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Trial registered on ANZCTR

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

Titles & IDs
Public title
Optimized carbon dioxide pressure in retroperitoneoscopic adrenalectomy
Scientific title
Comparison of physiological response between different insufflated carbon dioxide pressures in patients undergoing retroperitoneoscopic adrenalectomy for adrenal tumors
Secondary ID [1] 284691 0
Universal Trial Number (UTN)
Trial acronym
Linked study record

Health condition
Health condition(s) or problem(s) studied:
Adrenal tumors 292045 0
Condition category
Condition code
Surgery 292381 292381 0 0
Surgical techniques
Anaesthesiology 292399 292399 0 0
Metabolic and Endocrine 292400 292400 0 0
Other metabolic disorders

Study type
Description of intervention(s) / exposure
Study Procedures:
All patients will undergo retro-peritoneoscopic adrenalectomy. A opening into the retroperitoneal space will be created below the tip of the 12 th rib. A 12 mm balloon port will be placed into the retroperitoneal space after which carbon dioxide will be administered into the retroperitoneal space. The carbon dioxide will be administered throughout the procedure. The current study proposes to administer a pressure of 25 mmHg in group A and 20 mmHg in Group B.
If the surgeon believes there is impaired visibility or bleeding in group B, the CO2 pressure is increased to 25 mmHg. If the patient experiences CO2 retention, the operation will be halted, and then restarted at the pressured used, in line with current clinical routine.

Routine clinical blood samples (arterial line blood gases) will be taken every thirty minutes according to the clinical routine. The results of these blood samples are recorded for data analysis. Also, clinical data such as blood pressure, central venous pressure, respiratory minute volume, Tidal volume, and End tidal carbon dioxide level will be collected every thirty minutes. Other clinical data such as patient age, gender, tumor size, pathology of tumor, and operative time are also recorded.
Intervention code [1] 289481 0
Treatment: Surgery
Comparator / control treatment
20 mmHg (low pressure) versus 25 mmHg (standard pressure) of insufflated carbon dioxide pressure
Control group

Primary outcome [1] 292241 0
Pressure of carbon dioxide (CO2) by arterial blood gas analysis

Timepoint [1] 292241 0
60 minutes after insufflation
Primary outcome [2] 292260 0
pH in an arterial bloodgas analysis
Timepoint [2] 292260 0
60 minutes
Primary outcome [3] 292261 0
End tidal CO2 (measurement of CO2 by Capnography.)
Timepoint [3] 292261 0
60 minutes
Secondary outcome [1] 308521 0
Pressure of carbon dioxide (CO2) by arterial blood gas analysis
Timepoint [1] 308521 0
30 minutes
Secondary outcome [2] 308581 0
Subjective increase of bleeding defined as surgeon decision to increase pressure.
Timepoint [2] 308581 0
Duration of surgery.
Secondary outcome [3] 308582 0
pH in an arterial bloodgas analysis
Timepoint [3] 308582 0
30 minutes
Secondary outcome [4] 308583 0
End tidal CO2 (measurement of CO2 by Capnography.)
Timepoint [4] 308583 0
30 minutes
Secondary outcome [5] 308584 0
Operative time
Timepoint [5] 308584 0
From start of surgery to end of surgery.
Start defined as time of skin incision
End defined as time of all wounds sutured.

Key inclusion criteria
All adult patients undergoing retroperitoneoscopic adrenalectomy at north shore private by Dr Mark Sywak.

Minimum age
18 Years
Maximum age
No limit
Both males and females
Can healthy volunteers participate?
Key exclusion criteria
Pregnancy. Mental impairment

Study design
Purpose of the study
Allocation to intervention
Randomised controlled trial
Procedure for enrolling a subject and allocating the treatment (allocation concealment procedures)
Allocation concealment was performed as randomization by sealed envelopes.
Methods used to generate the sequence in which subjects will be randomised (sequence generation)
Blocked randomization will be used and randomization will be done in the operating theatre after induction of anaesthetics.
Masking / blinding
Open (masking not used)
Who is / are masked / blinded?

Intervention assignment
Other design features
Not Applicable
Type of endpoint(s)
Statistical methods / analysis
A student T-test, assuming a common standard deviation of 1.5 mmHg and 43mmHg pCO2 in one group and 45 mmHg pCO2 in the other group, using a power of 90% and an alpha level of 0.05, a sample size of 12 patients in each group would be needed.

Data analysis will include statistical testing between groups of blood gas pCO2, pH and endtidal pCO2 after 30 and 60 minutes as well as difference in operative time.

Recruitment status
Date of first participant enrolment
Date of last participant enrolment
Date of last data collection
Sample size
Accrual to date
Recruitment in Australia
Recruitment state(s)
Recruitment hospital [1] 2517 0
North Shore Private Hospital - St Leonards
Recruitment postcode(s) [1] 8207 0
2065 - Royal North Shore Hospital

Funding & Sponsors
Funding source category [1] 289313 0
Self funded/Unfunded
Name [1] 289313 0
Address [1] 289313 0
Country [1] 289313 0
Primary sponsor type
Dr Mark Sywak
Dr Mark Sywak
Sydney Endocrine Surgical Unit
suite 202, 69 Christie Street
St Leonards 2065
Secondary sponsor category [1] 287984 0
Name [1] 287984 0
Address [1] 287984 0
Country [1] 287984 0

Ethics approval
Ethics application status
Ethics committee name [1] 291077 0
North shore Private hospital ethics committee
Ethics committee address [1] 291077 0
North Shore Private Hospital, Westbourne Street, ST LEONARDS NSW 2065
Ethics committee country [1] 291077 0
Date submitted for ethics approval [1] 291077 0
Approval date [1] 291077 0
Ethics approval number [1] 291077 0
NSPHEC 2013-008

Brief summary
Surgical removal of the adrenal glands is in our unit performed by a posterior approach were the adrenal is accessed from the back with keyhole surgery. The retroperitoneum (space around the adrenal) is inflated with pressurized carbon dioxide (CO2) to create an operative space. Normally, we use a starting pressure of 25mmHg, which may be increased to 28 mmHg, at the surgeon’s discretion. Occasionally, CO2 retention with increasing levels of CO2 in blood can occur and the retroperitoneum needs to be deflated for the patients CO2 levels to recover. On the other hand, with too low pressure, bleeding may increase and visibility may become be impaired.
In the early experiences of retroscopicadrenalectomy, centers reported that they used pressures of 12mmHg to 15mmHg with success. However, many authors claim to have less bleeding and better visibility using pressures over 20-24mmHg. Also, in the largest cohort of retroperitoneoscopic adrenalectomy published, a pressure between 20mmHg and 28mmHg was routinely used without any excess of adverse events.
The implications of using different pressures have been reported in a few studies. The first one compared pressures at 15 mmHg and at 20mmHg in retroperitoneoscopic adrenalectomy and showed a statistical, but not clinical, significant difference in arterial pCO2 levels. Another study did not show any difference in arterial carbon dioxide pressure between patients undergoing open and retroperitoneoscopic adrenalectomy at 12 to 16mmHg. There are no studies examining the different physiological effects of pressures between 25-20mmHg in retroperitoneoscopic adrenalectomy, but nonetheless high pressures are routinely used in general practise with very few adverse events.

The current study proposes to start with a pressure of 25 mmHg in group A and 20 mmHg in Group B as insufflation pressures during retroperitonescopic (keyhole) adrenalectomy.

Routine clinical blood samples (arterial line blood gases) will be drawn every 30 minutes, and these samples are, together with selected clinical data, recorded for data analysis.
Trial website
Trial related presentations / publications
Public notes

Principal investigator
Name 48806 0
A/Prof Mark Sywak
Address 48806 0
A/prof Mark Sywak
Sydney Endocrine Surgical Unit
Suite 202, 69 Christie Street
St Leonards 2065
Country 48806 0
Phone 48806 0
+61 2 9437 1731
Fax 48806 0
Email 48806 0
Contact person for public queries
Name 48807 0
A/Prof Mark Sywak
Address 48807 0
A/prof Mark Sywak
Sydney Endocrine Surgical Unit
Suite 202, 69 Christie Street
St Leonards 2065
Country 48807 0
Phone 48807 0
+61 2 9437 1731
Fax 48807 0
Email 48807 0
Contact person for scientific queries
Name 48808 0
A/Prof Mark Sywak
Address 48808 0
A/prof Mark Sywak
Sydney Endocrine Surgical Unit
Suite 202, 69 Christie Street
St Leonards 2065
Country 48808 0
Phone 48808 0
+61 2 9437 1731
Fax 48808 0
Email 48808 0

No information has been provided regarding IPD availability
Summary results
Have study results been published in a peer-reviewed journal?
Other publications
Have study results been made publicly available in another format?
Results – basic reporting
Results – plain English summary