Fluid and electrolyte management following open heart surgery

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Maintenance of correct fluid and electrolyte balance is important for the following reasons: (1) provision for optimal volemic status, which is a necessary prerequisite for stable hemodynamics; (2) maintenance of appropriate renal function; (3) optimization of electrolyte configuration of body fluids; and (4) achieving all above without increasing extravascular lung water or precipitating congestive heart failure.

Several factors affect the balance of body fluids and electrolytes following open heart surgery. (1) Amount of intraoperative fluid intake. This varies significantly from center to center. Criteria used for amount of and type of fluid used intraoperatively are not always supported by hard data. (2) The type of fluid used to prime the pump plays an important role, e.g., use of clear fluid instead of blood, use of mannitol, use of buffers.1–3 (3) Loss of albumin from circulation during the perioperative period would affect the oncotic pressure of the plasma.4 (4) Inappropriate ADH production occurring during and following major surgery or in response to some anesthetic agents. (5) The impact of positive pressure ventilation on cardiac output, renal blood flow, and ADH production.

Quantitative consideration

1. Left ventricular filling pressure. Measured by left atrial pressure (LAP) or pulmonary capillary wedge pressure (PCWP) is a valuable indicator. Pressure of 8 to 10 mm Hg is appropriate for patients with no left ventricular failure, otherwise the pressure of 15 to 18 mm Hg is probably optimal. In the low output syndrome a combination of fluid intake and vasodilators could be helpful. Fluid intake resulting . . .



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