The aim of the study was to compare the effect of gradual and abrupt increase of sevoflurane concentrations on intracranial pressure and systemic circulation in rabbits. The study was performed on 13 adult rabbits divided at random into two groups. In group I (8 rabbits), 2.2 vol%, 4.4 vol% and 6.6 vol% were subsequently administered in three 15 minutes intervals. Animals from group II (5 rabbits) received from the start 6.6 vol% concentration of sevoflurane for 45 minutes. Intracranial pressure (ICP), mean arterial blood pressure (MABP), heart rate (HR), end-expiratory CO2 concentration, temperature in nasopharynx were monitored continuously. Mean ETCO2 values did not differ in a statistically significant way in both groups and they remained at a stable level during observation period. Mean temperature in nasopharynx manifested a slight, though statistically significant decrease when compared to initial value - this was observed in 30th minute in group I, and in 25th minute in group II. Statistically significant increase of ICP observed in 30th minute in group I, was evident in group II as early as in 10th minute. Statistically significant changes when compared with initial values remained such until the end of observation period. There was a positive correlation between changes in ICP values with the changes in end-expiratory concentration of sevoflurane both in group I (p<0.05, r=0.8208) and in group II (p<0.05,r=0.6926). In group I, there was a statistically significant decline of MABP in 30th minute - this tendency was manifested until the end of observation period. Similar course was observed in group II since 5th minute. Changes in MABP values correlated negatively with changes in end-expiratory concentration of sevoflurane in group I (p<0.001, r=-9394) and in group II (p<0.05, r=-0.8299). Statistically significant decrease in heart rate was observed in group I from 25th minute onwards, and in group II - from 5th minute of observation.There was a negative correlation between changes in heart rate and changes in end-expiratory concentration of sevoflurane both in group I (p<0.001, r=-0.9251) and in group II (p<0.05, r=Ð0.7682). The results obtained indicate that the concentrations of sevoflurane below 1 MAC do not have a significant effect on intracranial pressure and systemic circulation. Irrespective of the method of sevoflurane administration, its concentration of 3 MAC results in ICP elevation, which, however, does not exceed upper normal range values. In the case of sevoflurane concentrations higher than 1.5 MAC, the degree of systemic circulatory depression is proportional to the dose administered.

Keywords: rabbit, Heart Rate, mean arterial blood pressure, Intracranial Pressure