he had a reduced oxygen level in blood. The neurotoxins released from the Kobra fangs were paralyzing his respiratory muscles. Since he couldn't take adequate breaths, the body was trying to compensate by increasing the respiratory rate. The arterial blood gas study showed that the body was in severe acidosis due to respiratory failure. We intubated the patient and connected it to a ventilator to prevent an impending respiratory arrest. Neurotoxins are a fascinating product of evolution that can outsmart the well-developed nervous system of animals. When you want to activate a certain muscle, the motor neuron releases a neurotransmitter called acetylcholine, which in turn binds to nicotinic receptors on muscle surface. The activated receptor will release calcium into the cell and cause muscular contraction. Unfortunately, neurotoxins released by the Cobra are identical to acetylcholine, but it doesn't produce muscle contraction when it binds with a nicotinic receptor.

This antagonizing or blocking effect of neurotoxins causes muscle paralysis. Paralysis happens in a descending order. The first symptom of neurotoxicity is pertussis. Then the patient will develop double vision due to the paralysis of ocular muscles. Swallowing difficulty and speech dysfunctions will appear when the toxicity involves throat muscles. Finally, when the respiratory muscles are paralyzed, the patient will gradually stop breathing. The indications for administration of anti-venom are having local effects, involving more than half the length of a limb, or the presence of systemic signs like neurotoxicity. Antivenin is the antibody rich serum extracted from the blood of animals like horses and sheep. That also explains why anti-venom is highly allergic to some patients. In addition to neurotoxicity, the medical literature associate’s cobra bites with cardiac toxicity as well. 15 to 30 minutes after the administration of antivenom, the patient's ptosis improved in about six hours, his neurotoxicity was completely reversed. After about one day of ICU care, we removed the ventilators, which allowed him to breathe spontaneously. But the sad thing is, even months after this event, the patient still has a poorly healed wound at the bite site.