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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CommonHematology

Anemia Workup

Classify by MCV first -microcytic, normocytic, or macrocytic. Then use iron studies, reticulocyte count, and peripheral smear to narrow the diagnosis. Iron deficiency is the most common cause worldwide.

🔍 MCV-Based Classification

MCV	Category	Differential	Key Labs
< 80	Microcytic	Iron deficiency (#1 -GI blood loss in men/postmenopausal women until proven otherwise), thalassemia (Mentzer index: MCV/RBC < 13 → thalassemia, > 13 → iron def), anemia of chronic disease (some), sideroblastic, lead poisoning	Iron studies, ferritin, TIBC, reticulocyte count, Hgb electrophoresis if thalassemia suspected
80–100	Normocytic	Anemia of chronic disease (#1), acute blood loss, CKD (↓ EPO), mixed deficiency (iron + B12), hemolysis (check hemolysis labs), bone marrow failure (aplastic, MDS, infiltration)	Reticulocyte count (↑ = destruction/loss, ↓ = underproduction), BMP (CKD), hemolysis labs (LDH, haptoglobin, indirect bili, smear)
> 100	Macrocytic	B12 deficiency (neurologic symptoms -subacute combined degeneration), folate deficiency, alcohol/liver disease, hypothyroidism, MDS, medications (methotrexate, hydroxyurea, azathioprine, AZT), reticulocytosis (reticulocytes are large → MCV ↑)	B12, folate, reticulocyte count, TSH, peripheral smear (hypersegmented neutrophils → megaloblastic), methylmalonic acid (↑ in B12 def, normal in folate def)

New iron deficiency anemia in a man or postmenopausal woman = GI malignancy until proven otherwise. These patients need colonoscopy + upper endoscopy. Do NOT just give iron and move on.

Reticulocyte Count -Production vs Destruction

Reticulocyte count > 2% (or reticulocyte index > 2): bone marrow is responding → the problem is blood loss or destruction (hemolysis)
Reticulocyte count < 2%: bone marrow is NOT responding → underproduction (iron/B12/folate deficiency, CKD, bone marrow failure, anemia of chronic disease)
Reticulocyte Production Index (RPI): (retic % × Hgb/15) / maturation factor. RPI > 2 = appropriate response.

🧪 Iron Studies Interpretation

Lab	Iron Deficiency	Anemia of Chronic Disease	Both (Mixed)
Serum iron	↓	↓	↓
Ferritin	↓↓ (< 30)	↑ or normal (acute phase reactant)	Low-normal (30–100)
TIBC	↑ (body wants more iron)	↓ (body not trying to absorb more)	Variable
Transferrin saturation (TSAT)	↓ (< 20%)	↓ (15–20%)	↓

Ferritin is an acute phase reactant -it rises with inflammation, infection, liver disease, and malignancy. A "normal" ferritin of 50–100 in an inflamed hospitalized patient may actually represent iron deficiency. Ferritin < 30 is diagnostic of iron deficiency. Ferritin < 100 in the setting of inflammation is suggestive.

What is TSAT (Transferrin Saturation)? The percentage of transferrin (the iron-carrying transport protein) that is currently bound to iron. Formula: TSAT = (serum iron ÷ TIBC) × 100. Normal range: 20-50%. Iron deficiency: < 20%. Iron overload: > 45-50% (consider hemochromatosis or transfusion overload).

Why it complements ferritin: TSAT reflects the iron actually available right now for erythropoiesis (the "circulating" iron pool), while ferritin reflects storage iron. TSAT is less affected by inflammation, so it's the more reliable marker when ferritin is unreliable -hospitalized inflamed patients, HF, CKD, chronic infection, malignancy. A patient with ferritin 80 + TSAT 12% is iron-deficient even though the ferritin looks "OK."

Pre-test pearls: hold oral iron for 24-48 h before drawing labs (recent iron pill falsely elevates TSAT). TSAT has a diurnal rhythm -higher in the morning -so a fasting AM draw is most reliable when the result is borderline.

Iron Replacement

Route	Agent	Notes
Oral	Ferrous sulfate 325 mg PO daily–TID	Take on empty stomach with vitamin C (enhances absorption). GI side effects are dose-limiting. Every-other-day dosing may improve absorption and tolerability. Takes 3–6 months to replete stores.
IV (preferred if)	Iron sucrose (Venofer) 200 mg IV × 5 doses or ferric carboxymaltose (Injectafer) 750 mg IV × 2	Preferred if: oral intolerant, CKD/dialysis, IBD, ongoing blood loss exceeding oral repletion, Hgb < 7 with symptoms, pre-surgery. Injectafer: can give 750 mg in one sitting (fewer visits).

🧪 Workup

Workup

CBC + retic count (#1 test)
Peripheral smear
Iron studies
B12 + folate
LDH, haptoglobin, indirect bili -hemolysis
Direct Coombs
EPO level
Bone marrow biopsy if unclear

🚨 Management

Management

Iron deficiency: FIND SOURCE + IV iron (ferric carboxymaltose 750mg×2) or PO. Transfuse: Hgb<7 in most patients TRICC, Hébert 1999
B12: IM cyanocobalamin 1000mcg daily×7→weekly×4→monthly
Hemolytic: autoimmune→steroids±rituximab. TTP→PLEX. Mechanical→treat cause.
CKD: iron first, then ESA (Hgb 10-11)
Transfuse: Hgb<7 most, <8 ACS TRISS, Holst 2014 TITRe2, Murphy 2015

📋 On Rounds

How do you distinguish iron deficiency from anemia of chronic disease when both have low serum iron?

Ferritin and TIBC. In iron deficiency, the body is truly depleted of iron → ferritin is low (< 30) and TIBC is high (the body upregulates transferrin to grab any available iron). In anemia of chronic disease, iron is trapped in macrophages by hepcidin (the inflammatory "iron warden") → ferritin is normal or high (iron is stored, just not released) and TIBC is low (no need to absorb more -there's plenty, just sequestered).

A patient has a ferritin of 80 but you still suspect iron deficiency. How is that possible?

Ferritin is an acute phase reactant -it rises with inflammation, infection, liver disease, and malignancy regardless of iron stores. A 'normal' ferritin of 80 in a patient with active inflammation (elevated CRP) may actually represent iron deficiency. In the setting of chronic disease or inflammation, a ferritin < 100 with transferrin saturation < 20% suggests functional iron deficiency even though ferritin appears 'normal'.

A patient has pancytopenia. What's your differential and what do you order?

Pancytopenia = all three lines down (anemia + leukopenia + thrombocytopenia). Differential by mechanism: Decreased production (bone marrow failure): aplastic anemia, MDS, leukemia/lymphoma, myelofibrosis, B12/folate deficiency (megaloblastic), drug-induced (methotrexate, chemotherapy), infections (HIV, hepatitis, parvovirus, TB). Increased destruction: hypersplenism (cirrhosis), DIC, TTP/HUS, autoimmune (SLE). Workup: CBC with peripheral smear (blasts → leukemia; schistocytes → TTP/DIC; hypersegmented neutrophils → B12/folate; teardrop cells → myelofibrosis). Reticulocyte count (↓ = production problem, ↑ = destruction/loss). B12, folate, LDH, haptoglobin, Coombs. HIV, hepatitis serologies. Fibrinogen, D-dimer, PT/PTT if DIC suspected. ADAMTS13 if TTP suspected. SPEP/free light chains if myeloma on smear (rouleaux). Bone marrow biopsy if etiology unclear after initial labs, or if blasts / leukoerythroblastic picture on smear.

How do you approach anemia when the MCV is normal (normocytic)?

Normocytic anemia (MCV 80-100): the broadest differential. Step 1: Reticulocyte count. High retic (> 2%): the marrow is responding → blood LOSS or blood DESTRUCTION. Check: LDH, haptoglobin, Coombs test. If hemolysis markers positive → hemolytic anemia (autoimmune, TTP, DIC, G6PD, sickle cell, PNH). If hemolysis markers negative → acute blood loss (look for the source). Low retic (< 2%): marrow is NOT responding → production problem.

Clinical Examples

📋 Case 1, Microcytic Anemia from Menorrhagia

Patient: 34-year-old premenopausal woman with heavy menstrual periods presents with fatigue and pica (ice craving).

Key findings: Hgb 7.6, MCV 65, ferritin 4, TIBC 520, TfSat 4%, reticulocyte index 0.5%. Smear: microcytic hypochromic cells, pencil cells.

Management:

IV iron (ferric carboxymaltose 750 mg x 2) due to severity
Gynecology referral for menorrhagia management
GI workup deferred given clear gynecologic source and young age

Teaching point: Pica (pagophagia) is specific for iron deficiency. In premenopausal women, menorrhagia is the most common cause. IRON-MIDE, 2020

📋 Case 2, Normocytic Anemia with Hemolysis

Patient: 42-year-old woman with SLE presents with jaundice, dark urine, and worsening fatigue. Splenomegaly on exam.

Key findings: Hgb 6.2, MCV 102 (elevated from reticulocytosis), reticulocyte count 12%, LDH 680, haptoglobin undetectable, indirect bilirubin 4.8, DAT positive (IgG + C3).

Management:

Warm AIHA secondary to SLE: prednisone 1 mg/kg/day
Transfuse if hemodynamically unstable
If steroid-refractory: rituximab or splenectomy

Teaching point: Warm AIHA (IgG-mediated) is associated with SLE, CLL, and drugs. MCV may be falsely elevated because reticulocytes are larger than mature RBCs. Haptoglobin is the most sensitive hemolysis marker.

📋 Case 3, Macrocytic Anemia from B12 Deficiency

Patient: 68-year-old vegan woman presents with fatigue, glossitis, and bilateral lower extremity paresthesias. Decreased vibration sense, positive Romberg.

Key findings: Hgb 9.2, MCV 124, reticulocyte index 0.6. B12 less than 100. Methylmalonic acid 2400 (markedly elevated). Smear: macro-ovalocytes, hypersegmented neutrophils.

Management:

IM cyanocobalamin 1000 mcg daily x 7d, then weekly x 4, then monthly lifelong
Monitor K+ and phosphate (drop during rapid erythropoiesis)
Neurology follow-up for subacute combined degeneration

Teaching point: B12 deficiency causes subacute combined degeneration (posterior columns + lateral corticospinal tracts). Methylmalonic acid differentiates B12 from folate deficiency. Neurologic damage may be irreversible if treatment is delayed.

📣 Sample Presentation

One-Liner

"Mrs. Rivera is a 48-year-old premenopausal woman with fatigue and Hgb 8.2, MCV 72. Iron studies: ferritin 8, TIBC 450, transferrin sat 6%. Consistent with iron deficiency anemia."

Key Points to Cover on Rounds

Microcytic anemia -iron deficiency confirmed (ferritin 8, Tsat 6%). Source: heavy menstrual bleeding (menorrhagia × 2 years, soaking through pads). No GI symptoms, no melena. Given her age and clear gynecologic source, GI workup deferred. Treatment: IV iron infusion (ferric carboxymaltose 750 mg × 2 doses, 1 week apart) -chose IV over PO due to severity and faster repletion. Gynecology referral for menorrhagia management. Plan: recheck CBC + ferritin in 6-8 weeks, expect Hgb rise 1 g/dL per week of iron.

💊 Medications

Key Medications -Anemia

Treatment depends on the cause. Iron deficiency = replace iron + find source. B12 deficiency = replace B12. Anemia of CKD = iron first, then ESA. Hemolytic = treat underlying cause.

Drug	Dose	Route	Indication
Ferrous sulfate	325 mg PO daily–TID	PO	Iron deficiency anemia (mild-moderate). Take on empty stomach with vitamin C. Every-other-day dosing may improve absorption.
Iron sucrose (Venofer)	200 mg IV x 5 doses	IV	IV iron preferred if: oral intolerant, CKD/dialysis, IBD, Hgb < 7, ongoing blood loss, pre-surgery.
Ferric carboxymaltose (Injectafer)	750 mg IV x 2 (1 week apart)	IV	Convenient IV iron -can give 750 mg in one sitting (fewer visits).
Cyanocobalamin (B12)	1000 mcg IM daily x 7d → weekly x 4 → monthly	IM	B12 deficiency. High-dose oral (1000–2000 mcg/day) may be adequate if no absorption issues.
Folic acid	1 mg PO daily	PO	Folate deficiency. Always check B12 first -folate alone can mask B12 deficiency (corrects anemia but NOT neuro damage).
Epoetin alfa (Procrit)	50–300 units/kg 3x/week	IV/SQ	Anemia of CKD (after iron repletion). Target Hgb 10–11.5. Never > 13.

⚡ Summary

Summary

MCV Approach

Microcytic (< 80): iron deficiency, thalassemia, chronic disease, sideroblastic. Normocytic (80-100): chronic disease, CKD, hemolysis, bleeding. Macrocytic (> 100): B12/folate, MDS, liver disease, hypothyroid, drugs.

Iron Deficiency

Ferritin < 30 (or < 100 in CKD/inflammation), low Tsat. Find the source: GI (colonoscopy), menstrual, malabsorption. IV iron for severe/refractory.

Hemolysis Workup

LDH ↑, haptoglobin ↓, indirect bilirubin ↑, reticulocyte ↑. Coombs test: positive = autoimmune. Negative = mechanical (TTP, DIC, prosthetic valve).

Transfusion Threshold

Hgb < 7 for most patients [TRICC, TRISS]. Hgb < 8 for active cardiac ischemia. Never transfuse to a number -transfuse for symptoms.

B12 Deficiency

Can cause pancytopenia mimicking leukemia. Hypersegmented neutrophils on smear. Neuro symptoms (subacute combined degeneration). Check methylmalonic acid.

Reticulocyte Count

The single most important test. High retic = bone marrow is working (loss or destruction). Low retic = production failure (check iron/B12/folate, consider biopsy).

📄 One Pager

Anemia Workup -Quick Reference Card

Print this page (Ctrl/Cmd + P) for a condensed reference card. All tabs will print on the same page for a complete topic summary.

ANEMIA WORKUP -AT A GLANCE

📋 Diagnose: See Overview tab for criteria
🧪 Workup: Focused labs + imaging → see Workup tab
⚡ Treat: Evidence-based algorithm → see Management tab
💊 Drugs: Key medications with dosing → see Medications tab
📣 Present: One-liner + key points → see Rounds tab

📄 One Pager

Hematology · One Pager

Anemia

MCV-based approach: micro (iron), normo (chronic disease, hemolysis, bleeding), macro (B12/folate). Reticulocyte count = production vs destruction. Transfuse Hgb < 7.

🧪 MCV Approach

Microcytic (< 80): iron deficiency (#1), thalassemia, chronic disease, sideroblastic. Normocytic (80-100): chronic disease, CKD, hemolysis, acute bleeding. Macrocytic (> 100): B12/folate, MDS, liver disease, hypothyroid, drugs.

🚨 Iron Deficiency

Ferritin < 30 (or < 100 in inflammation/CKD), low transferrin sat. FIND THE SOURCE: GI (colonoscopy if > 50 or alarm features), menstrual, malabsorption. IV iron for severe or refractory.

💊 Hemolysis Workup

LDH ↑, haptoglobin ↓, indirect bili ↑, reticulocyte ↑. Coombs positive = autoimmune (warm vs cold). Coombs negative = mechanical (TTP, DIC, valve), PNH, G6PD, sickle cell.

💊 Key Drugs

Ferric carboxymaltose750 mg IV × 2 doses

Cyanocobalamin1000 mcg IM daily × 7d

Folic acid1 mg PO daily

EPO50-300 U/kg 3×/wk (CKD)

⚠️ Pitfalls

Transfusing above Hgb 7 threshold without indication
Not checking reticulocyte count (production vs destruction)
Missing B12 deficiency (can cause pancytopenia mimicking leukemia)
Iron infusion without finding the source of loss