COVID-19 and the use of AnaConDa
The reason for the recent questions is that inhaled anaesthetics in ARDS have been associated with improved oxygenation and reduced cytokine release, experimentally as well as in ARDS patients1-5.
Besides this potential therapeutic effect, inhaled anaesthetics in critically ill patients might contribute to faster discharge from the ICU after extubation, which could mean a lot from a patient flow perspective. In clinical trials of critically ill ICU patients, inhaled anaesthetics have been associated with short wake-up and extubation times and fast cognitive recovery 6,7.
Regarding some of the recent technical questions, we would like to share the following information:
- The virus filtration capacity of the AnaConDa is >99.9% for 27 nm particles, less than one quarter of the size of the SARS-CoV-2 virus (120-160 nm). This implies a very low risk for SARS-CoV-2 virus passing the AnaConDa8.
- During use of the AnaConDa exhaled air is sampled to the anaesthetic gas analyser from the patient side of the filter and is thus not filtered. However, most gas analysers have viral filters in the water trap, with different degrees of virus filtering capacity9.
- Some ICU´s have introduced an additional filter, connected to the expiratory port of the breathing circuit, to protect the ventilator from exhaled virus entry. The use of such additional filters needs to be verified by the ventilator manufacturer. It is possible to return the waste gas from the gas analyser in the expiratory side of the breathing circuit, before the additional virus filter, by using the standard bypass connector (normally placed at the FlurAbsorb filter). See the enclosed picture10.
1. Voigtsberger S et al. Sevoflurane ameliorates gas exchange and attenuates lung damage in experimental lipopolysaccharide-induced lung injury. Anesthesiology 2009;111:1238–1241.
2. Ferrando C et al. Sevoflurane, but not propofol, reduces the lung inflammatory response and improves oxygenation in an acute respiratory distress syndrome model. Eur J Anaesthesiol. 2013;30:455–463.
3. Strosing KM et al. Inhaled anesthetics exert different protective properties in a mouse model of ventilator-induced lung injury. Anesth Analg. 2016;123:143-151.
4. Kellner P et al. Sevoflurane abolishes oxygenation impairment in a long-term rat model of acute lung injury. Anesth Analg. 2017;124:194–203.
5. Jabaudon M et al. Sevoflurane for sedation in acute respiratory distress syndrome a randomized controlled pilot study. Am J Respir Crit Care Med. 2017;195:792–800.
6. Sackey P et al. Prolonged isoflurane sedation of intensive care unit patients with the Anaesthetic Conserving Device. Crit Care Med. 2004;32(11):2241-46.
7. Mesnil M et al. Long-term sedation in intensive care unit: a randomised comparison between inhaled sevoflurane and intravenous propofol or midazolam. Intensive Care Med. 2011;37(6):933-41.