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Supplements Practice: Bloodstream infections and their control

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Author:Brian I. Duerden, FRCP Edin, FRCPath, MD, BSc, inspector of microbiology and infection control, Department of Health.

Bloodstream infections, otherwise known as bacteraemias, are an important component in the spectrum of healthcare-associated infections (HCAIs). Although they are not the most common of the HCAIs, they represent the most severe end of the infection spectrum. The bloodstream should be sterile and the presence of bacteria in the blood is a very significant clinical finding as it can lead to rapid clinical deterioration and sepsis syndrome, and be potentially fatal. This is one the key reason why MRSA bacteraemia was chosen as the indicator infection for the Department of Health’s target for the reduction of MRSA infections generally.

The Health Protection Agency (and formerly the Public Health Laboratory Service) has operated a voluntary surveillance scheme for bacteraemias caused by all types of organisms for many years, based upon voluntary reporting from the great majority of microbiology laboratories serving the NHS.

This system showed a rapid rise in the number of cases of MRSA bacteraemia during the 1990s and it was against this background that mandatory surveillance of MRSA bacteraemia was introduced in 2001. The first three years of this surveillance showed a continued increasing trend from 7,291 in 2001–2002 to 7,426 in 2002–2003, with a peak of 7,700 in 2003–2004.

Clearly this was unacceptably high, particularly for infections caused by MRSA, and at that point it was decided to implement a targeted reduction programme which required the NHS in England to reduce the number of MRSA infections (monitored as MRSA bacteraemias) by half by 2008. This has been backed by an intensive support programme that was implemented from 2005. It is a major task to turn around the organisational and clinical activity in an organisation as large as the NHS, but we began to see reductions, albeit at a relatively small level, in 2004–2005 (7,212 cases) and this reduction has accelerated as the activity in the programme has increased. The figure for 2006–2007 was 6,381 (HPA, 2007) and the decline has continued in the early part of 2007–2008.

Bacteraemia and intravascular devices
General risk factors for patients developing MRSA bacteraemia include age, presence of serious underlying disease and chronic conditions, and frequent contact with the health services. However, the single most important risk factor in terms of clinical procedure was the presence of an indwelling intravascular device, whether a central venous catheter, a peripheral line or a renal dialysis catheter.

In the 2006 HCAI prevalence survey, over 60% of patients surveyed had a peripheral intravenous cannula or catheter in place and 8% had a central intravenous catheter. Thus most inpatients have this important risk factor for developing a bacteraemia.

In 2005, it became clear that we needed to focus on improving clinical procedures and to help clinical staff working at the front line in the NHS. The first edition of the Saving Lives package was published in 2005 and an updated version was reissued in June 2007 (DH, 2007).

An important part of the Saving Lives approach is the implementation of a series of high-impact interventions (HII), which are care bundles to help clinical staff perform common clinical procedures properly and safely with the aim of minimising the risk of infection. The interventions cover the proper care of intravenous catheters and cannulas and renal dialysis catheters as well as the key elements for the insertion and care of central venous catheters.


Central venous catheters (HII number 1)
The 2006 prevalence survey found that 42.3% of bloodstream infections were related to central venous catheters, making this a key area. The main elements of care are listed in Box 1.


Peripheral venous cannulas (HII number 2)
Although the percentage of peripheral lines that lead to infection is less than that of central lines, the huge number of peripheral lines in use means that they are still a source of many infections, hence the importance of HII 2.

This follows a similar set of recommendations to HII 1, with a reminder that the need for a cannula should be reviewed at least daily, with removal as soon as it is not needed. Peripheral cannulae should be replaced after 72–96 hours if still needed.


Renal dialysis catheter care (HII number 3) HII 3 was introduced because bacteraemia, particularly due to MRSA, has been a major problem in many renal units, being implicated in 29% of dialysis-related admissions in 2005.


Screening for Staphylococcus aureus
Because Staphylococcus aureus (including MRSA) is a normal inhabitant of the skin and nose, asymptomatic carriage is very often a precursor to clinical infection such as bacteraemia. If patients are screened before or on admission, they can then receive decolonisation treatment to reduce their risk of developing an infection.

Guidance on screening patients for MRSA was issued as part of Saving Lives in October 2006. Trusts were advised to review patient groups that had the higher risks of developing MRSA bacteraemia and implement a screening policy focused on them.

As experience developed, a ministerial announcement in October 2007 confirmed that the NHS should move towards universal screening, initially for all elective admissions in 2008 and to include emergency admissions as soon as practicable (see p8).


Enhanced surveillance
Development of the HCAI improvement programme has been informed by the experience gained by the DH improvement team and information from the enhanced surveillance scheme over the past two years. We have learnt that: men over 65 years old (15% of all admissions) represent 43% of patients with MRSA bacteraemia; 80% of bacteraemias occur in patients admitted as emergencies; 35% of patients with a bacteraemia have been in hospital in the month prior to the current admission; and a stay of over seven days increases the risk.

As indicated above, 14% of bacteraemias have been associated with central lines and 10% with peripheral lines, but another 14% have been associated with chronic wounds which indicates a further risk factor to address.


Blood cultures
A repeated concern in a number of trusts we have visited under the improvement programme was that a significant number of MRSA bacteraemia reports represented contaminated blood cultures and were not clinically significant.

This was worrying, not just because of false positive reports but also because a blood culture is an important clinical investigation with major implications for patient care.

Therefore, in the June 2007 issue of Saving Lives, guidance on best practice for taking blood cultures was included. The aim is to ensure that blood cultures are taken for the right indication, at the right time and using the right technique. Cultures should be taken by properly trained staff from fresh venepunctures (not through existing intravenous cannulas) with careful skin decontamination, good hand hygiene and aseptic technique. All trusts have been asked to review their protocols in the light of this guidance.


Summary
MRSA bacteraemia is an important clinical diagnosis in its own right, as well as being a marker of overall infection prevention and control practice. The national approach in the NHS with a target applied to all acute hospitals is unique in the world. The consistent downward trend over the past 18 months gives every encouragement that this focused approach can get on top of the problem and reverse the unacceptable upward trend of HCAI of the past 20 years.


Box 1. Central venous catheters

The nine elements for insertion include:
- Selection of appropriate catheter and insertion site (subclavian or internal jugular);
- Skin preparation with 2% chlorhexidine gluconate in 70% isopropyl alcohol;
- Use of personal protective equipment and proper hand hygiene and aseptic technique;
- Application of a sterile, transparent
semi-permeable dressing;
- Safe disposal of sharps;
- Clear documentation of the procedure.


Ongoing care requires:
- Attention to hand hygiene;
- Regular observation (and recording) of the cannula;
- Checking the dressing;
- Aseptic procedure for access;
- Appropriate replacement of the administration set (but not routine catheter replacement).

Key points

- Bloodstream infections are a serious complication and can be fatal.
- The single most important risk factor is the presence of an indwelling intravascular device.
- Infection rates can be reduced by safe and appropriate care of intravenous
catheters and cannulas, and renal dialysis catheters, as outlined in Saving Lives
high-impact interventions.
- Nurses are responsible for appropriate care in the management of these devices.


References

Department of Health (2006) Third Prevalence Survey of Healthcare-associated Infections in Acute Hospitals in England 2006. www.dh.gov.uk/en/Publicationsandstatistics/Publications/PublicationsPolicyAndGuidance/DH_078388

Department of Health (2007) Saving Lives: Reducing Infection, Delivering Clean and Safe Care.
www.clean-safe-care.nhs.uk/public/default.aspx?level=1&load=ArticleViewer&ArticleID=471


Saving Lives Tools to Reduce Bacteraemia:
High Impact Intervention No 1. Central Venous Catheter Care Bundle. www.clean-safe-care.nhs.uk/cms/toolfiles/14/SL_HII_1_v2.pdf

High Impact Intervention No 2. Peripheral venous cannula bundle. www.clean-safe-care.nhs.uk/cms/toolfiles/16/SL_HII_2_v2.pdf

High Impact Intervention No 3. Renal dialysis catheter care bundle. www.clean-safe-care.nhs.uk/cms/toolfiles/19/SL_HII_3_v2.pdf

Screening for meticillin-resistant Staphylococcus aureus (MRSA) colonisation. A strategy for NHS trusts:
a summary of best practice. www.clean-safe-care.
nhs.uk/cms/toolfiles/106/
281812SCR_MRSA_screening.pdf

Taking blood cultures. A Summary of Best Practice.
www.clean-safe-care.nhs.uk/cms/toolfiles/105/281812BC_blood_cultures.pdf

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