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. AORN JOURNAL, June 1997 v65 n6 p1039(24) 24 Hour Urine Test Biochemical Tests: Laboratory tests that reflect catecholomine metabolism can confirm the presence of phechromocytomas. Patients' dopamine, norepinephrine, epinephrine, metanephrine, and VMA levels are measured through 24- hour urine output analyses. Physicians may also request random urine specimens after patients' hypertensive episodes because briefly elevated catecholomine levels may be missed in 24-hour urine output analyses. Approximately, 90% to 95% of all patients diagnosed with pheochromocytoma have elevated VMA and metanephrine levels and 98% of these patients have altered catecholomine levels. Twenty-four hour urine outputs are collected in sealed leak-proof containers that contain strong acid preservatives. Normal urine creaninine levels confirm that 24-hour urine collections are complete. If patients experience paroxysmal hypertension, 24 hour urine collections should begin at the onset of these episodes. Normal metanephrine levels in 24-hour urine collections indicate that patients do not have chromaffin tumors. If the results of 24-hour urine output analyses are uncertain, laboratory technicians examine patients' total and fractionated levels of plasma catecholamines (ie: postural change, exercise, emotional arousal, time of day, ). Before patients' catecholomine and metabolite levels can be tested, they must restrict their consumption of foods that contain tyramine (eg, aged cheese, red wine, pickled herring, yogurt, liver, caffeine, vanilla extract) and must avoid certain medications (eg, MAO inhibitors because they increase epinephrine levels by blocking intraneural metabolism. Anti-hypertensive medications (eg, vasodilators, (Beta)-blockers, diuretics) may increase catecholamine secretion, whereas other antihypertensive medications (e, methyldopa, clonidine hydrochloride) may decrease catecholamine secretion. Perioperative nurses should remember that some medications initially promote the release of stored catecholomines before they exert their hypotensive side effects. Listed below are medications that may increase or decrease levels of catecholomine and metabolites in laboratory tests.
Medications that alter Catecholomine and Metalbolite Laboratory Values: |