British journal of anaesthesia
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Using the single breath test for carbon dioxide (SBT-CO2), the components of physiological deadspace were investigated during anaesthesia with IPPV in 58 patients. A square-wave inspiratory flow and an end-inspiratory pause (25% and 10% of cycle time, respectively) were used. At tidal volumes of 0.45 litre (f = 17 b.p.m.), and 0.75 litre (f = 9 b.p.m.), median values for VDphys/VT were 0.44 and 0.31. ⋯ The median arterial--end-tidal PCO2 difference, (PaCO2-PE'CO2), was 0.6 kPa at small and 0.3 kPa at large tidal volumes (P less than 0.001). Three patients had zero and four had negative (PaCO2-PE'CO2) values at large tidal volumes. When phase III slopes steeply, negative (PaCO2-PE'CO2) values may be observed in the presence of alveolar deadspace.
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Treatment with drugs and exposure to many environmental chemicals results in enzyme induction. However, the clinical significance of increased (or altered) metabolism of the inhaled anaesthetics appears to be trivial. Enzyme induction does not affect the conduct of inhalation anaesthesia. ⋯ Whether induction of halothane biotransformation and the production of reactive intermediates may lead to hepatoxicity is not yet settled. It is quite clear that induction, in the presence of hypoxia, leads to hepatic necrosis in rats. However, a similar relationship has not been established in surgical patients.
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Comparative Study Clinical Trial Controlled Clinical Trial
Extradural morphine for the relief of pain following caesarean section.
Thirty patients took part in a double-blind trial to compare morphine 10 mg i.m. with morphine 5 mg into the extradural space for pain relief following Caesarean section. With the extradural route the mean time to first analgesia was 7.95 h compared with 4.75 h for the i.m. route. ⋯ There was a small but definite advantage in the use of the extradural route for the initial dose of morphine. No serious side-effects were noted in either group.
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A description is given of a new microprocessor-based device for EEG analysis. The Cerebral Function Analysing Monitor (CFAM) analyses the EEG amplitude and frequency distribution. It produces a detailed plot of amplitude trends and separate traces of the percentage activity in each of the classical EEG frequency bands. ⋯ Discontinuation of nitrous oxide resulted in a marked increase in EEG amplitude and an increase in alpha and beta band activity. Discontinuation of halothane resulted in smaller alterations in the CFAM trace. This device provides easily interpreted processed EEG data and merits further investigation.