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Approach to the Critical Patient
Immediate priorities
Airway and breathing threats
Malignant edema of head, neck, or thorax
Stridor or voice change
Progressive facial or cervical swelling
Airway obstruction risk
Dysphagia or drooling
Tongue or pharyngeal swelling
If impending airway compromise, early definitive airway control
Anesthesia and ENT at bedside
Prepare for difficult airway and surgical airway
Circulation and systemic toxicity threats
Shock physiology
SBP < 90 mmHg
MAP < 65 mmHg
Systemic dissemination markers
High fever and rigors
Tachycardia and hypotension
If septic, broad spectrum antibiotics within 1 hour
Blood cultures before antibiotics when feasible
Balanced crystalloid resuscitation
Key early branching
Uncomplicated localized cutaneous anthrax
Painless eschar with minimal edema
No systemic symptoms
Complicated cutaneous anthrax
Extensive malignant edema
Head or neck involvement with systemic features
If neurologic signs, evaluate for anthrax meningitis
Headache with meningismus
Altered mental status or seizures
Monitoring and targets
Monitoring bundle
Continuous pulse oximetry
SpO2 target 92% to 96%
Trend for occult inhalational involvement
Cardiac monitor
Tachycardia as toxicity marker
Hemodynamic trend in systemic disease
Serial airway reassessment
Edema progression on head and neck
Voice and swallowing changes
Escalation triggers
Rapidly expanding edema
Spread toward face, neck, or chest
Critical care and surgical involvement
Persistent hypotension after fluids
Norepinephrine initiation
ICU level care
Suspected concurrent inhalational exposure
Chest imaging for widened mediastinum
Extend therapy and add antitoxin planning
Immediate consults and notifications
Consultation triggers
Infectious diseases for all suspected cases
Antibiotic selection guidance
Antitoxin and vaccine decisions
ENT or surgery for malignant edema
Airway protection planning
No incision or debridement of eschar
Critical care for systemic disease
Meningitis management
Hemodynamic instability
Mandatory public health reporting
Immediate notification of local and state health department
Confirmed or suspected case
Coordinate specimen handling with reference laboratory
CDC notification
Bioterrorism concern escalation
Co-exposed contact identification
History
Presentation pattern
Core syndrome
Initial pruritus at inoculation site
Painless papule onset
Skin break at exposure site
Vesicle formation
Clear or serosanguinous fluid
Satellite vesicles around primary lesion
Evolution to black eschar
Painless ulcer then eschar over 24 to 48 hours
Surrounding non-pitting edema
Symptom timeline
Incubation period
1 to 12 days
Mean approximately 5 days
Characteristically painless lesion
Pain suggests secondary bacterial superinfection
Non-purulent unless superinfected
Exposure and risk factors
Animal and occupational exposure
Livestock contact
Cattle, goats, and sheep
Sick or dead animals
Animal product handling
Hides, wool, and bone meal
Drum makers using animal skins
High risk occupations
Farmers and veterinarians
Abattoir, wool, and hide processors
Geographic and travel exposure
Endemic regions
Sub-Saharan Africa and Central Asia
Middle East and parts of South America
Recent travel to endemic areas
Rural agricultural settings
Contact with imported animal products
Bioterrorism context
Suspicious powder or mail handling
Mass casualty event setting
Multiple simultaneous cases
Concern for concurrent inhalational exposure
Aerosolized spore exposure
Extended prophylaxis implications
Associated and alarm features
Associated systemic symptoms
Mild constitutional features
Low grade fever and headache
Malaise and fatigue
Regional lymphatic symptoms
Tender regional lymphadenopathy
Lymphangitis tracking
Alarm features
Extensive malignant edema
Head, neck, or thorax involvement
Airway compromise risk
Systemic involvement
High fever, chills, and tachycardia
Hypotension and bacteremia
Neurologic deterioration
Headache with cranial nerve deficits
Seizures or altered mental status
Gastrointestinal symptoms
Nausea and vomiting
Abdominal pain associated with fatal outcomes
Physical Exam
Vitals and general
Stability snapshot
Temperature
Mild to moderate fever in uncomplicated disease
High fever as systemic marker
Blood pressure
SBP < 90 mmHg as alarm sign
MAP < 65 mmHg
Heart rate
Tachycardia as toxicity marker
Trend with resuscitation
General appearance
Well appearing in localized disease
Stable vitals common
Painless lesion despite striking appearance
Toxic appearance in systemic disease
Rigors and diaphoresis
Altered mental status
Skin and lesion exam
Classic lesion progression
Early stage
Pruritic papule
Vesicle with clear or serosanguinous fluid
Late stage
Painless depressed black eschar
Satellite vesicles at margin
Surrounding edema
Non-pitting and disproportionate to lesion size
Prominent on head and neck
Lesion characterization
Non-purulent character
Pus suggests secondary infection
Painless unless superinfected
Common locations
Hands and forearms
Face and neck
Regional and systemic exam
Lymphatic and airway exam
Regional lymphadenopathy and lymphangitis
Tender draining nodes
Proximal tracking erythema
Airway assessment with head or neck involvement
Stridor or voice change
Dyspnea from malignant edema
Neurologic exam
Mental status assessment
Confusion as meningitis clue
Drowsiness in systemic disease
Meningeal and cranial nerve signs
Neck stiffness
Focal cranial nerve deficits
PITFALLS
Misattribution of lesion
Mistaken for purulent furuncle or carbuncle
Anthrax is painless and non-purulent
Eschar with gelatinous edema is characteristic
Underestimating edema severity
Disproportionate head and neck swelling
Early airway risk recognition
Harmful interventions
Incision, debridement, or excision of eschar
Can worsen systemic spread
Avoid manipulation
Squeezing lesion for culture
Do not squeeze to obtain material
Use swab technique instead
Differential Diagnosis
Infectious mimics
Bacterial skin infections
Staphylococcal furuncle or carbuncle
Typically painful and purulent
No gelatinous edema
Ecthyma and ecthyma gangrenosum
Ecthyma gangrenosum in neutropenic hosts
Pseudomonas bacteremia association
Rat bite fever
Eschar at bite site
Systemic symptoms
Zoonotic and travel related
Tularemia ulceroglandular form
Painful ulcer with lymphadenopathy
Rabbit or tick exposure
Cutaneous leishmaniasis
Painless slowly evolving ulcer
No black eschar
Orf or ecthyma contagiosum
Sheep or goat contact
No large eschar or gelatinous edema
Buruli ulcer
Painless expanding ulcer
Tropical freshwater exposure
Rickettsial and other
Scrub typhus and spotted fevers
Eschar with fever
Tick or mite exposure
Brown recluse spider bite
Painful necrotic lesion
No surrounding gelatinous edema
Noninfectious mimics and coding
Inflammatory mimics
Vasculitis
Noninfectious eschar
Systemic inflammatory features
Pyoderma gangrenosum
Painful ulcer with violaceous border
Pathergy phenomenon
Diagnostic coding
Cutaneous anthrax
ICD-10 A22.0
SNOMED CT cutaneous anthrax disorder
Distinguishing feature triad
Painless black eschar
Non-purulent edema with exposure history
Laboratory Tests
Microbiologic studies
Lesion sampling
Vesicular fluid swabs
Unroof vesicle and soak 2 dry swabs
Positive in over 80% of untreated lesions
Eschar edge swabs
Rotate 2 moist swabs under eschar edge
Avoid squeezing the lesion
Gram stain of vesicular fluid
Large gram-positive bacilli in chains
Boxcar appearance
Blood cultures
Usually negative in uncomplicated disease
Negative supports localized infection
Obtain before antibiotics when feasible
Positive result implications
Indicates systemic dissemination
Associated with mortality
Hematology and chemistry
Complete blood count
Often normal white count
Mild leukocytosis possible
Marked leukocytosis in systemic disease
Hemoglobin and platelets
Baseline for trend
Thrombocytopenia with DIC
Coagulation studies
DIC screening when systemic disease suspected
PT and aPTT
Fibrinogen and D-dimer
Interpretation
Coagulopathy as alarm feature
Supports systemic involvement
Confirmatory and reference testing
Molecular and tissue testing
PCR for B. anthracis
Vesicular fluid, swabs, or biopsy tissue
Highly specific
Punch biopsy
Immunohistochemical staining when cultures negative
Useful after antibiotic pretreatment
Serology and laboratory safety
Anti-protective antigen IgG serology
Retrospective confirmation
Paired acute and convalescent samples
Laboratory handling precautions
BSL-2 precautions at minimum
Notify laboratory before sending specimens
Diagnostic Tests
Scoring Systems
Anthrax triage and severity tools
CDC anthrax triage checklist
Developed for mass exposure events
Sensitivity approximately 95% for adult cases
Clinical severity stratification
Uncomplicated localized disease
Complicated and systemic disease
qSOFA for systemic illness
RR >= 22 per minute
SBP <= 100 mmHg
Altered mental status
Limitations
No validated cutaneous-specific severity score
Clinical trajectory supersedes single tools
Exposure history central to diagnosis
Triage tools for screening only
Not a substitute for microbiologic confirmation
ACEP Level C recommendation for adjunct use
MRI
Soft tissue MRI role
Limited acute utility
Availability constraints
Reserved for problem solving
Problem solving indications
Deep tissue edema extent
Neck involvement near airway
Contraindications
Unstable patient
Non-compatible implants
Central nervous system imaging
MRI brain with meningeal signs
Hemorrhagic meningoencephalitis pattern
Leptomeningeal enhancement
Interpretation
Supports anthrax meningitis diagnosis
Correlate with CSF findings
CT
Chest CT indications
Concern for inhalational anthrax
Widened mediastinum
Mediastinal lymphadenopathy and pleural effusions
Bioterrorism exposure context
Aerosolized spore concern
Screen for hemorrhagic mediastinitis
Contrast considerations
Renal function assessment
Allergy history
Head and neck and CNS CT
CT head with meningeal signs
Hemorrhage or edema
Mass effect screen
Soft tissue neck CT
Airway patency assessment
Edema extent characterization
Evidence and guidance
CT for complication assessment by expert consensus
ACEP Level C recommendation
Ultrasound
Soft tissue ultrasound
Edema and fluid characterization
Subcutaneous edema cobblestoning
Exclude drainable abscess
Lymph node assessment
Regional lymphadenopathy
Lymphangitis correlation
Operator dependence
Limited depth in extensive edema
Adjunct to clinical exam
Bedside cardiac and hemodynamic POCUS
Shock differential support
Gross LV function estimate
Pericardial effusion screen
Volume status adjunct
IVC assessment limitations
Integrate with clinical exam
Disposition
Level of care selection
Admission indications
Extensive or malignant edema
Head or neck involvement
Airway compromise risk
Systemic involvement
High fever, hypotension, or tachycardia
Bacteremia
Neurologic symptoms suggesting meningitis
Meningismus
Altered mental status
Inability to tolerate oral medications
Persistent vomiting
Need for parenteral therapy
ICU indications
Airway compromise
Intubation or surgical airway need
Malignant edema progression
Septic shock
Vasopressor requirement
Rising lactate despite resuscitation
Anthrax meningitis
Seizure management
Intracranial complication monitoring
Discharge criteria and follow up
Outpatient criteria
Uncomplicated localized lesion
No systemic symptoms
Minimal surrounding edema
Able to tolerate oral antibiotics
No vomiting
Reliable adherence plan
Reliable follow up and return precautions
Understanding of red flags
Access to care
Specialist and public health follow up
Infectious diseases follow up
Susceptibility-guided therapy adjustment
Confirmation testing review
Public health coordination
Mandatory case reporting
Contact evaluation and prophylaxis
Wound reassessment schedule
Reassess within 24 to 48 hours
Then every 2 to 3 days until eschar separates
Treatment
Initial stabilization and wound care
Immediate measures
ABC assessment
Airway evaluation with head or neck edema
IV access for systemic symptoms
Resuscitation for systemic disease
Balanced crystalloid for hypotension
Vasopressors for refractory shock
Wound management
Conservative local care
Keep lesion clean and covered
Do not incise or debride eschar
Avoid harmful manipulation
No excision of eschar
No squeezing of lesion
First-line antibiotics
Naturally acquired uncomplicated disease
Ciprofloxacin
500 mg PO every 12 hours
7 to 10 day course
Doxycycline
100 mg PO every 12 hours
7 to 10 day course
Duration principle
Antibiotics prevent systemic spread
Do not accelerate eschar healing
Penicillin-susceptible isolates
Penicillin V
500 mg PO every 6 hours
7 to 10 day course
Amoxicillin alternative
500 mg PO every 8 hours
Use only when susceptibility confirmed
Guideline support
IDSA strong recommendation when susceptible
Switch by susceptibility testing when available
Severe and systemic disease
Parenteral therapy
IV ciprofloxacin
400 mg IV every 12 hours
Step down to oral when clinically stable
IV doxycycline alternative
100 mg IV every 12 hours
Total course 7 to 10 days
Indications for IV therapy
Systemic signs or extensive edema
Head or neck lesions
Combination therapy for systemic anthrax
Add protein synthesis inhibitor
Linezolid or clindamycin to reduce toxin production
Combine with bactericidal fluoroquinolone
Antitoxin adjunct
Raxibacumab or obiltoxaximab for systemic disease
Coordinate with infectious diseases and public health
Meningitis coverage
Add CNS-penetrating agent such as meropenem
Triple therapy for confirmed meningitis
Bioterrorism and adjuncts
Bioterrorism-related exposure
Extended antibiotic duration
Ciprofloxacin 500 mg PO every 12 hours for 60 days
Doxycycline 100 mg PO every 12 hours for 60 days
Post-exposure prophylaxis vaccine
Anthrax vaccine adsorbed with antibiotics
Avoid AVA in prior severe vaccine reaction
Corticosteroids and airway adjuncts
Corticosteroids for malignant edema
May reduce edema duration in retrospective data
Consider case-by-case given limited evidence
Airway interventions
Intubation for severe head or neck edema
Tracheostomy when intubation not feasible
Special Populations
Pregnancy
Pregnancy considerations
Antibiotic selection
Ciprofloxacin preferred for life-threatening anthrax
Avoid prolonged doxycycline due to fetal effects
Severe disease management
Do not withhold effective therapy for systemic anthrax
Antitoxin when systemic disease present
Maternal and fetal monitoring
Maintain maternal SpO2 >= 95%
Fetal monitoring when viable gestation
Imaging approach
Chest radiograph with shielding when indicated
CT only when benefits outweigh risks
Geriatric
Older adult features
Atypical presentation
Blunted fever response
Delirium as early systemic clue
Medication considerations
Renal dosing adjustment for ciprofloxacin
QT prolongation risk with fluoroquinolones
Comorbidity impact
Reduced physiologic reserve
Lower threshold for admission
Edema and airway risk
Higher complication risk with head or neck disease
Early airway planning
Pediatrics
Pediatric differences
Weight-based antibiotics
Ciprofloxacin 15 mg/kg PO every 12 hours up to adult dose
Doxycycline 2.2 mg/kg per dose every 12 hours
Severe disease dosing
Ciprofloxacin 10 to 15 mg/kg IV every 12 hours
Add clindamycin for toxin suppression in systemic disease
Duration considerations
7 to 10 days for naturally acquired disease
60 days for bioterrorism-related exposure
Monitoring and safety
Hydration and feeding tolerance
Public health notification for all cases
Background
Epidemiology
Frequency and burden
Most common form of anthrax
Over 95% of all anthrax infections
Spore inoculation through skin breaks
Demographic pattern
Male predominance approximately 79% in case series
Occupational and agricultural exposure
Mortality outcomes
Untreated mortality 10% to 20%
Near zero with appropriate antibiotics
Pathophysiology
Organism and toxins
Bacillus anthracis
Spore-forming gram-positive rod
Spores germinate after skin inoculation
Virulence factors
Edema toxin causing tissue edema
Lethal toxin driving systemic toxicity
Antiphagocytic capsule
Poly-D-glutamic acid capsule
Evades immune clearance
Disease evolution
Local lesion development
Papule to vesicle to eschar
Surrounding gelatinous edema from edema toxin
Systemic dissemination pathway
Lymphatic and hematogenous spread
Bacteremia and meningitis in severe cases
Therapeutic Considerations
Antibiotic strategy principles
Empiric bactericidal therapy
Fluoroquinolone or tetracycline first-line
Penicillins only when susceptibility confirmed
Toxin-directed therapy in systemic disease
Add protein synthesis inhibitor
Antitoxin for systemic involvement
Susceptibility-guided refinement
Narrow therapy once results available
Consider induced beta-lactamase risk
Supportive and preventive measures
Eschar non-intervention
Eschar separates spontaneously over 1 to 2 weeks
Avoid debridement to prevent spread
Public health and prevention
Contact evaluation and prophylaxis
Vaccine in bioterrorism context
Patient Discharge Instructions
copy discharge instructions
Cutaneous anthrax home care
Take all antibiotics exactly as prescribed until finished
Complete the full course even if the sore looks better
Keep the sore clean and covered
Do not pick, squeeze, or cut the black scab
What to expect
The black scab dries and falls off over about 2 weeks
Most sores heal without scarring
Anthrax is not spread person to person
Return to ER immediately for
Increasing swelling spreading to face, neck, or chest
New fever, chills, or worsening tiredness
Trouble breathing or swallowing
Headache with neck stiffness or confusion
New skin sores at other sites
Follow up
Clinician reassessment within 24 to 48 hours
Repeat visits every 2 to 3 days until the scab loosens
Tell close contacts to seek evaluation if exposed
References
Guidelines and key sources
Guideline sources
CDC Guidelines for the Prevention and Treatment of Anthrax 2023
IDSA Skin and Soft Tissue Infection Guidelines 2014
JAMA Anthrax as a Biological Weapon updated recommendations
Evidence summaries
NEJM Anthrax review and update articles
Systematic review of hospital treatment outcomes for anthrax 1880 to 2018
Retrospective study on corticosteroids and antibiotics in cutaneous anthrax
Decision tools and coding
CDC anthrax mass exposure triage checklist
ICD-10 A22.0 cutaneous anthrax
SNOMED CT cutaneous anthrax disorder concept
SymptomDx is an educational tool for medical professionals. It does not replace clinical judgment. Verify all clinical data and drug dosages with authoritative sources.