Canadian journal of anaesthesia = Journal canadien d'anesthésie
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The authors evaluated the accuracy of an intrathecal test dose (TD) to rule out unintentional subarachnoid injection in a prospective and double-blind study. Twenty-nine unmedicated patients scheduled to receive continuous spinal analgesia for their surgical procedures entered the study. After placement of non-invasive monitoring (ECG, BP and SpO2), an intrathecal catheter was placed in the lumbar area. ⋯ At four minutes SN reached 100% (CI 78-100%) for R and H, while only R obtained a SP of 93% (CI 66-100%). Using R as detector of intrathecal injection the -PV was 100% and the +PV 25% (assuming a 2% prevalence of unintentional spinal). We conclude that, with our test dose; (a) four minutes are needed to recognize signs of intrathecal injection; (b) leg-raising is a reliable sign; and (c) inquiring about other signs may only decrease the diagnostic accuracy of this test.
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In order to determine the prevalence of psychoactive substance use in three specialty groupings, 1,624 questionnaires were sent to physicians in medicine, surgery and anaesthesia; all had trained at the same academic institution. A response rate of 57.8% was achieved. Comparison of prevalence of impairment rates showed no differences between Surgery (14.4%), Medicine (19.9%) and Anaesthesia (16.8%). ⋯ Seventy-three used psychoactive drugs which were non-prescribed. Drug counselling programmes were judged inadequate by most. Use of alcohol and drugs by faculty members was reported by a number of respondents.
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The cuff of the laryngeal mask airway (LMA) is highly permeable to nitrous oxide (N2O), and cuff pressure increases during N2O/O2 anaesthesia. The extent of these changes and their effect on LMA position have previously only been investigated for short procedures. The current study was designed to investigate the effects of nitrous oxide-oxygen (N2O/O2) anaesthesia lasting one to two hours on cuff pressure, LMA positioning and pharyngeal morbidity. ⋯ Three of 19 patients had a mild sore throat. This study demonstrates that the increase in LMA cuff pressure is self limiting over a one-to-two-hour period and does not cause displacement of the LMA. There is no evidence that cuff pressure monitoring and pressure limitation is necessary during LMA anaesthesia.
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A two-dimensional model of the factors relevant to difficult laryngoscopy was analysed mathematically to determine clinical implications and limitations. The model describes the space into which the "inevitable residual volume" of the tongue (that part remaining anterior to the blade at laryngoscopy) can be displaced to permit a view of the larynx. Four points are used: the tip of the upper incisors; a point on the anterior airway just above the larynx; the mid-point between the mandibular condyles and the internal mid-point of the symphysis. ⋯ An otherwise normal jaw with this configuration recedes markedly on opening. Further studies are required to validate the model. Accurate quantification of individual factors in difficult laryngoscopy may then be feasible.
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Transcranial Doppler sonography (TCD) constitutes an advance in noninvasive monitoring of the cerebral circulation. However, as long as the diameter and cross-sectional area of the insonated middle cerebral artery (MCA) remain unknown, the derived flow velocities (v) are not informative. It is not known how the human MCA is influenced by anaesthetic agents. ⋯ The MAP, FECO2, and v showed only minor alterations; HR increased after 6, 10 and 20 min. Transcranial "vessel area" and "volume flow" showed increases after isoflurane inhalation. The increase of "vessel area" supports the assumption that isoflurane greater than 1 MAC dilates large human cerebral arteries, so that if flow velocities are considered alone, alterations of cerebral blood flow may easily be underestimated.