Canadian Anaesthetists' Society journal
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In general, the cardiovascular system is more resistant to the toxic actions of local anaesthetics than is the central nervous system. However, if sufficient doses and blood levels of local anaesthetics are achieved, signs of profound cardiovascular depression may be observed. Differences exist between local anaesthetics in terms of their relative potential for cardiotoxicity. ⋯ However, large dosages of chloroprocaine solutions administered intrathecally have been associated with prolonged sensory-motor deficits in a few patients due probably to the low pH and presence of sodium bisulfite in the chloroprocaine solutions. In general, the incidence of toxic reactions to local anaesthetic agents is extremely low. However, as with any class of pharmacological agents, local anaesthetics may cause severe toxic reactions, due usually to the improper use of these drugs.
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Expired carbon dioxide measurements (PeCO2) were used (1) to assess the adequacy of initial alveolar ventilation, and (2) to document intraoperative airway events and metabolic trends. Three hundred and thirty-one children were studied. Thirty-five intraoperative events were diagnosed by continuous PeCO2 monitoring; 20 were potentially life-threatening problems (malignant hyperthermia, circuit disconnection or leak, equipment failure, accidental extubation, endobronchial intubation, or kinked tube); only two of these were also diagnosed clinically. ⋯ Hypocarbia (peak expired PeCO2 less than or equal to 30) was more frequent in intubated cases (11 per cent) than in unintubated cases (three per cent) (p = 0.03). There was a high incidence of hypocarbia in infants less than one year of age (p = 0.02). We conclude: (1) life-threatening airway problems are common during anaesthesia in paediatric patients; (2) quantitative measurement of PeCO2 provides an early warning of potentially catastrophic anaesthetic mishaps; (3) the incidence of events increases with duration of anaesthesia.
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An overall management plan for malignant hyperthermia susceptible (MHS) parturients is presented based on the experience of managing 14 of these patients. A summary of the pertinent features of their deliveries and care plus a case report of one of these parturients is described. Discussion centres around the problems of diagnosis of malignant hyperthermia susceptibility in pregnancy, the differential diagnosis and management of fever and tachycardia in a MHS parturient during labour and the use of dantrolene prophylaxis. ⋯ The importance of being prepared for a potential crisis is stressed with particular emphasis on early diagnosis by monitoring of temperature at two sites, of heart rate and rhythm with a continuous ECG and of end-tidal carbon dioxide, should a general anaesthetic be required. Recommendations are made for appropriate anaesthetic agents for both regional and general anaesthesia. Treatment of a MH crisis is outlined, with emphasis on availability of appropriate resuscitative drugs.
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Large-volume low-pressure cuffs have been introduced in an endeavour to reduce the incidence of tracheal mucosal damage. These cuffs when inflated to clinical seal develop folds, which together with low clinical seal pressure may not protect against aspiration. ⋯ The incidence of dye tracking past the large-volume cuffs studies was 100 per cent whereas no aspiration of dye was seen past the red rubber tubes. Increasing cuff pressure in the large-volume cuffs beyond clinical seal to 50 cm H2O did not obliterate the dye-filled cuff folds, despite wide variation in the thickness of the cuff material.