Variation in Arterial CO 2 is a Stronger Determinant of Brain Tissue Oxygenation Than its Synchronous Value in Critically Ill Patients With Acute Brain Injury
Bibliographic record
Abstract
OBJECTIVES: In critically ill patients with acute brain injury (ABI), maintaining intracranial pressure (ICP) and brain tissue oxygenation (PbtO2) within targets could prevent secondary neurologic injury. Tight control of CO2 (Paco2), a potent regulator of cerebrovascular tone, is generally advocated, but its vasomotor effect may be short-lived. Our aim was to compare the effect of the synchronous Paco2 vs. its variation from a previous baseline on PbtO2 and ICP. DESIGN: We performed a post hoc analysis of a prospective cohort study collecting arterial blood gas (ABG) values alongside synchronous neuromonitoring variables. Linear mixed-effects models were fitted to evaluate the association between Paco2 and/or Paco2 variation from its average of the last 8-24 hr vs. PbtO2 and ICP, while controlling for cerebral perfusion pressure and Pao2. SETTING: Mixed medical-surgical ICU of Sacré-Coeur Hospital, an academic trauma center in Montreal, Canada. PATIENTS: All consecutive adult patients admitted for ABI with ICP and PbtO2 monitoring between May 2017 and November 2021. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: We included 78 patients with 3047 ABG-neuromonitoring couplets. The model using the variation of Paco2 from its average of the last 24 hr displayed the best performance for the prediction of PbtO2 (coefficient 0.37; 95% CI 0.21-0.53). The strongest predictor of ICP was the variation of Paco2 from its average of the last 8 hr (coefficient 0.17; 95% CI 0.10-0.23). CONCLUSIONS: Variation in Paco2 from baseline is a more significant determinant of PbtO2 and ICP than the absolute Paco2 value at a given time. There may be a baseline vasomotor reset when patients are exposed to a given level of CO2 for 8 to 24 hr. Therefore, sustained intentional manipulation of Paco2 is unlikely to have lasting effects and slower correction rates of high or low Paco2 could help prevent brain tissue hypoxia or intracranial hypertension, respectively.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.002 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".