Development of a random forest model for hypotension prediction after anesthesia induction for cardiac surgery

Table 1 Patient characteristics

Variable	Training set	Test set	P value
Patient population, n	2121	909
Age (yr)	63 (53-70)	62 (53-69)	0.323
Male, n (%)	1444 (68.1)	591 (65.0)	0.307
BMI (kg/m2)	24.8 (17.8-29.8)	24.8 (17.3-28.9)	0.956
Smoking, n (%)	775 (36.5)	328 (36.1)	0.937
Surgery type, n (%)
CABG only	750 (35.4)	378 (41.6)	0.128
Valve surgery only	1113 (52.5)	455 (50.0)	0.560
CABG + valve surgery	258 (12.2)	76 (8.4)	0.156
Previous cardiac surgery, n (%)	267 (12.6)	166 (18.3)	0.052
Preoperative ventilator support, n (%)	148 (7.0)	54 (5.9)	0.603
Preoperative IABP, n (%)	45 (2.1)	40 (4.5)	0.096
Diabetes mellitus, n (%)	687 (32.4)	284 (31.2)	0.756
Dyslipidemia, n (%)	800 (37.7)	365 (40.1)	0.564
Cerebrovascular accident, n (%)	123 (5.8)	54 (5.9)	0.926
Myocardial infarction within 90 d, n (%)	329 (15.5)	135 (14.9)	0.879
Serum creatinine (mg/dL)	0.91 (0.71-1.16)	0.90 (0.70-1.14)	0.128
Hemoglobin (g/dL)	13.2 (11.4-14.6)	13.1 (11.4-14.3)	0.403
Preoperative EF (%)	62.0 (35.0-70.0)	61.0 (30.0-71.3)	0.323
ASA score, n (%)
Class I	21 (1.5)	14 (1.5)	0.994
Class II	380 (17.9)	157 (17.3)	0.856
Class III	1525 (71.9)	666 (73.3)	0.708
Class IV	172 (8.1)	58 (6.4)	0.455
EuroSCORE I	3.2 (0.83-8.95)	2.96 (0.67-9.65)	0.355
Beta blocker use, n (%)	959 (45.2)	383 (42.1)	0.455
Aspirin use, n (%)	575 (27.1)	243 (26.7)	0.926
Dobutamin use, n (%)	19 (0.9)	14 (1.5)	0.460
Insulin use, n (%)	99 (4.7)	76 (8.4)	0.059
Systolic blood pressure	111 (88-154.8)	119 (95-165.5)	0.658
Diastolic blood pressure	73 (55-84)	75 (58-89)	0.537
Mean arterial pressure	93 (71-119)	108 (68-121)	0.437

ASA: American Society of Anesthesiologists; BMI: Body mass index; CABG: Coronary artery bypass graft; EF: Ejection fraction; IABP: Intra-aortic balloon pump.