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13 High-Yield CCS Cases for USMLE Step 3 - Detailed Walkthrough

How CCS Scoring Works (Read This First)

• Timely stabilization - act on danger signs immediately
• Correct care setting - wrong venue costs hidden points
• Focused, not shotgun, diagnostics - every test should change management
• Time advancement - you must actively advance the clock to get results and observe response
• Monitoring, counseling, and follow-up - these earn background points at the end

IV access + O2 + monitors (ECG, pulse ox, BP cuff) + focused history/exam -> initial orders -> advance clock -> reassess -> adjust -> disposition

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Case 1: STEMI (Acute MI)

1. Immediate stabilization orders (all at once):
   • Continuous ECG monitoring, pulse ox, BP monitoring
   • IV access x2
   • O2 via nasal cannula (only if sat <94%)
   • 12-lead ECG - do this first, do not delay
   • Aspirin 325 mg PO (chew)
   • Sublingual nitroglycerin (if no RV infarct, no hypotension)
   • Morphine 2-4 mg IV (for pain, use judiciously)
   • Troponin, BMP, CBC, PT/INR, type & screen
   • CXR portable
2. ECG shows ST elevation in leads II, III, aVF (inferior STEMI):
   • Right-sided leads (V4R) to rule out RV infarction - if present, avoid nitrates
   • Heparin IV bolus + infusion (or enoxaparin)
   • Clopidogrel (P2Y12 inhibitor) loading dose
   • Call cardiology / activate cath lab
3. Definitive management:
   • Primary PCI is goal within 90 minutes of first medical contact - this is the answer on CCS
   • If PCI not available within 120 min: thrombolysis with tPA (if no contraindications)
   • Transfer to ICU/CCU after stabilization
4. Advance time, check results:
   • Troponin elevated: confirms MI
   • Monitor for Mobitz II / complete heart block (inferior STEMI complication)
   • Temporary pacemaker orders ready
5. Discharge counseling (before case ends):
   • Beta-blocker, statin, ACE inhibitor, dual antiplatelet therapy
   • Cardiac rehab referral, dietary counseling, smoking cessation

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Case 2: Sepsis / Septic Shock

1. First screen - all simultaneous:
   • IV access x2 (large bore)
   • O2 (high-flow if sat low)
   • Continuous monitoring
   • Blood cultures x2 sets (before antibiotics - this earns a major point)
   • Urinalysis + urine culture + urine Gram stain
   • CBC, BMP, lactate, LFTs, coagulation panel, blood gas
   • CXR
2. Start antibiotics within 1 hour (do not wait for culture results):
   • Broad-spectrum: Piperacillin-tazobactam or Cefepime + Vancomycin
   • If penicillin allergic: Aztreonam + Vancomycin
3. Fluid resuscitation:
   • 30 mL/kg IV crystalloid bolus (normal saline or lactated Ringer's)
   • Reassess BP and lactate after
4. Advance time 30-60 minutes:
   • If BP still <65 mmHg MAP despite fluids: Norepinephrine (vasopressor of choice)
   • If adrenal insufficiency suspected: Hydrocortisone 200 mg/day IV
5. Transfer to ICU
6. Narrow antibiotics when cultures result (usually Gram-negative rods from urine -> switch to ceftriaxone or fluoroquinolone if sensitive)
7. Before case ends:
   • Foley catheter for urine output monitoring
   • DVT prophylaxis
   • Stress ulcer prophylaxis
   • Glycemic control (keep glucose <180)

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Case 3: Acute Ischemic Stroke

1. Immediate orders:
   • ABCs, IV access, O2 (only if sat <94%)
   • Continuous monitoring
   • Non-contrast CT head STAT (must rule out hemorrhage before tPA)
   • Blood glucose STAT (hypoglycemia mimics stroke)
   • CBC, BMP, PT/INR, PTT, type & screen
   • 12-lead ECG (look for Afib as source)
2. CT head = no hemorrhage, glucose normal:
   • tPA (alteplase) IV within 4.5 hours of symptom onset is the answer
   • tPA dose: 0.9 mg/kg (max 90 mg) - 10% bolus, rest over 60 min
   • Blood pressure must be <185/110 before tPA - use labetalol or nicardipine to lower if needed
3. Contraindications to tPA (know these cold):
   • Hemorrhage on CT
   • BP >185/110 uncontrolled
   • Anticoagulant use (recent)
   • Recent surgery within 14 days
   • Stroke/head trauma within 3 months
   • Platelet <100,000, glucose <50
4. Advance time:
   • Monitor BP every 15 min during/after tPA
   • Neuro checks frequently
   • If large vessel occlusion (MCA): Mechanical thrombectomy within 24 hours of last known well (neurology/interventional radiology consult)
5. Admit to stroke unit / ICU:
   • No heparin/anticoagulation for 24 hours after tPA
   • NPO initially (aspiration risk) - get speech therapy/swallowing eval
   • Start aspirin 24 hours post-tPA
   • MRI brain, MRA (carotid ultrasound, echocardiogram for source)
6. Discharge:
   • Aspirin + statin
   • Antihypertensive
   • If Afib found: anticoagulate (DOACs preferred)
   • PT, OT, speech therapy referrals

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Case 4: Hypertensive Emergency / Encephalopathy

1. Immediate orders:
   • IV access, monitoring
   • Non-contrast CT head (rule out hemorrhage/stroke first)
   • BMP (renal function - assess end-organ damage)
   • Cardiac enzymes (rule out ACS)
   • Urinalysis (proteinuria/hematuria = renal injury)
   • CXR (pulmonary edema, aortic widening)
   • 12-lead ECG
   • Fundoscopic exam (papilledema, flame hemorrhages)
2. CT shows no hemorrhage, no focal deficits = Hypertensive Encephalopathy:
   • Nicardipine or Labetalol IV (titratable IV agents)
   • Nitroprusside IV drip is acceptable if SBP >220
   • Goal: Reduce MAP by 15-20% in first hour (NOT normalize BP - too fast = ischemia)
   • Avoid: Hydralazine (unpredictable), nifedipine sublingual (reflex tachycardia)
3. Advance time, monitor BP every 15-30 minutes:
   • Titrate drip to target MAP
   • Watch for deterioration (new focal deficits = possible hemorrhagic conversion)
4. Once BP controlled, transition to oral agents:
   • Lisinopril, amlodipine, metoprolol
   • Taper IV drip as oral agents take effect
5. Admit to ICU/step-down:
   • 24-hour monitoring
   • Nephrology consult if creatinine elevated

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Case 5: Pulmonary Embolism

1. Immediate orders:
   • IV access, O2 (high-flow), continuous monitoring
   • 12-lead ECG (look for S1Q3T3, sinus tachycardia, new RBBB)
   • ABG
   • D-dimer (high pre-test probability here - will be elevated but NOT used to rule out)
   • BMP, CBC, troponin, BNP
   • CXR (Hampton's hump, Westermark sign - usually normal)
   • Lower extremity Doppler
2. Definitive diagnosis: CT Pulmonary Angiography (CTPA):
   • High pre-test probability + hemodynamic instability = start treatment immediately
   • CTPA confirms massive/submassive PE
3. Treatment:
   • Hemodynamically stable (submassive): Anticoagulation - Heparin IV or enoxaparin SC, then transition to DOAC (rivaroxaban, apixaban) or warfarin
   • Massive PE (BP <90 despite fluids, or cardiac arrest): Systemic thrombolysis (tPA 100 mg IV over 2 hours) or surgical embolectomy
   • Avoid excessive IV fluids (worsens RV dilation)
4. Admit to floor vs ICU:
   • Massive PE: ICU
   • Submassive (RV strain on echo/troponin): step-down or ICU
5. Long-term:
   • DOAC for 3-6 months (provoked PE - post-op context)
   • IVC filter only if anticoagulation contraindicated
   • Compression stockings

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Case 6: Community-Acquired Pneumonia (CAP)

1. Orders:
   • O2, monitoring
   • CXR (right lower lobe infiltrate expected)
   • Sputum Gram stain and culture (before antibiotics)
   • Blood cultures x2 (hospitalized patients - especially if immunocompromised)
   • CBC, BMP, procalcitonin
   • Pulse oximetry continuous
   • Urinary pneumococcal antigen + Legionella antigen
2. Calculate PSI/PORT score or CURB-65 to determine admission vs outpatient:
   • CURB-65: Confusion, Urea >7, RR >30, BP <90/60, Age >65 - score 2+ = admit
   • This patient: Age 67, RR 22, O2 sat 93% -> admit to floor
3. Antibiotic selection (inpatient, non-ICU):
   • Beta-lactam (ceftriaxone 1g IV daily) + Azithromycin (500 mg IV/PO)
   • OR respiratory fluoroquinolone monotherapy (levofloxacin 750 mg)
4. Advance time 24-48 hours:
   • Reassess fever, O2 requirement, respiratory status
   • Switch to oral antibiotics when tolerating PO and improving
5. Total antibiotic duration: 5 days (if responding well)
6. Discharge criteria:
   • Afebrile x2, HR <100, RR <24, O2 sat >90% on room air, tolerating oral intake
7. Counseling:
   • Pneumococcal vaccine (Prevnar 20 or PCV15+PPSV23) at discharge
   • Influenza vaccine (seasonal)
   • Smoking cessation

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Case 7: Acute Asthma Exacerbation

1. Immediate orders:
   • O2, continuous pulse ox and monitoring
   • Albuterol (salbutamol) nebulizer STAT - continuous vs every 20 min x3 doses
   • Ipratropium bromide nebulizer (add to first 3 doses)
   • IV methylprednisolone 125 mg (or prednisone PO if mild-moderate)
   • ABG if O2 sat not improving
   • CXR (rule out pneumothorax, pneumonia trigger)
   • Peak expiratory flow rate (PEFR)
2. Advance time 20-30 minutes:
   • If improving (O2 sat >95%, speaking full sentences, PEFR >70% predicted): Observe, transition to MDI, may discharge
   • If not improving: Magnesium sulfate 2g IV (bronchodilator for severe acute asthma)
   • Heliox (helium-oxygen) mixture for severe refractory cases
3. Warning signs of impending respiratory failure (intubate):
   • "Silent chest" (no wheeze = no air movement)
   • Rising PaCO2 (normal or elevated = patient tiring out)
   • Altered mental status
   • If intubating: use ketamine for RSI (bronchodilator), set permissive hypercapnia on ventilator
4. Discharge criteria (if improving):
   • O2 sat >92% on room air
   • PEFR >70% predicted
   • Able to tolerate PO
   • Prescription: ICS + LABA controller inhaler, albuterol rescue
   • Follow up with pulmonologist/PCP in 1-2 weeks
   • Identify and avoid triggers
   • Asthma action plan

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Case 8: Diabetic Ketoacidosis (DKA)

1. Immediate orders:
   • IV access x2, continuous monitoring
   • BMP, ABG, CBC, beta-hydroxybutyrate (or urine ketones)
   • UA, urine culture (look for infection as precipitant)
   • CXR, 12-lead ECG (hyperkalemia effects)
   • Blood cultures if sepsis suspected
2. Fluids FIRST (before insulin):
   • Normal saline (0.9% NaCl) 1-2L IV bolus over first hour
   • Then 250-500 mL/hour until hemodynamically stable
3. Insulin drip (only after K+ >3.5 - critical!):
   • Regular insulin IV 0.1 units/kg/hr
   • If K+ <3.5: Give potassium first, hold insulin (hypokalemia from insulin can cause cardiac arrest)
   • Switch to D5W + 0.45% NS when glucose <250 (to avoid hypoglycemia while continuing insulin for ketone clearance)
4. Potassium replacement:
   • Add K+ to IV fluids to keep serum K+ 3.5-5.0 mEq/L throughout
   • Initial high K+ will drop dramatically once insulin is started
5. Monitor every 1-2 hours:
   • BMP (glucose, K+, HCO3)
   • Repeat ABG
   • Anion gap resolution is the marker of DKA resolution (NOT glucose normalization)
6. Transition to subcutaneous insulin when:
   • pH >7.3, HCO3 >15, AG normal, able to eat
   • Overlap IV and SC insulin by 2 hours
7. Identify and treat precipitant:
   • Infection: start antibiotics
   • Missed insulin: patient education
   • New diagnosis: diabetes education

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Case 9: Meningitis

1. This is a medical emergency - speed matters:
   • IV access, monitoring, O2
   • Blood cultures x2 IMMEDIATELY
   • CBC, BMP, coagulation panel (DIC from meningococcemia?)
   • Start empirical antibiotics immediately - do NOT wait for LP
2. Empirical antibiotics (adult 18-50):
   • Ceftriaxone 2g IV q12h (covers N. meningitidis, S. pneumoniae)
   • Vancomycin 15-20 mg/kg IV q8-12h (for resistant S. pneumoniae)
   • Dexamethasone 0.15 mg/kg IV q6h x4 days (start before or with first antibiotic dose - reduces neurologic complications)
   • For age >50 or immunocompromised: Add Ampicillin (covers Listeria)
3. LP (lumbar puncture) after antibiotics if:
   • No papilledema, no focal neurologic deficit, not coagulopathic
   • CT head first if any risk factors for herniation
4. CSF results:
   • Bacterial: cloudy, high WBC (PMNs), low glucose, high protein
   • Viral: clear, lymphocytes predominant, normal glucose, mildly elevated protein
5. Advance time, reassess:
   • If improving on antibiotics: narrow based on CSF cultures
   • Contact precautions for meningococcal meningitis
   • Prophylaxis for close contacts: Rifampin or Ciprofloxacin
6. Admit to ICU (this patient has petechial rash = meningococcemia - high risk of septic shock, DIC, Waterhouse-Friderichsen syndrome)
7. Complications to watch:
   • SIADH (restrict free water)
   • Seizures (levetiracetam or phenytoin)
   • Hydrocephalus

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Case 10: Acute Appendicitis

1. Initial orders:
   • IV access, monitoring
   • NPO immediately
   • IV fluids (maintenance)
   • CBC, BMP, LFTs, amylase/lipase
   • UA (rule out renal colic, UTI)
   • Beta-hCG (female patients - always rule out ectopic pregnancy first)
   • Morphine/ketorolac for pain (do NOT withhold analgesics - old teaching was wrong)
2. Imaging:
   • CT abdomen/pelvis with contrast is the gold standard
   • Ultrasound first in pregnant women or children (radiation avoidance)
   • Alvarado score can supplement
3. CT confirms acute appendicitis:
   • Surgery consult
   • Metronidazole + Cefoxitin IV (or ceftriaxone + metronidazole) - pre-op antibiotics
   • Consent, anesthesia consult
   • Laparoscopic appendectomy
4. Perforation/abscess found:
   • Broad-spectrum antibiotics (piperacillin-tazobactam)
   • May need IR-guided drainage first, then interval appendectomy in 6-8 weeks
5. Post-op:
   • Advance diet when bowel function returns
   • Discharge when tolerating PO, afebrile, pain controlled on oral meds
   • Wound care instructions, return precautions

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Case 11: Pre-eclampsia / Eclampsia

1. Immediate orders:
   • IV access, continuous fetal monitoring (cardiotocography)
   • Magnesium sulfate IV: 4-6g loading dose over 20 min, then 1-2g/hour maintenance (seizure prophylaxis AND treatment)
   • Labs: CBC, BMP, LFTs, uric acid, 24-hour urine protein (or spot protein:creatinine ratio), coagulation panel (rule out HELLP)
   • Fetal biophysical profile / non-stress test
   • Urine output monitoring (Foley catheter)
2. Control BP:
   • Acute: Labetalol IV 20mg (repeat q10 min, max 300mg) OR Hydralazine 5-10mg IV OR Nifedipine 10mg PO
   • Target: SBP 140-155, DBP 90-105 (avoid over-correction - placental perfusion)
3. Definitive treatment = DELIVERY:
   • Severe features (BP >160/110, headache, visual changes, thrombocytopenia, elevated LFTs): deliver at 34+ weeks
   • This patient at 36 weeks: Deliver
   • Vaginal delivery preferred if cervix favorable; C-section for obstetric indications
4. If seizure occurs (eclampsia):
   • Magnesium sulfate is treatment AND prophylaxis (not diazepam or phenytoin)
   • If breakthrough seizure on Mg: additional 2g IV bolus
   • Check Mg levels (therapeutic: 4-7 mEq/L; toxic: >7)
   • Calcium gluconate at bedside (reverses Mg toxicity)
5. HELLP Syndrome (Hemolysis, Elevated Liver enzymes, Low Platelets):
   • Also warrants delivery
   • Corticosteroids can be given for fetal lung maturity if <34 weeks
   • Platelet transfusion if <50,000 and C-section planned
6. Post-partum monitoring:
   • Continue Mg for 24-48 hours post-delivery
   • BP monitoring for 72 hours (BP can worsen post-partum)

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Case 12: Major Depressive Episode / Suicidal Patient

1. Toxicology emergency first (TCA overdose signs - anticholinergic + cardiac toxicity):
   • IV access, continuous cardiac monitoring, O2
   • ECG immediately (wide QRS >100ms = TCA toxicity - risk of ventricular arrhythmia)
   • Fingerstick glucose
   • Tylenol and salicylate levels (always check with unknown overdose)
   • BMP, CBC, LFTs, ABG
   • Serum drug screen, urine toxicology
   • Activated charcoal 1g/kg PO if <1-2 hours since ingestion and airway protected
2. TCA overdose management:
   • QRS >100ms or ventricular arrhythmia: Sodium bicarbonate IV (1-2 mEq/kg bolus, then drip to maintain pH 7.45-7.55)
   • Avoid physostigmine (increases seizure risk)
   • Benzodiazepines for seizures (NOT phenytoin)
   • Avoid flumazenil if benzodiazepines co-ingested (precipitates seizures)
3. Once medically stable:
   • Psychiatric consult
   • Suicide risk assessment (Columbia Suicide Severity Rating Scale)
   • Involuntary hold / Baker Act if patient refuses and remains at risk
4. For underlying MDD (once medically clear):
   • SSRI (first-line): sertraline, escitalopram
   • SNRIs: venlafaxine, duloxetine
   • Avoid TCAs in suicidal patients (lethal in overdose - this is why she's here)
   • Mirtazapine: good for insomnia + depression
5. Discharge/Disposition:
   • Inpatient psychiatric admission for suicidal ideation with plan and intent
   • Remove means from home (lethal means counseling)
   • Safety plan
   • Follow-up with outpatient psychiatry in 1 week

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Case 13: Pediatric Febrile Seizure vs. Meningitis

1. Immediate assessment:
   • ABCs, O2 via mask
   • Fingerstick glucose
   • IV/IO access
   • Continuous monitoring
   • Full physical exam (look for meningismus, Kernig/Brudzinski signs, rash)
   • Ear exam (otitis media as fever source), throat exam, skin
2. This is a simple febrile seizure if:
   • Age 6 months - 5 years
   • Duration <15 minutes
   • Generalized (not focal)
   • Single episode in 24 hours
   • Returns to normal baseline
   • No signs of meningitis/encephalitis
3. Workup for simple febrile seizure:
   • Identify and treat the fever source (UA, CXR if respiratory symptoms)
   • CBC, BMP, blood culture if toxic-appearing
   • LP is NOT routinely required for simple febrile seizure in immunized child
   • EEG is NOT required acutely for first simple febrile seizure
4. Management:
   • Antipyretics: ibuprofen or acetaminophen (for comfort, does NOT prevent recurrence)
   • Treat underlying infection (if otitis media: amoxicillin; if viral: supportive)
   • Observe in ED 4-6 hours
5. Parent counseling (critical for CCS points):
   • Risk of recurrence is 30-50%
   • Does NOT cause brain damage or epilepsy (simple febrile seizures)
   • If seizure >5 minutes: Rectal diazepam (Diastat) for home use
   • Return precautions: prolonged seizure, focal features, not returning to baseline
6. Complex febrile seizure (focal, >15 min, multiple in 24h) = admit and consider LP/EEG
7. Meningitis signs present = treat as meningitis (see Case 9):
   • LP
   • Empirical ceftriaxone + vancomycin + dexamethasone

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Universal CCS Strategies - Quick Reference

1. Ordering antibiotics before blood/CSF cultures
2. Giving insulin without checking potassium (DKA)
3. Giving nitrates with RV infarct
4. Lowering BP too fast in ischemic stroke
5. Not giving tPA within window for ischemic stroke
6. Not delivering in severe pre-eclampsia
7. Not checking beta-hCG before surgery in women of reproductive age
8. Discharging a suicidal patient without psychiatric evaluation
9. Doing LP before CT when herniation is a risk
10. Not advancing the clock (sitting on orders without moving time forward)

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1. Cardiology - HTN compelling indications, GDMT for HF, ACS/STEMI MONA-BASH, antiarrhythmics
2. Endocrinology - DM2 algorithm, insulin types, thyroid storm protocol, adrenal disorders
3. Pulmonology - Asthma step therapy, COPD pharmacotherapy
4. Infectious Disease - CAP, UTI, STI, HIV, TB antibiotic selection
5. Neurology - Seizure ladder, migraine acute vs. preventive, Parkinson's, dementia
6. Psychiatry - SSRIs, bipolar, schizophrenia, EPS management, anxiety/OCD
7. Gastroenterology - GI bleeds, IBD, hepatic encephalopathy, C. diff
8. Nephrology - CKD, hyperkalemia, SIADH, gout, nephrolithiasis
9. Hematology/Oncology - Anemias, HIT, VTE, TTP, ITP
10. Rheumatology - RA, SLE, osteoporosis, GCA
11. OB/GYN - Prenatal care, pre-eclampsia, PPH, ectopic pregnancy
12. Drug Interactions & Contraindications - The pitfalls that generate MCQ traps
13. Rapid Review First-Line Drug List - 50+ must-know "drug of choice" pairings

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High-Yield Nutrition for USMLE Step 3

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PART 1: VITAMIN DEFICIENCIES

Fat-Soluble Vitamins (A, D, E, K)

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Vitamin A (Retinol)

• Early: Night blindness (nyctalopia) - first and most sensitive sign
• Progressive: Xerophthalmia (dry eyes), Bitot's spots (foamy white plaques on conjunctiva), corneal ulceration → blindness
• Skin: follicular hyperkeratosis ("toad skin")
• Immune: increased susceptibility to infections (especially measles and respiratory infections)

• Acute: headache, vomiting, increased ICP (pseudotumor cerebri)
• Chronic: alopecia, dry skin, hepatotoxicity, hypercalcemia, bone pain
• Teratogenic - causes neural tube defects and craniofacial anomalies (avoid isotretinoin/high-dose vitamin A in pregnancy)

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Vitamin D (Cholecalciferol)

• Lack of sun exposure (elderly, institutionalized, dark skin)
• Fat malabsorption
• Chronic kidney disease (cannot 1-alpha-hydroxylate → use calcitriol, not D3)
• Chronic liver disease (cannot 25-hydroxylate → give D3 supplements)
• Anticonvulsants (phenytoin, phenobarbital → accelerate D catabolism)
• Strict veganism (D2 only in plants)

• Children: Rickets - craniotabes, rachitic rosary (costochondral beading), frontal bossing, Harrison's groove, bowlegged (genu varum) or knock-knee (genu valgum), delayed dentition
• Adults: Osteomalacia - diffuse bone pain, muscle weakness, pathological fractures, Looser's zones (pseudofractures on X-ray)
• Labs: low calcium, low phosphorus, high PTH, high alkaline phosphatase, low 25-OH vitamin D

• Deficiency (25-OH D <20 ng/mL): ergocalciferol (D2) or cholecalciferol (D3) 50,000 IU PO weekly x8-12 weeks, then maintenance 1,500-2,000 IU/day
• CKD: calcitriol (active form) - do NOT use regular D3 (kidney cannot activate it)

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Vitamin E (Tocopherol)

• Spinocerebellar ataxia (degenerative)
• Peripheral neuropathy (loss of deep tendon reflexes, proprioception)
• Skeletal muscle atrophy
• Retinopathy
• Hemolytic anemia in premature infants

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Vitamin K

• Made by gut bacteria; found in green leafy vegetables

• Newborns (sterile gut, poor placental transfer, low breast milk content) → hemorrhagic disease of the newborn - prevented by vitamin K IM at birth
• Parents who refuse IM Vit K at birth: 81x higher risk of bleeding
• Fat malabsorption
• Prolonged antibiotic use (kills gut flora)
• Warfarin, salicylates, cholestyramine

• PT is prolonged BEFORE aPTT in vitamin K deficiency (factor VII has shortest half-life)
• Treatment: vitamin K IM for several days; FFP in acute crises
• Warfarin reversal: vitamin K + 4-factor PCC (Kcentra)

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Water-Soluble Vitamins (B-complex + C)

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Vitamin B1 - Thiamine

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Vitamin B2 - Riboflavin

• Cheilosis (cracking at corners of mouth)
• Corneal vascularization
• Dermatitis (seborrheic)
• Diarrhea
• Magenta (glossy red) tongue, angular stomatitis, photophobia

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Vitamin B3 - Niacin (Nicotinic Acid)

• Alcoholism
• Isoniazid (INH) treatment (depletes B6 which is needed for niacin synthesis)
• Hartnup disease (tryptophan malabsorption)
• Carcinoid syndrome (tryptophan diverted to serotonin)
• Corn-based diets (corn is low in niacin and tryptophan; niacin in corn is bound - not bioavailable)

• Dermatitis: hyperpigmented, scaly rash on sun-exposed skin (Casal's necklace around neck), symmetrical
• Diarrhea
• Dementia (confusion, memory loss, disorientation, psychosis)
• Death (if untreated)

• Flushing (prostaglandin-mediated; prevent with aspirin 30 min before or use extended-release)
• Hepatotoxicity (extended-release form > immediate release)
• Hyperglycemia
• Hyperuricemia (gout)
• Pruritus

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Vitamin B6 - Pyridoxine

• Isoniazid (INH) - most tested cause; INH is a structural analog that depletes B6 → give pyridoxine 25-50 mg/day with all INH regimens
• Alcoholism
• Oral contraceptives (rare)

• Peripheral neuropathy
• Seborrheic dermatitis, glossitis
• Sideroblastic anemia (microcytic; iron cannot be incorporated into heme)
• Seizures (in infants)
• Depression, confusion

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Vitamin B9 - Folate (Folic Acid)

• Alcoholism (most common in US)
• Poor diet (elderly, poverty)
• Pregnancy (increased demand)
• Methotrexate (DHFR inhibitor - blocks folate activation)
• Trimethoprim (DHFR inhibitor)
• Sulfasalazine, pyrimethamine, triamterene (folate antagonists)
• Phenytoin (impairs absorption)
• Celiac disease (proximal small bowel absorption)

• Megaloblastic anemia (large RBCs, hypersegmented neutrophils ≥5 lobes)
• Glossitis (smooth, beefy red tongue), cheilosis
• Elevated homocysteine (but NORMAL methylmalonic acid - distinguishes from B12)
• NO neurological symptoms (unlike B12 deficiency)

• All women of childbearing age: 400-800 mcg/day folic acid
• Prior neural tube defect: 4 mg/day starting 1-3 months before conception
• Prevents: neural tube defects (spina bifida, anencephaly), cleft lip/palate

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Vitamin B12 - Cobalamin

• Pernicious anemia - autoimmune destruction of parietal cells → no IF → B12 malabsorption (anti-parietal cell and anti-IF antibodies)
• Strict vegetarianism/veganism (B12 only in animal products)
• Gastrectomy / bariatric surgery (no parietal cells → no IF)
• Terminal ileal disease or resection (Crohn's, ileal resection)
• Metformin (reduces absorption by up to 30% - check B12 annually)
• Acid suppression (H2 blockers, PPIs) - impairs release from food-bound form
• Fish tapeworm (Diphyllobothrium latum) - competes for B12
• Nitrous oxide exposure (inactivates B12 irreversibly)

• Megaloblastic anemia (same as folate)
• Subacute combined degeneration of the spinal cord:
  • Posterior columns (dorsal): loss of vibration, proprioception, Romberg positive
  • Lateral columns: upper motor neuron signs (spasticity, hyperreflexia, Babinski)
  • Combined = both UMN and LMN signs
• Dementia, depression, psychosis ("megaloblastic madness")
• Glossitis (smooth tongue)
• Elevated methylmalonic acid AND homocysteine (distinguishes from folate - folate deficiency has normal MMA)

• Pernicious anemia: cyanocobalamin 1,000 mcg IM daily x7d → weekly x4 → monthly (lifelong)
• Dietary deficiency: high-dose oral B12 1,000 mcg/day (effective even without IF via passive absorption)

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Vitamin C - Ascorbic Acid

• Perifollicular petechiae and corkscrew/coiled hairs (pathognomonic)
• Bleeding gums (gingivitis, periungual hemorrhage)
• Subperiosteal hemorrhage → bone pain in children
• Poor wound healing
• Hemarthrosis (joint bleeding)
• Anemia (iron malabsorption + bleeding)
• Fatigue, depression

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PART 2: TRACE ELEMENT DEFICIENCIES

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PART 3: MACRONUTRIENT DISORDERS

Protein-Energy Malnutrition

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Refeeding Syndrome

• Anorexia nervosa
• Prolonged NPO/fasting (>5-7 days)
• Chronic alcoholism
• Cancer patients on prolonged chemo
• Post-bariatric surgery
• Kwashiorkor/marasmus

• Impaired ATP synthesis → muscle weakness, respiratory failure (can't wean from vent)
• Hemolytic anemia
• Cardiac arrhythmias and cardiac failure
• Seizures, encephalopathy
• Rhabdomyolysis

• Identify high-risk patients BEFORE refeeding
• Correct electrolytes (phosphate, K+, Mg2+) BEFORE starting nutrition
• Start at LOW caloric rate (10-20 kcal/kg/day; some use 50% of estimated needs initially)
• Slow and gradual increase over 4-7 days
• Daily electrolyte monitoring (especially phosphate) during refeeding
• Thiamine supplementation before and during refeeding
• Target phosphate >1.0 mmol/L at all times

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PART 4: ENTERAL VS. PARENTERAL NUTRITION

General Principle: "If the gut works, use it"

• Maintains gut mucosal integrity (prevents bacterial translocation)
• Lower cost
• Lower infection risk
• Preserves gut immune function
• Reduces stress ulcers

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Enteral Nutrition (EN / Tube Feeding)

• Nasogastric (NG): Short-term (<4 weeks), gastric emptying intact
• Nasojejunal (NJ): High aspiration risk, gastroparesis, post-op
• Percutaneous endoscopic gastrostomy (PEG): Long-term (>4 weeks)
• Jejunostomy tube (J-tube): Post-operative, pancreatitis, gastroparesis

• Gastroparesis
• High aspiration risk
• Pancreatitis (jejunal bypasses pancreatic stimulation)
• Post-op after gastric/esophageal surgery

• Bowel obstruction
• Severe ileus
• Bowel ischemia
• High-output enteric fistula

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Total Parenteral Nutrition (TPN)

• Bowel obstruction (mechanical)
• Short bowel syndrome (insufficient absorptive surface)
• Severe inflammatory bowel disease with failed EN
• High-output fistula
• Severe malabsorption
• Prolonged ileus
• Inability to place enteral access

• Dextrose (carbohydrate): 3.4 kcal/g; typical 150-350g/day
• Amino acids (protein): 4 kcal/g; typical 1-1.5 g/kg/day (higher in critically ill: 1.5-2 g/kg/day)
• Lipid emulsion (fat): 9 kcal/g; 20-30% of calories
• Electrolytes: Na, K, Ca, Mg, Phosphate, Acetate, Chloride
• Vitamins: all water and fat soluble
• Trace elements: Zn, Cu, Mn, Cr, Se
• Insulin: add to TPN if glucose >180 mg/dL

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PART 5: SPECIAL NUTRITIONAL SITUATIONS (HIGH-YIELD FOR STEP 3)

Pregnancy Nutrition

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Alcoholism - Nutritional Deficiencies to Know

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Post-Bariatric Surgery Deficiencies

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Inflammatory Bowel Disease - Nutritional Concerns

• Crohn's (terminal ileum involvement): B12 deficiency (ileum is sole absorption site), fat malabsorption → fat-soluble vitamins (A, D, E, K)
• Both IBD types: Iron deficiency anemia (blood loss), zinc deficiency, protein-energy malnutrition
• Sulfasalazine: Folate antagonist - supplement folate

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Malabsorption Syndromes - Nutritional Consequences

• Jejunum loss: most absorption still intact (ileum compensates)
• Terminal ileum loss: B12 (irreversible), bile salts (→ fat malabsorption, fat-soluble vitamin deficiency), oxalate hyperabsorption (→ calcium oxalate kidney stones)

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PART 6: RAPID-REVIEW DEFICIENCY TABLE (Step 3 Board Format)

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PART 7: CLINICAL NUTRITION CALCULATIONS (Step 3)

• Average adult: 25-30 kcal/kg/day
• Critically ill/ICU: 25-30 kcal/kg/day (avoid overfeeding)
• Obese patients: use adjusted body weight

• Normal adults: 0.8 g/kg/day
• Hospitalized patients: 1.0-1.5 g/kg/day
• Critically ill (ICU): 1.5-2.0 g/kg/day
• Burns, severe trauma: up to 2.5 g/kg/day
• CKD (non-dialysis): 0.6-0.8 g/kg/day (restrict protein)
• CKD on dialysis: 1.2-1.5 g/kg/day (dialysis removes protein waste)

• Carbohydrate: 4 kcal/g
• Protein: 4 kcal/g
• Fat: 9 kcal/g
• Alcohol: 7 kcal/g

• Positive = anabolic (building); Negative = catabolic (breaking down)

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Sources: Harrison's Principles of Internal Medicine 22e, Robbins & Cotran Pathologic Basis of Disease, Andrews' Diseases of the Skin, Biochemistry (Lippincott), Goldman-Cecil Medicine, Adams & Victor's Neurology, Current Surgical Therapy.

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