Crawford 1985.
| Methods | Study design: randomized parallel groups Study dates: not stated | |
| Participants | Country: England Sex: female Age: parturients ASA: not stated Procedure: emergency caesarean section Enrolled and completed study size: 237 + 540 = 777 |
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| Interventions |
Randomized portion of anaesthetic: volatile agent types Intervention 1: maintenance: trichloroethylene 0.2 vol. %, N = 135 Intervention 2: maintenance: trichloroethylene 0.3 vol. %, N = 128 Intervention 3: maintenance: halothane (0.2 vol. %), N = 129 Intervention 4: maintenance: halothane (0.3 vol. %), N = 129 Intervention 5: maintenance: halothane (0.4 vol. %), N = 127 Intervention 6: maintenance: halothane (0.5 vol. %), N = 129 |
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| Outcomes | Primary outcomes: intra and postoperative parameters specific to C‐sections: anaesthesia consumption and time to surgical/anaesthesia endpoints such as entry of uterus and delivery of fetus, blood loss, surgical/anaesthesia duration, fetal wellbeing parameters and maternal recovery parameters (table IV, table V) Secondary outcome: awareness and unpleasant dreams (table VI), awareness/wakefulness as defined using an awareness classification system (see Table 1): class 4 Comment: Table VI: 22 awareness events; dreams: 13 Low dose: trichloroethylene 0.2 + H 0.2 + H 0.3 = 19 aware/393 vs high dose: trichloroethylene 0.3 + H 0.4 + H 0.5 = 3 aware/384 Quote: "Our results clearly show that trichloroethylene 0.2 vol.%, halothane 0.2 vol.% or halothane 0.3 vol.% [low dose]...produces an unacceptably high incidence of "awareness plus unpleasant dreams" |
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| Notes |
Non‐randomized portion of anaesthetic: parts of volatile agent (parts of potent volatile technique)/nitrous/hypnotic/muscle relaxants (succinylcholine infusion) induction yes/maintenance yes Induction: hyoscine 0.4 mg + thiopentone 250 mg to 300 mg + suxamethonium 100 mg Maintenance: O2 8 L/min + nitrous 4 L/min + infusion suxamethonium 1 mg/mL No titration anaesthetic strategy for light anaesthesia Trichloroethylene 8/263 = 3% The incidence of maternal awareness unpleasant dreams was unacceptably high in the lower concentrations were used, and it is recommended that either trichloroethylene 0.3 vol. % or halothane 0.4 or 0.5 vol. % be used Comment: since the mechanism of intraoperative dreams is controversial, we simulated a reduction of 50% in patient awareness/dream reports balanced across both groups as a method to exclude a portion of dream reports and the significant difference between low and high‐dose inhalation agents persisted (2/384 vs 9/393), Peto OR 0.28 (95% CI 0.09 to 0.93) No email address available for ROB survey |
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| Risk of bias | ||
| Bias | Authors' judgement | Support for judgement |
| Random sequence generation (selection bias) | Low risk | Quote: "The choice of volatile agent was made by reference to a series of randomised numbers..." |
| Allocation concealment (selection bias) | Unclear risk | Comment: no information provided |
| Blinding of participants and personnel (performance bias) All outcomes | High risk | Comment: inadequate information |
| Blinding of outcome assessment (detection bias) All outcomes | Unclear risk | Comment: assessor: no information provided Quote: "On the day following operation, the mother was asked if she had had any dreams during the operation. If the answer was affirmative, the possibility of "awareness" was pursued...The entire series showed a significantly higher incidence of awareness or unpleasant dreams, or both, when.." |
| Incomplete outcome data (attrition bias) All outcomes | Low risk | Comment: no missing outcome data |
| Selective reporting (reporting bias) | Low risk | Comment: awareness outcome part of inclusion criteria |
| Other bias | Unclear risk | Comment: insufficient information provided |