Validation of Open-Heart Intraoperative Risk score to predict a prolonged intensive care unit stay for adult patients undergoing cardiac surgery with cardiopulmonary bypass

Figures & data

Table 1 OHIR score model for predicting prolonged ICU stay

Risk factors	Score
	Present	Absent
Age (≥60 years)	1	0
P/F ratio (≤200 mmHg)	1	0
Platelet count (≤120,000/mm^3)	1	0
Inotrope/vasopressor requirement (≥2 drugs)	2	0
Serum potassium (≤3.2 mEq/L)	1	0
AFa (grading ≥2)	1	0

Notes: OHIR score, total score =7; score ≥3 suggests a prolonged stay in ICU.

a AF grade 0= no AF, AF grade 1= mild degree/need no therapy, AF grade 2= moderate degree/need drug therapy, and AF grade 3= severe degree/refractory to drug therapy.

Abbreviations: ICU, intensive care unit; OHIR, Open-Heart Intraoperative Risk; P/F, P_aO₂/F_iO₂; AF, atrial fibrillation.

Table 2 Demographic and clinical data

Characteristics	Total (n=123)	Prolonged ICU (n=58)	Nonprolonged ICU (n=65)	P-value
Age (years)	56.67±12.34	61.97±10.42	51.94±12.07	<0.001
BMI (kg/m^2)	22.94±4.80	22.68±4.46	23.16±5.09	0.584
Gender
Male	67 (54.47%)	35 (60.34%)	32 (49.23%)	0.217
Type of operation
CABG	43	24	19	0.158
Valve surgery	70	26	44	0.011
CABG + valve surgery	10	8	2	0.029
NYHA class
I–II	102	41	61	<0.001
III–IV	21	17	4
ASA classification
1–2	85	31	54	<0.001
3–5	38	27	11
Ejection fraction	55.36±14.69	52.61±15.77	57.70±13.39	0.062
Preoperative variables
Hypertension		35	17	<0.001
Diabetes mellitus		24	15	0.029
Myocardial infarction		10	7	0.299
Dyslipidemia		22	18	0.226
Atrial fibrillation		18	25	0.388
Congestive heart failure		13	4	0.009
Kidney impairment/failure		12	4	0.017
Creatinine value (mg/mL)	1.05±0.53	1.24±0.68	0.88±0.25	<0.001
CPB time (minutes)	145.29±74.43	159.90±92.73	132.26±50.35	0.039
Aortic cross-clamp time (minutes)	95.93±38.46	101.05±39.53	91.35±39.14	0.175
Mechanical ventilation (hours)	18.75±37.01	29.75±51.50	9.11±8.12	0.004
Endotracheal tube retaining (hours)	19.01±36.99	29.96±51.45	9.40±8.36	0.004
OHIR score	2 (2–3)	3 (3–4)	2 (1–2)	<0.001
	2.50±1.28	3.5±1.06	1.6±0.63
ICU stay (hours)	42 (40–62)	63 (45–88)	40 (31–41)	<0.001
	58.58±5.08	84.57±64.27	35.38±8.94
Hospital stay (days)	14 (11–20)	14 (10–23)	15 (11–20)	0.100
	17.18±9.62	18.82±12.71	15.77±5.50

Note: Values are presented as mean ± SD, number (%), or median (IQ range).

Abbreviations: ICU, intensive care unit; BMI, body surface area; CABG, coronary artery bypass graph; NYHA, New York Heart Association; ASA, American Society of Anesthesiologists; CPB, cardiopulmonary bypass; OHIR, Open-Heart Intraoperative Risk; SD, standard deviation.

Table 3 Number of patients and mean ICU stay for each OHIR score

OHIR score	Number of patients	ICU stay (hours)
0	6	44.3±15.90
1	19	35.2±9.02
2	43	38.5±19.18
3	27	62.7±19.91
4	21	95.4±73.06
5	5	119.2±116.22
6	2	161.5±167.58
7	0	0

Note: Values are presented as mean ± SD.

Abbreviations: ICU, intensive care unit; OHIR, Open-Heart Intraoperative Risk; SD, standard deviation.

Figure 1 AUC for ROC of the OHIR score to discriminate a prolonged ICU stay.

Abbreviations: OHIR, Open-Heart Intraoperative Risk; A, area; AUC for ROC, area under the receiver operating characteristic curve; ICU, intensive care unit.

Figure 2 Cutoff point for the OHIR score.

Abbreviation: OHIR, Open-Heart Intraoperative Risk.

Table 4 Sensitivity, specificity, positive predictive value, negative predictive value, and AUC for ROC of the OHIR score ≥3

Parameter	Value	95% CI
Sensitivity (%)	93.10	83.27–98.09
Specificity (%)	98.46	91.72–99.96
Positive predictive value (%)	98.18	88.52–99.74
Negative predictive value (%)	94.12	86.13–97.63
Accuracy (%)	95.9	–
Positive likelihood ratio	60.52	–
AUC for ROC	0.96	0.92–1.00

Abbreviations: AUC for ROC, area under the receiver operating characteristic curve; OHIR, Open-Heart Intraoperative Risk; CI, confidence interval.