British journal of anaesthesia
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Review Meta Analysis
Isolated forearm technique: a meta-analysis of connected consciousness during different general anaesthesia regimens.
General anaesthesia should prevent patients from experiencing surgery, defined as connected consciousness. The isolated forearm technique (IFT) is the current gold standard for connected consciousness monitoring. We evaluated the efficacy of different anaesthesia regimens in preventing IFT responses. ⋯ Standard general anaesthesia regimens might not prevent connected consciousness. More accurate anaesthesia brain monitor methodology to reduce the likelihood of connected consciousness is desirable.
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Clinical risk factors for postoperative nausea and vomiting (PONV) are evaluated with the Apfel score, however patients with low Apfel scores still experience PONV suggesting a genetic predisposition. PONV risk associates with specific M3 muscarinic acetylcholine receptor (CHRM3) rs 2165870 polymorphism. We investigated whether the Apfel score and this genetic variation independently contribute to PONV risk and whether prophylaxis reduces PONV in patients with low Apfel score but at high genetic risk. ⋯ DRKS00005664.
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Despite its designation as a 'dissociative anaesthetic,' the dissociative and psychoactive effects of ketamine remain incompletely understood. The goal of this study was to characterise the subjective experiences and accompanying EEG changes with subanaesthetic doses of ketamine. ⋯ Ketamine induces altered states of consciousness during periods of reduced alpha power in the precuneus and temporal-parietal junction. Modulation of these temporal-parietal loci are candidate mechanisms of the psychoactive effects of ketamine, given that this region is involved in multisensory integration, body representation, and consciousness.
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Explicit memory after anaesthesia has gained considerable attention because of its negative implications, while implicit memory, which is more elusive and lacks patients' explicit recall, has received less attention and dedicated research. This is despite the likely impact of implicit memory on postoperative long-term well-being and behaviour. Given the scarcity of human data, fear conditioning in animals offers a reliable model of implicit learning, and importantly, one where we already have a good understanding of the underlying neural circuitry in awake conditions. ⋯ In some cases, low doses of general anaesthetics can actually lead to a paradoxical opposite effect. The underlying mechanisms involve several neurotransmitter systems, acting mainly in the amygdala, hippocampus, and neocortex. Here, we review animal studies of aversive conditioning under anaesthesia, discuss the complex picture that arises, identify the gaps in knowledge that require further investigation, and highlight the potential translational relevance of the models.
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In clinical practice, analgesic drug doses applied during general anaesthesia are considered sufficient when clinical responses (e.g. movement, blood pressure and heart rate elevations) are suppressed during noxious stimulation. We investigated whether absent clinical responses are indicative of suppressed spinal and brain responsiveness to noxious stimulation in anaesthetised subjects. ⋯ Nociceptive activation persists during deep general anaesthesia despite abolished clinical responses. Absent clinical responses are therefore not indicative of absent nociception-specific activation. Thus, commonly accepted clinical responses might be inadequate surrogate markers to assess anti-nociception during general anaesthesia. Further research is required to investigate whether persistent nociception causes adverse effects on patient outcome.