Accurate device information and proper sterilization or disinfection are crucial to ensure safety during ultrasound procedures.
Ultrasound-guided percutaneous procedures are a varied and complex group of medical procedures involving needle puncture of the skin under the guidance of ultrasound imaging. The growth of these procedures has been considerable, creating unique challenges for infection prevention.
There are over 140 unique ultrasound-guided percutaneous procedures with different requirements for placement of the probe and needle used to conduct the intervention. Other factors such as the technique used, level of training of the clinician, patient’s medical condition and unique patient anatomy also impact the type of tissue the probe contacts, making this a complex area of infection prevention that needs to be assessed carefully. The level of disinfection required for ultrasound probes used in percutaneous procedures varies and transcends all three categories of Spaulding. While many probes will only contact intact skin, others risk contacting broken skin or sterile tissue, such as the needle puncture site.
Clinicians need to be equipped with the right information to correctly classify the ultrasound probes used in these procedures, ensuring that devices have undergone sufficient disinfection or sterilization prior to use.
This article offers an overview of the complexities of percutaneous procedures and the key infection prevention considerations in this area.
The Spaulding Classification determines disinfection requirements
Spaulding Classification is a cornerstone of infection control practice and a foundational aspect of federal and international infection prevention regulations, standards, and guidelines. The FDA and CDC use the Spaulding Classification in official medical device reprocessing guidance, as do the World Health Organization, The Joint Commission (TJC), and the Association for the Advancement of Medical Instrumentation (AAMI), an internationally recognized standards development organization.1-6
Under Spaulding, a device is classified as non-critical if it only contacts intact skin (Table 1). Devices that contact non-intact skin or mucus membranes are classified as semi-critical, while those that contact sterile tissue or the bloodstream are classified as critical. Semi-critical and critical devices require high-level disinfection (HLD) and the use of an FDA-approved sterile sheath at a minimum.1-3
The Spaulding classification needs to be assigned to medical instruments prior to their use so they can undergo the appropriate level of disinfection/sterilization to manage risk during the procedure. For percutaneous procedures, the clinician must decide in advance whether the probe might contact sterile tissue, broken skin, or only intact skin during the procedure. An ultrasound probe that has been appropriately disinfected or sterilized for the procedure can then be used.
Percutaneous procedures span all categories of Spaulding.
More than 140 ultrasound-guided percutaneous procedures spanning at least 9 types of procedural categories (Table 2). Ultrasound is often used to guide the needle during percutaneous procedures, resulting in better first-attempt success rates and fewer overall needle insertions.7-9 This can lower the risk of infection or complications for patients, with ultrasound-guided techniques associated with reduced rates of adverse events in some procedures.10,11 However, the use of ultrasound guidance requires special consideration for infection control, as there is a risk of contact between the non-sterile ultrasound probe and adjacent sterile devices (such as the needle), as well as penetration of the sterile field.
The wide variation in ultrasound-guided percutaneous procedures leads to variation in the patient tissue sites contacted during use (Figure 1). Many percutaneous procedures only involve contact between the probe and healthy, intact skin. Low-level disinfection (LLD) is appropriate in these cases.
In some cases, there may be a risk of contact with broken skin during the procedure, meaning the device is semi-critical and requires HLD. Other times, the probe may break the sterile field and might also directly contact sterile tissue, such as the puncture site and adjacent sterile devices. In these scenarios, the device is critical and requires sterilization or, if sterilization is not possible, HLD.
Ultrasound-guided percutaneous biopsies are a varied collection of clinical procedures encompassing 2 broad methods (fine needle aspiration and core needle)and many medical interventions. At least 20 distinct percutaneous biopsy procedures regularly involve ultrasound guidance. These procedures differ in location on the body, tissue accessed, proximity between the ultrasound probe and needle, and technique used. All these factors create variables that can change the risk of contact between the ultrasound probe and sterile tissue during the procedure.
FDA guidance on reprocessing of ultrasound probes specifically highlights biopsy procedures as semicritical or critical in nature, requiring a minimum of high-level disinfection.2
Percutaneous procedures to gain venous or arterial access are some of the most frequently performed procedures in hospital settings. Ultrasound guidance is increasingly used as standard of care for central line placements, with the ultrasound probe and needle often in close proximity. Because of the widespread nature of these procedures, they are performed throughout many departments in a range of clinical settings, under varying levels of medical promptness. This creates variation in the risk of contact between the probe and puncture site, meaning that an absence of contact cannot be guaranteed. These procedures can also have added complexity due to the clinician using their hands to apply skin tension while also manoeuvring the probe and needle.
Use of a sheath does not change the level of reprocessing required.
FDA-approved, single-use, sterile sheaths are also recommended for semi-critical and critical applications. However, it’s important to note that using a sheath does not change the level of disinfection required.2,3 Condoms used on ultrasound probes can fail up to 13% of the time, while commercial covers fail up to 5% of the time.12 A surface ultrasound probe used in central venous catheter (CVC) placement was found to have gouge marks on the transducer head, demonstrating that the needle had penetrated the sheath (minimally twice) and contacted the probe during the procedures (Figure 2).13 This means biological material on the sheath and transducer head could be directly introduced into the patient’s sterile tissue.
Needle stick injuries also occur at a significant rate during percutaneous procedures, even among experienced interventionalists.14
Individual variables can influence the risk of contact
As well as the variation between different types of percutaneous procedures, individual patient or clinician factors may change the level of reprocessing required. These include:
The “no touch” technique for ultrasound-guided procedures aims to keep the transducer entirelyout of the sterile field, away from contact with broken skin, sterile tissue, and sterilized devices. While LLD is acceptable if the no-touch technique is performed without error, the operator's experience level can significantly impact the technique’s success. A higher level of disinfection should always be used if the success of the no-touch technique cannot be guaranteed.
Percutaneous procedures are performed by a range of clinicians with different medical backgrounds and clinical expertise. Infection prevention measures must account for junior staff performing procedures who may have received less formal training. Even with adequate training, multiple attempts are common for percutaneous procedures. Widely used procedures like peripheral intravenous cannula (PIVC) insertion can have first-attempt success rates as low as 65%.15 Each successive attempt increases the risk of contact between the ultrasound probe and needle, increasing patient infection risk.
Condition of patient
The patient may be immunocompromised or at high mortality risk, requiring a more nuanced consideration of infection risk. There is a general clinical acceptance for heightened awareness for and application of infection prevention practices for those patients in a medically fragile state. There may also be physical characteristics (eg burns, abrasions, wounds, rashes, or pox) that mean the probe is likely to contact with broken skin, therefore requiring HLD or sterilization.
Guidance varies in recommendations for percutaneous procedures.
FDA and CDC guidance states that ultrasound probes must be reprocessed according to the Spaulding classification. That is, probes that come into contact with non-intact skin or sterile tissue must be high-level disinfected at a minimum and should preferably be sterilized. This guidance considers the diversity of percutaneous procedures, allowing for a different level of disinfection depending on the specific clinical procedure and implementation.
In 2021, the American Institute of Ultrasound in Medicine (AIUM) released a position statement on the disinfection of ultrasound probes used for percutaneous procedures, stating that they can safely undergo low-level disinfection (LLD).16
While guidance is needed in this complex area, this position statement only accounts for a subset of percutaneous procedures–those that contact intact, healthy skin. Some may come in contact with non-intact skin (eg burns, abrasions, wounds, rashes, or pox) and would be semi-critical, minimally requiring HLD. Others will involve contact between the probe and puncture site (sterile tissue), requiring sterilization or HLD with a sterile sheath if sterilization is not possible.
A simplified, universal approach, where all percutaneous procedure probes are considered non-critical, does not account for the reality that some probes have a higher Spaulding classification. Deviation from Spaulding has the potential to create unnecessary risk for patients. To maintain patient safety, clinicians must be aware of the requirements of the Spaulding classification and able to correctly classify probes used in percutaneous procedures as non-critical, semi-critical, or critical.