Ultrasounds and Infection

Ultrasound guided vascular access is routine in the Intensive Care Unit, and Point of Care Ultrasound (POCUS) for diagnosis and procedural guidance is increasing in scope and frequency.

This means that the ultrasound machines are one of the most mobile devices that come into patient contact within the hospital. This mobility and patient contact carries a risk of transference of significant organisms between patients or infecting a patient in the course of a procedure.

Body fluids and harmful organisms may be carried on any of the ultrasound surfaces including the probe, cables, screen, keyboard or stand (1,2).

To reduce this risk, it is responsibility of all staff members to ensure the machine and probes are clean before and after use, ultimately the responsibility lies with the person who is performing the ultrasound.

Levels of Disinfection

Using ultrasound on intact skin for a diagnostic scan carries a different risk of probe contamination compared to probes used for invasive procedures. In order to ensure that the disinfection is sufficient for the type of risk and we are in keeping with ASUM guidelines, disinfection is categorised into levels depending on how the probe has been used. (6)

High Level Disinfection

HLD will kill vegetative microorganisms and inactivates viruses, and small numbers of bacterial spores. It is required for probes that are used on broken skin or for invasive procedures (known as semi-critical devices). This is not the same as sterilisation.

Intermediate Level Disinfection

ILD kills vegetative microorganisms, including Mycobacterium tuberculosis, all fungi, and inactivates most viruses. This can be used on probes that has been in contact with intact skin (known as non-critical devices).

Low Level Disinfection

This procedure kills most vegetative bacteria except M. tuberculosis, some fungi, and inactivates some viruses. This can be used on non-critical devices.

In Cairns ICU we use Intermediate Level Disinfection on probes for ALL general ultrasound scanning including echocardiography, and High Level Disinfection for probes used in procedures or on broken skin.

Gel

Multi-use, non sterile ultrasound Gel has been associated with transmission of infections (including blood streeam infections) from organisms such as pseudomonas, mycobacterium, klebsiella, burkholderia capaccia. (7)

For this reason, Cairns ICU does not use multi-use ultrasound gel bottles at all.

Individual sterile gel sachets are to be used for all ultrasound in the unit, either on their own, or in conjunction with a probe cover for procedures or where there is broken skin.

Probe Covers

Probe covers should be used whenever there is the risk of contact with body fluids either via non-intact skin (grazes, wounds) or when procedures are performed, regardless of whether they are sterile procedures (CVC, chest drain, paracentesis) or not (PIVC insertion).

Evidence shows that despite offering protection, probe covers are no substitute for a complete decontamination procedure.

To limit cases of cross-contamination, it is vital to use a system that incorporates all the decontamination stages: cleaning, high-level disinfection, and rinsing.

Clean the Machine

Alcohol based wipes

All surfaces of the machine must be cleaned between patient, paying particular attention to high touch areas such as screens, keyboards and levers and stands. Alcohol based wipes such as Isowipes are sufficient to clean these areas. Probe cleaning wipes tend to leave sticky residue or opaque film on the screen, which is why alcohol wipes are preferred.

They should NOT be used on the probes as they will cause damage to the probe surface.

Please ensure that the baskets of the machine only a minimal stock of Gel sachets and NO other clinical equipment to limit the risk of cross contamination.

The screen can be locked on the GE Venue Go to ensure ease of cleaning.

Clean the Probe

Tristel Duo NCU - After General Ultrasound Use

Tristel Duo NCU (non-critical ultrasound) is an Intermediate Level Disinfection. It is suitable after general ultrasound use, so long as the probe is not contaminated with blood or body fluids. It should be used as outlined below, along with Isowipes for the remainder of the machine.

Tristel Trio- After procedures or broken skin

Tristel Trio is a form of high-level disinfection. It should be used any time the ultrasound probe has been used over broken skin or after an invasive procedure

This should be used even if the probe cover has been on and remains intact.

It is a 3 stage process, all steps are required to complete disinfection:

All episodes of High Level Disinfection must be recorded so they are traceable. Cairns ICU are currently using a book to record Tristel Trio use, please record the code in the procedure note.