critical illness polyneuropathy
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DR. SACHIN ADUKIA Critical illness polyneuropathyand myopathy
DefinitionsCritical illness polyneuropathy (CIP) refers to ICU-acquired weakness with electrophysiological evidence of an axonal polyneuropathy. Critical illness myopathy (CIM) refers to ICU-acquired weakness with myopathy that is documented electrophysiologically or histologically. Critical illness neuromyopathy (CINMP) refers to electrophysiological or histologic findings of both critical illness polyneuropathy and critical illness myopathy.
HistoryOsler described neuromuscular dysfunction in patients with sepsis Olsen reported peripheral neuropathy complicating protracted coma. In 1977, myopathy was described in a patient with status asthmaticus who received high doses of hydrocortisone and simultaneous neuromuscular blockade.
IntroductionNeuromuscular weakness develops in 25 percent of patients who are ICU and ventilated for atleast 7 daysmay result in a lifelong loss of function CIP first described by Bolton and colleagues in 1984causes severe limb weakness prolonged weaning, increases stay in ICUcompromises rehabilitation
Muscles involved in CIP/CIMaffects the limbs (particularly LL) in a symmetric pattern. proximal predominant (shoulders and hip girdle) involvement of respiratory muscles can impede weaning from mechanical ventilation.Facial and ocular muscles are rarely involved.Autonomic features are not seen
Pathology in CIMAlso known as acute quadriplegic myopathy and thick filament myopathyThere is loss of thick filament myosin and Type II fiber atrophy, mainly with proximal weaknessPathologically classified into five subtypes: (1) thick filament myopathy(2) acute myopathy with scattered necrosis(3) acute myopathy with diffuse necrosis(4) disuse cachectic myopathy(5) rhabdomyolysis
Postulated pathophysiology- CIMReduced muscle membrane excitabilityreduced uptake and release of calcium by the sarcoplasmic reticulum producing a decrease in muscle contractility.Decreased contractile protein function and muscle fibre force generation.Mitochondrial dysfunction and bioenergetic failure with consequent reduction in oxygen utilization and ATP production.Muscle denervation either pharmacological (neuromuscular block) or structural (CIP) mechanisms produces an increased expression of corticosteroid receptors within myocytes, sensitizing them to the deleterious effects of corticosteroids.Muscle atrophy during critical illness occurs - 34% decrease in muscle cross-sectional area per day. Is due to increased proteolysis, decreased protein synthesis, and increased apoptosis.
Pathology and Pathophysiology for CIPdysfunctional microcirculation leads to neuronal injury and axonal
degeneration.E-selectin expression in peripheral-nerve vascular endothelium, suggesting endothelial-cell activation with microvascular leak and alterations in microvascular environment.Hyperglycemia exacerbates this by inducing neural mitochondrial dysfunctionpresents as morphological signs of axonal degeneration in both type 1 and type 2 fibers, resulting in extensive denervation atrophy of muscles
Clinical featuresMuscle wasting is variable and frequently disguised by oedema. flaccid and usually symmetrical weaknessUsually noted as lack of movement after regaining consciousness, loss of deep tendon reflexes that had been present earlierearliest sign may be facial grimacing without limb movement to painEOM involvement warrants investigation for different aetiologyFacial muscles - relatively sparedCIP may show a distal loss of sensitivity to pain, temperature, and vibrationBut difficult to assess sensory system in Critically ill patientAutonomic function is not affected.
Difficulty in WeaningWeaning problems - involvement of the phrenic nerves and the diaphragm, and intercostal and other accessory respiratory musclesNeuromuscular weakness typically becomes apparent during attempted weaning
Full ventilatory support can trigger muscle atrophy within 72 hours in adults
Evidence of oxidative stress and protein breakdown in the musclesLevine et al. noted atrophy in diaphragm myofibers within 18 hours of complete diaphragmatic inactivity Jaber et al. reported a loss of diaphragmatic strength within hours after initiating mechanical ventilation
Diagnosis Serum CK -not helpful since they are normal if muscle necrosis is absent or scattered ,which is usually the caseRoutine electrophysiological examination often times cannot discriminate between CIP and CIM in critically ill, sedated, uncooperative or extremely weak patientsLocal oedema can interfere with optimal sensory nerve stimulation and recordingTo differentiate between CIP and CIM patient co operation is needed for voluntary motor unit potential recruitmentMuscle biopsy
CRIMYNE studyCRIMYNE for critical illness to monitor for CIM and/or CIP) showed that serial electrodiagnostic studies are helpful in predicting development of CIM and/or CIP
Diagnosis of ICU Associated weakness- ICUAWPresence of 1, 2, 5, and either 3 or 4 from:
1. Weakness developing after the onset of critical illness2. weakness being generalized (involving both proximal and distal muscles), symmetrical, flaccid, and generally sparing the cranial nerves 3. Muscle power assessed by MRC sum score of 48 (or a mean score of , 4 in all testable muscle groups) noted on 2 occasions separated by 24 h4. Dependence on mechanical ventilation5. Causes of weakness not related to the underlying critical illness excluded.
MRC Sum scoreinvolves the assessment of muscle power from three movements of each limb: shoulder abductionelbow flexionwrist extensionhip flexionknee extension ankle dorsi-flexion The maximal power obtained for each movement is graded according to the MRC scale and a score out of 60 is calculated
Prevention and therapyAggressive treatment of sepsisCorticosteriods and Neuro-muscular blockade agents, if indicated, to use at minimal dose for shortest periodRehabilitation programsAvoiding additional pressure neuropathies by careful positioningSeveral specific therapies have been mentioned
nutrition supplements,antioxidant therapy,testosterone derivatives,growth hormones immunoglobulins NONE EFFECTIVE
Insulin therapyIntensive insulin therapy- Insulin itself has some potential beneficial effectsanti-inflammatory effects endothelial protection, improvement of dyslipemia, and neuroprotective effects in animals an anabolic hormone2 unpublished studies report that intensive insulin therapy (target blood glucose 80 to 110 mg/dL) may lower the incidence of CIM and CIP
Physiotherapy and trainingApplying an early activity protocol ICU environment may contribute unnecessarily to immobilizationSedation substantially reduce the likelihood of ambulation
Electrical muscle stimulationAn RCT including 24 patients with COPD receiving MV showed that EMS sessions of 30 minutes in 28 days significantly improves muscle strength and decreases no. of days needed before mobilization to chairresults in a shorter duration MV and shorter ICU staydoes not require patient cooperation and can be applied to any muscle group
Recovery from CIP/ CIMPatients who survive ARDS or sepsis or both have these problems with the greatest frequency and intensity. patients requiring prolonged mechanical ventilation, neuromuscular recovery is typically prolonged and incomplete.Up to 65% of such patients have functional limitations after dischargeNeuromuscular abnormalities may last for many years in someA 1 year follow-up of 13 survivors from the CRIMYNE study showed a mixture of tetraplegia, partial recovery, and full recovery in combined CIM/CIP complete recovery in three to six months for CIM aloneminority of patients with CIP has persistent weakness.
PrognosisCIPNM significantly increases the length of MV and the lengths of ICU and hospital stayMortality increases from 19-56.5% to 48-84%Recovery CIM > CIP > CINM
ConclusionCritical illness myopathy and/or critical illness neuropathy are frequent and serious complications to intensive care that:
delay weaning from mechanical ventilation increase the stay in ICU compromise rehabilitation - may result in a lifelong loss of function and in a reduction in quality of life.Ensure maximal functional status for survivors of ICU stays using multimodal therapeutic approach including:
screening and early diagnosis is possible intensive insulin therapy minimal sedation early physiotherapy electrical muscle stimulation
ReferencesKress JP, Hall JB. ICU-acquired weakness and recovery from critical illness. New England Journal of Medicine. 2014 Apr 24;370(17):1626-35.Appleton R, Kinsella J. Intensive care unit-acquired weakness. Continuing Education in Anaesthesia, Critical Care & Pain. 2012 Apr 1;12(2):62-6.Ydemann M, Eddelien HS, Lauritsen A. Treatment of critical illness polyneuropathy and/or myopathy a systematic review. Dan Med J. 2012 Oct 1;59(10):A4511.Zhou C, Wu L, Ni F, Ji W, Wu J, Zhang H. Critical illness polyneuropathy and myopathy: a systematic review. Neural regeneration research. 2014 Jan 1;9(1):101.Bolton CF. Neuromuscular manifestations of critical illness. Muscle Nerve 2005 32:140.Hermans G, Wilmer A, Meersseman W, et al. Impact of intensive insulin therapy on neuromuscular complications and ventilator dependency in the medical intensive care unit. Am J Respir Crit Care Med 2007 175:480