Related Experiment Video
Updated: Dec 28, 2025
Evaluation of Capnography Sampling Line Compatibility and Accuracy when Used with a Portable Capnography Monitor
Published on: September 29, 2020
Randomised controlled trial to investigate the relationship between mild hypercapnia and cerebral oxygen saturation
Clarence Wong1, Leonid Churilov2, Dean Cowie1
1Department of Anaesthesia, Austin Health, Heidelberg, Victoria, Australia.
Objectives:
The effects of hypercapnia on regional cerebral oxygen saturation (rSO2) during surgery are unclear. We conducted a randomised controlled trial to investigate the relationship between mild hypercapnia and rSO2. We hypothesised that, compared with targeted normocapnia (TN), targeted mild hypercapnia (TMH) during major surgery would increase rSO2.
Design:
A prospective, randomised, controlled trial in adult participants undergoing elective major surgery.
Setting:
A single tertiary centre in Heidelberg, Victoria, Australia.
Participants:
40 participants were randomised to either a TMH or TN group (20 to each).
Interventions:
TMH (partial pressure of carbon dioxide in arterial blood, PaCO2, 45-55 mm Hg) or TN (PaCO2 35-40 mm Hg) was delivered via controlled ventilation throughout surgery.
Primary And Secondary Outcome Measures:
The primary endpoint was the absolute difference between the two groups in percentage change in rSO2 from baseline to completion of surgery. Secondary endpoints included intraoperative pH, bicarbonate concentration, base excess, serum potassium concentration, incidence of postoperative delirium and length of stay (LOS) in hospital.
Results:
The absolute difference between the two groups in percentage change in rSO2 from the baseline to the completion of surgery was 19.0% higher in both hemispheres with TMH (p<0.001). On both sides, the percentage change in rSO2 was greater in the TMH group than the TN group throughout the duration of surgery. The difference between the groups became more noticeable over time. Furthermore, postoperative delirium was higher in the TN group (risk difference 0.3, 95% CI 0.1 to 0.5, p=0.02). LOS was similar between groups (5 days vs 5 days; p=0.99).
Conclusion:
TMH was associated with a stable increase in rSO2 from the baseline, while TN was associated with a decrease in rSO2 in both hemispheres in patients undergoing major surgery. This resulted in a clear separation of percentage change in rSO2 from the baseline between TMH and TN over time. Our findings provide the rationale for larger studies on TMH during surgery.
Trial Registration Number:
The Australian New Zealand Clinical Trials Registry (ACTRN12616000320459).
Related Concept Videos
01:17Assessment of Diffusion and Perfusion
The Role of Diffusion in Respiration
Diffusion is the process by which molecules move from an area of higher concentration to an area of lower concentration. In the respiratory system, this...
01:30Acute Respiratory Failure-III
01:23Physiological Control of Respiration
Breathing, a seemingly passive process, is regulated by the respiratory center in the brainstem. This center coordinates the involuntary control of respirations, which means it occurs without conscious effort, ensuring a smooth and uninterrupted pattern.
Regulation of Ventilation
The body maintains ventilation by monitoring levels of carbon dioxide (CO2), oxygen (O2), and hydrogen ion concentration (pH) in the arterial blood. Among these factors, the level of CO2 plays a crucial...
01:19Respiratory Assessment: Purpose and Indications
Objectives and Importance:
The primary goal of respiratory assessment is to evaluate patients at early risk of clinical deterioration. Since respiratory distress often precedes other signs of declining health, breathing patterns and sounds become a...
01:19Special considerations while measuring oxygen saturation
Ensuring accuracy in vital sign recordings while prioritizing patient comfort and minimizing anxiety is...
01:27Chronic Obstructive Pulmonary Disease-IV: Assessement and Diagnostic Studies
Medical History