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Postoperative delirium (POD) is an acute onset of disturbance in attention/consciousness combined with cognitive deficits. It is unclear if intraoperative fluctuations in intraoperative blood pressure are independent risk factors for POD.
Secondary analysis of a randomized controlled trial, primarily aimed to test the efficiency of BIS guided anaesthesia for the prevention of POD.
The “Surgery Depth of anaesthesia and Cognitive Outcome”- (SuDoCO) trial, carried out 03-2009 untill 04-2010, included ≥ 60-year-old patients scheduled for elective non-cardiac surgery of ≥ 60 minutes under general anaesthesia 1. Intra-operative hand written blood pressure record sheets were digitalized and analyzed using univariate and multivariate analyses. Endpoint was the cumulative POD incidence (defined according to DSM-IV) within seven post-operative days.
Overall 917 complete data on all independent variables as well as outcomes were available. The mean age was 70.0±6.5 years and n=489 (53.3%) were males. The median surgical time was 2.3 (range: 0.1 up 10.1) hours and 197 patients (21.5%) developed POD. In univariate analysis, patients with POD showed higher mean systolic blood pressure (117.1±10.5 vs. 114.9±11.0 mmHg, p= 0.014) while there were no differences in diastolic blood pressure and mean arterial pressure (MAP). The absolute values of blood pressure fluctuation in systolic and diastolic blood pressure as well as MAP were significantly higher in patients with POD compared to patients without POD (all p< 0.05). After adjustments for randomization status, age, gender, ASA physical status, Mini Mental State Examination (MMSE) pre-operatively, as well as site of operation, length of hospital stay and length of procedure, systolic blood pressure fluctuations (p=0.048), diastolic blood pressure fluctuations (p= 0.09) as well as fluctuations in MAP (p= 0.027) were associated with POD, independently from their interactions with length of operation (p=0.038, p= 0.71, and p= 0.14, respectively).
Fluctuations in systolic blood pressure, despite significant interaction with operation time, as well as fluctuations in MAP seem to be independent predictors for POD. Future studies should evaluate whether a strict blood pressure regimen, avoiding intraoperative blood pressure fluctuations, prevents POD.