Serous fluids analysis

Serous fluids analysis

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Serous fluids Serous fluid is a small amount of fluid (of plasma ultrafiltrate) that lies between the membranes lining the body cavities (parietal) and those covering the organs within the cavities (visceral)It is functions to keep the membrane lining moist (lubricant), provide nutrients, & remove wastesEffusion: accumulation of fluid in a body cavity due to a pathologic process

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Factors controlling serous fluidsCapillary permeabilityFluid absorption by the lymphatic systemHydrostatic pressure (i.e., blood pressure) in capillariesOncotic (osmotic) pressure produced by presence of plasma proteins in capillaries

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Types & collection proceduresSerous fluids Types Pericardial fluid around heartPleural fluid (thoracic fluid) lung cavityPeritoneal (ascitic fluid) abdominal cavityThe serous fluid is normally collected from a needle aspiration performed by a physicianNeedle aspiration Paracentesis is the term for the removal of the peritoneal / abdominal fluidThoracentesis - is the removal of fluid from the thorax or lung cavity and Pericardiocentesis is removing fluid from around the heart

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TransdatesThe Transudate is an effusion that is a result of a systemic disorder that has disrupted the balance of fluid production / fluid re-absorptionIncrease in hydrostatic pressure or a decrease in plasma oncotic pressure; fluid moves out of the vessel and into the body cavity; serous fluid accumulatesNon-inflammatory processes; a protein-poor fluid is producedAssociated disease states include: CHF, cirrhosis, nephrotic syndrome (hypoproteinemia)Finding: WBCs 500/lWBC Early neutrophils/late mononuclear cells predominateGlucose concentration less than serum

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Lights CriteriaFluid is exudative if it meets ANY criteria: fluid LDH/serum LDH > 0.6fluid protein/serum protein > 0.5fluid LDH > 2/3 upper limit of normal serum LDH LDH is increased in exudates from damaged tissue and dead leukocytes (LDH is the ubiquitous enzyme which catalyzes the last step in glycolysis and its increased presence represents the liberation of intracellular contents into surrounding fluid) LDH is normal in transudates, except when a lymph duct drains a tumor; the increased LDH results from liberation from rapidly turning over neoplastic tissueIf all 3 negative, fluid is transudative

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Serous fluid sampleSerous fluids should be collected in EDTA/sodium heparin (CBC), & sodium heparin (microbiology/cytology, & chemistry) tubes to be analyzed as soon as possible after collection. In addition, a non-additive / clot tube may also be collected to see if the specimen contains enough fibrinogen to form a clotAppearance: Pale yellow & clearWhite, turbid: WBCs / infectionBloody :RBCs/ hemorrhage Milky: Chyle lymph & emulsified fats Viscous: Increased hyaluronic acid / malignant mesothelialoma

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Serous fluid sampleEffusion does not normally contain fibrinogen or red blood cells (RBCs). Bloody or clotted specimens may be the result of a traumatic puncture, hemorrhagic effusion, or a ruptured blood vessel (active bleeding)Blood specimens usually collected at same time and comparisons of test results made

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Testing overview

Variety of tests used to aid in determining the cause of the effusionAppearanceEvaluation of clotting ability whether or not it will form a clot, etc Cell countsProtein level Both fluid and current serum level to make comparison: fluid protein / serum protein LDH enzymesBoth fluid and current serum level to make comparison: fluid LDH/ serum LDHCulturesSerology rarely done on serous fluids as blood testing is adequateCytology / Pathology if malignancy is suspected

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Chemistry testsChemistry tests ordered on serous fluids vary greatly depending on the diagnosis or suspected problem

Total protein and the enzyme LDH are generally performed on both the fluid and the patients serum

The information obtained from these test are then used to form a ratio between the serum and fluid

Serous fluid Glucose levels compared to plasma

Amylase & Lipase. These enzymes provide information about pancreatic disorders

Bilirubin test and alkaline phosphatase may be ordered on peritoneal fluid when there suspicion of perforated intestine or gall bladder

Serous fluid pH & ammonia levels are occasionally ordered as well

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Causes of pleural effusionTransdateCongestive heart failureHepatic cirrhosis Nephrotic syndromeExudateInfection Malignancy/neoplasm Systemic rheumatic disease (SLE, RA) Gastrointestinal disorders Pancreatitis Trauma/surgery

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Causes of Pericardial effusionTransdateCongestive heart failure Hepatic cirrhosisExudateInfection Myocardial infarction Systemic rheumatic disease (SLE, RA) Metastatic cancer/mesothelioma Trauma/surgery

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Causes of Peritoneal effusionTransdateCongestive heart failure Hepatic cirrhosis Nephrotic syndromeExudateInfection Malignancy/neoplasm PancreatitisMetabolic disease (e.g., uremia) TuberculosisTrauma/surgery

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Serum-ascites albumin gradient (SAAG)The serum-ascites albumin gradient or gap (SAAG) is a calculation used to help determine the cause of ascitesSAAG = (albumin concentration of serum) - (albumin concentration of ascitic fluid) N.R < 1.1High SAAG ascites (> 11 g/L) include:Low protein in ascitic fluid (< 25 g/L ): cirrhosis of the liverHigh protein in ascitic fluid (> 25 g/L): heart failure, Budd-Chiari syndromeA low gradient (< 11 g/L ) indicates causes of ascites not associated with increased portal pressure. Examples include peritoneal tuberculosis, pancreatitis, nephrotic syndrome, serositis, and various types of peritoneal cancer (peritoneal carcinomatosis

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