A novel spectral entropy-based index for assessing the depth of anaesthesia

Anaesthesia is a state of temporary controlled loss of awareness induced for medical operations. An accurate assessment of the depth of anaesthesia (DoA) helps anesthesiologists to avoid awareness during surgery and keep the recovery period short. However, the existing DoA algorithms have limitations, such as not robust enough for different patients and having time delay in assessment. In this study, to develop a reliable DoA measurement method, pre-denoised electroencephalograph (EEG) signals are divided into ten frequency bands (α, β1, β2, β3, β4, β, βγ, γ, δ and θ), and the features are extracted from different frequency bands using spectral entropy (SE) methods. SE from the beta-gamma frequency band (21.5–38.5 Hz) and SE from the beta frequency band show the highest correlation (R-squared value: 0.8458 and 0.7312, respectively) with the most popular DoA index, bispectral index (BIS). In this research, a new DoA index is developed based on these two SE features for monitoring the DoA. The highest Pearson correlation coefficient by comparing the BIS index for testing data is 0.918, and the average is 0.80. In addition, the proposed index shows an earlier reaction than the BIS index when the patient goes from deep anaesthesia to moderate anaesthesia, which means it is more suitable for the real-time DoA assessment. In the case of poor signal quality (SQ), while the BIS index exhibits inflexibility with cases of poor SQ, the new proposed index shows reliable assessment results that reflect the clinical observations.

Low neuronal metabolism during isoflurane-induced burst suppression is related to synaptic inhibition while neurovascular coupling and mitochondrial function remain intact

Deep anaesthesia may impair neuronal, vascular and mitochondrial function facilitating neurological complications, such as delirium and stroke. On the other hand, deep anaesthesia is performed for neuroprotection in critical brain diseases such as status epilepticus or traumatic brain injury. Since the commonly used anaesthetic propofol causes mitochondrial dysfunction, we investigated the impact of the alternative anaesthetic isoflurane on neuro-metabolism. In deeply anaesthetised Wistar rats (burst suppression pattern), we measured increased cortical tissue oxygen pressure (ptiO2), a ∼35% drop in regional cerebral blood flow (rCBF) and burst-associated neurovascular responses. In vitro, 3% isoflurane blocked synaptic transmission and impaired network oscillations, thereby decreasing the cerebral metabolic rate of oxygen (CMRO2). Concerning mitochondrial function, isoflurane induced a reductive shift in flavin adenine dinucleotide (FAD) and decreased stimulus-induced FAD transients as Ca2+ influx was reduced by ∼50%. Computer simulations based on experimental results predicted no direct effects of isoflurane on mitochondrial complexes or ATP-synthesis. We found that isoflurane-induced burst suppression is related to decreased ATP consumption due to inhibition of synaptic activity while neurovascular coupling and mitochondrial function remain intact. The neurometabolic profile of isoflurane thus appears to be superior to that of propofol which has been shown to impair the mitochondrial respiratory chain.

The effect of anaesthetic dose on response and remission in electroconvulsive therapy for major depressive disorder: nationwide register-based cohort study

Background Electroconvulsive therapy (ECT) is a safe and effective treatment for major depressive disorder (MDD). ECT treatment effect relies on induced generalised seizures. Most anaesthetics raise the seizure threshold and shorten seizure duration. There are no conclusive studies on the effect of anaesthetic dose on response and remission rates with ECT for MDD. Aims We aimed to examine the effect of different dose intervals of anaesthetics on response and remission after ECT for MDD. Method We conducted a nationwide cohort study, using data from Swedish registers. Low-, medium- and high-dose intervals, adjusted for age and gender, were constructed for each anaesthetic drug. Response and remission were measured with the Clinical Global Impression – Severity and Improvement scales (CGI-I and CGI-S), and a self-rated version of the Montgomery–Åsberg Depression Rating Scale (MADRS-S). Logistic regression models were used to calculate adjusted odds ratios for response and remission rates. Results The study included 7917 patients who received ECT for MDD during 2012–2018. Patients were given either thiopental (64.1%) or propofol (35.9%). Low-dose intervals of anaesthetics were associated with increased rates of response (CGI-I: odds ratio 1.22, 95% CI 1.07–1.40, P = 0.004; MADRS-S: odds ratio 1.31, 95% CI 1.09–1.56, P = 0.004) and remission (CGI-S: odds ratio 1.37, 95% CI 1.17–1.60, P ≤ 0.001; MADRS-S: odds ratio 1.31, 95% CI 1.10–1.54, P = 0.002). Conclusions We found improved treatment outcomes with low- compared with high-dose anaesthetic during ECT for MDD. To enhance treatment effect, deep anaesthesia during ECT for MDD should be avoided.

Depth of Anaesthesia Assessment Based on Spectral Entropy

Anaesthesia is a state of temporary controlled loss of awareness induced for medical purposes. An accurate assessment of the depth of anaesthesia (DoA) has always been required. However, the current DoA algorithms have limitations such as inaccuracy or inflexibility. In this study, for more reliable DoA assessment, pre-denoised electroencephalograph (EEG) signals are divided into ten frequency bands (α, β1, β2, β3, β4, β, βγ, γ, δ and θ), and the basic complexity measure is done by using spectral entropy (SE). SE from beta-gamma frequency band (21.5 - 38.5 Hz) and SE from beta frequency band show the highest R squared value (0.8458 and 0.7312, respectively) with currently the most popular DoA index, bispectral index (BIS). A new DoA index is developed based on these two SE values for monitoring the DoA and evaluated by comparing with the BIS index. The highest Pearson correlation coefficient is 0.918, and the average is 0.80. In addition, the proposed index shows an earlier reaction than BIS index when the patient from deep anaesthesia to moderate anaesthesia, and the consistency in the case of poor signal quality (SQ) while the BIS Index exhibits inflexibility with cases of poor SQ.

Intraoperative hypotension and perioperative outcomes

Intraoperative hypotension is associated with adverse outcomes. Although a causal relationship is yet to be fully established, proactive management of vulnerable patients and use of bispectral index monitoring is recommended to avoid deep anaesthesia.

Characterization of Hippocampal Histomorphology Following R. vomitoria Root Extract Treatment

Rauwolfia vomitoria Afzel. is an antipsychotic plant used by several African communities in the management of psychiatric conditions with good outcomes. Concerns about its dosages on brain activity lead to this investigation of its action on the hippocampal microstructure. Twenty-four adult male Wistar rats of average weight 200 g, were assigned into four groups (n = 6): control; 200, 300 and 400 mg/kg body weight of RV root bark extract, respectively. The administration was once daily, and orally for seven days. Daily observation of the animals was done till on day eight when they were sacrificed after deep anaesthesia. Each brain was processed for histology and immunohistochemical studies. Animals in the 200, 300 and 400 mg/kg RV groups appeared generally dull and drowsy, and barely fed. Their hippocampal histology showed neuronal atrophy and karyorrhexis, with no difference in cell count, although the pyramidal cell numbers decreased in the 300 and 400 mg/kg RV groups. Neuron-specific enolase decreased in the 400 mg/kg RV group, while neurofilament decreased in all test groups. Glial fibrillary acidic protein expression and density increased in the 200 and 300 mg/kg RV groups, but not the 400 mg/kg RV group, all compared with the control group. The given doses of RV root bark extract in adult Wistar rats showed sedative activities with hippocampal histopathological changes, which may not be reversible, thereby leading to the hippocampal functional deficit.

Effect of Moringa oleifera Lam. Leaf Extract Against Aluminium Chloride Induced Hippocampal Histology and Serum Enzyme activities in adult Wistar rats

Introduction: Aluminium, a ubiquitous metal implicated in some neurodegenerative diseases is linked to activation of free oxygen species. The antioxidant-rich plants, Moringa oleifera (MO) is reported to protect against Aluminium activities. This study investigated the actions of MO leaf extract (MOLE) against Aluminium chloride (AlCl3 )- induced hippocampal cellular changes and serum levels of alkaline phosphatase (ALP), aspartate transaminase (AST) and alanine transaminase (ALT) in adult Wistar rats. Materials and Methods: Thirty Wistar rats weighing between 150 g and 220 g were grouped (n=5) into; 1-control (5 mL/kg distilled water), 2-AlCl3 (100 mg/kg), 3-low dose MOLE (250 mg/kg), 4-high dose MOLE (1,000 mg/kg), 5-concurrent AlCl3 and low dose MOLE, and 6-concurrent AlCl3 and high dose MOLE. All administrations were by oral gavages for 21 days. On day 22, following deep anaesthesia and cardiac puncture, blood was obtained for serum enzyme analysis, and the brain perfusion fixed, harvested and processed for histological study. Results: Results showed significantly (p < 0.05) higher ALP level in the AlCl3 group compared with the control, as well as the other test groups. However, there was no significant (p > 0.05) AST and ALT levels. The hippocampal CA3 of the AlCl3 group showed hypertrophic cells, with some of the cells having karyorrhectic features. The concurrent AlCl3 and low and high doses, MOLE groups showed less of these adverse features. Conclusion: These results suggest that MOLE may protect enzymatic activities against Aluminium chloride. However, its action on hippocampus is still subject to further investigation.