14. Chemistry Panels Flashcards
What are the main tubes used for chemical analysis?
red top
Tigertop/serum separator
Greentop
What is the order of draw for red top, tiger top and green top?
Red top > Tiger top > Green
What does a red top and tiger top do?
Blood collected and allowed to clot for 20-30m (depending on prescene or absence of clot activator) and centrifuged for 10 m at 2000-3000 rpm to obtain SERUM
If testing can not be performed within 1hr, aliquot serum into a sterile, labelled red top tube and refrigerate/freeze to preserve
WHat is the purpose of green top tubes?
After collection, mix well and centrifuge immediately to obtain plasma
If unable to centrifuge within 1hr, refrigerate sample
for best results, remove plasma from cells before testing or sending out the sample
Transfer plasma into a labelled red top tube
What are some factors that might influence results?
hemolysis
lipemia
Icterus
How would hemolysis affect results?
occurs when blood mixed too vigorously, a small gauge needle is used, or excess alcohol is applied to the skin of the patient
Intracellular fluid from the ruptured cells will dilute the sample
intracellular components from ruptured cells may cause artificial increased in potassium, bilirubin and some enzymes including lipase
How would lipemia affect results?
occurs when patient not fasted and in some dz conditions
may be difficult to obtain results on an undiluted sample
increase risk of hemolysis
How might icterus affect results?
occurs when a patient has an excess of bilirubin in the peripheral blood
Results in a falsely decreased creatinine, cholesterol and total protein measurement
Once a sample is collected, what are some general notes to keep in mind in regards to storage and labelling?
Remove serum/plasma from cells for testing, chipping or storage
store in fridge or freeze sample for longer term storage or transport - for referred out tests, check to see what the req’s for shipping is
Do NOT freeze whole blood - only serum and plasma
A fasted sample is ideal to prod most reliable results
Samples must be labeled w/ patient and owner name, date, time of collection and sample type
Where are the majority of plasma proteins produced? WHat other systems play a role in making some proteins?
Majority produced in liver
Immune system (reticuloendothelial tissues, lymphoid tissues, plasma cells) are also responsible for making some proteins
What proteins are most commonly evaluled?
total protein, albumin, fibrinogen
What are the main functions of proteins?
sever as transport or carrier molecule for many plasma constituents
role in coagulation
hormones
buffers to help maintain acid-base balance
enzymes in biochemical reactions
maintain oncotic pressure
role in immune response to pathogens
What are protein assays not considered, but results could still be indicative of ….
Protein assays not considered to be liver function tests, results are indicative of a variety of dz, especially liver, kidney and potentially GI dz
What is total protein?
protein lvls affected by impaired hepatic synthesis, altered protein distribution, altered protein breakdown or excretion, dehydration and overhydration
What is knowing the total protein lvls useful for?
determining animals state of hydration
Dehydration > hyperproteinemia
Overhydration > hypoproteinemia
Great overall screening test for animals w/ edema, ascites, diarrhea, weight loss, hepatic or renal dz, blood clotting problems
How do we test total protein?
Refractometer
biuret method
How do we test total protein with a refractometer?
measures the refractive index of the sample, influenced by concentration of solid particles in the plasma/serum sample. most of the solid particles in the sample are proteins
fast, inexpensive and accurate
How do we test total protein doing the biuret method?
measures thr # of molecules in serum/plasma that contain more than 3 peptide bonds - simple and accurate, commonly used by analytic instruments in the lab
additional, specialized methods used in research
What is albumin?
makes up 30-50% of plasma total protein in most mammals
states of hypoproteinemia are usually due to decreased albumin lvls
What are the main functions of albumin?
binding to other molecules in the plasma (including meds)
transporting molecules thruout the body
Maintaining oncotic pressure
How does diffuse liver dz affect albumin lvls?
causes albumin lvls to fall below the reference range due to dec albumin production
What are conditions resulting in increased albumin?
dehydration
What are conditions that decrease albumin?
blood loss, overhydration, malabsorption, malnutrition and starvation
renal disease (protein losing nephropathy)
GI dz (protein losing enteropathy)
hepatic insufficiency
exudative skin dz
What are globulins?
A complex group of proteins
Alpha globulins: synthesized in the liver, carrier molecules for other proteins including HDL’s and LDL’s
Beta globulins: synthesized in the liver, include proteins responsible for iron transport, heme binding, complement, fibrin formation and lysis
Gama globulins or immunoglobulins: produced in plasma cells, Ab’s (IgG, IGE, IgA, IgM +/- IgD)
Albumin + Globulins = total protein
What is the albumin/globulin ratio?
A/G imbalance is often the first sign of a protein abnormality
can detect increased or decreased albumin or globulin lvls
Both can be reduced in equal proportions, as with hemorrhage - ratio will remain unchanged in this case
What is the A/G ratio in dogs, horses, sheep and goats?
> 1.00
Albumin > globulin
What is the A/G ratio in cattle, pigs and cats?
<1.00
Albumin < Globulin
What is fibrinogen?
Soluble protein that converts fibrin to form the matrix of blood clots
makes up 3-6% of total plasma proteins
decreased fibrinogen, as seen with hepatic insufficiency, means that the time for clot formation is prolonged or the blood will not clot at all
Fibrinogen lvls may be increased in acute inflam in lg animals and with tissue damage
What is the function of liver?
metabolism of AAs, carbs, and lipids
Synthesis of albumin, cholesterol and plasma proteins (including clotting factors)
Digestion and absorption of nutrients related to bile formation
Secretion of bile and bilirubin
Breakdown and elimination of toxins and drugs
What does the gallbladder do?
works and sits alongside liver
primary func to store bile that is produced by the liver
pathology affecting liver or gallbladder may = jaundice, clotting factors, hypoalbuminemia, hypoglycemia, hyperlipoproteinemia, hepatoencephalopathy
What are hepatobiliary assays?
no single test that can be performed to fully eval liver
dz’s of liver tend to be fairly advanced by time they are clinically apparent
only 100 tests available
What are some tests done to evaluate the liver?
lvls of molecules that liver produces and metabolizes
Bile acids - hepatic function test
Bilirubin - hepatic function test
Molecules that are released when hepatic cells are damaged or with cholestasis (impaired flow of bile)
What are the major enzymes released from damaged hepatocytes?
ALT, AST, ID, GLDH
What are the enzymes associated with cholestasis?
ALP and GGT
What is bilirubin?
Macrophages in spleen break down hemoglobin > insoluble bilirubin molecules released in process
Albumin binds to bilirubin and transports it to the liver
Hepatic cells metabolize bilirubin and it conjugates (or binds to) to glucuronide > will become component of bile
Conjugated bilirubin passes from liver into intestine where bact convert bilirubin glucuronide to urobilinogen
Urobilinogen broken down into urobilin and excreted in feces and urine, or absorbed back into the bloodstream
What amount of total bilirubin in serum in most animals is prehepatic bilirubin?
about 2/3rds
It is bound to albumin
What happens when there is an increase of unconjugated bilirubin?
When there is an increase of RBC destruction and there are problems with transport or uptake of bilirubin into the hepatocytes
What happens when there is an increase on conjugated bilirubin
increased when there is an obstruction of the bile ducts
What can an assay measure in regards to bilirubin?
Can measure total bilirubin (uncon/conjugated) as well as separately measures uncon/conjugated bilirubin
will help to determine cause of jaundice
What are bile acids/
bile acids are prod from cholesterol by hepatocytes in the liver
they aid in fat absorption and regulate cholesterol lvls
bile acids pass into the intestine via the biliary system and are stored in the gallbladder (except in horses)
Most of the bile is reabsorbed by the intestine and then processed by the liver, the rest is excreted in the feces
What are some reasons that serum bile acid lvls may be reduced?
prolonged fasting/starvation
diarrhea
malabsorptive dz’s
What might cause serum bile acids to be elevated?
When the hepatocytes, biliary or portal systems are impaired bc of
chronic hepatitis (viral, bact or fungal)
chronic cirrhosis (due to dz, drugs or toxins)
Cholestasis, portosystemic shunts (PSS)
neoplasia
What might an inc of bile acids in horses be from?
They are inc due to hepatobiliary dz and dec food intake
Is bile acids sensitive in cettle?
bile acid testing not sensitive indicator of hepatic dz in cattle
What might stimulate bile acid relase?
eating, or smelling food can release bile into the duodenum and increase in serum bile acids
How do we test for bile acid testing?
a serum sample is collected after a 12hr fast, a subsequent sample is collected 2hrs after a high fat meal is ingested
Horses: a single sample is collected
What are leakage enzymes?
enzymes that leak out of damaged hepatocytes
What are transaminases?
catalyze reactions during AA prod > found in tissues where protein breakdown occurs
Alanine transaminase (ALT)
aspartate transaminase (AST)
What are dehydrogenases?
catalyze the transfer of hydrogen during glycolysis
iditol dehydrogenase (ID)
Glutamate dehydrogenase (GLDH
What is alanine transferase?
ALT considered to be liver-specific screening test in D/C
when liver is damaged, inc ALT lvls are seen within 12hr, will peak at 24-48 hrs and will return to normal within a few weeks
For horses, ruminants, pigs and birds, the hepatocytes do not contain enough to be an ALT to be considered liver specific (ID is a better test)
ALT also found in cells of kidneys, pancreas and skeletal muscle, therefore damage to any of those organs will result in an inc in ALT
What is aspartate transaminase?
AST is present in cells of liver, RBCs, heart, skeletal muscle, kidneys and pancreas
blood AST lvls increase more slowly than ALT lvls but return to normal within a day
Most common causes of inc AST are hepatic dz, muscle inflam - strenuous exercise, IM injections or necrosis
Hemolysis - spontaneous or artifact - look at sample
Can be correlated w/ creatinine kinase (CK) to determine if muscle inflam likely to be the cause of inc ASt in a patient
What is iditol dehydrogenase?
ID especially helpful for testing liver damage in lg species like sheep, goat, swing, eq and cattle (as opposed to ALT) but ID testing often not readily available in labs
ID lvls rise quickly w/ hepatocellular damage or necrosis
this enzyme is very unstable in plasma or serum so specimens to be saved, transported or referred out must be frozen
What is glutamate dehydrogenase?
GLDH found in highest con in liver cells of cattle, sheep and goats
elated lvls are indicative of liver damage or necrossis in cattle and sheep
What are some enzymes indicative of cholestasis?
plasma and serum lvls of some enzymes are predictably elevated in
cholestasis (impaired flow in bile)
Metabolic defects in liver cells
with use of certain meds
due to action of certain hormones (ex. corticosteroids, thyroid hormones)
What is alkaline phosphatase?
ALP is enzyme found in osteoblasts in bone, chrondroblasts in cartilage, intestine, placenta and liver
Inc ALP in lg breed pups common during bone development; older anims the bones no grow so inc lvl of ALP more common w/ cholestasis
Steroid induction in dogs
ALP testing not useful in cattle + sheep
Most often used for D/C
What is gamma glutamyltransferase?
Primary sounce of GGT is liver in most animals
Blood GGT lvls higher in cows, eq, sheep, goat than in D/C
GGT found in several other organs including renal, biliary and mammary epithelium
elevated GGT lvls suggestive of liver dz, especially obstructive liver dz
When evaluating liver enzymes, what should they be correlated with?
results are associated w. other organs - correlating glucose (pancease and liver results), correlating AST and CK (muscle) results
hx and clin signs
signalment
What is the kidney’s function?
conserve and elim h2o and electrolytes
conserve and elim hydrogen and maintain pH balance
conserve nutrients: glucose and protein
elim toxins and end products of nitrogen metabolism: urea and creatinine
What do kidney’s produce?
Renin: an enzyme for controlling blood pressure
Erythropoietin
Prostaglandins: fatty acids that stim smooth muscle contraction
What are some other system functions of kidney’s besides conserve and eliminate water and waste?
blood pressure regulation, regulation of acid secretion in the stomach, regulation of body temp and platelet aggregation, activation of vitamin D and controlling inflammation
What is the renal physiology?
Blood enters kidney via renal arteries into glomerulus of nephron
Almost all water and sm particles pass into collecting tubules
Each nephron has parts that reabsorb or secrete certain solutes; the amount of solute that kidney is reabsorbed is pre-decided > renal threshold
Approx. 99% of water is reabsorbed by kidney, remaining is urine
Tests to eval kidney func are performed on urine and blood
What is azotemia? (NEED TO KNOW)
An increase in BUN and creatinine
Rarely is just one elevated out of the two
What is uremia?
An increase in BUN and creatinine but is now severe enough to cause animal to feel ill.
They will be dehydrated, inappetent and lethargic
May be V/D, have “uremic” oral and or/gastric ulcers and central nervous dysfunction
seen w/ advanced renal disease
How do we classify azotemia?
Pre-renal azotemia: underlyding cause of azotemia is occurring “before” kidney
Renal azotemia: Occuring within the kidney
Post-renal azotemia: Occuring after the kidney
What is pre-renal azotemia?
dehydration most common underlying cause
PVC and TP may be mildly elevated
USG is elevated - urine is well concentrated bc animals kidneys are functioning normally and are conserving water
What is renal azotemia?
Can be due to renal failure, congenital disorders or pyelonephritis
Renal failure can be classified as acute or chronic
PCV and TP may be elevated if the animal is dehydrated (often are, especially as dz progresses)
Animal may become anemic with end stage, chronic renal disease due to dec prod of EPO
USG will be dec (urine will be dilute)
What is the difference between acute and chronic renal azotemia?
Acute: often very severe, sudden onset, often (but not always) younger animals; may be associated w/ known toxin exposure
Chronic: gradual decrease in renal function and onset of clinical signs
What is post renal azotemia?
An obstruction in the ureter, neck of the bladder or urethra can cause a post renal azotemia
These animals are often dehydrated so PCV and TP will likely be elevated
USG will be elevated (urine is well concentrated)
What is BUN?
Blood urea nitrogen, the principal end-product of AA breakdown in mammals
used to eval kidney function due to kidney’s ability to filter urea from blood
What normaly happens with BUN and kidney excretion?
All urea passes thru glomerulus into renal tubules
about half of urea is reabsorbed into the bloodstream and other half is excreted in the urine
What abnormally happens with BUN and renal excretion?
urea is not transported into renal tubules as efficiently
When blood exits the kidney back into circulation, there is an increased concentration of urea
What might an increased BUN mean?
does not guarantee an absolute diagnosis of kidney disease
What are some non-renal causes of increased BUN include?
dehydration - urea is insoluble, high volumes of water are needed for its excretion in urine
High protein diets or strenuous exercise - leads to an increase in protein breakdown
How is BUN evaluated?
using an automated analyzer or w/ semi-qualitative dipstick
What serum creatinine?
creatinine is formed from creatine (component of muscle) as part of muscle metabolism
During muscle metabolism, creatinine diffuses out of muscle cells into body fluids and blood
creatinine lvls are influences by animal’s muscle mass
What typically happens with serum creatinine in the body?
normally, blood creatinine active filtered out of blood and into renal tubules - any condition that alters glomerular filtration rate (GFR) will alter the creatinine concentration in plasma
What needs to happen before blood creatinine lvls increase
Renal function has to be reduced by ~75% b4 blood creatinine lvls inc - creatinine alone is also not an accurate indicator of renal function
What is the blood BUN/creatinine ratio, why does it matter?
Urea/creatinine limited in use for eval renal dz bc their reference ranges are too wide
GFR could be 4x below normal b4 changes in urea and creatinine are observed (both will inc in renal dz)
Both urea and creatinine are filtered by the glomerulus but tubular reabsorption of urea can be regulated whereas creatinine stays constant
What is symmetric dimethylarginine?
SDMA - run w/ idexx machines
SDMA more sensitive indicator of kidney func - as little as 25% loss of renal func (usually elevated b4 creatinine and BUN are inc)
more reliable indicator of kidney func than creatinine bc its kidney specific
inc lvls may indicate another dz process affecting kidneys
What does SDMA detects?
Diseases of the kidney at an
earlier stage
Chronic kidney disease
Acute kidney injury
Pyelonephritis
Upper urinary obstruction
Kidney stones
Glomerulonephritis
Congenital disease
What does SDMA reflect?
Other disease processes
affecting the kidney
Hyperthyroidism
Vector borne disease
Systemic hypertension
Cardiorenal syndrome
Lower urinary obstruction
Sepsis
Neoplasia
Drug Toxicity
What is cystatin B?
A protein found in renal tubular cells
With ^^ cell injury occurs, cystatin B released in urine
inc lvls of Cy-B in urine indicate active kidney injury
Able to detect changes earlier, inc ability to recog subclinical changes
not used to analyze kidney function
What is used to measure kidney function?
SDMA, creatinine, BUN and USG
What is the urine protein/creatinine ratio (UPC)
proteinuria may indicate glomerular dysfunction
Reference ranges avail for K9+fel
2ml urine by cysto needed
What is the ratio of normal, borderline proteinuric and proteinuric in cats and dogs?
UPC ratio <0.2 = Normal
UPC ratio 0.2-0.4 (0.2-0.5)= Borderline proteinuric
UPC ratio >0.4 (cats), >0.5 (dogs) = Proteinuric
What is uric acid?
uric acid is by-product of nitrogen breakdown
in mammals, normally converted to allantoin and excreted into urine
What is unique about uric acid and dalmations?
impaired ability to convert uric acid to allantoin so excrete in urine
What is unique about uric acid in bird?
makes up 68-80% of total nitrogen that they excrete in urine - w/ renal disease, serum concentrations of uric acid will increase w/ >70% loss of renal function
What are the two primary types of renal clearance tests
effective renal plasma flow (ERPF) -utilizes substances that are elim’d by both glomerular filtration and renal secretion
GFR - only uses substances that are eliminated by glomerular filtration
Urine and blood are taken at specific times
What are some other tests used to eval glomerular function?
Creatinine clearance tests – endogenous and exogenous
clearance tests, iohexol clearance test
Single-injection inulin clearance test
Water-Deprivation Tests
Vasopressin Response Test
Fractional Clearance of Electrolytes
Inorganic Phosphorus
Enzymuria
What are endogenous and exogenous creatinine clearance test?
require measurement of blood and urine creatinine lvls
urinary bladder is cath’d and rinsed out at beginning and end of test
all voided urine collected for 24h
What is the iohexol clearance test?
iohexol given IV after a 12 hr fast
serum samples are taken 2,3 and 4 hrs after admin and sent to a referral lab for eval
What is the inulin clearance test
Inulin is excreted entirely by glomerular filtration, therefore it
may be the best test for evaluating GFR
Inulin is injected IV after a 12 hour fast
Serum samples obtained at 20, 40, 80 and 120 minutes after
injection to measure inulin concentration
What is the water deprivation test?
to identify whether or not the kidneys are able to concentrate urine
Normally anti-diuretic hormone (AKA vasopressin) from brain signals kidney to retain water
Tests involve dehydrating patient to point where patient should secrete ADH to promote water retention, and inc urine conc
if urine conc does not inc, then indicates lack of ADH, or nephrons that are unresponsive to ADH
What might we be able to differentiate with water deprivation tests?
PU/PD can be seen w/ renal dz as well as diabetes mellitus and insipidus, cushing’s dz and psychogenic polydipsia
Kidneys may func normally, may not be getting signal to concentrate urine OR polyuria may be physiological consequence of polydipsia (as physogenic polydipsia)
There is basic and modified versions of this
What is the vasopressin response test?
performed when patient is not able to concentrate their urine during water deprivation test
exogenous ADH is given, USG and urine osmolality evaluate
What is the fractional clearance of electrolytes
calculation that describes the excretion of electrolytes (usually sodium, occasionally potassium and phosphorus relative to GFR
Differentiates pre-renal from post-renal azotemia
What is inorganic phosphorus?
used to eval glomerular func
serum Pi usually reciprocal of serum Ca
initially, renal damage that alters the GFR leads to dec urinary Pi and inc Ca
Seruma Ca and Pi also effected
What does enzymuria test for?
evals glomerular funct
refers to presence of enzymes in urine
enzymes may be present in urine of patient sw/ renal dz like GGT and NAG which are released from damaged renal tubular cells
a comparison of enzyme lvls to creatinine can give an indication of the extent of renal damage
renal enzyme lvls will inc rapidly after nephrotoxicity
What is the pancreas?
witho exocrine tissue are sm “islands” of cells called islets of Langerhans that mak up endocrine tissues
What are the 4 types present in islet of Langerhans? What are the main ones?
Alpha and beta cells most important
Alpha cells: almost 20% of cells in islets, secrete glucagon and somatostatin
Beta: ~80% of cells in islets, secrete insulin
Delta: <1% of cells in islets, secrete somatostatin
Pancreatic polypeptide cells: <1% of cells in islets, secrete pancreatic polypeptide
What happens to the pancreas when the islets are damaged?
Tissue becomes firm and modular and has a limited ability to regenerate
What is the exocrine gland?
Gland that secrete products thru ducts rather than directly into blood stream
Amylase and lipase common enzyme tests to eval for pancreatitis
both can be within normal range in cats w/ pancreatitis
What is amylase?
primary source in pancreas, also found in salivary glands and small intestine
breaks down starches and glycogen
How is amylase used to test the exocrine pancreas?
blood amylase lvls inc in: acute and chronic pancreatitis, obstruction of pancreatic ducts, intestinal obstruction/perforation, if there is a dec in DFR, may be inc in amylase
Amylase >3x normal range is suggestive of pancreatitis - rise in conc not directly proportional to severity of disease
How is lipase used to test the exocrine pancreas?
derived mostly from pancreas
breaks down long-chain fatty acids of lipids
lvls tend to be normal during early stages of pancreatic dz and gradually inc over time
in chronic pancreatic dz, damaged pancreatic cells are replaced with CT that is unable to prod enzymes > both amylase and lipase begin to dec
K9+fel lipase can be tested using ELISA immunologic methods - serum cPL and fPL SNAP tests
What is trypsin?
trypsin is proteolytic enzyme that catalyzes the reaction that breaks down proteins
prods exclusively in pancreas
trypsin is readily detected in feces, many tests are performed on fecal samples - absence of trypsin in a fecal sample is abnormal, not commonly used
What can you use trypsin test for
serum trypsin-like immunoreactivity (TLI) is on immunoassay test that uses Ab specific to trypsin and trypsinogen (the precursor to trypsin) to measure lvls in blood
used to dx exocrine pancreatic insufficiency (EPI) - lvls will be below the normal range in affected animals
May be performed w/ folate and cobalamin (B12) tests as well
this test only available for K9+fel
Overnight fast required
What is the endocrine gland?
gland that secrete hormones directly into the circulatory system
blood glucose, fructosamine, B-hydroxybutyrate, serum cholesterol and triglycerides as well as urinalysis provide info about pancreatic func
What is glucose?
Blood sugar, pancreatic islets respond directly to blood glucose conc> release insulin from beta cells or glucagon from Alpha cells to regulate blood sugar lvls
What lowers blood glucose?
only insulin. If insulin is under-prod, or under-performing, will be clinically obvious
Blood glucose lvls are net balance btw glucose prod (food intake, conversion from other carbs), glucose and storage
Why might we test glucise?
glucose uptake and metabolism depends on insulin and glucagon secretion from pancreas
If insulin lvls are high, rate of glucose absorption into cells for metab will inc > cause glucose lvls to dec
If insulin lvls are dec (DM) glucose is not absorbed and will go up
What is the glucose tolerance test?
test challenges pancreas and evaluates the effects of insulin
Glucose bolus is given and then blood and urine glucose conc are monitored
if adequate insulin prod and cells are responding appropriately, blood glucose lvls should peak about 30m after glucose admin and return to normal within 2hr
Glucose should not appear in urine
What is the glucose tolerance test used to diagnose?
diabetes mellitus - prolonged hyperglycemia, glucosuria
Hyperactive beta-cell tumors - profound hypoglycemia
Other concurrent endocrinopathies
Test is rarely necessary to dx DM, persistent high blood glucose lvls, glucosuria and a hx for PU/PD, weight loss +/- polyphagia are sufficient for dx
Test may be used for animals that are borderline hyperglycemic or to differentiate stress hyperglycemia from DM
What is a functional tumor
cells are doing what they’re supposed to do, but in excess
ex. betacells prod insulin like crazy (anims look like they’ve had an OD of insulin
What is the fructosamine test?
fructosamine is formed when glucose in bloodstream binds to proteins
if there is a persistent hyperglycemia, fructosamine lvls will be elevated
can be run on some clinic analyzers or may be a referred out test, fasting is not required
Test will give us an indication as to what the blood sugar lvls have been doing for the past 2-3wks
may be used for long term monitoring of diabetic cats, can also be used to dx of suspect cases of DM
What is the insulin tolerance test?
A fasted blood glucose sample is obtained, then patient is injected w/ short-acting insulin
Subsequent blood glucose measurements are taken @ 30m intervals for 3hrs
If serum glucose fails to drop to 50% of fasting lvl within 30m, then it can be concluded that insulin receptors are unresponsive or the insulin is being antagonized
Insulin resistance profoundly affects the anims therapy and px
patient needs to be monitored closely for signs of hypoglycemia during test - need to have glucose solution on hand to admin if needed
What is the insulin/glucose ratio?
simultaneous measurement of fasting serum glucose and insulin can identify the cause of hyperinsulinemia
Hypoglycemia normally inhibits insulin secretion, however, pancreatic beta cell tumors (insulinomas) are hyperactive and unresponsive to glucose and secrete an abundance of insulin
Anims w/ hyperinsulinemia may have a “normal” fasting insulin, but the RATIO is abnormal
What are electrolytes and their functions?
the pos and neg ions found in all body fluids of all organisms
Func: maintain water balance and fluid osmotic pressure, muscular and nervous func, maintain and activate of several enzyme systems, acid-base regulation
What are anions? ex?
neg ions
Chloride, bicarb, phosphate
What are cations?
pos ions
Na, K, Ca, Mg, H
What is the acid-base balance?
The steady state of pH in the body
PH describes H ion conc In body
every change of pH scale of one number represents a power of ten diff in H+ conc
Normal pH is 7.35-7.45
What happens if we are outside the normal range of pH?
Function of proteins is compromised
Acidosis - pH <7.5 = excess of H ions in peripheral blood
Alkalosis - pH >7.45 = deficiency of H ions in peripheral blood
Why might we have an acid-base balance?
normal metab processes will result in prod of acids (lactic acid, ketoacids)
buffer systems work to counter the buildup of acids by altering the conc of H ions
What two systems work in tandem to regulate pH?
respiratory > responds in minutes
Renal/metab > responds over days
What is the bicarb buffer?
if blood pH becomes too acidic, bicarb binds to excess H ions > carbonic acid > breaks down to water and carbon dioxide which is removed by respiration
Kidney regulate bicarb by reabsorbing or secreting it into the glomerular filtrate in response to blood pH
HCO3- + H+ <>H2CO3 <> H2O + CO2
What is the potassium buffer?
K and H both passively charged ions that move btw intracellular fluid and extracellular fluid
A dec in plasma K = K moving out of cells and into ECF, H moves into cell > blood pH more alkaline
An inc of plasma K causes opposite. ECF K moves into cell and H moves out > more acidic
What is the protein buffer?
proteins bind and release H ions
Hemoglobin has the ability to bind CO2 and H
Co2 is transported to the lungs and exhaled
How is alkalosis and acidosis categorized?
Metabolic acidosis or alkalosis
Respiratory acidosis or alkalosis
Imbalances inter-related
if pH imbalance occurs, the resp and renal systems will work to correct abnormality
What is the respiratory buffer
if RR is dec there is inc of pCO2 (hypercapnia)
If RR is inc there is dec of pCO2 (hypocapnia)
CO2 reacts w/ water
What is resp acidosis and alkalosis?
Resp acidosis: due to dec RR or volume
Resp alkalosis: due to inc RR or volume
What may cause metabolic acidosis/alkalosis?
any condition that results in an accumulation of acids in the body leads to a metabolism acidosis?
Ketoacid prod due to DM > dec HCO3- > metabolic acidosis
Abnormal elyte conc and loss of acid d/t vomiting > inc relative HCO3 > metabolic alkalosis
What are electrolyte assays?
elytes are affected by:
inc or dec dietary intake, shifts of ions btw ECF/ICF
renal loss or retention
GI malabsorption
resp system
*lipemia and hemolysis can affect elyte measurements
*arterial samples are ideal for analysis of blood gases; must be analyzed quickly after collection bc room air affects conc of dissolved gases and sample pH
What are the normal volumes of pH, pCO, HCO3 and pO arterial vs venous
pH: Art(7.40), Ven (7.35)
pCO: Art (40), Ven (45)
HCO: Art(25), ven (24)
pO: Art (95), ven (40)
What electrolytes are measured during elyte assays?
Na, K, Ca, Mg, H, Cl, bicarb, inorganic P
How might hemolysis affect electrolyte assays?
chem panels measure ions and compounds present in serum/plasma ONLY, does not measure the conc of products in the cell
With ECF ions > hemolysis will dilute sample causing lower ion lvls
With ICF ions > hemolysis will cause ions to be released and artificially raise ion lvls
What is sodium/
major cation of plasma and ECF
Main func is water distribution and maintenance of body fluid osmotic pressure
Na is filtered by kidney and reabsorbed back into body as needed in exchange for H - vital role in pH regulation of urine and acid-base balance
What is hypernatremia, hyponatremia
hypernatremia - in blood sodium conc (in water deprivation, hyperventilation, osmotic diuresis)
Hyponatremia - dec blood sodium concentration (V/D, ketonuria, hypoadrenocorticism, CHF)
What is potassium?
major ICF cation
Important for muscle func, resp, cardiac func, nerve impulse transmission and carb metabolism
What is hyper and hypokalemia?
Hyperkalemia: inc blood K conc (cellular damage, acidosis, urinary tract obstructions)
Hypokalemia - dec blood K conc (low intake, alkalosis, fluid loss d/t v/d, ketonuria, diuresis
How might potassium affect the heart at high and low lvls?
can cause fatal cardiac arrest due to an abnormal HR
Which sample is preferred when looking at potassium? Plasma or serum?
Plasma as platelets can release K during clotting process - however analyzer type may dictate sample requirements
If sample is going to be refrigerated, the plasma should be separated from the cells - refrigeration will cause K tomove from ICF and ECF
What is chloride?
predominant eCF anion
maintains water distribution, osmotic pressure, normal anion/cation ratio
closely related to Na and bicarb lvls
Hyperchloremia - inc blood chloride conc
Hypochloremia - dec blood chloride conc
if sample is to be stored, serum/plasma should be separated from cells to prevent artificial reductions in Cl conc
What is bicarbonate?
2nd most common anion in plasma
kidneys work to regulate bicarb lvls by excreting excesses after it is reabsorbs what is needed from urine
Bicarb lvls commonly estimated from blood CO2 lvls - done by a blood gas analyzer or part of a e- panel or chem analyzer
What is magnesium?
2nd most common ICF cation
found in all body tissues, more than 50% found in bones
works closely w/ Ca and phosphorus
activates enzyme systems, involved in making and breaking down ACH - imbalance of mg/ca ration = muscle tetany bc of release of ACH
Which species are the only ones to show clinical signs of magnesium deficiencies?
cattle and sheept
What is calcium?
more than 99% found in bone
remaining 1% help to maintain enzyme activity, plays a role in blood coagulation, neuromuscular excitability and tone (dec ca can also result in muscle tetany), and maintenance of inorganic ion transfer across cell membrane
Ca inversely related to P, if one goes up, other goes down
What is phosphorus?
80% found in bone
20% serves to store, release and transfer energy, involved w/ carb metab and is used to prod nucleic acid and phospholipids
within serum/plasma, P is in an inorganic form
within RBCs, its in an organic form
DO NOT USE HEMOLYZES SAMPLES - falsely elevated results
separate cells from serum/plasma asap
What is the anion gap?
total # of cations EQUALS total # of anions
neutrality is maintained by various buffering systems
any diff btw pos/neg is called anion gap
chiefly used to ID metabolic acidosis
How do we calculate the anion gap?
(Na+K) - (Cl+HCO3) = gap
What is the normal anion gap in cats and dogs? What happens with an inc and dec of an anion gap?
Dogs: 12-24mEq/L
Cats: 13-27mEq/L
Inc anion gap: lactic acidosis, renal failure, diabetic ketoacidosis
Dec anion gap: often due to hypoalbuminemia > the proteins req to transport bicarb are lacking
What is creatinine kinase?
CK is enzyme found predominantly in striated muscle cells and to a lesser extent, the brain
When skeletal muscle (namely cardiac) is damaged, CK leaks out of cells and = elevated CK in peripheral blood
CK is frequently tested if anim has elevated AST but shows no symptoms of liver damage - if elevated CF, would suggest muscular issue (possibly cardiac)
if also elevated in CSF w/ non-specific damage to neural tissue (hypoxia, trauma, inflam, space-occupying tumors) - CSF CF can also be useful prognostically in k9 neuro cases and premature foals
What conditions can cause an increase in CK?
seizures, IM injections (repeased IV blood draws)
sx, vigorous exercise, electric shock
lacerations,b using, hypothermia
persistent recumebncy
Myositis and myopathies
essentially anything that damages the cell membranes, a delay in testing may cause an inc in reported CK lvls
What is lactate?
Lactate, or lactic acid, is prod by anaerobic cellular metabolism
inc lactate indicates hypoxia or hypoperfusion
lactate can be analyzed in plasma, CSF and peritoneal fluid
Blood/peritoneal fluid analysis is a dx acid in equine colic cases - in healthy horses, the blood lactate is always higher than in the peritoneal fluid, if horses have a GI disorder such as an impaction or torsion, the peritoneal fluid lactate will be higher than the blood lactate lvls
collect sample in fluoride oxalate or lithium heparin tubes
hand held lactate meters are available
WHat are endocrine system assays?
variety of endocrine orangs and tissues prod and release hormones directly into capills
includes: adrenal glands, thyroid and parathyroid glands and the pituitary gland
What are adrenocortical function tests used for?
stressors cause the hypothalamus to secrete corticotropin-releasing hormone > causes the anterior pituitary to secrete adrenocorticotropic hormone (ACTH) > stims adrenocortical growth and secretion
Cortisol is import hormone secreted by adrenal glans in mammals - cortisol inhibs both CRH and ACTH release
What is hyperadrenocorticism
cushing’s dz - excessive cortisol release
caused by brain/pituitary tumors, idiopathic hyperplasia of adrenal glands
neoplasia of one or both of adrenal gland
over-enthusiastic use of glucocorticoids
What is hypoadrenocorticism
addision’s dz
reduced cortisol release
may be caused by adrenal atropy, autoimmune dz, neoplasia, medications
What is the adrenocorticotropic hormone stimulation test?
To test for hyper/hypoadrenocorticism
Evaluates adrenal glands response to synthetic ACTH
Degree of glucocorticoid prod is expected to be proportional to adrenal gland’s size and development
Hyperplastic (cell proliferative) exaggerated adrenal response
Hypoplastic (atrophied) - dec adrenal response
Test can detect abnormalities but not underlying cause, also evals efficacy of tx
How do we interpret ACTH tests for crushing dz?
cortisol lvls tested b4 and after ACTH admin
accuracy in hyperadrenocorticism is 80% and 50% in dogs
Used to eval response to mitotane or trilostane therapy
What are the clinical signs of cushing’s dz?
PU/PU, panting, polyphagia, pot-bellied abdomen, altered fat distribution, alopecia, mild muscle weakness, lethargy
Fragile skin syndrome in cats
How do we interpret ACTH results with addison’s dz?
cortisol lvls are tested b4 and after ACTH admin
adrenal glands are unable to respond to the ACTH so post-ACTH cortisol lvls are below normal range
What are the clinical signs of addison’s dz?
depression, lethargy, lack of appetite, weight loss, V/D, bloody stool, weakness
Dehydration and bradycardia
What are low/high dose dexamethasone suppression tests?
Low (LDDST) - can confirm a dx of cushing’s dz or can be used in place of ACTH stim test to dx cushing’s dz
High (HDDST) - to differentiate btw pituitary causes of hyperadrenocorticism from adrenal causes
Dexmethasone is a potent glucocorticoid that suppresses ACTH release
How do we intrepret LDDST and HDDST or UHDDST
LLDST - adrenal dependent - no cortisol suppression at 4 or 8 hrs post dexamethasone// pituitary dependent - cortisol suppression at 4+/-8hr post dexamethasone
HDDST/UHDDST - adrenal dependent - no cortisol suppression // pituitary dependent - cortisol suppresion
What is the combined dexamethasone suppression and ACTH stim tests?
dexamethasone is admin IV, ACTH admined by IV 4hrs later - cortisol lvls measured before dex and ACTH admin, and after acth admin
Interpretation: inc cortisol after dex + ACTH = hyperadrenocorticism
Inc after dex and NORMAL ACTH - hyperadreno
Inc after dex and very high acth - pituitary hyer
What is the urine cortisol/creatinine ratio and what does it have to do with adrenocortical function tests?
used as a screening tool to rule OUT cushin’s dz
if ratio low - very unlikely
if ratio is elevated - test further for hyperadrenocorticism
What is equine cushing’s dz?
occurs in older horses bc of adenomas of the pars intermedia of the pituitary gland
clin signs: PU/PD, polyphagia, muscle weakness, excessive sweating, long hair coat (fail to shed)
Lab findings: hyperglycemia + glucosuria (likely bc of insulin resistance)
dx w/ overnight dexamethasone suppression
insulin and anti-adrenocortical meds not useful, dopamine antagonists may be helpful
What are thyroid hormones and how do they work?
Influence metab rate, growth and differentiation of cells
Thyrotropin-releasing hormone (TRH) from hypothalamus stims anterior pituitary to release thyroid sim hormone (TSH)
TSH enhances thyroid gland growth, funct and release of thyroxine which is prod as T2 (triiodothyronine: active form), T4 (thyroxine; can convert to T3 in tissues)
thyroxine inhibs TRH and TSH release
What does thyroid disease manifest as?
hypothyroidism: dogs, horses, ruminants, swine
Hyperthyroidism: cats
may attributable to dietary iodine imbalances or exposure to goitrogens in lg anims
How do we dx thyroid hormones illness in food animals?
clin signs: spontaneous abortion, stillbirths, alopecia, goiter in fetuses
Serum T4 concentrations
Protein bound iodine lvls in serum
Pasture iodine analysis - feed may be analyzed for goitrogenic plants or excess calcium (which dec iodine uptake)
Primary glandular dz due to neoplasia, autoimmune dz, or idiopathic atropy much more common than pituitary dz
What are goitrogens?
substances that disrupt the prod of thyroid hormones, interfering w/ iodine uptake in the thyroid gland -brassica spp
triggers the release of TSH from pituitary gland and promotes growth of thyroid tissue > goiter
What are some drugs/meds that affect thyroid hormones?
insulin and estrogen inc T4
glucocorticoids, anticonvulsants, penicillin, trimethoprim, sulfamethoxazole (TMS), and others dec T4
How do we dx hypo/hyperthryoidism in SA?
measuring free T4, +/- TSH lvls
Hypothy: low free T4 and elevated TSH
Hyperthy: elevated free T4
What are some additional thyroid function tests to do?
T3 - less reliable than free T4
Total T4 (TT4) - will measure anti-thyroid hormones so not as reliable as free T4
thyroglobulin Ab test - canine specific test, used to detect autoimmune thyroiditis
thyroid stimulating hormone response test: primarily used for research purposes at this time
How do we test the thyroid in horses?
in horses, iodine-deficient hypothyroidism is rare since iodized salt is available
However, overeating iodion can provoke hypothyroidism and goiter bc excess iodine inhibs thyroid functio
Why might we test pituitary function?
elevated growth hormone (GH) prod by P-gland will cause canine acromegaly
Serial assays of GH tests bc dogs w/ acromegaly show consistent lvl of GH
GH will fluctuate in a normal dog
What are GI function tests?
func of GIT to digest/absorb nutrients and excrete waste products
GI dz are common in anims so specific testing + dx important
biopsy may be req to arrive at a definitive dx; func test rule out other dz and confirm need for more invasive procedures
What is maldigestion?
altered gastric secretion or reduced digestive enzymes (from the pancreas and to a lesser degree the sm int) - approx 90% of pancreas needs to be a non-func before clin signs become apparent
What is malabsorption?
often caused by dz of sm int wall or bact overgrowth syndromes - a loss of funct of >50% of sm int in dogs will = short bowl syndrome
What is fecal occult blood?
blood loss into gut may appear as melena or hematochezia depending on where bleeding is occurring
If blood loss less severe, may not be apparent by gross examination of feces
If blood loss into GIT suspected, a fecal occult blood test can be run
Test will prod a color change if comes into contact w/ hemoglobin or myoglobin - SA will need to be fed a meat free diet for up to 3d prior to testing
ensure LA not being supplemented w/ meat or bone meal
What is the d-xylose absorption test?
d-xylose absorbed in the SI and eliminated unchanged int he urine - relatively easy to trace
Primarily in horses and dogs
Xylose is given orally and serial blood conc are measured every 30m-4/5hrs
abnormal test results suggest malabsorptive problem in SI
Vomiting and ascites will dec xylose blood conc
Renal dz will lead to an inc xylose blood conc
Why might we test serum folate and cobalamin (B12)?
B vitamins are reduced in anims w/ malabsoprtion issues
Folate absorbed in prox int, while cobalamin in ileum
bact overgrowth may cause folate lvls to inc and cobalamin lvls to dec
Often eval in conjunction w/ TLI
overnight fast req prior to blood sampling
What samples might be sent out for toxicology and how do they need to be sent out?
Fluids, tissues, feed must be in separate, clean, leak-proof, hard, plastic containers
can send serum/plasma, urine, feces, water, suspicious bait, stomach contents (in form of vomit, gastric lavage or post mortem collection)
samples must be individually Id’d w/ O’s and Vets names, anim name/ID # and specimen type
For toxicology, how should blood samples, necropsy or biopsy samples kept?
blood best refrigerated, gut contents may be frozen
Necropsy/biopsy tissues > should be placed in a 10% formalin solution in a 10:1 formalin to tissue ratio
What is lead poisoning?
Fairly common enviro pollutant - found in old paint, ammunition, car batteries, solder, linoleum, petroleum and roofing products
“plumbism”, lead poisoning can occur in all species, clin sings = GIT and nervous signs
hematology exam = basophilic stopping of RBCs and inc nRBCs w/o anemia
What changes will you see with lead poisoning on a chem panel?
not any specific changes
blood collected in EDTA, heparin or citrate may be analyzed for lead at a reference lab
Feces, liver, kidney or bone can be analyzed for the presence of lead
What is nitrate/nitrite poisoning?
Common in ruminants, pigs, horses that ingest feeds containing high nitrate/nitrite conc
excessive lvls found in cereals, grasses and root crops heavily fertilized with these, also runoff may contain lg quantities of nitrate
How do nitrate/nitrites work in the body
Nitrates > nitrites in feed or GIT > nitrites absorbed from gut dec O-carrying capacity of RBCs by degrading hemoglobin to methemoglobin > blood becomes red - brown in color
A dilute diphenylamine solution can test for nitrites in feed, serum/plasma, urine and body fluid samples > if nitrites or nitrates present in sample, turns blue
Hemolysis may mask the color change
What are anticoagulant rodenticides
chems designed to kill rodents
inhibs metab of Vit K
VK needed for prod of clotting factors (2, 7, 9 and 10) in liver
affected anims will have prolonged prothrombin and partial thromboplastin time as blood clotting is impaired
a presumptive dx is made on routine coagulation testing and patient response to Vit K therapy
What are chemicals that denature hemoglobin?
ingestion results in oxidative damage to RBC’s > heinz bodies are formed
Horses - red maple leaves
Cattle - brassica spp
Dogs - onions
Cats _ acetaminophen
Selenium deficient anms more prone to oxidative injury
What is ethylene glycol poisoning?
commonly causes accidental poisoning that can lead to fatal toxicosis in dogs and cats
dx can be presumed based on urinalysis and observation of a high conc of Ca-Ox monohydrate crystals
5ml kills cat, 15ml kills med-sized dog
formation of urinary crystals causes irreversible kidney damage
ethylene glycol > glycolic acid > oxalic acid crystals
