What is the relationship between Central Venous Catheters (CVCs) and International Normalized Ratio (INR)?

From the Guidelines

Central lines can be safely placed in patients with elevated INR values, but the risk of bleeding complications increases as INR rises, and an INR below 1.5 is generally considered safe for non-emergent central line placement. For non-emergent central line placement, an INR below 1.5 is generally considered safe, while values between 1.5-2.0 may be acceptable with caution 1. The risk of bleeding complications increases as INR rises, and the decision to proceed with central line placement should be individualized based on the urgency of the situation, the patient's overall clinical status, and the specific indication for the central line.

Key Considerations

• For urgent or emergent situations, central lines can be placed even with higher INR values, but the benefits must outweigh the bleeding risks.
• If time permits and the INR is significantly elevated (>2.0), correction with fresh frozen plasma, prothrombin complex concentrate, or vitamin K should be considered before the procedure 1.
• Using ultrasound guidance, selecting larger vessels like the internal jugular vein rather than the subclavian, choosing an experienced operator, and applying prolonged pressure after insertion can help minimize bleeding complications.
• The maintenance of an international normalized ratio (INR) in the therapeutic range (2.0-3.0) is essential for patients receiving vitamin K antagonists (VKA), and the proportion of time spent in this range (TTR) should be at least 65% but the ultimate aim/target should be 100% 1.

Evidence-Based Recommendations

• The 2008 guidelines for the prevention and treatment of thrombosis associated with central venous catheters in patients with cancer suggest that fixed low doses of VKA (1 mg/day) with an INR <1.5 were not effective in preventing venous thrombosis associated with a superior vena cava catheter in patients with cancer 1.
• A meta-analysis of five studies evaluating the efficacy and safety of VKA in the prevention of CVC-associated thrombosis found that none showed that VKA exerted a beneficial effect on the occurrence of symptomatic thromboses versus placebo or no treatment 1.
• However, another study found that fixed low doses of VKA were more effective than placebo in preventing both asymptomatic and symptomatic CVC-associated thrombosis, with a relative risk of 0.37 (95% confidence interval 0.26-0.52), P < 0.001 1.

From the Research

Central Lines and INR

• The relationship between central lines and INR is complex, with several studies investigating the use of prophylactic plasma transfusions prior to central line insertion in patients with abnormal coagulation 2, 3.
• A study published in 2016 found that there was insufficient evidence to determine a difference in major procedure-related bleeding within 24 hours of central line insertion, and that the quality of the evidence was low or very low across different outcomes 2.
• Another study published in 2012 found that the use of prophylactic plasma transfusion before central line placement in patients with an elevated INR did not reduce the risk of bleeding, and that the occurrence of bleeding was very low overall with central line placement (0.3%; 95% confidence interval, 0%-2%) 3.
• The measurement of INR in patients with heparin-locked central venous catheters can be challenging, and a novel blood sampling method has been evaluated to improve the accuracy of INR measurement in these patients 4.
• The use of low-molecular-weight heparin as a bridging anticoagulation during interruption of warfarin has been studied, and a standardized periprocedural anticoagulation regimen with low-molecular-weight heparin has been found to be associated with a low risk of thromboembolic and major bleeding complications 5.

Prophylactic Plasma Transfusions

• The use of prophylactic plasma transfusions prior to central line insertion in patients with abnormal coagulation is a topic of debate, with some studies suggesting that it may not be beneficial in reducing the risk of bleeding 2, 3.
• A study published in 2016 found that the included study was at high risk of bias due to lack of blinding of participants and personnel, and that the quality of the evidence was low or very low across different outcomes 2.
• Another study published in 2012 found that the occurrence of bleeding was very low overall with central line placement, and that the use of prophylactic plasma transfusion did not reduce the risk of bleeding 3.

INR Measurement

• The measurement of INR in patients with heparin-locked central venous catheters can be challenging, and a novel blood sampling method has been evaluated to improve the accuracy of INR measurement in these patients 4.
• The novel sampling method consists of measuring the INR directly from the dialysis circuit (arterial bloodline sample port) after 1 hour of treatment, regardless of heparin administration during dialysis 4.
• The study found that INRs obtained using the novel sampling method were only minimally overestimated compared to venipuncture values, and that this overestimation was not clinically significant 4.