Page 1775 - Hall et al (2015) Principles of Critical Care-McGraw-Hill

1244 PART 11: Special Problems in Critical Care

■
of SRC. At its onset patients experience a marked increase in blood RESPIRATORY FAILURE
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pressure that may be accompanied by abnormalities of both urinary Patients with polymyositis/dermatomyositis may develop respiratory
sediment (erythrocytes and protein) and the peripheral blood smear failure secondary to muscle weakness involving the diaphragm, intercos-
(fragmented cells and thrombocytopenia). Headache, visual distur- tals, and accessory muscles. If pharyngeal muscles are involved, acute respi-
bance, congestive heart failure, and cognitive dysfunction may accom- ratory failure may be precipitated by aspiration pneumonia. Patients
pany the hypertension. The pathogenesis of hypertensive renal crisis is with respiratory failure have a poor prognosis. Some patients with
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complex and involves a very high renin state. Although combinations dermatomyositis and this type of profound weakness harbor an under-
of older antihypertensive agents were occasionally successful, the lying malignancy. Such patients can be refractory to treatment. Steroids
advent of ACE inhibitors revolutionized the outlook for this problem. are the mainstay of acute management of inflammatory myositis.
Rheumatologists have a low threshold for using these agents in sclero- Prednisone, 1 to 2 mg/kg per day or its approximate intravenous equiva-
derma patients and typically initiate them at the first diagnosis of hyper- lent of methylprednisolone (in single or divided doses) may be given. In
tension. In the setting of acute hypertensive renal crisis, larger doses the ventilator-dependent patient, a short trial of pulse steroids may be
of ACE inhibitors should be used. Although captopril and newer ACE justified up to 1000 mg methylprednisolone intravenously every day for
inhibitors have been used, some prefer captopril because the dose can be 3 days. Improvement in respiratory muscle strength can be judged by a
adjusted more flexibly. The evidence supporting the use of angiotensin rise in the maximal inspiratory pressure. Intravenous immunoglobulin
receptor blockers in place of ACE inhibitors is limited and mixed. They (IVIg) is another option for the acute management of the severely ill
may have a role (along with calcium channel blockers, prostacyclin, patient refractory to therapy with corticosteroids. Second-line agents
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and endothelin receptor antagonists) as adjunctive therapy for patients in polymyositis/dermatomyositis (eg, methotrexate, azathioprine, cyclo-
refractory to (or intolerant of) maximum doses of ACE inhibitors. 17,18 sporine, and rituximab) are most commonly used after corticosteroids.
Some patients may progress to complete renal failure despite blood The role of plasmapheresis/leukapheresis is unclear with only limited
pressure control. Continued use of ACE inhibitors and dialysis may be data available. 23
required for months prior to recovery of renal function. Such improve-
ment can continue for up to 2 years. Progressive renal failure can occur
in the absence of significant hypertension in as many as 10% of patients RHEUMATOID ARTHRITIS
on peripheral smear. Treatment with ACE inhibitors is indicated for this ■ METHOTREXATE PNEUMONITIS
with scleroderma renal crisis. Microangiopathic changes may be seen
normotensive subset of patients. Oral low-dose methotrexate given intermittently emerged as the major
therapeutic innovation in the treatment of rheumatoid arthritis (RA)
POLYMYOSITIS/DERMATOMYOSITIS during the 1980s and it continues to be the gold standard of RA therapy
■ DIAGNOSIS IN THE ICU and a frequent adjunct to cytokine-directed therapy. Methotrexate
therapy is both highly effective and generally well tolerated. A major,
Very ill patients in the ICU may be weak and have elevations of creatine albeit uncommon, toxicity is an acute pneumonitis characterized by
phosphokinase (CK). Such clinical data prompt speculation about the dyspnea and nonproductive cough. Fever is a frequent accompaniment.
presence of immune-mediated myositis. The most common presentation Diffuse alveolar and interstitial infiltrates can be present: either at diag-
of polymyositis is the insidious onset of proximal muscle weakness. The nosis or appearing within days. Opportunistic infections mimicking
acute development of de novo polymyositis in the ICU is unlikely. this syndrome while unusual, need to be excluded. The risk factors for
Similarly, acute fulminant disease requiring ICU admission with subse- the development of methotrexate-induced lung injury include elderly
quent diagnosis is uncommon. Nonetheless, patients with undiagnosed patients, preexisting lung disease, and previous use of disease-modifying
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polymyositis may be discovered in the ICU following admission for antirheumatic agents. Patients can suffer profound hypoxemia. They
another reason (eg, aspiration pneumonia). More likely is the presence may appear extremely ill, and deaths have been reported. The mecha-
of weakness (usually generalized) in combination with a spurious or nism is unclear but is presumed to be a hypersensitivity reaction to the
nonimmune cause of CK elevation. Intramuscular injections and myo- drug. Some patients have been rechallenged without developing the
necrosis during severe episodes of hypotension are common causes of syndrome while others have relapsed. Diagnosis depends on recogni-
increased CK levels in critically ill patients. ICU-acquired myopathy tion of the clinical scenario developing in a patient taking methotrex-
can usually be distinguished from polymyositis by clinical history. It is ate at any dose. Duration of treatment prior to symptoms has been
usually characterized by normal or modestly elevated serum CK levels. variable. Bronchoscopy with brushings and biopsy shows nonspecific
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The skin lesions of dermatomyositis are so highly characteristic as to be inflammation, and bronchoscopy’s main justification is to rule out an
diagnostic of dermatomyositis when accompanied by weakness and an opportunistic infection. Because these are rare, it is not unreasonable to
elevated CK value. Nearly all patients with active polymyositis will dis- forego bronchoscopy initially. Open-lung biopsy is usually unnecessary.
play an elevated CK or aldolase level, although occasional patients will Treatment includes O 2, withdrawal of drug, and the use of corticoste-
have normal muscle enzymes. A unilateral electromyogram (EMG) roids. Some have argued that steroids are not critical to recovery. The
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can provide supportive evidence for the presence of myopathy and iden- usual dose is prednisone 1 mg/kg per day or its equivalent in daily or
tify a biopsy site. Fibrillation potentials suggest active inflammation. A divided doses. Most patients will show signs of recovery within a week.
complicate the interpretation. Magnetic resonance imaging (MRI) may ■ CERVICAL SPINE SUBLUXATION
bedside EMG can be done in the ICU, although technical artifact may
also confirm the presence of inflammatory muscle disease, but is gener- Rheumatoid arthritis commonly affects the cervical spine with estimates
ally impractical for ICU patients. The EMG should be done unilaterally as high as 80% of patients. Subluxation of vertebrae secondary to liga-
because EMG needle artifact may be confused with muscle inflammation mentous laxity may occur at single or multiple levels. Anterior atlanto-
histologically. Because polymyositis/dermatomyositis is a symmetrical axial subluxation of C1 on C2 is the most frequent cervical abnormality
disease, the corresponding maximally affected muscle group can be and is particularly dangerous because of the capacity of the odontoid
biopsied on the opposite side. Open biopsy can be done at the bed- process (or dens) of C2 to compress the anterior spinal cord with
side by an experienced surgeon to ensure proper handling of muscle motion. Sudden hyperextension of the neck during intubation could
tissue. Needle biopsies can be done with local anesthesia, have few result in quadriplegia. In reality, such occurrences are rare. The expla-
complications and can be done repetitively to follow the disease course. nation may in part include the fact that progressive resorption of the
However, some diseases such as polymyositis or systemic vasculitis have dens often accompanies the most severely unstable necks. Symptomatic
patchy involvement which may limit the yield of a needle biopsy. 21 patients can be diagnosed with MRI or a myelogram. However, some

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