Lecture 1: Diagnostic and Therapeutic Techniques Flashcards
What is step 1 of diagnosing?
Recognizing the S/S of an infection.
What are some general symptoms of infection?
Fatigue
Fever
Chills
What are some skin/wound symptoms of infection?
Redness
Swelling
Tenderness
Discharge
What are some lower respiratory tract symptoms of infection?
Productive cough
SOB
Pleuritic chest pain
What are some upper respiratory tract symptoms of infection?
Congestion
Discharge/drainage
HA/pain/pressure
What are some abdominal symptoms of infection?
Abd pain
N/V/D
What are some GU symptoms of infection?
Pain/burning upon urination
Vaginal/urethral discharge
What are some neuro symptoms of infection?
HA
Confusion
AMS
What are some MSK symptoms of infection?
Arthralgia
Edema
Erythema
Warmth
What are some general signs of infection?
Fever
Tachycardia
What are some skin/wound signs of infection?
Erythema
Edema
Discharge
Lesions
What are some lower respiratory tract signs of infection?
Wheezing/rhonchi/rales
Dullness to percussion
Hypoxia
What are some upper respiratory tract signs of infection?
Ears: bulging, erythematous TMs
Nose: Edematous, eythematous nasal mucosa/turbinates, sinus tenderness.
Throat: Erythematous oropharyngeal mucosa, tonsillar hypertrophy, exudates.
What are some GI signs of infection?
Abd tenderness
Increased bowel sounds
What are some GU signs of infection?
Cloudy/dark urine
Vaginal/urethral discharge
Lesions/sores
What are some neuro signs of infection?
Papilledema
Meningeal signs
Focal neurologic deficits
What are some MSK signs of infection?
Tenderness
Joint effusion
Decreased ROM
What is step 2 of diagnosing an infection?
Confirming the presence of an infection.
What is the category we are concerned with in a CBC regarding infection?
Leukocytes, which are typically ELEVATED in the presence of an infection.
What are the granulocytes and agranulocytes?
Granulocytes: Neutrophils, Eosinophils, Basophils
Agranulocytes: Lymphocytes, monocytes
What is the general proportion of leukocytes in the blood?
Neutrophils: 60-70%
Lymphocytes: 20-30%
Monocytes: 1-6%
Eosinophils: 1-3%
Basophils: <1%
Never Let Monkeys Eat Bananas
When are neutrophils typically elevated?
Bacterial infections
Sometimes fungal infections and general physiological stress.
What is a left shift and what does it indicate?
Increased presence of IMMATURE neutrophils.
Suggests Acute/early bacterial infection.
When do I see lymphocytosis?
Mainly in viral infections.
Leukemias and lymphomas as well.
What is the most common WBC in lymph?
Lymphocytes
What is the largest WBC?
Monocytes
When are monocytes typically elevated?
Late/chronic infection.
When are eosinophil counts elevated?
Allergic
Parasitic
Chronic skin conditions
When are basophil counts elevated?
Hypersensitivity reactions
Note:
Least common cause of leukocytosis.
What is a clean catch?
Collecting a clean urine sample that has typically only been in the bladder for 2-3 hours max.
What does getting a clean catch require?
Women must clean the labia.
Men must clean the head of the penis.
Children must be potty trained. If not, catherization will be used.
Describe the clean catch process.
Clean GU area.
Pee a little into the toilet.
Stop and then pee the cup to the marker.
Close the cup with the lid, never touching the inside of the cup.
Note:
If at home, refrigerate in a plastic bag afterwards.
What does a cloudy/turbid urine suggest?
Pyuria. (color)
What does a strong/fishy odor urine suggest?
Infection. (odor)
What main things are we testing for in a dipstick test of urine?
Leukocyte esterase
Nitrites
Blood
What are we looking for in a microscopic examination of urine?
WBCs
RBCs
Microorganisms
Casts
What does elevated leukocyte esterase suggest?
Increased WBC count and therefore infection.
Note:
Enzyme made by WBCs.
What does elevated nitrites suggest?
Presence of G- bacteria.
What does presence of casts indicate?
Kidney infection
When is a wet mount/KOH prep used?
Primary indication for vaginal/cervical/urethral discharge.
What is a wet mount used to observe?
Looking for microorganisms.
Clue cells indicate bacterial vaginosis.
Protozoans indicate Trichomonas
What is a KOH prep used to observe?
Fungal cells.
Note:
KOH degrades skin cells.
Can a wet mount be used to identify bacteria?
NO.
What does a clue cell look like?
Stippled appearance, covered in bacteria.
See slide 32 for visual
What is the purpose of an LP?
Obtain CSF for analysis
Therapeutic:
Relieve ICP
Administer intrathecal medications.
When are LPs indicated?
Sudden/severe HA and/or stiff neck.
Fever
Confusion, hallucinations, seizures, difficulty with speech, light sensitivity, dizziness, lethargy, and muscle weakness.
What positions are used for an LP?
Lateral decubitus is used when opening pressure is needed.
Upright, hunched over position is used when opening pressure is not needed.
What are the two pops I will feel on an LP?
Pop 1 will be the ligamentum flavum.
Pop 2 will be the dura mater.
Where is an LP performed?
Around L4-L5 vertebral level.
How many tubes do I get when collecting CSF? Why?
4
- Cell count and Diff
- Glucose and protein levels
- Gram stain, C&S
- Other
If my CSF looks yellowy, what is that called and what is it indicative of?
Xanthochromic.
Bleeding!!
What is the normal viscosity of CSF?
Same as water.
Thicker would imply an infection or malignancy.
What does presence of RBCs in tube 1 indicate?
CNS bleed
OR
Traumatic tap
How does an adult and neonate WBC range differ for tube 1?
Neonates can go up to 30 WBCs before being considered abnormal.
What kind of glucose abnormality indicates infection or malignancy in tube 2?
Low glucose.
What does elevated protein in tube 2 suggest?
Infection
Malignancy
Autoimmune disease
What is the purpose of tube 4?
So we can do other specific tests if needed.
Which type of meningitis causes extremely high opening pressure?
Bacterial
What is the main complication that occurs with LPs?
HA
Why are LPs relatively contraindicated in patients with increased bleed risk or increased ICP?
Hemorrhage may occur with increased bleed risk.
Cerebral herniation may occur with increased ICP.
How is pleural fluid obtained?
Thoracentesis
When is a thoracentesis for pleural fluid indicated?
Pleural effusion
What is measured on a microscopic fluid analysis of pleural fluid?
Total cell counts
Cytology
Define transudate.
Imbalance between the pressure within blood vessels and the amount of protein in blood, resulting in the abnormal accumulation of fluid.
What is the most common cause of transudate?
CHF
What does transudate look like?
A clear fluid with low protein/albumin/LDH and low cell count.
Define exudate.
Caused by injury or inflammation of the pleura, resulting in a pleural effusion.
What are the etiologies of an exudate?
Infectious diseases
Bleeding
Inflammation
Malignancies
What does exudate usually look like?
Cloudy fluid with a high protein/albumin/LDH and high cell count.
What is Light’s criteria? When do I use it?
Classifying pleural fluid as transudative or exudative.
Likely exudative if at least one of these conditions exist:
Pleural fluid protein:serum protein ratio > 0.65
Pleural fluid LDH: serum LDH ratio > 0.6
Pleural fluid LDH > 0.6 or >2/3 times the normal upper limit for serum LDH
AKA transudates are low in protein and LDH and exudates are high in proteins and LDH
What does a milky pleural fluid suggest?
Lymphatic system involvement
What does a reddish pleural fluid suggest?
Presence of blood.
What does a cloudy/thick pleural fluid suggest?
Presence of microorganisms and/or WBC.
If I have decreased glucose in my pleural fluid, what does that suggest?
Infection.
Decreased pH on top of that would indicate malignancy.
How does infectious pleuritis affect lactate levels in pleural fluid?
Increases it.
What does increased amylase in my pleural fluid suggest?
Pancreatitis
Esophageal rupture
Malignancy
What does increased TG in my pleural fluid suggest?
Lymphatic system involvement.
What is the purpose of a pericardiocentesis?
Obtain pericardial fluid to diagnose the cause of pericarditis or a pericardial effusion.
What is a key PE finding that suggests pericarditis?
CP that is relieved by bending forward.
Where is a pericardiocentesis performed?
Subxiphoid process with a 40deg angle towards the left shoulder.
Inserted between the xiphoid and left costal margin
What is a water bottle sign?
Shape of a cardiac silhouette on CXR, caused by pts who have very large pericardial effusions.
See slide 57 for visual.
What is the purpose of a paracentesis?
Diagnose the cause of peritonitis or ascites.
What is the purpose of an arthrocentesis?
Diagnose the cause of a joint effusion.
What is the purpose of a diagnostic CXR?
To help diagnose a pulmonary infection when S/S are present.
What is the purpose of a screening CXR?
Screening for pulmonary infections, masses, trauma, and other pathologies.
What does lobar consolidation look like on CXR?
Thickened lobes.
See slide 68 for visual.
What does patchy nodular infiltrate look like on CXR?
Patches of sparse, white everywhere.
See slide 68 for visual.
What does a CXR ultimately offer?
A diagnosis, but not the underlying cause.
What are CTs good for?
Quick scans that give great bone detail and can use contrast to highlight certain structures.
What are MRIs good for?
High-res of soft tissue and the ability to use contrast to highlight certain structures.
What are the cons of CTs and MRIs?
CT cons:
Radiation exposure is a lot.
MRI cons:
Long scan time
Safety issues with indwelling metal
Small imaging space
What is step 3 of diagnosing a patient?
Determining the actual source/pathogen causing the infection via gram stain and cultures.
What do G- bacteria have that G+ don’t?
An outer lipopolysaccharide wall and outer membrane.
Describe the process of a gram stain.
Slide stained with crystal violet dye.
Gram’s iodine solution added to improve adherence.
Decolorization with ethyl alcohol and acetone.
G+ with thick cell walls will retain the dye, so they look purple.
G- with thin cell walls decolorize.
Counterstain with safranin red turns G- pinkish red and G+ stay purple.
What color do atypicals stain?
None.
They are atypical because they do not stain either color.
What are the two main types of G+ cocci?
Strep (alpha, beta, and gamma hemolytics)
Staphylo (S. aureus mainly)
What are the two main shapes of G- bacteria?
Cocci
Rods (Majority)
What happens if a culture comes up positive? Negative?
Positive is highly suggestive of cause of infection.
Negative does not rule out.
Could be due to insufficient bacteria quantity
Viral infection
Previous ABX use by pt.
If I want to treat a patient empirically, do I collect samples prior or post?
PRIOR to beginning ABX!
How long does it take for culture results?
Bacteria can take 24-72 hours.
Fungal and mycobacterial can take even longer.
When are blood cultures ordered?
Bacteremia/septicemia.
How do I order blood cultures?
2 samples from 2 or more locations.
How do I interpret blood cultures?
Both positive for same organism = positive culture.
1 positive, 1 negative = retest, possible contamination.
Both negative = negative culture.
When are wound cultures ordered?
Draining of fluid or pus
Heat, redness, swelling, tenderness at site
Wound that is slow to heal
When are stool cultures ordered?
Suspected GI infections.
It is only for extended diarrhea, ingestion of suspected contaminated food, or recent travel outside of US.
DO NOT ORDER on everyone with GI symptoms.
What are stool cultures usually evaluating for?
Common intestinal bacterial pathogens like E. coli, Salmonella, Shigella, or Campylobacter.
How do you evaluate for parasites in stool?
Stool for Ova and parasites must be added onto order.
What is the most common source of a UTI and how is it treated?
E. Coli
Treated empirically.
What indicates a positive urine culture?
> = 100,000 colonies of a SINGLE bacteria.
What is a sputum culture indicated for?
Bacterial infection in the lungs, usually pneumonia.
What does rust colored sputum suggest?
Strep Pneumoniae
What does yellowish/green sputum suggest?
Haemophilus influenzae
What does green sputum suggest?
Pseudomonas
What does Red, currant-jelly sputum indicate?
Klebsiella
What does bloody sputum indicate?
TB
What does a foul-smelling/bad tasting sputum indicate?
Anaerobes
What does thin/scant sticky sputum indicate?
Atypicals:
Mycoplasma pneumoniae
Chlamydia pneumoniae
How is TB diagnosed via a sputum culture?
Acid Fast testing + culture specific testing + 3 separate samples and 12 weeks…
What does NOT grow on typical sputum culture media?
Atypical bacteria
Mycobacterium (TB)
Fungus
How are fungal infections in the lungs diagnosed?
Serum or biopsy testing.
What is a rapid strep test for?
Check if someone with pharyngitis has group A strep
What does a positive and negative rapid strep indicate?
Positive = no further testing.
Negative = throat culture.
Note:
Confirmatory testing is not needed on adults unless you are suspicious of something else.
Who should not be strep throat tested?
Children under 3 yo unless at HIGH RISK
Avoid routine screening of asymptomatic people, even if they came in close contact.
Also do not test if symptoms match a viral infection more closely.
What symptoms suggest an infection is more likely to be viral than strep?
Cough
Runny Nose
Mouth sores
What are the criteria for a throat culture called? How is it measured?
Centor criteria 0-4.
History of fever = +1
Tonsillar exudate = +1
Tender anterior cervical adenopathy = +1
Absence of cough = +1
<15 = +1
>44 = -1
What Centor criteria levels require treatment?
0-1 = no tx.
2-3 = Throat culture. If positive, treat with ABX.
4-5 = Empirical ABX tx
What is the most common cause of a viral sore throat?
Adenovirus. Will usually appear as a negative rapid strep and negative throat culture.
When is sensitivity testing indicated?
Unknown or mixed pathogens
Known resistance
Severe infection
Infection not responding to first-line tx.
How do I order sensitivity testing?
C&S
Culture and Sensitivity testing
What is the process of sensitivity testing?
Disk diffusion.
Disks of ABX are plated along the border of an agar plate.
If the ABX is effective against a bacteria, aka bacteria is SENSITIVE to the ABX, a clear ring will appear around the abx disk.
If not effective, no change in growth.
What is the alternative to disk diffusion?
Broth dilution.
Tests for the MIC.
How long does C&S take?
24-48 hours AFTER organisms have been identified on culture.
When should abx treatment begin relative to C&S results?
PRIOR to C&S results.
Start with broad spectrum and adjust once results are obtained.
