Thanks to Dr. Francis DeRoos for walking us through a case of a young woman who presented with shock, and was ultimately found to have overdosed on calcium-channel blockers.
First, we talked about the importance of (1) the physical exam and (2) the EKG in diagnosing and risk stratifying patients with toxic ingestions. Assessing the skin, pupils, and sweat/lack thereof can give you valuable clues. See the toxidromes post from a few months ago for more info.
Here’s a cute chart that illustrates that:
We also talked about various causes of drug-induced bradycardia:
Lithium tends to cause bradycardia most commonly in patients with underlying cardiac disease. Amiodarone has particularly been known to cause bradycardia in concert with certain of the new HCV medications (sofosbuvir or daclatasvir), including slow VT!
CCB toxicity can cause a variety of ECG changes, including sinus bradycardia and varying degrees of AV blockade. Remember to look at the rhythm strip carefully to make sure you’re not missing complete heart block!
Treatment options for CCB toxicity
- Calcium: may improve inotropy and blood pressure. You can give either calcium gluconate (short acting, can give peripherally but lower Ca content) or calcium chloride (3x the Ca content of Ca gluconate, must give centrally given risk of tissue damage w/ extravasation).
- Pacing: unlikely to be of much benefit even in hemodynamically significant bradycardia, given that the CCB is still bathing cardiomyoctes with its negative chronotropic effect.
- Vasopressors: something (like norepinephrine) with inotropic and vasoconstrictive effects is best, but there’s no trial proving the superiority of one vs another. Large doses may be needed.
- High-dose insulin/euglycemic therapy: CCBs block the calcium-dependent release of insulin from pancreatic beta cells, while at the same time increasing glycogenolysis. Insulin is also postulated to have a positive inotropic effect, especially in these patients in whom CCBs are exerting a negative inotropic effect. Massive doses of insulin (to the tune of 0.5-1U/kg/hour) may be needed given (along with dextrose) to maintain euglycemia.
- Lipid formulations: intravenous lipid rescue (initially used for bupivicaine toxicity) can be used as a ‘lipid sink’ to bind up unbound CCB. This is not without risks, as it can cause lipemic serum and higher rates of pancreatitis!
- ECMO/CPB: with refractory shock, there is also a role for putting patients on ECMO while using adjunctive therapies (above) to support them
Lastly, the paper of the day– which suggests that earlier Lasix administration in patients with decompensated heart failure may have a mortality benefit! See their central illustration, which suggests that there is a critical period (<60 min) where early diuretic administration might be particularly beneficial:
- Matsue, Y. et al. 2017. Time-to-Furosemide Treatment and Mortality in Patients Hospitalized With Acute Heart Failure. Journal of the American College of Cardiology. 69, 25 (2017), 3042–3051.
- Kerns, W. 2007. Management of β-Adrenergic Blocker and Calcium Channel Antagonist Toxicity. Emergency Medicine Clinics of North America. 25, 2 (2007), 309–331.
- Life in the fast lane. Calcium Channel Blocker Toxicity.