Perioperative supplemental oxygen and NT-proBNP concentrations after major abdominal surgery - A prospective randomized clinical trial.

STUDY OBJECTIVE: Supplemental oxygen is a simple method to improve arterial oxygen saturation and might therefore improve myocardial oxygenation. Thus, we tested whether intraoperative supplemental oxygen reduces the risk of impaired cardiac function diagnosed with NT-proBNP and myocardial injury after noncardiac surgery (MINS) diagnosed with high-sensitivity Troponin T. DESIGN: Parallel-arm double-blinded single-centre superiority randomized trial. SETTING: Operating room and postoperative recovery area. PATIENTS: 260 patients over the age of 45 years at-risk for cardiovascular complications undergoing major abdominal surgery. INTERVENTION: Administration of 80% versus 30% oxygen throughout surgery and for the first two postoperative hours. MEASUREMENTS: The primary outcome was the postoperative maximum NT-proBNP concentration in both groups, which was assessed within 2 h after surgery, and on the first and third postoperative day. The secondary outcome was the incidence of MINS in both groups. MAIN RESULTS: 128 patients received 80% oxygen and 130 received 30% oxygen throughout surgery and for the first two postoperative hours. There was no significant difference in the median postoperative maximum NT-proBNP concentration between the 80% and the 30% oxygen group (989 pg.mL-1 [IQR 499; 2005] and 810 pg.mL-1 [IQR 409; 2386], effect estimate: 159 pg.mL-1, 95%CI -123, 431, p = 0.704). There was no difference in the incidence of MINS between both groups. (p = 0.703). CONCLUSIONS: There was no beneficial effect of perioperative supplemental oxygen administration on postoperative NT-proBNP concentration and MINS. It seems likely that supplemental oxygen has no effect on the release of NT-proBNP in patients at-risk for cardiovascular complications undergoing major abdominal surgery. TRIAL REGISTRATION: ClinicalTrials.gov: NCT03366857. https://clinicaltrials.gov/ct2/results?cond=NCT+03366857&term=&cntry=&state=&city=&dist=.

The effect of supplemental oxygen on perioperative brain natriuretic peptide concentration in cardiac risk patients - a protocol for a prosprective randomized clinical trial.

BACKGROUND: Elevated postoperative N-terminal pro-B-type natriuretic peptide (NT-proBNP) concentrations are predictive for cardiac adverse events in noncardiac surgery. Studies indicate that supplemental oxygen decreases sympathetic nerve activity and might, therefore, improve cardiovascular function. Thus, we will test the effect of perioperative supplemental oxygen administration on NT-proBNP release after surgery. METHODS/DESIGN: We will conduct a single-center, double-blinded, randomized trial at the Medical University of Vienna, including 260 patients with increased cardiac risk factors undergoing moderate- to high-risk noncardiac surgery. Patients will be randomly assigned to receive 80% versus 30% oxygen during surgery and for 2 h postoperatively. The primary outcome will be the difference in maximum NT-proBNP release after surgery. As secondary outcomes we will assess the effect of supplemental oxygen on postoperative maximum troponin T concentration, oxidation-reduction potential, von Willebrand factor concentration and perioperative fluid requirements. We will perform outcome measurements 2 h after surgery, on postoperative day 1 and on postoperative day 3. The NT-proBNP concentration and the oxidation-reduction potential will also be measured within 72 h before discharge. DISCUSSION: Our trial should determine whether perioperative supplemental oxygen administration will reduce the postoperative release of NT-proBNP in patients with preoperative increased cardiovascular risk factors undergoing noncardiac surgery. TRIAL REGISTRATION: ClinicalTrials.gov, ID: NCT03366857. Registered on 8th December 2017.