Rehabilitation for Patients with Critical Illness Polyneuropathy (CIP) and Critical Illness Myopathy (CIM)

What Is Critical Illness Polyneuropathy and Critical Illness Myopathy?

Critical illness polyneuropathy (CIP) and myopathy (CIM) are similar syndromes of extensive, equal, floppy muscular weakness affecting all limbs and the diaphragm with comparatively little impact on the cranial nerves. They occur in critically ill patients. Similar symptoms and appearances, CIP and CIM, can frequently be separated primarily through sophisticated electrophysiologic screening or muscle and nerve biopsy. Though their causes are uncertain, systemic inflammatory response syndrome is hypothesized to have a neurological component that may present in CIP and CIM. An increase in blood sugar, which frequently happen in critically sick patients, may also have a role in CIP and CIM, as may the use of neuromuscular blocking medications and corticosteroids, which are both commonly used in intensive care.

What Is the Pathophysiology of Critical Illness Polyneuropathy and Critical Illness Myopathy?

Although the clinical manifestations of CIM and CIP may be similar, there are variations in the underlying pathophysiology. The clinical abnormalities of CIP, an axonal sensorimotor polyneuropathy, are brought on by the death of specific nerve fibers. In contrast, the loss of thick myofilaments and consequent myofiber death in skeletal muscle without a neurogenic etiology cause weakness in CIM. Even though these two disorders have distinct pathophysiologic characteristics, research on the underlying mechanisms and risk factors contributing to their development is still underway.

Pathophysiology of Critical Illness Polyneuropathy:

• Without a significant demyelinating component, as in certain other acute neuropathic diseases, CIP is caused by peripheral nerve axonal malfunction and death. One suggested mechanism underlying CIP is a modification to the microvasculature of the axons of peripheral nerves. In some early research, scientists proposed that CIP might result from heightened permeability to the vasa nervorum. E-selectin, a membrane activation marker, was discovered to be much more expressed in human patients with CIP, which may cause this enhanced permeability. An inflammatory response is produced from immune cells migrating into nerve tissue and releasing inflammatory mediators like TNF (tumor necrosis factor) and IL-1 (interleukin-1). Reactive oxygen species (ROS) are more likely to develop, and energy production may be reduced due to the resulting edema. Axonal degeneration can follow from energy deficiencies, and elevated ROS can add to bioenergetic failure by structurally harming mitochondria. Systemic immune response syndrome (SIRS) has been named for this inflammatory reaction when no infection exists.

• It has been suggested that hyperglycemia, a characteristic of patients with severe illnesses, has direct toxic effects on the axons, as has been demonstrated in diabetic polyneuropathy, and it has been demonstrated to impair mitochondrial activity.

• Alterations in membrane depolarization brought on by hypoxia or hyperkalemia may contribute to the onset of CIP, though the evidence for this theory is still very weak.

Pathophysiology of Critical Illness Myopathy:

Myosin is a selectively lost protein in CIM, leading to myofiber atrophy and death. Systemic inflammation, structural alterations in skeletal muscle, metabolism, microcirculation at the level of the muscle, biological energy production, autophagy, and failure of membrane/ion channels are a few potential underlying reasons.

• Systemic Inflammation: Proinflammatory cytokines are significantly elevated in critically ill patients, regardless of the underlying cause, and this inflammation may play a role in the onset of paralysis. Critical illness-related muscular atrophy has been linked to a stress-induced cytokine called Growth and Differentiation Factor-15 (GDF-15).

• Immobilization: Myofibrillar protein is generally lost in CIM patients, while myosin is preferentially lost within myofibers. The use of artificial ventilation in the case of diaphragmatic myosin loss and extended immobility (>5 days) may also contribute to this selective myosin loss. It has been shown that the CIM phenotype can be reproduced in animal models by mechanical silencing, the state of absence of external and internal strain.

• Microvascular: The pathophysiology of CIM has been linked to increased permeability and vasodilation of the microvasculature. Elevated leukocyte dissemination and infiltration of tissues in CIM patients cause local cytokine release that causes edema. Edema in the muscular tissue impairs perfusion and oxygen supply, impairing the ability to produce energy. Muscle atrophy results from these metabolic circumstances' activation of catabolic and/or apoptotic pathways.

How Are Critical Illness Polyneuropathy and Critical Illness Myopathy Diagnosed?

Critical Illness Polyneuropathy: Despite its uncommon use, electrodiagnostic testing is still the gold standard for identifying critical disease polyneuropathy. Examples of these include nerve conduction tests and needle electromyography. Even though EMG is the best method for diagnosing CIP, conducting a comprehensive examination in an ICU setting may be challenging because of electrical interference, anasarca, hypothermia, peripheral edema, or limited patient participation.

Critical Illness Myopathy: CIM is probably underdiagnosed due to the lack of early and practical diagnostic techniques and the requirement for a muscle biopsy for a definitive diagnosis under current diagnostic criteria. Clinical trials studying preventive and therapeutic approaches like glucose management, early mobility, and physical therapy may be made possible by early diagnosis of CIM, which is evolving.

Current guidelines include evaluating a patient's medical history, physical examination, traditional nerve conduction tests (NCS), electromyography (EMG), and muscle biopsy to diagnose CIM. Because of this, the existing standards only permit CIM diagnosis at an advanced level, leaving those who are just starting at risk for misunderstanding.

What Are the Diagnostic Criteria for Critical Illness Polyneuropathy and Critical Illness Myopathy?

Diagnostic Criteria for Critical Illness Polyneuropathy:

According to Bolton 2005 and Latronico 2011, the diagnostic criteria for CIP as a malfunction of (many) peripheral nerves are as follows:

1. The patient has several organ failures and is in serious condition.

2. After ruling out factors other than neuromuscular disease, such as heart and lung conditions, the person exhibits limb weakness or finds it difficult to wean off a ventilator.

3. The presence of axonal motor and sensory polyneuropathy is demonstrated electrophysiologically.

4. On repeated nerve stimulation, there is no diminishing response (Latronico, 2011).

According to Bolton 2005 and Latronico 2011, CIP is definitely diagnosed if all four requirements are met. If all three of the first, third, and fourth criteria are met, CIP is presumed to be the cause.

Diagnostic Criteria for Critical Illness Myopathy:

The following are Latronico's (2011) diagnostic standards for critical disease myopathy:

1. The patient has several organ failures and is in serious condition.

2. After ruling out factors other than neuromuscular disease, such as heart and lung conditions, the person exhibits limb weakness or finds it difficult to wean off a ventilator.

3. When recorded without a conduction block, compound muscle action potential (CMAP) amplitudes in two or more nerves are less than 80 % of the lower limit of normal.

4. The amplitudes of sensory nerve action potentials exceed 80 % of the lower bound of normal.

5. Electromyography needle detected:

   1. Short duration, low amplitude motor unit potentials in awake, cooperative patients, with early or normal complete recruitment, with or without fibrillation potentials; or

   2. In patients unwilling to cooperate, direct muscular stimulation results in longer CMAP durations or lower muscle membrane excitability.

6. Lack of a diminishing reaction to repeated stimulation of the nerves.

7. Histopathological signs of primary myopathy in the muscles, such as myosin loss or muscular necrosis.

A definitive diagnosis of CIM is made when all criteria are met (Latronico, 2011). A likely diagnosis of CIM is established by fulfilling just criteria one and three to six.

What Are the Rehabilitation Techniques for Managing Critical Illness Polyneuropathy and Critical Illness Myopathy?

In persons with CIP and CIM, physical therapy may enhance function or functional capacity and may prevent consequences such as contractures. Physical and occupational therapy techniques such as stretching (e.g., ranging exercises), strength training, and mobility training (e.g., instruction in dressing and transfers or to improve balance, sit-to-stand, and walking) are examples of physical rehabilitation interventions.

Physiotherapy:

Long durations of immobility are now understood to be a critical issue in CIP management.

Early mobilization speeds up patients' long-term recovery and functional independence while reducing their time to be ventilated and hospitalized. Treatment options, which may be based on the patient's clinical presentation, include:

• Passive range of motion to keep muscles flexible and avoid contractures brought up by extended bed rest.

• Exercises that are actively performed with assistance.

• Improving lung function by changing one's position in bed.

• To help with trunk control and balance, sit on the edge of the bed.

• Improving lung function while sitting outside a chair (either by pat sliding or transfers).

• Mobilizing to boost independence, muscle strength, cardiovascular fitness, and lung function.

Conclusion:

The importance of rehabilitation for those with critical illnesses has been highlighted by improvements in medical care, higher survival rates, improved CIP and CIM diagnosis, and the availability of more effective therapy. Rehabilitation guidelines offer recommendations, but there is little data on which to base actual therapy. The likelihood that someone with ICU-acquired weakness may benefit from continuous therapy may be higher.