Short-term adverse effects of antibiotic prophylaxis for open-heart surgery

Antibiotic therapy and the anesthesiologist

The anesthesiologist is frequently responsible for administering antibiotics in the immediate preoperative and intraoperative periods. Anesthesiologists often are not trained in the administration of antibiotics, which can be associated with both acute and long-term complications including potentiation of neuromuscular blocking agents, allergic reactions, and end-organ toxicity. The indications for perioperative antibiotics, proper method of administration, and occurrence and treatment of major side effects of the more commonly recommended prophylactic antibiotics are discussed.

Bacterial wound colonization after broad-spectrum versus narrow-spectrum antibiotics

Broad-spectrum versus narrow-spectrum antibiotic prophylaxis for patients who undergo cardiac operations is variously advocated to reduce the incidence of all infections or, conversely, to prevent resistant superinfections. Previous studies of prophylaxis have shown a reduction in the incidence of staphylococcal infections with some increased resistance. We studied preoperative and postoperative wound colonization as a surrogate for infection. Among 78 patients undergoing cardiac procedures, the type of prophylaxis was allocated as follows: narrow-spectrum (nafcillin), 24 patients; midspectrum (cephapirin), 26 patients; and broad-spectrum (ceftriaxone), 28 patients. Seventeen patients who underwent other procedures received no antibiotics and served as controls. Cultures of the operative site were done preoperatively, and 3 and 6 days postoperatively. The incidence of preoperative skin colonization with staphylococci was identical (95%) in all groups. Postoperatively, more patients receiving nafcillin (48%) were culture-negative for all organisms than were either of the other groups receiving antibiotics (27% and 22%) (p < 0.05). Gram-negative bacilli were infrequent colonizers and neither did the incidence of infection with these organisms increase nor did resistance develop in any group. The infection rates were not different among the treatment groups. Thus, a narrow-spectrum antistaphylococcal penicillin may offer an advantage in terms of both prophylaxis for cardiac operations and hospital costs.

Predictors for infection following open-heart surgery

A large open-heart surgery unit dealing with approximately 1000 elective patients per annum and housed in a dedicated suite, including a specialized intensive therapy unit, has provided a unique model for the study of predictors of infections and related phenomena. Over more than 10 years a series of studies has shown: the powerful effect of antibiotic usage on the colonization/infection rates with Gram-negative bacilli; the predictive relationships between preoperative chest status and the development of postoperative chest problems; an important correlation between preoperative peak urine flow rates and susceptibility to postoperative urinary tract infections; and the predictive significance of preoperative antibodies to enteric Gram-negative bacilli in relation to postoperative pyrexia and Gram-negative infection. The lessons learned from this easily studied group of patients may have important applications in other surgical settings.

Postoperative infection in cardiac surgery: the influence of a change in prophylactic antibiotic regimen

A total of 448 patients undergoing cardiovascular surgery were followed for the development of postoperative infection. Non-extracorporeal procedures were assigned to group 1 and open-heart procedures to group 2. The incidence of infection was compared in two groups who received prophylactic antibiotics. Patients (n = 253) received ampicillin alone (group 1) or in combination with gentamicin (group 2) for 7 days starting 1 day before the operation (period A). One hundred and ninety-five patients (period B) received cefazolin starting preoperatively 30 min before induction, alone (group 1) or in combination with gentamicin (Group 2) for 3 days. The percentage of patients developing infection in periods A and B for group 1 patients was 4.2% and 3.5% and for group 2 it was 25.8% and 18.7% respectively. The overall infection rate was 13%. The number of infection sites involved were 1.5 per infected patient. Urinary tract infections were the most frequent followed by endocarditis and other deep infections, wound infections and respiratory infection. Gram-negative rods were the predominant pathogens (Klebsiella spp. and Pseudomonas aeruginosa) during both periods (47 out of 70 isolates). Wound infections due to Gram-positive cocci were higher in period A (4/8) as compared to period B (1/5). During period B there were three cases of fungal endocarditis whereas no case occurred during period A. Although the incidence of infection was reduced during the period of cefazolin prophylaxis, the difference was not statistically significant.

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.

Antibiotic usage in surgery in a large teaching hospital

A prevalence study of the antibiotic usage in the surgical departments at the Karolinska Hospital, Stockholm, showed that 126/517 hospitalized patients (24%) received antibiotics and that 100/306 operated patients (33%) received antibiotics. 44 (44%) of the operated patients were given their antibiotics as prophylaxis and 46 (37%) of all patients receiving antibiotics were given them as prophylaxis. Antibiotics were administered intravenously to 35 (28%) patients, orally to 75 (60%), and topically to 16 patients (13%) (eye department only). The most commonly used drugs in prophylaxis were isoxazolylpenicillins and trimethoprim-sulphonamide while cephalosporins accounted for a minor part. In therapy the most commonly used drug was isoxazolylpenicillin, followed by ampicillin derivatives, metronidazole, tetracyclines, trimethoprim-sulphonamide and cephalosporins. The pattern of antibiotic usage differed markedly between departments.

Reduction of infection after cardiac surgery: a clinical trial

Between January 1, 1975, and June 1, 1984, 3,275 patients underwent cardiac operations with cardiopulmonary bypass. No operations were performed in 1978. In Phase I of the study, general operating rooms were used for cardiac operations, and standard methods of antisepsis and asepsis were used. Phase II began in January, 1979, with the opening of two specially constructed operating rooms with complete separation of incoming and outgoing personnel and supplies, and with a laminar airflow system. All personnel scrubbed 3 minutes and changed into autoclaved clothing before entering the operating suite, and scrubbed again for 5 minutes before putting on gowns. By Phase III, which began in July, 1982, all additional protocols against infection were in place including strict techniques in the intensive care unit and a continuous antiinfection surveillance program. In Phase I, 7.3% (70% confidence limits [CL] 6.4 to 8.2%) of patients had an infectious complication; in Phase II, 2.7% (CL 2.3 to 3.2%), and in Phase III, 0.8% (CL 0.5 to 1.2%). The reductions were similar in the four subtypes of infection (superficial presternal infection, mediastinitis, endocarditis, and septicemia). The study indicates that improving the surgical environment, improving the surgical and operating room protocols, and increasing the awareness of the dangers of infection among the personnel can strikingly reduce the incidence of infections after cardiac operations.

Per-operative antibiotic treatment in cardiovascular surgery: the influence of methicillin versus cephalothin on post-operative infections and bacterial colonization

This paper reports the results of a prospective study of antibiotic prophylaxis in 543 patients undergoing open-heart surgery. All patients were given per-operatively either methicillin, 1 g four times a day, or cephalothin, 1 g four times a day. There was no significant difference in the frequency of postoperative infections between the two groups. It was established that per-operative antibiotic prophylaxis selected resistant coagulase-negative staphylococci (CNS) in the nasal flora of cardiac surgery patients, that this change occurred to the same degree whether methicillin or cephalothin was used, that cephalothin favoured colonization with antibiotic resistant species other than CNS. It was found that the staff of the intensive care unit formed a reservoir of multi-resistant CNS.

Rises in antibody to enteric gram negative bacilli after open heart surgery: a possible mechanism for postoperative pyrexia

Paired sera, taken before operation and 10-14 days after operation from 64 patients having open heart surgery and 10 having closed heart surgery, were examined for agglutinins to seven common serotypes of Escherichia coli. The results showed that, while 20% of both groups of patients had detectable agglutinins before operation, new antibodies appeared after operation in 69% of patients having open heart surgery compared with only 10% of those having closed heart surgery, a significant difference. Thirty six pairs of sera were also examined for the preoperative presence and postoperative development of antiendotoxin. Of 22 open heart patients shown not to possess antiendotoxin before operation, 18 showed the antibody after operation, whereas none of the eight seronegative patients acquired the antibody after closed heart surgery-again a highly significant difference. These results are consistent with the hypothesis that endotoxin and other products of enteric Gram negative bacilli circulate shortly after cardiopulmonary bypass, possibly arising directly from the gut and perhaps explaining the pyrexia seen commonly at this time.