Publications
42 results found
Fiorentino F, Jaaly EA, Durham AL, et al., 2019, Low-frequency ventilation during cardiopulmonary bypass for lung protection: A randomized controlled trial, Journal of Cardiac Surgery, Vol: 34, Pages: 385-399, ISSN: 0886-0440
OBJECTIVE: Pulmonary dysfunction is a common complication in patients undergoing heart surgery. Current clinical practice does not include any specific strategy for lung protection. To compare the anti-inflammatory effects of low-frequency ventilation (LFV), as measured by nuclear factor κ-light-chain-enhancer of activated B cells (NF-κB) p65 pathway activation, for the entire cardiopulmonary bypass (CPB) vs both lungs left collapsed in patients undergoing coronary artery bypass grafting (CABG). METHODS: Two groups parallel randomized controlled trial. The primary outcome was inflammation measured by NF-κB p65 activation in pre- and post-CPB lung biopsies. Secondary outcomes were additional inflammatory markers in both biopsy tissue and blood. RESULTS: Thirty-seven patients were randomly allocated to LFV (18) and to both lungs left collapsed (19). The mean concentration of NF-κB p65 in the biopsies before chest closure (adjusted for pre-CPB concentration) was higher in the LFV group compared to both lungs left collapsed group but this was not significant (0.102, 95% confidence interval, -0.022 to 0.226, P = 0.104). There were no significant differences between groups in the other inflammatory markers measured in tissue and blood. CONCLUSIONS: In patients undergoing elective CABG, the use of LFV during CPB when compared to both lungs left collapsed does not seem to reduce inflammation in lung biopsies and blood.
Lockwood GG, Cabreros L, Banach D, et al., 2017, Continuous bilateral thoracic paravertebral blockade for analgesia after cardiac surgery: a randomised, controlled trial, PERFUSION-UK, Vol: 32, Pages: 591-597, ISSN: 0267-6591
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- Citations: 9
Jones JG, Lockwood GG, Fung N, et al., 2016, Influence of pulmonary factors on pulse oximeter saturation in preterm infants, ARCHIVES OF DISEASE IN CHILDHOOD-FETAL AND NEONATAL EDITION, Vol: 101, Pages: F319-F322, ISSN: 1359-2998
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- Citations: 13
Lockwood GG, Fung NLS, Jones JG, 2014, Evaluation of a computer program for non-invasive determination of pulmonary shunt and ventilation-perfusion mismatch, JOURNAL OF CLINICAL MONITORING AND COMPUTING, Vol: 28, Pages: 581-590, ISSN: 1387-1307
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- Citations: 27
Koertzen M, Punjabi PP, Lockwood GG, 2013, Pre-operative serum albumin concentration as a predictor of mortality and morbidity following cardiac surgery, PERFUSION-UK, Vol: 28, Pages: 390-394, ISSN: 0267-6591
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- Citations: 22
Nawaz MA, Patni R, Chan KMJ, et al., 2011, Hyperinflation of lungs during redo-sternotomy, a safer technique, Heart Lung and Circulation, Vol: 20, Pages: 722-723
Lockwood G, 2010, Theoretical context-sensitive elimination times for inhalation anaesthetics., Br J Anaesth, Vol: 104, Pages: 648-655
BACKGROUND: Context-sensitive times to 50%, 80%, and 90% elimination from the brain have been calculated for volatile anaesthetics. This does not represent complete recovery because there are important residual effects even at 90% elimination, and the effect of anaesthetic metabolism on the rate of elimination has not been considered. METHODS: A physiologically based model of anaesthetic uptake and distribution was elaborated to include anaesthetic metabolism and fluoride kinetics. It was validated by comparing its predictions with real data, then experiments were undertaken to calculate the partial pressure of anaesthetic in the brain after the administration of 1 MAC of halothane, enflurane, isoflurane, sevoflurane or desflurane, or 50% of inspired nitrous oxide or xenon, for up to 6 h. RESULTS: The model generated data that were compatible with many published measurements of anaesthetic kinetics and fluoride production. Metabolism had a negligible effect on kinetics. After 4 h of anaesthesia, the model predicted body content to be 28 g nitrous oxide, 26 g desflurane, 14 g sevoflurane, or 15 g isoflurane, and 99.9% brain elimination times were then 9 h for nitrous oxide, 33 h for desflurane, 52 h for sevoflurane, and 71 h for isoflurane. At this stage of elimination, the whole body still retained between 4% and 13% of the absorbed dose. Differences between sevoflurane and desflurane were obvious only during the final stages of elimination (>99% from the vessel-rich group). CONCLUSIONS: Large amounts of anaesthetics are absorbed during anaesthesia and significant amounts remain in the body for days after apparent recovery.
Lockwood GG, Franks NP, Downie NA, et al., 2006, Feasibility and safety of delivering xenon to patients undergoing coronary artery bypass graft surgery while on cardiopulmonary bypass - Phase I study, ANESTHESIOLOGY, Vol: 104, Pages: 458-465, ISSN: 0003-3022
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- Citations: 42
Lockwood GG, Aleksander I, 2003, Predicting the behaviour of G-RAM networks, NEURAL NETWORKS, Vol: 16, Pages: 91-100, ISSN: 0893-6080
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- Citations: 7
Lockwood G, 2002, Expansion of air bubbles in aqueous solutions of nitrous oxide or xenon., Br J Anaesth, Vol: 89, Pages: 282-286, ISSN: 0007-0912
BACKGROUND: Anaesthesia using xenon may be contraindicated in some situations because of its diffusion into intravascular bubbles. The expansion of air bubbles in water equilibrated with either nitrous oxide or xenon was studied. METHODS: Equilibrated water was transferred to a stirred vial, closed except for a long, narrow-bore tube. Injection of an air bubble caused displacement of water along the tube, allowing expansion of the bubble to be charted on a linear scale. RESULTS: At 20 degrees C, bubbles expanded from 10 microliters to a median volume of 23 microliters (range 20-23 microliters) and 30 microliters (range 27-34 microliters) in water equilibrated with xenon and nitrous oxide, respectively. Half of the expansion took place in the first 20 s (15-45 s) for xenon and in the first 5 s (5-10 s) for nitrous oxide. At 37 degrees C the expansion was less with both gases, but the relative differences were maintained between them. CONCLUSION: Xenon anaesthesia may be less likely to aggravate injury from intravascular bubbles than anaesthesia with nitrous oxide.
Lockwood GG, White DC, 2001, Measuring the costs of inhaled anaesthetics., Br J Anaesth, Vol: 87, Pages: 559-563, ISSN: 0007-0912
The cost of inhalation anaesthesia has received considerable study and is undoubtedly reduced by the use of low fresh gas flows. However, comparison between anaesthetics of the economies achievable has only been made by computer modelling. We have computed anaesthetic usage for MAC-equivalent anaesthesia with isoflurane, desflurane, and sevoflurane in closed and open breathing systems. We have compared these data with those derived during clinical anaesthesia administered using a computer-controlled closed system that measures anaesthetic usage and inspired concentrations. The inspired concentrations allow the usage that would have occurred in an open system to be calculated. Our computed predictions lie within the 95% confidence intervals of the measured data. Using prices current in our institution, sevoflurane and desflurane would cost approximately twice as much as isoflurane in open systems but only about 50% more than isoflurane in closed systems. Thus computer predictions have been validated by patient measurements and the cost saving achieved by reducing the fresh gas flow is greater with less soluble anaesthetics.
Renna M, Lang EM, Lockwood GG, 2000, The effect of sevoflurane on implicit memory: a double-blind, randomised study, ANAESTHESIA, Vol: 55, Pages: 634-640, ISSN: 0003-2409
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- Citations: 13
Bagary M, Fluck E, File SE, et al., 2000, Is benzodiazepine-induced amnesia due to deactivation of the left prefrontal cortex?, PSYCHOPHARMACOLOGY, Vol: 150, Pages: 292-299, ISSN: 0033-3158
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- Citations: 22
Lockwood GG, Dziersk J, Sapsed-Byrne SM, 1999, Potential errors in the measurement of anesthetic partial pressure in blood., Anesthesiology, Vol: 91, Pages: 1550-1553, ISSN: 0003-3022
Holdcroft A, Bose D, Sapsed-Byrne SM, et al., 1999, Arterial to inspired partial pressure ratio of halothane, isoflurane, sevoflurane and desflurane in rats, BRITISH JOURNAL OF ANAESTHESIA, Vol: 83, Pages: 618-621, ISSN: 0007-0912
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- Citations: 11
Lockwood GG, Sapsed-Byrne SM, Adams S, 1999, A comparison of anaesthetic tensions in arterial blood and oxygenator exhaust gas during cardiopulmonary bypass., Anaesthesia, Vol: 54, Pages: 434-436, ISSN: 0003-2409
This study evaluates the usefulness of the analysis of gas sampled from the exhaust port of a membrane oxygenator in the estimation of anaesthetic tension in arterial blood. Sixty-seven arterial blood samples were drawn from patients undergoing hypothermic cardiopulmonary bypass with anaesthesia maintained by either isoflurane or desflurane. Anaesthetic tensions in the oxygenator exhaust gas were measured using an infrared analyser and in arterial blood using a two-stage headspace technique with a gas chromatograph. Both measurement systems were calibrated with the same standard gas mixtures. There was no difference in anaesthetic tension measured in arterial blood and gas leaving the oxygenator exhaust (isoflurane: n = 29, range: 0.3-0.8%, 95% limits of agreement: -0.08% to 0.09%; desflurane: n = 38, range: 1.5-5.4%; 95% limits of agreement -0.65% to 0.58%). We conclude that anaesthetic tensions in arterial blood can be accurately monitored by analysis of the gas emerging from the exhaust port of a membrane oxygenator.
Shaw AD, Chamberlain SK, Spased-Byrne SM, et al., 1998, Nitrous oxide and carbon dioxide have no effect on the blood-gas solubilities of sevoflurane and isoflurane., Anesth Analg, Vol: 87, Pages: 1412-1415, ISSN: 0003-2999
UNLABELLED: Nitrous oxide (N2O) has been shown to decrease the solubility (lambdaB:G) of volatile anesthetics in human blood and, consequently, affect their rate of uptake. If this is true, then carbon dioxide (CO2) may also have an effect, which is important because methods that measure the tension of volatile anesthetics in blood washout CO2 in the process. Blood samples were obtained from fasted, healthy volunteers and patients undergoing major surgery. Each sample was divided into two aliquots: one was equilibrated at 37 degrees C in a closed glass tonometer with a mixture of isoflurane 1% and sevoflurane 2% in a test gas mixture of either 50:50 N2O/O2 or 5:95 CO2/O2; the other aliquot was equilibrated with isoflurane and sevoflurane in O2 alone as a control. Using a two-stage headspace technique using gas chromatography, we measured the lambdaB:G of isoflurane and sevoflurane in the presence and absence of the test gas in each subject. There was no significant difference between the lambdaB:G of sevoflurane and isoflurane obtained from the N2O group and their controls or between the CO2 group and their controls. We conclude that neither N2O nor CO2 has an effect on the lambdaB:G of sevoflurane or isoflurane in the concentrations tested. IMPLICATIONS: The blood solubilities of sevoflurane and isoflurane were measured with and without nitrous oxide and carbon dioxide. No differences were found. Nitrous oxide does not affect the kinetics of other anesthetics by altering their solubility. Carbon dioxide tensions need not be controlled when measuring anesthetic tensions in blood.
Vagts DA, Lockwood GG, 1998, The uptake of sevoflurane during anaesthesia., Anaesthesia, Vol: 53, Pages: 862-866, ISSN: 0003-2409
The rate of uptake of sevoflurane during clinical anaesthesia (1.3 MAC) was measured by computer-controlled injection of liquid anaesthetic into a closed breathing system. The cumulative uptake of sevoflurane was 4.8 ml, 7.4 ml, 9.5 ml and 11.5 ml at 30, 60, 90 and 120 min, respectively. The ratio of inspired to end-expired sevoflurane was greater than similar measurements we have made for desflurane in the past, but the absolute rate of sevoflurane uptake was less than the rate of uptake of desflurane in these cases. The rate of uptake was equivalent to 059e-0.32t + 0.039e-0.036t + 0.105e-0.0034t ml.min-1 liquid sevoflurane. Plasma urea and creatinine measured on the first postoperative day were not significantly different from pre-operative values.
Taylor SRJ, Khan OA, Swart ML, et al., 1998, Effects of a low concentration of isoflurane on contrast sensitivity in volunteers, BRITISH JOURNAL OF ANAESTHESIA, Vol: 81, Pages: 176-179, ISSN: 0007-0912
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- Citations: 6
Ma DQ, Wang C, Soo CKP, et al., 1998, The effect of sevoflurane on spontaneous sympathetic activity, Aγ and C somatosympathetic reflexes, and associated hemodynamic changes in dogs, ANESTHESIA AND ANALGESIA, Vol: 86, Pages: 1079-1083, ISSN: 0003-2999
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- Citations: 9
Hall JD, Lockwood GG, 1998, Bispectral index: comparison of two montages., Br J Anaesth, Vol: 80, Pages: 342-344, ISSN: 0007-0912
We have compared fronto-central and bifrontal montages using a new EEG monitor, the Aspect A-1000. The monitor uses bispectral analysis to derive an index of anaesthetic depth, the bispectral index (BIS). We compared reliability, impedance and BIS for each montage. ECG electrodes placed in a bifrontal montage were more reliable than silver dome electrodes in a fronto-central montage and both types of electrodes had impedances in the clinically useful range. However, BIS values derived from each montage were found to differ in an unpredictable manner. The bifrontal montage is easy to apply and reliable but it is not comparable with a fronto-central montage. We conclude that the BIS may be useful for following trends in anaesthetic depth in individual cases but it is less helpful when making comparison between patients or as a single value.
Lockwood GG, Dob DP, Bryant DJ, et al., 1997, Magnetic resonance spectroscopy of isoflurane kinetics in humans .1. Elimination from the head, BRITISH JOURNAL OF ANAESTHESIA, Vol: 79, Pages: 581-585, ISSN: 0007-0912
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- Citations: 10
Lockwood GG, Dob DP, Bryant DJ, et al., 1997, Magnetic resonance spectroscopy of isoflurane kinetics in humans .2. Functional localization, BRITISH JOURNAL OF ANAESTHESIA, Vol: 79, Pages: 586-589, ISSN: 0007-0912
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- Citations: 8
Lockwood GG, SapsedByrne SM, Smith MA, 1997, Effect of temperature on the solubility of desflurane, sevoflurane, enflurane and halothane in blood, BRITISH JOURNAL OF ANAESTHESIA, Vol: 79, Pages: 517-520, ISSN: 0007-0912
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- Citations: 37
Vagts DA, Lockwood GG, 1997, The loss of sevoflurane from a closed breathing system., Anaesthesia, Vol: 52, Pages: 636-639, ISSN: 0003-2409
When volatile anaesthetics are used in a closed breathing system it is usually assumed that inflow of anaesthetic to the system matches uptake by the patient. Early laboratory reports on the interactions between sevoflurane and soda lime cast doubt on that assumption. We have measured the loss of sevoflurane, desflurane and isoflurane from a closed breathing system and found no differences of consequences.
Smith MA, SapsedByrne SM, Lockwood GG, 1997, A new method for measurement of anaesthetic partial pressure in blood, BRITISH JOURNAL OF ANAESTHESIA, Vol: 78, Pages: 449-452, ISSN: 0007-0912
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- Citations: 26
Toner I, Taylor KM, Lockwood G, et al., 1997, EEG changes during cardiopulmonary bypass surgery and postoperative neuropsychological deficit: The effect of bubble and membrane oxygenators, EUROPEAN JOURNAL OF CARDIO-THORACIC SURGERY, Vol: 11, Pages: 312-319, ISSN: 1010-7940
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- Citations: 11
Susay SR, Smith MA, Lockwood GG, 1996, The saturated vapor pressure of desflurane at various temperatures, ANESTHESIA AND ANALGESIA, Vol: 83, Pages: 864-866, ISSN: 0003-2999
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- Citations: 6
Gowrie-Mohan S, Muralitharan V, Lockwood GG, 1996, The estimation of inspired desflurane concentration in a low-flow system., Anaesthesia, Vol: 51, Pages: 904-907, ISSN: 0003-2409
We have examined the predictability of inspired desflurane concentration during low-flow anaesthesia using a to-and-fro breathing system. Twenty-two adult patients requiring mechanical ventilation of the lungs during surgery took part in the study. Using a fresh gas flow of 1 l.min-1, the ratio of inspired desflurane concentration to desflurane vaporizer setting was found to be approximately 0.75 after 9 min of anaesthesia and at 2 l.min-1 fresh gas flow the ratio was approximately 0.9 after 2 min of anaesthesia. These ratios were maintained throughout the procedure, except for a few minutes following each change in vaporizer setting.
Pac-Soo CK, Deacock S, Lockwood G, et al., 1996, Patient-controlled sedation for cataract surgery using peribulbar block., Br J Anaesth, Vol: 77, Pages: 370-374, ISSN: 0007-0912
Patients undergoing cataract surgery using peribulbar block were allocated randomly to self-administer doses of either midazolam 0.1 mg or propofol 3.3 mg without a lock-out facility; in the control group the syringe was charged with saline, not as a placebo, but to "blind" the surgeon and the nurse observer. For midazolam and propofol, median doses were 2.54 (0.1-6.0) mg and 87.4 (0-145) mg, respectively. Patient-controlled sedation significantly reduced the level of anxiety, with median visual analogue anxiety scores in the midazolam, propofol and saline groups of 5 (0-38) mm, 5 (0-25) mm and 15 (0-92) mm, respectively (P < 0.05). Some patients did not administer the sedative when available while others in the saline group would have benefited from anxiolytic drugs. While both drugs prevented an increase in heart rate, only midazolam prevented an increase in arterial pressure during surgery.
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