British journal of anaesthesia
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Comparative Study
Differential nerve block by bupivacaine and 2-chloroprocaine. An experimental study.
The differential blocking effect of bupivacaine and 2-chloroprocaine was studied on isolated rabbit cervical sympathetic trunks (B and C fibres) and phrenic nerves (A fibres). The B fibres (myelinated, preganglionic) were more sensitive than C fibres (unmyelinated, postganglionic) to nerve block by bupivacaine and 2-chloroprocaine, as assessed by changes in action potential amplitude and latency. The blocking action of both bupivacaine and 2-chloroprocaine caused a decrease in amplitude in the B fibres approximately twice as great as that produced in the C fibres. ⋯ The average action potential amplitude of A fibres at that time was 78%. 2-Chloroprocaine 300 mumol litre-1 completely blocked B fibres in 4 min and C fibres in 15 min. At 15 min the average action potential amplitude of the A fibres was still approximately 35%. Although these two local anaesthetics differ structurally and physico-chemically, the rates of block of the different fibres were in the same order in vitro.
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The obstetric and anaesthetic problems of Ehlers-Danlos syndrome are discussed. A new unclassified type of the syndrome is described. ⋯ The anaesthetic management of two parturients with Ehlers-Danlos syndrome is illustrated. Caudal, extradural, and subarachnoid block techniques for labour and Caesarean section were used safely on three occasions in these two patients.
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The effect of halothane on the respiratory pattern was investigated in lightly anaesthetized cats. Following the administration of 2.0% halothane there was a transient increase in respiratory frequency because of a decrease in the duration of expiration, followed by a progressive decrease in respiratory frequency as a result of prolongation of inspiration; both events could be demonstrated before and after vagotomy. ⋯ Tidal phrenic output decreased progressively as the concentration of halothane was increased. These results suggest that changes in respiratory pattern seen during halothane anaesthesia might involve some excitatory central mechanisms other than the bulbopontine system.