Myasthenic Crisis and Guillain-Barré Syndrome

In depth

The one-page summary above is what the PDF prints. These sections go further.

Pump failure: why the gas changes last

Neuromuscular respiratory failure is pump failure in normal lungs. Four problems combine (Mehta 2006): bulbar weakness lets the tongue and pharynx collapse and saliva reach the larynx; inspiratory weakness shrinks the vital capacity; expiratory weakness leaves a cough too weak to clear the airway; and atelectasis and aspiration pneumonia follow.

As vital capacity falls from its normal 60–70 mL/kg, the cough and the deep sighs that hold alveoli open go first, so atelectasis and secretions build while the blood gas is normal. Smaller, faster breaths keep PaCO₂ normal or low until the muscles tire; then it rises, often within hours. SpO₂ falls only when atelectasis, aspiration or late hypoventilation adds shunt, and supplemental oxygen keeps it normal while CO₂ climbs. A normal gas does not reassure; an abnormal one is late.

GBS is inherently unpredictable, though rapid progression, bulbar or bilateral facial weakness and dysautonomia flagged ventilation (Lawn 2001), hence scheduled testing. MG fluctuates: strength can collapse within hours, and bulbar weakness can block the airway before vital capacity falls far.

Measuring strength and deciding to ventilate

Measure sitting up, with a flanged mouthpiece or a face mask when facial weakness breaks the lip seal; take the best of three. NIF is pulled against an occluded airway after full exhalation, MEP blown after a full breath; both depend on effort and seal, so look at the patient as well as the number.

Single-breath count: after a maximal breath the patient counts aloud at about two numbers a second; the middle half of healthy young adults reach 31–49. In GBS a count of 19 or less caught 95% of patients who later needed ventilation, and 5 or less was 95% specific for it; in MG a count under 25 flagged exacerbation with 80% sensitivity (Bhandari 2024 review). EAN/PNS 2023 uses under 20.

Of 722 GBS adults not ventilated at admission, 43% later were; six features predicted it (under 7 days from onset to admission, inability to cough, stand, lift the elbows or lift the head, and raised liver enzymes), and with 4 or more, over 85% were ventilated (Sharshar 2003).

NIV, intubation, the ventilator and liberation

In myasthenic crisis, BiPAP can rest the muscles while IVIG or plasma exchange works. It avoided intubation in 7 of 11 episodes (failure with PaCO₂ above 50 mm Hg at the start; Rabinstein 2002) and in 14 of 24 (failure predicted by PCO₂ above 45; Seneviratne 2008); in 250 ventilated German crises, NIV alone sufficed in 38% of 92 attempts (Neumann 2020). It suits an alert patient who clears secretions; recheck VC, PaCO₂ and secretions within hours.

In GBS, weakness keeps progressing for days, bulbar weakness and dysautonomia are common, and ventilation often lasts weeks. Both patients Wijdicks and Roy reported (2006) improved on BiPAP and then needed emergency intubation, and an ICU review warns that NIV can turn an elective intubation into an emergency (Shang 2021).

Intubate electively, upright for preoxygenation. Dysautonomic patients can drop their pressure at induction and with positive pressure or slow abruptly with suctioning: have a vasopressor ready, draw up atropine, reduce induction doses. With normal lungs most units use 6–8 mL/kg PBW and PEEP 5–8 against atelectasis (older MG reviews used 8–10 mL/kg IBW; Wendell 2011), chest physiotherapy, and bronchoscopy for lobar collapse.

Median ventilation in myasthenic crisis was 12 days (Neumann 2020). Extubation needs VC above about 15 mL/kg (Godoy 2013; 25 in one German SOP), a strong cough, few secretions and safe swallowing. It failed in 44% of 46 crisis episodes, with atelectasis the strongest predictor (Seneviratne 2008 extubation series). In GBS, 71% of 150 ventilated patients needed 2 weeks or more (median 28 days); a week after intubation, inability to lift the arms from the bed predicted that in 87%, and axonal or unexcitable nerves in 90% of those who could, so consider tracheostomy (Walgaard 2017).

Guillain-Barré syndrome: mechanism, forms and diagnosis

About two-thirds of patients had an infection in the 6 weeks before onset; Campylobacter jejuni, CMV, hepatitis E, Mycoplasma, EBV and Zika have the strongest links, and influenza vaccination adds about one case per million doses (Leonhard 2019). In AIDP, immune attack strips myelin and conduction slows or blocks; remyelination takes weeks. C. jejuni sugars mimic the gangliosides GM1 and GD1a, and cross-reacting antibodies fix complement at the nodes of Ranvier, causing the axonal form (AMAN), commoner in Asia (EAN/PNS 2023).

The diagnosis is clinical: progressive, relatively symmetric weakness of arms and legs with reduced or absent reflexes, worsening for no more than 4 weeks. CSF protein was raised in 50% within 3 days of onset and 84% after a week; cells were under 5/µL in 80%, 5–50 in 19% and over 50 in 2% (EAN/PNS 2023). Nerve conduction may be normal early. Features that make GBS less likely (EAN/PNS 2023):

• Marked, persistent asymmetry; a sensory level; extensor plantars
• Bladder or bowel dysfunction or fever at onset
• Severe respiratory failure with mild limb weakness
• Nadir within 24 h, or worsening beyond 4 weeks
• CSF over 50 cells/µL; altered consciousness

Mimics include cord compression or myelitis, botulism (weakness descending from the cranial nerves), myasthenia gravis, tick paralysis, acute flaccid myelitis, critical illness neuropathy or myopathy, and low potassium or phosphate (Leonhard 2019).

GBS: predicting the course and choosing immunotherapy

EGRIS came from 397 patients (22% ventilated in week 1; AUC 0.84; Walgaard 2010). The mEGRIS (1,133 international patients) uses days to admission, bulbar palsy, and neck and hip flexion, works in mild disease and variants, and can be repeated (Luijten 2023); EAN/PNS 2023 recommends it. mEGOS uses age, preceding diarrhea and the MRC sum at admission or day 7 to predict inability to walk unaided at 4 weeks, 3 and 6 months (Walgaard 2011).

Against supportive care, plasma exchange nearly halved ventilation (RR 0.53) and improved walking with aid at 4 weeks (RR 1.60) and full strength at 1 year (RR 1.24) (Cochrane, Chevret 2017). In the 1997 trial of 379 patients, disability improved 0.9 grades with exchange (five 50 mL/kg sessions), 0.8 with IVIG 0.4 g/kg for 5 days and 1.1 with both, not significantly different; IVIG is completed more often (Cochrane, Hughes 2014). Steroids alone did not help, and oral steroids slowed recovery (Cochrane, Hughes 2016).

SID-GBS (2021) gave 93 poor-prognosis patients (mEGOS 6 or more) a second IVIG course: no benefit (common OR 1.4, 95% CI 0.6–3.3) and more serious adverse events (35% vs 16%), including thromboembolism. EAN/PNS 2023 advises one course for patients unable to walk unaided (IVIG within 2 weeks, 2–4 weeks as good practice; exchange within 4 weeks), treating walking patients who worsen fast or have bulbar, autonomic or respiratory risk, and no switch when the first therapy seems to fail.

A treatment-related fluctuation, worsening within 2 months after improvement or stabilization, occurs in 6–10% and is usually retreated without trial evidence (Leonhard 2019); worsening beyond 8 weeks or 3 or more fluctuations suggests acute-onset CIDP (EAN/PNS 2023).

GBS in the ICU: dysautonomia, pain and complications

Autonomic involvement affects up to two-thirds, and deaths attributed to it now exceed those from respiratory failure (Zaeem 2019). Sympathetic overactivity gives sustained tachycardia and hypertension; vagal surges give bradycardia and asystole. In 100 patients, serious arrhythmias occurred only in ventilated ones (11 of 33, 7 died), often after wide pulse and pressure swings and transient asystole with tracheal suction (Winer 1988). In 36 ventilated patients, all bradycardias but one were preceded by a daily systolic range above 85 mm Hg (Pfeiffer 1999).

• Continuous ECG; arterial line when pressure swings; record the daily systolic range
• Preoxygenate, keep suction brief, stop for bradycardia; atropine drawn up; temporary pacing if severe (Shang 2021)
• Hypotension: check volume, sedation and PEEP first; titrate a short-acting vasopressor
• Hypertension is often transient: treat only sustained extremes, with titratable drugs
• Bowel regimen and lowest effective opioid for ileus; bladder scans for retention
• Daily sodium: SIADH in 24 of 50 in one series (Saifudheen 2011); IVIG can cause pseudohyponatremia (label)

Pain affected 66% in the acute phase, began before weakness in 36% and persisted at 1 year in 38% (Ruts 2010): back, radicular, muscular or burning. EAN/PNS 2023 weakly recommends gabapentin or carbamazepine (trial doses 300 mg and 100–200 mg three times a day), suggests gabapentinoids or tricyclics before carbamazepine, warns about tricyclics with autonomic failure and about opioid ileus and confusion, and advises against high-dose steroids for pain.

Immobility adds pneumonia, urinary infection, pressure injury and VTE (DVT 4–7%, PE 3–7% in case series; NCS 2016), and corneal ulcers when the eyes do not close (Leonhard 2019). Two-thirds of GBS deaths occur after ICU discharge, mostly from respiratory or cardiovascular causes (EAN/PNS 2023), so monitoring continues on the ward.

Myasthenia gravis and the crisis

About 80% of patients have antibodies to the acetylcholine receptor, which destroy the end plate through complement or speed receptor loss by crosslinking; MuSK antibodies (7–10%) disturb receptor clustering (Dresser 2021). Nerves normally release more acetylcholine than needed; with fewer receptors, repeated firing falls below threshold, so weakness fatigues with use. MuSK disease is bulbar, neck and respiratory predominant, responds poorly to pyridostigmine and may respond better to plasma exchange than IVIG (Sanders 2016).

Crisis means worsening that needs intubation, or NIV to avoid it (Sanders 2016). It affects 15–20%, usually in the first year of illness, and is the first presentation in about a fifth; infection triggers about 40%, and 30–40% have no clear trigger (Godoy 2013). In-hospital mortality was 4.5% in a US sample (Alshekhlee 2009) and 12% among ventilated German patients, mostly from sepsis (Neumann 2020). The 2026 consensus asks for close respiratory and bulbar checks in impending crisis and ICU or step-down care in crisis (Narayanaswami 2026).

Corticosteroids give durable control but transiently worsen 25–75% of patients in the first 10 days (Sheikh 2021); 42% of 55 started on 40–80 mg prednisone worsened, more when older or severely bulbar (Bae 2006). Starting after IVIG or exchange has taken effect, or titrating from a low dose, limits this (Sanders 2016; Sheikh 2021); with IVIG first, early worsening fell to 2.2% in one series (Díez-Porras 2020). Maintenance adds steroid-sparing drugs, complement C5 inhibitors (meningococcal vaccination first) or FcRn blockers such as nipocalimab (approved April 2025).

Pyridostigmine treats symptoms only; it is usually stopped while intubated, because it increases secretions, and restarted when strength clearly returns (Wendell 2011). Cholinergic crisis is now rare (Sanders 2016): excess acetylcholine adds fasciculations and muscarinic signs (salivation, bronchorrhea, sweating, small pupils, bradycardia, cramps, diarrhea). Stop the drug, support the airway and give atropine; the Mestinon label notes that routine atropine can hide early overdose.

Drugs that worsen myasthenia

Fluoroquinolones block transmission on both sides of the junction, with worsening from 15 minutes to 4 days after starting (Sheikh 2021); cephalosporins are among the safer choices for pneumonia. Check every new order, including IV magnesium in asthma, arrhythmia and electrolyte protocols.

Nursing care by system and the awake paralyzed patient

• Respiratory: scheduled strength tests in the same position; cough and secretions; HOB 30° or more; assisted cough, suction, insufflation-exsufflation
• Cardiovascular (GBS): continuous ECG, daily systolic range, atropine and pacing plan; no scheduled β-blocker for transient tachycardia
• Neurologic: daily MRC sum or GBS disability grade, cranial nerves, eye closure; pain and delirium screening adapted to paralysis
• GI and GU: swallow screen before oral intake, early enteral feeding if unsafe; bowel regimen; bladder scans
• Skin and mobility: turning, heel and elbow offloading, eye lubrication and lid closure, splints, early PT and OT
• VTE: UFH, LMWH or fondaparinux plus IPC until walking (NCS 2016)

IVIG: check kidney function and hydration, start at the product's lowest rate and step up, and watch for headache and meningism, thrombosis (boxed warning; worse with age, immobility, central lines), kidney injury, hemolysis in non-O recipients, TRALI and fluid overload; IgA-deficient patients with anti-IgA antibodies risk anaphylaxis (Gamunex-C label). Plasma exchange needs a large-bore catheter; watch for hypotension (worse with dysautonomia), citrate hypocalcemia (perioral tingling, cramps), bleeding as albumin replacement depletes fibrinogen (EAN/PNS 2023) and line infection, and give drugs after sessions.

Patients with GBS, even fully paralyzed, usually keep consciousness, vision and hearing (Leonhard 2019). Speak to them, not over them, and explain each procedure first. Agree on yes and no signals (blinks, eye gaze, a letter board, a speaking valve once a tracheostomy cuff can be deflated) and keep a call device within reach of whatever still moves. Ask about pain, fear, hallucinations and low mood: 31% of 139 patients had vivid dreams, illusions, hallucinations or paranoid delusions, from a median of day 9 for about 8 days, more with dysautonomia and ventilation (Cochen 2005). Protect sleep, reorient, limit benzodiazepines, involve family and offer psychological support (EAN/PNS 2023). Honest hope helps: about 80% walk independently by 6 months (Leonhard 2019).

Exam pearls

• Neuromuscular respiratory failure is pump failure: follow VC, NIF and MEP (20/30/40), not SpO₂ or the ABG.
• Intubate electively for falling VC, bulbar failure or rising CO₂; BiPAP suits myasthenic crisis before hypercapnia, not GBS with bulbar weakness.
• GBS: ascending symmetric weakness, areflexia and dysautonomia after an infection; CSF high protein with normal cells.
• GBS: IVIG 0.4 g/kg/day for 5 days or plasma exchange, equally effective; no steroids, no second IVIG course.
• GBS dysautonomia: bradycardia or asystole with suctioning; atropine ready; treat only sustained BP extremes.
• No succinylcholine in GBS; MG resists succinylcholine but is very sensitive to rocuronium.
• In MG, question fluoroquinolones, aminoglycosides, macrolides, magnesium and β-blockers.
• Cholinergic crisis: secretions, small pupils, bradycardia, fasciculations; stop pyridostigmine, give atropine.
• Prednisone can worsen MG in the first 10 days; start after IVIG or exchange, or low.