Table 1.

The FH-algorithm

Adjusting the Oral Anticoagulation Treatment
2.0–3.0	Therapeutic INC interval		2.5–3.5
INR	Acute treatment	Maintenance dosage	INR
>10	Give Vitk with or without FFP. Pause VKA until INR is within therapeutic interval (2- > 7 days)	Reduce to 50% or more	>10
6.0–10	Pause VKA for 2–3 days. Vitk may be administered	Reduce 30–40%	7.0–10
5.0–5.9	Pause VKA for 1–2 days	Reduce 20–30%	5.5–6.9
3.5–4.9	Pause VKA for 0–1 day	Reduce 10–20%	4.0–5.4
3.1–3.4	None	Reduce 0–10%	3.6–3.9
2.0–3.0	None	No change	2.5–3.5
1.7–1.9	None	Increase 0–10%	2.1–2.4
1.5–1.6	Double dosage of VKA 1 day	Increase 20–30%	1.7–2.0
<1.5	Double dosage of VKA 1 day. Heparin may be administered	Increase 40–50%	<1.7

The FH-algorithm was a modification to the algorithm used in this scheme (6). VitK: Vitamin K₁. FFP: Freshly frozen plasma. VKA: Vitamin K- antagonist. The suggested changes to the maintenance dosages presume a steady state corresponding to an unchanged dosage of warfarin for more than 1 week or phenprocoumon for more than 1 month, and that the sensitivity for VKA is unchanged in the following period of time.