Critical care is shifting towards using volatile anesthetics such as isoflurane and sevoflurane as sedatives for patients on mechanical ventilation. An ever-expanding body of research vividly illustrates the advantages and disadvantages of utilizing them for long term sedation. For this shift in procedure to maintain safety and effectiveness, a reliable, cost effective and protective delivery system ought to be instituted that corresponds simultaneously with the standards in modern critical care ventilation and protocols while safeguarding care workers and the environment from overexposure to medications.
The anesthetic conserving device (ACD) is a device that ensures patient safety when administering a sedative dose of both isoflurane and sevoflurane. It operates in tandem with critical care ventilators, syringe pumps, and gas monitors. This innovative technology is designed to function like a small vaporizer – delivering vaporized anesthetic to the patient. The device has a unique reflecting medium with a proprietary carbon filament material, allowing it to absorb and release over 90% of anesthetics while still returning moisture to the patient [1].
In recent years, volatile anesthetics have received increasing attention as a potential alternative to propofol-based sedation regimens in the intensive care unit. In addition, due to positive results from their utilization during surgical procedures and diagnostic interventions, volatile anesthetics have been used safely and successfully for conscious sedation purposes in critically ill patients for more than 30 years. Randomized controlled trials, recently published, have explored the use of volatiles with the ACD device. Results suggest that this method creates a comparable level of sedation as midazolam and propofol, as well as a shorter time to awakening. Additional findings indicate its potential to positively impact in-hospital mortality and 1-year survival rates [2].
A more recent study that was published in the journal of critical care, prospectively randomized 79 intubated patients requiring at least 48 hours of sedation, to receive sevoflurane or intravenous sedation and looked at the sevoflurane efficacy and safety. The measured outcome was the time to spontaneous breathing and extubation, opioid consumption, hemodynamics, ICU and hospital length of stay (LOS) and adverse events. Sedation quality measured by RASS was comparable between the two groups and the use of sevoflurane was associated with a reduction in time to spontaneous breathing (26 min vs. 375 min, P < 0.001). There was no difference in hemodynamics, LOS or the occurrence of adverse events between the two groups. However, patients sedated with propofol had lower opioid requirements compared to sevoflurane group (remifentanil:400 μg/h vs. 500 μg/h, P = 0.007; sufentanil:40 μg/h vs. 30 μg/h, P = 0.007) [3].
According to a recent trial by Soukup et al, all of the following regarding the use of sevoflurane as a sedative in the ICU is true except:
- No difference with adverse effects compared to propofol
- Patients on inhalative sedation showed shorter weaning time
- Patients on sevoflurane had a higher opioid requirement
- Patients on sevoflurane had more hemodynamic instability
Volatile agents offer an array of advantages including a fast time to awakening. One potential reason for this quicker recovery is their low metabolization rate of only 2 to 5 percent. Additionally, after the administered sevoflurane is no longer employed, there is a relatively rapid “washout” period which does not perpetuate the remaining effects of sevoflurane into prolonged sedation. As such, it is apparent from these two factors why volatile agents are so advantageous when compared to other sedation options.
Concerns with the use of these devices would be the dead space that is added to the circuit which may lead to a significantly increased end-tidal CO2-values due to the lack of compensation for dead space ventilation. However, this study showed a constant and similar end-tidal CO2 compared to intravenous sedatives. The other concern would be about performance of these devices in patients with protective lung strategy where lower tidal volume is used. This was initially investigated in the pilot SESAR study (Sevoflurane for Sedation in ARDS) and showed that sevoflurane improved oxygenation and decreased levels of a marker of epithelial injury and of some inflammatory markers, compared with midazolam [4].
In conclusion, clinical research has identified long-term inhalative sedation of critically ill patients using sevoflurane as a viable option for obtaining comparable sedation quality to intravenous agents. Additionally, there is promise that this technique could reduce weaning times. Current and ongoing studies suggest the possibility of using volatile anesthetics in the ICU as an alternate to conventional sedation with intravenous means. However, further research is needed in order to accurately assess the physiological mechanisms, safety and impact on longer term outcomes.
Reference
Farrell R, Oomen G, Carey P. 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. J Clin Monit Comput. 2018 Aug;32(4):595-604. doi: 10.1007/s10877-017-0097-9. Epub 2018 Jan 31. PMID: 29388094; PMCID: PMC6061082.
A. Meiser, T. Volk, J. Wallenborn, U. Guenther, T. Becher, H. Bracht, et al. Inhaled isoflurane via the anaesthetic conserving device versus propofol for sedation of invasively ventilated patients in intensive care units in Germany and Slovenia: an open-label, phase 3, randomised controlled, non-inferiority trial. Lancet Respir Med, 9 (2021), pp. 1231-1240.
Jens Soukup, Peter Michel, Annett Christel, Gregor Alexander Schittek, Nana-Maria Wagner, Patrick Kellner, Prolonged sedation with sevoflurane in comparison to intravenous sedation in critically ill patients – A randomized controlled trial, Journal of Critical Care, Volume 74, 2023, 154251.
M. Jabaudon, P. Boucher, E. Imhoff, R. Chabanne, J.S. Faure, L. Roszyk, et al.Sevoflurane for sedation in acute respiratory distress syndrome. A randomized controlled pilot study. Am J Respir Crit Care Med, 195 (2017), pp. 792-800