The serum thiopental concentration producing a 50% probability of no movement ranged from 15.6 micrograms/ml for verbal command to 78.8 micrograms/ml for laryngoscopy and intubation.
RCT (n=26)
Randomly assigned target serum concentrations
What is the relationship between steady-state serum thiopental concentrations, clinical anesthetic depth, and EEG changes in ASA 1 or 2 patients?
This study quantifies the specific steady-state serum thiopental concentrations required to suppress movement in response to various clinical stimuli and correlates these with EEG changes.
This study examined the relationship among pseudo-steady-state (constant) serum thiopental concentrations, clinical anesthetic depth as assessed by several perioperative stimuli, and the electroencephalogram (EEG). Twenty-six ASA physical status 1 or 2 patients participated in the study. Two constant serum thiopental concentrations were maintained in each patient using a computer-controlled infusion pump. The first randomly assigned target serum concentration of 10-30 micrograms/ml was maintained for 5 min to allow serum:brain equilibration. Then the following stimuli were applied at 1-min intervals: verbal command, tetanic nerve stimulation, trapezius muscle squeeze, and laryngoscopy. A second, higher, randomly assigned target serum concentration of 40-90 micrograms/ml was then achieved and maintained by the computer-controlled infusion pump. The previously described stimuli were reapplied, after which laryngoscopy and intubation was performed. A positive response was recorded if purposeful extremity movement or coughing was observed. Using the quantal movement or cough response and the measured constant serum thiopental concentration, the probability of no movement to each stimulus was characterized using logistic regression. The serum thiopental concentrations that produced a 50% probability of no movement response for the clinical stimuli were as follows: 15.6 micrograms/ml for verbal command, 30.3 micrograms/ml for tetanic nerve stimulation, 39.8 micrograms/ml for trapezius muscle squeeze, 50.7 micrograms/ml for laryngoscopy, and 78.8 micrograms/ml for laryngoscopy followed by intubation. The EEG was analyzed using aperiodic waveform analysis to derive the number of waves per second. A biphasic relationship between constant serum thiopental concentration and the EEG number of waves per second was observed. Loss of responsiveness to verbal stimulation occurred when the EEG was activated at 15-18 waves/s.(ABSTRACT TRUNCATED AT 250 WORDS)
Hung et al. (1992) conducted an RCT in Anesthesia (n=26). Thiopental was evaluated on Serum thiopental concentration producing a 50% probability of no movement response to clinical stimuli. The serum thiopental concentration producing a 50% probability of no movement ranged from 15.6 micrograms/ml for verbal command to 78.8 micrograms/ml for laryngoscopy and intubation.