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Relationship between red blood cell potassium and plasma digitoxin concentrations in intoxicated patients
M Urtizberea1, M Rochdi, A Sabouraud
1INSERM U 26, Fernand Widal Hospital, Paris, France.
Insights
Severe digitalis poisoning depletes red blood cell potassium (RBC K+). This study links RBC K+ levels to digitoxin concentration, predicting depletion duration for better patient management.
Area of Science:
- Pharmacology
- Toxicology
- Biochemistry
Background:
- Cardiac glycoside poisoning, specifically digitoxin, causes significant red blood cell potassium (RBC K+) depletion.
- This depletion results from Na+/K+-ATPase inhibition and is persistent.
- The delayed relationship between plasma digitalis levels and RBC K+ depletion has limited its use as a prognostic indicator.
Purpose of the Study:
- To establish a predictive relationship between digitoxin concentration at the site of action and RBC K+ depletion.
- To determine if RBC K+ depletion can be utilized as a prognostic indicator in digitoxin poisoning.
Main Methods:
- Measured RBC K+ using atomic absorption spectrophotometry.
- Assayed plasma digitoxin concentration.
- Applied the Sheiner effect compartment model with a sigmoid Emax model.
Main Results:
- A relationship was established between digitoxin concentration and RBC K+ depletion.
- The duration of RBC K+ depletion could be predicted using in vitro assays.
- RBC K+ serves as a marker for Na+/K+-ATPase inhibition by digitoxin.
Conclusions:
- The developed method allows prediction of RBC K+ depletion duration from simple in vitro assays.
- This approach can aid in managing patients with digitalis self-poisoning.
- RBC K+ depletion, linked to Na+/K+-ATPase inhibition, offers prognostic value.
Abstract:
After severe acute self-poisoning by cardiac glycosides, significant and persistent depletion of red blood cell K+ due to inhibition of Na+K+ ATPase is seen. Because of a delay between the time course of plasma digitalis concentrations and that of red blood cell K+ depletion, no direct relation exists between the two, and RBC K+ has hitherto not been considered useful as prognostic indicators of clinical outcome. In an effort to solve this problem, red blood cell K+ was measured by atomic absorption spectrophotometry and plasma digitoxin concentration assayed in six patients admitted to an intensive care unit after digitoxin self-poisoning. Using the effect compartment model of Sheiner, a relationship based on a sigmoid Emax model was able to relate the digitoxin concentration at the action site to red blood cell K+ depletion. Thus the duration of red blood cell K+ depletion could be predicted from two relative simple in vitro assays. Since RBC K+ is a marker of the inhibition of Na+K+ ATPase by digitoxin, this method could be of use for the management of patients self-poisoned with digitalis.