Blog entry by Meguid El Nahas
This study by Hemmelgarn and colleagues (NEJM January 27, 2011) addresses the important issue of the prevention of dialysis central venous catheters infections. the authors studied a small number of patients (n=225) randomised to have either heparin locks of the catheter's lumen three weekly after each HD session or heparin twice weekly + once a week usage of recombinant tissue plasminogen activator (rt-PA) 1mg in each lumen. Patients were followed up for 6 months and catheter malfunction was used as a surrogate marker for catheter infection. Secondary outcome was catheter-related bacteremia. The authors noted a risk of catheter malfunction almost twofold higher in patients treated with heparin alone compared to those receiving one a week a rt-PA lock. Catheter related bacteremia was also significantly reduced.
Whilst this is an interesting observation, it has a number of shortcomings including:
1) Small sample size (n=225) increasing the risk of bias and false positive results (type1 statistical error)
2) Short follow-up period (6 months)
3) The use of a surrogate endpoint for catheter infection; namely catheter malfunction instead of harder endpoints such as catheter removal, hospitalization or even death.
4) Lack of comparative analysis to other, current and cheaper, strategies such as antibiotics, citrate or taurolidine locks. Some of these have proved quite effective and much cheaper than rt-PA.
It is most important to realise that the best approach to prevent catheter related infections and their complications is the AVOIDANCE of usage of central venous catheters and use of AV fistulas or even AV grafts! Unfortunately, In the USA, a high proportion of patients starting RRT by HD depend for access on central venous catheters. It has been estimated in 2008, that 74% of those starting HD used a central venous catheter and only 16% had an AVF or functioning graft in place! This is a reflection of poor practice and inadequate planning for RRT by HD.
In order to avoid inadequate access for HD, planning of RRT is essential. For that, patients should be seen and followed-up by Nephrologists from CKD stage 4 onward. At the Sheffield Kidney Institute (UK) all CKD 5 patients are referred to a multidisciplinary outpatient clinic where a number of issues including vascular access are addressed. These include the psychological impact of ESRD on the patient and his family. The review of CVD risks and their investigation and management. The review of the patients' nutritional status. Also review of patients' suitability for renal transplantation including listing for pre-emptive transplantation. But the most important role of this pre-dialysis review clinic is to discuss with the patient his/her dialysis options and prepare access. The timing of access is key to its longterm success and to minimise complications.
Central venous catheters are poor excuses for:
Delayed referrals of ESRD patients
Poor pre-Dialysis management
Poor surgical approach and skills hampering availability of native AVF or AVgrafts.