British journal of anaesthesia
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The veterinary neurosteroid anaesthetic Saffan has the same formulation as Althesin now withdrawn from human use and is a mixture of two neurosteroids, alphadolone, and alphaxalone. The molecular structures of these two pregnanes and their properties as i.v. anaesthetics were reported to be similar. Preliminary experiments showed that alphadolone caused powerful antinociceptive effects without sedation when given i.p. ⋯ These effects were reversed at the level of the spinal cord by intrathecally-administered bicuculline (10 pmol). We conclude that a metabolite of alphadolone acetate produced in the liver leads to antinociceptive effects after i.p. and intragastric administration of the parent compound. This antinociception involves spinal cord GABA(A) receptors, even though the drug was administered via a non-spinal route.
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Randomized Controlled Trial Clinical Trial
Effects of fentanyl, alfentanil, remifentanil and sufentanil on loss of consciousness and bispectral index during propofol induction of anaesthesia.
The bispectral index (BIS) and a sedation score were used to determine and compare the effect of propofol in the presence of fentanyl, alfentanil, remifentanil and sufentanil. Seventy-five non-premedicated patients were assigned randomly into five groups (15 in each) to receive fentanyl, alfentanil, remifentanil, sufentanil or placebo. Opioids were administered using a target-con-trolled infusion device, to obtain the following predicted effect-site concentrations: fentanyl, 1.5 ng ml(-1); alfentanil, 100 ng ml(-1); remifentanil, 6 ng ml(-1); and sufentanil, 0.2 ng ml(-1). ⋯ The relationship between propofol effect-site concentration and BIS was preserved with or without opioids. In the presence of an opioid, LOC occurred at a lower effect-site concentration of propofol and at a higher BIS50 (i.e. the BIS value associated with 50% probability of LOC), compared with placebo. Although clinically the hypnotic effect of propofol is enhanced by analgesic concentrations of mu-agonist opioids, the BIS does not show this increased hypnotic effect.
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Estimation of changes in cardiac output from the arterial blood pressure waveform in the upper limb.
We have developed a new pulse contour cardiac output (PulseCO) algorithm based on frequency analysis studies of the arterial system. PulseCO was compared with thermodilution cardiac output (TDCO) in 10 patients undergoing cardiac surgery. Results from one patient were unsuitable for analysis. ⋯ Least squares regression gave y = 0.71 x (r2 = 0.70) and the limits of agreement were from -21% to +25%. After phenylephrine had been given to five patients, PulseCO showed an increase in systemic vascular resistance consistent with the known pharmacological actions of the drug. The PulseCO algorithm was incorporated into a computer program that acquires arterial pressure data from an analogue-to-digital converter and displays beat-to-beat trend values.