Anesthesia and the Aging Vasculature: Effects of Propofol on Hemodynamics and Vascular Function
Bibliographic record
Abstract
An increasing life expectancy in Canada has resulted in increasing proportions of elderly patients requiring anesthetic care for surgical procedures. Aging is associated with cardiovascular changes resulting in increased vasoconstriction and hypertension, and medications such as angiotensin converting enzyme (ACE) inhibitors are commonly prescribed for this reason. Propofol, a commonly used general anesthetic agent, is known to cause hypotension that can be exaggerated in the elderly population. Propofol’s influence on vascular reactivity has not been investigated in the aging vasculature. Moreover, patients using ACE inhibitors in the perioperative period may exhibit refractory hypotension when given a general anesthetic. Whether propofol differentially alters vascular function in arteries exposed to chronic ACE inhibition is also not known. Therefore, this thesis focused on 1) determining if there is a difference in vasodilating ability between the young and aging vasculature when exposed to propofol, and 2) determining if chronic ACE inhibition differentially alters vasodilation in the presence of propofol in the aging vasculature. Additionally, the utility of Intralipid as a potential treatment for propofol-induced hypotension was investigated in this thesis. Previous publications suggest that multiple mediators are involved in propofol-induced vascular relaxation. Here, the focus was on nitric oxide (NO) given the age-dependent decrease in NO bioavailability and based on studies documenting the contribution of NO following propofol administration in young mesenteric arteries, the primary vascular bed studied here. The experiments presented in this thesis demonstrate enhanced bioavailability of NO in the aging vasculature in the presence of propofol. Although NO is important, the aging vasculature chronically treated with ACE inhibitors possesses an enhanced vasodilation in the presence of propofol that results from a non-NO source. Finally, Intralipid is able to reverse propofol-induced vasodilation and hypotension in aging animals, demonstrating its potential to be utilized as a hemodynamic agent following propofol use. In conclusion, the results presented in this thesis are an important contribution to understanding the effects of propofol, a widely used general anesthetic agent, on the aging vasculature. This is of particular importance given the increasing proportion of the aging population presenting for surgery and requiring the care of the Anesthesiologist.
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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 | 0.001 |
| 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 | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| 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".