The Use of Central Venous to Arterial Carbon Dioxide Tension Gap for Outcome Prediction in Critically Ill Patients: A Systematic Review and Meta-Analysis*
Bibliographic record
Abstract
OBJECTIVES: In this systematic review and meta-analysis, we assessed whether a high CO2 gap predicts mortality in adult critically ill patients with circulatory shock. DATA SOURCES: A systematic search of MEDLINE and EMBASE electronic databases from inception to October 2019. STUDY SELECTION: Studies from adult (age ≥ 18 yr) ICU patients with shock reporting CO2 gap and outcomes of interest. Case reports and conference abstracts were excluded. DATA EXTRACTION: Data extraction and study quality assessment were performed independently in duplicate. DATA SYNTHESIS: We used the Newcastle-Ottawa Scale to assess methodological study quality. Effect sizes were pooled using a random-effects model. The primary outcome was mortality (28 d and hospital). Secondary outcomes were ICU length of stay, hospital length of stay, duration of mechanical ventilation, use of renal replacement therapy, use of vasopressors and inotropes, and association with cardiac index, lactate, and central venous oxygen saturation. CONCLUSIONS: We included 21 studies (n = 2,155 patients) from medical (n = 925), cardiovascular (n = 685), surgical (n = 483), and mixed (n = 62) ICUs. A high CO2 gap was associated with increased mortality (odds ratio, 2.22; 95% CI, 1.30-3.82; p = 0.004) in patients with shock, but only those from medical and surgical ICUs. A high CO2 gap was associated with higher lactate levels (mean difference 0.44 mmol/L; 95% CI, 0.20-0.68 mmol/L; p = 0.0004), lower cardiac index (mean difference, -0.76 L/min/m; 95% CI, -1.04 to -0.49 L/min/m; p = 0.00001), and central venous oxygen saturation (mean difference, -5.07; 95% CI, -7.78 to -2.37; p = 0.0002). A high CO2 gap was not associated with longer ICU or hospital length of stays, requirement for renal replacement therapy, longer duration of mechanical ventilation, or higher vasopressors and inotropes use. Future studies should evaluate whether resuscitation aimed at closing the CO2 gap improves mortality in shock.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.019 | 0.052 |
| Meta-epidemiology (narrow) | 0.003 | 0.002 |
| Meta-epidemiology (broad) | 0.022 | 0.046 |
| Bibliometrics | 0.008 | 0.008 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.004 | 0.002 |
| Open science | 0.002 | 0.002 |
| Research integrity | 0.003 | 0.002 |
| Insufficient payload (model declined to judge) | 0.002 | 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 source (direct Gemma or distilled Codex), 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".