AnaConDa Device: Solution to Perform Cardiac Surgery Without Intravenous Anesthetic During the Corona Virus Disease 2019 Pandemic

To the Editor:

The corona virus disease 2019 pandemic has led to an increase in the consumption of sedative drugs all over the world and is responsible for a shortage of supply. Intravenous anesthetics, such as propofol or midazolam, have made their appearance on the Food and Drug Administration's shortage list.¹ Difficulties in supply have an effect on the capacity to manage surgical pathologies, especially those that cannot be delayed. Cardiac surgery is of particular concern. Propofol is most often required to induce and maintain anesthesia, especially during cardiopulmonary bypass (CPB) and/or in the first hours after surgery in the intensive care unit (ICU).² Volatile (inhaled) agents represent an alternative to intravenous drugs. Although their administration via the venous oxygenator during CPB is possible, their use is not common, especially in European centers.² This practice is common in many North American centers but requires dedicated halogen vaporizers to be attached to CPB equipment. Moreover, because conventional ICU ventilators do not have a vaporizer, postoperative sedation frequently does not involve their use.

We describe our solution to provide sedation without intravenous anesthetics used for conscious sedation. We used the Anaesthetic Conversing Device (AnaConDa; BOMImed, Winnipeg, Manitoba, Canada) to ensure the continuous administration of sevoflurane during and after surgery. AnaConDa, an anesthetic delivery system, was developed for the administration of volatile agents via common intensive care ventilators.^{3 , 4}

After anesthesia induction, which requires intravenous drugs (etomidate), sedation was maintained with sevoflurane via administration through the vaporizer of the anesthesia machine. At the beginning of CPB, the AnaConDa was placed just before the oxygenator of the CPB, on the oxygen airline. To adapt the system on the airline, 2 connectors (Intersurgical Complete Respiratory Systems, Berkshire, UK) were inserted: 0² 6 mm (22 F) and 0² 6 mm 22M (15F). The montage is shown in figure 1 . The gas exhaust port of the oxygenator was connected to a FlurAbsorb anesthetic gas filter (Sedana Medical, Danderyd, Sweden). A 6- mm (22F) connector was necessary to connect the gas exhaust port of the oxygenator to the gas filter. During CPB, a 3-way cock was inserted at the gas outlet of the oxygenator to allow for gas monitoring. Liquid sevoflurane was delivered by a syringe pump. After priming the system with a bolus of 1.5 mL, sevoflurane was started at the rate of 15 mL/h, and the pump flow was adjusted to target a minimum alveolar concentration ranging from 0.8 to 1.2. Moreover, the bispectral index permitted us to determinate the depth of anesthesia, with a target range of 40 to 60. During CPB, we observed an increase of sevoflurane pump flow, ranging 15-to -20 mL/h. Indeed, during CPB, the flow in the device was continuous. Thus, the consumption was higher because the reflection function of the AnaConDa was not exploited. After CPB, the AnaConDa was moved back to the breathing circuit between the endotracheal tube and the Y-piece. When the surgery was completed, during patient transfer to the ICU, the AnaConDa was kept on the patient. In the ICU, the sevoflurane infusion via the AnaConDa was continued until the decision was made to allow the patient to emerge from anesthesia. Then, the gas outlet of the ventilator was connected to another FlurAbsorb anesthetic gas filter.

Fig 1.

The AnaConDa connection on the cardiopulmonary bypass circuit. The AnaConDa was inserted on the airline between the oxygen delivery system (eg, Sechrist air/oxygen gas mixers) and the cardiopulmonary bypass oxygenator. Two kinds of connectors were needed. CPB, cardiopulmonary bypass.