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Gen Med Intro


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Symptom (defined by stedmans medical dictionary)
Any morbid phenomonon or departure from the normal in function, appearance, or sensation, experienced by the patient and indicative of disease
any abnormality indicative of disease discoverable by the physician (PA) at his or her exam of the patient.
Symptom (generic definition)
indicator of disease as interpreted by the patient
Sign (generic definition)
objective finding of the examiner
morbid process or event occuring during a disease which is not an essential part of the the disease, although it may result from it or from dependent causes
-concerned with the technical aspects of performing procedures
-perform minimally invasice procedures
-use real time imaging to guide procedures
-utilize lasers to cut and obliterate tissues
-trasplant organs
-perform highly specialized invasive procedures
-stent occulded vessels
-perform gi and pulmonary endoscopy
-transplant cells/tissue
-deal with end-of-life treatment
Current medical specialties
family medicine
internal medicine
general surgery
Aspects of Prevention
-dietary restraint;moderation of calories; low Na, saturated fats, trans fatty acids, and simple CHO
-regular strenuous exercise and strengh training
-maintain adequate bone density
-avoid risky behavior (drugs, tabacco, EtOH)
-dental hygeine
-quality sleep
-minimize stress
-regular physicals and surveillance for common diseases
Regular Health Monitoring should include:
-routine blood and urine screens
-fecal occult blood
-breast exam and mammogram
-digital rectal exam + PSA
medical conditions in pregnancy
-gestational diabetes
How we get sick
-autoimmune disease
Diseases that have no defineable single cause are likely due to...
a combination of:
-genetics (multiple alleles with incomplete penetrance),
- environment (and behavior)
- infection (active, latent, or past)
- bodies overall response
eg. artherosclerosis
how immune system normally functions
Normally, thymus removes lymphocytes that are capable of attacking normal cells
normally, bone marrow removes B cells that are self reactive
Immune attack may be triggered by...
-alterations to cell surface antigens by viral infection
-deposition of foreign protein
-antigen-antibody complex deposition
-lack of immune suppressor cells (supressor T cells)
Environmental factors c autoimmune diseases
tissue damage from infection, toxic exposure causes activation of monocytes
molecular mimicry
infectious organisms express antigens similar to self-antigens
eg. rheumatic fever, beta-hemolytic streptococcus infection
Discovery of xray
Wilhelm Konrad Roentgen
passed current through cathode ray tube
widespread use by 1913
introduction of CT scan
introduction of MRI
Introduction of US
first in 1940s
accredited medical purposes 1950s
Non ionizing radiation modalities
Ionizaing radiation modalities
conventional radiographs
CT scans
nuclear imaging modalities
Radiation absorption dose
amount of radiation your body was exposed to
Radiation effect in man
amount of biological damage recieved from the exposed radiation
lethal dose of radiation exposure
5000 RADS
(kills 50% of humans)
High doses of radiation cause..
hematologic effects
Prolonged repeated exposure to radiation causes...
accelerated induction of malignant disease
Lifetime permissable dose of radiation
RADS = 5 x (age -18)
Health care workers permissable exposure to radiation
whole body/gonads/eye lens: 5 RADs/year (5000 mrads)
hands/forearms/feet: 75 RADs/year
how an xray is generated
-an anode (tungsten or molybdenum) is bombarded with electrons from a cathode
- xrays pass through pt and expose the film
use of fluorescent sheets in xrays
-fluorescent sheets glow after xray to lengthen exposure (bc xrays require long exposure for film development).
-reduces length of exposure to xrays for pt
xrays pass through
picture is dark
xrays bounce off (dont pass through)
picture is light
radiographic appearance is determined by:
atomic number
overlap of structures
objects shape
distance from film
object density
radiographic densities
(darkest to lightest)
air - darkest
soft tissue (muscle)/ fluid
non-physiologic density - lightest
radiographic density is...
sum of all densities and thickness interposed between the xray beam source and the film
the greater the difference in adjacent densities....
the sharper the border
when similar densities are in the same plane...
borders become indistinct and blend together into 1 common density
overpenetrated xray
over exposed
radiographs are too dark
too many RADs
radiographic projections describe...
path of the xray beam

eg. AP, PA, lateral, oblique
object is clearest when it is..
up against the film (or as close to the film as possible)
computerized tomography
uses ionizing radiaiton (like xray)
rapid scanning
axial plane ONLY
visualizes bone better than soft tissue
real time visualization
continuous xray beam
fluoroscopy uses
venous and angiographic procedures
fracture reduction
Diagnostic ultrasound
-non ionizing radiation
-sound waves generated and reflected back (sends and catches sound waves)
-frequency is >15,000 cycles
advantages of US
easy to use
can insert into every orifice
disadvantage of US
bone and air filled structures interfere with image
indications for US
gall bladder disease
arterial and venous pathology
ob/gyn diagnostics
-pt placed at core of large magnet
-radiowaves passed through body in a particular sequence of very short pulses
-waves knock hydrogen atoms (in fat and water) out of alignment
-hydrogen atoms eventually re-establish the previous equilibrium/alignment with the surrounding magnet
-causes absorbed radiowaves to be emitted
-SO each pulse causes a responsing pulse of radio waves to be emitted from the patients tissue
-location from which the signals have originated is recorded by a detector and sent to a computer
relaxation time on MRI
-time required by H+ atom to regain equilibrium state (get back into alignment in the magnetic field)
-has an initial energy when it is knocked into a higher orbit and another energy when it comes back down to original orbit
2 relaxation times
T1- time to recovery
longitudinal relaxation time

T2 - time to relaxation
transverse relaxation time
-time to recovery
-longitudinal relaxation time
-fat appears white
-air cortical bone, CSF appears dark
time to relaxation
transverse relaxation time
blood, CSF appears white
MRI can visualize
-gray matter vs white matter
-better for visualizing soft tissues
-different views (not just axial view like CT scan)
advantages of MRI
-utilizes non-ionizing radiation
-can scan in multiple planes
-can scan in 1 mm to several cm increments
-better soft tissue detail
-noninvasive evaulation of cerebral blood vessels (MRA angiogram)
disadvantages of MRI
-poor bone detail
-longer scanning time than CT (~1 hr per body part)
-cant be scanned with certain kinds of metal
-poor quality of images of abdomen and chest due to breathing and peristalsis (takes slow pics so anything moving results in poor quality pics)
radioisotope scanning
-visualize living organs and tissues (measures physiology)
-attach radioactive tracer to something that is taken up into the cells
-isotope emits gamma rays for breif period of time
-ray are recorded by gamma camera
radioisotope scanning can identify:
bone cancer
occult fx
pulmonary emboli
thyroid cancer
cardiac ischemia
kidney not working
-most useful tracer
-short half-live (so doesn't expose to as much radiation)
-readily available from portable generator
-high concentrations of isotope will congregate in tissues with inc metabolism
-gives less precise anatomic information
technetium 99m pertechnetate
trapped by thyroid
technetium 99m macroaggregated albumin
trapped by thyroid gland
technetium 99m methylene diphosphonate
trapped by bone tissue
used for bone scan
thallium 201
used for evaluation of myocardial blood flow
iodine 131
for thyroid imaging
cardiac thallium scan
used to eval heart
can do in real time to see movement of heart
iodine contrast
-water soluble
-can be given IC, IA, intrathecal, endobronchial, directly to GI
-risk for allergic rxn
-can cause renal failure
-contraindicated in renal insufficiency
barium contrast
-water insoluble
-given po or rectally
-good for GI tract imaging
-very irritating if GI tract is perforated
-risk of fecal impaction, aspiration, perforation
gastrograffin contrast
-water soluble
-iodine based contrast
-good for GI tract imaging, but not as good as barium
- used if GI tract perforation is suspected
-promotes peristalisis
-may cause serious lung edema in cases of esphageal-trachea fistulas
-rare earth, metallic, paramagnetic contrast
-used only for MRI enhancement
-no risk of allergic rxn
-nontoxic to kidneys
microbial entry sites
respiratory, GI, GU, skin, conjunctiva
Microbial adherence
anchorage to tissue or tissue matrix
growth after entry depedns on...
temp, pO2, pH, nutrients,
present but no an infection
Nasocomion infections
infections aquired during the process of getting treatment for other problems (usually hospital acquired infections)
2,000,000 pts
88,000 deaths
$4.5 billion
Common nasocomial infections
surgical wound infection
vascular access infection
clostridium Difficile colitis
Urinary tract infection
often due to foley catheter
What is most important factor that correlates the incidence of infection in a pt with an indwelling urinary catheter?
amt of time catheter is in
-collection of microorganisms surrounded by the slime they secrete
-99% of all bacteria live in biofilm communities
-interfere with antiobiotic efficiency and enhance accumulation of bacteria
Hospital aquired pneumonia
-host unable to clear bronchial secretions
-unable to sustain immune response to bacteria in lung tissue
-microbes often more virulent and resistant to standard bacteria
Hospital aquired pneumonia is common in...
mechanical ventilator pts (bacteria forms a biofom around the endotracheal or traceostomy tubes)
Vascular access infection
due to infected ports from IV sites
Risks of infections IV site infections
staph on aortic valve
pulmonary abcess
Surgical wound infection
-contamination with bacteria during procedure
-skin or viscera
-foreign body (suture material)
-poor surgical technique
Factors the predipose to postoperative infections
-compromised immune sys (HIV, elderly, diabetes, malignancy, chemo)
-impaired vascular supply (vascular dz, radiation therapy can damage microvasculature)
initiating events for Clostridium Difficile pathogenesis
-exposure to antibiotics - usually broad spectrum (inhibits normal intestinal bacterial flora so C.Diff can now colonize it)
-established susceptabiility to infection
Drug resistant bacteria
1. methicillin-resistant staphylococcus aureus (MRSA)
2. vancomycin resistant enterococcus (VRE)
3. fluoroquinolone resistant gram negatives
How do most antibiotics work?
-inhibition of cell wall synthesis
-inhibition of protain synthesis
-inhibition of DNA synthesis/transciption
Antibiotics that work by inhibition of cell wall synthesis
Antibiotics that work by inhibition of protien synthesis
antiobiotics that work by inhibtion of DNA synthesis/transciption
quinolones (inhibits DNA gyrase)
Mechanism of antiobiotic resistace for MRSA
-methicillin resistant staph aureus
-bacteria produce beta lactamase (gram neds already produced it, gram pos learned to synthesize it d/t transfer of DNA instructions from other bacteria
-production of beta lactamase by bacteria destroys antibiotic, so beta lactames (of the antibiotics) are ineffective in inhibiting cell wall synthesis
Mechanism of antibiotic resistance for VRE
-appeared in 1988
-alteration of cell wall peptide
- so no longer allows vancomycin to interferes with cell wall synthesis
-DNA instructions for new cell wall found in plasmids
Mechanism of antibiotic resistance for fluoroquinolone resistane gram negatived
-widespread use of antibiotic
-mutation of DNA gyrase so no longer effective
-some bacteria developed ability to expel drug from bacterial cytoplasm
-most likely due to mutation of bacteial DNA
Roles of animals in spread of resistance
-farmers use cipro in food/drink of chicken and turkeys to make the animals bigger
-so common resevoir for antibiotic resistance
Children are common resevoirs for what resistance?
Mechanisms to overcome bacterial resistance
-follow hygienic practices
-synthesis of agents with improved antimicrobial activity
-antibiotic control programs
-prescribe judiciously
-pharm industry should be more limtied in promotion of antibiotic use
Etiologic Factors
-causes of disease
-includes biologic agents (bacteria, viruses), physical forces (trauma, burns, radiation), chemical agents (poisons, alcohol), nutritional deficits/excesses
risk factors
factors that predispose to a particular disease
-sequence of cellular and tissue events that take place from the time of intial contact with an etiologic agent until the ultimate expression of the disease
-how the disease process evolves
what sets the disease process in motion
fundamental structure or form of cells or tissues
study of cells and extracellular matrix of body tissues
-study of disease in populations
-used to study spread of disease, risk factors for multifactorial diseases
-looks at patterns such as race, ditery habits, age, lifestyle, geographic location etc
number of new cases arising in a population during a specified time
number of people in a population who have a particular disease at a given point in time
effects an illness has on a person's life
compilation of signs and symptoms that are characterisitc of a specified disease state
eg chronic fatigue syndrome
lesions or impairments that follow or are caused by disease
designation as to the nature or cause of a health problem
extent to which an observation, if repeated, gives the same result
extent to which a measurement tool measures what it is intended to measure
proportion of people with a disease who are positive for that disease on a given test
proportion of people without a disease who are negative for that diseasee on a given test
positive predictive value
refers to proportion of true-postives that occur in a given population
negative predictive value
true-negatives that occur in a given population
preclinical stage
not clinically evident but destined to progress to the clinical disease
subclinical disease
not clinically apparent and not destined to become clincally apparent
Clinical disease
manifested by signs and symptoms
natural history
progession and projected outcome of a disease without medical intervention
probable outcome and prospect of recovery from a disease
primary prevention
keeping disease from occuring by removing all risk factors
eg. immunizations
secondary prevention
early detection so disease is still asymptomatic and treatment measure can affect a cure
eg pap smear for early detection of cervical CA
tertiary prevention
clinical interventions that prevent further deterioration or reduce complications of disease once it had been diagnosed

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