Introduction: The strategy of perioperative fluid therapy has an important impact not only on the circulating volume and perfusion of organs and tissues but also on the patient's internal environment. The study aimed at comparing the effects of perioperatively administered balanced crystalloid infusion solutions containing different amounts of metabolizable anions on homeostasis.

Methods: In the prospective randomized study, patients were assigned to Plasmalyte (PL) and Ringerfundin (RF) Groups after their postoperative transfer to an intensive care unit (ICU). The infusion solutions were parenterally administered at 1000 mL/6 hours. Arterialized capillary blood was sampled at the time of transfer to the ICU (Time 0), and again at 2 hours and 6 hours from Time 0. The collected blood was tested for blood gas parameters using the Astrup method.

Study design

The study was designed as a single-center, randomized, prospective study and approved by the University Hospital Olomouc and Faculty of Medicine and Dentistry, Palacky University Olomouc ethics committee. It comprised patients over 18 years of age undergoing surgery at the hospital's Department of Surgery I and subsequently placed in an ICU bed. As there were no limitations concerning the type of procedures, these involved a wide range of abdominal and thoracic surgeries; however, all of them were elective procedures. No patients were critically ill, being classified as ASA III or less.

Sample collection and processing To determine the present status of the internal environment, arterialized capillary blood was drawn from the fingertip at the time of patients' transfer from the operating room to the ICU (Time 0), and again at 2 hours and 6 hours from Time 0. The collected blood was tested in the laboratory using the Astrup method to measure the following parameters: pH, BE, actual bicarbonate (aBi), standard bicarbonate (sBi), partial pressure of oxygen (pO2) and carbon dioxide (pCO2). The obtained values were entered into a table and statistically analyzed. Both patients groups were adjusted for age and length of surgery to allow their comparison.

Infusion solutions

The following infusion solutions were parenterally administered using a central or, more frequently, peripheral venous catheter:

1. Plasmalyte in 5% glucose infusion solution (PL), manufactured by Baxter Healthcare as slightly alkalizing (Na+ 140; K+ 5.0; Mg2+ 1.5; Cl- 98; acetate 27; gluconate 23) and
2. Ringerfundin infusion solution (RF), manufactured by B. Braun as acid-base neutral (Na+ 145; K+ 4.0; Mg2+ 1.0; Ca2+ 2.5; Cl- 127; acetate 24; malate 5.0).

At the time of their transfer to the ICU, patients were randomized into PL and RF Groups. Parenteral administration of the two solutions was initiated immediately after collection of the first blood sample at 166 mL/hour. Thus, all patients received 1000 mL of infusion solution over 6 hours. Patients requiring more rapid fluid replacement due to postoperative hypovolemia were excluded from the study. Patients were routinely rewarmed with a warm air blanket and received humidified oxygen via a face mask or, in case of good oxygenation, via a nasal cannula.

Inclusion Criteria:

• age 18+
• elective surgery procedures

Exclusion Criteria:

• critically ill, being classified as ASA III or less
• surgery longer than 6 hrs
• hypersensitivity to PL or RF
• requiring more rapid fluid replacement (than 1000 ml/6 hrs) due to postoperative hypovolemia