No 36

Inhalationsanästesie mittels"Anaesthetic Conserving Device" zur Langzeitsedierung eines schwer sedierbaren Patienten
Uwe Veismann, Sebastian Rehberg, Janina Rehberg, Martin Westphal , Intenzivmedizin 2009; 17: 64-67

Die adäquate Analgosedierung von Intensivpatienten stellt für Ärzte und Pflegekräfte stets eine besondere Herausforderung dar. Das „Anaesthetic Conserving Device“ (AnaConDa®) ermöglicht die Applikation volatiler Anästhetika mittels konventioneller Intensiv-Respiratoren und erleichtert somit die Anwendung einer Therapieoption, die der totalintravenösen Sedierung möglicherweise überlegen ist. Dieser Artikel schildert zunächst einen Fallbericht eines Patienten mit akuter Pankreatitis und anamnestischem Alkoholabusus, der nach zahlreichen (jedoch nicht zufriedenstellenden) intravenösen Therapieregimen schließlich mit Isofluran via AnaConDa adäquat sediert werden konnte. Im Anschluss werden die technischen Anforderungen des AnaConDa-Systems sowie die Vorteile und Anwendungseinschränkungen volatiler Anästhetika zur Langzeitsedierungen auf der Intensivtherapiestation auf der Grundlage der aktuellen Literatur kritisch diskutiert.

No 35

Prolonged Inhalational Sedation Using Sevoflurane: Evaluation of Inorganic Fluoride Levels and Kidney Function
Kerstin D Röhm, Swen N Piper and Joachim Boldt, Adv anesth crit care Volume 1, Issue 2

Inhalational sedation in the intensive care unit has become increasingly common in mechanically ventilated patients since technical improvements in the form of the Anaesthetic Conserving Device (AnaConDa®, Sedana Medical, Uppsala, Sweden) were introduced. This evaporator and reflector system enables the low-flow administration of volatile anaesthetics. In terms of their pharmacological properties, volatile anaesthetics possess nearly all the ideal features of a sedative agent – rare adverse events, a lack of metabolite accumulation, and its ability to rapidly adjust the depth of anaesthesia – but their impact on organ function during prolonged administration has rarely been studied. Sevoflurane is the most commonly used volatile agent in the operation room, but suggestions of a potential association with renal impairment caused by inorganic fluorides have been repeatedly made since its approval. In this review, past experiences of sevoflurane exposure and renal function as well as recent findings of the effects of sevoflurane inhalational sedation in postsurgical critical care patients are described.

No 34

State of the art: Sedation concepts with volatile anesthetics in critically ill patients
Jens Soukup, Katarina Schärff, Kristina Kubosch, Carsten Pohl, Michael Bomplitz Jesco Kompardt, Journal of Critical Care (2009) 24, 535–544

Abstract
The use of volatile anesthetics in the intensive care unit (ICU) has only been possible at great cost with the use of commercially available anesthesia systems. A new anesthetic-conserving device
(AnaConDa™) now facilitates, from a technical viewpoint, the routine use of volatile anesthetics in intensive care patients as part of prolonged sedation, using ICU ventilators. The volatile anesthetic is hereby applied continually via a syringe pump into a miniature vaporizer, which is integrated into the ventilator circuit in place of the usual respiratory filter. During expiration, the anesthetic exhaled by the patient enters the recirculation system, is predominantly stored in the active carbon layer of the anesthetic-conserving device, and redirected into the inspiratory air. At clinically relevant concentrations, more than 90% of the gas is recirculated in such a way. Aside from the possibility of using a central anesthetic gas scavenging system, the use of special passive residual gas filters, which can be connected to the expiratory outlet of the respirator machine, appears above all to be practical. The use of volatile anesthetics on the ICU could adopt a permanent position in various intensive care analgosedation concepts in future. It may be possible thereby to optimize the treatment process both in medical and economical terms.

No 33

Renal Integrity in Sevoflurane Sedation in the Intensive Care Unit with the Anesthetic Conserving Device – A Comparison with Intravenous Propofol Sedation
Kerstin D. Röhm, Andinet Mengistu, Joachim Boldt, Jochen Mayer, Grietje Beck, Swen N. Piper, Anesthesia & Analgesia Vol.108, 1848-54, No. 6, June 2009
BACKGROUND: Increased inorganic fluoride levels after methoxyflurane exposure in the 1970s and prolonged intraoperative sevoflurane use have been suggested to be potentially nephrotoxic. In the intensive care unit we evaluated the effect on renal integrity of short-term inhaled postoperative sedation with sevoflurane using the Anesthetic Conserving Device (ACD) compared with propofol.
METHODS: In this prospective, randomized, single-blinded study, after major abdominal, vascular or thoracic surgery 125 patients were allocated to receive either sevoflurane (n = 64) via the ACD (end-tidal 0.5–1 vol%) or IV propofol (n =61) for postoperative sedation up to 24 h. Urinary -glutathione-s-transferase as primary outcome variable, urinary N-acetyl-glucosaminidase, serum creatinine, and inorganic fluoride concentrations, urine output and fluid management were measured preoperatively, at the end of surgery, and at 24 and 48 h postoperatively.
RESULTS: The sedation time in the intensive care unit was comparable between the sevoflurane (9.2 ±4.3 h) and the propofol (9.3±4.7 h) group. Alpha-glutathione- S-transferase levels were significantly increased at 24 and 48 h postoperatively compared with preoperative values in both groups, without significant differences between the groups. N-acetyl-glucosaminidase and serum creatinine remained unchanged in both study groups, and urine output and creatinine clearance were comparable between the groups throughout the study period. Inorganic fluoride levels increased significantly (P<0.001) at 24 h after sevoflurane exposure (39 ± 25 mol/L) compared with propofol (3 ± 6 mol/L) and remained elevated 48 h later (33 ± 26 vs. 3 ± 5 mol/L). One patient in each group suffered from renal insufficiency, requiring intensive diuretic therapy, but not dialysis, during hospital stay.
CONCLUSIONS: Short-term sedation with either sevoflurane using ACD or Propofol did not negatively affect renal function postoperatively. Although inorganic fluoride levels were elevated after sevoflurane exposure, glomerular and tubular renal integrity were preserved throughout the hospital stay.

No 32

Wash in kinetics for sevoflurane using a disposable delivery system (AnaConDa®) in cardiac surgery patients
L. W. Sturesson, A. Johansson, M. Bodelsson and G. Malmkvist Br J Anaesth 2009; 102: 470-6

No 22

Sedation with Inhaled Anesthetics in Intensive Care
Belda et al, Yearbook 2008 ISICEM
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No 21

"The Predictive Performance of a Pharmacokinetic Model for Manually Adjusted Infusion of Liquid Sevoflurane for Use with the Anesthetic-Conserving Device (AnaConDa): A Clinical Study"
Javier F. Belda, Marina Soro, Rafael Badenes, Andreas Meiser, Maria Luisa García, Gerardo Aguilar, Francisco J. Martí Anesth Analg 2008; 106: 1207-14

BACKGROUND: The Anesthetic-Conserving Device (AnaConDa) can be used to administer inhaled anesthetics using an intensive care unit (ICU) ventilator. We evaluated the predictive performance of a simple manually adjusted pump infusion scheme, for infusion of liquid sevoflurane to the AnaConDa.
METHODS: We studied 50 ICU patients who received sevoflurane via the AnaConDa. They were randomly divided into three groups. A 6-h infusion of liquid anaesthetic was adjusted according to the infusion scheme to a target end-tidal sevoflurane concentration of 1% (Group 1%, n = 15) and 1.5%, n = 15). The initial rate was adjusted to reach the target concentration in 10 min and then the infusion was reduced to the first hour maintenance rate and readjusted once each hour afterwards. The actual concentrations were measured in the breathing circuit and compared with the target values. In the third group (n = 20) we used the model to increase and decrease the target concentration (±0.3%) for 3 h and evaluated the actual change in concentration achieved. The ability of the infusion scheme to provide the target concentration was quantified by calculating the performance error (PE). Infusion scheme performance was evaluated in terms of accuracy (median absolute PE, MDAPE) and bias (median PE, MDPE).
RESULTS: Performance parameters (means ± sd, %) were for 1%, 1.5%, increase of the concentrations by 0.3 % and decrease of concentration by o.3% groups, respectively: MDAPE 5.3 ± 5.5, 2.6 ± 4.0, 5.0 ± 5.6, 5.5 ± 5.4, MDPE -5.3 ± 5.5, -2.3 ± 4.1, -0.1± 7.1, 0.2 ± 5.4. No significant differences were found between means of all performance parameters when the 1% and 1.5% groups were compared.
CONCLUSIONS: There is an excellent 6-h predictive performance of a simplified pharmacokinetic model for manually adjusted infusion of liquid sevoflurane when using the AnaConDa to deliver sevoflurane to ICU patients.

No 20

"AnaConDa Reflection Filter: Bench and Patient Evaluation of Safety and Volatile Anesthetic Conservation"
Jerôme Berton, MD, Cyril Sargentini, MD, Jean-Luc Ngyen, MD, Adrian Belii, MD and Laurent Beydon, MD, Anesth Analg 2007 ; 104 :130-134

Background The AnaConDa filter permits administration of volatile anesthetic without the use of an anesthesia machine. It is intended for use in the intensive care unit.
Methods We studied the AnaConDa reflection filter on the bench and in anesthetized patients. The bench analysis used a test lung, a gas analyzer, an intensive care ventilator, the AnaConDa filter, and a syringe pump. We studied a range of tidal volume, respiratory rate, and positive end-expiratory pressure values. We simulated errors during syringe refilling and patient transportation. In 15 anesthetized patients, we used the AnaConDa with constant ventilation variables, a constant sevoflurane infusion rate (4 – 5 mL/h), and two consecutive fresh gas flow levels.
Results In the bench study, the expired volatile anesthetic fraction decreased linearly with respiratory frequency at constant minute ventilation, and decreased markedly in a hyperbolical manner when tidal volume increased at a constant respiratory rate. Changing the positive end-expiratory pressure level and inspiration/expiration ratio did not modify the AnaConDa performance. Several safety failures were observed: refilling caused a transient change in AnaConDa output because of a pumping effect, and a standard Luer lock made it possible to connect the halogenate syringe on an IV infusion line. In anesthetized patients, reducing fresh gas flow from 8 to 1 L/min led to a median 40% increase in the expired volatile anesthetic fraction.
Conclusions This study shows that the device is generally reliable, but that there are several conditions under which it might deliver more anesthetic than intended.

No 19

Use of sevoflurnae sedation by the AnaConDa deveice as an adjunct to extubation in a pdeiatric burn patient
Jung et al, Burns 2007
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No 18

Sedierung mit volatile Anästhetika auf der Intensivstation: Technische Umsetzung und aktuelle Möglichkeiten der Restgasfilterung.
Jens Soukup, Katharina Schärff, Michael Bomplitz, Mirja Zielonka, Kristina Kubosch, Krh.-Hyg. + Inf.verh. 29Heft 3 (2007): 95-99

Sedation concepts with volatile anaesthetics in intensive care – Technical application and current experiences

Summary The routine use of volatile anaesthetics in intensive care medicine has been limited so far due to technical difficulties and the need for an anaesthesia machine. The new Anaesthetic Conserving Device (AnaConDa®) is a modified heat and moisture exchanger which includes activated carbon fibres. It works as a miniaturized vaporizer with recirculation facilitating the use of volatile anaesthetic for long-term sedation with any classical ventilator. The Anaesthetic Conserving Device (AnaConDa®- System) replaces the common heat and moisture exchanger in the ventilator circuit. The volatile anaesthetic is continuously applied in liquid form via a syringe pump to the mini-vaporizer where the anaesthetic is vaporized. The expired anaesthetic gas is stored in the carbon filter and about 90 % are re-supplied into the breathing circle. Beside the active central hospital scavenging system three passive scavenging systems with different modified activated charcoal can be used for anaesthesia gas scavenging from the ventilator.
Current studies have shown a safe application route, no development of tolerance as well as short wake-up times after long-term sedation with volatile anaesthetics. There is still need for studies on economical aspects. The current experiences suggest that volatile anaesthetics present an alternative for long-term sedation in intensive care units, providing optimized pathways from a medical as well as from an economical viewpoint. According to current drug-approval –laws the use of volatile anaesthetics for a longer period is an off-label use and should only be applied by medical professionals at their own responsibility.

No 17

"AnaConDa als Ultima-Ratio-Therapie"
E.A. Nickel, I. Benken, U. Bartels, W.G. Voelkel, M. Quintil, Anaesthesist 2007, doi 10.1007/s00101-007-1152-6

Abstract Treatment of patients suffering from decompensated chronic pulmonary disease (COPD) not responding to pharmacological therapy is still a major challenge in intensive care medicine. Administration of volatile anaesthetics may be a therapy of last resort in these cases. We report on a 65-year-old woman suffering from exacerbated COPD, who could not be sufficiently ventilated despite comprehensive pharmacological therapy. In order to administer a volatile anaesthetic in the ICU, we employed the “Anaesthetic Conserving Device” (AnaConDa) consisting of a vaporizer chamber embedded in a charcoal filter system. With this device, every standard intensive care ventilator can be used to deliver volatile anaesthetics in a safe and economical manner. The AnaConDa converts the open breathing system of the intensive care ventilator into a de facto half-closed system. The very low pulmonary compliance of the patient increased dramatically after administration of 0.75 vol% halothane for 48 h (27 vs. 150 ml/bar). Elimination of CO2 was improved and weaning from controlled ventilation was achieved. After surgical removal of a pulmonary abscess and a total of 78 days of intensive care therapy, the patient was discharged in good health.

No 16

Use of AnaConDa anaesthetic delivery system to treat life-threatening asthma
Thomson et al, Anaesthesia 62 (3), 95 295-296
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No 15

"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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No 14

"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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No 13

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.

No 12

"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.

No 11

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.

No 10

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
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No 9

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.

No 8

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."

No 7

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."

No 6

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:

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."

No 5

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.

No 4

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."

No 3

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."

No 2

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."

No 1

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%."