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Bites & Envenomation

Animal bites High-yield Verified · Sep 2026

Bites and envenomation are injuries from an animal's or person's teeth (with risk of infection, tetanus and rabies) or from a venomous snake or spider that injects toxin (local tissue damage, coagulopathy, neurotoxicity or systemic illness).

A bite is a contaminated puncture, and sometimes a venom injection. The nurse washes it, asks what animal and when, checks tetanus status, knows when rabies prophylaxis starts, and — for a snakebite — marks the swelling edge with the time and watches for bleeding, low blood pressure, weakness and an allergic reaction to antivenom.

What’s going wrong in the body

The normal physiology, where it fails, and why the body’s compensation backfires.

01 Bite wounds — mouth flora driven into tissue

StatPearls: "Infections resulting from animal bites are typically polymicrobial, involving aerobic and anaerobic bacteria. The specific pathogens present often reflect the oral flora of the biting animal."

Cats. "Pasteurella multocida is the most commonly isolated pathogen." "Cat bites are narrow and deep and may appear innocuous until infection is evident." "Cat bites have the highest infection rate and often trigger significant localized or systemic inflammatory responses, leading to osteomyelitis, sepsis, meningitis, endocarditis, and pneumonia" (StatPearls).

Dogs. "Dog bites often result in crush injuries due to their strong jaws, leading to a combination of tearing, puncture wounds, and avulsions." Pasteurella canis is the most frequently isolated organism. "Immunocompromised individuals, particularly those who are asplenic, face an increased risk of infection from Capnocytophaga canimorsus" (StatPearls).

Rates (StatPearls, not merged). "The incidence of infection after a dog bite ranges from 2% to 25%." "Cat bites have an infection rate of about 30% due to the inoculation depth of pathogens." In one prospective study, "14% of dog bites were infected compared with 58% of cat bites." "Hand bites require close monitoring, as nearly 33% of hand bites become infected."

Humans — the fight bite. "Unlike other animal bites, human bites are commonly acquired as a closed-fist injury where one individual punches another in the face and lacerates their hand on the other’s teeth." "Direct joint and tendon sheath inoculation after the fist is relaxed allow bacteria deep penetration to normally sterile anaerobic environments" (StatPearls, Human Bites). "Herpes, hepatitis, and human immunodeficiency viruses are all transmissible through bite injuries."

Bite wounds by species: cat bites are deep punctures with the highest infection rate, dog bites crush and tear, and human fist bites seed the MCP joint and tendon sheath (StatPearls).

02 Rabies — a race to the nervous system

"Rabies is a zoonotic infection transmitted to humans through contact with the saliva of an infected animal's saliva via a bite, open wound, abrasion, conjunctiva, or mucous membranes, including genitalia." "Bite exposures carry a much higher risk of rabies transmission than nonbite exposures" (StatPearls).

Incubation. "The incubation period of rabies can range from a few days to a few years, with an average of 20 to 90 days." "Once peripheral neuroinvasion occurs, RABV travels proximally through retrograde axoplasmic flow." "Exposure in a proximal location, such as the head and neck, often results in a shorter incubation period" (StatPearls).

Why immune globulin plus vaccine. ACIP: "Once in tissues at the entry site, rabies virus can be neutralized by passively administered rabies immune globulin (RIG). Active immunization (vaccine) stimulates the host immune system, and, as a result, virus-neutralizing antibodies (VNA) are produced approximately 7--10 days after initiation of vaccination."

Once symptoms start. "Once symptoms manifest, the infection has an almost 100% fatality rate" (StatPearls). "Observational studies indicate that PEP is universally effective in preventing human rabies when administered promptly and appropriately" (ACIP).

Carriers. "Wild animals such as bats, raccoons, skunks, and foxes are the most common rabies carriers in the United States" (StatPearls). "Exposure to healthy-appearing, normal-behaving rabbits, hares, and small rodents rarely constitutes a risk requiring PEP."

US rabies postexposure prophylaxis (ACIP 2010): wash immediately, give rabies immune globulin once on day 0 into and around the wound, and vaccinate in the deltoid on days 0, 3, 7 and 14 (plus day 28 if immunosuppressed); previously vaccinated people get days 0 and 3 only.

03 Snake venom — tissue, blood and nerves

Local damage. "Local tissue destruction is primarily due to hyaluronidase and proteolytic enzymes in the snake venom, which can lead to local tissue edema, blistering, and tissue necrosis" (StatPearls).

Blood. "Most of the toxins lead to an increased bleeding tendency secondary to a consumptive coagulopathy and defibrination" (StatPearls).

Nerves. "Presynaptic neurotoxins, such as phospholipase A2, damage the terminal axon, which prevents the release of acetylcholine, causing diffuse paralysis" (StatPearls). For North American pit vipers, "Neurotoxins are uncommon among North American Crotalids" (StatPearls, Crotalidae Envenomation).

Pit vipers (US). Rattlesnakes, copperheads and cottonmouths are the three US Crotalidae (StatPearls). "The most common localized findings following pit viper envenomation are pain, edema, ecchymosis, and erythema in descending order." "Approximately 20 to 25% of bites result in no envenomation" — a dry bite (StatPearls, Crotalidae Envenomation).

Pit viper envenomation: first aid without tourniquet, ice, cutting, suction or NSAIDs; serial swelling measurements and coagulation labs; antivenom if swelling progresses or systemic signs appear; dry or mild bites are observed 6–8 hours (NIOSH; StatPearls).

04 Spiders — neurotoxic vs necrotic

Black widow (Latrodectus). "The primary toxin found in the venom of the black widow is alpha-latrotoxin." The resulting neurotransmitter release "leads to the characteristic symptomatology of pain, muscle rigidity, vomiting, and sweating." It is "easily identified by its characteristic shiny black body and strikingly red hourglass-shaped marking on the abdomen" (StatPearls).

Brown recluse (Loxosceles). "Brown recluse spider venom is cytotoxic and hemolytic." "Sphingomyelinase D, one of the more well-studied components, has been shown to direct toxin-mediated hemolysis and complement-mediated erythrocyte destruction" (StatPearls). Many suspected bites are something else — "like methicillin-resistant staph aureus skin infections."

Causes & risk factors

Modifiable factors are teaching targets — the patient can act on them.

Dogs and cats — "Dog bites account for 60% to 90%, and cat bites 5% to 20% of bites receiving care" (StatPearls); "the dog is often known to the patient" Children — bitten "on the head, face, and neck due to their proportionately larger heads and shorter stature" (StatPearls) Unsupervised children around pets — "Parents should supervise children around pets" (StatPearls) modifiable Fights — human bites "are most commonly closed-fist injuries" (StatPearls, Human Bites) modifiable Unvaccinated pets; wildlife and bats — "All persons with pets should be counseled regarding the importance of pet vaccinations" (StatPearls); wildlife is the main US rabies source modifiable Handling snakes — NIOSH: "NEVER handle a venomous snake, not even a dead one or its decapitated head." modifiable Infection risk factors — "comorbidities, location, and bite size, including bites greater than 3 cm, bites on the hand, and time from bite to medical attention" (StatPearls); asplenia (Capnocytophaga)

Signs & symptoms

Each finding tied to the mechanism that produces it — and the triage it calls for.

Any venomous snakebite — even without symptoms yet Report immediately
Why: NIOSH: "Seek emergency medical attention as soon as possible to start antivenom (if needed) and stop irreversible damage." "Do not wait for symptoms to appear; get medical help right away."
Severe envenomation — hypotension, angioedema, weakness, ptosis, trouble breathing, bleeding from the bite, nose or elsewhere Report immediately
Why: StatPearls: "5 to 10% of envenomations result in life-threatening coagulopathies." Neurotoxicity can progress to "respiratory failure secondary to obstruction or paralysis of the diaphragm." NIOSH: "In extreme cases, breathing may stop."
Animal bites to the face, hands or genitals, or with extensive tissue damage; animal bites to the head, neck or chest Report immediately
Why: StatPearls: patients need "Clear guidance on when to seek emergency care, such as for bites involving the face, hands, or genitals, or those with extensive tissue damage." Head, neck and face bites "have a high mortality, especially in children"; "Chest bites pose a risk for pneumothorax and spinal cord injury."
Possible rabies exposure — bite or scratch from a bat, raccoon, skunk, fox or unknown animal; a bat found in a room with a child or a deeply sleeping, mentally disabled or intoxicated adult Hold & notify
Why: ACIP: "All PEP should begin with immediate thorough cleansing of all wounds with soap and water." "The first dose of the 4-dose regimen should be administered as soon as possible after exposure." StatPearls: a bat in a room with a child or a deeply sleeping adult typically constitutes an exposure; puncture marks "can be extremely small."
Rabies symptoms — fever, pain or tingling at the old wound, then confusion, hallucinations, hyperactivity, hydrophobia, paralysis Report immediately
Why: StatPearls: "Once symptoms manifest, the infection has an almost 100% fatality rate." Early illness is "vague, febrile" with "pain and paresthesias at the wound site."
Increasing redness, swelling, warmth, pus or lymphangitis at a bite, 12 to 18 hours or more later Hold & notify
Why: StatPearls: "Infections typically present within 12 to 18 hours after injury, characterized by erythema, induration, pain, and purulent drainage." Signs "may be muted in the immunocompromised." Joint or systemic involvement needs IV antibiotics and admission.
Any laceration over a knuckle (MCP joint) Hold & notify
Why: StatPearls: "Any laceration to the MCP-joint is a closed-fist injury until proven otherwise." These wounds are "less than 2cm long" and easy to overlook.
Pit viper bite: swelling spreading past the marked edge Hold & notify
Why: StatPearls: "Antivenom is indicated if swelling progresses beyond the bite site."
Rash or a flu-like illness up to 2 weeks after antivenom Hold & notify
Why: StatPearls: serum sickness "may occur up to 2 weeks after administration. This usually presents as an influenza-like illness with a rash, and possible microhematuria."
Black widow: spreading muscle pain, rigidity, cramping, abdominal pain, sweating, tachycardia, hypertension Hold & notify
Why: StatPearls: "Neuromuscular symptoms, including severe muscle pain and cramping, usually occur within an hour." "Most pain and systemic symptomatology are self-limited"; antivenom is considered when symptoms are "not effectively treated with analgesics."
Brown recluse: painless bite that becomes painful, then a blister and a violet, sunken center Hold & notify
Why: StatPearls: "The initial bite will be painless, but over the subsequent two to eight hours it will become increasingly painful." Healing "can take several weeks."
Brown recluse in a child: weakness, fever, joint pain, hemolysis, seizures Report immediately
Why: StatPearls: in children "the systemic reaction is more severe" and can include "hemolytic anemia, thrombocytopenia, organ failure, disseminated intravascular coagulation, seizures, and death." "Hemolysis has been reported up to 7 days after spider bite."
Local pain and redness after a spider bite that stays local Expected
Why: StatPearls (black widow): the bite area "may become painful, erythematous, and edematous"; in a large series most patients had minor effects, and "Recovery is usually complete within 24 to 48 hours."

Diagnostics

Test In this disorder Normal
Bite history StatPearls: "Determine if the bite was provoked or unprovoked, as unprovoked attacks may raise concerns about rabies risk." Review "allergies; immunosuppressive conditions" and "tetanus and rabies vaccination status." Time, place, provoked or not, species, animal's health and vaccination, where it is now —
Wound exam StatPearls: "Assess for any nerve or vascular injury by evaluating sensation, motor function, and distal pulses." "Test the movement of affected and adjacent joints to detect potential tendon or joint involvement." Infection signs; nerve, vessel, tendon or joint injury; embedded teeth —
X-ray; wound culture StatPearls: radiographs detect bone involvement, "retained foreign bodies, such as teeth fragments or debris," and gas; culture before antibiotics "If there are signs of infection." Fracture, retained tooth fragments, gas; organism if infected —
Pit viper labs StatPearls, citing the Wilderness Medical Society: "All potential victims of pit viper envenomation should have a complete blood count (CBC), partial thromboplastin time (PTT), prothrombin time (PT), international normalized ratio (INR), and fibrinogen level checked where available." CBC, PT, INR, PTT, fibrinogen — repeated at the end of observation —
Serial swelling measurements StatPearls: "Place an ink mark on the proximal edge of the bite swelling as a baseline for serial measurements." "Measure the swelling extension and record circumference every 15 to 30 minutes"; hourly after four measurements without progression. Leading edge marked with the time; circumference every 15–30 minutes —
Compartment pressure (if suspected) StatPearls (Crotalidae Envenomation): diagnosis should not rely on "soft" signs "but should be through direct compartment pressures or evidence of neurovascular compromise where direct pressures are unobtainable." "Compartment syndrome is a rare but serious complication of pit viper envenomation." > 30 mm Hg consistent with early compartment syndrome —
Brown recluse: urinalysis; labs if systemic StatPearls: "At a minimum, one should obtain a urinalysis at the initial visit if the working diagnosis is a brown recluse spider bite and the patient is being discharged." Labs otherwise only "if there are systemic complaints, especially in children." Hemoglobinuria / hemolysis —

Complications

Black-box warning — most severe: ■ Severe snake envenomation Report immediately
StatPearls (Crotalidae Envenomation): "5 to 10% of envenomations result in life-threatening coagulopathies with profound localized findings of erythema and edema. Severe systemic signs such as hypotension, angioedema, and any signs of neurotoxicity may present." StatPearls: "Reports exist of massive coagulopathies leading to profound blood loss."
StatPearls: "Antivenom should be administered within four hours, or as soon as possible thereafter, from the snakebite for optimal effect. Antivenom administration is intravenous." Resuscitation includes "intubation for those with respiratory distress or paralysis and IV fluids for those exhibiting signs of shock." "There is no evidence of the empiric use of blood products, such as platelets or fresh frozen plasma."
Black-box warning — most severe: ■ Rabies Report immediately
StatPearls: "Once symptoms manifest, the infection has an almost 100% fatality rate. In all but the rarest of cases, clinicians can only provide palliative care to minimize the patient's pain and suffering before death." StatPearls: "Without appropriate prophylaxis, tetanus and rabies can have fatal consequences."
Warning: Antivenom reactions
StatPearls: an "anaphylactic reaction that may occur within the first few minutes of administration and up to 2 hours. If a severe anaphylactic response is suspected, the infusion should stop, and the administration of epinephrine and an anti-histamine should follow." Serum sickness may follow up to 2 weeks later. Black widow antivenom "has been associated with several severe allergic reactions."
Warning: Deep bite infection Hold & notify
StatPearls: "Common infectious complications include cellulitis, abscess formation, osteomyelitis, tenosynovitis, endocarditis, and meningitis." Human bites: "patients who delay treatment tend to have adverse outcomes. In most cases, a florid infection develops which can involve the entire hand."
Warning: Systemic loxoscelism (brown recluse)
StatPearls: "hospital admission is the recommendation for patients with hemolytic anemia, rhabdomyolysis, disseminated intravascular coagulation or end-stage organ failure." "Death is rare but has been reported especially in children."
Caution: Lasting injury and distress
NIOSH: "Among people bitten by rattlesnakes, an estimated 10%–44% have lasting effects, such as loss of part or all of a finger or impaired use of the affected area." StatPearls: "Psychological effects, including post-traumatic stress disorder, may also develop following an animal bite in both adults and children."

Medications for this condition

Why each class is prescribed here — every card links to its full pharmacology page.

Penicillins First-line
Immune / Anti-infective · amoxicillin

Amoxicillin-clavulanate — bite prophylaxis. StatPearls: "Prophylactic antibiotics targeting oral flora and skin microbes are warranted for all bites penetrating the epidermis or deeper." "Amoxicillin-clavulanate is the preferred prophylactic antibiotic, with extended-spectrum cephalosporins recommended for patients who are allergic to penicillin." Human bites: "All human bite wounds that pierce the skin should receive amoxicillin-clavulanate prophylaxis for a week." Systemic, joint or intracavitary infection: IV "ampicillin-sulbactam, and hospital admission for further care."
Vaccines & Immunizations
Immune / Anti-infective

Tetanus and rabies vaccines. CDC: bites are dirty wounds ("Wounds containing dirt, soil, feces, or saliva (e.g., animal or human bites)"); give tetanus vaccine for an unknown, absent or incomplete primary series, or if the last dose was 5 or more years ago. Rabies (ACIP): "The deltoid area is the only acceptable site of vaccination for adults and older children. For younger children, the outer aspect of the thigh may be used. Vaccine should never be administered in the gluteal area." Pre-exposure vaccination is considered for "veterinarians, animal handlers, and laboratory workers" (StatPearls).
Opioid Analgesics High-alert
Nervous · morphine

Envenomation pain. Pit viper: "clinicians should avoid NSAIDs due to the potential to worsen coagulopathy and platelet aggregation." "Because of this theoretical risk, opioid analgesics are the recommended agents for adequate pain control" (StatPearls, citing the Wilderness Medical Society). Black widow, moderate–severe: "the use of opioids for pain management and benzodiazepines for muscle spasm control, as needed. Caution is necessary when co-administering opioids and benzodiazepines" — "Prescribing agents from both classes at discharge is not recommended" (StatPearls).

Beyond medications

  • Irrigate and debride — StatPearls: "Proper wound care, including thorough irrigation, debridement of devitalized tissue, and prompt antibiotic administration when indicated, significantly reduces the risk of infection."
  • Leave open or close? — "Cat bites are inherently high-risk and typically left open." "Deep puncture wounds and those involving joint spaces should not be closed." "Uncomplicated wounds can be safely closed after extensive cleaning and debridement if presenting within 8 hours of injury." StatPearls, citing IDSA: leave bite wounds open "unless there is a cosmetic concern, such as on the face." Human bites "in most cases should be left to heal by secondary intention."
  • Fight bite — "If signs or symptoms of infection in a joint space or tendon sheath are present orthopedics should be consulted for evaluation for surgical washout and inpatient treatment with IV antibiotics" (StatPearls, Human Bites). "HIV prophylaxis is only indicated if the wound is percutaneous and the mouth was contaminated with blood."
  • Tetanus immune globulin (CDC) — "TIG is never indicated for clean and minor wounds." For dirty wounds such as bites, TIG is for unknown or incomplete vaccination history, people who never received tetanus vaccine, people with HIV, and people with a severe immunodeficiency. "Healthcare providers shouldn't use antibiotics (topical or systemic) to try to prevent tetanus after a wound injury (potential tetanus exposure)."
  • Rabies immune globulin (ACIP) — "If anatomically feasible, the full dose should be infiltrated around and into the wound(s), and any remaining volume should be administered at an anatomical site (intramuscular [IM]) distant from vaccine administration. Also, HRIG should not be administered in the same syringe as vaccine." Given once, on day 0, only to people never vaccinated against rabies. WHO's 2018 schedule, relayed by StatPearls, differs — follow ACIP and public health in the US.
  • Snakebite first aid (NIOSH) — "Lay or sit down with the bite in a neutral position of comfort." "Remove rings and watches before swelling starts." "Wash the bite with soap and water." "Cover the bite with a clean, dry dressing." "Mark the leading edge of tenderness/swelling on the skin and write the time alongside it." "Do not drive yourself to the hospital because the snakebite can make you dizzy or pass out."
  • Snakebite — never (NIOSH) — "Do not apply a tourniquet, electric shock, or folk therapies." "Do not slash the wound with a knife or cut it in any way." "Do not try to suck out the venom." "Do not apply ice or immerse the wound in water." "Do not drink alcohol as a painkiller or take pain relievers (such as, aspirin, ibuprofen, naproxen)." StatPearls, citing the Wilderness Medical Society: ice "is ineffective at controlling swelling due to envenomation"; tourniquets "can increase tissue damage"; excision and suction "increases local tissue damage." Heart-level positioning is debated and "should only occur if it will not delay transportation."
  • Pit viper — observe or treat — "Patients with an apparent dry bite or mild envenomations should have monitoring for 6 to 8 hours." "All patients with more than a mild envenomation should receive antivenom." "Aggressive surgical intervention is not indicated, including prophylactic wound excision or fasciotomy" (StatPearls). A regional poison center or medical toxicologist can help decide on antivenom (StatPearls).
  • Black widow — "The initial management for all cases of black widow envenomation includes local wound management and tetanus prophylaxis. Calcium gluconate and methocarbamol have been shown to be ineffective and are no longer recommended" (StatPearls). Do not try to catch the spider.
  • Brown recluse (spider scope only) — StatPearls: "Elevate the extremity above the heart or at least in a neutral position. The activity of sphingomyelinase D is temperature dependent so an ice pack to the area should help halt the necrosis process." "Antibiotics are only necessary if there is associated cellulitis." "Early surgical debridement is not advisable." Dapsone has scant evidence and "can also cause deadly hypersensitivity reactions."

Nursing considerations

The RN-specific layer — each action paired with the reason it matters.

Assessment
Take the bite history — animal, provoked or not, the animal's vaccination and whereabouts — plus tetanus and rabies vaccination status and immune status.
Why: StatPearls: unprovoked attacks "may raise concerns about rabies risk"; immunosuppression, asplenia and diabetes change infection risk and treatment.
Check sensation, motor function, distal pulses and joint movement beyond the bite; examine the hands of anyone injured in a fight.
Why: StatPearls: "Any patient arriving after or due to an altercation should have his or her hands examined for possible fight bites."
Snakebite: mark the leading edge of swelling with the time, measure circumference every 15 to 30 minutes, and check distal pulse, sensation and motor function.
Why: StatPearls: "Antivenom is indicated if swelling progresses beyond the bite site." "The nursing staff will continuously monitor the patient for any progression of systemic toxicity."
Neurotoxic snakebite: frequent neurologic checks and end-tidal CO2 or blood gases.
Why: StatPearls: monitoring for "developing respiratory acidosis" as paralysis can reach the diaphragm.
In a child with a bite, measure an occlusion bite and consider who bit the child.
Why: StatPearls (Human Bites): an intercanine distance over 3 cm "most likely came from an adult and should raise suspicion of abuse"; "CPS should be contacted."
Interventions
Wash the wound immediately and thoroughly with soap and water; irrigate as ordered; give pain relief before exploration or debridement.
Why: ACIP: "All PEP should begin with immediate thorough cleansing of all wounds with soap and water." StatPearls: "Provide appropriate pain management before exploration, irrigation, or debridement of the wounds."
Give rabies immune globulin once (day 0) as ordered, infiltrated into and around the wound, never in the same syringe as the vaccine; give rabies vaccine IM in the deltoid (outer thigh in young children), never the gluteal area.
Why: ACIP 2010 PEP rules; "Vaccine should never be administered in the gluteal area."
Start antivenom slowly as ordered and stay with the patient; have epinephrine and an antihistamine ready; stop the infusion for anaphylaxis.
Why: StatPearls: "Start infusion at 25 to 50 mL/hr for the first 10 minutes and monitor for allergic reactions"; anaphylaxis can occur "within the first few minutes of administration and up to 2 hours."
Remove any tourniquet, rings and constricting clothing on a snakebitten limb; do not ice it; give opioids, not NSAIDs, for pain as ordered.
Why: StatPearls, citing the Wilderness Medical Society: "any tourniquet should be removed"; ice is ineffective and "intensive cryotherapy has been shown to worsen outcomes"; NSAIDs may "worsen coagulopathy and platelet aggregation."
Update tetanus by wound type and history; do not expect antibiotics to prevent tetanus.
Why: CDC: bites are dirty wounds; "TIG cannot neutralize toxin that's already bound to nerve endings."
Patient teaching
Return for increasing redness, swelling, warmth or pus at the bite; seek emergency care for animal bites to the face, hands or genitals or with extensive damage.
Why: StatPearls: patients "should understand the signs of infection" and need "Clear guidance on when to seek emergency care."
Finish every rabies vaccine dose on schedule (days 0, 3, 7, 14; day 28 too if immunosuppressed).
Why: ACIP: PEP "is universally effective in preventing human rabies when administered promptly and appropriately."
After antivenom, report a rash or a flu-like illness over the next 2 weeks; after a dry or mild snakebite, return for bleeding, swelling or worse symptoms.
Why: StatPearls: serum sickness "may occur up to 2 weeks after administration"; discharged patients "should be counseled to return for any signs of bleeding, swelling, or worsening symptoms."
Brown recluse bite in a child: keep follow-up and return for weakness, fever or joint pain in the week after the bite.
Why: StatPearls: "Hemolysis has been reported up to 7 days after spider bite so adequate follow up instructions should be given to parents of children even if there are no systemic findings during the ED visit."
Photograph a snake from a safe distance — never try to catch, kill or handle a snake or spider. Supervise children around pets and vaccinate pets.
Why: NIOSH: "Do not pick up the snake or try to trap it." StatPearls: patients should not "capture, harm, or handle the spider"; "All persons with pets should be counseled regarding the importance of pet vaccinations."

How a real nurse thinks

The clinical-judgment loop, worked for a typical presentation — reasoning, not reference.

  1. 1
    Recognize cues

    Pit viper bite with swelling spreading up the leg, severe pain, and a constricting band still on the calf. No hypotension, bleeding or neurotoxic signs yet.

  2. 2
    Analyze cues

    Swelling progressing beyond the bite means more than a mild envenomation, so antivenom is indicated. The tourniquet can increase tissue damage, and the bracelet can become constricting as the leg swells.

  3. 3
    Prioritize

    Remove the band and the jewelry, mark and measure the swelling, start antivenom safely, and watch for anaphylaxis, bleeding and hypotension.

  4. 4
    Generate solutions

    Mark the edge with the time; circumference every 15–30 minutes; distal checks; opioid analgesia as ordered (no NSAIDs); tetanus update; antivenom started slowly with epinephrine at the bedside.

  5. 5
    Take action

    The nurse removes the belt and the ankle bracelet, marks the swelling with the time, starts the antivenom at the slow initial rate and stays at the bedside for the first minutes, and gives IV opioid analgesia as ordered.

  6. 6
    Evaluate

    Over the next hours the swelling edge stops advancing, vital signs stay stable and no allergic reaction occurs. Before discharge she is told to report a rash or a flu-like illness over the next 2 weeks.

Scenario — you’re the nurse

Work each question before revealing the answer. Rationales explain the wrong options too.

Emergency department · early evening

A 42-year-old was bitten on the left ankle by a rattlesnake while clearing brush 50 minutes ago. A friend drove her in. She has a ring and an ankle bracelet on; a belt was tied around her calf at the scene.

Vital signs — HR 104 · BP 128/80 · RR 18 · SpO2 98%
Bite — two fang marks; swelling and bruising up to mid-calf; severe pain
Systemic — no bleeding; alert, no ptosis
Plan — CBC, PT/INR, PTT, fibrinogen; poison center consulted; antivenom ordered
Q1 Select all that apply
Which first-aid actions for a venomous snakebite are correct? Select all that apply.
  1. A. Remove rings and watches before swelling starts
  2. B. Apply ice to slow the venom
  3. C. Mark the edge of the swelling and write the time next to it
  4. D. Keep the bitten limb in a neutral position of comfort
  5. E. Cut over the fang marks and suck out the venom
Reveal answer & rationale
Answer: A, C, D
NIOSH: "Remove rings and watches before swelling starts" (A); "Mark the leading edge of tenderness/swelling on the skin and write the time alongside it" (C); "Lay or sit down with the bite in a neutral position of comfort" (D). "Do not apply ice" (B); "Do not slash the wound" and "Do not try to suck out the venom" (E).
Q2 Multiple choice
The patient asks for ibuprofen for her leg pain. What is the best response?
  1. A. Give ibuprofen — it also reduces swelling
  2. B. Explain that NSAIDs can worsen the bleeding tendency after a pit viper bite, and ask the provider about an opioid
  3. C. Apply ice instead of giving medication
  4. D. Pain relief should wait until the antivenom is finished
Reveal answer & rationale
Answer: B
StatPearls, citing the Wilderness Medical Society: "clinicians should avoid NSAIDs due to the potential to worsen coagulopathy and platelet aggregation," so "opioid analgesics are the recommended agents for adequate pain control" (B). Ice is ineffective and can worsen outcomes (C); there is no reason to withhold analgesia (D).
Q3 Multiple choice
Five minutes into the antivenom infusion the patient shows signs of a severe anaphylactic reaction. What should the nurse do first?
  1. A. Slow the infusion and recheck in 15 minutes
  2. B. Stop the infusion and prepare epinephrine and an antihistamine as ordered
  3. C. Continue the infusion because the envenomation is progressing
  4. D. Give acetaminophen and continue
Reveal answer & rationale
Answer: B
StatPearls: an anaphylactic reaction "may occur within the first few minutes of administration and up to 2 hours. If a severe anaphylactic response is suspected, the infusion should stop, and the administration of epinephrine and an anti-histamine should follow" (B). Slowing or continuing (A, C, D) leaves the allergen running during anaphylaxis.
Q4 Select all that apply
A man is bitten on the hand by a raccoon and has never had rabies vaccine. Which parts of US postexposure prophylaxis are correct? Select all that apply.
  1. A. Wash the wound immediately and thoroughly with soap and water
  2. B. Infiltrate rabies immune globulin into and around the wound on day 0
  3. C. Give the vaccine in the gluteal muscle
  4. D. Give vaccine on days 0, 3, 7 and 14
  5. E. Mix the immune globulin and vaccine in one syringe
Reveal answer & rationale
Answer: A, B, D
ACIP: "immediate thorough cleansing of all wounds with soap and water" (A); immune globulin once on day 0, infiltrated "around and into the wound(s)" (B); vaccine on days 0, 3, 7 and 14 (D). "Vaccine should never be administered in the gluteal area" (C); "HRIG should not be administered in the same syringe as vaccine" (E).
Q5 Multiple choice
A patient who punched someone yesterday has a small cut over a knuckle. Why does the nurse treat this as serious?
  1. A. Small cuts over the knuckle rarely become infected
  2. B. Any laceration over the MCP joint is a closed-fist injury until proven otherwise, and bacteria can reach the joint and tendon sheath
  3. C. Human bites carry no risk of viral infection
  4. D. It needs only a bandage and no antibiotics
Reveal answer & rationale
Answer: B
StatPearls: "Any laceration to the MCP-joint is a closed-fist injury until proven otherwise"; joint and tendon sheath inoculation lets bacteria penetrate deeply (B). Human bites can transmit herpes, hepatitis and HIV (C), and "All human bite wounds that pierce the skin should receive amoxicillin-clavulanate prophylaxis for a week" (D).

Common questions

What causes bites & envenomation?
Common causes and risk factors include dogs and cats — "dog bites account for 60% to 90%, and cat bites 5% to 20% of bites receiving care" (statpearls); "the dog is often known to the patient", children — bitten "on the head, face, and neck due to their proportionately larger heads and shorter stature" (statpearls), unsupervised children around pets — "parents should supervise children around pets" (statpearls), fights — human bites "are most commonly closed-fist injuries" (statpearls, human bites), unvaccinated pets; wildlife and bats — "all persons with pets should be counseled regarding the importance of pet vaccinations" (statpearls); wildlife is the main us rabies source, and others.
Why are cat bites more worrying than dog bites?
StatPearls: "Cat bites are narrow and deep and may appear innocuous until infection is evident," and they can reach bones and joints. Infection is about 30% for cat bites versus 2% to 25% for dog bites (StatPearls figures, from different reports).
Should a snakebitten arm be raised above the heart or put on ice?
No. NIOSH: keep the bite "in a neutral position of comfort" and "Do not apply ice." StatPearls says views on heart-level splinting vary. Elevation above the heart and an ice pack are StatPearls first aid for a brown recluse spider bite only.
Does every animal bite need rabies shots?
No — it depends on the animal and the exposure, and clinicians "should consult public health officials, according to local guidelines" (StatPearls). Bats, raccoons, skunks and foxes are the main US carriers; healthy rabbits and small rodents rarely require PEP. StatPearls adds: "If the rabies status of the biting animal may be ascertained, rabies treatment may be deferred. However, any bite, or even a suspected bite, especially from high-risk animals such as bats and skunks, requires treatment."
Does a bite always need a tetanus shot?
CDC: no vaccine is needed if the primary series is complete and the last dose was less than 5 years ago. Bites are dirty wounds, so a dose is given if the last one was 5 or more years ago or the series is incomplete or unknown.
How are black widow and brown recluse bites different?
Black widow venom is neurotoxic — pain, rigidity, cramping, sweating — and usually resolves in 24 to 48 hours. Brown recluse venom is "cytotoxic and hemolytic" — a painless bite that becomes a necrotic ulcer, with hemolysis possible in children (StatPearls).

Sources

Reviewed by Hae Suk Lee, RN

Educational summary for nursing students. Scenarios are fictional teaching cases. Always verify against current guidelines and your institution's protocols before acting in practice. Not medical advice.

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