Pre-renal renal failure

　　Common causes of acute pre-renal renal failure include diarrhea, vomiting, and excessive use of diuretics, which cause renal or extrarenal dehydration; less common causes include septic shock, acute pancreatitis, and high doses of antihypertensive drugs. They cause relative or absolute hypovolemia. During heart failure, a decrease in cardiac output also leads to insufficient effective renal blood flow. A careful clinical evaluation is helpful in distinguishing the primary disease causing acute renal failure.

　　Liver cirrhosis (hepatorenal syndrome), cyclosporine, non-steroidal anti-inflammatory drugs, and angiotensin-converting enzyme inhibitors can also cause a sudden drop in glomerular filtration rate. These factors seem to regulate renal physiological changes through prostaglandins and renin-angiotensin, leading to a sudden failure of glomerular capillary function. The urine analysis results are similar to those of pre-renal renal failure, but clinical evaluation may not always confirm the existence of true pre-renal renal failure. Stopping the above drugs, actively treating liver disease, or undergoing liver transplantation can often improve glomerular filtration rate.

　　It often complicates with hypertension, anemia, heart failure, pericarditis, cardiomyopathy, electrolyte and acid-base disturbances, renal osteodystrophy, fractures, infections, and so on. In addition to the above systemic complications, patients with chronic renal insufficiency and long-term dialysis may also have the following complications:

　　One, Aluminum toxicity:Patients with end-stage renal disease receiving routine dialysis treatment are prone to aluminum toxicity.

　　Two, Dialysis-related amyloidosis:Dialysis-related amyloidosis (DRA) is a bone and joint disease seen in patients with long-term dialysis. Its clinical symptoms and incidence are closely related to the duration of dialysis.

　　Three, Changes in trace elements:Renal failure and dialysis have a great impact on the metabolism of trace elements, which can accumulate in various parts of the body and cause toxic reactions.

　　1, Aluminum:See aluminum toxicity.

　　2, Copper:The plasma copper levels in patients with chronic renal failure who have not undergone dialysis are usually normal, but they can also be slightly low.

　　3, Zinc:The plasma zinc content is often extremely low in patients with chronic renal failure who are on a low-protein diet and those with nephrotic syndrome who lose a large amount of urinary protein.

　　1. In addition to a few cases of pre-renal renal failure caused by heart failure, most patients usually have symptoms such as thirst, orthostatic dizziness, and a history of fluid loss. Sudden weight loss often reflects the degree of dehydration.

　　2. Physical examination shows poor skin elasticity, venous collapse, dry mucous membranes and armpits. The most important sign is orthostatic or postural hypotension and tachycardia.

　　1. Limit Fluid Intake

　　If the amount of urine excreted decreases, the liquid taken orally remains in the body, causing body swelling, increased blood pressure, and even pulmonary edema. At this time, it is necessary to limit the daily intake of liquid. Usually, the amount of liquid taken orally should be approximately equal to the total daily urine output plus 500cc.

　　2. High-Quality Low-Protein Diet

　　For patients with chronic renal failure, it is recommended to have a high-quality protein diet, which is rich in essential amino acids, such as milk, eggs, lean meat, fish, and others. The intake of protein should be adjusted according to the patient's creatinine clearance rate. Generally, the recommended protein intake is 0.6 grams per kilogram of body weight per day. For example, if the weight is 50 kilograms, the daily protein intake should be controlled at 30 grams. At the same time, under strict control of protein intake, it is necessary to carefully select the source of protein to ensure its full utilization by the human body. It is recommended that at least two-thirds of the daily allowance of protein be supplied by high-quality protein. Foods rich in plant protein, such as peanuts, beans, and their products (tofu, tofu skin, soy milk, bean curd, etc.), should be used with caution.

　　3. Low-Sodium Diet

　　Eighty percent of patients with chronic renal failure also have hypertension. When kidney function is impaired, the body cannot excrete excess sodium ions, leading to hypertension, edema, ascites, pleural effusion, increasing the burden on the heart, and eventually leading to heart failure. Excessive intake of sodium can lead to sodium and water retention, which not only worsens edema but also exacerbates hypertension. Therefore, it is essential to limit the intake of sodium, and the intake of sodium salt can be restricted to 2-3g/d according to the condition. At the same time, it is advisable to avoid eating preserved foods. Salt, soy sauce, monosodium glutamate, ketchup, and saucy sauce all contain a large amount of sodium, and the amount of sodium in processed and preserved canned food is also considerable. Therefore, in daily life, it is best to choose natural foods, and in cooking, it is advisable to use sugar, vinegar, scallions, ginger, garlic, five-spice powder, cinnamon, Sichuan pepper, coriander, and other ingredients to add other flavors to the food, increasing the palatability of the food.

　　4. Limit Phosphorus Ions

　　The main function of phosphorus is to strengthen bones, and almost all foods contain phosphorus. Due to kidney failure, the kidneys cannot work normally, leading to the accumulation of excess phosphorus in the blood, causing hyperphosphatemia, which can lead to skin itching and bone lesions. Physicians usually prescribe aluminum hydroxide or calcium carbonate tablets, both of which are phosphorus binders that can bind with phosphorus in food and be excreted through feces. In addition to taking phosphorus binders, it is also advisable to avoid eating foods high in phosphorus, such as dairy products, sodas, colas, yeast, offal, dried beans, whole grains (brown rice, whole wheat bread), eggs, and dried small fish. For chronic renal failure with hyperuricemia, high-purine foods such as milk, egg yolks, animal offal, bone marrow, seafood, and others should be strictly controlled in diet.

　　5. Limit Potassium Ions

　　When kidney function is poor, it may not be possible to effectively remove excess potassium. High blood potassium levels can cause serious cardiac conduction and contraction abnormalities, even death. Potassium intake does not need to be restricted as long as the urine output is greater than 1000ml. When blood potassium levels are high, it is advisable to choose vegetables and fruits with low potassium content. Such as seaweed, bamboo shoots, spinach, Chinese cabbage, corn flour, mushrooms, cauliflower, spinach, amaranth, bamboo shoots, carrots, mustard greens, pomegranate, loquat, hard persimmons, oranges, bananas, longan, etc.; other foods such as coffee, strong tea, chicken essence, beef essence, ginseng essence, strong soup, light soy sauce, salt-free soy sauce, half-salt, substitute salt, etc. also have high potassium content.

　　6. Supplementation of calories

　　Chronic renal failure patients should be provided with adequate amounts of carbohydrates and fats to ensure sufficient calories to reduce protein catabolism, so that the nitrogen from low-protein diet is fully utilized, and to reduce the consumption of protein in the body. It is recommended to provide at least 30kcal/kg per day, and edible vegetable oils and sugar can be consumed. Since rice and flour also contain poor-quality protein, patients are encouraged to eat more sweet potatoes, taro, potatoes,山药 powder, lotus root powder, etc. At the same time, attention should also be paid to provide foods rich in vitamin C, B vitamins, folic acid, and iron. The recommended daily calorie intake is 35-45 calories per kilogram of body weight.

　　1. Urinalysis:Urine output usually decreases, and indwelling urinary catheterization can accurately determine the urine output per hour, while also excluding lower urinary tract obstruction. Urine specific gravity and urine osmolality increase (respectively >1.025, >600mosm/kg), and routine urine tests are generally of little value.

　　2. Urine and blood chemistry analysis:The normal ratio of blood urea nitrogen to creatinine is 10:1. The ratio increases in patients with prerenal renal dysfunction. Mannitol and other diuretics can disrupt the excretion and reabsorption of urea, sodium, and creatinine in the renal tubules, so these drugs will affect the evaluation of the measurement results.

　　3. Central venous pressure:A decrease in central venous pressure often indicates an insufficient blood volume, which can be caused by bleeding or dehydration. However, if the main cause of prerenal renal dysfunction is severe heart failure, then the cardiac output decreases and the central venous pressure increases.

　　4. Fluid load test:The fluid load test has diagnostic and therapeutic value for prerenal renal dysfunction. If the urine output increases after careful fluid resuscitation, it can be considered as prerenal renal dysfunction. The test starts with rapid intravenous infusion of 300-500ml of normal saline and 125ml of 20% mannitol. After 1-3 hours, the urine output is measured. If the urine output exceeds 50ml per hour, it indicates that the treatment is effective, and normal saline is continued to be administered intravenously to expand blood volume and correct dehydration. If the urine output does not increase, it should be carefully reviewed to review the blood and urine biochemical analysis results, re-evaluate the patient's fluid status, and re-examine the patient's physical condition to determine whether it is necessary to perform another fluid load test (with or without furosemide).

　　For patients with prerenal renal failure, due to the destruction of renal function, the toxins and waste produced by food after being ingested cannot be normally excreted from the body, so special attention must be paid to diet to avoid placing a burden on the body:

　　1. Limit Protein Intake:For patients who have not undergone dialysis, because the kidneys cannot excrete the waste produced by protein metabolism, the condition of renal failure becomes more severe. Therefore, it is recommended to reduce protein intake; however, if dialysis is performed, attention must be paid to the fact that dialysis can cause protein loss in the body, so it is necessary to follow the advice of a nutritionist to maintain the body's nutritional needs.

　　2. Limit Sodium Intake:Because salt contains a high sodium content, if there is too much sodium in the body of renal failure patients, it can cause water retention in the body, leading to respiratory and cardiac failure and exacerbating renal failure. However, do not use low-sodium salt, as low-sodium salt contains a high amount of potassium ions.

　　3. Limit Potassium Intake:The accumulation of potassium in the body can cause muscle weakness, and in severe cases, it can cause arrhythmia, leading to heart failure.

　　4. Limit Phosphorus Intake:Because excessive phosphorus in the body can cause calcium loss, doctors will use drugs to assist in controlling the phosphorus content in the blood to prevent the occurrence of osteoporosis.

　　5. Water Intake:If too much water is consumed and the kidneys cannot excrete it, edema or respiratory and cardiac failure may occur, therefore, the control of water intake is a very important issue. Doctors will decide the amount of water intake based on the amount of urine excreted or the amount of water removed during dialysis, generally adding 500-750c.c. to the previous day's urine output.

　　In the case of dehydration, pre-renal oliguria is mainly caused by fluid loss, and at this time, rapid fluid resuscitation should be performed. Insufficient fluid can further worsen renal hemodynamics, eventually leading to tubular necrosis (acute tubular necrosis). Although fluid has been replenished, if oliguria persists, hypertension drugs can be used to treat septic shock or hypotension caused by cardiogenic shock, and antihypertensive drugs that can maintain blood pressure while protecting renal blood flow and function should be selected. Dopamine at a dose of 1-5 μg/kg per minute can increase renal blood flow without causing changes in systemic blood pressure. However, if hypotension persists despite adequate fluid resuscitation, larger doses (5-20 μg/kg) of dopamine may be required. Sometimes, merely discontinuing antihypertensive drugs or diuretics can reverse significant pre-renal renal failure.