Approach to the Critical Patient

Cardiac emergency recognition

High-degree AV block identification

Escalation triggers

Neurologic emergency recognition

Lyme meningitis red flags

Monitoring and targets

Cardiac monitoring bundle

History

Exposure history

Tick exposure context

Symptom characterization

Dermatologic history

Cardiac symptoms

Neurologic symptoms

Constitutional symptoms

Timeline

Symptom onset relative to tick bite

Risk factors and past history

Risk stratification

Comorbidities affecting management

Physical Exam

Vital signs

Hemodynamic assessment

Skin examination

Multiple erythema migrans lesions

Neurologic examination

Cranial nerve examination

Meningeal signs

Motor and sensory examination

Cardiac examination

Rhythm and rate

Signs of heart failure

Musculoskeletal and lymph nodes

Joint examination

Lymphadenopathy

Differential Diagnosis

Dermatologic mimics

Multiple EM differential

Facial palsy differential

Causes of facial nerve palsy

Cardiac mimics

AV block and conduction disease differential

Co-infection considerations

Tick-borne co-infections from Ixodes scapularis

Laboratory Tests

Serologic testing

Two-tiered Lyme serology — primary diagnostic test for disseminated disease

Hematology and chemistry

Complete blood count interpretation

Metabolic panel and hepatic function

Inflammatory markers

Acute phase reactants

Cardiac biomarkers

Troponin and BNP if cardiac involvement suspected

CSF analysis

Lumbar puncture — indicated if meningitis or CNS involvement suspected

Diagnostic Tests

Scoring Systems

Lyme carditis severity stratification

Neuroborreliosis clinical severity

MRI

Brain MRI with gadolinium contrast

CT

CT head — limited role in Lyme disease

Ultrasound

Echocardiography — cardiac ultrasound

Point-of-care ultrasound

Disposition

Admission indications

Mandatory hospitalization criteria

Discharge criteria

Safe for outpatient management

Observation indications

Borderline presentations requiring monitoring

Consultation triggers

Cardiology

Neurology

Infectious Disease

Treatment

Multiple erythema migrans — oral regimens

First-line oral therapy — doxycycline

Alternative oral options — penicillin class

Second-line — azithromycin

Cranial nerve palsy without meningitis

Oral antibiotics — equivalent to IV for isolated CN palsy

Supportive care for facial palsy

Lyme meningitis and CNS disease

IV antibiotics for CNS involvement

Lyme carditis

IV antibiotics — hospitalized patients

Temporary pacing

Monitoring during carditis treatment

Antibiotic contraindications and adjustments

Doxycycline contraindications

Post-treatment Lyme disease syndrome

Special Populations

Pregnancy

Antibiotic selection in pregnancy

Maternal and fetal outcomes

Geriatric

Clinical presentation differences in older adults

Medication considerations in older adults

Pediatrics

Age-specific antibiotic dosing

Pediatric presentations

Background

Epidemiology

Incidence and distribution

Stage 2 — early disseminated prevalence

Seasonal and vector epidemiology

Pathophysiology

Infectious agent and transmission

Dissemination mechanism

Cardiac pathophysiology

Neurologic pathophysiology

Therapeutic Considerations

Evidence base for treatment recommendations

Antibiotic mechanism and selection rationale

Post-treatment Lyme disease syndrome — PTLDS

Patient Discharge Instructions

copy discharge instructions

Discharge instructions for Lyme Disease Stage 2

Your diagnosis

Your medications

Activity

Facial palsy care if applicable

Follow-up appointments

Return to the emergency department immediately if you experience

Prevention of future tick bites

What to expect during recovery

References

Guidelines and key sources

IDSA/AAN/ACR 2020 Joint Clinical Practice Guidelines

CDC Tickborne Diseases Reference Manual — 6th edition 2022

JAMA Review 2016

NEJM Review — Shapiro ED 2014

Wilderness Medical Society 2021 Guidelines

BMJ Review — Kullberg et al 2020

IDSA/ASM Microbiology Laboratory Guide 2024

PLoS ONE — Uzomah et al 2021

Nature Reviews Disease Primers — Strle et al 2026