Acute renal failure in the elderly

Introduction to acute renal failure in the elderly Acute renal failure (acuterenalfailureintheelderly, ARF) refers to a sudden loss of renal function caused by various reasons, which may be reversed if properly treated. In recent years, with the continuous advancement of dialysis, intravenous high nutrition, antibiotics and other medical technologies, the treatment of ARF has been significantly improved. However, the mortality rate continues to be as high as 50% to 70%, one of the main reasons may be the elderly patients in the ARF. The proportion of patients increased and the number of elderly patients receiving complex surgery increased. Studies have shown that in the elderly with multiple organ failure, the mortality rate of those with renal failure is significantly increased. Therefore, in recent years, the ARF of the elderly has become more and more concerned. basic knowledge The proportion of sickness: 0.01% Susceptible people: the elderly Mode of infection: non-infectious Complications: upper gastrointestinal bleeding, hypertension, heart failure, arrhythmia, upper gastrointestinal bleeding, upper gastrointestinal bleeding in the elderly

The cause of acute renal failure in the elderly

Causes:

ARF can occur in various diseases and its causes are diverse. It can usually be divided into a sharp decline in renal blood flow (pre-arenal ARF), various kidney diseases (renal substantial ARF, intrinsic ARF) and Urinary tract obstruction (post-renal ARF) (Figure 1), the most common type of ARF clinically is acute tubular necrosis due to renal ischemia and / or nephrotoxicity damage (acute tubular necrosis, ATN), sometimes different types exist at the same time, this chapter will focus on the clinical features of ATN and its diagnosis and treatment.

Pathogenesis:

The pathogenesis of ARF has not yet been fully elucidated. It is thought that it may be caused by renal hemodynamic changes, renal tubular epithelial cell damage due to nephrotoxin or renal ischemia-reperfusion, and epithelial cell shedding, tubular formation leading to renal tubules. The result of a combination of various factors such as cavity obstruction.

Renal hemodynamic changes during ARF, intrarenal, and intraglomerular hemodynamic abnormalities are the initiating factors of ATN, which are characterized by a decrease in renal plasma flow and a redistribution of intrarenal blood flow, manifested as renal cortical blood. Reduced flow and renal medullary congestion, leading to increased intravascular renal vascular resistance are endogenous vasoconstrictor (such as endothelin) and vasodilators (such as nitric oxide) production and balance of imbalance, renal sympathetic nerves, Intrarenal renin-angiotensin and prostaglandins may also be partially involved in the regulation process. Renal tubular bulb feedback dysfunction may aggravate renal hemodynamic abnormalities, ischemia, hypoxia, nephrotoxic substances and deficiency. Blood reperfusion, renal injury, etc. can cause metabolism and dysfunction of renal tubular epithelial cells. These changes in cell biology are the basis for structural and functional damage of renal tubules in ARF. If these metabolic and dysfunctions persist, then Renal tubular epithelial cells can be necrotic and detached, forming a cast, causing obstruction of the renal tubules and leakage of renal tubule fluid to the renal interstitial, leading to a significant reduction in glomerular filtration rate.

The completion of renal tubular epithelial cell damage repair is the basis of clinical recovery of renal function in patients. Renal tubular epithelial cell repair can begin in the early stage of injury, and cells undergoing reversible damage or uninjured cells first undergo cell phenotypic transformation (ie dedifferentiation). ), under the action of a variety of locally produced growth factors (such as epidermal growth factor, hepatocyte growth factor, insulin-like growth factor, etc.), cell proliferation or apoptosis, ultimately through cell differentiation, migration, intercellular or cell and Interstitial interactions restore the structural and functional integrity of the renal tubules. The clinical outcome of ARF patients depends on the final outcome of the dynamic balance of renal tubular epithelial damage and repair processes.

Prevention of acute renal failure in the elderly

At present, it is not possible to prevent acute tubular necrosis with certainty, but it is important to take preventive measures to prevent it from occurring in susceptible populations. The main measures include: active control of primary disease or pathogenic factors (such as lack of Blood, trauma and infection, etc., rational use of various drugs and contrast agents in susceptible populations, timely release of vascular lesions, etc., closely monitor changes in renal function, urine output and urine enzymes in susceptible populations, early diagnosis of acute kidney Injury of the tubules and timely treatment can help prevent the occurrence of ATN.

Elderly patients with acute renal failure complications Complications upper gastrointestinal bleeding hypertension heart failure arrhythmia upper gastrointestinal bleeding upper gastrointestinal bleeding

Often complicated by hypertension, anemia, heart failure, pericarditis, cardiomyopathy, hydroelectric disorders and acid-base imbalance, renal osteodystrophy, fractures, infections, etc.

In addition to the above systemic complications, long-term dialysis patients with chronic renal failure can also have the following complications:

1. Patients with end-stage renal disease treated with conventional dialysis for aluminum poisoning are susceptible to aluminum poisoning.

2. Dialysis-related amyloidosis dialysis-related amyloidosis (DRA) is an osteoarthrosis found in long-term dialysis patients. The clinical symptoms and incidence are closely related to the length of dialysis.

3. Trace element changes Renal failure and dialysis have a great influence on the metabolism of trace elements. They can accumulate in various parts of the body and cause toxicity. Such as:

(1) Aluminum: See aluminum poisoning.

(2) Copper: Plasma copper levels in patients with chronic renal failure who are not dialysis are often normal, but can be slightly lower.

(3) Zinc: Chronic renal failure eating low-protein diet and nephrotic syndrome, a large number of urine protein loss in patients with plasma zinc is often extremely low.

Symptoms of acute renal failure in the elderly Common symptoms Loss of appetite, sleepiness, nausea, urinary azotemia, upper gastrointestinal bleeding, disturbance of consciousness, arrhythmia, traumatic bloating

The initial symptoms of ARF patients are related to their etiology. Most of the patients have acute onset, often with changes in urine volume and azotemia. Water, electrolyte and acid-base balance disorders and various complications may occur. Uremia manifestations, including early digestive system loss of appetite, nausea and vomiting, abdominal distension, diarrhea or upper gastrointestinal bleeding, severe hypertension, heart failure and arrhythmia, and even apathy, lethargy or disturbance of consciousness, part The patient may also develop anemia due to trauma, bleeding, hemolysis or severe infection.

According to clinical manifestations and disease course, typical ischemic ARF can be divided into three stages: oliguric or anuric phase, polyuric phase and recovery phase.

1 oliguria (or no urine) period: urine volume is less than 400ml / d (or 50ml / d), the duration is generally 1 to 2 weeks, when the glomerular filtration rate is significantly reduced, the patient's serum creatinine and The level of urea nitrogen is significantly increased, and the rate of increase per day depends on the decomposition state of the body's protein. The high decomposition state can be seen in patients with extensive tissue trauma, severe infection, insufficient heat supply, gastrointestinal bleeding or application of adrenocortical hormone. Related factors, patients often have obvious water, electrolyte and acid-base balance disorders and varying degrees of uremia.

2 polyuria: progressive urine output indicates that renal function begins to recover, when the urine volume exceeds 2500ml / d, it is polyuria, generally lasting 1 to 3 weeks or longer, when the glomerular filtration rate is significantly increased (It takes about 1 week), azotemia is gradually reduced, urinary symptoms gradually improve, water, electrolyte imbalance and various complications can still occur due to the recovery of renal function.

3 recovery period: urine output returned to normal, renal function gradually recovered, recovery of glomerular filtration function takes 3 months to 1 year, and some cases of renal tubular concentration function can be restored for more than 1 year, a small number of patients with persistent renal function Does not recover, suggesting that the kidneys leave varying degrees of permanent damage.

Many ATF patients have clinical manifestations that lack the above typical course of disease. 30% to 60% of ATN patients show non-oliguric type, and the urine volume is maintained above 500ml/d or up to 1000-2000ml/d, which is common in nephrotoxic drugs. ARF after major thoracoabdominal surgery or kidney transplantation, and a small number of patients with oliguria may be more than 1 to 2 months, may be related to ARF caused by the original kidney disease, or not just ATN (with renal cortical or renal papillary necrosis) .

According to the primary cause, sudden onset of progressive azotemia with oliguria, combined with clinical manifestations and laboratory tests, is generally not difficult to make a diagnosis, no urine should first exclude the possibility of urinary tract obstruction, history and past Patients with schistosomiasis with unclear and acute onset can follow the mental procedure of Figure 4 for differential diagnosis. Patients with renal adenoma should be identified whether their lesions involve glomeruli, renal blood vessels or renal interstitium. Those diagnosed with ATN should further analyze whether they are oliguria or have high decomposition status and complications, in order to determine the correct treatment plan.

Examination of acute renal failure in the elderly

Blood test

Used to understand the presence or absence of anemia and its extent, combined with red blood cell morphology, reticulocyte, etc., can help identify acute and chronic renal failure and diagnose the cause.

2. Urine check

It is extremely important for diagnosis, differential diagnosis and clinical judgment classification. It is necessary to combine clinical comprehensive analysis. In addition to routine examination, urinary diagnostic index can often be used to identify pre-renal azotemia and ATN. The urinary diagnostic index has the highest sodium excretion score. Sensitive, the positive rate is as high as 98%; the positive rate of urinary sodium excretion can also be as high as 90% or more. The application of diuretics or hypertonic drugs affects the accuracy of the above indicators, so it should be tested before administration.

3. Renal function and biochemical indicators check

According to changes in serum creatinine, urea nitrogen, serum potassium and blood HCO3, the degree of ARF can be judged and whether there is a high decomposition state. In addition, hyponatremia, hypocalcemia or elevated blood phosphorus can be found, and blood gas analysis can help determine Metabolic acidosis or alkalosis.

Renal biopsy pathological examination: ATN patients with typical clinical manifestations generally do not need to have a renal biopsy. For clinical manifestations that meet ATN, but the oliguria period is more than 2 weeks or the cause of ARF is unknown, and the renal function cannot be recovered after 3 to 6 weeks, there may be Other severe renal parenchymal diseases leading to ARF should be performed as soon as possible in order to confirm the cause of the disease as early as possible. Because the incidence of complications such as gross hematuria and perirenal hematoma after ARF puncture is higher than that of the general case, kidney should be done well. Prepare the work before puncture and carefully select the timing of the inspection.

Diagnosis and diagnosis of acute renal failure in the elderly

Diagnostic identification basis:

1. Have a history of shock or intravascular hemolysis, drug poisoning or allergies.

2. After correcting or eliminating acute blood volume deficiency, dehydration, and urinary tract obstruction, the urine volume is still 17/ml/h or the urine volume is still 400/ml/24h.

3. The specific gravity of urine is below 1.015, even fixed at 1.010.

4. Rapid and increasing azotemia.

5. Urine osmotic pressure <350mOsm/Kg.H2O, urine sodium>40mmol/L.

6. Excluding pre-renal azotemia and post-renal oliguria or no.

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