Volume 2 Flashcards
The term that best describes the water found within cells is
intracellular water.
An example of calculated supplemental data is
the anion gap.
A trend in high or low anion gaps indicates that
there may be a consistent error in at least one of the analytes.
The ultimate regulators of sodium levels in the body are the
kidneys through reabsorption and excretion.
Hemolyzed samples for potassium analysis should be avoided because
intracellular potassium will be released, affecting results.
In the disease cystic fibrosis, the concentration of chloride ions in sweat is
elevated due to a genetic defect.
If you discover that a sample for bicarbonate analysis has been left open in a test tube rack, the result could be
falsely decreased due to CO2 escaping into the air.
Because the lungs and kidneys regulate acid-base balance, a patient with disorders affecting these organs will be followed using
blood gas analysis.
What happens during internal respiration when the partial pressure of oxygen is 90 mm Hg and carbon dioxide is about 40 mm Hg?
Oxygen moves into the cell and carbon dioxide moves out of the cell.
Blood gas samples should be collected only by
providers or specially trained personnel.
What do you do if you receive a blood gas sample with an air bubble in it?
Annotate the final report with the condition the sample was in when it arrived in the laboratory.
The importance of pH in the blood is critical because
a pH outside of 6.8 to 7.8 is incompatible with life.
Which one of the following substances is a buffer found in large amounts and has its concentrations within the body controlled by the lungs and the kidneys?
Bicarbonate.
The lungs help maintain body pH by converting carbonic acid into carbon dioxide and water, which
are then expelled during exhalation.
What are the body processes that water and electrolytes work hand-in-hand to accomplish?
Water balance, osmolality, electrolyte balance, pH balance, and blood gas exchange.
What are intracellular and extracellular water?
Intracellular water is found within the cells. Extracellular water is water found outside of the cells.
What is the concept of water balance?
Water balance is keeping the intracellular and extracellular compartments of water at a constant volume. This is done by ensuring that the rate of water loss is equal to the rate of water intake.
List the factors that regulate water balance?
It’s regulated by the body’s thirst mechanism, anti-diuretic hormone produced by the posterior pituitary gland, and excretion or reabsorption of water by the kidneys.
What are the six causes of fluid imbalances?
Vomiting. Excessive urination. Sweating. Diarrhea. Bleeding. Exudation.
In chemistry, the term electrolytes refer to what analytes?
Sodium, potassium, chloride, and bicarbonate.
- (204) Respiratory acidosis means the blood pH is
decreased due to a respiratory problem.
- (204) A tourniquet, used during venous blood collection, affects pH readings by causing
the blood to stagnate, resulting in a decrease of venous pO2.
- (205) Decreased levels of calcium are often associated with tetany,
a hyperexcitability of nerves and muscles.
- (205) Increased calcium levels are known as
hypercalcemia.
- (205) Hemolyzed samples should not be used for phosphate analysis because
red blood cells contain high concentrations of organic phosphate esters.
- (206) The main dietary sources of magnesium are
meat and green vegetables.
- (206) One of the more serious complications of magnesium deficiency is the effect on the
cardiovascular system.
- (206) Analysis of which one of the following analytes is often requested to track patients with manic-depressive illnesses?
Lithium.
- (207) All test methods for serum iron measure
iron carried by transferrin.
- (207) Iron levels in the body are regulated by
absorption.
- (207) Total iron binding capacity (TIBC) measures
maximum amount of iron-carrying capacity of transferrin.
- (207) Iron overload may be accelerated by
chronic alcoholism.
- (208) Among some of the liver’s functions is the ability to
convert glucose to glycogen and glycogen back to glucose, as needed.
- (208) The liver is the primary storage site for
glycogen.
- (208) Hepatitis A virus is primarily transmitted through
the fecal oral route.
- (208) Due to the amount of time it takes for antibodies to reach detectable levels and prior to the use of nucleic acid amplification testing (NAT), which type of hepatitis could not be eliminated completely by blood donor screening?
Hepatitis C virus.
- (208) What hepatitis virus occurs as a simultaneous infection with the Hepatitis B (coinfection) or as a superimposed infection in someone with chronic Hepatitis B (superinfection)?
Hepatitis D.
- (209) Bilirubin that has become joined with glucuronic acid is called
conjugated bilirubin.
- (209) When jaundice, a condition characterized by the deposit of a yellowish pigment in the skin and eyes, can be detected visually, the bilirubin level is
well above normal.
- (209) In newborns, bilirubin levels can increase for the first few days of life before returning to normal because
the transferase enzyme system is not fully developed.
- (209) Bilirubin levels increase due to the impairment or obstruction of the excretion of bile into the intestines, because bilirubin builds up in the hepatocytes, and is
regurgitated into the blood.
- (209) Conditions such as hepatitis, which damage or destroy liver cells, are known as
intrahepatic disorders.
- (209) Posthepatic disorders differ from intrahepatic disorders in that posthepatic disorders
can be corrected by surgical methods.
- (209) Samples for bilirubin analysis should be protected from light because
both conjugated and unconjugated bilirubin are light sensitive.
- (210) Carbohydrate classes, such as monosaccharides, disaccharides, and polysaccharides, are determined based on
the number of sugars a carbohydrate can be broken down into during hydrolysis
- (210) When excess carbohydrates are eaten, the body will change some of the excess into
fats and store them in that form.
- (210) The breakdown of glycogen into glucose is called
glycogenolysis.
- (211) The chief source of energy and the only monosaccharide found in significant amounts in the body fluids of living organisms is
glucose.
- (211) When epinephrine is released due to physical or emotional stress, it causes
increased glucose levels for energy.
- (211) The cause of Type 2 diabetes is
unknown.
- (211) If an unconscious patient’s glucose result has been verified and it’s 35 mg/dl,
notify the attending physician at once, because the patient is hypoglycemic.
- (211) When diagnosing diabetes mellitus, once the patient has met all required criteria, what other evaluations must be performed?
Hypertension and cardiovascular assessment.
- (211) Which one of the following glucose tests requires patient preparation for 3 days prior to the testing date?
Oral glucose tolerance.
- (211) Cerebrospinal fluid (CSF) glucose levels in bacterial meningitis patients are usually
lowered because glucose is utilized by the bacteri
- (211) Serum for glucose testing should not be allowed to sit on the red blood cells for extended periods of time because
glycolysis can decrease the glucose level.
- (211) One advantage of the hexokinase method over the glucose oxidase method, for glucose analysis, is
fewer substances will interfere with the hexokinase method.
- (212) The active site of an enzyme is where the substrate bonds are strained, ruptured, and the
substrate is converted into a new substance.
- (212) Substances that decrease enzyme activity, and are either competitive or non-competitive, are called
inhibitors.
- (212) The point where the concentration of enzyme no longer effects the rate of the reaction is known as the
zero order reaction.
- (212) Enzyme activators are usually
cations.
- (213) Amylase is secreted by the
salivary and pancreatic glands.
- (213) What source of amylase is the primary source of amylase responsible for carbohydrate break down?
Pancreatic.
- (213) All of the following are starch-based methods used to measure amylase activity, except
flame photometric.
- (214) The enzyme that splits off the phosphate group from organic phosphate esters in an alkaline solution is
alkaline phosphatase.
- (214) Elevated amounts of alkaline phosphatase is normal in children because
of normal bone growth.
- (215) Because alanine aminotransferase is found in moderately high concentrations in the liver and has low concentrations in skeletal and cardiac muscle, it is primarily used to
diagnose intracellular hepatic diseases.
- (215) Alanine aminotransferase (ALT) will increase, even before the patient shows any clinical signs, in cases of
viral hepatitis or other liver diseases, which cause hepatic necrosis.
- (215) After a myocardial infarction (MI), aspartate aminotransferase (AST) levels
increase and ALT levels will remain near normal.
- (215) You have just run a panel and the alanine aminotransferase (ALT) and aspartate aminotransferase (AST) are elevated beyond the linear range of your analyzer. Although you can dilute the sample with saline, the preferred dilutant is
albumin solution.
- (216) The function of gamma glutamyltransferase (GGT) is to
transport amino acids across cell membranes.
- (216) Gamma glutamyltransferase (GGT) is considered a better indicator of obstructive jaundice than aspartate aminotransferase (AST), alanine aminotransferase (ALT), or alkaline phosphatase (ALP) because
its levels increase earlier and persist longer than the other enzymes.
- (216) In addition to liver disease, the release of gamma glutamyltransferase (GGT) into the serum reflects
the toxic effects of alcohol or drugs on the liver cells.
- (216) Normal reference ranges for gamma glutamyltransferase (GGT) run higher in males than in females because
there are high levels of GGT in the prostate.
- (217) The peptide chains that make up lactic dehydrogenase (LD) isoenzymes are classified into two types—
M for skeletal muscle and H for heart muscle.
- (217) Lactate dehydrogenase (LD) testing is often useful in making a delayed diagnosis of a myocardial infarction (MI) because
the increase in LD occurs later than the increase in creatine kinase (CK).
- (217) In a normal lactate dehydrogenase (LD) isoenzyme pattern, the LD2 isoenzyme level is greater than the LD1 isoenzyme level. In a myocardial infarction (MI), the patient’s isoenzyme pattern will
be flipped, with LD1 greater than LD2.
- (217) Lactate dehydrogenase (LD) isoenzymes analysis is performed by
electrophoresis.
- (218) Creatine kinase (CK) is an enzyme that takes part in a reversible reaction—the direction of the reaction is dependent on the
pH of the reaction media.
- (218) Although creatine kinase (CK) is found predominately in the heart, skeletal muscle, and brain, accurate differentiation for conditions involving CK is accomplished using
CK isoenzymes.
- (218) Creatine kinase (CK) activity is most commonly used to assess patients with a myocardial infarction (MI) because it
begins to increase 3 to 6 hours after the MI.
- (218) What creatine kinase (CK) isoenzyme makes up most of the normal circulating CK, but can be increased with exercise?
CK-MM (CK3).
- (218) Most analyzer use the reverse reaction for creatine kinase (CK) analysis because
the reverse reaction is six times faster than the forward reaction.
- (219) In addition to acid phosphatase (ACP), which of the following helps to investigate and monitor prostatic cancer?
Prostate-specific antigen (PSA).
- (219) Forensic testing for acid phosphatase (ACP) is sometimes done during rape investigations because
seminal fluid contains high levels of ACP.
- (219) Prostate-specific antigen (PSA) can be detected in all males; however,
levels are greatly increased in males with prostatic cancer.
- (219) Prostate-specific antigen (PSA) is replacing acid phosphatase (ACP) as a screening tool for early detection of prostatic cancer due to
lack of sensitivity of ACP in early disease stages.
- (220) Calcium is required for lipase activity, but at high concentrations will serve as a(n)
inhibitor.
- (221) The best use of a myoglobin determinations is
to rule out a myocardial infarction.
- (221) Interference with troponin cTnT studies can be caused by
renal dialysis.
- (221) It is anticipated that the gold standard for the diagnosis of myocardial infarction (MI) will be
troponin.
- (222) Serum complement is a group of proteins, which act as enzymes, that facilitate the
body’s immunologic and inflammatory responses.
- (222) The functions of immunoglobulins are to recognize antigens and
initiate a response for destruction or neutralization of the antigen.
- (222) The IgM class of immunoglobulins
is the largest in molecular size and are the most primitive.
- (223) Albumin and globulin make up most of the protein in the body and can be measured together as
total protein.
- (223) When serum proteins are separated by electrophoresis, the most prominent band of protein seen is
albumin.
- (223) Total protein is most commonly determined by
either biuret or refractive index.
- (224) If a bloody tap cerebrospinal fluid (CSF) sample is sent to the laboratory, the results will reflect
contamination of blood proteins.
- (224) Dye-binding methods for testing cerebrospinal fluid (CSF) protein are preferred over turbidimetric methods because
a smaller amount of sample is needed.
- (225) In order for cells to covert fatty acids into triglycerides, what other substance must be present?
Glucose.
- (225) Which of the following substances make up 90 to 95 percent of the stored fats in the body?
Triglycerides.
- (226) Cholesterol levels decrease in all of the following conditions, except
high animal fat diets.
- (226) Cholesterol samples are normally drawn fasting even though cholesterol levels are
not significantly affected by non-fasting samples as triglycerides are.
- (226) When possible, perform high-density lipoprotein (HDL) separation
on the day of collection.
- (227) Specimens for triglyceride testing should not be drawn unless the patient has been fasting for at least 12 hours because triglyceride levels
are quickly affected by food in-take.
- (227) A potential source of error for triglyceride testing includes using
tubes with stoppers that have been lubricated with glycerol.
- (228) The three general categories for the functions of hormones are
regulatory, morphogenesis, and integrative action.
- (228) The specificity of hormone-receptor complexes allow the target cell to
recognize the hormone from all other substances.
- (229) Each step in the synthesis of thyroid hormones is regulated by the pituitary hormone
thyroid stimulating hormone.
- (229) When collecting samples for thyroid testing, remember that although plasma samples may be used, these samples
tend to form fibrin clots after freezing and thawing.
- (230) Pituitary hormones are classified based on
the portion of the gland they are secreted from.
- (230) In addition to promoting protein synthesis in young mammals, growth hormone (GH) also promotes
skeletal growth.
- (230) An adrenomedullary hormone that facilitates the generation of energy in response to fear, anger, or aggression is
epinephrine.
- (231) The tracking of a patient’s drug concentration is known as
therapeutic drug monitoring.
- (231) The phenomenon that occurs when the liver metabolizes a drug before it gets into the systemic circulation is known as the
first-pass effect.
- (231) The difference between a peak and a trough sample is the
peak is drawn at a drug’s maximum absorption.
- (232) When monitoring antipsychotic drugs, one of the most commonly observed requests is for
lithium.
- (233) When ingested, the principle action of ethanol is
the depression of the central nervous system.
- (233) Which one of the following statements best illustrates a reason for a legal blood alcohol case to be dismissed?
Technician did not follow laboratory operating instructions.
- (233) When an intoxicated patient refuses to have his or her blood drawn for an alcohol test, who can authorize the sample collection anyway?
Competent authority, usually with the advise of the Staff Judge Advocate.
- (233) What can cause a low ethanol result in a patient who is obviously intoxicated?
Patient drank isopropanol and you performed an enzymatic ethanol test.
- (234) The problem with initial clinical findings in patients who have overdosed on acetaminophen is the
initial findings are mild and do not indication the degree of hepatic damage.
- (234) When testing for an overdose of aspirin, you are actually
testing for the metabolite, salicylate, and not the original drug.
- (234) Treatment for salicylate intoxication is aimed at preventing further absorption of the drug. This is accomplished by
inducing vomiting or by giving activated charcoal.
- (235) The effects of poisons are either
. local or remote.
- (235) Improper use of insecticides can lead to significant exposure to
heavy metals.
- (235) The threshold levels for positive codeine and morphine, in urine drug testing programs, are usually adjusted to take into account the
consumption of poppy seeds in breads, cakes, and muffins.
- (236) It has been theorized that cancer is a multi-stage genetic process. Which of the following represents the stages in the correct sequence?
DNA damage, chromosome breakdown, selection of successful growing mutant cells.
- (236) Which of the following carcinogens could cause the initial change to the cellular DNA during the cancerous process?
All the above.
- (236) Which of the following types of tumor are generally more aggressive and have a poorer prognosis?
Poorly differentiated.
- (236) Which of the following is not a suggested criterion for the ideal tumor marker?
Be non-specific to the tumor studied and commonly associated with it.
- What two electrolytes are components of table salt?
Sodium ions (cations) and chloride ions (anions).
- What are some bodily functions regulated by electrolytes?
Electrolytes regulate water distribution (intracellular and extracellular fluids), osmotic pressure, maintain blood pH, regulate heart and other muscles, play a part in the body’s oxidation-reduction reactions, cell permeability, and nerve impulse conduction.
- Why is electrolyte analysis often performed as an emergency procedure?
Because an imbalance cannot be tolerated by a patient for very long and irreversible damage or death can result.
In what fluids do you find sodium, potassium, chloride, and bicarbonate?
Sodium ions are the principal cations of extracellular fluid. Potassium ions make up the majority of the cations found in the intracellular fluid. Chloride and bicarbonate anions are found predominately in extracellular fluid.
What is osmotic pressure?
The physical force that is exerted when water passes from an area of lower ion concentration to one of higher ion concentration.
Why is most clinical chemistry analysis performed on serum or plasma?
Because it’s more practical to measure the extracellular ions than to measure intracellular ions.
In what fluids do you find sodium, potassium, chloride, and bicarbonate?
Urine, spinal fluid, and sweat.
- What conditions bring on dehydration?
Sustained fever, diarrhea, inadequate fluid intake, and other clinical problems.
- How do you calculate an anion gap?
By subtracting the total chloride and bicarbonate anions from the total sodium cations.
Given the following patient electrolyte values––sodium=130 mmol/l, chloride = 100 mmol/l, and bicarbonate = 25 mmol/l––what is the anion gap?
Anion gap = (130 mmol/l) – (100 mmol/l + 25 mmol/l)
Anion gap = 130mmol/l – 125 mmol/l
Anion gap = 5 mmol/l
- What are two conditions that cause an increased anion gap?
A decrease in the unmeasured cations or an increase in the unmeasured anions.
- When does an abnormal anion gap become clinically significant?
Once it has been determined that the testing and retesting was valid.
- In addition to clinical diagnostic applications, how else does a laboratory technician use anion gap results?
As a quality control measure.
What is the major cation of extracellular fluid?
Sodium
- What organ regulates sodium levels?
The kidneys.
- What hormone helps to regulate sodium levels?
Aldosterone.
- What is hyponatremia and what causes it?
Hyponatremia is a decreased plasma concentration of sodium that can be caused by the patient not ingesting enough sodium or sodium loss due to diarrhea, prolonged vomiting, or sweating brought on by fever
Decreased sodium levels can also be caused by metabolic acidosis (due to diabetes mellitus), renal disease, diuretics, and Addison’s disease..
- What is hypernatremia and what causes it?
Hypernatremia is an increased plasma concentration of sodium that can be caused by severe dehydration, Cushing’s syndrome, insulin treatment of diabetic coma patients, and inappropriate forms of saline treatment or high sodium feedings.
- How does the sodium ISE work?
The sodium ISE has a glass membrane that selectively exchanges sodium ions. As the sodium ions react with the membrane, a potential-measuring circuit between the measuring electrode and reference electrode determines a change in the electromotive force. This change is proportional to the sodium concentration.
- How are indirect methods of sodium analysis affected by samples with high lipid or protein content?
Indirect samples for sodium are diluted before testing. Samples high in lipids or proteins can have these (lipids and proteins) displace some of the fluid that would normally be tested for sodium content.
- Potassium is primarily what type of cation?
An intracellular cation.
- How is potassium absorbed and excreted?
Potassium is absorbed rapidly in the intestinal lumen and excesses are excreted by the kidneys.
- How do potassium levels affect the heart?
Too much potassium inhibits the irritability of the heart and paralyzes it so that it ceases to beat. Not enough potassium increases the irritability of the heart to the point where it ceases during a contraction.
- What is hyperkalemia and what causes it?
Hyperkalemia is an increased plasma level of potassium. It occurs when potassium leaves the cells at a rate faster than the kidneys can excrete it. This overload occurs in conditions of anoxia, metabolic or renal acidosis, shock or circulatory failure, Addison’s disease, dehydration, or severe red blood cell lysis.
- What is hypokalemia and what causes it?
Hypokalemia is a decreased plasma level of potassium. This condition occurs as a result of low potassium intake over a period of time, increased loss of potassium through vomiting, diarrhea, gastrointestinal problems, or long-term use of diuretics. In addition, low potassium levels are seen in cases of increased aldosterone production, causing increased excretion of potassium by the kidneys, in chronic starvation patients and post-operative patients.
- How does hemolysis affect potassium analysis?
Since most of the body’s potassium is intracellular, hemolysis of a sample greatly affects the potassium level of the sample.
- Chloride is an anion found in what type of fluid?
Extracellular.
- Chloride is only found inside of what type of cell?
Red blood cells.
- What two primary functions does chloride serve?
Maintaining osmotic pressure and acid-base balance.
- What is hypochloremia and what causes it?
Decreased plasma chloride levels caused by uncontrolled diabetes (overproduction of ketoacids), renal disease (chloride lost as salts not reabsorbed), prolonged vomiting, intestinal blockage, and Addison’s disease.
What is hyperchloremia and what causes it?
Increased plasma chloride levels caused by dehydration, prolonged diarrhea, renal tubular acidosis, respiratory alkalosis, heavy salt ingestion, and over-treatment with saline solutions.
- Chloride contamination, prior to analysis, can result from what sources?
Tap water and the use of sodium fluoride as an anti-coagulant.
- What is the chloride ISE membrane made of and what medications can affect this test method?
A composite of silver sulfide and silver chloride. Medications containing bromides.
- Why is bicarbonate sometimes referred to as total carbon dioxide?
Bicarbonate is a term often interchanged with others used to describe carbon dioxide levels. About 90 percent of all carbon dioxide in the bloodstream is in the form of bicarbonate.
- What conditions cause increased bicarbonate levels?
Metabolicalkalosis,compensatedrespiratoryacidosis(suddenstopinbreathing––canbecausedbydrugs, blockage, or long-term pulmonary disease), or alkalosis accompanying a large potassium deficiency
- What conditions cause decreased bicarbonate levels?
Metabolic acidosis and compensated respiratory alkalosis (hyperventilation—deep, rapid breathing).
- What are sources of error affecting samples for bicarbonate analysis?
Blood collected in anti-coagulants other than heparin can upset the balance between the red blood cells and the plasma CO2. Allowing the sample to become exposed to room air also affects sample levels as CO2 in the sample escapes into the room air (room air has a lower CO2 concentration than blood).
- What are three methods commonly used for bicarbonate analysis?
Enzymatic, colorimetric, and ISE.
(1) The measure of the partial pressure of carbon dioxide in the blood.
pCO2.
(2) The partial pressure of oxygen dissolved in blood plasma.
pO2
(3) The percentage of available hemoglobin that is saturated
with oxygen.
sO2
(4) The ion that measures the metabolic component of the
acid-base equilibrium.
HCO3-
5) Expresses the extent to which the blood is acidic or
alkaline.
a. pH
- Blood gases are used to evaluate what functions?
A patient’s ability to transport oxygen, to assess disturbances in the fluid or electrolyte balance, and to monitor problems with the lungs or kidneys (since these organs regulate the body’s acid-base balance).
- What is external respiration?
The exchange of oxygen and carbon dioxide that takes place in the lungs as a person inhales and exhales.
What concept allows oxygen and carbon dioxide to move across the alveolar and capillary membranes?
Partial pressure helps oxygen and carbon dioxide move across the alveolar and capillary membranes through the process of osmosis.
- What is internal respiration?
It is the exchange of gases (oxygen and carbon dioxide) between the plasma in the capillaries and the tissue cells.
- What are oxyhemoglobin and carbaminohemoglobin and how are they transported?
Oxyhemoglobin is hemoglobin that has bound with oxygen. Carbaminohemoglobin is hemoglobin that has bound with carbon dioxide. Arterial blood carries the oxygenated blood to the tissue cells. Venous blood carries the carbon dioxide laden blood from the tissues back to the lungs.
- What are chemoreceptors and what function do they play in breathing?
They are special cells adapted to excitation by chemical substances. They are sensitive to the levels of pO2 and pCO2 in the body, sending impulses to the brain to speed up or decrease breathing as needed.
- What is hypoxemia and what can cause this condition?
Deficient oxygenation of the blood. It can be caused by breathing air low in oxygen, hypoventilation (from suffocation, submersion, trauma, obesity, or drug-induced respiratory failure), premature mixing of venous and arterial blood, or inability to oxygenate blood due to diffusion difficulties.
- What is the difference between hypercapnia and hypocapnia?
Hypercapnia is increased pCO2 in the blood (caused by decreased alveolar ventilation), while hypocapnia is a decreased pCO2 level (caused by increased ventilation rates).
- When specimens are collected for venous blood gas analysis, why should a tourniquet not be used or the fist clenched?
Because it decreases the venous pO2 and allow acid metabolites to accumulate.
- Why are plastic syringes avoided when blood gas samples are collected?
Because plastic syringes can allow gases to be exchanged between the blood sample and the outside air
through the barrel wall.
- Why do blood gas samples have their exposure to room air minimized and air bubbles expressed out immediately following collection?
Exposure to room air affects the blood gas levels in a sample. Exposure to room air normally increases the pO2 in the sample because the oxygen in the room air is of a higher concentration than that in the blood. Exposure to room air decreases the pCO2 because the concentration in the sample is much higher than that in room air. Air bubbles in the sample must be expressed out so that any gases in the bubbles are not allowed to affect the sample’s blood gas levels.
- Why is blood pH important and how does the body regulate it?
Blood pH is important because levels outside the range of 6.8 to 7.8 are incompatible with life. The body uses a series of chemical buffers, the lungs and the kidneys to regulate pH.
- What is the body’s most important buffer and why?
Bicarbonate is probably the most important buffer in the body because it is present in large amounts and can be controlled by the kidneys and the lungs.
- In what forms is carbon dioxide, produced by cellular metabolism, carried in the bloodstream?
A small amount of carbon dioxide is carried in the bloodstream as carbon dioxide and carbonic acid (about 5 percent), the majority is carried as bicarbonate (about 75 percent), and the remainder (about 20 percent) is bound to hemoglobin and other plasma proteins.
- How do the lungs help expel carbon dioxide?
As blood containing carbonic acid circulates through the lungs, the lungs convert the carbonic acid into carbon dioxide and water, which are expelled during exhalation.
- How do the kidneys help regulate pH?
They play a major role in getting rid of excess hydrogen ions. They will either directly excrete them into the urine or take them and expel them in the form of water, sodium dihydrogen phosphate, or ammonium chloride. The kidneys also form bicarbonate, as needed, which buffers the excess hydrogen ions in the plasma.
- What are acidosis and alkalosis, and how are they further categorized?
Acidosis is when the pH of the blood falls below 7.35 and alkalosis is when the pH of the blood rises above 7.45. The terms are categorized further based on what they are caused by. Respiratory acidosis and respiratory alkalosis are caused by respiratory problems while metabolic acidosis and metabolic alkalosis are caused by metabolic problems.
- How does the pH meter in a blood gas analyzer differ from the typical pH meter found in a laboratory?
The pH meter in a blood gas analyzer is calibrated using two buffers that fall within the ranges compatible with life. The pH meter in a blood gas analyzer is also much more sensitive because it has to be calibrated to measure within such a narrow range.
- What are some sources of error for blood pH testing?
Some blood pH testing sources of error include improper sample handling (same as for blood gas testing), use of tourniquet during sample collection, protein buildup on electrodes, bacterial contamination of the sample probe, and improper instrument temperature.
- In what three states can calcium be found in the blood?
In the first state, calcium is free or ionized. In the second state, calcium is bound to plasma proteins (primarily albumin). In the third, calcium is bound to diffusible anions such as phosphate, bicarbonate, lactate, and citrate.
- How do alkalosis and acidosis affect the amount of free calcium in the bloodstream?
Because calcium binds to the negatively charged sites on albumin, the rate of binding is pH dependent. Alkalosis leads to an increase in the binding of calcium and a decrease in the free calcium in the blood. Acidosis causes less calcium to bind with albumin, so there is more free calcium found in the blood.
- How does calcium function as an intracellular messenger?
By binding or being released from specific intracellular proteins. When proteins bind or release calcium their structure and function change. The calcium messenger system is responsible for things such as the contraction of muscles, secretion of fluids and hormones, mitosis, and the transfer of ions across cell membranes.
- How are plasma concentrations of calcium regulated?
By two substances, parathyroid hormone (PTH) and the active form of vitamin D (1,25-dihydroxy vitamin D3). The 1,25-dihydroxy vitamin D3 can increase the intestinal absorption of dietary calcium. PTH is secreted in response to low levels of calcium in the blood. The body responds by retrieving calcium and phosphate from the bones, increasing the reabsorption of calcium by the kidneys and increasing the absorption of calcium in the intestines from foods eaten.
- What is hypocalcemia and how is it caused?
Hypocalcemia is a decreased level of calcium. Critically decreased levels of calcium are associated with tetany. Low calcium levels can be caused by hypoparathyroidism, vitamin D deficiency, gastrointestinal problems that block the absorption of calcium or vitamin D, chronic renal failure, magnesium deficiencies and by increased demand due to pregnancy or lactation.
- What is hypercalcemia and how is it caused?
Hypercalcemia is an increased level of calcium. Primary hyperparathyroidism is the most common cause of hypercalcemia in outpatients, and malignancy is the most common cause in inpatients. It can also be caused by vitamin D overdose, ingestion of large amounts of dairy products, excessive ingestion of antacids, Paget’s disease, and chronic renal disease.
- Why are anti-coagulants, such as citrate, oxalate, and EDTA, not used for collecting samples for calcium analysis?
Because they form complexes with the calcium in the sample and affect test results.
- How does pH affect the binding of calcium in the blood?
When the sample pH is raised, the ionization and negative charge of the albumin is also raised, causing more calcium to bind with the albumin (thus lowering the free calcium values). Decreasing the pH has the reverse effect, decreasing the calcium bound to the albumin and increasing the free calcium values.
- How are organic and inorganic phosphate found in the body?
Organic phosphate is found in soft tissues in the form of organic phosphate esters. Both organic and inorganic phosphate ions are present within the cell, but most of the phosphates are found in the cells are of the organic form. Within the cells the organic phosphate ions are incorporated into nucleic acids, phospholipids, and high-energy compounds involved in cellular integrity and metabolism. Inorganic phosphate is found in extracellular fluids and serves as part of the body’s buffer system.
- How does the body obtain phosphate and how are its levels regulated?
Phosphorus is in almost everything you eat. It is absorbed by the body in the small bowel. Phosphorus is primarily excreted through the urine. The control of phosphate is closely linked to that of calcium. The regulators of calcium (PTH and active vitamin D) affect phosphate concentration. PTH stimulates the kidneys to excrete phosphate while retaining calcium. This causes an inverse relationship between calcium and phosphorus (as one goes up, the other goes down and vice versa).
- What is hypophosphatemia and what kind of clinical problems might be observed with this condition?
Hypophosphatemia is a decreased level of phosphate. Severe decreases in phosphate can result in neuromuscular disturbances, hemolytic anemia, decreased oxygen released from hemoglobin, and profound muscle weakness. These conditions are normally found in patients recovering from diabetic ketoacidosis, severe respiratory alkalosis, acute alcoholism, and severe burns.
- What is hyperphosphatemia and how is it caused?
Hyperphosphatemia is a increased level of phosphate. This condition is caused by chronic or acute renal failure, hypoparathyroidism, vitamin D intoxication, or hypersecretion of growth hormone. In infants and children high phosphate levels are associated with normal increased levels of growth hormone.
- Why is pH important during phosphate analysis?
All the common testing methods for phosphate are based on the reaction of phosphate ions with ammonium molybdate. In order for the complex to be formed, an acidic pH is required. The pH level must be carefully controlled because a less acidic pH can result in spontaneous reduction of the molybdate complex.
- Why do you avoid using anti-coagulated samples for phosphate analysis?
Because the anti-coagulants interfere with the formation of the phosphomolybdate complex in the testing procedure.
- Why do you avoid using hemolyzed samples for phosphate analysis?
Because red blood cells contain high concentrations of organic phosphate esters. When the cells lyse, these esters are released and can be hydrolyzed into inorganic phosphates during storage (raising phosphate levels).
- What are the functions of magnesium in the body?
Magnesium is an activator for more than 300 enzymes in the body. Its intracellular roles include phosphorylation, protein synthesis, glycolysis, cell replication, and nucleotide metabolism, and it affects neuromuscular excitability.
- What is hypomagnesemia and what are some of the causes and clinical indications of this condition?
Hypomagnesemia is a decreased level of magnesium in the body. Low magnesium levels can cause tetany, impair PTH secretion, and tachycardia (abnormally fast heartbeat) and fibrillation (abnormal heart muscle contractions).
- What is hypermagnesemia and what are some of the causes and clinical indications of this condition?
Hypermagnesemia is an increased level of magnesium. This condition is usually caused by an excessive intake of magnesium salts (used to relieve constipation), renal problems, severe dehydration, aldosterone deficiencies, and during therapy for pre-eclampsia and eclampsia in pregnant women. The most common signs of magnesium intoxication are neuromuscular symptoms. Deep tendon reflexes disappear and breathing rates can slow or stop. High magnesium levels can also cause cardiac arrest.
- Why is hemolysis avoided in magnesium samples?
Red blood cells contain high levels of magnesium.
- Why is lithium analysis usually requested?
As a tracking mechanism for lithium carbonate treatments. Lithium carbonate is used to treat the manic phase of affective disorders, mania, and manic-depressive illness.
- What are the signs of lithium intoxication?
Early signs of lithium intoxication (about 2 mmol/l) include apathy, sluggishness, drowsiness, speech difficulties, and twitching. Severe intoxication (about 2.5 mmol/l) is characterized by muscle rigidity, hyperactive deep tendon reflexes, and epileptic seizures.
- When performing flame emission photometry for lithium analysis, what two substances are used as the internal standards?
Cesium or potassium.
- What process does the body use to regulate iron and why is this unique?
Intestinal absorption (and to a lesser degree, the bloodstream), which is unique because most other elements are regulated by excretion.
- Why do adult females typically suffer greater losses of iron than do adult males?
Female losses are greater due to normal menstruation as well as the burdens associated with pregnancy.
- Why must laboratories establish local reference ranges for iron?
Because of the wide-ranging differences found between commercial methods.
- Name a potential source of error to consider when conducting iron studies.
Because iron is widely distributed in the environment great care must be taken to avoid contamination of testing equipment or reagents.
- In the total iron binding capacity (TIBC) test, why is iron added to the sample?
To saturate the transferrin iron binding sites.
- What are potential sources of error in ferritin assessments?
In conditions such as chronic infections, rheumatoid arthritis, renal disease, heart disease and several types of malignancies, that are present with concurrent iron deficiency, the ferritin levels may be within normal limits, but would still be considered as increased because of the other underlying condition(s).
- Why are the effects of hereditary hemochromatosis manifested in men often twenty years or more before the same effects are seen in women?
Because of the protection from menstruation. Women are typically affected post-menopausal.
- What is the treatment regimen for hemochromatosis?
Periodic therapeutic phlebotomy.
- Describe the location and appearance of the liver.
It is located in the upper right quadrant of the abdomen. The upper portion of the liver is overlaid by the lungs and diaphragm. The lower portion of the liver overlaps the stomach and intestines. The liver is covered by a collagenous capsule, and although it appears to be divided into a right and left half, it is actually divided into four lobes.
- What are the two sources of blood to the liver?
The portal vein and the hepatic artery. The portal vein carries blood from the capillary bed of the digestive system to the liver and the hepatic artery carries well-oxygenated blood to the liver.
- What are the liver’s functions for providing energy to the body?
The liver converts glucose into glycogen for storage. When energy is needed, the liver converts the glycogen back into glucose for release into the body. The liver maintains the release of glucose as a steady process, but in emergencies can release massive amounts of glucose in response to epinephrine.
- What are some of the clearinghouse functions of the liver?
The liver disposes of worn out red blood cells by breaking them down into different components, some of which are stored for future use, and others, which are excreted by the kidneys. The liver also filters and destroys bacteria, neutralizes poisons, and regulates sex hormone levels.
- Where is bile formed, what route does it take, and what is its function?
Bile is formed in the liver and flows into the gallbladder where it is concentrated and stored. Bile is released from the gallbladder into the intestines. In the intestines, bile (in the form of bile salts) breaks down large fat globules into smaller ones that can be acted on by fat-splitting enzymes.
- What are some of the metabolism functions that take place in the liver?
The liver plays a key role in the metabolism of carbohydrates. The liver is also responsible for synthesizing all plasma proteins except for gamma globulins. Other proteins formed in the liver are proteins for blood coagulation. The liver is also active in the anabolism and catabolism of lipids.
- What other substances are stored in the liver besides glycogen?
The liver stores vitamins A, D, and B12. It stores iron in significant amounts. And, it temporarily stores small amounts of proteins and lipids.
