British journal of anaesthesia
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Clinical Trial Controlled Clinical Trial
In vivo investigation into the effects of haemodilution with hydroxyethyl starch (200/0.5) and normal saline on coagulation.
We have investigated the effects of haemodilution with either saline or hydroxyethyl starch (200/0.5) (HES) on blood coagulation in healthy volunteers in vivo. Standard haematological tests (packed cell volume (PCV), platelets, prothrombin time (PT), activated partial thromboplastin time (aPTT), fibrinogen, antithrombin III, bleeding time and platelet aggregation), and thrombelastography (TEG) were performed before and after administration of either 0.9% saline 1000 ml or HES 1000 ml i.v. over a 30-min period. Dilution of PCV and platelet concentrations as a result of volume load were 9% in the saline group and 19% in the HES group. ⋯ Circulating concentrations of antithrombin III were depleted more than could be explained by haemodilution alone, leading to a hypercoagulable state. This effect was offset by an antiplatelet action of HES, which was not seen with saline. The mechanism is unknown.
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Comparative Study
Effect of xenon on central nervous system electrical activity during sevoflurane anaesthesia in cats: comparison with nitrous oxide.
We have compared the effects of xenon and nitrous oxide on central nervous system (CNS) electrical activity during sevoflurane anaesthesia in cats by recording the electroencephalogram (EEG), multi-unit activity of the midbrain reticular formation (R-MUA) and somatosensory evoked potentials (SEP). Basal anaesthesia with 2% and 5% sevoflurane was used. With 2% sevoflurane, 70% xenon initially produced rhythmic slow waves which were followed by bursts of high-amplitude sharp waves interrupted by low amplitude slow waves on the EEG. ⋯ Xenon suppressed the amplitude of both the initial positive and negative deflections of the SEP to a greater extent than nitrous oxide. With 5% sevoflurane anaesthesia, both anaesthetics increased the frequency of spikes on the EEG and facilitated R-MUA. These findings indicate that xenon has a stimulatory action on CNS background activity and a suppressive action on CNS reactive capability which is more potent than that of nitrous oxide.
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The upper airway abnormalities predisposing to difficult tracheal intubation may also predispose to obstructive sleep apnoea (OSA). The potential association is important as both conditions increase perioperative risk and patients with a trachea that is difficult to intubate may need assessment for OSA. We determined if patients with difficult intubation are at greater risk of OSA and, if so, whether or not they have characteristic clinical or radiographic upper airway changes. ⋯ We conclude that difficult intubation and OSA are related significantly. They share anatomical features which act to reduce the skeletal confines of the tongue. Patients with OSA may compensate, when awake, by increasing craniocervical angulation, which increases the space between the mandible and cervical spine and elongates the tongue and soft tissues of the neck.
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Respiratory failure following cardiopulmonary bypass (CPB) is a major complication after cardiac surgery. A vital capacity inflation of the lungs, performed before the end of CPB, may improve gas exchange, but the necessity to repeat it is unclear. Therefore, we studied 18 pigs undergoing hypothermic CPB. ⋯ From 3 to 6 h after CPB, there was no more improvement and more than 10% atelectasis remained at 6 h. In contrast, the two groups treated before termination of CPB with VCM showed only minor atelectasis and no abnormal changes in gas exchange directly after bypass or later. We conclude that the protective effect of VCM remained for 6 h after bypass, and there was no extra benefit on gas exchange by repeating the VCM.