European journal of anaesthesiology. Supplement最新文献

Patients undergoing surgery under regional anaesthesia may be anxious, uncomfortable or in pain. Therefore, effective sedation throughout the procedure is an important aspect of patient management. The balanced sedation technique uses combinations of sedatives to meet the anxiolytic and analgesic needs of the individual patient. For example, benzodiazepines are effective anxiolytics, while propofol can be used to provide a suitable level of sedation, especially in patients who have expressed a wish to remain asleep during the procedure. Analgesics should be considered only in those patients who are likely to experience pain during the procedure. Basic measures to increase the comfort of the patient and to facilitate the effect of pharmacological methods include supplementary non-pharmacological techniques, for example the use of a soft mattress to prevent back pain, infusion of warmed fluids and a warm operating atmosphere. This may extend to the opportunity for patients to listen to music if they have a fear of the sounds associated with the operating room, such as technical discussions by surgical staff or the sound of surgical instruments being used and discarded. The balanced sedation technique can, therefore, help to achieve the ideal goal of a comfortable patient who is free from anxiety and pain, and can sleep if desired.

Monitored patient-controlled sedation (MPCS) is a technique that allows patients to administer intravenous sedatives, under the supervision of an anaesthetist, to achieve a level of conscious sedation that meets their individual requirements. Experience to date has shown that this technique is effective and highly acceptable to patients. Propofol is an appropriate choice of agent for MPCS. Criteria for such agents include short arm-brain circulation time, which results in a rapid and clearly defined onset of action. The MPCS technique offers a number of benefits to the patient and the theatre staff.

Combination therapy with two or more different drugs, with the intention of reaching the same therapeutic goal, was heavily criticized for a long time. However, it is accepted today, especially when advantages over monotherapy can be shown. For the induction of anaesthesia or for long-term sedation in the intensive care unit, combination therapy may offer an improved effect profile, a more balanced ratio of desired versus adverse effects, an improved time-course of effect, simpler treatment requirements or lower costs. Midazolam and propofol have been investigated as potential partners for those two indications. The mechanism of action, pharmacokinetic properties, pharmacological effect, the way in which they interact at the receptor site, the differences in pharmaceutical formulations, the side-effect profiles and economic considerations were compared. Animal experiments and clinical pharmacology studies have shown that midazolam and propofol have synergy with other centrally active drugs. It could be expected that the relationship between desired effects and adverse effects could be improved by skilful use of the synergism between midazolam and propofol. Co-induction of anaesthesia and co-administration in long-term sedation can offer improvements in therapeutic situations compared with monotherapy. These improvements are in terms of a more suitable effect profile, a more favourable ratio of desirable effects to side-effects, optimization of the time-course of effects and reduced costs.

We evaluated the addition of midazolam to propofol during induction of anaesthesia by assessing laryngeal mask tolerance, haemodynamic variables, recovery times and cost. Forty patients (ASA grades I-IV) undergoing elective surgery were allocated randomly to receive a standard dose of propofol or a smaller dose of propofol combined with midazolam. A laryngeal mask was inserted and any episodes of coughing or hiccuping during its insertion or removal were recorded. Anaesthesia was maintained with nitrous oxide and enflurane with fentanyl for analgesia. After surgery, recovery times, pain, shivering, nausea, vomiting and analgesic requirements were recorded. The cost of the drugs used was also calculated. No significant differences were detected in any variables, except that patients given propofol needed more morphine in the recovery ward. The average cost of propofol alone was 3.47 pounds per anaesthetic, while the midazolam plus propofol cost was 2.03 pounds. Adding midazolam to propofol allowed a reduced dose of propofol to be used without adverse effects, while reducing the anaesthetic costs.

We investigated the bacterial contamination of commonly used intravenous anaesthetic agents. Ten trainee anaesthetists drew up four syringes each of propofol, midazolam, thiopentone, 0.9% saline and a culture medium control using their normal practice. A set of syringes was cultured at the time of drawing up and at 2, 4 and 8 h afterwards. No anaesthetist washed his or her hands before drawing up the drugs. Six anaesthetists capped the syringes using sheathed needles. Eight syringes were contaminated with bacteria. Coagulase-negative staphylococci were isolated from six syringes (four sheathed and two unsheathed) and an Acinetobacter sp. from two syringes (one sheathed and one unsheathed). No bacteria were cultured from the midazolam syringes. However, two syringes from each of the other solutions were contaminated. This implies that one syringe was contaminated when it was drawn up, at 2 h a further two had detectable contamination, two more were contaminated at 4 h and three more at 8 h. We cannot recommend drawing up drugs at the start of a list for use later in the day. They should be used immediately after drawing up. Basic hand washing before drawing up drugs may reduce contamination.

The spectrum of effects that constitutes the state of general anaesthesia can be induced by the combined use of drugs. Each drug has a predominant action regarding one of the anaesthesia components, hypnosis, analgesia and amnesia. However, each agent, when used in combination, not only produces its own expected effect, but it can also modify the effect of another agent acting on a different component. For example, an opioid, in addition to its anti-nociceptive effect, can also potentiate the hypnotic effect of a benzodiazepine. Anaesthetists have long recognized these effects but did not quantify them until recently. Pharmacologists have provided us with techniques to measure drug interactions. We have utilized these techniques to demonstrate and quantify significant pharmacological interactions for hypnotic effect with commonly used intravenous agents. The clinical utility of these combinations can now be exploited precisely for the benefit of all our patients.

Cardiac patients pose special problems to the anaesthetist because of their underlying disease and the nature of the corrective surgery. Information about new methods of induction of anaesthesia obtained in fit patients may not be applicable directly to patients with heart disease. More suitable are patients undergoing cardioversion. Titrating intravenous induction agents to response elicited appears to be more important than the agent used, although it is possible to inject too slowly with drugs whose offset of action is by distribution. Anaesthetic agents alone are not sufficient to ablate the response to tracheal intubation, skin incision and sternotomy. Balancing induction of anaesthesia with small doses of opioid can obtund the haemodynamic responses. The effects of a drug used solely for induction of anaesthesia are unlikely to be present at the end of 3 or 4 h of surgery. However, this is not the case with agents used to maintain anaesthesia if early extubation after anaesthesia is practised. Reports of anaesthetic techniques for cardiac surgery tend to give total doses used rather than the timing and dose of the constituent agents. At Papworth Hospital, Cambridge, UK, after opioid premedication, midazolam sedation is used during insertion of some, or all, vascular cannulae. Two main techniques then exist. Either an intravenous or volatile anaesthetic agent is started immediately, supplemented by an opioid and muscle relaxant, or anaesthesia is induced with opioid and relaxant and the anaesthetic agent is begun only after transfer to the operating theatre, just before skin preparation. Either way, the end-point of induction of anaesthesia is difficult to discern in heavily premedicated patients with midazolam sedation.