Interpretation of Lab Tests

Question 1

Lab Testing general principles

Answer 1

1-routine testing diff per facility (EKG and preg) 2-indicated testing based on patient disease states 3- timing of testing 60 considered “current”, w/ disease req closer to surgery

Question 2

Hematology Testing: CBC+diff 1/2 WBC count

Answer 2

CBC/diff(measures diff type of leukocytes which aid in Dx, leukocytosis: appy, inflammation, dehydration vs leukopenia: bone marrow failure)

Question 3

Hematology Testing: CBC+diff 2/2 RBC Count

Answer 3

RBC: M4.7-6.0, W4.2-5.4 -transport oxygen/CO2 inbetween tissues/lungs. “Anemia” decr by 10% of NL value: bone marrow failure, GIB, renal failure (no erythropoieten) / Erythrocytosis: dehydration, high altitude compensation, COPD compensation, congenital heart disease. Polycythemia vera = acquired disorder, uncontrolled RBCs production, incr viscosity

Question 4

Indications for CBC/WBC

Answer 4

hemtologic disorder, vascular procedure, chemotherapy, unknown sickle cell status // leukemia/lymphoma, radiation/chemo, susp infection, aplastic anemia, hypersplenism, autoimmune disorder

Question 5

Hematology Testing: Hgb

Answer 5

Main component of RBC. Threshold for non systemic disease patient 7g/dL.Higher threshold in systemic disease, CV disease, elderly, critical pts. M 13.5-17.5, W12-16.

Question 6

Hemoglobin Characteristics

Answer 6

4 polypeptide chains, 2 alpha, 2 beta. Heme molecule in middle in Fe2+ state. Binding site for o2, up to 4 o2 molecules per Hgb. Elevated: COPD, CHF, dehydration, high altitudes. Decreased: anemia, hemorrhage, CRF. incr viscosity

Question 7

Hematology Testing: Hct

Answer 7

“packed cell volume”. # of cells by %, remainder is plasma. Reflective of Hgb and RBC, Hct:Hgb = 3:1. M42-52%, W37-47%. Decreased: hemorrhage, anemia (<30 is mod-severe), leukemia, hemolytic rxn. Increased: dehydration, polycythemia, COPD, congenital heart disease.

Question 8

Hematology Testing: Platelets

Answer 8

> 400,000 = cancer, polycythemia vera. <150,000

Question 9

Indications for H&H

Answer 9

hematologic malignancy, recent radiation/chemo, renal disease, anticoag Rx, high EBL potential, systemic disorders

Question 10

Coagulation Testing: PT (prothrombin time) (factor 2)

Answer 10

NL 10-14 secs, Protein made in liver, dependent on Vit K. Measures VitK dependent factors: 1,2,5,7,10. longer PT with deficient factors, monitors coumadin therapy (2-2.5 x nl). increased: liver disease, cirrhosis, hepatitis, biliary disease (limited bile for fat (vitk) metabolism.

Question 11

Coagulation Testing: Ptt (activated partial thromboplastin time)

Answer 11

NL 25-32 secs. Monitors heparin therapy. Eval clotting factors: intrinsic path 8,9,11,12, common path1,2,5,10 Increased: liver disease, heparin therapy, hemphilia (fx 8=a, 9=b), VW disease. NO SPINAL/EPIDURAL WHILE ON HEPARIN THERAPY, must have normal aPtt.

Question 12

Indications for Coag Test

Answer 12

leukemia, hepatis disease, bleeding disorder, anti coag threapy, severe malnutrition/absorption, baseline for post op anti coag therapy

Question 13

Indications for Chemistry Test

Answer 13

renal disease, adrenal or thyroid disease, chemo, pituitary/hypothalamic disorder, body fluid loss/shifts (bowel prep, lasix), CNS disease

Question 14

Calcium levels and fxn

Answer 14

Total 8.5-10.5, Ionized (non-protein bound-active form we care about, 50%) 4.4-5.4 mg/dL. Fxns: NM transmission, skeletal/cardiac contraction, coagulation, 2nd messenger H-mone release, membrane stability. Total serum levels dependent on albumin levels.

Question 15

Causes // Tx of hypocalcemia

Answer 15

massive transfusion (citrated blood), hypervent (incr pH more pro-bound Ca), hypoPTH (no rls of Ca from bone), VitD insuff (decr GI calc absorption), CRF & hyperphospatemia (inverse to Ca) // Calc Gluc or Calc Chloride (more bio-available, burns inj) 10% over 10m, admin Vitd, monitor ECG

Question 16

Causes // Tx of hypercalcemia

Answer 16

> 14mg/dL!! Bone dumping of calcium overloads capacity to excrete: Most commonly hyper PTH, malignancy. (acidosis shift to more active Ca) // NS infusion, loop diuretic, fix other lyte issues.

Question 17

Signs and Symtpoms: Hypocalcemia

Answer 17

Increased nerve excitability: Paresthesia, confusion, laryngospasm, Trousseau(arm)/Chvosteks(face), Seizures, Prolong QT

Question 18

Signs and Symptoms: Hypercalcemia

Answer 18

Depressed excitability: anorexia, n/v, polyuria, muscle weakness, imparied memory, lethargy/stupor, short QT & prolonged PR

Question 19

Sodium levels and fxn (must assess balance of solute Na and solvent Water, what is the net gain loss of each comparitively)

Answer 19

135-148 meq/L, most abundant ECF ion. Fxn- maintain osmotic gradient, acid base balance, transmit nerve impulses. Reg by: aldosterone (renal retention), ANP (renal secretion), ADH (retain water, salt follows).

Question 20

Causes // Tx hyponatremia

Answer 20

severe vomit/diarrhea, excessive free water intake/SIADH, ascites/peri edema, diuretics. Possibility of cerebral edema as sodium content determines vascular tonicity in brain. Tx: should eval serum osmo/urine Na to determine fluid excess:Na loss balance // fluid restriction, diuresis, poss 3% (symptomatic pts) saline 1-2 cc/kg/hr, goal of 1-2 meq/hr increase, then 10-15 mmol/24 hours.

Question 21

Causes // Tx hypernatremia

Answer 21

dehydration & poor water intake, ID, Cushings syndrome (excess aldosterone). Tx: replacement of water deficit w/ hypotonic solutions (acute hyperNa), Isotonic solutions (chronic hyperNa) then hypotonic once euvolemic, slowed focused process similar to hypoNa tx.

Question 22

Signs and Symptoms: Hyponatremia // hypernatremia

Answer 22

HypoNa: anorexia, n/v, cramps, weakness, confusion, agitation, Sz/coma // HyperNa: thirst, weakness, muscle twitching, irritability, disorientaiton, Sz/coma

Question 23

Chloride measurement // Hypo/Hyper Causes: usually involved with metabolic derangement (r/t bicarb status)

Answer 23

NL 96-106. Ion follow Na, major ECF anion. Fxn: water balance, acid base balance. Hypo: vomit, gastric sxn, metabolic alkalosis (acid lost) & resp acidosis (comp) // Hyper: dehdration, metabolic acidosis (sub bicarb for Cl) and resp alkalosis (comp)

Question 24

Potassium Levels and Fxn

Answer 24

NL 3.5-5meq/L. Major cation of ICF, K is excreted by kidneys w/o resoprtion. Imbalance creates disorder or RMP. Fxn: nerve conduction and muscle fxn, assist in controlling rate/force of cardiac contraction, helps with osmotic and acid base balances

Question 25

Causes // Tx hypokalemia

Answer 25

<3.5 meq/L. Causes: GI loss vomit/diarrhea, acute metab alkalosis (acid shifts), hyperaldosterone (Na in, K out), diuretics (excess renal loss at loop), beta agonists (insulin also) Tx: KCL IV 10-20 meq/hr, ECG

Question 26

Causes // Tx hyperkalemia

Answer 26

> 5 meq/L. Causes: renal failure (unable to remove), acidosis (fluid shift), K sparing diuretics, cell lysis, beta antagonists (block Na/K pump, no K back to cell) Tx: Glucose/insulin (pusk K to cell), Bicarb (for acidosis, push K into cell), Loop diuretic, kayexalate, dialysis, beta agonisits (incr Na/K pump)

Question 27

Signs and Symptoms: Hypokalemia // Hyperkalemia

Answer 27

Hypokalemia: flat t wave, u wave (weak repolarization), wide QRS, fatigue, muscle weakness // Hyperkalemia: tall T wave, prolonged PR, widened QRS, vent dysrhythmias, cardiac arrest

Question 28

Renal Function Tests: BUN, Cr

Answer 28

BUN = 8-20 mg/dL: directly r/t metabolic function of the LIVER & excretory function of KIDNEYs / 50-100 serious impairment, 150-250 severe impairment/renal failure // Cr = M 0.8-1.3mg/dL, W 0.6-1.2mg/dL. More specific measure of renal disease, is a by product of skeletal muscle metabolism (therefore influenced by patients’ muscle mass). Cr rises later then BUN, inverse to GFR representing chronic nature of disease. CrCl most accurate picture of renal disease.

Question 29

Causes of BUN derangements

Answer 29

Elevated: rapid protein catabolism, impaired renal excretion, dehydration, excess protein injestion // Decreased: liver failure (poor hepatic metabolism), overhydration/fluid overload, malnutrition/malabsorption (limited protein intake)

Question 30

Causes of Cr derangments

Answer 30

Increased: impaired kidney fxn, chronic nephritis, urinary tract obstruction // Decreased: reduced skeletal muscle mass

Question 31

Fasting Blood Glucose

Answer 31

70-110 mg/dL, Elevated: DM, CRF, Diuretic therapy, Corticosteroid therapy / Decreased: insulin OD, hypothyroid, liver disease

Question 32

Glycolated Hgb (hgb1ac)

Answer 32

Assess long-term compliance, check RBC glucose (3 month shelf life). Good=12%

Question 33

Therapeutic Rx Levels

Answer 33

Digoxin: 0.5-2ng/ml Toxicity: vision changes, confusion, nausea, vent arrhythmias, AV block (risk incr with elderly, renal insuff, lyte abnls (hypokalemia) / Phenytoin: 10-20mcg/ml