Common Learning Issues:
Cases 371 (1) and 323 (2):
Arterial blood gases (p. 114-119 in Mosby’s; concepts only)
--used to monitor patients on ventilators, monitor critically ill nonventilator patients,
establish preoperative baseline parameters, and regulate electrolyte therapy
1. pH
A. pH= -log[H+]
B. Acids normally found in blood:
I. carbonic acid
II. Dietary acids
III. Lactic acid
IV. ketoacids
2. Pco2
A.
B.
C.
D.
E.
3. HCO3A.
B.
C.
D.
4. Po2
A.
B.
C.
measure of partial pressure of CO2
10% carried in blood; 90% carried in RBCs
Measure of ventilation
Referred to as the respiratory component of acid-base determination
CO2 and pH are inversely proportional
also called CO2 content
measure of metabolic (renal) component of the acid-base equilibrium
Regulated by kidney
HCO3- and pH are directly proportional
Indirect measurement of O2 content
Measure of the tension (pressure)of O2 dissolved in plasma
Pressure determines the force of O2 to diffuse across pulmonary alveolar
membrane
D. Helps determine the effectiveness of oxygen therapy
5. O2 saturation
A. An indication of the percentage of hemoglobin saturated with O2
B. Pulse oximetry
I. noninvasive method of determining O2 saturation
II. measures all forms of hemoglobin saturation including
carboxyhemoglobin (CO poisoning) so if there is CO poisoning, the
oximetry will indicate an inaccurately high O2 saturation
6. O2 Content
A. amount of O2 in the blood (equation on p.118)
7. Base Excess
A. represents the amount of buffering anions in the blood.
I. HCO3- is the largest of these
II. Others include: hemoglobin, proteins, phosphates, etc.
B. Negative base excessmetabolic acidosis
C. Positive base excessmetabolic alkanosis
8. Alveolar (A) to Arterial (a) O2 Differences
A. If A-a gradient is abnormally high, there is a problem in diffusing O2
across the alveolar membrane (thickened edematous alveoli or
deoxygenated blood is mixing with the oxygenated blood)
I. Thick walls: Occurs in patients with pulmonary edema,
pulmonary fibrosis, and acute respiratory distress syndrome
II. Deoxygenated blood mixture: Occurs in patients with septal
defects, AV shunts, etc.
Complete Blood Cell Count and Differential Count (p. 185-186)
--series of tests of the peripheral blood the provides a tremendous amount of information
1. RBC (p.455)
A. # of circulating RBCs in 1 mm3 of peripheral venous blood
B. Normal life span of RBCs is 120 days
C. Lysed and extracted from circulation by spleen
D. Normal Findings (RBC x 106/L)
I. Adult/elderly
a. Male: 4.7-6.1
b. Female: 4.2-5.4
II. Child
a. 2-8 weeks: 4.0-6.0
b. 2-6 months: 3.5-5.5
c. 6 mo.-1 yr: 3.5-5.2
d. 1-18 yrs: 4.0-5.5
III. Newborn: 4.8-7.1
2. Hemoglobin (p.299)
3. Hematocrit (p.295)
4. RBC indices (p.459)
A. Mean Corpuscular volume (MCV)
I. measure of average volume, or size, of a single RBC and is
therefore used for classifying anemias
II. derived by dividing hematocrit by total RBC count
III. If abnormally large, signs on Vitamin B12 or folic acid deficiency
IV. If abnormally small, signs of iron deficiency anemia or
thalassemia
V. Normal findings
a. Adult/elderly/child: 80-95 fL (femoliter)
b. Newborn: 96-108 fL
B. Mean corpuscular hemoglobin (MCH)
I. measure of the average amount (weight) of hemoglobin within an
RBC
II. derived by dividing total hemoglobin concentration by # of RBCs
5.
6.
7.
8.
III. closely resemble MVC
IV. Normal Findings:
a. Adult/elderly/child: 27-31 pg
b. Newborn: 32-34 pg
C. Mean Corpuscular hemoglobin concentration (MCHC)
I. measure of the average concentration or % of hemoglobin within a
single RBC
II. derived by dividing total hemoglobin concentration by hematocrit
III. Normal Findings:
a. Adult/elderly/child: 32-36 g/dL (or 32-36%)
b. Newborn: 32-33 dL (32-33%)
D. RBC distribution width (RDW)
I. indication of the variation in size of RBC
II. helpful in classifying certain types of anemia
III. Normal Findings:
a. Adult: variation of 11-14.5%
WBC count and differential (p.548)
I. Normal Findings:
a. Adult/child>2 yrs: 5,000-10,000/mm3
b. Child <2yrs: 6,200-17,000/mm3
c. Newborn: 9,000-30,000/mm3
A. Neutrophils
I. 55-70%; 2500-8000/mm3
B. Lymphocytes
I. 20-40%; 1000-4000/mm3
C. Monocytes
I. 2-8%; 100-700/mm3
D. Eosinophils
I. 1-4%; 50-500/mm3
E. Basophils
I. 0.5-1.0; 25-100/mm3
Blood Smear (p.749)
A. examine RBCs, platelets, and WBCs
B. can provide information concerning drugs and diseases that affect RBCs
and WBCs
Platelet Count (p.416)
A. measures the number of platelets per mm3
B. platelets formed in bone marrow of megakaryocytes
C. Normal Findings:
I. Adult/elderly: 150,000-400,000/mm3
II. Child: 150,000-400,000/mm3
III. Infant: 200,000-475,000/mm3
IV. Premature Infant: 100,000-300,000/mm3
V. Newborn: 150,000-300,000/mm3
Mean Platelet volume (MVP) (p.419)
A. evaluates platelet disorders, especially thrombocytopenia
B. measure of volume of a large number of platelets
C. MPV is to platelets as MCV is to RBC
D. Normal Findings: 7.4-10.4 fL
Alpha-fetoprotein (p.54-55)
1. test used as a screening marker indicating increased risk for birth defects, such
as fetal body wall defects, neural tube defects, and chromosomal abnormalities
2. Normally produced by fetal liver and yolk sac
3. dominant fetal serum in 1st trimester
4. Also used as a tumor marker
5. Normal Findings:
A. Adult: <40 ng/mL
B. Child younger than 1 yr: <30 ng/mL
C. Ranges vary by weeks of gestation
I. Normally AFP is detected around 10 weeks of gestation
II. Peak levels between weeks 16 and 18
Maternal Screening/ triple test (p.370-372)
1. series of tests that are provided to pregnant women in early pregnancy as a
screening test to identify potential birth defects or serious chromosomal/genetic
abnormalities
2. i.e. tests for down syndrome for pregnant women over 35
3. “double test”: measures hCG and AFP
4. “triple test”: measures hCG and estriol (produced in placenta) and AFP
5. “quadruple test”: measures hCG, AFP, estriol, and inhibin A
Amniocentesis (p.664-667)
1. used to gather information on fetus
2. assesses fetal maturity, fetal distress, risk for respiratory distress syndrome,
genetic abnormalities, neural tube defects, etc.
3. Important in assessing:
A. Fetal maturity status:
I. Lecithin and sphingomyelin (L/S ratio) to evaluate lung maturity
a. lecithin is a surfactant required for alveolar ventilation
b. at 35 weeks, lecithin concentration rapidly increases
c. 2:1 ratio is good (3:1 ratio for diabetic mothers)
II. Phosphatidylglycerol (PG)
a. minor component (10%) of ling surfactant phospholipids
b. produced almost entirely by mature lung alveolar cells
III. Lamellar body count
a. newer; based again on surfactant
b. are concentrically layered structures produced by type II
pneumocytes—looks like an onion and 3 m diameter
c. represent the storage form of pulmonary surfactant
d. indistinguishable to platelets in cell counters
IV. Microviscosity
a. microviscosity in lipid aggregates is dependent on the L/S ratio
and degree of saturation of fatty acid side chains
b. high in early gestation
c. abruptly decreases by 28th to 36th week of gestation
d. measurements are an accurate reflection of surfactant
B. Sex of fetus
C. Genetic and chromosome abnormalities
D. Fetal status affected by Rh isoimmunization
I. If mothers have Rh isoimmunizations, series of amnios are done
during 2nd half of pregnancy to assess the level of bilirubin pigment
II.
The higher the bilirubin, the lower the amt. of fetal
hemoglobin
a. The quantity of bilirubin is used to assess the severity of
hemolytic anemia in Rh-sensitive pregnancies
E. Hereditary metabolic disorders
I. i.e. cystic fibrosis
F. Anatomic abnormalities
I. neural tube defects
II. AFP levels
G. Fetal distress
I. Detected by meconium staining of the amniotic fluid
a. normally colorlessgreen
b. if changes yellowmay be blood incompatibility
c. if changes yellow-brown opaqueintrauterine death
d. if changes redblood contamination from mother or fetus
H. Normal Findings:
I. Weeks gestation
a. 15: 450 mL
b. 25: 750 mL
c. 30-35: 1500 mL
d. full term: >3500 mL
II. Amniotic fluid appearance: clear; pale to straw yellow
III. L/S ratio: >2:1
IV. Bilirubin: <0.2 mg/dL
V. No chromosomal abnormalities
VI. PG: positive
VII. Lamellar body count: >30,000
VIII. AFP: depends of age
IX. Fetal Lung maturity
a. Mature: <260 mPOL
b. Transitional: 260-290 mPOL
c. Immature: >290 mPOL
hCG (p.427-429) (general concepts)
1.
2.
3.
4.
5.
used to diagnose pregnancy
secreted by placental trophoblast
appear as early as 10 days after conception
glycoprotein similar to the pituitary proteins
Methods of testing:
A. Immunologic (Agglutination Inhibition Test) (Blood and Urine)
I. have high false-positive rate
II. antibodies detects whole hCG unit (alpha and beta)
a. cross-reactions with LH
III. completed in 2 min-2hrs
B. Radioimmunoassay (RIA) (serum)
I. highly sensitive detection of beta unit of hCG
II. done in 1-5 hrs
C. Radioreceptor Assay (RRA) (Serum)
I. performed in 1 hr
II. very reliable
III. can measure very minute amounts like in ectopic pregnancies,
early spontaneous abortions, hydatidiform mole of the uterus, and
choriocarcinoma of the uterus
IV. valuable in tumor marker
Coagulation Studies (p.448-450; PT and INR) (p.396-398; PTT) (concepts)
1. PT (prothrombin-time) is used to evaluate the adequacy of the extrinsic
system and common pathway in the clotting mechanism
A. 1st reaction to injury in vessel constriction
B. Next clotting occurs (platelet aggregation)(intrinsic)
2. PT measures the clotting ability of factors I (fibrinogen), II (prothrombin), V,
VII, and X
3. When these clotting factors exist in deficient quantities, PT is prolonged;
many diseases and drugs are associated with decreased levels:
A. hepatocellular liver disease-- (factors I, II, V, VII, IX, and X are
produced in the liver
B. Obstructive biliary disease- bile obstruction secondary to tumor or
gallstones
I. Vit. A, D, E, and K are not absorbed
II. factors II, VII, IX, and X depend on vit. K
III. different from h.l.d give vit. K and if get better, o.b.d.
C. Coumarin ingestion
I. coumarin derivatives dicumarol and warfarin prevent coagulation
4. PT test results were usually given in seconds, but WHO recommended an
international normalized ratio (INR)
Karyotyping (p.173-175)
1. used to study an individual’s chromosome makeup to determine
chromosomal defects
2. 22 pairs or autosomal chromosomes; 1 pair sex ch.
3. most common form of karyotyping is performed by a banding technique to
pair similar chromosomes based on size, location of centromere, banding
patterns, etc.
Gravida-para notation (p.526 in Bates)
1. G = gravida, or total number of pregnancies
2. P = para, or outcomes of pregnancies
3. After para, you will often see the notations:
A. F (full term)
B. P (premature)
C. A (abortion)
D. L (living)
APGAR (p.744-745 in Bates)
1.
2.
3.
4.
5.
key assessment of the newborn immediately after birth
measures heart rate, respiratory effort, muscle tone, reflex irritability, and color
tests at 1 and 5 minutes
based on a 3 point scale (0,1,2)
Must score greater than 7
Vital Signs (p. 758-759 in Bates)
1. Blood Pressure
A. Most easily used measure of systolic bp in infants is the Doppler method
I. detects arterial blood flow vibrations; converts them to systolic
II. systolic pressure gradually increases throughout childhood
a. e.x. normal systolic pressure in males:
1. At birth: 70 mm Hg
2. At 1 month: 85 mm Hg
3. At 6 months: 90 mm Hg
B. Causes of sustained hypertension in newborns include renal artery
disease (stenosis, thrombosis), congenital renal malformations, and
coarctation of aorta
2. Pulse
A. More sensitive to effects of illness, exercise, and emotion than adults
B. Easiest to palpate the femoral artery (inguinal) or brachial (antecubital)
C. Heart Rates:
I. Birth-2 mo: 90-190; average: 140
II. 2-6 mo: 80-180; average: 130
III. 6-12 mo: 75-155; average: 115
D. Rapid pulse count (>180-200/min) usually indicates paroxymal
supraventricular tachycardia
E. Bradycardia may be from drug ingestion, hypoxia, intracranial or
neurologic conditions, or rarely, cardiac arrhythmia
3. Respiratory Rate
A. Greater range in infants than adults
I. Newborns: 30-60 respirations/min
II. Rate can vary; alternating periods of rapid and slow breathing
III. In infancy and early childhood, diaphragmatic breathing is
predominant; thoracic excursion is minimal
B. Common cutoffs for defining tachypnea (a sign of puemonia)
I. Birth-2 mo.: >60/min
II. 2-12 mo.: >50/min
C. Extremely rapid and shallow respiratory rates are seen in newborns with
cyanotic cardiac disease, RL shunting, and metabolic acidosis
D. Fevers can raise respiratory rate 10/min per degree centigrade of fever
4. Temperature
A. Axillary and thermal skin temp. readings in infants are inaccurate
B. Obtaining rectal temp. is relatively simple.
I. Place infant prone
II. insert to 2-3 cm
III. keep in place for at least 2 min.
C. Body temp. in infants is less constant than adults.
I. Average rectal temp is usually above 99.0°F until 3 yrs old
II. May fluctuate as much as 3°F
Cases 363 (3) and 341 (4)
Arthrocentesis (p.673-675)
---with synovial fluid analysis
1. Performed to establish the diagnosis of joint infection, arthritis, crystal-induced
arthritis (gout and psuedogout), synovitis, or neoplasms involving the joint
2. inserting a sterile needle into joint space to obtain synovial fluid
3. Normal Findings:
A. Synovial Fluid: clear and straw colored with few WBCs, no crystals,
good mucin clot
I. bad mucin clot in inflammatory joint disease, rheumatoid arthritis
II. normally about 200 WBCs/mm3 in synovial fluid
B. Chemical test values: approximating those found in bloodstream
I. Glucose determination: normally 10 mL/dL in synovial fluid
a. should be drawn after 6 hrs of fasting
II. Also tested for protein, uric acid, and lactate levels
a. increased uric acid levels—gout
1. urate crystalsgouty arthritis
2. calcium pyrophosphate crystalspseudogout
b. increased protein and lactate levels—bacterial infection
Erythrocyte Sedimentation Rate (ESR) (p.234)
1. nonspecific test used to detect illnesses associated with acute and chronic
infection, inflammation (collagen-vascular diseases), advanced neoplasm, and
tissue necrosis or infarction
2. measurement of rate at which RBCs settle in a saline solution or plasma
3. Normal Findings (Westergren Method):
A. Male: up to 15 mm/hr
B. Female: up to 20 mm/hr
C. Child: up to 10 mm/hr
D. Newborn: 0-2 mm/hr
Antinuclear Antibodies (ANA) (p.90)
1. used to diagnose systemic lupus erythematosus (SLE) and other autoimmune
diseases
2. directed to screen for SLE
3. directed to nuclear materials or to cytoplasmic materials
4. Normal findings: negative at 1:40 dilution
Rheumatiod Factor (RF) (p.471-472)
1. useful in diagnosis of rheumatoid arthritis
A. inflammatory disease that affects joints
B. criteria of diagnosis of RA:
I. morning stiffness for at least 6 wks
II. pain in at least one joint for the preceding 6 wks
III. swelling in at least one join for the preceding 6 wks
IV. Symmetric bilateral joint swelling
V. Presence of subcutaneous nodules
VI. Radiographic changes compatible with RA
C. abnormal immunoglobulin G antibodies produced by lymphocytes in the
synovial membranes act as antigens and other IgG and IgM antibodies
form immune complexes
D. tests for RF are directed toward identification of IgM antibodies
2. Normal Findings: Negative (<60 units/mL)
A. elderly patients may have slightly increased values
Blood Urea Nitrogen (BUN) (p. 533-534)
1. Indirect and rough measurement of renal function and glomerular filtration rate
(if normal liver function exists)
2. Measurement of liver function
3. Amount of urea nitrogen in the blood
A. Urea formed as an end product of protein metabolism and digestion
B. Forms by combining ammonia molecules from the break down of a.a.s
C. If have a high amount of urea in blood signs of renal disease
4. Patients with elevated BUN levels said to have azotemia
5. Patients with decreased BUN levels is a sign on severe primary liver disease
6. Normal Findings:
A. Adult: 10-20 mg/dL (3.6-7.1 mmol/L)
B. Elderly: may be slightly higher then adult
C. Child: 5-18 mg/dL
D. Infant: 5-18 mg/dL
E. Newborn: 3-12 mg/dL
F. Cord: 21-40 mg/dL
Blood Creatinine/ creatinine clearance (p. 204,205,207)
---blood creatinine
1. Creatinine is used to diagnose impaired renal function
2. Test measures amount of creatinine in blood
3. Creatinine is a catabolic product of creatine phosphate, and subsequently
creatinine, depends on muscle mass
A. Creatine phosphate is used in skeletal muscle contraction
4. Creatinine, as in BUN, is excreted entirely by the kidneys
A. With normal renal excretory function, serum creatinine levels should be
constant
5. Unlike BUN, creatinine levels are minimally affected by liver function
6. BUN/ creatinine ratio is a good measurement of kidney and liver function
A. Normal range is 6-25 with 15.5 being optimal adult value
7. Creatinine is used as an approximation of glomerular filtration rate (GFR)
A. In critically ill patients, acute changes in renal function can make realtime evaluation of creatinine levels difficult
B. Cystatin C is used
I. Might predict the risk for developing chronic kidney disease
8. Normal Findings:
A. Elderly: Decrease in muscle mass may cause decreased values
B. Adult: Male: 0.6-1.2 mg/dL Female: 0.5-1.1 mg/dL
C. Adolescent: 0.5-1.0 mg/dL
D. Child: 0.3-0.7 mg/dL
E. Infant: 0.2-0.4 mg/dL
F. Newborn: 0.3-1.2 mg/dL
---creatinine clearance
1. used to measure the GFR of the kidneys
2. Normal Findings:
A. Adult (<40 yrs): Male: 107-139 mL/min Female: 87:107 mL/min
B. Values decrease 6.5 mL/min/decade of life after age 20 yrs with decline
in GFR
C. Newborn: 40-65 mL/min
Vertex presentation (Stedman, p.1557)
1. presentation of any part of the fetal head during birth
2. head /neck is in flexion so chin is pushed against chest
3. May be different degrees of flexion
Congenital Adrenal Hyperplasia (Cecil, p.683)
1. Refers to disorders of adrenal steroid biosynthesis that result in glucocorticoid
and mineralocorticoid deficiencies
2. Because of deficient cortisol biosynthesis, increase in ACTH occurs, inducing
adrenal hyperplasia and overproduction of steroids that precede blockage of
enzyme production
3. 21-Hydroxylase (CPY21) deficiency is the most common (95% of patients)
A. Failure of 21-hydroxylation of 17-hydroxyprogesterone and
progesterone to 11-deoxycortisol and 11-deoxycorticosterone,
respectively, with deficient cortisol and aldosterone production
4. Aim of treatment for classin 21-hydroxylase deficiency is to replace
glucocorticoids and mineralocorticoids, suppress ACTH and androgen
overproduction, and allow for normal growth and sexual maturation in children
Southern Blot (Marks, p.299)
1. Developed by E. M. Southern
2. used for identifying DNA sequences on gels
3. southern blots are produced when DNA on a nitrocellulose blot of an
electrophoretic gel is hybridized with a DNA probe
4. Northern blots are produced when RNA is hybridized with a DNA probe
5. Western blot involves spreading proteins by gel electrophoresis and probing
with labeled antibodies for specific proteins
Case 364 (5)
Fremitus (Bates’, p.298)
1. Fremitus refers to the palpable vibrations transmitted through the
bronchopulmonary tree to the chest wall when the patient is speaking
2. Fremitus is decreased or absent when the voice is soft or when the transmission
of vibrations from the larynx to the surface of the chest is impeded
3. Causes:
A. very thick chest wall
B. obstructed bronchus
C. COPD
D. separation of the pleural surfaces by fluid (pleural effusion)
E. Fibrosis (pleural thickening)
F. air (pneumothorax)
G. tumor
Hyper-resonance (Bates’, p.300-301)
1. Very loud, lower pitch, longer duration
2. Generalized hyper-resonance may be heard over the hyper-inflated lungs of
COPD or asthma, but it is not a reliable sign
3. Unilateral hyper-resonance suggests a large pneumothorax or possibly a large
air-filled bulla in the lung
Medication Class/ General Function (Golan)
1. Hydrochlorothiazide
A. protypical thiazide diuretic (inhibits sodium reabsorption in the distal
convoluted tubule)
B. decreases glucose tolerance and may unmask diabetes
C. predisposes to torsades de pointes
2. Ibuprofen
A. NSAID
B. derivative of propionic acid
C. used primarily for analgesia and anti-inflammatory action; lower
incidence of adverse effects than aspirin
3. Salsalate (see salicylates)
A. includes aspirin (acetylsalicylic acid) and its derivatives
B. oldest NSAID
C. widely used to treat mild-to-moderate pain, headache, myalgia, and
arthralgia
4.
5.
6.
7.
8.
9.
D. in contrast to other NSAIDs, aspirin acts in an irreversible manner by
acetylating the active-site serine resudue in both COX-1 and COX-2
E. May inhibit neutrophil oxidative burst by reducing NADPH oxidase
activity
Triamcinolone
A. An inhaled glucocorticoid
B. Used for treatment of asthma
C. inhibits airway inflammatory responses, especially eosinophil-mediated
inflammation
D. Thought to inhibit cytokine release
Betamethasone (corticosteroid)
A. Major preventative treatment fir patients with asthma
B. increases the transcription of genes coding for -adrenergic receptors
and a number of anti-inflammatory proteins
C. Reduces vascular permeability in airway
Naproxen
A. Proprionic acid derivative
B. more potent that ibuprofen; administered less frequently
C. can cause GI complications ranging from dyspepsia to bleeding
Acetaminophen (paracetamol)
A. preferentially reduces central prostaglandin synthesis
B. In a class of compounds that has analgesic and antipyretic effects but not
anti-inflammatory
C. Frequently paired with weak opioids (codeine, hydrocodone,
oxycodone, etc.)
Hydrocodone
A. Opioid used for pain control
B. more effective analogue of codeine that are readily orally
Penicillin
A. Inhibits synthesis of bacterial cell walls (peptidoglycan)
I. Bacteria’s cell wall important for tensile strength
II. Gram-positivepurplelarge peptidoglycan coat
III. Gram-negativepinkthin peptidoglycan coat between 2 c.ms
B. Treats bacterial infections
Know the values for the normal EKG as presented in the case:
Reference Range
PR
(0.12 - 0.20 sec.)
QRS
(up to 0.10 sec.)
QT
(0.32 ±0.4 at HR 100, 0.40 ± 0.04 sec. at HR60)
QRS axis frontal plane:
(-30o to +90o)