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Approach to the Critical Patient
Immediate threats
Time critical stabilization
Airway compromise
Stridor
Oropharyngeal edema
Respiratory failure
Hypoventilation
Progressive bulbar weakness
Shock
Anaphylaxis physiology
Hemorrhagic physiology from venom induced coagulopathy
Rapid neurologic decline
Cranial nerve dysfunction
Ascending paralysis
Limb threat
Rapidly progressive swelling crossing a joint
Compartment syndrome concern
Early high yield actions
First minutes bundle
Resuscitation bay triggers
Hypotension
Hypoxia
Rapidly progressive facial or neck swelling
Venom exposure control
Remove rings and constrictive clothing
Limb at heart level
Analgesia and anxiolysis
Opioid analgesia for severe pain
Benzodiazepine for severe muscle spasm
Antivenom readiness
Immediate poison center consultation
Species specific antivenom availability check
Monitoring and targets
Physiologic monitoring
Continuous pulse oximetry
Oxygen saturation trend
Early desaturation trigger for airway planning
Cardiac monitoring
Dysrhythmia surveillance
QT prolongation risk with some antiemetics and analgesics
Serial extremity checks
Mark leading edge of swelling with time noted in chart
Circumference measurements proximal and distal
Hemodynamic targets
Systolic blood pressure appropriate for age and baseline
Urine output trend when critically ill
Antivenom reaction preparedness
Infusion safety
Anaphylaxis kit at bedside
Epinephrine IM dosing ready
Airway equipment ready
Immediate hypersensitivity signs
Urticaria
Bronchospasm
Delayed serum sickness risk
Fever
Arthralgias
Consultation triggers
Team activation
Toxicology or poison center
Any systemic toxicity
Any coagulopathy concern
Surgery
Necrotizing soft tissue infection concern
Compartment syndrome concern
ICU
Need for airway support
Need for antivenom with systemic instability
History
Exposure characterization
Exposure details
Time of bite or sting
Symptom onset time
Time to progression
Species identification
Photo of animal or insect if safe
Geographic region and habitat
Number of bites or stings
Multiple sting risk for venom load
Swarm exposure risk
Anatomic location
Face and neck higher airway risk
Distal extremity common snakebite site
Prehospital interventions and pitfalls
Field actions
Tourniquet use
Duration
Neurovascular symptoms after release
Incision suction cryotherapy
Skin injury risk
No proven venom removal benefit
Pressure immobilization
Relevant for some neurotoxic elapid bites
Not for cytotoxic pit viper bites with swelling
Medications taken
NSAIDs and bleeding risk
Sedatives and hypoventilation risk
Symptom inventory by toxidrome
Local toxidrome
Pain severity
Rapid severe pain
Delayed pain after brown recluse pattern
Swelling progression
Proximal spread
Crossing joints
Bleeding and bruising
Oozing at puncture site
Ecchymosis
Neurotoxic toxidrome
Diplopia ptosis dysarthria
Bulbar symptoms
Dysphagia
Paresthesias and fasciculations
Perioral tingling
Muscle twitching
Respiratory symptoms
Dyspnea
Weak cough
Systemic inflammatory toxidrome
Nausea vomiting abdominal pain
Autonomic features
Diaphoresis
Chest pain and palpitations
Catecholamine surge pattern in latrodectism
Hypertension
Anaphylaxis toxidrome
Urticaria angioedema wheeze
Prior sting reactions
Epinephrine autoinjector use
Risk factors and modifiers
Patient factors
Age and weight
Pediatric venom dose relative burden
Frailty and reserve
Comorbidities
Asthma and severe bronchospasm risk
Cardiovascular disease and shock vulnerability
Medications
Anticoagulants and bleeding risk
Beta blockers and refractory anaphylaxis risk
Allergy history
Prior antivenom exposure
Equine ovine antiserum reactions
Pregnancy status
Fetal monitoring needs
Maternal hypoxia risk
Physical Exam
General and vital signs pattern recognition
Global assessment
Toxic appearance
Diaphoresis
Agitation
Vital sign trends
Hypotension
Hypertension and tachycardia
Airway and breathing
Voice change
Increased work of breathing
Local wound and limb exam
Bite or sting site
Puncture marks
Single puncture possible
Multiple punctures possible
Erythema edema ecchymosis
Rate of spread
Lymphangitic streaking
Bullae and necrosis
Hemorrhagic bullae concern
Necrotic center concern
Retained stinger or foreign body
Visible stinger
Palpable foreign body
Neurovascular status
Capillary refill and pulses
Pulse deficit
Coolness
Motor and sensory function
Paresthesia distribution
Weakness progression
Compartment syndrome indicators
Pain out of proportion
Pain with passive stretch
Neurologic exam
Neurotoxicity screen
Cranial nerves
Ptosis
Ophthalmoplegia
Bulbar function
Dysarthria
Drooling
Respiratory muscle function
Single breath count trend
Neck flexor weakness
Autonomic findings
Mydriasis
Diaphoresis
Anaphylaxis and systemic findings
Hypersensitivity findings
Urticaria and flushing
Generalized distribution
Rapid onset
Angioedema
Lips tongue
Periorbital swelling
Wheeze and bronchospasm
Prolonged expiration
Silent chest risk
GI involvement
Repetitive vomiting
Abdominal cramping
PITFALLS
Common diagnostic traps
Overcalling compartment syndrome early in snakebite
Swelling related pain without true compartment pressure elevation
Fasciotomy worsened outcomes risk
Mislabeling skin necrosis as infection early
Venom induced tissue injury without bacterial infection
Antibiotics not routinely indicated
Differential Diagnosis
Limb swelling and pain
Limb swelling differential
Venomous snake envenomation
Pit viper pattern
Elapid neurotoxic pattern
Cellulitis
ICD-10 L03
Fever and progressive erythema over days
Necrotizing soft tissue infection
ICD-10 M72.6
Pain out of proportion systemic toxicity
Deep vein thrombosis
ICD-10 I82
Unilateral swelling without puncture site findings
Compartment syndrome
ICD-10 T79.A
Passive stretch pain neuro deficits
Coagulopathy and bleeding
Bleeding differential
Venom induced consumption coagulopathy
Defibrination
Thrombocytopenia
Anticoagulant related bleeding
Warfarin DOAC exposure
Elevated INR pattern
Liver failure coagulopathy
Chronic stigmata
Mixed factor deficiency
Neurotoxicity and paralysis
Neuro weakness differential
Neurotoxic snake envenomation
Cranial nerve involvement
Descending paralysis
Tick paralysis
Ascending weakness
Rapid improvement after tick removal
Guillain Barre syndrome
Albuminocytologic dissociation
Areflexia
Botulism
Pupil involvement
Constipation prodrome
Systemic pain spasm syndromes
Pain spasm differential
Latrodectism black widow
Diffuse muscle cramping
Autonomic storm
Acute abdomen
Peritonitis signs
Localized tenderness pattern
Acute coronary syndrome
Ischemic symptoms
ECG changes
Laboratory Tests
Initial baseline studies
Baseline labs
Complete blood count
Platelets for thrombocytopenia
Leukocytosis nonspecific stress marker
Electrolytes renal function
Creatinine for rhabdomyolysis and dehydration risk
Potassium for hemolysis and renal dysfunction
Creatine kinase
Myonecrosis screening
Rhabdomyolysis trend
Liver enzymes
Baseline for systemic illness
Hemolysis indirect marker when paired with bilirubin
Glucose
Stress hyperglycemia
Hypoglycemia confounder for altered mental status
Hemostasis assessment for snake envenomation
Coagulation profile
INR and PT
Venom induced factor consumption
Baseline anticoagulant confounder
aPTT
Mixed pathway involvement
Heparin confounder
Fibrinogen
Defibrination marker
Antivenom response trend
D dimer
Consumption and fibrinolysis marker
Limited specificity
Type and screen
Transfusion readiness
Massive bleeding contingency
Infection and inflammation adjuncts
Infection adjuncts
Lactate
Shock marker
Necrotizing infection risk marker
Blood cultures
Systemic infection concern
Immunocompromised host
C reactive protein
Limited specificity
Trend support for infection when combined with exam
Point of care testing
Point of care tools
Venous blood gas
Hypercapnia in respiratory weakness
pH trend in shock
Pregnancy test
Medication risk assessment
Imaging decision context
Diagnostic Tests
Scoring Systems
Decision tools and criteria
Snakebite Severity Score
Local effects domain
Swelling and ecchymosis extent
Bullae and necrosis presence
Systemic effects domain
Hypotension vomiting altered mental status
Neurotoxicity signs
Hematologic domain
Platelets low
Fibrinogen low or INR elevated
Clinical use
Antivenom consideration support
Serial reassessment framework
Anaphylaxis clinical criteria
Acute onset with skin mucosal involvement plus respiratory compromise
Wheeze stridor hypoxemia
Persistent hypotension
Two system involvement after likely allergen
Skin mucosal
Respiratory GI cardiovascular
Hypotension after known allergen exposure
Systolic blood pressure low for age
Syncope or collapse
MRI
MRI considerations
Deep soft tissue evaluation
Myositis
Osteomyelitis late presentation
Neuro symptoms alternative diagnosis
Brainstem stroke concern
Spinal cord pathology concern
Limitations
Delays definitive therapy
Motion artifact in painful patients
CT
CT applications
Necrotizing soft tissue infection evaluation
Gas in soft tissues
Deep fascial edema
Facial or neck swelling
Airway threat anatomy
Abscess alternative diagnosis when delayed presentation
Neuro symptoms alternative diagnosis
Intracranial hemorrhage concern
Stroke pathway activation if focal deficits
Limitations
Early necrotizing infection may have normal CT
Contrast considerations in kidney injury
Ultrasound
Ultrasound and POCUS
Retained foreign body or stinger
Hyperechoic linear structure
Local fluid collection
Soft tissue evaluation
Cellulitis cobblestoning
Abscess fluid collection
Vascular evaluation
DVT assessment for unilateral swelling
Arterial flow when pulse concern
Shock evaluation
Cardiac function and tamponade screen
IVC size trend in volume assessment
Disposition
Observation and admission criteria
Level of care decisions
ICU indications
Airway edema
Progressive neurotoxicity
Step down or monitored bed
Systemic symptoms without instability
Antivenom infusion with reaction risk
ED observation
Mild local effects with stable labs
Need for serial limb and coag reassessment
Transfer criteria
Antivenom not available locally
Pediatric severe envenomation without ICU support
Suggested monitoring windows
Time based reassessment
Anaphylaxis after sting
Observation for biphasic reaction risk
Longer observation for severe reactions or multiple epinephrine doses
Suspected pit viper bite without initial progression
Serial exams and coagulation reassessment
Delayed coagulopathy counseling when discharged
Black widow syndrome
Discharge after pain control and stable vitals
Admission for refractory pain or hypertension
Discharge readiness
Discharge criteria
No progression of swelling on serial exams
Stable circumference and markings
No new bullae
Stable hemostasis labs when relevant
Platelets stable
Fibrinogen stable and INR stable
Reliable follow up plan
Return precautions understood
Access to recheck labs if needed
Treatment
General measures for all bites and stings
Supportive care bundle
Wound care
Clean with soap and water
Avoid incision suction
Tetanus prophylaxis
Vaccination status review
Tdap update per routine schedule
Limb management
Heart level positioning
Splinting for comfort and decreased venom spread by movement
Pain control
Opioid analgesia titrated to effect
Avoid NSAIDs when coagulopathy concern
Antibiotics strategy
No routine prophylaxis for uncomplicated bites
Targeted therapy for clear infection or high risk wounds
Rabies prophylaxis
Not indicated for snakes spiders insects
Consider only if mammal bite co exposure
Anaphylaxis from insect stings
Anaphylaxis protocol
Epinephrine IM
Adult epinephrine 1 mg/ml 0.3 mg to 0.5 mg IM lateral thigh
Repeat every 5 minutes to 15 minutes as needed
Early repeat if persistent hypotension or bronchospasm
Pediatric epinephrine 1 mg/ml 0.01 mg/kg IM lateral thigh
Maximum single dose 0.3 mg in many protocols
Repeat every 5 minutes to 15 minutes as needed
Airway and oxygen
High flow oxygen for hypoxemia
Goal oxygen saturation above baseline and clinical improvement
Early airway planning for progressive edema
Nebulized bronchodilator for wheeze
Albuterol dosing per age and weight
Add ipratropium for severe bronchospasm
Fluids
Crystalloid bolus for hypotension
Adult 10 ml/kg to 20 ml/kg as clinically indicated
Pediatric 20 ml/kg isotonic crystalloid
Adjuncts
H1 antihistamine for cutaneous symptoms
Diphenhydramine adult 25 mg to 50 mg IV or PO
Diphenhydramine pediatric 1 mg/kg IV or PO maximum 50 mg
H2 blocker option
Famotidine adult 20 mg IV or PO
Famotidine pediatric 0.5 mg/kg IV or PO maximum 20 mg
Corticosteroid option
Methylprednisolone adult 125 mg IV
Methylprednisolone pediatric 1 mg/kg to 2 mg/kg IV
Refractory shock
Epinephrine infusion initiation for persistent hypotension after IM dosing and fluids
Start low dose and titrate to perfusion targets
Continuous cardiac monitoring
Snake envenomation
Suspected venomous snakebite management
Antivenom indications
Progressive swelling crossing a joint
Rapid progression on serial marking
Severe pain out of proportion
Systemic toxicity
Hypotension
Recurrent vomiting or altered mental status
Hematologic toxicity
Platelets low
Fibrinogen low or INR elevated
Neurotoxicity
Ptosis ophthalmoplegia
Bulbar weakness
Pit viper antivenom pathway
Regional first line antivenom per poison center
Initial control dosing per product protocol
Repeat dosing for failure of initial control
Coagulation reassessment schedule
Repeat INR platelets fibrinogen after antivenom
Serial reassessment for delayed coagulopathy
Blood products approach
Avoid routine FFP cryoprecipitate platelets before adequate antivenom control
Use blood products for life threatening bleeding after antivenom initiation
Neurotoxic elapid pathway
Early airway planning
Declining single breath count
Bulbar dysfunction with aspiration risk
Species specific antivenom coordination
Poison center and regional antivenom bank
Transport planning if not available locally
Spider envenomation
Latrodectism black widow syndrome
Symptom control
Opioid analgesia
Titrate to pain control
Monitor for hypoventilation
Benzodiazepine for muscle spasm
Diazepam or lorazepam per institutional dosing
Avoid oversedation in older adults
Antivenin considerations
Severe refractory pain or hypertension
Toxicology consultation
Hypersensitivity risk assessment
Observation for symptom recurrence
Pain rebound after initial control
Delayed allergic reaction counseling
Loxoscelism brown recluse syndrome
Local care
Cold packs early for pain and inflammation
Elevation for swelling
Necrosis management
Early surgical debridement avoidance
Demarcation delay days to weeks
Worsening tissue loss risk with early surgery
Infection management only if clinical infection
Purulence and fever
Progressive cellulitis pattern
Systemic hemolysis monitoring
Hemoglobin trend
Indirect bilirubin and LDH if hemolysis concern
Scorpion and other arthropod envenomation
Scorpion sting neurotoxicity
Supportive care
Benzodiazepine for severe agitation or muscle jerking
Airway support for excessive secretions or respiratory compromise
Antivenom considerations
Severe cranial nerve dysfunction
Drooling
Abnormal eye movements
Pediatric severe symptoms
Toxicology consultation
Regional antivenom availability
Fire ant stings
Cutaneous care
Topical corticosteroid for pruritus
Oral antihistamine for itching
Anaphylaxis pathway when systemic symptoms
Epinephrine IM as above
Observation for recurrence
Complications and escalation
Compartment syndrome pathway
High suspicion features
Progressive neurovascular compromise
Pain with passive stretch plus tense compartments
Compartment pressure measurement consideration
Objective confirmation when diagnosis unclear
Surgery consultation early
Fasciotomy caution in snakebite
Prefer antivenom and elevation first when consistent with venom edema
Fasciotomy reserved for confirmed compartment syndrome with objective data
Secondary infection pathway
Infection indicators
Fever after initial stabilization period
Purulent drainage
Antibiotic selection
Coverage based on local patterns and wound type
Tetanus update completed
Special Populations
Pregnancy
Pregnancy considerations
Maternal stabilization priority
Epinephrine for anaphylaxis when indicated
Antivenom when maternal indications met
Fetal considerations
Viability dependent fetal monitoring when systemic toxicity
Obstetrics consultation for moderate to severe envenomation
Medication considerations
Avoid teratogenic agents without clear benefit
Prefer established anaphylaxis medications when indicated
Geriatric
Older adult considerations
Higher adverse effect risk
Sedation and falls with benzodiazepines
Respiratory depression with opioids
Comorbidity interactions
Anticoagulants and bleeding risk
Cardiovascular disease and hypertension complications
Disposition bias toward observation
Limited reserve
Higher complication risk
Pediatrics
Pediatric considerations
Weight based dosing
Epinephrine 0.01 mg/kg IM
Fluid bolus 20 ml/kg for shock
Venom burden
Higher severity with same venom amount
Lower threshold for antivenom when progression
Monitoring needs
Early airway planning with neurotoxicity
Longer observation for evolving swelling
Background
Epidemiology
Frequency patterns
Snakebites
Outdoor exposure and warm season clustering
Most bites on distal extremities
Spider bites
True medically significant bites uncommon
Misdiagnosis common in skin infections
Hymenoptera stings
Very common exposures
Anaphylaxis uncommon but high consequence
Pathophysiology
Venom mechanisms
Hemotoxic venoms
Consumption coagulopathy via procoagulant toxins
Endothelial injury with local hemorrhage
Cytotoxic venoms
Local tissue necrosis
Secondary inflammation and edema
Neurotoxic venoms
Presynaptic or postsynaptic neuromuscular blockade
Bulbar and respiratory muscle weakness
Allergic mechanisms
IgE mediated mast cell degranulation in stings
Biphasic reaction possibility
Therapeutic Considerations
Treatment principles
Antivenom
Neutralization of circulating venom
Best effect before severe tissue injury established
Supportive care
Airway protection in neurotoxicity
Hemodynamic support in anaphylaxis and shock
Antibiotics restraint
Venom injury not equal infection
Targeted antibiotics when infection signs present
Avoidance of harmful field practices
Tourniquets and incisions increase complications
Ice and heat extremes worsen local injury in some bites
Patient Discharge Instructions
copy discharge instructions
Discharge instructions
Wound and limb care
Keep limb elevated when resting
Gentle range of motion as tolerated after pain improves
Medications
Use prescribed pain medicine as directed
Avoid NSAIDs if told bleeding risk is present
Return to ED now
Trouble breathing
Lip tongue face swelling
Fainting or severe dizziness
Rapidly increasing swelling spreading up the limb
New numbness weakness or severe pain
Bleeding from gums urine stool or from the bite site
Fever with worsening redness or pus
Follow up plan
Recheck visit for worsening swelling or pain within 24 hours
Lab recheck for snakebite related coagulopathy when advised
References
Key sources for local protocol alignment
Clinical references
Regional poison center guidance for antivenom selection and dosing
Species specific antivenom protocols
Delayed coagulopathy follow up recommendations
Emergency medicine toxicology texts for envenomation syndromes
Snakebite severity and antivenom response monitoring
Latrodectism and loxoscelism supportive care
Anaphylaxis consensus criteria and emergency treatment pathways
IM epinephrine first line
Observation guidance for biphasic reactions
Source file
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SymptomDx is an educational tool for medical professionals. It does not replace clinical judgment. Verify all clinical data and drug dosages with authoritative sources.