Hypoxemic reperfusion exacerbates the neurological injury sustained during neonatal deep hypothermic circulatory arrest: a model of cyanotic surgical repair☆
Bibliographic record
Abstract
OBJECTIVE: Deep hypothermic circulatory arrest (DHCA) is frequently used in infants undergoing the Norwood procedure. These infants are necessarily hypoxemic after separation from CPB. Considerable energy has been spent characterizing the physiological and histological consequences of DHCA, but these have largely focused on a normoxemic period of reperfusion. Furthermore, evidence has accumulated to suggest that the cerebral vascular autoregulatory mechanisms are dysfunctional following DHCA. In particular, the vasodilatation that elevates cerebral blood flow (CBF) in response to hypoxemia is absent. This study therefore aimed to investigate whether post-CPB hypoxemia exacerbates brain injury resulting from DHCA. METHODS: Twelve neonatal piglets were subjected to 2h DHCA and then separated from CPB. They were then randomized to either: Group 1, normoxic ventilation (n=5); or Group 2, hypoxemia (n=7), in which the arterial PaO(2) was reduced to 40-50 mmHg for the duration of reperfusion. Following a 20 h period of warm reperfusion, the animals were perfusion fixed and the brain analyzed for histological evidence of injury. Nine additional animals were studied in one of three control groups. RESULTS: All animals survived the protocol. Post-operative parameters - including mean arterial pressure, acid-base status, inotrope requirements and arterial PaCO(2) - were similar. None of the control animals had any evidence of ischemia. Group 1 animals had moderate injury (total score 7.4+/-1.6). In Group 2, three animals sustained irretrievable brain injury evidenced by gross edema and early liquefactive necrosis. The remaining four had severe ischemic histological changes (score 14.5+/-1.6, p<0.03). CONCLUSIONS: Hypoxemic reperfusion after prolonged DHCA results in increased neuronal loss. The use of DHCA for staged palliation may confer disproportionately greater cerebral risk than other patient groups. Alternatively, methods to augment oxygen delivery - such as by ECMO - may be of particular benefit in the early re-perfusion window.
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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 | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| 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 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".