Validation of these data in future cohorts of patients will need to be conducted. Conclusion AG,

ACAG, and BD failed to detect the presence of clinically significant hyperlactatemia. The PP2 assessment of AG in critically ill patients is highly limited given the prevalence of hypoalbuminemia. If an assessment of the AG is needed, it should be done in concert with serum albumin and serum lactate measurements (ACAG and ALCAG). We believe that serum lactate levels should be routinely obtained in all patients admitted to the ICU in whom the possibility of shock/hypoperfusion Inhibitors,research,lifescience,medical is being considered. Unmeasured anions exclusive of serum lactate and serum albumin are frequently present in significant quantities in patients who are critically ill. Competing

interests The authors declare that they have no competing interests. Authors’ contributions Inhibitors,research,lifescience,medical SS participated in the conduct, design, and data acquisition of the study. DD conducted the surveys, and helped draft the manuscript. CJ participated in its design and coordination of the study. MS participated in the design of the study and helped to draft the manuscript. LC conceived of the study, participated in its design and coordination, performed the statistical analysis, and helped to draft the manuscript. All authors read and approved Inhibitors,research,lifescience,medical the final manuscript. About the authors LC is a nephrologist and intensivist. SS is a general surgeon. DD is an intensivist. CJ is an anesthesiologist and an intensivist. MS is the Director of the ICU at George Washington University Hospital. Pre-publication history The pre-publication history Inhibitors,research,lifescience,medical for this paper can be accessed here: http://www.biomedcentral.com/1471-227X/8/18/prepub Acknowledgements This paper was supported by Satellite Research: Norman S. Inhibitors,research,lifescience,medical Coplon Extramural Research Grant.
For some time, health services research has focused on the issue of frequent use of the ED. This growing literature finds that smaller subgroups of patients with repeat visits use disproportionate

amounts of services. [1-4] From both clinical and policy perspectives, few would argue that frequent use of the ED is an optimal next treatment approach. It is incumbent upon the field to identify the health and social issues driving frequent use of the ED and to identify suitable interventions to improve care and reduce the strain on scarce ED resources. Research on frequent users of the ED find that they have fewer resourcesand higher rates of mortality and morbidity than non-frequent users. [5,6] Psychiatric and substance use problems are commonly found to be contributing factors to frequent ED use. [3,7-14] Little research, however, has focused on the association between substance use and psychiatric comorbidity and the frequency of ED use. A group of studies has found that comorbid substance use disorders were associated with increased ED use among persons with schizophrenia.