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Chapter 29: Body Fluid Analysis

Chapter 29: Body Fluid Analysis. By Kristy Shanahan, Lillian A. Mundt. Amniotic Fluid (AF). Functions Provides cushioning medium for fetus Regulates temperature of fetal environment Allows fetal movement Serves as matrix for influx & efflux of constituents Sources

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Chapter 29: Body Fluid Analysis

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  1. Chapter 29: Body Fluid Analysis By Kristy Shanahan, Lillian A. Mundt

  2. Amniotic Fluid (AF) • Functions • Provides cushioning medium for fetus • Regulates temperature of fetal environment • Allows fetal movement • Serves as matrix for influx & efflux of constituents • Sources • Mother is ultimate physiologic source for AF. • Other sources: maternal secretion across amnion, transudation across fetal skin, fetal micturition or urination

  3. Amniotic Fluid (AF) (cont’d) • Dynamic balance between production & clearance of AF • Balance is maintained by fetal urination & swallowing. • AF sample contains cells originating from fetus & may be obtained by transabdominal amniocentesis. • Amniocentesis & subsequent AF analysis test for: • Congenital diseases • Neural tube defects • Hemolytic disease • Fetal pulmonary development

  4. Amniotic Fluid (AF) (cont’d) • Neural Tube Defects (NTDs) • Elevated levels of -fetoprotein (AFP) associated with spina bifida, anencephaly, abdominal hernias into umbilical cord, cystic hygroma, & poor pregnancy outcome • Low maternal serum AFP associated with Down’s syndrome • Protocol for AFP testing: • 1. Serum AFP, assay of hCG, unconjugated estriol, & inhibin A • 2. Repeat if positive • 3. Diagnostic ultrasound • 4. Amniocentesis for confirmation

  5. Amniotic Fluid (AF) (cont’d) • Hemolytic Disease of Newborn (HDN) • A syndrome of fetus resulting from ABO incompatibility of maternal & fetal blood • Maternal antibodies to fetal erythrocytes cause hemolytic reaction varying in severity. • Resultant hemoglobin breakdown products appear in AF & provide a measure of severity of incompatibility reaction. • Method of measurement: direct spectrophotometric scan of undiluted AF & calculation bilirubin • Treatment options: immediate delivery, intrauterine transfusion, or observation

  6. Amniotic Fluid (AF) (cont’d) • Assessment of fetal prognosis

  7. Amniotic Fluid (AF) (cont’d) • Fetal Lung Maturity • Primary reason for AF testing is assessment of fetal pulmonary maturity. • Testing indicates whether specific phospholipid levels are sufficient to prevent atelectasis (alveolar collapse) at delivery. • Risk factors to fetus or mother must be weighed against interventions. • Respiratory distress syndrome: alveolar collapse in neonatal lung during changeover from placental oxygen to air • Lung maturation is function of differentiation of alveolar epithelial cells into types I & II cells.

  8. Amniotic Fluid (AF) (cont’d) • Fetal Lung Maturity • Tests for assessing fetal lung maturity • Functional assays: bubble or shake test, foam stability index • Quantitative assays: lecithin-sphingomyelin ratio (L/S ratio), phosphatidylglycerol, fluorescence polarization, lamellar body counts • Classic technique for separation & evaluation of lipids involves thin-layer chromatography of an extract of AF. • Classic breakpoint for judgment of maturity has been an L/S ratio of 2.

  9. Amniotic Fluid (AF) (cont’d) • Thin-layer chromatogram of amniotic fluid phospholipids

  10. Phosphatidylglycerol (PG) • A phospholipid essential for fetal lung maturity (FLM) is PG that increases in proportion to lecithin. • Development of PG is delayed in diabetic mothers. • Thus, L/S ratio of 2 cannot be relied upon unless PG is included in interpretation. • An immunologic assay using antibody specific for PG can be used to determine FLM .

  11. Fluorescence Polarization • Compares polarization of a fluorescent dye that combines with albumin & surfactant in AF specimen • Lamellar Body Counts • Type II alveolar cells produce & secrete phospholipids in form of lamellar bodies. • As FLM increases, these lamellated packets of surfactant also exhibit an increased presence in AF. • The fact that lamellar bodies are about same size as platelets provides a convenient method to determine their concentration using platelet channel on automated hematology analyzers.

  12. Cerebrospinal Fluid (CSF) • Description • Liquid that surrounds brain & spinal cord • Flows between arachnoid & pia mater in subarachnoid space • Total CSF volume is about 150 mL (8% of CNS cavity volume). • Functions • Physical support & protection • Provision of a controlled chemical environment for nutrient supply & waste removal • Intracerebral & extracerebral transport

  13. Cerebrospinal Fluid (CSF) (cont’d) • Formation • Formed predominantly at choroid plexus deep within brain & by ependymal cells lining ventricles • Formed at average rate of 0.4 mL/min, or 500 mL/day • Formation results from selective ultrafiltration of plasma & active secretion by epithelial membranes. • Analysis • Investigated for cases of suspected CNS infection, demyelinating disease, malignancy, & hemorrhage in CNS • Normal CSF is clear, colorless, free of clots, & free of blood.

  14. Cerebrospinal Fluid (CSF) (cont’d) • Analysis • Common reasons for blood to be found in CSF: traumatic tap & subarachnoid hemorrhage • Tests of interest: glucose, protein, lactate, glutamine • Plasma sample should be obtained 2–4 hours prior to tap so plasma & CSF glucose levels can equilibrate. • Decreased CSF glucose levels can be result of: • 1. Disorder in carrier-mediated transport of glucose to CSF • 2. Active metabolism of glucose by cells or organisms • 3. Increased metabolism by CNS

  15. Cerebrospinal Fluid (CSF) (cont’d) • Analysis • Increased lactate level with a normal to decreased glucose level has been suggested as a readily accessible indicator for bacterial vs. viral meningitis. • Protein levels in CSF reflect selective ultrafiltration of CSF blood–brain barrier. • Increased level of CSF total protein is useful nonspecific indicator of pathologic states.

  16. Sweat • Eccrine Sweat Glands • Regulate body temperature • Are innervated by cholinergic nerve fibers & are type of exocrine gland • Analysis • Generally not proven to be a clinically useful model • Used effectively, however, for determination of chloride levels in diagnosis of cystic fibrosis (CF)

  17. Sweat (cont’d) • Analysis • Diagnostic algorithms for CF rely on abnormal sweat electrolytes, pancreatic or bronchial abnormalities, & family history. • Sweat glands, although affected in their secretion, remain structurally unaffected by CF. • Both sodium & chloride are measured in sweat, but chloride remains more important. • Standard method of measurement is based on pilocarpine nitrate iontophoresis method of Gibson & Cooke. • Other methods include osmolarity, conductivity, & chloride electrodes or patches placed on skin.

  18. Synovial Fluid • Fluid found in the cavities of movable joints • Formed by ultrafiltration of plasma across synovial membrane • Serves as transport medium for delivery of nutrients & removal of cell wastes • Normal fluid is clear, colorless to pale yellow, viscous, & nonclotting. • Variations are indicative of pathologic conditions. • Sample is collected via arthrocentesis of joint.

  19. Serous Fluids • Lungs, heart, & abdominal cavities are surrounded by 2 serous membranes: • Parietal membrane lining cavity wall • Visceral membrane lining organs • Serous fluids, ultrafiltrates of plasma, are located between membranes. • Formed by serum dialyzing across these membranes • 3 types: pleural (lung), pericardial (heart), peritoneal (abdominal)

  20. Serous Fluids (cont’d) • Pleural Fluid • Essentially interstitial fluid of systemic circulation • Normally, there is 3–20 mL of pleural fluid in pleural space. • Fluid is removed from pleural space by needle & syringe. • Classifications • Transudate: secondary to remote pathology; indicates that treatment should begin elsewhere • Exudate: primary involvement of pleura & lung; demands immediate attention • Fluid is classified based on series of fluid/plasma ratios known as Light’s criteria.

  21. Serous Fluids (cont’d) • Pericardial Fluid • Relationship of pericardium, pericardial fluid, & heart is similar to that of pleura, pleural fluid, & lungs; formation & drainage are same. • Pericardial sampling & lab analysis is rare. • Peritoneal Fluid • Excess fluid (>50 mL) in peritoneal cavity indicates disease. • Presence of excess fluid is ascites, & fluid is called ascitic fluid. • Samples are obtained by needle aspiration (paracentesis). • Exudative causes of ascites are metastatic ovarian, prostate, & colon cancer, & infective peritonitis.

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