Kidney creatinine, serum

RISK FOR INEFFECTIVE TISSUE PERFUSION RENAL When the patient is taking a drag tiiat is potentially toxic to die kidneys, die nurse must carefully monitor fluid intake and output. In some instances, die nurse may need to perform hourly measurements of die urinary output. Periodic laboratory tests are usually ordered to monitor the patient s response to therapy and to detect toxic drag reactions. Seram creatinine levels and BUN levels are checked frequentiy during the course of therapy to monitor kidney function. If the BUN exceeds 40 mg dL or if the serum creatinine level exceeds 3 mg cIL, the primary health care provider may discontinue the drug therapy or reduce the dosage until renal function improves. 

The study of the mechanism of urinary excretion of amylase and the amylase clearance has been the subject of many studies in recent years. Levitt et. al (79) studied the renal clearance of amylase in renal insufficiency, acute pancreatitis and macro-amylasemia. In acute pancreatitis, the kidney cleared amylase at a markedly increased rate. The ratio of the amylase clearance rate to the creatinine clearance rate (Cgm/Ccr) averaged 3 times normal early in the course of acute pancreatitis, and this elevation could persist after the serum amylase returned to normal. Comparison of an lase clearance to creatinine clearance was to minimize irrelevant changes due to variation in renal function. The increased clearance of amylase makes the urinary amylase a more sensitive indicator of pancreatitis. 

Nitrogen compounds commonly determined are creatinine, urea, and uric acid. Creatinine is an end product of the energy process occurring within the muscles, and is thus related to muscle mass. Creatinine in urine is commonly used as an indicator and correction factor of dilution in urine. Creatinine in serum is an indicator of the filtration capacity of the kidney. Urea is the end product of the nitrogen luea cycle, starting with carbon dioxide and ammonia, and is the bulk compoimd of urine. The production of uric acid is associated with the disease gout. In some cases, it appears that the excess of uric acid is a consequence of impaired renal excretion of this substance. 

Saline laxatives containing magnesium, potassium, or phosphates should be used cautiously in persons with reduced kidney function. Monitor appropriate serum electrolyte concentrations in patients with unstable renal function evidenced by changing serum creatinine or creatinine clearance. 

Direct measurement of creatinine clearance (CrCl) requires collection of urine over an extended time interval (usually 24 hours) with measurement of urine volume, urine creatinine concentration, and serum creatinine concentration (Table 22-1). Because kidney function can fluctuate significantly during ARF, this method may underestimate or overestimate kidney function depending on whether ARF is worsening or resolving. 

Several equations have been developed to assess unstable kidney function. The Jelliffe equation (Table 22-1) estimates creatinine clearance by considering the change in serum creatinine over a specified time period.11 While it is more mathematically difficult to calculate, it better estimates creatinine clearance in patients with rapidly changing kidney function compared to an equation that only includes a single creatinine concentration. 

A 73-year-old man with a history of diabetes mellitus, chronic kidney disease, gout, osteoarthritis, and hypertension is hospitalized with possible urosepsis. He recently completed a 10-day course of antibiotics and was ready for discharge when his morning labs showed an increase in BUN and serum creatinine concentration. Upon examination, he was found to have 2+ pitting edema, weight gain, nausea, elevated blood pressure, and rales on chest auscultation. 

Although determination of creatinine clearance rate is a standard clinical procedure, it is difficult to carry out mainly because accurate collection of total urine output over a 24-hour period is required. It can never be certain that this requirement has been met. Since creatinine is produced continuously in muscle and is cleared by the kidney, renal failure is characterized by elevated serum creatinine levels. The degree of elevation is directly related to the degree of renal failure—if it is assumed that the production of creatinine in the muscle mass is constant and that renal function is stable. When these assumptions are valid, there is a direct relationship between serum creatinine level and kanamycin half-life, as shown in Fig. 9. The equation of the line in Fig. 9 is... 

Increased serum creatinine and serum alanine aminotransferase in birds, suggestive of kidney and liver alterations (Hoffman etal. 1981)... 

Baseline serum creatinine, hematology profiles, and serum transaminases with repeat levels at 6- to 12-month intervals are useful in identifying specific toxicities to the kidney, liver, GI tract, or bone marrow. 

Creatinine is a metabolic breakdown product of muscle and usually has a constant value in an individual. Its value ranges from 0.6 mg/100 mL of serum to 1.2 mg/100 mL of serum. Creatinine is almost exclusively eliminated by the kidneys. Therefore, if the level of creatinine increases in the serum, it is likely that the capability of kidneys to eliminate the drugs is reduced. As a general rule, if the serum creatinine level (Ccr) is doubled, the kidney function is one-half. If the Ccr is quadrupled, the renal (kidney) function is one-fourth or 25%. 

Kidney Failure, Acute A clinical syndrome characterized by a sudden decrease in glomerular filtration rate, often to values of less than 1 to 2 ml per minute. It is usually associated with oliguria (urine volumes of less than 400 ml per day) and is always associated with biochemical consequences of the reduction in glomerular filtration rate such as a rise in blood urea nitrogen (BUN) and serum creatinine concentrations. [NIH]... 

Figure 3. Improved renal function in rats with AKI after MSC treatment. Serum creatinine (mean + SD) at baseline and days 1, 2 and 3 after acute kidney injury (AKI) in control animals (/ =6, white bars) and in mesenchymal stem cell treated animals (n=7, black bars). Mesenchymal stem cell treatment led to a significant improvement in renal function on days two and three after AKI, as determined by ftest.

Renal function impairment Metformin is known to be excreted by the kidney, and the risk of metformin accumulation and lactic acidosis increases with the degree of impairment of renal function. Do not give metformin to patients with serum creatinine levels above the upper limit of normal for their age. 

Monitoring Periodically determine liver and kidney function especially during the first few months of therapy. Perform BUN, serum creatinine, or Ccr and reassess the patient s dosage. 

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