Fluid balance and acute kidney injury

Abstract

Intravenous fluids are widely administered to patients who have, or are at risk of, acute kidney injury (AKI). However, deleterious consequences of overzealous fluid therapy are increasingly being recognized. Salt and water overload can predispose to organ dysfunction, impaired wound healing and nosocomial infection, particularly in patients with AKI, in whom fluid challenges are frequent and excretion is impaired. In this Review article, we discuss how interstitial edema can further delay renal recovery and why conservative fluid strategies are now being advocated. Applying these strategies in critical illness is challenging. Although volume resuscitation is needed to restore cardiac output, it often leads to tissue edema, thereby contributing to ongoing organ dysfunction. Conservative strategies of fluid management mandate a switch towards neutral balance and then negative balance once hemodynamic stabilization is achieved. In patients with AKI, this strategy might require renal replacement therapy to be given earlier than when more-liberal fluid management is used. However, hypovolemia and renal hypoperfusion can occur in patients with AKI if excessive fluid removal is pursued with diuretics or extracorporeal therapy. Thus, accurate assessment of fluid status and careful definition of targets are needed at all stages to improve clinical outcomes. A conservative strategy of fluid management was recently tested and found to be effective in a large, randomized, controlled trial in patients with acute lung injury. Similar randomized, controlled studies in patients with AKI now seem justified.

Fluid management and goal-directed therapy as an adjunct to Enhanced Recovery After Surgery (ERAS)

“…81 Fluid overload results in tissue edema; in an encapsulated organ such as the kidney, tissue edema may participate directly in the progression of AKI as the kidney lacks the capacity to accommodate additional volume without an increase in interstitial pressure and compromised organ blood flow. 82 Within an ERAS protocol, postoperative hypotension and low UOP are common within the first 24 hr, whereas renal dysfunction is extremely rare. 83 Therefore, in the absence of other concerns, detrimental postoperative fluid overload is not justified, and ''permissive oliguria'' can be tolerated.…”

Conservative fluid management or deresuscitation for patients with sepsis or acute respiratory distress syndrome following the resuscitation phase of critical illness: a systematic review and meta-analysis

“…Clinically this fluid overload is apparent as peripheral and pulmonary oedema, although other organs may be affected [1]. A number of cohort studies have demonstrated an association between fluid overload and mortality [2][3][4], and it has been suggested that strategies aimed at prevention or treatment of fluid overload may be beneficial following haemodynamic stabilisation [5].…”

Frequency of Fluid Overload and Usefulness of Bioimpedance in Patients Requiring Intensive Care for Sepsis Syndromes

“…In patients treated for sepsis, the combination of increased capillary permeability and increased intravascular hydrostatic pressure from fl uid loading both favor the accumulation of extracellular fl uid. Tissue edema is not a benign condition, as it can result in impaired tissue oxygenation, obstruction of capillary blood fl ow, disruption in metabolite clearance, and altered cell-cell interactions (15).…”