Sarah Chapman looks at evidence from Cochrane Reviews on central venous catheter (CVC) management in this blog for nurses.
When it comes to preventing complications associated with central venous catheters, there is a good deal of variation between and within countries, in guidelines and clinical practice. With the updating of a Cochrane review on normal saline (0.9% sodium chloride) versus heparin intermittent flushing for the prevention of occlusion in long‐term central venous catheters in infants and children, this seems like a good time to have a round-up of Cochrane evidence on this and other aspects of managing CVCs.
Heparin vs normal saline for flushing CVCs
In children with CVCs
Published in April 2020, the latest version of the Cochrane Review on intermittent flushing with normal saline versus heparin to prevent occlusion in long-term CVCs in infants and children highlights that there is still an evidence gap. One new study was added but there are only four included in all with 255 people. There is continued uncertainty about how they compare in terms of occlusion and CVC-related blood stream infection (very low and low-certainty evidence). There is moderate-certainty evidence that there is probably little or no difference between them for the duration of catheter placement.
In adults with CVCs
A Cochrane Review comparing heparin with normal saline locking for prevention of occlusion in central venous catheters in adults (11 studies with a total of 2392 people, published July 2018) found that it remains uncertain how intermittent locking with heparin or normal saline compare (The certainty (or quality) of evidence is the extent to which we can be confident that what the research tells us about a particular treatment effect is likely to be accurate. Concerns about factors such as bias can reduce the certainty of the evidence. Evidence may be of high certainty; moderate certainty; low certainty or very-low certainty. Cochrane has adopted the GRADE approach (Grading of Recommendations Assessment, Development and Evaluation) for assessing certainty (or quality) of evidence. Find out more here: https://training.cochrane.org/grade-approach More evidence) and that heparin may have little or no effect on catheter patency (low-certainty evidence).
The review authors also say that while they found no evidence of a difference between them in terms of sepsis, mortality, or haemorrhage, the combined trials are not powered to detect rare adverse events such as heparin‐induced thrombocytopaenia.
The previous version of this review was used as a Cochrane Quality and Productivity Case Study for NICE, to help the NHS identify practices that could be reduced or stopped completely, releasing resources without negatively affecting quality of care. Cochrane evidence at the time (as now, with five studies added) showed no good evidence that flushing CVCs with heparin is better than flushing with normal saline. Heparin is more expensive and NICE estimated that switching to saline would result in an estimated 91% saving (at 2015 prices £3.30 per single day use vs £0.30).
Infection prevention measures
Infection prevention is of huge importance when it comes to vascular access devices. Micro-organisms can get into the bloodstream through the point where the skin has been penetrated and along the outer surface of the catheter, or internally through the catheter and its connectors. Minor infections at the entry site or in device connectors can lead to more serious bloodstream infections. The possible consequences include the whole gamut of infection-related miseries for the patient, including pain, anxiety, delayed treatments and a longer stay in hospital as well as greater demands on resources.
This is one approach to preventing catheter-related bloodstream infection (BSI). A Cochrane Review (September 2015) looking at whether antimicrobial-impregnated CVCs can help prevent bloodstream infection in newborns found only one small study, not enough evidence to guide practice. Nor is there any trial data to tell us whether early removal of CVCs in neonates with BSI is beneficial, according to another Cochrane Review, which had hoped to compare early removal with expectant management of CVCs in neonates with BSI.
A Cochrane Review (March 2016) on catheter impregnation, coating or bonding for reducing CVC-related infections in adults found reliable (high-certainty) evidence from 57 studies with 16,784 catheters that antimicrobial CVCs are effective in reducing catheter colonisation and catheter-related BSI in adults, but they do not appear to reduce clinically diagnosed sepsis or deaths from all causes.
Here in the UK, NICE guidance recommends using 2% chlorhexidine gluconate in 70% alcohol, or povidone iodine in alcohol for patients sensitive to chlorhexidine to clean the CVC site during dressing changes. It also suggests considering daily cleansing with chlorhexidine in adults with a CVC as a strategy to reduce catheter-related bloodstream infection.
A Cochrane Review (July 2016) on skin antisepsis for reducing CVC-related infections brought together from 12 studies with 3446 CVCs (number of patients unknown), comparing different skin antisepsis regimens with each other and with none. Whilst there is nothing here to overturn the guidance, the evidence is mostly low or very low-certainty and, beyond saying that chlorhexidine solution may be more effective than povidone iodine, any questions about which regimen is best or whether skin antisepsis benefits patients are left unanswered.
There is high-certainty evidence from a Cochrane Review on dressings and securement devices for CVCs (22 studies with 7436 people, September 2015) that medication-impregnated dressings reduce the incidence of CVC-related bloodstream infection compared with all other dressing types. The review also found moderate-certainty evidence that chlorhexidine gluconate-impregnated dressings probably also reduce catheter-related bloodstream infection compared with dressings without medication.
Another Cochrane Review (March 2016) explored the evidence on antimicrobial dressings to prevent CVC-related infections in newborns, hoping to explore both effectiveness and safety. Three studies were included, with 855 infants from neonatal intensive care units; the majority of babies were in one large The potential benefits and harms of silver-alginate patches remain unclear. . There was moderate-certainty evidence that chlorhexidine CVC dressing with alcohol skin cleansing probably carries a high of skin irritation and only modest reduction in catheter colonisation, without benefit in terms of clinical such as catheter-related bloodstream infection.
A Cochrane Review looking at the effects of the frequency of dressing changes for CVCs on catheter-related infections in adults patients (5 studies with 2277 people, February 2016) found that impact of the frequency of dressing changes (2 to 5 days compared with 5 to 15 days) on catheter-related bloodstream infection, catheter site infection, death from any cause, skin damage or pain remain uncertain. That’s a pretty big evidence gap on something so basic!
Frequency of changing the administration set
The tubing, or administration set, attached to venous and arterial catheters may contribute to BSI, so does the frequency with which they are changed make a difference? This was considered in a Cochrane Review on optimal timing for intravascular administration set replacement, which included data from 5000 people in 16 trials. There was some evidence that sets that do not contain lipids, blood or blood products may be left in place for up to 96 hours without increasing the risk of infection, but the studies were mostly of low to moderate quality which means that we can’t be certain. It would be good to see this 2013 review, one of several here which has been used in guidelines, updated with new and hopefully better quality studies.
Another Cochrane Review (November 2013) looked at whether there is evidence that giving antibiotics before inserting a long-term CVC, or flushing or locking it with an antibiotic plus heparin solution, can help prevent Gram-positive catheter-related infections in adults and children being treated for cancer. Moderate-certainty evidence from 11 studies with 828 people showed that flushing the catheter with an antibiotic and heparin solution probably reduces the number of catheter-related infections. Giving antibiotics prior to catheter insertion does not seem to be helpful.
There’s some really interesting work being done by the AVATAR (Alliance for Vascular Access Teaching and Research) Group, established by Professor Claire Rickard who is an author on some of the Cochrane Reviews discussed here. They state that their mission is to make vascular access complications history. They are doing some really interesting research in six broad areas. Worth taking a look.
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Sarah Chapman has nothing to disclose.