DIP Episode 199 - USMLE Step 2CK Rapid Review Series 29

Source / episode info

• Episode: 199
• Title: Divine Intervention Episode 199 – USMLE Step 2 CK Rapid Review Series 29.
• Published: 2020-01-06
• Source: Episode page

One-liner

This rapid review covers critical board associations including optimal nutrition support in ventilated patients, zinc chelation therapy contraindications, prosthetic valve endocarditis timing, muscular dystrophy differentials (Duchenne vs Becker), chagas disease manifestations, and the pathophysiology of mineralocorticoid excess syndromes.

High-yield summary

• Nutrition Support: Internal nutrition via a feeding tube is preferred over Total Parenteral Nutrition (TPN) due to better gut integrity maintenance and lower infection risk; TPN carries a high risk of selenium deficiency.
• Endocrine/Mineralocorticoids: 11-hydroxylase deficiency leads to the accumulation of 11-deoxycorticosterone (DOC), which has mineralocorticoid activity, causing hypertension, hypokalemia, and metabolic alkalosis.
• Infectious Disease Timing: Prosthetic valve endocarditis must be classified by timing: < 60 days (S. bacteremias); > 60 days (S. furus); > 12 months (Strep viridans).
• GI Emergencies: Toxic megacolon is a surgical emergency, often caused by C. difficile, and requires consideration of distal colonic pseudo-obstruction (e.g., in-be-em-examptus) or other causes like scleroderma/bacterial overgrowth.
• Genetics & Screening: Down Syndrome (Trisomy 21) is most commonly due to maternal non-disjunction; the quad screen findings are high -hCG and hIN, with low AFP and TSF.

Learning objectives

• Differentiate between various types of nutrition support based on patient stability and GI tract function.
• Recognize the specific timing criteria for prosthetic valve endocarditis pathogens.
• Identify key clinical features and differential diagnoses for muscular dystrophies (DMD vs Becker).
• Understand the pathophysiology and management of mineralocorticoid excess syndromes (e.g., 11\beta-hydroxylase deficiency).
• Master the high-yield associations in genetic screening (Down Syndrome, Trisomy 18) and infectious disease (Chagas, Leptospirosis).

Board exam buzzwords

Rapid review table

Board-speak -> diagnosis

Differential diagnosis / distinguishing features

Pseudo-obstruction Syndromes

Adrenal Insufficiency/Mineralocorticoid Excess

Management pearls

• Zinc Chelation: When treating Wilson's disease with chelators (e.g., Penicillamine), monitor for zinc deficiency symptoms and supplement zinc proactively.
• Prosthetic Valve Care: All patients receiving a prosthetic valve require lifelong anticoagulation, typically with Warfarin.
• Air Embolism Prevention: If air embolism is suspected post-vascular procedure, place the patient in the left lateral cubitus position and use Trendelenburg positioning to prevent right heart/pulmonary artery embolization.
• Toxic Megacolon Management: This is a surgical emergency; do not wait for symptoms to worsen.

Don't miss

Integration & clinical reasoning

• Endocrine Integration: The mineralocorticoid excess seen in 11\beta-hydroxylase deficiency (DOC buildup) mimics primary hyperaldosteronism, leading to the same electrolyte derangements (HTN, hypokalemia, metabolic alkalosis). This highlights that the effect of a hormone can be independent of its source.
• GI/Vascular Integration: The pathophysiology of air embolism (gas bubbles entering circulation and causing vascular occlusion) is conceptually similar to gas emboli seen in severe sepsis or other conditions, emphasizing the need for immediate circulatory management.
• Genetics/Developmental Integration: Developmental dysplasia of the hip requires careful imaging (ultrasound preferred over MRI) and physical reduction maneuvers before casting.

OMM / COMLEX integration

• Acute/Unstable Management Priority: In any acute setting (e.g., septic shock, severe metabolic derangement), standard emergency stabilization and resuscitation take absolute priority over OMT.
• GI Emergencies: Toxic megacolon or bowel obstruction requires immediate surgical consultation; supportive care is paramount before considering advanced interventions.

Concept connections / cross-references

• For detailed review on endocrine disorders and mineralocorticoid excess: [Episode 12]
• For comprehensive coverage of infectious disease protocols, including antibiotic stewardship: [Episode 45]
• For advanced topics in GI motility disorders and pseudo-obstruction: [Episode 78]

High-yield association table

Key terms glossary

Study optimization

Question pattern recognition

• The "Best Next Step" Pattern: Given a clinical scenario (e.g., ventilated patient), determine the optimal management modality (Internal Nutrition > TPN).
• Differential Diagnosis by Timing/Location: Identifying the correct pathogen or cause based on time elapsed (PVE) or anatomical location (hernias, pseudo-obstruction).
• The "Mimic" Pattern: Recognizing that a deficiency in one system (e.g., 11\beta-hydroxylase) can produce metabolites that mimic the pathology of another system (e.g., hyperaldosteronism).

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