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

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Presentation on theme: "Moonlight Medicine Adrian Paul J Rabe, MD, DPCP Laboratory Interpretation."— Presentation transcript:

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

2 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 – Microcytic Hypochromic (ITIM) Iron deficiency anemia or chronic blood loss Anemia of chronic inflammation Thalassemia Myelodysplasia – Normocytic Normochromic 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 = intrinsic renal Replaced by the Fractional excretion of sodium (FE Na ) – (U Na P Cr )/(P Na U Cr ) – 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: 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 mmol/day (0.5 mEqs/hour) – Na deficit = TBW x (Desired-Actual Na) – Calculate sodium deficit of mmol/day E.g. Na 100 in a 50 kg female Desired sodium should be TBW = 50 x 50%= 25 L Na def = 25 x 12 = 300 mmol in 24h 0.9% pNSS 1L x 12h 5% NaCl855 3% NaCl % NaCl % NaCl77 0.2% NaCl34 Plain LR130 D5W0

29 Sodium (Na): Correction Hypernatremia – Stop ongoing water losses – Should correct dehydration – Oral correction is the safest – No more than 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 [( )/140] = 3.57 L Change in serum Na = (77-160)/(25+1) = 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 0.9% NaCl % NaCl77 0.2% NaCl34 Plain LR130 D5W0

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 0.9% NaCl % NaCl77 0.2% NaCl34 Plain LR130 D5W 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 0.9% NaCl % NaCl77 0.2% NaCl34 Plain LR130 D5W 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 = 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 mEqs KCl 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 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 D 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 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 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

51 pH – reflects primary defect pCO2 – Elevated: decreased ventilation of CO2 – Decreased: increased ventilation of CO2 pO2 – Elevated: too high FiO2, hemoglobin abnormality – Decreased: Poor oxygenation, or oxygen binding

52 Arterial Blood Gas HCO3 – Elevated: Alkaline – Decreased: Acidic O2 saturation – If >90%: regular pulse oximeter cannot reliable distinguish frequencies

53 ABG Interpretation Identify adequate oxygenation and saturation – Oxygenation: enough oxygen in the blood (pO2) – Saturation: enough oxygen bound to RBCs (O2 Sat)

54 ABG Interpretation Identify Acid-Base problem: – Acidosis or Alkalosis? – Choose between pCO2 and HCO3 Acidosis: increased pCO2 OR decreased HCO3 Alkalosis: decreased pCO2 OR increased HCO3 – Establish predominant pathology (pCO2 – 40)/40 (HCO3-24)/24 Biggest absolute value is the predominant pathology

55 ABG Interpretation Identify Acid-Base problem: – Determine if primary problem is compensated (pCO2 – 40)/40 (HCO3-24)/24 Biggest absolute value is the predominant pathology

56 ABG Interpretation Identify Acid-Base problem: Predominant pathologyCompensation Metabolic Acidosis (Low HCO3) For every mmol decrease in HCO3, pCO2 decreases by 1.25 Metabolic Alkalosis (High HCO3) For every mmol increase in HCO3, pCO2 increases by 0.75 Respiratory Acidosis (High pCO2) Acute For every mmol increase in pCO2, HCO3 increases by 0.1 Chronic For every mmol increase in pCO2, HCO3 increases by 0.4 Respiratory Alkalosis (Low pCO2) Acute For every mmol decrease in pCO2, HCO3 decreases by 0.2 Chronic For every mmol decrease in pCO2, HCO3 decreases by 0.4

57 ABG Interpretation If there is metabolic acidosis – Take anion gap (Na + K) – (Cl + HCO3) Normal is 10 to 12 – HAGMA: MUDPILES Methanol, uremia, DKA, Propylene glycol/Paraldehyde, Isoniazid/Iron, Lactic Acid, Ethanol/Ethylene glycol, Sulfates/Salicylates – NAGMA: STRaND Spironolactone, TPN, RTA, Na-containing solutions, Diarrhea

58 ABG Interpretation If there is HAGMA – Take changes in anion gap and HCO3 – Δ AG > Δ HCO3 = HAGMA with Metabolic alkalosis – E.g. Uremia with vomiting If there is NAGMA – Take changes in HCO3 and Cl – Δ AG > Δ Cl= NAGMA with HAGMA – E.g. Diarrhea and lactic acidosis, treatment of DKA

59 ABG Interpretation L 750 mEqs 360 mEqs Plain LR 1L x 115 cc/hr 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

60 ABG Interpretation – pH 7.1, pCO2 28, pO2 78, HCO3 10, O2 Sat 88% Oxygenation /Saturation? Acidosis or Alkalosis? Respiratory or Metabolic? Compensated? Anion Gap? Secondary problems? Poor; Poor Acidosis Metabolic Expected pCO2 27.5; compensated 15 (High Anion Gap) 3 < 14; None 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


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