Ann Acad Med Singap
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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.
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The anaesthetic machine used by most anaesthetists today closely resembles the anaesthetic machine of the late 1940s, with the addition of a multitude of devices and monitors necessary for the complexity of modern anaesthesia. Although modern anaesthesia boasts of a high level of safety, the ad hoc development of the anaesthetic machine has done little to enhance this safety record. Future improvements in patient safety will at least partially depend on improved ergonomics and human factor engineering in the design and arrangement of the anaesthetic workplace. Some innovative designs are now being seen both commercially and experimentally in which all monitoring is integrated and servo feedback control loops are used to deliver anaesthetic agents to the patient.
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Magnetic resonance imaging (MRI) has become an increasingly popular non-invasive radiological diagnostic procedure, with several distinct advantages over computerised tomography (CT). The images are produced using a strong (1.5-Tesla) magnetic field and radiofrequency (RF) pulses. Due to the effects of the strong magnetic field, certain groups of patients with implanted ferromagnetic objects and women in their first trimester of pregnancy are precluded from undergoing MRI. ⋯ The problems related to anaesthesia in MRI include the constant presence of a strong magnetic field, the RF pulses and their effect on the anaesthesia machine, monitoring devices, magnetically coded material, and loose ferromagnetic objects. In this article, the current availability of MRI-compatible anaesthesia machine, various monitoring devices, and safe conduct of anaesthesia during MRI for patients of all ages are discussed. In addition, the implications of the strong magnetic field on patient resuscitation inside the MRI suite and the recommended procedure for a successful outcome are outlined.