Faculty Bibliography

Background.: Most current surgical risk models contain many variables: some of which may be esoteric, require a physician's assessment or must be obtained intraoperatively. Early preoperative risk stratification is essential to identify high risk, elective surgical patients for medical optimization and care coordination across the perioperative period. We sought to create a simple, patient-driven scoring system using: gender, age and list of medications to predict in-hospital postoperative morbidity. We hypothesized that certain medications would elevate risk, as indices of underlying conditions. Methods.: Two Logistic regression models were created based on patient's gender, age, and medications: GAMMA (Gender, age and type of medications to predict in-hospital morbidity) and GAMMA-N (Gender, age and number of medications to predict in-hospital morbidity). A logistic regression models predicting in-hospital morbidity based on ASA score alone was also created (ASA-M). The predictive performance of these models was tested in a large surgical patient database. Results.: Our GAMMA model predicts postoperative morbidity after perioperative care with high accuracy (c-statistic 0.819, Brier score 0.034). This result is similar to a model using only the ASA score (c-statistic 0.827, Brier score 0.033) and better than our GAMMA-N model (c-statistic 0.795, Brier score 0.050). Conclusions.: The combination of a patient's gender, age, and medication list provided reliable prediction of postoperative morbidity. Our model has the added benefit of increased objectivity, can be conducted preoperatively, and is amenable to patient-use as it requires only limited medical knowledge.

We used multivariate analyses to assess the association of pre-operative variables with kidney function in 41,523 adults after scheduled surgery in a single large academic hospital. Eight variables were independently associated with a reduction in postoperative estimated glomerular filtration rate: pre-operative renal function; age; ASA physical status; cardiac failure; anaemia; cancer; type of surgery; and the lowest quartile of pre-operative mean arterial blood pressure (< 71 mmHg). The estimated glomerular filtration rate fell by a mean (95% CI) of 2.7 (0.04-5.40) ml.min-1 .1.73 m-2 for patients with a pre-operative mean arterial pressure < 71 mmHg, p = 0.047. The same variables and male sex were associated with postoperative acute kidney injury. The odds ratio (95% CI) for acute postoperative kidney injury was 1.9 (1.2-2.9) for patients with a pre-operative mean arterial blood pressure < 71 mmHg, p = 0.005.

BACKGROUND: Making a formal diagnosis of chronic kidney disease (CKD) in the preoperative setting may be challenging because of lack of longitudinal data. We explored the predictive value of a single reduced preoperative estimated glomerular filtration rate (eGFR) value on adverse patient outcomes in the first 30 days after elective surgery. We compared the rate of major postoperative adverse events, including 30-day readmission rate, hospital length of stay, infection, acute kidney injury (AKI), and myocardial infarction across patients with declining preoperative eGFR values. We hypothesized that there is an association between decreasing preoperative eGFR values and major postoperative morbidity including readmission within 30 days of discharge and that the reasons for unplanned readmissions may be associated with poor preoperative renal function. METHODS: This was a retrospective analysis of the electronic health record of 39 989 adult patients who underwent elective surgery between June 2011 and July 2013 at our institution. Patients with reduced eGFR (<60 mL/min/1.73 m) were identified and categorized by the stages of CKD that correlated with the preoperative eGFR value. Odds of readmission to our hospital within 30 days, as well as new diagnosis of AKI, myocardial infarction, and infection, were determined with multivariate logistic regression. The subset of patients who were readmitted within 30 days also were subdivided further into patients who had an eGFR <60 mL/min/1.73 m and those with an eGFR >/=60 mL/min/1.73 m, as well as whether the readmission was planned or unplanned. RESULTS: Of the 4053 patients with eGFR <60 mL/min/1.73 m, 3290 (81.2%) did not carry a preoperative diagnosis of CKD. Adjusted odds ratios of being readmitted were 1.48 (99% confidence interval [CI], 1.18-1.87; P < .001) for eGFR 30 to 44 mL/min/1.73 m to 2.06 (99% CI, 1.32-3.23; P < .001) for eGFR <15 mL/min/1.73 m compared with patients with a preoperative eGFR value >/=60 mL/min/1.73 m. Patients with a lower eGFR also demonstrated increasing odds of AKI from 2.78 (99% CI, 1.86-4.17; P < .001) for eGFR 45 to 59 mL/min/1.73 m to 3.81 (99% CI, 1.68-8.16; P < .001) for eGFR <15 mL/min/1.73 m. CONCLUSIONS: This study highlights that preoperative renal insufficiency may be underreported and appears to be significantly associated with postoperative complications. It extends the association between a single low preoperative eGFR and postoperative morbidity to a broader range of surgical populations than previously described. Our results suggest that preoperative calculation of eGFR may be a relatively low-cost, readily available tool to identify patients who are at an increased risk of readmission within 30 days of surgery and postoperative morbidity in patients presenting for elective surgery.

STUDY OBJECTIVE: Obese patients regularly present for surgery and have greater hypoxemia risk. This study aimed to identify the risk and incidence of intraoperative hypoxemia with increasing body mass index (BMI). DESIGN: This was a retrospective cohort study. SETTING: Operating room. PATIENTS: A total of 15,238 adult patients who underwent general anesthesia for elective noncardiac surgery at a single large urban academic institution between January 2013 and December 2014. INTERVENTIONS: Unadjusted and risk-adjusted logistic regression analyses explored the relationship between increasing categories of BMI and intraoperative hypoxemia, severe hypoxemia, and prolonged hypoxemia. MEASUREMENTS: Intraoperative pulse oximeter readings and preoperative patient characteristics. MAIN RESULTS: With normal BMI, 731 (16%) patients experienced hypoxemia compared with 1150 (28%) obese patients. Adjusted odds ratio (AOR) of intraoperative hypoxemia increased with each category of BMI from 1.27 (95% confidence interval [CI], 1.12-1.44) in overweight patients to 2.63 (95% CI, 2.15-3.23) in patients with class III obesity. AOR of severe hypoxemia was significant with class I obesity (AOR, 1.32; 95% CI, 1.08-1.60), class II obesity (AOR, 2.01; 95% CI, 1.59-2.81), and class III obesity (AOR, 2.27; 95% CI, 1.75-2.93). AOR of prolonged hypoxemia increased with BMI from 3.29 (95% CI, 1.79-6.23) with class I obesity to 9.20 (95% CI, 4.74-18) with class III obesity. CONCLUSIONS: Despite existing practices to limit hypoxemia in obese patients, the odds of experiencing intraoperative hypoxemia increase significantly with increasing categories of BMI. Further practices may need to be developed to minimize the risk of intraoperative hypoxemia in obese patients.

BACKGROUND: As specialists in perioperative medicine, anesthesiologists are well equipped to design and oversee the preoperative patient preparation process; however, the impact of an anesthesiologist-led preoperative evaluation clinic (PEC) on clinical outcomes has yet to be fully elucidated. The authors compared the incidence of in-hospital postoperative mortality in patients who had been evaluated in their institution's PEC before elective surgery to the incidence in patients who had elective surgery without being seen in the PEC. METHODS: A retrospective review of an administrative database was performed. There were 46 deaths from 64,418 patients (0.07%): 22 from 35,535 patients (0.06%) seen in PEC and 24 from 28,883 patients (0.08%) not seen in PEC. After propensity score matching, there were 13,964 patients within each matched set; there were 34 deaths (0.1%). There were 11 deaths from 13,964 (0.08%) patients seen in PEC and 23 deaths from 13,964 (0.16%) patients not seen in PEC. A subanalysis to assess the effect of a PEC visit on deaths as a result of failure to rescue (FTR) was also performed. RESULTS: A visit to PEC was associated with a reduction in mortality (odds ratio, 0.48; 95% CI, 0.22 to 0.96, P = 0.04) by comparison of the matched cohorts. The FTR subanalysis suggested that the proportion of deaths attributable to an unanticipated surgical complication was not significantly different between the two groups (P = 0.141). CONCLUSIONS: An in-person assessment at the PEC was associated with a reduction in in-hospital mortality. It was difficult to draw conclusions about whether a difference exists in the proportion of FTR deaths between the two cohorts due to small sample size.

Importance: The value of routine preoperative testing before most surgical procedures is widely considered to be low. To improve the quality of preoperative care and reduce waste, 2 professional societies released guidance on use of routine preoperative testing in 2002, but researchers and policymakers remain concerned about the health and cost burden of low-value care in the preoperative setting. Objective: To examine the long-term national effect of the 2002 professional guidance from the American College of Cardiology/American Heart Association and the American Society of Anesthesiologists on physicians' use of routine preoperative testing. Design, Setting, and Participants: Retrospective analysis of nationally representative data from the National Ambulatory Medical Care Survey and National Hospital Ambulatory Medical Care Survey to examine adults in the United States who were evaluated during preoperative visits from January 1, 1997, through December 31, 2010. A quasiexperimental, difference-in-difference (DID) approach evaluated whether the publication of professional guidance in 2002 was associated with changes in preoperative testing patterns, adjusting for temporal trends in routine testing, as captured by testing patterns in general medical examinations. Main Outcomes and Measures: Physician orders for outpatient plain radiography, hematocrit, urinalysis, electrocardiogram, and cardiac stress testing. Results: During the 14-year period, the average annual number of preoperative visits in the United States increased from 6.8 million in 1997-1999 to 9.8 million in 2002-2004 and 14.3 million in 2008-2010. After accounting for temporal trends in routine testing, we found no statistically significant overall changes in the use of plain radiography (11.3% in 1997-2002 to 9.9% in 2003-2010; DID, -1.0 per 100 visits; 95% CI, -4.1 to 2.2), hematocrit (9.4% in 1997-2002 to 4.1% in 2003-2010; DID, 1.2 per 100 visits; 95% CI, -2.2 to 4.7), urinalysis (12.2% in 1997-2002 to 8.9% in 2003-2010; DID, 2.7 per 100 visits; 95% CI, -1.7 to 7.1), or cardiac stress testing (1.0% in 1997-2002 to 2.0% in 2003-2010; DID, 0.7 per 100 visits; 95% CI, -0.1 to 1.5) after the publication of professional guidance. However, the rate of electrocardiogram testing fell (19.4% in 1997-2002 to 14.3% in 2003-2010; DID, -6.7 per 100 visits; 95% CI, -10.6 to -2.7) in the period after the publication of guidance. Conclusions and Relevance: The release of the 2002 guidance on routine preoperative testing was associated with a reduced the incidence of routine electrocardiogram testing but not of plain radiography, hematocrit, urinalysis, or cardiac stress testing. Because routine preoperative testing is generally considered to provide low incremental value, more concerted efforts to understand physician behavior and remove barriers to guideline adherence may improve health care quality and reduce costs.

INTRODUCTION: Chronic Kidney Disease (CKD) has long been recognized as an independent predictor of major adverse cardiac events1,2, and recent studies have demonstrated that the impact of CKD extends to other significant postoperative events including cerebrovascular accidents, all-cause mortality, and increased hospital length of stay3,4. However, whether CKD predisposes patients to other postoperative complications has not been elucidated. We examined the incidence of CKD in our surgical population and compared the rates of significant postoperative complications including: acute kidney injury (AKI), venous thromoboembolism (VTE), myocardial infarction (MI), infection, and 30-day readmission to our hospital across declining preoperative glomerular filtration rate (eGFR) values. We hypothesized that there is a direct association between rates of major surgical complications and stage of CKD. Methods: With IRB approval, a retrospective analysis of a database of adult patients who underwent elective surgery between June 2011 and July 2013 at a single large academic institution was performed. Patients with reduced GFR (<60 ml/min/1.73m2) were identified and categorized by stage of CKD. Odds of readmission to hospital within 30 days, as well as new diagnosis of AKI, VTE, MI, and infection in these patients were determined using logistic regression. RESULTS: Of the 48714 patients in the database with an available GFR on record, 43072(88%) met inclusion criteria. Of the 4097 patients with eGFR <60 ml/min/1.73m2, 3448 (84%) did not have a preoperative ICD-9 diagnosis of CKD on record. When categorized by increasing stage of CKD and compared to GFR >60 ml/ min/1.73m2, increasing numbers of these patients were readmitted to the hospital within 30 days of their procedure (OR 1.5, 95% CI 1.3-1.7, p<0.001 to OR 3.5, 95% CI 2.6-4.5, p<0.001 for Stage 3A to Stage 5 CKD respectively) [Figures 1,2]. Patients with higher stage CKD also tended to demonstrate increasing odds of acute kidney injury (OR 21.5, 95% CI 15.3-29.6, p<0.001 for stage 4 CKD), myocardial infarction (OR 8.2, 95% CI 4.7-13.3, p<0.001 for stage 5 CKD), infection (OR 4.4, 95% CI 2.7-6.8, p<0.001 for stage 4 CKD) and venous thromboembolism (OR 3.3, 95% CI 1.4- 6.6, p<0.001 for stage 5 CKD). DISCUSSION: This study highlights that CKD is a common, underreported comorbidity in the surgical population with significant impact on major postoperative complications. Interestingly, the rates of postoperative VTE, AKI, MI, infection and hospital readmission increased with increased stage of CKD. Furthermore, our study extends the association between preoperative CKD and postoperative adverse events to a broader range of surgical populations than previously described. Recognizing the association between preoperative low eGFR and increased rates of postoperative complications and hospital readmissions will facilitate the development of perioperative protocols to enhance patient safety and reduce hospital costs. (Figure Presented)

INTRODUCTION: The mechanisms by which reduced preoperative glomerular filtration rate (eGFR) predispose patients to adverse postoperative outcomes are not well defined1. Furthermore, the effects of medications commonly prescribed to slow the progression of chronic kidney disease (CKD) are unclear in the perioperative period2,3,4. The goal of this study was to evaluate these medications on the following postoperative outcomes: acute kidney injury (AKI), myocardial infarction (MI), infection, venous thromboembolism (VTE), and readmission within 30 days. We hypothesized that patients with CKD who were on an angiotensin converting enzyme inhibitor (ACE-I), angiotensin receptor blocker (ARB), diuretic, statin, beta blocker, insulin or calcium channel blocker (CCB) preoperatively would have lower rates of surgical complications than CKD patients who were not on these medications. METHODS: With institutional review board approval, patients with reduced eGFR (<60 ml/min/1.73m2) and a list of their prescribed medications at the time of surgery were isolated from a database of adult patients who underwent elective surgery at a single large academic institution between June 2011 and July 2013. Patients were identified as either taking or not taking ACE-Is, ARBs, diuretics, statins, beta blockers, insulin, or CCBs. Propensity score matching was done by first performing logistic regression with each medication individually as the dependent treatment variable. Preoperative medical comorbidities, age, and gender were used as covariates that may influence preoperative medication use. One-to-one matching without replacement was performed based on the derived propensity scores. The outcomes of interest were AKI, MI, infection, VTE, and readmission within 30 days, and were analyzed by logistic regression. RESULTS: After applying exclusion criteria, 2865 patients remained. Matching resulted in between approximately 250 and 1100 pairs depending on the medication. After matching, there was no apparent association between the preoperative medications explored and the outcomes of interest, except for a statistically significant association between beta blocker use and readmission within 30 days (Table 1). CONCLUSIONS: This study suggests that common medications taken by patients with CKD preoperatively do not have a significant effect on the development of postoperative complications. Furthermore, our results do not support discontinuation of preexisting medications or the addition of any of these agents prior to surgery. Identifying factors modifiable by medication management or lifestyle interventions is a critical step toward developing protocols to enhance patient safety and postoperative recovery in the CKD population. Further investigation is needed to determine the effect of other factors such as surgical severity, smoking status and volume status on postoperative outcomes to define optimal protocols for CKD patients. (Table Presented)