To the Editor:
In their study, “Intravenous versus Volatile Anesthetic Effects on Postoperative Cognition in Elderly Patients Undergoing Laparoscopic Abdominal Surgery,” Li et al.1 reported no difference in the incidence of delayed neurocognitive recovery in patients undergoing laparoscopic abdominal surgery with general anesthesia using sevoflurane versus propofol. Their secondary outcome involved measuring biomarkers at five prespecified perioperative timepoints to assess their potential to predict delayed neurocognitive recovery. They found that the interleukin-6 concentration at 1 h after the start of surgery (Timepoint 3 [T3]) was significantly different between patients with and without delayed neurocognitive recovery. We have two points of discussion regarding this finding.
First, we wonder about the true significance of interleukin-6 at T3. Thirteen biomarkers were tested at five different timepoints, yielding 65 distinct data points. Testing this many variables increases the likelihood of achieving a “significant” P value simply by chance, especially when the alpha level has not been adjusted for multiple testing. Is it more likely that of all the biomarkers tested, only interleukin-6 (and only at 1 h after the start of surgery) would be a true predictor of delayed neurocognitive recovery, or that this one significant value occurred solely by chance? Adding to this question is the fact that the CI of the odds ratio for interleukin-6 at T3 (1.04 [1.01 to 1.07]) nearly encompassed 1.0.
Second, the authors note that both sevoflurane and propofol have been implicated in cellular injury and may play roles in the neuroinflammatory process that occurs with surgery and anesthesia. They report data for the measured biomarkers between patients with and without delayed neurocognitive recovery, but they don’t compare biomarkers between the propofol and sevoflurane groups. We would be curious to see this comparison, because it could potentially guide the choice of anesthetic medications.
We read this study with great interest and congratulate the authors on their efforts. Perioperative neurocognitive disorders are truly an important topic, and patients would benefit from discovering ways to predict them and/or interventions that decrease their incidence. Although this article found support for interleukin-6 as a predictive biomarker, we think more data are needed before this claim can be confidently made.
The authors declare no competing interests.