Preoperative Ultrasound-based Protocol for Optimization of Fluid Therapy to Prevent Early Intraoperative Hypotension

Plain-language summary

Background: Intraoperative hypotension increases 30-day mortality and the risks of myocardial injury and acute renal failure. Patients with inadequate volume reserve before the induction of anesthesia are highly exposed. The identification of latent hypovolemia is therefore crucial. Ultrasonographic measurement of the inferior vena cava collapsibility index (IVCCI) is able to detect volume responsiveness in circulatory shock and growing evidence support the theory that higher IVCCI can predict intraoperative hypotension. The aim of the present study is to evaluate the potential benefit of an ultrasound-based protocol for preoperative fluid optimization. The investigators will perform a randomized-controlled study involving elective surgical patients. An ultrasound-based protocol (USP) arm and a conventional fluid therapy group (CFT) are to be formed. Ultrasound examinations will be performed twice in both groups: 2 hours and 30 minutes preoperatively. The inferior vena cava and the anterior lung fields will be scanned. In the USP group the participants will receive fluid therapy according to the ultrasonographic findings: high level of IVCCI and absence of signs of pulmonary edema will indicate fluid therapy. In the CFT group the attending anesthesiologist (blinded to the results of ultrasonography) will order fluid therapy on the basis of daily routine and clinical judgement. The investigators will evaluate the incidence of intraoperative hypotension (primary outcome), postoperative metabolic status and organ functions and the amount of the administered intravenous fluids in both groups.

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