Preoperative Anemia versus Blood Transfusion: Which is the Culprit for Worse Outcomes in Cardiac Surgery?

Transcription

1 Preoperative Anemia versus Blood Transfusion: Which is the Culprit for Worse Outcomes in Cardiac Surgery? Damien J. LaPar MD, MSc, James M. Isbell MD, MSCI, Jeffrey B. Rich MD, Alan M. Speir MD, Mohammed Quader, MD, Irving L. Kron MD, John A. Kern MD, Gorav Ailawadi MD Investigators for the Virginia Cardiac Surgery Quality Initiative 95 th Meeting of the American Association for Thoracic Surgery, Seattle, WA April 27, 2015

2 Disclosures None

3 Virginia Cardiac Surgery Quality Initiative (VCSQI) Voluntary consortium of 17 collaborating cardiac surgical centers with Virginia. Capture approximately 99% of Virginia s cardiac operations Each center contributes data to STS Adult Cardiac Surgery Database

4 Blood Transfusion and CABG Cardiac surgical procedures responsible for ~20% of the annual blood transfusions in the United States. Blood transfusion following CABG occurs in up to 60% of cases. Allogenic blood product transfusion associated with significant adverse patient effects Several series have investigated the independent effects of either perioperative anemia or packed red blood cell (PRBC) transfusion. Question of which factor (anemia vs. transfusion) contributes more to adverse cardiac surgical morbidity and mortality remains unanswered.

5 Purpose To investigate the relative association between preoperative hematocrit (Hct) versus PRBC transfusion on postoperative outcomes after CABG.

6 Hypotheses 1. A significant non-linear relationship exists between preoperative Hct level and patient outcomes as well as the need for postoperative PRBC transfusion. 2. That PRBC transfusion would have a stronger relative strength of association with postoperative mortality and morbidity compared to preoperative Hct alone.

7 Methods VCSQI Data Registry Study Period: 1/2007-6/2014 Patients: Primary, Isolated CABG No Prior Sternotomy No Concomitant Operations (CABG Only)

8 Methods Primary Outcomes: Risk adjusted associations: Preoperative Hct ~ Mortality and Morbidity PRBC Transfusion ~ Mortality and Morbidity Outcome Measures: Operative Mortality Postop Renal Failure Postop Stroke Postop PRBC Transfusion Preop Hct model only

9 Statistical Analyses Descriptive Statistics: Modeled factor frequency and distribution. Multivariable logistic regression: Response variable: Mortality or Morbidity Covariates of interest: Preoperative Hct (restricted cubic spline) PRBC Transfusion Adjustment: STS Risk Indices (restricted cubic spline) Operative Year Hospital Surgeon Comparison of Likelihood Ratios and Model Performance

10 Results

11 Preoperative Characteristics Factor Frequency Mean or Median Patient age (yr) 64 +/- 10 Cerebrovascular Disease 14.3% Stroke 5.2% Hypertension 85.7% Diabetes 42.8% Dyslipidemia 99.3% Peripheral Arterial Disease 13.4% Renal Failure (Hemodialysis) 2.8% Ejection Fraction (%) 55 [45,60] Preoperative Hematocrit (%) 39 [35,42] STS PROM (%) 0.9 [0.5,1.9]

12 Distribution of Preoperative Hct

13 Operative Features Factor Cardiopulmonary Bypass Support Frequency Mean or Median None 8.3% Full 91.2% Combination 0.6% Operative Status Elective 35.4% Urgent 60.8% Emergent 3.7% Emergent Salvage 0.1% Aortic Cross Clamp Time (min) 66 [51,84] Lowest Intraoperative Hematocrit (%) 24 [20,27]

14 Unadjusted Outcomes Factor Frequency Mean or Median Postoperative Blood Product Transfusion 31.4% Median Transfused PRBC (units) 2 [1,3] Atrial Fibrillation 19.6% Stroke 1.4% Myocardial Infarction 0.1% Pneumonia 2.5% Prolonged Mechanical Ventilation 9.9% Renal Failure 3.1% Hemodialysis 1.3% Operative Mortality 2.2%

15 Risk Adjusted Association Between Mortality/Morbidity and Preoperative Hct vs. PRBC Transfusion

16 MODEL 1: Risk-Adjusted Impact of Preoperative Hct on Mortality and Morbidity Factor Likelihood Ratio (Wald statistic) AOR [95% C.I.] P Mortality [0.70,0.95] <0.001 Renal Failure [0.58,0.76] <0.001 PRBC Transfusion 1, [0.43, 0.47] <0.001

17 MODEL 1: Preoperative Hct Highly Associated with Mortality and Renal Failure Factor Likelihood Ratio (Wald statistic) AOR [95% C.I.] P Mortality [0.70,0.95] <0.001 Renal Failure [0.58,0.76] <0.001 PRBC Transfusion 1, [0.43, 0.47] <0.001

18 MODEL 1: Preoperative Hct Most Strongly Associated with PRBC Transfusion Factor Likelihood Ratio (Wald statistic) AOR [95% C.I.] P Mortality [0.70,0.95] <0.001 Renal Failure [0.58,0.76] <0.001 PRBC Transfusion 1, [0.43, 0.47] <0.001

19 Preoperative Hct vs. Risk-Adjusted Probability of PRBC Transfusion

20 Preoperative Hct vs. Risk-Adjusted Probability of Mortality

21 Preoperative Hct vs. Risk-Adjusted Probability of Renal Failure

22 MODEL 2: Risk-Adjusted Impact of PRBC Transfusion on Mortality and Morbidity Factor Likelihood Ratio (Wald statistic) AOR [95% C.I.] P Mortality [3.10,5.20] <0.001 Renal Failure [4.50,6.97] <0.001 Stroke [2.30,3.90] <0.001

23 MODEL 2: PRBC Transfusion Associated with Mortality, Renal Failure, Stroke Factor Likelihood Ratio (Wald statistic) AOR [95% C.I.] P Mortality [3.10,5.20] <0.001 Renal Failure [4.50,6.97] <0.001 Stroke [2.30,3.90] <0.001

24 MODEL 2: Higher Relative Strength of Association with Mortality and Morbidity Factor Likelihood Ratio (Wald statistic) AOR [95% C.I.] P Mortality [3.10,5.20] <0.001 Renal Failure [4.50,6.97] <0.001 Stroke [2.30,3.90] <0.001

25 Limitations Retrospective design De-identified data points Preoperative Hct Level (single measurement) Inability asses impact of preoperative transfusion Limited to 30 day data

26 Conclusions PRBC transfusion appears more strongly associated with risk-adjusted morbidity and mortality compared to Hct alone. Preoperative Hct independently increases the risk of morbidity and mortality, but more strongly increases the likelihood of postoperative PRBC transfusion. Data support efforts to reduce unnecessary PRBC transfusions.

27 Conclusions Results suggest that preoperative Hct levels should be considered for inclusion in the STS risk calculators. Efforts to optimize preoperative hematocrit to avoid anemia should be investigated as a potentially modifiable risk factor for mortality and morbidity.

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