Anaesthesia
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Randomized Controlled Trial
Volume of ropivacaine 0.2% and common peroneal nerve block duration: a randomised, double-blind cohort trial in healthy volunteers.
The volume-duration relationship using low concentrations of ropivacaine for peripheral nerve blocks is unknown, even though low concentrations of ropivacaine are increasingly used clinically. We investigated the effect of ropivacaine 0.2% on common peroneal nerve block duration. With ethical committee approval, 60 consenting, healthy volunteers were randomly allocated to receive one of five volumes of ropivacaine 0.2% (2.5, 5.0, 10, 15 or 20 ml) administered by ultrasound-guided, catheter-based injection (at 10 ml.min-1 ) near the common peroneal nerve. ⋯ Mean (SD) motor block durations were 3.3 (2.1), 7.2 (2.5), 9.2 (2.2), 12.7 (2.5) and 12.5 (2.5) h. Regression analysis showed that the effect of volume on block duration was progressively smaller with increasing volume, reaching a threshold volume above which there was no effect on nerve block duration (10 ml for sensory block and 15 ml for motor block). We conclude that there is a ceiling effect of increasing volume of ropivacaine 0.2% on both sensory and motor block duration of the common peroneal nerve.
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Despite being infrequent, complications of airway management remain an important contributor to morbidity and mortality during anaesthesia and care of the critically ill. Developments in the last three decades have made anaesthesia safer, and this has been mirrored in the equipment and techniques available for airway management. ⋯ Randomised controlled trials provide little useful information about safety in this setting, and data from registries and databases are likely to be of more value. This narrative review focuses on recent evidence in this area.
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Volatile anaesthetic agents are a potential occupational health hazard to theatre and recovery staff. Operating theatres and anaesthetic rooms are required to be equipped with scavenging systems, but recovery units often are not. We compared exhaled, spectrophotometric sevoflurane and desflurane concentrations 15 cm from the mouth ('patient breathing zone') and 91 cm laterally to the patient ('nurse work zone') in 120 patients after tracheal extubation who were consecutively allocated to either ISO-Gard mask oxygen/scavenging or standard oxygen mask, 0 min, 10 min and 20 min after arrival in the theatre recovery unit. ⋯ Using the ISO-Gard mask, the 20-min mean patient breathing zone and nurse work zone exhaled anaesthetic levels were ~ 90% and 78% lower than those recorded in the control group, respectively, and were within the recommended 2 ppm maximum environmental exposure limit in the patient breathing zone of 53 out of 60 (88%) and the nurse work zone of all 60 (100%) patients on first measurement in the recovery room (vs. 10 out of 60 (17%) and 40 out of 60 (67%) in the control group). Our study indicates that the ISO-Gard oxygen/scavenging mask reduces the level of exhaled sevoflurane and desflurane below recommended maximum exposure limits near > 85% of extubated patients within ~ 20 s of application in the recovery unit after surgery. We encourage the use of this mask to minimise the occupational exposure of recovery staff to exhaled volatile agents.
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Randomized Controlled Trial
The effect of spinal hyperbaric bupivacaine-fentanyl or hyperbaric bupivacaine on uterine tone and fetal heart rate in labouring women: a randomised controlled study.
The mechanism for fetal heart rate abnormalities following spinal opioids remains controversial. We evaluated uterine tone, using an intra-uterine pressure catheter, and fetal heart rate abnormalities in 30 women in spontaneous labour with cervical dilation of 3-5 cm having combined spinal-epidural analgesia. Women were randomly assigned to receive a spinal with 2.0 mg hyperbaric bupivacaine plus 15 μg fentanyl, or 2.5 mg hyperbaric bupivacaine. ⋯ Seven (47%) in the bupivacaine-fentanyl group showed new onset fetal heart rate changes during the 30-min period after the spinal, compared with two (13%) in the bupivacaine group (p = 0.04); however, these were transient and responded to intra-uterine resuscitation. Pain scores, sensory and motor block as well as neonatal outcomes were comparable between the groups. We found that raised baseline uterine tone was not more frequent when using bupivacaine-fentanyl rather than bupivacaine in the spinal component of combined spinal-epidural, although absolute values of baseline tone were higher, and fetal heart rate changes more frequent, in the former group.
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Bleeding during and after surgery ranges from trivial to fatal. Bleeding is in part determined by the patient's coagulation status. The UK National Institute for Health and Care Excellence recommends a pre-operative clotting test for patients with a history of abnormal bleeding. ⋯ The activated partial thromboplastin time may be prolonged due to contamination, anticoagulant therapy, clotting factor deficiencies, lupus anticoagulant or acquired inhibitors of specific clotting factors. A prolonged activated partial thromboplastin time should lead to: further testing to exclude heparin contamination or therapy, mixing studies to identify factor deficiencies and if necessary dynamic studies, such as the dilute Russell's viper venom time and the Actin FS-activated partial thromboplastin time, to identify direct factor inhibitors. These tests identify abnormalities and their implications for bleeding, helping anaesthetists and haematologists to manage haemostasis for individual patients.