Improvement of the Surgical Apgar Score by Addition of Intraoperative Blood Transfusion Among Patients Undergoing Major Gastrointestinal Surgery

Abstract

BackgroundThe surgical Apgar score (SAS) has been shown to correlate with postoperative outcomes. A key component of the SAS is estimated blood loss (EBL), which has been shown to be inaccurate and discordant with intraoperative blood transfusion. Given this, the objective of the current study was to assess the added predictive value of the including receipt of intraoperative transfusion to the SAS. MethodsWe identified 1833 patients undergoing major gastrointestinal surgery (pancreatic, hepato-biliary, and colorectal) between January 1, 2010 and August 31, 2013 at Johns Hopkins Hospital. The primary outcome was postoperative complications or death. A modified SAS was created by assigning a “0” EBL score for every patient who received an intraoperative blood transfusion, regardless of the actual EBL. Model performance was tested using logistic regression and c-statistic. ResultsMean EBL of the entire cohort was 250 mL. Two hundred ninety-two patients (15.9 %) received at least 1 unit of blood intraoperatively. Approximately, one half of patients (55.1 %) who had an EBL <1000 mL received an intraoperative transfusion. Patients who received an intraoperative transfusion (transfusion n = 94, 32.2 % vs. no transfusion n = 221, 14.3 %; P < 0.001) and those with increasing EBL had a higher incidence of postoperative morbidity and/or death (≤100 mL: 11.6 %, 101–600 mL: 16.9 %, 601–1000 mL: 24.5 %, >1000 mL: 29.2 %; P < 0.001). The variance inflation factor between EBL and intraoperative transfusion was 1.23 for postoperative morbidity/mortality, suggesting that the multicollinearity between the two variables was low. With the inclusion of intraoperative transfusion in the modified SAS, the modified model (c-statistic 0.6552) had an improved discrimination of predicting postoperative morbidity and mortality as compared to the original SAS (c-statistic 0.6391) (P = 0.01). The modified SAS demonstrated improvement in predicting raw differences in the incidence of postoperative morbidity/mortality based on the overall score (P < 0.05). ConclusionsThe inclusion of intraoperative transfusion in a modified SAS significantly improves the risk-stratifying ability of the score with regard to postoperative morbidity and mortality. Given the variability of intraoperative transfusion, its discordance with EBL, and its strong negative impact on postoperative outcomes, we strongly support the inclusion of this factor in a modified SAS.