Intracranial PressureTILTDOWN-3NCT06865027
The Effect of Arterial Carbon Dioxide Levels on Cerebral Blood Flow and Cerebral Autoregulation in the Steep Trendelenburg Position During Robot-assisted Prostatectomy, and Its Effect on Postoperative Cognition
A study testing Ventilation strategy in people with Intracranial Pressure and Circulation System, run by University Hospital, Akershus at 1 site in Norway.
Trial summary
Patients scheduled for robot-assisted prostatectomy will be randomized to either high or low concentrations of carbon dioxide in the blood. This will be managed by applying different ventilation strategies during anesthesia.The levels will be distinctly different. Read more about this study
- Who is it for?
- Ages 55 to 80 years, men only
- Conditions the study is for
- Intracranial Pressure, Circulation System, Cerebral Perfusion Pressure
- What is being tested?
- Ventilation strategy
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 46 participants
- Where
- 1 siteNorway
- Study dates
- 24 Jan 2025to 28 May 2026
- Phase
- Interventional
- Are there results?
- None posted in the registry
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 55 to 80 years
- Men only
- No healthy volunteers
- Adult, Older adult
Who may be able to join
None listed.
Who cannot join
- Poorly controlled hypertension (resting BP >165/90 on pre-study consult).
- Emphysema of the lung.
- Previous spontaneous pneumothorax.
- Cerebrovascular disease. Including but not limited to previous SAH, EDH, SDH, hemorrhage from AVM, known AVM and stenosis in carotid or cerebral arteries.
- Intracranial malignancy or metastases from primary cancer.
- Significant cardiovascular disease (NYHA class III or IV).
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- Renal failure grade 4 or 5 (estimated GFR <30).
- Anatomical hinders for performing ultrasound of the right carotid artery or middle cerebral artery.
- Primary language other than Scandinavian.
- Diagnosed dementia of any subtype.
Trial locations and contacts
1 site in 1 country.
About this study
Official title: Effect of Arterial Carbon Dioxide Levels on Cerebral Blood Flow and Cerebral Autoregulation in Steep Trendelenburg Position During Robot-assisted Prostatectomy, and Its Effect on Postoperative Cognition - A Clinical Blinded Randomized Trial
Patients scheduled for robot-assisted prostatectomy will be randomized to either high or low concentrations of carbon dioxide in the blood. This will be managed by applying different ventilation strategies during anesthesia.The levels will be distinctly different.
The investigators will assess whether different concentrations of carbon dioxide in blood results in different brain blood flow levels and different intracranial pressure during laparascopic surgery in the head-down tilted position. The investigators also will assess if different carbon dioxide level will manifest in different cognitive abilities in the two study groups, measured on day 1 post-surgery.
Read the detailed description
Detailed Description: The carotid artery carries blood into the brain. Therefore, blood flow levels in the carotid artery may be used to assess brain perfusion. Brain perfusion is carefully regulated by the body, to ensure that the brain always receives enough oxygen and nutrients. During prostate surgery using laparoscopic techniques, the patient lies tilted on the operating table, with their head markedly lower than their legs. The investigators aim to study the effect on cerebral blood flow of a head-down tilted body position in combination with anesthesia and laparoscopic surgery, and particularly how cerebral blood flow is influenced by the participants' breathing pattern. The study aims to achieve insights that may be used to improve the treatment of vulnerable surgical patients, such as those with cerebrovascular disease or severe heart disease.
Anesthesia and surgery will proceed as usual, with the exception that the respiratory support the participants receive during the surgery will be adjusted as described below. The participants will receive standard monitoring of heart rate, blood pressure, and blood oxygen levels. Before surgery, the anesthesia team will per routine insert two plastic cannulas into the left arm for administering medication, and a plastic cannula into the participant's left wrist for close monitoring of the participant's blood pressure.
Study participants will undergo four additional steps:
- Before surgery, an anesthesiologist will insert a thin plastic cannula into a superficial vein on the side of the neck. The cannula is the same type as the ones used on the arm and has a diameter of 1.1 mm. The purpose of this cannula is to measure the pressure of the blood returning from the brain to the heart. The procedure involves brief, moderate pain associated with the needle insertion. The plastic cannula will be removed before the participant wakes up from anesthesia.
- Just before and during surgery, a trained anesthesiologist will perform ultrasound measurements on the right side of the participant's neck, temple, and the outside of the eyelid. Each measurement lasts 4-5 minutes. This will not prolong the time spent in the operating room. The measurements will cause no discomfort.
- All patients undergoing prostate removal with robotic surgery receive respiratory support with a ventilator during anesthesia. In this study, the investigators will adjust the ventilator to control the carbon dioxide (CO2) levels towards either the lower or upper normal range for CO2. A blinded randomization will determine the group assignment. Regardless of which group a participant is assigned to, their CO2 level will be maintained within a range routinely used during anesthesia and considered completely safe.
In the project, the investigators will collect and record participant information. The investigators will store recordings of the participants' pulse, blood pressure, breathing depth and rhythm, levels of oxygen and CO2 in the participants' blood, medication doses used during surgery, and results of blood tests taken during surgery. From the participants' medical records, the investigators will retrieve and record the participants' age, gender, height, weight, whether the participants have chronic diseases, and which regular medications the participants use.
Cognitive tests of reaction time and problem-solving abilities will be administered a few days before and one day after surgery.
Receiving information about an illness, undergoing a surgical procedure, receiving general anesthesia, peroperative CO2 levels, body position during robotic surgery, and postoperative pain medication all affect the body physically and may trigger stress and anxiety. The investigators want to assess this impact using a well-established method that tests reaction time through five exercises on an iPad. The method has been developed for use in patients. Those participating in the study will be asked to perform this test at the outpatient clinic a few days before surgery and one day after surgery.
- Conditions
- Intracranial Pressure, Circulation System, Cerebral Perfusion Pressure, Cognitive Function
- Being tested
- Ventilation strategy
- Keywords
- RALP surgery, Postoperative cognitive disorder, Cerebral perfusion pressure, Cerebral circulation, Cerebral autoregulation, Trendelenburg position, Robot-assisted laparoscopic prostatectomy, Transcranial Doppler ultrasound
- Medical subject headings
- Postoperative Cognitive Complications
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Ventilation strategyOther
Also called normocapnia, hypercapnia
The selected PaCO2 targets are:
Normocapnia: PaCO2: 5.0-5.5 kPa Hypercapnia: PaCO2: 6.4-7.0 kPa
The adjustments on the ventilator needed to achieve these targets will be administered by the anesthetic nurse and attending anesthesiologist and held within the following limitations:
Tidal volume: 4 - 8ml ml/kg IBW Inspiratory pressure 5-30 cm H2O Respiration rate 10-18 per minute PEEP 5-10 mmHg
*IBW: 50 + 0.91 (height in centimeters - 152.4) Peep, I:E ratio, and FiO2 will be administered at the anesthetic nurse's and the anesthesiologist's discretion.
| Study group | Role | What they receive |
|---|---|---|
| Hypercapnia | Other | PaCO2: 6.4-7.0 kPa Receives: Other: Ventilation strategy |
| Normocapnia | Other | PaCO2: 5.0-5.5 kPa Receives: Other: Ventilation strategy |
What is being measured
The primary outcome is the main question the study is designed to answer.
ICA flow
Changes in cerebral blood flow (ml/s) during surgery
Measured: day of surgery
Secondary outcomes (3)
Cognitive performance
Measurements of cognitive performance by CANTAB tests (Cambridge Cognition, England)
Measured: 5 days pre-surgery and 1 day post-surgery
Cerebral perfusion pressure
Estimated ICP (mmHg) minus Mean arterial pressure (mmHg).
Measured: Day of surgery
Cardiac index (L/min)
Measured by LidCO arterial pulse contour analysis
Measured: Day of surgery
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted7 Mar 2025
- Study start24 Jan 2025
- Primary completion4 May 2026
- Study completion28 May 2026
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Intracranial PressureStudies of the same condition, open and under way.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase N/A
- Primary purpose
- Prevention
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Model description
- Clinical double blinded randomized interventional study
- Masking
- Triple blind
- Who is masked
- Participant, Investigator, Outcomes assessor
- Enrolment
- 46 participants (actual)
Sponsor and investigators
- Lead sponsor
- University Hospital, Akershus
- Sponsor type
- University, hospital or other
- Collaborators
- University of Oslo
- Responsible party
- Principal investigator, Signe Søvik, University Hospital, Akershus
- Investigators
- Signe Søvik, Professor, MD, PhD, Study director, University Hospital, Akershus
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT06865027
- Sponsor's protocol ID
- REK:744921
- Other IDs
- 2022088
- Acronym
- TILTDOWN-3
- Status last verified
- Dec 2025
- First submitted
- 26 Feb 2025
- Last updated
- 2 Jun 2026
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- No: Any sharing of patient-level data from this study would have to be pre-approved by the Regional Committee for Medical and Health Research Ethics in South-Eastern Norway as well as by the Personal Data Protection Officer at Akershus University Hospital
Study at a glance
From the registry record, last updated by the sponsor on 2 Jun 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Effect of Arterial Carbon Dioxide Levels on Cerebral Blood Flow and Cerebral Autoregulation in Steep Trendelenburg Position During Robot-assisted Prostatectomy, and Its Effect on Postoperative Cognition - A Clinical Blinded Randomized Trial
- ClinicalTrials.gov ID
- NCT06865027
- Acronym / sponsor ID
- TILTDOWN-3 / REK:744921
- Conditions
- Intracranial Pressure, Circulation System, Cerebral Perfusion Pressure, Cognitive Function
- Keywords
- RALP surgery, Postoperative cognitive disorder, Cerebral perfusion pressure, Cerebral circulation, Cerebral autoregulation, Trendelenburg position, Robot-assisted laparoscopic prostatectomy, Transcranial Doppler ultrasound
- Study type
- Interventional
- Recruitment status
- Completed
- Enrolment
- 46 participants (actual)
- Lead sponsor
- University Hospital, AkershusUniversity, hospital or other
- Collaborators
- University of Oslo
- Study start
- 24 Jan 2025 (actual)
- Primary completion
- 4 May 2026 (actual)
- Study completion
- 28 May 2026 (actual)
- First posted
- 7 Mar 2025 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
Patients scheduled for robot-assisted prostatectomy will be randomized to either high or low concentrations of carbon dioxide in the blood. This will be managed by applying different ventilation strategies during anesthesia.The levels will be distinctly different.
The investigators will assess whether different concentrations of carbon dioxide in blood results in different brain blood flow levels and different intracranial pressure during laparascopic surgery in the head-down tilted position. The investigators also will assess if different carbon dioxide level will manifest in different cognitive abilities in the two study groups, measured on day 1 post-surgery.
Detailed description
Detailed Description: The carotid artery carries blood into the brain. Therefore, blood flow levels in the carotid artery may be used to assess brain perfusion. Brain perfusion is carefully regulated by the body, to ensure that the brain always receives enough oxygen and nutrients. During prostate surgery using laparoscopic techniques, the patient lies tilted on the operating table, with their head markedly lower than their legs. The investigators aim to study the effect on cerebral blood flow of a head-down tilted body position in combination with anesthesia and laparoscopic surgery, and particularly how cerebral blood flow is influenced by the participants' breathing pattern. The study aims to achieve insights that may be used to improve the treatment of vulnerable surgical patients, such as those with cerebrovascular disease or severe heart disease.
Anesthesia and surgery will proceed as usual, with the exception that the respiratory support the participants receive during the surgery will be adjusted as described below. The participants will receive standard monitoring of heart rate, blood pressure, and blood oxygen levels. Before surgery, the anesthesia team will per routine insert two plastic cannulas into the left arm for administering medication, and a plastic cannula into the participant's left wrist for close monitoring of the participant's blood pressure.
Study participants will undergo four additional steps:
- Before surgery, an anesthesiologist will insert a thin plastic cannula into a superficial vein on the side of the neck. The cannula is the same type as the ones used on the arm and has a diameter of 1.1 mm. The purpose of this cannula is to measure the pressure of the blood returning from the brain to the heart. The procedure involves brief, moderate pain associated with the needle insertion. The plastic cannula will be removed before the participant wakes up from anesthesia.
- Just before and during surgery, a trained anesthesiologist will perform ultrasound measurements on the right side of the participant's neck, temple, and the outside of the eyelid. Each measurement lasts 4-5 minutes. This will not prolong the time spent in the operating room. The measurements will cause no discomfort.
- All patients undergoing prostate removal with robotic surgery receive respiratory support with a ventilator during anesthesia. In this study, the investigators will adjust the ventilator to control the carbon dioxide (CO2) levels towards either the lower or upper normal range for CO2. A blinded randomization will determine the group assignment. Regardless of which group a participant is assigned to, their CO2 level will be maintained within a range routinely used during anesthesia and considered completely safe.
In the project, the investigators will collect and record participant information. The investigators will store recordings of the participants' pulse, blood pressure, breathing depth and rhythm, levels of oxygen and CO2 in the participants' blood, medication doses used during surgery, and results of blood tests taken during surgery. From the participants' medical records, the investigators will retrieve and record the participants' age, gender, height, weight, whether the participants have chronic diseases, and which regular medications the participants use.
Cognitive tests of reaction time and problem-solving abilities will be administered a few days before and one day after surgery.
Receiving information about an illness, undergoing a surgical procedure, receiving general anesthesia, peroperative CO2 levels, body position during robotic surgery, and postoperative pain medication all affect the body physically and may trigger stress and anxiety. The investigators want to assess this impact using a well-established method that tests reaction time through five exercises on an iPad. The method has been developed for use in patients. Those participating in the study will be asked to perform this test at the outpatient clinic a few days before surgery and one day after surgery.
Study design
- Primary purpose
- Prevention
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- Triple blind (participant, investigator, outcomes assessor)
- Number of arms
- 2
- Model description
- Clinical double blinded randomized interventional study
| Arm | Type | Receives |
|---|---|---|
| Hypercapnia | Other | Other: Ventilation strategyPaCO2: 6.4-7.0 kPa |
| Normocapnia | Other | Other: Ventilation strategyPaCO2: 5.0-5.5 kPa |
Who may qualify
- Ages
- 55 to 80 years
- Sex
- Male only
- Healthy volunteers
- Not accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (0 listed)
Key exclusion criteria (10 listed)
- Poorly controlled hypertension (resting BP >165/90 on pre-study consult).
- Emphysema of the lung.
- Previous spontaneous pneumothorax.
- Cerebrovascular disease. Including but not limited to previous SAH, EDH, SDH, hemorrhage from AVM, known AVM and stenosis in carotid or cerebral arteries.
- Intracranial malignancy or metastases from primary cancer.
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| Ventilation strategyAlso: normocapnia, hypercapniaThe selected PaCO2 targets are: Normocapnia: PaCO2: 5.0-5.5 kPa Hypercapnia: PaCO2: 6.4-7.0 kPa The adjustments on the ventilator needed to achieve these targets will be administered by the anesthetic nurse and attending anesthesiologist and held within the following limitations: Tidal volume: 4 - 8ml ml/kg IBW Inspiratory pressure 5-30 cm H2O Respiration rate 10-18 per minute PEEP 5-10 mmHg *IBW: 50 + 0.91 (height in centimeters - 152.4) Peep, I:E ratio, and FiO2 will be administered at the anesthetic nurse's and the anesthesiologist's discretion. | Other | Hypercapnia, Normocapnia |
Primary outcome
ICA flow
Time frame: day of surgery
Changes in cerebral blood flow (ml/s) during surgery
3 secondary outcomes
Cognitive performance
Time frame: 5 days pre-surgery and 1 day post-surgery
Cerebral perfusion pressure
Time frame: Day of surgery
Cardiac index (L/min)
Time frame: Day of surgery
Results and safety
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 2 Jun 2026.
- Individual participant dataSharing planned: No. Any sharing of patient-level data from this study would have to be pre-approved by the Regional Committee for Medical and Health Research Ethics in South-Eastern Norway as well as by the Personal Data Protection Officer at Akershus University Hospital
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part. This study is not recruiting at the moment.
Signe Søvik, Professor, MD, PhD study director
University Hospital, Akershus
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A study testing Ventilation strategy in people with Intracranial Pressure and Circulation System, run by University Hospital, Akershus at 1 site in Norway.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 0 inclusion and 10 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: finished, as of the sponsor's last update on 2 Jun 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in Norway. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
How can a doctor refer a patient or contact the research team?
The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
ICA flow (time frame: day of surgery). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 2 Jun 2026.