Cardiovascular Disorders
What the exam rewards
Cardiovascular items in critical care test a small set of repeated decisions: is this patient perfusing, which vasoactive drug and dose, and which timing or reversal rule applies. Build everything around shock physiology (preload, contractility, afterload) and the four rhythms that kill - VF/pVT, unstable VT with a pulse, symptomatic bradycardia, and unstable tachyarrhythmia.
Concepts to own
- ACS: chewed aspirin 162–325 mg, P2Y12 inhibitor plus anticoagulant before PCI; fibrinolysis only when timely PCI is unavailable; avoid NSAIDs.
- Inferior STEMI with hypotension suggests right ventricular involvement - nitrates and aggressive diuresis worsen it; give volume.
- Amiodarone dosing is setting-specific: 300 mg IV push in VF/pVT arrest versus 150 mg over 10 minutes for stable VT with a pulse, then 1 mg/min for 6 hours.
- Vasoactive selection: norepinephrine first for septic and most distributive shock; add vasopressin 0.03 units/min at high norepinephrine doses; dobutamine or milrinone for low output with adequate MAP.
- Cardiogenic shock: inotrope plus pressor, cautious fluids, urgent revascularization.
- Hypertensive emergency: titratable IV agent (nicardipine, clevidipine, labetalol) with controlled, not abrupt, reduction.
Traps
Nitroglycerin within 24–48 hours of sildenafil or tadalafil; low-dose dopamine for renal protection (no benefit); beta-blockade in decompensated low-output heart failure; mixing the arrest and stable-VT amiodarone doses; forgetting that calcium channel blockers are contraindicated in systolic dysfunction.
Worked example
Blood pressure 68/40 mmHg: MAP = (68 + 2×40)/3 = 49 mmHg, well below the 65 mmHg target. In a patient with clear congestion, the answer is norepinephrine, not another fluid bolus.
Rule of thumb
MAP = (SBP + 2×DBP)/3. Titrate to 65 mmHg in most shock, higher (75–80) if chronic hypertension or spinal cord injury.