European journal of anaesthesiology. Supplement最新文献

Remifentanil is a new potent mu-agonist with a unique pharmacokinetic profile due to a rapid metabolism by non-specific tissue esterases. As a consequence, remifentanil pharmacokinetics are not modified by severe renal or hepatic dysfunction. During general anaesthesia, any dosage of remifentanil may be used without undue lengthening of emergence times. In cardiac surgery, remifentanil combines the requirement for intra-operative control of stress responses and rapid recovery. The rapid termination of remifentanil action warrants modifications of the current practice concerning early postoperative pain control. Remifentanil may be used as a sedative during monitored analgesia, or as a postoperative analgesic in spontaneously breathing patients, provided bolus doses are avoided. Remifentanil may increase patients' safety by eliminating the risk of delayed respiratory depression, but its correct use requires major changes in our prescribing habits.

From the patient's point of view, the Intensive Care Unit is both a frightening place and a safe haven. Psychologically, what we see most commonly are regression, delirium and paranola. Regression requires no treatment; delirium is treatable not only medically but psychologically as well; paranoia is best treated by prevention.

Intravenous anaesthetics have diverse effects on neurones within the central nervous system. Only those that occur at clinical concentrations are likely to be relevant. The dominant effect of many agents is the potentiation of the inhibitory neurotransmitter gamma amino butyric acid (GABA) by various mechanisms while inhibiting the effects of excitatory transmitters seems to be less dominant, except for ketamine.

The pro- or anticonvulsant properties of propofol remain a matter of controversy. Although numerous case reports describe the appearance of abnormal movements, posturing and seizure-like activity related to the use of propofol, systematic studies in both humans and animals strongly suggest that it possesses antiepileptic properties. Propofol consistently reduces the seizure duration during electroconvulsive therapy, its use has been successful in controlling refractory status epilepticus and in animals it offers a strong protection against lignocaine- or pentylene-tetrazol-induced epilepsy. The beneficial effects of propofol may be related to its uniform depressant action on the central nervous system, to a potentialization of GABA-mediated pre- and postsynaptic inhibition, and by decreasing the release of excitatory transmitters, glutamate and aspartate.

In clinical practice, indirect and non-specific signs are used for monitoring anaesthetic adequacy. These include haemodynamic, respiratory, muscular and autonomic signs. These measures do not indicate adequacy of anaesthesia in a reliable manner. Many attempts have been made to find a more accurate monitor. Direct monitoring of anaesthetic effect should be possible by EEG measurement. EEG information can be reduced, condensed and simplified, leading to single numbers (spectral edge frequency and median frequency). These methods appear insufficient for assessing anaesthetic adequacy. The bispectral index, derived from bispectral analysis of the EEG, is a very promising tool for measuring adequacy of anaesthesia. An alternative approach is to monitor evoked potentials. Middle latency auditory evoked potentials may be helpful in assessing anaesthetic adequacy. Both techniques need further validation.

Adequate treatment of pain in ICU patients should be an integral part of ICU management, as inadequately treated pain leads to a series of complications that may counteract the success of ICU treatment. For continuous intravenous use we recommend sufentanil in a dose of 0.75-1.0 microgram kg-1 h-1 in mechanically ventilated patients and in a dose of 0.25-0.35 microgram kg-1 h-1 in intubated and spontaneously breathing patients. On-demand analgesia, administered via the intravenous or epidural route, may be an alternative to a relatively fixed continuous infusion of an analgesic drug, and in some ICU patients the transdermal use of opioids can be an alternative to continuous intravenous drug application or PCA. Increased sizes of the patch (25, 50, 75, 100 cm2) provide sustained transdermal rates of approximately 25, 50, 75 and 100 micrograms h-1 of fentanyl over a period up to about 72 hours. Patients with trauma to the thorax, pelvic fracture, or after major surgical interventions will be better managed by regional application of analgesic drugs alone or in combination with a systemic analgesic drug infusion. To achieve the best results it is necessary to be well informed and trained in the method, to know the advantages and disadvantages, the correct and modified dosages of the drugs used, and the indications and contraindications.

Multiple drugs are used to provide anaesthesia. On average, four to six drugs are used during anaesthesia and, therefore, drug interactions are common. These interactions are primarily either pharmacokinetic or pharmacodynamic. Due to the relatively short duration of drug administration for anaesthesia, pharmacokinetic drug interactions resulting from alterations in drug metabolism do not generally produce clinically significant effects. Pharmacodynamic-drug interactions between anaesthetic drugs, however, are potentially serious. This may reflect that anaesthesia is not a single entity, but a process provided by a combination of drugs; i.e. loss of consciousness, analgesia and neuromuscular blockade. An understanding of each drug's pharmacokinetics, pharmacodynamics and drug interactions will allow clinicians to administer drugs to provide a more optimal anaesthetic.