Cardiovascular Critical Care I
| • | Eliminated renally; thus, may pose risks of digoxin toxicity in patients with acute |
|---|
or chronic renal failure
| (3) | Although the volume of distribution is relatively large (7–10 L/kg in healthy adults), |
|---|
only a small percentage of total body stores are present in the serum.
| (4) | Digoxin has a smaller volume of distribution in patients with renal failure (around 4.5 |
|---|
L/kg); thus, loading doses may be lower in these patients.
| (5) | Digoxin efficacy and toxicity do not correlate well with drug concentrations. |
|---|---|
| • | Common therapeutic targets for heart rate control are 0.8–1.5 ng/mL, although |
many clinical laboratories report therapeutic concentrations within 0.5–2.0 ng/
mL. For patients with HFrEF, the recommended serum concentration is 0.5−0.9
ng/mL
| • | Toxicity, which can present at any serum concentration, should be evaluated |
|---|
according to clinical manifestations, including: nausea, vomiting, anorexia,
mental status changes, visual disturbances, ventricular arrhythmias, bradycardia,
and hyperkalemia.
| • | Efficacy is largely based on clinical control of the heart rate; steady-state |
|---|
concentrations (more than 5–7 days after initiation) are typically used only to
validate that concentrations are not supratherapeutic.
Anticoagulation for AF or atrial flutter
According to the 2023 ACC/AHA/ACCP/HRS Guideine for the Diagnosis and Management of Atrial
Fibrillation Guidelines all patients with atrial flutter or paroxysmal, persistent, or permanent AF
should be evaluated for anticoagulation, preferably using the CHA2DS2-VASc score to approximate
stroke risk (Circulation 2024;149:e1-156).
For a CHA2DS2-VASC score of 2 or greater in men and 3 or greater in women, an oral
anticoagulant is recommended (J Am Coll Cardiol 2019;12:104-32).
ii.
It is reasonable to omit anticoagulation in patients with a CHA2DS2-VASc score of 0 in men or
1 in women. Antiplatelet therapy is not recommended for stroke prevention in atrial fibrillation
patients, even in those who are low risk.
iii.
For patients with AF and a mechanical prosthetic heart valve or valves, warfarin anticoagulation
and international normalized ratio (INR) goals should be consistent with the type and location
of the prosthetic valve. Bridging is no longer routinely recommended (Chest 2022;165:1127-
39). Bridging with unfractionated heparin can be considered in those at high risk for
thromboembolic events, including:
| (a) | Older generation mechanical valves (e.g., tilting-disc valve) |
|---|---|
| (b) | A mechanical mitral valve with one or more other risk factors for thromboembolism |
| (c) | A recent thromboembolic event in preceding 3 months |
| (d) | History of a perioperative thromboembolism |
iv.
In patients with AF at intermediate risk for thromboembolism (average CHADS2 score of
2-3), the use of bridging with low-molecular-weight heparin was non-inferior to no bridging
for elective procedures. However, there was a significant excess of major bleeding in the
low-molecular-weight heparin group. Note that patients with a mechanical valve or stroke/
transient ischemic attack/systemic embolism within the preceding 12 weeks were not eligible
for inclusion in the study (N Engl J Med 2015;373:823-33).
Although the CHADS2 and CHA2DS2-VASc scores are commonly used to estimate annual
stroke risk, these scoring systems were not founded in the context of critically ill patients.