Chapter 16 Laboratory Assessment ● ● ● ● ● ● ● ● ● ● ● ● ● ●

Serum osmolality increases with (1,5): hypernatremia dehydration

hyperglycemia mannitol therapy azotemia uremia

ingestion of ethanol, methanol, ethylene, or glycol hyperosmolar nonketotic hyperglycemia diabetes insipidus hypercalcemia

renal tubular necrosis severe pyelonephritis ketosis shock

Serum osmolality decreases with (1,5): ●

● ●

hyponatremia overhydration

syndrome of inappropriate antidiuretic hormone (ADH) secretion

●

paraneoplastic syndromes associated with lung carcinoma

● excess fluid intake Potassium, Serum

Normal Values ●

Adults: 3.5 to 5 mEq/L; 3.5 to 5 mmol/L (SI) (5) Nutritional Significance

The normal potassium levels within cells are approxi- mately 150 mEq/L, compared with 3.5 to 5 mEq/L in serum. The level of potassium found outside the cells is the level measured by this laboratory test. As a posi- tively charged ion, potassium is involved in regulating the osmolality of the extracellular fluid by exchanging with sodium. Its level is essential to maintain the trans- membrane electrical potential between the intracellular fluid and the extracellular fluid (1). Potassium levels increase with (1):

● ● renal failure excessive intake

● cell damage burns

➤ ➤ ➤ ➤ ● surgery

crushing injuries chemotherapy

acidosis ● ● ● ●

Addison’s disease internal hemorrhage uncontrolled diabetes dehydration

Potassium levels decrease with (1): ●

● ● ● ● ● ● ● ● ●

protein-energy malnutrition malabsorption diarrhea

severe vomiting

renal tubular acidosis diuretic therapy

liver disease with ascites chronic stress

chronic laxative abuse Cushing’s syndrome

● IV fluids without adequate K+

The following drugs may increase potassium levels (1): ●

● ● ● ● ● ● ● ● ● ● ●

aminocaproic acid antibiotics

antineoplastic drugs captopril

epinephrine heparin

histamine isoniazid lithium

mannitol

K-sparing diuretics K-supplements

The following drugs may decrease potassium levels (1): ●

acetazolamide

aminosalicylic acid ● amphotericin B carbenicillin insulin

● ● ● ● ● ●

laxatives aspirin

K-wasting diuretics

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