Cerebral Blood Volume and Blood Flow Responses to Hyperventilation in Brain Tumors During Isoflurane or Propofol Anesthesia
Bibliographic record
Abstract
UNLABELLED: Using computerized tomography, we measured absolute cerebral blood flow (CBF) and cerebral blood volume (CBV) in tumor, peri-tumor, and contralateral normal regions, at normocapnia and hypocapnia, in 16 rabbits with brain tumors (VX2 carcinoma), under isoflurane or propofol anesthesia. In both anesthetic groups, CBV and CBF were highest in the tumor region and lowest in the contralateral normal tissue. For isoflurane, a significant decrease in both CBV and CBF was observed in all tissue regions with hyperventilation (P < 0.05), but without accompanying changes in intracranial pressure. However, the percent reduction in regional CBF with hypocapnia was two times larger than that observed in the CBV response (P < 0.01). In contrast, there were no significant changes in CBV and CBF in the Propofol group with hyperventilation for all regions (P > 0.10). In addition, there were no differences between CBV values for isoflurane at hypocapnia when compared with CBV values for propofol at normo- or hypocapnia (P > 0.34 and P > 0.35, respectively, in the tumor regions). Our results indicate that propofol increases cerebral vascular tone in both neoplastic and normal tissue vessels compared with isoflurane. CBV and CBF during normocapnia were significantly greater in all regions (tumor, peri-tumor, and contralateral normal tissue) with isoflurane than with propofol. CBV and CBF remained responsive to hyperventilation only with isoflurane. IMPLICATIONS: In rabbits with brain tumors, brain blood flow and volume were significantly larger in all regions (tumor, peri-tumor, and contralateral normal tissue) with isoflurane than with propofol during normocapnia, and remained responsive to a reduction in PaCO(2). Consequently, during hypocapnia, brain blood flow and volume values with isoflurane were similar to values with propofol.
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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 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| 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) | 0.001 | 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".