Effect of anesthesia and measurement site on baseline blood pressure in rats (2021-2024)

Rats are frequently used in laboratory experiments and are suitable animal models for physiology, pharmacology, pathophysiology, or behavioral studies. Since rats are also used in experimental surgery, adequate anesthesia and analgesia must be ensured to comply with the principle of refinement within the "3R" rules. This study evaluated all available numerical blood pressure (BP) values reported in studies identified through a comprehensive search using PubMed, Web of Science, Scopus, ScienceDirect, and Google Scholar between 2021 and 2024 to examine whether control (baseline) BP values differ at the beginning of the experiment between various anesthetics and the site of invasive BP measurement in normotensive and hypertensive rats. Statistical analysis in normotensive male rats focused on conscious animals and those under the most commonly used anesthetics, with individual agents and their combinations categorized into four groups: urethane, ketamine, barbital, and isoflurane. No statistical comparison could be performed in hypertensive rats due to the insufficient number of data extracted. Our results suggest that the choice among these anesthetics is probably not a consistent determinant of control baseline BP values in normotensive rats when considering only the carotid and femoral arteries, which are the two most frequent sites of invasive measurement. These findings should be interpreted with caution because of several limitations, including the small number of extracted data in some groups, their uneven distribution, underpowered data in hypertensive rats, and variability related to experimental conditions, e.g., circadian rhythms, animal handling, omission of females, among others. However, we propose that most anesthetics may cause a slight initial decrease in control baseline BP at the beginning of the experiment compared to conscious rats, which warrants further investigation particularly concerning the invasive measurement site and aforementioned limitations.