Letters to the Editor: Letters & Announcements
To the Editor
The Anaesthetic Conserving Device AnaConDa© (ACD) (Sedana Medical, Uppsala, Sweden) is a small vaporizer inserted into a ventilator circuit that allows vaporization of liquid sevoflurane from a syringe pump, and has been used to deliver volatile anesthetics for sedation of patients in the intensive care unit.1 We recently cared for such a patient receiving inhaled nitric oxide (NO), the concentration of which appeared to be altered by the ACD.
A 64-year-old man, with severe chronic obstructive pulmonary disease and hypertension, underwent both aortic and mitral valve replacement. Permission was obtained from the patient for this report. Postoperatively, severe pulmonary hypertension and right ventricular failure required treatment with levosimendan, dobutamine, epinephrine, and inhaled NO at 16 ppm. NO concentrations were monitored using the NOxBOX© (Bedfont Medical, Kent, England). The patient later developed pneumonia and acute respiratory distress syndrome with increasing hypoxia, and the method of sedation was changed from intermittent midazolam to sevoflurane administered via the ACD. While aiming for Bispectral Index values between 60 to 70, an end-tidal concentration of sevoflurane between 0.5% and 0.7% was accompanied by a decrease in the hemoglobin oxygen saturation (SpO2) from 96% to 91%. The NO concentration measured at 2 sites in the system both before and after using the ACD revealed a 50% decrease in the concentration measured after using the ACD. Changing the site of NO delivery into the breathing system after rather than before using the ACD resulted in an increased inspired NO concentration to 16 ppm and an increased SpO2 of 98%.
We hypothesize that the decreased SpO2 was related to decreased inhaled NO concentration caused by absorption of NO in the carbon-activated filter of the ACD.2–4
Jose Luis Guerrero Orriach
Manuel Galan Ortega
Manuel Rubio Navarro
Jose Cruz Manñas
Hospital Virgen de la Victoria
AnaConDa declined invitation to respond.
1. Soukup J, Schärff K, Kubosch K, Pohl C, Bomplitz M, Kompardt J State of the art: sedation concepts with volatile anesthetics in critically ill patients. J Crit Care 2009; 24: 535–44
2. Meiser A, Laubenthal H Inhalational anaesthetics in the ICU: theory and practice of inhalational sedation in the ICU, economics, risk-benefit. Best Pract Res Clin Anaesthesiol 2005; 19: 523–38
3. Chatterjee A, Black SM, Catravas JD Endothelial nitric oxide (NO) and its pathophysiologic regulation. Vascul Pharmacol 2008; 49: 134–40
4. Dhillon JS, Kronick JB, Singh NC, Johnson C A portable nitric oxide scavenging system designed for use on neonatal transport. Crit Care Med 1996; 24: 1068–71