Articles: anesthetics.
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Randomized Controlled Trial Comparative Study Clinical Trial
Anaesthesia for evacuation of retained products of conception. Comparison between alfentanil plus etomidate and fentanyl plus thiopentone.
Forty-four patients presenting for evacuation of retained products of conception were anaesthetized with either fentanyl and thiopentone, or alfentanil with etomidate, along with 70% nitrous oxide in oxygen. There was no difference between the two techniques in indices of immediate recovery (time to opening eyes and obeying a simple command), but the rate of return of higher mental functions (assessed by a coin counting test) was significantly better using the alfentanil-etomidate technique. There was no statistically significant difference between the techniques for apnoea or abnormal movements during anaesthesia, but alfentanil with etomidate was associated with significantly more pain on injection and a higher frequency of postoperative vomiting (40%).
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Randomized Controlled Trial Comparative Study Clinical Trial
Effect of gravity on the spread of extradural anaesthesia for caesarean section.
The effect of gravity on the spread of extradural anaesthesia was evaluated in a series of parturients undergoing elective Caesarean section. Following placement of an extradural catheter, 25 patients were placed 30-40 degrees head-up for 20 min during the administration of the local anaesthetic drug; 25 additional patients remained supine during injection. ⋯ There were no differences in the rate of onset of sacral blockade or in the extent of neural blockade between the two groups. The semi-upright position was not necessary to ensure adequate sacral anaesthesia for Caesarean section.
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The respiratory effects of sevoflurane were studied in seven patients and compared with values obtained in another seven patients anesthetized with halothane. Resting ventilation, resting PaCO2, and ventilatory response to CO2 were measured awake and at 1.1 and 1.4 MAC levels of both anesthetic agents. ⋯ At 1.1 MAC, sevoflurane produced almost the same degree of respiratory depression as halothane. At 1.4 MAC, sevoflurane produced more profound respiratory depression than halothane.
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Comparative Study
Differential nerve blockade: esters v. amides and the influence of pKa.
The in vitro sensitivities to local anaesthetic blockade of A, B and C fibres in rabbit vagus nerves were examined using a series of structurally similar amide agents, which varied in lipid solubility and anaesthetic potency. The actions of these drugs were compared with one another, and with those of a series of amino-ester local anaesthetics studied previously. The results demonstrated that A fibres are the most, and C fibres the least, sensitive to blockade by local anaesthetic agents. ⋯ As the latter increased, so did the rate of A fibre blockade. Combining the results of the two studies suggests that an agent of low lipid solubility and high pKa might be used to produce differential C fibre blockade. Comparison of the results obtained with the two different classes of drug indicates that the ester structure may have an inherently more potent action than the amide.
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The modulation of the gamma-aminobutyric acidA (GABAA) receptor by alphaxalone has been investigated by use of voltage-clamp recordings from enzymatically isolated bovine chromaffin cells maintained in cell culture. Alphaxalone (greater than 30 nM) reversibly and dose-dependently potentiated the amplitude of membrane currents elicited by locally applied GABA (100 microM). The potentiation was not associated with a change in the reversal potential of GABA-evoked currents and was not influenced by the benzodiazepine receptor antagonist, Ro15-1788 (300 nM). ⋯ The beta-hydroxy isomer of alphaxalone, betaxalone (100 nM-1 microM), did not potentiate GABA-induced currents, nor did higher concentrations of the steroid (10-100 microM) directly evoke a membrane current. However, over the latter concentration range, betaxalone suppressed the amplitude of currents elicited either by GABA or ACh. The relevance of the present results to the anaesthetic action of alphaxalone is discussed together with the broader implications of steroidal modulation of the GABAA receptor.