Canadian journal of anaesthesia = Journal canadien d'anesthésie
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Venous air embolism is a well-recognized complication of central venous catheterization. Although previous reports have documented venous air embolism occurring in a number of ways, including during initial catheterization, when catheters crack or are disconnected, and after catheter removal, no reports mention the possibility of air embolism occurring when a guide wire without a catheter was in place. ⋯ It is postulated that a previously described gasp reflex or some sort of sustained negative pressure manoeuvre caused venous air embolism around the guide wire and accounted for the patient's signs and symptoms. During central venous catheter placement, a high index of suspicion for venous air embolism should be maintained, pulse oximetry should be used, the skin entrance site should be kept covered by an occlusive dressing, and the patient should be positioned head-down.
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Randomized Controlled Trial Comparative Study Clinical Trial
Continuous infusion epidural analgesia for obstetrics: bupivacaine versus bupivacaine-fentanyl mixture.
Continuous infusion epidural analgesia (CIEA) using a mixture of bupivacaine and fentanyl was evaluated in this randomized, double-blind study involving 75 nulliparous women by comparing the mixture (Group I, Bupivacaine 0.125% and fentanyl 4 micrograms.ml-1 -24 patients) with two concentrations of bupivacaine alone (Group II, bupivacaine 0.25% - 24 patients; and Group III, bupivacaine 0.125% - 27 patients). Epidural anaesthesia was established in Group I with 6 ml 0.125% bupivacaine with fentanyl 50 micrograms and in both Groups II and III with 6 ml 0.25% bupivacaine. In the women whose pain score (Visual Analogue Scale) decreased by at least 50% within 15 min, CIEA was given until delivery. ⋯ The proportion of women reporting excellent/good analgesia during the second stage was approximately 65% in all three groups. The total cumulative dose of bupivacaine in Group I was 54 +/- 36 mg, compared with 107 +/- 47 mg for Group II (P = 0.001), and 71 +/- 41 mg for Group III (NS). Group I patients required less supplementation with bupivacaine than either Group II or III patients during the first stage but only with Group III patients during the second stage.(ABSTRACT TRUNCATED AT 250 WORDS)
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Review
Perioperative stroke. Part I: General surgery, carotid artery disease, and carotid endarterectomy.
Although stroke, defined as a focal neurological deficit lasting more than 24 hr, is uncommon in the perioperative period, its associated mortality and long-term disability are high. No large-scale data are available to identify the importance of recognized risk factors for stroke in the perioperative period. A review of the literature shows that the incidence and mechanism of its occurrence are influenced by the presence of cardiovascular disease and the type of surgery. ⋯ The risk of stroke associated with carotid endarterectomy is closely related to the preoperative neurological presentation, and the experience of the surgical/anaesthetic team. Symptomatic cerebrovascular disease, acute stroke, asymptomatic carotid lesions, preoperative assessment of risk, local and general anaesthesia, cerebral protection and monitoring during carotid endarterectomy are discussed with reference to reducing the risk of perioperative stroke. Adequate monitoring and protection have minimized the risk of ischaemia from carotid clamping, and the major mechanism of stroke is embolization.
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The literature dealing with the magnitude, mechanism and effects of reduced FRC in the perioperative period is reviewed. During general anaesthesia FRC is reduced by approximately 20%. The reduction is greater in the obese and in patients with COPD. ⋯ Postoperative hypoxaemia is a function of reduced FRC and airway closure. There is no real difference among the various methods of active lung expansion in terms of the speed of restoration of lung function, or in preventing postoperative atelectasis/pneumonia. Epidural analgesia does not influence the rate of recovery of lung function, nor does it prevent atelectasis/pneumonia.
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Comparative Study
Time-cycled inverse ratio ventilation does not improve gas exchange during anaesthesia.
Inverse ratio ventilation (IRV) has been reported to improve oxygenation at lower peak airway pressures in patients with respiratory failure. Therefore we hypothesised that IRV might also improve oxygen exchange during anaesthesia. Conventional ratio ventilation (CRV) and IRV were compared in 24 low-risk surgical patients who were paralysed and whose lungs were ventilated with air/O2 by a non-rebreathing circuit and a Siemens 900-C servo ventilator. ⋯ Multivariate models were tested to identify variables which predicted O2 exchange during CRV. Patient age was the only predictor consistently significant in all models. We conclude that age is an important determinant of impaired pulmonary oxygen exchange during anaesthesia, and that increasing mean AWP by TC-IRV has no beneficial effects on pulmonary mechanics or gas exchange.