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Osmolality is mainly controlled bythe concentrations of sodium(most abundant) and other electrolytes.

Serum OsmolalityUrine-24-hour osmolality

Urine/Serum Osmolality Ratio

Serum – 289 – 308 mOsm/kgUrine-24-hour osmolality 300-900 mOsm/kg(Up to 3 X serum level)Urine/Serum Osmolality Ratio – Random 1.0 – 3.0

Hormone ADHAnti-diuretic

Acts on kidney tubules to reabsorb water

Hyponatremia Lower than normal sodium levels in the blood

Hypertension can occur when(extra blood volume)osmolality of the blood is

increased osmolality (Na+ retension)

Dehydration

Increased osmolalityExcessive loss of water from the body tissues, often accompanied by imbalance of sodium, potassium, chloride, and other electrolytes

Edema

Decreased osmolalityAbnormal collection of fluid in spaces between cells, esp. just under the skin or in a given cavity (e.g., peritoneal cavity) or organ (e.g., the lungs-pulmonary edema)

the conditions under which non-electrolytes can contribute significantly to the serum's

osmolality

In addition to proteins all other non-ionic molecules like glucose, billirubins, medications etc, can effect osmotic pressure when they are in abundance in a solution.

increased serum osmolalityOsmotic pressure with cause water to be

drawn from the interstitial compartment into the vascular compartment

Decreased serum Osmotic pressure with cause water to be

drawn from the vascular compartment into the interstitial compartment

Calculated Osmolality = (2 x Na) + (BUN / 2.8) + (Glucose / 18)

Normal Gap = 0 - 20 mmol/L

Osmolal gap isthe difference between the measured osmolality (with an osmometer), and the calculated osmolality

Osmolal gap > 20 = ketone bodies = Diabetes Mellitus

Urine osmolality – reference range 300 – 900 mOsm/Kg

Renal failure = Low osmolality

Colligative properties of solutions as amount of solute increases.

Boiling point raises Freezing point lowers

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Vapor pressure decreases Osmotic pressure increases

vapor pressure depression

The presence of a solute lowers the vapor pressure of the solution at each temperature, making it necessary to heat the solution to a higher temperature to boil the solution.

freezing-point depressionthe lowering of the freezing point of a liquid by

addition of a solute.

colloid osmotic pressure osmometer For osmotic pressure of proteinsBoth sides have pressure sensors

Particles are too big to get through pores

the fate of dietary fructose and galactose, and explain why the only sugar found in fasting

patients' blood should be glucose.

Other sugars must be converted into glucose by the liver’s isomerase enzymes. Immediately after a meal, non-glucose sugars may be found

in the blood, but after an hour or so, have all been removed from the blood by the liver,

converted into glucose, and stored as glycogen.

why patients with Hereditary Galactosemia or Hereditary Fructosemia would have galactose

or fructose in their fasting blood and urine.

They lack the liver isomerase enzymes necessary to convert fructose or galactose into

glucose.

normal fasting blood glucose range 70 – 110 mg//dL

explain how this glucose level is maintained by the hormones Insulin and Glucagon

The liver and kidney are constantly replenishing the blood’s supply of glucose by

breaking down glycogen, as directed by glucagon (pancreas) and epinephrine (adrenal)

Explain why patients which produce elevated blood levels of the following hormones could have a slightly elevated fasting blood glucose level. a.Epinephrine b. ACTH c. Growth Hormone (GH) d.Cortisol e.Thyroid Hormone (T3 or T4) f. Human Placental Lactogen (HPL)

a.Epinephrine – stimulates glycogenolysisb. ACTH – causes an overproduction of Cortisolc. Growth Hormone (GH) – stimulates glycogenolysis and gluconeogenesis (generation of glucose from non-carbohydrate carbon substrates such as lactate, glycerol, and glucogenic amino acids)d.Cortisol – stimulates glycogenolysis, gluconeogenesis, and lipolysis.e.Thyroid Hormone (T3 or T4) – stimulate

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lipolysis and glycogenolysisf.Human Placental Lactogen (HPL) - stimulates glycogenolysis and gluconeogenesis

Diabetes Mellitus resulting from lack or underproduction of insulin

Diabetes Insipidushas nothing to do with sugar and not serious.

Due to underproduction of the pituitary hormone

Diabetes MellitusType 1 ( IDDM)

Blood and urine glucose levelsBlood and urine ketone levelsBlood pH Blood Insulin levels

majority of patients are under 20 at the onset of disease10% of all diabeticsDestruction of Beta cells (insulin producing) in pancreasWithout medical intervention, death will occur within days.a. Blood and urine glucose levels - panic valuesb. Blood and urine ketone levels – extremely highc. Blood pH – very low, severe acidosisd. Blood Insulin levels – absolute deficiency of insulin,

Diabetes MellitusType 2 ( NIDDM)

Blood and urine glucose levelsBlood and urine ketone levelsBlood pH Blood Insulin levels

majority over age 20 on onsetInsulin resistance and obesity-most common causea. Blood and urine glucose levels – high, but not panic levelsb. Blood and urine ketone levels - high, but not panic levelsc. Blood pH - mild acidosisd. Blood Insulin levels normal or elevated

OGTTPreparation

The OGTT requires fasting for at least 12 hours before the test.

Coffee, tea, gum, cigarettes, etc. interfere with resultsSmall amounts of water are allowed.

recommended glucose loads for: Children

Non-pregnant adultsPregnant adults

Children – 1.75 grams drink per Kg body weight, up to 75 grams

Non-pregnant adults - 75 gramsPregnant adults - 100 grams

Random urine glucose test.Test not specific for DM

Procedure – collect urine

Result that indicates a problem?

Used to detect increased urine excretionSeveral random measurements may be taken throughout the day. Random testing is useful because glucose levels in healthy people do not vary widely throughout the day.

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Blood glucose levels that vary widely may indicate a problem.Normal 160 – 180 md/dLBlood glucose <160, no glucose should be found in urine.Adv. – no preparationmeasures blood glucose regardless of when you last ate.

Fasting Blood glucoseblood test after 12 hour fastUseful screening test for all carbohydrate disordersDiagnosis can be made (ADA/WHO)

If FBS < 126 mb/dL, a follow up test needed

OGTTProcedure

Urine test?

• Do not administer glucose load to anyone with elevated fasting glucose level.

1. A FBS is obtained in green heparin tube. No smoking or eating is permitted during the test. 2. Patient must during standardized load of glucose within a 5 minute period. Someone must observer patient actually drink glucose load. If patient vomits, discontinue test.3. At exactly 30 minutes, blood and urine specimen.4. At one hour, another blood specimen.5. Each additional hour, blood specimens obtained, up to 5 hours. All blood glucose specimens are measured as a batch.

Result Diagnosis levels2-Hour Plasma Glucose Result (mg/dL)

139 and below - Normal140 to 199 - Pre-diabetes (impaired glucose tolerance)200 and above - Diabetes

conditions which an I.V. Glucose Tolerance Test should be used in place of the oral test.

If patient has gastric resection or any form of malabsorption.

2-Hour Postprandial blood glucose test.  (2HPP)

blood test for glucoseUsed for glucose intolerance, measured 2 hours after a regular balanced meal.Normal – normal blood glucose after 2 hours.

Explain why the fasting blood glucose levels may be abnormally low for patients suffering:

Hyperinsulinemia disordersSevere hepatitis

Hypothyroid diseaseVon Gierke's disease

Addison's disease

a. Hyperinsulinemia disorders - elevated levels of insulin in the body, Typically as a result of insulin resistance pancreas no longer has enough beta cell capacity to keep up even with the production of even low levels of insulin needed for basal insulin secretion.b. Severe hepatitis – the diseased liver cannot store adequate glycogen to meet the body’s

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needs for glucose reserves - c. Hypothyroid disease – insufficient production of thyroid hormones result in inadequate lipolysis and glycogenolysysd. Von Gierke's disease – glycogen storage disease, glycogen stores can be broken down, but enzyme that cleaves off phosphate is not producede. Addison's disease – under production of cortisol.

lipolysis break down of stored fat to free fatty acids

2-Hour Oral Post-challenge blood glucosethe rationale for, the advantages of, and the

procedures

Used for glucose intolerance, give 2 hours after glucose drink.ADA recommends a FBS be included a part of test to establish fasting baselineIf 2 hour blood glucose is >200mg/dL, diagnostic for DM.Recommended for DM diagnosis if FBS but <126ml/dL.Normal – normal blood glucose after 2 hours.

Glycosylated Hemoglobin test. (Glycohemaglobins)

- estimates the patient’s blood glucose level over the last 4 – 6 weeks (time averaged)glycosylation is a function of blood glucose level and timeNormal person – 5% - 9% is glycosylatedDiabetic – 9% - 24%Hypoglycemic - <5%Used for monitoring diabetes therapy.Adv. – No patient preparation or fasting

Serum Fructosamine test

– gives time averaged estimate of blood glucose level over previous 7 – 21 daysAdv. - more sensitive than GHTHyperglycemic – elevated fructosamine Hypoglycemic - decreased fructosamine

Insulin assayto distinguish between DM type 1 and type 2Type 1 – very low or non-detectable insulin

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levelsType 2 - normal glucose tolerance

C-Peptide assay - insulin and C-Peptide are products of the same parent protein

Measures how much insulin is being produced.Adv. – 1)used to measure Type 2 DM patients being treated with insulin injections.Any C-Peptide in the serum represents insulin patient is producing.2) tests for autoimmune antibodies against insulin. Test antibodies cannot bind insulin if autoimmune antibodies are already bound to it.3) C-Peptide has a longer biological half-life than insulinSample can be collected for a longer time after release in the body.

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BUN test

blood urea nitrogen test reveals that your urea nitrogen levels are higher than normal, it probably indicates that your kidneys aren't working properly. Or it could point to high protein intake, inadequate fluid intake or poor circulation.

If analytes are deficient, oslmolality will be low

If analytes are excessive, oslmolality will be high

Urine Osmolality – to evaluate? renal tubule function

isomeraseChanges one 6 C sugar to another

(glucose, mannose, galactose(milk))

Glucose 6 phosphate cannot Exit the cell membrane

Hormone that lowers blood glucoseInsulin

Makes glucose permeable to cell membranes

Hormones that raises blood glucose

Glucagon, epinephrineCortisol, ACTH

Thyroid hormonesGrowth hormone

Human placental lactogen

glycogenolysis Breaking down glycogen to glucose

Gluconeogenesis Forming glucose from non-carbohydrates

Ketone bodies

Produced by the liver by lipolysisAcids - Change pH body fluids

Metabolic acidosis in DMCan be used as fuel by brain and CNS

Symptoms of both Diabetes insipidus and Mellitus Thirst, dehydration,Excessive volumes of urine

Hyperglycemic diseases

Diabetes mellitusPheochromocytomas-(epinephrine and

norepinephrine producing tumors)Cushing’s disease

Gigantism and acromegalyGrave’s disease and thyrotoxicosis

pregnancy

Cushings’ disease (tumor)Elevated cortisol causes glycogenolysis

Elevates blood glucose level

conditions under which non-electrolytes can contribute significantly to the serum's

osmolality.

In addition to proteins all other non-ionic molecules like glucose, billirubins, medications, etc can effect osmotic

pressure when they are in abundance in a solution.

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Hypoglycemia diseases

Hepatic disease – liver can’t store enough glycogenMyxedema – thyroid does not produce hormoneHashimoto’s disease – autoimmune destroys thyroidAddison’s disease – failure of adrenal to produce aldosterone and cortisolVonGeirke’s disease – liver cannot produce G6PP and chop off phosphate so glucose can’t leave liver cell(Epinephrine tolerance test is diagnostic)Positive if epinephrine does not raise blood glucose level

Complications of Diabetes Mellitus

CNS neuropathy PNS neuropathyCataracts Renal hemorrhageBlindness(degeneration) Renal failureAtherosclerosis MI and strokesLoss of feeling loss of circulationNon-healing wounds amputations

True definitive test for DM type

Type 1 = No insulin or C-PeptideType 2 = Low to Normal insulin and C-Peptide Measure C-Peptide because insulin has a short half-life. C-Peptide last 4 times longer – test how much patient is

producing, does not measure added insulin.FBS>126 mg/dL on more than one

occasion

Type 1 (juvenile or IDDM) 15%

Most severe All of a sudden, you cannot produce insulin Insulin undetectable, glucose levels extremely high Severe ketoacidosis Insulin Shock - comas from hyperglycemia or severe

hypoglycemia Must be treated with insulin Caused by a virus triggering an autoimmune

response against the beta cells that produce insulin.

Type 2 (Adult onset or NIDDM) 85%

Most common Insulin produced, but is low or doesn’t work correctly managed by diet or oral insulin-stimulation drugs that

make the pancreas produce insulin Obesity can be sole cause. adipose cells enlarge, insulin receptors change position

Glucose Tests

Urine GlucoseNegative if blood glucose < 165 mg/dL Does not rule out DM, based on renal threshold 5-hour glucose tolerance test Gold standard - 5th hour for hypoglycemia

5HGTTWhat to expect - Normal

Fasting – no urine sugar - ½ hour – no urine sugar

1 hour – none to trace urine sugarAfter that, back to normal

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5HGTT

Test urine and FBS before drink***If urine has no glucose, you are safe.

If FBS>126mg/dL, don’t do test, contact Dr.½ hour after glucose load – blood and urine

Take blood at 1, 2, 3, 4, 5 hourGraph results for interpretation

For Hypoglycemia – hours 3-5 results

5HGTTWhat to expect – Diagnostic Criteria

Fasting – above 126mg/dL or lower½ hour – FBS > 170, positive urine sugar1 hour –FBS >200, positive urine sugar

After that, FBS >200, variable urine sugar

Impaired Glucose Tolerance (IGT)

Used when the glucose test is abnormal but does not meet DM criteria

FBS = <126 mg/dLOGTT(2Hr) = <200 mg/dL

Impaired Fasting Glucose (IFG)

Used when fasting glucose is abnormally high, but below126mb/dL. Rest of test is normal

FBS = Elevated, <126 mg/dlOGTT(2Hr) = Normal Range

GDM screening test

Get fasting specimenIf > 140 don’t give glucose load

50 gms glucose, then get 1 hr. specimenIf >140, continue with confirmatory test

GDM screening test(3HGTT)

Get fasting specimen100 gms glucose, get 1, 2, 3 hr. specimens

GDM screening test(3HGTT)confirmed if any 2 are exceeded

Fasting > 105 mg/dL1-Hr > 190 mg.dL2-Hr > 165 mg.dL3-Hr > 145 mg.dL

Global use test for both Hyper and hypoglycemia

5HGTT

2HPPNo standardization of glucose load

For geriatric patients

Take fasting samplePatient goes out for a meal

Take 2 hr specimen

2HGTT

Accepted by ADA/WHO as cost effective

Check FBS, If FBS>126mg/dL, don’t do test Take blood at 2 hour

If > 200 mg/dL, patient had DM

Glycosylated HemoglobinAny changes do not show for at least 4 weeks

Normal 5 – 9%> hyperglycemic <hypoglycemic

Hemoglobins separated based on charge

Xylose test for malabsorptionUrine Xylose * Urine Volume

Normal – 25 grams ingested, eliminate at least 4.1 gms If Urine Xylose = 128 mg/dL+ Urine Volume -= 470 mL

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No malabsorption if > 4.1 gms (4.7 dL)123mg/dL x 4.7 dL = .602 grams = abnormal

Lactose tolerance testLike oral 2HGTT, but lactose load

blood glucose, not intolerant

CSF glucose and lactic acidViral meningitis – normal CSF glucose and lactateBacterial meningitis - CSF glucose, lactate levels

CSF glucose normal40 – 70 mg/dL

Use 2/3 of plasma glucose

Patients in shock =Anaerobic glycolysis = lactic acid

CSF handling Process as STAT – glucose and lactate

Venous glucose handling

Keep sample coolGlucose is not stable for very long

Oxalate/Fl (gray)Heparinized (least problems of anticoags)

(green) second bestCentrifuge, ASAP, remove plasma from cells

Serum ok, but centrifuse as soon as blood clots and remove serum from cells

Serumclear liquid that can be separated from clotted

blood

plasma

obtained from centrifuged whole blood that has been prevented from clotting by the addition of

anticoagulants such as citrate, oxalate, or heparin.

Lactic acid collection

Collect in Oxalate/Fl (gray) tubeAssay STAT

Fluoride is a glycolysis inhibitorOtherwise, RBC and WBCs will catabolize

glucose anaerobically, lactic acid.

Whole blood is ??? in glucose than serum or plasma

10 – 12% lower

Arterial blood(or capillary) is ??? in glucose than normal venous

Above normal range, ???

5% higher

10 mg/dL higher

Cystic fibrosis – sweat is saltier than normal

sweat glands do not reabsorb salt from sweat.If the sweat has NaCl and KCl, osmolarity will be Sweat is assayed for osmolality, chloride, sodium, potassium

Glucose Dehydrogenase method – one step

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NADH absorbs light – unaffected by oxalate/Fl

O-Toluidine methodUses high heat (stinky)

Can measure xylose and galactoseUse standards for what you are measuring

Glucose Oxidase Method

The specificity of the method for glucose. – step 1, Second step is non-specificInterfering substances

anything that can be oxidized will cause falsely low glucose – billirubin, creatinine, uric acid, etc.

Specific for glucose all stepsHexokinase requires Mg++ as an activator (uses NAD+ or NADH)

Anticoagulants that chellate Ca++ will chellate Mg++ - add extra Mg++highly specific method by spectrophotometrically measuring the NADP formed from hexokinase-

catalyzed transformations of glucose

Diagnostic criteria for FBS and OGTT results - The American Diabetes Association recommends either the fasting glucose or the OGTT to diagnose diabetes but says that testing should be done twice, at different times, in order to confirm a diagnosis of diabetes.

FBS OGTT(2Hr)Normal 70 – 110 mg/dL Normal rangeDiabetes Mellitus (DM – Type 1)Extreme acidosis, panic values for blood glucose

>126 mg/dl >200 mg/dL

Diabetes Mellitus (DM – Type 2) >126 mg/dl >200 mg/dLOther Specific Types of DM 111 – 126 mg/dL Normal rangeGestational Diabetes Mellitus (GDM) >105 mg/dL >165 mg/dLImpaired Fasting Glucose (IFG) Elevated, <126 mg/dl Normal RangeImpaired Glucose Tolerance (IGT) <126 mg/dL <200 mg/dL

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