Less Fluids and a More Physiological Approach

Abstract

T he goals to achieve a "zero fluid balance" and to minimize the early weight gain over the perioperative period are fully shared with our Italian colleagues. Indeed, based on convincing clinical and experimental data, we all agree that weight gain exceeding 10% is associated with increased mortality and that positive fluid balance is an independent risk factor of postoperative morbidity (1).Despite the growing body of knowledge regarding perioperative hemodynamic optimization, we remain dubious and critical about the clinical applicability of the goal-directed therapy (GDT) and its real impact on postoperative outcome. Our Italian colleagues suggest that the aim of the GDT approach should be to optimize cardiac output (CO) or stroke volume (SV) intraoperatively and in the early 8-12 hours after surgery, particularly in high-risk patients and high-risk surgery.The term "optimization" is extensively used to express the investigator and clinician's wishes to deliver the best interventions that will not harm and provide beneficial effects to the patient. As clinicians, we must admit having difficulties to grasp the real difference (if any) between hemodynamic optimization and hemodynamic maximization (2). To our understanding, "optimization" should encompass, -not only intravenous fluid titration-, but also the administration of cardiovascular drugs (e.g., vasodilators, vasopressors, inotropes, beta-blockers, alpha-2 agonists) with the aims to control the determinants of cardiac output (preload, cardiac contractility/relaxation, afterload and heart rate) and to match flow/oxygen delivery (DO 2 ) to the changing metabolic needs and oxygen consumption (VO 2 ). From our point of view, hemodynamic maximization is an appropriate strategy in patients with shock-like situation who need resuscitative interventions (Figure 1a) whereas it may lead to deleterious effects in patients undergoing major elective surgery (Figure 1b).Assuming that some patients may experience an oxygen debt during the pre-intra-and postoperative period, preemptive GDT has been advocated as a promising approach for reducing mortality-morbidity after major surgery. The GDT strategy with optimization/maximization of CO/SV was believed to correct the oxygen debt and, -by maintaining oxygen delivery well above the critical anaerobic threshold-, to prevent postoperative organ dysfunction and enhance wound healing (3, 4).In the eighties, landmark papers from Dr Shoemaker's group clearly demonstrated a link between the presence of a perioperative oxygen debt (calculated by subtracting the measured VO 2 from the estimated VO 2 requirements corrected for temperature and anesthesia) and the development of postoperative organ