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Research from the University of South Australia (UniSA) has revealed certain catheter-vein ratios (CVRs) can more than double the risk of blood clots when used for intravenous chemotherapy in cancer patients. 

Drawing on a sample study of more than 2,400 patients across four hospitals in Australian and NZ, the study, published in the British Medical Journal Open, analysed the outcomes for patients who received a peripherally inserted central catheter (PICC).

Thirty nine patients within the sample experienced thrombosis, with the study finding in cases that “if the vein is too small, and the catheter occupies more than 45% of the vein,” the risk of blood clots and thrombosis is more than double for cancer patients.

Concurrently, the study found there was no “increased risk of blood clots” clotting for non-cancer patients who received a catheter as part of their infection treatment.

Dr Rebecca Sharp, leader of the study and a researcher at UniSA, explained, both the cancer (especially blood cancers like leukaemia) and chemotherapy treatments can significantly heighten the risk of thrombosis, especially if a catheter restricts the blood flow.

“Catheters are commonly used to infuse medications or liquid nutrition, but they come with risks, particularly if the catheter is too big for the vein. Previous research has shown they can impede blood flow by up to 80%,” Dr Sharp said.

Dr Sharp said the guidelines for CVRs were unclear.

“Many clinicians use a CVR of less than 33%, where the catheter occupies only one third of the vein. Others adhere to a 45% limit. However, there is a lack of evidence showing which CVRs are safe for individual patients. Some clinicians don’t measure veins at all.”

However, with PICCs a common treatment option across the world because of their ease, affordability and non-invasiveness.

Dr Sharp said the study will help reduce some of the risks associated with their use.

“We have identified how to reduce some of these risks, by recommending specific limits on catheter-to-vein ratios for individual patients. These results will help nurses and doctors to provide safe care and reduce harm for people with cancer,” Dr Sharp said.

An explainer video on the findings of the study is available here.