A 45-year-old male with acute renal failure has BUN of 100 and creatinine of 4.5. Which indicates he may require dialysis?

In the context of acute renal failure, increased potassium levels are significant indicators for the potential need for dialysis. Renal failure often leads to an accumulation of potassium in the blood, known as hyperkalemia, which can have serious cardiac implications, including arrhythmias and can potentially be life-threatening. When potassium levels rise beyond a certain threshold, usually around 6.0 mEq/L or higher, this condition may require dialysis to remove excess potassium and restore safe levels in the body.

While decreased urine output, metabolic alkalosis, and hypertension can be associated with renal failure, they do not specifically indicate the immediate need for dialysis in the same way that high potassium levels do. Decreased urine output could be present without requiring dialysis, metabolic alkalosis may arise from various causes unrelated to immediate renal function, and hypertension, while important to manage, is not an emergency signal in the context of dialysis need as hyperkalemia is.