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

Hemolytic Anemia

Accelerated RBC destruction. Coombs test is the branch point: positive = immune (autoimmune, drug, transfusion). Negative = non-immune (mechanical, intrinsic RBC defect). Always check the smear.

🔍 Overview

Overview

Hemolytic anemia = shortened RBC lifespan (< 120 days) causing anemia with compensatory reticulocytosis. Hallmark labs: elevated LDH, elevated indirect bilirubin, low/undetectable haptoglobin, elevated reticulocyte count. Two categories by mechanism: Intravascular hemolysis (RBCs destroyed in circulation -hemoglobinuria, hemoglobinemia, very low haptoglobin -PNH, TTP, mechanical valve, transfusion reaction, DIC). Extravascular hemolysis (RBCs destroyed by splenic macrophages -splenomegaly, jaundice, no hemoglobinuria -AIHA, hereditary spherocytosis, sickle cell, hypersplenism). The direct Coombs test (DAT) is the critical branch point: positive = antibody on RBCs → immune hemolysis. Negative = non-immune → check smear for mechanistic clues.

🧪 Workup

Workup

Hemolysis labs: LDH (↑), haptoglobin (↓ or undetectable), indirect bilirubin (↑), reticulocyte count (↑). All four should be checked together.
Direct Coombs test (DAT) -the branch point.
- DAT positive: warm AIHA (IgG -most common, responds to steroids), cold agglutinin disease (IgM + complement -associated with Mycoplasma, lymphoma), drug-induced (cephalosporins, piperacillin, methyldopa), transfusion reaction
- DAT negative: microangiopathic (TTP, DIC, HUS -schistocytes on smear), mechanical (prosthetic valve), PNH (flow cytometry for GPI-anchored proteins), intrinsic RBC defects (G6PD, hereditary spherocytosis, sickle cell, thalassemia). If TTP suspected → calculate PLASMIC score (predicts ADAMTS13 deficiency) PLASMIC Score, Bendapudi 2017
Peripheral smear -essential. Schistocytes (TMA), spherocytes (AIHA, HS), sickle cells, bite cells (G6PD), target cells (thalassemia, liver)
Flow cytometry -if PNH suspected (dark urine, pancytopenia, abdominal vein thrombosis). Tests for CD55/CD59 (GPI-anchored proteins absent in PNH).
G6PD level -check BETWEEN episodes (level is falsely normal during acute hemolysis because young RBCs have more G6PD). Common triggers: sulfa drugs, dapsone, fava beans, infections.
Cold agglutinin titer -if DAT positive for complement only (C3d) with IgG negative. Associated with Mycoplasma pneumonia, EBV, lymphoma.
Osmotic fragility -hereditary spherocytosis (spherocytes lyse more easily in hypotonic solution)

🚨 Management

Management

Warm AIHA (DAT positive, IgG):
- First-line: Prednisone 1 mg/kg daily → taper when Hgb stabilizing. Response in 70-85% within 1-3 weeks.
- Second-line: Rituximab 375 mg/m² × 4 (steroid-refractory or relapsing). Also consider: mycophenolate, azathioprine. Lechner & Jäger, 2015
- Third-line: Splenectomy (if failing medical therapy). Vaccinate before surgery.
- Transfuse if life-threatening anemia -DO transfuse despite positive DAT making crossmatch difficult. Use "least incompatible" units. The blood bank will work with you.
Cold agglutinin disease (DAT positive, C3d): Keep patient warm (avoid cold exposure, warm IV fluids). Steroids less effective than in warm AIHA. Rituximab first-line. Sutimlimab (anti-C1s complement inhibitor) for chronic CAD CARDINAL, 2022. Avoid RBC transfusion if possible (complement activates on transfused cells).
TTP/HUS: See TTP topic (PLEX, steroids, caplacizumab). HERCULES, Scully 2019
PNH: Eculizumab (anti-C5 complement inhibitor) TRIUMPH, 2006. Meningococcal vaccine required before starting. Ravulizumab (longer-acting) available.
G6PD: Remove trigger (stop offending drug, treat infection). Supportive care. Avoid oxidant drugs lifelong.
Mechanical valve hemolysis: Usually mild. If severe → evaluate for paravalvular leak (echo). Iron/folate supplementation for chronic hemolysis.

💊 Medications

Medications

Drug	Dose	Route	Notes
Prednisone	1 mg/kg daily → taper	PO	First-line for warm AIHA. 70-85% respond. Taper slowly (relapse if too fast). Chronic steroid toxicity limits duration.
Rituximab	375 mg/m² weekly × 4	IV	Second-line for warm AIHA, first-line for CAD. Anti-CD20. Screen HBV. Response in 1-3 weeks.
Eculizumab	600 mg IV q7d × 4 → 900 mg q14d	IV	PNH -anti-C5 complement inhibitor. Meningococcal vaccine ≥ 2 weeks before. Lifelong therapy. TRIUMPH, 2006

🏥 Rounds

Pimp Questions

❓ What is the difference between intravascular and extravascular hemolysis?

Intravascular: RBCs destroyed IN the circulation → free hemoglobin released → hemoglobinuria (dark/red urine), hemoglobinemia, very low haptoglobin (consumed binding free Hgb), hemosiderinuria. Causes: TTP, DIC, PNH, transfusion reaction, mechanical valve. Extravascular: RBCs destroyed by splenic macrophages → splenomegaly, jaundice (indirect bili), no hemoglobinuria. Causes: AIHA, hereditary spherocytosis, sickle cell, hypersplenism.

❓ Should you withhold transfusion in AIHA because the crossmatch is incompatible?

NO -transfuse if clinically indicated. In warm AIHA, autoantibodies react with virtually ALL donor RBCs, making all crossmatches "incompatible." The blood bank performs extended testing to identify any underlying alloantibodies (from prior transfusions). They provide "least incompatible" units. Transfused RBCs will be destroyed faster than normal, but they provide critical oxygen delivery. Life-threatening anemia always trumps crossmatch difficulty.

❓ Why should you check G6PD levels BETWEEN episodes, not during?

During acute hemolysis, the oldest RBCs (with the LOWEST G6PD activity) are selectively destroyed first. The remaining RBCs + reticulocytes have higher G6PD levels because they're younger → the G6PD level can be falsely normal during the attack. Wait 2-3 months after the episode for the RBC population to normalize, then check. If you must diagnose acutely, a level that is low DURING hemolysis is definitely diagnostic -but a normal level doesn't exclude G6PD deficiency.

❓ What is Evans syndrome?

Evans syndrome = AIHA + immune thrombocytopenia (ITP) (positive DAT + low platelets from antiplatelet antibodies). May also include autoimmune neutropenia. Commonly associated with SLE and lymphoproliferative disorders. More refractory than isolated AIHA or ITP. Treatment: steroids, rituximab, mycophenolate. Splenectomy less effective than in isolated ITP. Always check platelets in new AIHA.

❓ What is the most sensitive lab marker for hemolysis?

Haptoglobin. It binds free hemoglobin and is rapidly cleared by the liver during hemolysis → levels become undetectable. It is the first lab to become abnormal and the last to normalize. Sensitivity ~96%. However, it is also an acute phase reactant -can be falsely "normal" during concurrent inflammation. The combination of undetectable haptoglobin + elevated LDH has the highest sensitivity/specificity for hemolysis.

Clinical Examples

📋 Case 1, Warm Autoimmune Hemolytic Anemia (AIHA)

Patient: 45F with SLE presenting with fatigue, jaundice, dark urine × 5 days. Hgb 5.8 (baseline 11.5), retic 14%, LDH 620, haptoglobin < 10, indirect bili 5.1. DAT positive (IgG + C3d). Smear: spherocytes.

Key findings: Warm AIHA, IgG antibodies on DAT, spherocytes from splenic macrophage partial phagocytosis. SLE is the classic autoimmune association. Severe anemia requiring urgent treatment.

Management:

Prednisone 1 mg/kg/day (first-line, response in 60-80% within 1-3 weeks)
Transfuse pRBCs, do NOT withhold despite "incompatible" crossmatch (all units will be incompatible; blood bank provides "least incompatible")
Folic acid 1 mg daily (hemolysis depletes folate stores)
If steroid-refractory or relapsing: rituximab 375 mg/m² weekly × 4 (second-line)
Check for Evans syndrome (AIHA + ITP), check platelet count

Teaching point: Never withhold transfusion in AIHA because the crossmatch is incompatible. All crossmatches will be incompatible, the autoantibody reacts with all RBCs. Transfused cells are destroyed faster but provide critical oxygen delivery.

📋 Case 2, Cold Agglutinin Disease

Patient: 68M with progressive fatigue and acrocyanosis (blue fingers/toes) in winter. Hgb 8.4, retic 8%, LDH 380, haptoglobin < 10. DAT positive (C3d only, IgG negative). Cold agglutinin titer 1:2048. SPEP: IgM kappa M-spike.

Key findings: Cold agglutinin disease, IgM antibodies bind RBCs at cold temperatures → complement activation → intravascular hemolysis. C3d-only DAT is the hallmark. IgM M-spike suggests underlying lymphoproliferative disorder (Waldenström's, marginal zone lymphoma).

Management:

Avoid cold exposure (the most important intervention, prevents antibody binding)
Steroids are INEFFECTIVE in cold agglutinin disease (unlike warm AIHA)
Rituximab ± bendamustine for symptomatic disease requiring treatment Berentsen, 2020
If transfusing: use blood warmer (cold blood triggers more agglutination)
Hematology workup: CT chest/abdomen/pelvis, bone marrow biopsy (rule out lymphoma)

Teaching point: Cold agglutinin disease is fundamentally different from warm AIHA, steroids don't work, splenectomy doesn't help (complement-mediated destruction is intravascular, not splenic). Treatment targets the B-cell clone producing the IgM.

📋 Case 3, G6PD Deficiency Hemolytic Crisis

Patient: 28M of Mediterranean descent with acute onset dark urine, back pain, jaundice 2 days after starting TMP-SMX for UTI. Hgb 7.2 (was 14), retic 2% (inappropriately low acutely), LDH 1200, haptoglobin < 10. DAT negative. Smear: bite cells, Heinz bodies on supravital stain.

Key findings: G6PD deficiency, oxidant stress (TMP-SMX) → Heinz body formation → splenic "biting" of Heinz bodies → bite cells. DAT negative distinguishes from AIHA. Low retic acutely because marrow hasn't responded yet (rises by day 5-7).

Management:

Stop the offending drug (TMP-SMX) immediately
Supportive care: IVF hydration, transfuse if symptomatic or Hgb < 7
Avoid oxidant triggers: sulfonamides, dapsone, nitrofurantoin, primaquine, fava beans, mothballs (naphthalene)
Do NOT check G6PD level now (falsely normal during hemolysis, older cells already destroyed). Recheck in 2-3 months
Hemolysis is self-limited, resolves once offending agent removed and affected RBCs cleared

Teaching point: G6PD level during acute hemolysis can be falsely normal because the most deficient cells have already been destroyed. A "normal" level during crisis does NOT exclude G6PD deficiency. Always recheck between episodes.

Sample Presentation

Mrs. Okafor is a 48-year-old woman with SLE presenting with fatigue, jaundice, and dark urine × 5 days. Exam: pallor, scleral icterus, mild splenomegaly. Labs: Hgb 6.2 (baseline 11), retic 12%, LDH 580, haptoglobin < 10, indirect bili 4.2. DAT strongly positive (IgG + C3d). Smear: spherocytes.

Key Points: Warm AIHA (DAT positive IgG, spherocytes on smear) in the setting of SLE (classic association). Start prednisone 1 mg/kg. Transfuse -Hgb 6.2 is dangerously low, even though crossmatch will be difficult (blood bank uses "least incompatible" units). Folic acid 1 mg daily. Check for Evans syndrome (concurrent thrombocytopenia).

Hemolysis markers q1-2 days during acute episode: LDH (simplest trending marker), haptoglobin, reticulocyte count
Hgb daily during active hemolysis -transfuse if < 7 (or < 8 if symptomatic/cardiac)
DAT -recheck if clinical picture changes or treatment response unexpected
On steroids: blood glucose, BP, mood assessment, bone protection (calcium + vitamin D)
On eculizumab/ravulizumab: meningococcal vaccination status, breakthrough hemolysis (LDH spike), Cr, CBC
Cold agglutinin: titer levels, avoid cold triggers, monitor for worsening during winter
Folate level -chronic hemolysis depletes folate → megaloblastic crisis if not supplemented

📋 Summary

Summary

Establish That It Is Hemolysis

High LDH, high indirect bilirubin, low haptoglobin, high reticulocyte count. A low haptoglobin with a high LDH is the most useful pair, and a normal haptoglobin makes significant intravascular hemolysis unlikely. Reticulocytosis takes 3 to 5 days to develop, so a normal count early does not exclude it.

The Coombs Test Is the Branch Point

Direct antiglobulin test positive = immune: autoimmune, drug-induced or a transfusion reaction. Negative = non-immune: mechanical, an intrinsic red cell defect, infection or a toxin. Everything downstream follows from this single result.

Always Look at the Smear Yourself

Schistocytes mean a microangiopathy (TTP, HUS, DIC, a mechanical valve, malignant hypertension). Spherocytes mean warm autoimmune hemolysis or hereditary spherocytosis. Bite cells and Heinz bodies mean G6PD deficiency. Sickle cells, target cells, agglutination each point somewhere specific. The smear frequently makes the diagnosis before the serology returns.

Warm and Cold AIHA Behave Differently

Warm (IgG, extravascular, splenic): the commoner type, associated with lupus, CLL, lymphoma and drugs. Treat with prednisone 1 mg/kg, to which 70 to 85% respond, tapering slowly because a fast taper relapses. Cold agglutinin disease (IgM, complement-mediated): associated with Mycoplasma, EBV and lymphoproliferative disease. Steroids work poorly; keep the patient warm and use rituximab as first line.

Schistocytes Are a Stop-Everything Finding

Thrombocytopenia with schistocytes is TTP until proven otherwise, and TTP is fatal without urgent plasma exchange. Use the PLASMIC score, send ADAMTS13, and do not wait for the result to start exchange in a high-probability patient. Do not transfuse platelets in suspected TTP unless there is life-threatening bleeding: it fuels further microthrombosis.

Ask What the Patient Took and Where They Have Been

G6PD deficiency hemolyzes after oxidative stress from dapsone, primaquine, nitrofurantoin, rasburicase, sulfa drugs, fava beans or an acute infection. Test after the acute episode, because the level is falsely normal during a crisis once the older, most deficient cells have already lysed. Also consider malaria and babesiosis in the returning traveler, and drug-induced immune hemolysis from cephalosporins and penicillins.

Do Not Miss PNH

Hemolysis with thrombosis at unusual sites, cytopenias, and dark morning urine. Flow cytometry for CD55 and CD59 loss makes the diagnosis, and it is easily overlooked in a patient labeled as having aplastic anemia or unexplained hemolysis. Eculizumab controls it, but it blocks terminal complement, so meningococcal vaccination at least 2 weeks before the first dose plus antibiotic prophylaxis is mandatory.

Supportive Care With Two Cautions

Give folate, since high turnover consumes it, and treat iron loss in chronic intravascular hemolysis. Crossmatching may be difficult or impossible in AIHA, so involve the blood bank early and do not withhold transfusion from an unstable patient because the units are incompatible: least-incompatible blood is safer than untreated anemia. Screen for the underlying disorder, since AIHA is frequently secondary to lymphoproliferative disease, lupus or a drug rather than idiopathic.

📄 One Pager

Hemolytic Anemia one-page infographic. Confirm hemolysis, then let the DAT split it. Tap to open the full-size printable PDF.

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Text version

One-Pager

Hemolytic Anemia

DAT is the branch point

Algorithm

Confirm hemolysis (LDH ↑ + haptoglobin ↓ + retic ↑ + indirect bili ↑) → DAT. Positive: warm AIHA vs cold vs drug. Negative: check smear -schistocytes (TMA), spherocytes (HS), bite cells (G6PD). PNH: flow cytometry.

Smear Clues

Schistocytes → TTP/DIC/valve. Spherocytes → AIHA or HS. Bite cells/Heinz bodies → G6PD. Sickle cells → SCD. Target cells → thalassemia/liver.

Trials

TRIUMPH 2006 (eculizumab for PNH) · CARDINAL 2022 (sutimlimab for CAD)