Daily Anesthesiology Research Analysis
Three anesthesia-critical care studies stand out today: a comprehensive meta-analysis finds no survival or functional benefit from restrictive oxygen targets or mild hypercapnia after cardiac arrest; an evidence synthesis shows ultrasound-guided percutaneous dilatational tracheostomy reduces major bleeding and complications versus landmark techniques; and a large database study suggests metformin use halves postoperative delirium risk in diabetic patients undergoing cardiovascular surgery with a
Summary
Three anesthesia-critical care studies stand out today: a comprehensive meta-analysis finds no survival or functional benefit from restrictive oxygen targets or mild hypercapnia after cardiac arrest; an evidence synthesis shows ultrasound-guided percutaneous dilatational tracheostomy reduces major bleeding and complications versus landmark techniques; and a large database study suggests metformin use halves postoperative delirium risk in diabetic patients undergoing cardiovascular surgery with a dose-response effect.
Research Themes
- Post–cardiac arrest ventilation targets and outcomes
- Ultrasound guidance to reduce procedural complications in ICU
- Drug repurposing to prevent postoperative delirium
Selected Articles
1. Metformin's impact on delirium in diabetic cardio surgery patients.
In a national claims study with propensity score matching, metformin use in T2DM patients undergoing CABG or valve surgery was associated with a 48% lower odds of postoperative delirium, with a clear dose-response relationship. Socioeconomic and clinical factors also modulated risk.
Impact: Suggests a readily implementable, low-cost strategy to reduce postoperative delirium in a high-risk surgical population, with supportive dose-response evidence. It advances drug repurposing in perioperative neuroprotection.
Clinical Implications: Consider perioperative continuation/optimization of metformin in eligible T2DM cardiac surgery patients as part of delirium prevention bundles, while awaiting RCT confirmation and ensuring glycemic and renal safety.
Key Findings
- Metformin use was associated with lower POD risk (aOR 0.52, 95% CI 0.40–0.67).
- Dose-response trend: higher cumulative exposure corresponded to greater protection.
- Protective correlates included higher income, urban residency, and statin use; risk correlates included older age, prolonged anesthesia, higher aDCSI/CCI, and depression.
Methodological Strengths
- Large, nationwide administrative dataset with propensity score matching to balance covariates.
- Demonstration of dose-response relationship strengthens causal inference.
Limitations
- Observational design with potential residual confounding and coding biases.
- Lack of granular intraoperative variables and standardized delirium assessment details.
Future Directions: Conduct randomized controlled trials to test perioperative metformin strategies for delirium prevention and elucidate mechanistic pathways (e.g., inflammation, insulin signaling).
PURPOSE: The effect of metformin on postoperative delirium (POD) in patients with type 2 diabetes mellitus (T2DM) undergoing cardiovascular surgery remains unclear. This study aimed to evaluate whether metformin use reduces POD risk in this high-risk population by analyzing data from Taiwan's National Health Insurance Research Database using propensity score matching (PSM). METHODS: We included T2DM patients who underwent coronary artery bypass grafting (CABG) or valve replacement between 2015 and 2018. PSM was used to balance covariates between metformin users and non-users. Logistic regression and Kaplan-Meier analyses were performed to assess POD risk and its cumulative incidence. RESULTS: Metformin use was associated with a significantly reduced risk of POD (adjusted odds ratio [aOR], 0.52; 95% confidence interval [CI], 0.40-0.67). A dose-response trend was observed, with decreasing aORs for higher cumulative metformin exposure. Protective factors included higher income, urban residency, and statin use; risk factors included older age, prolonged anesthesia, higher aDCSI, CCI scores, and depression. CONCLUSION: Metformin significantly lowers the risk of POD in T2DM patients undergoing cardiovascular surgery, showing a clear dose-dependent protective effect. These findings highlight metformin's potential as a chemopreventive agent against post-surgical complications in this population.
2. Oxygen and carbon dioxide targets after cardiac arrest: an updated systematic review.
Across 12 randomized trials, restrictive oxygen strategies and mild hypercapnia did not improve survival or functional outcomes after cardiac arrest compared with conventional targets. Certainty was low-to-moderate, with consistent null effects in both prehospital and ICU settings.
Impact: Clarifies that altering oxygen or CO2 targets post–cardiac arrest does not confer outcome benefits, supporting current pragmatic targets and preventing low-value protocol changes.
Clinical Implications: Maintain conventional oxygenation and normocapnia targets after ROSC rather than adopting restrictive oxygen or mild hypercapnia strategies routinely.
Key Findings
- No survival or favorable functional outcome differences between restrictive vs liberal oxygen targets in prehospital or ICU settings.
- No outcome benefit of mild hypercapnia compared with normocapnia.
- Evidence certainty rated low to moderate; risk of bias generally moderate.
Methodological Strengths
- Systematic search with predefined criteria and GRADE assessment.
- Random-effects meta-analyses spanning prehospital and ICU settings.
Limitations
- Overall low-to-moderate certainty with heterogeneous protocols and sample sizes.
- Adult-only trials; applicability to pediatric populations unknown.
Future Directions: Targeted trials focusing on subgroups (e.g., hypoxic ischemic brain injury phenotypes) and personalized oxygen/CO2 strategies with cerebral monitoring.
AIM: To perform an updated systematic review and meta-analysis of oxygen and carbon dioxide targets in patients with sustained return of spontaneous circulation after cardiac arrest. METHODS: Searches were conducted in MEDLINE, Embase, and Evidence-Based Medicine Reviews from August 2019 to March 2025 for randomised trials comparing specific oxygen or carbon dioxide targets in post-cardiac arrest patients. Two investigators independently reviewed trials for relevance, extracted data, and assessed risk of bias. Data were pooled using random-effects models. The certainty of evidence was evaluated using GRADE methodology. RESULTS: Fifteen manuscripts from 12 trials were included. All trials were limited to adult patients, primarily including out-of-hospital cardiac arrests. Five trials evaluated oxygen targets in the prehospital setting, while six evaluated oxygen targets and three evaluated carbon dioxide targets in the intensive care unit setting. Risk of bias was assessed as moderate for most outcomes. Meta-analyses found no differences in survival or favourable functional outcomes when comparing restrictive to liberal oxygen targets in either setting. There was also no difference in outcomes when comparing mild hypercapnia to normocapnia. The certainty of evidence was rated as low to moderate. CONCLUSIONS: Among patients resuscitated from cardiac arrest, neither restrictive oxygen targets nor mild hypercapnia, compared to conventional targets, improved survival or functional outcomes.
3. Effectiveness of ultrasound-guided versus anatomical landmark-guided percutaneous dilatational tracheostomy: a systematic review and meta-analysis.
Across 609 patients from six studies (five RCTs), ultrasound-guided PDT reduced major bleeding and periprocedural complications and markedly increased first-puncture success compared with landmark-guided techniques. Procedure duration was similar.
Impact: Provides aggregated evidence supporting ultrasound as the procedural standard to enhance safety and efficiency in ICU tracheostomy.
Clinical Implications: Adopt ultrasound guidance for bedside PDT to reduce bleeding and complications and to improve first-pass success; incorporate training and equipment into ICU airway protocols.
Key Findings
- Ultrasound guidance reduced major bleeding versus landmark-guided PDT (OR 0.35, 95% CI 0.14–0.90).
- First-puncture success was higher with ultrasound guidance (OR 4.41, 95% CI 2.54–7.65).
- Periprocedural complications were lower with ultrasound (OR 0.35, 95% CI 0.22–0.54); procedure time did not differ.
Methodological Strengths
- Includes multiple RCTs with consistent direction of effect.
- Evaluated clinically meaningful outcomes (major bleeding, complications, first-pass success).
Limitations
- Small number of studies and mixed designs (one non-RCT).
- Potential operator and device heterogeneity across studies.
Future Directions: Large multicenter RCTs to confirm benefits across operator experience levels and to assess cost-effectiveness and long-term tracheal outcomes.
BACKGROUND: Percutaneous dilatational tracheostomy (PDT) is increasingly used in intensive care units owing to its advantages of reduced surgical trauma and fewer complications. Recently, ultrasonography has become a potentially useful tool for assisting PDT. OBJECTIVE: To compare ultrasound- and landmark-guided PDT for major bleeding, first-puncture success rates, periprocedural complications, and tracheotomy procedure times. METHODS: Randomized controlled trials (RCTs) or non-RCTs comparing ultrasound- and landmark-guided PDT were searched for in PubMed, Web of Science, MEDLINE, CINAHL, Cochrane Library, Wanfang Data Knowledge Service Platform, China National Knowledge Infrastructure (CNKI) and the Chinese Biomedical Literature Service System (SinoMed). The primary outcomes were major bleeding and first puncture success rate. Secondary outcomes were periprocedural complications and the tracheotomy procedure time. The meta-analysis was performed using RevMan 5.3 software. RESULTS: This meta-analysis included five RCTs and one non-RCT, with a total of 609 patients. Compared with landmark-guided PDT, ultrasound-guided PDT can reduce the incidence of major bleeding (odds ratio [OR] = 0.35, 95% confidence interval [CI; 0.14, 0.90], P = 0.03) and improved the success rate of first puncture (OR = 4.41, 95% CI [2.54, 7.65], P < 0.000001). Additionally, ultrasound-guided PDT is associated with a lower incidence of periprocedural complications (OR = 0.35, 95% CI [0.22, 0.54], P < 0.00001). However, there was no advantage in reducing the tracheotomy procedure time between the two methods (mean difference = - 0.64, 95% CI [-4.14, 2.85], P = 0.72). CONCLUSION: Compared to landmark-guided PDT, ultrasound-guided PDT can reduce the incidence of major bleeding and periprocedural complications and increase the success rate of the first puncture. However, the advantage of ultrasound-guided PDT in reducing the tracheotomy procedure time is unclear.