Spider Bite (Brown Recluse)MANAGEMENT

ENVIRONMENTAL AND EXPOSURE PRESENTATIONS · 12 SECTIONS

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595 items

☷ Legend

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Cardiovascular Presentations71▾

Respiratory Presentations52▾

Neurological Presentations83▾

Gastrointestinal Presentations74▾

Genitourinary and Reproductive Presentations48▾

Infectious Disease Presentations148▾

Trauma Presentations89▾

Toxicologic Presentations80▾

Psychiatric Presentations26▾

Musculoskeletal and Rheumatologic Presentations96▾

Dermatology Presentations23▾

Environmental and Exposure Presentations27▾

Acute Mountain Sickness Arterial Gas Embolism Bee-Wasp Sting (Anaphylaxis)Chilblains Ciguatera Fish Poisoning Coral Cut Decompression Sickness Electrical Burn Injury Envenomation (snake, spider, insect)High Altitude Cerebral Edema (HACE)High Altitude Pulmonary Edema (HAPE)High-altitude illness Hypothermia Hypothermia (Mild)Hypothermia (Severe)Immersion Foot Lightning Strike Injury Scombroid Fish Poisoning Scorpion Envenomation Sea Urchin Injury Shark Bite Snake Envenomation Spider Bite (Black Widow)Spider Bite (Brown Recluse)Stingray Spine Injury Tick paralysis White Phosphorus Burn

Hematologic and Oncologic Presentations36▾

Pediatric-Specific Presentations19▾

Endocrine and Metabolic Presentations45▾

ENT and Maxillofacial Presentations27▾

Ophthalmologic Presentations19▾

Obstetric Presentations23▾

Systemic and Miscellaneous Presentations17▾

01Approach to the Critical Patient/attcp47

Systemic loxoscelism recognition

›Alarm features for systemic envenomation

›Fever, rigors, malaise within 24-48 hours of bite

›Constitutional symptoms in up to 50% of systemic cases

›Myalgia independently associated with hemolysis (aOR 12.76)

›Dark or red urine (hemoglobinuria)

›Indicates intravascular hemolysis

›Hematuria in 32% of hemolytic cases

›Jaundice

›Bilirubin elevation from hemolysis

›Elevated transaminases in ~29% of hemolytic cases

›Petechiae or mucosal bleeding

›Suggests DIC

›DIC carries OR 82.9 for death

Hemodynamic and resuscitation priorities

›Immediate hemodynamic assessment

›Hypotension

›SBP < 90 mmHg requires IV fluid resuscitation

›Hemoglobin < 4 g/dL associated with vasopressor requirement

›Tachycardia

›Often reflects hemolysis-driven anemia or systemic toxicity

›Persistent tachycardia triggers urgent labs

›Resuscitation targets

›IV access and aggressive hydration

›Target urine output 1-2 mL/kg/hr to protect renal perfusion

›Hemoglobinuria requires high-volume hydration

›RBC transfusion threshold

›Transfuse if hemoglobin acutely < 7 g/dL or symptomatic anemia

02History/hx57

Bite event

›Bite circumstances

›Spider identified or captured

›Definitive diagnosis requires arachnologist identification

›Only confirmed if spider submitted for expert identification

›Typical exposure settings

›Rolling onto spider in bed

›Donning stored clothing or shoes

›Reaching into dark undisturbed areas (closets, attics, basements)

›Geographic plausibility

›Endemic to south-central US: Missouri, Kansas, Oklahoma, Arkansas, Tennessee

›Bites outside endemic range are extremely unlikely

Symptom timeline

›Wound progression

›Initial phase (0-4 hours)

›Often painless or mild burning

›Patients may be unaware of bite

›Early wound change (6-24 hours)

›Single flat erythematous lesion with central pallor

›Red, white, and blue sign: erythema, ischemia, ecchymosis

›Evolving wound (24-72 hours)

›Painful edema and induration

›Hemorrhagic blisters in necrotic cases

›Late wound (72+ hours)

›Necrotic eschar with well-defined borders

›Approximately 10% of bites develop necrosis

›Systemic symptoms

›Constitutional features

03Physical Exam/exam44

Vital signs

›Hemodynamic assessment

›Temperature

›Fever > 38.0 C suggests systemic loxoscelism

›Hypothermia possible in severe septic presentation

›Heart rate

›Tachycardia driven by hemolysis or systemic toxin

›Hemodynamic instability trigger for resuscitation

›Blood pressure

›Hypotension in severe systemic loxoscelism

›SBP < 90 mmHg triggers aggressive resuscitation

Wound assessment

›Local wound characterization

›Early wound (0-24 hours)

›Single flat lesion, distinguishes from other arthropod bites

›Central pallor with surrounding erythema

›Minimal surrounding edema at this stage

›Intermediate wound (24-72 hours)

›Ecchymosis and induration

›Hemorrhagic vesicle or blister

›Painful on palpation

›Late wound (72+ hours)

›Necrotic eschar with defined border

›Sunken center with surrounding induration

›Healing without intervention in most cases

›Common anatomic locations

›Upper arm, thorax, inner thigh, trunk

›Facial bites may produce extensive edema with less necrosis (oedematous variant)

04Differential Diagnosis/ddx40

Infectious mimics

›Bacterial skin infections

›MRSA or Staphylococcal abscess (ICD-10: L02)

›Most common mimic of necrotic spider bite

›Look for purulence, fluctuance, surrounding cellulitis

›Culture and sensitivities if drainage present

›Necrotizing fasciitis (ICD-10: M72.6)

›Rapidly progressive with systemic toxicity

›Pain out of proportion to findings

›Surgical emergency requiring immediate debridement

Viral skin infections

›Herpesvirus infections

›Herpes simplex virus (ICD-10: B00.1)

›Grouped vesicles on erythematous base

›Recurrent distribution pattern

›Tzanck smear or PCR for confirmation

›Herpes zoster (ICD-10: B02.9)

›Dermatomal distribution

›Burning prodrome before vesicles

›Older adults and immunocompromised at risk

Inflammatory and other dermatologic conditions

›Pyoderma gangrenosum (ICD-10: L88)

›Autoimmune etiology

›Undermined violaceous wound borders

›Associated with IBD, rheumatoid arthritis, hematologic malignancy

›Worsens with debridement (pathergy)

›Cutaneous anthrax (ICD-10: A22.0)

›Bioterrorism consideration

05Laboratory Tests/lt63

Initial screening labs

›Uncomplicated cutaneous bite

›Laboratory evaluation generally not required

›Reserved for systemic symptoms

›Observation with return precautions adequate if no systemic features

›Complete blood count

›Hemolytic anemia detection

›Average hemoglobin drop 3.1 g/dL over approximately 2 days in hemolytic cases

›Hemoglobin < 4 g/dL associated with complications requiring ICU

›Serial CBC every 6-12 hours if hemolysis suspected

Hemolysis markers

›LDH and total bilirubin

›Most sensitive combination for preclinical hemolysis

›Sensitivity 94% for hemolysis detection

›Specificity 91% for hemolysis detection

›Elevated before CBC shows significant drop

›LDH elevation pattern

›Rise precedes clinical jaundice

›Trend guides severity monitoring

›Reticulocyte count

›Bone marrow compensatory response

›Elevated reticulocytes confirm hemolytic process

›Reticulocytopenia would suggest aplastic crisis

›Haptoglobin

›Consumed by free hemoglobin

›Low or undetectable in intravascular hemolysis

›Acute phase reactant limitation (may be falsely normal in inflammation)

›Peripheral blood smear

06Diagnostic Tests/dt37

Scoring Systems

›No validated clinical scoring system for loxoscelism severity

›Risk stratification based on clinical and laboratory features

›Constitutional symptoms (myalgia aOR 12.76, malaise aOR 7.1) predict hemolysis

›Geographic plausibility is a key diagnostic requirement

›Loxoscelism clinical classification

›Cutaneous loxoscelism: local wound only

›Cutaneous-hemolytic loxoscelism: wound plus systemic hemolysis

›Systemic loxoscelism: multiorgan involvement with hemolysis, DIC, renal failure

MRI

›MRI role in wound assessment

›Generally not indicated for routine spider bite evaluation

›Reserved for concern about deep tissue infection

›Necrotizing fasciitis evaluation if diagnosis uncertain

›MRI characteristics of necrotizing fasciitis

›T2 hyperintensity along fascial planes

›Gas tracking in fascial layers (hypointense on all sequences)

›Sensitivity for necrotizing fasciitis approximately 90%

›CT indications in loxoscelism

›Deep tissue infection assessment

›CT of soft tissue if necrotizing fasciitis suspected

›Gas in soft tissues is diagnostic of gas-forming infection

›Abdominal CT in systemic loxoscelism

›Hepatosplenomegaly quantification

›Excludes alternative diagnoses causing systemic illness

›CT chest if respiratory compromise

›Pulmonary edema in severe hemolysis

07Disposition/dispo39

Discharge criteria

›Safe discharge requirements

›Uncomplicated cutaneous bite criteria

›No systemic symptoms (fever, myalgia, malaise)

›Normal vital signs

›No laboratory evidence of hemolysis if tested

›Wound appearance at discharge

›Stable or early-stage wound

›No rapidly expanding necrosis or hemorrhagic blisters

›Follow-up plan

›Wound recheck in 48-72 hours

›Weekly wound assessment until healed

›Return precautions provided

Admission indications

›Observation or floor admission criteria

›Constitutional symptoms

›Fever, myalgia, malaise especially in children

›High risk of progression to hemolysis

›Laboratory hemolysis evidence

›Elevated LDH or total bilirubin

›Hemoglobinuria on urinalysis

›Wound complications

›Rapidly expanding necrosis

›Hemorrhagic blisters

›Secondary infection concern

ICU admission indications

›Critical care criteria

›Severe hematologic complications

08Treatment/t94

Initial wound care

›First-line local wound management

›Wound cleaning

›Soap and water irrigation

›Remove any remaining venom material

›Tetanus prophylaxis

›Administer if not up to date

›Td booster for adults > 5 years since last dose

›TIG (tetanus immune globulin) if unvaccinated

›Wound dressing

›Clean dry dressing

›Elevation of affected extremity

›Ice pack application to reduce local inflammation

Analgesia

›Pain management

›Acetaminophen

›500-1000 mg orally every 6-8 hours

›Maximum 4000 mg per day

›First-line for mild to moderate pain

›NSAIDs

›Ibuprofen 400-600 mg orally every 6-8 hours

›Use caution if renal function impaired

›Avoid in G6PD deficiency-related hemolysis (heme-stability concern)

›Opioid analgesia

›Reserved for severe pain not controlled with above agents

›Tramadol or morphine as appropriate

Cutaneous loxoscelism management

›Conservative wound care approach

›Expectant management

›Most lesions heal without intervention

›NEJM review supports conservative approach as standard

›Healing time for mild bites approximately 1 week

›Antibiotics

›Only if secondary bacterial infection develops

›No role for prophylactic antibiotics

›Coverage: MRSA-directed if purulence or abscess (TMP-SMX or doxycycline)

›Avoid early surgical excision

›Associated with delayed wound healing and objectionable scarring

›Delayed surgical revision after full demarcation (typically weeks later)

›Rees et al. Ann Surg 1985: excision worsens outcomes vs conservative care

›Dapsone (controversial)

›Mechanism and rationale

›Inhibits neutrophil-mediated tissue destruction

›No prospective human study confirms efficacy

›Dosing if used

›50-100 mg/day orally

›Duration typically until wound stabilizes (1-2 weeks)

›Monitor CBC and LFTs weekly

›Contraindications and risks

›G6PD deficiency is absolute contraindication

›Causes dose-dependent hemolysis in all patients to some degree

›Screen G6PD before any prescription

›Medical toxicology consultation before use

Systemic loxoscelism management

›IV hydration

›Aggressive resuscitation for hemolysis and renal protection

›Normal saline or lactated Ringer solution

›Rate to achieve urine output 1-2 mL/kg/hr

›Adjust rate based on hemodynamic status and urine output response

›Corticosteroids

›Use in selected systemic cases (limited evidence)

›Prednisone 40-80 mg/day orally for 5 days

›May reduce extent of hemolysis (expert opinion, no RCT data)

›Weigh against infection risk before initiation

›RBC transfusion

›Hemolytic anemia treatment

›Packed RBC transfusion for hemoglobin < 7 g/dL or symptomatic anemia

›Type and screen on admission for any hemolysis

›76.9% of hemolytic patients required transfusion

›Hyperkalemia management

›Complication of massive hemolysis

›Calcium gluconate 1-2 g IV for cardiac membrane stabilization if EKG changes

›Sodium bicarbonate for potassium shift

›Kayexalate or patiromer for GI elimination

›Dialysis for refractory hyperkalemia

Renal replacement therapy

›Indications for dialysis

›Acute kidney injury criteria

›Refractory hyperkalemia not responding to medical management

›Severe metabolic acidosis (pH < 7.2)

›Fluid overload refractory to diuretics

›Uremic encephalopathy

›Modality selection

›CRRT preferred in hemodynamically unstable patients

›Intermittent hemodialysis in stable patients

Interventions without proven benefit

›Treatments to avoid

›Antivenom

›Not available in the United States

›No commercially approved product for Loxosceles

›Hyperbaric oxygen

›No prospective evidence of benefit

›AFP and NEJM reviews recommend against routine use

›Antihistamines for necrosis prevention

›No proven benefit for wound outcome

›Prophylactic antibiotics

›No evidence base for prevention of secondary infection

›Suction devices or tourniquets

›AHA/Red Cross first aid guidelines recommend against

›Increase tissue damage

09Special Populations/sp42

Pregnancy

›Pregnancy considerations

›Physiologic vulnerability

›Anemia of pregnancy compounds hemolysis-related anemia

›Baseline hemoglobin lower; transfusion threshold may be reached earlier

›Fetal monitoring indicated for systemic loxoscelism

›Medication safety

›Dapsone: Category C; avoid in first trimester and near term (neonatal hemolysis risk)

›Corticosteroids: generally considered safe in pregnancy; preferred systemic agent

›NSAIDs: avoid after 20 weeks gestational age (premature ductus arteriosus closure)

›Obstetric consultation

›Required for any pregnant patient with systemic loxoscelism

›Fetal non-stress test and biophysical profile if hemolysis confirmed

›Delivery planning if hemolysis is severe near term

Geriatric

›Geriatric considerations

›Comorbidity burden

›Chronic kidney disease reduces tolerance to hemoglobinuria-induced AKI

›Anticoagulant use increases bleeding risk if DIC develops

›Cardiac disease reduces tolerance to acute anemia

›Wound healing

›Delayed healing due to reduced tissue perfusion and immune response

›Higher risk of secondary wound infection

›Earlier wound follow-up schedule recommended

›Medication considerations

›Dapsone: use with caution due to polypharmacy and renal impairment

›NSAIDs: avoid due to renal impairment and GI bleeding risk in elderly

›Hydration: monitor carefully for fluid overload in cardiac disease

10Background/b63

Epidemiology

›Geographic distribution

›Endemic range

›South-central United States: Missouri, Kansas, Oklahoma, Arkansas, Tennessee

›Also present in parts of the Southwest

›Loxosceles reclusa is the primary North American species

›Seasonal pattern

›Bites more frequent in warmer months

›Increased indoor activity during summer increases human contact

›Demographics

›Slightly more women bitten, likely reflecting domestic indoor exposure

›Children and young adults at greater risk for severe systemic disease

›Incidence and severity

›Frequency of complications

›Approximately 10% of bites develop necrosis after 24-48 hours

›Up to 10% of cases develop systemic loxoscelism

›Most bites are self-limited and heal without intervention

›Hemolytic cases

›Median hemoglobin nadir in hemolytic cases 6.4 g/dL

›76.9% require RBC transfusion

›DIC present in a subset with OR 82.9 for mortality

Pathophysiology

›Venom composition

›Sphingomyelinase D (phospholipase D)

›Primary pathogenic enzyme

›Cleaves sphingomyelin in cell membranes triggering complement activation

›Causes direct endothelial and RBC membrane damage

›Hyaluronidase

11Patient Discharge Instructions/pdi41

copy discharge instructions

›Diagnosis and expected course

›You were evaluated for a brown recluse spider bite

›Most bites heal on their own without specific treatment

›Mild bites resolve within approximately 1 week

›Necrotic (tissue death) wounds may take 5 to 17 or more weeks to fully heal

›Wound care at home

›Clean the wound gently with soap and water twice daily

›Apply a clean dry dressing

›Keep the wound elevated when possible to reduce swelling

›Do not puncture or drain blisters at home

›Medications

›Pain relief

›Acetaminophen (Tylenol) 500-1000 mg every 6-8 hours as needed for pain

›Ibuprofen 400-600 mg every 8 hours with food as needed for pain

›Take only as directed; do not exceed recommended daily doses

›Additional prescriptions

›Take all prescribed medications exactly as directed

›Do not stop dapsone without consulting your physician if prescribed

›Follow-up plan

›Wound recheck appointment

›Return for wound recheck in 48-72 hours

›Weekly wound checks until fully healed

›Photographs of the wound daily at home help track progression

›Return to emergency department immediately for

›Urine changes

›Dark, red, brown, or tea-colored urine

›Decreased urine output or no urination

12References/r28

Guidelines and key sources

›Primary evidence sources

›Herness J, Snyder MJ, Newman RS. Arthropod Bites and Stings. American Family Physician. 2022. PMID 35977137

›Comprehensive review of brown recluse management

›Supports conservative wound care as first-line approach

›Swanson DL, Vetter RS. Bites of Brown Recluse Spiders and Suspected Necrotic Arachnidism. NEJM. 2005. DOI 10.1056/NEJMra041184

›Landmark review on overdiagnosis outside endemic regions

›Defines diagnostic criteria and management principles

›Isbister GK, Fan HW. Spider Bite. Lancet. 2011. PMID 21762981

›Global review including Loxosceles species

›Epidemiology and systemic loxoscelism characterization

›Hemolysis and hematology evidence

›Loden JK, Seger DL, Spiller HA, et al. Cutaneous-Hemolytic Loxoscelism Following Brown Recluse Spider Envenomation. Clinical Toxicology. 2020. PMID 32186919

›Defines predictors of hemolysis including myalgia aOR 12.76 and malaise aOR 7.1

›Characterizes 61% rhabdomyolysis rate and 76.9% transfusion rate

›Jacobs JW, Bastarache L, Thompson MA. Laboratory Predictors of Hemolytic Anemia in Patients With Systemic Loxoscelism. AJCP. 2022. PMID 34643670

›LDH plus bilirubin combination: sensitivity 94%, specificity 91% for hemolysis

›Hart SA, Gailani D, Bibb LA, et al. Coagulation Abnormalities Following Brown Recluse Spider Envenomation. AJCP. 2025. PMID 39883062

›DIC associated with OR 82.9 for mortality

›Robinson JR, Kennedy VE, Doss Y, et al. Defining the Complex Phenotype of Severe Systemic Loxoscelism. PloS One. 2017. PMID 28422977

›Median age 14 years in hemolytic cohort

›Large electronic health record characterization of systemic loxoscelism

›First aid and guidelines

›Hewett Brumberg EK, Douma MJ, Alibertis K, et al. 2024 AHA and American Red Cross Guidelines for First Aid. Circulation. 2024

›Recommends against suction devices and tourniquets

›Supports basic wound care and analgesia

›Rees RS, Altenbern DP, Lynch JB, King LE. Brown Recluse Spider Bites: Early Excision Versus Dapsone. Ann Surg. 1985. PMID 4051613

›Early excision inferior to conservative management

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