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Background: The mechanisms of acid-base changes during cardiopulmonary bypass (CPB) remain unclear. We tested the hypothesis that, when used as CPB pump prime solutions, Plasma-Lyte 148 (PL) and Hartmann's solution (HS) have differential mechanisms of action in their contribution to acid-base changes. Methods: We performed a prospective, double-blind, randomized trial in adult patients undergoing elective cardiac surgery with CPB. Participants received a CPB prime solution of 2000 mL, with either PL or HS. The primary endpoint was the standard base excess (SBE) value measured at 60 minutes after full CPB flows (SBE60min). Secondary outcomes included changes in SBE, pH, chloride, sodium, lactate, gluconate, acetate, strong ion difference and strong ion gap at two (T2min), five (T5min), ten (T10min), thirty (T30min) and sixty (T60min) minutes on CPB. The primary outcome was measured using a two-tailed Welch's t-test. Repeated measures ANOVA was used to test for differences between time points. Results: Twenty-five participants were randomized to PL and 25 to HS. Baseline characteristics, EURO and APACHE scores, biochemistry, hematology and volumes of cardioplegia were similar. Mean (SD) SBE at T60min was -1.3 (1.4) in the PL group and -0.1 (2.7) in the HS group; p=0.55. No significant differences in SBE between the groups was observed during the first 60 minutes (p=0.48). During CPB, there was hyperacetatemia and hypergluconatemia in the PL group and hyperlactatemia and hyperchloremia in the HS group. No significant difference between the groups in plasma bicarbonate levels and total weak acid levels were found. Complications and intensive care unit and hospital length of stays were similar. Conclusions: During CPB, PL and HS did not cause a significant metabolic acidosis. There was hyperacetatemia and hypergluconatemia with PL and hyperchloremia and hyperlactatemia with HS. These physiochemical effects appear clinically innocuous. [ABSTRACT FROM AUTHOR]

Background: Studies in critically ill patients suggest a relationship between mechanical power (an index of the energy delivered by the ventilator, which includes driving pressure, respiratory rate, tidal volume and inspiratory pressure) and complications., Objective: We aimed to assess the association between intra-operative mechanical power and postoperative pulmonary complications (PPCs)., Design: Post hoc analysis of a large randomised clinical trial., Setting: University-affiliated academic tertiary hospital in Melbourne, Australia, from February 2015 to February 2019., Patients: Adult patients undergoing major noncardiothoracic, nonintracranial surgery., Intervention: Dynamic mechanical power was calculated using the power equation adjusted by the respiratory system compliance (CRS). Multivariable models were used to assess the independent association between mechanical power and outcomes., Main Outcome Measures: The primary outcome was the incidence of PPCs within the first seven postoperative days. The secondary outcome was the incidence of acute respiratory failure., Results: We studied 1156 patients (median age [IQR]: 64 [55 to 72] years, 59.5% men). Median mechanical power adjusted by CRS was 0.32 [0.22 to 0.51] (J min-1)/(ml cmH2O-1). A higher mechanical power was also independently associated with increased risk of PPCs [odds ratio (OR 1.34, 95% CI, 1.17 to 1.52); P < 0.001) and acute respiratory failure (OR 1.40, 95% CI, 1.21 to 1.61; P < 0.001)., Conclusion: In patients receiving ventilation during major noncardiothoracic, nonintracranial surgery, exposure to a higher mechanical power was independently associated with an increased risk of PPCs and acute respiratory failure., Trial Registration: Australia and New Zealand Clinical Trials Registry no: 12614000790640., (Copyright © 2021 The Author(s). Published by Wolters Kluwer Health, Inc. on behalf of the European Society of Anaesthesiology and Intensive Care.)