Preoperative Ultrasound-based Protocol for Optimisation of Fluid Therapy to Prevent Early Intraoperative Hypotension: A Randomised Controlled Study

Abstract

Abstract Background: Intraoperative hypotension is a risk factor for postoperative complications. Preoperative dehydration is a major contributor, although it is difficult to estimate its severity. Point-of-care ultrasound offers several potential methods, including measurements of the inferior vena cava. The addition of lung ultrasound may offer a safety limit. We aimed to evaluate whether the implication of an ultrasound-based preoperative fluid therapy protocol can decrease the incidence of early intraoperative hypotension. Methods: Randomised controlled study in a tertiary university department involving elective surgical patients of ASA 2-3 class, scheduled for elective major abdominal surgery under general anaesthesia with intubation. We randomized 40–40 patients; 38–38 were available for analysis. Conventional fluid therapy was ordered on routine preoperative visits. Ultrasound-based protocol evaluated the collapsibility index of inferior vena cava and lung ultrasound profiles. Scans were performed twice: 2 h and 30 min before surgery. A high collapsibility index (≥40%) indicated a standardised fluid bolus, while the anterior B-profile of the lung ultrasound contraindicated further fluid. The primary outcome was the incidence of postinduction and early intraoperative (0–10 minutes) hypotension (MAP<65 mmHg and/or ≥30% of decrease from baseline). Secondary endpoints were postoperative lactate level, urine output and lung ultrasound score at 24 h. Results: The absolute criterion of postinduction hypotension was fulfilled in 12 patients in the conventional group (31.6%) and 3 in the ultrasound-based group (7.9%) (p=0.0246). Based on composite criteria, we observed 17 (44.7%) and 7 (18.4%) cases, respectively (p=0.0136). The incidence of early intraoperative hypotension was also lower: HR for absolute hypotension was 2.10 (95%CI 1.00–4.42) in the conventional group (p=0.0387). Secondary outcome measures were similar in the study groups. Conclusion: We implemented a safe and effective point-of-care ultrasound-based preoperative fluid replacement protocol into perioperative care. Trial registration: The study was registered to Clinicaltrials.gov on 10/12/2021, registration number: NCT05171608 (registered prospectively on 10/12/2021)