ABSTRACT

Background: Infections of the saphenous vein donor site have received very little attention in the surgical literature. Studies have focused on infections of the sternotomy site and mediastinum. At The Toronto Hospital, a 1000 bed tertiary care teaching hospital, we have followed patients with surgical site infections (SSI) and studied the bacteriology of SVDSI for the past 3 years.

Purpose: To describe the basic epidemiology and microbiology of SVDSI in a cohort of cardiovascular patients over a 3 year period at an urban tertiary referral center.

Methods: All patients undergoing cardiovascular surgery from April 1, 1990 through September 17, 1993 were included for analysis. Pacemaker insertions were not included. SVDSI were identified according to the CDC classification of SSI. Patients were evaluated for the presence of infection prospectively form the time they were operated until discharge. There was no post-hospital discharge surveillance. Bacteriology of donor site infections were obtained from a computerized microbiology report.

Results: There were a total of 5,868 cardiovascular operations during this period. There were a total of 327 (5.6%) SSI with SVDSI representing 41% of the total. Few patients developed more than one donor site infection. The pathogens most frequently isolated were coagulase negative Staphylococci (23.6%), followed by Enterococci (15.3%), and Escherichia coli (13.8%). The frequency with which gram-negative bacilli are isolated from SVDSI is not appreciated. The proportion of SVDSI associated with gram-negative organisms was 44.3%.

Conclusion: The descriptive epidemiology and microbiology of SVDSI will lead to better understanding of trends and more timely and appropriate therapeutic management of donor site infections.

INTRODUCTION

Infections of the saphenous vein donor site is one of the complications of coronary artery bypass surgery. Saphenous vein donor site infections (SVDSI) are not as serious as sternotomy site infections. However, there are very few studies focused on the complications of the saphenous vein donor site (2,3,4). The objective of our study was to determine the incidence and bacteriology of SVDSI. At The Toronto Hospital, a 1,000 bed tertiary care teaching hospital, 7,818 cardiovascular surgery were performed over the past 4 years. We have followed patients with surgical site infections (SSI) and studied the basic bacteriology and epidemiology of saphenous vein donor site infections (SVDSI)

METHOD

Patients who underwent cardiovascular surgery from April 1, 1990 through March 31, 1994 were evaluated prospectively for the presence of SVDSI. Patients were followed from the time they were transferred to the cardiac intensive care unit until they were discharged from the hospital. A modified CDC definition [1] of surgical site infection (SSI) was used. A positive culture was not a prerequisite for SVDSI. Heart transplants and pacemaker insertions were not included in our study. Wound cultures were obtained if infection was suspected on the donor site. Bacteriology of donor site infections were generated from a computerized microbiology report. Denominator data were obtained from the operating room computerized surgical record and the cardiovascular surgery service summary of cases compiled by a research nurse. Patients readmitted with SVDSI within 4 weeks after surgery were included but there was no formal posthospital discharge surveillance.

RESULTS

Incidence of SVDSI

Between April 1, 1990 and March 31, 1994 7,818 patients undergone cardiovascular surgery. A total of 369/7,818 (4.7%) surgical site infections were identified. From the total SSI 153/369 (41.5%) infections of the saphenous vein donor site developed in 134 patients. Sixty-nine of the 134 were men and 65 females. A summary of the cardiovascular surgical site infections is shown in Table 1 and Figure 1.

Bacteriology of SVDSI

Saphenous donor site cultures were obtained in 157 cases and 219 organisms were isolated. The pathogens most frequently isolated were coagulase-negative Staphylococci 55/219 (25.1%) followed by Enterococci 33/219 (15.1%) and E. coli (13.7%). The proportion of SVDSI associated with gram-negative bacilli was 45.2%. Details are shown in Tables 2,3 and Figure 2.

DISCUSSION

Data on SVDSI were studied over the past 4 years on patients who had undergone cardiovascular surgery at The Toronto Hospital to determine the incidence rate and bacteriology of donor site infections. There were 153 saphenous vein donor site infections for this time period, corresponding to and overall infection rate of 1.9%. Although previous studies have described the complications of saphenous vein excision [2-4], only small numbers of patients were studied. Our data represented one of the largest series of SVDSI with 134 patients identified with 153 site infections. Few patients had more than one donor site infection. Wound cultures were obtained in 157 instances with 219 organisms isolated. Ten wound cultures had no growth and 9 patients had no wound cultures. The pathogens most commonly isolated from SVDSI were gram-positive with Coagulase-negative Staphylococci and Enterococci isolated most frequently. However, polymicrobial infections (> 2 organisms) were found in almost 40% of cases in our series. The frequent occurrence of the polymicrobial nature of these SVDSI has not been appreciated. Our review of pathogens associated with saphenous site infections may lead to a better understanding of trends and more appropriate therapeutic management of SVDSI.

TABLE 1. CARDIOVASCULAR SURGERY SURGICAL SITE INFECTIONS

	April-March 1990-1991	April -March 1991-1992	April -March 1992-1993	April -March 1993-1994	TOTAL
No. of Operations	1817	2003	2048	1950	7818
No. of Infections	101	89	89	90	369 (4.7%)
No. of Sternum Infections	62 (3.4%)	51(2.5%)	55 (2.7%)	48 (2.5%)	216 (2.8%)
No of SVDSI	39 (2.1%)	38 (1.9%)	34 (1.7%)	42 (2.1%)	153 (1.9%)

TABLE 2. BACTERIOLOGY OF SAPHENOUS VEIN DONOR SITE INFECTION

	April-March 1990-1991	April -March 1991-1992	April -March 1992-1993	April -March 1993-1994	TOTAL
GRAM POSITIVE
Coagulase-neg Staphylococci	16	21	7	11	55
S. aureus	9	6	8	6	29
Enterococci	9	7	10	7	33
GRAM NEGATIVE
E. coli	11	10	2	7	30
Pseudomonas aeruginosa	9	10	4	6	29
Citrobacter diversus	4	0	0	0	4
Enterobacter cloacae	4	1	5	4	14
Enterobacter aerogenes	0	0	2	1	3
Serratia marcescens	1	0	0	0	1
Proteus mirabilis	0	0	3	4	7
Morganella morganii	0	0	1	0	1
Klebsiella pneumoniae	0	0	5	3	8
Acinetobacter baumanni	0	0	2	0	2
Others	0	0	2	1	3
Total	63	55	51	50	219

TABLE 3. SUMMARY OF PATHOGENS ISOLATED FROM SVDSI

NUMBER OF PATIENT CULTURES	157
SINGLE ORGANISM(PURE CULTURE)
GRAM-POSITIVE	47
GRAM-NEGATIVE	40
*TWO ORGANISMS	43
*MORE THAN 2 ORGANISMS	17
NO GROWTH	10
NO CULTURE TAKEN	9

*When there were more than one organism isolate, it was usually a mixture of gram-positive and gram negative

REFERENCES

Garner JS, Jarvis WR, Emori TG, et al. CDC definition for nosocomial infections. Am J Infect Contr 1988;16:128-140.

DeLaria GA, Hunter JA, Goldin MD, et al. Leg wound complications associated with coronary revascularization. J Thorac Cardiovascular Surg 1981:81:403-407.

Lavee G. Schneiderman J, Yorav S, et al. Complications of saphenous vein harvesting following coronary artery bypass surgery. J Cardiovascular Surg Nov-Dec. 1989:30(6):989-91.

Utleg JR, Thomason ME, Wallace DG, et al. Pre-operative correlates of impaired wound healing after saphenous vein excision. J Thorac & Cardiovascular Surg 1989:98(1):147-9.

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