The dynamic nature of fluid resuscitation in acute pancreatitis.

In a recent study by Warndorf et al,1Warndorf M.G. Kurtzman J.T. Bartel M.J. et al.Early fluid resuscitation reduces morbidity among patients with acute pancreatitis.Clin Gastroenterol Hepatol. 2011; 9: 705-709Abstract Full Text Full Text PDF PubMed Scopus (142) Google Scholar it is concluded that those patients with acute pancreatitis receiving one-third or more of the total 72-hour fluid volume within 24 hours of presentation have reduced incidence of systemic inflammatory response syndrome and organ failure, so an early aggressive fluid therapy is recommended. The benefits of this approach have not been confirmed in prospective studies.2Mao E.Q. Tang Y.Q. Fei J. et al.Fluid therapy for severe acute pancreatitis in acute response stage.Chin Med J (Engl). 2009; 122: 169-173PubMed Google Scholar, 3Wu B.U. Hwang J.Q. Gardner T.H. et al.Lactated Ringer's solution reduces systemic inflammation compared with saline in patients with acute pancreatitis.Clin Gastroenterol Hepatol. 2011; 9: 710-717Abstract Full Text Full Text PDF PubMed Scopus (311) Google Scholar, 4de-Madaria E. Soler-Sala G. Sanchez-Paya J. et al.Influence of fluid therapy on the prognosis of acute pancreatitis: a prospective cohort study.Am J Gastroenterol. 2011; 106: 1843-1850Crossref PubMed Scopus (132) Google Scholar Furthermore, it has been suggested that it might be associated with increased incidence of complications (particularly respiratory failure).2Mao E.Q. Tang Y.Q. Fei J. et al.Fluid therapy for severe acute pancreatitis in acute response stage.Chin Med J (Engl). 2009; 122: 169-173PubMed Google Scholar, 4de-Madaria E. Soler-Sala G. Sanchez-Paya J. et al.Influence of fluid therapy on the prognosis of acute pancreatitis: a prospective cohort study.Am J Gastroenterol. 2011; 106: 1843-1850Crossref PubMed Scopus (132) Google ScholarThe linear association between fluid volume and outcome (Figure 1, Model A) is exposed to bias. Fluid administration is characterized by a dynamic nature in clinical practice; it is influenced by the course of the disease. We can classify fluid therapy into 2 scenarios: (1) initial resuscitation at admission and (2) subsequent extra fluid requirements (Figure 1, Model B). Patients who develop local complications after admission are prone to fluid sequestration, so they frequently require an increase in fluid administration. Extra fluid requirements on the second and third days lead to decreased total 72-hour fluid volume within 24 hours of presentation. Therefore, we think that a reverse causation bias might explain the poorer prognosis associated with “late resuscitation.” Patients who develop complications in the first day, which are associated with later systemic inflammatory response syndrome and organ failure, are identified by increased fluid requirements in the second and third days. In a recent study by Warndorf et al,1Warndorf M.G. Kurtzman J.T. Bartel M.J. et al.Early fluid resuscitation reduces morbidity among patients with acute pancreatitis.Clin Gastroenterol Hepatol. 2011; 9: 705-709Abstract Full Text Full Text PDF PubMed Scopus (142) Google Scholar it is concluded that those patients with acute pancreatitis receiving one-third or more of the total 72-hour fluid volume within 24 hours of presentation have reduced incidence of systemic inflammatory response syndrome and organ failure, so an early aggressive fluid therapy is recommended. The benefits of this approach have not been confirmed in prospective studies.2Mao E.Q. Tang Y.Q. Fei J. et al.Fluid therapy for severe acute pancreatitis in acute response stage.Chin Med J (Engl). 2009; 122: 169-173PubMed Google Scholar, 3Wu B.U. Hwang J.Q. Gardner T.H. et al.Lactated Ringer's solution reduces systemic inflammation compared with saline in patients with acute pancreatitis.Clin Gastroenterol Hepatol. 2011; 9: 710-717Abstract Full Text Full Text PDF PubMed Scopus (311) Google Scholar, 4de-Madaria E. Soler-Sala G. Sanchez-Paya J. et al.Influence of fluid therapy on the prognosis of acute pancreatitis: a prospective cohort study.Am J Gastroenterol. 2011; 106: 1843-1850Crossref PubMed Scopus (132) Google Scholar Furthermore, it has been suggested that it might be associated with increased incidence of complications (particularly respiratory failure).2Mao E.Q. Tang Y.Q. Fei J. et al.Fluid therapy for severe acute pancreatitis in acute response stage.Chin Med J (Engl). 2009; 122: 169-173PubMed Google Scholar, 4de-Madaria E. Soler-Sala G. Sanchez-Paya J. et al.Influence of fluid therapy on the prognosis of acute pancreatitis: a prospective cohort study.Am J Gastroenterol. 2011; 106: 1843-1850Crossref PubMed Scopus (132) Google Scholar The linear association between fluid volume and outcome (Figure 1, Model A) is exposed to bias. Fluid administration is characterized by a dynamic nature in clinical practice; it is influenced by the course of the disease. We can classify fluid therapy into 2 scenarios: (1) initial resuscitation at admission and (2) subsequent extra fluid requirements (Figure 1, Model B). Patients who develop local complications after admission are prone to fluid sequestration, so they frequently require an increase in fluid administration. Extra fluid requirements on the second and third days lead to decreased total 72-hour fluid volume within 24 hours of presentation. Therefore, we think that a reverse causation bias might explain the poorer prognosis associated with “late resuscitation.” Patients who develop complications in the first day, which are associated with later systemic inflammatory response syndrome and organ failure, are identified by increased fluid requirements in the second and third days. Early Fluid Resuscitation Reduces Morbidity Among Patients With Acute PancreatitisClinical Gastroenterology and HepatologyVol. 9Issue 8PreviewEarly fluid resuscitation is recommended to reduce morbidity and mortality among patients with acute pancreatitis, although the impact of this intervention has not been quantified. We investigated the association between early fluid resuscitation and outcome of patients admitted to the hospital with acute pancreatitis. Full-Text PDF ReplyClinical Gastroenterology and HepatologyVol. 10Issue 1PreviewWe appreciate the comments by Dr de-Madaria and colleagues and thank them for their thoughtful letter. They raise an important issue that we have also commented on in our discussion section—the role of reverse causation or “effect-cause” bias in our findings.1 In any retrospective cohort or case-control study, a potential does exist for an effect-cause explanation—ie, the observed association is real, but the causal pathway is reversed. Dr de-Madaria and colleagues have suggested that patients who develop complications from acute pancreatitis in the first day received more fluids in the second and third day, thereby being identified as being in the “late resuscitation” group. Full-Text PDF