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Sunday, July 26, 2015

Renal Function Test: BUA, BUN and Creatinine

RENAL FUNCTION TEST (RFT)

            The major function of the kidneys is to eliminate waste products from the body and reabsorbed the substances essential for body function. When the kidneys’ functions are impaired, one or both processes are altered. 


Image credit: Allfeline.on.com



Measurements of the ability of the kidneys to carry out their major processes provide vital data in knowing whether they’re normally functioning or not.
           
            To know whether a kidney functions correctly we may perform different tests such as, test for Blood Urea Nitrogen (BUN), Creatinine and Blood Uric Acid (BUA).

CREATININE

            Creatinine is used to diagnose impaired renal function.

            This test measures the amount of creatinine in the blood. Creatinine is a catabolic product of creatinine phosphate, which is used in skeletal muscle contraction. 

The daily production of creatine and subsequently creatinine depends on muscle mass, which fluctuates very little. 

Creatinine, as BUN, is excreted entirely by kidneys and therefore is directly proportional to renal excretory function. Thus, with normal renal excretory function, the serum creatinine level should remain constant and normal. 

Only renal disorders such as glomerulonephritis, pyelonephritis, acute tubular necrosis, and urinary obstruction, will cause an abnormal elevation in creatinine. 

There are slight increases in creatinine levels after meals, especially after ingestion of large quantities of meat. Furthermore, there may be some diurnal variation in cr.
           
            The serum creatinine test, as with the BUN, is used to diagnose impaired renal function. Unlike BUN, however, the creatinine level is affected minimally by hepatic function. 

The serum creatinine level has much the same significance as the BUN level but tends to rise later. Therefore elevations in creatinine suggest chronicity of the disease process. 

In general, a doubling of creatinine suggests a 50% reduction in the glomerular filtration rate. The creatinine level is interpreted in conjunction with the BUN.

             
NORMAL VALUES:

v  ELDERLY         decrease in muscle mass may cause decreased values
v  ADULT
FEMALE        0.5-1.1 mg/dL or 44-97 umol/L
MALE             0.6-1.2 mg/dL or 53-106 umol/L
v  ADOLECENT                        0.5-1.0 mg/dL
v  CHILD                       0.3-0.7 mg/dL
v  INFANT                     0.2-0.2 mg/dL
v  NEWBORN               0.3-1.2 mg/dL

INTERFERING FACTORS

v  A high diet in meat content can cause transient elevations of serum creatinine.
v  Drugs may increase creatinine values include aminoglycoside (e.g. gentamicin), cimetidine, heavy-metal chemotherapeutic agents (e.g. cisplatin), and other nephrotoxic drugs such as cephalosporins (e.g. cefoxitin)

TEST RESULTS AND CLINICAL SIGNIFICANCE

    LEVELS

Disease affecting renal function, such as glomerulonephritis, pyelonephritis, acute     tubular necrosis, urinary tract obstruction, renal blood flow (e.g. shock, dehydration, congestive heart failure, atherosclerosis), diabetic nephropathy, nephritis. With these illnesses, renal function is impaired and creatinine levels rise.

Rhabdomyolysis. Injury of the skeletal muscle causes myoglobin to be released in the blood stream. Large amounts are nephrotoxic. Creatinine levels rise.

Acromegaly
Gigantisim
These diseases are associated with increased muscle mass, which causes the “normal” creatinine level to be high

    LEVELS

Debilitation
Decreased muscle mass (e.g. muscular dystrophy, myasthenia gravis)
The diseases are associated with decreased muscle mass, which causes “normal” creatinine level to be low.



Saturday, July 18, 2015

Potassium, the Major Intracellular Cation




Potassium is the primary intracellular cation. It is also an integral part of the transmission of nerve impulses.  It participates in the sodium-potassium pump in the body. 

Unhemolyzed serum should be used because hemolysis will markedly increase the potassium values because potassium is present in large amounts inside the cell.





Clinical Significance

1.      Hyperkalemia – increased concentration of potassium in the bloodstream. It’s found in the following conditions:

         Decreased renal excretion

         Acute or chronic renal failure
         Hypoaldosteronism
         Addison’s disease
         Diuretic

·         Cellular shift

         Acidosis
         Muscle/cellular injury
         Chemotherapy
         Leukemia
         Hemolysis

Increased intake

             Oral or IV potassium replacement therapy

-          Artifactual

                        Sample hemolysis
                        Thrombocytosis
                        Prolonged tourniquet use of excessive fist clenching

2.      Hypokalemia – decreased concentration of potassium in the blood stream, seen in the following conditions:

            GI loss

                        - Vomiting
                        - Diarrhea
                        - Gastric suction
                        - Intestinal tumor
                        - Malabsorption
                        - Cancer therapy
                        - Large doses of laxatives

          Normal values:

                           K = 3.5-5.3

         Plasma and serum: 3.4 – 5.0 mmol/L
         Urine: 25 -125 mmol/L



Wednesday, June 24, 2015

Outline of Methamphetamine

Methamphetamine 

 Class of drugs is sympathomimetic

 Has direct stimulant activity on the CNS and Myocardium

 It is widely used to treat obesity

 They are extensively abused by individuals who try to stay awake for long period of time





 the effects of Methamphetamine generally last 2-4 hours

 has a half-life of 9-24 hours in the body

 generally detectable in the urine for 3-5 days

 Confirmatory testing is performed using GCMS.

 the effects of Methamphetamine generally last 2-4 hours

 has a half-life of 9-24 hours in the body

 generally detectable in the urine for 3-5 days

 Confirmatory testing is performed using GCMS.

Screening Sample – Urine
Confirmatory Sample - Blood

Methods

1. Immunoassay Systems Screening procedure (Methamphetamine card test)

2. Liquid or gas chromatography

Precautions 

-Adulterants, such as bleach or other strong oxidizing agents.

- Clean container w/o any preservatives

- Store the urine specimen at 2-8 degrees C or freeze urine specimen (-20degrees C) for longer storage

Friday, June 19, 2015

Solving the weight of substances needed to produce molar and normal solutions





To be able to solve the weight of substances needed to prepare certain molar and normal solutions, you can use the general formulas:

For Normal solutions

N = GEW/L of solution

GEW = W/MW/v

N = (W/MW/v)/L of solution

Where:

GEW = Gram Equivalent Weight

L = Liter

W = weight in grams of substance

EW = Equivalent Weight

MW = Molecular Weight

v = valence


The short cut formula is:

W = DN X DV X EW (MW/v)

Where:

DN = Desired Normality
DV = Desired Volume
EW = Equivalent Weight
MW = Molecular weight
v = valence

Here’s a sample problem.

How much CaCl2 will you need in preparing 500 mL of a 0.5 N solution?
W = DN X DV X EW (MW/v)
W = 0.5 X 0.5 X (111/2)
W = 13.875 grams of CaCl2

To prepare the 0.5 N CaCl2 solution:

Weigh 13.875 grams of CaCl2 and dilute it to 500 mL of solution in  a volumetric flask. You can first dispense 250 ml of the distilled water to the flask, dissolve the 13.875 CaCl2, and then add the diluent up to the 500 mL mark of the volumetric flask.

Take note of the following:

1.    Volume must always be converted to liters when using this formula, or if you don’t want to convert, divide your answer by 1,000.

2.    The powder must not be added to 500 ml or 0.5 L but diluted TO 500 mL to in a volumetric flask to get the exact volume. The resulting volume in your 500 ml flask after dissolving the CacL2 must not be more or less than 500 ml. This will ensure accuracy of your measured solution.


For Molar solutions

M = GMW/L of solution

GMW = Weight/MW

M = (W/MW)/L of solution

Where:

GMW = Gram Molecular Weight

L = Liter

W = weight in grams of substance

MW = Molecular Weight

v = valence


Hence for Molar solutions the formula is:

W = DM X DV X MW

Where:

DM = Desired Molarity
DV = Desired Volume
MW= Molecular Weight

If you're given the same data but asked to solve for the molarity this is the formula and substitution:


Here’s a sample problem.

How much CaCl2 will you need in preparing 500 mL of a 0.5 M solution?
W = DN X DV X MW
W = 0.5 X 0.5 X 111
W = 27.75 grams of CaCl2
 
The only difference from the Normal solution is the absence of valence. 


To prepare the 0.5 M CaCl2 solution:

Weigh 27.75 grams of CaCl2 and dilute it to 500 mL of solution in  a volumetric flask. 
You can first dispense 250 ml of the distilled water in the flask, dissolve the 27.75 CaCl2, and then add the diluent up to the 500 mL mark of the volumetric flask.


Saturday, June 13, 2015

Clinical Chemistry 1 - Lipids and Its Major Functions, Fatty Acids Powerpoint Presentation

Lipids are unique from other substances in the blood because they are non polar and insoluble in water, but soluble in organic solvents.

Lipids (fats) in food are more difficult to digest than proteins and carbohydrates. Lipids are present in the body through various forms, such as triglyceride (storage form of lipid), phospholipid (important parts of biomembranes), cholesterol (important component of steroid hormones),fatty acids (the simplest forms of lipids).

Lipids have crucial functions in the body that include the following:

1. Acts as a body insulator. So, it's true Virginia, that when you're fat, you have more "heat insulators" in your body, hence, will feel less susceptible to the cold weather,

2. Acts as biomembranes (protector) of vital organs, such as the brain and the lungs.

3. Acts as an enzyme in the form of prostaglandin.

4. Acts as the basic component of steroid hormones.

5. Acts as carrier proteins for non-polar substances.

6. Acts as a source of energy when there's a dysfunction of carbohydrate being converted to energy.

Below is a slide presentation submitted by a previous student that you can read to let you understand more about lipids.


Thursday, June 11, 2015

Review on Lab Instrumentation, Clinical Chemistry 1



Spectrophotometer

An instrument used for measuring the transmission or reflection of light by comparing various wavelengths of the light. It also makes use of the Beer-Lambert’s principle which is “Light transmitted is inversely proportional to the concentration, while the absorbance is directly proportional to it.”




Some of the precautions in this test:

1.    Never brush cuvettes because it will lead to scratches and give inaccurate results
2.    Use rather a clean soft cloth to wipe the cells before reading it
3.    Ideal amount of the sample is ¾ full so that the light will strike the given sample and not the empty space.
4.    Let the machine be warmed up first for about 10-15 min before use, so that fluctuation is avoided.

There are four essential parts of a spectrophotometer

            1. Light source
            2.  Monochromator or filter
            3.  Sample cell with holder
            4.  Detector

Turbidimetry

-      The determination of the quantity of insoluble suspended matter in a liquid by measuring the loss of intensity of light in the direction of propagation of the incident beam, with reference to a standard solution

Gravimetry

-      Gravimetric methods of analysis are used where weights of reactants and products of chemical reactions are reproducible, stable and reflect the presence of constituents which are important in the establishment of identity. 
-      Two important methods deal with the trapping and weighing of products in the solid and gaseous phases.

Osmometry

-      Measurement of the amount of osmotic pressure that a particular solution  exerts
-      Can be vapor pressure osmometry, freezing point depression osmometry or membrane osmometry

Emission Flame Photometry

A type of flame photometry in which molecules in a flame are volatilised to generate free atoms that are excited to higher energy levels. When these atoms return to the ground state, they produce a characteristic emission spectrum. These typically use a low-temperature, air-gas, laminar flame burner which is inherently subject to drift and therefore lithium (Li), which is not a normal serum constituent, is excited as a known added constituent to "standardize" the results despite the drifting of the flame output. This approach does not permit addition of Ca as a third determined constituent as the emission of the Ca at serum levels in the low-temperature flame is below measurable intensity; furthermore the Li would interfere optically with the Ca determination.           

Atomic Absorption Spectrophotometry

             Atomic Absorption Spectrophotometry is the measurement of the concentration of an element in a given sample. This technique can be done in three ways: Flame type, Electrothermal type, and Color Vapor type. In the flame type, gas and combustible substance are used to ignite the mixture of gases.
            The second type which is electrothermal makes use of electric current and slit width. On the other hand is the cold vapor method wherein a reducing agent is added and vaporized.

Volumetry

            Volumetry is t he measurement of volumes of liquids, solids, and gas.
-the quantitative analysis of an unknown chemical solution by determining the amount of reagent of known concentration necessary to effect a reaction in a known volume of the solution
Chromatography

            It is a broad range of physical methods used to separate and or to analyze complex mixtures. The components to be separated are distributed between two phases: a stationary phase bed and a mobile phase which percolates through the stationary bed.

  1. Thin Layer Chromatography
TLC is a simple, quick, and inexpensive procedure that gives the chemist a quick answer as to how many components are in a mixture. TLC is also used to support the identity of a compound in a mixture when the Rf of a compound is compared with the Rf of a known compound (preferably both run on the same TLC plate).
A TLC plate is a sheet of glass, metal, or plastic which is coated with a thin layer of a solid adsorbent (usually silica or alumina). A small amount of the mixture to be analyzed is spotted near the bottom of this plate. The TLC plate is then placed in a shallow pool of a solvent in a developing chamber so that only the very bottom of the plate is in the liquid. This liquid, or the eluent, is the mobile phase, and it slowly rises up the TLC plate by capillary action.

B.   Gas chromatography 

    specifically gas-liquid chromatography - involves a sample being vaporized and injected onto the head of the chromatographic column. The sample is transported through the column by the flow of inert, gaseous mobile phase. The column itself contains a liquid stationary phase which is adsorbed onto the surface of an inert solid.

C.   ‘High Performance Chromatography 

       High-performance liquid chromatography   (HPLC) is a form of liquid chromatography  to  separate compounds that are dissolved in solution. HPLC instruments consist of a reservoir of mobile phase, a pump, an injector, a separation column, and a detector. Compounds are separated by injecting a plug of the sample mixture onto the column. The different components in the mixture pass through the column at different rates due to differences in their partitioning behavior between the mobile liquid phase and the stationary phase.

Electrophoresis

Electrophoresis is a separations technique that is based on the mobility of ions in an electric field. Positively charged ions migrate towards a negative electrode and negatively-charged ions migrate toward a positive electrode. For safety reasons one electrode is usually at ground and the other is biased positively or negatively. Ions have different migration rates depending on their total charge, size, and shape, and can therefore be separated.

Instrumentation

An electrode apparatus consists of a high-voltage supply, electrodes, buffer, and a support for the buffer such as filter paper, cellulose acetate strips, polyacrylamide gel, or a capillary tube. Open capillary tubes are used for many types of samples and the other supports are usually used for biological samples such as protein mixtures or DNA fragments. After a separation is completed the support is stained to visualize the separated components. 
Resolution can be greatly improved using isoelectric focusing. In this technique the support gel maintains a pH gradient. As a protein migrates down the gel, it reaches a pH that is equal to its isoelectric point. At this pH the protein is neutral and no longer migrates, i.e., it is focused into a sharp band on the gel.