Use of transcutaneous electrical acupoint stimulation for prevention of postoperative delirium in geriatric patients with silent lacunar infarction

Dear editor

In a preliminary study, Gao et al¹ assessed the preventive effect of transcutaneous electrical acupoint stimulation (TEAS) on postoperative delirium (POD) in geriatric patients with silent lacunar infarction. They showed that TEAS could reduce the development of POD and might be related to attenuated neuroinflammation by reducing the permeability of the blood–brain barrier. Given that POD is a common postoperative complication associated with adverse events and outcomes including functional decline, and increased risks of morbidity and mortality in elderly surgical patients, their findings have the potential implications. To differentiate the real effect of one factor on primary endpoint in a randomized trial, however, all of other factors must be standardized for avoidance of potential bias. Other than the limitations described in the discussion, we noted several issues in this study that were not addressed well.

First, study subjects were elderly patients undergoing spine surgery. The study did not provide the baseline education level and preoperative serum albumin concentration of patients. In available literature, both lower baseline education level and preoperative albumin concentration have been identified as significant risk factor of POD in elderly surgical patients.^2,3 Regarding intraoperative factors, moreover, only providing anesthesia and operation durations were insufficient. It has been shown that intraoperative major blood loss and blood transfusion are significantly associated with an increased risk of POD after noncardiac surgery in elderly patients.⁴ In addition, the authors did not observe and compare the incidences of postoperative adverse events and complications between groups. In fact, prolonged hospital and intensive care unit stay, postoperative complications including urinary tract infection, pneumonia, and cognitive impairment can increase the risk of POD after noncardiac surgery.⁵ We are concerned that any imbalance in the above unknown factors would have biased their findings.

Second, this study excluded patients with an increased risk of POD, such as those with mini-mental state examination score of <24 or dementia, preoperative delirium, history of neurological or mental illness, current use of tranquilizers or antidepressants.⁵ Thus, an important question that remains unanswered in this study is whether TEAS is an effective treatment in elderly patients with an increased risk of POD. Furthermore, this study only assessed the incidence of POD, but not the severity and duration of POD due to a short observed time. The available evidence indicates that both more severe POD and longer in-hospital POD duration are significantly associated with worse postoperative outcomes.⁶ We believe that the results of this study would be more informative if the design had included these issues.

Finally, because of the small sample size, small inter-group mean differences and large standard deviations in this study, we questioned their results that serum levels of TNF-α and IL-6 were higher at T_2–3 and serum levels of MMP-9 and S100β were higher at T₃ in group C compared with group TEAS (P<0.05). Revalidation of these results with statistical software confirms our doubts.