Cortical and spinal assessment - a comparative study using encephalography and the nociceptive withdrawal reflex.

BACKGROUND: Standardized objective methods to assess the analgesic effects of opioids, enable identification of underlying mechanisms of drug actions in the central nervous system. Opioids may exert their effect on both cortical and spinal levels. In this study actions of morphine at both levels were investigated, followed by analysis of a possible correlation between the cortical processing and spinal transmission. METHODS: The study was conducted after a double-blinded, two-way crossover design in thirty-nine healthy participants. Each participant received 30mg morphine or placebo as oral solution in randomized order. The electroencephalogram (EEG) was recorded during rest and during immersion of the hand into ice-water. Electrical stimulation of the sole of the foot was used to elicit the nociceptive withdrawal reflex and the reflex amplitude was recorded. RESULTS: Data from thirty subjects was included in the data analysis. There was no change in the activity in resting EEG (P>0.05) after morphine administration as compared to placebo. During cold pressor stimulation, morphine significantly lowered the relative activity in the delta (1-4Hz) band (P=0.03) and increased the activity in the alpha (8-12Hz) band (P=0.001) as compared to placebo. The reflex amplitudes significantly decreased after morphine administration (P=0.047) as compared to placebo. There was no correlation between individual EEG changes during cold pressor stimulation and the decrease in the reflex amplitude after morphine administration (P>0.05). CONCLUSIONS: Cold pressor EEG and the nociceptive reflex were more sensitive to morphine analgesia than resting EEG and can be used as standardized objective methods to assess opioid effects. However, no correlation between the analgesic effect of morphine on the spinal and cortical assessments could be demonstrated.

Impact of bispectral index for monitoring propofol remifentanil anaesthesia. A randomised clinical trial.

BACKGROUND: Previous research has shown that the use of the bispectral index (BIS) monitor to measure the depth of anaesthesia reduces the amount of anaesthetics administered and the recovery time from general anaesthesia. The effect of BIS on recovery from anaesthesia and consumption of anaesthetics in a paediatric population receiving total intravenous anaesthesia (TIVA) with propofol and remifentanil has not been studied. METHODS: A single-blind, single-centre clinical trial. One hundred fifty-seven patients were enrolled. They were scheduled for ear, nose, and throat surgery and stratified according to age groups (1-3 years, 4-11 years, 12-17 years, 18-65 years) and type of operation, yielding a total of nine subgroups. Patients were randomly allocated to receive either a TIVA with propofol and remifentanil according to conventional clinical practice (control) or guided by BIS. Normalised propofol (µg/kg/min) and remifentanil (µg/kg/min) consumption and time to extubation (s) were the outcome measures. RESULTS: Children aged 1-3 years in the BIS group had a longer time to extubation compared with controls (P: 0.04). Patients aged 12-17 years in the BIS group received higher maintenance infusion rates of propofol compared with controls (P = 0.02). No significant difference for the outcome variables was evidenced in the other age groups. CONCLUSION: BIS monitoring for guidance of propofol-remifentanil anaesthesia does not result in reduced consumption of anaesthetics and does not reduce time to extubation in adult and children compared with conventional practice.