A sodium level of 129 mEq/L puts a client at increased risk for which potential complication?

A sodium level of 129 mEq/L indicates hyponatremia, which has significant implications for neurological health. Sodium is essential for maintaining osmotic balance across cell membranes, and when levels drop, it can cause brain cells to swell due to the movement of water into them. This cerebral edema can lead to a range of neurological issues, including confusion, lethargy, and in severe cases, seizures. Seizure activity is particularly concerning because it can arise from the rapid changes in osmotic pressure and the effects on neuronal excitability. Therefore, low sodium levels put the patient at a heightened risk for neurological deficits and seizures, making this the most accurate answer.

The other complications, such as cardiac arrhythmias, renal failure, and hypervolemia, are not as directly connected to the immediate effects of low sodium levels. While electrolyte imbalances can affect the heart and renal function over time, they are not the most immediate risks associated with significant hyponatremia.