Abstract
BackgroundBilateral regional brain oxygen saturation (rSO2) trends, reflecting intraoperative brain oxygen imbalance, could warn of brain dysfunction. Various types of cognitive impairment, such as memory decline, alterations in executive function or subjective complaints, have been described three months after surgery. Our aim was to explore the potential utility of rSO2 values as a warning sign for the development of different types of decline in postoperative psychological function.MethodsObservational post-hoc analysis of data for the patient sample (n = 125) of a previously conducted clinical trial in patients over the age of 65 years undergoing total knee replacement under spinal anesthesia. Demographic, hemodynamic and bilateral rSO2 intraoperative values were recorded. An absolute rSO2 value of <50% or a reduction of >20% or >25% below baseline were chosen as relevant cutoffs. Composite function test scores were created from baseline to three months for each patient and adjusted for the mean (SD) score changes for a control group (n = 55). Tests were used to assess visual-motor coordination and executive function (VM-EF) (Wechsler Digit Symbol-Coding and Visual Reproduction, Trail Making Test) and memory (Auditory Verbal Learning, Wechsler Memory Scale); scales were used to assess psychological symptoms.ResultsWe observed no differences in baseline rSO2 values; rSO2 decreased significantly in all patients during surgery (P < 0.0001). Seventy-five patients (60%) had no sign of cognitive decline or psychological symptoms. Twenty-one patients (16.8%) had memory decline, 3 (2.4%) had VM-EF decline, and 33 (26.4%) had psychological symptoms. Left and right rSO2 values were asymmetric in patients who had memory decline (mean [SD] left-right ratio of 95.03 [8.51] vs 101.29 [6.7] for patients with no changes, P = 0.0012). The mean right-left difference in rSO2 was also significant in these patients (-2.87% [4.73%], lower on the right, P = 0.0034).ConclusionsDetection of a trend to asymmetry in rSO2 values can warn of possible postoperative onset of memory decline. Psychological symptoms and memory decline were common three months after knee replacement in our patients over the age of 65 years.
Highlights
Bilateral regional brain oxygen saturation trends, reflecting intraoperative brain oxygen imbalance, could warn of brain dysfunction
We recruited patients of both sexes over the age of 65 years who were scheduled for total knee replacement under spinal anesthesia, applying the following exclusion criteria: a history of central nervous system disorder, recognized abnormalities in supraaortic branches, prior neurosurgery or use of medications acting on the central nervous system
The mean (SD) baseline absolute Regional cerebral oxygen saturation (rSO2) values in the study group were 65% (7.3%) for the right hemisphere and 65% (6%) for the left hemisphere. rSO2 values for both hemispheres were seen to decrease over the course of study (P < 0.0001) (Figure 1), and the largest declines coincided with cuff deflation and reperfusion of the extremity
Summary
Bilateral regional brain oxygen saturation (rSO2) trends, reflecting intraoperative brain oxygen imbalance, could warn of brain dysfunction. Casati et al [5] hypothesized that controlling intraoperative rSO2 may help attenuate the possible effects of brain hypoxia on cognitive function. These and other authors [6,7,8,9] have found rSO2 reduction to be significantly correlated with decline, postoperative cognitive dysfunction (POCD) after abdominal and cardiac surgery under general anesthesia. When Price et al [13] analyzed a subgroup of the non-cardiac surgical patients of Monk et al, they were able to identify different types of decline, finding memory impairment in 13.6%, executive function impairment in 8.4%, and a combination of both in 2.9%. Some of the neuropsychological tests utilized evaluated functions predominantly related to one hemisphere or the other
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