Considerations on the Management of Acute Postoperative Ischemia After Cardiac Surgery: A Scientific Statement From the American Heart Association.

Acute postoperative myocardial ischemia (PMI) after cardiac surgery is an infrequent event that can evolve rapidly and become a potentially life-threatening complication. Multiple factors are associated with acute PMI after cardiac surgery and may vary by the type of surgical procedure performed. Although the criteria defining nonprocedural myocardial ischemia are well established, there are no universally accepted criteria for the diagnosis of acute PMI. In addition, current evidence on the management of acute PMI after cardiac surgery is sparse and generally of low methodological quality. Once acute PMI is suspected, prompt diagnosis and treatment are imperative, and options range from conservative strategies to percutaneous coronary intervention and redo coronary artery bypass grafting. In this document, a multidisciplinary group including experts in cardiac surgery, cardiology, anesthesiology, and postoperative care summarizes the existing evidence on diagnosis and treatment of acute PMI and provides clinical guidance.

Association Between Surgeon/Anesthesiologist Sex Discordance and 1-year Mortality Among Adults Undergoing Noncardiac Surgery: A Population-based Retrospective Cohort Study.

OBJECTIVE: To investigate the association between surgeon-anesthesiologist sex discordance and patient mortality after noncardiac surgery. BACKGROUND: Evidence suggests different practice patterns exist among female and male physicians. However, the influence of physician sex on team-based practices in the operating room and subsequent patient outcomes remains unclear in the context of noncardiac surgery. METHODS: We conducted a population-based, retrospective cohort study of adult Ontario residents who underwent index, inpatient noncardiac surgery between January 2007 and December 2017. The primary exposure was physician sex discordance (ie, the surgeon and anesthesiologist were of the opposite sex). The primary outcome was 1-year mortality. The association between physician sex discordance and patient outcomes was modeled using multivariable Cox proportional hazard regression with adjustment for relevant physician, patient, and hospital characteristics. RESULTS: Of 541,209 patients, 158,084 (29.2%) were treated by sex-discordant physician teams. Physician sex discordance was associated with a lower rate of mortality at 1 year [5.2% vs. 5.7%; adjusted HR: 0.95 (0.91-0.99)]. Patients treated by teams composed of female surgeons and male anesthesiologists were more likely to be alive at 1 year than those treated by all-male physician teams [adjusted HR: 0.90 (0.81-0.99)]. CONCLUSIONS: Noncardiac surgery patients had a lower likelihood of 1-year mortality when treated by sex-discordant surgeon-anesthesiologist teams. The likelihood of mortality was further reduced if the surgeon was female. Further research is needed to explore the underlying mechanisms of these observations and design strategies to diversify operating room teams to optimize performance and patient outcomes.

Age, Not Sex, Modifies the Effect of Frailty on Long-term Outcomes After Cardiac Surgery.

OBJECTIVE: To examine the prevalence of frailty in surgical patients and determine whether age and sex modify the relationship between frailty and long-term mortality. BACKGROUND: Frailty is a complex and prevalent clinical syndrome. The cardiac surgery literature consists mostly of small, single-center studies, and the epidemiology of frailty remains to be fully elucidated in a real-world surgical population. METHODS: This retrospective cohort study included patients who underwent coronary artery bypass grafting, and/or aortic, mitral or tricuspid valve surgery in Ontario, Canada, between 2008 and 2016. The primary outcome was all-cause mortality. Survival probabilities were calculated using the Kaplan-Meier method, and the association of covariates with the hazard of death was assessed using multivariable Cox proportional hazard models. Frailty was assessed using the Johns Hopkins Adjusted Clinical Groups frailty-defining diagnoses indicator. RESULTS: Of 72,824 patients, 11,685 (16%) were frail. At median 5 ±â€Š2 years of follow-up, 2921 (25.0%) frail patients and 8637 (14.1%) non-frail patients had died [adjusted hazard ratio 1.60; 95% confidence interval (CI), 1.53-1.68]. The adjusted hazard ratio was highest in patients who underwent isolated mitral (2.18; 95% CI, 1.71-2.77) and mitral + aortic valve surgery (1.85; 95% CI, 1.33-2.58) and lowest after coronary artery bypass grafting + mitral valve surgery (1.38; 95% CI, 1.11-1.70). Age, but not sex, modified the effect of frailty on mortality; such that the rate of death decreased linearly with increasing patient age. CONCLUSIONS: We observed a high prevalence of frailty in patients undergoing cardiac surgery, and a statistically significant association between frailty and long-term mortality after cardiac procedures. Importantly, the rate of death was inversely proportional to age, such that frailty had a stronger adverse impact on younger patients. Our findings highlight the need to incorporate frailty into the preoperative risk stratification and investigate strategies to support younger patients who are frail.

Patient Sex and Postoperative Outcomes after Inpatient Intraabdominal Surgery: A Population-based Retrospective Cohort Study.

BACKGROUND: Intraabdominal surgeries are frequently performed procedures that lead to a high volume of unplanned readmissions and postoperative complications. Patient sex may be a determinant of adverse outcomes in this population, possibly due to differences in biology or care delivery, but it is understudied. The authors hypothesized that there would be no association between patient sex and the risk of postoperative adverse outcomes in intraabdominal surgery. METHODS: This retrospective, population-based cohort study involved adult inpatients aged 18 yr or older who underwent intraabdominal surgeries in Ontario, Canada, between April 2009 and March 2016. The authors studied the association of patient sex on the primary composite outcome of all-cause death, hospital readmission, or major postoperative complications, all within 30 postoperative days. Inverse probability of exposure weighting based on propensity scores (computed using demographic characteristics such as rural residence status and median neighborhood income quintile, common comorbidities, and surgery- and hospital-specific characteristics) was used to estimate the adjusted association of sex on outcomes. RESULTS: The cohort included 215,846 patients (52.3% female). The primary outcome was observed in 24,712 (21.9%) females and 25,486 (24.7%) males (unadjusted risk difference, 2.8% [95% CI, 2.5 to 3.2%]; P < 0.001). After adjustment, the association between the male sex and the primary outcome was not statistically significant (adjusted risk difference, -0.2% [95% CI, -0.5 to 0.2%]; P = 0.378). CONCLUSIONS: In a large population of intraabdominal surgical patients, there was no differential risk between sexes in the composite outcome of all-cause death, hospital readmission, or major postoperative complications, all within 30 postoperative days.

Relationship of frailty with excess mortality during the COVID-19 pandemic: a population-level study in Ontario, Canada.

BACKGROUND: There is a paucity of the literature on the relationship between frailty and excess mortality due to the COVID-19 pandemic. METHODS: The entire community-dwelling adult population of Ontario, Canada, as of January 1st, 2018, was identified using the Cardiovascular Health in Ambulatory Care Research Team (CANHEART) cohort. Residents of long-term care facilities were excluded. Frailty was categorized through the Johns Hopkins Adjusted Clinical Groups (ACG® System) frailty indicator. Follow-up was until December 31st, 2020, with March 11th, 2020, indicating the beginning of the COVID-19 pandemic. Using multivariable Cox models with patient age as the timescale, we determined the relationship between frailty status and pandemic period on all-cause mortality. We evaluated the modifier effect of frailty using both stratified models as well as incorporating an interaction between frailty and the pandemic period. RESULTS: We identified 11,481,391 persons in our cohort, of whom 3.2% were frail based on the ACG indicator. Crude mortality increased from 0.75 to 0.87% per 100 person years from the pre- to post-pandemic period, translating to ~ 13,800 excess deaths among the community-dwelling adult population of Ontario (HR 1.11 95% CI 1.09-1.11). Frailty was associated with a statistically significant increase in all-cause mortality (HR 3.02, 95% CI 2.99-3.06). However, all-cause mortality increased similarly during the pandemic in frail (aHR 1.13, 95% CI 1.09-1.16) and non-frail (aHR 1.15, 95% CI 1.13-1.17) persons. CONCLUSION: Although frailty was associated with greater mortality, frailty did not modify the excess mortality associated with the pandemic.

Prediction of acute kidney injury risk after cardiac surgery: using a hybrid machine learning algorithm.

BACKGROUND: Acute kidney injury (AKI) is a serious complication after cardiac surgery. We derived and internally validated a Machine Learning preoperative model to predict cardiac surgery-associated AKI of any severity and compared its performance with parametric statistical models. METHODS: We conducted a retrospective study of adult patients who underwent major cardiac surgery requiring cardiopulmonary bypass between November 1st, 2009 and March 31st, 2015. AKI was defined according to the KDIGO criteria as stage 1 or greater, within 7 days of surgery. We randomly split the cohort into derivation and validation datasets. We developed three AKI risk models: (1) a hybrid machine learning (ML) algorithm, using Random Forests for variable selection, followed by high performance logistic regression; (2) a traditional logistic regression model and (3) an enhanced logistic regression model with 500 bootstraps, with backward variable selection. For each model, we assigned risk scores to each of the retained covariate and assessed model discrimination (C statistic) and calibration (Hosmer-Lemeshow goodness-of-fit test) in the validation datasets. RESULTS: Of 6522 included patients, 1760 (27.0%) developed AKI. The best performance was achieved by the hybrid ML algorithm to predict AKI of any severity. The ML and enhanced statistical models remained robust after internal validation (C statistic = 0.75; Hosmer-Lemeshow p = 0.804, and AUC = 0.74, Hosmer-Lemeshow p = 0.347, respectively). CONCLUSIONS: We demonstrated that a hybrid ML model provides higher accuracy without sacrificing parsimony, computational efficiency, or interpretability, when compared with parametric statistical models. This score-based model can easily be used at the bedside to identify high-risk patients who may benefit from intensive perioperative monitoring and personalized management strategies.

Derivation and validation of a clinical model to predict death or cardiac hospitalizations while on the cardiac surgery waitlist.

BACKGROUND: Waitlist management is a global challenge. For patients with severe cardiovascular diseases awaiting cardiac surgery, prolonged wait times are associated with unplanned hospitalizations. To facilitate evidence-based resource allocation, we derived and validated a clinical risk model to predict the composite outcome of death and cardiac hospitalization of patients on the waitlist for cardiac surgery. METHODS: We used the CorHealth Ontario Registry and linked ICES health care administrative databases, which have information on all Ontario residents. We included patients 18 years or older who waited at home for coronary artery bypass grafting, valvular or thoracic aorta surgeries between 2008 and 2019. The primary outcome was death or an unplanned cardiac hospitalizaton, defined as nonelective admission for heart failure, myocardial infarction, unstable angina or endocarditis. We randomly divided two-thirds of these patients into derivation and one-third into validation data sets. We derived the model using a multivariable Cox proportional hazard model with backward stepwise variable selection. RESULTS: Among 62 375 patients, 41 729 patients were part of the derivation data set and 20 583 were part of the validation data set. Of the total, 3033 (4.9%) died or had an unplanned cardiac hospitalization while waiting for surgery. The area under the curve of our model at 15, 30, 60 and 89 days was 0.85, 0.82, 0.81 and 0.80, respectively, in the derivation cohort and 0.83, 0.80, 0.78 and 0.78, respctively, in the validation cohort. The model calibrated well at all time points. INTERPRETATION: We derived and validated a clinical risk model that provides accurate prediction of the risk of death and unplanned cardiac hospitalization for patients on the cardiac surgery waitlist. Our model could be used for quality benchmarking and data-driven decision support for managing access to cardiac surgery.

Derivation and validation of predictive indices for 30-day mortality after coronary and valvular surgery in Ontario, Canada.

BACKGROUND: Coronary artery bypass grafting (CABG) and surgical aortic valve replacement (AVR) are the 2 most common cardiac surgery procedures in North America. We derived and externally validated clinical models to estimate the likelihood of death within 30 days of CABG, AVR or combined CABG + AVR. METHODS: We obtained data from the CorHealth Ontario Cardiac Registry and several linked population health administrative databases from Ontario, Canada. We derived multiple logistic regression models from all adult patients who underwent CABG, AVR or combined CABG + AVR from April 2017 to March 2019, and validated them in 2 temporally distinct cohorts (April 2015 to March 2017 and April 2019 to March 2020). RESULTS: The derivation cohorts included 13 435 patients who underwent CABG (30-d mortality 1.73%), 1970 patients who underwent AVR (30-d mortality 1.68%) and 1510 patients who underwent combined CABG + AVR (30-d mortality 3.05%). The final models for predicting 30-day mortality included 15 variables for patients undergoing CABG, 5 variables for patients undergoing AVR and 5 variables for patients undergoing combined CABG + AVR. Model discrimination was excellent for the CABG (c-statistic 0.888, optimism-corrected 0.866) AVR (c-statistic 0.850, optimism-corrected 0.762) and CABG + AVR (c-statistic 0.844, optimism-corrected 0.776) models, with similar results in the validation cohorts. INTERPRETATION: Our models, leveraging readily available, multidimensional data sources, computed accurate risk-adjusted 30-day mortality rates for CABG, AVR and combined CABG + AVR, with discrimination comparable to more complex American and European models. The ability to accurately predict perioperative mortality rates for these procedures will be valuable for quality improvement initiatives across institutions.

Can Biomarkers Provide Right Ventricular-Specific Prognostication in the Perioperative Setting?

Since the introduction of biomarkers in the late 1980s, considerable research has been dedicated to their validation and application. As a result, many biomarkers are now commonly used in clinical practice. However, the role of biomarkers in the prediction of right ventricular failure (RVF) and in the prognostication for patients with RVF remains underexplored. Barriers include a lack of awareness of the importance of right ventricular function, especially in the perioperative setting, as well as a lack of reproducible means to assess right ventricular function in this setting. We provide an overview of biomarkers with right ventricular prognostic capabilities that could be further explored in patients expecting cardiac surgery, who are notoriously susceptible to developing RVF. We discuss biomarkers' mechanistic pathways and highlight their potential strengths and weaknesses in use in research and clinical care.

Defining an Intraoperative Hypotension Threshold in Association with De Novo Renal Replacement Therapy after Cardiac Surgery.

BACKGROUND: Acute kidney injury (AKI) is a frequent and deadly complication after cardiac surgery. In the absence of effective therapies, a focus on risk factor identification and modification has been the mainstay of management. The authors sought to determine the impact of intraoperative hypotension on de novo postoperative renal replacement therapy in patients undergoing cardiac surgery, hypothesizing that prolonged periods of hypotension during and after cardiopulmonary bypass (CPB) were associated with an increased risk of renal replacement therapy. METHODS: Included in this single-center retrospective cohort study were adult patients who underwent cardiac surgery requiring CPB between November 2009 and April 2015. Excluded were patients who were dialysis dependent, underwent thoracic aorta or off-pump procedures, or died before receiving renal replacement therapy. Degrees of hypotension were defined by mean arterial pressure (MAP) as less than 55, 55 to 64, and 65 to 74 mmHg before, during, and after CPB. The primary outcome was de novo renal replacement therapy. RESULTS: Of 6,523 patient records, 336 (5.2%) required new postoperative renal replacement therapy. Each 10-min epoch of MAP less than 55 mmHg post-CPB was associated with an adjusted odds ratio of 1.13 (95% CI, 1.05 to 1.23; P = 0.002), and each 10-min epoch of MAP between 55 and 64 mmHg post-CPB was associated with an adjusted odds ratio of 1.12 (95% CI, 1.06 to 1.18; P = 0.0001) for renal replacement therapy. The authors did not observe an association between hypotension before and during CPB with renal replacement therapy. CONCLUSIONS: MAP less than 65 mmHg for 10 min or more post-CPB is associated with an increased risk of de novo postoperative renal replacement therapy. The association between intraoperative hypotension and AKI was weaker in comparison to factors such as renal insufficiency, heart failure, obesity, anemia, complex or emergent surgery, and new-onset postoperative atrial fibrillation. Nonetheless, post-CPB hypotension is a potentially easier modifiable risk factor that warrants further investigation.

Readmission rates following heart failure: a scoping review of sex and gender based considerations.

BACKGROUND: Although hospital readmission for heart failure (HF) is an issue for both men and women, little is known about differences in readmission rates by sex. Consequently, strategies to optimize readmission reduction programs and care strategies for women and men remain unclear. Our study aims were: (1) to identify studies examining readmission rates according to sex, and (2) to provide a qualitative overview of possible considerations for the impact of sex or gender. METHODS: We conducted a scoping review using the Arksey and O'Malley framework to include full text articles published between 2002 and 2017 drawn from multiple databases (MEDLINE, EMBASE), grey literature (i.e. National Technical information, Duck Duck Go), and expert consultation. Eligible articles included an index heart failure episode, readmission rates, and sex/gender-based analysis. RESULTS: The search generated 5887 articles, of which 746 underwent full abstract text consideration for eligibility. Of 164 eligible articles, 34 studies addressed the primary outcome, 103 studies considered sex differences as a secondary outcome and 25 studies stratified data for sex. Good inter-rater agreement was reached: 83% title/abstract; 88% full text; kappa: 0.69 (95%CI: 0.53-0.85). Twelve of 34 studies reported higher heart failure readmission rates for men and six studies reported higher heart failure readmission rates for women. Using non composite endpoints, five studies reported higher HF readmission rates for men compared to three studies reporting higher HF readmission rates for women. Overall, there was heterogeneity between studies when examined by sex, but one observation emerged that was related to the timing of readmissions. Readmission rates for men were higher when follow-up duration was longer than 1 year. Women were more likely to experience higher readmission rates than men when time to event was less than 1 year. CONCLUSIONS: Future studies should consider different time horizons in their designs and avoid the use of composite measures, such as readmission rates combined with mortality, which are highly skewed by sex. Co-interventions and targeted post-discharge approaches with attention to sex would be of benefit to the HF patient population.

Renal insufficiency and severe coronary artery disease: should coronary artery bypass grafting, off-pump coronary artery bypass grafting or percutaneous coronary intervention be performed?

PURPOSE OF REVIEW: Chronic kidney disease (CKD) is an important determinant of long-term survival. However, the optimal revascularization strategy for patients with CKD is still controversial. Herein we review the impact of different treatment modalities on the outcomes of patients with CKD. RECENT FINDINGS: CABG could confer better long-term outcomes than PCI in patients with CKD, irrespective of CKD severity. CABG as compared with PCI may be associated with improved long-term survival albeit higher short-term risk. Off-pump as compared with on-pump CABG may be associated with better short-term outcomes but no demonstrable long-term benefit. In CKD patients who are treated with PCI, the use of drug-eluting stents may be associated with better intermediate-term outcomes than bare metal stents. SUMMARY: There is insufficient evidence to inform the optimal revascularization strategy for patients with CKD and severe coronary artery disease. CABG as compared with PCI confers greater long-term benefit but higher upfront risk. A multidisciplinary, team-based evaluation based on individual patient comorbidity, frailty and anatomical disease burden, is recommended when making treatment decisions.

Sex-Specific Trends in Incidence and Mortality for Urban and Rural Ambulatory Patients with Heart Failure in Eastern Ontario from 1994 to 2013.

BACKGROUND: Differences in outcomes have previously been reported between urban and rural settings across a multitude of chronic diseases. Whether these discrepancies have changed over time, and how sex may influence these findings is unknown for patients with ambulatory heart failure (HF). We examined the temporal incidence and mortality trends by geography in these patients. METHODS AND RESULTS: We conducted a retrospective cohort study of 36,175 eastern Ontario residents who were diagnosed with HF in an outpatient setting from 1994 to 2013. The primary outcome was 1-year mortality. We examined temporal changes in mortality risk factors with the use of multivariable Cox proportional hazard models. The incidence of HF decreased in women and men across both rural and urban settings. Age-standardized mortality rates also decreased over time in both sexes but remained greater in rural men compared with rural women. CONCLUSIONS: The incidence of HF in the ambulatory setting was greater for men than women and greater in rural than urban areas, but mortality rates remained higher in rural men compared with rural women. Further research should focus on ways to reduce this gap in the outcomes of men and women with HF.

Left ventricular function recovery after revascularization: comparative effects of percutaneous coronary intervention and coronary artery bypass grafting.

PURPOSE OF REVIEW: In 2013, heart failure with recovered ejection fraction (HFrecEF) was introduced as a new heart failure phenotype. This review provides an overview of HFrecEF and the comparative effects of percutaneous coronary intervention (PCI) and coronary artery bypass grafting (CABG) on left ventricular ejection fraction (LVEF) recovery in patients with ischemic cardiomyopathy. RECENT FINDINGS: There has been emerging data indicating that LV functional recovery is possible and HFrecEF is associated with improved survival and better quality of life. CABG may be associated with larger improvement in LVEF when compared with PCI. However, there is significant paucity of studies, which directly compare the impact of PCI and CABG on LVEF recovery in the setting of ischemic cardiomyopathy. SUMMARY: LVEF recovery is emerging as an important outcome with demonstrated survival and quality-of-life benefits. Future randomized clinical trials comparing the impact of contemporary PCI and CABG on LVEF recovery are needed in patients with ischemic cardiomyopathy.

Defining an Intraoperative Hypotension Threshold in Association with Stroke in Cardiac Surgery.

WHAT WE ALREADY KNOW ABOUT THIS TOPIC: WHAT THIS ARTICLE TELLS US THAT IS NEW: BACKGROUND:: Stroke is a leading cause of morbidity, mortality, and disability in patients undergoing cardiac surgery. Identifying modifiable perioperative stroke risk factors may lead to improved patient outcomes. The association between the severity and duration of intraoperative hypotension and postoperative stroke in patients undergoing cardiac surgery was evaluated. METHODS: A retrospective cohort study was conducted of adult patients who underwent cardiac surgery requiring cardiopulmonary bypass at a tertiary center between November 1, 2009, and March 31, 2015. The primary outcome was postoperative ischemic stroke. Intraoperative hypotension was defined as the number of minutes spent within mean arterial pressure bands of less than 55, 55 to 64, and 65 to 74 mmHg before, during, and after cardiopulmonary bypass. The association between stroke and hypotension was examined by using logistic regression with propensity score adjustment. RESULTS: Among the 7,457 patients included in this analysis, 111 (1.5%) had a confirmed postoperative diagnosis of stroke. Stroke was strongly associated with sustained mean arterial pressure of less than 64 mmHg during cardiopulmonary bypass (adjusted odds ratio 1.13; 95% CI, 1.05 to 1.21 for every 10 min of mean arterial pressure between 55 and 64 mmHg; adjusted odds ratio 1.16; 95% CI, 1.08 to 1.23 for every 10 min of mean arterial pressure less than 55 mmHg). Other factors that were independently associated with stroke were older age, hypertension, combined coronary artery bypass graft/valve surgery, emergent operative status, prolonged cardiopulmonary bypass duration, and postoperative new-onset atrial fibrillation. CONCLUSIONS: Hypotension is a potentially modifiable risk factor for perioperative stroke. The study's findings suggest that mean arterial pressure may be an important intraoperative therapeutic hemodynamic target to reduce the incidence of stroke in patients undergoing cardiopulmonary bypass.

Sex differences in outcomes of heart failure in an ambulatory, population-based cohort from 2009 to 2013.

BACKGROUND: Heart failure remains a substantial cause of morbidity and mortality in women. We examined the sex differences in heart failure incidence, mortality and hospital admission in a population-based cohort. METHODS: All Ontario residents who were diagnosed with heart failure in an ambulatory setting between Apr. 1, 2009, and Mar. 31, 2014, were included in this study. Incident cases of heart failure were captured through physician billing using a validated algorithm. Outcomes were mortality and hospital admission for heart failure within 1 year of the diagnosis. Probability of death and hospital admission were calculated using the Kaplan-Meier method. The hazard of death was assessed using a multivariable Cox proportional hazard model. RESULTS: A total of 90 707 diagnoses of heart failure were made in an ambulatory setting during the study period (47% women). Women were more likely to be older and more frail, and had different comorbidities than men. The incidence of heart failure decreased during the study period in both sexes. The mortality rate decreased in both sexes, but remained higher in women than men. The female age-standardized mortality rate was 89 (95% confidence interval [CI] 80-100) per 1000 in 2009 and 85 (95% CI 75-95) in 2013, versus male age-standardized mortality rates of 88 (95% CI 80-97) in 2009 and 83 (95% CI 75-91) in 2013. Conversely, the rates of incident heart failure hospital admissions after heart failure diagnosis decreased in men and increased in women. INTERPRETATION: Despite decreases in overall heart failure incidence and mortality in ambulatory patients, mortality rates remain higher in women than in men, and rates of hospital admission for heart failure increased in women and declined in men. Further studies should focus on sex differences in health-seeking behaviour, medical therapy and response to therapy to provide guidance for personalized care.

Association of intraoperative hypotension with acute kidney injury after elective noncardiac surgery.

BACKGROUND: Intraoperative hypotension (IOH) may be associated with postoperative acute kidney injury (AKI), but the duration of hypotension for triggering harm is unclear. The authors investigated the association between varying periods of IOH with mean arterial pressure (MAP) less than 55, less than 60, and less than 65 mmHg with AKI. METHODS: The authors conducted a retrospective cohort study of 5,127 patients undergoing noncardiac surgery (2009 to 2012) with invasive MAP monitoring and length of stay of 1 or more days. Exclusion criteria were preoperative MAP less than 65 mmHg, dialysis dependence, urologic surgery, and surgical duration less than 30 min. The primary exposure was IOH. The primary outcome was AKI (50% or 0.3 mg/dl increase in creatinine) during the first 2 postoperative days. Multivariable logistic regression was used to model the exposure-outcome relationship. RESULTS: AKI occurred in 324 (6.3%) patients and was associated with MAP less than 60 mmHg for 11 to 20 min and MAP less than 55 mmHg for more than 10 min in a graded fashion. The adjusted odds ratio of AKI for MAP less than 55 mmHg was 2.34 (1.35 to 4.05) for 11- to 20-min exposure and 3.53 (1.51 to 8.25) for more than 20 min. For MAP less than 60 mmHg, the adjusted odds ratio for AKI was 1.84 (1.11 to 3.06) for 11- to 20-min exposure. CONCLUSIONS: In this analysis, postoperative AKI is associated with sustained intraoperative periods of MAP less than 55 and less than 60 mmHg. This study provides an impetus for clinical trials to determine whether interventions that promptly treat IOH and are tailored to individual patient physiology could help reduce the risk of AKI.