Venomous snake bite are a combined lesion of biological xenobiotics and infectious agents contained on the animal’s fangs. Manifestations include pain, swelling, necrosis, and the release of bloody fluid. Systemic signs – hypercoagulation or hemorrhagic syndrome, tachycardia, vomiting, dizziness, paralysis or paresis, impaired consciousness. The complex of symptoms depends on the type of snake. Diagnosis is made on the basis of signs (characteristic wounds), anamnesis. Laboratory methods are of auxiliary importance. First aid involves immobilization of the limb, removal of the toxicant, aseptic dressing. Specific therapy – polyvalent serum.
X20 Contact with venomous snakes and lizards
According to WHO, about 5 million cases of snake venom intoxication are registered annually in the world. The number of deaths varies from 94 to 125 thousand. The number of people who, after being attacked by a reptile, have undergone limb amputation or have other irreversible consequences reaches 400 thousand. Venomous snake bite are found all over the world, except for permafrost zones. They are most common in the countries of Southeast Asia and Africa, where the largest number of animal species live. The risk group for poisoning with biological toxicants includes hunters, fishermen, berry pickers, small children, farmers, villagers.
Venomous snake bite occur mainly through accidental contact, when a person steps on an animal or puts his foot in close proximity to it. The reptile perceives this as an attempt to attack and takes measures to protect itself. It is unable to bite through a thick shoe or boot, so injuries occur only in people who move in light shoes or do it barefoot. Other possible reasons:
- Trapping. Specialists who catch reptiles to obtain poison from them or for gastronomic purposes are at high risk. An attack becomes possible in case of violation of safety regulations, incorrect technology of catching an animal. Such cases are most common in African countries, where snakes are caught even with their bare hands.
- Care. The defeat of snake venom occurs when dangerous reptiles are kept in terrariums. The bite usually happens during cleaning, when the owner is forced to move the animal, otherwise contact it. Dangerous are representatives of the animal world who have not had their fangs and venom glands removed.
- Self-medication. Snake venom in minimal dosages is used for the treatment of certain diseases. The substance is used locally, for rubbing. Illiterate attempts to independently use animal xenobiotics sometimes cause poisoning. This is especially true for ingestion of the substance or its parenteral administration.
- Training. There are situations when inexperienced trainers were attacked by a snake trying to prepare it for a performance. Careless handling caused death or serious injuries.
Risk factors include living in warm and humid areas that are optimal for reptile reproduction. People employed in the agricultural industry, harvesting wild berries, and harvesting wood are particularly at risk. Venomous snake bite often occur during fishing or hunting, as well as during outdoor recreation. Anglers who catch prey with nets are at risk of being bitten by a sea snake of the asp subfamily. This happens rarely, since animals of this species are not too aggressive.
Taking into account the peculiarities of the venom action, the pathogenesis of snake bites can be divided into two large groups. The secret of the glands of vipers, muzzles, rattlesnakes has a hemovasotoxic effect. The main active ingredient is viperotoxin or crotatoxin. The enzyme enhances blood clotting, causes the development of defibrination-fibrinolytic phenomena. DIC syndrome is formed, which is initially characterized by hypercoagulation. Then there is a sharp decrease in clotting ability, internal bleeding occurs.
The poison has a cytolytic and necrotizing effect. Foci of dead cells appear in the area of damage, fluid proliferation occurs from the vascular bed into the fiber and muscles, tissue destruction products enter the bloodstream. A decrease in CBV is accompanied by disorders of the cardiovascular system. The activity of detoxifying liver enzymes decreases, as a response to the penetration of foreign proteins, sensitization develops.
Cobra toxin has a neurotoxic effect. It acts like curare poison, disrupts neuromuscular conduction, leads to paralysis and paresis. Especially dangerous is considered to be lesions of the respiratory muscles, often ending in the death of the victim. After a snake attack, the effectiveness of several coagulation factors decreases at once, which leads to increased bleeding. Directly in the bite area, the skin peels off in flaps due to trophic disorders.
Venomous snake bite are divided according to the type of animal (viper, roller, asp, narrow-mouthed, etc.) or the characteristics of the effects of the toxin (neurotropic, hemovasotoxic). Since it is only sometimes possible to determine the type of reptile, this principle of classification has no clinical significance. Therapy and first aid are provided depending on the severity of the signs. According to the severity of poisoning , it can be as follows:
- Easy. There is no danger to life, the symptoms are mainly local: swelling, pain, redness. A medical allowance is required to reduce the time of convalescence, without the help of a doctor, a person recovers in 7-10 days. The number of predators whose bites cause mild intoxication includes the muzzle, tiger snake.
- Medium. Local signs are bright, there are systemic reactions of various levels of severity. Without the introduction of a specific serum, the death of the victim is possible. Moderate injuries occur after an attack by a steppe, common or Caucasian viper.
- Heavy. A detailed picture of intoxication by an animal xenobiotic is noted. There are pronounced general and local symptoms. The threat to life is maximum. It is not always possible to save a person, even if first aid was provided in a timely and correct manner. Such consequences are caused by the poison of gyurza, cobra.
The symptoms differ directly depending on the type of toxic substance. When viperotoxin enters the bloodstream, a sharp pain immediately occurs at the site of injury, which increases for several hours. Hemorrhagic edema develops on the affected area, which progresses, can shift from the extremities to the trunk. The skin around is bluish or gray, covered with blisters. Later, abscesses may form, which transform into long-healing ulcers.
The victims complain of dizziness, increasing general weakness, drowsiness. Syncopal states are possible. There is a feeling of pain in the eyes, visual disturbances, vomiting, nausea. A bitter taste appears in the mouth. On objective examination – ptosis of the eyelids, bleeding of the mucous membranes, tachycardia, shortness of breath, psychomotor agitation. Sometimes there is a slight hyperthermia, which after a few hours is replaced by hypothermia. Hypotension is detected. If the poison gets directly into the blood vessel, death occurs after a few minutes.
The bites of venomous snakes, whose venom has a neurotropic effect, manifest themselves differently. The pain subsides 2-4 hours after the injury. Intoxication develops at lightning speed. After 3-5 minutes, the patient experiences weakness, nausea. Salivation, visual impairment, unsteadiness of gait are noted. Muscle paralysis begins to develop from the bite site, quickly capturing new areas. Speech becomes slurred, there is ptosis of the eyelids, spontaneous defecation, urination. Death occurs after 2-7 hours from respiratory arrest.
The most common complication is the formation of trophic ulcers at or near the bite site. Develops after a week or more from the time of injury. It is diagnosed in 35-40% of victims. In severe cases, gangrene forms, which requires amputation of the limb. Properly provided first aid can reduce the percentage of delayed trophic disorders to 20-22%. The second most common is infection of the bite site with the formation of abscesses. Tetanus bacillus infection is possible.
Internal bleeding is considered a less common, but more severe complication. They begin against the background of coagulopathy in 28-32% of patients. Most often hemorrhages occur in the gastrointestinal tract, the spleen, kidneys, and liver are affected somewhat less often. Hemorrhagic stroke is particularly dangerous. 2-3% of patients develop sepsis by the end of 3-7 days, which is accompanied by multiple organ failure. At the same time, mortality increases many times.
A preliminary diagnosis is made by a medical officer who first examines the victim. They should also be given first aid. Usually this is a member of the SMP brigade, but in his place there may be a therapist, a general practitioner, a paramedic. The final diagnosis is carried out by narrow specialists of the toxicological hospital. The following types of examination are assigned:
- Physical. It includes an examination using the simplest methods of objective diagnostics. The patient has characteristic clinical signs of a snake bite – a double wound with edema and inflammation. The victim reports the fact of contact with a predator. Blood pressure is above 139/89 or below 100/60, pulse is more than 80-90 beats / minute. The skin temperature at the initial stage is 37 ° C, then below 36.5 °C.
- Laboratory. During a clinical blood test, a reduced number of red blood cells and hemoglobin is detected. There is eosinophilia, a shift of the leukocyte formula to the left, an increase in ESR. Protein, cylinders, and blood elements are present in the urine. Fibrinolytic activity is increased, the content of V, VII, IX, X coagulation factors is reduced.
- Hardware. During ultrasound, disseminated focal or diffuse changes in parenchymal organs may be detected. With the development of hemorrhagic stroke, a corresponding picture appears on CT (dense lightened foci). With a significant liver lesion, there is a level of free fluid in the abdominal cavity.
Snake bite therapy is divided into several stages: pre-hospital measures, planned inpatient treatment, rehabilitation. Severe edema and necrosis require surgical intervention. The hospitalization of the victims is carried out in the toxicology department, in case of a significant violation of vital functions – in the nearest intensive care unit, where the patient’s condition is stabilized, after which they are transferred to the specialized medical unit.
Venomous snake bite require immediate first aid. Most sources recommend attempting to suck the poison out of the wound. With this technique, no more than 20% of the toxicant can be removed, which allows some authors to claim its insufficient effectiveness. The procedure is carried out for 5-7 minutes exclusively by mouth. Manipulation should not be carried out by people who have injuries and damage to the mucous membranes. Preliminary incisions of the affected area are unacceptable.
After cleaning the wound from the poison, the injury site should be treated with a water–based antiseptic solution, along the edges with fucorcine, diamond green or methylene blue, and closed with a bandage. The limb must be immobilized. For this purpose, splints are used as in case of a fracture. It is permissible to apply cold to the injured area. If long-term transportation is expected, a tourniquet is applied to the limb, carefully observing the technique of the procedure.
Both at the stage of SMP and in the hospital, symptomatic treatment is carried out. The patient is prescribed infusions of saline solutions and colloids. Water balance monitoring is mandatory. Calcium chloride and ascorbic acid are used to correct coagulopathy. Infusions of glucocorticosteroids, antihistamines, prophylactic administration of antibiotics, tetanus serum are recommended. Hemodialysis and exchange blood transfusion are indicated. The transfer to artificial respiratory support, monitoring of heart rate, blood pressure, respiratory rate, saturation is carried out.
A specific way to correct the condition is the introduction of polyvalent anti–snake serum in a dose of up to 1,000 IU intramuscularly. Modern drugs act on almost all types of snake venom, do not require accurate identification of the reptile species. The best effect is achieved if the serum is used on the first day after the incident. In severe lesions, slow intravenous infusion of the drug is allowed. It is necessary to take into account the extremely high risk of anaphylactoid reactions.
Surgical treatment is used to remove the poison. The incisions are longitudinal, continuing the wound left by the bite. Then a thorough hemostasis is performed, an aseptic dressing is applied. Intervention may be required with massive edema of the limb and infection of the affected area with anaerobic microflora. In this case, wide lamp-shaped incisions are used. With widespread gangrene, amputation of the limb with subsequent prosthetics is required.
Venomous snake bite heal for 6-30 days. The term depends on the type of predator and on how quickly first aid was implemented and anti-snake serum was administered. All this time, the patient receives funds that improve microcirculation. When poisoning with neurotropic toxins, drugs that stimulate the nerve impulse are required. For timely detection and correction of long-term consequences (formation of trophic defects, neuropathy), monthly visits to the doctor for 1 year are recommended.
Prognosis and prevention
The prognosis for life is favorable for mild and moderate intoxication. Lethality in severe injuries without timely assistance is extremely high. Early and delayed health effects are found in one of the 24 victims. As a rule, this happens when you go to medical institutions late. The largest number of cases of amputation of limbs is registered among residents of countries with low availability of medical benefits, who have been trying to be treated independently for a long time using traditional medicine.
Prevention consists in using tight high shoes when hiking in the woods, lakes and swamps. When catching predatory reptiles or working with them, it is necessary to adhere to safety requirements: wear thick gloves, have a phone nearby to call a doctor. Animals kept in terrariums must undergo a procedure for removing poisonous glands. This does not make them completely safe, but it can significantly reduce the severity of the consequences of the bite.