Cephalothin Prophylaxis and valve replacement

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.

Cefazolin and netilmicin serum levels during and after cardiac surgery with cardiopulmonary bypass

The kinetics of cefazolin and netilmicin were studied in 10 patients undergoing elective cardiac surgery with hemodilution and cardiopulmonary bypass (CPB). During surgery, but before CPB, cefazolin, 25 mg/kg, and netilmicin, 2 mg/kg, were administered intravenously over 30 minutes. For the 48-hour period following CPB, cefazolin, 25 mg/kg, and netilmicin, 1 mg/kg, were administered intravenously every 8 hours. Initiation of CPB was accompanied by a 28% to 30% decrease in hematocrit and serum antibiotic levels. At the conclusion of surgery, cefazolin and netilmicin serum levels were 41 +/- 12 micrograms/L and 2.5 +/- 0.6 micrograms/mL (mean +/- SD), respectively. During the postoperative period, cefazolin levels were consistently greater than the minimum inhibitory concentration (MIC) for sensitive bacteria (4 micrograms/mL); average netilmicin levels were greater than MIC of sensitive bacteria (2 micrograms/mL) for 2 hours after antibiotic infusion. The netilmicin trough levels were 0.6 +/- 0.5 micrograms/mL. Pharmacokinetic parameters were determined using a model-independent method, and gave the following results during surgery: cefazolin--elimination half-life, 231 minutes, total body clearance, 1.05 mL/kg/min, and steady-state volume of distribution, 243 mL/kg. The values for netilmicin were 249 minutes, 1.18 mL/kg/min, and 353 mL/kg, respectively. Postoperatively there were no significant changes in the disposition of cefazolin, but the elimination half-life of netilmicin was shorter (124 minutes, P less than 0.01) and the total body clearance greater (3.58 mL/kg/min, P less than 0.01) than during surgery.

Perioperative antibiotic prophylaxis in cardiovascular surgery: a prospective randomized comparative trial of cefazolin versus ceftriaxone

With a view of possible reduction in antibiotic dosage, several prospective randomized comparative trials performed in our institution showed that a 4-day prophylactic antimicrobial regimen with cefazolin was equally effective as a 2-day prophylaxis with cefuroxime and that the best regimen was equally as effective as a double dose of ceftriaxone prophylaxis in major cardiovascular surgery. In this prospective randomized comparative study, 1-day cefazolin prophylaxis (4 X 0.5 g intravenously) was compared with a single dose of ceftriaxone prophylaxis (2 g intravenously). Of the 900 patients enrolled in the study, 17 were subsequently excluded. Of the remaining 883 patients, 439 were in the cefazolin group and 444 were in the ceftriaxone group. The overall postoperative infection rate was 5.0% in the cefazolin group and 4.5% in the ceftriaxone group. In view of the almost identical infection rates in both groups, we considered that a single 2 g dose of ceftriaxone offers patients a reliable antimicrobial prophylaxis. The single-dose prophylaxis has the additional advantage of reducing the dosage administered and the costs of administration.

Oxacillin and tobramycin serum levels during cardiopulmonary bypass

Antibiotic prophylaxis in cardiac surgery is recommended to combat acquired infections caused by staphylococci and gram-negative bacilli. Prophylaxis seems effective provided blood levels are greater than minimal inhibitory concentrations (MIC). In this study, two doses of antibiotics were compared in 45 patients with normal renal function during cardiopulmonary bypass (CPB). All patients received 50 mg/kg of oxacillin. Group 1 (30 patients) also received 1 mg/kg of tobramycin, while group 2 (15 patients) received 2 mg/kg of tobramycin. Blood samples were taken after the administration of antibiotics, as well as at the onset and conclusion of CPB. Additional samples were taken before and after heparin injection before CPB, and from the arterial and venous cannulae of the bubble oxygenator during CPB. In both groups, oxacillin serum levels were constantly greater than MIC for susceptible bacteria. In group 1, tobramycin levels less than 2 micrograms/mL (MIC for most susceptible bacteria) occurred in four patients before CPB, in 14 patients at the onset of CPB, and in 19 patients at the conclusion of CPB. These low levels were not explained by heparin administration or absorption onto the CPB circuit, but were the result of hemodilution. In group 2, in which all the tobramycin levels were higher than 2 micrograms/mL, serum levels decreased from 9.9 +/- 3.4 (mean +/- SD) to 3.7 +/- 0.7 micrograms/mL throughout the procedure. Plasma creatinine did not change significantly in either group. It is concluded that in patients with normal renal function, doses as high as 50 mg/kg of oxacillin and 2 mg/kg of tobramycin may be necessary before CPB to provide adequate serum levels throughout CPB.

Mediastinal infection after cardiac surgery

Mediastinitis is an uncommon complication after cardiac surgery; however, its associated morbidity and mortality demand early recognition and emergency therapy. This review is intended to emphasize certain features of the incidence, pathogenesis, and bacteriology of this complication in patients undergoing cardiopulmonary bypass through a median sternotomy. The diagnosis and treatment of mediastinitis after cardiac surgical procedures, as well as methods of prevention, are also reviewed.

The prophylactic use of antimicrobials in surgery

During the period August 1976 to June 1982, there were 98 reports of antimicrobial prophylaxis in human surgery that were judged unevaluable. Our review, coupled with that of Chodak and Plaut, identified studies of 126 antibiotic regimens that were considered evaluable and a total of 205 studies considered unevaluable. A decrease in infection rate in antibiotic-treated patients compared to non-antibiotic-treated patients was seen in 120 (95%) of the evaluable regimens. Ninety-nine (79%) of these 120 regimens produced statistically significant reductions in the infection rate (P less than .05, chi 2 analysis). The majority of the antibiotic regimens were tested in procedures that were classified as clean-contaminated. Of the regimens that yielded a statistically significant reduction in infection rate with antimicrobial therapy, in 66 (67%) the agents were used for 24 hours or less. Five regimens were identified in which a higher infection rate occurred in specific patient groups when prophylactic antibiotics were used, but the differences were not statistically significant. In the overwhelming majority of evaluable studies, antibiotics decreased the incidence of surgical infection compared with non-antibiotic groups. The available data also support the effectiveness of short prophylactic antibiotic courses of 24 hours' duration or less. The duration necessary for antibiotic prophylaxis was specifically tested in nine regimens. In all nine, a short course (less than 24 hours) of antibiotic prophylaxis was as effective as longer periods of therapy (24 hours to 5 days) in preventing infection.

Comparative study of cefamandole versus ampicillin plus cloxacillin: prophylactic antibiotics in cardiac surgery

A randomized, prospective study of the efficacy of cefamandole naftate versus a combination of ampicillin and cloxacillin was undertaken in 109 adult patients operated on in Leeds during 1979. Sixty patients underwent valve replacement, and 49 had either aortocoronary bypass grafts or other forms of open-heart operation. Teh two groups matched well in age, sex, and type of operation. One gram of either antibiotic was given intravenously during the induction of anesthesia and every 6 hours thereafter for 48 hours. Two additional grams of antibiotic were placed in the prime of the heart lung machine. The overall rate of infection was 7.5% for the entire series, with 1.7% for the group given cefamandole and 13.7% for the group given ampicillin plus cloxacillin (p less than 0.05). The only patient with infection in the former group (1.7%) had sternal wound involvement. Major sternal wound infection occurred in 3 (5.9%) patients in the latter group. All wound infections were caused by Staphylococcus aureus. In 2 of these patients (ampicillin plus cloxacillin group) the infection proceeded to endocarditis. Urinary and respiratory tract infections occurred in 1.9% and 5.9%, respectively, of patients given ampicillin plus cloxacillin. The duration of hospital stay was shorter in the cefamandole group. The results of this study demonstrated that cefamandole confers effective prophylaxis in cardiac operations.

Serum cefazolin levels during cardiopulmonary bypass

This study was done to assess the adequacy of a regimen using cefazolin as a prophylactic antibiotic for patients undergoing open-heart operation. At the time of the preoperative medication, adult patients received 1 gm of cefazolin intramuscularly, and pediatric patients were given a dose of 20 mg per kilogram of body weight. Group I consisted of 10 adults undergoing a variety of cardiac procedures. The mean serum cefazolin level after institution of cardiopulmonary bypass was 27.36 micrograms/ml (range, 13.1 to 40.3 micrograms/ml). This level remained fairly stable throughout cardiopulmonary bypass. Group II consisted of 10 pediatric patients undergoing cardiac procedures for repair of a variety of congenital anomalies. The mean serum cefazolin level after institution of cardiopulmonary bypass was 20.01 micrograms/ml (range, 11.4 to 28.9 micrograms/ml) and remained stable for the duration of the procedure. In both groups perfusion pressure, urinary output, and body temperature did not seem to have any influence on these levels. It is concluded that the administration of one dose of cefazolin intramuscularly before operation results in an adequate and stable serum cefazolin level in patients undergoing cardiopulmonary bypass for up to three hours, possibly longer.