Infectious Diseases - Anesthesia Lecture

Infectious Diseases

Concepts, Manifestations, Diagnosis, and Management

Essential Knowledge for Anesthetic Practitioners | October 26, 2025

Core Concepts

Infectious diseases result from pathogenic microorganisms invading the body and disrupting normal function. As anesthetists, we encounter infected patients daily and must understand transmission dynamics, host defenses, and implications for perioperative care.

10M

Annual surgical site infections

700K

HAIs in US hospitals

35%

Antibiotic misuse

1.27M

AMR deaths globally

Major Pathogen Categories

Bacteria

Viruses

Fungi

Parasites

Prions

Transmission Routes

• Contact: Direct (person-to-person) or indirect (fomites)
• Droplet: Respiratory droplets (>5µm) within 3-6 feet
• Airborne: Small particles (<5µm) that remain suspended
• Vector-borne: Mosquitoes, ticks, etc.
• Vehicle: Food, water, blood products

Host Defense Mechanisms

Physical barriers (skin, mucosa), innate immunity (phagocytes, complement), and adaptive immunity (T/B cells) protect against infection. Anesthesia and surgery can temporarily impair these defenses.

Anesthesia-Specific Considerations

Why Infectious Diseases Matter to Anesthetists

• Increased perioperative morbidity and mortality
• Altered pharmacokinetics/pharmacodynamics of anesthetics
• Risk of disease transmission to healthcare workers
• Potential for intraoperative sepsis or septic shock
• Impact on airway management and ventilation
• Need for infection control precautions in OR

High-Risk Patient Scenarios

• Active systemic infection (fever, leukocytosis)
• Immunocompromised states (HIV, chemotherapy, transplants)
• Known multidrug-resistant organisms (MRSA, VRE, ESBL)
• Recent travel to endemic areas
• Prosthetic implants or devices
• Recent antibiotic exposure

Critical Principle

Elective surgery should be postponed in patients with active systemic infection until the infection is controlled. Proceeding increases risk of sepsis, poor wound healing, and mortality.

Clinical Manifestations

Systemic Signs of Infection

• Fever (>38°C) or hypothermia (<36°C)
• Tachycardia and tachypnea
• Leukocytosis or leukopenia
• Malaise, fatigue, anorexia
• Altered mental status (especially in elderly)

Localizing Signs

• Respiratory: Cough, sputum, dyspnea, consolidation
• Urinary: Dysuria, frequency, suprapubic pain
• Abdominal: Pain, distension, peritoneal signs
• Skin/Soft tissue: Erythema, warmth, swelling, purulence
• CNS: Headache, neck stiffness, photophobia

Sepsis Recognition

Use qSOFA criteria for rapid bedside assessment:

• Respiratory rate ≥22/min
• Altered mentation
• Systolic BP ≤100 mmHg

≥2 criteria indicates high risk for poor outcomes.

Remember: Elderly and immunocompromised patients may present with atypical symptoms (e.g., no fever, subtle mental status changes).

Diagnostic Approach

Initial Assessment

• Detailed history (travel, exposures, sick contacts)
• Thorough physical exam with focus on potential sources
• Vital signs including temperature trends
• Basic labs: CBC, CRP, lactate, cultures

Microbiological Testing

• Cultures: Blood, urine, sputum, wound before antibiotics
• Molecular tests: PCR for viruses, TB, etc.
• Serology: Antibody detection for specific pathogens
• Antigen tests: Rapid diagnostics (e.g., influenza, RSV)

Imaging

• Chest X-ray for respiratory symptoms
• CT/MRI for suspected abscess or CNS infection
• Ultrasound for soft tissue or abdominal infections

Preoperative Testing Considerations

Obtain cultures before starting antibiotics. Avoid routine preoperative screening cultures unless clinically indicated. Focus on identifying active infection that would contraindicate elective surgery.

Management Principles

General Approach

1. Source control (drainage, debridement, device removal)
2. Appropriate antimicrobial therapy
3. Supportive care (fluids, vasopressors if needed)
4. Infection prevention and control measures

Antimicrobial Stewardship

• Start empiric therapy based on likely pathogens and local resistance patterns
• De-escalate once culture results available
• Use narrowest spectrum effective agent
• Optimize dosing and duration
• Avoid unnecessary antibiotic use

Standard + Transmission-Based Precautions

Standard: Hand hygiene, PPE for anticipated exposure

Contact: Gloves + gown (MRSA, C. diff, VRE)

Droplet: Surgical mask (influenza, meningitis)

Airborne: N95 respirator + negative pressure room (TB, measles)

Antibiotic Red Flags

• Vancomycin trough levels must be monitored
• Aminoglycosides require therapeutic drug monitoring
• Fluoroquinolones have black box warnings for tendinitis
• Metronidazole causes disulfiram-like reaction with alcohol

Key Takeaways for Anesthetists

Preoperative assessment: Identify active infection and postpone elective surgery when appropriate.

Infection control: Strict adherence to standard precautions and appropriate transmission-based precautions in OR.

Pharmacology awareness: Understand antibiotic side effects and interactions with anesthetic agents.

Sepsis recognition: Early identification of sepsis can be life-saving during perioperative period.

Antibiotic timing: For surgical prophylaxis, administer within 60 minutes before incision (120 min for vancomycin/fluoroquinolones).

Final Thought

"As anesthetists, we are on the front lines of infection prevention and control. Our vigilance protects both patients and healthcare workers."

© 2025 Department of Anesthesiology | This educational material is for training purposes only

References: IDSA Guidelines 2023, Surviving Sepsis Campaign, CDC Isolation Guidelines, Miller's Anesthesia 9th Edition