Sevoflurane Concentrations During Induction of Anesthesia With the Drager Apollo and General Electric (GE) Ohmeda Workstations in Children
Conditions: Anesthetic, Sevoflurane, Age
Sponsor: State University of New York at Buffalo

 
Official Title: 
Sevoflurane Concentrations in Children 
NCT number: 
NCT06510803 
Document Type: 
Study Protocol and Statistical Analysis Plan 
Date of the 
Document: 
August 20, 2024 
 
 

All children were ASA P/S 1 or 2, 2–7 years of age, fasted and unmedicated, and scheduled for 
elective surgery after an inhalational induction with sevoflurane by face mask. Children were 
excluded if the parents refused consent, they were outside the age range, they had craniofacial or 
airway abnormalities, malignant hyperthermia or any other myopathies, recent upper or lower 
respiratory tract infections, and moderate to severe chronic cardiorespiratory disorders. 
The breathing circuit consisted of a pediatric circle circuit (Vyaire™, Vyaire Medical, Inc. 
Mettawa, IL, USA) and a 1 L reservoir bag fitted with an appropriately sized cushioned 
facemask. After application of standard anesthesia monitors, anesthesia was induced by an 
attending anesthesiologist or nurse anesthetist with a gas mixture of 4 lpm nitrous oxide and 2 
lpm oxygen. Once the end-tidal nitrous oxide concentration reached 50%, the vaporizer was 
dialed to 8% in a single step. Respiration continued spontaneously through the induction. If 
hypopnea or apnea occurred, respiration was assisted manually by the operator to maintain the 
end-tidal pCO2 at 35-45 mmHg. Positive end-expiratory pressure was avoided. All vital signs, 
anesthetic concentrations and airway responses/unanticipated movements were recorded by an 
independent observer. Data collection ceased when the airway was manipulated. 
During the induction, the vital signs together with the inspired and expired sevoflurane 
concentrations were recorded every 30 seconds for the first 5 minutes, and every minute 
thereafter until 10 minutes or until intravenous access was established. All notable patient 
responses, including unexpected movement or airway reactions, along with the time when they 
occurred.  
A convenience sample of 12 children was selected for each anesthesia workstation a priori. A 
total of 24 patients completed the study, divided equally between the Dräger Apollo and Ohmeda 
Aisys workstations. All vaporizers were in clinical use at the time of the study; none of the 
vaporizers were recalibrated for this investigation.  
Our operating rooms are divided equally between two floors. Dräger Apollo workstations were 
deployed in the operating rooms on one floor and children who were scheduled for surgery on 
that floor were anesthetized with the new workstations. The Ohmeda Aisys workstations 

remained in the operating rooms on the second floor and children who were scheduled for 
surgery on that floor were anesthetized with the older workstations. 
Post hoc, the data were analyzed using the unpaired Student’s t test and two-factor repeated 
measures analysis of variance with the Sidak test for multiple comparisons for continuous 
measurements (GraphPad Prism 10.4.1, Boston MA) (P<0.05 was accepted).  
The FA/FI ratios for sevoflurane, where FA is the alveolar (expired) sevoflurane concentration 
and FI is the inspired sevoflurane concentration at each designated time for each patient, were 
calculated. The mean (± standard deviation, SD) of the FA/FI ratios for each workstation are 
presented graphically. The mean (± SD) inspired sevoflurane concentrations over time, inspired 
sevoflurane concentration at 1 minute of induction, maximum inspired and expired sevoflurane 
concentrations for each patient during the induction period, and time to reach 90% of the 
maximum inspired concentration during the induction for each workstation were determined.