Internal medicine is the dominant discipline on Step 2 CK — roughly 35–40% of the exam. Mastering clinical decision-making in medicine is the single highest-leverage investment you can make for this exam.
Chest Pain: The Step 2 CK Decision Tree
Chest pain is the most tested chief complaint on Step 2 CK. Every vignette requires you to triage correctly before you diagnose specifically.
Step 1: Identify the emergent conditions first
- STEMI — ST elevations in contiguous leads → activate cath lab immediately, do not delay for anything
- Aortic dissection — tearing/ripping pain radiating to back, hypertension, pulse differential between arms → CTA chest, NOT tPA
- Tension pneumothorax — tracheal deviation, absent breath sounds, hypotension → needle decompression immediately (before X-ray)
- Massive PE — hypotension + hypoxia + tachycardia after immobilization/surgery → CTA or bedside echo → thrombolytics if hemodynamically unstable
- Pericardial tamponade — Beck's triad (JVD + muffled heart sounds + hypotension) → pericardiocentesis
NSTEMI vs. unstable angina
Both present with chest pain + dynamic EKG changes without ST elevation. NSTEMI: troponin elevated. Unstable angina: troponin normal. Both go to the cath lab — timing depends on risk stratification. TIMI score guides management.
Sepsis and Septic Shock
Definitions
Sepsis: Life-threatening organ dysfunction from dysregulated host response to infection. Defined by SOFA score ≥2 above baseline. Clinical suspicion: fever/hypothermia + tachycardia + tachypnea + altered mental status or organ dysfunction.
Septic shock: Sepsis + persistent hypotension (MAP <65) requiring vasopressors + lactate >2 mmol/L despite adequate fluid resuscitation.
Step 2 CK management sequence (the Hour-1 Bundle)
- Obtain blood cultures (before antibiotics, but don't delay antibiotics for this)
- Broad-spectrum antibiotics within 1 hour of recognition
- 30 mL/kg IV crystalloid bolus for hypotension or lactate ≥4
- Norepinephrine if still hypotensive after fluids (first-line vasopressor)
- Measure lactate — repeat if initial >2
Diabetic Ketoacidosis (DKA) vs. Hyperosmolar Hyperglycemic State (HHS)
| Feature | DKA | HHS |
|---|---|---|
| Patient | Type 1 DM (mostly) | Type 2 DM (elderly) |
| Glucose | >250 mg/dL | >600 mg/dL |
| pH | <7.3 (acidosis) | Normal (no acidosis) |
| Ketones | Positive (moderate-large) | Absent or trace |
| Osmolarity | Variable | >320 mOsm/kg |
| Mental status | Variable | Severely altered (coma) |
| Management | IV fluids (NS first), insulin drip, K+ replacement, monitor glucose q1h | IV fluids (aggressive), slow glucose correction, cautious insulin |
Key Step 2 CK DKA pearls: Do not start insulin until K+ ≥3.5 (insulin drives K+ into cells → fatal hypokalemia). Switch to D5 when glucose reaches 200–250. Give bicarbonate only if pH <6.9. Identify precipitant (infection, missed insulin, new DM).
Acute Kidney Injury (AKI): Classification and Management
| Type | BUN:Cr ratio | FENa | Urine Na+ | Cause |
|---|---|---|---|---|
| Prerenal | >20:1 | <1% | <20 mEq/L | Dehydration, CHF, hypovolemia — kidneys intact, just underperfused |
| Intrinsic (ATN) | <20:1 (often) | >2% | >40 mEq/L | Ischemia (post-prerenal), nephrotoxins (aminoglycosides, contrast, myoglobin), "muddy brown casts" |
| Postrenal | Variable | Variable | Variable | Obstruction — BPH (elderly men), bilateral ureteral stones, bladder outlet obstruction |
Contrast nephropathy prevention: Hold metformin 48 hours before/after, IV saline hydration before procedure, consider N-acetylcysteine, use iso-osmolar contrast.
Heart Failure: EF-Based Management
HFrEF (EF <40%): ACE inhibitor/ARB + beta-blocker (carvedilol, metoprolol succinate) + aldosterone antagonist (spironolactone) + loop diuretic for symptoms. SGLT2 inhibitors now first-line in addition.
HFpEF (EF ≥50%): No proven mortality benefit from any therapy. Control hypertension aggressively. Diuretics for symptom relief. SGLT2 inhibitors may help. Avoid negative inotropes.
Acute decompensated HF: IV diuresis (furosemide IV), oxygen, upright positioning. BiPAP for respiratory distress. Vasodilators (nitroprusside, nesiritide) if hypertensive. Avoid beta-blockers in acute decompensation.
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