Which electrolyte imbalances are known to increase sensitivity to digitalis toxicity?

The correct choice highlights the electrolyte imbalances that can increase the risk of digitalis toxicity, specifically hypokalemia, hypercalcemia, and hypomagnesemia.

Digitalis, a medication used primarily in treating heart conditions, can be toxic in cases where electrolyte levels are out of balance. Hypokalemia (low potassium levels) is particularly significant because potassium and digitalis compete for the same receptor site on the Na+/K+ ATPase pump. When potassium levels are low, digitalis binds more effectively to these sites, leading to an increased effect and potential toxicity.

Hypercalcemia (elevated calcium levels) can also heighten digitalis toxicity. Calcium can augment the force of cardiac contractions but high levels can lead to increased excitability of cardiac myocytes, amplifying the effects of digitalis.

Hypomagnesemia (low magnesium levels) can further exacerbate digitalis toxicity as magnesium plays a role in maintaining stable cardiac electrical activity. Low levels can increase the susceptibility to digitalis' effect on the heart, again contributing to toxicity.

These three imbalances together create an environment that enhances the risk of adverse effects from digitalis, making the correct answer particularly relevant for understanding the safety of digitalis therapy in clinical practice.