Chronobiology and anesthesia

What is it about?

There are many studies refering to fact that disruption of circadian rhythms is a significant risk factor for many cardiovascular diseases and, furthermore, that the emergence of cardiovascular diseases may be a time-dependent process. To perform ethically acceptable cardiovascular research involving animals, the use of general anaesthesia is often necessary. But anaesthetic drugs alter normal physiology in some way and may confound the results of physiological studies as well as have a significant effect on circadian rhythms. This editorial has a methodological character, where we want to refer to the importance of respecting the circadian rhythms in cardiovascular in vivo animal models and to warn investigators that we need to understand how animals are affected by anaesthetic drugs in order to formulate anaesthetic protocols with minimal effects on data. Therefore, appropriate anaesthesia should be selected according to its particular effect on the organism, including circadian rhythmicity.

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Why is it important?

Our study warns that the use of various anesthetic agents can influence the initial state of rat cardiac electrophysiology in in vivo animal models also in the circadian dependence. The small number of chronobiological studies that have examined interactions between general anesthesia and circadian rhythms report that general anesthesia has a significant effect on vital functions. To date, however, there are no published investigations that have evaluated the effect of general anesthesia on basic electrophysiological myocardial parameters and their dependence on circadian rhythms or the light-dark (LD) cycle. Nearly all evaluable ECG parameters are used to identify cardiac abnormalities in rats; however, some studies have investigated the reliability of this tool. The time when the experiments were performed and the synchronization of the animals to the LD cycle were not, however, accounted for in the methodologies of these studies. From a chronobiological perspective, this is of concern, because all functions of the cardiovascular system exhibit circadian variations, which makes inter-study comparisons very problematic.