深野 賢太朗

BACKGROUND: Ascorbic acid is a strong antioxidant that prevents postoperative delirium by inhibiting reactive oxygen species production. This pilot study was designed to investigate the prevalence of postoperative delirium among older patients undergoing cardiovascular surgery, who received perioperative ascorbic acid administration, to estimate an appropriate sample size for further randomized controlled trials. METHODS: This single-arm prospective interventional study enrolled patients aged > 70 years scheduled to undergo elective cardiovascular surgery using cardiopulmonary bypass. Ascorbic acid (500 mg) was administered intravenously every 6 h for a total of eight times following the induction of general anesthesia. The incidence of postoperative delirium was evaluated until discharge using the Confusion Assessment Method for the Intensive Care Unit. RESULTS: Data from 48 patients were analyzed. Of the 48 patients, 16 developed postoperative delirium (33.3%). Patients in the delirium group had more severe heart failure (New York Heart Association Classification), higher European System for Cardiac Operative Risk Evaluation scores, lower intraoperative Bispectral Index, longer duration of cardiopulmonary bypass and surgery, incidence of postoperative cerebral infarction, longer intubation time, and length of intensive care unit stay. CONCLUSIONS: The incidence of postoperative delirium among older patients undergoing cardiovascular surgery who received ascorbic acid perioperatively (2 g/day for 2 days) was 33%. This incidence was comparable to that observed in a previous observational study, suggesting that ascorbic acid administration may not be effective in preventing the incidence of postoperative delirium.

BACKGROUND: Tracking preload dependency non-invasively to maintain adequate tissue perfusion in the perioperative period can be challenging.The effect of phenylephrine on stroke volume is dependent upon preload. Changes in stroke volume induced by phenylephrine administration can be used to predict preload dependency. The change in the peripheral perfusion index derived from photoplethysmography signals reportedly corresponds with changes in stroke volume in situations such as body position changes in the operating room. Thus, the peripheral perfusion index can be used as a non-invasive potential alternative to stroke volume to predict preload dependency. Herein, we aimed to determine whether changes in perfusion index induced by the administration of phenylephrine could be used to predict preload dependency. METHODS: We conducted a prospective single-centre observational study. The haemodynamic parameters and perfusion index were recorded before and 1 and 2 min after administering 0.1 mg of phenylephrine during post-induction hypotension in patients scheduled to undergo surgery. Preload dependency was defined as a stroke volume variation of ≥ 12% before phenylephrine administration at a mean arterial pressure of < 65 mmHg. Patients were divided into four groups according to total peripheral resistance and preload dependency. RESULTS: Forty-two patients were included in this study. The stroke volume in patients with preload dependency (n = 23) increased after phenylephrine administration. However, phenylephrine administration did not impact the stroke volume in patients without preload dependency (n = 19). The perfusion index decreased regardless of preload dependency. The changes in the perfusion index after phenylephrine administration exhibited low accuracy for predicting preload dependency. Based on subgroup analysis, patients with high total peripheral resistance tended to exhibit increased stroke volume following phenylephrine administration, which was particularly prominent in patients with high total peripheral resistance and preload dependency. CONCLUSION: The findings of the current study revealed that changes in the perfusion index induced by administering 0.1 mg of phenylephrine could not predict preload dependency. This may be attributed to the different phenylephrine-induced stroke volume patterns observed in patients according to the degree of total peripheral resistance and preload dependency. TRIAL REGISTRATION: University Hospital Medical Information Network (UMIN000049994 on 9/01/2023).