Intravenous fluid therapy in major open abdominal surgery: comparing standard of care versus bolus therapy

Abstract

Volume and fluid deficits are common in surgical patients. Determination of adequate volume resuscitation is an important clinical challenge, especially in major abdominal surgery. The ability to avoid both hyper and hypovolemia is challenging, and perioperative fluid excess seems to have as many significant side effects in several organ systems as fluid deficit. Perioperative fluid therapy has been studied extensively, but the optimal strategy remains controversial and uncertain. Accordingly, the present study aims to compare two strategies of fluid replacement during the perioperative period in patients undergoing major open abdominal surgeries - the standard of care (continuous fluid infusion) versus bolus therapy. Methods: After the written informed consent was obtained for all patients prior to surgery, a randomized, controlled, single blind study will be performed in 80 adult patients scheduled to undergo major open abdominal surgery under general anesthesia at the Botucatu Clinics Hospital. Patients will be randomly allocated in two groups according to the strategy of fluid therapy used during the perioperative period - standard of care (SOC) and bolus. Several studies have been shown that the use of specific hemodynamic goals (goal-directed therapy) to titrate fluid therapy is beneficial when compared with liberal use of fluids. Accordingly, in the present study the fluid replacement will be guided by pulse pressure variation (PPV) values in both groups. We determined PPV > 12% as the threshold to trigger the fluid replacement or fluid increments. In SOC-group, fluids will be administered continuously by the Anesthesiologists during surgery and Post-Anesthetic Care Unit (PACU) periods. The Anesthesiologists will be free to decide which type of fluid - crystalloids (lactate Ringer - LR) or colloids (Hetastarch - HES) - they will administer and in which velocity. In Bolus-group, patients will receive a continuous infusion of 4 ml.kg-1.h-1 of LR over the surgical and PACU periods. Besides, when PPV increases above 12%, a bolus of fluid will be administered based on the following algorithm: 1st bolus = 300 ml of LR over 5 minutes; 2nd bolus = 300 ml of LR over 5 minutes; 3th bolus = 200 ml of HES over 5 minutes. This algorithm sequence must be repeated every time that PPV achieve a value higher than 12%. A time frame of 5 minutes after bolus must be respected to perform a new evaluation of PPV values. The intra and postoperative complications will be evaluated and compared between the two groups by an Anesthesiologist that did not know about which group the patient was allocated. The renal function, intestinal function and mortality rates at the 7th and 30th days after surgery will be also evaluated in the present study. (AU)