Which of the following is a key sign of hypermagnesemia at levels of 8-10?

Hypermagnesemia refers to an elevated level of magnesium in the blood, which can have significant physiological effects, particularly at levels of 8-10 mg/dL. A key sign of hypermagnesemia is respiratory arrest, as high magnesium levels can lead to neuromuscular blockade that affects respiratory muscle function. Magnesium acts as a muscle relaxant; consequently, severe elevations can impair the diaphragm and other muscles necessary for breathing, leading to respiratory failure.

In contrast, the other choices do not typically align with the physiological consequences of elevated magnesium levels. Vasoconstriction tends to occur with low magnesium or other electrolyte imbalances, elevated blood pressure is not a typical response to hypermagnesemia, and muscle twitching would more likely be associated with hypomagnesemia (low magnesium levels) rather than hypermagnesemia. Understanding these impacts helps to assess and manage patients who may experience complications from increased magnesium levels.