The influence of gradually increasing the concentration of desflurane on cerebral perfusion pressure in rabbit

In nearly all cases of general anaesthesia with a volatile agent, the anaesthetic concentration has to be increased. Since the anaesthetic affects both the factors determining intracranial homeostasis and the systemic circulation, it is crucial that cerebral perfusion pressure (CPP) is protected. The aim of the present study was to assess the influence of gradually increased concentrations of desflurane on the cerebral and systemic circulations based on CPP, mean arterial pressure (MAP), intracranial pressure (ICP) and their correlations.

The study was carried out on 25 rabbits of the same gender (male) randomly assigned to two groups: control (n = 10) and group I (n = 15). Over three 15-minute periods, the animals were exposed to increase concentrations of desflurane so as to achieve 1/3, 2/3 and 1 MAC Minimal Alveolar Concentration (3, 6, 9 vol%) of the effective end-tidal concentration of desflurane (Et) at the end of each period, respectively.

Intragroup analysis of CPP changes demonstrated decreases in its successive values from minute 18, compared with baseline values. The mean values of ICP did not differ throughout the experiment. From minute 19 on, all successive values of MAP decreased compared with baseline values. A weak correlation (r = -0.2179) was found between ICP and CPP and a strong correlation between MAP and CPP (r = 0.98829). Moreover, there was a strong correlation between Etdesflurane vs. CPP (r = -0.8769) and MAP (r = -0.8224) and a weak correlation versus ICP (r = 0.15755).

A decrease in CPP induced by desflurane was associated with a decrease in MAP but not an increase in ICP. The depressive effect of desflurane on the cerebral and systemic circulations is a consequence of its effector site concentration.