The effect of vitamin K on prothrombin time in critically ill patients: an observational registry study.

Background: Previous studies have indicated that vitamin K deficiency is common in non-bleeding critically ill patients with slightly prolonged prothrombin time-international normalized ratio (PT-INR). It has never been investigated thoroughly whether the administration of vitamin K to these patients could affect their PT-INR. Therefore, the aim of this registry study was to evaluate changes in PT-INR in response to vitamin K in critically ill patients with PT-INR in the range of 1.3-1.9.

Methods: Patients admitted to a mixed 9-bed general intensive care unit at a University Hospital, between 2013 and 2019 (n = 4541) with a PT-INR between 1.3 and 1.9 at any time during the stay were identified. Patients who received vitamin K with appropriate sampling times for PT-INR and without exclusion criteria were matched with propensity score to patients from the same cohort who did not receive vitamin K (controls). PT-INR was measured at admission, within 12 h before vitamin K administration and 12-36 h following vitamin K administration. Exclusion criteria included pre-existing liver cirrhosis, any plasma or platelet transfusion, or > 1 unit red blood cell transfusion between PT-INR samplings.

Results: Propensity score matching resulted in two groups of patients with 129 patients in each group. PT-INR decreased in both groups (1.4 [1.3-1.4] in the vitamin K group and 1.4 [1.3-1.6] in the controls, p < 0.001 and p = 0.004, respectively). The decrease in PT-INR was slightly more pronounced in patients who received vitamin K (delta PT-INR - 0.10 [- 0.30 to - 0.10] in the vitamin K group and - 0.10 [- 0.20 to 0.10] in the controls, p = 0.01).

Conclusion: In critically ill patients with a PT-INR of 1.3-1.9, the administration of vitamin K resulted in a slightly larger decrease of PT-INR 12-36 h after administration compared to controls. Future studies should focus on identifying which patient populations may benefit most from vitamin K administration as well as whether vitamin K could be a better alternative than plasma or prothrombin complex concentrate to improve PT-INR before non-emergent invasive procedures.