What are the risks of rapid intravenous administration of potassium?

The most significant risk associated with the rapid intravenous administration of potassium is that it can lead to cardiac arrest due to hyperkalemia. When potassium is administered too quickly, it can cause an excessive increase in serum potassium levels. This condition, known as hyperkalemia, can have severe consequences, particularly affecting the heart's electrical activity.

Potassium is crucial for normal heart function, and any drastic fluctuations in its concentration can disrupt the heart's rhythm. High levels of potassium can lead to life-threatening arrhythmias, including ventricular fibrillation or asystole, both of which can result in cardiac arrest. This risk highlights the importance of administering potassium slowly and monitoring the patient closely for signs of complications.

Other options, while they may have some relevance in different contexts, do not present the same level of immediate life-threatening risk associated with rapid potassium administration. For instance, while gastrointestinal irritation can occur with potassium intake, it is not a direct consequence of intravenous administration. Similarly, allergic reactions to potassium are rare, and skin necrosis is typically more connected to intravenous infusions that are too concentrated or improperly administered rather than potassium alone. Thus, the potential for hyperkalemia and its associated cardiac consequences makes the second choice the correct answer.