British journal of anaesthesia
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Comparative Study
Effects of varying inspiratory flow waveform and time in intermittent positive pressure ventilation: emphysema.
Emphysema was induced in mongrel dogs by four weekly inhalations of papain. The effects of IPPV were studied using four different inspiratory flow waveforms and each at three different inspiratory times. Tidal volume and respiratory frequency were kept constant and inspiratory time and flow waveform were varied independently. ⋯ With a longer inspiratory time of 2.2s and with the reversed ramp flow waveform VD/VT was decreased. With the reversed ramp flow waveform there was a greater total compliance, increased (PAo2-Pao2) and reduced PaCO2. There were statistically significant differences in mean airway and oesophageal pressures which indicate valid differences in the flow waveforms and times.
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If the anaesthetic circle system is arranged to increase the humidity of fresh anaesthetic gases by placing the carbon dioxide absorbent canister between the fresh gas inlet and the patient, drying of the soda-lime can occur. Very dry soda-lime adsorbs significant quantities of halothane. Using fresh soda-lime, effluent halothane concentration reached 50% of the input concentration in 35s, but this time increased to 500 s when dry soda-lime was used. The use of dry soda-lime can result in a slow inhalation induction or in the release of absorbed halothane during a subsequent anaesthetic.
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The Swedish Society of Anaesthetists conducted a nationwide retrospective survey of clinical experience with extradural and intrathecal opiates. Special interest was focused on the frequency and type of ventilatory depression. The questionnaire was answered by 84 of 93 departments (90%). ⋯ Only two of these 22 patients experienced ventilatory depression later than 6 h after the last dose of opiates (S. C., i.m., i.v. or extradural). Patients aged 70 yr or more, those receiving thoracic extradural puncture and those with reduced ventilatory capacity seemed to be overrepresented.
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Twenty-five healthy women in labour received morphine 1-1.75 mg in normal saline intrathecally. The residual pain was evaluated on a scale from 0 to 5 at 10 min (score 2.5) and at 25 min (score 1.5). ⋯ The maternal and fetal plasma concentrations of morphine were 6 ng ml-1 or less. The intrathecal (but not extradural) administration of morphine is effective and could provide an interesting alternative for pain relief in labour.
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Randomized Controlled Trial Clinical Trial
A controlled trial of extradural fentanyl in labour.
In a double-blind trial carried out on patients in the first stage of labour, either fentanyl 80 micrograms (n = 35) or physiological saline (n = 33) was added to the test dose of bupivacaine and administered extradurally. Thereafter analgesia was maintained as necessary with 0.5% bupivacaine alone. ⋯ Analgesia was more rapid in onset and more complete in the fentanyl group, and the duration from first dose to first top-up was 2.36 h, compared with 1.66 h (supplements notwithstanding) in the control group. No serious side-effects were encountered in either group, although eight patients in the fentanyl group experienced mild itching, compared with one in the control group.