Anaesthesia
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We measured heating of isotonic saline by three fluid warmers in six experiments: saline at 5 °C or 20 °C delivered at 30, 50 or 100 ml.min(-1). At the three flow rates, the enFLOW(®) , buddy lite(™) and ThermoSens(®) systems heated 5 °C saline to mean (SD) temperatures of: 41.1 (0.5) °C, 37.7 (0.6) °C and 39.1 (0.6) °C; to 40.3 (0.8) °C, 33.9 (1.6) °C and 39.3 (0.7) °C; and to 37.1 (0.8) °C, 24.0 (1.3) °C and 37.6 (1.0) °C, respectively, p < 0.0001 for each experiment. ⋯ The results for saline at 20 °C were similar. The enFLOW system heated saline above 36 °C faster than the ThermoSens system, whereas the buddy lite often failed to achieve 36 °C.
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Animal studies have shown that injection pressures > 75 kPa indicate probable intrafascicular needle tip position. This study describes the flow/pressure characteristics of seven common needle systems. A syringe pump delivered flow rates of 5, 6.67, 10, 13.3, 15 and 20 ml.min(-1) through these needle systems, while keeping the needle tips open to atmosphere. ⋯ Flow rates > 17 ml.min(-1) and needle sizes 22 G and smaller produced mean plateau pressures > 75 kPa. Pressure monitors upstream from the needle may produce false-positive alarms at high flow rates due to needle resistance, and unreliable readings due to non-laminar flow. We recommend injection rates ≤ 15 ml.min(-1) (0.25 ml.s(-1) ) to reduce the effect of factors upstream from the needle tip as a cause of high pressure readings.
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Epidural blood patches may be used to treat post-dural puncture headache following accidental dural puncture in parturients. Their mode of action and the optimum volume of blood for injection remain controversial, with the interaction between injected blood and cerebrospinal fluid unknown. We aimed to establish the effects of serial haemodilution of whole blood with cerebrospinal fluid from 34 pregnant patients compared with serial haemodilution with Hartmann's solution, using the thromboelastogram. ⋯ Cerebrospinal fluid led to a mean (95% CI) decrease in r-time by 2.4 (1.6-3.2) min, a decrease in k-time by 0.6 (0.4-0.8) min, an increase in alpha angle by 7.3 (5.5-9.0)°, and a decrease in maximum amplitude by 2.0 (0.6-3.4) mm. This may have implications for epidural blood patch, as success may be reduced near the time of dural puncture when cerebrospinal fluid leak is at its greatest, and large volumes of blood may be required to reduce haemodilution and clot destabilisation by cerebrospinal fluid. In addition, blood patching should be performed at the level of the dural puncture in order to ensure that the maximum volume of blood comes into contact with the cerebrospinal fluid.
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It is important to detect and treat hypovolaemia; however, detection is particularly challenging in the conscious, spontaneously breathing patient. Eight healthy male volunteers were monitored using four minimally invasive monitors: Vigileo FloTrac(™) ; LiDCOrapid(™) ; USCOM 1A; and CardioQ(™) oesophageal Doppler. ⋯ Receiver operator characteristic curves for predicting > 10% blood loss had areas under the curve of 0.68-0.82. The minimally invasive cardiac output devices tested can detect blood loss by a reduction in stroke volume in awake volunteers, and may have a role in guiding fluid replacement in conscious patients with suspected hypovolaemia.
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Measurement of left ventricular stroke volume and cardiac output is very important for managing haemodynamically unstable or critically ill patients. The aims of this study were to compare stroke volume measured by three-dimensional transoesophageal echocardiography with stroke volume measured using a pulmonary artery catheter, and to examine the ability of three-dimensional transoesophageal echocardiography to track stroke volume changes induced by haemodynamic interventions. This study included 40 cardiac surgery patients. ⋯ The concordance rate in the 4-quadrant analysis after phenylephrine and ephedrine administration was 75% and 84%, respectively. In the polar-plot analysis, the angular concordance rate was 66% and 73% after phenylephrine and ephedrine administration, respectively. Three-dimensional transoesophageal echocardiography was clinically acceptable for measuring stroke volume; however, it was not sufficiently reliable for tracking stroke volume changes after haemodynamic interventions.