Tina Yan, HBSc RRT CHT

Madeeha Chatoo, HBSc RRT

Lynae Cooper, BSc SRT

Laura Tangelder, HBSc SRT

The COVID-19 pandemic continues to put a lot of strain on healthcare systems. Hospitals across Canada and around the world have experienced shortages of anesthetic medications used for total intravenous anesthesia (TIVA), which is essential for sedation management of patients in intensive care units (ICU) (Basky, 2020). The use of sedation in the ICU for mechanically ventilated patients is critical to ensure tolerance of ventilation, as well as treating anxiety and pain (Bansky, 2020; Jerath et al., 2015). For years, propofol or benzodiazepines are the key agents along with systemic opioids as the medication of choice (Landoni et al., 2016; Jerath et al., 2015). However, there are several disadvantages to the use of TIVA. When overused or underused, propofol or benzodiazepines create undesirable effects resulting in prolonged intubation; thus, increasing the risk of ventilator-acquired pneumonia (Jerath et al., 2015). Hemodynamic instability and agitation are also common side effects when patients are inadequately sedated, increasing their risk of self-harm and accidental extubations (Barr et al., 2013; Jerath et al., 2015). Nonetheless, this unexpected shortage of medication has led to the exploration of other methods for sedation management for patients in ICU.

More recently, the use of volatile anesthetic agents, such as isoflurane and sevoflurane, have shown improved outcomes with less undesirable effects (Bellgardt et al., 2016; Jerath et al., 2015). Several randomized control trial studies have demonstrated the benefits of using volatile anesthetic agents to provide sedation in the ICU using a portable vaporizer called the Anesthesia Conserving Device (AnaConDa, Sedana Medical, Uppsala, Sweden) (Landoni et al., 2016; Jerath et al., 2015). Not only are volatile anesthetic agents easy to titrate, but they can also be cleared by respiratory exhalation and have no active metabolites (Jerath et al., 2020; Jerath et al., 2015). When used for short-term sedation, these agents have shown to significantly promote faster extubation times, maintain stable hemodynamics, and do not cause renal or hepatic toxicity (Landoni et al., 2016; Jerath et al., 2015; Misra & Koshy, 2012). This not only provides optimal sedation for patients with minimal side effects, but it also reduces the economic impact by reducing prolonged ventilation that is often attributed to oversedation (Bellgardt et al., 2016; Landoni et al., 2016; Jerath et al., 2015).

This general review introduces the AnaConDa device, limitations for use, and discussion of the clinical implications for registered respiratory therapists (RRTs) managing these devices. Given the ongoing medication shortages resulting from this pandemic, the use of the AnaConDa could become a more frequent and potentially routine therapy in the future.

AnaConDa Device

The concept for the AnaConDa was created by Louis Gibeck, who also designed the first heat-moisture exchange (HME) device; the original versions of today’s product were designed by Hans Lambert, with the first patented product available in 1999 (Farrell, Oomen & Carey, 2018). Initially, this device was used as an HME in 2005, which was then adapted to have the ability to conserve anesthetic agents and was marketed for use in the ICU to provide sedation for patients (Misra & Koshy, 2012). Each package includes the device, a 50 millilitre (mL) keyed, colour-coded syringe, and a 22 centimetre (cm) supply line that can be assembled together (Sedana Medical, 2020a). Through a syringe pump system, liquid anesthetic agents can be continuously infused into a porous evaporator rod inside the device that converts the liquid to a vapour state (Sedana Medical, 2020a; Misra & Koshy, 2012). The device’s holding capacity is 10 mL and requires 1.2 mL of liquid anesthetic agent to be primed before it can start converting the liquid agent to vapours (Sedana Medical, 2020a). There are also activated carbon fibres interlaced with the HME that help absorb, hold and recycle the anesthetic vapours (Misra & Koshy, 2012). By placing this device in the breathing circuit between the Y-piece and the patient, the anesthetic vapours are carried to the patient during inspiration (Sedana Medical, 2020a; Misra & Koshy, 2012). Ninety percent of the vapours get captured and recycled back to the patient during subsequent inspiratory breaths (Sedana Medical, 2020a). The Richmond Agitation and Sedation Scale (RASS), a ten-item scoring metric, is recommended to guide the titration of inhaled anesthetic agents to sedate patients in ICU settings by changing the rate at which liquid anaesthetic agent is being delivered on the infusion pump (Sedana Medical, 2020a; Sessler et al., 2002).

Limitations

There are several limitations to consider when using the AnaConDa in the ICU: the type of compatible vapours, device dead space, and the accuracy of end-tidal vapour measurements. According to Misra and Koshy (2012), isoflurane and sevoflurane are the most compatible volatile agents to use with this device because desflurane has a high vapour pressure. The device also has a dead space of 100 mL, creating the potential of mild hypercapnia for patients receiving mechanical ventilation and making this device more suited for the adult population (Misra & Koshy, 2012). Misra and Koshy (2012) also explain that this dead space can lead to inaccuracies for end-tidal measurements of anesthetic agent concentrations through the gas sampling line; hence, healthcare providers should use averages of these measurements instead. The device also needs to be changed every 24 hours (Sedana Medical, 2020a).

Other considerations when choosing the AnaConDa for anesthetic agent delivery to patients in the ICU include environmental factors and contraindications. Despite the AnaConDa’s ability to absorb and recycle 90% of the exhaled volatile vapours through the activated carbon fibres, there needs to be an active or passive scavenging system in place to capture the remaining 10% and prevent air contamination (Misra & Koshy, 2012). These halogenated fluorocarbons can also contribute to the amount of heat trapped in the atmosphere, potentially increasing the greenhouse gas effect and overall global warming (Alexander, Poznikoff & Malherbe, 2018). Adding a scavenging system can help mitigate the impact of these factors. Most importantly, an absolute contraindication of this device would include a family history or diagnosis of malignant hyperthermia; this precaution would also apply to any staff involved in the care of these patients (Farrell, Oomen & Carey, 2018).

Clinical Implications

As more of these AnaConDa device setups are potentially introduced into ICUs across the country as an alternative for the shortage in supply of sedation medication used for TIVA, RRTs play an essential role in initiating, maintaining and terminating this therapy. The expertise of RRTs is required to help with the initial setup of the device, which includes:

  1. assembling the AnaConDa device (syringe pump, sample line, and device),
  2. putting the AnaConDa device in-line (between the Y-piece and the patient), and
  3. attaching the scavenging system (active or passive) properly to the different types of ventilators/circuits (Sedana Medical, 2020a).

For maintenance, the ventilation management for patients on vapour anesthetics will be similar to those on TIVA, with the slight difference that patients may emerge quicker when on the inhaled anesthetic agent (Jerath et al., 2020; Jerath et al., 2015). The device also needs to be changed every 24 hours, so RRTs are involved with putting the ventilator on standby and properly disposing of the used device by capping off the ends and disposing the device correctly and safely (Sedana Medical, 2020a, 2020b).  The remaining liquid anesthetic agent also needs to be properly disposed of through the scavenging system (Sedana Medical, 2020a).

Our experiences with taking care of patients in the ICU on the AnaConDa has overall been positive. Initially, there was a steep learning curve to understand how to assemble the equipment, the scavenging system for different ventilators, and safely manage patients on this device. Inherently, the introduction of this new way of sedating patients led to a temporary increase in workload. However, after overcoming the initial unfamiliarity, through repeated exposure and practice, the general workload for patients on the AnaConDa was similar to those on TIVA.  This interim solution has the potential of changing how patients receive sedation management during this pandemic and in the future. As Respiratory Therapists, we need to keep up to date with practice changes, understand how to apply new methods like this at the bedside, and recognize the strengths and limitations of this setup.

References

Alexander, R., Poznikoff, A. & Malherbe, S. (2018). Greenhouse gases: the choice of volatile anesthetic does matter. Canadian Journal of Anesthesia, 65, 221-222.

Barr, J., Fraser, G. L., Puntillo, K., Ely, E. W., Gélinas, C., Dasta, J. F., … & Coursin, D. B. (2013). Clinical practice guidelines for the management of pain, agitation, and delirium in adult patients in the intensive care unit. Critical care medicine, 41(1), 263-306.

Basky, G. [2020, July 16]. Temporary fixes to chronic drug shortages leave Canada vulnerable. CMAJ News. https://cmajnews.com/2020/07/16/covid-drugshortage-1095886/

Bellgardt, M., Bomberg, H., Herzog-Niescery, J., Dasch, B., Vogelsang, H., Weber, T. P., … & Meiser, A. (2016). Survival after long-term isoflurane sedation as opposed to intravenous sedation in critically ill surgical patients: retrospective analysis. European Journal of Anaesthesiology (EJA), 33(1), 6-13.

Farrell, R., Oomen, G., & Carey, P. (2018). A technical review of the history, development and   performance of the anaesthetic conserving device “AnaConDa” for delivering volatile anaesthetic in intensive and post-operative critical care. Journal of Clinical Monitoring and Computing, 32, 595-604.

Jerath, A., Ferguson, N. D., Steel, A., Wijeysundera, D., Macdonald, J., & Wasowicz, M. (2015). The use of volatile anesthetic agents for long-term critical care sedation (VALTS): study protocol for a pilot randomized controlled trial. Trials, 16(1), 560.

Jerath, A., Wong, K., Wasowicz, M., Fowler, T., Steel, A., Grewal, D., … & Ferguson, N. D. (2020). Use of Inhaled Volatile Anesthetics for Longer Term Critical Care Sedation: A Pilot Randomized Controlled Trial. Critical Care Explorations, 2(11), e0281.

Landoni, G., Pasin, L., Cabrini, L., Scandroglio, A. M., Redaelli, M. B., Votta, C. D., … & Zangrillo, A. (2016). Volatile agents in medical and surgical intensive care units: a meta-analysis of randomized clinical trials. Journal of cardiothoracic and vascular anesthesia, 30(4), 1005-1014.

Misra, S., & Koshy, T. (2012). A review of the practice of sedation with inhalational anaesthetics in the intensive care unit with the AnaConDa® device. Indian Journal of Anaesthesia, 56(6), 518.

Sedana Medical. [2020a, June]. AnaConDa: User guide. https://www.sedanamedical.com/wp-content/uploads/2017/_downloads/user-guides/AnaConda-UserGuide-English/AnaConDa%20UserGuide%20English%20for%20Own%20Printing.pdf

Sedana Medical. [2020b]. AnaConDa. https://www.sedanamedical.com/?page_id=5032

Sessler, C. N., Gosnell, M. S., Grap, M. J., Brophy, G. M., O’Neal, P. V., Keane, K. A., … & Elswick, R. K. (2002). The Richmond Agitation–Sedation Scale: validity and reliability in adult intensive care unit patients. American journal of respiratory and critical care medicine, 166(10), 1338-1344.

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