Goal-directed perioperative fluid management: why, when, and how?

PRINCIPLES of perioperative fluid management have received increased interest in recent years within type and amount of crystalloid and colloid, the concept of individualized goal-directed cardiovascular optimization (GDT), and finally assessed on a procedure-specific basis. In this issue, Kimberger et al., investigated the underlying tissue mechanisms during GDT management with crystalloids or colloids for abdominal surgery with a colonic anastomosis. This elegant experimental study in pigs included detailed techniques of postsurgical assessments of conventional cardiovascular variables (blood pressure, heart rate, urinary output) and microcirculatory blood flow and tissue oxygen tension in healthy and perianastomotic colonic tissue. Three types of fluid management were instituted at the end of surgery: restricted Ringer lactate (RL) versus GDT RL or GDT colloid to achieve a mixed venous oxygen saturation (SvO2) greater than 60%. The results show no significant differences between the groups in conventional cardiovascular functional parameters or urinary output, but an increased oxygen tension in healthy colonic tissue compared with RL and a further increase with GDT colloid compared with GDT RL. Of special interest, oxygen tension in perianastomotic tissue increased to 245% with GDT colloid versus 147% in the GDT RL group versus 116% in the restricted RL group. Furthermore, microcirculatory flow was higher with GDT colloid. Interestingly, anastomotic tissue edema was not different between groups. The study by Kimberger et al. may add important new knowledge to the understanding of the apparent beneficial effects of GDT in surgical patients, where the 11 randomized clinical studies have mostly shown outcome benefits within postoperative nausea and vomiting, ileus, morbidity, and hospital stay. Until now, however, only limited pathophysiological data are available to explain this benefit. Thus, Mythen and Webb showed GDT to improve morbidity and hospital stay after cardiac surgery related to the demonstrated increased gut mucosal perfusion (gastric intramucosal pH), but this could not be confirmed by a less well-designed study in abdominal surgery. In the colorectal surgery study by Noblett et al., the reduced morbidity and hospital stay by GDT was associated with a reduced interleukin-6 response. These findings together suggest that GDT may attenuate stress-induced organ dysfunctions and thereby have a pivotal role on outcome, including anastomotic complications. The recent studies on perioperative changes of the vascular barrier suggest that the endothelial glycocalyx plays a key role, which needs to be studied within the context of GDT and use of colloid. In the discussion of GDT, it is essential that the present individualized GDT approach includes optimization of flow-related parameters, such as cardiac stroke volume, within the limit of the individual patient’s cardiac capacity. The concept is therefore different from the original Shoemaker concept for optimization, which used predetermined supraphysiologic values of cardiac index and DO2 as therapeutic goals. 12 Interestingly, the study by Kimberger et al. also used fixed goals for GDT optimization (SvO2 60%) and not the individualized approach. Most of the 11 clinical GDT outcome studies are positive and may have widespread implications for clinical practice; therefore, there is an urgent need to evaluate the pathophysiological mechanisms, such as done by Kimberger et al. and others. In addition, when to institute GDT needs to be clarified. The studies predominantly perform GDT in the intraoperative period, and there have been only 2 studies within the very early postoperative period and no studies in the later postoperative period, where major fluid shifts and requirements may occur. Interestingly, the GDT optimization by Kimberger et al. was done postabdominal closure. However, the studies provide little or no detailed data of GDT in relation to type of anesthesia, including epidural anesthesia and its well-known effects on cardiovascular function; therefore, the practicing anesthesiologist is left with several unanswered questions for the interpretation of the GDT approach during the entire anesthetic-surgical period. In this context, precision of GDT requires averaging of stroke volume over at least 10 heartbeats when using the esophageal Doppler technology. Also, it has been suggested that the timing of GDT may be important because the total perioperative administration of crystalloid and colloid was not different between the GDT and control groups, despite major differences in outcome in favor of GDT. These results again call for confirmative studies, as well as pathophysiological explanations. Colloids for GDT have been used in the clinical studies and are supported by the study by Kimberger et al. as well as by a previous study demonstrating that GDT-administered crystalloid This Editorial View accompanies the following article: Kimberger O, Arnberger M, Brandt S, Plock J, Sigurdsson GH, Kurz A, Hiltebrand L: Goal-directed colloid administration improves the microcirculation of healthy and perianastomotic colon. ANESTHESIOLOGY 2009; 110:496 –504.