Daily Bolus of LR: Subtherapeutic INR

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August 26, 2011 by dailybolusoflr

Subtherapeutic INR


Many patients in the ED are noted to have subtherapeutic INRs.  What do you do with these patients?  Cover them with low molecular weight heparin while their INR is rising?  Admit them?


I found one article published in Pharmacotherapy in 2008  that looked at patients who had previously had stable INRs (two prior INRs were therapeutic) and had an isolated INR which was at least 0.5 or more units below the patients recommended INR.  All disease processes were included.  90 day follow up was completed to look for risk of thromboembolism compared to matched controls with stable and therapeutic INRs (at no point could this group have an INR below 0.2 or more units below the recommended INR).


·         N=1080 patients were in the low INR cohort  (VTE 0.4%)

·         N=1517 patients in the therapeutic INR cohort  (VTE 0.1%)

·         No significant difference was found with a p=0.214

·         Most patients in both groups had either a-fib or h/o VTE



Some things to consider. .a relatively low % of patients with artificial valves (both groups around 5%).  These patients are potentially at higher risk and should be considered separately when making decisions.  Otherwise, there appears to be a very low risk for 90 day thromboembolic events.


All patients had an extra boost dose of warfarin and good follow up.


(Pharmacotherapy 2008;28(8):960–967)


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