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Moonlight Medicine

Moonlight Medicine. Laboratory Interpretation. Adrian Paul J Rabe, MD, DPCP. Laboratory Interpretation. Supplements the history and physical examination Objective evidence of disease/health. Laboratory Interpretation. Complete blood count Bleeding tests PT/PTT, Bleeding time

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Moonlight Medicine

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  1. Moonlight Medicine Laboratory Interpretation Adrian Paul J Rabe, MD, DPCP

  2. Laboratory Interpretation • Supplements the history and physical examination • Objective evidence of disease/health

  3. Laboratory Interpretation • Complete blood count • Bleeding tests • PT/PTT, Bleeding time • Blood chemistry • Electrolytes (Na, K, Ca, Mg) • BUN and Creatinine • Liver enzymes (AST, ALT) and bilirubins • Urinalysis • Arterial Blood Gas

  4. CBC

  5. Complete Blood count • Hemoglobin and Hematocrit • High hemoglobin: Erythrocytosis • High hematocrit: Dehydration (hemoconcentration) or erythrocytosis • Low hemoglobin/hematocrit: anemia

  6. Complete Blood count • Hemoglobin and Hematocrit • MCV – size of the RBC (“-cytic”) • MCH – amount of hemoglobin in the RBC (“-chromic”) • MCHC – concentration of hemoglobin the RBC • RDW – distribution of cell sizes

  7. Complete Blood count • Hemoglobin and Hematocrit • MicrocyticHypochromic (ITIM) • Iron deficiency anemia or chronic blood loss • Anemia of chronic inflammation • Thalassemia • Myelodysplasia • NormocyticNormochromic • Early stages of microcytic, hypochromic disease • Acute blood loss • Hemolytic Anemia • Megaloblastic • Folate or Vitamin B12 deficiency

  8. Complete Blood count • Hemoglobin and Hematocrit • Transfusion changes • For every unit of packed RBC, increase in 10 g/L • Start of equilibration: 6 hours post transfusion • Full equilibration: 72 hours post transfusion

  9. Complete Blood count • WBC • Neutrophils and stabs • Elevated: Bacterial or early viral Infection, Stress, Inflammation • Low: Neutropenia • Absolute neutrophil count (ANC) = WBC x (Neutrophils in %) x 1000 • Lymphocytes • Elevated: viral/fungal/mycobacterial infection • Low: Lymphopenia • Absolute lymphocyte count (ALC) = same as ANC

  10. Complete Blood count • Platelets • Very evanescent • Low platelets: Consumption, Viral infection • Hard to predict platelet count after transfusion • Adults: never transfuse less than 4 units • Coats the tubing • A Repeat platelet count should be taken immediately up to 2 hours post transfusion

  11. Bleeding Tests

  12. Laboratory Interpretation • PT/PTT • Prothrombin time: Measures the extrinsic pathway (1572 = Factors 1, 10, 5, 7 and 2) • Liver disease: poor production of factor VII • Warfarin • Partial thromboplastin time: Measures the intrinsic pathway • Heparin • APAS • Coagulation factor deficiency (hemophilia) • Both prolonged • DIC • End-stage liver disease • Warfarin

  13. Laboratory Interpretation • Bleeding Time • Does not predict bleeding risk even in surgery • No longer recommended

  14. Blood Chemistry

  15. BUN and Creatinine • BUN – produced by the body and converted through the urea cycle • Increased BUN: Increased production • GI bleed • Creatinine – produced by the muscles, excreted by the kidney with little tubular reabsorption • Increased Creatinine: Increased production or decreased clearance

  16. BUN and Creatinine • BCR = BUN:Creatinine ratio • BUN/Creatinine in mmol x 247 • If > 20 = pre-renal • If 10-15 = intrinsic renal • Replaced by the Fractional excretion of sodium (FENa) • (UNaPCr)/(PNaUCr) • If < 1% = pre-renal • If > 2% = intrinsic renal failure

  17. BUN and Creatinine • Creatinine Clearance = GFR • (140-age) x weight x 88.4 (x 0.85 if female) 72 x Plasma creatinine • Estimates amount of creatinine filtered

  18. Sodium (Na) • Correlated with body water • Sodium is normally present in equimolar amounts • Water diffuses through semipermeable compartments to equilibrate

  19. Sodium (Na) • Total body water • % body water x kg body weight • Males: 60% • Females and Elderly (Age > 60): 50% • Plasma osmolality • 2(Na+K) + BUN + RBS in mmol/L • BUN/2.8 if in mg/dL • RBS/18 if in mg/dL • Normal: 275-290 mmol/L

  20. Sodium (Na) • Total body water • 50 kg male? • 70 kg female? • Plasma osmolality • Na 135, K 3.5, BUN 8, RBS 5 • Na 125, K 4.0, BUN 10, RBS 8

  21. Sodium (Na) • Hyponatremia • Check Plasma osmolality • High osmolality • Hyperglycemia • Mannitol • Normal osmolality • Hyperlipidemia/proteinemia • Bladder irrigation • Low osmolality • Check Urine output

  22. Sodium (Na) • Hyponatremia (Low osmolality) • Maximal urine output • Primary polydipsia (patient drinks a lot, diluting Na) • Pituitary problem/fever • Poor urine output • Check ECF volume

  23. Sodium (Na) • Hyponatremia (Low osmolality, Poor UO) • Increased ECF volume (dilutional) • Heart failure • Liver failure • Kidney failure/nephrotic syndrome • Normal ECF volume • SIADH • Hypothyroidism • Adrenal insufficiency • Decreased ECF volume • Loss of Na (renal, sweat, diuretics)

  24. Sodium (Na) • Hypernatremia • Check ECF volume • High ECF volume • Use of hypertonic solutions • Low ECF volume • Check Urine output

  25. Sodium (Na) • Hypernatremia (Low ECF volume) • Minimal urine output • Free water losses/Dehydration • Good urine output • Check urine osmolality • 24 hour urine TV, Na, K, Crea

  26. Sodium (Na) • Hypernatremia (Low ECF volume, Good UO) • Urine osmolality > 750 • Diuresis • Urine osmolality < 750 • Diabetes insipidus • Central vs Nephrogenic (through response to DDAVP)

  27. Sodium (Na): Correction • Hyponatremia • Increased ECF, no HypoNa symptoms • Used isotonic solutions • Restrict fluid to less than urine output • Loop diuretics • Normal ECF, no HypoNa symptoms • Restrict fluid • Low ECF or with HypoNa symptoms • Correct!

  28. Sodium (Na): Correction • Hyponatremia Correction • No more than 10-12 mmol/day (0.5 mEqs/hour) • Na deficit = TBW x (Desired-Actual Na) • Calculate sodium deficit of 10-12 mmol/day • E.g. Na 100 in a 50 kg female • Desired sodium should be 110-112 • TBW = 50 x 50%= 25 L • Na def = 25 x 12 = 300 mmol in 24h • 0.9% pNSS 1L x 12h

  29. Sodium (Na): Correction • Hypernatremia • Stop ongoing water losses • Should correct dehydration • Oral correction is the safest • No more than 10-12 mmol per day (0.5mmol/hr)

  30. Sodium (Na): Correction • Hypernatremia Correction • Water deficit = TBW x [(Actual-140)/140] • Change in serum Na = (infusate Na – serum Na) (TBW+1) • Amount of infusate = 10 or 12/Change in serum Na • E.g. Na 160 in a 50 kg female • TBW = 50 x 50%= 25 L • Water deficit = 25L x [(160-140)/140] = 3.57 L • Change in serum Na = (77-160)/(25+1) = -3.19 mmol for every liter of 0.45% NaCl • Amount of 0.45% NaCl = 12/3.19 = 3-4 L per day • 0.45 NaCl 1L x 6-8h

  31. Sodium (Na): Correction • 60 kg 23 year-old female with diarrhea and vomiting presents with new-onset seizure • BP 90/60, HR 110, RR 24, Febrile to touch • BUN 12, Crea 127, Na 150, K 3.5 • Creatinine Clearance • Plasma Osmolality • Total Body Water • H20/Na Deficit • Plain LR is available • Change in Na per liter • Order • 57 • 311 • 30 L • 2 L • -0.65mmol/L • 15 L of plain LR • 1L per hour for 4 hours

  32. Sodium (Na): Correction • 50 kg 40 year-old male diabetic with decreased sensorium • BP 140/80, HR 90, RR 28, afebrile • BUN 8, Crea 150, Na 115, K 3.5, Cl 90 • Creatinine Clearance • Plasma Osmolality • Total Body Water • H20/Na Deficit • Daily Na correction • Plain LR is available • 40 • 239 • 30 L • 750 mEqs • 360 mEqs • Plain LR 1L x 115 cc/hr

  33. Potassium (K) • Hypokalemia (<3.5 mmol/L) • 24h urine K and ABG • Urine K > 15 mmol/d • Acidotic = lower GI losses • Alkalotic = vomiting, sweat/renal losses, diuresis • Urine K < 15 mmol/d • Acidotic = DKA, RTA • Alkalotic = vomiting, Bartter’s/Liddle’s, HypoMg

  34. Potassium (K): Correction • Hypokalemia Correction • Concentration • 60 mEqs via central line • 40 mEqs via peripheral line • Rate • ≤ 20 mmol/h unless with paralysis, malignant ventricular arrhythmias • Amount • Every 1mmol/L decrease = 200-400 mmol deficit • pNSS is the ideal medium

  35. Potassium (K): Correction • Hypokalemia Correction • 19 year-old male comes in for progressive lower extremity weakness • K 2.7 • Deficit? • Correction via peripheral line? • 160 to 320 mEqs • pNSS 1L + 40 mEqsKCl x 6 hours, both arms

  36. Potassium (K) • Hyperkalemia (>5.0 mmol/L) • Failure of excretion • Intrinsic Renal problem • Drug-induced (spironolactone, K-sparing diuretics) • Iatrogenic (overcorrection) • Intake of massive amounts

  37. Potassium (K): Correction • Hyperkalemia Correction • Calcium gluconate (10% solution) over 2-3 minutes • NaHCO3 push • Glucose (G-I) solution = 10 u regular insulin + 1 vial D50-50 • Beta-agonists (salbutamol) • Diuretics (Furosemide) • Dialysis

  38. Calcium (Ca) and Albumin • Corrected Calcium • (40-actual albumin) x 0.02 + Actual calcium • Do for both increased and decreased calcium

  39. Calcium (Ca) and Albumin • Hypocalcemia Correction • Chronic • Calcium Carbonate best taken with food (acid soluble) • Calcium citrate can be taken anytime • <600 mg of calcium per dose • Age 19-50: 1000 mg/day • Age 51 and older: 1200 mg/day • Acute, symptomatic • Calcium gluconate 10 mL of a 10% solution diluted in D50-50 or 0.9% saline over 5 minutes • Calcium gluconate drip 10 ampules or 900 mg in 1L of D5 or 0.9% saline over 24 hours

  40. Calcium (Ca) and Albumin • Hypercalcemia Correction • Volume expansion (4-6 L of 0.9% saline in first 24 hours) until normal volume status is restored • Loop diuretics (Furosemide) • Bisphosphonates • Zoledronic Acid 4 mg IV over 30 minutes • Pamidronate 60-90 mg IV over 2-4 hours • Onset of action is 1-3 days • Dialysis

  41. Magnesium (Mg) • Part of the inseparable trio (K, Ca, Mg) • Hypomagnesemia needs to be corrected to facilitate correction of other electrolytes • 1g Mg = increase in 0.1 mmol/L • Target 1.0 mmol/L in Cardiac patients • Target 0.8 mmol/L in Renal patients • E.g. post-MI patient with Mg 0.6 mmol/L • MgSO4 4g in D5W 250 cc x 24h

  42. Liver enzymes and bilirubins • Prothrombin time • Albumin • TB, DB, IB • Elevated DB = Cholestatic • Elevated IB = Hemolytic • Both could be elevated in liver failure • AST and ALT • NOT liver function test • Help estimate amount of liver parenchymal damage • Hundreds to Thousands: Toxic, Viral, Ischemic • AST: ALT ratio > 2:1, likely alcoholic

  43. Lipid profile • Total Cholesterol (>200 mg/dL) • Statin • HDL (<40 mg/dL in males, < 50 mg/dL in females) • Nicotinic Acid • Statin • LDL (> 150 mg/dL) • Statin • Triglycerides (> 150 mg/dL) • Fibrate (fenofibrate) • Statin

  44. Urinalysis

  45. Urinalysis • pH • Specific gravity • Albumin • Glucose • WBC • RBC • Casts • Crystals • Epithelials

  46. Urinalysis • pH • Important in drug excretion • E.g. Methamphetamines eliminated with acidic pH • Specific gravity • If ≤1.010: hydrated vs inability to concentrate • If ≥ 1.020: dehydrated vs compensation by concentration • Albumin • Glucose

  47. Urinalysis • Albumin • Related to the integrity of the basement membrane • Albuminuria: infection, nephrotic syndrome/kidney disease • Glucose • Non-specific • May be elevated in diabetes

  48. Urinalysis • Epithelials • Used to gauge urine catch • If < 5: “clean catch” • WBC • If > 5: infection in the presence of a clean catch • RBC • If > 5: suspect kidney injury (hematuria? Nephritis? Infection?)

  49. Urinalysis • Casts • WBC casts: pyelonephritis or allergic interstitial nephritis • RBC casts: hematuria • Broad casts: chronic kidney disease • Crystals • Very non-specific • Even “uric acid crystals” are seen in normal patients

  50. Arterial Blood Gas

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