1. A Novel Score to Estimate the Risk of Pneumonia After Cardiac Surgery
Arman Kilic, MD1, Rika Ohkuma, MD 1, J. Trent Magruder, MD1, Joshua C. Grimm, MD1, Marc Sussman, MD1,
Eric B. Schneider, PhD1, Glenn J.R. Whitman, MD1
1Division of Cardiac Surgery, Johns Hopkins Hospital, Baltimore, MD
None of the authors have any relevant financial relationships to disclose.

2. Background
Pneumonia is the most common nosocomial infection after cardiac surgery
Postoperative pneumonia is associated with increased risk of mortality and readmission, as well as prolonged ICU and hospital stay and increased costs of care
A composite risk index for estimating pneumonia risk after cardiac surgery would have clinical utility

3. Study Aim
To derive and validate a risk score for postoperative pneumonia after cardiac surgery

4. Study Design Data Source Single institution series Study Population
Adult patients (18 or older)
Study period: January 1, 2005 to December 31, 2012
Excluded: ECMO or heart transplant patients

5. Data Analysis Primary Outcome
Postoperative pneumonia – STS definition – “positive sputum cultures, transtracheal fluid, bronchial washings, and/or clinical findings consistent with pneumonia”
Study Population
Randomly divided 3:1 into training and validation sets

6. Data Analysis Generation of Risk Score in the Training Set
Univariable logistic regression analysis to evaluate association between multiple preoperative and intraoperative variables and postoperative pneumonia
Variables associated with pneumonia in univariable analysis (p<0.20) and <10% missing data entered into a multivariable model
Points were assigned to significant risk factors based on the relative magnitudes of the odds ratios .

7. Data Analysis Validation of Risk Score in the Validation Set
Predictive accuracy of the risk score evaluated using logistic regression, area under receiver operating characteristic curve (c-index)
C-indices also compared between risk score and STS prolonged ventilation model in predicting pneumonia .

8. Baseline Patient Characteristics
Variable
Training Set
(n=4,666)
Validation Set
(n=1,556)
p-value
Age (years)
61.2 ± 14.9
61.4 ± 14.7
0.69
Male
3,067 (66%)
1,020 (66%)
0.90
Body Mass Index (kg/m2)
28.8 ± 7.6
29.0 ± 9.4
0.38
Chronic Lung Disease
None
Mild
Moderate
Severe
4,053 (87%)
338 (7%)
184 (4%)
90 (2%)
1,346 (87%)
131 (8%)
54 (3%)
25 (2%)
0.32
Diabetes Mellitus
1,257 (27%)
404 (26%)
0.45
Hypertension
3,411 (73%)
1,112 (71%)
0.21
Dialysis Dependence
135 (4%)
38 (4%)
0.34
Serum Creatinine (mg/dL)
1.20 ± 1.10
1.18 ± 1.12
0.56
Cerebrovascular Disease
467 (10%)
177 (11%)
0.13
Peripheral Vascular Disease
473 (10%)
160 (10%)
0.87
Prior Cardiac Intervention
1,437 (31%)
486 (31%)
0.75
Cardiogenic Shock
124 (3%)
37 (2%)
0.55
Myocardial Infarction
1,294 (28%)
413 (27%)
0.36

9. Baseline Operative Characteristics
Variable
Training Set
(n=4,666)
Validation Set
(n=1,556)
p-value
Elective Case
2,886 (62%)
976 (63%)
0.54
Type of Operation
Valve
CABG
Combined Valve and CABG
Other
1,613 (35%)
1,776 (38%)
487 (10%)
790 (17%)
534 (34%)
595 (38%)
172 (11%)
255 (16%)
0.88
Cardiopulmonary Bypass Time (minutes)
122.1 ± 53.3
122.1 ± 55.7
0.98
Aortic Cross Clamp Time (minutes)
78.6 ± 34.5
77.9 ± 34.6
0.52
Intra-Aortic Balloon Pump
427 (9%)
127 (8%)
0.24
Timing of Intra-Aortic Balloon Pump
Preoperative
Intraoperative
Postoperative
262 (61%)
140 (33%)
25 (6%)
79 (62%)
39 (31%)
9 (7%)
0.83

10. Results Postoperative pneumonia rate of 4.5% (n=282)
In-hospital mortality rate
15.3% (pneumonia) versus 4.8% (no pneumonia)
p<0.001
30-day mortality rate
8.0% (pneumonia) versus 4.6% (no pneumonia)
p=0.01 .

11. Multivariable Model for Pneumonia
Covariate
Odds Ratio (95% Confidence Interval)
P-value
Points Assigned
Age ≥ 65 Years
1.40 ( )
0.04 3
Chronic Lung Disease
None
Mild
Moderate
Severe
Reference
1.97 ( )
3.07 ( )
3.31 ( )
0.005
<0.001
0.002 4 6 7
Peripheral Vascular Disease
1.69 ( )
0.01
Cardiopulmonary Bypass Time >100 Minutes
1.71 ( )
Intraoperative Red Blood Cell Transfusion
1.08 ( ) 2
Pre- or Intraoperative Intra-Aortic Balloon Pump
2.01 ( )
TOTAL POINTS POSSIBLE - 22
*other variables included in the multivariable model but not significant predictors:
hypertension, prior cardiac intervention, myocardial infarction in last 24 hours, cardiogenic shock, increasing serum creatinine, emergent operation, type of operation, increasing aortic cross clamp time, and tricuspid valve procedure

12. Probability of Pneumonia Based on the Training Set

13. Probability of Pneumonia Based on the Training Set
Predicted Rate
95% CI for Predicted Rate

14. Probability of Pneumonia Based on the Training Set
Predicted Rate
95% CI for Predicted Rate
Score=0
Rate=1.2%

15. Probability of Pneumonia Based on the Training Set
Score=22
Rate=55%
Predicted Rate
95% CI for Predicted Rate
Score=0
Rate=1.2%

16. Predicted Rates of Pneumonia in the Training Set by Score Categories

17. Actual Rates of Pneumonia in the Validation Set by Score Categories

18. Correlation Between Predicted and Actual Rates of Pneumonia
Correlation between predicted rates in training set and actual rates in validation set
r= p<0.001

19. Predictive Accuracy of the Risk Score in the Validation Set
Logistic regression
Odds ratio 1.32, 95% CI
p<0.001
C-index
0.74 (risk score) versus 0.71 (STS prolonged ventilation model) in predicting postoperative pneumonia .

20. Summary Component Points Age ≥ 65 years 3 Chronic Lung Disease None
Mild
Moderate
Severe 4 6 7
Peripheral Vascular Disease
Cardiopulmonary Bypass Time >100 Minutes
Intraoperative Red Blood Cell Transfusion 2
Pre- or Intraoperative Intra-Aortic Balloon Pump
TOTAL POINTS POSSIBLE 22

21. Limitations Clinical diagnosis of pneumonia can be subjective
In-hospital pneumonia diagnoses only
Potential for other risk factors not captured in our analysis
Did not account for interrelationship between pneumonia and other postoperative complications

22. Conclusions
We derived and validated a risk score for postoperative pneumonia in adult patients undergoing cardiac surgery
Immediately applicable on ICU arrival
Risk score may aid in identifying high risk patients, and therefore have applications in:
clinical research stratification
targeting patients who will benefit from tailored preoperative management

23. A Novel Score to Estimate the Risk of Pneumonia After Cardiac Surgery
Arman Kilic, MD1, Rika Ohkuma, MD 1, Joshua C. Grimm, MD1,
J. Trent Magruder, MD1, Marc Sussman, MD1,
Eric B. Schneider, PhD1, Glenn J.R. Whitman, MD1
1Division of Cardiac Surgery, Johns Hopkins Hospital, Baltimore, MD