3.2 Infection Control & Hazardous Materials

Ultrasound is often described as noninvasive, but transducers contact broken skin, mucous membranes, blood, and body fluids every day, and gels, linens, and keyboards all move between patients. The Centers for Disease Control and Prevention (CDC) framework for infection control is a core ARRT Patient Care topic.

The Chain of Infection

Infection spreads only when six links connect. Breaking any link prevents transmission:

1. Pathogen - the infectious agent (bacterium, virus, fungus, parasite)
2. Reservoir - where the pathogen lives and multiplies (humans, water, equipment, contaminated gel)
3. Portal of exit - how it leaves the reservoir (respiratory secretions, blood, exudate, feces)
4. Mode of transmission - how it travels:
   • Direct: droplet (large respiratory droplets traveling ~3-6 feet) or direct contact (skin-to-skin, blood exposure)
   • Indirect: airborne (small particles that remain suspended, e.g., tuberculosis), vehicle-borne (a contaminated inanimate object or fomite - a transducer, gel bottle, or keyboard), vector-borne (an insect or animal, mechanical carriage or biological replication inside the vector as with mosquitoes and malaria)
5. Portal of entry - how it enters the new host (mucous membranes, broken skin, respiratory tract, needlestick)
6. Susceptible host - a person whose defenses are down (immunosuppressed, elderly, neonatal, diabetic, post-surgical)

In the ultrasound suite, the most realistic vehicle-borne scenario is a poorly disinfected endocavitary transducer or a contaminated multi-use gel bottle passing a pathogen between patients.

Asepsis: Disinfection, Sterilization, and Technique

Asepsis means the absence of pathogenic organisms. The Spaulding classification matches the device to the required process:

Disinfection destroys most pathogens but not all spores; sterilization destroys all microbial life including spores. Endocavitary transducers must undergo high-level disinfection with agents such as glutaraldehyde, ortho-phthalaldehyde (OPA), or hydrogen peroxide-based systems between every patient - even when a probe cover was used, because covers have a documented failure rate. Covers and gels do not substitute for HLD.

Medical asepsis (clean technique) reduces organism numbers - hand hygiene, clean gloves, disinfected surfaces - and applies to routine scanning. Surgical asepsis (sterile technique) eliminates all organisms and applies to interventional procedures: sterile gloves, sterile drapes, sterile transducer covers, and sterile single-use gel packets.

Proper gel handling: multi-use bottles must not contact the patient or the transducer between patients, are never topped off (which contaminates the new gel), and are discarded by their expiration date. For procedures near broken skin, neonates, or any sterile field, use single-use sterile gel packets. Warmed gel bottles must be cleaned and disinfected per policy.

CDC Standard Precautions

Standard Precautions apply to every patient, treating all blood, body fluids, secretions, excretions (except sweat), non-intact skin, and mucous membranes as potentially infectious:

• Hand hygiene - the single most effective infection-control practice: alcohol-based rub or soap and water before and after every patient contact, after glove removal, and after touching contaminated surfaces
• Personal protective equipment (PPE) - gloves for contact with blood/body fluids or mucous membranes; gowns and masks/eye protection when splash or spray is anticipated
• Safe handling of contaminated equipment and surfaces - transducers, cables, consoles, and stretchers are cleaned and disinfected between patients
• Disposal of contaminated materials: soiled linens bagged at the bedside without shaking; needles and sharps directly into rigid puncture-resistant sharps containers (never recapped by hand); patient supplies and blood/body fluid waste into biohazard containers

Transmission-Based Precautions

Used in addition to Standard Precautions for known or suspected pathogens:

• Contact precautions (gown + gloves on entry): MRSA, VRE, Clostridioides difficile, draining wounds - note C. difficile spores require soap-and-water handwashing, since alcohol rub does not kill spores
• Droplet precautions (surgical mask within 3-6 feet): influenza, pertussis, Neisseria meningitidis
• Airborne precautions (fit-tested N95 respirator, negative-pressure isolation room): tuberculosis, measles, varicella (chickenpox)

Neutropenic precautions (reverse isolation) protect the immunocompromised patient from us: meticulous hand hygiene, no fresh flowers or standing water, mask for anyone with a cold, and healthy staff only. Healthcare-associated (nosocomial) infections (HAIs) - infections acquired during care, such as catheter-associated urinary tract infections, central-line bloodstream infections, ventilator-associated pneumonia, and surgical site infections - affect roughly 1 in 31 hospital patients on any given day and are the outcome these precautions exist to prevent.

Hazardous Materials: Disinfectants and Safety Data Sheets

High-level disinfectants are themselves hazards: glutaraldehyde and OPA cause respiratory irritation, dermatitis, and ocular injury. They must be used with adequate ventilation, gloves and eye protection, covered soaking basins, and proper neutralization or disposal per local regulations - never poured down a drain unless the product's disposal instructions permit it. Under the Occupational Safety and Health Administration (OSHA) Hazard Communication Standard, every hazardous chemical must have a Safety Data Sheet (SDS) available to employees. The standardized 16-section SDS covers, in order: product identification, hazard identification, composition, first-aid measures, firefighting measures, accidental release, handling and storage, exposure controls/PPE, physical and chemical properties, stability and reactivity, toxicological information, ecological information, disposal, transport, regulatory information, and other information (including the preparation or revision date). Know where your department's SDS binder or database lives - the exam expects you to know the SDS is the first reference when a spill or exposure occurs.