Abstract
Introduction: Ketamine is increasingly being used in various pain settings. The purpose of this study was to assess the effect of an analgesic dose of ketamine in the bispectral index (BIS), spectral edge frequency (SEF-95), density spectral array (DSA), cerebral oximetry (rSO2) and mean arterial pressure (MAP) during general anaesthesia with a target controlled infusion. Methods: A prospective, single-blinded and randomized study on adult patients scheduled for elective spine surgery was carried out. After anaesthesia induction with propofol, remifentanil and rocuronium, when a stable BIS value (45-55) was achieved, an automatic recording of BIS, SEF-95, rSO2 and MAP values during 9 min was performed to establish patients baseline values. Subsequently, patients were randomly assigned to receive a ketamine bolus dose of 0.2 mg/kg, 0.5 mg/kg or 1 mg/kg; all variables were recorded for additional 9 min after the ketamine bolus, in the absence of any surgical stimulus. A p-value <0.05 was considered significant in the statistical analysis. Results and discussion: Thirty-nine patients were enrolled in the study. Our results show a dose-related increase of SEF-95 and BIS values. DSA demonstrate a shift in the frequency range and power distribution towards higher frequencies. Our results do not show significant differences in MAP and rSO2 values. Conclusion: When ketamine is used intraoperatively in analgesic doses, the anaesthetist should anticipate an increase in SEF-95 and BIS values which will not be associated with the level of anaesthesia.
Highlights
Ketamine is increasingly being used in various pain settings
The purpose of the present study was to assess the effect of an analgesic dose of ketamine in bispectral index (BIS) and SEF-95 values, density spectral array (DSA) of the EEG, rSO2 and mean arterial pressure (MAP) during a stable target controlled infusion general anaesthesia
Our results show an increase in SEF-95 and BIS values related to the bolus dose
Summary
The purpose of this study was to assess the effect of an analgesic dose of ketamine in the bispectral index (BIS), spectral edge frequency (SEF-95), density spectral array (DSA), cerebral oximetry (rSO2) and mean arterial pressure (MAP) during general anaesthesia with a target controlled infusion. Ketamine produces the so-called “dissociative” anaesthetic state and it increases cerebral metabolism, cerebral blood flow and intracranial pressure. It does not follow the basic anaesthesia related electroencephalogram (EEG) pattern. Ketamine alone has been shown to reduce the spectral edge frequencies (SEF-95), an effect that is driven predominantly by increases in absolute theta band power at the expense of alpha band power [5,7,8]
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