British journal of anaesthesia
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Randomized Controlled Trial Clinical Trial
Comparison of the maternal and fetal effects associated with intermittent or continuous infusion of extradural analgesia.
Eighty normal primigravidae received an extradural dose of 0.25% bupivacaine and were then allocated randomly to receive "top-ups" of 0.25% bupivacaine (group A) or an infusion of 0.125% bupivacaine (group B). Group B received supplementary top-ups if required. Group A required more top-ups (147 vs 80) (P < 0.01). ⋯ More episodes in group A were related to top-ups (42/71 vs 18/69; P < 0.01) but the incidence of episodes after a top-up was similar (group A, 42/147 (28.6%); group B, 18/80 (22.5%)). In group A, 31/42 events (73.8%) were transient compared with 11/18 persistent episodes (61.1%) (> 10 min duration) in group B. However, the difference in the deceleratory patterns did not influence the condition of the fetuses at delivery.
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Pain threshold, nociceptive flexion reflex (NFR) threshold and responses to suprathreshold stimulation were investigated in 15 female patients (mean age 32 yr (range 22-48 yr)) before and 68 (range 48-96) h after gynaecological laparotomy. Control measurements were performed in 17 healthy human volunteers (five males, age 30 yr (range 24-41 yr)). In the surgical patients, pain threshold decreased and pain to suprathreshold stimulation increased significantly (P = 0.006 and P = 0.04, respectively) from before to after surgery. ⋯ The correlations between the relative change in pain and reflex thresholds, and time from surgery, were statistically significant (pain threshold: rs = 0.53, P = 0.04; NFR thresholds: rs = 0.54, P = 0.04). In the healthy volunteers, no significant differences in thresholds and responses to suprathreshold stimulation were observed between two recordings with an interval of at least 48 h. The allodynia and hyperalgesia observed in postsurgical patients may be related to postoperative sensitization of central neurones.
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Randomized Controlled Trial Clinical Trial
Learning during general anaesthesia: implicit recall after methohexitone or propofol infusion.
Forty-four patients undergoing coronary artery surgery were allocated randomly to receive an infusion of propofol or methohexitone as a hypnotic supplement to a fentanyl-based anaesthetic technique. A taped message was played to the patients, consisting of 10 words associated with prompt sentences and a suggestion for a specific postoperative behavioural response. Twenty patients (10 propofol and 10 methohexitone) (perioperative group) were exposed to the taped message during surgery and in the immediate postoperative period and the other 24 patients (postoperative group) were exposed to the tape only in the postoperative period, after return to the intensive care unit (ICU). ⋯ The patients who were played the tape whilst receiving identical infusion regimens for sedation in the ICU did not demonstrate implicit recall of the word associations in either the propofol or the methohexitone groups. There was no evidence of a response to the specific behavioural suggestion during the postoperative interview. The results confirm that auditory perception can occur during clinically adequate anaesthesia, and that suppression of auditory awareness or learning is a function of both the pharmacological degree of sedation and the degree of surgical stimulation.
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The postoperative period after major abdominal surgery is known to be a period of increased episodic oxygen desaturation. In order to assess the risk factors for episodic desaturation, we have studied 29 surgical patients using pulse oximetry during the preoperative night (Npre) when they received benzodiazepine premedication and breathed air, and also during the first three nights after operation when they received nasal oxygen supplementation. Modal oxygen saturation (SpO2) exceeded 95% during all nights studied. ⋯ At the same time, t90 and t85 correlated with body mass index (P = 0.02 and P = 0.05, respectively). During N2, t90 correlated with radiological lung consolidation (P = 0.05) and SpO2, nadir correlated with FEV1 (P = 0.03). We conclude that there are several mechanisms responsible for oxygen desaturation and that these mechanisms differ before and after surgery.
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Randomized Controlled Trial Clinical Trial
The laryngeal mask airway for intraocular surgery: effects on intraocular pressure and stress responses.
Tracheal intubation, performed routinely during general anaesthesia in patients undergoing intraocular surgery, may have adverse effects on cardiovascular function and intraocular pressure. This study assessed the suitability of the laryngeal mask airway (LMA) as a substitute for tracheal intubation. ⋯ Mean (SEM) rate-pressure product was significantly smaller in the LMA group compared with the TT group after both insertion (8276 (730) vs 13307 (1348), P < 0.01) and removal (10152 (595) vs 14137 (1044), P < 0.01) of the airway device. The change in intraocular pressure was significantly less in the LMA group at all time points after airway instrumentation than that in the TT group, with the greatest difference after extubation (-2.3 (2.4) mm Hg vs 14.5 (3.4) mm Hg, P < 0.01).