Obesity and Preoperative Anaemia as Independent Risk Factors for Sternal Wound Infection After Coronary Artery Bypass Graft Surgery with Pedicled (Non-Skeletonized) Internal Mammary Arteries: The Role of Thoracic Wall Ischemia?

Figures & data

Table 1 Pre- or Peri-operative Factors Associated with Sternal Wound Infection (SWI) in Univariate Analysis

	All Patients (n=182)	SWI Patients (n=23)	Patients without SWI (n=159)	MD	p
Male gender, n (%)	145 (79.6)	17 (73.9)	128 (80.5)	0	0.42^a
Median age [range] (years)	68.5 [45.0–87.0]	68.0 [47.0–82.0]	69.0 [45.0–87.0]	0	0.72
Diabetes mellitus,n (%)	64 (35.1)	14 (60.8)	50 (31.4)	1	0.003
Arterial hypertension, n (%)	133 (73.0)	19 (82.6)	114 (71.6)	1	0.14
Hypercholesterolemia, n (%)	121 (66.4)	15 (65.2)	106 (66.6)	1	0.88
Active smoking, n (%)	41 (22.5)	5 (21.7)	36 (22.6)	1	0.99^b
Immunodepression, n (%)	68 (37.3)	14 (60.8)	54 (33.9)	1	0.07
Obesity, n (%)	51 (28.0)	12 (52.1)	39 (24.5)	3	0.003
Overweight, n (%)	79 (43.4)	8(34.7)	71 (44.6)	3	0.43
Median BMI [range] (kg/m^2)	27.7 [18.7–50.5]	30.7 [23.0–50.5]	27.5 [18.7–42.4]	3	0.002
Concomitant valve surgery, n (%)	26 (14.2)	3 (13.0)	23 (14.4)	0	0.99^b
Median number of grafts [range]	2.0 [1.0–4.0]	2.0 [2.0–4.0]	2.0 [1.0–4.0]	0	0.48
Bilateral IMA^b grafts, n (%)	138 (75.8)	21 (91.3)	117 (73.5)	0	0.06
Sequential grafts, n (%)	50 (27.4)	4 (17.3)	46 (28.9)	0	0.24
Preoperative anaemia, n (%)	51 (28.0)	11 (47.8)	40 (25.1)	0	0.02
Median preHb^c [range] (g/L)	135.0 [95.0–183.0]	129.0 [95.0–154.0]	137.0 [105.0–183.0]	0	0.004
Median postHb^d [range] (g/L)	115.0 [88.0–149.0]	115.0 [91.0–139.0]	115.0 [88.0–149.0]	0	0.42
Median ΔHb^e [range] (g/L)	−20.0 [−64.0 - +22.0]	−10.0 [−50.0 - +9.0]	−22.0 [−64.0 - +22.0]	0	0.069
Patients transfused with RBC^f, n (%)	131 (71.9)	21 (94.3)	110 (69.1)	0	0.02
Median number of RBC^f units transfused [range] (units)	2.0 [0.0–29.0]	3.0 [0.0–29.0]	2.0 [0.0–13.0]	0	0.001
Median Charlson Index [range]	5.0 [0.0–11.0]	5.0 [2.0–10.0]	5.0 [0.0–11.0]	2	0.19
Median SAPSII^g score[range]	25.0 [12.0–48.0]	24.0 [20.0–39.0]	25.0 [12.0–48.0]	112	0.89
Median ASA score [range]	3.0 [2.0–4.0]	3.0 [2.0–3.0]	3.0 [2.0–4.0]	50	0.59
Median NNIS score [range]	1.0 [0.0–2.0]	1.0 [0.0–2.0]	1.0 [0.0–2.0]	55	0.66
Extracorporeal circulation duration (min)	104.0 [30.0–267.0]	92.5 [56.0–156.0]	104 [30.0–267.0]	3	0.47
Surgery duration (min)	240.0 [100.0–470.0]	240.0 [165.0–300.0]	245.0 [100.0–470.0]	5	0.70

Notes: ^aFischer’s exact test; ^binternal mammary artery; ^cpreoperative haemoglobin value; ^dpostoperative haemoglobin value; ^edelta haemoglobin value defined as the difference between postoperative and preoperative haemoglobin values; ^fred blood cell units transfused during coronary artery bypass graft surgery or in intensive care unit; ^gNew Simplified Acute Physiology Score.

MD, missing data; BMI, body mass index; ASA, American Society of Anesthesiologists Score; NNIS, National Nosocomial Infection Surveillance Score.

Table 2 Pre- or Peri-operative Factors Independently Associated with Sternal Wound Infection in Multivariate Analysis Using a Stepwise Logistic Regression Model

	All Patients (n=182)			Bilateral IMA Patients (n=138)
	OR^b	95% CI^c	P	OR	95% CI	P
Obesity	14.61	[2.64–80.75]	0.002	4.04	[1.26–12.93]	0.01
Preoperative anaemia	4.64	[1.61–13.34]	0.004	5.45	[1.76–16.80]	0.003
Number of RBC units transfused	1.27	[1.02–1.58]	0.03	1.47	[1.09–1.96]	0.009

Abbreviations: CAD, coronary artery disease; CABG, coronary artery bypass graft surgery; SWI, sternal wound infection; CDC, Centre for Disease Control; BMI, body mass index; ARF, acute renal failure; RBC, red blood cell; ICU, intensive care unit; IMA, internal mammary artery grafts; OR, odds ratio; CI, confidence interval.