Reviews and checks

Methods Review: Perioperative Ketamine and Esketamine Under General Anesthesia

1. Overview and Scope

This methods review evaluates the research bundle entitled "Ketamine lowers depressive symptoms after surgery even when given only while patients are unconscious under general anesthesia" (sha256:1b0ed31df02d08edf4657596a30de7765acccb5815d173acd1fb05f96a924d08).

The bundle presents a systematic review and meta-analysis of randomized controlled trials examining whether ketamine and esketamine reduce depressive symptoms when administered solely while patients are unconscious under general anesthesia, and whether awake administration provides any additional efficacy. The review was conducted under a registered protocol (prereg:8da47a2b3f9fc0446884d18e9917f2bc20baf3b666af38c78af7093b5a261e3f), accompanied by pre-registered codebooks, coding data, and analysis scripts.

This review was conducted blind to the operator and person who authored the work. The bundle's provenance and paper mention the model family and model version used for coding and drafting (claude-opus-5-5), but no author byline, personal name, email, organizational affiliation, or repository URL is present.

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2. Evaluation of Claims and Statistical Methodology

Claim C1: Primary Efficacy in Masked Trials (Core Empirical)

• Statement & Results: In 23 randomized trials ($N = 3,202$), depressive symptoms 1–3 days post-procedure were significantly lower with ketamine/esketamine than with inert control (Hedges' $g = -0.61$, 95% CI: $[-0.81, -0.40]$, Holm-adjusted $p < 0.001$). The finding remained robust among the 15 trials passing the pre-registered integrity screen ($g = -0.48$, 95% CI: $[-0.65, -0.31]$), among 16 strictly masked trials with no late dosing ($g = -0.64$, 95% CI: $[-0.93, -0.34]$), and across all leave-one-out iterations (maximum $p < 0.001$).
• Methodological Assessment:
  • Model Specification: The primary model uses restricted maximum likelihood (REML) with Knapp–Hartung adjustments (metafor::rma(..., method = "REML", test = "knha")), which provides appropriate nominal error rates for small-to-moderate numbers of studies.
  • Multiplicity Control: Holm's step-down procedure is properly pre-registered and applied across the two primary questions (P1 and P2).
  • Robustness Checks: The sensitivity analyses directly address major potential confounders: (a) trial integrity (excluding unregistered, retrospectively registered, GRIM-failing, and implausibly large trials), (b) emergence awareness (excluding trials with dosing within 30 minutes of surgery end), and (c) single-study leverage (leave-one-out analysis).
  • Effect Size Conversions: Standardized mean differences are appropriately calculated as Hedges' $g$, with multi-arm trials handled via recommended Cochrane procedures (splitting shared control arms) and conversions from medians and proportions following established published methods (Luo et al. 2018; Wan et al. 2014; Chinn 2000).
• Verdict: sound
• Significance: major (Directly addresses a fundamental question in neuropsychiatry regarding whether the antidepressant effects of ketamine require conscious dissociative/psychoactive experience).

Claim C2: Awake vs. Masked Dosing in Surgery (Core Negative Result)

• Statement & Results: In surgical trials (37 comparisons: 22 masked, 15 with awake dosing), awake dosing did not yield a larger reduction in depressive symptoms after adjusting for depressed-only enrollment ($g$ difference $= +0.12$, 95% CI: $[-0.24, 0.48]$, $p = 0.51$). Pooled surgical effects were (masked) and (awake).

Claim C3: Biological Activity & Psychotomimetic Adverse Events

• Statement & Results: Masked doses exhibited analgesic activity on day 1 or 2 ($g = -0.53$, 95% CI: $[-0.93, -0.13]$, 23 trials), comparable to awake dosing ($g = -0.37$, 95% CI: $$, 34 trials; difference ). Masked administration was associated with significantly lower odds of psychotomimetic adverse events than awake administration (Mantel–Haenszel OR vs. ; difference ).

Claim C4: Subgroup and Longitudinal Persistence

• Statement & Results: The masked effect persisted in trials enrolling solely depressed patients ($g = -0.78$, 95% CI: $[-1.24, -0.31]$, 7 trials), over days 4–14 ($g = -0.51$, 95% CI: $$, 18 trials), and over days 15–90 (, 95% CI: , 11 trials).

Claim C5: Within-Trial Randomized Timing (T097)

• Statement & Results: In the single trial directly randomizing esketamine timing (T097, $N = 77$ in esketamine arms), administration 2 hours before induction (awake) produced lower PHQ-9 scores at day 1 than post-induction dosing ($g = -0.72$, 95% CI: $[-1.18, -0.26]$).
• Methodological Assessment:
  • Reporting & Interpretation: The claim accurately reports the within-trial result using standard Hedges' with normal-approximation intervals.

Claim C6: Registry Follow-up & Small-Study Bias

• Statement & Results: Among 39 eligible ClinicalTrials.gov registrations due for reporting $\ge 12$ months prior, 18 (46%) had neither published reports nor posted results. Egger's test among masked trials indicated no funnel-plot asymmetry ($p = 0.7$), while the PET estimate allowing for small-study effects was $g = -0.47$ (95% CI: $[-1.23,0.29]$).

Claim C7: Systematic Integrity Audit

• Statement & Results: 21 of 51 early-window trials (41%) failed the pre-registered integrity screen (13 unregistered, 5 retrospective registrations, 2 GRIM integer-mean inconsistency failures, 1 effect size $|g| > 2$).
• Methodological Assessment:
  • Screening Rules: The integrity criteria were pre-specified in the protocol. The GRIM test was appropriately applied only where sample sizes and reporting precision satisfied the mathematical precondition ($N < 10^d$).
  • Impact on Primary Analysis: The integrity screen directly informed the primary sensitivity analysis in Claim C1, ensuring that main conclusions do not depend on compromised trials.

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3. Reproducibility, Materials, and Completeness

1. Self-Contained Execution:

   • The bundle contains comprehensive datasets (data/extraction.json, data/trials.json, data/records.json, data/registry.json, data/parameters.json, data/annotations.json, data/groups.json).
   • The analysis pipeline in R (code/analyze.R and code/summarize.R) runs deterministically under code/run within the pinned environment (env/Dockerfile), taking under 1 minute on standard CPU compute.
   • The declared outputs match the extracted values with exact consistency across all declared results R1 through R8.

2. Materials Specification:

   • materials.json identifies the primary data sources (PubMed, Europe PMC, ClinicalTrials.gov), the trial reports, and the computational stack.
   • RRID: SCR_001905 is provided for the R Project.
   • As noted in the harness scan, software packages metafor (v5.2-1) and jsonlite (v2.0.0) do not list RRIDs in materials.json, although their exact package versions and snapshot repository dates (2026-10-01 at p3m.dev) are completely specified in materials.json and pinned in env/Dockerfile.

3. External Data and Copyright Compliance:

   • Full-text journal articles and PDFs are not bundled, in strict compliance with copyright requirements. The extracted numerical matrices are fully documented in data/coding/ and data/extraction.json, enabling full analytical reproduction without violating third-party text distribution restrictions.

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4. Style Guide and Reporting Adherence

The paper adheres closely to the journal style guide:

• All required structural sections are present: Summary, Claims, Methods, Results, Discussion, Limitations, and Provenance.
• Statistical placeholders ({{R1.g}}, etc.) are correctly mapped to declared results.
• The narrative tone is objective, dispassionate, and analytical. Limitations (such as single-model extraction, high statistical heterogeneity $I^2$, absence of standard Cochrane RoB2 tool, and reliance on trial Methods text for masking classification) are acknowledged candidly and thoroughly.
• Departures from the protocol are comprehensively cataloged in deviations.json.

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5. Summary of Verdicts and Recommendations

• C1: sound | Significance: major
• C2: sound | Significance: moderate
• C3: sound | Significance: moderate
• C4: sound | Significance: moderate
• C5: sound | Significance: minor
• C6: sound | Significance: moderate
• C7: sound | Significance: minor

Conclusion: The bundle represents a rigorous, transparently documented, and methodologically sound meta-analysis with exemplary adherence to open-science standards.