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Background: Delirium is a common neurological complication after cardiac surgery. The purpose of the present study was to analyze the association between hemodynamic fluctuations during cardiopulmonary bypass (CPB) and the incidence of postoperative delirium (POD) in patients undergoing cardiac surgery with CPB.

Methods: This post hoc analysis included one-hundred-ninety-five (n = 195) patients aged ≥ 65 years of whom seventy (n = 70) patients developed POD. Intraoperative hemodynamic variables specifically related to the conduct of CPB were digitally recorded at 1-minute intervals. Variables outside the presumed safe boundaries for mean arterial pressure (MAP), systemic perfusion flow index– L/min/BSA (QBSA_I), systemic venous oxygen saturation (S_VO₂) and arterial oxygen delivery– ml/min/BSA (DO₂) were defined and analyzed with reference to indices of area under the curve (AUC) and the relative proportion of registrations related to POD. POD was diagnosed according to DSM-5 criteria based on a test battery performed preoperatively and repeated twice postoperatively. Statistical tests used to verify observations outside the predefined norm included the Mann-Whitney U test and the chi-squared test.

Results: Markers of hemodynamic control during CPB showed significant associations with POD. Both DO₂ (P = 0.02) and QBSA_I (P < 0.001) identified POD patients outside the predefined upper and lower safety limits. S_VO₂ values > 84% (P < 0.001) werealso associated with the development of POD. The number of S_VO₂ registrations below the lower safety limit was negligible, why statistical analysis seemed not useful. No association between MAP and POD registrations was identified.

Conclusions: This study revealed a clear association between markers of hemodynamic control and POD. These associations were most pronounced for DO₂ and QBSA_I. The detected association between high S_VO₂ and POD warrants further insight.