British journal of anaesthesia
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Randomized Controlled Trial Clinical Trial
Use of tranexamic acid for an effective blood conservation strategy after total knee arthroplasty.
We have investigated the effect of treatment with tranexamic acid, an inhibitor of fibrinolysis, on blood loss, blood transfusion requirements and blood coagulation in a randomized, double-blind, placebo-controlled study of 42 patients after total knee arthroplasty. Tranexamic acid 15 mg kg-1 (n = 21) or an equivalent volume of normal saline (n = 21) was given 30 min before surgery and subsequently every 8 h for 3 days. Coagulation and fibrinolysis values, blood loss and blood units administered were measured before administration of tranexamic acid, 8 h after the end of surgery and at 24 and 72 h after operation. ⋯ Postoperative concentrations of plasminogen were decreased significantly in the tranexamic acid group (P < 0.001). Platelet count, PT, aPTT, bleeding time, beta-thromboglobulin, fibrinogen and FDP concentrations did not differ between groups, but D-dimer concentrations were increased in the control group. Thromboembolic complications occurred in two patients in the control group compared with none in the tranexamic acid group.
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Randomized Controlled Trial Clinical Trial
Midazolam premedication and thiopental induction of anaesthesia: interactions at multiple end-points.
We have studied the effects of midazolam premedication on multiple anaesthetic end-points (hypnotic, loss of verbal contact (LVC); motor, dropping an infusion flex or bag (DF); analgesic, loss of reaction to painful stimulation (LRP); and EEG, attainment of burst suppression (BUR)) during induction by slow thiopental infusion at a rate of 55 mg kg-1 h-1. Patients received midazolam 0.05 mg kg-1 i.v. (group TM, n = 12) or no midazolam (group T0, n = 13). ED50 and ED95 values and group medians for times and doses at the end-points were measured. ⋯ There were no such increases for LVC or BUR. The interaction between midazolam and thiopental varied with the anaesthetic end-point and may also depend on the dose of thiopental. Our data suggest that the mechanism of interaction between midazolam premedication and thiopental was different for motor effects or analgesia (DF, LRP) compared with hypnotic effects or cortical depression (LVC, BUR), in agreement with the different central nervous system substrates underlying these distinct anaesthetic end-points.
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Postoperative cognitive dysfunction (POCD) has been attributed to long-acting sedatives. We hypothesized that diazepam and its active metabolites could be detected in blood after surgery and correlated with POCD, 1 week after surgery in elderly patients. We studied 35 patients, 60 yr or older, undergoing abdominal surgery with general anaesthesia, including diazepam. ⋯ Diazepam or desmethyldiazepam was detected in 34 patients; median postoperative blood concentrations were 0.06 and 0.10 mumol kg-1, respectively. In a multiple regression analysis considering age, duration of anaesthesia and blood concentrations of diazepam and desmethyldiazepam, only age was found to correlate with the composite z-score (F test, P < 0.01). The postoperative cognitive dysfunction we found in elderly patients after operation could not be explained by benzodiazepine concentrations detected in blood.
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The response to tissue injury includes sensitization of peripheral nociceptors and central neuronal pathways leading to acute clinical and inflammatory pain. A further response is sprouting of sensory nerve terminals in the region of skin damage. This hyperinnervation response is particularly intense in neonates compared with adults. ⋯ Cutaneous innervation was studied by image analysis of immunostained skin sections, 7 days after wounding, and sensory thresholds were assessed using von Frey hairs. The results showed that both hyperinnervation and hypersensitivity were not significantly altered by the application of a regional nerve block at the time of injury. This suggests that regional analgesia, used commonly in clinical practice, is unlikely to prevent the hyperinnervation that follows skin wounding.
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The inspired partial pressure of an anaesthetic is often used as an index of arterial partial pressure in small animal experiments. We have investigated the influence of anaesthetic solubility on the ratio of arterial to inspired partial pressure in 24 rats, allocated randomly to receive halothane, isoflurane or desflurane at four different inspired concentrations. ⋯ Analysis of variance showed a significant effect of anaesthetic agent (P = 0.008) on the arterial to inspired ratio. Thus volatile anaesthetic agents do not demonstrate a fixed arterial to inspired ratio in rats.