1.10 Infection Control & Sterile Technique in Radiation Therapy

1.10 Infection Control & Sterile Technique in Radiation Therapy

Infection control is a foundational safety discipline in radiation oncology. Cancer patients frequently present with severe immunosuppression resulting from radiation-induced bone marrow suppression, cytotoxic chemotherapy, mucosal tissue breakdown, malnutrition, and the presence of indwelling central venous access devices. Preventing Healthcare-Associated Infections (HAIs) requires rigorous application of the chain of infection concept, standard precautions, transmission-based isolation protocols, surgical aseptic technique, and protective neutropenic isolation.

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The CDC Chain of Infection

Disease transmission within a radiation therapy department requires six interconnected epidemiological links. Interrupting any single link completely halts pathogen transmission:

  [ 1. INFECTIOUS AGENT ] (Bacteria, Viruses, Fungi, Spores)
            |
  [ 2. RESERVOIR ] (Humans, Contaminated Equipment, Linac Table Tops)
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  [ 3. PORTAL OF EXIT ] (Respiratory Droplets, Blood, Open Skin, Stool)
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  [ 4. MODE OF TRANSMISSION ] (Direct Contact, Indirect Fomite, Airborne)
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  [ 5. PORTAL OF ENTRY ] (Non-intact Skin, Mucosa, IV Ports, Catheters)
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  [ 6. SUSCEPTIBLE HOST ] (Immunocompromised Oncology Patient)

1. Infectious Agent: The pathogen responsible for infection (e.g., Staphylococcus aureus, Clostridioides difficile, Influenza virus, Aspergillus).
2. Reservoir: The environment or habitat where the pathogen lives and multiplies (e.g., infected individuals, standing water, contaminated positioning sponges, linac couch tops, laser remotes).
3. Portal of Exit: The pathway by which the pathogen exits the reservoir (e.g., respiratory secretions, blood, wound exudate, feces, urine).
4. Mode of Transmission: The mechanism by which the pathogen travels from reservoir to host (e.g., direct physical contact, indirect contact via contaminated equipment/fomites, respiratory droplets, airborne droplet nuclei).
5. Portal of Entry: The site through which the pathogen enters the susceptible host (e.g., non-intact skin, mucous membranes, intravenous catheter sites, urinary catheters, brachytherapy applicator tracts).
6. Susceptible Host: An individual with compromised defense mechanisms (e.g., neutropenic radiation therapy patients receiving concurrent chemotherapy).

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Hand Hygiene Protocols & CDC Standards

Hand hygiene is universally recognized as the single most effective intervention for preventing Healthcare-Associated Infections. The Centers for Disease Control and Prevention (CDC) and World Health Organization (WHO) establish strict hand hygiene guidelines for healthcare personnel.

+-------------------------------------------------------------------------+
|                    HAND HYGIENE METHOD SELECTION                        |
+-------------------------------------------------------------------------+
|  ROUTINE CLINICAL CONTACT (No visible soil)                             |
|  - Use Alcohol-Based Hand Rub (60% to 95% alcohol)                      |
|  - Apply to palm and rub all surfaces vigorously for 20 to 30 seconds   |
|  - Allow hands to dry completely before applying gloves                |
+-------------------------------------------------------------------------+
|  C. DIFFICILE / VISIBLY SOILED HANDS / SPORE PATHOGENS                  |
|  - MANDATORY Soap and Water Handwashing                                 |
|  - Lather and scrub all surfaces thoroughly for 40 to 60 seconds        |
|  - Alcohol-based rubs DO NOT kill C. diff endospores or bacterial spores|
+-------------------------------------------------------------------------+

WHO 5 Moments for Hand Hygiene

Radiation therapists must perform hand hygiene:

1. Before touching a patient (e.g., prior to positioning on the treatment couch).
2. Before performing a clean/aseptic procedure (e.g., accessing a central port or handling brachytherapy needles).
3. After body fluid exposure risk (e.g., handling urinary drainage bags or suctioning).
4. After touching a patient (e.g., following completion of treatment alignment).
5. After touching patient surroundings (e.g., touching linac table hand controls, immobilizers, or side rails).

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Standard Precautions vs. Transmission-Based Precautions

Standard Precautions

Applied universally to all patients in all healthcare settings, regardless of suspected or confirmed infection status. Standard precautions assume all blood, body fluids, secretions, non-intact skin, and mucous membranes contain transmissible infectious agents.

• Components: Hand hygiene, use of Personal Protective Equipment (PPE) based on anticipated exposure (gloves, gown, mask, face shield), safe injection practices, respiratory hygiene/cough etiquette, and environmental decontamination of treatment equipment.

Transmission-Based Precautions

Implemented in addition to Standard Precautions for patients with documented or suspected infection with highly transmissible or epidemiologically important pathogens.

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Protective (Reverse / Neutropenic) Isolation

Protective isolation is designed to protect severely immunocompromised patients—specifically those with Absolute Neutrophil Counts (ANC) $<500/\mu\text{L}$ (severe neutropenia)—from acquiring opportunistic environmental pathogens.

  AIRBORNE ISOLATION (Negative Pressure)       PROTECTIVE ISOLATION (Positive Pressure)
  [ Corridor ] ----> (Air Inward) ----> [ Room ]   [ Corridor ] <---- (Air Outward) <---- [ Room ]
  Prevents contagious airborne pathogens          Protects immunocompromised patient
  from escaping room into corridor.               from corridor pathogens entering room.

• Airflow Controls: Requires a Positive-Pressure Room equipped with HEPA filtration. Air flows outward from the patient room into the corridor when doors open, preventing airborne corridor contaminants from entering.
• Clinical Rules:
  • Strict hand hygiene prior to entering the patient room.
  • Absolute prohibition of fresh flowers, potted plants, standing water, and raw unpasteurized foods in care areas (to prevent exposure to Aspergillus fungal spores and Pseudomonas bacteria).
  • Staff displaying any upper respiratory or viral symptoms are strictly barred from patient contact.
  • Fever in a neutropenic patient ($>38.0^\circ\text{C}$ or $100.4^\circ\text{F}$) is a critical medical emergency requiring immediate blood cultures and broad-spectrum IV antibiotics.

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Aseptic Technique & Sterile Field Protocols in Radiation Therapy

Sterile technique (surgical asepsis) is mandatory during invasive radiation oncology procedures, including permanent seed brachytherapy implants, High-Dose Rate (HDR) prostate/cervical catheter insertion, fiducial marker placement under ultrasound/CT guidance, and central venous access port cannulation.

Mandatory Rules of Surgical Asepsis

1. Sterile Touches Sterile Only: Only sterile items may touch other sterile items. An unsterile item touching a sterile item causes immediate contamination.
2. Field Boundaries & Height Controls: Any sterile item, drape, or gloved hand that falls below waist level or out of the direct line of vision is considered contaminated.
3. The 1-Inch Border Rule: The 1-inch (2.5 cm) outer margin along the perimeter of a sterile field is considered non-sterile. All sterile instruments and items must be placed strictly within the center of the field.
4. No Reaching Across: Healthcare personnel must never reach over or across a sterile field; micro-particles shed from arms contaminate the sterile surface.
5. Prevention of Strike-Through Contamination: If a sterile drape becomes wet or damp, capillary action draws microorganisms up from the unsterile surface underneath (strike-through contamination), rendering the entire field unsterile.
6. Opening & Gowning Protocols: Sterile packages must be opened away from the body first. Gowning and gloving for invasive brachytherapy procedures require the closed-gloving technique after performing a surgical hand scrub.