Antibiotic prophylaxis for coronary bypass grafting

Cephradine and cefazolin plasma levels during cardiac surgery

A prospective, randomized, double-blind study was carried out to evaluate two prophylactic regimes in patients undergoing cardiac surgery with cardiopulmonary bypass. Antibiotic plasma levels were measured in fifty consecutive adult patients undergoing valve and coronary surgery. They were divided into two comparable groups of 25 patients, each matched in age, sex, type of operation and duration of cardiopulmonary bypass. Group 1 received 1 g of cephradine with the anaesthetic premedication, 1 g in the prime of the oxygenator and 1 g every six hours during the first 72 hours of the postoperative course. Group 2 received cefazolin following the same protocol except that they received 1 g every eight hours during the postoperative course.

There were no allergic or toxic reactions and no infections up to two months follow-up in both groups. Antibiotic plasma levels were significantly higher (p < 0·001) in the cefazolin group in four out of five sampling periods. Antibiotic plasma levels for group 1 versus group 2 were as follows: initial level 11·7 ± 5.2 mcg/ml vs 31 4 ± 35·4 mcg/ml. During cardiopulmonary bypass 26·6 ± 9·5 mcg/ml vs 51·7 ± 21 ·1 mcg/ml. Final levels 13·6 ± 7·0 mcg/ml vs 32·2 ± 17·8 mcg/ml. Baseline levels 2·7 ± 2·3 mcg/ml vs 6·· ± 7·7 mcg/ml and peak level 44·0 ± 16·2 mcg/ml vs 51·2 ± 23·4 mcg/ml (NS). The results of this study demonstrate that cefazolin achieved significantly higher plasma levels during the different phases of the operation and early postoperative period. Also, cefazolin and cephradine levels are above the minimal inhibitory concentrations for the gram positive and gram negative susceptible bacteria, except for the basal levels obtained by cephradine. The favourable pharmacokinetic characteristics of cefazolin, makes it a good choice for prophylactic use during cardiac surgery.

Intra-aortic balloon counterpulsation: outcome in cardiac surgical patients

OBJECTIVE

To identify the major determinants of survival and nonsurvival for patients in need of intra-aortic balloon pump (IABP) support after cardiac surgery and to define the role of ventilator-associated pneumonia.

DESIGN

Retrospective study.

SETTING

University and general hospital.

PARTICIPANTS

A total of 105 consecutive patients undergoing cardiac surgery requiring IABP support and prolonged mechanical ventilation for >24 hours.

INTERVENTION

All patients were assigned into 1 of 2 groups: survival (n = 69) and nonsurvival (n = 36).

MEASUREMENTS AND MAIN RESULTS

Differences between the survival and nonsurvival groups were tested with the Student's t-test, chi-square test, and frequency analysis. The overall survival rate was 65.7%. Nonsurvivors (34.3%) had higher rates of acute myocardial infarction (27.7% v 4.3%; p < 0.002), Canadian Cardiovascular Society functional class III and IV (44.4% and 13.8%; p < 0.001), and depressed left ventricular ejection fraction (31.3 +/- 6.4% v 42.4 +/- 7.2%; p < 0.001). The nonsurvival group had longer duration of cardiopulmonary bypass (165 +/- 74.3 minutes v 135 +/- 36 minutes; p < 0.006) and aortic occlusion (81.8 +/- 9 minutes v 68.6 +/- 25.7 minutes; p < 0.004). In the nonsurvival group, 21 patients were not weaned from the IABP, and 15 patients were weaned from the IABP but died from renal failure (26.6%), multiorgan failure (13.3%), infection, and respiratory failure (66.6%). In the nonsurvival group, mechanical ventilation time was longer in patients weaned from the IABP.

CONCLUSION

These data suggest that for patients not weaned from the IABP, the major determinants of death are low cardiac output (33.3%) and multiorgan failure (47.6%). Patients with a left ventricular ejection fraction of <30% have a poorer outcome. In patients weaned from the IABP, ventilator-associated pneumonia (66.6%) was the major cause of death.

Pneumonia after cardiac surgery is predictable by tracheal aspirates but cannot be prevented by prolonged antibiotic prophylaxis

BACKGROUND

The purpose of this study was to assess the value of tracheal aspirate as a predictor of pneumonia after coronary artery bypass grafting and to evaluate the efficacy of prolonged perioperative antibiotic prophylaxis.

METHODS

Tracheal aspirates of 500 patients undergoing coronary artery bypass grafting were taken immediately after intubation and analyzed for microorganisms by Gram stain and semiquantitative microbiologic cultures. All patients received 2 g ceftriaxone as a single-dose perioperative antibiotic prophylaxis before operation. Results of Gram stains were available before the patients were transferred to the intensive care unit. After the results were known, both groups of patients (positive Gram stain, group 1; negative Gram stain, group 2) were randomly assigned to either conventional antibiotic prophylaxis (A), consisting of ceftriaxone 2 g on postoperative day 1, or prolonged antibiotic prophylaxis (B), with ticarcillin + clavulanic acid 3 x 5.2 g during 72 hours.

RESULTS

From 500 patients, 91 had a positive Gram stain whereas 409 had a negative one. The incidence of pneumonia was significantly higher in patients with preoperative positive tracheal aspirates (15.3%) than in patients with a negative one (3.6%; p < 0.01). However, prolonged prophylaxis did not reduce the rate of postoperative pneumonia, which was as high as 13% in untreated positive patients versus 17% in treated positive patients, and 2% in untreated negative patients versus 4% in treated patients. In patients who had pneumonia, there was a high correlation between the microorganisms found in preoperative aspirates and those observed when aspirates were repeated (100% correlation in patients with conventional antibiotic prophylaxis and 87% in those with prolonged prophylaxis).

CONCLUSIONS

Early postoperative pneumonia (<7 days) is most likely caused by microorganisms that colonize the respiratory tract before operation. The risk of pulmonary infection after coronary artery bypass grafting can be predicted from the preoperative tracheal aspirates. Prolonged perioperative antibiotic prophylaxis has no efficacy in reducing the incidence of pulmonary infections.

Cardiac surgery in a high-risk group of patients: is prolonged postoperative antibiotic prophylaxis effective?

OBJECTIVE

In a prospective, randomized study, postoperatively prolonged antibiotic prophylaxis is evaluated in a high-risk group of patients undergoing cardiac operations. These patients had postoperative low cardiac output necessitating inotropic support and intraaortic balloon pumping.

METHODS

Between January 1991 and 1994, 53 patients were enrolled in the study (42 men, mean age 65 years). All patients received the usual perioperative (24 hours) cefazolin prophylaxis. In the study group (n = 28) a prolonged regimen of prophylaxis with ticarcillin/clavulanate was performed for 2 days and vancomycin was added in a low dose until removal of the intraaortic balloon pump. The control group (n = 25) did not receive a prolonged regimen of prophylaxis. Follow-up ended at hospital discharge.

RESULTS

Early mortality was 7 of 28 patients (25%) in the prophylaxis group and 8 of 25 patients (32%) in the control group (p = 0.397). Defined infections (pneumonia, n = 22; sepsis, n = 8; deep sternal wound infection, n = 2) occurred in 50% of the study group and 68% of the control group (p = 0.265). In all patients with septicemia, only coagulase-negative staphylococci could be isolated from the bloodstream (5 patients in the prophylaxis group vs 3 in the control group). Infectious parameters were controlled daily and did not differ significantly between groups. A total of 1158 bacteriologic tests were performed (blood cultures, n = 389; intravascular catheters, n = 208; bronchial aspirates, n = 411; intraaortic balloon pumps, n = 42; wound secretions, n = 108) showing bacterial growth in 322 (28%) without a significant difference between the groups. In the prophylaxis group, 13 intravascular catheters and intraaortic balloon pumps showed bacterial growth versus 11 in the control group. No side effects were seen.

CONCLUSIONS

In a high-risk group of patients undergoing cardiac operations, infectious outcome could not be effectively influenced by an additional and prolonged postoperative prophylaxis regimen with low-dose vancomycin and ticarcillin/clavulanate. Low-dose vancomycin did not reduce the rate of infections or colonizations of intravascular catheters with gram-positive organisms.

The risk factors of median sternotomy infection: a current review

Sternal sepsis following median sternotomy is an infrequent yet devastating complication of cardiac surgery, leading to prolonged hospitalization, increased hospital expense, and a high associated morbidity and mortality. The development of sternotomy infection is multifactorial. Numerous prospective and retrospective studies have pointed to a multitude of clinical and perioperative variables as being causative, with as many other studies presenting evidence of the contrary. This has led to confusion about which clinical variables should be modified so as to minimize the individual patient's risk for developing this severe complication. Other less obvious factors also come into play. Malnutrition, whether overt or subclinical, is not uncommon in cardiac patients. Immune competency is affected by operative trauma, as well as a variety of perioperative factors including underlying nutritional status, transfusion, cardiopulmonary bypass, and anesthesia. This creates a complex milieu for the development of postoperative infection. In this review, the multiple risk factors of median sternotomy infection are studied and treatment options briefly discussed.

Antimicrobial prophylaxis in coronary bypass surgery: a critical appraisal

The literature has been examined to assess the optimal prophylactic antimicrobial regimen for patients undergoing coronary bypass surgery. Antimicrobial surgical prophylaxis should be based on the two main potential pathogens, Staphylococcus epidermidis and S. aureus. It is unclear whether the prophylactic use of antimicrobials can or should be guided by in vitro antimicrobial susceptibility testing; data from well-performed clinical trials should be evaluated. The data fail to demonstrate consistently a significant difference within the cephalosporin class of antimicrobials with regard to prevention of infectious complications. Although it does not reach statistical difference, the trend with respect to efficacy appears to be cefuroxime, then cefamandole, and then cefazolin. The lack of significant difference among antimicrobials suggests an institution-individualized approach to the selection of the optimal antimicrobial for prophylaxis. For our facilities we recommend the following regimen: cefazolin sodium 1-2 g iv q8h for two days. There are not enough data at this time to recommend less than two days of antimicrobial prophylaxis for this type of surgery. In addition, aminoglycosides provide no added benefit when added to cephalosporins.

Serum levels of cloxacillin and benzylpenicillin in adults undergoing open-heart surgery

Serum levels of cloxacillin and benzylpenicillin were monitored in 35 consecutive adult patients undergoing elective open-heart surgery. Serial serum samples were analyzed during a 24-hour period. After oral intake of cloxacillin and phenoxymethylpenicillin on the preceding evening, very low concentrations remained in serum at the start of operation. Such preoperative medication is inappropriate. Intravenously administered cloxacillin (2 g) and benzylpenicillin (3 g) appeared to be adequate during the first 4 hours of surgery, as the serum half-life of the drugs was twice as long in the patients as in healthy adults, but repetition of the doses is recommended for further antibiotic protection during surgery.

Infection following coronary artery surgery. Comparison of two antibiotic prophylaxis regimens

A prospective randomized study was conducted in 200 patients undergoing coronary artery bypass surgery. All patients received intravenous (IV) cephalothin prophylaxis for 48 hours beginning with anesthetic induction. Group A (99 eligible patients) received cephalexin 500 mg po, qid for three extra days. Group B (94 eligible patients) received no oral therapy. The overall infection rate was 9.3 percent (18 patients). Six patients had multiple sites of involvement. There was no difference between group A (9.0 percent, nine patients) vs B (9.5 percent, nine patients) (p greater than 0.5). The median sternotomy infection rate, superficial or deep, was 2.6% (five patients). The surgical wound infection rate was 4.7 percent (nine patients). The overall infection rate compares favorably with that of high risk groups for clean surgical procedures defined in SENIC study. There was no advantage to prolonged oral cephalexin prophylaxis following coronary artery bypass (CAB) surgery.

Influence of preoperative showers on staphylococcal skin colonization: a comparative trial of antiseptic skin cleansers

We undertook a prospective randomized observer-blinded study comparing the ability of preoperative showers with chlorhexidine gluconate (Hibiclens), povidone-iodine (Betadine), and a lotion soap (Safe 'N Sure) to diminish the staphylococcal skin flora of patients. By block randomization, patients scheduled for an elective cardiac operation or coronary artery angioplasty were assigned to shower with one of the study skin cleansers either once (evening only) or twice (both evening and morning) before the procedure. Semiquantitative samples for culture were obtained from the subclavian and inguinal sites on the evening before the procedure (baseline culture) and again the next morning before the operation. The chlorhexidine skin cleanser consistently reduced staphylococcal colony counts at both the subclavian and inguinal sites before the procedure. This reduction was significant for patients showering both evening and morning (p less than 0.05). The use of the povidone-iodine skin cleanser inconsistently affected skin flora. Patients using lotion soap either experienced no change or had an increase in colony counts. Chlorhexidine is more effective than povidone-iodine in diminishing skin colonization with staphylococci in patients before operation. Repeated applications of chlorhexidine are superior to a single shower with this agent.

Prophylactic antibiotic treatment prevents infection after cardiopulmonary bypass: a study in dogs

The effect of two prophylactic antibiotic regimens during cardiopulmonary bypass (CPB) was investigated in dogs. Airborne contamination was determined by spraying two different bacterial strains (Staphylococcus aureus and Serratia marcescens) into the air of the operating room. Dogs were operated on and underwent CPB with a bubble oxygenator. Pericardial suction, either conventional (blood-air) or selective (only blood), was used. Particularly in the first situation, an impaired humoral host defense is induced. In dogs given the regimen consisting of penicillin G (benzylpenicillin), gentamicin sulfate, and flucloxacillin, the number of contaminated sites for both bacteria was reduced (p less than .01) compared with those given cefuroxime. The effectiveness of the combined antibiotic regimen could be ascribed to increased serum bactericidal activity and polymorphonuclear leukocyte (PMN) killing capacity. Cefuroxime enhanced the PMN respiratory burst. As a result, two weeks postoperatively the rate of infection was small in both groups. We conclude that prior to CPB, antibiotics should be administered prophylactically to overcome a period of impaired humoral host defense during CPB.

The economic implications of infection in cardiac surgery

To assess the economic impact of infection, the records of 496 patients aged 18 to 82 years (mean, 61 years) undergoing open-heart operations in 1981 and 1982 were reviewed, and the costs (length of stay, hospital charges, pharmacy charges) were compared for matched pairs of patients with and without infection who had coronary artery bypass grafting (CABG) procedures. Patients received a 5-day regimen of prophylactic cephalosporin. Operative site infections occurred within 6 months of operation in 17 patients (3.4%), urinary tract infections in 9 (1.8%), and pulmonary infections in 6 (1.2%). Early and late mortality was each 2%. No deaths were infection related, and no postoperative bacterial endocarditis occurred (minimum one-year follow-up). For the matched CABG patient in whom a postoperative wound infection developed, the average length of hospital stay was 16.7 days longer and the average hospital bill was $8,118 greater, with the average cost to the hospital $6,605 greater.

Surgical antimicrobial prophylaxis: principles and guidelines

Antimicrobial prophylaxis for surgical procedures is an area that is recognized as being subject to individual clinical variations. This review gives practitioners some basic principles of rational prophylaxis as defined by the medical literature. In addition, this literature is evaluated and condensed to provide clinicians with guidelines for particular procedures: obstetric, gynecologic, gastric, biliary, colonic, urologic, cardiac, thoracic, vascular, orthopedic and head and neck. Each section concludes with recommendations for the clinically most accepted prophylactic regimens. Antibiotics discussed include not only the older agents, but where good information exists, the newer cephalosporins. The suggested regimens consider efficacy, safety and cost as determinants in rational prescribing. Although research into even shorter, and perhaps more cost-effective, regimens continues, this compilation lists state-of-the-art recommendations.