Plasma urea

Chemistry Plasma urea Plasma sodium Plasma potassium Plasma creatinine... 

Urease. An enzyme of the hydrolase class that catalyzes the hydrolysis of urea to COj and ammonia. It is nickel protein found in micro-organisms and plant that is frequently used in clinical assays of plasma urea concentrations. 

Fate of urea Urea diffuses from the liver, and is transported in the blood to the kidneys, where it is filtered and excreted in the urine. A portion of the urea diffuses from the blood into the intestine, and is cleaved to CO2 and NH3 by bacterial urease. This ammonia is partly lost in the feces, and is partly reabsorbed into the blood. In patients with kidney failure, plasma urea levels are elevated, promoting a greater transfer of urea from blood into the gut. The intestinal action of urease on this urea becomes a clinically important source of ammonia, contributing to the hyperam-... 

Take, as an example, the use of dialysis in renally compromised patients. We have an established method, but want to evaluate a possible alternative which would be simpler, if it is clinically acceptable. A key endpoint is plasma urea concentration. If changing the dialysis method were to lead to an increase in urea levels, this would be unacceptable. On the other hand, a decrease in urea levels would be a bonus, but is not essential. Clinical judgement is that a difference in urea levels of 1 mM is the smallest change likely to cause a noticeable effect in the patient. 

Figure 9.5 Interpretation of non-inferiority testing. Comparison of new dialysis method with old. Difference in plasma urea concentration (mM)...

Baseline levels of urea and creatinine can be highly variable. Plasma urea reflects hepatic synthesis rate and will be elevated with increased protein catabolism (increased dietary protein intake, gastrointestinal hemorrhage, fever, severe bums, corticosteroid administration, sustained exercise or muscle wasting),... 

Kevin s [K+] is somewhat higher than the normal range and a high plasma potassium concentration could account for his weakness and possibly contributes to his nausea. However, the increased plasma urea concentration, which Kevin also shows, is known to cause nausea and vomiting and is more likely to be responsible for these symptoms. 

Laboratory parameters Like in the upper GIB, certain parameters are initially important, such as haemogram, haematocrit, blood group, coagulation values, electrolytes, plasma urea, creatinine, Allgower-Burri index, (s. 

Of 121 patients who ingested Dettol 200-500 ml, three developed renal impairment, as evidenced by raised plasma urea and creatinine (7). Two of these patients also had serious complications, including aspiration leading to pneumonia and adult respiratory distress syndrome one died. Renal impairment only appears to be observed when relatively large amounts of Dettol are ingested (7). 

In rats with lithium-induced tubulo-interstitial damage, a rise in plasma urea levels after 16 weeks of treatment has been demonstrated even though plasma lithium levels were in the accepted therapeutic range for humans with mood disorders [111]. In contrast to this finding in rats, progression of the chronic tubulointerstitial lesion towards renal insufficiency is unusual in humans. 

The plasma urea nitrogen concentration decreases after birth as the infant synthesizes new protein, and the concentration does not begin to rise until tissue catabolism becomes prominent. The plasma amino acid concentration is low as a result of synthesis of tissue protein, although urinary excretion of amino acids may be quite high because of immaturity of the tubular reabsorptive mechanisms. The plasma urate concentration is high at birth, but the high clearance of urate soon reduces the plasma concentration below the adult value. 

Renal concentrating abiUty is reduced in the elderly adult, so that creatinine clearance may decline by as much as 50% between the third and ninth decades. This decreased clearance is caused more by a decrease in urinary creatinine excretion as a result of decreased lean body mass than by altered renal function. The tubular maximum capacity for glucose is reduced. The plasma urea concentration rises with age, as does the urinary excretion of protein. The serum median IgG and IgM concentrations are reduced in the elderly although serum IgA concentrations in men increase shghtly in the elderly. 

In 1999 Levey et aF proposed a formula that also included plasma urea and albumin concentrations and race... 

In practice, rather than using full UKM, the simplest calculation is the urea reduction ratio (URR). The percentage fall in plasma urea attained during a dialysis session is measured as follows ... 

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