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Peter Biro - One of the best experts on this subject based on the ideXlab platform.
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Reliability of the Volatile Agent consumption display in the Draeger Primus™ anesthesia machine
Journal of Clinical Monitoring and Computing, 2015Co-Authors: Peter Biro, Oliver Kneschke, Oliver M. TheusingerAbstract:Knowledge of the consumed amount of Volatile anesthetic (VA) expressed in liquid Agent is necessary to enable Agent sparing dosing measures and for billing purposes. The widespread Draeger Primus™ anesthesia machine displays in its logbook the amount of consumed VA at the end of each anesthesia, but the reliability of this parameter is yet unknown. The objective was to evaluate the precision and reliability of the inbuilt VA consumption display in Draeger Primus™ anesthesia machines as compared with the gold standard of weighing the vaporizer before and after anesthesia. In this prospective laboratory investigation we compared the VA consumption displayed by the Draeger Primus™ anesthesia machine with measured vaporizer weight differences before and after 10 sevoflurane and 10 desflurane anesthesias. We assessed the average difference and spread of values between the predicted (displayed) and measured (control) values for VA consumption. The displayed sevoflurane consumption overestimated the measured values by 4.3 ± 5.4 ml (7.6 %). The displayed desflurane consumption underestimated the measured values by −3.5 ± 6.3 ml (6.2 %). Nine from 10 sevoflurane pairs of values and all desflurane pairs of values were within ±1.96 SD. The displayed VA consumption calculations for sevoflurane and desflurane in the Draeger Primus™ are sufficiently reliable to estimate the pharmacoeconomic impact of VA delivery during inhalational anesthesia.
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Accuracy of calculated Volatile Agent consumption from fresh gas content
Acta anaesthesiologica Scandinavica, 2015Co-Authors: Peter Biro, Oliver Kneschke, Oliver M. TheusingerAbstract:BACKGROUND: Case-by-case assessment of Volatile anesthetic (VA) consumption is necessary to perform Agent sparing dosing measures and for billing purposes. The gold standard technique for this purpose is to measure the weight difference of the vaporizer that occurs during VA delivery. Because suitable equipment is rarely available and weighing the vaporizer is only possible in prospectively planned fashion, a calculation method from recorded fresh gas flow (FGF) and VA courses is a viable alternative. The objective was to evaluate the accuracy of VA calculation from fresh gas composition vs. the gold standard of weighing the vaporizer before and after anesthesia. METHODS: In this prospective laboratory investigation, we compared the formula-based calculations of VA consumption to the measured vaporizer weight differences before and after 10 sevoflurane and 10 desflurane anesthesia. We assessed the average difference and spread of values between the calculated and the measured values. RESULTS: The calculated sevoflurane consumption overestimated the measured values by 3.0 ± 2.9 ml (6.2%). The calculated desflurane consumption overestimated the measured values by 3.5 ± 6.7 ml (5.0%). All pairs of values from both Agents were within ± 1.96 standard deviations. CONCLUSION: The calculated VA consumption for sevoflurane and desflurane are sufficiently accurate to estimate the economic impact of VA delivery during inhalational anesthesia. This method enables the assessment of VA consumption both ways: (1) retrospectively from sufficiently detailed and accurate anesthesia recordings, as well as (2) by using this method in a prospective setting.
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calculation of Volatile anaesthetics consumption from Agent concentration and fresh gas flow
Acta Anaesthesiologica Scandinavica, 2014Co-Authors: Peter BiroAbstract:Background The assessment of Volatile Agents' consumption can be performed by weighing vapourisers before and after use. This method is technically demanding and unavailable for retrospective analysis of anaesthesia records. Therefore, a method based on calculations from fresh gas flow and Agent concentration is presented here. Methods The presented calculation method herein enables a precise estimation of Volatile Agent consumption when average fresh gas flows and Volatile Agent concentrations are known. A pre-condition for these calculations is the knowledge of the vapour amount deriving from 1 ml fluid Volatile Agent. The necessary formulas for these calculations and an example for a sevoflurane anaesthesia are presented. Results The amount of Volatile Agent vapour deriving from 1 ml of fluid Agent are for halothane 229 ml, isoflurane 195 ml, sevoflurane 184 m, and desflurane 210 ml. The constant for sevoflurane is used in a fictitious clinical case to exemplify the calculation of its consumption in daily routine resulting in a total expenditure of 23.6 ml liquid Agent. Conclusions By application of the presented specific Volatile Agent constants and equations, it becomes easy to calculate Volatile Agent consumption if the fresh gas flows and the resulting inhaled concentration of the Volatile Agent are known. By this method, it is possible to extract data about Volatile Agent consumption both ways: (1) retrospectively from sufficiently detailed and accurate anaesthesia recordings, as well as (2) by application of this method in a prospective setting. Therefore, this method is a valuable contribution to perform pharmacoeconomical surveys.
Joseph D. Tobias - One of the best experts on this subject based on the ideXlab platform.
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A preliminary study of Volatile Agents or total intravenous anesthesia for neurophysiological monitoring during posterior spinal fusion in adolescents with idiopathic scoliosis.
Spine, 2014Co-Authors: David P Martin, Julie Rice, Tarun Bhalla, Arlyne Thung, Allan Beebe, Walter P Samora, Jan Klamar, Joseph D. TobiasAbstract:STUDY DESIGN A prospective randomized controlled trial. OBJECTIVE The purpose of this study was to prospectively compare the efficacy of neurophysiological monitoring during general anesthesia with either a total intravenous technique or with the Volatile anesthetic Agent, desflurane. SUMMARY OF BACKGROUND DATA A total intravenous anesthetic technique is generally chosen when neurophysiological monitoring is used as it has been shown to facilitate such monitoring. Despite this, with prolonged infusions of propofol, prolonged awakening times may be seen, which may impact the time required for postoperative neurological assessment or more importantly result in significant delays, should a wake-up test become necessary. To date, there are no prospective trials comparing intravenous techniques with a Volatile Agent-based anesthetic technique and its effects on neurophysiological monitoring. METHODS This prospective study compares somatosensory evoked potential and motor evoked potential monitoring during posterior spinal fusion in 30 adolescents. The patients were randomized to receive a total intravenous technique with propofol-remifentanil or a Volatile Agent-based technique with desflurane-remifentanil. RESULTS The groups were similar with regard to age, weight, height, body mass index, Cobb angle, and distribution of Lenke classifications. No differences were noted in anesthesia time, surgery time, intraoperative fluids, or estimated blood loss between the 2 groups. Time to eye opening, time to following commands, and time to tracheal extubation were shorter in the Volatile anesthesia group than the total intravenous anesthesia group. No clinically significant difference was noted in the amplitude or latency of somatosensory evoked potential monitoring. Although statistically significantly greater voltage amplitude was required to generate a motor evoked potential, the voltage amount was within a clinically acceptable range. CONCLUSION Our data demonstrate that a Volatile Agent-based anesthetic regimen is feasible even during neurophysiological monitoring. Advantages include a more rapid awakening and the feasibility of a rapid wake-up test (
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a preliminary study of Volatile Agents or total intravenous anesthesia for neurophysiological monitoring during posterior spinal fusion in adolescents with idiopathic scoliosis
Spine, 2014Co-Authors: David P Martin, Julie Rice, Tarun Bhalla, Arlyne Thung, Allan Beebe, Walter P Samora, Jan Klamar, Joseph D. TobiasAbstract:STUDY DESIGN A prospective randomized controlled trial. OBJECTIVE The purpose of this study was to prospectively compare the efficacy of neurophysiological monitoring during general anesthesia with either a total intravenous technique or with the Volatile anesthetic Agent, desflurane. SUMMARY OF BACKGROUND DATA A total intravenous anesthetic technique is generally chosen when neurophysiological monitoring is used as it has been shown to facilitate such monitoring. Despite this, with prolonged infusions of propofol, prolonged awakening times may be seen, which may impact the time required for postoperative neurological assessment or more importantly result in significant delays, should a wake-up test become necessary. To date, there are no prospective trials comparing intravenous techniques with a Volatile Agent-based anesthetic technique and its effects on neurophysiological monitoring. METHODS This prospective study compares somatosensory evoked potential and motor evoked potential monitoring during posterior spinal fusion in 30 adolescents. The patients were randomized to receive a total intravenous technique with propofol-remifentanil or a Volatile Agent-based technique with desflurane-remifentanil. RESULTS The groups were similar with regard to age, weight, height, body mass index, Cobb angle, and distribution of Lenke classifications. No differences were noted in anesthesia time, surgery time, intraoperative fluids, or estimated blood loss between the 2 groups. Time to eye opening, time to following commands, and time to tracheal extubation were shorter in the Volatile anesthesia group than the total intravenous anesthesia group. No clinically significant difference was noted in the amplitude or latency of somatosensory evoked potential monitoring. Although statistically significantly greater voltage amplitude was required to generate a motor evoked potential, the voltage amount was within a clinically acceptable range. CONCLUSION Our data demonstrate that a Volatile Agent-based anesthetic regimen is feasible even during neurophysiological monitoring. Advantages include a more rapid awakening and the feasibility of a rapid wake-up test (<5 min) in the event that irreversible changes in neurophysiological monitoring are noted. LEVEL OF EVIDENCE 2.
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effect of cuffed and uncuffed endotracheal tubes on the oropharyngeal oxygen and Volatile anesthetic Agent concentration in children
International Journal of Pediatric Otorhinolaryngology, 2012Co-Authors: Vidya T Raman, Charles A Elmaraghy, Meredith Merz, Julie Rice, Jason Bryant, Kris R Jatana, Joseph D. Tobias, Richard D KangAbstract:Abstract Background Over the past 5 years, there has been a change in the clinical practice of pediatric anesthesiology with a transition to the use of cuffed instead of uncuffed endotracheal tubes (ETTs) in infants and children. As the trachea is sealed, one advantage is to eliminate the contamination of the oropharynx with oxygen which should be advantageous during adenotonsillectomy where there is a risk of airway fire. The current study prospectively assesses the oropharyngeal oxygen and Volatile anesthetic Agent concentration during adenotonsillectomy in infants and children. Methods Following the induction of general anesthesia in patients scheduled for adenoidectomy, tonsillectomy or adenotonsillectomy, the trachea was intubated. The use of a cuffed or uncuffed ETT and the use of spontaneous (SV) or positive pressure ventilation (PPV) were at the discretion of the anesthesia team. The oxygen concentration was kept at 100% oxygen until the study was completed. Following placement of the mouth gag, the otolaryngolist placed into the oropharynx a small bore catheter, which was attached to a standard anesthesia gas monitoring device which sampled the gas at 150 mL/min. The concentration of the oxygen and the concentration of the anesthetic Agent in the oropharynx were measured for 5 breaths. Results The cohort for the study included 200 patients ranging in age from 1 to 18 years. With the use of a cuffed ETT and either SV or PPV, the oxygen concentration in the oropharynx was 20–21% and the Volatile Agent concentration was 0% in all 118 patients. With the use of an uncuffed ETT and the administration of 100% oxygen, there was significant contamination of the oropharynx noted during both PPV and SV. The mean oxygen concentration was 71% during PPV with an uncuffed ETT and 65% during SV with an uncuffed ETT. In these patients, the oropharyngeal oxygenation concentration exceeded 30% in 73 of the 82 patients (89%). The oropharyngeal oxygen and Agent concentration was greater when the leak around the uncuffed ETT was ≥10 cmH 2 O versus less than 10 cmH 2 O and when the leak around the uncuffed ETT was ≥15 cmH 2 O versus less than 15 cmH 2 O. Conclusions With the use of an uncuffed ETT and the administration of 100% oxygen, there was significant contamination of the oropharynx noted during both PPV and SV. The oropharyngeal concentration of oxygen is high enough to support combustion in the majority of patients. The use of a cuffed ETT eliminates oropharyngeal contamination with oxygen during the administration of anesthesia and may be useful in limiting the incidence of an airway fire.
Oliver M. Theusinger - One of the best experts on this subject based on the ideXlab platform.
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Reliability of the Volatile Agent consumption display in the Draeger Primus™ anesthesia machine
Journal of Clinical Monitoring and Computing, 2015Co-Authors: Peter Biro, Oliver Kneschke, Oliver M. TheusingerAbstract:Knowledge of the consumed amount of Volatile anesthetic (VA) expressed in liquid Agent is necessary to enable Agent sparing dosing measures and for billing purposes. The widespread Draeger Primus™ anesthesia machine displays in its logbook the amount of consumed VA at the end of each anesthesia, but the reliability of this parameter is yet unknown. The objective was to evaluate the precision and reliability of the inbuilt VA consumption display in Draeger Primus™ anesthesia machines as compared with the gold standard of weighing the vaporizer before and after anesthesia. In this prospective laboratory investigation we compared the VA consumption displayed by the Draeger Primus™ anesthesia machine with measured vaporizer weight differences before and after 10 sevoflurane and 10 desflurane anesthesias. We assessed the average difference and spread of values between the predicted (displayed) and measured (control) values for VA consumption. The displayed sevoflurane consumption overestimated the measured values by 4.3 ± 5.4 ml (7.6 %). The displayed desflurane consumption underestimated the measured values by −3.5 ± 6.3 ml (6.2 %). Nine from 10 sevoflurane pairs of values and all desflurane pairs of values were within ±1.96 SD. The displayed VA consumption calculations for sevoflurane and desflurane in the Draeger Primus™ are sufficiently reliable to estimate the pharmacoeconomic impact of VA delivery during inhalational anesthesia.
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Accuracy of calculated Volatile Agent consumption from fresh gas content
Acta anaesthesiologica Scandinavica, 2015Co-Authors: Peter Biro, Oliver Kneschke, Oliver M. TheusingerAbstract:BACKGROUND: Case-by-case assessment of Volatile anesthetic (VA) consumption is necessary to perform Agent sparing dosing measures and for billing purposes. The gold standard technique for this purpose is to measure the weight difference of the vaporizer that occurs during VA delivery. Because suitable equipment is rarely available and weighing the vaporizer is only possible in prospectively planned fashion, a calculation method from recorded fresh gas flow (FGF) and VA courses is a viable alternative. The objective was to evaluate the accuracy of VA calculation from fresh gas composition vs. the gold standard of weighing the vaporizer before and after anesthesia. METHODS: In this prospective laboratory investigation, we compared the formula-based calculations of VA consumption to the measured vaporizer weight differences before and after 10 sevoflurane and 10 desflurane anesthesia. We assessed the average difference and spread of values between the calculated and the measured values. RESULTS: The calculated sevoflurane consumption overestimated the measured values by 3.0 ± 2.9 ml (6.2%). The calculated desflurane consumption overestimated the measured values by 3.5 ± 6.7 ml (5.0%). All pairs of values from both Agents were within ± 1.96 standard deviations. CONCLUSION: The calculated VA consumption for sevoflurane and desflurane are sufficiently accurate to estimate the economic impact of VA delivery during inhalational anesthesia. This method enables the assessment of VA consumption both ways: (1) retrospectively from sufficiently detailed and accurate anesthesia recordings, as well as (2) by using this method in a prospective setting.
Walid Habre - One of the best experts on this subject based on the ideXlab platform.
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Protective effects of Volatile Agents against acetylcholine-induced bronchoconstriction in isolated perfused rat lungs.
Acta anaesthesiologica Scandinavica, 2006Co-Authors: Eniko Lele, Ferenz Petak, Fabienne Fontao, Denis R. Morel, Walid HabreAbstract:Background: Bronchoactive properties of Volatile Agents against lung constriction are well established. The purpose of this study was to investigate the ability of halothane (Hal), isoflurane (Iso), sevoflurane (Sev) and desflurane (Des) to alter the lung mechanics in the absence of an airway tone and during acetylcholine (Ach)-induced bronchoconstriction. Methods: Low-frequency pulmonary impedance data (ZL) were collected from isolated, normo-perfused rat lungs under baseline conditions and following the injection of Ach (0.1 mg/kg) into the pulmonary artery. Measurements were performed without the administration of any anaesthetic Agent in the first phase of the experiments and during inhalation without any Volatile Agent (control group, n = 6) or during inhalation of Hal (n = 6), Iso (n = 9), Sev (n = 6) or Des (n = 8) at 1 minimum alveolar concentration (MAC). The airway resistance (Raw) and parenchymal damping and elastance were estimated from the ZL data by model fitting. Results: Under baseline conditions, the basic value of Raw was significantly decreased by Des (− 31.2 ± 3.8%) and Sev (− 18.0 ± 4.5%) administration, whereas Hal and Iso did not have a statistically significant effect on Raw (− 3.3 ± 5.1% and − 8.6 ± 2.4%, respectively). Moreover, all four inhalation anaesthetics prevented the increase in Raw following Ach administration, the findings ranging between − 14.3 ± 11.4% for Hal and − 37.5 ± 10.9% for Sev. Conclusions: Our results on a denervated isolated perfused lung model demonstrate the potential of Des and Sev to decrease the basal airway tone, whereas Iso and Hal are ineffective in this regard. All of these Volatile Agents markedly protect against Ach-induced bronchoconstriction.
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Viscosity and density of common anaesthetic gases: implications for flow measurements
British journal of anaesthesia, 2001Co-Authors: Walid Habre, Tibor Asztalos, Peter D. Sly, Ferenc PetákAbstract:Although viscosity (mu) is a crucial factor in measurements of flow with a pneumotachograph, and density (rho) also plays a role in the presence of turbulent flow, these material constants are not available for the Volatile anaesthetic Agents commonly administered in clinical practice. Thus, we determined experimentally mu and rho of pure Volatile anaesthetic Agents. Input impedance of a rigid-wall polyethylene tube (Zt) was measured when the tube was filled with various mixtures of carrier gases (air, 100% oxygen, 50% oxygen+50% nitrogen) to which different concentrations of Volatile anaesthetic inhalation Agents (halothane, isoflurane, sevoflurane, and desflurane) had been added. Mu and rho were calculated from real and imaginary portions of Zt, respectively, using the appropriate physical equations. Multiple linear regression was applied to estimate mu and rho of pure Volatile Agents. Viscosity values of pure Volatile Agents were markedly lower than those for oxygen or nitrogen. Clinically applied concentrations, however, did not markedly affect the viscosity of the gas mixture (maximum of 3.5% decrease in mu for 2 MAC desflurane). In contrast, all of the Volatile Agents significantly affected rho even at routinely used concentrations. Our results suggest that the composition of the carrier gas has a greater impact on viscosity than the amount and nature of the Volatile anaesthetic Agent whereas density is more influenced by Volatile Agent concentrations. Thus, the need for a correction factor in flow measurements with a pneumotachograph depends far more on the carrier gas than the concentration of Volatile Agent administered, although the latter may play a role in particular experimental or clinical settings.
David P Martin - One of the best experts on this subject based on the ideXlab platform.
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a preliminary study of Volatile Agents or total intravenous anesthesia for neurophysiological monitoring during posterior spinal fusion in adolescents with idiopathic scoliosis
Spine, 2014Co-Authors: David P Martin, Julie Rice, Tarun Bhalla, Arlyne Thung, Allan Beebe, Walter P Samora, Jan Klamar, Joseph D. TobiasAbstract:STUDY DESIGN A prospective randomized controlled trial. OBJECTIVE The purpose of this study was to prospectively compare the efficacy of neurophysiological monitoring during general anesthesia with either a total intravenous technique or with the Volatile anesthetic Agent, desflurane. SUMMARY OF BACKGROUND DATA A total intravenous anesthetic technique is generally chosen when neurophysiological monitoring is used as it has been shown to facilitate such monitoring. Despite this, with prolonged infusions of propofol, prolonged awakening times may be seen, which may impact the time required for postoperative neurological assessment or more importantly result in significant delays, should a wake-up test become necessary. To date, there are no prospective trials comparing intravenous techniques with a Volatile Agent-based anesthetic technique and its effects on neurophysiological monitoring. METHODS This prospective study compares somatosensory evoked potential and motor evoked potential monitoring during posterior spinal fusion in 30 adolescents. The patients were randomized to receive a total intravenous technique with propofol-remifentanil or a Volatile Agent-based technique with desflurane-remifentanil. RESULTS The groups were similar with regard to age, weight, height, body mass index, Cobb angle, and distribution of Lenke classifications. No differences were noted in anesthesia time, surgery time, intraoperative fluids, or estimated blood loss between the 2 groups. Time to eye opening, time to following commands, and time to tracheal extubation were shorter in the Volatile anesthesia group than the total intravenous anesthesia group. No clinically significant difference was noted in the amplitude or latency of somatosensory evoked potential monitoring. Although statistically significantly greater voltage amplitude was required to generate a motor evoked potential, the voltage amount was within a clinically acceptable range. CONCLUSION Our data demonstrate that a Volatile Agent-based anesthetic regimen is feasible even during neurophysiological monitoring. Advantages include a more rapid awakening and the feasibility of a rapid wake-up test (<5 min) in the event that irreversible changes in neurophysiological monitoring are noted. LEVEL OF EVIDENCE 2.
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A preliminary study of Volatile Agents or total intravenous anesthesia for neurophysiological monitoring during posterior spinal fusion in adolescents with idiopathic scoliosis.
Spine, 2014Co-Authors: David P Martin, Julie Rice, Tarun Bhalla, Arlyne Thung, Allan Beebe, Walter P Samora, Jan Klamar, Joseph D. TobiasAbstract:STUDY DESIGN A prospective randomized controlled trial. OBJECTIVE The purpose of this study was to prospectively compare the efficacy of neurophysiological monitoring during general anesthesia with either a total intravenous technique or with the Volatile anesthetic Agent, desflurane. SUMMARY OF BACKGROUND DATA A total intravenous anesthetic technique is generally chosen when neurophysiological monitoring is used as it has been shown to facilitate such monitoring. Despite this, with prolonged infusions of propofol, prolonged awakening times may be seen, which may impact the time required for postoperative neurological assessment or more importantly result in significant delays, should a wake-up test become necessary. To date, there are no prospective trials comparing intravenous techniques with a Volatile Agent-based anesthetic technique and its effects on neurophysiological monitoring. METHODS This prospective study compares somatosensory evoked potential and motor evoked potential monitoring during posterior spinal fusion in 30 adolescents. The patients were randomized to receive a total intravenous technique with propofol-remifentanil or a Volatile Agent-based technique with desflurane-remifentanil. RESULTS The groups were similar with regard to age, weight, height, body mass index, Cobb angle, and distribution of Lenke classifications. No differences were noted in anesthesia time, surgery time, intraoperative fluids, or estimated blood loss between the 2 groups. Time to eye opening, time to following commands, and time to tracheal extubation were shorter in the Volatile anesthesia group than the total intravenous anesthesia group. No clinically significant difference was noted in the amplitude or latency of somatosensory evoked potential monitoring. Although statistically significantly greater voltage amplitude was required to generate a motor evoked potential, the voltage amount was within a clinically acceptable range. CONCLUSION Our data demonstrate that a Volatile Agent-based anesthetic regimen is feasible even during neurophysiological monitoring. Advantages include a more rapid awakening and the feasibility of a rapid wake-up test (
