Hung 1992.

Methods	Study design: randomized parallel groups Study dates: not stated
Participants	Country: Canada, USA Sex: male Age: aged: 30 to 79 ASA: I‐II Procedure: not specified Study size: 26
Interventions	Randomized portion of anaesthetic: IV hypnotic (thiopental) (TCI) infusion serum levels Intervention 1: thiopental serum concentrations 10 µg to 30 µg/mL 5/26 had noxious stimulation because they were arousable and responded to verbal command Intervention 2: higher, randomly assigned target serum concentration of 40 µg to 90 µg/mL tracheas of 6 could not be intubated due to inability to intubate without muscle relaxants
Outcomes	Primary: outcomes: association thiopental serum concentrations and clinical signs anaesthetic depth as defined by EEG and several perioperative stimuli (verbal command, tetanic nerve stimulation, trapezius muscle squeeze, and laryngoscopy) Secondary outcomes: awareness/wakefulness as defined using an awareness classification system (see Table 1): class 1 Quote: "When interviewed 24 h postoperatively, none of the subjects could recall the events that occurred during the study"
Notes	Non‐randomized portion of anaesthetic: ADM EEG recorded No post‐intubation anaesthetic technique described: classified as "other" technique Quote: "A positive response was recorded if purposeful extremity movement or coughing was observed the probability of no movement to each stimulus was characterized using logistic regression. The biphasic thiopental concentration‐EEG relationship and the isoelectric EEG at the high serum thiopental concentrations needed to prevent purposeful movement responses limit the utility of the EEG as a measure of anaesthetic depth when thiopental is used alone ...The movement responses may be associated with spinal (brain stem in the case of laryngoscopy and intubation) reflexes to peripheral noxious stimuli. However, they also may be associated with light anaesthesia and inadequate cortical CNS suppression, since most of these movement responses were associated with an increase of mean arterial pressure and heart rate. It is not possible for us to separate the cortical from spinal components of a movement or cough response....Laryngoscopy followed by intubation can be considered the most noxious stimulus that has been quantitated with available methodology in humans. Because of the concurrent peri operative use of anaesthetic drugs with specific actions...traditional clinical signs of anaesthetic depth such as movement and hemodynamic responses to noxious stimuli become less interpretable" No email survey
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "The first randomly assigned target serum concentration of 10‐30 mcg/ml was maintained ..."
Allocation concealment (selection bias)	Unclear risk	Comment: inadequate information
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Comment: inadequate information
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Comment: inadequate information
Incomplete outcome data (attrition bias) All outcomes	Low risk	Comment: no dropouts
Selective reporting (reporting bias)	Low risk	Comment: awareness outcome part of inclusion criteria
Other bias	Unclear risk	Comment: inadequate information