Incidence and risk factors for delirium in cardiac surgery intensive care unit patients: A single-center study

Table 1 Demographics, comorbidities, type of surgery, and other parameters for all study participants are presented according to delirium occurrence

Parameters	All (n = 202)	No delirium (n = 143)	Delirium (n = 59)	P value
Males	143 (70.8)	103 (72.0)	40 (67.8)	0.481
Age (years)	66 ± 13	65 ± 13	71 ± 11	0.002
Body mass index (kg/m2)	28.5 ± 5	28.6 ± 5	28.2 ± 5	0.644
Comorbidities
Hypertension	158 (78.2)	111 (77.6)	47 (79.7)	0.811
Diabetes mellitus	65 (32.2)	45 (31.5)	22 (37.3)	0.656
Dyslipidemia	97 (48.0)	68 (47.6)	29 (49.2)	0.963
Smoking	47 (23.3)	33 (23.1)	14 (23.7)	0.39
Chronic obstructive pulmonary disease	17 (8.4)	10 (7.0)	7 (11.9)	0.235
Chronic kidney disease	13 (6.4)	6 (4.2)	7 (11.9)	0.04
Coronary arterial disease	67 (33.2)	49 (34.3)	18 (30.5)	0.683
Stroke	3 (1.5)	1 (0.7)	2 (3.4)	0.199
Thyroid disease	35 (17.3)	27 (18.9)	8 (13.6)	0.4
Pacemaker	5 (2.5)	3 (2.1)	2 (3.4)	0.572
Peripheral arterial disease	10 (5.0)	8 (5.6)	2 (3.4)	0.727
Anemia	11 (5.4)	7 (4.9)	4 (6.8)	0.516
EuroSCORE II	1.67 (1.1-2.8)	1.38 (0.9-2.2)	2.32 (1.6-4.6)	< 0.001
Type of surgery				0.18
CABG	80 (39.6)	58 (40.6)	22 (37.3)
CABG and valve replacement or valvuloplasty	34 (16.8)	21 (14.7)	13 (22.0)
Valvuloplasty	5 (2.5)	4 (2.8)	1 (1.7)
Valve replacement	50 (24.8)	32 (22.4)	18 (30.5)
Aortic dissection	3 (1.5)	1 (0.7)	2 (3.4)
Aneurysm repair and other cardiac surgery	22 (10.9)	19 (13.3)	3 (5.1)
Duration of extracorporeal circulatory support (minute)	121 ± 52	117 ± 49	131 ± 59	0.076
Duration of aortic closure (minute)	80 (59-107)	76 (57-104)	89 (67-109)	0.052
Duration of general anesthesia (minute)	240 (190-300)	231 (183-300)	244 (208-324)	0.07

Continuous variables with a normal distribution are presented as mean ± SD, and those with a non-normal distribution as median and interquartile range (25^th-75^th percentile). Categorical variables are shown as n (%). CABG: Coronary artery bypass grafting.

Table 2 Delirium status and clinical outcome

Parameters	All (n = 202)	No delirium (n = 143)	Delirium (n = 59)	P value
RASS scale				< 0.001
-5 to -4	0 (0)	0 (0)	0 (0)
-3 to -1	13 (6.4)	7 (4.9)	6 (10.2)
0	145 (71.8)	125 (87.4)	20 (33.9)
> 1	44 (21.8)	11 (7.7)	33 (55.9)
Day of onset of delirium (days)	0 (0-1)	0 (0-0)	2 (1-2)	< 0.001
Duration of delirium (days)	0 (0-1)	0 (0-0)	1 (1-2)	< 0.001
Hemodialysis in the ICU	5 (2.5)	1 (0.7)	4 (6.8)	0.023
Duration of anesthesia from ICU to awakening (minute)	360 (270-540)	300 (240-450)	540 (300-900)	< 0.001
Duration of total anesthesia/sedation (minute)	600 (484-842)	544 (480-713)	960 (562-1141)	< 0.001
Duration of mechanical ventilation (minute)	779 (586-1154)	717 (480-931)	1230 (774-1696)	< 0.001
Reintubation	7 (3.5)	0 (0)	7 (11.9)	< 0.001
ICU acquired weakness	15 (7.4)	3 (2.1)	12 (20.3)	< 0.001
Length of ICU (days)	2 (2-4)	2 (2-3)	4 (3-6)	< 0.001
ICU outcome				0.272
Improvement	190 (94.1)	138 (96.5)	52 (88.1)
Death	1 (0.5)	0 (0)	1 (1.7)

Continuous variables with a non-normal distribution as median and interquartile range (25^th-75^th percentile). Categorical variables are shown as n (%). RASS: Richmond Agitation-Sedation Scale; ICU: Intensive care unit.

Table 3 Exploratory receiver operating characteristic analysis of variables associated with delirium occurrence in the cardiac surgery intensive care unit

Variable	AUC	Standard error	P value	95%CI
Duration of total anesthesia	0.702	0.042	< 0.001	0.619-0.785
Age	0.635	0.044	0.030	0.547-0.722
EuroSCORE II	0.730	0.038	< 0.001	0.655-0.804
Urea before surgery	0.690	0.041	< 0.001	0.609-0.771
Plasma lactate	0.622	0.043	0.008	0.537-0.707
Vasopressors	0.598	0.046	0.032	0.508-0.688

AUC: Area under the curve; 95%CI: 95% confidence interval.

Table 4 Simplified multivariable logistic regression model with delirium as the dependent variable

Variable	Odds ratio	95%CI	P value
Age	1.047	1.010-1.086	0.013
Duration of total anesthesia	1.001	1.000-1.002	0.006
EuroSCORE II	1.260	1.090-1.457	0.002

The initially considered 6-variable candidate model demonstrated poor calibration according to the Hosmer-Lemeshow goodness-of-fit test (χ² = 51.47, df = 8, P < 0.001) and was therefore not retained as a final prediction model. Odds ratios and 95% confidence intervals were derived from the simplified multivariable logistic regression model. The model included age, total anesthesia/sedation duration, and EuroSCORE II. The model was interpreted as an exploratory association model and not as a validated risk prediction tool. 95%CI: 95% confidence interval.