Study Design: Analysis of Published Results

Narrative Reviews

• Narrative reviews are often considered nonsystematic and subjective as interpretations may vary by author.¹ They are helpful as they provide a broad summary, with interpretation/critique of various studies.1 Types of narrative reviews include state-of-the-art, meta-ethnographic, critical, and integrative reviews (Table 1).¹
• Narrative reviews help translate research into practical insights and can offer clinicians new information about evolving techniques and standards of care.¹
• For instance, Belrose et al. illustrate how narrative reviews integrate diverse findings to thoroughly understand complex issues by highlighting the link between anesthesia and postoperative cognitive dysfunction through mechanisms like tau protein alterations and inflammation.²

Systematic Reviews

• SRs are generally considered the best level of evidence.³
• When conducting an SR, researchers identify, analyze, and synthesize data from all studies on a specific topic.³ They involve a detailed plan and search strategy developed a priori.³
• SRs evaluate the quality of studies during the review process and often include a meta-analysis component.³
• SRs are standardized and improved by guidelines such as the QUORUM (Quality of Reporting of Meta-analyses) statement and PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) statement.³

Conducting a SR

• A flow diagram outlining critical steps in the SR process is provided (see Figure 1).⁴

Meta-Analysis

• Meta-analyses (Mas) combine data from multiple studies to pool the effects of intervention (i.e., drugs, treatments) into a single quantitative estimate or effect size (strength of the relationship between two variables).³
• They are typically conducted on randomized clinical trials (RCTs).³
• Types of effect sizes include odds ratios, weighted/standardized mean differences, and relative risk or risk ratios.³
• The QUORUM statement ensures that all relevant information is included in the MA of RCTs, helping the readers fully understand the scope, methods, characteristics, and findings of the study.^5,6
• QUORUM has been updated to include new standards for reporting SRs and MAs called PRISMA.⁵
• PRISMA focuses on improving the quality and transparency of reviews to ensure reproducibility and reliability.⁵
  • Critical features of PRISMA include a 27-item checklist covering all aspects of reporting, along with a flow diagram to visually represent study selection (Figure 2).⁵
• Both guidelines promote a standardized approach to reporting across SRs and MAs.^5,6

Importance in Anesthesiology

• SRs and MAs are crucial in anesthesiology for improving treatments.⁷ They are valuable in perioperative management, intensive care, and outpatient anesthesia.⁷
• For example, Bainbridge et al. conducted an SR and MA that assessed changes in perioperative mortality related to anesthesia over decades.⁸
• The authors highlight the importance of utilizing such study designs to provide insights that enhance patient safety, guide improvements, and address disparities in anesthesiology.⁸

Practice Guidelines

• Practice guidelines are carefully crafted recommendations designed to help clinicians and patients make informed decisions about medical care.⁹
• These guidelines are based on a comprehensive review of the current literature and expert opinions. As medical knowledge advances, these guidelines are updated to reflect newer developments.⁹

Practice Guidelines in Anesthesiology

• For example, the ASA has published “Practice Guidelines for Management of the Difficult Airway” to reflect best practices.⁹
• These guidelines were developed through an SR of peer-reviewed literature.⁹
• According to these guidelines, when managing a difficult airway:
  • Begin with a thorough risk assessment and physical exam before starting anesthesia to identify potential difficulties.⁹
  • If a difficult airway is anticipated, ensure a skilled assistant is nearby, inform the surgeon, and prepare for oxygen supplementation/monitoring.⁹
  • Ensure that a strategy is developed for managing anticipated difficulties, including intubation and emergency rescue plans.⁹
  • Confirm proper intubation using capnography or end-tidal CO₂ monitoring and consider other methods if necessary.⁹
  • Plan extubation carefully by assessing patient readiness and using airway exchange catheters if needed.⁹
  • Following completion, provide the patient with appropriate postextubation medications and document the airway challenges/difficulties that were encountered.⁹