Transcript TSRC 37th Annual Convention Critical illness Myopathy

TSRC 37th Annual Convention
Critical illness Myopathy
&
Critical illness Polyneuropathy
By Elizabeth Kelley Buzbee AAS, RRT, NPS
Lone Star System- Kingwood [formerly known as Kingwood
College]
Failure to wean due to muscle
weakness
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The effect of invasive mechanical ventilation on the
patient’s ventilatory skeletal muscles is a well-known yet
fairly complex problem.
Full ventilatory support can trigger muscle atrophy within
72 hours in adults. According to MacIntyre, both muscle
mass and cross-section of muscle fibers are affected. [MacIntyre
pp. 1http://www.medscape.com/viewarticle/514526]
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“There is….. evidence of oxidative stress and protein
breakdown in the muscles.” [MacIntyre pp. 1]
When a patient’s FRC is raised above normal by PPV, the
effect on resting muscle length results in a decrease in
muscle strength. [MacIntyre pp. 1]
Alterations in the blood flow to the ventilatory muscles
secondary to PPV just adds to the problem. [MacIntyre pp. 1]
Not only is muscle strength affected, we will see a decrease
in muscle endurance. [MacIntyre pp. 1]
Other problems are more subtle
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malnutrition & electrolyte imbalances:
The effects of malnutrition on the pulmonary system are
distinct and well known.
 Patient’s who cannot take oral nutrition may be on IV
glucose, which is fine for a day or so, but TPN with its
more complete nutritional support is needed to keep
metabolism going.
 Carbohydrates are needed for both the diaphragm and
the myocardium [Peters pp. 350]
The effect of electrolyte imbalances on the myocardium is
well-known but potassium levels can also affect skeletal
muscle action of the chest and abdominal muscles.
 Hypokalemia can cause muscle weakness even paralysis
[Garth]
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while hyperkalemia also results in muscle weakness and
flaccid paralysis
serum magnesium levels of 8.0-10.0 mEq/L are
associated with flaccid skeletal muscle paralysis. [Novello ]
The new threat in the ICU
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There are new problems discovered in the ICU that
result in various degrees of muscle weakness--even
paralysis-- that can keep a person from weaning off
mechanical ventilation [Dhand pp. 1025]
But is this a new problem? A review of the literature
shows that as early as the 1970s, a small number of
severe asthmatic patients who were intubated, paralyzed
and ventilated had significant, generalized muscle
weakness.
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Critical illness polyneuropathy
Critical illness myopathy
Prolonged neuromuscular blockage
Occurrence of CIP, CIM or a
combination of the two
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as many as 30-50% of patients with
critical illness. [Dhand pp. 1026]
Another study [n=206] found 25% of
critical care patients who had been
mechanically ventilated for more than 7
days had a degree of muscle weakness.
This study included only persons who
were awake and responsive [Deems pp. 1043]
Critical illness myopathy
Critical illness myopathy
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According to the American College of
Rheumatology, myopathy is a disease of
the muscles. The actual manifestation of
the muscle disease varies widely based on
etiology and the location of the defect.
In the case of CIM, we seem to have a
syndrome of ‘symmetric weakness of all
extremities, of muscle wasting,
hyporeflexia and failure to wean from
mechanical ventilation.’ [Dhand pp. 1036]
Risk factors for Critical illness
myopathy
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Persons who have received high levels of
corticosteroids & neuromuscular blocking
agents
for diseases such as severe asthma, COPD
exacerbation, sepsis, ARDS and s/p organ
transplants. [Dhand pp. 1036]
S/S of Critical illness myopathy
Inspection and interview of the patient
 There also seem to be is little in the
inspection and interview to differentiate
between critical illness myopathy and
critical illness polyneuropathy.
 The patient will c/o weakness in both
situations.
S/S of Critical illness myopathy
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Serum Creatine Kinase
a product of muscle damage. Need to
differentiate between myocardial CK and skeletal
muscle CK. [Egan’s pp. 351]
“Normal levels of serum creatine kinase are
usually between 25 and 200 U/L. This test is not
specific for the type of CK that is elevated.”
[http://en.wikipedia.org/wiki/Creatine_kinase]

Serum creatine kinase may be 10-100 x higher
than normal in CIM in the first 3-4 days-- then
stabilize after 10 days. [Dhand pp. 1028]
S/S of Critical illness myopathy
EMG: the electromyogram
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. There are two basic techniques:
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One can study a specific muscle fiber’s reaction to the insertion
of a needle electrode in a particular muscle fiber.
A less-invasive procedure uses a surface electrode to monitor
the general picture of muscle activation. During this study the
patient has auditory or visual stimuli to help them know when
they are activating the muscle. Again the action potential is
measured
http://en.wikipedia.org/wiki/Electromyography
It is possible to perform an EMG of the phrenic nerve by
placing the percutaneous electrode onto the neck at the
supraclavicular fossa and measurements will be made at
two spots along the anterior rib cage,
but the presence of a central line in either neck will make
this EMG impossible. [Dhand pp. 1031-1032]
S/S of Critical illness myopathy
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EMG results
In myopathic disorders there will be
decreases in duration of the action
potential,
and in the ratio of area to amplitude
and in the number of motor unit in
the muscles [worse cases only]
[http://en.wikipedia.org/wiki/Amplitude]
S/S of Critical illness myopathy
Nerve conduction study
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In the nerve conduction study the patient is given
an electrical shock at various spots along a nerve.
Among other measurements, the velocity of the
nerve conduction is measured at different points,
as is the intensity of the response [amplitude.]
The tester will study both the motor and the
sensory nerve conduction.
http://en.wikipedia.org/wiki/Nerve_conduction_study
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In the case of CIM, there should be no real
problems with conduction
S/S of Critical illness myopathy
Problems w/ Nerve conduction studies
in the ICU:
 the patient’s skin temperature will change
the speed of conduction; cool bodies result
in slow conduction
 and the presence of pacemakers &
indwelling defibrillators can make for
difficulties [MedlinePlus: nerve conduction studies]
 Picture of NCS: http://0www.nlm.nih.gov.catalog.llu.edu/medlineplus/ency/imagepages/
9743.htm
S/S of Critical illness myopathy
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What are we left with?
Muscle and nerve biopsy
Both muscle and nerve biopsy can
differentiate between CIP and CIM
and even combinations of both
disorders. [Dhand pp.1033]
Critical illness
polyneuropathy
Critical illness polyneuropathy
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The Merck manual describes
polyneuropathy as “the simultaneous
malfunction of many peripheral nerves
throughout the body.”
In CIP, with biopsy, one sees that the
patient develops both motor and sensory
degeneration without inflammation. [Dhand pp.
1033]
Risk factors for
polyneuropathy
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“Poor control of blood sugar levels in diabetes
causes several forms of polyneuropathy,
collectively referred to as diabetic
neuropathy.” [Merck Manual]
Diphtheria toxins, autoimmune reaction, heavy
metals such as lead and mercury and CO
poisoning can all lead to polyneuropathy.
The drugs include the anticonvulsant, Dilantin,
some antibiotics (such as nitrofurantoin and
sulfonamides), some chemotherapy drugs and
some sedatives such as barbital. [Merck Manual]
Risk factors for Critical illness
polyneuropathy
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History of sepsis, trauma, burn followed
by organ failure, septic encephalopathy.
[Dhand pp. 1033.]
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in addition, according to the CDC, CIP is
associated with a recent history of SIRV
[septic inflammatory response syndrome.
[CDC] http://www.cdc.gov/nchs/data/icd9/icd501a.pdf
S/S critical illness
polyneuropathy
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On inspection:
Because cranial nerves are generally
unaffected in CIP, the patient’s facial
grimace and limb movement on painful
stimulation may be strikingly different. [CDC]
A muscle biopsy would show neuropathic
changes. [Dhand pp. 1034.]
S/S critical illness
polyneuropathy
 He
have a normal Creatine
kinase. [Dhand pp. 1034.]
 he would have a reduction in
both motor & sensory nerve
conduction. [Dhand pp. 1029.]
S/S critical illness
polyneuropathy
EMG results
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the EMG showed action potentials
twice normal with increased fibers per
motor unit and an increase in
duration of the action potential.
[http://en.wikipedia.org/wiki/Amplitude]
Prolonged neuromuscular
blockage
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Nondepolarizing neuromuscular blocking agents
such as pancuronium generally have duration of
action of a few hours, but a few patients may
suffer persistant weakness that can prevent
successful weaning from ventilatory support.
This paralysis could last additional hours--- or
even weeks. [Dhand pp. 1037]
Prolonged neuromuscular
blockage
Prolonged neuromuscular
blockage
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Prolonged neuromuscular blockage with nondepolarizing
blocking agents results in metabolites.
“Prolonged neuromuscular blockade after the
termination of long-term treatment with vecuronium is
associated with metabolic acidosis, elevated plasma
magnesium concentrations, female sex, and probably
more important, the presence of renal failure, and high
plasma concentrations of 3-desacetylvecuronium.” [V
Segredo]
Risk factors for Prolonged
neuromuscular blockage
Patients at increased risk seem to be those
with:
 hepatic dysfunction
 renal failure
 acidosis
 or hypermagnesemia [Dhand pp. 1036]
Differential DX
Differential DX
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Polyneuropathies such as Guillian Barre
syndrome can be triggered by infection,
while exacerbations of myasthenia gravis
[MG crisis] can be triggered by stress,
certain medications and illness.
Spinal cord infarction is a complication of
aortic surgery [Dhand pp. 1026.]
myotonic dystrophy may have been
undiagnosed
Differential DX
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Guillian Barre.
There are no … antibodies in the serum of
patients with critical illness
polyneuropathy as would be seen with
Guillian Barre. http://jnnp.bmj.com/cgi/content/extract/68/3/397
Differential DX
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myasthenia gravis.
Patients have increasing muscle weakness
with repetitive motions
they also antibodies against acetylcholine
receptors
tendency to have a degree of facial
paralysis [inability to protect the airway],
a transient improvement when given
cholinesterase inhibitors. [Egan’s pp. 576]
Differential DX
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Spinal cord infarction
Comes on suddenly and catostrophically
with 80% c/o severe pain
http://www.emedicine.com/NEURO/topic3
48.htm
Differential DX
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myotonic dystrophy
Persons with myotonic dystrophy
have increased sensitivities not only
to paralytic agents, but to CNS
depressants. [Egan’s pp. 576]
Treatment?
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According to the CDC, there are no
medications for these problems,
rather we need to consider
‘conservative management.’ [CDC]
We need to stop killing black
widow spiders with a sledge
hammer.
May just tear up the house
Conservative measures w/
steroids
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According to the American Heart Association 2005 CPR
guidelines, severe asthma needs to be treated with
systemic steroids rather than topical:
 but maybe we need more studies to be done with
inhaled dosages so that the systemic side effects such
as myopathy can be minimized?
 In these studies, how are these patients given inhaled
steroids? [mixed with Beta II or alone? SVN or MDI,
DPI? ]
 Exactly what are the links between steroid-induced
diabetes and neuropathy: how much steroid is too
much?
Conservative measures w/
steroid TX
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could we use offline measurements for intubated
patients?
Research is on going on the question of using exhaled
nitric oxide monitors to fine-tune the level of systemic
steroids in the acute asthmatic. [Phua pp. 857]
Offline measurement of FENO has been compared
favorably with online modes
One UK single-blind study over a period of 8 months [n
=116] showed no clinically significant improvement in
controlling patient’s steroid dosages by monitoring FENO
http://ajrccm.atsjournals.org/cgi/content/abstract/176/3/
231
Conservative measures w/
Nondepolarizing
neuromuscular blockers
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Limit time of paralysis. ‘Sedation
vacations’ are used to decrease VAP by
getting patient’s off mechanical ventilation
sooner. [Kress]
Maybe this same technique might be
helpful with CIM & prolonged
neuromuscular blockage?
Conservative measures w/
Beta II
Never forget the Beta II agonists have as side effects:
 increases both insulin and glucose levels, when
combining high dosage Beta II and corticosteroids
this could get serious
 Causes hypokalemia. According to the AHA,
inhaled 10-20 mg Albuterol over 15” will shift
Potassium into the cell to treat both moderate &
severe hyperkalemia [AHA 2005 CPR guidelines pp. 121-122]
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Compare this to the AHA recommendations regarding
continuous Albuterol TX : 2.5-5mg Q 20 minute x 3 or 10-15
mg/hour
Conservative measures w/
Beta II
The AHA recommend these drugs as adjuncts to
albuterol/IV steroid treatment:
 A trial of ipratropium bromide as adjunct to
albuterol, possibly more that one dose [AHA
pp.140]
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IV Magnesium Sulfate
Leukotriene antagonists by IV has been
studied but the AHA wants more research
Other bronchodilators can have
neuromuscular side effects
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According to the post-marketing experience with
Singulair TM a few patients have reported
paraesthesia & hypoesthesia—these side effects
have not been investigated yet. [drug insert]
Cromolyn Na has peripheral neuritis as a rare
side effect [1 in 100,000]
Magnesium by IV has respiratory failure due to
skeletal muscle paralysis as a side effect
references
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Neil MacIntyre Understanding Ventilator-Induced Diaphragmatic
Dysfunction
http://www.medscape.com/viewarticle/514526
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Deem S.; Intensive-Care-Unit-Acquired Muscle Weakness.
Respiratory Care 2006: 51(9): 1024-1041
Dhand, U.; Clinical Approach to the Weak patient in the Intensive
Care Unit. Respiratory Care 2006: 51(9): 1024-1041
Boitano, L.J. Management of Airway Clearance in Neuromuscular
Disease Respiratory Care August 2006, vol 51 (8) pp. 913-921.
references
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Nutritional Assessment of patients with respiratory
Disease Peters, J.A. & Thomas-Peters, C.D., editors
Wilkin’s Clinical Assessment in Respiratory Care 5th
edition Elsevier-Mosby
Medline: Rhabdomyolysis
http://www.nlm.nih.gov/medlineplus/ency/article/00047
3.htm
E-medicine: Hypokalemia David Garth, MD,
http://www.emedicine.com/emerg/topic273.htm
American College of
Rheumatology:http://www.rheumatology.org/public/fact
sheets/myopathies_new2.asp
references
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Kress JP, Pohlman AS, O'Connor MF, Hall JB. Daily interruption of
sedative infusions in critically ill patients undergoing mechanical
ventilation. New England Journal of Medicine. May 18 2000;342
(20):1471-1477.
Phua, GC & MacIntyre NR, Inhaled Corticosteriods in COPD,
Respiratory Care July 2007 , vol 52 #7
Critical illness polyneuropathy and myopathy
http://www.aic.cuhk.edu.hk/web8/critical_illness_neuropa
thy.htm
CDC pamphlet on CIM and
CIPhttp://www.cdc.gov/nchs/data/icd9/icd501a.pdf
Merck Manual: Polyneuritis
http://www.merck.com/mmhe/sec06/ch095/ch095h.html
eMedicine: Hypermagnesemia by Novello NA;
http://www.emedicine.com/EMERG/topic262.htm
references
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Medline Plus: nerve conduction studies http://0www.nlm.nih.gov.catalog.llu.edu/medlineplus/ency/articl
e/003927.htm
AMERICAN THORACIC SOCIETY
Recommendations for Standardized Procedures for the
Online and Offline Measurement of Exhaled Lower
Respiratory Nitric Oxide and Nasal Nitric Oxide in Adults
and Children1999
http://ajrccm.atsjournals.org/cgi/content/full/160/6/2104
?ijkey=43b2934ac6dfa8de010ee9b85d910dbfed797135&
keytype2=tf_ipsecsha
references
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V Segredo, JE Caldwell, et al. Persistent paralysis in
critically ill patients after long-term administration of
vecuronium. NEJ Vol 327:524-528 #8 August 20, 1992
http://content.nejm.org/cgi/content/abstract/327/8/524?
ijkey=8e4db6aea6531d7ea4f0d9c3eb1a90f706fb333f&ke
ytype2=tf_ipsecsha