Relation between acute and long-term cognitive decline after surgery: Influence of metabolic syndrome

IntroductionThe relationship between persistent postoperative cognitive decline and the more common acute variety remains unknown; using data acquired in preclinical studies of postoperative cognitive decline we attempted to characterize this relationship.MethodsLow capacity runner (LCR) rats, which have all the features of the metabolic syndrome, were compared postoperatively with high capacity runner (HCR) rats for memory, assessed by trace fear conditioning (TFC) on the 7th postoperative day, and learning and memory (probe trial [PT]) assessed by the Morris water-maze (MWM) at 3 months postoperatively. Rate of learning (A_L) data from the MWM test, were estimated by non-linear mixed effects modeling. The individual rat’s TFC result at postoperative day (POD) 7 was correlated with its A_L and PT from the MWM data sets at postoperative day POD 90.ResultsA single exponential decay model best described A_L in the MWM with LCR and surgery (LCR–SURG) being the only significant covariates; first order A_L rate constant was 0.07 s⁻¹ in LCR–SURG and 0.16 s⁻¹ in the remaining groups (p < 0.05). TFC was significantly correlated with both A_L (R = 0.74; p < 0.0001) and PT (R = 0.49; p < 0.01).ConclusionSeverity of memory decline at 1 week after surgery presaged long-lasting deteriorations in learning and memory.