Page 715 - First Aid for the USMLE Step 1 2020, Thirtieth edition [MedicalBooksVN.com]_Neat
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RespiRatoRy ` RESPIRATORY—PhYSIOlOgY RespiRatoRy ` RESPIRATORY—PAThOlOgY seCtioN iii 671
` RESPIRATORY—PAThOlOgY
Rhinosinusitis Obstruction of sinus drainage into nasal cavity inflammation and pain over affected area.
Typically affects maxillary sinuses, which drain against gravity due to ostia located superomedially
A
(red arrow points to fluid-filled right maxillary sinus in A ).
Orbit
Superior meatus—drains sphenoid, posterior ethmoid; middle meatus—drains frontal, maxillary,
and anterior ethmoid; inferior meatus—drains nasolacrimal duct.
Max
Most common acute cause is viral URI; may lead to superimposed bacterial infection, most
commonly H influenzae, S pneumoniae, M catarrhalis.
Paranasal sinus infections may extend to the orbits, cavernous sinus, and brain, causing
complications (eg, orbital cellulitis, cavernous sinus syndrome, meningitis).
Epistaxis Nose bleed. Most commonly occurs in anterior Kiesselbach drives his Lexus with his LEGS:
segment of nostril (Kiesselbach plexus). Life- superior Labial artery, anterior and posterior
threatening hemorrhages occur in posterior Ethmoidal arteries, Greater palatine artery,
segment (sphenopalatine artery, a branch of Sphenopalatine artery.
maxillary artery). Common causes include
foreign body, trauma, allergic rhinitis, and
nasal angiofibromas (common in adolescent
males).
Head and neck cancer Mostly squamous cell carcinoma. Risk factors include tobacco, alcohol, HPV-16 (oropharyngeal),
EBV (nasopharyngeal). Field cancerization: carcinogen damages wide mucosal area multiple
tumors that develop independently after exposure.
Deep venous Blood clot within a deep vein swelling, d-dimer lab test used clinically to rule out
thrombosis redness A , warmth, pain. Predisposed by DVT in low-to-moderate risk patients (high
A Virchow triad (SHE): sensitivity, low specificity).
Stasis (eg, post-op, long drive/flight) Imaging test of choice is compression ultrasound
Hypercoagulability (eg, defect in with Doppler.
coagulation cascade proteins, such as Use unfractionated heparin or low-molecular
factor V Leiden; oral contraceptive use; weight heparins (eg, enoxaparin) for
pregnancy) prophylaxis and acute management.
Endothelial damage (exposed collagen Use oral anticoagulants (eg, rivaroxaban,
triggers clotting cascade) apixaban) for treatment and long-term
Most pulmonary emboli arise from proximal prevention.
deep veins of lower extremity.
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