Is single-dose antibiotic prophylaxis sufficient for coronary artery bypass surgery? An analysis of peri- and postoperative serum cefuroxime and vancomycin levels

Incidence and risk factors for potentially suboptimal serum concentrations of vancomycin during cardiac surgery

AIM

To investigate the incidence and risk factors for vancomycin concentrations less than 10 mg/L during cardiac surgery.

METHODS

In this prospective study, patients undergoing cardiac surgery received a single dose of 1000 mg of vancomycin. Multiple arterial samples were drawn during surgery. Exclusion criteria were hepatic dysfunction; renal dysfunction; ongoing infectious diseases; solid or hematologic tumors; severe insulin-dependent diabetes; body mass index of < 17 or > 40 kg/m²; pregnancy or lactation; antibiotic, corticosteroid, or other immunosuppressive therapy; vancomycin or nonsteroidal anti-inflammatory drug therapy in the previous 2 wk; chemotherapy or radiation therapy in the previous 6 mo; allergy to vancomycin or cefazolin; drug abuse; cardiac surgery in the previous 6 mo; previous or scheduled organ transplantation; preoperative stay in the intensive care unit for more than 24 h; emergency procedure or lack of adequate preparation for surgery; and participation in another trial.

RESULTS

Over a 1-year period, 236 patients were enrolled, and a total of 1682 serum vancomycin concentrations (median 7/patient) were measured. No vancomycin levels under 10 mg/L were recorded in 122 out of 236 patients (52%), and 114 out of 236 patients (48%) were found to have at least 1 serum sample with a vancomycin level < 10 mg/L; 54 out of 236 patients (22.9%) had at least 5 serum samples with a vancomycin level lower than 10 mg/L. Vancomycin infusion was administered for 60 min in 97 out of 236 patients (41%). In 47 patients (20%), the duration of infusion was longer than 60 min, and in 92 patients (39%) the duration of infusion was shorter than 60 min. The maximum concentration and area under the concentration-time curve were significantly higher in patients with no vancomycin levels less than 10 mg/L (P < 0.001). The multivariate analysis identified female gender, body mass index (BMI) > 25 kg/m², and creatinine clearance above 70 mL/min as risk factors for vancomycin levels less than 10 mg/L.

CONCLUSION

Results of this study identified female gender, BMI > 25 kg/m², and creatinine clearance above 70 mL/min as risk factors for suboptimal vancomycin serum concentration during cardiac surgery; no relationship was found between infusion duration and vancomycin levels less than 10 mg/L. These findings call attention to the risk of facilitating the emergence of vancomycin-resistant methicillin-resistant Staphylococcus aureus strains.

The Effect of Modified Ultrafiltration on Serum Vancomycin Levels During Cardiopulmonary Bypass in Cardiac Surgery

OBJECTIVE

The aim of this study was to investigate whether the use of modified ultrafiltration at the end of cardiopulmonary bypass for cardiac surgical procedures significantly changes vancomycin serum concentrations.

DESIGN

Prospective study.

SETTING

Single tertiary cardiac center.

PARTICIPANTS

Twenty-six elective adult patients undergoing cardiac surgery with cardiopulmonary bypass from April 2014 to April 2015.

INTERVENTIONS

Serum vancomycin concentrations were measured just before cardiopulmonary bypass; during cardiopulmonary bypass at 5, 30, 60 minutes and then every 60 minutes; after completion of cardiopulmonary bypass before initiation of modified ultrafiltration; and at the end of modified ultrafiltration.

MEASUREMENTS AND MAIN RESULTS

Seventeen patients received modified ultrafiltration at the end of cardiopulmonary bypass. Serum vancomycin concentrations prior to cardiopulmonary bypass (45.9 ± 17.3 μg/mL) were significantly higher (P < 0.0001) than each time point following cardiopulmonary bypass (5 min 20.4 ± 6.4 μg/mL, 30 min 18.8 ± 5.4 μg/mL, 60 min 16.6 ± 4.9 μg/mL, and 120 min 14.3 ± 4.7 μg/mL). In the modified ultrafiltration group, serum vancomycin concentrations were 14.7 ± 4.6 μg/mL prior to modified ultrafiltration and 13.9 ± 4.3 μg/mL after ultrafiltration; this difference was statistically significant (P  =  0.0288). The mean modified ultrafiltration volume was 465 ± 158 mL.

CONCLUSIONS

Using modified ultrafiltration at the end of cardiopulmonary bypass significantly decreases serum vancomycin levels, but not by a clinically relevant amount. The decrease is to a concentration that is still significantly higher than the minimum inhibitory concentration for Staphylococcus epidermidis and Staphylococcus aureus; thus additional vancomycin administration is not recommended.

Pharmacokinetics of cefuroxime in infants and neonates undergoing cardiac surgery

AIMS

Very little data exist regarding the effect of cardiopulmonary bypass (CPB) on cefuroxime (CXM) pharmacokinetics in children less than one year of age.

METHODS

50 mg kg^-1 CXM i.v. after induction were followed by 75 mg kg^-1 into the CPB circuit. In 42 patients undergoing cardiac surgery, 15-20 samples were obtained between 5 and 360 min after the first dose. Total CXM concentrations were measured by high-performance liquid chromatography and a pharmacokinetic/pharmacodynamic (PK/PD) modelling was performed.

RESULTS

Using a fixed protein binding of 15.6% for CXM, peak plasma concentrations of unbound CXM were 229 ± 52 μg ml^-1 after the first bolus and 341 ± 86 μg ml^-1 on CPB. Nadir concentrations before CPB were 69 ± 20 μg ml^-1 and six hours later decreased to 41 ± 19 μg ml^-1 with and 24 ± 14 μg ml^-1 without CPB. A two-compartment model was fitted with the main covariates body weight, CPB and postmenstrual age (PMA). PK parameters were as follows: systemic clearance, 5.15 [95% CI 4.5-5.8] l h^-1 ; central volume of distribution, 11.25 [9.41-13.09] l; intercompartmental clearance, 18.19 [14.79-21.58] l h^-1 ; and peripheral volume, 17.07 [15.7-18.5] L. ƒT > MIC of 32 μg ml^-1 for an 8-h time period was between 70 and 100% (2.5-10 kg BW). According to our simulation, 25 mg ml^-1 CXM as a primary bolus and into the prime plus a 5 mg kg^-1  h^-1 infusion maintain CXM concentrations continuously above 32 μg ml^-1 .

CONCLUSIONS

The routine dosing regimen provided was sufficient for prophylaxis, but continuous dosing can provide a higher percentage of ƒT > MIC.

Population Pharmacokinetic Model for Vancomycin Used in Open Heart Surgery: Model-Based Evaluation of Standard Dosing Regimens

The purpose of this study was to investigate the population pharmacokinetics of vancomycin in patients undergoing open heart surgery. In this observational pharmacokinetic study, multiple blood samples were drawn over a 48-h period of intravenous vancomycin in patients who were undergoing open heart surgery. Blood samples were analyzed using an Architect i4000SR immunoassay analyzer. Population pharmacokinetic models were developed using Monolix 4.4 software. Pharmacokinetic-pharmacodynamic (PK-PD) simulations were performed to explore the ability of different dosage regimens to achieve the pharmacodynamic targets. A total of 168 blood samples were analyzed from 28 patients. The pharmacokinetics of vancomycin are best described by a two-compartment model with between-subject variability in clearance (CL), the volume of distribution of the central compartment (V₁), and volume of distribution of the peripheral compartment (V₂). The CL and the V₁ of vancomycin were related to creatinine CL (CL_CR), body weight, and albumin concentration. Dosing simulations showed that standard dosing regimens of 1 and 1.5 g failed to achieve the PK-PD target of AUC_0-24/MIC > 400 for an MIC of 1 mg/liter, while high weight-based dosing regimens were able to achieve the PK-PD target. In summary, the administration of standard doses of 1 and 1.5 g of vancomycin two times daily provided inadequate antibiotic prophylaxis in patients undergoing open heart surgery. The same findings were obtained when 15- and 20-mg/kg doses of vancomycin were administered. Achieving the PK-PD target required higher doses (25 and 30 mg/kg) of vancomycin.

Coronary artery bypass surgery in diabetic patients - risk factors for sternal wound infections

The incidence of sternal wound infections (SWI) after coronary artery bypass surgery (CABG) as reported worldwide is low. However, it is associated with significant increase of postoperative mortality and treatment costs. The major risk factors discussed are diabetes mellitus and bilateral IMA harvesting of the internal mammary artery. This study analyses data of 590 patients receiving CABG concerning the risk factors for SWI. Sternal wound infections occur significantly more often in diabetic patients, one crucial and significant additional risk factor is obesity.

Tissue and plasma concentrations of cephuroxime during cardiac surgery in cardiopulmonary bypass — a microdialysis study

Aim: Wound and mediastinal infections are still very serious complications of open-heart surgery, in spite of the use of prophylactic antibiotics. The use of cardiopulmonary bypass (CPB) is associated with profound physiological changes affecting the pharmacokinetic behaviour of antibiotics.

The aim of this pilot study was to monitor the tissue concentrations of cephuroxime (prophylactic antibiotic) in skeletal muscle during cardiac surgery using CPB by interstitial microdialysis. These concentrations were compared with plasma concentrations of cephuroxime.

Material and methods: Nine adult patients operated on using CPB were enrolled in this study. Cephuroxime was used as a prophylactic antibiotic (1st dose — 3 g of cefuroxime i.v. with anesthesia induction, 2nd dose — 1.5 g i.v. after CPB with protamine sulphate, 3rd dose — 1.5 g i.v. 8 hours after the surgery).

Interstitial microdialysis was performed by probe CMA 60 (CMA Microdialysis AB, Sweden) inserted into the patient's deltoid muscle. Concentrations of cephuroxime in dialysates and in plasma were determined by the modified fluid chromatography method. The unbound cephuroxime fraction in plasma was obtained by using an ultrafiltration method. Samples of dialysates were collected at the following intervals: before CPB, each 30 minutes of CPB, at the end of CPB. Samples of blood were collected at these intervals: incision, start of CPB, each 30 minutes of CPB, at the end of CPB, at the end of surgery. Concentrations of cephuroxime in tissue were corrected by in vivo recoveries of the microdialysis probes.

Results: Plasma concentrations of cephuroxime were 163.5 ± 40.1, 79.3 ± 17.4, 73.7 ± 16.8, 66.1 ± 18.3, 57.0 ± 10.9, 120.7 ± 29.9 (mg . L—1) and concentrations of free plasma fraction of cephuroxime were 119.5 ± 35.2, 67.8 ± 15.5, 66.0 ± 12.5, 54.8 ± 12.2, 49.6 ± 9.8, 102.6 ± 26.0 (mg . L—1).

The concentrations of cephuroxime in dialysates were 44.3 ± 15.7, 36.1 ± 11.6, 31.9 ± 9.3, 34.6 ± 12.3, 27.6 ± 12.9, 56.7 ± 17.6 (mg . L—1).

The mean in vivo recovery of cephuroxime in this study was 30%.

Corrected concentrations (calculated by in vivo recovery) of cephuroxime in skeletal muscle were 148, 120, 106, 115, 92, 189 (mg . L—1).

Conclusion: Our preliminary results show that CPB can modify the time course of cephuroxime plasma and tissue concentrations. A decrease in plasma drug concentrations occurred at the start of CPB and lasted until CPB ended. An increase in plasma concentrations corresponds to the second drug dose after CPB. The concentrations of cephuroxime in skeletal muscle (corrected by recovery) during CPB are higher than plasma concentrations. It is influenced by important changes during CPB; closely associated with hemodilution, a shift of intravascular volume, solutes and albumin to the extravascular space and inconstant protein binding of cephuroxime during operation. Perfusion (2007) 22, 129—136.

Intraoperative vancomycin pharmacokinetics in cardiac surgery with or without cardiopulmonary bypass

BACKGROUND

Vancomycin is administered as antimicrobial prophylaxis to patients undergoing cardiac surgery, an intervention that usually requires cardiopulmonary bypass (CPB). Previous studies reported that CPB modifies vancomycin pharmacokinetic parameters.

OBJECTIVE

To investigate intraoperative vancomycin pharmacokinetic changes in a large population of patients undergoing cardiac surgery with CPB (on-pump) and without CPB (off-pump).

METHODS

In this prospective study, patients undergoing cardiac surgery received a single dose of vancomycin 1000 mg in a 60-minute intravenous infusion, with skin incision performed between 16 and 120 minutes after the end of the infusion. For the on-pump group, arterial samples were drawn before CPB (end of infusion, skin incision), during CPB (5, 30, and 60 minutes, and then every 60 minutes until CPB end), and after CPB (wound closure). For the off-pump group, arterial samples were drawn time-matched to the CPB period of the on-pump group.

RESULTS

Two hundred thirty-six consecutive patients were enrolled: 215 in the on-pump group and 21 in the off-pump group. A total of 1682 serum vancomycin concentrations (median 7/patient) were measured. Vancomycin maximum concentration ([Cmax] on-pump, 45.6 mg/L; off-pump, 47.3 mg/L); area under the concentration-time curve, zero to 8 hours ([AUC0-8] on-pump, 104.6 mg*h/L; off-pump, 96.1 mg*h/L); volume of distribution ([Vd] on-pump, 31 L; off-pump, 28.2 L); and total body clearance ([Cl] on-pump, 6.23 L/h; off-pump, 7.05 L/h) were similar. Moreover, Cmax and AUC0-∞ (AUC, zero to infinity) showed values comparable to those found in previous studies performed on noncardiac surgery patients.

CONCLUSIONS

In our study there were no significant differences in vancomycin Cmax, AUC0-8, Vd, and Cl between the on-pump and off-pump groups. CPB does not seem to significantly modify intraoperative vancomycin pharmacokinetics in patients undergoing cardiac surgery. The results of this study may contribute to increased knowledge of vancomycin pharmacokinetics.

The Efficacy of Post-Cardiopulmonary Bypass Dosing of Vancomycin in Cardiac Surgery

Objective. Vancomycin is administered widely to patients undergoing cardiac surgery as prophylaxis against resistant Gram-positive sternal wound and venous donor site infections. The purpose of this study was to determine the efficacy of a standardized prebypass and postbypass dosing regimen of vancomycin by assessing plasma concentrations in the immediate postoperative period and postoperative surgical site infections (SSIs). Design. Retrospective cohort study. Setting . Cardiothoracic surgical intensive care unit in a tertiary care academic medical center. Methods. A total of 34 consecutive adult patients who had undergone cardiac surgery with cardiopulmonary bypass (CPB) were analyzed retrospectively. Each patient received 1000 mg of vancomycin administered over 1 hour around the time of induction of anesthesia and 500 mg after discontinuation of CPB. Trough vancomycin levels were sampled in the intensive care unit 12 hours after the last dose given in the operating room. Along with patient characteristics, postoperative readmission rates and SSIs were recorded for 1 year after surgery. Results. The nadir serum vancomycin level before the next dose was 9.3 ± 4.5 µg/mL (mean ± standard deviation). One superficial SSI was noted. Readmission rate for SSIs was 2.94%. Conclusion . Vancomycin concentrations in the serum were greater than the minimum inhibitory concentration for most staphylococci ranging from 4 to 19.3 µg/mL producing acceptable therapeutic serum concentrations and low rate of infectious complications. Thus postbypass dosing is acceptable in vancomycin cardiac surgical prophylaxis.

Survey of prophylactic antibiotic use amongst UK cochlear implant surgeons

Cochlear implant patients are at an increased risk of pneumococcal meningitis. Recent government guidelines require all implant patients to undergo pneumococcal vaccination. The guidelines also suggest antibiotic prophylaxis but no clear guidelines regarding which antibiotic to use or for how long were issued.We asked each implant centre within the UK to describe their antibiotic protocol for cochlear implantation.Our results have showed that 100% of UK implant surgeons use antibiotic prophylaxis. The type of antibiotic and duration vary significantly between centres. Interestingly, however, the regimes followed by most practices do not adhere to surgical principles of antibiotic prophylaxis.

Prophylactic use of vancomycin in adult cardiology and cardiac surgery

The recent appearance of Staphylococcus aureus and Staphylococcus epidermidis strains that have reduced susceptibility to vancomycin, and the spread of vancomycin-resistant enterococci, raise the specter of endovascular infections that will be difficult or impossible to cure with available drugs. We review issues concerning the prophylactic use of vancomycin in adult cardiology and cardiac surgery with special attention to dosing and indications. There is no indication for the routine use of prophylactic vancomycin in pacemaker implantations, cardiac catheterization, and transesophageal echocardiography. In institutions with a high incidence of methicillin-resistant S. aureus and S. epidermidis, vancomycin may be used for antibiotic prophylaxis in place of cephalosporins for pacemaker or defibrillator implantation. The strongest evidence in support of the prophylactic use of vancomycin is during cardiac surgeries, particularly valvular surgeries in institutions with a high prevalence of methicillin-resistant S. aureus and S. epidermidis. When vancomycin is used prior to open heart surgery, the dose should be 15 mg/kg rather than the standard 1 g dose that is often recommended in the literature and used by 85% of institutional pharmacists who responded to our survey. Cardiologists and cardiac surgeons should assume leadership roles in promoting its responsible use.

Infection control measures for adult cardiac surgery in the UK--a survey of current practice

The aim of the study was to define current UK practice for antimicrobial prophylaxis and preoperative screening for bloodborne viruses and methicillin-resistant Staphylococcus aureus (MRSA) before routine cardiac surgery. An e-mail survey was sent to the Association of Cardiothoracic Anaesthetists (ACTA) Linkmen in all 36 UK adult cardiac surgical units, during May 2001. Questions were asked regarding MRSA, hepatitis B, C and human immunodeficiency virus (HIV) screening. Regarding antimicrobial prophylaxis questions were asked regarding agent(s), dose, frequency and duration of use for coronary artery and value surgery. Responses were received from 29 units (response rate 81%). There was a wide variety of practices for all units surveyed. For MRSA screening, 19 units (65%) screened all patients before surgery, but two (7%) screened none, with the remaining eight units (28%) screening selected high-risk groups. Regarding screening for bloodborne viruses: eight units (28%) tested all patients routinely for hepatitis B, 11 units (39%) selectively tested only high-risk patients and transplant recipients. No units tested for hepatitis C and HIV infection routinely. All units used prophylactic antibiotics routinely, but the type and number of agents, along with dose and duration of therapy all varied widely. For coronary artery bypass graft (CABG) surgery, a single agent was used by 16 units (55%), two agents by 12 units (41%) and three agents by one unit (4%). There is a wide variation in infection control practice in adult cardiac units throughout the UK. Rationalization of preoperative screening and use of prophylactic antibiotics, by adopting nationally agreed practice guidelines, could significantly reduce costs and potentially reduce the incidence of resistant organisms.

Antibiotic prophylaxis with cefazolin and gentamicin in cardiac surgery for children less than ten kilograms

OBJECTIVE

Antibiotic prophylaxis is recommended in pediatric cardiac surgery, but no data concerning the current antibiotic regimen were available.

DESIGN

Prospective study from April to June 2000.

SETTING

University hospital operating room and postoperative intensive care unit.

PARTICIPANTS

Nineteen consecutive infants less than 10 kg with normal renal function undergoing cardiac surgery with cardiopulmonary bypass longer than 30 minutes.

INTERVENTIONS

Intravenous administration of cefazolin, 40 mg/kg, and gentamicin, 5 mg/kg, at induction of anesthesia; followed by cefazolin, 35 mg/kg every 8 hours, and gentamicin, 2 mg/kg every 12 hours, over 48 hours.

MEASUREMENTS AND MAIN RESULTS

Levels of serum antibiotics were measured: cefazolin (microbiologic) and gentamicin (fluorescence immunoassay) with 8 intraoperative and 5 postoperative samplings. Intraoperatively, cefazolin levels decreased from 166 +/- 44 (mean +/- standard deviation) down to 54 +/- 16 microg/mL and gentamicin from 20.8 +/- 9.5 down to 5.9 +/- 1.5 microg/mL. The postoperative trough levels were 12 +/- 7, 15 +/- 10, and 19 +/- 22 microg/mL for cefazolin and 1.1 +/- 0.5, 0.8 +/- 0.4, and 0.8 +/- 0.9 microg/mL for gentamicin.

CONCLUSIONS

Antibiotic serum levels are consistent with satisfactory efficacy, but intraoperative gentamicin peak levels appeared too high.

Vancomycin sequestration during cardiopulmonary bypass surgery

OBJECTIVE

The present study was designed to analyze vancomycin disposition in adult patients undergoing coronary bypass grafting during and following cardiopulmonary bypass (CPB).

METHODS

Coronary bypass surgery was performed on 11 adults with a mean age (SD) of 62.9 (9.0) years old, who received a mean (SD) vancomycin prophylactic dose of 12.7 (1.0) mg/kg in a mean period of 41 (0.7) min. Using a two-compartment open model for pharmacokinetic analysis, the following parameters were obtained: alpha half-life, minutes (t(1/2alpha)); beta half-life, hours (t(1/2beta)); apparent volume of distribution, (V(d) l/kg); volume of the central compartment, (V(c) l/kg), constant between the "central to the peripheral" compartment, (k(12)); constant between the "peripheral to the central" compartment, (k(21)); total area under the concentration-time curve, (AUC mg/lxh) and a vancomycin clearance, (Cl(van) ml/min), respectively.

RESULTS

The mean (SD) calculated pharmacokinetic parameters were: t(1/2alpha)17.6 (6) min, t(1/2beta) 8.4 (3.8) h, V(d) 0.803 (0.259) l/kg, V(c) 0.270 (0.162) l/kg, k(12) 0.03 (0.015), k(21) 0.012 (0.012), total AUC 10377.2 (3687.6) mg/lxh. The mean (SD) vancomycin clearance by the CPB machine was 9.51 (2.66) l/h, and the mean (SD) total vancomycin sequestrated by CPB was 331.7 (84) mg. A significant difference (6.3%; p = 0.001) was measured between the mean measured AUC during CPB (1088.1 +/- 253.9) and the same calculated parameter (1160.2 +/- 282). Five minutes after starting CPB, a decrease in vancomycin level was detected; this difference was found to be nearly 11% in absolute values.

CONCLUSIONS

This confirmatory study demonstrated that the vancomycin blood concentrations obtained during the study allow recommending a safety prophylactic dose of 12mg/kg in adults who undergo open-heart surgery under CPB conditions. Sequestration of vancomycin by the oxygenator or/and tubing system of the CPB machine had occurred and had been measured in this study.

[Antibiotic prophylaxis in cardiac surgery: practice patterns]

OBJECTIVE

To assess the prescription patterns in French and foreign centres for antibiotic prophylaxis in cardiac surgery.

MATERIAL AND METHODS

Phone and written surveys concerned 64 French and 70 foreign centres. It focused on the first injection, the duration of treatment and the recommended agents.

RESULTS

87% of the French centres and 67% of the foreign centres answered the questionnaire. The first injection took place at anaesthesia induction in all French centres but during administration of premedication in 11% of foreign centres (p < 0.05). The duration of prophylaxis was restricted to the intraoperative period only in 20% and 15% of centres, respectively (ns), as specified by the recommendations. No French centres carried on the antibiotics more than 48 h versus 11% of foreign centres (p < 0.05). Cephalosporines of the second generation were prescribed in 84 and 49% of centres, respectively (p < 0.05). The combination of two antibiotics was less frequent in France than in foreign countries (5 versus 17%, p < 0.01). In absence of betalactamin allergy glycopeptides were not utilized in France versus 8% in foreign countries (p < 0.05). In case of allergy vancomycin was used in 66% of French and 42% of foreign centres.

CONCLUSION

The French recommendations may have influenced favourably the antibiotic choice but the prophylaxis duration was too long in most of the non French European centres.