Association Between the Admission Serum Bicarbonate and Short-Term and Long-Term Mortality in Acute Aortic Dissection Patients Admitted to the Intensive Care Unit

Figures & data

Figure 1 The flow chart describing the procedure used for patients selection.

Table 1 Characteristics of Subjects

Characteristics	Total (n=336)	Serum HCO3^− Levels (mmol/L)
		<22 (n=96)	22–24 (n=118)	>24 (n=122)	P value
Gender					0.764
Male	213 (63.39%)	61 (63.54%)	72 (61.02%)	80 (65.57%)
Female	123 (36.61%)	35 (36.46%)	46 (38.98%)	42 (34.43%)
Age, years	69.00 (56.00–78.00)	67.00 (54.75–78.00)	70.50 (59.00–80.00)	71.00 (57.25–77.00)	0.347
Insurance					0.55
Government	20 (5.95%)	5 (5.21%)	7 (5.93%)	8 (6.56%)
Medicaid	17 (5.06%)	7 (7.29%)	3 (2.54%)	7 (5.74%)
Medicare	176 (52.38%)	46 (47.92%)	63 (53.39%)	67 (54.92%)
Private	118 (35.12%)	38 (39.58%)	43 (36.44%)	37 (30.33%)
Selfpay	5 (1.49%)	0 (0.00%)	2 (1.69%)	3 (2.46%)
Ethnicity					0.261
White	233 (69.35%)	69 (71.88%)	88 (74.58%)	76 (62.30%)
Black	44 (13.19%)	11 (11.46%)	15 (12.71%)	18 (14.75%)
Hispanic	13 (3.87%)	5 (5.21%)	4 (3.39%)	4 (3.28%)
Others	46 (13.69%)	11 (11.46%)	11 (9.32%)	24 (19.67%)
Stanford type					0.003
A type	230 (68.45%)	68 (70.83%)	75 (63.56%)	87 (71.31%)
B type	106 (31,55%)	28 (29.17%)	43 (36.44%)	35 (28.69%)
Dissection site					0.392
Thoracic	187 (55.65%)	56 (58.33%)	68 (57.63%)	63 (51.64%)
Abdominal	62 (18.45%)	21 (21,88%)	21 (17.80%)	21 (17.21%)
Thoracoabdominal	87 (25.89%)	19 (19.79%)	30 (25.42%)	38 (31.15%)
Aorta replacement	198 (58.93%)	57 (59.38%)	72 (61.02%)	69 (56.56%)	0.777
ICU MV	170 (50.60%)	69 (71.88%)	60 (50.85%)	79 (64.75%)	0.005
Comorbidities
Hypertension	44 (13.1%)	46 (47.92%)	80 (67.80%)	73 (59.83%)	0.013
Diabetes	30 (8.93%)	11 (11.46%)	10 (8.47%)	9 (7.38%)	0.564
HC	53 (15.77%)	16 (16.67%)	20 (16.95%)	17 (13.93%)	0.782
Valvular disease	33 (9.82%)	9 (9.38%)	11 (9.32%)	13 (10.66%)	0.927
Maligancy	11 (3.27%)	3 (3.13%)	4 (3.39%)	4 (3.28%)	0.994
Stroke	26 (7.74%)	9 (9.38%)	8 (6.78%)	9 (7.38%)	0.765
CAD	60 (17.86%)	25 (26.04%)	17 (14.41%)	18 (14.75%)	0.046
CHF	31 (9.23%)	10 (10.42%)	11 (9.32%)	10 (8.20%)	0.853
Atrial fibrillation	57 (16.96%)	16 (16.67%)	20 (16.95%)	21 (36.84%)	0.994
Renal disease	45 (13.39%)	15 (15.63%)	15 (12.71%)	15 (12.30%)	0.745
Liver disease	10 (2.98%)	2 (2.08%)	4 (3.39%)	4 (3.28%)	0.83
Respiratory disease	64 (19.05%)	12 (12.50%)	17 (14.41%)	35 (28.69%)	0.003
AKI	135 (40.18%)	50 (52.08%)	43 (36.44%)	42 (34.43%)	0.018
RRT	29 (8.63%)	13 (13.54%)	8 (6.78%)	8 (6.56%)	0.127
Laboratory variables
WBC, 10^3/µL	8.80 (6.20–11.00)	9.05 (5.90–12.43)	9.00 (6.85–10.80)	8.45 (6.05–10.38)	0.192
RBC, 10^3/µL	3.66 (2.26–4.16)	3.52 (3.22–3.92)	3.64 (3.29–4.11)	3.82 (3.29–4.33)	0.03
PLT, 10^3/µL	164 (119–228)	139 (93.75–193.50)	159 (123–224.75)	185.5 (128.5–273.75)	<0.001
RDW, %	14.40 (13.60–15.30)	14.50 (13.60–15.30)	14.35 (13.50–15.30)	14.40 (13.73–15.50)	0.85
Hematocrit, %	28.95 (23.00–33.80)	26.65 (21.98–30.78)	28.75 (23.75–33.95)	30.55 (23.68–34.20)	0.02
Hb, g/dL	9.75 (7.80–11.60)	9.10 (7.38–10.53)	9.85 (7.93–11.60)	10.25 (8.15–11.70)	0.023
Anion gap, mmol/L	12.50 (10.00–14.00)	14.00 (11.00–16.00)	13.00 (10.00–14.00)	12.00 (10.00–13.00)	<0.001
Lactate, mmol/L	3.20 (1.70–5.85)	4.10 (2.20–6.88)	3.60 (1.70–5.80)	2.00 (1.30–3.75)	<0.001
pH value	7.39 (7.33–7.43)	7.37 (7.27–7.42)	7.39 (7.34–7.44)	7.41 (7.36–7.44)	<0.001
BUN, mg/dL	16.00 (12.00–22.00)	18.00 (13.00–26.00)	16.50 (12.00–20.75)	16.00 (11.00–20.75)	0.037
Creatinine, mg/dL	1.05 (0.80–1.53)	1.20 (0.90–1.90)	1.00 (0.80–1.40)	0.95 (0.73–1.30)	<0.001
Chloride, mmol/L	103 (100–105)	104 (101.75–106)	103 (101–105)	101 (99–104)	<0.001
Glucose, mg/dL	103 (89.00–119.25)	101 (86–119)	104 (88–118)	102 (93–121.75)	0.541
APTT, s	28.15 (25.20–32.63)	28.70 (25.50–36.20)	27.35 (24.50–31.38)	28.75 (25.50–32.00)	0.47
PT, s	13.40 (12.50–14.40)	13.50 (12.40–14.53)	13.35 (12.70–14.10)	13.30 (12.50–14.60)	0.932
INR	1.20 (1.10–1.30)	1.20 (1.10–1.30)	1.20 (1.10–1.30)	1.20 (1.10–1.30)	0.836
Sodium, mmol/L	137 (134–139)	135.50 (133–138)	136 (134–139)	137.50 (135–139)	0.001
Potassium, mmol/L	3.60 (3.30–3.90)	3.60 (3.30–3.90)	3.70 (3.40–4.00)	3.60 (3.30–3.90)	0.264
Total Ca, mg/dL	8.50 (8.10–9.00)	8.50 (7.90–8.83)	8.50 (8.10–9.00)	8.60 (8.30–9.10)	0.02
Magnesium, mg/dL	2.00 (1.90–2.30)	2.10 (1.90–2.40)	2.00 (1.90–2.30)	2.00 (1.90–2.20)	0.439
Vital signs
SBP, mmHg	151 (136–165)	149.50 (134–168)	151 (136–167.50)	150.50 (136–162)	0.526
DBP, mmHg	81.00 (72 0.00–91.00)	81.00 (72.00–94.00)	81.00 (72.00–94.00)	85.50 (72.25–87.00)	0.604
MBP, mmHg	102 (93–113)	101.50 (95–114.25)	103 (92.25–117.50)	101 (91.75–109.75)	0.193
HR, beats/min	90 (80–102.25)	95.00 (84.00–112.00)	90.50 (79.25–99.75)	87.50 (78.00–101.00)	0.015
RR, times/min	25.00 (22.00–29.00)	26.00 (23.00–30.00)	24.00 (22.00–29.00)	26.00 (22.00–29.00)	0.201
Temperature, °C	37.28 (36.78–37.83)	37.30 (36.72–38.01)	37.31 (36.78–37.89)	37.22 (36.89–37.70)	0.942
SPO2, %	92.00 (90.00–94.00)	92.00 (01.00–94.00)	92.00 (91.00–94.00)	92.00 (90.00–94.00)	0.365
Severity score
SAPSII	35.00 (28.00–43.00)	43.00 (33.75–53.50)	34.00 (28.25–39.00)	31.00 (25.00–39.00)	<0.001
OASIS	32.00 (26.75–39.00)	37.00 (32.00–42.25)	31.00 (26.00–37.00)	29.50 (25.00–34.00)	<0.001
SOFA	4.00 (2.00–6.00)	6.00 (3.75–9.00)	3.00 (2.00–5.00)	3.00 (1.00–5.00)	<0.001
SIRS	3.00 (2.00–3.00)	3.00 (2.00–4.00)	3.00 (2.00–3.00)	2.00 (1.00–3.00)	<0.001

Abbreviations: ICU MV, intensive care unit mechanical ventilation; HC, hypercholesterolemia; CAD, coronary artery disease; CHF, congestive heart failure; AKI, acute kidney injury; RRT, renal replacement therapy; WBC, white blood cell; RBC, red blood cell; PLT, platelet; RDW, red cell distribution width; BUN, blood urea nitrogen; APTT, activated partial thromboplastin time; PT, prothrombin time; INR, international normalized ratio; Total Ca, total calcium; SBP, systolic blood pressure; DBP, diastolic blood pressure; MBP, mean blood pressure; HR, heart rate; RR, respiratory rate; SAPS II, simplified acute physiology score; OASIS, Oxford acute severity of illness score; SOFA, sequential organ failure assessment; SIRS, systemic inflammatory response syndrome.

Figure 2 The KM survival curve of low-HCO3⁻, mid-HCO3⁻ and high-HCO3⁻ groups.

Table 2 HRs (95% CIs) for Mortality Across Groups of Serum HCO3⁻

Serum HCO3^− Level	Non-Adjusted		Model 1		Model 2
	HR (95% CIs)	P value	HR (95% CIs)	P value	HR (95% CIs)	P value
30-day mortality
HCO3^−, mmol/L
<22 mmol/L	3.54 (1.67, 7.49)	<0.001	3.54 (1.67, 7.49)	0.001	5.11 (1.41, 18.46)	0.013
22–24 mmol/L	1.0 (ref)	/	1.0 (ref)	/	1.0 (ref)	/
>24 mmol/L	0.77 (0.32, 1.87)	0.567	0.74 (0.30, 1.82)	0.507	0.75 (0.20, 2.78)	0.663
90-day mortality
HCO3^−, mmol/L
<22 mmol/L	3.95 (1.96, 7.98)	<0.001	3.95 (1.93, 8.08)	<0.001	5.58 (1.86, 16.77)	0.002
22–24 mmol/L	1.0 (ref)	/	1.0 (ref)	/	1.0 (ref)	/
>24 mmol/L	1.02 (0.47, 2.23)	0.951	0.98 (0.44, 2.19)	0.969	1.49 (0.49, 4.54)	0.486
1-year mortality
HCO3^−, mmol/L
<22 mmol/L	2.71 (1.43, 5.13)	0.002	2.67 (1.39, 5.13)	0.003	3.30 (1.24, 8.78)	0.016
22–24 mmol/L	1.0 (ref)	/	1.0 (ref)	/	1.0 (ref)	/
>24 mmol/L	1.06 (0.54, 2.07)	0.864	1.06 (0.53, 2.10)	0.877	1.51 (0.57, 3.98)	0.402
5-year mortality
HCO3^−, mmol/L
<22 mmol/L	2.19 (1.23, 3.91)	0.008	2.13 (1.18, 3.83)	0.012	4.08 (1.70, 9.78)	0.002
22–24 mmol/L	1.0 (ref)	/	1.0 (ref)	/	1.0 (ref)	/
>24 mmol/L	1.18 (0.67, 2.09)	0.574	1.14 (0.63, 2.04)	0.668	1.67 (0.75, 3.72)	0.209

Notes: Models were derived from Cox proportional hazards regression models. Non-adjusted model adjusted for: none. Model 1 adjusted for: gender; age; ethnicity and insurance. Model 2 adjusted for: age; gender; ethnicity; insurance; Stanford type; dissection site; ICU MV; therapy type; hypertension; diabetes; hypercholesterolemia; valvular disease; malignancy; stroke; CAD; CHF; atrial fibrillation; renal disease; liver disease; respiratory disease; AKI; WBC; RDW; RBC; Hb; PLT; BUN; creatinine; chloride; glucose; APTT; INR; sodium; potassium; total Ca; magnesium; anion gap; pH value; SBP; DBP; MBP; HR; RR; temperature and SPO₂.

Table 3 Subgroup Analysis of the Associations Between Serum HCO3⁻ and 30-Day All-Cause Mortality

	No. of Patients	Serum HCO3^− Levels (mmol/L)			P for Interaction
		<22	22–24	>24
Gender					0.828
Male	213	2.96 (1.29, 6.80)	ref	0.66 (0.23, 1.89)
Female	123	3.25 (1.00, 10.56)	ref	1.09 (0.27, 4.38)
Age, years					0.924
<69	165	3.18 (1.26, 8.01)	ref	0.92 (0.30, 2.85)
≥69	171	2.66 (0.95, 7.48)	ref	0.651 (0.18, 2.31)
Insurance					/
Government	20	/	ref	/
Medicaid	17	/	ref	/
Medicare	176	2.32 (0.90, 5.99)	ref	0.39 (0.10, 1.53)
Private	118	3.66 (1.32, 10.16)	ref	0.91 (0.24, 3.37)
Selfpay	5	/	ref	1.00 (1.00, 1.00)
Ethnicity					0.89
White	233	3.18 (1.38, 7.33)	ref	0.87 (0.30, 2.49)
Black	44	1.38 (0.28, 6.84)	ref	0.49 (0.08, 2.94)
Hispanic	13	/	ref	/
Others	46	5.88 (0.69, 50.40)	ref	0.91 (0.08, 10.01)
Stanford type					0.387
A type	230	8.50 (1.05, 16.26)	ref	0.95 (0.06, 16.29)
B type	106	2.27 (1.17, 5.94)	ref	0.65 (0.20, 2.09)
Aorta replacement					0.768
No	138	5.27 (1.44, 8.94)	ref	0.64 (0.72, 3.16)
Yes	198	2.75 (0.98, 7.13)	ref	0.54 (0.17, 2.83)
ICU MV					0.753
No	166	3.57 (2.26, 5.23)	ref	0.79 (0.33, 2.54)
Yes	170	4.92 (1.67, 9.91)	ref	0.88 (0.12, 4.58)
Hypertension					0.179
No	137	1.77 (0.72, 4.35)	ref	0.32 (0.08, 1.22)
Yes	199	4.64 (1.63, 13.17)	ref	1.53 (0.48, 4.81)
Diabetes					0.091
No	306	2.572 (1.27, 5.20)	ref	0.78 (0.34, 1.81)
Yes	30	/	ref	/
Hypercholesterolemia					0.156
No	283	3.56 (1.64, 7.69)	ref	1.04 (0.42, 2.55)
Yes	53	1.597 (0.36, 7.14)	ref	/
Valvular disease					0.668
No	303	3.00 (1.42, 6.33)	ref	0.87 (0.36, 2.15)
Yes	33	3.36 (0.65, 17.39)	ref	0.38 (0.03, 4.19)
Malignancy					0.478
No	325	2.93 (1.48, 5.81)	ref	0.79 (0.34, 1.83)
Yes	11	/	ref	/
Stroke					0.891
No	310	3.22 (1.47, 7.02)	ref	0.85 (0.33, 2.21)
Yes	26	2.27 (0.56, 9.18)	ref	0.54 (0.09, 3.23)
CAD					0.16
No	276	4.25 (1.88, 9.59)	ref	1.09 (0.42, 2.81)
Yes	60	1.00 (0.28, 3.54)	ref	0.21 (0.02, 1.90)
CHF					0.307
No	305	3.29 (1.57, 6.88)	ref	0.94 (0.39, 2.25)
Yes	31	1.91 (0.32, 11.43)	ref	/
Atrial fibrillation					0.735
No	279	3.49 (1.62, 7.55)	ref	0.84 (0.32, 2.18)
Yes	57	1.80 (0.40, 8.03)	ref	0.64 (0.11, 3.83)
Renal disease					0.094
No	291	3.16 (1.44, 6.94)	ref	1.07 (0.43, 2.62)
Yes	45	2.35 (0.61, 9.13)	ref	/
Liver disease					0.049
No	326	2.77 (1.39, 5.51)	ref	0.79 (0.34, 1.83)
Yes	10	/	ref	/
Respiratory disease					0.727
No	272	3.51 (1.55, 7.92)	ref	0.87 (0.30, 2.50)
Yes	64	2.21 (0.62, 7.86)	ref	0.42 (0.11, 1.69)
AKI					0.507
No	201	3.10 (1.22, 7.87)	ref	1.06 (0.39, 2.93)
Yes	135	2.83 (1.03, 7.80)	ref	0.40 (0.08, 2.03)
RRT					0.418
No	307	2.94 (1.43, 6.06)	ref	0.86 (0.37, 2.03)
Yes	29	3.31 (0.39, 28.38)	ref	/
WBC, 10^3/µL					0.84
<8.8	167	2.47 (0.85, 7.26)	ref	0.63 (0.17, 2.35)
≥8.8	169	3.58 (1.49, 8.64)	ref	0.99 (0.33, 2.94)
RDW, %					0.873
<14.4	159	3.58 (1.26, 10.17)	ref	0.84 (0.23, 3.12)
≥14.4	177	2.65 (1.08, 6.50)	ref	0.74 (0.25, 2.22)
Hematocrit, %					0.985
<28.9	167	2.91 (1.21, 7.01)	ref	0.80 (0.25, 2.51)
≥28.9	169	3.16 (1.08, 9.26)	ref	0.83 (0.24, 2.85)
Hb, g/dL					0.895
<9.7	163	2.75 (1.15, 6.60)	ref	0.65 (0.19, 2.23)
≥9.7	173	3.25 (1.09, 9.71)	ref	0.99 (0.30, 3.23)
RBC, 10^3/µL					0.254
<3.66	167	5.46 (1.9, 16.06)	ref	1.30 (0.33, 5.21)
≥3.66	169	1.67 (0.63, 4.46)	ref	0.55 (0.19, 1.58)
Platelet, 10^3/µL					0.561
<164	165	4.06 (1.50, 11.00)	ref	1.29 (0.37, 4.45)
≥164	171	2.29 (0.87, 6.03)	ref	0.53 (0.17, 1.67)
Anion gap, mmol/L					0.313
<12	126	1.42 (0.41, 4.91)	ref	0.63 (0.18, 2.18)
≥12	210	4.18 (1.79, 9.80)	ref	0.89 (0.28, 2.81)
pH value					0.072
<7.39	167	6.19 (2.15, 10.74)	ref	0.68 (0.58, 3.20)
≥7.39	169	2.63 (1.39, 6.18)	ref	0.87 (0.31, 2.01)
Lactate, mmol/L					0.311
<4.1	166	5.13 (1.27, 8.84)	ref	1.12 (0.32, 3.84)
≥4.1	170	3.11 (1.33, 5.26)	ref	0.91 (0.33, 2.50)
BUN, mg/dL					0.979
<16	153	3.19 (0.80, 12.74)	ref	0.92 (0.19, 4.57)
≥16	183	2.83 (1.29, 6.18)	ref	0.76 (0.28, 2.04)
Creatinine, mg/dL					0.735
<1	132	4.12 (1.24, 13.70)	ref	1.12 (0.32, 3.95)
≥1	204	2.65 (1.16, 6.04)	ref	0.58 (0.17, 1.91)
Chloride, mmol/L					0.719
<103	167	2.36 (0.90, 6.19)	ref	0.69 (0.24, 1.97)
≥103	169	4.00 (1.47, 10.84)	ref	0.82 (0.20, 3.45)
Glucose, mg/dL					0.876
<103	167	3.29 (1.05, 10.34)	ref	0.65 (0.15, 2.90)
≥103	169	3.10 (1.33, 7.26)	ref	0.91 (0.33, 2.50)
APTT, s					0.59
<28.1	167	2.82 (1.11, 7.16)	ref	1.03 (0.35, 3.06)
≥28.1	169	3.33 (1.21, 9.17)	ref	0.60 (0.16, 2.22)
INR					0.628
<1.2	152	3.61 (1.39, 9.41)	ref	0.63 (0.18, 2.22)
≥1.2	184	2.69 (1.02, 7.06)	ref	0.96 (0.31, 2.96)
PT, s					0.775
<13.4	165	3.19 (1.21, 8.40)	ref	0.62 (0.18, 2.20)
≥13.4	171	2.96 (1.14, 7.69)	ref	0.97 (0.31, 3.01)
Sodium, mmol/L					0.831
<137	166	3.22 (1.26, 8.23)	ref	1.03 (0.32, 3.38)
≥137	170	2.92 (1.08, 7.91)	ref	0.63 (0.19, 2.08)
Potassium, mmol/L					0.726
<3.6	143	4.40 (1.23, 15.77)	ref	0.81 (0.16, 4.03)
≥3.6	193	2.65 (1.17, 6.00)	ref	0.83 (0.31, 2.22)
Total calcium, mg/dL					0.332
<8.5	152	6.16 (1.75, 21.63)	ref	1.46 (0.33, 6.51)
≥8.5	184	2.06 (0.89, 4.756)	ref	0.57 (0.20, 1.59)
Magnesium, mg/dL					0.521
<2	119	2.20 (0.82, 5.91)	ref	0.48 (0.12, 1.84)
≥2	217	4.32 (1.60, 11.64)	ref	1.21 (0.38, 3.82)
SBP, mmHg					0.728
<151	166	3.27 (1.17, 9.18)	ref	1.09 (0.33, 3.57)
≥151	170	2.96 (1.19, 7.32)	ref	0.56 (0.17, 1.93)
DBP, mmHg					0.561
<81	162	2.92 (1.00, 8.55)	ref	1.13 (0.34, 3.69)
≥81	174	3.10 (1.28, 7.48)	ref	0.55 (0.16, 1.87)
MBP, mmHg					0.102
<102	162	2.57 (0.79, 8.35)	ref	1.46 (0.43, 4.98)
≥102	174	3.62 (1.57, 8.34)	ref	0.40 (0.11, 1.50)
HR, beats/min					0.914
<90	162	3.59 (1.12, 11.44)	ref	0.83 (0.21, 3.30)
≥90	174	2.76 (1.19, 6.40)	ref	0.82 (0.29, 2.37)
RR, times/min					0.599
<25	155	3.17 (0.79, 12.68)	ref	0.35 (0.04, 3.40)
≥25	181	2.76 (1.26, 6.03)	ref	0.86 (0.34, 2.15)
Temperature, °C					0.293
<37.28	166	2.22 (0.97, 5.07)	ref	0.79 (0.30, 2.04)
≥37.28	170	5.59 (1.58, 19.82)	ref	0.67 (0.11, 4.03)
SPO2, %					0.853
<92	135	2.41 (0.98, 5.92)	ref	0.65 (0.22, 1.93)
≥92	201	3.63 (1.28, 10.31)	ref	0.87 (0.23, 3.24)

Table 4 Area Under Receiver Operating Characteristic Curve of HCO3⁻ and Severity Scores

Terms	AUC
30-day mortality
HCO3^−	0.69
SAPSII	0.68
OASIS	0.71
SOFA	0.58
SIRS	0.57
90-day mortality
HCO3^−	0.68
SAPSII	0.70
OASIS	0.74
SOFA	0.60
SIRS	0.55
1-year mortality
HCO3^−	0.68
SAPSII	0.71
OASIS	0.72
SOFA	0.64
SIRS	0.56
5-year mortality
HCO3^−	0.60
SAPSII	0.65
OASIS	0.65
SOFA	0.58
SIRS	0.57

Note: P value <0.05.

Abbreviation: AUC, area under curve.