Comparison of Different Ventilator and Vaporizer Technologies to Study Economic and Environmental Implications

Anesthetic Gas Consumption and Cost-Effectiveness

general anesthesia, anesthesia machines, sevoflurane, low volume ventilator, anesthetic costs, cost-effectiveness, fresh gas flow

The purpose of this study is to test whether or not the use of a low volume ventilator in an anesthesia machine reduces anesthetic costs significantly as compared to other high volume machines. The study will compare the a low-flow anesthesia machine to a traditional anesthesia machine during routine elective general surgery in patients with ASA ratings of 1-2 under general anesthesia receiving standard care.

The study member will screen for potential subjects using the UCIMC surgical schedule. If a subject is deemed ineligible based on the inclusion and exclusion criteria after reviewing the medical history, his/her record will be discarded. No records will be retained from ineligible subjects. After discussing with the patient's surgeon, study team member will initiate the informed consent process by approaching each eligible subject to explain the study and what it entails. The Lead Researcher will address all questions and concerns from the subject before asking the subject to sign the research consent form. The GE anesthesia machines currently owned by the operating room will be used to serve as the comparator to the Flow-i machine. The high volume anesthesia machines do not use a low volume system. Subjects will be randomized by recruitment day. On a given recruitment day, all consented subjects will receive anesthesia from one of two groups: (1) MAQUET FLOW-i device (2) GE anesthetic device Time points for both groups include: T0: Time of intubation, when volatile anesthetic are typically first delivered to the patient. We will use 15L/min fresh gas flow, while dictating tidal volumes of 6-8 mL/kg ideal body weight and a PEEP of 6 centimeters of water (cm H2O) in accordance with current best practices. T1: Time of incision, which typically represents the time of reaching steady state conditions of volatile anesthetic delivery. We will reduce fresh gas flow to 2 L/min in accordance with local practice and weigh the vaporizer at this point, allowing us to measure comparative anesthetic consumption during this wash-in time period (T0-T1). T2: Time of anesthetic weaning, typically the time when preparing for patient emergence begins by discontinuing the delivery of volatile anesthetics to the patient. The vaporizer will be re- weighed at this point, allowing us to measure comparative anesthetic consumption at steady state maintenance of anesthetic depth (T1-T2) Logically, we will also be able to use T0-T2 in order to understand total comparative anesthetic consumption. Aside from the randomization to either Group 1 or Group 2, there will be no changes in the surgical or anesthetic procedure, including the medication or treatments given to the subjects as determined by the treating physician. All subjects will receive general anesthesia in accordance to local practice. For this study, the vaporizer(s) will be weighed on a tared scale before research procedures commence, after induction, and when the gas is shut off during weaning of anesthesia in preparation for extubation to calculate the amount consumed during this time (grams/minute). In addition, the following variables will be recorded: Subject weight (kg) Tidal Volume (TV) Respiratory Rate (RR) 9 of 24 Positive end-expiratory pressure (PEEP) Fresh Gas Flow Volume % gas End Tidal (%) Time of extubation Time when Aldrete score \> 8 This is not a physician-blinded study being that the physical characteristics of the standard delivery units are distinguishable from the MAQUET FLOW-i machine. All MAC concentrations are standard of care: After the surgical procedure, patient will be assessed for time to reach Aldrete score greater than 8, level of pain and time to extubation. Their medical records will be reviewed to determine need for times and adverse events. Patients will not be contacted for study-related follow-up after they are discharged from recovery. No photographs or audio/video recording will be collected for this study. Subject's Privacy: The study team member will screen for potential subjects using the UCIMC surgical schedule. If a subject is deemed ineligible based on the inclusion and exclusion criteria after reviewing the medical history, his/her record will be discarded. No records will be retained from ineligible subjects. Study team member will approach each eligible patient to explain the study and what it entails. The study team member will address all questions and concerns from the subjects before asking the patient to sign the research consent form.

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