Treatment of bites of poisonous snakes: antidote

General approach to the treatment of bites of poisonous snakes

Immediately after the bite, the victim must move away from the snake to a safe distance or it must be moved to this distance. The victim should avoid tension, the person must be reassured, put in warmth and quickly transported to the nearest medical institution. The bitten limb should be immobilized in a functional position below the level of the heart, remove all rings, clocks and squeezing clothes. To prevent the spread of venom during immobilization, it is necessary to squeeze a limb (for example, with a pressing circular bandage), this can be used with coral snake bites, but it is not recommended in the USA, where most bites from dwarf snakes. The compression of the limb in this case can cause arterial ischemia and necrosis. Providers of first aid should maintain upper airway patency and breathing, give O ₂, establish intravenous access to the intact limb, while simultaneously organizing the transportation of the victim to the nearest medical facility. The benefits of any other prehospital interventions (for example, harnesses, sucking poison with the mouth, with or without a cut, cryotherapy, electric shock) are not proven, on the contrary, they can harm and delay the necessary treatment. However, the strands that have already been applied, in the absence of the threat of limb ischemia, can be left in place while the patient is being transported to the hospital, until poisoning is ruled out or treatment is finally begun.

In the emergency department, attention should, first of all, be given to the patency of the respiratory tract, the state of the respiratory and cardiovascular systems. The circumference of the limb is measured on arrival and every subsequent 15-20 minutes, until the limb size increases; It is useful to mark the edges of the local edema with an indelible marker to assess the progress of local poisoning events. All non-trivial bites of rattlesnakes require a complete clinical blood test (including platelets), a coagulogram (eg, prothrombin time, APTT, fibrinogen), concentration of fibrin degradation products, clinical urine analysis, and electrolytes, urea nitrogen and creatinine in the blood. In case of moderate and severe poisoning, patients are assessed blood group and compatibility, perform ECG and chest x-ray, and also test for CK, usually every 4 hours for the first 12 hours and then daily or depending on the patient's condition. When biting coral snakes with neurotoxic poison, control of oxygen saturation, determination of initial parameters and dynamics of functional pulmonary tests (for example, peak flow, vital capacity of the lungs) is necessary.

All victims of biting rattlesnakes need careful medical supervision for at least 8 hours after bite. Patients without obvious signs of poisoning within 8 hours can be released after appropriate treatment of wounds. Victims of bites of the coral snake should be observed for at least 12 hours, paying special attention to the possibility of paralysis of breathing. Poisoning, initially regarded as moderate, can become severe within a few hours. Without constant observation and appropriate treatment, the patient may die.

Treatment may include support breathing, the introduction of benzodiazepines during excitation, opioid analgesics for pain, transfusion of liquids and the injection of vasopressors in shock. Most coagulopathies react to sufficient amounts of a neutralizing antidote. You may need blood transfusion (for example, washed red blood cells, fresh frozen plasma, cryoprecipitate, platelets), but they can not be performed before the patient receives the required amount of antidote. In the case of trismus, laryngospasm, or excessive salivation, trachostomy is indicated.

Antidote

With moderate and severe poisoning, apart from aggressive symptomatic therapy, the correct choice of antidote plays an important role.

In the treatment of poisoning from a rattlesnake bite, horse antidote was replaced with a sheep polyvalent immune FAb-antidote against the poison of the family of yamkogolovyh (purified FAb fragments of IgG are taken from sheep immunized with rattlesnake venom). The effectiveness of equine antidote depends on time and dose; it is most effective within 4 hours after the bite and its effectiveness decreases after 12 hours, although it can prevent coagulopathy and after injection after 24 hours. According to the latest data, the effect of the polyvalent immune FAb antidote against the poison of the family of the Yamkogolovye does not depend on either time or dose and it can be effective even after 24 hours from the moment of the bite. It is also safer than the horse antidote. However, it can still cause early reactions (cutaneous or anaphylactic) and late hypersensitivity reactions (serum sickness). Serum sickness develops in 16% of patients for 1-3 weeks after the application of FAb-antidote. The dose of 4-6 vials of the reconstituted polyvalent immune FAb antidote against the poison of the family of pits, dissolved in 250 ml of 0.9% sodium chloride solution, is administered slowly at a rate of 20-50 ml / h for the first 10 min. After, if there are no adverse reactions, the remainder is administered within the next hour; the same dose can be reintroduced as needed to treat coagulopathy or correct physiological parameters. For children, the dose is not reduced (that is, the dose is not adjusted for body weight or height). Measuring the circumference of the affected limb at 3 points proximally from the site of the bite and measuring the widening border of the edema every 15-30 minutes, you can decide on the need for additional doses. As soon as swelling ceases to build up, the contents of 2 bottles dissolved in 250 ml of 0.9% sodium chloride solution are injected through 6.12 and 18 hours to prevent the resumption of edema of the limb and other effects of the poison.

With the bites of aquatic thyroid mucosa, the dose can be reduced. When biting the copper-head of snakes and dwarf thunders, an antidote is usually not required, except for children, elderly people and patients with certain diseases (for example, diabetes mellitus, coronary heart disease).

With bites of the coral snake, the horse antidote is administered in a dose of 5 vials in case of suspected poisoning and an additional 10-15 vials if signs of poisoning develop. The dose in adults and children is the same.

In cases where a horse antidote is required, the determination of sensitivity to horse serum using skin tests is questionable. Skin tests do not have predictive value for the development of immediate-type hypersensitivity reactions, and a negative test result does not completely exclude the possibility of this reaction. However, if the result of skin tests is positive, and the poisoning poses a threat to the limb or life, before blocking the antidote introduce H1 and H2 receptor blockers in an intensive care unit ready for the treatment of anaphylactic shock. Early pseudo-anaphylactic reactions to the antidote occur frequently, usually due to too rapid administration. The introduction is temporarily discontinued, epinephrine, H - and H receptors and intravenous blockers are injected, depending on the severity of the reactions. The introduction of the antidote is usually renewed, reducing its concentration by dilution and at a lower rate. After 7-21 days after treatment, there may be a serum sickness, which manifests itself in the form of fever, rash, malaise, urticaria, arthralgia and enlarged lymph nodes. Serum disease is treated with the administration of H1-receptor blockers and a reduced course of glucocorticoids administered internally.

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Additional measures

Patients need tetanus prophylaxis in accordance with their immunological history. Infection of places of snake bites occurs rarely, and antibiotics are used only in the occurrence of clinical manifestations. If necessary, appoint cephalosporins of the first generation (for example, cephalexin inwards, cefazolin intravenously) or a group of broad-spectrum penicillins (eg, inside amoxicillin + [clavulanic acid], intravenously ampicillin + [sulbactam]). The subsequent choice of antibiotic should be based on the results of bacteriological inoculation from the wound.

Bite wounds should be treated, like everyone else, and clean and close the area of the bite with an aseptic bandage. When bitten in the limb, it is immobilized in a functional position, imposing the tire and lifting. The wound is inspected daily, sanitized, and the bandage is changed. Surgical repair of blisters, bloody vesicles or superficial necrosis is performed on the 3rd-10th day (several stages may be required). To sanitize the wound, you can appoint sterile whirlpool baths and other physiotherapy procedures. Fasciotomy in compartmental syndrome is required in rare cases, but is used when the pressure in the interfascial space exceeds 30 mm Hg. For an hour, causes vascular disorders and does not decrease with a change in the position of the limb, intravenous administration of mannitol in a dose of 1-2 g / kg or with the antidote. The motor activity, muscular strength, sensitivity and limb diameter should be monitored for 2 days after the bite. To avoid contractures, immobilization is often interrupted by periods of light exercise, moving from passive to active movements.

In the United States, regional poison control centers and zoos are excellent sources of information in cases of a snake bite, even if it is not endemic to a given territory. These institutions have a list of doctors trained in the treatment of snake bites, published and periodically updated by the American Association of Zoos and Aquariums and the American Association of Poison Control Centers, a directory that catalogs the location and the number of antidote vials from the bites of all available and known venomous snakes, as well as the most exotic ones varieties.

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