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
Sign: 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
Complication: 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
Surgeons: -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
Internists: -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
ob/gyn
peds
ER
psychiatry
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
-DVT
-cholelithiasis/pancreatitis
-eclampsia/hypertension
-hyperthyroidism
-HIV
How we get sick: -trauma
-heredity
-infection
-autoimmune disease
-malignancy
-aging/degeneration
-bahvior/environment
-pregnancy
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: 1895
Wilhelm Konrad Roentgen
passed current through cathode ray tube
widespread use by 1913
introduction of CT scan: 1971
introduction of MRI: 1980
Introduction of US: first in 1940s
accredited medical purposes 1950s
Non ionizing radiation modalities: ultrasound
MRI
Ionizaing radiation modalities: conventional radiographs
fluoroscopy
CT scans
nuclear imaging modalities
RAD: Radiation absorption dose
amount of radiation your body was exposed to
REM: 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
Radiolucent: xrays pass through
picture is dark
radiopaque: xrays bounce off (dont pass through)
picture is light
radiographic appearance is determined by:: atomic number
thickness
overlap of structures
objects shape
distance from film
object density
radiographic densities (darkest to lightest): air - darkest
fat
soft tissue (muscle)/ fluid
bone
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)
CT: computerized tomography
uses ionizing radiaiton (like xray)
rapid scanning
axial plane ONLY
visualizes bone better than soft tissue
Fluoroscopy: 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
noninavasive
portable
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
neonatal
MRI: -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
T1: -time to recovery
-longitudinal relaxation time
-fat appears white
-air cortical bone, CSF appears dark
T2: 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
implants
-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
technetium-99m: -most useful tracer
-inexpensive
-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
gadolinium: -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,
Colonization: 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: UTI
pneumonia
surgical wound infection
vascular access infection
clostridium Difficile colitis
UTI: 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
biofilm: -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: endocarditis
staph on aortic valve
pulmonary abcess
Surgical wound infection: -contamination with bacteria during procedure
-skin or viscera
-foreign body (suture material)
-poor surgical technique
-malnutrition
Factors the predipose to postoperative infections: -malnutrition
-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: penicillin
vancomycin
cephalosporins
Antibiotics that work by inhibition of protien synthesis: macrolides
tetracycline
aminoglycosides
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?: MRSA
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
Pathogenesis: -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
Etiology: what sets the disease process in motion
morphology: fundamental structure or form of cells or tissues
Histology: study of cells and extracellular matrix of body tissues
epidemiology: -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
incidence: number of new cases arising in a population during a specified time
prevalence: number of people in a population who have a particular disease at a given point in time
Motality: death
Morbidity: effects an illness has on a person's life
syndrome: compilation of signs and symptoms that are characterisitc of a specified disease state
eg chronic fatigue syndrome
sequelae: lesions or impairments that follow or are caused by disease
diagnosis: designation as to the nature or cause of a health problem
reliability: extent to which an observation, if repeated, gives the same result
validity: extent to which a measurement tool measures what it is intended to measure
Sensitivity: proportion of people with a disease who are positive for that disease on a given test
Specificity: 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
prognosis: 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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