Understanding Weakness: A Framework for Diagnosis

Today we’re talking about a topic that is relevant for all critical care physicians but under-examined: ICU Acquired Weakness. We are joined by two excellent guests to walk through a case and discuss the diagnosis, pathophysiology, prevention, and treatment of ICU Acquired Weakness. Check out our associated infographics and key learning points below.

Meet Our Guests

Jim Devanney is a Physiatrist who just completed a neurocritical care fellowship at BIDMC. He is transitioning to a clinical associate position at University Health Network – University of Toronto where he will be working as a PM&R consultant within the ICU.

Kalaila Pais is a third year internal medicine resident at BIDMC, interested in pulmonary and critical care and medical education and is returning for her third Pulm PEEPs episode.

Key Learning Points

Definition & Clinical Presentation

ICU-AW refers to new-onset, generalized muscle weakness that arises during critical illness, not explained by other causes.It typically presents as:

• Symmetric, proximal > distal weaknessRespiratory muscle involvementPreserved cranial nerve functionNo sensory deficits in myopathy (sensory loss points toward neuropathy)

Differential Diagnosis Using Neuroanatomical ApproachAn anatomical approach (central → peripheral) helps localize the etiology weakness

CNS: trauma, stroke, encephalitis, seizuresAnterior horn cells: viral myelitis, motor neuron diseasePeripheral nerves: Guillain-Barré, vasculitis, critical illness polyneuropathy (CIP)Neuromuscular junction: myasthenia gravis, botulism, Lamber EatonMuscle: rhabdomyolysis, inflammatory or drug-induced myopathies, critical illness myopathy (CIM)

Subtypes of ICU-AW

Critical Illness Myopathy (CIM):

• Muscle dysfunctionEarly onset (within 48 hrs)Sensation intactproximal > distal weakness

Critical Illness Polyneuropathy (CIP):

• Nerve involvementDistal > proximal weakness, sensory deficits

• Critical Illness Polyneuromyopathy (CIPNM): Combination of both

Diagnosis

• Medical Research Council Score (MRC-SS):
  • Score < 48: ICU-AW
  • Score < 36: severe ICU-AW
• Handgrip dynamometry: <11 kg (men), <7 kg (women)
• Electrophysiology: EMG/NCS to distinguish CIM vs CIP
• Muscle ultrasound: bedside monitoring
• MRI/CT/Muscle biopsy: rarely used due to practical limitation

Risk Factors

Modifiable:

• Hyper/hypoglycemia
• Electrolyte derangement
• Parenteral nutrition
• Immobility
• Medications (steroids, NM blockers, sedatives, aminoglycosides)

Non-modifiable:

• Age, female sex, comorbidities
• Severity of illness, prolonged ventilation
• Sepsis, multi-organ failure

 Management & Prevention

• Prevention is key:
  • Early treatment of sepsis and inflammation
  • Glycemic control
  • Early enteral nutrition
  • Minimize sedation (A-F bundle)
  • Early mobilization and physical therapy
• NMES (neuromuscular electrical stimulation): emerging therapy, needs more evidence

Outcomes

• Short-term: increased LOS, ventilation duration, mortality
• Long-term: decreased function, discharge to rehab, prolonged recovery

Final Takeaways

• Prevention is crucial — start interventions early.
• Systematic approach to ICU weakness helps rule out dangerous mimics.
• ICU-AW is common but often under-recognized — awareness and early rehab can significantly impact recovery.

Infographics

References and Further Reading

Clinical Practice Guidelines for the Prevention and Management of Pain, Agitation/­Sedation, Delirium, Immobility, and Sleep Disruption in Adult Patients in the ICU. Devlin JW, Skrobik Y, Gélinas C, et al. Critical Care Medicine. 2018;46(9):e825-e873. doi:10.1097/CCM.0000000000003299.

The ABCDEF Bundle: Science and Philosophy of How ICU Liberation Serves Patients and Families. Ely EW. Critical Care Medicine. 2017;45(2):321-330. doi:10.1097/CCM.0000000000002175.

Caring for Critically Ill Patients With the ABCDEF Bundle: Results of the ICU Liberation Collaborative in Over 15,000 Adults. Pun BT, Balas MC, Barnes-Daly MA, et al. Critical Care Medicine. 2019;47(1):3-14. doi:10.1097/CCM.0000000000003482.

Delirium in Critical Illness: Clinical Manifestations, Outcomes, and Management. Stollings JL, Kotfis K, Chanques G, et al. Intensive Care Medicine. 2021;47(10):1089-1103. doi:10.1007/s00134-021-06503-1.

ICU-acquired Weakness. Vanhorebeek I, Latronico N, Van den Berghe G. Intensive Care Medicine. 2020;46(4):637-653. doi:10.1007/s00134-020-05944-4.

Clinical Review: Intensive Care Unit Acquired Weakness. Hermans G, Van den Berghe G. Critical Care (London, England). 2015;19:274. doi:10.1186/s13054-015-0993-7.

Best Practices for Conducting Interprofessional Team Rounds to Facilitate Performance of the ICU Liberation (ABCDEF) Bundle. Stollings JL, Devlin JW, Lin JC, et al. Critical Care Medicine. 2020;48(4):562-570. doi:10.1097/CCM.0000000000004197.

ABCDE and ABCDEF Care Bundles: A Systematic Review of the Implementation Process in Intensive Care Units. Moraes FDS, Marengo LL, Moura MDG, et al. Medicine. 2022;101(25):e29499. doi:10.1097/MD.0000000000029499.