None listed
Conditions
Brief summary
We will collect observational data on patients undergoing cardiac surgery under general anaesthesia with volatile agent maintenance (sevoflurane or desflurane). We will collect simultaneous samples of end-tidal gas concentrations, and arterial and mixed venous blood samples for partial pressure measurement for O2 and CO2, and anaesthetic gases, as we done in several previous studies), along with measurements of alveolar ventilation, and of pulmonary blood flow using bolus thermodilution. We will study 10 patients with sevoflurane and 10 patients with desflurane. Samples will be collected once in the pre-cardiopulmonary bypass period and once post-cardiopulmonary bypass. In a further group of 10 patients we will also perform the Multiple Inert Gas Elimination Technique (MIGET). This is the gold standard method for measuring precise distributions of V/Q ratios in patients. We have developed and validated an adaptation of the MIGET for use in ventilated patients under general anaesthesia. The V/Q distributions generated will be used for application within the model, to obtain precise measurements of shunt fraction and alveolar deadspace. These models will allow us the plot the precise pattern of distribution of anaesthetic gas uptake across the lungs in these patients. An index of severity of V/Q scatter will be obtained by calculations of shunt fraction and alveolar deadspace using the traditional 3-compartment Riley model, from the Shunt equation and the Bohr-Enghoff equation. Parallel calculations of shunt fraction and alveolar deadspace will be made using measurements of volatile agent for comparison.
Interventions
The partial pressure cascade for sevoflurane and desflurane will be measured in patients undergoing inhalational general anaesthesia for cardiac surgery. Measurements of inspired, end-tidal, arterial and mixed venous partial pressure of anaesthetic agent and oxygen and CO2 will be made at one time point during the pre-cardiopulmonary bypass phase. Calculation of pulmonary deadspace and shunt will be done as indices of ventilation perfusion scatter in all patients. In a further group of 10 patien
The partial pressure cascade for sevoflurane and desflurane will be measured in patients undergoing inhalational general anaesthesia for cardiac surgery. Measurements of inspired, end-tidal, arterial and mixed venous partial pressure of anaesthetic agent and oxygen and CO2 will be made at one time point during the pre-cardiopulmonary bypass phase. Calculation of pulmonary deadspace and shunt will be done as indices of ventilation perfusion scatter in all patients. In a further group of 10 patients ventilation perfusion scatter will be formally quantified uisng the mIGET.
Sponsors
Austin Health
Eligibility
Sex/Gender
All
Age
18 Years to 85 Years
Healthy volunteers
No
Inclusion criteria
Patients undergoing coronary artery bypass surgery
Exclusion criteria
Patients unable to provide informed consent Women who are pregnant Patients with cognitive impairment Patients with moderately or severely impaired respiratory function on history and examination (FEV1 or FVC < 50% predicted) Patients with morbid obesity (Body mass index (BMI) > 40 kg/m2)
Outcome results
None listed