Intro to ID Part 1 Flashcards
Temperature for fever
> 38C or >100.4
Non-infectious causes of fever (false-positives)
-Drug-induced fevers
-Malignancies
-Blood transfusions
-Auto-immune disorders
False-negatives (absence of fever in patients with signs/symptoms consistent with infection)
-Antipyretics (acetaminophen, NSAIDs, aspirin)
-Corticosteroids
-Overwhelming infection (may be hypothermic (<36C or 96.8F)
Systemic signs of infection
-Hypotension (SBP <90 or MAP <70)
-Tachycardia (BP >90)
-Tachypnea (>20 RPM)
-Fever (>38C or 36C)
-Increased/decreased WBC count (>12000 or <4000 or >10% immature forms (bands))
Systemic symptoms of infection
-Chills
-Rigors
-Malaise
-Mental status changes
Local signs and symptoms of infection
-Symptoms referable to specific body systems (ex: local pain)
-Pain and inflammation
-Inflammation in deep-seated infections (pneumonia, meningitis, UTIs)
-May be absent in neutropenic patients (main sign is fever)
Function of white blood cells
Defend the body against invading organisms
Types of white blood cells
-Neutrophils
-Lymphocytes
-Monocytes
-Eosinophils
-Basophils
Potential non-infectious causes for elevated white blood cell count
-Steroids
-Leukemia
-Stress
-Rheumatoid arthritis
-Pregnancy
Mature neutrophils (PMNs, polys, segs) description
-Most common WBC
-Fight infections
Immature neutrophils (bands) description
-Increased during infection = left shift
-Released by bone marrow into blood during infection
Eosinophil description
Involved in allergic reaction and immune response to parasites
Basophil description
Associated with hypersensitivity reactions
Lymphocyte description
Humoral (B-cell) and cell-mediated (T-cell) immunity
Monocyte description
-Mature into macrophages
-Serve as scavengers for foreign substances
What is leukocytosis?
-Increased neutrophils +/- bands associated with bacterial infections
-Presence of bands indicates increased bone marrow response to infection (left shift)
-May be elevated due to non-infectious diseases (leukemia, stress) or drugs (steroids)
-Leukopenia (abnormally low WBC) may be a sign of overwhelming infection; poor prognostic sign
What is lymphocytosis?
-Associated with viral, fungal or tuberculosis infections
-B-lymphocytes: proliferate into plasma cells -> produce antibodies and memory B-cells
-T-lymphocytes: HIV type infections
What is an absolute neutrophil count?
Total number of circulating segs and bands
What is neutropenia?
-ANC <500
-ANC expected to decrease to <500 in the next 48 hours
-ANC less than 100 is termed profound neutropenia
-Start getting worried when ANC <1000
What are the acute phase reactants?
-ESR
-CRP
-Procalcitonin (more specific for bacterial infections)
-Does NOT confirm infection
Normal ESR levels
-0-15 for males
-0-20 for females
Normal CRP levels
0-0.05
Normal procalcitonin
-<0.5
-Increase 3-12 hours after stimulation; decline over 24-72 hours
-Magnitude of elevation provides useful diagnostic information
How often should procalcitonin levels be taken?
Serial measurements every 1-2 days useful to assess response to therapy and when to discontinue antibiotics
Radiographic tests for infections
-X-rays
-Computed tomography (CT)
-Magnetic resonance imaging (MRI)
-Nuclear imaging (bone scans, WBC-related scans)
-Echocardiography (transthoracic echocardiogram (TTE) or transesophageal echocardiogram (TEE))
What type of culture would be collected for osteomyelitis?
Bone biopsy
What type of culture would be collected for meningitis?
CSF
What type of culture would be collected for endocarditis?
Blood cultures, heart valve tissues
When should blood cultures be obtained?
Should be performed in acutely ill febrile patients
How should blood cultures be obtained?
Two sets from two different sites
What is one set in a blood culture?
One aerobic and one anaerobic bottle
What is a colonization?
A potentially pathogenic organism present at the body site but is not invading host tissue or eliciting a host immune response
What is an infection?
A pathogenic organism is present at the body site and is damaging host tissue and eliciting host responses and symptoms consistent with an infection
