Cardiothoracic & vascular anaesthesia
Determining Cerebrovascular Sensitivity to pH Using Continuous Arterial Blood Gas Analysis—A Prospective Observational Study
Authors' conclusion
This exploratory study provides a quantitative estimate of the relationship between CBFV and pH, and suggests that changes in CBFV are more closely related to arterial pH than to CO2. This estimate of the cerebrovascular sensitivity to pH was used to describe a feasible pH-guided approach in the management of CBF during the treatment of partially compensated acid-base disorders.
Study context
- Population
- Patients undergoing cardiac surgery with continuous in-line arterial blood gas monitoring incorporated in the cardiopulmonary bypass circuitpatients included in the analysis, with a total of 1960 datapoints
- Participants
- Thirteen patients
- Exposure
- Arterial pH vs PaCO2 as explanatory variables for percentage change in CBF velocity (CBFV) (mixed-effects models)
- Outcome
- Percentage change in CBFV per 0.1 increase in arterial pH
Methodological detailsexploratory
- Exploratory
Main finding
As reported in the abstract
CBFV decreased per 0.1 increase in arterial pH
30.6%
95% CI 28.9–32.2; P < .0001
Observational data: associations, not effects.
Further findings
Percentage change in CBFV per mm Hg increase in PaCO2
- CBFV increased per mm Hg increase in PaCO2
- 1.95% (95% CI, 1.76-2.14; P < .0001)
Proportion of variance explained (arterial pH vs PaCO2)
- Marginal R2, pH vs PaCO2
- 0.444 vs 0.294
- Conditional R2, pH vs PaCO2
- 0.744 vs 0.530
Model fit and parsimony
- Adding arterial pH to the null CO2-model, likelihood-ratio test (LRT)
- 616.4
- Adding arterial pH to the null CO2-model, ΔAIC
- −615
- Adding arterial CO2 to the pH-model, LRT
- 4.6
- Adding arterial CO2 to the pH-model, ΔAIC
- −3
Original publication
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