Bilateral Nephrectomy Impairs Cerebral Oxygen Delivery After Acute Hemodilution Anemia in Rats
Bibliographic record
Abstract
Hypothesis We hypothesize that renal sensing of hypoxia is essential for activation of cardiovascular responses needed to maintain cerebral oxygen delivery during acute anemia and that bilateral nephrectomy will negatively affect brain oxygen delivery during acute hemodilutional anemia. Methods All experiments were approved by the Animal Care and Use Committee at St. Michael’s Hospital and conducted in accordance with ARRIVE‐2 guidelines. Sham or bilateral nephrectomy (n=5) were performed on isoflurane anesthetized Sprague‐Dawley rats prior to performing acute hemodilution (50% estimated blood volume) 1:1 with 6% hydroxyethyl starch. Heart rate (HR), mean arterial pressure (MAP) and rectal temperature were monitored continuously. Arterial blood gases and cooximetry samples were measured before and after hemodilution. Continuous measurements of brain microvascular oxygen tension (P br O 2 ) were measured via a phosphorescence quenching method using an intravascular oxygen probe, Oxyphor PdG4, and an OxyLED phosphorometer. Data were tested for normality and analysis performed by two‐way ANOVA with p<0.05 taken to be significant. Results Bilateral nephrectomy resulted in a reduction in baseline HR (p<0.004). Hemodilution resulted in a comparable reduction in hemoglobin concentration in both groups (Sham: 5.1±0.3 g/dL; Nephrectomy: 4.2±0.4 g/dL) with no differences in arterial P a O 2 or P a CO 2 . After hemodilution, HR increased significantly in both groups (p<0.05). MAP tended to be lower in the bilateral nephrectomy group and decreased transiently in both groups following hemodilution (p<0.01). Brain microvascular pO 2 (P br O 2 )was not significantly different between nephrectomy and sham at baseline. Post‐hemodilution the P br O 2 was significantly lower in nephrectomised rats (11.5±5.1 mmHg) compared to sham operated rats (25.4±11.3 mmHg) (p=0.031). Conclusions We observed that bilateral nephrectomy resulted in changes in baseline physiology, including a lower HR. Hemodilution resulted in a comparable reduction in hemoglobin concentration, without difference in P a O 2 or P a CO 2 . MAP decreased more profoundly immediately after hemodilution in nephrectomised animals, and recovered with time. Nephrectomy resulted in a significant drop in brain microvascular pO 2 (P br O 2 ) immediately after hemodilution. This was not observed in sham controls. These data suggest that the kidney serves an important sensing role during acute anemia which supports cardiovascular responses and preserves the adequacy of brain tissue oxygen delivery. Hypoxia sensing by the kidney, and other integrative systemic mechanisms, may be central to these findings.
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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 | 0.000 | 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 | 0.000 | 0.000 |
| Research integrity | 0.000 | 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".