Rheumatology in ICU
Authors: Raza Tasleem 
Published: December 2019

Autoimmune rheumatological disorders are rare but important to consider in Intensive Care Unit (ICU) patients. Overall prevalence of these disorders is approximately 3% in the general population. About 25% of patients presenting with these disorders to the emergency room (ER) require hospital admission and up to one third require ICU admission. Mortality is variable and reported to be around 20% in recent studies.
The most common rheumatological diseases requiring ICU admission are systemic lupus erythematous (SLE), antineutrophilic cytoplasmic antibody (ANCA)-associated vasculitides, rheumatoid arthritis, scleroderma, and dermatomyositis. The most common reasons for admission are infections and exacerbation of an underlying disease. The factors associated with mortality include Acute Physiology and Chronic Health Evaluation (APACHE) - II or Sequential Organ Failure Assessment (SOFA) score, vasopressors support, and prolonged hospital stay.
In most patients with rheumatological disorders, the underlying disease is known at the time of admission. The diagnostic considerations in these patients include infections, underlying disease exacerbation, iatrogenic toxicity, or a rheumatologically unrelated disorder. The most difficult and challenging problem in these patients is differentiating between sepsis and exacerbation of an underlying disease, and laboratory markers may help in this differentiation. In SLE patients an ESR/CRP ratio >15 is suggestive of disease flare while < 2 is suggestive of infection. CD64, 2’5’-oligoadenylate synthetase (OAS) and soluble triggering receptor expressed on myeloid cell type 1 (sTREM1) are also promising biomarkers in differentiating infection and disease flare in SLE. A “bioscore” combining different biomarkers may be more useful than a single biomarker in differentiating disease flare versus infection.
Some medical conditions should always be on the radar of an ICU physician when patients present with multisystem disease with no clear underlying etiology. These include macrophage activation syndrome which may occur at any stage of rheumatic disease (onset, during active disease, during quiescent disease). A ferritin level of >10,000 microgram/L is pathognomonic, and >5,000 is highly suggestive of this diagnosis. Elevated aspartate aminotransferase (AST), alanine aminotransferase (ALT), lactate dehydrogenase (LDH), high CRP with low ESR may also help with this diagnosis. In scleroderma, renal crisis should never be missed and initiation of angiotensin converting enzyme inhibitors (ACEI) should be prompt to avoid morbidity. In any patient with livedo reticularis, digital ischemia, splinter hemorrhages, ulceration and superficial gangrene of lower limbs with multi-organ failure and SIRS, catastrophic antiphospholipid (APL) syndrome should be suspected. Any patient on methotrexate (MTX) should be evaluated for pneumonitis and bone marrow toxicity related to MTX. ANCA-associated vasculitis should be considered in any patient with combined respiratory and renal failure. Bronchoscopy should be prompt in this situation to rule out diffuse alveolar hemorrhage.
In summary, rheumatological disorders are relevant considerations in any patient with single or multi-organ failure in ICU when the underlying etiology is not obvious. A routine immunological screening may be lifesaving in this setting and prompts further work-up and diagnosis. It is extremely important to involve a rheumatologist early in the management of any patient with known or suspected rheumatological disorder. Frequent collaborative discussions and meetings may go a long way to improve prognosis of these patients in the short and long term.