دانشجویان پزشکی 87 کرمان
1-The answer is c.
Rhabdomyolysisinduced ARF may follow influenza. It is characterized by a creatinine disproportionately elevated compared to BUN (usual BUN-creatinine ratio ∼10), hyperkalemia, hyperphosphatemia, and hyperuricemia, all due to release of intracellular muscle products. The high phosphorus causes hypocalcemia.
All nonsteroidal agents may cause decreased renal function. Usually this is due to decreased blood flow—less commonly, to druginduced nephritis. The laboratory abnormalities discussed are not seen in either situation. However, stopping the ibuprofen in this patient would be prudent.
The absence of orthostatic hypotension makes the diagnosis of volume depletion very unlikely. Nothing on history, physical examination,or electrolyte abnormalities suggests obstruction. However, in a 76-yearold man, considering occult obstruction is always appropriate.
2- The answer is b
Urinalysis showing muddy brown granular casts is diagnostic of acute tubular necrosis and consistent with rhabdomyolysis induced ARF. In oliguric (<20 mL urine per hour) ARF, a urine sodium less than 10 meq/L suggests prerenal azotemia; a value greater than 20 meq/L suggests acute tubular necrosis.
Urine sodium is not useful in nonoliguric ARF (greater than 20 mL urine per hour). Obstructive uropathy is unlikely with the multiple electrolyte disorders in this patient. However, renal ultrasound is an appropriate test in a 76-year-old male to be sure occult obstruction is not contributing to renal failure.
Despite the high serum uric acid, acute urate nephropathy does not occur with rhabdomyolysis. Acute urate nephropathy may occur with chemotherapy of aggressive tumors (e.g., Burkitt’s lymphoma) and is characterized by a urine uric acid–creatinine ratio greater than 1.
3- The answer is d
Rhabdomyolysis induced ARF is partly due to tubular obstruction by myoglobin and partly due to nephrotoxicity of myoglobin. Diuresis may relieve obstruction, and alkalization of the urine with bicarbonate may decrease nephrotoxicity of myoglobin. Frequently used in the past, mannitol no longer has a role in ARF.
Low-dose dopamine may increase renal blood flow, but does not improve ARF. Natriuretic peptide has many theoretical hemodynamic effects, but has not been proved to improve ARF.
4- The answer is c
Pericarditis in renal failure (acute or chronic) is an indication to initiate hemodialysis, because untreated uremic pericarditis may progress to pericardial tamponade. Other indications include encephalopathy, volume overload, and intractable hyperkalemia. There is no absolute number for BUN to initiate dialysis.
No degree of oliguria is a specific indication for dialysis, although this situation must be closely watched for volume overload. Bone marrow depression, mainly due to reduced erythropoetin combined with mildly reduced red cell half-life, causes hematocrit to fall almost universally in renal failure (acute and chronic). This does not determine need for dialysis.
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