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
Average values of the estimated GFR?
