Plourde 1996.
| Methods | Study design: randomized parallel groups Study dates: Quote: "Jan to Oct 1991" (email bias survey, see notes) |
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| Participants | Country: Canada Sex: female Age: 19 to 50 ASA: I‐II Procedure: reduction mammoplasty Study size: 12 |
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| Interventions |
Randomized portion of anaesthetic: volatile agent doses ±N2O Intervention 1: maintenance N2O (66% end‐tidal (ET)) enflurane 0.5% ET, N = 4 Intervention 2: maintenance N2O (66% end‐tidal (ET)) enflurane 0.8% ET, N = 4 Intervention 3: maintenance N2O (66% end‐tidal (ET)) enflurane 1.1% ET, N = 4 |
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| Outcomes | Primary outcomes: 40 Hz ASSR/AML, AMLR amplitude, latency, or phase data Secondary outcome: awareness/wakefulness as defined using an awareness classification system (see Table 1): class 1 Comment: no patient had any recollection of intraoperative events |
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| Notes |
Non‐randomized portion of anaesthetic: volatile (randomized) (potent inhalation) technique: IV hypnotic/PRN narcotic/muscle relaxants both induction/maintenance ADM AMLR recorded Anaesthesia induction: fentanyl 3 µg/kg + thiopental 3 mg to 5 mg/kg + vecuronium 0.08 mg/kg Anaesthesia maintenance: fentanyl 1.0 µg/kg as needed + vecuronium 0.01 mg/kg Time of outcome determination: 4 to 8 weeks postoperative Method of outcome determination: interview Neostigmine 40 µg/kg + glycopyrrolate 10 µg/kg used to reverse muscle paralysis Primary author responded to email bias survey. Responses are recorded in 'Risk of bias' table below. Comment: study was not powered to assess for awareness but electrophysiology (author's response to survey) Survey response: 13 February 2011, Gilles Plourde gilles.plourde@mcgill.ca |
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| Risk of bias | ||
| Bias | Authors' judgement | Support for judgement |
| Random sequence generation (selection bias) | Low risk | Quote paper: "four patients per concentration; random assignment..." Quote survey: "Assignment (concentration of enflurane, recording order i.e. ASSR or AMLR first) written on cards which were shuffled and individually places in a sealed envelope by the department secretary who was familiar with these procedures" (email bias survey, see notes) |
| Allocation concealment (selection bias) | Unclear risk | Quote: "Anaesthesiologist did not keep track of cases done. So each envelope brought a surprise" (email bias survey, see notes) |
| Blinding of participants and personnel (performance bias) All outcomes | High risk | Quote: "Patient, Awareness outcome assessor (interviewer), Data analyst" (email bias survey, see notes) |
| Blinding of outcome assessment (detection bias) All outcomes | Low risk | Quote: "Patient, Awareness outcome assessor (interviewer), Data analyst" (email bias survey, see notes) |
| Incomplete outcome data (attrition bias) All outcomes | Low risk | Quote: "One patient was excluded because of poor baseline AMLR" (email bias survey, see notes) |
| Selective reporting (reporting bias) | Low risk | Quote: "Main goal of study was electrophysiology. Awareness was only outcome examined...Yes. Some findings did not reach significance" (email bias survey, see notes) Comment: awareness outcome part of inclusion criteria |
| Other bias | Low risk | Quote: "No obvious bias" (email bias survey, see notes (email) |