The Rate of Postoperative Mortality and Renal and Respiratory Complications are Increased in Patients with Extreme Obesity Undergoing Cardiac Surgery – A Retrospective Observational Cohort Study of 8848 Patients

Figures & data

Figure 1 Study flowchart.

Notes: Test log rank p=0.019. Blue line is BMI<40, Red Line is BMI≥40.

Table 1 Characteristic of Demographical Data and Medical Data Before Operation

		Group I BMI≥40 (n=112)	Group II BMI<40 (n=8736)	p
Demographic data
Age [years]	Mean±SD	64.07±7.76	65.10±9.68	0.123
BMI [kg/m^2]	Mean±SD	42.13±2.44	28.55±4.23	<0.001
Gender, n (%)	Female	65 (58.04%)	2539 (29.06%)	<0.001
	Male	47 (41.96%)	6197 (70.94%)
Smoking, n (%)	Never smoked	25 (22.32%)	2135 (24.44%)	0.639
	Ex–smoker	74 (66.07%)	5400 (61.82%)
	Current smoker	13 (11.61%)	1200 (13.74%)
Smoking [years], mean±SD		30.38±12.39	32.42±11.55	0.569
Preoperative data
Euro Score Logistic II [%], mean±SD		4.74±5.80	3.93±6.15	<0.001
EF [%], mean±SD		49.43±11.00	48.61±11.58	0.489
PAP, mean±SD		43.17±12.53	45.85±16.34	0.364
Case priority, n (%)	Planned	73 (65.18%)	6228 (71.29%)	0.473
	Accelerated	30 (26.79%)	1924 (22.02%)
	Urgent	8 (7.14%)	469 (5.37%)
	Emergent	1 (0.89%)	115 (1.32%)
Stroke, n (%)		1 (0.89%)	488 (5.59%)	0.051
TIA/RIND, n (%)		3 (2.68%)	131 (1.50%)	0.531
EPI, n (%)		0 (0.00%)	49 (0.56%)	0.878
CCS 4, n (%)		20 (17.86%)	1485 (17.0%)	0.81
NYHA III and IV, n (%)		38 (33.83%)	2626 (30.06%)	0.375
ICA stenosis, n (%)		0 (0.00%)	181 (2.07%)	0.229
ICA occlusion, n (%)		0 (0.00%)	28 (0.332%)	0.805
Carotid artery endarterectomy, n (%)		3 (2.68%)	276 (3.16%)	0.986
Acute renal failure, n (%)		0 (0.00%)	29 (0.33%)	0.825
Chronic renal failure n (%)		13 (11.61%)	611 (6.99%)	0.058
End-stage renal failure (dialysis), n (%)		0 (0.00%)	99 (1.13%)	0.495
Renal transplant, n (%)		0 (0.00%)	11 (0.13%)	0.33
Impaired insulin tolerance, n (%)		2 (1.79%)	273 (3.13%)	0.591
Diabetes on oral medications, n (%)		34 (30.4%)	2624 (30.04%)	0.94
Diabetes on insulin and on oral medications, n (%)		26 (23.21%)	959 (10.98%)	<0.001
Arterial hypertension, n (%)		90 (80.36%)	5964 (68.27%)	0.006
Acute myocardial infarction, n (%)		3 (2.68%)	77 (0.88%)	0.719
Unstable angina, n (%)		29 (25.89%)	1590 (18.20%)	0.049
AF paroxysmal, n (%)		14 (12.50%)	921 (10.54%)	0.503
AF persistent or permanent, n (%)		10 (8.93%)	536 (6.14%)	0.222
Hyperlipidemia, n (%)		48 (42.86%)	3656 (41.85%)	0.829
Thyroid disease, n (%)		10 (8.93%)	738 (8.45%)	0.856
Diseases of the biliary ducts, n (%)		15 (13.39%)	559 (6.40%)	0.003
COPD, n (%)		16 (14.29%)	619 (7.09%)	0.003
Extracardiac arteriopathy, n (%)		16 (14.29%)	1683 (19.27%)	0.184
Gout, hyperuricemia n (%)		10 (8.93%)	359 (4.11%)	0.011
Critical condition on admission, n (%)		1 (0.89%)	131 (1.50%)	0.893
CKMB [I.U./l], mean±SD		26.97±23.50	29.30±54.98	0.712
CRP [mg/l], mean±SD		15.54±42.59	8.96±24.068	0.017
Glycated hemoglobin [%], mean±SD		6.63±1.38	6.05±0.99	<0.001
Creatinine [mg/dl], mean±SD		1.05±0.62	1.03±0.66	0.316
GFR [mL/min/1,73 m2], mean±SD		77.57±22.72	78.76±22.81	0.444

Abbreviations: n, number of patients; SD, standard deviation; BMI, body mass index; EF, ejection fraction; PAP, angio-pulmonary pressure; TIA, transient ischemic attack; RIND, reversible ischemic neurologic deficit; EPI, epilepsy; NYHA, New York Heart Association; ICA, internal carotid artery; CCS, Canadian Cardiovascular Society; AF, atrial fibrillation; COPD, chronic obstructive pulmonary disease; CKMB, phosphocreatine kinase; CRP, C-reactive protein; GFR, glomerular filtration rate.

Table 2 Characteristic of Intra- and Postoperative Data

		Group I BMI≥40 (n=112)	Group II BMI<40 (n=8736)	p
Intraoperative data
CPB time [min], mean±SD		68.26±37.90	68.74±32.63	0.227
Aortic cross-clamping [min], mean±SD		44.32±29.00	44.91±23.85	0.358
Reperfusion time [min], mean±SD		15.96±7.33	17.55±10.99	0.095
Hemofiltration [mL], mean±SD		2136.00±900.4	2046.73±866.89	0.469
Intubation time [min], mean±SD		2946.00±15,740.0	1161.00±3410.0	0.300
Type of surgery	Isolated CABG	70 (62.5%)	5263 (60.24%)	0.628
	CABG+AV	6 (5.36%)	679 (7.77%)	0.342
	CABG+MV	2 (1.79%)	403 (4.61%)	0.155
	CABG+AAA	1 (0.89%)	38 (0.43%)	0.467
	DV	2 (1.79%)	173 (1.98%)	0.883
	AV	12 (10.71%)	711 (8.14%)	0.323
	MV	5 (4.46%)	623 (7.13%)	0.275
	AAA	11 (9.82%)	685 (7.84%)	0.439
	TV	3 (2.68%)	78 (0.89%)	0.141
	Other	0 (0.00%)	83 (0.95%)	0.587
Number of CABG, n (%)	1	8 (9.41%)	524 (7.73%)	0.307
	2	20 (23.53%)	1456 (21.49%)
	3	42 (49.41%)	2857 (42.17%)
	4	15 (17.65%)	1760 (25.98%)
	5	0 (0.00%)	176 (2.60%)
	6	0 (0.00%)	2 (0.03%)
Arterial grafts, mean±SD		1.04±0.26	1.13±0.43	0.323
BIMA, n (%)		0 (0.00%)	421 (6.88%)	0.032
Radial artery, n (%)		1 (0.89%)	189 (2.16%)	0.553
Venous grafts, mean±SD		1.93±0.70	2.11±0.79	0.098
Postoperative data
CKMB [I.U./l], mean±SD		78.64±125.59	76.15±170.77	0.494
RBC [mL], mean±SD		3.05±1.95	3.10±2.56	0.785
Plasma [mL], mean±SD		2.85±0.37	6.33±49.55	0.418
Platelets [mL], mean±SD		370.00±193.5	311.00±179.1	0.330
Drainage [mL], mean±SD		463.53±391.12	521.97±442.09	0.065
CRP after surgery [mg/l], mean±SD	Day 2	64.02±41.74	63.42±39.97	0.911
	Day 4	233.5±110.69	223.64±87.15	0.497
	Day 6	186.81±98.46	162.55±98.38	0.134
	Day 8	144.74±96.68	139.73±93.33	0.769
Highest creatinine [mg/dl], mean±SD		1.50±0.82	1.42±1.03	0.021
Lowest GFR [mL/min/1,73 m2], mean±SD		54.10±25.32	63.09±26.74	0.002
Long stay ICU, mean±SD		10.57±4.54	14.35±16.88	0.428
Long stay hospital, mean±SD		9.19±5.20	9.53±7.86	0.557

Notes: All other cardiac operations (ASD, VSD, pericarditis, tumors, trauma, stab wounds), ICU- intensive care unit.

Abbreviations: n, number of patients; CABG, coronary bypass graft; SD, standard deviation; BMI, body mass index; CPB, cardiopulmonary bypass; CKMB, phosphocreatine kinase; RBC, Red-blood-cell concentrate; CRP, C-reactive protein; GFR, glomerular filtration rate; MV, mitral valve; AV, aortic valve; DV, aortic + mitral valve; AAA, aortic aneurysm; TV, tricuspid valve.

Table 3 Univariate Logistic Regression of Postoperative Complication Depending on Index BMI (Normal, Overweight, Obese)

	Normal (n=1784)		Overweight (n= 3807)		Obese (n=3252)
Cardiac complications
FAP	1.000	–	1.133 (0.976–1.314)	0.100	1.241 (1.067–1.443)	0.005
FAP with positive anamnesis	1.000	–	1.554 (1.086–2.224)	0.016	1.627 (1.131–2.341)	0.009
Neurological complications
Delirium (until the 7th day)	1.000	–	1.078 (0.512–2.270)	0.843	1.098 (0.513–2.350)	0.810
Central nervous system complications	1.000	–	1.010 (0.869–1.174)	0.898	0.955 (0.817–1.116)	0.564
Renal complications
AKIN I (serum creatinine ≥0.3mg/dl)	1.000	-	1.023 (0.877–1.192)	0.775	1.174 (1.005–1.371)	0.043
AKIN II (serum creatinine ≥100%)	1.000	-	0.903 (0.711–1.146)	0.399	1.086 (0.856–1.378)	0.493
AKIN III (serum creatinine ≥200%)	1.000	-	1.180 (0.769–1.813)	0.448	1.325 (0.862–2.037)	0.199
Postoperative hemofiltration	1.000	-	1.410 (1.168–1.703)	<0.001	1.312 (1.083–1.590)	0.005
Pulmonary complications
Pneumonia	1.000	_	1.310 (1.068–1.607)	<0.001	1.161 (0.945–1.427)	0.156
Post operative respiratory failure	1.000	-	1.555 (1.255–1.927)	<0.001	1.321 (1.066–1.639)	0.011
Surgical complications
Wound infection	1.000	-	0.820 (0.240–2.804)	0.754	2.615 (0.888–7.699)	0.081
Mortality
30-day mortality	1.000	-	1.757 (1.407–2.194)	<0.001	1.786 (1.417–2.250)	<0.001
Mortality at equal time of observation (114 days)	1.000	-	1.730 (1.514–1.976)	<0.001	1.538 (1.344–1.761)	<0.001
6-month mortality	1.000	-	0.650 (0.467–0.904)	0.010	0.872 (0.631–1.204)	0.405
1-year mortality	1.000	-	1.242 (0.783–1.969)	0.357	1.564 (0.950–2.576)	0.079
5-year mortality	1.000	-	1.579 (1.287–1.937)	<0.001	1.422 (1.156–1.749)	<0.001
10-year mortality	1.000	-	1.468 (1.095–1.968)	0.010	1.173 (0.878–1.568)	0.281

Notes: Analysis with Index BMI (norm, overweight, obesity), Wounds infection include sternal and saphenous vein infection.

Abbreviations: n, number of patients; AKIN, Acute Kidney Injury Network; FAP, Paroxysmal atrial fibrillation.

Table 4 Logistic Regression of Postoperative Complication Depending on BMI≥40

	BMI≥40
	OR (CI-95% - CI+95%)*	p	OR (CI-95% - CI+95%)**	p
Cardiac complications
FAP	1.002 (0.621–1.615)*	0.995	1.012 (0.562–1.823)**	0.968
FAP with positive anamnesis	0.537 (0.132–2.186)*	0.385	0.429 (0.105–1.757)**	0.239
Neurological complications
Delirium (until the 7th day)	0.906 (0.539–1.523)*	0.708	0.779 (0.460–1.319)**	0.352
Central nervous system complications	1.505 (0.206–10.98)*	0.687	1.057 (0.142–7.848)**	0.957
Renal complications
AKIN I (serum creatinine ≥0.3mg/dl)	1.465 (0.879–2.441)*	0.143	1.498 (0.887–2.530)**	0.131
AKIN II (serum creatinine ≥100%)	2.147 (1.070–4.309)*	0.032	2.082 (1.020–4.250)**	0.044
AKIN III (serum creatinine ≥200%)	2.752 (1.074–7.056)*	0.035	2.743 (1.053–7.140)**	0.039
Postoperative hemofiltration	2.177 (0.296–16.02)*	0.445	1.690 (0.224–12.76)**	0.611
Pulmonary complications
Pneumonia	1.711 (0.609–2.252)*	0.637	1.058 (0.540–2.072)**	0.869
Post operative respiratory failure	2.120 (1.258–3.573)*	0.005	1.760 (1.017–3.045)**	0.043
Surgical complications
Wound infection	2.119 (0.663–6.775)*	0.205	1.650 (0.508–5.361)**	0.405
Mortality
30-day mortality	2.033 (1.109–3.725)*	0.022	1.898 (0.979–3.681)**	0.058
Mortality at equal time of observation (114 days)	1.426 (0.936–2.174)*	0.099	1.336 (0.858–2.079)**	0.200
6-month mortality	0.627 (0.154–2.555)*	0.515	0.467(0.113–1.926)**	0.292
1-year mortality	1.413 (0.345–5.792)*	0.631	1.342 (0.324–5.552)**	0.685
5-year mortality	1.261 (0.656–2.427)*	0.438	1.123 (0.580–2.174)**	0.730
10-year mortality	1.003 (0.367–2.739)*	0.997	0.963 (0.350–2.650)**	0.942

Notes: Wounds infection include sternal and saphenous vein infection. *Model non adjusted. **Model adjusted by Potentially Distorting data: ESL, gender, comorbidities, CRP, and glycated hemoglobin before surgery.

Abbreviations: n, number of patients; AKIN, Acute Kidney Injury Network; FAP, Paroxysmal atrial fibrillation.

Figure 2 Kaplan–Meier curve illustrating the probability of patients’ survival depending on BMI.