British journal of anaesthesia
July 7, 2025
Connor T A Brenna, Xuan W He, Daheng Liu et al.
8 citations
Postoperative delirium and other cognitive problems are common in older surgical patients. Ketamine, given before or during anesthesia, might protect cognition by reducing inflammation or allowing lower doses of other drugs, but its effectiveness is debated. This review of 58 studies involving 6830 patients found that ketamine provided no cognitive benefit in 60% of studies, while 40% reported reduced incidence or duration of cognitive disorders. No clear patterns emerged for dose, formulation, or timing. Studies assessing cognition only early after surgery were more likely to show no benefit. Most trials were too small and methods too varied for meta-analysis. The inconsistent results support the need for larger, well-designed trials to identify which patient subgroups might benefit.
Bipolar disorders
May 1, 2023
William S H Kim, Mikaela K Dimick, Danielle Omrin et al.
In a double-blind randomized controlled trial, 25 adults with bipolar I or II disorder and treatment-resistant depression received either nitrous oxide (25% concentration for 20 minutes) plus intravenous saline or medical air plus intravenous midazolam (2 mg total). No significant between-group differences emerged in depression severity change or treatment response 24 hours after treatment. However, the nitrous oxide group showed significantly greater same-day reductions in depression severity. Lower baseline regional cerebral blood flow predicted greater 24-hour improvement with nitrous oxide but not midazolam. Midazolam was associated with regional cerebral blood flow reductions compared to nitrous oxide. These secondary findings suggest differential associations of the two agents with depression severity and brain hemodynamics, warranting larger studies.
Contemporary clinical trials communications
September 1, 2020
Mikaela K Dimick, Danielle Omrin, Bradley J MacIntosh et al.
A randomized, double-blind trial will test whether a single administration of nitrous oxide (N2O) improves mood and increases frontal cerebral blood flow in adults with treatment-resistant bipolar depression. Participants with bipolar I or II disorder currently in a major depressive episode will be assigned to either inhaled N2O plus intravenous saline or inhaled room air plus intravenous midazolam. Mood will be assessed with the Montgomery-Asberg Depression Rating Scale, and cerebral blood flow measured by arterial spin labelling MRI. The authors suggest N2O may act as a cerebral vasodilator to counteract hypoperfusion in depression, and if effective, could become a low-cost, safe, and accessible acute treatment.