鐮刀型紅血球危象

Buzzwords → Dx

Diagnostic / Triage Concepts

• Always r/o ACS in any SCD pt with chest pain or dyspnea — get CXR.
• VOC vs other: VOC is exclusion diagnosis once ACS, infection, AVN, gallstones, stroke ruled out.
• Crisis = SCD presentation requiring acute medical attention; many can be managed outpatient with hydration + oral analgesia.

Workup

• CBC + retic + smear + LDH + bilirubin + haptoglobin baseline + serial.
• Cultures + lactate if febrile / unstable.
• CXR + ABG if any respiratory symptom or VOC.
• Doppler / MRI/MRA for stroke or AVN.
• Type & screen + crossmatch (antigen-matched) if transfusion anticipated.
• TCD in children for stroke screening.

Treatment Algorithm

flowchart TD
  A[SCD acute presentation] --> B[ABCs + IV access + O₂ if hypoxic]
  B --> C{Crisis type}
  C -- VOC pain only --> D[IVF + opioid PCA + warmth + spirometry<br>monitor for ACS]
  C -- ACS new infiltrate / hypoxia --> E[O₂ + IV abx (covering atypicals) + IVF + analgesia<br>+ EXCHANGE TRANSFUSION if severe<br>± NIV / intubation]
  C -- Stroke / TIA --> F[Emergent neuroimaging<br>EXCHANGE TRANSFUSION target HbS <30%<br>chronic transfusion ppx]
  C -- Splenic sequestration --> G[Transfuse + observe<br>splenectomy if recurrent]
  C -- Aplastic crisis --> H[Supportive RBC transfusion<br>parvovirus B19 PCR + isolation]
  C -- Priapism >4 h --> I[Urology + aspiration / phenylephrine<br>EXCHANGE TRANSFUSION if persistent]
  D --> J{Improvement in 24-48 h?}
  E --> J
  J -- yes --> K[Discharge planning<br>Hu, vaccinations, FU heme]
  J -- no --> L[Reassess: missed dx? AVN, abscess, undiagnosed infection?<br>consider exchange transfusion]

Pearls / Pitfalls

• ACS is the leading cause of adult SCD mortality — early O₂ + antibiotics (cover S. pneumo + atypicals) + analgesia + exchange transfusion.
• Exchange transfusion vs simple transfusion in severe ACS / stroke / priapism: exchange achieves HbS <30 % without ↑viscosity. Goal Hb 9–10 (not >10 — viscosity).
• Don't over-transfuse SCD — Hb >10 g/dL increases viscosity worsening sickling.
• Stroke prevention in children: TCD velocity ≥200 cm/s annually = chronic transfusion until age 16–18 (STOP / TWITCH); transition to hydroxyurea if stable on TCD.
• Hyperhemolysis post-transfusion = severe Hb drop + hemoglobinuria + reticulopenia within 1–3 wk; treat with IVIG + steroids + avoid further transfusion; rituximab if recurrent.
• Avoid hypoxia / dehydration / cold as triggers — patient education.
• Priapism >4 h is a urologic emergency — irreversible damage if delayed; aspiration + phenylephrine + exchange transfusion.
• Aplastic crisis (parvovirus B19) is transient (2–4 wk) — supportive transfusion. Universal aplastic crisis precaution: airborne isolation in immunocompromised contacts.
• Pain control: opioid PCA preferred for severe VOC; multimodal (NSAIDs + acetaminophen + opioid); avoid meperidine (seizure risk with norverbal accumulation).
• G6PD-deficient SCD pts (overlap) → avoid oxidant drugs (similar G6PD list).
• Hemoglobin SC patients are NOT immune to crises — milder course but still get ACS, retinopathy (more than HbSS), AVN.

Cross-references

• SCD — chronic disease management
• Apheresis — RBC exchange
• Alloimmunization — antigen-matched RBCs
• Pain — opioid management
• Infection prophylaxis (PCN, vaccines)
• PRCA — parvovirus aplastic crisis

相關題目

• Q-193 — SCD vaso-occlusive pain crisis — pain management
• Q-194 — SCD priapism management
• Q-195 — Hyperhemolysis post-transfusion in SCD

Sources