Electrolyte Guide PDF

113 REMEMBER! REMEMBER! Hepatitis vs....

113 REMEMBER! REMEMBER! Hepatitis vs. Muscle Man Obstruction M u AST Adapte 60 mM/L - cystic fibrosis d. Renal failure e. Addison's disease 9. Chloride Shift a. Buffering system of the blood (for 8. Method: Ion-selective electrode acid-base balance) a. Valinom cin membrane selectively b. HC03 pulled out of erythrocytes binds K 4 and CJ· moves into erythrocytes, t resulting in serum ci-  115 6. +Anion gap a.+in concentration of unmeasured anions ❖ Ethanol ❖ Ketones ❖ Lactic acid b. tin unmeasured cations ❖ Low serum Mg++ ❖ Low serum Ca++ Reasents Used m Sweat Chloride 7. t Anion gap a. tin unmeasured anions- albumin loss Definition. of Chloride Shiite b. +in unmeasured cations ❖ High serum Mg++ ❖ High serum Ca++ CO2 (TOTAL CARBON DIOXIDE) ❖ Lithium therapy c. Hemodilution 1. CO2 + HCO3 + H 2CO3 = total CO2 OSMOl..ALITY 2. Reflects bicarbonate (HCO3) 1. Measure of total concentration concentration (n umber) of dissolved particles in a solution (molecular weight, size, 3. Methods: density or typ e of particle does not a. Volumetric matter) b. Manometric c. Colorimetric 2. Can be measured directly - practical d. pCO2 electrode measures change in methods are freezing point depression internal pH due to CO2 (most precise) and vapor pressure ANION GAP depression - 2 colligative properties 1. Calculation that r eflects differences between unmeasured cation s and 3. One equation (there are others that anions; u sed as analytical QC for give similar results) Calculated Osmolality = measuring all electrolytes 2Na + Glucose + BUN a. If abnormal gaps for multiple 18 2.8 patients, suspect problem with electrolyte measurements 4. Can compare calculated osmolality to measured osmolality; measured 2. Major unmeasured cations a. K+ osmolality > 10 higher than calculated b. ca++ osmolality indica tes presence of c. Mg++ exogenous unmeasured anions (methanol, ethanol , k etone bodies, etc.) 3. Major unmeasured anions a. Albumin b. Sulfate c. Phosphate 4. Two calculations (with or w:ithout K+): a. [(Na+) +(K+)] - [(Cr) +(HC03)] b. (Na+) - [(Cr)+ (HC03)] 5. Reference ran ge a. 10-20 mM/L (using equation 4a Ev.aluate Anion Gap and above) Talre Cornetive Action b. 7-16 mM/L (using equation 4b above) 116 5. Methods a. Atomic absorption spectroscopy - ·· REMEMBER! Conditions Causing ,t.. in reference method b. Colorimetric method - most common Unmeasured Anions ❖ Ca++ reacts wi.th o- (ethanol, ketones, etc.) ucsolphthalein to form r eddish S alicylate intoxication complex L actic acidosis ❖ 8-hydroxyquinoline is added to Unmeasured ions remove Mg++ Methanol P olyethylene glycol c. ISE - measures ionized Ca++ ❖ pH dep endent Ethanol D iabetic Ketoacidosis ❖ Collection - anaerobically to prevent CO2 loss ( ,t- pH) MAGNESIUM (MG++) d. Most methods measure total Ca++ 1. Ca++ channel blocking agent ( affects including protein-bound Ca++ heart) ( ,t- protein causes ♦ Ca++; ISE avoids problem) 2. i in r enal failure e. Falsel y t if using EDTA (purple top) 3. tin: or oxalate; due to binding Ca++ a. Cardiac disorder s b. Diabetes mellitus c. Diuretics, alcohol and other drugs 4. Methods a. Atomic absorption b. Colorimetric method - calmagite, @REMEMBER! formazen or methylthymol blue, or magon In Cases of Tetany, suspect CALCIUM (Ca~ ca++ first, then Mg++ or K+ 1. Combines with phosphate in bone 2. Controlled by 3 hormones: PHOSPHOROUS a. PTH (parathyroid) ,t- Ca++ 1. Majority of phosphate in body b. Calcitonin inhibits bone expressed as phosphorous; laboratory reabsorption ( t Ca++) measures inorganic phosphorous (PO,i) c. Vitamin D causes ,t- absorption in only intestines(+ ca++) 2. Inverse r elationship with Ca++ (when 3. Hyper calcemia ( ♦ Ca++) - muscle ca++ is ♦, P04 is f and vice vei-sa) weakness, disorientation a. Hyperparathyroidism 3. ,t- PO4 b. Cancer with bone metastasis a. H ypoparathyroidism c. Multiple myeloma b. Chronic renal failure d. Renal failure c. Excess vitamin D 4. Hypocalcemia (t ca++) - tetany 4. t PO4 a. Hypoparathyroidism a. H yperparathyroidism b. t serum albumin (1 mg/dL ca++ b. Impaired r en al absorption p_er 1 gldL t albumin) 5. Methods c. t vitamin D (malabso1ption, a. Spectrophotometric methods use inadequate diet) - impaired bone molybdate to combine with PO4 ions release, impaired renal r eabsorption b. Molybdenum blue is formed by the reduction of phosphomolybdate  117 REGULATORS OF CALCIUM AND PHOSPHORUS LEVELS ❖ Stimulation of renal hydroxylation of 25-(OH)D to 1. Vitamin D l ,25-(OH)2D a. Functions more like a prohormone than a vitamin c. Intraoperative PTH monitoring: b. Exists in 2 forms: ❖ Rapid (POCT) assaying of PTH ❖ D2 (ergocalciferol) dieta1-y form d111·ing surgery- use to determine found in fl.sh, plants, and fungus ii' abnormal PTH producing tissue ❖ D3 (cholecalciferol), most has been removed produced by photosynthesis in ❖ Baseline plasma PTH and then at skin from exposure to simlight but 5 and 10 minute intervals after also found in dietary animal removal of the parathyroid tissue products ❖ Look for >50% decline in PTH c. Both forms metabolized to more from O to 5 min postexcision active dihydroxy forms (l,25- (OH)2D) in a 2-step process 3. Procalcitonin (PCT) occurring first in liver (producing a. Normally made in thyroid and 25 hydroxyvitamin D) and then in converted to calcitonin which the kidneys causes T blood Ca++ d. 1,25-Dihydroxyvitamin D causes ,t.. b. In bacterial infection elevated levels blood calcium and phosphorus by (greater than 2.0 ng/mL) marker of increasing intestinal Ca and PO4 high risk of sepsis absorption and renal reabsorption IRON and increasing mineralization during bone formation 1. Over 65% of total body iron is in e. Deficiency causes: hemoglobin - 0 2 transport ❖ Rickets: childhood disease 2. Transported by transferrin, characterized hy softening and haptoglobin and hemopexin weakening ofbones ❖ Osteopenia and osteoporosis 3. Stored as ferritin and hemosiderin ❖ Linked to other conditions such as hypertension, obesity, diabetes, 4. Methods cardiovascular disease, multiple a. Serum iron - colorimetric - avoid sclerosis, cancer (colon and hemolysis breast), autism, systemic lupus b. TIBC (total iron-binding capacity) erythematosus (SLE), and other ❖ Reflects transferrin lel'els autoimmune diseases ❖ Excess ferric salts are added to f. Appropriate test for assessing serum to saturate binding sites on vitamin D stores: transferrin ❖ serum 25-hydroxyvitamin D (25- ❖ Unbound iron precipitated with 0II D2 & D3) magnesium carbonate g. Methods: ❖ After centrifugation, supe1·natant ❖ Immunoassay analyzed for iron ❖ Liquid cbromatography (high- c. Direct methods for transferrin are pPrfnrm:mce liquid immunochemical (nephelometry) chrnmatography [HPLC] and d. Ferritin liquid chromatography tandem ❖ A.ssess iron storage mass spectrometry [LCMSMS]) ❖ Immunoassay methods ❖ Sensitive for detection ofiron 2. PTH (.Parathyroid Hormone) deficiency a. Synthesis by parathyroid glands ❖ +in infection, inflammation, stimulated by low Ca, suppressed chronic diseases by high Ca concentrations b. Causes ♦blood calcium by ❖ Bone resorption ❖ Renal tubula1· reabso1ption of calcium but 1,25-(0H)2 vit. D most active form