clinical chemistry - body fluids

what is normal fluid formation controlled by?

permeability of capillaries in parietal membrane

hydrostatic pressure in these capillaries

oncotic pressure (colloid osmotic pressure) produced by plasma proteins in capillaries

absorption of fluid by lymphatic system

transudates

excess filtration of blood serum across a physically intact vascular wall due to disruption of reabsorption

occurs in systemic diseases that alter the hydrostatic pressure of the capillaries, ex: congestive heart failure, hepatic cirrhosis or neprotic syndrome

exudates

active accumulation of fluid within body cavities associated with inflammation of the membranes and vascular wall damage

close to serum in chemical composition than transudates

caused by inflammatory disorders, malignancies and infections

thoracentesis

to obtain pleural fluid

pericardiocentesis

for pericardial fluid collection

perioneocentesis

for peritoneal fluid collection

physical examination of transudates

clear, pale. yellow

viscosity similar to serum

does not spontaneously clot (no fibrinogen)

physical examination of exudates

usually cloudy - due to WBCs or bacteria

various colors (yellow, green pink, red)

may have a shimmer or sheen

often with spontaneous clotting

appearance of bacteria in body fluids

produce white, turbid fluid

WBC/RBCs in body fluids

the presence of blood in the fluid can indicate malignancy

pleural fluid: hemothorax

pericardial fluid: cardiac puncture

peritoneal fluid: trauma

chylous effusions

milky after centrifugation

caused by obstruction or damage to lymphatic system

high triglycerides and chylomicrons present

pseudochylous effuions

chronic inflammation can produce cholesterol

low triglycerides and no chylomicrons

cell counts for WBCs

<1000 cells/ul in transudates

>1000 cells/ul in exudates

traumatic taps

RBCs decrease later in collections, small clots may form

hemorrhagic effusion

blood homogeneously distributed, no clotting

normal cells seen in differential cell counts

lymphocytes, monocytes, macrophages, mesothelial cells (lack of these cells in pleural fluid indicates tuberculosis)

disease/nonmalignant cells seen in differential cell counts

neutrophils (in exudates in inflammatory diseases)

eosinophils (infections, malignancies, MI, hypersensitivity reactions)

RBCs (associated with hemorrhage, malignancy, or traumatic puncture)

malignant cells seen in differential cell counts

leukemia, lymphoma, metastic tumors

amylase body fluid test

high pleural or peritoneal fluid amylase is associates with: pancreatitis, esophageal rupture, gastric duodenal perforation, metastatic disease

chemistry body fluid tests

total protein

glucose - only low fluid glucose is significant

amylase

lipids - used to identify chylous effusions

pH - abnormally low helps identify pleural exudates caused by pneumonia or lung abscess, if <7.30 while on antibiotics, requires more aggressive treatment

carcinoembryonic antigen (CEA) - a tumor marker

arthrocentesis

collection of synovial fluid

patient should be fasting a minimum of 4-6 hours

blood sample collected at the same time

three portions of synovial fluid collection

1. no anticoagulant tube for chemical and immunologic studies

2. anticoagulant tube for hematology/microscopic studies

3. sterile anticoagulant tube for microbiological studies

physical exam of synovial fluid

normal color - pale yellow or colorless

red/brown - associated with trauma during collection or disorders that disrupt synovial membrane allowing blood to enter joint (fracture, tumor, hemophilic arthritis, traumatic arthritis)

green - infection (septic arthritis, gout, pseudogout)

white/milky - rheumatoid arthritis, chronic arthritis, SLE

rice bodies

white, free floating substances made up of collagen covered by fibrinous tissue, resemble polished shiny grains of rice of various sizes, seen most commonly in rheumatoid arthritis

string test

performed by expelling fluid from collection syringe and observing for a normal string formation, at least 4 cm

shorter string indicates decreased viscosity

ropes test

also known as mucin clot test

dilute fluid with 2% acetic acid - 1 part fluid 4 parts acid

hyaluronate from joint fluid will form a clot in acid

clot formation in synovial fluid

normal synovial fluid does not clot

spontaneous clot formation indicates abnormal presence of fibrinogen

pathologic processes that damage synovial membrane can cause fibrinogen to be present

traumatic arthrocentesis with blood contamination can also cause fibrinogen presence

cell count/differential in synovial fluid

RBCs normally >2000, increases RBCs form traumatic tap or hemorrhagic effusions

WBCs normally >200, increased typically seen in bacterial arthritis

normally 60% of WBCs are monocytes or macrophages, 30% lymphocytes, and 10% neutrophils

more than 80% neutrophils associated with bacterial arthritis and urate gout

monosodium urate crystals

present in gouty arthritis

needle like

polarized microscopy

calcium pyrophosphate dihydrate in synovial fluid

seen in degenerative arthritis and arthritis accompanying metabolic disease

commonly known as pseudogout

are rodlike or rhomboid

other crystals in synovial fluid

cholesterol - seen in chronic inflammation

corticosteroids - seen for months after steroid injections

calcium oxalate - renal dialysis

apatite - osteoarthritis

puncture site for CSF collection

at the L3-L4 vertebrae or lower to avoid damaging the spinal cord

order of tubes for CSF collection

1. chemistry

2. microbiology

3. hematology

4. special tests

abnormal findings of CSF

turbidity/cloudiness

leukocytes - at least 200

erythrocytes - at least 400

microorganisms - bacteria, fungi

aspiration of epidural fat during puncture

causes of xanthochromia in CSF

oxyhemoglobin, methemoglobin, bilirubin, increased CSF protein (>150)

clotting of CSF

because of low viscosity, not normal

occurs with: traumatic tap, subarachnoid blockage, suppurative meningitis, TB meningitis, neurosyphilis

increased viscosity has been reported with metastatic mucinous adenocarcinoma to the meninges

differential cell count for CSF findings

increased neutrophils - infections including bacterial meningitis, TB, cerebral hemorrhages

increased lymphocytes - infections including viral meningitis, TB meningitis, fungal meningitis, syphilitic meningoencephalities, multiple sclerosis

increased monocytes - viral, fungal, tubercular meningitis

increased plasma cells - multiple sclerosis

total protein findings in CSF

increased - seen in traumatic tap, when the blood CSF barrier is damaged, increased protein synthesis within the CNS

decreased - may be due to leakage of CSF caused by trauama or prevous puncture removal of large volume of CSF

glucose findings in CSF

increased - seen with diabetes

decreased - hypoglycemic individuals, impairment of activ trnasport, bacterial meningitis