None listed
Conditions
Brief summary
Movement of gases (such as carbon dioxide or inhaled anaesthetic agents) that dissolve in the blood, in and out of the lungs, can indicate blood flow through the lungs. Because lung blood flow changes in parallel with cardiac output, we can measure the levels of these gases in the lungs to obtain information about cardiac output. It is already well known that expired CO2 levels change as cardiac output changes. Our newest anaesthetic machines allow the user to set an expired concentration. The machine then adjusts delivery of the agent to maintain this expired level, with delivery increasing as uptake (& hence lung blood flow) increases and vice versa. We speculate that this system offers a unique opportunity to investigate the relationship between inhaled anaesthetic uptake and cardiac output. During off-pump coronary artery bypass surgery (OPCAB), manipulation of the heart to access the various graft sites causes abrupt changes in cardiac output. These changes occur frequently during OPCAB surgery and produce visible changes in CO2 and anaesthetic agents levels. We monitor cardiac output during OPCAB with a device that provides a continuous measure of cardiac output based on the shape of the pulse waveform. The combination of frequent large changes in cardiac output, a continuous measure of cardiac output and a new way to follow anaesthetic agent uptake gives us the opportunity to explore these relationships.
Interventions
An observational study to determine whether changes in anaesthetic agent delivery, using End-Tidal control (ETc), can be used as an indicator of cardiac output changes. We are monitoring changes in inspired concentration to determine whether these changes may provide an accurate indicator of cardiac output changes, before, during and immediately following periods of cardiac manipulation during OPCAB. We are particularly interested to see if monitoring the inspired concentration can detect car
An observational study to determine whether changes in anaesthetic agent delivery, using End-Tidal control (ETc), can be used as an indicator of cardiac output changes. We are monitoring changes in inspired concentration to determine whether these changes may provide an accurate indicator of cardiac output changes, before, during and immediately following periods of cardiac manipulation during OPCAB. We are particularly interested to see if monitoring the inspired concentration can detect cardiac output (CO) changes greater than 25%; that is, is there a given percentage fall in inspired sevoflurane that corresponds to a 25% drop in CO? This level of change is about the level of sensitivity of CO estimations using a pulmonary artery catheter and is frequently taken as the standard to which less invasive monitors should perform. Since we are comparing time periods within single patient treatments, participants are their own control.
Sponsors
Dr Frances Cammack
Eligibility
Sex/Gender
All
Age
18 Years to No maximum
Healthy volunteers
No
Inclusion criteria
Patients undergoing off-pump coronary artery bypass surgery (OPCAB) where the anaesthetic technique is based on sevoflurane and where use of flo trac/Vigileo monitors is not contra-indicated.
Exclusion criteria
Aged <18 yrs;flo trac/Vigileo not required;
Outcome results
None listed