Page 22 - ANZCP Gazette May 2023

Table 4. Frequency of candidate variables included in model building and model validation.
At least 90%
At least 60% 2858 0.0203
At least 50% 2892 0.0203
All variables 3004 0.0207
Model building
0.0207
BIC: Bayesian information criteria, MSE; mean square error, H-L; Hosmer—Lemeshow. ROC: receiver
Model validation (100-fold)
% of time candidate variables* in the bootstrap models
BIC MSE
Average ROC
H-L p-value MSE
100% 2931 0.0212
2849
0.7654 <0.001 0.0234
0.8061
0.8258
0.0002
0.5111
0.8311 0.5439 0.023
0.0231
At least 80%
At least 70% 2851 0.0205
2842
0.0206
0.8112
0.2736
0.8189 0.2113 0.0229
0.023
0.8214 0.2882 0.0229
0.023
operator curve, H-L: Hosmer-Lemeshow. *Candidate variables shown in Table 3
The beta coefficients and odds ratio for the variables included in the final model are reported in Table 5. Increasing age, respiratory disease, preoperative dialysis, ejection fraction estimate, urgency of procedure, were
Age (<60, reference group)
identified as independent patient risk factors. Modifiable CPB parameters included red blood cell transfusion, minimum oxygen delivery, duration of arterial pressure <50 mmHg, cardiac index <1.6 l/min/m2, and CPB time.
Table 5. Preoperative risk and intraoperative management factors for predictive model for 30-day mortality for patients undergoing cardiac surgery.
Risk Factors Coefficient OR (95% CI) p
60-69 0.4 1.5 (1.09 - 2.05) 0.012
70-79
80+ 1.07 2.91 (2.05 - 4.12) <0.001
0.56
1.75 (1.29 - 2.37)
<0.001
Respiratory disease 0.16 1.18 (0.88 - 1.57) 0.272
Preoperative dialysis 0.72 2.06 1.32 - 3.21) 0.001
Ejection fraction estimate (>60, reference group)
46-60 0.78 2.18 (0.65 - 7.32) 0.209
30-45 0.21 1.23 (0.91 - 1.65) 0.176
<30
Urgency of procedure (elective, reference group)
Emergency 1.01 2.74 (1.89 - 3.97) <0.001
1.06
2.9 (2.08 - 4.03)
<0.001
Urgent 0.29 1.34 (1.05 - 1.7) 0.019
Salvage 3.06 21.4 (3.72 - 123.17) 0.001
CPB time (<65 , reference group) (minutes)
66-83 -0.04 0.96 (0.61 - 1.52) 0.873
84-101 0.05 1.05 (0.67 - 1.65) 0.821
102-128
>128 1.11 3.03 (2.08 - 4.42) <0.001
0.51
1.67 (1.11 - 2.51)
0.014
Red blood cell transfusions (0, reference category)
1
2 0.9 2.47 (1.73 - 3.52) <0.001
0.6
1.82 (1.2 - 2.77)
0.005
3+ 1.66 5.26 (3.83 - 7.23) <0.001
CPB mean arterial pressure <50 mmHg (min) 0.01 1.01 (1 - 1.01) 0.001
CPB minimum oxygen delivery (<235, reference group) (ml/min/m2)
236-267 -0.11 0.89 (0.67 - 1.19)
268-296
-0.14
0.87 (0.62 - 1.21)
0.444 0.411 0.012
297-331 -0.52 0.59 (0.4 - 0.89)
>331
CPB cardiac index <1.6 l/min/m2 (minutes) 0.01 1.01 (1 - 1.02) 0.006
-0.89
0.41 (0.26 - 0.67)
<0.001
Constant -5.15 0.01 (0 - 0.01) <0.001
19 MAY 2023 | www.anzcp.org