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Trial registered on ANZCTR

Registration number
Ethics application status
Date submitted
Date registered
Date last updated
Type of registration
Prospectively registered

Titles & IDs
Public title
Effect of warm humidified carbon dioxide insufflation on de-airing in patients undergoing aortic valve replacement
Scientific title
Effect of warm humidified carbon dioxide insufflation on de-airing during aortic valve replacement
Secondary ID [1] 295439 0
Universal Trial Number (UTN)
Trial acronym
Linked study record

Health condition
Health condition(s) or problem(s) studied:
cardiac de-airing following cardio-pulmonary bypass 308697 0
Condition category
Condition code
Cardiovascular 307634 307634 0 0
Coronary heart disease
Surgery 307704 307704 0 0
Surgical techniques

Study type
Description of intervention(s) / exposure
This is a blinded randomized controlled, prospective trial in patients undergoing aortic valve replacement. Subjects will be randomly allocated to one of three groups.
• Group 1: Dry CO2 insufflation (Bone dry, 21 degrees Celsius)
• Group 2: Warm humidified CO2 insufflation (37 degrees celsius, 98% relative humidity)
• Group 3: Ambient air
For the duration of the surgery patients in the dry CO2 insufflation group will have bone dry room temperature CO2 insufflated into their thorax, similarly the warm humidified CO2 group will have humidified normothermic CO2 insufflated into their thorax, and the ambient air group will not be insuflated and left open to ambient room air.
Participants, surgeon, anaesthetist will be blinded to their allocation. The perfusionist will remain un-blinded and be responsible for delivering CO2 and turning the HumiGard™ system on or off depending on what group the patient is allocated to.
HumiGard™ system:
• F&P HumiGard™ MR870AEU surgical humidifier
• F&P HumiGard™ ST320 Surgical Humidification Kit
• ST300DF VITA-diffuser® Cardia Innovation
• 900ST100 Adapter

The intervention is complete at end of surgery, the performance of the HumiGard machine has been validated as per FDA and MEDDEF requirements.
Intervention code [1] 301751 0
Treatment: Surgery
Intervention code [2] 301752 0
Intervention code [3] 301822 0
Treatment: Other
Comparator / control treatment
The control group is group 3 : ambient air. this group will not recieve CO2 insufflation
Control group

Primary outcome [1] 306621 0
number of bubbles on Transesophageal echocardiogram during the deairing period, from release of cross clamp until the end of deairing.
Timepoint [1] 306621 0
The deairing period, from release of cross clamp until the end of deairing.
Secondary outcome [1] 349040 0
Volume of microemboli .
Timepoint [1] 349040 0
from the release of the aortic cross clamp (T0) to 10 minutes after removal of cross clamp (T10). The total volume of the emboli seen on the transesophageal echocardiogram in this time period
Secondary outcome [2] 349267 0
De-airing time before cardiac ejection (minutes) starting at removal of aortic cross clamp and ending at beginning of cardiac ejection. Time recorded to be judged by blinded anaesthetist.
Timepoint [2] 349267 0
before cardiac ejection (minutes) starting at removal of aortic cross clamp and ending at beginning of cardiac ejection
Secondary outcome [3] 349268 0
Serum cardiac troponin levels prior to surgery and the day after surgery.
Timepoint [3] 349268 0
Levels of troponin in the blood will be assessed from blood taken prior to and the day after surgery.
Secondary outcome [4] 349269 0
Peri-operative core temperature as measured by nasoesophageal temperature probe.
Timepoint [4] 349269 0
in 15 min intervals during the peri-operative period including induction and recovery
Secondary outcome [5] 349270 0
Temperature on the heart as measured by intramuscular probe at 15 minute intervals.
Timepoint [5] 349270 0
when the heart becomes accessible till when it is no longer accessible in 15 min intervals

Key inclusion criteria
1. Patients scheduled for aortic valve replacement, will be included in the study.
2. Able to give informed consent
3. Male or female =18 - 65 years of age
Minimum age
18 Years
Maximum age
65 Years
Both males and females
Can healthy volunteers participate?
Key exclusion criteria
1. Significant chronic obstructive pulmonary disease/emphysema
2. Significant (>50%) carotid artery disease
3. Prior cardiac or pulmonary surgery
4. Thoracic trauma and concomitant left internal thoracic artery grafting
5. At anaesthetist discretion on ability to compensate for CO2

Study design
Purpose of the study
Allocation to intervention
Randomised controlled trial
Procedure for enrolling a subject and allocating the treatment (allocation concealment procedures)
sealed opaque envelopes
Methods used to generate the sequence in which subjects will be randomised (sequence generation)
Simple randomisation using a randomisation table created by
computer software (i.e. computerised sequence generation)
Masking / blinding
Blinded (masking used)
Who is / are masked / blinded?
The people receiving the treatment/s
The people administering the treatment/s
The people assessing the outcomes
The people analysing the results/data
Intervention assignment
Other design features
Not Applicable
Type of endpoint(s)
Statistical methods / analysis
A total of 117 subjects to be enrolled to participate in the study n = 39 per treatment group.
Statistical rational
An unpublished audit on 77 patients performed by the investigation site found that when bubbles were scored on a 0-4 scale by a blinded anaesthetist subjects exposed to cold dry CO2 insufflation had an average score of 2.218 (SD = 1.392). Patients exposed to heated humidified CO2 insufflation had an average score of 1.307 (SD = 0.655). To detect the same order of magnitude in the actual number of microemboli with 80% power and 95% confidence 37 subjects per arm are required. Assuming a 5% drop out 39 patients per group will be recruited.
Continuous variables will be analysed using the independent samples t-test (reporting mean and standard deviation) and Mann Whitney U (reporting median and interquartile range) test for parametric and non-parametric data respectively. The Shapiro-Wilk test will be used to assess normality of data as well as assessment of the data histogram. A p-value of <0.05 will mean that the data are not normally distributed.
Multiple linear regression to adjust for covariate data including age, gender, type of operation, surgical technique (open/laparoscopic). Where data are not normally distributed for the primary outcome, continuous data will be log-transformed prior to regression analysis.
We will use SPSS version 24 to analyse all data and 2-sided p values of <0.05 will be deemed significant, and 95% confidence intervals presented where appropriate.
Categorical data will be analysed using the Chi-squared test or Fischer’s exact test where appropriate.
Due to the low risk of the intervention and relatively small sample size no interim analysis or statistical stopping rules are planned.

Recruitment status
Not yet recruiting
Date of first participant enrolment
Date of last participant enrolment
Date of last data collection
Sample size
Accrual to date
Recruitment outside Australia
Country [1] 10621 0
New Zealand
State/province [1] 10621 0

Funding & Sponsors
Funding source category [1] 300030 0
Name [1] 300030 0
waikato hospital
Address [1] 300030 0
Pembroke Street
Hamilton 3204
New Zealand
Country [1] 300030 0
New Zealand
Funding source category [2] 300087 0
Commercial sector/Industry
Name [2] 300087 0
Fisher and Paykel Healthcare
Address [2] 300087 0
15 Maurice Paykel Place
East Tamaki 2013 Auckland
Country [2] 300087 0
New Zealand
Primary sponsor type
Commercial sector/Industry
Fisher and Paykel Healthcare
Fisher & Paykel Healthcare
15 Maurice Paykel Place
East Tamaki, Auckland 2013
New Zealand
New Zealand
Secondary sponsor category [1] 300319 0
Name [1] 300319 0
Address [1] 300319 0
Country [1] 300319 0

Ethics approval
Ethics application status
Ethics committee name [1] 300878 0
Northern B Health and Disability Ethics Committee
Ethics committee address [1] 300878 0
Health and Disability Ethics Committees
Ministry of Health
133 Molesworth Street
PO Box 5013
Ethics committee country [1] 300878 0
New Zealand
Date submitted for ethics approval [1] 300878 0
Approval date [1] 300878 0
Ethics approval number [1] 300878 0
Ethics ref: 18/NTB/88
Ethics committee name [2] 300880 0
Waikato District Healthboard Ethics Committee
Ethics committee address [2] 300880 0
Waikato District Health Board
Pembroke Street
Private Bag 3200
Hamilton 3240
Ethics committee country [2] 300880 0
New Zealand
Date submitted for ethics approval [2] 300880 0
Approval date [2] 300880 0
Ethics approval number [2] 300880 0

Brief summary
Neurological complications are common and occur in 32 to 83% of patients that have undergone cardiac surgery. This clinical outcome is believed to be due to the presence of gas, which enters the blood stream to the brain when the patient comes off the cardio pulmonary bypass machine, and may persist for up to 5 years. In addition to temporary neurocognitive effects, gas in the bloodstream can also cause permanent neurological defects and life 
threatening arrhythmia's. To avoid these consequenses several deairing techniques are used, one of which is the flooding of the chest cavity with Carbon Dioxide, an inert gas that is easily absorbed by the body, to minimize the gas bubbles in the bloodstream. We believe that the humidification of the Carbon Dioxide used to fill the chest cavity will further improve deairing by making the gas easier for the body to be absorbed. In a previous study there was a benefit to heating and 
humidifying the Carbon Dioxide used to deair. It reduced the time it took to deair the heart from 16 minutes to 2 minutes, reduced the percentage of patients that had gas bubbles from 70% to 24% and the number of patients that showed neurological symptoms from 29% to 2%.
In this trial we aim to assess the impact of heating and humidifying the Carbon Dioxide used to fill the chest cavity on the number of gas bubbles after deairing and whether as a consequence will reduce the neurological complications. Further we hope to develop a method of objectively measuring the amount of bubbles in the blood.  
Trial website
Trial related presentations / publications
Public notes

Principal investigator
Name 85134 0
Dr David McCormack
Address 85134 0
Waikato Hospital
Pembroke Street
Hamilton 3204

Country 85134 0
New Zealand
Phone 85134 0
+64 7 839 8899 ext 96514
Fax 85134 0
Email 85134 0
Contact person for public queries
Name 85135 0
Dr David McCormack
Address 85135 0
Waikato Hospital
Pembroke Street
Hamilton 3204

Country 85135 0
New Zealand
Phone 85135 0
+64 7 839 8899 ext 96514
Fax 85135 0
Email 85135 0
Contact person for scientific queries
Name 85136 0
Dr David McCormack
Address 85136 0
Waikato Hospital
Pembroke Street
Hamilton 3204

Country 85136 0
New Zealand
Phone 85136 0
+64 7 839 8899 ext 96514
Fax 85136 0
Email 85136 0

No information has been provided regarding IPD availability
Summary results
No Results