Blood Chemistry and Renal function Flashcards
What tests are part of the Basic Metabolic Panel (BMP) ?
sodium, potassium, chloride, carbon dioxide, BUN, creatinine, glucose, and calcium
What tests are part of the Comprehensive Metabolic Panel (CMP)?
BMP + most of the hepatic panel (albumin, alkaline phosphatase, AST, ALT, bilirubin, total protein)
Way to write notes for BMP
What is sodium used to evaluate? What are the normal and critical values?
Used to evaluate and monitor fluid and electrolyte balance and therapy
Normal = 136-145 mEq/L
Critical values are < 120 or > 160
Sodium is the major cation in what space?
extracellular space
Sodium content in the body is a balance between?
dietary sodium intake and renal excretion
Nonrenal losses (sweat) normally are minimal
What is sodium balance regulated by?
Aldosterone stimulates the kidneys to reabsorb sodium and decrease renal losses by conserving sodium
Natriuretic hormone is stimulated by increased sodium levels and decreases renal absorption and increases renal losses of sodium
Antidiuretic hormone (ADH), which controls reabsorption of water at the distal tubules of the kidneys, affects serum sodium levels by dilution or concentration
What happens to sodium if free body water is increased?
sodium is diluted and the concentration may decrease. The kidneys compensate by conserving sodium and excreting water.
What happens to sodium if free body water is decreased?
If free body water is decreased, sodium concentration will rise and the kidneys will compensate by conserving free water.
What daily intake of sodium is required to maintain balance?
Average dietary intake of 90-250 mEq/day is required to maintain sodium balance
What are the symptoms of decreased sodium and at what levels do they appear?
Symptoms of decreased sodium may begin when levels are < 125 mEq/L.
First symptom is weakness.
When level falls below 115, confusion and lethargy occur and may progress to stupor or coma.
What are the symptoms of increased sodium?
Symptoms of increased sodium include dry mucous membranes, thirst, agitation, restlessness, hyperreflexia, mania, and convulsions.
What are the interfering factors for sodium?
Recent trauma, surgery, or shock may cause increased levels because renal blood flow is decreased.
Aldosterone is secreted which stimulates increased renal absorption of sodium.
Drugs may increase levels – antibiotics, corticosteroids, estrogens, contraceptives, laxatives
Drugs may decrease levels – antihypertensives, loop diuretics, antipsychotics, antiepileptics, NSAIDs.
Causes of hypernatremia?
Increased sodium intake
Decreased sodium loss
Excessive free body water loss
Causes of decreased sodium loss?
Cushing syndrome – corticosteroids have effect like aldosterone
Hyperaldosteronism – aldosterone stimulates kidneys to absorb sodium
What can cause excessive free body water loss?
Gastrointestinal loss (without rehydration) – loss of free water concentrates sodium
Excessive sweating – most sweat is free water causing sodium to concentrate
Extensive thermal burns – serum and free water lost through open wounds causing sodium to concentrate
Diabetes insipidus – ADH deficiency and inability of kidneys to respond to ADH causes large free water losses
Osmotic diuresis – water lost at rate greater than sodium loss
What causes Hyponatremia?
Decreased Sodium Intake
Increased Sodium Loss
Increased Free Body Water
What causes increased sodium loss?
Addison disease – aldosterone and corticosteroid hormone levels are low so sodium is not reabsorbed by the kidneys and is lost in the urine
Diarrhea, vomiting, or nasogastric suctioning – sodium in the GI contents is lost with the fluid
Intraluminal bowel loss (ileus, mechanical obstruction) – large amount of extracellular fluids are third-spaced into the lumen of the dilated bowel. This fluid contains sodium
Diuretic administration – inhibit sodium reabsorption by the kidney
Chronic renal insufficiency – kidneys lose their ability to reabsorb sodium
Large volume aspiration of pleural or peritoneal fluid – aspiration of these fluids is compensated by secretion of ADH, which increases absorption of free water to dilute sodium
What causes increased free body water?
Excessive oral water intake – psychogenic polydipsia
Hyperglycemia – osmotic effect of glucose pulls in free water from the extracellular space and dilutes sodium
Excessive IV water intake
Congestive heart failure and peripheral edema – increased free water retention
Ascites, peripheral edema, pleural effusion, intraluminal bowel loss – third space losses of sodium
Syndrome of inappropriate or ectopic secretion of ADH – oversecretion of ADH stimulates kidneys to reabsorb free water.
Function of potassium in the body?
Major cation within the cell. Intracellular potassium concentration is about 150 mEq/l and normal serum potassium concentration is about 4. This ratio is the most important determinant in maintaining membrane electrical potential, especially in neuromuscular tissue.
Potassium is also involved in protein synthesis and contributes to the metabolic portion of acid base balance – kidneys can shift potassium ions for hydrogen to maintain a normal pH.
What is the function of Potassium test? What are the normal and critical values?
Part of all routine evaluations as well as in patients with any type of serious illness. Important to cardiac function with significant effects on heart rate and contractility.
Normal range: 3.5-5.0 mEq/L
Critical values < 2.5 or > 6.5
What does the serum potassium concentration depend on?
**Aldosterone **– increases renal losses of potassium
Sodium reabsorption – as sodium is reabsorbed, potassium is lost
Acid base balance – alkalotic states lower serum potassium levels by shifting potassium into the cell. Acidotic states raise the potassium by reversing the shift
Minor changes in serum concentration have significant consequences since the serum concentration is so small
What is the treatment for hyperkalemia?
Sodium bicarbonate administration and dieuretics.
How are potassium levels maintained in the body?
Potassium is excreted by the kidneys without any reabsorption, so potassium must be adequately supplied by the diet as levels can drop rapidly.
What are the symptoms of Hyperkalemia
Irritability
Nausea and vomiting
Intestinal colic
Diarrhea
Symptoms of hypokalemia?
Decreased contractility of smooth, skeletal, and cardiac muscles
Weakness
Paralysis
Hyporeflexia
Ileus
Dysrhythmias
When should potassium levels be closely monitored?
Follow potassium levels closely in uremia, Addison disease, vomiting and diarrhea, and in patients taking steroids, potassium depleting diuretics, and digoxin (hypokalemia can induce arrhythmias)
Can hypokalemia or hyperkalemia cause EKG changes?
YES
Serum potassium level interfering factors
Opening and closing hand with tourniquet in place may increase levels
Hemolysis of blood during the draw or in the lab causes increased levels – WHY?
Drugs may increase levels – antibiotics, some antihypertensives, lithium, potassium sparing diuretics, potassium supplements, and succinylcholine
Drugs may decrease levels – antibiotics, diuretics, insulin, laxatives, Kayexalate (sodium polystyrene sulfonate)
Causes of Hyperkalemia
**Excessive dietary intake or **Excessive IV intake
Acute or chronic renal failure – most common cause of hyperkalemia – due to decreased excretion
Addison disease, hypoaldosteronism, aldosterone inhibiting diuretics (spironolactone, triamterene) – Aldosterone enhances potassium excretion but is absent in these states
Crush injury to tissues, hemolysis, transfusion of hemolyzed blood, infection – cellular injury and lysis causes potassium within the cells to be released
Acidosis – hydrogen ions are driven from the blood and into the cells to maintain physiologic pH. To maintain electrical neutrality, potassium is released from the cell
Dehydration
Causes of Hypokalemia?
Deficient dietary intake, deficient IV intake – kidneys cannot reabsorb potassium to compensate for reduced potassium intake
Burns, GI disorders (vomiting, diarrhea) – potassium is lost due to ongoing fluid and electrolyte losses
Diuretics – increase renal excretion of potassium
Hyperaldosteronism – aldosterone enhances potassium excretion
Cushing syndrome – glucocorticosteroids have an aldosterone-like effect
Renal tubular acidosis – increased excretion
Licorice ingestion – licorice has an aldosterone-like effect
Alkalosis – to maintain physiologic pH during alkalosis, hydrogen ions are driven out of the cell and into the blood. Potassium is driven into the cell
Insulin administration – glucose and potassium are driven into the cell***
Glucose administration – causes insulin to be secreted***
Ascites – decreased renal blood flow from reduced intravascular volume from the collection of fluid. Reduced blood flow stimulates secretion of aldosterone which increases potassium excretion
Renal artery stenosis – reduced renal blood flow
Cystic fibrosis – increased potassium loss in secretions and sweat
Trauma/burns/surgery – body’s response mediated by aldosterone which increases potassium excretion
What is the function of Cholride in the body?
Major extracellular anion, it maintains electrical neutrality, mainly as a salt with sodium.
Water moves with sodium and chloride, so chloride also affects water balance.
Chloride acts as a buffer to assist in acid base balance. As carbon dioxide and hydrogen increase, bicarbonate must move from the intracellular space to the extracellular space. To maintain neutrality, chloride shifts back into the cell
What do chloride values indicate? What are the normal and critical values?
With other electrolytes, chloride gives an indication of acid base status and hydration status
Normal: 98-106 mEq/L
Critical values: < 80 or > 115
Signs of hyperchloremia?
lethargy
weakness
deep breathing.
Signs of hypochloremia?
Hyperexcitability of the nervous system and muscles
shallow breathing
hypotension
tetany
Serum Chloride interfering factors?
Excessive infusions of saline can increase chloride levels
Drugs may increase or decrease levels
Causes of Hyperchloremia?
Dehydration
Excessive infusion of normal saline
Metabolic acidosis, renal tubular acidosis, Cushing syndrome, kidney dysfunction, hyperparathyroidism, eclampsia –urinary excretion of chloride is decreased
Respiratory alkalosis – chloride is driven out of cells in place of bicarbonate
Causes of Hypochloremia?
Overhydration, Syndrome of Inappropriate Secretion of Antidiuretic Hormone (SIADH) – chloride is diluted
Congestive heart failure – chloride is diluted by excess total body water
Vomiting or prolonged gastric suction, chronic diarrhea or high output GI fistula – chloride cation is high in the stomach and GI tract due to HCl acid produced
Chronic respiratory acidosis, metabolic alkalosis – chloride is driven into the cell to compensate for the bicarbonate that leaves the cell – this maintains pH neutrality
Salt losing nephritis, Addison disease, diuretic therapy, hypokalemia, aldosteronism – chloride excretion increased
Burns – sodium and chloride losses
What is CO2 Bicarbonate measure used for? What are the normal and critical ranges?
It is used to assist in evaluating the pH status of the patient and to assist in electrolyte evaluation
Normal = 23-30 mEq/L
Critical values < 6
What does the CO2 + Bicarbonate measure?
Measures the H2CO3 (carbonic acid), dissolved CO2, and the bicarbonate ion (HCO3-) that exists in the serum. The amounts of the first two are small, so CO2 content is an indirect measure of the HCO3- anion, which is second in importance to the chloride ion in electrical neutrality of extracellular and intracellular fluid
In what organ are CO2 and Bicarbonate levels regulated?
Levels are regulated by the kidney. Levels are increased with alkalosis and decreased with acidosis
What is the role of CO2 and Bicarbonate in the body?
Plays a major role in acid base balance
What are the CO2 and Bicarbonate interfering factors?
Underfilling the tube allows carbon dioxide to escape and may reduce values
Drugs may increase levels – aldosterone, barbiturates, bicarbonates, loop diuretics, steroids
Drugs may decrease levels – some antibiotics, thiazide diuretics
What causes increased levels of CO2 and Bicarbonate?
Severe vomiting, high volume gastric secretion, aldosteronism, use of mercurial diuretics – hydrogen ions are lost
Chronic obstructive pulmonary disease – ions are increased to compensate for chronic hypoventilation – compensation for respiratory alkalosis
Metabolic alkalosis – defined by an increased number of anions in the blood
What causes decreased levels of CO2 and Bicarbonate?
Chronic diarrhea, chronic use of loop diuretics – persistent loss of base ions
Renal failure, diabetic ketoacidosis, starvation – ketoacids and other anions build up, neutralizing the acids and causing levels to drop
Metabolic acidosis – defined by a decreased amount of anions in the blood
Shock – lactic acid builds up and is buffered, causing levels to drop
What is Anion gap used for?
Assists in the evaluation of patients with acid base disorders. It is used to attempt to identify the potential cause of the disorder and can be used to monitor therapy for acid base abnormalities
Helpful in identifying the cause of metabolic acidosis
What is the anion gap? What are the normal ranges? What is the formula?
Anion gap is the difference between the cations and anions in the extracellular space.
Normal = 12 +/- 4 mEq/L
AG = Sodium – (Chloride + Bicarbonate)
What creates the anion gap?
Gap is created by small amounts of anions in the blood (lactate, phosphates, sulfates, organic anions, and proteins) that are not measured
How does bicarbonate affect the anion gap (AG)?
As acids accumulate in the bloodstream (lactic acid or ketoacids), bicarbonate neutralizes them to maintain normal pH in the blood.
When bicarbonate decreases, AG increases
How does albumin affect the anion gap?
As albumin (negatively charged) increases, the AG will increase. If albumin is normal, a high AG is usually due to an increase in non-chloride-containing acids or organic acids.
Most metabolic acidotic states have increased or decreased AG?
increased
What causes a decreased AG?
A decreased AG is rare and is due to an increase in unmeasured cations (calcium or magnesium).
A reduction in anionic proteins (nephrotic syndrome) will also decrease AG. If proteins are lost, the bicarbonate increases to maintain electrical neutrality
Increases in cationic proteins (some immunoglobulins) will also decrease AG.
Hyperaldosteronism – lose large amounts of potassium and hydrogen ions causing a metabolic alkalosis with a decreased AG
Hypoproteinemia – loss of anionic proteins directly causes decrease in AG
Lithium toxicity – increase in inorganic cations decreases the measured cations to decrease the AG
Excess alkali ingestion (antacids) – increases bicarbonate to decrease the AG
Multiple myeloma – proteins produced by neoplastic cells are cationic, causing a compensatory decrease in measured cations and increase in measured anions to maintain electrical neutrality
Chronic vomiting or gastric suction – loss of hydrochloric acid causes a decrease in chloride and an increase in bicarbonate to decrease the AG
What causes an increased AG?
An increased AG, despite a normal pH, will indicate an acidotic component to the metabolic picture
Lactic acidosis, diabetic ketoacidosis, alcoholic ketoacidosis, alcohol intoxication, starvation – increased acid ions such as lactate, hydroxybutyrate, or acetoacetate are formed
Renal failure – uremic organic acids (phosphate, sulfates) accumulate in the blood due to poor excretion. Hydrogen combines with the bicarbonate to maintain a normal pH, so bicarbonate levels decrease and AG rises.
Increased GI losses of bicarbonate (diarrhea or fistula) – bicarbonate and other base losses can occur, increasing the AG
Hypoaldosteronism – aldosterone stimulates acid secretion in the distal renal tubule in exchange for sodium. Acid can build up and combine with bicarbonate, which decreases to increase the AG
AG interfering factors?
Hyperlipidemia – may cause under measurement of sodium to falsely decrease AG
Drugs may increase AG – diuretics, ethanol, methanol, salicylate, some antibiotics
Drugs may decrease AG – lithium, spironolactone
What is BUN and what does it measure?
Blood Urea Nitrogen
Rough measurement of renal function and glomerular filtration rate. Also a measurement of liver function.
Measures the amount of urea nitrogen in the blood
What are the normal and critical ranges for BUN?
Normal range : 10-20 mg/dL
Critical value > 100 mg/dL indicates serious impairment of renal function
An elevated BUN alone does not indicate that renal function is inadequate.
Explain how Urea is formed.
Urea is formed in the liver as the end product of protein metabolism and digestion.
Protein is broken down into amino acids which are catabolized in the liver to form free ammonia.
Ammonia molecules are combined to form urea, which enters the blood and is transported to the kidneys for excretion
What is azotemia?
Patients with elevated BUN are said to have azotemia.
What affect does renal disease have on BUN?
Renal diseases cause an inadequate excretion of urea, which causes blood concentration to rise.
If only one kidney is diseased, the unaffected kidney can compensate for the diseased kidney, and the BUN may stay normal
An elevated BUN alone does not indicate that renal function is inadequate.
What is Prerenal Azotemia?
Elevation of BUN due to pathologic conditions that affect urea nitrogen accumulation before it gets to the kidney
Shock, dehydration, CHF, excessive protein catabolism
GI bleeding causes blood in the intestinal tract – the proteins in the blood and blood cells are digested to urea and get absorbed, causing BUN to increase
What is Postrenal Azotemia?
Elevation of BUN due to pathologic conditions that affect BUN after it gets to the kidney
What would cause this??????
Ureteral and urethral obstruction
How will liver disease affect the BUN?
Synthesis of urea also depends on the liver, so severe liver disease will have decreased BUN
What is hepatorenal syndrome?
Combined liver and renal disease.
May have a normal BUN because of poor hepatic function resulting in decreased urea formation. A normal BUN is not an indicator that renal function is adequate
What is interpreted with BUN for a good measurement of kidney and liver function?
BUN is interpreted with the creatinine. These are referred to as renal functions.
The BUN/creatinine ratio is a good measurement of kidney and liver function.
Normal range is 6-25 with 15.5 being optimal
Name the interfering factors for BUN.
Changes in protein intake – low protein diets will decrease BUN if caloric intake is maintained with carbohydrates. High protein diets will elevate BUN.
Muscle mass has an effect on BUN levels
Advanced pregnancy may increase BUN due to high protein metabolism
GI bleeding can increase BUN
Overhydration dilutes BUN and causes lower levels.
** Dehydration** concentrates BUN and raises levels.
Many drugs can increase BUN
List the Prerenal causes for increased BUN
Hypovolemia, shock, burns, dehydration – reduced blood volume decreases renal blood flow, so excretion of BUN is decreased and levels rise
CHF, MI – decreased cardiac function decreases renal blood flow
**GI bleeding, excessive protein ingestion ** – gut is overloaded with protein so urea is formed at a higher rate and BUN accumulates
Excessive protein catabolism, starvation – increased rate of protein breakdown leads to increased urea formation
Sepsis – renal blood flow and renal function are reduced, so BUN rises
What are the Renal causes for an increased BUN?
Renal disease (glomerulonephritis, pyelonephritis, acute tubular necrosis), renal failure, nephrotoxic drugs – primary renal diseases all have reduced excretion of BUN
What are the Postrenal causes of an increased BUN?
Ureteral obstruction from stones, tumor, congenital abnormalities, bladder outlet obstruction from prostatic hypertrophy or cancer or bladder/urethral congenital abnormalities – obstruction of urinary flow reduces excretion and BUN rises
What are the causes of decreased levels of BUN?
Liver failure – BUN is made in the liver, so reduced liver function causes reduced BUN levels.
Overhydration due to fluid overload from SIADH – BUN is diluted by fluid overload
Negative nitrogen balance (malnutrition, malabsorption) – protein depletion causes reduced urea production to reduce BUN
Pregnancy – early pregnancy has increased water retention and BUN dilution
Nephrotic syndrome – protein loss in urine. With protein depletion, BUN is reduced.
Creatine is used to diagnose? What are the normal and critical ranges?
Used to diagnose impaired renal function
Normal ranges:
Females: 0.5-1.1 mg/dL
Males: 0.6-1.2 mg/dL
Critical values > 4 mg/dL indicates serious impairment in renal function
Creatine is excreted by?
the kidneys
Creatine levels are directly proportional to?
Renal excretory function. It is an approximation of glomerular filtration rate
With normal renal function the creatinine level should remain normal and constant
Where is creatine used in the body?
Creatinine is a catabolic product of creatine phosphate, which is used in skeletal muscle contraction.
Daily production depends on muscle mass
What do eleveations in creatine suggest?
Tends to rise later than the BUN, so elevations in creatinine suggest the disease process is chronic.
Doubling of the creatinine indicates a 50% reduction in GFR.
In unstable critically ill patients, acute changes in renal function may not initially be reflected by serum creatinine.
Is creatine affected by hepatic function?
Minimally affected by hepatic function
Interfering factors of Creatine?
- *Diet high in meats** may cause transient elevation in creatinine
- *Drugs** may increase creatinine – ACE inhibitors, nephrotoxic drugs
Causes of increased Creatine levels?
Diseases affecting renal function (glomerulonephritis, pyelonephritis, acute tubular necrosis, urinary tract obstruction, reduced renal blood flow due to shock, dehydration, CHF, atherosclerosis, diabetic neuropathy, nephritis) – renal function is impaired and creatinine rises
Rhabdomyolysis – skeletal muscle injury causes myoglobin to be released into the bloodstream. Large amounts are nephrotoxic and creatinine levels rise.
Acromegaly, gigantism – increased muscle mass causes “normal” creatinine level to be high
Dehydration
Causes of decreased Creatine?
Debilitation, decreased muscle mass (muscular dystrophy, myasthenia gravis) – decreased muscle mass causes “normal” creatinine to be low
What is the Creatinine Clearance (CrCl) used for?
A measure of the GFR (the number of milliliters of filtrate made by the kidneys per minute).
What does the amount of filtrate made in the kidneys depen on?
the amount of blood to be filtered and on the ability of the glomeruli to act as a filter
Can a bilateral obrstruction to urinary flow affect CrCl?
Bilateral obstruction to urinary outflow affects CrCl only after the obstruction is longstanding
What are the normal values for CrCl?
Adult < 40 years
Male: 107-139 mL/min
Female: 87-107 ml/min
Values decrease 6.5 mL/min/ per decade of life after age 20.
Urine collections are timed in CrCl measurements, how will incomplete collections affect the CrCl?
incomplete collections will falsely decrease CrCl
When measuring CrCl what is the time period for urine collection and what is formula for calculating it?
Test requires a 24-hour urine collection and a serum creatinine level.
CrCl = [(Cr excreted in urine over 24 hrs in mg/dl) X (vol of urine in mL/min)] / (serum creatinine in mg/dL)
What is the estimated GFR?
Difficult to collect 24 hour urine collections, so a new measure is the estimated GFR, which uses the serum creatinine, age, and numbers that vary depending on gender and ethnicity to calculate the GFR.
Average values of the estimated GFR?
CrCl interfering factors?
Exercise may increase creatinine
Incomplete urine collection may lower value
Pregnancy increases CrCl – increased load on kidneys by the fetus
Diet high in meat may transiently elevate creatinine and CrCl. When creatinine is high, its clearance is increased and GFR is overestimated
Estimated GFR may be inaccurate in extremes of age and in patients with malnutrition or obesity, paraplegia or quadriplegia, and in pregnancy
Drugs may increase levels – same as creatinine
Drugs that may cause a decrease in estimated GFR interfere with creatinine secretion (cimetidine or trimethoprim) or creatinine assay (cephalosporins) – may need a 24 hour creatinine clearance.
Causes of Increased levels of CrCl?
Exercise, pregnancy, high cardiac output syndromes – blood flow increases to the kidney causing GFR and CrCl to increase
Causes of decreased level of CrCl?
Impaired kidney function (renal artery atherosclerosis, glomerulonephritis, acute tubular necrosis), decreased GFR (CHF, cirrhosis with ascites, shock, dehydration) – decreased renal blood flow will decrease GFR
Decreased muscle mass
What is the Cockcroft Gault equation?
Cockcroft and Gault equation:
CrCl = (140 - age) x BM(kg) / (Plasma creatine x 72) (x 0.85 for females)
Estimated Creatining Clearance
What is the glucose measurement commonly used for? What are the normal and critical ranges?
Most commonly used in the evaluation of diabetic patients
Normal range: Fasting adult – 70-110 mg/dL
Critical values: < 40 and > 400 mg/dL
What are glucose levels controlled by?
Levels controlled by insulin and glucagon
Levels must be evaluated according to the time of day they are obtained.
What is the function of glucagon?
In the fasting state, glucose levels are low, so glucagon is secreted.
Glucagon breaks down glycogen to glucose in the liver so glucose levels rise
If fasting persists, protein and fatty acids are broken down due to glucagon stimulation so glucose levels continue to rise.
Where is glucagon made?
made in the alpha cells of the pancreatic islets of Langerhans.
Where is insulin made?
made in the beta cells of the pancreatic islets of Langerhans
What is the function of insulin?
Glucose levels rise after eating.
Insulin is secreted and attaches to insulin receptors in muscle, liver, and fatty cells.
This drives glucose into these cells to be metabolized to glycogen, amino acids, and fatty acids and causes glucose levels to decrease.
What is the most common cause of hypoglycemia?
Inadvertent insulin overdose
In new diabetic patients what must be monitored regularly?
Glucose measurements must be performed frequently in new diabetic patients to monitor insulin dosage – finger stick measurements are often performed before meals and at bedtime.
List the interfering factors of Glucose measurements?
Stressors (trauma, general anesthesia, infection, burns, MI) can increase glucose levels
Caffeine may cause increased levels
Pregnancy may cause glucose intolerance – gestational diabetes
IV fluids containing dextrose, which gets converted to glucose to raise levels
Drugs may increase (TCAs, corticosteroids, diuretics, epinephrine, glucagon, lithium, salicylates) or decrease (alcohol, anabolic steroids, insulin, propranolol, oral hypoglycemics) levels
Causes of Hyperglycemia?
- *Diabetes mellitus** – glucose intolerance and hyperglycemia
- *Acute stress response** – infections, burns, and surgery stimulate catecholamine release to stimulate glucagon secretion to cause hyperglycemia
Cushing syndrome – cortisol levels are high, leading to hyperglycemia
Pheochromocytoma – catecholamine stimulates glucagon secretion
Chronic renal failure – glucagon is metabolized by the kidney, so impaired renal function causes glucagon and glucose levels to rise.
Glucagonoma – glucagon autonomously secreted to cause hyperglycemia
Acute pancreatitis – glucagon spilled into the bloodstream as the cells of the pancreas are injured – glucagon causes hyperglycemia
Diuretic therapy
Corticosteroid therapy – cortisol causes hyperglycemia
Acromegaly – growth hormone stimulates glucagon
Causes of Hypoglycemia?
Insulinoma – insulin autonomously produced
Hypothyroidism – thyroid hormones affect glucose metabolism – decreased levels cause glucose levels to fall
Hypopituitarism – ACTH and growth hormone, both secreted from the pituitary gland, affect glucose metabolism. Decreased hormone levels cause glucose levels to fall
Addison disease – diminished cortisol levels cause glucose levels to fall
Extensive liver disease – decreased liver function causes glucose levels to decrease
Insulin overdose – most common cause of hypoglycemia
Starvation – decreased carbohydrate ingestion causes glucose levels to fall.
What are calcium levels used to evaluate?
Evaluates parathyroid function and calcium metabolism.
Used to monitor patients with renal failure or transplant, hyperparathyroidism, and various malignancies as well as calcium levels during and after large volume blood transfusions.
What are the normal and critical values of calcium?
Normal:
Total calcium 9.0-10.5 mg/dL
Ionized calcium 4.5-5.6 mg/dL or 1.05-1.30 mmol/L
Critical values:
Total calcium < 6 or > 13 mg/dL
Ionized calcium < 2.3 or > 7 mg/dL or < 0.78 or
> 1.58 mmol/L
In what forms does Calcium exist in the blood?
About half of the total calcium exists in blood in its free ionized form and half exists in protein bound form (mostly to albumin)
What form of Calcium is measured in the blood
Serum calcium level is a measure of both free ionized and protein bound calcium. So if albumin is low the calcium level will also be low.
Total serum calcium decreases by 0.8 mg for every 1 gm decrease in albumin
The ionized form is not affected by changes in albumin levels
A normal calcium with reduced albumin (calcium should be reduced)– patient may have hypercalcemia
When calcium levels drop what hormone is released to stimulate production and uptake? Where does the uptake occur?
Parathyroid Hormone (PTH) is released from the parathyroid gland when calcium levels drop.
This hormone stimulates realease of calcium from the bones.
It also stimulates Ca2+ uptake in the kidneys and along with Vitamind D stimulates uptake in the intestines
What is the most common cause of hypercalcemia?
hyperparathyroidism – causes increased GI absorption, decreased urinary excretion, and increased bone resorption.
What are the symptoms of elevated hypercalcemia?
Elevated levels cause anorexia, nausea, vomiting, somnolence, and coma.
How can malginancies affect calcium levels?
Malignancy can elevate calcium due to metastasis (myeloma, lung, breast, renal cell) to the bone which then destroys the bone and pushes calcium into the blood.
Some cancers (lung, breast, renal cell) can also produce a parathyroid hormone like substance that increases calcium.
What is secondary hyperparathyroidism?
Renal failure patients have high phosphate levels and other anions that chronically lower serum calcium, so parathyroid hormone is persistently stimulated to increase calcium levels. Calcium levels return to normal in time, but that level actually represents a “high” level as it should be low in these patients
Interfering factors for Calcium?
Vitamin D intoxication can increase calcium
Excessive milk ingestion can increase calcium
Serum pH – a decrease in pH causes increased calcium levels
Prolonged tourniquet time lowers pH and factitiously increases calcium levels
Hypoalbuminemia associated with decreased levels of total calcium
Drugs may increase levels (alkaline antacids, calcium salts, lithium, thiazide diuretics, and vitamin D) or decrease levels (albuterol, anticonvulsants, aspirin, corticosteroids, estrogens, heparin, laxatives, loop diuretics, magnesium salts, and oral contraceptives.
What causes Hypercalcemia?
Hyperparathyroidism, nonparathyroid PTH producing tumor (lung or renal) – PTH mobilizes calcium stores from bone to blood
Metastatic tumor to bone, Paget disease of bone, prolonged immobilization – bone destruction or thinning pushes calcium from bone into blood
Milk-alkali syndrome – increased ingestion of milk products or antacids (which contain calcium) causes elevation
Vitamin D intoxication – vitamin D works with PTH to increase levels
Lymphoma, granulomatous infections (sarcoidosis and tuberculosis) – have enhanced vitamin D levels
Addison disease – glucocorticosteroids inhibit vitamin D activity – when steroid activity is decreased, vitamin D action is increased
- *Acromegaly**
- *Hyperthyroidism**
What are some causes of Hypocalcemia?
Hypoparathyroidism –Reduced PTH causes decreased calcium
Renal failure, hyperphosphatemia due to renal failure – excess anions present in renal failure patients bind calcium
Rickets, vitamin D deficiency
Osteomalacia, hypoalbuminemia, malabsorption – less calcium available to the blood
Pancreatitis, fat embolism – saponification (binding of calcium to fats) of the peripancreatic tissue
Alkalosis – high pH in blood drives calcium intracellularly.
What are the normal and critical values of magnesium?
Normal: 1.3-2.1 mEq/L
Critical values < 0.5 or > 3 mEq/L
Where is magnesium found in the body?
Most is found intracellularly with half in bone.
Most is bound to ATP molecule and is important in phosphorylation of ATP , so it is critical in the metabolic process
What is the function of Magnesium?
Carbohydrate, protein, and nucleic acid synthesis and metabolism depends on magnesium.
Also is a cofactor that modifies enzyme activity
Most organ functions depend on magnesium
Low magnesium levels may increase cardiac irritability and aggravate arrhythmias
High magnesium levels retard neuromuscular conduction to slow cardiac conduction, diminish deep tendon reflexes, and cause respiratory depression.
In what way is magensium important in calcium metabolism?
hypocalcemia may respond to magnesium replacement
What are the common causes of hypomagnesemia?
Magnesium deficiency occurs in malnourished patients due to malabsorption or maldigestion or lack of food intake.
Important in postop patients who don’t eat for several days and whose metabolism is accelerated.
Alcohol abuse increases magnesium loss in the urine
Low magnesium occurs in diabetes mellitus, hypoparathyroidism, hyperthyroidism, hyperaldosteronism, and toxemia of pregnancy.
Chronic renal tubular disease – magnesium is reabsorbed in renal tubule. Diseases affecting this area of the kidney or drugs toxic to this area of the kidney allow increased losses of magnesium in the urine
Diabetic acidosis – magnesium levels fall with treatment of diabetic ketoacidosis. Insulin drives glucose into the cells and magnesium follows.
What are the symptoms of hypomagnesemia
Symptoms of decreased magnesium are mostly neuromuscular (weakness, irritability, tetany, EKG changes, delirium, and convulsions
What are the most common causes of Hypermagnesemia?
Increased magnesium levels usually are associated with ingestion of magnesium containing antacids
Most magnesium is excreted by the kidneys, so chronic renal diseases may elevate magnesium.
Hemolysis of a blood sample will create a falsely elevated magnesium since it is an intracellular cation.
Hyperparathyroidism – calcium levels are high so magnesium levels increase
Hypothyroidism
Addison disease – aldosterone enhances magnesium excretion. With reduced aldosterone, magnesium excretion is reduced
Symptoms of hypermagnesemia?
Symptoms of elevated magnesium are lethargy, nausea and vomiting, and slurred speech.
Interfering factors of Magnesium?
Hemolysis causes falsely elevated results
Drugs may increase levels (antacids, calcium containing meds, laxatives, lithium, loop diuretics, thyroid meds) or decrease levels (some antibiotics, diuretics, and insulin)
