New Nomenclature of Peri-Operative Cognitive Impairments

0
0
0

New Nomenclature of Peri-Operative Cognitive Impairments: Impacts on Practice and Research

The recognition and understanding of cognitive impairments associated with anesthesia and surgery have undergone a significant transformation with the introduction of the term peri-operative neurocognitive disorders (PND). This new nomenclature, recommended by an international, multidisciplinary consensus group in 2018, replaces outdated terms like post-operative cognitive dysfunction (POCD) and aligns peri-operative cognitive research with broader neurocognitive disorder (NCD) classifications used in psychiatry, neurology, and geriatrics. This shift aims to harmonize diagnostic criteria, improve interdisciplinary communication, and refine research methodologies to better understand the etiology, prevention, and management of peri-operative cognitive deficits.

Evolution from POCD to PND

Historically, cognitive impairments observed after surgery and anesthesia were categorized into three entities: emergence delirium, post-operative delirium (POD), and post-operative cognitive dysfunction (POCD). These terms were defined based on temporal onset and symptom severity:

  • Emergence delirium: Acute confusion occurring immediately after anesthesia in the post-anesthesia care unit.
  • POD: Delirium manifesting 24–72 hours post-operatively.
  • POCD: Cognitive deficits detected weeks to months after surgery through neuropsychological testing, without requiring subjective complaints or assessment of daily functional impairments.

While these terms facilitated early research, their limitations became evident over time. POCD, in particular, faced criticism for its narrow focus on objective neuropsychological testing, exclusion of subjective patient-reported symptoms, and lack of alignment with widely accepted diagnostic frameworks like the Diagnostic and Statistical Manual of Mental Disorders (DSM-5). This isolation hindered collaboration with non-anesthesia disciplines and limited clinical recognition of peri-operative cognitive impairments as a legitimate medical concern.

The new nomenclature, peri-operative neurocognitive disorders (PND), addresses these limitations by adopting diagnostic criteria consistent with DSM-5 classifications for NCDs. PND encompasses cognitive impairments identified before surgery (pre-existing deficits) and those emerging after surgery, up to 12 months post-operatively. This framework not only integrates peri-operative cognitive research into mainstream neurocognitive science but also emphasizes functional and subjective assessments critical for clinical relevance.

Key Components of the New Nomenclature

1. Pre-Operative Neurocognitive Disorders

Pre-existing cognitive impairments are now classified as pre-operative NCD, categorized as mild or major based on severity. Epidemiological data indicate that 14%–48% of individuals aged ≥70 years have mild NCD, while 10% meet criteria for major NCD (equivalent to dementia). Identifying pre-operative NCD is critical, as these impairments are unrelated to anesthesia or surgery but may influence post-operative outcomes and recovery trajectories.

2. Post-Operative Delirium (POD)

Under the new framework, POD is defined as delirium occurring within the first 7 post-operative days or until discharge (whichever comes first). This replaces the previous distinction between “emergence delirium” and “POD,” eliminating ambiguity in timing. POD must meet DSM-5 criteria, including:

  • Acute onset of fluctuating attention, awareness, and cognition.
  • Exclusion of pre-existing NCD or severe arousal disorders (e.g., coma).

The requirement for DSM-5 alignment ensures standardized diagnosis and facilitates cross-disciplinary research.

3. Delayed Neurocognitive Recovery (DNR)

DNR is a novel term describing cognitive impairments persisting up to 30 days post-operatively. Unlike POCD, which focused solely on objective testing, DNR incorporates functional assessments (e.g., activities of daily living, ADLs) and subjective reports from patients, caregivers, or clinicians. This holistic approach acknowledges the impact of even transient cognitive declines on recovery and quality of life.

4. Post-Operative Neurocognitive Disorder (NCD Post-Operatively)

Cognitive deficits detected between 30 days and 12 months post-operatively are classified as mild or major NCD post-operatively. Severity is determined by:

  • Objective neuropsychological testing.
  • Assessment of ADLs (e.g., using validated tools like the Barthel Index or Lawton Scale).
  • Subjective reports of cognitive decline.

This classification mirrors the NIA-AA (National Institute on Aging–Alzheimer’s Association) criteria for mild cognitive impairment and dementia, enhancing clinical utility.

Time Frame Adjustments and Diagnostic Implications

The temporal reclassification under PND markedly differs from prior frameworks [Figure 1]. Key changes include:

  • Extended Follow-Up: Post-operative assessments are now recommended at 7 days (or discharge), 30 days, and 12 months. This extended timeline captures both acute and chronic cognitive changes, addressing the previously understudied long-term effects of surgery.
  • Inclusion of Pre-Operative Baseline: Mandatory pre-operative cognitive screening identifies pre-existing NCD, enabling differentiation between surgery-related and pre-existing deficits.
  • Functional and Subjective Assessments: Diagnosis of PND requires evaluation of ADLs and patient/caregiver reports, moving beyond purely objective testing.

Implications for Clinical Practice

1. Diagnostic Challenges

While the new framework enhances diagnostic rigor, it introduces complexities:

  • Resource Intensiveness: Prolonged follow-up (up to 12 months) and multi-modal assessments (neuropsychological testing + ADLs) may strain clinical resources.
  • Standardization Gaps: No specific neuropsychological test battery is mandated, risking variability across studies. The consensus group recommends using Z-scores to quantify deficits but leaves test selection to researcher discretion.

2. Pre-Operative Screening

Routine pre-operative cognitive screening (e.g., Mini-Mental State Examination) is advised to identify high-risk patients. However, screening tools alone cannot diagnose PND; full neuropsychological evaluations remain essential.

3. Reduced Incidence Estimates

Stricter diagnostic criteria, particularly the inclusion of functional assessments, will likely lower reported PND incidence compared to historical POCD rates. This underscores the importance of distinguishing clinically significant deficits from transient, non-disabling impairments.

Research Considerations

1. Methodological Adjustments

Future studies must adopt the PND framework to ensure consistency. Key recommendations include:

  • Longitudinal Designs: Extended follow-up to 12 months post-operatively.
  • Telemedicine Adaptations: Telephone-based cognitive assessments (e.g., modified Telephone Interview for Cognitive Status) may reduce attrition but require validation against in-person testing.
  • Multidisciplinary Collaboration: Integration of neurologists, geriatricians, and psychologists into research teams to align with DSM-5 and NIA-AA standards.

2. Basic Science Implications

While animal models of peri-operative cognitive decline remain unchanged, the PND nomenclature encourages alignment with translational neurocognitive research. For example, studies investigating postoperative tauopathy or neuroinflammation should now contextualize findings within mild/major NCD classifications.

Unresolved Issues and Future Directions

  • Diagnostic Thresholds: Clear cut-offs for Z-scores in defining cognitive decline are needed to standardize research.
  • Etiological Specificity: The role of anesthesia vs. surgical stress in PND pathogenesis remains unclear. Future studies should stratify patients by procedure type and anesthesia modality.
  • Prevention and Treatment: Evidence-based interventions for PND are limited. The new framework may stimulate trials targeting DSM-5-aligned outcomes, such as cholinesterase inhibitors or non-pharmacological strategies (e.g., cognitive rehabilitation).

Conclusion

The transition from POCD to PND represents a paradigm shift in peri-operative cognitive research, emphasizing clinical relevance, interdisciplinary alignment, and patient-centered outcomes. By adopting DSM-5 criteria and extending diagnostic timelines, this framework enhances the validity and applicability of research findings. However, its success hinges on overcoming logistical challenges in implementation and fostering collaboration across medical specialties. As the field evolves, the PND nomenclature promises to bridge the gap between peri-operative medicine and cognitive neurology, ultimately improving care for vulnerable surgical populations.

doi.org/10.1097/CM9.0000000000000350

Was this helpful?

0 / 0