anaesthetists be cleaner


anaesthetists be cleaner


anaesthetists be cleaner

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Professors Alan Merry and Simon Mitchell (School of Medicine, University of Auckland; Department of Anaesthesia, Auckland District Health Board) and associates have been awarded funding by the Australian and New Zealand College of Anaesthetists (ANZCA) for a study entitled A bundle for anaesthetists to reduce postoperative infection: the Anaesthetists Be Cleaner (ABC) Study. Further funds have been awarded by NZ Lottery Health Research.

The study will investigate whether the implementation of a bundle that combines a selection of key aseptic practices with the routine use of 0.2μm filters for all IV bolus medications during anaesthesia (except propofol) reduces clinically relevant postoperative infections in a targeted group of high risk patients.

ANZCA has recognised the importance of this research, awarding the project the 2018 Harry Daly Research Award for highest ranked grant.

This study has received approval from the Northern B Health and Disability Ethics Committee (18/NTB/61), the Auckland DHB Research Review Committee (A+8036), the Waitemata DHB Research Review Committee (RM14287), and the Counties Manukau DHB Research & Evaluation Office (Ref:1227).

The study protocol has been published in Trials (

Bundle implementation dates
Auckland DHB Arthroplasties November 2018
Waitematā DHB Arthroplasties May 2019
Starship Children's Hospital Cardiac November 2019
Auckland DHB Adult Cardiac July 2020
Counties Manukau DHB Arthroplasties November 2020
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March 2021

End date has been established as 17 December 2021.

December 2020

Lottery Health Research grant awarded.

November 2020

An issue arose with the filters in adult cardiac theatres. Below is the communication that was sent to the participants at this site.

The filters seem to be blocking or slowing the injection rate after several drugs or drug combinations have been used. If this occurs, we suggest replacing the filter unit with a fresh one.

This blocking sometimes occurs after bypass and when the filter unit is being accessed again after some time has passed. You should feel free to use a new filter unit once bypass is completed if this is happening to your cases.

Attached below is a photo of a suggested filter unit set up on the CVL that you may want to consider using. This setup will make it easier to replace the filter and also allow a 3-way connection with a flush syringe to keep the unit secure. In the end the way you set up the filter is up to you – you should do whatever works best for you.

Please remember that in an emergency, the filter can be bypassed. Once the emergency is resolved the filter can be used again. These cases will still be counted as ABC cases. This is a real-world study so it was always envisaged that not every case would be managed perfectly.

One of the drugs that seems to be causing some concern with blocking the filter is Cefazolin. We suggest that this drug not be injected through the filter unit as it is unlikely to support contamination.

May 2020

The ABC study has restarted at two sites including StarShip Children's Hospital. Additional sites are due to restart in July.

April 2020

The ABC study has been suspended at all sites due to the COVID-19 pandemic. We will provide an update when the restart date becomes clearer.

February 2020

The ABC study has been suspended at Starship Childrens hospital due to an issue with the use of the study filters in the paediatric cohort. Below is a copy of the communication sent to all study participants at all sites.

First, some background on the filters themselves. Among other things, these particular filters are designed to protect the line from injected air. They have an air removal device on their reverse side, and if air is injected from the syringe it will pass via this device into the atmosphere, and not pass through the filter. However, one potentially disconcerting feature of this device is that if you apply negative pressure to the filter, for example, attach a syringe and aspirate, it will entrain air through the device into the syringe. If you then inject that entrained air through the filter it should pass back out into the atmosphere through the protection device, so no harm done. But if you do aspirate on the filter and find air entraining into the syringe, you may find that disconcerting, so we think it is worth being aware of the feature.

We expect that anaesthetists doing adult cases do not routinely aspirate on the filter before injecting through it, hence we have had no reports of concerns related to this practice. But with paediatric cardiac patients, many of the anaesthetists at Starship are in the habit of aspirating slightly after connecting a syringe to any port, to remove any vestige of “connection air” because even small amounts of venous air in some of these cases do matter, potentially a great deal. This is problematic with the filters because they invariably entrain air through the protection device (as above) and this means that aspirating in this way does not reliably remove “connection air.” In a meeting with several of the Starship anaesthetists, a potential solution to this issue has been identified.

Because of the potential seriousness of air embolus in certain paediatric patients we have suspended ABC at Starship while continuing to work with our Starship colleagues and the manufacturer to fully understand this issue and resolve it. We are also convening a Data Safety Monitoring Committee to provide independent advice on the matter. However, we see no reason to be concerned about the adult cases likely to be included in the ABC study in the present cohorts. We reiterate that the filters are designed specifically to protect the line from air, and our own testing in which we have deliberately tried to inject air through the filters suggests that they work well in this regard.

November 2019

Implementation of the bundle has commenced at two sites: Auckland DHB (hip or knee arthroplasties) and Waitematā DHB (hip or knee arthroplasties).

Starship Children’s Hospital will implement the bundle in November 2019 for cardiac cases.

Compliance rate in the use of the bundle is 78.9% (836 out of 1059) across all sites. We are aiming for 90% at all sites.

In recent correspondence in the BJA, our previous studies were cited (Gargiulo et al, 2016; Gargiulo et al, 2017) and the ABC study cited as a future direction for anaesthetists to prevent perioperative transmission of potential pathogens, postoperative infection, and patient colonisation (Kwanten, 2019).

The study protocol has been published (Merry et al, 2019).

Case numbers (April 2021)
Eligible cases where bundle was used 3,027
Eligible cases where bundle was not used 902
Eligible cases total 3,929
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Study Synopsis


Postoperative infection is a serious problem in New Zealand (NZ), and internationally with considerable human and financial costs. Moreover, in NZ, certain factors that contribute to postoperative infection are more common in Māori and Pacific populations. To date, most efforts to reduce postoperative infection have focused on surgical aspects of care and on antibiotic prophylaxis, but recent research shows that anaesthesia providers may also have an impact on infection transmission. Some of the many intravenous (IV) medications drawn up and administered to each patient may become contaminated during this process. These contaminating bacteria could be filtered at the point of injection. In addition, these providers sometimes have imperfect hand hygiene and frequently transfer the blood or saliva of their patients to their work environment. Working with anaesthetists, anaesthetic technicians, microbiologists and others, we have developed an evidence-informed infection prevention bundle to improve key aseptic practices by anaesthetists which aims to reduce postoperative infection. The bundle includes the use of 0.2μm filters for all IV bolus medications during anaesthesia, except propofol.

The Problem

Post-operative infection.


We know that anaesthetists inadvertently inject potentially pathogenic micro-organisms into about 6% of patients. We do not know whether this matters clinically, but it is a plausible cause of catastrophic postoperative infection in operations such as major joint replacement or cardiac surgery.


To investigate whether the implementation of a bundle that combines a selection of key aseptic practices with the routine use of 0.2μm filters for all IV bolus medications during anaesthesia except propofol will reduce clinically relevant postoperative infections in a targeted group of high risk patients. Clinically relevant implies infections severe enough to require prolonged hospitalisation or readmission to hospital.

Primary outcome

Our primary outcome variable will be days alive and out of hospital to 90 days (DAOH90), which is available from the NZ Ministry of Health’s National Minimum Dataset (NMDS), and so can be readily collected for all patients. With our cluster randomised study design it will be reasonable to attribute any reduction in DAOH90 following implementation of the bundle to a reduction in clinically important postoperative infections of any type.

Secondary outcome

Our secondary (explanatory) outcome will be the rate of specified postoperative infections, as defined and collected by the NZ National Surgical Site Infection Improvement Surveillance Programme for patients undergoing hip or knee arthroplasty or cardiac surgery.


This study is a quality improvement project. In general, quality improvement projects involve the implementation of practices that are: a) supported by evidence or strong consensus; b) very unlikely to result in harm; and c) practicable to adopt. In essence, the aim is to achieve improvement in practice and the point of evaluation is to show the real-world effectiveness of the implementation of change.

We will build local consensus on the content of our bundle, refine it if necessary, and seek support for its implementation from senior anaesthesia and hospital leadership and departmental “champions”. We will implement the bundle in patients undergoing hip or knee arthroplasty or cardiac surgery in a five-site, stepped wedge, cluster randomised quality improvement design, comparing approximately 5000 patients before implementation of our bundle with approximately 5000 patients after its implementation. Consent will not be sought from participating patients. The required data will be collected from existing national database systems and hospital databases.

Setting and participants

The study will be conducted in five departments (or clusters) in four large metropolitan hospitals in Auckland, New Zealand: Auckland City Hospital, Starship Children’s Hospital, Middlemore Hospital, and North Shore Hospital. The participants will be patients undergoing hip or knee arthroplasty or cardiac surgery in these hospitals during the duration of the study, and the anaesthetists and anaesthetic technicians who manage their anaesthetic care. These surgical subgroups have been chosen because of the existence in our jurisdiction of well-developed systems for reporting surgical site infection to national databases in these particular subgroups. In addition, these patients are subject to moderately high rates of postoperative infection, and the consequences of infection when it occurs are devastating – for example, implanted prostheses may need removal after arthroplasty, and sternal wounds may dehisce after cardiac surgery.

Significance and translation

If effective, our bundle may offer a practical clinical intervention to reduce postoperative infection and its associated substantial human and financial costs.

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The Bundle

  1. Wipe skin with alcohol (with or without chlorhexidine) and allow to dry before inserting any IV line.

  2. Inject all IV bolus medications except propofol through a 0.2µm filter incorporated into each patient’s IV line.

    • Use aseptic technique when attaching the filter to the IV and, unless it has been freshly opened from sterile packaging, wipe the IV injection port with alcohol (with or without chlorhexidine) for 15 seconds and allow to dry.

    • If the filter is moved from one access point to another during the case the new access point should first be wiped with alcohol (with or without chlorhexidine) for 15 seconds and allowed to dry.

    • Use more than one filter if necessary or desired (e.g. for cardiac patients, one filter in the peripheral line, one on a central line port where bolus medications may be given, and a third onto the medication injection port on the bypass machine for the perfusionist to use when administering medications).

    • Remove the filter(s) on discharge from the Post Anaesthesia Care Unit or on admission to the Intensive Care Unit.

    • Filter and injection port with a 3-way tap to be attached to IV line.

    • Filter and injection port attached to a side port on the IV line.

    • Filter and injection port attached to a side port on the IV line with a 20mL syringe filled with sterile sodium chloride 0.9% (for easy flushing) attached via a 3-way tap

  3. Use meticulous aseptic technique when drawing up or injecting propofol, and discard syringes, needles or the medication in the event of any suspected contamination.

    • Note that the rubber bungs on propofol vials are not sterile even with the cap in place, so they should be wiped with alcohol (with or without chlorhexidine) for 15 seconds and allowed to dry before propofol is drawn up. If the medication is supplied in an ampoule, wipe the outside of the neck and surrounding part of the ampoule with alcohol (with or without chlorhexidine) before opening.

    • Use a new needle or spike for each occasion.

    • Cap the syringe with a syringe cap or capped needle.

    • Administer as soon as possible and discard propofol after one hour if not used.

    • Do not reuse syringes or needles for propofol, even for the same patient.

    • Flush IV port with sterile sodium chloride 0.9% after propofol has been administered to ensure no residual propofol remains to support bacterial growth, using meticulous aseptic technique to draw up the flush.

  4. Perform hand hygiene

    • Before and after interacting with each new patient (i.e. on entering the operating room and on leaving a patient in the Post Anaesthesia Care Unit).

    • Before and after any procedure creating risk of infection (e.g. IV insertion, airway manipulation, administering propofol, etc).

    • After blood and body fluid exposure (e.g intubation, IV line insertion etc); remove gloves (if they have been worn) and, if practicable, perform hand hygiene before spreading contamination to the work station, computer key board and other surfaces.

  5. Maintain clean working surfaces

    • Place used laryngoscopes, masks and other contaminated objects into a tray designated for this exclusive purpose; maintain strict separation of clean and contaminated areas - do not use this tray for clean instruments, swabs or other items even at the start of a procedure.

    • Wipe the anaesthetic machine bench top and the circuit pressure-relief valve with alcohol (with or without chlorhexidine) once the patient has settled into the maintenance phase of anaesthetic (i.e. after intubation of the trachea if this is done).

  6. Note
    • Propofol should not be injected through the filter.

    • The filter has a dead space of 0.45 mL and the injection port has a dead space of 0.11 mL (= 0.56 mL in total); therefore, as with any IV setup, it is necessary to prime the filter with sterile sodium chloride 0.9% or sterile water for injection to eliminate air, and it is also necessary to ensure that medications are flushed through.

    • Hand hygiene implies either hand washing with medicated soap and water or using alcohol-based hand rub; it is important for hands to dry properly

    • Provided the medications are injected through a 0.2µm filter, the study does not ask for hand hygiene in relation to the injection and drawing up of medications other than propofol.

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Exemplar Video

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The Team

Principal Investigators
Associate Investigators
Site Investigators
Consumer Advisor
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