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Postoperative chest wound infections in patients requiring coronary bypass
Postoperative chest wound infections in patients requiring coronary bypass A controlled study evaluating prophylactic antibiotics A controlled study investigating clean chest wound infections in 904 patients undergoing myocardial revascularization was performed. Four hundred fifty-one patients received systemic antibiotics before and after the operation, and 453 patients received no prophylactic systemic antibiotics. The infection rate was 1.10 per cent and 1.76 per cent, respectively, indicating no statistical difference between the two groups. Preoperative skin preparation and subsequent local antibiotic wound irrigation may be the most important factors in preventing clean wound infection.
R. D. Sutherland, M . D . , H. E. Martinez, M.D., W. A. Guynes, M.D., and LaWayne Miller, B.A., Amarillo, Texas
JLt is generally accepted that patients undergoing cardiac valvular replacement have a decreased incidence of postoperative prosthetic infection or endocarditis when antibiotics are administered preoperatively and postoperatively. In 1973 Engelman and associates 26 reported the incidence of mediastinal wound infection in patients undergoing myocardial revascularization to be 2.7 per cent and the incidence in patients having prosthetic valvular implantation to be 1.4 per cent. All patients in that series received antibiotics preoperatively and postoperatively. The usefulness of prophylactic antibiotics for the prevention of mediastinal wound infection in patients undergoing myocardial revascularization has never been determined. In this study 904 patients were prospectively randomized into two groups, with one group receiving preoperative and postoperative antibiotics and the other group not receiving antibiotics, and the incidence of chest wound infections was analyzed in each group. Methods and patients Over a 44 month period (January, 1973, through August, 1976), 904 patients who had only coronary bypass operations were studied. During the study From the Amarillo Surgical Group, Associated, Amarillo, Texas. Received for publication Nov. 5, 1976. Accepted for publication Feb. 7, 1977.
944
Table I Infections Group
No. ofpts.
No.
%
Antibiotics
I II
451 453
5 8
1.10 1.76
Yes No
period, those patients operated upon by one author (H. E. M.) did not receive prophylactic antibiotics and those operated upon by another (W. A. G.) did receive prophylactic antibiotics. Patients operated upon by a third author (R. D. S.) did not receive antibiotics in 1974 or 1976 but did in 1973 and 1975. Hospital deaths within the first postoperative 48 hours were not included. Approximately one half of the patients (451) received preoperative and postoperative systemic antibiotics (Group I). The remainder (453) did not receive antibiotics (Group II) until an infection became clinically evident and positive wound cultures were obtained. Those patients receiving antibiotics (Group I) were treated the evening before operation and for 4 days postoperatively. The antibiotics utilized were penicillin and methicillin sodium unless there was known penicillin allergy, in which case cephalothin sodium was used. All patients had a hexachlorophene soap shower the night prior to operation and the morning of operation.
Volume 73 Number 6 June, 1977
945
Chest wound infections after coronary bypass
Table II. Clinical summary Pt.
Date of operation
Age, sex
Operation: Vein grafts!IMA
Interval: Op.-Inf. (days)
Patients wit h infections f rom Group I (prophylactic antibiotics) 1. R. J. 4/13/73 61, M 3/0 16 2. C. S. 3. S. P. 4. R. A.
7/17/73 6/9/75 7/20/75
68, M 55, M 53, M
5/0 3/0 3/0
7 15 8
5. T. S.
3/4/76
71, M
4/0
7
Patients wit h infections from Group II (no prophylactic antibiotics) 11/29/73 52, M 1. J. S. 13 4/0 2. 0 . R.
4/26/74
54, M
3/1
11
3. 4. 5. 6. 7. 8.
6/19/74 8/12/74 8/22/74 12/4/74 12/6/74 3/12/76
46, 66, 65, 54, 52, 50,
4/0 3/1 3/0 1/1 3/0 1/0
8 21 8 2 6 7
M. W. P. T. W. D. J. W. J. A. D. M.
M F M M M M
Other complications Stroke, respiratory, failure, sternal dehiscence Stroke
-
Sternal dehiscence CHF, renal failure, groin infection Sternal dehiscence, leg wound infection Respiratory failure, stroke, sternal dehiscence
-
Sternal dehiscence Septicemia, sternal dehiscence Myocardial infarct, low output syndrome, renal failure, respiratory failure, sternal dehiscence
Organism
Result
S. aureus
Died
Pseudomonas E. coli Proteus mirabilis, Aerobacter aerogenes S. aureus, E. coli
Died Recovered Recovered
S. aureus
Recovered
S. albus, Klebsiella
Died
S. aureus S. aureus S. aureus Alpha Streptococcus S. aureus S. albus, Klebsiella, Pseudomonas
Recovered Recovered Recovered Recovered Died Died
Died
Legend: IMA, Internal mammary artery, CHF, Congestive heart failure.
The preoperative preparation in the operating room was a skin wash with trichlorothane (Chlorothane) as a defatting agent and paint with 1 per cent iodine solution. The operative approach was through a median sternotomy incision. Saphenous vein and occasionally the left internal mammary artery were used to construct the bypass conduits. Cardiopulmonary bypass was used in each case with a hemodilution prime, moderate hypothermia (25° to 34° C ) , and a perfusion rate of 2.4 L. per minute per square meter. The mediastinum and pericardium were liberally irrigated with either 2 per cent neomycin solution or 0.4 per cent cephalothin sodium solution prior to wound closure. Mediastinal wound infection was recognized clinically by serous or purulent drainage and occasional wound and sternal dehiscence; the diagnosis was substantiated by positive wound culture. Patients with infections were then treated with appropriate antibiotics, the wound being opened, debrided, and occasionally secondarily closed. Results Thirteen clean chest wound infections occurred in the total 904 patients, 8 of 453 patients not receiving antibiotics and 5 of 451 receiving antibiotics (Table I). A statistical analysis of the incidence of infection in
the two groups shows no statistical difference p = 0.4066). However, a much greater variety of bacterial organisms was found in patients receiving antibiotics (Group I) than in those not receiving antibiotics (Group II). The Group II patients all had staphylococcal infections except one patient with streptococcal cellulitis (Table II). Of all the patients with infections, one had diabetes, one was operated upon on an emergency basis, and one patient was returned to the operating room for bleeding. All of these patients had received prophylactic antibiotics. Analysis of Table II shows there is no appreciable difference among patients with infections regarding age, sex, number of bypass grafts, and interval between operation and diagnosis of the infection. One patient in Group I and 2 patients in Group II required prolonged ventilator support. In each of these cases, sternal dehiscence and associated wound separation preceded the appearance of the wound infection. It is questionable whether these patients should be included in the total series, as the wounds were probably secondarily infected. These 3 patients with the combination of respiratory failure and mediastinal wound infection all died, indicating the poor prognostic outlook with this particular combination of events. The wound infection always appeared after the sixth
The Journal of Thoracic and Cardiovascular Surgery
94 6 Sutherland et al.
postoperative day and as late as the twenty-first day, regardless of the infecting organism, except in one case of severe streptococcal cellulitis which was apparent on the second postoperative day. In comparing all of the patients with infections to those without infections in both groups, we found no significance regarding duration of operation, time on cardiopulmonary bypass, postoperative bleeding, postoperative low output syndrome, number of bypass grafts inserted, and use of the mammary artery. All patients who postoperatively had concurrent infections, i.e., urinary tract, pneumonia, leg incisions, or occasionally fever of unknown origin, were treated with appropriate antibiotics, but we do not think these infections influenced the mediastinal wound. Discussion The surgical literature regarding the use of prophylactic antibiotics for the prevention of wound infections contains studies in gynecology,1 colon surgery, 2,3 ' 9 thoracic surgery, 4,6 hip fractures,5 biliary surgery,7, 10, n penetrating wounds of the abdomen,8 cancer surgery,12, 13 vascular surgery,14, 1S and general surgery. 16-23 There is general agreement on the use of prophylactic antibiotics in patients receiving cardiac valvular prostheses 24,25 to prevent prosthetic endocarditis. The incidence of mediastinal wound infection in patients undergoing all types of cardiac surgery has been presented in an excellent study by Engelman and associates.26 In that series the incidence of mediastinitis was 0.7 per cent in patients having repair of congenital heart defects, 1.4 per cent in patients having valvular replacement, and 2.7 per cent in patients having coronary bypass operations. All patients in that study received prophylactic antibiotics. We are unable to find any other reported series of chest wound infections in patients having myocardial revascularization. In the two groups reported herein, the incidence of mediastinal wound infection is less than 2 per cent whether or not the patients received prophylactic antibiotics. Those patients receiving antibiotics had a variety of infective organisms, and almost all of those not receiving antibiotics had Staphylococcus aureus infections. The combination of respiratory failure with prolonged ventilator support, subsequent sternal dehiscence, and wound infection was uniformly fatal. We found no evidence that other factors commonly thought to predispose to wound infection were significant. These factors include emergency operation, re-exploration for bleeding, diabetes, excessive postoperative bleeding, low output syndrome, and
prolonged operative time. Our routine of preparing the skin preoperatively with hexachlorophene soap shower, wash with trichlorothane (chlorothane), paint with 1 per cent iodine, and liberal irrigation of the mediastinum with either 2 per cent neomycin solution or 0.4 per cent cephalothin sodium solution prior to closure is probably of more benefit in maintaining a clean wound than pre- and postoperative systemic antibiotic therapy. Conclusions 1. Use of prophylactic antibiotics in patients having only myocardial revascularization does not change the incidence of chest wound infections but does alter the type of infecting organism. 2. In this study, diabetes, postoperative bleeding, low output syndrome, prolonged operative time, use of internal mammary artery, emergency procedures, and concurrent infections such as leg incisions, pneumonia, or urinary tract infections did not predispose to chest wound infection. 3. Any adequate preoperative skin preparation and local antibiotic wound irrigation may be the most important factors in preventing clean wound infections. Addendum Since completion of this study, we have performed coronary bypass procedures on 205 patients. Thirty patients received pre- and postoperative systemic antibiotics, with no chest wound infections, and 175 patients did not receive systemic antibiotics, with one clean chest wound infection (Staphylococcus aureus). Thanks to Miguel Tarrab, Professor of Mathematics and Statistics, West Texas State University, Canyon, Texas, for the statistical analysis of the data presented in this paper. REFERENCES 1 Allen, J. L., Rampone, J. F., and Wheeless, C. R.: Use of a Prophylactic Antibiotic in Elective Major Gynecologic Operations, Obstet. Gynecol. 39: 218, 1972. 2 Altemeier, W. A., Hummel, R. P., and Hill, E. O.: Prevention of Infection in Colon Surgery, Arch. Surg. 93: 226, 1966. 3 Azar, H., and Drapanas, T.: Relationship of Antibiotics to Wound Infection and Enterocolitis in Colon Surgery, Am. J. Surg. 115: 209, 1968. 4 Bhayana, J. N., Gillespie, J. F., Nolan, J. J., and Ashburn, F. S.: Prophylactic Antibiotics in Thoracic Surgery, J. THORAC. CARDIOVASC. SURG. 50: 868,
1965.
5 Boyd, R. J., Burke, J. F., and Colton, T.: A DoubleBlind Clinical Trial of Prophylactic Antibiotics in Hip Fractures, J. Bone Joint Surg. 55-A: 1251, 1973.
Volume 73 Number 6 June, 1977
6 Bryant, L. R., Dillon, M. L., and Mobin-Uddin, K.: Prophylactic Antibiotics in Noncardiac Thoracic Operations, Ann. Thorac. Surg. 19: 670, 1975. 7 Cheltin, S. H., and Elliott, D. W.: Preoperative Antibiotics in Biliary Surgery, Arch. Surg. 107: 319, 1973. 8 Fullen, W. D., Hunt, J., and Altemeier, W. A.: Prophylactic Antibiotics in Penetrating Wounds of the Abdomen, J. Trauma 12: 282, 1972. 9 Hughes, E. S. R., Hardy, K. J., Culbertson, A. M., and Rubbo, S. D.: Chemoprophylaxis in Large Bowel Surgery: Effect of Intravenous Administration of Penicillin on Incidence of Postoperative Infection, Med. J. Aust. 1: 305, 1970. 10 Keighley, M. R. B., Boddeley, R. M., Burdon, D. W., Edwards, J. A. C , Quoraishi, A. H., Oates, G. D., Watts, G. T., and Alexander-Williams, J.: A Controlled Trial of Parenteral Prophylactic Gentamycin Therapy in Biliary Surgery, Br. J. Surg. 62: 275, 1975. 11 Keighley, M. R. B., Drysdale, R. B., Quoraishi, A. H., Burdon, D. W., and Alexander-Williams, J.: Antibiotic Treatment of Biliary Sepsis, Surg. Clin. North Am. 55: 1379, 1975. 12 Ketcham, A. S., Bloch, J. H., Crawford, D. T., Liberman, J. E., and Smith, R. R.: The Role of Prophylactic Antibiotic Therapy in Control of Staphylococcal Infections Following Cancer Surgery, Surg. Gynecol. Obstet. 114: 345, 1962. 13 Ketcham, A. S., Lieberman, J. E., and West, J. T.: Antibiotic Prophylaxic in Cancer Surgery and its Value in Staphylococcal Carrier Patients, Surg. Gynecol. Obstet. 117: 1, 1963. 14 Lennihan, R.: Prophylactic Antibiotics in Arterial Surgery: A Personal Experience Covering 218 Operations, Del. Med. J. 45: 31, 1973.
Chest wound infections after coronary bypass
94 7
15 Moore, W. S., Rosson, C. T., and Hall, A. D.: Effect of Prophylactic Antibiotics in Preventing Bacteremic Infection of Vascular Prosthesis, Surgery 69: 825, 1971. 16 Armstrong Smith, R.: Prophylactic Antibiotics in Surgery, Clin. Bull. 4: 97, 1974. 17 Barnes, J., Pace, W. G., Trump, D. S., and Ellison, E. H.: Prophylactic Postoperative Antibiotics: A Controlled Study of 1,007 Cases, Arch. Surg. 79: 190, 1959. 18 Burke, J. F.: Use of Preventive Antibiotics in Clinical Surgery, Am. Surg. 39: 6, 1973. 19 Condon, R. E.: Rational Use of Prophylactic Antibiotics in Gastrointestinal Surgery, Surg. Clin. North Am. 55: 1309, 1975. 20 Cruse, P. J. E., and Foord, R.: A Five-Year Prospective Study of 23,649 Surgical Wounds, Arch. Surg. 107: 206, 1973. 21 Johnstone, F. R. C : An Assessment of Prophylactic Antibiotics in General Surgery, Surg. Gynecol. Obstet. 116: 1, 1963. 22 Karl, R. C , Mertz, J. J., Veith, F. J., and Dineen, P.: Prophylactic Antimicrobial Drugs in Surgery, N. Engl. J. Med. 275: 305, 1966. 23 MacLean, L. D.: Prophylactic Antibiotic Therapy in Surgery, Can. J. Surg. 18: 243, 1975. 24 Slaughter, L., Morris, J. E., and Starr, A.: Prosthetic Valvular Endocarditis: A 12-Year Review, Circulation 47: 1319, 1973. 25 Sabiston, D. C , Jr., and Spencer, F. C : Gibbon's Surgery of the Chest, ed. 3, Philadelphia, 1976, W. B. Saunders Company, pp. 1211-1219. 26 Engelman, R. M., Williams, C. D., Gouge, T. H., Chase, R. M., Jr., Falk, E. A., Boyd, A. D., and Reed, G. E.: Mediastinitis Following Open-Heart Surgery, Arch. Surg. 107: 772, 1973.
R. D. Sutherland, M . D . , H. E. Martinez, M.D., W. A. Guynes, M.D., and LaWayne Miller, B.A., Amarillo, Texas
JLt is generally accepted that patients undergoing cardiac valvular replacement have a decreased incidence of postoperative prosthetic infection or endocarditis when antibiotics are administered preoperatively and postoperatively. In 1973 Engelman and associates 26 reported the incidence of mediastinal wound infection in patients undergoing myocardial revascularization to be 2.7 per cent and the incidence in patients having prosthetic valvular implantation to be 1.4 per cent. All patients in that series received antibiotics preoperatively and postoperatively. The usefulness of prophylactic antibiotics for the prevention of mediastinal wound infection in patients undergoing myocardial revascularization has never been determined. In this study 904 patients were prospectively randomized into two groups, with one group receiving preoperative and postoperative antibiotics and the other group not receiving antibiotics, and the incidence of chest wound infections was analyzed in each group. Methods and patients Over a 44 month period (January, 1973, through August, 1976), 904 patients who had only coronary bypass operations were studied. During the study From the Amarillo Surgical Group, Associated, Amarillo, Texas. Received for publication Nov. 5, 1976. Accepted for publication Feb. 7, 1977.
944
Table I Infections Group
No. ofpts.
No.
%
Antibiotics
I II
451 453
5 8
1.10 1.76
Yes No
period, those patients operated upon by one author (H. E. M.) did not receive prophylactic antibiotics and those operated upon by another (W. A. G.) did receive prophylactic antibiotics. Patients operated upon by a third author (R. D. S.) did not receive antibiotics in 1974 or 1976 but did in 1973 and 1975. Hospital deaths within the first postoperative 48 hours were not included. Approximately one half of the patients (451) received preoperative and postoperative systemic antibiotics (Group I). The remainder (453) did not receive antibiotics (Group II) until an infection became clinically evident and positive wound cultures were obtained. Those patients receiving antibiotics (Group I) were treated the evening before operation and for 4 days postoperatively. The antibiotics utilized were penicillin and methicillin sodium unless there was known penicillin allergy, in which case cephalothin sodium was used. All patients had a hexachlorophene soap shower the night prior to operation and the morning of operation.
Volume 73 Number 6 June, 1977
945
Chest wound infections after coronary bypass
Table II. Clinical summary Pt.
Date of operation
Age, sex
Operation: Vein grafts!IMA
Interval: Op.-Inf. (days)
Patients wit h infections f rom Group I (prophylactic antibiotics) 1. R. J. 4/13/73 61, M 3/0 16 2. C. S. 3. S. P. 4. R. A.
7/17/73 6/9/75 7/20/75
68, M 55, M 53, M
5/0 3/0 3/0
7 15 8
5. T. S.
3/4/76
71, M
4/0
7
Patients wit h infections from Group II (no prophylactic antibiotics) 11/29/73 52, M 1. J. S. 13 4/0 2. 0 . R.
4/26/74
54, M
3/1
11
3. 4. 5. 6. 7. 8.
6/19/74 8/12/74 8/22/74 12/4/74 12/6/74 3/12/76
46, 66, 65, 54, 52, 50,
4/0 3/1 3/0 1/1 3/0 1/0
8 21 8 2 6 7
M. W. P. T. W. D. J. W. J. A. D. M.
M F M M M M
Other complications Stroke, respiratory, failure, sternal dehiscence Stroke
-
Sternal dehiscence CHF, renal failure, groin infection Sternal dehiscence, leg wound infection Respiratory failure, stroke, sternal dehiscence
-
Sternal dehiscence Septicemia, sternal dehiscence Myocardial infarct, low output syndrome, renal failure, respiratory failure, sternal dehiscence
Organism
Result
S. aureus
Died
Pseudomonas E. coli Proteus mirabilis, Aerobacter aerogenes S. aureus, E. coli
Died Recovered Recovered
S. aureus
Recovered
S. albus, Klebsiella
Died
S. aureus S. aureus S. aureus Alpha Streptococcus S. aureus S. albus, Klebsiella, Pseudomonas
Recovered Recovered Recovered Recovered Died Died
Died
Legend: IMA, Internal mammary artery, CHF, Congestive heart failure.
The preoperative preparation in the operating room was a skin wash with trichlorothane (Chlorothane) as a defatting agent and paint with 1 per cent iodine solution. The operative approach was through a median sternotomy incision. Saphenous vein and occasionally the left internal mammary artery were used to construct the bypass conduits. Cardiopulmonary bypass was used in each case with a hemodilution prime, moderate hypothermia (25° to 34° C ) , and a perfusion rate of 2.4 L. per minute per square meter. The mediastinum and pericardium were liberally irrigated with either 2 per cent neomycin solution or 0.4 per cent cephalothin sodium solution prior to wound closure. Mediastinal wound infection was recognized clinically by serous or purulent drainage and occasional wound and sternal dehiscence; the diagnosis was substantiated by positive wound culture. Patients with infections were then treated with appropriate antibiotics, the wound being opened, debrided, and occasionally secondarily closed. Results Thirteen clean chest wound infections occurred in the total 904 patients, 8 of 453 patients not receiving antibiotics and 5 of 451 receiving antibiotics (Table I). A statistical analysis of the incidence of infection in
the two groups shows no statistical difference p = 0.4066). However, a much greater variety of bacterial organisms was found in patients receiving antibiotics (Group I) than in those not receiving antibiotics (Group II). The Group II patients all had staphylococcal infections except one patient with streptococcal cellulitis (Table II). Of all the patients with infections, one had diabetes, one was operated upon on an emergency basis, and one patient was returned to the operating room for bleeding. All of these patients had received prophylactic antibiotics. Analysis of Table II shows there is no appreciable difference among patients with infections regarding age, sex, number of bypass grafts, and interval between operation and diagnosis of the infection. One patient in Group I and 2 patients in Group II required prolonged ventilator support. In each of these cases, sternal dehiscence and associated wound separation preceded the appearance of the wound infection. It is questionable whether these patients should be included in the total series, as the wounds were probably secondarily infected. These 3 patients with the combination of respiratory failure and mediastinal wound infection all died, indicating the poor prognostic outlook with this particular combination of events. The wound infection always appeared after the sixth
The Journal of Thoracic and Cardiovascular Surgery
94 6 Sutherland et al.
postoperative day and as late as the twenty-first day, regardless of the infecting organism, except in one case of severe streptococcal cellulitis which was apparent on the second postoperative day. In comparing all of the patients with infections to those without infections in both groups, we found no significance regarding duration of operation, time on cardiopulmonary bypass, postoperative bleeding, postoperative low output syndrome, number of bypass grafts inserted, and use of the mammary artery. All patients who postoperatively had concurrent infections, i.e., urinary tract, pneumonia, leg incisions, or occasionally fever of unknown origin, were treated with appropriate antibiotics, but we do not think these infections influenced the mediastinal wound. Discussion The surgical literature regarding the use of prophylactic antibiotics for the prevention of wound infections contains studies in gynecology,1 colon surgery, 2,3 ' 9 thoracic surgery, 4,6 hip fractures,5 biliary surgery,7, 10, n penetrating wounds of the abdomen,8 cancer surgery,12, 13 vascular surgery,14, 1S and general surgery. 16-23 There is general agreement on the use of prophylactic antibiotics in patients receiving cardiac valvular prostheses 24,25 to prevent prosthetic endocarditis. The incidence of mediastinal wound infection in patients undergoing all types of cardiac surgery has been presented in an excellent study by Engelman and associates.26 In that series the incidence of mediastinitis was 0.7 per cent in patients having repair of congenital heart defects, 1.4 per cent in patients having valvular replacement, and 2.7 per cent in patients having coronary bypass operations. All patients in that study received prophylactic antibiotics. We are unable to find any other reported series of chest wound infections in patients having myocardial revascularization. In the two groups reported herein, the incidence of mediastinal wound infection is less than 2 per cent whether or not the patients received prophylactic antibiotics. Those patients receiving antibiotics had a variety of infective organisms, and almost all of those not receiving antibiotics had Staphylococcus aureus infections. The combination of respiratory failure with prolonged ventilator support, subsequent sternal dehiscence, and wound infection was uniformly fatal. We found no evidence that other factors commonly thought to predispose to wound infection were significant. These factors include emergency operation, re-exploration for bleeding, diabetes, excessive postoperative bleeding, low output syndrome, and
prolonged operative time. Our routine of preparing the skin preoperatively with hexachlorophene soap shower, wash with trichlorothane (chlorothane), paint with 1 per cent iodine, and liberal irrigation of the mediastinum with either 2 per cent neomycin solution or 0.4 per cent cephalothin sodium solution prior to closure is probably of more benefit in maintaining a clean wound than pre- and postoperative systemic antibiotic therapy. Conclusions 1. Use of prophylactic antibiotics in patients having only myocardial revascularization does not change the incidence of chest wound infections but does alter the type of infecting organism. 2. In this study, diabetes, postoperative bleeding, low output syndrome, prolonged operative time, use of internal mammary artery, emergency procedures, and concurrent infections such as leg incisions, pneumonia, or urinary tract infections did not predispose to chest wound infection. 3. Any adequate preoperative skin preparation and local antibiotic wound irrigation may be the most important factors in preventing clean wound infections. Addendum Since completion of this study, we have performed coronary bypass procedures on 205 patients. Thirty patients received pre- and postoperative systemic antibiotics, with no chest wound infections, and 175 patients did not receive systemic antibiotics, with one clean chest wound infection (Staphylococcus aureus). Thanks to Miguel Tarrab, Professor of Mathematics and Statistics, West Texas State University, Canyon, Texas, for the statistical analysis of the data presented in this paper. REFERENCES 1 Allen, J. L., Rampone, J. F., and Wheeless, C. R.: Use of a Prophylactic Antibiotic in Elective Major Gynecologic Operations, Obstet. Gynecol. 39: 218, 1972. 2 Altemeier, W. A., Hummel, R. P., and Hill, E. O.: Prevention of Infection in Colon Surgery, Arch. Surg. 93: 226, 1966. 3 Azar, H., and Drapanas, T.: Relationship of Antibiotics to Wound Infection and Enterocolitis in Colon Surgery, Am. J. Surg. 115: 209, 1968. 4 Bhayana, J. N., Gillespie, J. F., Nolan, J. J., and Ashburn, F. S.: Prophylactic Antibiotics in Thoracic Surgery, J. THORAC. CARDIOVASC. SURG. 50: 868,
1965.
5 Boyd, R. J., Burke, J. F., and Colton, T.: A DoubleBlind Clinical Trial of Prophylactic Antibiotics in Hip Fractures, J. Bone Joint Surg. 55-A: 1251, 1973.
Volume 73 Number 6 June, 1977
6 Bryant, L. R., Dillon, M. L., and Mobin-Uddin, K.: Prophylactic Antibiotics in Noncardiac Thoracic Operations, Ann. Thorac. Surg. 19: 670, 1975. 7 Cheltin, S. H., and Elliott, D. W.: Preoperative Antibiotics in Biliary Surgery, Arch. Surg. 107: 319, 1973. 8 Fullen, W. D., Hunt, J., and Altemeier, W. A.: Prophylactic Antibiotics in Penetrating Wounds of the Abdomen, J. Trauma 12: 282, 1972. 9 Hughes, E. S. R., Hardy, K. J., Culbertson, A. M., and Rubbo, S. D.: Chemoprophylaxis in Large Bowel Surgery: Effect of Intravenous Administration of Penicillin on Incidence of Postoperative Infection, Med. J. Aust. 1: 305, 1970. 10 Keighley, M. R. B., Boddeley, R. M., Burdon, D. W., Edwards, J. A. C , Quoraishi, A. H., Oates, G. D., Watts, G. T., and Alexander-Williams, J.: A Controlled Trial of Parenteral Prophylactic Gentamycin Therapy in Biliary Surgery, Br. J. Surg. 62: 275, 1975. 11 Keighley, M. R. B., Drysdale, R. B., Quoraishi, A. H., Burdon, D. W., and Alexander-Williams, J.: Antibiotic Treatment of Biliary Sepsis, Surg. Clin. North Am. 55: 1379, 1975. 12 Ketcham, A. S., Bloch, J. H., Crawford, D. T., Liberman, J. E., and Smith, R. R.: The Role of Prophylactic Antibiotic Therapy in Control of Staphylococcal Infections Following Cancer Surgery, Surg. Gynecol. Obstet. 114: 345, 1962. 13 Ketcham, A. S., Lieberman, J. E., and West, J. T.: Antibiotic Prophylaxic in Cancer Surgery and its Value in Staphylococcal Carrier Patients, Surg. Gynecol. Obstet. 117: 1, 1963. 14 Lennihan, R.: Prophylactic Antibiotics in Arterial Surgery: A Personal Experience Covering 218 Operations, Del. Med. J. 45: 31, 1973.
Chest wound infections after coronary bypass
94 7
15 Moore, W. S., Rosson, C. T., and Hall, A. D.: Effect of Prophylactic Antibiotics in Preventing Bacteremic Infection of Vascular Prosthesis, Surgery 69: 825, 1971. 16 Armstrong Smith, R.: Prophylactic Antibiotics in Surgery, Clin. Bull. 4: 97, 1974. 17 Barnes, J., Pace, W. G., Trump, D. S., and Ellison, E. H.: Prophylactic Postoperative Antibiotics: A Controlled Study of 1,007 Cases, Arch. Surg. 79: 190, 1959. 18 Burke, J. F.: Use of Preventive Antibiotics in Clinical Surgery, Am. Surg. 39: 6, 1973. 19 Condon, R. E.: Rational Use of Prophylactic Antibiotics in Gastrointestinal Surgery, Surg. Clin. North Am. 55: 1309, 1975. 20 Cruse, P. J. E., and Foord, R.: A Five-Year Prospective Study of 23,649 Surgical Wounds, Arch. Surg. 107: 206, 1973. 21 Johnstone, F. R. C : An Assessment of Prophylactic Antibiotics in General Surgery, Surg. Gynecol. Obstet. 116: 1, 1963. 22 Karl, R. C , Mertz, J. J., Veith, F. J., and Dineen, P.: Prophylactic Antimicrobial Drugs in Surgery, N. Engl. J. Med. 275: 305, 1966. 23 MacLean, L. D.: Prophylactic Antibiotic Therapy in Surgery, Can. J. Surg. 18: 243, 1975. 24 Slaughter, L., Morris, J. E., and Starr, A.: Prosthetic Valvular Endocarditis: A 12-Year Review, Circulation 47: 1319, 1973. 25 Sabiston, D. C , Jr., and Spencer, F. C : Gibbon's Surgery of the Chest, ed. 3, Philadelphia, 1976, W. B. Saunders Company, pp. 1211-1219. 26 Engelman, R. M., Williams, C. D., Gouge, T. H., Chase, R. M., Jr., Falk, E. A., Boyd, A. D., and Reed, G. E.: Mediastinitis Following Open-Heart Surgery, Arch. Surg. 107: 772, 1973.