clinical chemistry Flashcards
what is the difference between plasma and serum
plasma has clotting factors, serum does not
ion selective electrodes
- converts activity of specific ion dissolved in a solution to an electrical potential
- measured by voltemeter
spectrophotometry
measures change in light absorbance at certain wave length
enzyme linked immunosorbet assay (ELISA)
detects serum antibodies or antigens
critical value
- any test result that may require rapid clinical attention to avoid pt morbidity or mortality
what studies make up a comprehensive metabolic panel (CMP)?
- basic metabolic panel (BMP)
- calcium
- liver function tests
what is measured in a basic metabolic pannel?
- Na
- K
- Cl
- CO2
- BUN
- creatinine
- glucose
serum sodium
- reflects changes in water balance
- makes up 90% of extracellular solutes
- strong cation
- normal levels = 135-145 mEq/L
functions of sodium
- maintain osmotic pressure of extracellular fluids
- acid base balance
- neuromuscular function
- absorption of glucose
hyponatremia
- first sx occur at less than 125 mEq/L
- less than 115 causes confusion, lethargy, muscle twitching, convulsions, coma, brain stem herniation
- 110-115 likely to cause severe and irreversible neurological damage
treatment of hyponatremia
- treat underlying cause
- dehydrate -> hydrate
- fluid overload -> diurese
normal saline
- 0.9% NaCl
- isotonic saline
- treats dehydration
IV1/2NS
- 0.45% NaCl
- used as maintenance fluid
lactated ringers
- contain NaCl, sodium lactate, KCl, CaCl in water
- used in trauma, surgery
hypertonic saline
- 3% NaCl
- used for sudden precipitous drops in Na
- i.e. marathon runners
treatment of hypernatremia
- admin free water with 5% dextrose (D5W)
why cant you administer just free water for hypernatremia
- will cause hemolysis
- water will flood cells through osmosis
why cant you correct sodium too rapidly?
- central pontine myelinolysis
- cerebral edema
- brain stem herniation
central pontine myelinolysis
- destruction of myelin covering nerve cells in brainstem
- confusion, encephalopathy, lethargy
- weakness, paralysis
main functions of serum potassium
- maintain intracellular osmolality
- acid-base balance
- transmission of nerve impulses
- essential to skeletal, cardiac, and smooth muscle function
when can you get falsely elevated K
- hemolysis
- common complication of collecting blood samples
how does insulin regulate potassium
- K enters portal circulation
- stimulates release of insulin
- glucose enters cell
- K follows into cell
how is potassium excreted
by kidneys in urine
causes of hypokalemia
- inadequate intake (Diet)
- excessive losses i.e. diarrhea, kidneys, burns
- redistribution into cells i.e. insulin
causes of hyperkalemia
- decreased renal elimination (most common)
- excessive rapid administration
- movement of K from inside the cell to outside i.e. trauma
signs/sx of hypokalemia
- weakness, muscle cramps, paralysis
- EKG changes and arrhythmias
- paralytic ileus
signs/sx of hyperkalemia
- weakness, muscle cramps, paresthesias
- EKG changes and arrhythmias
- intestinal cramping
chloride
- normal is 98-106
- maintain electrical neutrality by binding to pos charged ions
- indicator of hydration tatus
carbon dioxide
- in serum most is bicarb
- normal is 23-30
- assists in eval of pH
anion gap
- difference between the primary cations and anions in serum
- AG is normally 8-16
cations measured for anion gap
- sodium
- potassium
anions measured for anion gap
- chloride
- bicarb
blood urea nitrogen (BUN)
- directly related to excretory fn of kidneys
- if kidneys aren’t excreting properly then BUN will rise
- changes in protein levels can change BUN
how is urea formed?
- proteins broken down into AA
- free ammonia formed
- ammonia molecules combine to form urea
azotemia
elevated BUN levels
prerenal azotemia
elevated BUN as result of kidney dysfunction from hypoperfusion
postrenal azotemia
- elevated BUN as result of post renal obstruction
creatinine
- normal is 0.6- 1.2
- used to approximate renal function
- BUN:Cr ratio of >20:1 indicates dehydration
normal glucose levels
- fasting= 70-110
- random <200
- critical is <50 or >450
calcium
- 40% bound to albumin
- 15% bound to anions
- 45% physiologically active ionized calcium
- need to get corrected calcium level to account for albumin bound Ca
causes of hypocalcemia
- impaired ability to mobilize Ca from bone i.e. hypoparathyroidism
- decreased intake or absorption i.e. vit d def
- abnormal renal losses i.e. hyperphophatemia
causes of hypercalcemia
- excessive intake
- increased bone resorption i.e. hyperparathyroidism
- decreased elmination
signs and sx of hypocalcemia
- paresthesias
- skel muscle cramps
- tetany
- hyperreflexia
- cardiac arrhythmias (prlonged QT)
- bone fx
signs and sx of hypercalcemia
- kidney stones
- anorexia, N/V
- muscle weakness, atrophy
- lethargy, coma
- EKG changes (shortened QT)
- HTN
LFTs
- albumin
- total protein
- ALP- resides in walls of bile ducts
- ALT
- AST
- total bilirubin, direct bilirubin, indirect bilirubin
AST to ALT ratio
- ALT normally higher than AST
- AST to ALT ratio of 2:1 suggests alcoholic liver disease
labs for acute pancreatitis
- elevated amylase
- elevated lipase
- elevated amylase/creatinine clearance
labs for chronic pancreatitis
- amylase, lipase, and amylase/lipase clearance can all be variable
diagnosing pancreatitis
- lipase assays are best markers
- amylase peaks in 48 hours, normalizes in 5-7 days
- lipase doesn’t normalize for 8-14 days
lactic acid
- quantifies degree of tissue hypoxia
- correlated with severity of illness
cardiac biomarkers
- Troponin I and II (preferred)
- CK-MB and total CK
- if CK:CK-MB ratio is > 1.5 it indicates potential cardiac injury
why use arterial blood gas
- determine acid- base balance
- determine oxygen status
C/I to ABG
- no pulse
- cellulitis or compromised skin
- no ulnar A
- AV fistula
- coagulopathy
- must do Allen test before performing ABG
what does ABG report include
- pH
- PCO2 controlled by lungs
- HCO3 controlled by kidney, is the metabolic component
