Ann Acad Med Singap
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Weaning from mechanical ventilation may be influenced by factors relating to equipment, techniques and procedures. Criteria to initiate weaning and predictors of weaning outcome are generally unreliable, but mechanical work of breathing, the tidal volume: frequency ratio and the inspiratory pressure: maximal inspiratory pressure ratio may anticipate those likely to fail weaning. ⋯ Blow-by heated humidifiers and ventilators which compensate for the impedances of their inspiratory demand valves impose clinically acceptable spontaneous breathing loads. Close monitoring, adequate respiratory muscle rest, attention to mineral deficiencies, nutrition and pulmonary hygiene are also important parts of the weaning process.
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The development of new preoperative fasting guidelines in paediatrics was reviewed in the light of present knowledge and some recent investigations. Although the proportion of healthy children with the potential risk of aspiration pneumonitis is relatively high (60-75%), the incidence of aspiration is low--1 to 8.6 in 10,000. In healthy children, there is no increase in the risk of aspiration by allowing them to drink clear fluids up to 2-3 hours before anaesthesia when compared with the conventional fasting regimen. ⋯ It is useful to have simple and explicit preoperative fasting instructions for parents to follow, especially in the day case setting. It is essential to note that the laryngeal mask airway (LMA) does not protect the patient's airway against the risk of regurgitation and aspiration of gastric contents in the same way as an endotracheal tube. Hence, constant vigilance is required when LMA is used in children.
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Ann Acad Med Singap · Jul 1994
ReviewPharmacotherapy for cancer pain: an anaesthesiologist's viewpoint.
Cancer pain is prevalent and undertreated despite the availability of therapeutic options that, taken together are highly effective, economical and safe. Improved understanding of the pharmacology of chronically-administered opioids has resulted in reduced concerns about addiction and an increased emphasis on their use. The anaesthetist may play a pivotal role in cancer pain management by the provision of nerve blocks and other interventions, but, to be a truly effective consultant, must also be expert in all aspects of pharmacotherapy. A rationale for the development of pharmacologic expertise together with a review of assessment and pharmacologic management of cancer pain are provided.
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Considerable advances have been achieved in developing new techniques and equipment for the assessment of neuromuscular transmission during anaesthesia. This paper is a review of the methods currently used in research as well as in daily clinical practice. ⋯ The clinical evaluation of the responses to nerve stimulation, and which stimulation patterns to prefer during onset, maintenance and recovery of neuromuscular block are dealt with, as well as possible errors to be encountered. Arguments are given for routine use of neuromuscular monitoring in the clinical setting, and situations where monitoring of neuromuscular function are of particular importance are noted.
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The effects of anaesthesia and surgery on the chest wall may be responsible for impaired gas exchange and other pulmonary complications during the perioperative period. Current evidence supports the following sequence of events. Anaesthesia changes the shape and motion of the chest wall, either by changing the amount of tonic and phasic activity of the respiratory muscles (anaesthesia with spontaneous breathing) or by eliminating the activity entirely (paralysis with mechanical ventilation). ⋯ For example, it is now apparent that anaesthesia reduces the functional residual capacity not by changing the position of the diaphragm, but rather by affecting the rib cage, and, perhaps, the volume of intrathoracic blood. The effects of anaesthesia and surgery on postoperative chest wall function may be lessened by regional analgesia and the use of laparoscopic surgical techniques. However, it is not yet clear that this improvement is associated with a reduction in the incidence of pulmonary complications.