British journal of anaesthesia
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Clinical Trial Controlled Clinical Trial
Minimum local analgesic concentration of extradural bupivacaine increases with progression of labour.
We have used the technique of double-blind sequential allocation to quantify the minimum local analgesic concentration (MLAC) of extradural bupivacaine for women in early (median cervical dilatation 2 cm) and late (median cervical dilatation 5 cm) labour. The first bolus was 20 ml of the bupivacaine test solution. The concentration was determined by the response of the previous woman to a higher or lower concentration of bupivacaine according to up and down sequential allocation. ⋯ In early labour, the MLAC of bupivacaine was 0.048% w/v (95% confidence intervals (CI) 0.037-0.058% w/v), and 0.140% w/v (95% CI 0.132-0.150% w/v) in the late group. The MLAC of bupivacaine in late labour was greater by a factor of 2.9 (95% CI 2.7-3.2) compared with the MLAC in early labour (P < 0.0001, 95% CI difference 0.08-0.11). We conclude that advancing labour requires an increased concentration of extradural bupivacaine for pain relief.
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Comparative Study
Analysis of the EEG bispectrum, auditory evoked potentials and the EEG power spectrum during repeated transitions from consciousness to unconsciousness.
We have compared the auditory evoked potential (AEP) index (a numerical index derived from the AEP), 95% spectral edge frequency (SEF), median frequency (MF) and the bispectral index (BIS) during alternating periods of consciousness and unconsciousness produced by target-controlled infusions of propofol. We studied 12 patients undergoing hip or knee replacement under spinal anaesthesia. During periods of consciousness and unconsciousness, respective mean values for the four measurements were: AEP index, 60.8 (SD 13.7) and 37.6 (6.5); BIS, 85.1 (8.2) and 66.8 (10.5); SEF, 24.2 (2.2) and 18.7 (2.1); and MF, 10.9 (3.3) and 8.8 (2.0). ⋯ There was no recorded value for MF that was 100% specific for unconsciousness. Of the four measurements, only AEP index demonstrated a significant difference (P < 0.05) between all mean values 1 min before recovery of consciousness and all mean values 1 min after recovery of consciousness. Our findings suggest that of the four electrophysiological variables, AEP index was best at distinguishing the transition from unconsciousness to consciousness.
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We have studied prospectively the clinical course and serum concentrations of thromboxane B2 (TxB2) and leukotriene B4 (LTB4) in patients developing adult respiratory distress syndrome (ARDS) after oesophagectomy. The clinical course was assessed according to a validated ARDS score, and intra- and postoperative measurements of TxB2 and LTB4 in pre- and post-pulmonary blood were performed in 18 patients undergoing oesophagectomy for oesophageal carcinoma and 11 control patients undergoing thoracotomy and pulmonary resection. Six of 18 patients undergoing oesophagectomy, but no control patient, developed ARDS. ⋯ Only patients with ARDS had a significant postoperative increase in post-pulmonary, but not pre-pulmonary, TxB2 concentrations (P < 0.05 vs patients without ARDS). This study provides evidence that TxA2, originating from the lungs, was associated with the development of ARDS after oesophageal resection. In view of the high incidence of ARDS after oesophagectomy (10-30%), prophylactic treatment of patients undergoing oesophageal resection with clinically applicable thromboxane synthetase inhibitors may be warranted.