Page 1778 - Hall et al (2015) Principles of Critical Care-McGraw-Hill

CHAPTER 126: Rheumatology in the ICU 1247

vasculopathy although in small-vessel vasculitis angiography may be therapy is anticoagulation. The proclivity of lung infections (especially
nondiagnostic. Access to angiography can be problematic for the criti- bacterial) to generate positive antineutrophil cytoplasmic antibodies
cally ill patient. Leptomeningeal biopsy is the gold standard for diagno- (ANCAs) can create a diagnostic quandary when the question of GPA
sis of granulomatous angiitis of the CNS, an important subset of CNS is raised.
vasculitis. An empiric trial with steroids may be appropriate.
INTERPRETATION OF RHEUMATOLOGY LABORATORY
ISCHEMIC DIGITS: IS THIS VASCULITIS? ABNORMALITIES IN THE ICU
Patients in the ICU may develop ischemic digits. Contributing factors ■ ERYTHROCYTE SEDIMENTATION RATE
include hypotension, use of radial arterial lines, and vasoconstrictors.
Often the issue of vasculitis is raised. Single extremity involvement The ESR is an indirect determination of the acute phase response and
speaks strongly against systemic vasculitis as the cause. Similarly, iso- may be elevated in the setting of infection or active rheumatic disease.
lated toe involvement is more likely to be caused by a combination of Values are higher for women and the elderly. Although the exact appro-
noninflammatory vascular disease and diminished blood flow owing priate adjustments for age and gender are not certain, a common rule
to hypotension, vasoconstrictors, or cholesterol emboli. The latter may used to calculate a “upper limit of normal” for ESR in patients over 40 is
shower from the aorta and create a pseudovasculitic picture, particularly to divide the age by 2 for men and for women, add 10 to the age and divide
after anticoagulation therapy is initiated or following instrumentation by 2. The presence of monoclonal proteins, polyclonal hypergamma-
of the aorta. Extreme symmetry of lesions with all digits involved is globulinemia, hyperfibrinogenemia, and alterations in size, shape, and
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more suggestive of a generalized low-flow state than vasculitis. Clues number of red blood cells will influence the ESR. Conversely, marked
to vasculitis as the cause of digital ischemia include the coexistence of hypofibrinogenemia in DIC is associated with extremely decreased ESR.
a disease associated with digital vasculitis such as SLE or scleroderma, ESR rises during normal pregnancy and should not be used to moni-
random involvement of multiple limbs, the presence of nailbed infarcts, tor rheumatic diseases under these circumstances. The ESR increases
and other associated cutaneous markers specific to vasculitis such as in end-stage renal failure of whatever cause and is not indicative of
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palpable purpura. Likewise, extracutaneous markers of vasculitis includ- an underlying rheumatic disorder. Parallel confirmation of a normal
ing glomerulitis and patchy neurologic deficits would enhance suspicion C-reactive protein level often clarifies the noninflammatory origin of
for that diagnosis. Male patients with a history of heavy smoking should the elevated ESR. The level of the rise in ESR correlates imperfectly
be suspected of Buerger disease (thromboangiitis obliterans). Patients with disease activity and may at times be normal in patients with active
with lupus and other connective tissue diseases who have ischemic rheumatoid arthritis or SLE. Patients with a markedly elevated ESR
digits may have thrombotic complications secondary to ACL antibody (MESR) are those with values >100 mm/h. These patients deserve
and not true vasculitis. Biopsy of ischemic digits is usually impractical special attention because such elevations are unlikely to be explained by
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and potentially hazardous. The necessity to amputate a gangrenous digit age or normal physiologic state and are a more reliable sickness indica-
should prompt careful instruction to the surgeon to be sure to biopsy tor. The illnesses associated with MESR include infection, malignancy,
the digital artery immediately proximal to the gangrene. In this setting rheumatic disorders such as vasculitis (including temporal arteritis) and
angiography often reveals nonspecific findings of small-vessel disease, SLE, as well as end-stage renal failure, nephrotic syndrome, and other
but may suggest emboli, and at times reveal the source such as a subcla- inflammatory diseases such as hepatitis and colitis. In most series look-
vian plaque. An angiographic pattern suggestive of Buerger disease has ing at MESR, 3% to 10% of patients will have no diagnosis to explain the
been described. 46 abnormal laboratory value. Some of these patients will eventually reveal
an underlying pathology, whereas others will demonstrate spontaneous
improvement in the ESR. In the ICU, the ESR is likely to be elevated for
LUNG INFILTRATES AND ELEVATED SEDIMENTATION multiple reasons. An MESR should not prompt an unreasonable search
RATE: IS THIS VASCULITIS? for vasculitis or other concurrent rheumatic disease, particularly in the
presence of renal failure and nephrotic syndrome. 48
Elevated ESRs frequently become laboratory aberrations looking for a
for a costly and unrewarding workup. Once it is known that a patient ■ C-REACTIVE PROTEIN
disease state. The unwary clinician may let an elevated ESR be the driver
has an elevated ESR and the usual causes for this nonspecific labora- The availability of rapid, reproducible, low-cost assays for C-reactive
tory abnormality have been reasonably excluded, there is an impulse protein (CRP) in many circumstances obviates a clinician’s reliance on
is to link any and all remaining clinical abnormalities to the abnormal the vagaries of the ESR to detect inflammation. CRP is an acute phase
ESR. Unexplained pulmonary infiltrates, a common finding in criti- serum protein that acts as a surrogate for the proinflammatory inter-
cally ill patients, are good examples that provoke the question: Is this leukin IL-6. Serum/plasma levels of CRP are tightly linked not only to
a pulmonary vasculitis? Common sense should prevail and dictate that the absolute level of IL-6, but also to the rise and fall of the cytokine.
the diagnosis of pulmonary vasculitis as a principal entity should be Sequential CRP determinations, in contrast to the slowly responsive
one of exclusion. If a young female on corticosteroids with a fever, rash, ESR, can provide a more accurate assessment of inflammatory changes
alopecia, and pericarditis develops a pulmonary infiltrate, she should be in response to therapy. CRP determination is most helpful in assigning
considered to have an infectious disease or pulmonary embolism until a noninflammatory cause to a markedly abnormal ESR. An example
otherwise proved. If a patient with advanced scleroderma that includes would be a patient with a monoclonal protein without infection, who
the proximal gut develops pulmonary infiltrates, aspiration pneumonia could have an ESR of 100 but a normal CRP. The latter alleviates concern
should be strongly considered. Conversely, one can approach the patient that significant inflammation may be part of the clinical picture. Several
with pulmonary infiltrates and an elevated ESR in reductionist fashion. cautions apply to the interpretation of CRP levels. Although there are
If a careful search for extrapulmonary evidence of vasculitis is not weak correlations between CRP levels and age and gender, they are less
rewarding, it will be highly unlikely that primary pulmonary vasculitis marked than the same variables and the ESR. CRP also varies directly
is present, since vasculitis very rarely involves only the pulmonary tree. with body mass index. The very new ultrasensitive CRP assays have not
There are unusual instances when vasculitis can be isolated to the pul- only changed the normal ranges, but are expressed in markedly different
monary tree in a systemic rheumatic disease. Rarely, patients with ACL concentrations that can be very confusing to the unwary. The bottom
antibodies may develop pulmonary infiltrates secondary to in situ pul- line for the critical care clinician might be that significant elevations of
monary artery thrombosis and/or pulmonary embolism. These patients CRP usually signal the presence of clinically relevant inflammation, and
will simulate a primary vasculitic pulmonary picture, but the primary the absence of a high CRP helps in excluding it.

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