Anaesthesia
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A patient is presented in whom 15 ml of 15% potassium chloride (30 mM) mixed with bupivacaine was injected epidurally for relief of pain resulting from widespread pelvic malignancy. Within minutes the patient complained of severe pain in both the lower limbs and rapidly became paraplegic with bladder and bowel incontinence. The paraplegia was permanent. The transient symptoms of pain may have been partly due to the irritant effects of a hyperosmolar solution of potassium chloride in the epidural space, while the permanent neurological damage might have been due to the very high extracellular concentration of potassium leading on to a depolarising phenomenon initially followed by nerve tissue necrosis.
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The anaesthetic requirements for tracheal resection include a clear airway, adequate ventilation and good surgical access. Many techniques have been described, none of which is entirely satisfactory. This case reports on the use of high-frequency jet ventilation with 10Fg catheter combined with muscle relaxants and intravenous anaesthesia in a patient with tracheal stenosis.
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An expression for the splitting ratio (bypass gas/gas through vaporizing compartment) is derived formally. The factors affecting volatile agent gaseous fraction and, more importantly, partial pressure are discussed in relation to changes in temperature and barometric pressure. Low-boiling point, high saturated vapour pressure anaesthetics are more susceptible to the influence of barometric pressure variations.