Infection Control Recommendations for Regional Anaesthesia

Spinal, epidural and caudal procedures

Peripheral nerve blocks

The use of ultrasound

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Spinal, epidural and caudal procedures

A historical and physical examination and review of relevant laboratory studies should be conducted to identify patients who may be at risk of infectious complications. These include patients with retroviral disease, uncontrolled diabetes, oncology patients, post-transplant, etc. Consider alternatives to neuraxial techniques for patients who are at high risk.

When a neuraxial technique is used in a patient with known or suspected bacteraemia, prophylactic pre-procedure antibiotic therapy should be considered.

Aseptic technique should always be used during the preparation of equipment, e.g. ultrasound, the preparation of drugs to be administered, and the placement of neuraxial needles and catheters.

A caudal anaesthetic is considered to be a neuraxial technique as the caudal space is a continuation of the epidural space.

Maximal barrier precautions apply:

• Jewellery should be removed, and hands washed.
• Caps, masks (covering both mouth and nose and all facial hair), sterile gloves and gowns should be worn.
• Sterile drapes should be used.
• A face mask should also be worn by the anaesthetic assistant.
• An antiseptic, preferably a 0.5% solution of chlorhexidine with 70% alcohol, should be used for skin preparation, and adequate time allowed for drying.
• Meticulous care should be taken to avoid contact of chlorhexidine with the cerebrospinal fluid.
• Do not pour chlorhexidine into containers in close proximity to equipment that will be used for the neuraxial anaesthetic. Cover or protect equipment while cleaning with chlorhexidine.
• A sterile occlusive dressing must be applied over the catheter insertion site.
• Bacterial filters may be considered during extended continuous epidural infusion.
• Disconnection and reconnection of the neuraxial delivery system should be limited.
• The removal of unwitnessed, accidentally disconnected catheters should be considered.
• Catheters must not remain in situ for longer than clinically necessary

Rationale

Infectious complications of neuraxial anaesthesia include meningitis, encephalitis and epidural abscesses. The frequency of meningitis is estimated to range from 0.2–1.3 per 10  000, and that of epidural abscess to be one in 145 000.²²⁴ Although rare, the consequences of these complications are disastrous. In the Saving Mothers 2008-2010: fifth report on the Confidential Enquiries Into Maternal Deaths in South Africa, one maternal death was attributed to post-spinal meningitis.²²⁵

Meningitis usually occurs within 6–36 hours after dural puncture. It can be mistaken for post-dural puncture headache. The latter should always be a diagnosis of exclusion. Meningitis is usually associated with fever, neck stiffness, photophobia and increased septic markers. Prompt treatment with antimicrobial drugs is indicated as a delay can be associated with worse outcomes.

Chlorhexidine and alcohol are toxic to the tissues, and care should be taken not to contaminate the needles. Always allow alcohol to evaporate before inserting the needle.

The recommendations are mainly based on a practice advisory produced by the American Society of Anesthesiologists (ASA) in 2010.²²⁶ Guidelines produced by the Association of Anaesthetists of Great Britain and Ireland (AAGBI)⁹ and the Australian and New Zealand College of Anaesthetists (ANZCA) make similar recommendations.²²⁷

As infectious complications associated with neuraxial procedures are uncommon, evidence from the literature on the efficacy of interventions in their reduction is also scarce. The result is that the literature is insufficient in determining whether or not any of the interventions reduce infectious complications associated with neuraxial techniques.²²⁶

Patient factors

No controlled trials have addressed the impact of a focused history, physical examination or laboratory evaluation on infectious complications, but several studies suggest certain patient characteristics, e.g. cancer, diabetes and an impaired immune response, may be associated with neuraxial infection.²²⁶

Jewellery

Watches and rings should be removed during handwashing.^228,229 Higher microbial counts have been found in healthcare workers who do not remove rings during handwashing.²²⁹

Gowns

ASA members and consultants were equivocal with regards to the wearing of gowns.²²⁶ The AAGBI includes gowns as part of its maximal barrier precautions, which it recommends for neuraxial techniques⁹ There are insufficient data to make definitive recommendations with regards to routine gown use in this context.

Surgical face masks

This area is also not without controversy. However, in cases of neuraxial-associated meningitis in which the pathogen was known, 24% of the infections were of skin origin, while an overwhelming 76% were attributed to mouth commensals.²³⁰ Furthermore, Schneeberger reported on a cluster of four patients who developed streptococcal meningitis after spinal anaesthesia, performed by the same anaesthesiologist who was under treatment for recurrent tonsillitis and who did not wear a mask.²³¹ North and Brophy described an epidural abscess that was proven to be caused by a strain of Staphylococcus cultured from the nose of the anaesthetist who placed the epidural catheter.²³² In addition, Philips et al. showed that wearing a face mask resulted in marked reduction in the bacterial contamination of a surface in close proximity (30 cm) to the upper airway.²³³ Therefore, in line with a recent CDC recommendation, the use of a surgical face mask is recommended when performing a neuraxial procedure.²³⁴

Skin preparation

Two randomised controlled trials indicated that the rate of positive bacteriological cultures was reduced when the patient’s skin was prepared with chlorhexidine, rather than with povidoneiodine, before epidural catheterisation.^235,236 The anaesthetist must exercise extreme caution to prevent the contact of chlorhexidine and alcohol with cerebrospinal fluid and neural structures as both are neurotoxic. The 0.5% solution is preferred over the 2% solution due to the lack of clear evidence for the use of the one over the other. The antimicrobial action of alcohol is denaturation of proteins and its dehydrating properties. Therefore, it must be allowed to dry completely before the procedure.

Bacterial filters

Three observational studies showed that infections and epidural abscesses occur in the presence of micropore filters.^237-239 Therefore, an aseptic technique should be used when drawing up drugs to be administered via the neuraxial route.

Duration of epidural catheterisation

Observational studies indicate that infections and epidural abscesses occur in the presence of longer duration of catheterisation.^240-244

Peripheral nerve blocks

• Maximal barrier precautions are generally not necessary. Maximum barrier precautions should be used if the patient is immunocompromised or a perineural catheter needs to be inserted.
• Jewellery should be removed, and hands washed. Sterile gloves must be worn. Aseptic techniques should always be used during the preparation of equipment, e.g. ultrasound, the drawing up of drugs and the placement of needles and catheters.
• An antiseptic, preferably chlorhexidine with alcohol should be used for skin preparation and adequate time allowed for drying.
• Do not put the probe on the patient until the alcohol has evaporated to prevent alcohol induced damage to the probe.

The insertion of a perineural catheter

• Use a sterile occlusive dressing.
• Limit disconnection and reconnection of the delivery system.
• Catheter should not remain in situ for longer than is clinically necessary.

The use of ultrasound

A sterile probe and handle covering should be used, e.g. a sterile transducer sheath. The ultrasound machine and probe should be decontaminated before and after use by following the instructions from the manufacturer manual. Product information should be consulted with regards to which cleaning agents are appropriate for the specific machine or probe. Use single-use, sterile gel, e.g. K-Y^® lubricating gel sachet.

Rationale

Even with a perineural catheter in situ, infectious complications relating to peripheral nerve blocks are rare, e.g. local infections of 0–3.2% and abscess formation of 0–0.9%.²⁴⁵ The risk is much smaller still for “single-shot” blocks. There have been only occasional case reports in the literature.²⁴⁶

Unless a perineural catheter is to be placed, or the patient is immunocompromised, both the AAGBI and ANZCA guidelines agree that maximal barrier precautions are unnecessary when performing peripheral nerve blocks.^9,227 If a perineural catheter is to be inserted, the procedure should be as for the previously described neuraxial techniques.

Ultrasound transducers and gel have both been implicated in outbreaks of hospital-acquired infection.^247-251 There are no universally adopted guidelines for the decontamination of ultrasound machines and transducers used for ultrasound-guided regional anaesthesia. The result is a wide variety of different practices. Only gel that is manufactured to be used as ultrasound gel should be used. There are a number of substances in the various gels that can cause physical damage to the probe. Such substances include alcohol-based solutions, mineral oil, olive oil, iodine, lotions, aloe vera and methyl/ethyl parabens.

The Spaulding classification recommends different levels of decontamination of medical equipment, depending on the risk of infection. It categorises equipment as critical (a high risk of infection), semi-critical (equipment in contact with mucous membranes or non-intact skin) and non-critical (equipment in contact with intact skin).⁹⁵

Ultrasound-guided regional techniques involve skin puncture and possible blood contamination of the transducer. Therefore, in this context, ultrasound probes for regional procedures should be considered to be semi-critical equipment, which, according to the Spaulding classification, requires full sterilisation or the use of a sterile sheath, followed by prolonged immersion with high-level disinfectants. It is however of critical importance to consult with the manufacturers to ensure that the correct methods are used to prevent damage of the ultrasound probes. The ultrasound probe needs to be cleaned after every use by following the user manual.

Washing the ultrasound probe

• Remove coupling gel with a soft cloth.
• Wash the probe with mild soap in lukewarm water.
• A soft cloth or gauze should be used to remove all visible soap. Air dry or dry using a clean, soft cloth.
• Refer to the user manual to determine the immersion level of each specific probe.

Disinfection

• Please refer to the user manual.
• For disinfection to be effective, all visible contamination should be washed off.
• Liquid germicides such as 2% glutaraldehyde-based solutions are used to disinfect the probe.
• Cidex^® is the only liquid disinfectant that has been evaluated for compatibility with the materials of the probe.
• The rinsed and dried probe should be placed in the Cidex^® solution for the time specified by the germicide manufacturer.
• Following this, the probe should be thoroughly rinsed to remove any residual disinfectant.
• The transducer can be damaged by contact with alcoholcontaining solutions, ammonium chloride compounds, hydrogen peroxide and temperatures above 60 °C

Enforcing this level of decontamination would impose an extra burden on theatre staff and reduce the availability of equipment. It is also unclear whether or not this level of decontamination is required for ultrasound-guided regional anaesthesia, or if a modification is acceptable.²⁵²

Ideally, a sterile sheath should be used for all peripheral nerve blocks especially in the following cases:²⁵³

• Patients with multidrug-resistant organisms.
• Patients undergoing perineural catheter placement.
• When there is a risk of blood contamination of the probe.

Taking into account Spaulding’s classification, South Africa’s context and the burden of disease, and the fact that blood contamination of the probe may be unpredictable, use of a sterile sheath that covers both the probe and the handle is recommended. (Large size sterile gloves have been used in some centres where sterile sheaths were not available.)

In 2004, Health Canada issued a warning about the risk of infection from ultrasound gel and recommended that sterile gel is used for invasive procedures, including needle localisation.²⁵⁴ In 2012, Oleszkowicz et al.²⁵⁵ proposed similar guidelines for the USA. In line with these, the use of sterile, single-use, ultrasound gel for invasive procedures is recommended.

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South African Society of Anaesthesiologists (SASA) Guidelines for Infection Control and Prevention in Anaesthesia in South Africa 2021