Journal Club : Relationship between Intraoperative Mean Arterial Pressure and Clinical Outcomes after Noncardiac Surgery

Toward an Empirical Definition of Hypotension

Journal Club : Relationship between Intraoperative Mean Arterial Pressure and Clinical Outcomes after Noncardiac Surgery

Toward an Empirical Definition of Hypotension

Dr Liwei RenAnaesthetic Trainee

Nepean HospitalAugust 2013

Dr Liwei RenAnaesthetic Trainee

Nepean HospitalAugust 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

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

ResultsResults

• 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 55-59 mmHg (more than 5 min). OR 1.65.

• No risk of AKI associated with MAP>60 or myocardial injury with MAP>55mmHg

Final model category

• Time spent with MAP<55mmHg

• 0 min

• 1-5

• 6-10

• 11-20

• >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!

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