Effects of different propofol infusion rates on EEG activity and AEP responses in rats

Abstract

Parameters calculated from the auditory-evoked potential (AEP) recorded over the auditory cortex and from the electroencephalogram (EEG) recorded over the near vertex were compared in rats at three different infusion rates of propofol (62.5, 35 and 25 mg/kg/h). Depth of anaesthesia was assessed clinically using the strength of the pedal withdrawal reflex. Well-defined AEP responses were consistently obtained. As the propofol concentration was reduced, peak latencies decreased and peak to peak amplitudes increased. Amplitude and latency values were closely associated with the strength of the pedal withdrawal responses. Parameters calculated from the EEG showed no significant change as the propofol concentration was reduced. Periods of burst suppression became more frequent as the propofol infusion rate was increased. The study showed some of the difficulties that may be encountered when using EEG as a tool to assess depth of anaesthesia during propofol infusion. The AEP showed dose dependent changes in rats at different infusion rates of propofol. However, large variability between animals limits the use of this technique for monitoring depth of anaesthesia.

Loudness Dependence of Auditory Evoked Potentials as Indicator of Central Serotonergic Neurotransmission: Simultaneous Electrophysiological Recordings and In Vivo Microdialysis in the Rat Primary Auditory Cortex

“…A possible explanation for why we did not find a significant effect for the LDAEP of the P2 component in our experiments is that the mean amplitude of the P2 component is lower in rats than in humans (Sambeth et al, 2003). Furthermore, anesthesia reduces the AEP amplitudes, probably through a concomitant inhibition of the excitatory postsynaptic potentials of cortical pyramidal cells (Maclver et al, 1996;Schwender et al, 1997;Thornton and Sharpe, 1998;Antunes et al, 2003). As the animals in our study were anesthetized, the amplitude of the P2 component might have been decreased to a level at which differences were not significantly measurable whereas the naturally higher N1 component still showed a pronounced LDAEP.…”

Propofol and Ketamine-induced Anesthetic Depth-dependent Decrease of CaMKII Phosphorylation Levels in Rat Hippocampus and Cortex

“…Studies showed poor relation between EEG activity and clinical signs both in humans [20][21][22] and rats, 23,24 and even inverse relationship between anesthetic depth and facilitation of AEP responses. [25][26][27] Instead of EEG and AEPs, a range of nociceptive stimuli and their related clinical responses might be used to evaluate anesthetic depth. 28 In this study, we also found both propofol and ketamine induced anesthetic FIGURE 6.…”

The effect of different anesthetics on neurovascular coupling

“…Different anesthetics act differently on neurotransmitters and neuronal membrane polarization thresholds (Hyder et al, 2002; Maandag et al, 2007; Sibson et al, 1998; Sicard et al, 2003), and as a result modulate the measured EEG evoked signals differently (Antunes et al, 2003a; Antunes et al, 2003b). The main properties/characteristics of the anesthetics we chose for this study are briefly listed here.…”