Der Anaesthesist
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Ventilatory control in humans depends on complex mechanisms which aim to maintain a cellular CO2-, O2- and H(+)-homeostasis under physiological conditions. This regulation is based on chemical control which predominantly acts via peripheral chemoreceptors in the carotid bodies and central chemoreceptors in the ventral medulla of the brainstem on the one hand, and behavioural control on the other, by which it is possible to adapt respiration to conditions of daily living. ⋯ This review will give an overview of ventilatory control and discuss the most relevant responses, describe the effects of pain, anaesthetics and opioids on ventilatory control and their interaction. The current body of knowledge is put into perspective to identify patients at risk for perioperative respiratory depression.
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Despite the fact that neonates and infants are not capable of expressing their subjective pain sensations, it has become clear that they do perceive nociception, as pain correlates to hormonal, metabolic, immune, and cardiovascular changes. New findings support the notion that repetitive painful stimuli result in long term psycho-physiological effects with ensuing decreased attentiveness and orientation, poor regulation of behavioral state and motor processes, increase in irritability as well as an altered pattern of feeding and sleeping. These sequelae of repetitive painful experiences with an increase in sensitization of sensory afferent input supports the view of a sufficient analgesia during all kinds of painful procedures in the preterm and neonate. ⋯ Sequelae of such differences are a more pronounced respiratory depression, often due to muscular rigidity, and bradycardia after which a full analgesic effect takes place. Despite such potential drawbacks, opioids are still the best choice as they sufficiently block nociceptive afferent input and when compared to other anesthetics, they show the least cardiovascular changes. One, however, has to bear in mind that dosing is done according to effect and not to body weight while potential side effects are most prominent in the preterm infant.
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Anaesthesia-related risk has been significantly reduced within the last decade. Nevertheless the risk and the possibility of dying or suffering permanent damage still exist. To improve patient safety, risk assessment and analysis must lead to the development of preventive strategies. ⋯ Human factors are responsible for individual mistakes as well as for organisational errors. Therefore besides traditional concepts of risk reduction (e.g. guidelines) new strategies (e.g. full-scale simulation) must be applied to minimise the negative impact of human factors on patient safety. Risk management has to consider technical, organisational and human factors to implement a higher standard of patient safety.
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The undecapeptide substance P is expressed by primary afferent neurons where it is considered to be a cotransmitter of other peptides and glutamate. Since it is predominantly found in sensory neurons with unmyelinated fibres (C-fibres), substance P has long been thought to be a "pain transmitter". Following stimulation of nociceptive afferents, substance P is released in the spinal cord and substance P-mediated transmission is primarily brought about by tachykinin NK1 receptors. ⋯ The hyperalgesic role of substance P has been corroborated by the sensory deficits seen in substance P and NK1 receptor knockout mice. However, the concept that NK1 receptor antagonists would represent a novel class of analgesic drugs, as suggested by the preclinical studies, has not been borne out by the clinical trials that have been reported thus far. This article offers an overview of those hyperalgesic conditions in which NK1 receptor antagonists may be of therapeutic value and discusses possible reasons for the discrepancies between preclinical and clinical trials with NK1 receptor antagonists.