Daily Anesthesiology Research Analysis

IMPORTANCE: Crossmatched packed red blood cells (pRBC) that are not transfused result in significant waste of this scarce resource. Efficient utilization should be part of a patient blood management strategy. OBJECTIVE: To develop and validate a prediction model to identify surgical patients at high risk of intraoperative pRBC transfusion. DESIGN, SETTING, AND PARTICIPANTS: This prognostic study used hospital registry data from 2 quaternary hospital networks from January 2016 to June 2021 (development: Montefiore Medical Center [MMC], Bronx, New York), June 2021 to February 2023 (internal validation: MMC), and January 2008 to June 2022 (external validation: Beth Israel Deaconess Medical Center [BIDMC], Boston, Massachusetts). Participants were patients aged 18 years or older undergoing surgery. MAIN OUTCOME AND MEASURES: The outcome was intraoperative transfusion of 1 or more pRBC units. Based on a priori-defined candidate predictors, stepwise backward regression was applied to develop a computational model of independent predictors for intraoperative pRBC transfusion. RESULTS: The development and validation cohorts consisted of 816 618 patients (273 654 at MMC: mean [SD], age 57.5 [17.2] years; 161 481 [59.0%] female; 542 964 at BIDMC: mean [SD] age, 56.0 [17.1] years; 310 272 [57.1%] female). Overall, 18 662 patients (2.3%) received at least 1 unit of pRBC. The final model contained 24 preoperative predictors: nonambulatory surgery; American Society of Anesthesiologists physical status; international normalized ratio; redo surgery; emergency surgery or surgery outside of regular working hours; estimated surgical duration of at least 120 minutes; surgical complexity; liver disease; hypoalbuminemia; thrombocytopenia; mild, moderate, or severe anemia; and surgery type. The area under the receiver operating characteristic curve (AUC) was 0.93 (95% CI, 0.92-0.93), suggesting high predictive accuracy and generalizability. Positive predictive value (PPV) and negative predictive value (NPV) were 8.9% (95% CI, 8.7%-9.2%) and 99.7% (95% CI, 99.7%-99.7%), respectively, with increased predictive values for operations with a higher a priori risk of pRBC transfusion. The model's performance was confirmed in internal and external validation. The prediction tool outperformed the established Transfusion Risk Understanding Scoring Tool (AUC, 0.64 [0.63-0.64]; PPV, 2.6% [95% CI, 2.5%-2.6%]; NPV, 99.2% [95% CI, 99.1%-99.3%]) (P < .001) and was noninferior to 3 machine learning-derived scores. CONCLUSIONS AND RELEVANCE: In this prognostic study of surgical patients, the Transfusion Forecast Utility for Surgical Events (TRANSFUSE) model for predicting intraoperative pRBC transfusion was developed and validated. The instrument can be used independently of machine learning infrastructure availability to inform preoperative pRBC orders and to minimize waste of nontransfused red blood cell units.

BACKGROUND: Prior studies identified thresholds for mean arterial pressure (MAP <65 mm Hg) and central venous pressure (CVP >12 mm Hg) beyond which risk for cardiac surgery-associated acute kidney injury (AKI) increases. Optimal hemodynamic targets-that is, where active protection from AKI is observed-are unclear; however, current guidelines suggest maintaining MAP >65 and CVP 8 to 12. The aim of this study was to identify hemodynamic ranges associated with both increased and decreased risk of AKI by evaluating narrow ranges of MAP, CVP, and joint exposure to MAP and CVP concurrently. METHODS: In a retrospective cohort study of adults undergoing coronary artery bypass surgery, we fine-mapped the association between AKI and the total number of minutes spent in each of the following narrow hemodynamic ranges: 14 MAP ranges in increments of 5 mm Hg (45-115), 10 CVP ranges in increments of 2 mm Hg (0-20), and 70 joint MAP/CVP ranges. Separate multivariable regression models estimated adjusted odds ratios (aOR) for each range including adjustments for correlations and multiple comparisons across ranges. Joint MAP/CVP ranges were grouped into 5 hemodynamic zones based on contiguity of the ranges and similarity of ORs observed across ranges in a color-coded heatmap. The 5 MAP/CVP zones were included in a single regression model to assess risk for AKI associated with time spent in each hemodynamic zone, independent of time spent in other zones. RESULTS: In 1199 participants, incidence of AKI was 28%. For every 5-minute spent in each hemodynamic range, risk of AKI was significantly increased in MAP range 45 to 50 (aOR 1.18; P = .002), 50 to 55 (aOR 1.13; P = .001), and 55 to 60 mm Hg (aOR 1.06; P = .001); and significantly decreased in MAP range 90 to 95 mm Hg (aOR 0.85; P <.001). Risk of AKI was significantly increased in CVP range 16 to 18 mm Hg (aOR 1.07 ; P = . 002) and significantly decreased in CVP range 4 to 6 mm Hg (aOR 0.97; P = . 025). In joint analyses, both MAP and CVP contributed to AKI risk estimates; risk decreased as CVP decreased within every MAP range and was significantly lower for joint ranges of CVP <8 and MAP >75. In analyses containing all 5 MAP/CVP hemodynamic zones, risk estimates suggested protection from AKI in zone 1 (high MAP/low CVP) and increased risk of AKI in zones 3 to 5 (low MAP/high CVP). CONCLUSIONS: Fine-mapping identified narrow ranges of MAP, CVP, and joint MAP/CVP associated with both AKI risk and protection. This report is among the first to characterize the association between joint MAP/CVP and AKI. Contrary to current guidelines, there was no evidence for protection associated with MAP 65 to 75 or CVP 8 to 12 mm Hg.

BACKGROUND: Minimum alveolar concentration (MAC) is used as the standard measure of potency for volatile anesthetic agents. However, there is a lack of effective and quantitative indicator of the combined potency of multiple coadministered inhalation and intravenous anesthetics. We hypothesized that an indicator of equivalent potency of multiple anesthetics, normalized by MAC and derived from response surface models as a fraction (abbreviated as eMAC fraction), can reflect the total potency of multiple anesthetics. METHOD: Fifty-three patients receiving general anesthesia were enrolled. A random dose combination of propofol and remifentanil was administrated before a tetanic electric stimulus which was used to simulate incision. The vital signals and responses of patients were recorded to tetanic stimulus and in turn used to calculate the prediction probability (Pk) of the response, using the eMAC fraction and the bispectral index (BIS). After induction, the doses administered during anesthesia maintenance were entirely determined by anesthesiologists. During emergence, the anesthesiologists facilitated the awakening of patients through a combination of auditory and tactile stimuli at eMAC fraction levels of 0.8, 0.6, 0.4, and 0.2, or every 2 minutes after the certain level was reached, whichever arrived first. RESULTS: The eMAC fraction for predicting the loss of movement response to tetanic electric stimulus yielded a mean ± standard deviation (SD) Pk of 0. 80 ± 0.06, which was higher than the Pk of the BIS value for predicting the loss of movement response to tetanic electric stimulus (0.71 ± 0.07, P < .001). During maintenance of anesthesia, the eMAC fraction showed changes related to anesthetic dose and surgical phase. In all patients, approximately 71.9% of eMAC fraction values were within the range of 1.3 to 2.6. During emergence, the mean eMAC fraction values at awakening were 0. 30 ± 0.15. CONCLUSIONS: The eMAC fraction showed a superior performance in indicating the loss of response to electric stimulus compared to BIS. Anesthesiologists are familiar with the clinical use range of MAC fraction, and the distribution of eMAC fraction values during maintenance is similar to this range. This similarity allows anesthesiologists to easily use eMAC fraction in practice. These results indicate that the eMAC fraction has the potential to assist anesthesiologists in titrating multiple anesthetics to estimate the depth of anesthesia during general anesthesia, and should further be evaluated in clinical studies.