Expanding the use of volatile anesthetic agents beyond the operating room

Abstract

Although volatile anesthetic agents (VAA) and conventional anesthesia workstations allowing for their delivery have been facets of modern-day operating rooms for many generations of anesthesiologists, they have also been used sporadically in the intensive care unit (ICU) with reports dating back for more than 30 years. The application of VAA as sedatives has been limited largely to patients suffering from severe reactive airway disease, status epilepticus, or other complex sedation scenarios. In spite of the success with VAA, a number of concerns have limited wider use of volatile-based sedation. Until recently, delivery of volatile-based sedation required the use of an anesthesia machine, which is difficult to accommodate within the confined space of the ICU environment and demands the constant presence of an anesthesiologist, neither of which is practical or feasible. In addition, concerns regarding occupational exposure to anesthetic gases have also been cited as reason for their limited uptake in the ICU. Several of these challenges have now been overcome with the introduction of the Anaesthetic Conserving Device (AnaConDa) (Sedana Medical, Sweden). The AnaConDa, an efficient lightweight and portable minivaporizer, is placed between the breathing circuit and the endotracheal tube and is universally compatible with ICU ventilators. The device is simple to use, and sedation can be easily monitored and titrated to the desired level by the nursing and respiratory therapy staff under the supervision of the attending critical care physician. Additionally, the AnaConDa is a highly efficient delivery system owing to a built-in carbon reflection filter that facilitates recycling more than 90% of the expired volatile agent. In this issue of the Journal, Ruszkai et al. describe the treatment of a patient suffering from status asthmaticus that was resistant to conventional medical therapy. Due to worsening hypoxemia, the patient required endotracheal intubation with subsequent mechanical ventilation. After intubation, the authors introduced treatment with sevoflurane administered via the AnaConDa. Sevoflurane, as with all VAA, provides bronchodilation which leads to decreased airway resistance and a reduction in shunt fraction. This strategy applied by Ruszkai et al. resulted in rapid relief of severe airway obstruction and simultaneously provided excellent ICU sedation which facilitated mechanical ventilation. Importantly, as previously documented, Ruszkai and coauthors showed that sedative doses of sevoflurane did not influence the patient’s hemodynamic status. Relatively short treatment and ICU ventilation resulted in rapid improvement of airway pressure, pulmonary compliance, and elimination of intrinsic positive end-expiratory pressure. The findings presented here by Ruszkai et al. confirm our previous experience with the use of inhaled VAA in the treatment of refractory asthma. But now this treatment can be applied simply and rapidly in critical care scenarios using the AnaConDa. This case report forms part of a growing body of evidence suggesting that inhaled volatile-based sedation in the ICU can potentially improve patient outcomes with better pulmonary ventilation-perfusion matching, shorter ventilation times, and good cardiovascular stability. On the other hand, the conventional sedation protocols (benzodiazepines, propofol, and opioids) are associated with high rates of oversedation, delirium, and cardiovascular depression which may potentially lead to a prolonged ICU stay and M. Wąsowicz, MD, PhD (&) A. Jerath, MD Department of Anesthesia and Pain Management, Toronto General Hospital, Toronto, ON, Canada e-mail: marcin.wasowicz@uhn.on.ca