Evaluation of the effect of targeted mild therapeutic hypercapnia during and after cardiopulmonary bypass on cerebral oxygenation and neuropsychological outcomes

A Pilot, Randomised, Unblinded, Feasibility, Safety and Biochemical and Physiological Efficacy Study of Targeted Mild Therapeutic Hypercapnia in Patients Undergoing Cardiopulmonary Bypass

Status

Completed

Phases

Unknown

Study type

Interventional

Source

ANZCTR

Registry ID

ACTRN12616000111471

Acronym

The CO2 in CPB Study

Enrollment

Registered

2016-02-02

Start date

2016-02-04

Completion date

2017-06-02

Last updated

2025-09-08

For informational purposes only — not medical advice. Sourced from public registries and may not reflect the latest updates. Terms

Conditions

None listed

Brief summary

Cardiopulmonary bypass (CPB) is commonly used in cardiac surgery to maintain blood flow to the brain. However, loss of pulse pressure during CPB means that brain blood flow may be low and brain oxygen levels may fall. This may be bad and affect brain performance after surgery. Oxygen levels in the brain can be monitored with Near Infrared Spectroscopy (NIRS) and brain performance can be assessed with psychological tests. One way to improve brain blood flow and oxygen levels may be to target a slightly higher carbon dioxide (CO2) concentration in the blood during and after CPB. This is because even a slight increase in CO2 can open up the blood vessels to the brain, increase blood flow to it and increase oxygen levels for brain cells. However, targeting such slightly higher CO2 levels in this setting has not been formally studied. The aim of this study is to compare the changes in cerebral oxygen levels (SctO2) and psychological test-assessed brain performance when a mildly increased CO2 level is targeted compared with a normal CO2 level during and after CPB. We plan to study forty adult patients having CPB (twenty targeting normal CO2 levels and twenty targeting mildly increased CO2 levels), and to measure their SctO2 and psychological test performance prior to surgery and before hospital discharge. The information derived from our investigation will be used by doctors to improve oxygen levels in the brain of patients during and after CPB in the future.

Interventions

Following blinded allocation, ETCO2 adjustment to target mild hypercapnia (50-55mmHg) will be made using ventilator settings (respiratory rate) throughout the procedure by the treating anaesthetist. ETCO2 levels, as measured using capnography, are similar to arterial levels - while the patient is on bypass, blood gases will be used to measure blood CO2 levels.

Study design

Allocation

Randomised controlled trial

Intervention model

Parallel

Primary purpose

Prevention

Masking

Open (masking not used)

Eligibility

Sex/Gender

All

Age

18 Years to No maximum

Healthy volunteers

Inclusion criteria

1. Admitted to the Austin Hospital for elective cardiac surgery 2. Aged 18 years or older 3. Able to speak and read English

Exclusion criteria

1. Pre-operative Mini-Mental State Examination score < 24 2. Emergency cases 3. History of neuropsychiatric disorders 4. Contraindications to increased CO2 levels, such as right-sided heart failure, pulmonary hypertension, metabolic acidosis 5. Aortic arch surgery

Outcome results