Heparin versus normal saline locking for prevention of occlusion in central venous catheters in adults
Central venous catheters are tubes (also called ‘lines’) temporarily implanted into patients when frequent intravenous access is needed. They can be used for monitoring patients in intensive care, for giving drugs or chemotherapy, or for providing intravenous nutrition. A Hickman line is an example of a central venous catheter. Blood clots and other factors can block these catheters. Blood clots in or on a catheter can also become infected or can travel to the lungs (this is known as a ‘pulmonary embolism‘). Heparin is a drug that helps to prevent blood clotting, so it may help prevent catheters from blocking or from causing pulmonary embolism. However, heparin can also cause bleeding, allergic reactions, and a drop in the number of platelets in the blood. When a catheter is not in use, a fluid is injected into the catheter until it is next used. This is called locking the catheter. Fluid used for locking is often heparin or normal saline (a sterile solution of salt in water at a concentration suitable for the blood). We did this review to find out whether locking catheters with heparin was better than locking them with saline to avoid blockages, and to determine how safe each method is. This work is an update of a review first published in 2014.
Study characteristics and main findings
For this update (most recent search performed 11 June 2018), we found five more studies, giving us a total of 11 studies involving 2392 participants. Our updated review found that locking catheters with heparin may or may not prevent blocking better than flushing with normal saline. We saw little or no difference in duration of catheter patency (length of time catheter remained unobstructed), rate of infection, mortality, bleeding, or heparin-induced fall in platelet count (thrombocytopaenia). We detected no effect with increasing concentrations of heparin dose.
Quality of the evidence
The quality of the evidence ranged from very low to moderate for the main outcomes. We downgraded the quality of evidence owing to risk of bias and imprecision, as the pooled result included an effect of both benefit and harm and the suggestion of publication bias. To sum up, we are uncertain on the effects of heparin compared to normal saline and the findings should be interpreted with caution.