Anaesthesia
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Randomized Controlled Trial
Timing of reversal with respect to three nerve stimulator end-points from cisatracurium-induced neuromuscular block.
After elective ear surgery with cisatracurium neuromuscular blockade, 48 adults were randomly assigned to receive neostigmine: (a) at appearance of the fourth twitch of a 'train-of-four'; (b) at loss of fade to train-of-four; or (c) at loss of fade to double-burst stimulation, all monitored using a TOF-Watch SX® on one arm. For each of these conditions, the recovery from train-of-four (TOF) ratio was measured in parallel objectively using a TOF-Watch SX placed on the contralateral arm. ⋯ This recovery time was significantly shorter when reversal was given at loss of fade to double-burst stimulation (c), than when given at the appearance of the fourth twitch (a), p = 0.046. However, the total time to extubation may be unaffected as it takes longer for fade to be lost after double-burst stimulation than for four twitches subjectively to appear.
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Observational Study
Continuous monitoring of haemoglobin concentration after in-vivo adjustment in patients undergoing surgery with blood loss.
Non-invasive monitoring of haemoglobin concentration provides real-time measurement of haemoglobin concentration (SpHb) using multi-wavelength pulse co-oximetry. We hypothesised that in-vivo adjustment using the mean of three haemoglobinometer (HemoCue®) measurements from an arterial blood sample at the first SpHb measurement (HCueART) would increase the accuracy of the monitor. The study included 41 adults for a total of 173 measurements of haemoglobin concentration. ⋯ The accuracy of in-vivo adjusted SpHb was compared with SpHb retrospectively adjusted using the same formula, except for haemoglobin level which was assessed at the central laboratory and then compared with all other available invasive methods of haemoglobin measurement (co-oximetry, HbSAT; arterial HemoCue, HCueART; capillary HemoCue, HCueCAP). Compared with laboratory measurement of haemoglobin concentration, bias (precision) for unadjusted SpHb, in-vivo adjusted SpHb, retrospectively adjusted SpHb, HbSAT, HCueART and HCueCAP were -0.4 (1.4), -0.3 (1.1), -0.3 (1.1), -0.6 (0.7), 0.0 (0.4) and -0.5 (1.2) g.dl(-1) , respectively. In-vivo adjustment of SpHb values using the mean of three arterial HemoCue measurements improved the accuracy of the device similar to those observed after a retrospective adjustment using central laboratory haemoglobin level.
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We measured total and free plasma concentrations of ropivacaine following high-volume, high-dose local infiltration analgesia in 28 patients aged 65 years or over undergoing unilateral total knee arthroplasty. Patients received infiltration of ropivacaine 400 mg followed by infusion at 20 mg.h(-1) through an intra-articular catheter. Total and free plasma levels of ropivacaine were measured at specified time intervals during a 24-h period after tourniquet release. ⋯ Six samples had total plasma ropivacaine levels greater the toxic threshold of 2.2 μg.ml(-1). No samples reached the toxic threshold for free venous ropivacaine concentration. We conclude that the use of high-dose ropivacaine infiltration and catheter infusion for total knee arthroplasty in an elderly population does not result in free plasma ropivacaine levels previously associated with toxicity but that raised total plasma levels may be observed.