"Wissenschaftliches Symposium und Workshop zur AnaConDa®"
Dr. K. D. Röhm, PD Dr. S. N. Piper, 01. Dezember 2007, Klinikum Ludwigshafen, Klinik für Anästhesiologie und Operative Intensivmedizin

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"Inhalational sedation during transport to ICU"
Bellgart M, Meiser A, Poster, ISICM Brussels, 2007

Conclusions
• For the first time inhalational transport sedation can be performed safely and with minimal effort (no vaporizer, no syringe pump, no gas monitor).
• AnaConDa® effectively retains sevoflurane in patients during >15 min.
• Hemodynamic stability and depth of sedation are as good as with the standard propofol.
• Less sevoflurane exhaled during transport also means less contamination of the workplace.

Reference: 1. A. Meiser, H. Laubenthal
Best.Pract.Res.Clin. Anaesthesiol. 19:523-38 (2005)

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"Performance Of The Anesthetic Conserving Device In A Bench Study - The Spill Over Effect"
Bellgart M, Meiser A, Poster, ASA, 2007

Summary In this bench study of the ACD we describe the influence of ventilatory settings and infusion rate on the sevoflurane concentration in a test lung.
At large tidal volumes or high concentrations, "spill over" occurs.

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"Technical Aspects of isoflurane sedation in the ICU"
PV Sackey, C-R Martling, PJ Radell
International Journal of Intensive Care, Autumn 2006

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"Population pharmacokinetics of sevoflurane in conjunction with the AnaConDa®, towards target controlled infusion of volatiles into semiopen breathing systems."
Mats Enlund, M.D., Ph.D.; Daniela Kietzmann, M.D., Ph.D.;
Thomas Bouillon, M.D., Klaus Züchner, Ph.D., Ingolf Meineke, Ph.D.
Dept.of Anesthesia & Intensive Care, Central Hospital, Västerås, Sweden
University Dept.of Anesthesia & Intensive Care, Uppsala, Sweden
Dept. of Anesthesia, University Hospital, Bern, Switzerland
Dept.of Anesthesia Engeneering, University of Göttingen, Göttingen, Germany
Dept.of Clincal Pharmacology University of Göttingen, Göttingen, Germany, 2006

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Background
The Anesthetic Conserving Device (AnaConDa) (Fig 1) combines low anesthetic expenditure with the opportunity to make rapid anesthetic concentration alterations (1). The anesthetic is infused in liquid form into the device, where it immediately vaporizes. However, dosing guidelines are empirical so far. We aimed to develop a population pharmacokinetic model for sevoflurane administration with AnaConDa, test its performance retrospectively and provide target controlled infusion (TCI) simulations.

Fig 1. AnaConDa®

Material and Methods
Eighteen females and 20 males, age 31-87, BMI 20- 34 underwent anesthesia with sevoflurane administered via continuous infusion through the AnaConDa. The end-tidal concentrations were varied and recorded together with the infusion rates, and ventilation- and demographic data (Fig 2). The concentration-time course of sevoflurane was described using linear differential equotions. After identification of the most suitable structural model and typical parameter values, the individual pharmacokinetic parameters were obtained and tested for covariate relationships. MDPE, MDAPE, the individual dosing histories and the individual concentration time courses were calculated. All calculations were performed in NONMEM.

Fig 2. An example of variations in pump rate and the resulting end-tidal sevoflurane concentration.

Results
No malfunction of the device was observed. The sevoflurane concentration-time courses on the patient side of the AnaConDa were adequately described with a two-compartment model (Fig 3). The model was capable to handle rapid changes in infusion rate (Fig 4), with a precision of the predictions within +/-20% (MDAPE) and a bias of -3% (MDPE).

Fig 3. The two-compartment model. KT1 = concentration gradient in AnaConDa.

Conclusion
A simple two-compartment model provided acceptable fit to the data. The predictive performance of the model compares favorably with that of pharmacokinetic models used for TCI application of intravenous drugs, highlighting the possibility of safe open loop administration of sevoflurane even in the absence of end-tidal monitoring. Further studies will focus on prospective testing and validation of the model implemented in a TCI device.

Reference
1. Enlund M, Lambert H, Wiklund L. Acta Anaesthesiol Scand 2002;46:506-11.

Fig 4. The prediction of the model in a single study patient.

"Mortallity and recovery after inhalational compared to intravenous ICU sedation"
Bellgardt, A Meisser et al, Poster ESA, Madrid, 2006

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PO-4.6,8 "Die Restgasabsorbtion mit Aldasorber™-Filter beeinflusst nicht die Messgenauigkeit für Tidalvolumina bei modernen Intensivrespiratoren"
Merten C, et al. Poster, Deutscher Anästesiecongress, Leipzig, 2006
Fragestellung: AnaConDa® ist ein System zur tubusnahen Applikation der Anästhesigasen Isofluran und Sevofluran. Mittels bidirektional durchströmtem Aktivkohlfilter wird das Narkosegas im Sytem zurückgehalten. Eine geringe Gasmenge wird mit dem Abgas in die Raumluft abgegeben. Auf Intensivstationen ist die Abgasreiningung durch einen Aktivkohlfilter hinter dem Gasauslass des Respirators zu empfehlen. Eine durch diesen Filter bedingte Beeinflussung der respiratorsetingen Flowmessung ist nicht auszuschliessen. In einem Laboraufbau wurden mehrere Intensivrespiratoren auf ihr diesbezügliches Verhalten untersucht.
Setting: Die Intensivrespiratoren Evita-4 (Drägerwerke), Servo-i (Maquet) und Centiva/5 (Datex-Ohmeda) wurden mit einer Testlunge versehen und volumekontrolliert mit Tidalvolumina von 400, 600 und 800 ml mit I:E = 1:2, AF 15, 12 und 10, PEEP 5 beatmet. Die von der Respiratoren mit und ohne Aktivkohlfilter (Aldasorber™) gemessenen Tidalvolumina wurden registriert.
Ergebnisse: Die Messungen zeigten bei keiner der Einstellungen einen relevanten Unterschied in der Tidalvolumina mit und ohne Filter.

	Centiva		Evita-4		Servo-i
	Ohne Aldasorber	Mit Aldasorber	Ohne Aldasorber	Mit Aldasorber	Ohne Aldasorber	Mit Aldasorber
15x400 ml	401	410	275	277	313	320
12x600 ml	598	609	501	494	472	482
10x800 ml	802	812	708	710	621	639

Diskussion: Evita-4 und Servo-i bestimmen die Tidalvolumina mittels Flowmessung durch Hitzedrahtmometrie. Dieses System ist unempfindlich gegen nachgeschalte Widerstände. Centiva hingegen nutzt ein System der Druckdifferentialmessung an einem Sieb. Dieses System ist direkt abhängig vom nachgeschalten Widerstand, der die Messung beeinflusst. Die gemessenen Differenzen sind bei allen getesteten Respiratoren für die Praxis völlig unerheblich. Sie können bedenkenlos mit dem Aldasorber™-Filter verwendet werden.

"Sevofluran zur Sedierung intensivmedizinisher Patienten-Erste Erfahrung mit dem Anästhesiegasrezirkulierungsystem Anaconda"
Soukup J, et al. Deutscher Anästesiecongress, Leipzig, 2006
Das neue Anästhesiegasrezirkulierungsystem AnaConDa® ermöglicht den Einsatz volatiler Anästhetika im Rahmen der Langzeitsedierung intensivmedizinicher Patienten. Wir berichten über die ersten Erfahrungen mit Sevoflurane.
Methode: Die Applikation von Sevofluran (Sevorane®, Abbott) erfolgte kontinuierlich über einen Perfusor in einen Miniaturverdampfer (AnaConDa®, SedanaMedical, Sweden), welcher an Stelle des üblichen Beatmungsfilters in das Beatmungschlauchsystem intergriert wurden. Die in- und expiratorische Anästhesigaskonzentration wurde via externen Gasmonitor (Vamos®, Fa Dräger) gemessen. Zur Restgasfiltration wurden spezielle Filter verwendet (Aldasorber®, Shirley Aldred & Co Ltd, Novasorb®, Fa.Novamed). Zur Analgesie erhalten die Patienten Remifentanil 0,1 – 0,3 µg/kg/min (Ultiva®). Die Steurung der Analgosedirungstiefe erfolgte standardgemäß anhand vegitativer Reaktion mit dem Ziel RAMSEY 3-4. Ergänzt wurde das klinische Monitoring bei Verfügbarkeit durch den Bispectral-index (BIS-module, Aspect-Medical systems Inc). Alle Patienten wurden druckkontrolliert beatmet (AZV: 4-6ml/kg, AF 20/min, PEEP 12 mbar). Entsprechend dem stationsinternen Standard wurde das System zunächst bei Patienten mit zu erwartender Langzeitsedierung, oder unzureichender intravenöser Analgosedierung eingesetzt. Die Datengewinnung erfolgte retrospektiv durch Analyse der elektronischen Patientenakte im Patientendatenmanagementsystem (ICM, F. Dräger, Lübeck). Die Ergebnisse werden als Median mit Angabe der Minimal- und Maximalwerten dargestellt.
Ergebnisse: Bisher konnten insgesamt 9 Patienten mit einer durchschnittlichen Anwendungsdauer von 100,2 h/Patient (min 8,3h, max171,8h) analysiert werden. Für das Erreichen einer adäquaten Sedierungstiefe waren 4,9 ml/h Sevofluran (min: 3,2 ml/h; max:6,5 ml/h) notwendig. Darunter lag die endexpiratorische Sevoflurankonzentration zwischen 0,5 -0,9 Vol%. Es konnten BIS-werte zwischen 25-57% (Median 39%) erreicht werden. Nach Beendigung der Sevofluranzufuhr konnten die Patienten bereits nach 14 min (min: 10 min; max: 106 min) je nach medizinischer Zielstellung entweder adäquat neurologisch beurteilt oder in die Spontanatmung überführt und extubiert werden.
Schlussfolgerung: Die Anwendung von Sevofluran im Rahmen der Analgosedierung auf det ITS ist mit dem Anästhesiagasrezirkulierungsystem AnaConDa® sicher möglich, gestattet in Kombination mit Remifentanil eine gute Steuerung der Analgosedierungstiefe mit schnellen Aufwachphasen.

Three cases of PICU sedation with isoflurane delivery by the AnaConDa®
Peter V. Sackey MD, Claes-Roland Martling MD PhD and Peter J. Radell MD PhD Pediatric Anesthesia Vol.15 Issue 10 October 2005
Summary: Prolonged sedation in the pediatric intensive care unit may be difficult because of tolerance, drug dependence and withdrawal, drug interactions and unwanted drug effects. We present three patients sedated with isoflurane via the Anesthetic Conserving Device, AnaConDa®. AnaConDa® is a modified heat and moisture exchanger that allows evaporation and delivery of inhalational anesthetics without an anesthesia machine, vaporizer or adapted ventilator. Two patients with abdominal complications and prolonged sedation for mechanical ventilation were converted to isoflurane sedation for several days. The third patient with refractory status epilepticus received isoflurane to treat epileptiform electroencephalogram activity. Patients weighing 40 and 30 kg were treated with AnaConDa® placed at the Y-piece, while the patient weighing 20 kg was treated with AnaConDa® in the inspiratory limb of the respiratory circuit. Adequate sedation was achieved with endtidal isoflurane concentration of 0.3 0.4%, while antiepileptic effect was achieved at a higher dose, 0.9%. Intravenous sedatives could be reduced or discontinued during isoflurane sedation. Inhaled sedation of isoflurane with AnaConDa® was effective in these patients. It may provide an alternative in difficult cases needing prolonged sedation and should be evaluated further.

Inhalational Sedation by Isoflurane Using the anaesthetic Conserving Device (AnaConDa®)
L’Her E, Dy L,Tonnelier J, Gut-Gobert C, Boumediene A, Prat G, Renault A, Boles J.
Réanimation Médicale, CHU de la Cavale Blanche, Brest France. Poster ESICM Amsterdam September 2005
Introduction: Most ICU physicians use a combination of hypnotic and opiods for long duration sedation. These protocols induce major economical costs. Isoflurane is a well-known and costless anaesthetic gas that has been used for a long time in the operating room. Until recently, its administration required specific evaporating devices that were not available on ICU ventilators. The AnaConDa® (Sedana), which is a modified heat and moisture exchanger (HME) is placed in the ventilatory circuit and has an active carbon layer which conserves the anaesthetic vapour and works as a re-circulating anaesthetic system. The anaesthetic is delivered to the device using a syringe driver. Whereas it is light weight, potentially cheap and uses only small volumes of volatile agents, the device has the potential to be ideal for long duration sedation in the ICU. The aim of this study were: 1 – to assess feasibility of isoflurane sedation (IS) using the AnaConDa® ; 2 – to evaluate the potential economical benefits and side- effects of such a procedure, as compared to conventional sedation (CS).
Methods: All patients were mechanically ventilated and sedated for at least 25 hrs (CS) in order to reach a RSS goal of 4-6. CS was then switched to IS (isoflurane plus 5 gamma/h sufentanyl). Isoflurane flow was to be adapted in order to reach the same RSS goal, keeping the isoflurane expiratory fraction (FE) equal or below 1%. Daily cost of the different procedures (medication and devices were compared. Side effects were collected on a daily basis (hemodynamic variations, renal and hepatic function, ventilatory parameters).
Results: 10 patients were included in the study (age 54 ± 13). IS was maintained for 8 ± 6 days (extreme 1 – 21), with a mean FE 0,6% ± 0,1%. Two patients required > 20 ml/kg crystalloid infusion following IS institution. One patient increased PaCO2 during the first 24 hrs of IS, resulting in a switch back to CS. No other side effects were noted. In 5 cases, IS was considered more efficient than CS. The daily cost of sedation was 223 ± 111 vs 103 ± 8 euros (p<0.0001).
Conclusion: The limits of IS are that it requires the use of passive humidification instead of heted humidifiers (dead space AnaConDa 100 ml), and the evacuation of expiratory gases on a active carbon filter. The major interests are that it provides adequate long duration sedation using a low FE, and its very cost effective.

Inhalational anaesthetics in the ICU: theory and practice of inhalational sedation in the ICU, economics, risk-benefit
Andreas Meiser. Best Practice & Research Clinical Anaesthesiology. Vol 19, No. 3, pp 523-538, 2005

Clinical Evaluation of Inhalation Sedation Following Coronary Artery Bypass Grafting
Mohamed A. Hanafy, MD. Eg J Anaesth. 2005; 21:237-242
Abstract
Background: The aim for this study was to evaluate the efficiency of isoflurane as a postoperative sedative following coronary artery bypass grafting (CABG) surgery.
Methods: Twenty four patients scheduled for CABG were randomized to either isoflurane group (number=12) which received isoflurane for post operative sedation via the Anaesthetic Conserving Device (ACD) to obtain an end tidal concentration of 0,5% or midazolam group (number=12) which received midazolam as conventional method of postoperative sedation in a dose of 0.02-0.05 mg/kg/h. Study started when patients arrived to surgical coronary care unit and Ramsay sedation score became 4 and continued for 24 hours or until extubation. All patients received standard anaesthetic regimen during surgery and postoperatively analgesia was achieved by morphine infusion 0.02 mg/kg/h. postoperative haemodynamic variables, Ramsay sedation score, total morphine used, liver enzymes, renal functions, cardiac enzymes were calculated and recorded.
Results: Wake-up time were significantly shorter in the isoflurane group where time to extubation [Mean (SD)] was 15.2 (5.3) min and in the midazolam group 120.1 (30.3) min, P value = 0.01. Time to follow verbal command was 16.3 (3.2) min versus 60.4 (20.4) min for the isoflurane group and midazolam group, respectively, P value = 0.03. Patients in the isoflurane group were mobilized significantly earlier from bed 8 (1.8) h, compared to 14 (3.3) h in midazolam group, P value < 0.05. No serious complications related to either sedative drug occurred.
Conclusion: Administration of isoflurane via ACD following CABG is a safe an efficient method for sedation with short wake-up time facilitating the growing fast track CABG surgery.

Ambient isoflurane pollution and isoflurane consumption during intensive care unit sedation with the Anesthetic Conserving Device
Sakey PV, et.al. Critical Care Medicine, Vol. 33, No. 3, p 585-590, 2005
"Conclusions: The use of the ACD for isoflurane sedation in the ICU appears to be environmentally safe with a low degree of isoflurane pollution, provided users follow instructions for standardizing routines in handling equipment and isoflurane. Although long-term working limits need not be exceeded in the absence of active evacuation systems, scavenging is recommended. Initial on-line monitoring of ambient isoflurane pollution may give feedback to users in understanding potential causes of isoflurane leakage and help reduce the risk of unnecessary isoflurane exposure among. Staff. The use of the ACD appears to reduce isoflurane consumption substantially when compared with isoflurane sedation via vaporizers and high-flow ventilators."

"Erste Erfahrungen mit dem Anästhetikareflektor AnaConDa® auf einer operativen Intensivstation"
Bellgart M, Meiser A et al, Poster, Deutscher Anästesiecongress, 2005

Schlussfolgerungen Inhalative Sedierung mit Isofluran mittels Anästhesiereflektor ist unter Berücksichtigung technischer Vorgaben (AGS, Gasmonitoring) einfach und kostengünstig durchführbar. Unter Verwendung moderner Intensivrespiratoren muss auf eine differenzierte Beatmungstherapie nicht verzichtet werden. Die Problematik von Rückatem-systemen mit Atemkalk entfällt. Der Anästhesiereflektor macht die Vorteile der volatilen Anästhetika wie fehlende Kumulation und Organprotektion für Intensivpatienten nutzbar.

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Prolonged Isoflurane sedation of intensive care unit patients with the anesthetic concerving device
Sackey PV, et. al. Crit Care Med 2004 Vol 32. No 11. 2241-46, 2004
Abstract:
"Objective: To test the efficacy and patient safety of a new method for administering isoflurane for prolonged sedation in the intensive care unit.
Measurements and Main Results: Primary end points were wake-up times from termination of sedative administration and proportion of time within a predefined desired interval on a sedation scale. Practical and patient-related complications with the Anesthetic Conserving Device were noted. Hemodynamic, hepatic, and renal side effects we monitored. Wake-up times were significantly shorter in the isoflurane group than in the control group. Proportion of time within the desired sedation interval was comparable between groups. Few minor practical problems with this new method for isoflurane administration were noted. No serious complications related to either sedative drug occurred. We found no hemodynamic, hepatic, or renal adverse effects related to either sedative protocol.
Conclusions: Isoflurane via the Anesthetic Conserving Device is a safe and efficacious method for sedation in the intensive care unit, with short wake-up times after termination of administration. The Anesthetic Conserving Device allows easily titratable administration of isoflurane without costly equipment and can be safely managed by nursing staff."

Use of the AnaConDa (anesthesia conserving device) with sevoflurane in critical care patients
Soro M, et.al. Abstract A708, 2004
"Background and Goals: The Anesthetic Conserving Devide (AnaConDa) is a modified heat and moisture filter connected to the breathing circuit at the endotracheal tube. A syringe pump delivers sevoflurane to ACD where is vaporized through a rod. Most of exhaled sevoflurane is retained in the filter's chamber and delivered to the patient in the following inspiration. We studied the clinical features of the ACD when used with sevoflurane for sedation of post surgical critical patients during a 6-hour period.
Conclusions: These results confirm the interest and safety for the potential application of the AnaConDa with sevoflurane in the ICU settings. Infusion rate can be maintained without further adjustments and sevoflurane consumption is low. However, 0.5% sevoflurane concentrations could not reach adequate sedation levels."

Efficency of the AnaConDa (Anasthesia concerving device) with sevoflurane: in vitro study
Soro M, et.al. Abstract A239, 2004
"Background and Goals: The Anesthetic Conserving Device (AnaConDa) is a new device for anesthetic vapors delivery. A syringe pump delivers the volatile anesthetic in liquid status to the ACD where the anesthetic is vaporized. We evaluated the anesthetic loss from the ACD filter (efficiency) during 24 hours of use at different sevoflurane end-tidal concentrations and minute volume ventilation.
Conclusions: Loss of anesthetic through the AnaConDa is directly related to the Et-concentration and the minute volume. Anesthetic loss was constant throughout the 24-hour period of study."

Efficiency of the AnaConDa (Anesthetic Conserving Device) used with sevoflurane in pigs
Soro M, et.al. Abstract S-116, 2004
"Introduction: The Anesthetic Conserving Device (AnaConDa) is a new device for anesthetic vapours delivery. The AnaCon Da consists of an anesthetic gas exchanger, which absorbs some of the expired anesthetic vapour by means of an activated carbon filter, and desorbs some of it in the next inspiration. A syringe pump delivers the volatile anesthetic in liquid status to the AnaConDa where the anesthetic is vaporized. A clinical study showed that due to the physical properties of the AnaConDa, the isoflurane sedation of ICU patients requires small volumes of isoflurane, and it is environmentally safe. However not all the anesthetic is retained in the device; in part pass through the filter and it is eliminated to the atmosphere. This study aimed to evaluate the concentration of anesthetic loss from the AnaConDa filter (efficiency) at different sevoflurane end-tidal concentrations.
Discussion: For a determined minute volume ventilation the loss of sevoflurane from the AnaConDa filter increases exponentially as end-tidal concentration increases. This can be explained knowing that the active carbon in the filter has a certain absorption capacity and when it is loaded with more Sevoflurane the efficiency goes down. However, for end-tidal concentrations of 1% or less, there is a maximal efficiency and the loss of anesthetic is negligible. These results confirm the interest for the potential application of the AnaConDa with sevoflurane around 1% concentration in the ICU settings without significant ambient pollution."

Monitoring alveolar anesthetic concentration with the AnaConDa (anesthesia conserving device
Soro M, et.al. Abstract A615, 2004
"Background and Goals: The new Anesthetic Conserving Device "AnaConDa" (ACD) is a modified heat and moisture filter with activated carbon in which liquid anesthetic is administered via a syringe pump to an evaporator rod located in the device. With ACD, estimation of alveolar anesthetic concentration from End-tidal values could be misleading. We measured the true alveolar anesthetic concentration in order to correlate this value with the inspired and End-tidal concentrations measured with a standard clinical monitor.
Results: Measured inspired concentrations were always lower than End-tidal values on the monitor. Alveolar concentration values were slightly lower to End-tidal values. The following correlations were found:

FEt = 1.7		Fi - 0.35		r = 0.94 p <0.001
FA = 0.75		FEt + 0.39		r = 0.90 p <0.001

Discussion: Alveolar sevoflurane concentration during anesthesia with the AnaConDa device is close and well correlated to the End-tidal values measured with a clinical monitor. This way, for clinical purposes, End-tidal anesthetic values can be used as a guide to adjust the rate of infusion of liquid anesthetic."

The Anesthetic concerving device compared with conventional circle system used under different flow conditions for inhaled anesthesia
Tempia A, et al Anesthesia & Analgesia Vol. 96, p 1056-61, 2003
"Summary: The Anesthetic Conserving Device (ACD) is a high-flow anesthesia system closed to volatile anesthetics only. We compared the ACD with a circle system under different fresh gas flow (FGF) conditions. Eighty-one patients undergoing major surgery were randomly allocated to receive sevoflurane from a circle circuit combined either with the ACD placed at the Y-piece or with a vaporizer. The FGF was set to 8 L/min in the ACD system, where the circle circuit served as a nonrebreather. In the conventional circle system without ACD, the vaporizer was supplied with 1-, 1.5, 3-, and 6-L/min FGFs. We compared the ACD with the circle system under four FGFs in terms of sevoflurane dosing, sevoflurane consumption, humidification efficiency, and environmental pollution. The ACD and the low-flow circle system resulted in the smallest sevoflurane consumption. The increase in inspired sevoflurane concentration was faster with the circle system than with the ACD only with FGFs <3 L/min. The removal of ACD from the circuit allowed the fastest washout of sevoflurane. Respiratory gas humidification was always adequate. Sevoflurane ambient concentration with the ACD was 1-70 ppb. The ACD is a valid and simple alternative to low-flow systems."

Sedation of ICU patients with isoflurane using the anesthetic conserving device
Sackey P.V, et al. Intensive Care Medicine, Vol. 28, Suppl. 1, 347, 2002
"Introduction: Isoflurande sedation of ICU patients has previously been shown to be useful but has not come into wide clinical use for a number of reasons. A new device (The Anesthetic Conserving Device, ACD) enables easy and safe administration of isoflurane in the ICU setting. We conducted a randomised, controlled study to evaluate efficacy of sedation and environmental safety during administration of isoflurane with the ACD.
Conclusion: Isoflurane administered via the ACD for sedation of ICU patients is environmentally safe, requires small volumes of isoflurane and may provide better quality of sedation than midazolam. It appears to be more titratable with a shorter time from adequate sedation to extubation and ability to cooperate."

The sevoflurane saving capacity of a new anaesthetic agent conserving device compared with a low flow circle system
Enlund M. et al. Acta Anaest. Scand. Vol. 46, p 506-11, 2002
"Background: An anaesthetic agent conserving device (ACD) has been added to a Bain system to approach the agent-saving capacity of a low flow circle system.
Conclusion: The expenditure of sevoflurane with a bain system + ACD was close to that in a circle system with 1.5l/min fresh gas flow. It is thereby possible to use sevoflurane to all its potential, performing for example rapid alterations and end-tidal concentration using high fresh gas flows by combining a Bain system with an ACD. Although the price is not decided for this not yet commercially available device, a potential for a lower cost exists. Additionally, there will be no concerns of toxic compounds produced in the absorber."

Mechanical effects of the anesthetic agent-conserving device during one-lung ventilation
Tempia A., et.al. Intensive Care Medicine, Vol. 28, Suppl. 1, 693, 2002
"Introduction: The Anesthetic Agent Conserving Device (ACD) is a new device for anesthetic vapours delivery. The operation of ACD is based on the same principle of an HME: the ACD retains the expired anesthetic vapours, returning them to the patient during inspiration. The ACD has been shown to remarkably reduce the anesthetic agent expenditure. However, the ACD performance has been so far studied only during volume-controlled ventilation. We evaluated the mechanical effects of the ACD and the influence of one-lung ventilation, applied both in volume-controlled ventilation and pressure-controlled modes, on the performance of the ACD.
Conclusion: The ACD does not increase significantly the resistive load. The performance of the ACD is not affected by one-lung ventilation applied either in volume-controlled ventilation and pressure-controlled ventilation. The results increase the interest for the potential application of the ACD not only in the anesthesia settings, but also in the ICU settings."

Evaluation of a new device for delivery of anaesthetic vapours
Olivei M. et al Poster CENSA Florence 2001. Minerva Anestesiologica, Vol. 67, Suppl. 1 al N.5, 2001
"The Anesthetic Conserving Device (ACD) is a new device for anaesthetic vapours delivery, consisting of a modified heat and moisture exchanger, which absorbs some of the expired anesthetic vapour and desorbs some of it in the next inspiration. The ACD is connected to a syringe pump, which delivers anaesthetic liquid into the ACD, where the agent is vaporised. The overall operation of ACD can be described as a system that is open in regard to oxygen, air and N2O delivery, but closed in regard to volatile anesthetics. We tested the ACD for Sevoflurane delivery during major surgery.
Results and conclusions: As shown in the table the time required to effect a change in the Sevoflurane concentration was the lowest with the ACD.

	ACD	Control 1.5 L/min	Control 1 L/min	P
t-rise (sec)	200 ± 30	226 ± 29	321 ± 39	<0.001
t-fall (sec)	34 ± 17	85 ± 48	60 ± 12	<0.01
Anaesthesia duration (min)	206 ± 67	195 ± 45	212 ± 58	ns
Sevoflurane consumption (ml/h)	6.2 ± 1.2	6.8 + 0.7	5.3 ± 0.3	<0.01
Respiratory gases temperature (oC)	33.2 ± 0.4	33.7 ± 0.3	33.4 ± 0.3	ns
Humidity of inspired gases (Beyond score)	3 ± 0	3 ± 0	3 ± 0	-

The duration of anaesthesia did not differ in the 3 groups. The Sevoflurane consumption was lowest with the low-flow system with 1 L/min flow of fresh gases. However, the difference in the Sevoflurane consumption was negligible between the ACD group and the control group with 1.5L/min flow of fresh gases. The inspired gases conditioning was adequate both with the ACD and with the conventional low-flow technique. The Sevoflurane ambient concentration was always negligible (1-7 ppb). In conclusion, the ACD is a valid alternative to conventional low-flow anaesthesia systems, offering the advantage over these latter, of a greater simplicity."

A new device to reduce the consumption of a halogenated anaesthetic agent
Enlund M, et al. Anaesthesia Vol. 56, p 429-32, 2001
"Summary: We report the first clinical application of a new anaesthetic agent-saving device. The principles of a heat-moisture exchanger have been further developed to create a device that reduces inhalational agent consumption. Sixteen patients were randomly allocated to receive isoflurane through either a vaporiser or through the agent-saving device. A coaxial Mapleson D system (Bain) was used in both groups. A standard ventilatory setting was used, aiming for normocapnia. Mean isoflurane consumption was 24.5 (2.8) ml. MAC-hour-1 with the vaporiser, compared with 15.2 (3.0) ml MAC-hour-1 with the new device (p <0.05). This corresponded to a 40% saving in the consumption of isoflurane. The amount of isoflurane that was scavenged to the atmosphere was reduced by an average of 55%."