CPSP IMM Medicine cheat sheet

Community-acquired pneumonia severity: CURB-65 scores confusion, urea >7 mmol/L, respiratory rate ≥30/min, low blood pressure, age ≥65; score ≥2 supports inpatient care.

Sepsis-3: sepsis = suspected infection plus SOFA increase ≥2; septic shock = sepsis with vasopressor need to keep MAP ≥65 mmHg and lactate >2 mmol/L despite fluids.

Anion gap = Na − (Cl + HCO3); normal 8–12 mEq/L; add 2.5 mEq/L to expected gap for every 1 g/dL fall in albumin.

Hyponatremia first step: check serum osmolality; hypotonic plus urine osmolarity >100 mOsm/kg suggests SIADH, thyroid and adrenal causes must be excluded first.

Wells score for DVT: ≥2 points indicates likely DVT, so proceed to compression ultrasound; <2 points, obtain D-dimer first.

Transfusion threshold for most stable hospitalized adults is hemoglobin 7 g/dL; 8 g/dL for cardiac surgery or active cardiovascular disease.

Alcohol withdrawal: thiamine before glucose to prevent Wernicke encephalopathy; benzodiazepines are first-line for seizures and delirium tremens.

Drug reaction with eosinophilia and systemic symptoms (DRESS) features: latency 2–6 weeks, eosinophilia, transaminitis, facial edema; stop the culprit drug.

Mean arterial pressure = DBP + (SBP − DBP)/3; target ≥65 mmHg in septic shock and most critically ill patients.

Corrected QT (Bazett) = QT/√RR in seconds; QTc >500 ms or increase >60 ms raises torsades risk and warrants drug review.

STEMI reperfusion: primary PCI within 120 minutes of first medical contact; otherwise fibrinolysis within 30 minutes of arrival if no contraindication.

Heart failure with reduced ejection fraction quadruple therapy: ARNI/ACE inhibitor, beta-blocker, mineralocorticoid antagonist, SGLT2 inhibitor.

Atrial fibrillation stroke risk uses CHA2DS2-VASc; score ≥2 in men or ≥3 in women supports anticoagulation.

Aortic stenosis severity: peak velocity ≥4 m/s, mean gradient ≥40 mmHg, or valve area <1.0 cm² indicates severe disease.

Pericarditis: diffuse ST elevation with PR depression; treat with NSAIDs plus colchicine; avoid anticoagulation if effusion is large.

Cardiac tamponade: Beck triad (hypotension, distended neck veins, muffled heart sounds); treat with fluid plus urgent pericardiocentesis.

ABG stepwise: pH determines acidemia or alkalemia; PaCO2 confirms respiratory cause; HCO3 confirms metabolic compensation.

Acute respiratory alkalosis: PaCO2 falls 1.2 mmHg per 1 mEq/L rise in HCO3 acutely; chronic fall is 0.4–0.5 mmHg per 1 mEq/L.

Asthma severity: peak flow 40–69% predicted = moderate exacerbation; <40% = severe; silent chest and exhaustion signal impending arrest.

COPD: post-bronchodilator FEV1/FVC <0.70 confirms obstruction; GOLD 1–4 by FEV1 percent predicted (≥80, 50–79, 30–49, <30).

Light criteria for exudative effusion: protein ratio >0.5, LDH ratio >0.6, or pleural LDH >2/3 upper normal serum limit.

Pulmonary embolism: PERC rule excludes PE only when all eight criteria are absent and pretest probability is low.

Obstructive sleep apnea: apnea-hypopnea index ≥5 with symptoms, or ≥15 regardless of symptoms, defines the disorder.

ARDS Berlin definition: onset within 1 week, bilateral opacities, no cardiac cause, PaO2/FiO2 ≤300 on PEEP ≥5 cmH2O.

Upper GI bleed: Glasgow-Blatchford score ≤1 identifies very low risk suitable for outpatient management; Rockall predicts mortality.

Acute pancreatitis: diagnosis needs 2 of 3 - characteristic pain, lipase/amylase >3× upper limit, or imaging findings.

Hepatorenal syndrome: creatinine rise in cirrhosis with no response to albumin challenge, absence of shock, and no nephrotoxins.

Child-Pugh score uses bilirubin, albumin, INR, ascites, and encephalopathy; class C indicates decompensated disease.

MELD-Na uses bilirubin, INR, creatinine, sodium, and dialysis status to prioritize transplant candidates.

Inflammatory bowel disease: ulcerative colitis is continuous from rectum; Crohn disease is skip lesions with transmural inflammation and fistulae.

Celiac disease: check tissue transglutaminase IgA with total IgA; duodenal biopsy shows villous atrophy and crypt hyperplasia.

Clostridioides difficile testing: use stool toxin or nucleic acid amplification only on unformed stool; avoid testing formed stool and test-of-cure.

Primary hypothyroidism: high TSH with low free T4; subclinical disease is high TSH with normal free T4.

Thyroid storm: Burch-Wartofsky score ≥45 is highly suggestive; treat with beta-blocker, thionamide, iodine after thionamide, and steroids.

Diabetic ketoacidosis: glucose >250 mg/dL, pH <7.3, bicarbonate <18 mEq/L, ketonemia; total body potassium is depleted even if serum is normal.

Hyperosmolar hyperglycemic state: glucose often >600 mg/dL, effective osmolality >320 mOsm/kg, minimal ketosis, profound dehydration.

HbA1c reflects mean glucose over roughly 3 months; estimated average glucose (mg/dL) = 28.7 × HbA1c − 46.7.

Primary aldosteronism screening: aldosterone-to-renin ratio; stop mineralocorticoid receptor antagonists 4–6 weeks before testing.

Adrenal crisis: give hydrocortisone before confirmatory testing when suspected; do not delay treatment for cortisol results.

Pheochromocytoma: plasma free metanephrines are the initial test; obtain imaging only after biochemical confirmation.

CKD-EPI 2021 creatinine equation uses race-free coefficients; eGFR <60 mL/min/1.73 m² for ≥3 months defines CKD.

KDIGO CKD staging combines GFR category G1–G5 with albuminuria category A1–A3 (A3 = urine albumin-to-creatinine ratio >300 mg/g).

Fractional excretion of sodium = (urine Na × plasma creatinine)/(plasma Na × urine creatinine) × 100; <1% suggests prerenal state.

Fractional excretion of urea <35% also suggests prerenal azotemia, useful when diuretics make FENa unreliable.

Hyperkalemia with ECG changes: give IV calcium first for membrane stabilization, then insulin-glucose and beta-agonist to shift potassium.

Hyponatremia correction limit: ≤8 mmol/L in 24 hours to avoid osmotic demyelination; lower for high-risk patients.

Metabolic acidosis with normal anion gap suggests bicarbonate loss; urine anion gap = (Na + K) − Cl; negative value implies GI loss.

Nephrotic syndrome: proteinuria >3.5 g/day, albumin <3.0 g/dL, edema, hyperlipidemia; nephritic syndrome features hematuria and hypertension.