British journal of anaesthesia
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Randomized Controlled Trial Comparative Study Clinical Trial
Intravenous opioids reduce airway irritation during induction of anaesthesia with desflurane in adults.
Desflurane is not used for the induction of anaesthesia despite its favourable pharmacokinetic characteristics because it causes airway irritation. We investigated whether pretreatment with i.v. narcotics reduced unwanted effects. One hundred and eighty adults were randomized to three groups (60 per group) to receive i.v. saline, fentanyl 1 microgram kg-1 and morphine 0.1 mg kg-1, respectively, before inhalational induction with desflurane in nitrous oxide and oxygen. ⋯ Laryngospasm developed in 11.7% of controls compared with 3.3 and 1.7% in the fentanyl and morphine groups, respectively. More patients in the control group had excitatory movements (46.7%) than in the fentanyl (16.7%) and morphine (8.3%) groups. These results demonstrate that i.v. opioids reduce airway irritability significantly during inhalational induction with desflurane in adults.
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Clinical Trial
Pharmacokinetics and clinical efficacy of long-term epidural ropivacaine infusion in children.
The clinical efficacy and pharmacokinetics of long-term epidural ropivacaine infusion were investigated in 18 postoperative children aged between 0.3 and 7.3 yr. A lumbar or thoracic epidural catheter was inserted after the anaesthetic induction. Sixty minutes following a bolus dose of ropivacaine 1 mg kg-1, 0.2% ropivacaine was infused at a fixed rate of 0.4 mg kg-1 h-1 for a mean of 61.3 h (range 36-96 h). ⋯ No clinical signs of local anaesthetic toxicity were seen. Total (100-3189 micrograms litre-1) and free (10-56 micrograms litre-1) ropivacaine concentrations were within the range reported to be 'safe' in previous studies in adults. Mean (95% CI) volume of distribution was 3.1 litre kg-1 (2.1-4.2 litre kg-1), total clearance was 8.5 ml kg-1 min-1 (5.8-11.1 ml kg-1 min-1), free clearance was 220 ml kg-1 min-1 (170-270 ml kg-1 min-1) and elimination half-life was 4.9 h (3.0-6.7 h).
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The aim of this study was to validate measurements of intraoperative left ventricular (LV) area by transoesophageal echocardiography against simultaneous measurements of LV volume by conductance catheter (CC) in cardiac surgical patients with normal systolic LV function. Echo area was compared with CC volume during steady state and during acute changes of pre- and afterload by partial clamping of the inferior vena cava and the ascending aorta in eight patients scheduled for coronary artery bypass grafting. ⋯ Intraoperative area measurements with transoesophageal echocardiography in cardiac surgical patients with normal systolic LV function show good correlation with CC volume measurements under steady-state conditions. During acute unloading by vena cava occlusion, the resulting small end-systolic echo area measurements differ significantly more from CC volume measurements than during acute increase in afterload by aortic occlusion.
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Comparative Study
Resistance of laryngeal mask airway and tracheal tube in mechanically ventilated patients.
We compared the airflow resistance of 7.5 and 8.5 mm internal diameter (i.d.) endotracheal tubes (ETTs) with that of a size 4 laryngeal mask airway (LMA). We thought that any difference in the resistance of the devices alone might be offset by the resistance of the larynx. Sixteen adult ASA physical status I and II patients (14 males, two females) undergoing general anaesthesia were anaesthetized and paralysed with intravenous propofol, ketamine and vecuronium. ⋯ Greater resistance occurred in two patients with a central LMA position and unobstructed view of the glottis and in one patient with marked lateral deviation. In conclusion, there is no clinically relevant difference between the resistance of a size 4 LMA plus that of the larynx and that of an 8.5 mm i.d. ETT.