**Author details**

Pavol Svorc

were the lowest in both light parts of the rat regimen day compared with K/X and Z anesthesias. Initially, acidosis is induced, irrespective of the synchronization of animals with the LD cycle, and therefore, it is not possible to monitor periodic changes in the functions of individual systems that are primarily dependent on changes in extracellular pH. As a result, P probably and immediately reduces either the activity of the buffer systems or inhibits the regulatory mechanisms associated with the maintenance of isohydria, independently of the LD cycle. In this regard, K/X and Z anesthesias may be more appropriate for general anesthesia because the arterial pH varies within the range of isohydria. This assumption is only valid if the rat experiments

Hypoxia modifies circadian oscillations of important variables, such as body temperature and metabolism, and may lead to the expectation that the rhythms of many functions are disrupted by hypoxia according to their relationships and association with the primary variables [146]. This effect appears to be apparent in rats under P anesthesia. From a chronobiological point of view, P anesthesia, therefore, is not a suitable form of general anesthesia. Using this type of anesthesia, with the exception of the initial hypoxia and hypercapnia, the LD differ-

nia on the circadian rhythms of oxygen-dependent systems, immediately after administration

Based on the results of this study, we concluded that general anesthesia affects the circadian fluctuation of arterial acid-base balance and plasma concentrations of some ions (**Table 9**). This should be taken into account, and experiments should start with a normal range of acidbase balance. Even at the beginning of the experiment, the altered internal environment may affect the activity of systems whose functions are primarily dependent on acid-base balance.

normokalemia to hyperkalemia, hypocalcemia, from hypochloremia to normochloremia

, from hyponatremia to hypernatremia, hyperkalemia, hypocalcemia, from

hypernatremia, from hypokalemia to hyperkalemia, hypocalcemia, from hypochloremia to

, from normonatremia to hypernatremia, hyperkalemia, hypocalcaemia,

are eliminated. As a result, the effect of initial hypoxia and hypercap-

, hypernatremia, hyperkalemia,

, hypernatremia, from

, from hyponatremia to

− , from

−

−

are performed under K/X and Z anesthesia in the dark (i.e., active) parts of the day.

ences in pO2

**Anesthetic Status**

**Pentobarbital**

**Ketamine/xylazine**

**Zoletil**

and pCO2

132 Circadian Rhythm - Cellular and Molecular Mechanisms

of anesthetics, can significantly affect the end result.

*Light* Acidosis, from hypoxia to hypercapnia, increased HCO3

normochloremia to hyperchloremia

*Light* Acidosis, from hypoxia to normoxia, hypercapnia, normal HCO3

*Dark* Acidosis, from normoxia to hypoxia, hypercapnia, increased HCO3

*Light* Acidosis, hypoxia, from normocapnia to hypercapnia, from decreased to increased level

*Dark* From normal pH to alkalosis, from hypoxia to normoxia, hypocapnia, decreased HCO3

hyponatremia to normonatremia, hyperkalemia, hypocalcemia,

*Dark* From acidosis to normal pH, from hypoxia to normoxia, hypercapnia, from normal to

**Table 9.** Internal environment under general anesthesia dependent on the light-dark cycle in the rat.

hypocalcemia, hypochloremia

of HCO3 −

hyperchloremia

increased HCO3

hyperchloremia

Address all correspondence to: pavol.svorc@upjs.sk

Department of Physiology, Medical Faculty Safarik's University, Kosice, Slovak
