A 28-year-old woman with GBS (day 5 of illness, FVC 22 mL/kg) is admitted to ICU. She has already received IVIG 2 g/kg over 5 days. On day 7 of admission, she develops worsening weakness in the lower limbs and new onset facial diplegia. Vital capacity has dropped to 18 mL/kg. What is the most appropriate next step in management?

Explanation

## Management of IVIG-Refractory or Progressive GBS **Key Point:** A patient who worsens or plateaus despite IVIG therapy (especially within 2 weeks of symptom onset) should be switched to plasmapheresis. Repeating IVIG or adding corticosteroids is not evidence-based; combination therapy (IVIG + plasmapheresis) is reserved for fulminant cases. **High-Yield:** In GBS, IVIG and plasmapheresis are equally effective when started early, but if one fails, switching to the other is the standard approach. Combination therapy is rarely needed and is not first-line. ## Rationale for Plasmapheresis in This Case 1. **Timing of deterioration:** Day 7 of illness with worsening weakness and declining FVC after IVIG completion suggests inadequate response. 2. **Evidence:** Plasmapheresis is equally effective as IVIG and should be offered if IVIG fails or if the patient is in the fulminant phase. 3. **Respiratory status:** FVC 18 mL/kg indicates imminent respiratory failure; plasmapheresis may provide faster improvement than observation or repeated IVIG. ## Treatment Algorithm for GBS ```mermaid flowchart TD A[GBS Diagnosed]:::outcome --> B{Respiratory compromise?}:::decision B -->|Yes: FVC <20 mL/kg| C[ICU admission]:::action B -->|No| D[Outpatient management possible] C --> E[Start IVIG 2 g/kg over 3-5 days]:::action E --> F{Improvement in 1-2 weeks?}:::decision F -->|Yes| G[Continue supportive care]:::action F -->|No or worsening| H[Switch to Plasmapheresis]:::action H --> I[5 exchanges over 7-10 days]:::action I --> J{Fulminant course?}:::decision J -->|Yes| K[Consider combination IVIG + PE]:::action J -->|No| L[Supportive care & rehabilitation]:::action ``` ## Comparison: IVIG vs Plasmapheresis | Feature | IVIG | Plasmapheresis | |---------|------|----------------| | **Efficacy** | ~70% improvement at 4 weeks | ~70% improvement at 4 weeks | | **Onset of action** | 3–5 days | 1–2 days (faster) | | **Contraindications** | IgA deficiency, renal impairment | Hemodynamic instability, thrombocytopenia <20k | | **When to switch** | If PE fails | If IVIG fails or fulminant course | | **Combination therapy** | Rarely needed; not first-line | Reserved for fulminant GBS | **Clinical Pearl:** Plasmapheresis has a slightly faster onset than IVIG (1–2 days vs 3–5 days) and may be preferred in fulminant cases or when respiratory failure is imminent. **Warning:** Repeating IVIG without evidence of benefit wastes time and resources. Corticosteroids are not effective in GBS. MRI is not indicated unless atypical features suggest alternative diagnosis (e.g., spinal cord lesion, demyelinating disease). [cite:Harrison 21e Ch 385; Robbins 10e Ch 27]