When to intubate in GCS?

GCS ≤ 8 requires intubation for airway protection. The patient cannot protect their own airway at this level of consciousness. Motor score is the most prognostically important component.

What is the best initial fluid for sepsis resuscitation?

Lactated Ringer's (LR) is the preferred resuscitation fluid. The SMART trial (2018) showed balanced crystalloids reduced death, new renal failure, and persistent renal dysfunction compared to normal saline.

When to start vasopressors in septic shock?

Start norepinephrine (first-line vasopressor) if MAP remains < 65 mmHg after initial 30 mL/kg crystalloid resuscitation, or earlier if patient is profoundly hypotensive. Do not delay pressors to complete full fluid resuscitation.

Why can serum uric acid be normal during acute gout?

During acute inflammation, IL-6 increases renal urate excretion and redistributes urate from plasma to tissues. Up to 40% of acute gout flares have normal serum uric acid. Joint aspiration with polarized microscopy is needed for definitive diagnosis.

How do you distinguish lupus flare from infection in SLE?

Key clues: CRP is low/normal in flare but elevated in infection. Complement (C3/C4) drops in flare but is normal/elevated in infection. Procalcitonin is elevated in bacterial infection but normal in flare. Anti-dsDNA rises in flare, stable in infection.

What is the difference between DKA and HHS?

DKA features acidosis (pH 600), hyperosmolality (> 320), and minimal ketosis -typically in Type 2 DM. DKA requires insulin drip; HHS requires aggressive fluid resuscitation first.

When to give tPA in acute ischemic stroke?

IV alteplase (tPA) can be given within 4.5 hours of last known well time in eligible patients. CT head must rule out hemorrhage first. For large vessel occlusion, mechanical thrombectomy can be performed up to 24 hours with favorable imaging.

What antibiotics for community-acquired pneumonia?

Inpatient non-ICU: ceftriaxone + azithromycin. ICU: ceftriaxone + azithromycin (add vancomycin if MRSA risk). Outpatient healthy: amoxicillin. Outpatient with comorbidities: augmentin + azithromycin or respiratory fluoroquinolone. Duration: 5 days if clinically stable for 48 hours.

How to interpret iron studies?

Iron deficiency: low ferritin (< 30), high TIBC, low iron, low transferrin saturation (< 20%). Anemia of chronic disease: normal/high ferritin (acute phase reactant), low TIBC, low iron. A ferritin of 50-100 in an inflamed patient may still represent iron deficiency.

What is the correction rate for hyponatremia?

Correct sodium no more than 8 mEq/L in 24 hours to avoid osmotic demyelination syndrome (ODS). For symptomatic severe hyponatremia with seizures, give 3% hypertonic saline 100-150 mL bolus over 10-20 minutes. If overcorrected, use D5W + DDAVP rescue protocol.

When to start antibiotics in meningitis?

Within 30-60 minutes. Do NOT delay antibiotics for LP or CT. Draw blood cultures, start empiric antibiotics (vancomycin + ceftriaxone ± ampicillin if > 50 or immunocompromised), then perform LP when possible. Dexamethasone should be given before or with the first antibiotic dose.

DOACs vs warfarin in antiphospholipid syndrome?

DOACs are contraindicated in APS. The TRAPS trial (2018) showed rivaroxaban was inferior to warfarin with more thrombotic events in triple-positive APS patients. Warfarin with INR target 2-3 is the standard for APS, indefinitely.

How to manage scleroderma renal crisis?

ACE inhibitors (captopril) are life-saving -start immediately and titrate aggressively. Do NOT hold for rising creatinine. Steroids > 15 mg prednisone per day precipitate scleroderma renal crisis. ARBs are NOT a substitute -evidence is only for ACEi.

What are the 4 pillars of heart failure treatment?

Guideline-directed medical therapy (GDMT) for HFrEF: (1) ARNI or ACEi/ARB, (2) beta-blocker (carvedilol, metoprolol succinate, or bisoprolol), (3) MRA (spironolactone or eplerenone), (4) SGLT2 inhibitor (dapagliflozin or empagliflozin). All four should be initiated and titrated to target doses.

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Hematology

Pancytopenia

Simultaneous reduction of all three cell lines. Systematic approach: peripheral smear first, then bone marrow biopsy. Think production vs destruction.

🔍 Overview

Overview

Pancytopenia = anemia + leukopenia + thrombocytopenia. Not a diagnosis but a lab finding requiring systematic workup. Framework: decreased production (marrow failure: aplastic anemia, MDS, leukemia, myelofibrosis, infiltration by solid tumor, infection, medication) vs increased destruction/sequestration (hypersplenism, autoimmune, HLH, DIC). The peripheral smear is the single most important initial test -it guides the entire workup.

🧪 Workup

Workup

Peripheral smear -the MOST important test. Blasts → leukemia. Teardrop cells + leukoerythroblastic picture → myelofibrosis/marrow infiltration. Dysplastic cells → MDS. Schistocytes → TTP/DIC. Megaloblastic → B12/folate deficiency. Normal morphology → aplastic anemia, drug-induced, viral.
Reticulocyte count -low = production problem. High (unexpected in pancytopenia) = peripheral destruction + splenic sequestration.
B12 + folate -megaloblastic anemia can cause pancytopenia (ineffective hematopoiesis)
LDH, haptoglobin, indirect bilirubin -hemolysis markers
HIV, HBV, HCV, EBV, CMV, parvovirus B19 -viral marrow suppression
ANA, RF -autoimmune causes (Felty syndrome = RA + splenomegaly + neutropenia)
Copper level -copper deficiency mimics MDS (sideroblastic anemia + neutropenia)
Flow cytometry -if blasts or abnormal lymphocytes on smear
Bone marrow biopsy + aspirate -definitive test. Hypercellular = MDS, leukemia, megaloblastic. Hypocellular = aplastic anemia. Dry tap = myelofibrosis. Granulomas = infection (TB, fungal). Send: morphology, cytogenetics, flow, iron stain, reticulin stain.

Differential Diagnosis by Mechanism

Mechanism	Cause	Key Clue
Decreased Production	Aplastic anemia	Hypocellular marrow, young patient, reticulocyte count low
	MDS	Elderly, dysplastic cells on smear, cytogenetic abnormalities
	Leukemia	Blasts on peripheral smear or bone marrow > 20%
	B12/folate deficiency	Megaloblastic changes, hypersegmented neutrophils, elevated MCV
	HIV	Risk factors, low CD4, direct marrow suppression
	Medications	Methotrexate, chemotherapy, TMP-SMX, linezolid, valproate
Increased Destruction	Hypersplenism	Splenomegaly on exam/imaging, liver disease history
	HLH	Ferritin > 10,000, fever, splenomegaly, hypertriglyceridemia
	TTP/HUS	Schistocytes, elevated LDH, low haptoglobin, renal failure
	DIC	Schistocytes, elevated D-dimer, low fibrinogen, prolonged PT/aPTT
Infiltration	Myelofibrosis	Teardrop cells, dry tap, splenomegaly, leukoerythroblastic picture
	Metastatic cancer	Known primary, leukoerythroblastic smear, bone pain
	Storage diseases	Gaucher (glucocerebrosidase deficiency), hepatosplenomegaly

Peripheral Smear Findings

Finding	Suggests
Blasts	Acute leukemia (AML or ALL), obtain flow cytometry urgently
Teardrop cells	Myelofibrosis, expect dry tap on aspiration, order reticulin stain on biopsy
Megaloblastic changes	B12 or folate deficiency, check levels, MMA, homocysteine
Schistocytes	TTP/HUS or DIC, check ADAMTS13, fibrinogen, D-dimer, coags
Hypersegmented neutrophils	B12 or folate deficiency, ≥ 5 lobes is pathologic
Rouleaux formation	Multiple myeloma, check SPEP, serum free light chains

⚠ When to Do Bone Marrow Biopsy

Unexplained pancytopenia after initial labs (smear, B12, folate, HIV unrevealing)
Suspected leukemia or MDS based on clinical picture or smear
Blasts seen on peripheral smear
Leukoerythroblastic picture (nucleated RBCs + immature WBCs in periphery)
Suspected infiltrative process (myelofibrosis, metastatic disease, storage disease)

🚨 Management

Management

Treat the underlying cause:
- B12 deficiency: IM cyanocobalamin 1000 mcg daily × 7 → weekly × 4 → monthly. Pancytopenia resolves within weeks.
- Drug-induced: Stop offending agent (methotrexate, chemotherapy, TMP-SMX, linezolid, valproate). Recovery in 1-3 weeks typically.
- Aplastic anemia: Age < 40 + matched sibling donor → allogeneic stem cell transplant. Older patients → immunosuppressive therapy: horse ATG + cyclosporine + eltrombopag. RACE, 2022
- MDS: Risk stratify (IPSS-R). Low-risk → ESA, lenalidomide (del5q). High-risk → azacitidine [AZA-001] or transplant if eligible.
- Leukemia: Induction chemotherapy per subtype. APL = ATRA + arsenic trioxide (curative in > 90%).
- HLH: Etoposide-based protocol (HLH-2004). Dexamethasone. Cyclosporine. Treat trigger.
Supportive care: pRBC for Hgb < 7 (or < 8 symptomatic). Platelets if < 10K or bleeding. Neutropenic precautions if ANC < 500. G-CSF if severe neutropenia with infection.

💊 Medications

Medications

Drug	Dose	Route	Notes
Cyanocobalamin	1000 mcg IM daily × 7d	IM	B12 deficiency. Expect retic crisis at day 5-7. Monitor K⁺ (drops with new cell production).
Horse ATG (ATGAM)	40 mg/kg/day × 4 days	IV	Aplastic anemia immunosuppression. Give with steroids (serum sickness prophylaxis). Scheinberg, 2011
Cyclosporine	5-6 mg/kg/day divided BID	PO	With ATG for aplastic anemia. Target trough 200-400. Nephrotoxicity, HTN, tremor.
Eltrombopag	150 mg daily	PO	Added to ATG+CsA in aplastic anemia improves response. RACE, 2022
Azacitidine	75 mg/m² SQ × 7 days q28d	SQ	High-risk MDS. Delays AML transformation. AZA-001, 2009
Lenalidomide	10 mg daily × 21/28 days	PO	MDS with del(5q). 67% transfusion independence. VTE prophylaxis required.
Filgrastim (G-CSF)	5 mcg/kg SQ daily	SQ	Severe neutropenia with infection. Not for chronic use in MDS (may accelerate AML).

🏥 Rounds

Pimp Questions

❓ What does a "dry tap" on bone marrow aspiration suggest?

A dry tap means the aspirate needle is correctly positioned but no marrow can be drawn. This occurs when the marrow space is replaced by fibrosis (myelofibrosis), packed with tumor cells (metastatic carcinoma, hairy cell leukemia), or in rare cases of severely aplastic marrow. The key next step is a core biopsy, this provides a tissue architecture sample even when aspiration fails. Reticulin and trichrome stains on the core biopsy will confirm fibrosis. Always suspect myelofibrosis when you see teardrop cells on smear + dry tap + splenomegaly.

❓ How do you differentiate aplastic anemia from MDS?

This is one of the most challenging distinctions in hematology. Key differences: Aplastic anemia → hypocellular marrow with normal morphology, no dysplasia, no increased blasts, younger patients, often responds to immunosuppression. Hypoplastic MDS → hypocellular marrow BUT with dysplastic changes (pseudo-Pelger-Huet cells, ring sideroblasts), cytogenetic abnormalities (especially -7, +8, del20q), and may have increased blasts. Cytogenetics is the key differentiator: present in ~50% of MDS but normal in aplastic anemia. Some cases require serial monitoring because aplastic anemia can evolve into MDS over time.

❓ What is the single most important initial test in pancytopenia?

Peripheral blood smear. It guides the entire workup: blasts (leukemia), teardrops (myelofibrosis), schistocytes (TTP/DIC), megaloblastic changes (B12/folate), dysplastic cells (MDS), normal morphology (aplastic anemia, viral, drug-induced).

❓ How can B12 deficiency cause pancytopenia?

B12 is required for DNA synthesis. Deficiency causes ineffective hematopoiesis -cells are produced but destroyed before release (intramedullary hemolysis). All three cell lines affected. The marrow is actually hypercellular (not empty) -megaloblastic precursors are dying before maturation. This can mimic MDS.

❓ What is a "dry tap" on bone marrow aspiration and what does it suggest?

A dry tap = inability to aspirate marrow despite proper needle placement. Classic for myelofibrosis (marrow replaced by reticulin/collagen fibrosis). Also seen in hairy cell leukemia, metastatic carcinoma (packed marrow), and some cases of aplastic anemia. Core biopsy is essential when aspirate fails.

❓ What electrolyte must you monitor when starting B12 repletion?

Potassium. As new red blood cells are rapidly produced (reticulocyte crisis), potassium shifts intracellularly. This can cause severe hypokalemia -potentially fatal if not monitored and repleted. Also monitor phosphate and magnesium for the same reason.

❓ Name a non-hematologic cause of pancytopenia that is commonly missed.

Copper deficiency. Causes sideroblastic anemia + neutropenia ± thrombocytopenia. Mimics MDS on smear and marrow. Risk factors: gastric bypass surgery, zinc supplementation (zinc competes with copper absorption), malnutrition, TPN without copper. Serum copper and ceruloplasmin are low. Responds to copper supplementation.

❓ What is HLH and how does it present?

Hemophagocytic lymphohistiocytosis (HLH) -uncontrolled immune activation with macrophage phagocytosis of blood cells. Presents with: persistent fever, splenomegaly, pancytopenia, hyperferritinemia (> 500, often > 10,000), hypertriglyceridemia, hypofibrinogenemia, elevated soluble IL-2 receptor. Triggers: infection (EBV), malignancy (lymphoma), autoimmune. Fatal without treatment -etoposide-based protocol. [HLH-2004]

Clinical Examples

📋 Case 1, Aplastic Anemia

Patient: 25F presenting with fatigue, easy bruising, and recurrent infections over 3 months.

Labs: WBC 1.2, Hgb 6.8, Plt 15K, reticulocyte count 0.2% (inappropriately low), MCV 98.

Peripheral smear: Pancytopenia with normal morphology, no blasts, no dysplasia, no schistocytes.

Workup:

B12, folate, HIV, hepatitis panel, all normal
LDH and haptoglobin, normal (no hemolysis)
Flow cytometry, no PNH clone
Bone marrow biopsy: markedly hypocellular (< 10% cellularity), fat-predominant, no blasts, no fibrosis

Diagnosis: Severe aplastic anemia (SAA), meets criteria: ANC < 500, Plt < 20K, retic < 1% with hypocellular marrow.

Treatment: No matched sibling donor → started on horse ATG + cyclosporine + eltrombopag. Supportive care with irradiated, leukoreduced blood products. Neutropenic precautions.

📋 Case 2, Megaloblastic Anemia (B12 Deficiency)

Patient: 68M presenting with progressive fatigue, paresthesias in both feet, and unsteady gait over 6 months.

Labs: WBC 3.1, Hgb 7.2, Plt 95K, MCV 112 (markedly elevated), reticulocyte count 0.8%.

Peripheral smear: Oval macrocytes, hypersegmented neutrophils (6-lobed), anisocytosis, poikilocytosis.

Workup:

B12: < 100 pg/mL (severely low, normal > 300)
Methylmalonic acid: elevated (confirms tissue B12 deficiency)
Homocysteine: elevated
Anti-intrinsic factor antibodies: positive → pernicious anemia

Diagnosis: Megaloblastic pancytopenia from B12 deficiency (pernicious anemia). No bone marrow biopsy needed, smear + B12 level diagnostic.

Treatment: IM cyanocobalamin 1000 mcg daily × 7 days → weekly × 4 → monthly for life. Reticulocyte crisis at day 5. Monitor K⁺ closely. Neuro symptoms may take months to improve.

📋 Case 3, Myelofibrosis

Patient: 72F presenting with early satiety, weight loss, night sweats, and progressive fatigue over 4 months.

Exam: Massive splenomegaly (palpable 8 cm below costal margin).

Labs: WBC 2.4, Hgb 8.5, Plt 68K, LDH elevated.

Peripheral smear: Teardrop cells (dacrocytes), nucleated RBCs, immature myeloid precursors, classic leukoerythroblastic picture.

Workup:

Bone marrow aspiration: dry tap, unable to aspirate despite multiple attempts
Core biopsy: extensive reticulin and collagen fibrosis, megakaryocyte atypia, osteosclerosis
JAK2 V617F mutation: positive
DIPSS-Plus risk score: intermediate-2

Diagnosis: Primary myelofibrosis (PMF). Dry tap + teardrop cells + leukoerythroblastic smear is the classic triad.

Treatment: Started ruxolitinib (JAK2 inhibitor) for symptom control and splenomegaly. Evaluated for allogeneic transplant given intermediate-2 risk.

Sample Presentation

Mrs. Chen is a 72-year-old woman referred for pancytopenia found on routine labs: Hgb 8.1, WBC 2.8 (ANC 900), platelets 78K. No B symptoms. No bleeding. No infections. Medications: metformin, lisinopril. Peripheral smear: macrocytosis, hypersegmented neutrophils, oval macrocytes. B12 level: 89 pg/mL (low). MMA elevated. Folate normal. Retic count 0.5%.

Key Points: Classic megaloblastic pancytopenia from B12 deficiency. Smear is diagnostic -hypersegmented neutrophils + oval macrocytes. Start IM B12 immediately. Expect reticulocyte crisis at day 5-7 and monitor K⁺ (drops with new hematopoiesis). No bone marrow biopsy needed if smear + B12 level confirm the diagnosis.

📋 Summary

Summary

Definition

Anemia + leukopenia + thrombocytopenia. A lab finding, not a diagnosis.

First Test

Peripheral smear. Blasts=leukemia. Teardrops=fibrosis. Megaloblastic=B12. Dysplastic=MDS.

Key Labs

Retic count, B12/folate, LDH, HIV/HBV/HCV, copper, ANA. Then bone marrow biopsy.

Production ↓

Aplastic anemia, MDS, leukemia, myelofibrosis, B12/folate, drugs, viral, infiltration

Destruction ↑

Hypersplenism, DIC, TTP, HLH, autoimmune

Pearl

Check copper. Hypersegmented neutrophils = B12 (not MDS). Dry tap = myelofibrosis.

📄 One Pager

One-Pager

Pancytopenia

Systematic Approach

Workup Algorithm

Step 1: Peripheral smear (most important). Step 2: Retic count (production vs destruction). Step 3: B12, folate, HIV, HCV, copper. Step 4: Bone marrow biopsy if not explained by above.

Common Causes by Smear

Blasts → leukemia. Teardrops → myelofibrosis. Megaloblastic → B12/folate. Dysplastic → MDS. Schistocytes → TTP. Normal → aplastic anemia, drug, viral.

Trials

RACE 2022 (ATG+CsA+eltrombopag for AA) · AZA-001 2009 (azacitidine for MDS) · HLH-2004 (etoposide protocol) · Scheinberg 2011 (horse vs rabbit ATG)