Management of Fluid Overload in Cardiorenal Patients: The Five B Approach

Fluid overload is a common result of cardiovascular disease (especially heart failure [HF]) and kidney disease. When heart and kidney present a combined dysfunction, such as in the case of cardiorenal syndromes (CRS), overhydration is almost the rule. The diagnosis, objective quantification, and management of this problem is integral in attempting to improve clinical outcomes, including mortality and quality of life. Many clinical conditions lead to fluid overload, including decompensated HF and acute kidney injury (AKI) after the use of contrast media, the administration of nephrotoxic drugs (e.g., amphotericin B) or drugs associated with precipitation of crystals (e.g., methotrexate, acyclovir), or shock resulting from cardiogenic, septic, or traumatic causes. Adequate fluid status should be obtained, but a target value should be set according to objective indicators and biomarkers. Once the fluid excess is identified, a careful prescription of fluid removal by diuretics or extracorporeal therapies must be made. While delivering these therapies, clinicians must monitor them adequately to prevent unwanted effects such as worsening of renal function or others. Thus the clinical challenge becomes the utilization of all currently available methods for objective measurement to determine the patient's volume status.

The CRS term is used to include the vast array of interrelated derangements between the heart and kidney and to stress the bidirectional nature their interactions. Generally, CRS are defined as pathophysiologic disorders of either organ system, where acute or chronic dysfunction of one may induce acute or chronic dysfunction of the other. CRS can be categorized into five subtypes that reflect the pathophysiology, time frame, and nature of concomitant cardiac and renal dysfunction ( Box 136.1 ). CRS are therefore typical conditions in which fluid overload may occur and may require specific diagnosis and management. The various types of CRS may present different signs and symptoms, but the fluid overload represents one of the common pathways toward hospitalization and bad outcomes.