In patients with tunneled central venous catheters used for dialysis, ethanol locks may reduce catheter-related bloodstream infections when compared with other locks, mainly saline. There was no increase in the risk of catheter blockage with ethanol locks in this study.
Long-term catheters carry a risk of bloodstream infection. ‘Locks’ are the small amount of fluid left inside along intravenous catheter between uses to reduce the risk of blockage with clotted blood and ideally also to reduce infections. Ethanol locks may offer an alternative to saline, but there were only a few studies comparing them with heparin locks. None of the studies compared ethanol locks to the commonly-used antibiotic locks.
The review had a broad scope, covering adults and children on hemodialysis, and other conditions such as cancer or gastrointestinal conditions requiring intravenous nutrition. So, it seems that further work needs to be done before making specific recommendations on type and context for using ethanol locks.
Why was this study needed?
Central venous catheters are used for patients requiring chemotherapy, hemodialysis or long-term total parenteral nutrition. Blockage necessitates removal and re-siting of the catheter, so heparin is often used as a lock to prevent clots. Catheter infection often spreads through the bloodstream and can be fatal if untreated. Estimated occurrence of catheter-related infection is between 2.5-18 cases per 1,000 catheter days. The risk increases for catheters that are left in for a long time.
To prevent catheter-related infection, lock solutions are placed in the catheter to kill bacteria in the line. Ethanol is one option; others in common use include antibiotics, citrate, and saline.
A Cochrane review of this topic already exists but in the light of recent trials, a new systematic review of ethanol locks was needed to combine the results of smaller studies and bring the evidence up to date.
What did this study do?
This was a meta-analysis of seven randomized controlled trials of 2,575 patients comparing ethanol lock with another solution lock: mostly heparinized saline or saline only in the two larger trials.
Most used 70% ethanol solution while one used 60% ethanol; flushed in four studies but not three. Ethanol lock volume ranged from 1.5 to 3.0ml and dwell time ranged from 2 minutes to 2 hours.
The main outcome was catheter-related bloodstream infection, usually defined as finding bacteria in more than one blood culture. The trials were carried out in high-income countries comparable to the UK, so findings should be applicable.
What did it find?
- Ethanol lock almost halved the risk of catheter-related bloodstream infections (41/1,735 catheters), compared with heparinized saline or saline only (73/1,639 catheters), (risk ratio [RR] 0.54; 95% confidence interval [CI] 0.38–0.78). The number needed to treat to prevent one infection was 48. This benefit was observed in patients with tunneled catheters but not in studies with untunnelled catheters.
- Thrombosis can be a concern with the use of ethanol lock compared with heparinized saline, but this study found no difference in the incidence of thrombosis between ethanol and control groups (RR 1.05; 95% CI 0.91–1.22). However, one study, contributing almost 90% of the weight to this comparison, used saline only as a control and had a very high thrombosis rate in both groups, so the effect of ethanol over heparin was not properly assessed.
- There was significant variability between studies by population characteristics, ethanol protocols and definitions of infection. Therefore, the results need to be treated with caution.
What does current guidance say on this issue?
There is little current national guidance on this issue. The NICE guideline on Healthcare-associated infections: prevention and control in primary and community care (2012, updated 2017) does not make any recommendations on the use of ethanol flush and lock solutions. Instead, it recommends using sterile 0.9% saline to flush and lock the catheter. It recommends against routinely using antibiotic lock solutions to prevent catheter-related bloodstream infections.
A UK Renal Association guideline (2015) suggests that antibiotic or antimicrobial locking solutions should be used. It does not mention using ethanol as a lock.
What are the implications?
Evidence is increasing on the advantages of ethanol locks compared with heparinised saline or saline alone.
The use of citrate, ethanol, antibiotic or other locks is currently based on local hospital policy as few trials exist. For now, the findings give us some evidence about the value of ethanol locks.
If concerns regarding antibiotic resistance escalate, it is possible that more research into this issue could directly compare the variety of locks in current practice.
The article first appeared in NIHR Signal