British journal of anaesthesia
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We have measured the partial pressure of isoflurane simultaneously in inspired gas (PIiso), end-expired gas (PE'iso), mixed-expired gas (PEiso), arterial (Paiso) and mixed venous blood (Pviso) in six patients (aged 57-79 yr) anaesthetized with nitrous oxide, oxygen and isoflurane before surgery and after PE'iso had been stable for at least 15 min. We related these changes to the various indices of pulmonary maldistribution to determine if they were sufficient to explain reported differences between PE'iso and Paiso. Alveolar deadspace dilution of end-expired gas was calculated for carbon dioxide and this dilution factor used to calculate the "ideal" alveolar Piso (PAiso) from the observed inspired and end-expired concentrations. ⋯ The difference was attributable in part to the effects of shunt and deadspace, but also a failure of equilibration of isoflurane between the alveolar gas and pulmonary end-capillary blood. It is likely to be different for other anaesthetics. We conclude that, while PE'iso may adequately reflect Paiso for isoflurane, it cannot be assumed that the relation between end-expiratory gas and arterial partial pressures is the same for all anaesthetics.
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We have performed serial haemodynamic investigations in 20 women undergoing elective Caesarean section under continuous spinal anaesthesia with a 32-gauge catheter with 0.5% heavy bupivacaine. Cardiac output was measured by Doppler and cross-sectional echocardiography at the aortic valve. Doppler flow velocity waveforms were recorded also from the umbilical artery. ⋯ Two subjects developed hypotension, although mean values of arterial pressure and umbilical artery pulsatility index did not change. The median umbilical artery pH was 7.27 (range 6.98-7.32) and there was a significant correlation between pH and the maximum percentage decrease in cardiac output. The results suggest that continuous spinal anaesthesia is associated with greater haemodynamic stability than single bolus spinal injection.
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Randomized Controlled Trial Clinical Trial
Efficacy of postoperative pain treatment regimens using both buprenorphine and papaveretum sequentially after abdominal hysterectomy.
We have undertaken a double-blind, controlled study to test the hypothesis that the efficacy of standard postoperative analgesia by papaveretum or buprenorphine is not compromised by previous or subsequent standard doses of the other agent. After total abdominal hysterectomy under a standardized general anaesthetic, 120 patients (four groups of 30) were allocated randomly to receive, on demand, a single i.v. dose of buprenorphine 0.15 mg or papaveretum 10 mg, followed sequentially by a single dose of i.m. buprenorphine 0.3 mg or papaveretum 20 mg. Three hours after the i.m. dose, all patients received sublingual buprenorphine 0.4 mg. ⋯ Observations were continued for 8 h after operation. The efficacy of papaveretum or buprenorphine was not compromised by previous or subsequent standard doses of the other agent. All four treatment regimens were similarly well tolerated and gave acceptable analgesia in the immediate postoperative period.
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Hypotension during central neural block may occur by three main mechanisms: decrease in venous return (in turn influenced by posture, bleeding and inferior vena cava compression), vasodilatation and decreased cardiac output. It is also important to recognize that, occasionally, other factors play a part. Bladder distension during central nerve block has been shown to produce hypotension inappropriate to the level of block [48, 62] and vagal overactivity may contribute in the unsedated patient. ⋯ The administration of up to 1 litre before surgery may be particularly advisable if significant blood loss is expected (no matter what the anaesthetic technique), but colloid solutions do not have clear proven benefit over crystalloid. The prevention or treatment of hypotension induced by central block by administration of large volumes of fluid is a more contentious subject, although the practice is widespread. Review of the literature has shown that many studies have been poorly designed and the results have often been contradictory, even in such basic principles as the incidence of hypotension in control groups.(ABSTRACT TRUNCATED AT 250 WORDS)
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Randomized Controlled Trial Comparative Study Clinical Trial
Pharmacokinetics and pharmacodynamics of ketamine enantiomers in surgical patients using a stereoselective analytical method.
In a randomized, double-blind study, we have examined the stereoselective disposition and pharmacodynamic characteristics of ketamine in surgical patients after i.v. administration of S(+)-ketamine 1 mg/kg body weight (25 patients) or racemic ketamine 2 mg/kg body weight (25 patients). S(+)-Ketamine was not inverted to R(-)-ketamine. After racemate administration we observed statistically significant (P < 0.01) smaller clearance and volume of distribution for R(-)-ketamine compared with S(+)-ketamine. ⋯ Systolic and diastolic arterial pressure and heart rate increased significantly (P < 0.005) in both groups. At 1, 3 and 15 min after S(+)-ketamine administration, significantly greater increase in systolic and diastolic pressures were observed compared with the racemate group. There was no correlation between the changes in haemodynamic variables and plasma catecholamine concentrations, which remained unaffected after administration of the medications.