Each year, two families of poisonous snakes have fatal encounters with their human neighbors. As warmer weather encroaches, hikers, athletes, gardeners and most anyone who spends a good deal of time outdoors is especially vulnerable to being bitten by a potentially venomous snake.
In the U.S., the majority of snakebite emergencies are caused from two main types of venomous snakes: pit vipers (Crotalidae) and coral snakes (Elapidae). The pit viper family includes rattlesnakes, copperheads and water moccasins. The coral snakes are rarely aggressive and account for only a small percentage of venomous snakebites.1
Pit vipers can be recognized by their triangular heads, elliptical pupils, facial pit between their eyes and nostrils, and retractable fangs. Coral snakes have a rounded head and a noticeable coloring of red, yellow, and black banding. They have non-retractable fangs that are shorter in length than the pit viper.
The first step in the assessment phase of nursing care is to determine if the patient has been envenomated. Signs and symptoms will vary based on the type of snake, temperature of the snake, time of day, amount of venom injected, the location and depth of the bite or bites, as well as the patient's age and current state of health.1
Signs & Symptoms
Within the first hour of a pit viper envenomation, the patient may experience pain, swelling, redness, or erythema at the site. Usually, the site will contain one or more fang marks or wounds in the skin. Occasionally, vesicles or hemorrhagic bullae may be present.1
Systemic symptoms from a pit viper bite include a metallic taste in the mouth, paresthesias, weakness, tachycardia, numbness, lethargy, altered mental status, muscle twitching, nausea, vomiting, hypotention, and seizures.
Severe envemonations may result in a prolonged PT, increased INR, decreased platlets, and a positive D-dimer.2 Pit viper venom can also increase the capillary permeability, leading to hemolysis. This may further lead to renal failure, DIC and shock.
Symptoms of coral snake envenomation are different from pit viper envenomation. On assessment, the patient may initially deny pain or swelling, but may complain of localized numbness. There may not be any noticeable fang marks. Systemic symptoms are delayed, not appearing for 12 or more hours after the bite (Nunnelee, 2007).2
Nursing Care & Treatment
Once symptoms do appear, however, they can be much more serious due to the fact that coral snake venom is a neurotoxin. Neurotoxic effects may include eyelid drooping, dysphagia, diplopia, diaphoresis, and tremors. Other symptoms are fatigue, salivation, weak muscles, dyspnea, euphoria, and respiratory depression. The patient may develop paralysis, respiratory failure, and death.
In the field, the first step is to get the patient to a place of safety, away from the snake. The patient needs to be instructed to move as little as possible in order to slow the circulation of venom. Remove all jewelry, clothing, and any constrictive item from the affected area.
Immobilize the extremity and keep it below the level of the heart. Discourage the patient from smoking, drinking caffeine or using any other stimulant.
Arrangements to transport the patient to a hospital should be made. Do not apply tourniquets, cut the incision, or suck the wound. If the patient is in a remote area, a constricting band may be applied to the wound two to four inches above the bite, but this action is controversial because it may worsen the effects on the tissues. This action is a judgment call; risks and benefits must be weighed.
If a constricting band is placed, it should be just tight enough to slip a finger underneath the band. Pulses should be checked often to assess arterial blood flow to the extremity. As the swelling rises up the extremity, the band should be moved higher up and loosened. Once the patient arrives at the hospital, the band is removed slowly, as not to release venom suddenly into the bloodstream.1
Patient assessment by nurses at this point should focus on ABC's, obtaining a history and gathering information about the snake itself.
Two large bore IVs should be started, with labs drawn concurrently. Baseline labs should include coagulation profile, CBC, electrolyte panel, blood typing, platelet count, D-dimer, urinalysis, metabolic panel, and liver panel (Nunnelee, 2007).2 Oxygen at 2- to 4L/min via nasal cannula should be administered. Other tests to consider include baseline EKG and chest X-ray. With coral snake envenomation, additional tests such as ABGs and neurological checks should be done because of the neurotoxic effects.
The bite area should be examined thoroughly and cleaned with soap and water. The circumference and characteristics of the extremity should be measured and marked every 15 to 30 minutes to evaluate edema progression. A tetanus booster is generally recommended if the patient has not had one within the last 5 years. Pain evaluation should be completed and discussed with the physician.3
Implications of Antivenin
If initial signs and symptoms are not severe enough to indicate antivenin, the patient must still be observed for at least eight hours due to the possibility of delayed onset. If there is a possibility that the bite was from a coral snake, the patient must be observed for 24-48 hours due to the fact that effects may take longer to arise.2
Because the coral snake bite is neurotoxic, the patient must be closely monitored for respiratory difficulty. Poison control should also be contacted when envenomation is suspected from either type of snake.
If the physician decides to order antivenin for the patient, the nurse must closely monitor the patient for anaphylactic reactions as well as serum sickness, or delayed hypersensitivity. The main types of antivenin for pit viper bites are Antivenin Crotalidae Polyvalent (ACP) and Crotalidae Polyvalent Immune Fab (CroFab).
Coral snake bites are treated with Eastern coral snake antivenin.4 Dosing is based on symptoms and titrated until the medication achieves control of local progression and resolves systemic issues.
Nursing care during and after antivenin treatment includes continual patient assessment, monitoring for systemic complications, and observing for reactions to the medication.
The wound should be kept clean and covered with a sterile dressing. Debridement may be indicated if tissue necrosis is present. Pulse checks and assessment for compartment syndrome in the affected extremity should be included in the assessment. Occasionally, a fasciotomy is performed if circulation is impaired.
Upon discharge, the patient should be instructed on signs and symptoms of a delayed hypersensitivity reaction to the antivenin, which can occur up to three weeks after administration. Symptoms include fever, joint pain, rash, or unusual bruising or bleeding.
Additionally, the patient will need follow-up appointments, especially when debridement or fasciotomy is part of the hospital care.
References for this article can be accessed here.