The main cause of death in the first week of acute renal failure would be hyperkalemia. The first week happens to be in the oliguric phase of acute renal failure, during which the glomerular filtration rate is very low, urine is rare, and not only water cannot be excreted, but also potassium and toxins cannot be excreted. The body’s blood potassium will gradually rise, coupled with the combination of metabolic acidosis, the rise in blood potassium will be more pronounced. Blood potassium is one of the most important electrolytes affecting the heart beat, the normal value is between 3.5-5.5mmol/L. High blood potassium is easy to cause malignant arrhythmia, which is a chaotic beating of the heart, and it is easy to cause sudden death, and it is the most important cause of sudden death in the first week of acute renal failure. Therefore, during this period, we must limit the intake of foods containing more potassium, such as oranges, bananas and big red dates. In addition, blood potassium level should be monitored dynamically, and if it exceeds 6.5 mmol/L, hemodialysis treatment needs to be given immediately.