Anaesthesia
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Randomized Controlled Trial
Quantitative analysis of changes in blood concentrations and 'presumed effect-site concentration' of sevoflurane during one-lung ventilation.
During one-lung ventilation, ventilation-perfusion mismatch decreases the arterial concentration of inhaled anaesthetics due to the arterial-to-venous concentration difference. This study tested the hypothesis that in humans, the 'presumed effect-site concentration' (taken as the mid-point between the arterial and superior jugular venous concentrations) of inhaled anaesthetic falls during one-lung (vs two-lung) ventilation. ⋯ During one-lung ventilation, the end-expiratory sevoflurane concentration was stable at ∼1.3% but the mean (SD) presumed effect-site concentration declined initially from 58 (6.7) to 43 (4.7) μg.ml(-1) (p=0.011) before slowly recovering. A period of insufficient depth of anaesthesia is thus a risk during one-lung ventilation.
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Randomized Controlled Trial
Evaluation of radial and ulnar blood flow after radial artery cannulation with 20- and 22-gauge cannulae using duplex Doppler ultrasound.
This study evaluated ulnar and radial artery blood flow after radial artery cannulation during general anaesthesia using Doppler ultrasound. A total of 80 patients were randomly assigned to receive radial artery cannulation with either a 20-G or 22-G cannula. Arterial diameter, peak systolic velocity, end-diastolic velocity, resistance index and mean volume flow were measured at four time points in both arteries: before anaesthesia; 5 min after intubation; immediately after cannulation; and 5 min after cannulation. ⋯ Radial blood flow was decreased immediately after cannulation and recovered to pre-cannulation values 5 min after cannulation. There were no statistical differences between groups at each time point. Radial artery cannulation causes compensatory increase in ulnar artery blood flow, and the difference in cannula size has minimal effect on this change.
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This study aimed to compare the haemodynamics in healthy pregnant women with the haemodynamics in women with untreated pre-eclampsia, to determine the cardiovascular reason for hypertension in pre-eclampsia. 40 women with untreated pre-eclampsia, 40 matched healthy pregnant women and 20 non-pregnant women were studied using transthoracic echocardiography. Untreated pre-eclampsia demonstrated (mean (SD), healthy non-pregnant vs healthy pregnant vs untreated pre-eclampsia) increased cardiac output (3400 (752) vs 4109 (595) vs 4789 (1416) ml.min(-1), p=0.002), increased stroke volume (53 (10) vs 53 (8) vs 59 (13) ml, p=0.04), increased fractional shortening (35 (5) vs 35 (7) vs 41 (8) %, p=0.006), increased fractional area change (57 (7) vs 57 (9) vs 65 (9)%, p=0.002) and increased systemic vascular resistance (2116 (457) vs 1613 (315) vs 2016 (625) dyne.s.cm(-5), p=0.001). Mitral E/septal e' was higher (6.0 (1.1) vs 6.7 (1.3) vs 10.4 (2.4), p=0.002) and left atrial size increased (3.2 (0.3) vs 3.8 (0.4) vs 4.0 (0.4) cm, p=0.002). Hypertension in untreated pre-eclampsia is due to increased cardiac output and mild vasoconstriction, with increased inotropy and reduced diastolic function.
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Case Reports
Catastrophic complication of an interscalene catheter for continuous peripheral nerve block analgesia.
We report a catastrophic postoperative complication of a prolonged interscalene block performed under general anaesthesia. The course of the anaesthetic was uneventful and the patient remained stable during his stay in the recovery area with the operative extremity paralysed and insensate. ⋯ The patient was next assessed 6.5 h later when he was found dead in his bed. A postmortem CT scan revealed the catheter to be sited intrathecally, presumably the result of dural sleeve penetration.
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Comparative Study
Epidural catheter connectors: a laboratory-based comparison of the Portex Tuohy-Borst and EpiFuse™ designs.
Disconnection of an epidural catheter from its connector may result in patient harm and commonly requires resiting of the epidural. Clamp-connector designs such as the novel Portex EpiFuse™ potentially offer an improved safety profile over screw-cap designs such as the Tuohy-Borst, but comparative studies are limited. We therefore compared the tensile strength of EpiFuse and Tuohy-Borst connectors in a laboratory setting. ⋯ The Tuohy-Borst was also less likely to meet British Standard requirements (13/20 sets vs 19/20 and 20/20, p=0.002). Modification of the EpiFuse did not affect lumen patency or connection strength. We conclude that under controlled conditions, EpiFuse connectors are superior to Tuohy-Borst connectors.