Journal Club : Relationship between Intraoperative Mean Arterial Pressure and Clinical Outcomes after Noncardiac Surgery Toward an Empirical Definition of Hypotension Dr Liwei Ren Anaesthetic Trainee Nepean Hospital August 2013 Dr Liwei Ren Anaesthetic Trainee Nepean Hospital August 2013

Anesthesiology, september 2013 Featured in “This Month in Anesthesiology” Editorial review

Q: association between the introperative hypotension and postoperative acute kidney injury (AKI) and myocardial injury?

Methods Retrospective cohort study Cleveland clinic, Ohio 1/2005-9/2010 Electronic medical record system

Measurement Introperative BP (invasive and noninvasive) Minutes with hypotension

Outcomes measurement Primary AKI Cr 1.5-fold or 0.3mg/dl (26.5μmol/L) Myocardial injury Trop>=0.04μg/l or creatine kinase >=8.8 ng/ml Secondary MI, heart failure and cardiac arrest Mortality within 30 days

Statistics ANOVA for patients characteristics Chi-square for frequency Adjusted odds ratios and associated 95% CI and P values (statistical significance P<0.05) Sensitivity analyses performed

Results Primary AKI 7.4% Myocardial injury 2.3% Secondary Cardiac complication 2.8% Death within 30 days of surgery 1.5%

Defining Hypotension MAP <?60? 55mmHg

Defining Hypotension Excluded patients with MAP<55mmHg Modest but statistically significant risk of AKI for a MAP of mmHg (more than 5 min). OR No risk of AKI associated with MAP>60 or myocardial injury with MAP>55mmHg

Final model category Time spent with MAP<55mmHg 0 min >20

Discussion MAP<55mmHg a/w AKI and myocardial injury and cardiac complications Risk escalates rapidly and no safe duration for MAP<55mmHg Therapeutic target - high M&M a/w AKI, myocardial injury Healthy vs critically ill patients e.g.217 Pt, MAP>82 required to prevent AKI 31pt, SBP<90 more than 30 min a/w higher cardiac enzymes

Limitations and bias retrospective study a single center potential residual confounders excluded population group without postoperative creatinine excluded longer operation, higher risks of hypotension invasive vs noninvasive BP measurement lack of data on adverse cerebral outcomes

Strengths of the study Large cohort Diverse surgical types and comorbidities Electronic BP recording

Conclusion Time spent with MAP less than 55 during noncardiac surgery is independently associate with an increased risk of AKI and myocardial injury Not for all patients Further trials required to determine whether outcomes improve with intervention of hypotension

Thank you!.