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.

A common approach to blood pressure management in the operating room is to keep the intraoperative, pressures within 20% of baseline blood pressure. One question that arises from this recommendation is; what is a patient's true baseline blood pressure? In order to get a more precise definition of baseline blood pressure, a comparison of the first operating room blood pressure was made with the blood pressure taken in a preoperative holding area before surgery, and the blood pressure taken in pre-surgical testing. (before day of surgery). A database of 2087 adult general anesthesia cases was generated, which contained the blood pressure (BP) in the pre-surgical testing clinic, the first BP in preoperative holding on the day of surgery, and the first BP in the operating room. Comparisons were made between the blood pressures taken at each phase of care. All components of BP taken in the OR were statistically significantly higher (p<0.001 for all comparisons) than in either PST or the holding area, while the BP in the latter locations were not significantly different. This blood pressure difference persists whether or not the patient is taking antihypertensive medications. The higher blood pressure measured in the operating rooms precludes using this measurement to determine baseline blood pressure. Blood pressures taken prior to arrival in the operating room are similar to blood pressures taken before the day of surgery. Blood pressure measurements taken prior to entrance in the operating room can be used to determine baseline blood pressure.

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.