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Pod Med II > Lab Medicine (Part 1) > Flashcards

Lab Medicine (Part 1) Flashcards

1
Q

Blood and plasma

A
  • Blood constitutes 6 - 8% total body weight
  • Plasma comprises 45 - 60% of blood volume
  • 5600 ml of blood in the 70 K male
  • Normal pH – 7.35 – 7.45
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2
Q

Sources of blood collection

A
  • Skin puncture
  • Venous puncture
  • Arterial puncture
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3
Q

Skin puncture

A
  • Specimen is mixed arterial and venous blood
  • Erroenously called “capillary blood”
  • May contain interstitial and intracellular fluid
  • Useful for glucose monitoring
  • Capillary tube utilized for hemataocrit
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4
Q

Blood collection technique of choice in pediatrics

A
  • Skin puncture
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5
Q

Skin puncture technique site selection

A
  • Infants: lateral or medial aspect of heel

- Adults: lateral to digital pulps

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6
Q

Skin puncture methods of collection

A
  • Warming area will increase blood flow (~42 C)
  • Prep with alcohol
  • Discard first drop
  • Do not “milk” area
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7
Q

Venous puncture

A
  • Composition dependent upon metabolic activity of perfused organs
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8
Q

Venous puncture site selection

A
  • Antecubital fossa (median cubital vein, cephalic vein)
  • Wrist, hand or ankle
  • Femoral vein
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9
Q

Venous puncture preparation

A
  • Cleanse with alcohol
  • Apply tourniquet proximal to selected site
  • Release tourniquet when blood begins to flow
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10
Q

Venous puncture technique

A
  • Flexing the hand may facilitate venous distention
  • Anchor vein distal and proximal
  • Deliver needle: Bevel up, enter at 15 degree angle, direct along proximal path of vein
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11
Q

Arterial puncture

A
  • Arterial blood uniform throughout body
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12
Q

Arterial puncture site selection in adults

A
  • Radial artery most common – Allen test
  • Femoral artery
  • Brachial artery
  • Pediatric patient: scalp artery
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13
Q

Modified Allen Test

A
  • Compress the radial and ulnar arteries until palm of the hand becomes blanched
  • Release pressure from the ulnar artery
  • The hand should become flushed
  • This verifies the ulnar artery can supply the hand
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14
Q

Arterial punture technique

A
  • Infiltration of local anesthetic may help
  • Collect blood gases in heparin tube
  • Prep skin with alcohol
  • Deliver distal to where the pulse is felt
  • Gently mix specimen
  • Apply firm compression for a minimum of 5 min
  • Transport on ice for blood gases
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15
Q

Interpretation of lab values

A
  • Look for trends in laboratory values
  • All abnormal labs should be repeated
  • Osler’s Rule
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16
Q

Osler’s rule

A
  • Applied to patients <60 years of age

- Seek to attribute all abnormal values to a single pathology

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17
Q

Serum collection tubule with coagulants

A
  • Red top or SST (tiger top
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18
Q

Plasma collection tubule with anti-coagulants

A
  • Citrate - blue top
  • EDTA - lavender top
  • Heparin - green top
  • Fluoride - gray top
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19
Q

Collection tube uses

A
  • Citrate (blue): used for coagulation studies
  • EDTA (lavender): blood collections RBC & Luekocytes
  • Heparin (green): blood, pophoryns, cortisol, vitamin assays
  • Flouride (gray): glucose, lactate, flouride also inhibits glycolysis
  • Serum has coagulation factor and plasma does not
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20
Q

Coagulation studies

A
  • Collect with a sodium citrate tube - blue top
  • Citrate was the original anticoagulant (1914)
  • Acts via chelation to calcium blocking coagulation cascade
  • Adenine increases red cell viability
  • PT, PTT, thrombin clotting time
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21
Q

Prothrombin time (PT)

A
  • Evaluates the extrinsic clotting pathway

Vitamin K dependent factors –II, VII IX, X, protein C and protein S - synthesized in liver

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22
Q

Conditions with prolonged PT

A
  • Vitamin K deficiency
  • Impaired fat absorption
  • Liver disease
  • Coumadin therapy
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23
Q

Prothrombin time reference values

A
  • 11 - 13 seconds

- Standardized by “international normalized ratio

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24
Q

International normalized rate (INR) calculation

A

(observed PT/control PT) x ISI

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25
Q

Prothrombin time prophylaxis values

A
  • For pulmonary embolism - 2.0 - 3.0

- For mechanical heart valve - 2.5 - 3.5

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26
Q

Partial prothrombin time (PTT)

A
  • Best singular test for coagulation

- Evaluates the intrinsic and final common pathway

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27
Q

Partial prothrombin time (PTT) is used for screening of

A
  • Disorders of fibrin formation

- Heparin therapy

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28
Q

Partial prothrombin time (PTT) reference values

A
  • PTT - 60 - 85 seconds

- aPTT - 30 - 40 seconds

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29
Q

Thrombin clotting time (TCT)

A
  • Assesses the terminal steps of pathway
  • Evaluates fibrin-fibrinogen interaction by introducing thrombin
  • Thrombin induced clotting is very rapid
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30
Q

Thrombin clotting time (TCT) elevated when

A
  • Fibrinogen levels are below 100 mg/dl
  • Heparin interferes with thrombin action
  • Fibrin degradation products are present
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31
Q

Thrombin clotting time (TCT) normal reference value

A
  • 10-15 seconds
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32
Q

Antifactor Xa assay

A
  • Monitors low-molecular weight heparins and danaparoid
  • Rarely warranted
  • Renal disease may result in higher than desirable levels
  • May be ordered factor deficiencies or in patients with lupus anticoagulants
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33
Q

Thrombin clotting time (TCT) reference values

A
  • Not on anticoagulants = 0 units/mL
  • Heparin = 0.3 - 0.7 units/mL
  • LMWH 30 mg twice daily = 0.4 - 1.1 units/mL
  • LMWH 40 mg once daily = 1 - 2 units/mL
  • Danaparoid (Orgaran) = 0.5 – 0.8 units/mL
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34
Q

Bleeding time

A
  • Good for screening platelet disorders
  • Ivy method = forearm with cuff @ 40mm/Hg - < 5 minutes
  • Duke method = ear lobe - < 3 minuts
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35
Q

Lee-White clotting time

A
  • Oldest but least accurate test
  • Time required for clot to form in test tube
  • 4 - 8 minutes is normal
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36
Q

D-Dimer assay

A
  • Protein released during fibrin clot breakdown
  • It is an area of cross-linked fibrin degradation product
  • Detected with an ELISA assay
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37
Q

D-Dimer assay will elevate with

A
  • Deep venous thombosis
  • Pulmonary embolism
  • DIC
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38
Q

Complete blood count

A
  • Includes data on red and white cells
  • Excellent for cell morphology
    lavender top tube - EDTA
  • EDTA prevents platelet aggregation
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39
Q

Red blood cell count

A
  • Expressed as cells per unit volume
  • Biconcave disc 6 - 8 µm in diameter (deeper staining periphery, pale central portion should be 1/3 size of cell)
  • Life span is ~ 120 days
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40
Q

Red blood cell count reference values

A
  • Males 4.6 - 6.2 x 10^6

- Females 4.2 - 5.4 x 10^6

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41
Q

Reticulocytes

A
  • Immature red blood cell
  • Circulates for approximately 24 hours
  • May be referred to polychromatophilia
  • Will increase with anemia when bone marrow is competent
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42
Q

Reticulocytes reference values

A
  • ~ 1% (range 0.5 to 1.8%)
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43
Q

Hemoglobin

A
  • Main component of red blood cells
  • Vehicle for oxygen and carbon dioxide transport
  • Concentration obtained by assessing the specific gravity of whole blood
  • Depth of staining may be a guide
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44
Q

Hemoglobin reference values

A
  • Males - 13.5 - 18 g/dL

- Females - 12 - 16 g/dL

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45
Q

Hematocrit

A
  • Measure of packed red cell volume

- Expressed as a percentage or decimal fraction

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46
Q

Hematocrit reference values

A
  • Males - 40 - 54%

- Females - 38 - 47%

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47
Q

Red blood cell indices

A
  • Calculations based on RBC total, Hb and Hct
  • Help determine the size, contend and HB concentration of the RBC
  • Useful in characterization of anemia
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48
Q

Mean cell volume

A
  • MCV reflects the “volume” of the average cell

- Calculated from the hematocrit and red cell count

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49
Q

Mean cell volume calculation

A
  • (Hct x 1000) / RBC
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50
Q

Mean cell volume reference values

A
  • Males - 80 - 98 fl

- Females - 81 -99 fl

51
Q

Mean cell hemoglobin

A
  • Hemoglobin content or “weight” of average red blood cell

- Calculated from Hb concentrtion and red cell count

52
Q

Mean cell hemoglobin calculation

A
  • Hb / RBC
53
Q

Mean cell hemoglobin reference values

A
  • Males - 26 - 32 pg

- Females - 26 - 32 pg

54
Q

Mean cell hemoglobin concentration

A
  • Ratio of the average amount of hemoglobin divided by the average hematocrit
  • Represents the average amount of hemoglobin in a set amount of packed cells
55
Q

Mean cell hemoglobin concentration calculation

A
  • Hb/Hct
56
Q

Mean cell hemoglobin concentration reference values

A
  • 32 - 36%
57
Q

Red cell distribution width

A
  • An estimate of anisocytosis

- First indicator to change in iron deficient anemia secondary to chronic blood loss or dialysis

58
Q

Red cell distribution reference values

A
  • 11.6 - 14.6%

- Average - 13.1%

59
Q

Erythrocyte morphology color

A
  • A reflection of hemoglobin concentration
  • Normochromic
  • Hypochromic
  • Hyperchromic
  • Anisochromia
  • Polychromatophilia
60
Q

Normochromic erythrocyte

A
  • Center of biconcave disc is ~1/3 diameter of RBC
61
Q

Hypochromic erythrocyte

A
  • Center of biconcave disc is enlarged and paler

- Seen in MCH & MCHC

62
Q

Hyperchromic erythrocyte

A
  • Center of biconcave disc is smaller and stain more deeply

- Megaloblastic anemia

63
Q

Anisochromia

A
  • Reflective of a dimorphic anemia
64
Q

Polychromatophilia

A
  • Reflects the presence of residual RNA within the RBC
  • Cells are larger, may lack central pallor
  • Represents a reticulocyte or immature RBC
  • May be referred to as shift cells
65
Q

Erythrocyte morphology size

A
  • Microcytes
  • Macrocytes
  • Anisocytosis
66
Q

Microcytes

A
  • Abnormally small
67
Q

Macrocytes

A
  • Abnormally large
68
Q

Anisocytosis

A
  • Variation in size

- A feature of most anemias

69
Q

Erythrocyte morphology shape

A
  • Poikilocytosis
  • Elliptocytes
  • Spherocytes
  • Target cells
  • Shistocytes
  • Acanthocytes
70
Q

Poikilocytosis

A
  • Variation in shape

- Tear drop, helment shaped, oval, pear shaped

71
Q

Elliptocytes

A
  • Iron deficiency anemia myelofibrosis
  • Megablastic anemia
  • Sickle cell anemia
72
Q

Spherocytes

A
  • Hereditary
  • Hemolytic disease
  • Splenic condition - hallmark
73
Q

Target cells

A
  • Liver disease

- Any hypochromia

74
Q

Shistocytes

A
  • Megaloblastic anemia

- Microangiopathic hemolytic anemia

75
Q

Acanthocytes

A
  • Crenated cells

- Echinocytes

76
Q

Normocytic anemias secondary to

A
  • Increased blood loss
  • Decreased red cell production
  • Anemia of chronic disease
77
Q

Normocytic anemias are identified by

A
  • Reticulocyte count

- Elevated with increased blood loss

78
Q

Acute blood loss

A
  • Trauma

- “Third” spacing: retroperitoneal pooling

79
Q

Hemolytic disorders

A
  • Hereditary spherocytosis or elliptocytosis
  • Sickle cell anemia
  • G6PD deficiencies
80
Q

G6PD deficiencies

A
  • Moth ball cells
  • Burr cells
  • Vulnerable to oxidation
81
Q

Decreased red cell production

A
  • Reticulocyte count is not elevated

- Primary marrow disease

82
Q

Decreased red cell production other causes

A
  • Human parvo virus B19 - “fifth” disease
  • Decreased erythropoietin production
  • Hypothyroidism
  • Liver disease
83
Q

Anemia of chronic disease

A
  • Associated with chronic inflammatory process (defective red cell production, faulty incorporation of iron)
  • Usually normocytic, normochromic (may border on hypochromic, Hb: 9 – 11 g/dl, MCHC ~32)
84
Q

Macrocytic anemia

A
  • From disorders of DNA synthesis in erythrocyte precursors

- Folate deficiency

85
Q

Folate deficiency

A
  • Absorbed in upper intestine
  • Stores last only a few months
  • Result of drug therapy (Methotrexate, Phenytoin, Bactrim)
86
Q

Macrocytic anemia(megaloblastic)

A
  • B12 deficiency

- Pernicious anemia

87
Q

Pernicious anemia

A
  • B12 absorbed in the ileum
  • Binds with intrinsic factor
  • Neurological disease
88
Q

Pernicious anemia is due to

A
  • Due to gastric mucosal atrophy

- Autoimmune reaction to gastric parietal cells or intrinsic factor

89
Q

Pernicious anemia (megaloblastic) symptoms

A
  • Neurologic
  • Psychologic
  • Cardiac
90
Q

Pernicious anemia diagnostics

A
  • Schilling test
  • Antibody assay for:
  • Abs against parietal cells
  • Abs against intrinsic factor
91
Q

Microcytic anemia

A
  • Hb < 7.5 g/dl

- Decrease in availability or synthesis of Iron, Porphyrin, Globin

92
Q

Microcytic anemia common causes

A
  • Iron-deficiency
  • Thalassemia
  • Sideroblasts
93
Q

Iron deficient anemia physical findings

A
  • Pallor
  • Tachycardia
  • Wide pulse pressure
  • Vertigo and headache
94
Q

Iron deficient anemia laboratory findings

A
  • Low serum iron and ferritin

- Elevated TIBC

95
Q

Properties of iron

A
  • 80% of iron is recycled
  • Erythropoiesis will not increase if transferrin saturation is maintained between 20-60%
  • Iron absorption occurs in the proximal small intestine
96
Q

Daily iron needs

A
  • 1 mg/day – male

- 1.4 mg/day females

97
Q

Transferrin has

A
  • Two iron binding sites

- Clearance of Fe+2 is 60-90 min

98
Q

Erythrocyte sedimentation rate

A
  • Rate at which RBC’s precipitate to bottom of vertical tube
99
Q

Erythrocyte sedimentation rate is influenced by

A
  • Rouleaux formation
  • Red blood cell factors
  • Plasma factors – presence of globulins
100
Q

Erythrocyte sedimentation rate reference values

A
  • Males: 8 mm/hr
  • Females: 15 mm/hr
  • Increases with age
101
Q

Erythrocyte sedimentation rate red cell factors

A
  • Anemia (Hct ~30-40%)
  • Red cell surface area
  • Rolleaux formation
102
Q

Erythrocyte sedimentation rate three main uses

A
  • Detecting inflammatory processes
  • Monitoring disease course
  • Screen for occult neoplastic processes
103
Q

White blood cells

A
  • Granulocytes (neutrophils, eosinophils, basophils)
  • Lymphocytes (T cells, B cells)
  • Monocytes
104
Q

Absolute cell count calculation

A
  • Total # of WBC’s x % cell type
105
Q

ANC (neutrophils) count

A
  • 1800-7000

- No elective procedures below 1000

106
Q

Absolute cell count (ACC) values

A
  • Eosinophils = 100-300
  • Basophils = 40-100
  • Lymphocytes = 1700-3500
  • Monocytes = 200-600
107
Q

Neutrophil reference values

A
  • 12 – 15μ diameter
  • PMN’s: 56%
  • Band cells: 3%
108
Q

Neutrophil role

A
  • First line against bacterial invaders
  • Interact with lymphocytes
  • Activation of complement
  • Phagocytosis
109
Q

Left shift (neutrophils)

A
  • Increase in band cells
  • Overall PMN’s > 75%
  • Infection is winning because you are using your immature PMNs and have pumped out more PMNs
110
Q

Neutrophilia

A
  • Shift neutrophilia
  • Actual influx of band cells from marrow
  • Increase in total number of PMNs
111
Q

Causes of neutrophilia

A
  • Infection
  • Tissue inflammation
  • Surgery – 12-36 hours s/p
  • Tissue trauma/injury
112
Q

Neutrophilia from infection

A
  • Elevation of band cells
  • Decrease in eosinophils
  • Elevation of monocytes
113
Q

Neutrophilia from drugs and chemicals

A
  • Cortisone

- Heavy metals

114
Q

Neutrophilia from tissue trauma

A
  • Surgery

- Crush injuries

115
Q

Neutropenia

A
  • Increased risk of bacterial infection
  • Congenital
  • Chronic infection
  • Nutritional
  • Acquired
116
Q

Nutritional neutropenia

A
  • B12 and folate

- Copper

117
Q

Acquired neutropenia

A
  • Drugs

- heavy metals

118
Q

Eosinophils reference values

A
  • ~ 13μ in diameter

- 3% of leukocytes

119
Q

Eosinophils role

A
  • Modulate the inflammatory response
  • Inactivate mast cells
  • Decrease PMN migration
  • Poor phagocytosis
  • Not bacteriocidal
120
Q

Eosinophilia (CHINA)

A
  • Absolute count > 450/μl (% eos x WBC count)
  • Collagen vascular diseases
  • Helminthic disease (can directly injure larvae)
  • Idiopathic hypereosinophic syndrome
  • Neoplasm (lymphomas, gastric and lung carcinomas)
  • Allergic
121
Q

Basophils reference values

A
  • 10 – 12μ diameter

- 1% leukocytes

122
Q

Basophil role

A
  • Possess IgE receptors

- Tissue mast cells

123
Q

Basophil granules possess

A
  • Histamine

- Slow reaction substance of anaphylaxis

124
Q

Basophilia

A
  • Absolute value: > 50/μl
  • Myeloproliferative disorders
  • Chronic hypersensitivity states

Pod Med II (3 decks)

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