Chemical pathology of GERR Flashcards
What is CSF used to test for?
Meningitis
What is a lavage test?
doctor puts fluid into body and then sucks it out and fluid will contain some of what’s in the organ (usually lungs)
What are some of the common sample types?
- blood
- urine
- CSF
- Faces
- Sputum
- Saliva
- Pus
- pleural, ascites or synovial fluid
- semen
What colours are used for blood samples?
yellow - U&E contains gel to make blood clot
purple - used to stop clotting as contains potassium EDTA (anti-coagulant) used for anaemia and high WBC count
What are the three types of blood samples?
- whole blood with anticoagulant (purple)
- blood with anticoagulant that is centrifuged to get plasma layer, Buffy coat and then RBC layer
- blood without anticoagulant which forms serum layer and then clotted blood layer (Yellow)
What is the difference between serum and plasma?
clotting has happened in serum so plasma contains clotting factors still whereas in serum clotting factors used up
What order do the blood sample containers need to be filled in?
Yellow first
orange/red
purple
What does chloride show?
- tracks sodium so should be high when sodium high
- can be low in vomiting as getting rid of lots of HCl
What does CO2 show?
- almost all CO2 in form of bicarbonate but is measure of all CO2
- bicarbonate main blood buffer so if CO2 off then acid-base abnormality may be present
- low = metabolic acidosis can happen in diabetes
What does urea and creatinine show?
- urea = end point of metabolism, high if GI bleeding, dehydration or kidney failure
- creatinine = waste product of muscle metabolism, higher if more muscle and large risk indicative of acute kidney injury (as excreted by kidney)
What does eGFR show?
- calculated using CKD-EPI equation which uses age, gender and creatinine
- measure of kidney function (low eGFR if failing)
How is chronic kidney disease graded?
eGFR and concentration of albumin in the urine (higher the albumin the worse kidney disease is)
Why does high albumin/creatinine ratio indicate kidney disease?
albumin isn’t meant to be excreted in the urine so the more is being excreted the worse kidney functioning is
What does hypernatraemia show?
- severe dehydration usually in elderly and rehabilitated who struggle to ask for water
- diabetes insipidus as get problem with ADH
Why can hyponatremia be fatal?
- osmolality of brain and blood should be equal
- low sodium in blood means low osmolality
- fluid starts moving into brain to lower brain osmolality causing brain to swell
- swelling can impinge on foramen magnum which contains vital structure in brainstem which stop breathing
