Neuroprotection against stroke and encephalopathy after cardiac surgery

Volatile Anaesthesia versus Total Intravenous Anaesthesia for Cardiac Surgery-A Narrative Review

Recent research has contested the previously accepted paradigm that volatile anaesthetics improve outcomes in cardiac surgery patients when compared to intravenous anaesthesia. In this review we summarise the mechanisms of myocardial ischaemia/reperfusion injury and cardioprotection in cardiac surgery. In addition, we make a comprehensive analysis of evidence comparing outcomes in patients undergoing cardiac surgery under volatile or intravenous anaesthesia, in terms of mortality and morbidity (cardiac, neurological, renal, pulmonary).

microRNA-455-5p alleviates neuroinflammation in cerebral ischemia/reperfusion injury

Neuroinflammation is a major pathophysiological factor that results in the development of brain injury after cerebral ischemia/reperfusion. Downregulation of microRNA (miR)-455-5p after ischemic stroke has been considered a potential biomarker and therapeutic target for neuronal injury after ischemia. However, the role of miR-455-5p in the post-ischemia/reperfusion inflammatory response and the underlying mechanism have not been evaluated. In this study, mouse models of cerebral ischemia/reperfusion injury were established by transient occlusion of the middle cerebral artery for 1 hour followed by reperfusion. Agomir-455-5p, antagomir-455-5p, and their negative controls were injected intracerebroventricularly 2 hours before or 0 and 1 hour after middle cerebral artery occlusion (MCAO). The results showed that cerebral ischemia/reperfusion decreased miR-455-5p expression in the brain tissue and the peripheral blood. Agomir-455-5p pretreatment increased miR-455-5p expression in the brain tissue, reduced the cerebral infarct volume, and improved neurological function. Furthermore, primary cultured microglia were exposed to oxygen-glucose deprivation for 3 hours followed by 21 hours of reoxygenation to mimic cerebral ischemia/reperfusion. miR-455-5p reduced C-C chemokine receptor type 5 mRNA and protein levels, inhibited microglia activation, and reduced the production of the inflammatory factors tumor necrosis factor-α and interleukin-1β. These results suggest that miR-455-5p is a potential biomarker and therapeutic target for the treatment of cerebral ischemia/reperfusion injury and that it alleviates cerebral ischemia/reperfusion injury by inhibiting C-C chemokine receptor type 5 expression and reducing the neuroinflammatory response.

Contemporary Neuroprotection Strategies during Cardiac Surgery: State of the Art Review

Open-heart surgery is the leading cause of neuronal injury in the perioperative state, with some patients complicating with cerebrovascular accidents and delirium. Neurological fallout places an immense burden on the psychological well-being of the person affected, their family, and the healthcare system. Several randomised control trials (RCTs) have attempted to identify therapeutic and interventional strategies that reduce the morbidity and mortality rate in patients that experience perioperative neurological complications. However, there is still no consensus on the best strategy that yields improved patient outcomes, such that standardised neuroprotection protocols do not exist in a significant number of anaesthesia departments. This review aims to discuss contemporary evidence for preventing and managing risk factors for neuronal injury, mechanisms of injury, and neuroprotection interventions that lead to improved patient outcomes. Furthermore, a summary of existing RCTs and large observational studies are examined to determine which strategies are supported by science and which lack definitive evidence. We have established that the overall evidence for pharmacological neuroprotection is weak. Most neuroprotective strategies are based on animal studies, which cannot be fully extrapolated to the human population, and there is still no consensus on the optimal neuroprotective strategies for patients undergoing cardiac surgery. Large multicenter studies using universal standardised neurological fallout definitions are still required to evaluate the beneficial effects of the existing neuroprotective techniques.

Low Heart Rate Variability Predicts Stroke and Other Complications in the First Six Postoperative Months After a Hip Fracture Operation

Background: One-year mortality after hip fractures is underestimated and is reported as 25%. An improved risk stratifying could contribute to a better follow up of these patients. Heart Rate Variability (HRV) is an easy point-of-care investigation and is been used in cardiology, endocrinology, and perioperative care. This observational study intended to explore relevant associations between HRV parameters and 6-months mortality and morbidity after a hip fracture. Methods: One hundred and sixty-five patients admitted to two hospitals were included, and short-time HRV measurements (5 min, and 10 min at the two hospitals, respectively) were obtained. Mortality data were gathered by means of the Norwegian central address register. Patients, close relatives of patients, and in some cases their general physicians or nursery home physicians were interviewed 6 months postoperatively regarding the incidence of pneumonia, cardiac events, or stroke. Results: One and hundred fifty-seven (95.2%) patients were followed up after 6 months post-surgery. Twenty-one (13%) died during this period. Twenty patients (13%) developed pneumonia, eight (5 %) stroke, and four (2%) myocardial infarction. No HRV parameter was associated with 6-month general mortality. However, patients who developed stroke had significantly lower High Frequency Power (HF, p < 0.001) and lower Very Low Frequency Power (VLF, p = 0.003) at inclusion compared to patients without complications. Patients who developed pneumonia had at the inclusion lower root mean square of successive differences (RMSSD, p = 0.044). Patients with a history of coronary heart disease (n = 41) showed a mortality of 7%. Mortality in this group was associated with standard deviation of beat-to-beat intervals (SDNN, p = 0.006), Total Power (TP, p = 0.009), HF (p = 0.026), and Low Frequency Power (LF, p = 0.012). Beta-blocker intake was associated with lower heart rate, but not with differences in HRV parameters. Conclusion: In this exploratory study, we present for the first-time significant associations between different preoperative HRV parameters and stroke, myocardial infarction, and pneumonia during a 6-month period after hip fracture. HRV might be a simple and effective tool to identify patients at risk that would warrant better follow-up.