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AAB Electrolytes
| Question | Answer |
|---|---|
| What is the most common method for measuring sodium? | Ion-selective electrode (ISE) |
| What is the most common method for measuring Potassium? | Ion-selective electrode (ISE) |
| What is the most common method for measuring Chloride? | Ion-selective electrode Amperometric-coulometric titration Mercurimetric titration Colorimetry |
| What is the most common method for measuring Carbon Dioxide? | Ion-selective eletrodes Colorimetric method Enzymatic method (results in oxidation of NADH for measurement |
| What is the major extracellular cation? | Sodium (Na+) |
| What is the major intracellular cation? | Potassium (K+) |
| What is the major extracellular anion? | Chloride (Cl-) |
| What mostly determines the osmolality of plasma? | Sodium |
| Which hormone acts on the distal convoluted tubule to increase sodium reabsorption? | aldosterone |
| Reference range for serum sodium | 136-145 mmol/L |
| Reference range for 24 hour urine for sodium | 40-220 mmol/L |
| Reference range for serum potassium | 3.4-5.0 mmol/L |
| Reference range for urine potassium | 25-125 mmol/L |
| Reference range for serum Chloride | 98-107 mmol/L |
| Reference range for urine Chloride | 110-250 mmol/L |
| Reference range for carbon dioxide | 22-29 mmol/L |
| Valinomycin can enhance the selectivity of which ISE electrode? | Potassium (has a selectivity for K over NA of about 4000:1) |
| Hypokalemia is: | Potassium levels below 3.4 mmol/L |
| Hyperkalemia is: | Potassium levels above 5.0 mmol/L |
| Hyponatremia is: | Sodium levels below 136 mmol/L |
| Hypernatremia is: | Sodium levels above 145 mmol/L |
| Hypochloremia is: | Chloride levels below 98 mmol/L |
| Hyperchloremia is: | Chloride levels above 107 mmol/L |
| Metabolic acidosis is: | Lowered levels of CO2 |
| Metabolic alkalosis is | Increased levels of CO2 |
| Hyperchloremia can be caused by: | metabolic acidosis, IV contamination |
| Hypochloremia can be caused by | vomiting, metabolic alkalosis, compensated respiratory acidosis |
| Hypernatremia can be caused by | (high sodium) dehydration, Cushing syndrome, increased dietary sodium intake |
| Hypokalemia can be caused by | (low Potassium)Decreased intake, GI loss, renal excretion, increased cellular uptake (with insulin therapy) |
| Hyperkalemia can be caused by | (high potassium) Increased intake, decreased renal excretion (renal failure), cellular shift (diabetic ketoacidosis OR imiproper specimen collection), |
| Sweat is an appropriate type of specimen for which electrolyte? | Chloride |
| In the coulometric-amperometric method for chloride, how is the amount of chloride measured? | time needed to reach the titration end point |
| IN the classic Schales-Schales (mercurimetric titration) method for chloride, what substance reacts with the indicator to form a violet color? | Excess HG |
| Most of the carbon dioxide in the blood is present in which form? | bicarbonate ion |
| Which electrolyte cannot be analyzed using a urine specimen? | carbon dioxide |
| Calculation for the anion gap: | (Na + K)-(Cl + HCO3) OR (Na+)-(Cl + HCO3) |
| Electrolytes with a positive charge are: | Cations (move towards Cathode) |
| Electrolytes with a negative charge are: | Anions (move towards Anode) |
| A physical property of a solution that is based on the concentration of solutes: | Osmolality |
| Osmolality is related to several changes in the properties of a solution relative to pure water such as: | Freezing point depression and vapor pressure decrease |
| What two things are stimulated by the hypothalamus in response to an increased osmolality of blood? | Sensation of thirst and arginine vasopressin hormone (AVP) aka antidiuretic hormone (ADH) |
| How does AVP act to reduce the osmolality of blood? | It is secreted by the posterior pituitary gland and acts on the cells of the collecting ducts in the kidneys to increase water reabsorption. |
| Clinical significance of Osmolality | It is the parameter to which the hypothalamus responds, increase in osmalolality (more NA+) triggers an increase in circulating AVP, a decrease in osmolality shuts off AVP production. |
| What accounts for 90% of the osmotic activity in plasma? | NA+ and its associated anions |
| Hypoosmolaltiy and hyponatremia usually only occur in patients with what condition: | Impaired renal excretion of water |
| Plasma Na+ concentration is controlled by what 3 processes? | Intake of water (thirst either stimulated or suppressed based on osmolality); excretion of water (AVP release in response to blood volume or osmolality); blood volume status (affects Na+ secretion through aldosterone, angiotensin II, and ANP) |
| Normally 60-75% of filtered Na+ is reabsorbed where? | In the proximal tubule(Kidney); electroneutrality is maintained by either Cl- reabsorption or H+ secretion) |
| Some Na+ is also reabsorbed where? | In the loop and distal tubule and (controlled by aldosterone) exchaged for K+ in the connecting segment and cortical collecting tubule. |
| Hyponatremia through increased sodium loss is the result of what conditions? | 1. Hypoaldosteronism, 2. prolonged vomiting or diarrhea, and also postassium deficiency, diuretic use, ketonuria, salt-losing nephropathy, , severe burns |
| Hyponatremia through increased water retention is the result of what conditions? | Renal failure, nephrotic syndrome, hepatic cirrhosis, conegestive heart failure |
| Hyponatremia through water imbalance is the result of what conditions? | Ecess water intake, SIADH (syndrom of inappropriate arginine vasopressin hormone secretion), pseudohyponatremia |
| In the regulation of sodium increased water intake does what to sodium levels? | Decreases sodium |
| In the regulation of sodium water excretion does what to sodium levels? | Increases sodium levels (follows the water through diffusion) |
| In the regulation of sodium Aldosterone does what to sodium levels? | Increases the retention of sodium |
| Symptoms of hyponatremia | Less severe: gastrointestinal, More severe: nausea, vomiting, muscular weakness, headache, lethargy, and ataxia, Most severe: seizures, coma and respiratory depression. A level below 120 mmol/L for 48 hours or less is considered a medical emergency |
| Hypernatremia through increased sodium intake/retention can be caused by? | Saline IV contamination or Hyperaldosteronism |
| Hypernatremia through decreased water intake can be caused by ? | Dehydration |
| Hypernatremia through excess water loss can be caused by? | Profuse sweating, diarrhea or severe burns. Also diabetes insipidus |
| Symptoms of hypernatremia | altered mental status, lethargy, irritability, restlessness, seizures, muscle twitching, hyperreflexes, fever, nausea, or vomiting, difficult respiration and increased thirst. >160 mmol/L has mortality rate of 60-75% |
| Acceptable specimens for Na+ are: | serum, plasma (heparanized), urine and whole blood |
| The most routinely used method for measuring sodium is? | ion selective electrode. Glass membrane favors Na+ over K+ |
| Classical method for sodium was? | Flame emission spectrophotometry |
| Functions of potassium | Many cellular functions require that the body maintain a low ECF concentration of K+ ions: Regulation of neuromuscular excitability, contraction of the heart, intracellular fluid volume, hydrogen ion concentration |
| What organ regulates potassium? | The kidneys |
| What part of the kidney reabsorbs potassium? | Proximal convoluted tubules |
| What part of the kidney secretes potassium? | Distal convoluted tubules (under the influence of aldosterone, K+ is secreted in into the urine in exchange for Na+) |
| Symptoms of Hypokalemia | weakness, fatigue, and constipation |
| Symptoms of Hyperkalemia | muscle weakness, tingling, numbness or mental confusion by altering neuromuscular conduction, can lead to cardiac arrhythmias and possible cardiac arrest |
| Acceptable specimens for K+ determinations are: | Serum, plasma (heparanized), urine and whole blood (hemolysis must be avoided) |
| The most routinely used method for measuing potassium is? | Ion selective electrode; with valinomycin membrane |
| Classical method for potassium was? | Flame photometry |
| What is chlorides function in the body | Its precise fx is not well understood, however it is involved in maintaining osmolality, blood volume and electric neutrality. |
| In what two ways does Cl maintain electrical neutrality? | 1. Cl acts as the rate limiting component in when reabsorbed with Na+ 2. Chloride shift: |
| What is chloride shift? | CO2 within the tissue diffuses into the plasma and the red cell, in the red cell CO2 forms carbonic acid, which splits into H+ and bicarbonate. Bicarbonate diffuses into plasma while Cl diffuses into red cell to maintain the electric balance of the cell |
| Acceptable specimens for Cl- determinations are: | Serum, heparinized plasma, whole blood and 24 hour urine. |
| The most routinely used method for measuring Chloride is? | Ion selective electrode with an ion-exchange membrane used to selectively bind Cl- ions |
| How does the amerometric-coulometric titration method for measuring chloride work? | Uses Coulometric generation of silver ions which combine with Cl- to quantitate the Cl- concentration |
| Three additional methods for Cl- measurement other than ISE are: | Amperometric-coulemtric titration (Ag); mercurimetric titration (Hg), colorimetry (mercuric thiocyanate, ferric nitrate) |
| Total carbon dioxide is comprised of what three things? | Bicarbonate ion, carbonic acid, dissolved CO2 |
| HCO3- (bicarbonate) accounts for what percentage of total CO2 at physiologic pH? | Over 90%; so total CO2 measurement is indicative of bicarbonate measurement |
| What is the main function of bicarbonate? | It is the major component of the buffering system in the blood. Potentially toxic CO2 is converted to H20 and H2CO3 which dissociates to bicarbonate, which diffuses out of the cell in exchange for CL (chloride shift) |
| Carbon dioxide is regulated by what? | The lungs |
| Bicarbonate is regulated by what? | The kidneys; 85% is reabsorbed by proximal tubules, 15% by distal tubules |
| Decreased bicarbonate is caused by? | Metabolic acidosis, and is compensated by hyperventilation |
| Increased bicarbonate is caused by? | Metabolic alkalosis, compensated by hypoventilation |
| Acceptable specimens for bicarbonate determinations are: | Serum, heparinized plasma, whole blood |
| What are two methods for measuring bicarbonate? | Ion selective electrodes, coupled enzymatic method |
| How does the ISE for measuring bicarbonate work? | A pH electrode is used to measure CO2 |
| How does the enzyme method for measuring bicarbonate work? | It aklalinizes the sample to convert all forms of CO2 to HCO3-; 1st reaction needs PEP carboxylase, coupled with a second reaction using malate dehydrogenase. The rate of change in absorbance of NADH is proportional to the bicarbonate concentration |
| Reference range for anion gap with Potassium included is? | 10-20 mmoles/L |
| Reference range of anion gap without potassium is? | 7-16 mmoles/L |
| What is the purpose of calculating the anion gap? | It determines int he electrolytes are in balance. |
| What can a low anion gap indicate? | Instrument error, improper calibration of instrument |
| What can a high anion gap indicate? | diabetic ketoacidosis, severe dehydration, salicylate (aspirin) ingestion, lactic acidosis. |
| Function of water in the body | Transports nutrients to cells, determines cell volume, removes waste products, acts as the body's coolant |
| Water load has what effect in the body? | Decreases osmolality |
| Water deficit has what effect in the body | Increases osmolality |
| Acceptable specimens for osmolality determinations are? | Serum, urine, feces |
| What are the methods used to measure osmolality? | Freezing point depression osmometer(most common) (increase in osmolality decreases freezing point) and vapor pressue osmometer (increase in osmo decreases vapor pressure) |
| What is the calculation for osmolality | 1.86*Na + GLU/18 + BUN/2.8 |
| How is the osmolar gap calculated? | Osmo gap= measured - calculated |
Created by:
Mlovik