Diabetes and elevated preoperative HbA1c level as risk factors for postoperative delirium after cardiac surgery: an observational cohort study

Figures & data

Figure 1 Study flowchart.

Table 1 Preoperative and perioperative characteristics of patients

Variable	No delirium (n=2,676)	Delirium (n=502)	P-value
Demographic data
Age (years), mean ± SD	65.10±9.59	70.09±8.43	<0.001
Gender, female, n (%)	777 (29.04)	153 (30.48)	NS
Smoking, n (%)	821 (30.68)	137 (27.29)	NS
BMI, mean ± SD, kg/m^2	28.73±4.62	28.69±4.39	NS
Concomitant diseases
Ischemic heart disease, n (%)	2,205 (82.40)	434 (86.45)	0.026
Diabetes, n (%)	799 (29.86)	211 (42.03)	<0.001
Glucose intolerance, n (%)	98 (3.66)	12 (2.39)	NS
TIA, n (%)	34 (1.27)	5 (1.00)	NS
Stroke, n (%)	134 (5.01)	36 (7.17)	NS
Arterial hypertension, n (%)	1,810 (67.64)	370 (73.71)	0.007
AF paroxysmal, n (%)	215 (8.03)	49 (9.76)	NS
AF persistent, n (%)	183 (6.84)	42 (8.37)	NS
ICA stenosis, n (%)	159 (5.94)	50 (9.96)	<0.001
COPD, n (%)	153 (5.72)	45 (8.96)	0.006
Chronic renal failure, n (%)	183 (6.84)	63 (12.55)	<0.001
Acute renal failure, n (%)	23 (0.86)	10 (1.99)	0.022
Ejection fraction <30%, n (%)	174 (6.50)	55 (10.96)	<0.001
NYHA III and IV, n (%)	697 (26.05)	193 (38.45)	<0.001
Extracardiac arteriopathy	375 (14.31)	124 (25.00)	<0.001
Preoperative data
HbA1c %, mean ± SD	5.91±0.95	6.18±1.15	<0.001
Creatinine (mg/dL) at admission, mean ± SD	1.00±0.61	1.16±0.89	<0.001
GFR at admission (mL/min/1.73 m^2), mean ± SD	79.93±26.73	68.99±21.66	<0.001
Operative risk
EuroSCORE Logistic 2, mean ± SD	3.01±4.64	4.57±5.57	<0.001
Operation type
Isolated CABG, n (%)	1,663 (62.14)	262 (52.19)	<0.001
CABG + valve, n (%)	386 (14.42)	136 (27.09)	<0.001
CABG + AAA, n (%)	44 (1.64)	9 (1.79)	NS
TAVI, n (%)	24 (0.90)	4 (0.80)	NS
Aortic aneurysm, n (%)	168 (6.28)	33 (6.57)	NS
Isolated valve, n (%)	391 (14.61)	58 (11.55)	NS
Case priority
Planned, n (%)	1,961 (73.28)	350 (69.72)	NS
Urgent, n (%)	563 (21.04)	113 (22.51)
Emergent, n (%)	152 (5.68)	39 (7.77)
Postoperative complications
Stroke/TIA, n (%)	85 (3.18)	26 (5.18)	0.025
Atrial fibrillation, n (%)	537 (20.07)	158 (31.47)	<0.001
Respiratory failure, n (%)	191 (7.14)	106 (21.12)	<0.001
Pneumonia, n (%)	58 (2.17)	49 (9.76)	<0.001
Acute kidney injury, n (%)	55 (2.06)	30 (5.98)	<0.001
AKI with CRRT, n (%)	239 (8.93)	121 (24.10)	<0.001
Sepsis, n (%)	11 (0.41)	3 (0.60)	NS
Outcome data
Hospital LOS (days), mean ± SD	9.21±9.10	13.79±14.77	<0.001
ICU LOS (days), mean ± SD	2.71±4.80	3.73±6.73	<0.001
Mortality, n (%)	130 (4.86)	27 (5.38)	NS

Abbreviations: AAA, ascending aorta aneurysm; AF, atrial fibrillation; AKI, acute kidney injury; BMI, body mass index (kg/m²); CABG, coronary artery bypass grafting; CRRT, continuous renal replacement therapy; GFR, glomerular filtration rate; HbA1c, glycated hemoglobin; ICA, internal carotid artery; ICU, intensive care unit; LOS, length of stay; n, number of patients; NS, not significant; NYHA, New York Heart Association; TAVI, transcatheter aortic valve implantation; TIA, transient ischemic attack.

Figure 2 Multivariate analysis for patients with delirium.

Abbreviation: HbA1c, glycated hemoglobin.

Table 2 Univariate analysis including all preoperative variables associated with postoperative delirium after cardiac surgery

Variables associated with delirium (n=3,178)	OR	−95% CI	+95% CI	P-value
Demographic data
Age (in years)a	1.063	1.051	1.076	<0.001
Female gender	1.071	0.871	1.319	NS
Smoking	0.848	0.685	1.049	NS
BMI (kg/m^2)	0.998	0.977	1.019	NS
Concomitant diseases
Ischemic heart disease	1.363	1.036	1.794	0.027
Diabetes	1.703	1.401	2.071	<0.001
Glucose intolerance	0.644	0.351	1.182	NS
Transient ischemic attack	0.782	0.304	2.009	NS
Stroke	1.466	1.001	2.145	0.049
Arterial hypertension	1.341	1.082	1.662	0.007
AF persistent	1.238	0.894	1.715	NS
AF paroxysmal	1.244	0.877	1.765	NS
Internal carotid artery stenosis	1.751	1.255	2.444	0.001
COPD	1.624	1.148	2.297	0.006
Chronic renal failure	1.955	1.443	2.649	<0.001
Acute renal failure	2.344	1.109	4.956	0.026
Ejection fraction <30%	1.769	1.285	2.434	<0.001
NYHA class III and IV	1.773	1.453	2.165	<0.001
Extracardiac arteriopathy	1.996	1.585	2.515	<0.001
Preoperative laboratory factors
Creatinine (mg/dL) at admission	1.285	1.148	1.439	<0.001
HbA1c %	1.269	1.161	1.387	<0.001
Operative risk
EuroSCORE Logistic 2	1.051	1.034	1.068	<0.001

Note:

a OR for an increase of 1 year in age.

Abbreviations: AF, atrial fibrillation; HbA1c, glycated hemoglobin; n, number of patients; NS, not significant; NYHA, New York Heart Association.

Table 3 Preoperative diabetes-related data and glycated hemoglobin for patients with and without delirium

Total no of patients (n=3,178)	No delirium (n=2,676)		Delirium (n=502)		P-value
	N	%	N	%
Diabetes mellitus	799	29.86	211	42.03	<0.001
Diabetes – insulin	139	5.19	37	7.37	0.050
Diabetes – oral diabetic medications	661	24.70	174	34.66	<0.001
Glucose intolerance	98	3.66	12	2.39	NS
HbA1c ≥5.7%	1,375	53.32	313	65.76	<0.001
HbA1c ≥6%	852	33.04	212	44.54	<0.001
HbA1c ≥6.5%	442	17.14	130	27.31	<0.001
Diabetes mellitus
HbA1c ≥5.7%	670	86.34	177	87.62	NS
HbA1c ≥6%	584	75.26	156	77.23	NS
HbA1c ≥6.5%	379	48.84	112	55.45	NS
Glucose intolerance
HbA1c ≥5.7%	45	47.87	6	50.00	NS
HbA1c ≥6%	15	15.96	2	16.67	NS
HbA1c ≥6.5%	4	4.26	1	8.33	NS
No diabetes
HbA1c ≥5.7%	705	39.10	136	49.64	<0.001
HbA1c ≥6%	268	14.86	56	20.44	0.018
HbA1c ≥6.5%	63	3.49	18	6.57	0.014

Abbreviations: HbA1c, glycated hemoglobin; n, number of patients; NS, not significant.

Table 4 Univariate diabetes-related variables associated with postoperative delirium after cardiac surgery

Variables associated with delirium (n=3,178)	OR	−95% CI	+95% CI	P-value
Diabetes mellitus	1.703	1.401	2.071	<0.001
Diabetes – insulin treatment	1.452	0.997	2.115	NS
Diabetes – treatment by oral medications	1.617	1.319	1.983	<0.001
Glucose intolerance	0.644	0.351	1.182	NS
HbA1c ≥6%	1.628	1.335	1.985	<0.001
HbA1c ≥6.5%	1.817	1.449	2.278	<0.001

Abbreviations: HbA1c, glycated hemoglobin; n, number of patients; NS, not significant.

Table 5 Preoperative and perioperative characteristics of diabetic patients

Variable	No delirium diabetic (n=799)	Delirium diabetic (n=211)	P-value
Demographic data
Age (years), mean ± SD	67.00±7.88	70.06±7.77	<0.001
Gender, female, n (%)	241 (30.16)	81 (38.39)	0.023
Smoking, n (%)	229 (28.66)	57 (27.01)	NS
BMI (kg/m^2), mean ± SD	30.29±4.53	29.93±4.32	NS
Concomitant diseases
Ischemic heart disease, n (%)	730 (91.36)	197 (93.36)	NS
Diabetes – insulin controlled, n (%)	139 (17.40)	37 (17.54)	NS
Diabetes – oral medications, n (%)	661 (82.73)	174 (82.46)	NS
HbA1c %, mean ± SD	6.74±1.19	6.89±1.34	NS
HbA1c ≥5.7%, n (%)	670 (86.34)	177 (87.62)	NS
HbA1c ≥6%, n (%)	584 (75.26)	156 (77.23)	NS
HbA1c ≥6.5%, n (%)	379 (48.84)	112 (55.45)	NS
TIA, n (%)	11 (1.38)	2 (0.95)	NS
Stroke, n (%)	60 (7.51)	15 (7.11)	NS
Arterial hypertension, n (%)	651 (81.48)	180 (85.31)	NS
AF paroxysmal, n (%)	64 (8.01)	21 (9.95)	NS
AF persistent, n (%)	53 (6.63)	17 (8.06)	NS
Extracardiac arteriopathy, n (%)	147 (18.40)	67 (31.75)	<0.001
ICA stenosis, n (%)	66 (8.26)	22 (10.43)	NS
COPD, n (%)	43 (5.38)	25 (11.85)	<0.001
Chronic renal failure, n (%)	84 (10.51)	36 (17.06)	0.009
Acute renal failure, n (%)	12 (1.50)	6 (2.84)	NS
Ejection fraction <30%, n (%)	61 (7.63)	32 (15.17)	<0.001
NYHA III and IV, n (%)	196 (24.53)	94 (44.55)	<0.001
EuroSCORE Logistic 2, mean ± SD	3.23±5.08	4.9±5.28	<0.001
Creatinine (mg/dL) at admission, mean ± SD	1.07±0.63	1.22±0.97	0.001
GFR at admission (mL/min/1.73 m^2), mean ± SD	74.86±29.11	66.01±21.71	<0.001
Operation type
Isolated CABG, n (%)	586 (73.34)	108 (51.18)	<0.001
CABG + valve, n (%)	108 (13.52)	72 (34.12)	<0.001
CABG + AAA, n (%)	10 (1.25)	4 (1.90)	NS
TAVI, n (%)	9 (1.13)	1 (0.47)	NS
Aortic aneurysm, n (%)	19 (2.38)	4 (1.90)	NS
Isolated valve, n (%)	67 (8.39)	22 (10.43)	NS
Case priority
Planned, n (%)	590 (73.84)	149 (70.62)	NS
Urgent, n (%)	174 (21.78)	48 (22.75)
Emergent, n (%)	35 (4.38)	14 (6.64)

Abbreviations: AAA, ascending aorta aneurysm; AF, atrial fibrillation; CABG, coronary artery bypass grafting; GFR, glomerular filtration rate; HbA1c, glycated hemoglobin; ICA, internal carotid artery; n, number of patients; NS, not significant; NYHA, New York Heart Association; TAVI, transcatheter aortic valve implantation; TIA, transient ischemic attack.

Table 6 Postoperative complications and outcome for diabetic patients with and without postcardiac surgery delirium

Postoperative complications	No delirium diabetic (n=799)	Delirium diabetic (n=211)	P-value
Stroke/TIA, n (%)	28 (3.50)	15 (7.11)	0.021
Atrial fibrillation, n (%)	142 (17.77)	61 (28.91)	<0.001
Respiratory failure, n (%)	54 (6.76)	47 (22.27)	<0.001
Pneumonia, n (%)	17 (2.13)	19 (9.00)	<0.001
Sepsis, n (%)	2 (0.25)	0 (0.00)	NS
Acute kidney injury, n (%)	22 (2.75)	14 (6.64)	0.007
AKI with CRRT, n (%)	84 (10.51)	57 (27.01)	<0.001
Creatinine (max), mean ± SD	1.41±1.02	1.94±1.28	<0.001
GFR (min), mean ± SD	61.56±25.92	43.87±23.91	<0.001
Postoperative outcome
ICU LOS (days), mean ± SD	2.74±5.64	3.77±6.22	<0.001
Hospital LOS (days), mean ± SD	9.41±12.27	15.61±18.34	<0.001
Mortality at 30 days, n (%)	42 (5.26)	14 (6.64)	NS

Abbreviations: AKI, acute kidney injury; CRRT, continuous renal replacement therapy; GFR, glomerular filtration rate; ICU, intensive care unit; LOS, length of stay; n, number of patients; NS, not significant; TIA, transient ischemic attack.