Authors: Pereira S
Anesthesia & Analgesia, 2026 (Letter to the Editor)
This Letter to the Editor proposes a cause-based classification system for intraoperative adverse events (IAEs) to complement existing severity-based frameworks such as ClassIntra.
Current Context
ClassIntra provides a validated severity grading scale from 0 (no deviation from intraoperative course) to V (death), focusing on how much an event deviates from the ideal intraoperative trajectory. However, it does not categorize the underlying cause of the adverse event.
The author argues that while severity grading is valuable, it does not sufficiently inform prevention strategies or institutional learning because it does not distinguish where the event originated.
Proposed Framework
The proposed system introduces a cause-based categorization with five domains:
I. Anesthetic
Events directly attributable to anesthetic causes.
II. Surgical
Events directly attributable to surgical causes.
III. Organizational
Events related to system failures, staffing, structural issues, or workflow problems.
IV. Multifactorial
Events resulting from interaction between multiple domains (e.g., anesthetic + surgical + organizational).
V. Indeterminate
Events where the cause remains unclear despite investigation.
Rationale
The author emphasizes that severity alone does not guide targeted prevention strategies. A low-severity anesthetic medication error and a low-severity surgical technical issue require very different quality-improvement interventions. By pairing severity with causation, institutions can:
• Improve interdisciplinary communication
• Enable more precise root cause analysis
• Strengthen quality improvement initiatives
• Benchmark adverse events more meaningfully across institutions
Importantly, the author clarifies that this framework is not intended to assign blame but to extend severity scoring into actionable quality learning.
Key Themes
-
Two-dimensional framework
Combining severity grading with causal categorization offers a more complete understanding of IAEs. -
Focus on system improvement
Organizational category inclusion highlights systemic contributors rather than individual fault. -
Alignment with patient safety evolution
The proposal emphasizes a learning-centered model of perioperative safety rather than a punitive approach.
Key Points
• ClassIntra grades severity but does not capture causation.
• A complementary cause-based system may improve prevention strategies.
• Five proposed cause categories: anesthetic, surgical, organizational, multifactorial, indeterminate.
• Severity + causation may enhance institutional quality improvement and benchmarking.
What You Should Know
For departments involved in morbidity and mortality review or perioperative QI, this dual-axis model reflects modern patient safety principles. Simply grading how severe an event was may not be enough; identifying where and why it occurred provides clearer direction for system-level improvements.
For multi-site anesthesia groups and hospital partnerships, adopting structured cause classification could improve internal reporting consistency and cross-institutional comparison without shifting toward a blame culture.
Thank you to Anesthesia & Analgesia for allowing us to summarize and share this letter.