Comparison of the use of AnaConDa® versus AnaConDa-S® during the post-operative period of cardiac surgery under standard conditions of practice.

Changes have been made to the AnaConDa device (Sedana Medical, Stockholm, Sweden), decreasing its size to reduce dead space and carbon dioxide (CO2) retention. However, this also involves a decrease in the surface area of the activated carbon filter. The CO2 elimination and sevoflurane (SEV) reflection of the old device (ACD-100) were thus compared with the new version (ACD-50) in patients sedated after coronary artery bypass graft surgery. After ERC approval and written informed consent, 23 patients were sedated with SEV, using first the ACD-100 and then the ACD-50 for 60 min each. With each device, patients were ventilated with tidal volumes (TV) of 5 ml/kg of ideal body weight for the first 30 min, and with 7 ml/kg for the next 30 min. Ventilation parameters, arterial blood gases, Bispectral-Index™ (BIS, Aspect Medical Systems Inc., Newton, MA, USA), SEV concentrations exhaled by the patient (SEV-exhaled) and from the expiratory hose (SEV-lost) were recorded every 30 min. A SEV reflection index was calculated: SRI [%] = 100 × (1 - (SEV-lost/SEV-exhaled)). Data were compared using ANOVA with repeated measurements and Student's T-tests for pairs. Respiratory rates, tidal and minute volumes were not significantly different between the two devices. End tidal and arterial CO2 partial pressures were significantly higher with the ACD-100 as compared with the ACD-50. SEV infusion rate remained constant. SEV reflection was higher (SRI: ACD-100 vs. ACD-50, TV 5 ml/kg: 95.29 ± 6.45 vs. 85.54 ± 11.15, p = 0.001; 7 ml/kg: 93.42 ± 6.55 vs. 88.77 ± 12.26, p = 0.003). BIS was significantly lower when using the higher TV (60.91 ± 9.99 vs. 66.57 ± 8.22, p = 0.012), although this difference was not clinically relevant. During postoperative sedation, the use of ACD-50 significantly reduced CO2 retention. SEV reflection was slightly reduced. However, patients remained sufficiently sedated without increasing SEV infusion.