Study on risk factors and interaction effects of delirium in patients with severe pneumonia in intensive care unit

Table 1 Comparison of general data, mean ± SD/n (%)

Index	Delirium group (n = 71)	Non-delirium group (n = 203)	χ2/t value	P value
Age (year)	48.10 ± 3.58	47.71 ± 3.41	0.807	0.420
Gender			1.392	0.238
Male	39 (54.93)	95 (46.80)
Female	32 (45.07)	108 (53.20)
BMI (kg/m2)	21.94 ± 1.28	22.10 ± 1.14	-1.005	0.316
Type of pneumonia (cases)			2.832	0.092
Community-acquired pneumonia	45 (63.38)	150 (73.89)
Hospital-acquired pneumonia	26 (36.62)	53 (26.11)
Smoking (cases)	30 (42.25)	76 (37.44)	0.514	0.473
Drinking (cases)	18 (25.35)	35 (17.24)	2.218	0.136
Previous history
Hypertension	24 (33.80)	59 (29.06)	0.559	0.455
Diabetes	18 (25.35)	22 (10.84)	8.889	0.003
Coronary heart disease	21 (29.58)	51 (25.12)	0.539	0.463
Insomnia	32 (45.07)	97 (47.78)	0.155	0.693
Course (day)	19.61 ± 0.67	19.43 ± 0.72	1.760	0.079
Mechanical ventilation time (hour)	191.09 ± 43.75	136.74 ± 40.92	9.460	< 0.001
WBC (× 109/L)	13.37 ± 2.16	12.89 ± 2.55	1.420	0.157
Platelet (× 109/L)	172.71 ± 35.06	181.63 ± 37.22	-1.763	0.079
Serum creatinine (μmol/L)	86.73 ± 25.59	83.26 ± 25.21	0.993	0.322
Lactic acid (mmol/L)	5.14 ± 1.55	2.91 ± 0.74	15.982	< 0.001
Urea nitrogen (mmol/L)	11.91 ± 3.29	11.23 ± 3.38	1.476	0.141
Hemoglobin (g/L)	98.72 ± 19.27	100.67 ± 25.37	-0.592	0.554
Calcium (mmol/L)	2.23 ± 0.15	2.36 ± 0.09	-8.889	< 0.001
Sodium (mmol/L)	139.13 ± 3.32	138.56 ± 3.41	1.227	0.221
Potassium (mmol/L)	3.89 ± 0.40	3.91 ± 0.42	-0.426	0.670
CRP (mg/L)	127.47 ± 37.67	121.01 ± 36.18	1.282	0.201
Arterial oxygen saturation			11.286	0.001
< 90%	41 (57.75)	71 (34.98)
≥ 90%	30 (42.25)	132 (65.02)
APACHE II			17.749	< 0.001
< 15	37 (52.11)	159 (78.33)
≥ 15	34 (47.89)	44 (21.67)
Sedatives			0.189	0.664
Yes	36 (50.70)	109 (53.69)
No	35 (49.30)	94 (46.31)
Nutritional risk			0.362	0.547
Yes	16 (22.54)	39 (19.21)
No	55 (77.46)	164 (80.79)

BMI: Body mass index; WBC: White blood cell; CRP: C-reactive protein; APACHE II: Acute Physiology and Chronic Health Evaluation II.

Table 2 Variable assignment

Index	Assignment
Diabetes	Yes = 1, no = 0
Mechanical ventilation time	Actual value entry
Lactic acid	Actual value entry
Calcium	Actual value entry
Arterial oxygen saturation	< 90% = 1, ≥ 90% = 2
APACHE II	< 15 points = 1, ≥ 15 points = 2

APACHE II: Acute Physiology and Chronic Health Evaluation II.

Table 3 Logistic regression analysis of risk factors for delirium in patients with severe pneumonia in the intensive care unit

Index	β	SE	Wald	P value	OR	95%CI
Diabetes	0.002	0.716	0.000	0.997	1.002	0.246-4.076
Mechanical ventilation time	0.029	0.007	16.499	< 0.001	1.029	1.015-1.044
Lactic acid	1.654	0.281	34.757	< 0.001	5.229	3.017-9.062
Calcium	-6.865	2.406	8.140	0.004	0.001	0.000-0.117
Arterial oxygen saturation	-0.201	0.521	0.149	0.700	0.818	0.295-2.271
APACHE II	1.214	0.515	5.552	0.018	3.368	1.227-9.246
Constant	2.505	5.974	0.176	0.675	12.238

APACHE II: Acute Physiology and Chronic Health Evaluation II; OR: Odds ratio; CI: Confidence interval.

Table 4 Interaction effect analysis of risk factors for delirium in intensive care unit patients with severe pneumonia

Model	Average test accuracy of training set	Test set average test accuracy	Cross-validation consistency rate	P value
APACHE II	0.6316	0.5917	8/10	< 0.001
Diabetes × APACHE II	0.6530	0.5980	5/10	< 0.001
Diabetes × arterial oxygen saturation ×APACHE II	0.6838	0.6638	10/10	< 0.001

APACHE II: Acute Physiology and Chronic Health Evaluation II.

Table 5 Multivariate logistic regression analysis of risk factors and interaction effects of delirium in patients with severe pneumonia in the intensive care unit

Index	β	SE	Wald	P value	OR	95%CI
Diabetes	-0.197	1.192	0.027	0.869	0.821	0.079-8.498
Mechanical ventilation time	0.073	0.314	0.055	0.815	1.076	0.582-1.991
Lactic acid	0.041	0.311	0.018	0.895	1.042	0.567-1.916
Calcium	-0.174	0.311	0.315	0.575	0.840	0.457-1.545
Arterial oxygen saturation	0.954	0.805	1.406	0.236	2.596	0.536-12.568
APACHE II	2.529	1.629	2.410	0.121	12.537	0.515-305.247
Diabetes × APACHE II	0.601	0.958	0.393	0.531	1.823	0.279-11.921
Diabetes × arterial oxygen saturation × APACHE II	-0.821	0.305	7.219	0.007	0.440	0.242-0.801
Constant	-3.811	2.822	1.823	0.177	0.022

APACHE II: Acute Physiology and Chronic Health Evaluation II; OR: Odds ratio; CI: Confidence interval.