Anaesthesia
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Randomized Controlled Trial
The influence of changes in end-tidal carbon dioxide upon the Bispectral Index.
Carbon dioxide is known to affect consciousness in animals and humans. We surmised that changes in end-tidal carbon dioxide during anaesthesia might affect the Bispectral Index. Twenty-four patients due to undergo surgery were anaesthetised with fentanyl and a propofol infusion. ⋯ The patients acted as their own controls as they were subjected to high, normal and low levels of end-tidal carbon dioxide (3-12 kPa) according to a randomised sequence. There were no changes in the Bispectral Index or haemodynamic variables resulting from manipulation of the end-tidal carbon dioxide. At the level of hypnosis involved in this study, changes in end-tidal carbon dioxide, within the range tested, do not result in changes in the Bispectral Index.
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Multicenter Study
The use of N-terminal pro-B type natriuretic peptide in a pre-operative setting to predict left ventricular systolic dysfunction on echocardiogram.
Heart failure is a major risk factor for adverse postoperative events following non-cardiac surgery. The use of transthoracic echocardiogram as a pre-operative investigation to assess cardiac dysfunction has limitations in this setting. The N-Terminal fragment of B-Type natriuretic peptide (NT proBNP) has been used in screening for heart failure. ⋯ In terms of pre-operative screening, a NT proBNP of <38.2 pmol x l(-1) had a 100% negative predictive value in predicting patients with normal left ventricular systolic function and would have prevented the requirement for echocardiogram in 43% of pre-operative patients. NT proBNP was superior to electrocardiological and clinical criteria for detection of a normal echocardiogram. This may have significant impact in the pre-operative assessment of patients undergoing non-cardiac surgery.
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We describe the anaesthetic management of a 21-year-old lady with central core disease for elective Caesarean section. Central core disease is characterised by muscle weakness, skeletal deformities and susceptibility to malignant hyperthermia. ⋯ The authors believe there is no previous report of propofol and remifentanil being used in these circumstances. A short review of central core disease and its anaesthetic implications is provided.
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The response of arterial PO(2) (P(a)O(2)) to airway pressure has been used as a measure of recruitment in mechanically ventilated patients. We hypothesised that mixed venous PO(2) (P(mv)O(2)) directly affects P(a)O(2). Sixteen patients with acute lung injury (ALI, lung injury score > or = 1) on volume-controlled mechanical ventilation (F(I)O(2) 0.40) were studied. ⋯ Changes in P(mv)O(2) contributed to changes in Q(va)/Q(t) in determining changes in P(a)O(2) (p < 0.05). P(mv)O(2) may be an independent determinant of P(a)O(2) during mechanical ventilation for ALI, so that dosing PEEP to recruit the lung should not be guided by arterial blood oxygenation alone. Arterial hypoxaemia with increasing PEEP may improve by reducing PEEP (or increasing tissue O(2) delivery), when the fall in P(mv)O(2) is greater than about 0.133 kPa.
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We examined the pressures produced by a construction intended for emergency ventilation through a needle cricothyroidotomy. This construction consisted of a standard hospital wall oxygen supply, flowmeter, oxygen tubing and a three-way tap. We measured the flow achieved through a transtracheal catheter and compared the construction to a Manujet jet ventilator and to a Sanders injector. ⋯ The flow through the transtracheal catheter was almost three times higher when the flowmeters were fully opened than when they were opened to the 15 l x min(-1) mark (44.5 vs 15.8 l x min(-1), respectively; p < 0.0001). When the flowmeters were fully opened the pressure measured before the catheter was over four times higher than when they were only opened to the 15 l x min(-1) mark (285.3 vs 66.4 kPa, respectively; p < 0.0001). This system of ventilation is inferior to a Manujet in terms of robustness and calibration throughout its range of pressures and flows, but seems appropriate for emergency use in the absence of a purpose-made jet ventilator.