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

Preventing Surgical Site Infections in the Era of Escalating Antibiotic Resistance and Antibiotic Stewardship

Importance

According to the Centers for Disease Control and Prevention and governing bodies within the American College of Surgeons, the administration of antibiotics as prophylaxis against infection prior to a planned elective procedure is, with rare exception, routinely recommended. The goal of "getting to zero" infections remains a high priority for policymakers, practitioners, and certainly for patients.

Observations

Despite the many advances in surgical technique, skin decontamination, sterile procedure, and enhanced recovery programs, surgical site infections continue to adversely affect procedures as diverse as dental implant surgery, joint arthroplasty, and major abdominal surgery. Although surgical site infection rates are at historically low levels, progress has stalled in recent reporting periods and such infections remain disabling, costly, and occasionally lethal. Stakeholders in the field, including surgeons, infectious diseases specialists, and industry, advocate for strategies emphasizing greater levels of intraoperative sterility or broader-spectrum antibiotic coverage as the most appropriate path forward.

Conclusions and Relevance

The current emphasis on ever-increasing levels of intraoperative sterility and extended-spectrum antibiotic use are not sustainable long-term solutions. Continuing to escalate these approaches may contribute to unintended consequences including antimicrobial resistance. Principles of antimicrobial stewardship and microbiome sciences can be applied to inform a more effective and sustainable approach to infection prevention in the field of surgery.

Assessment of the effectiveness of weight-adjusted antibiotic administration, for reduced duration, in surgical prophylaxis of primary hip and knee arthroplasty

BACKGROUND

Prophylactic antibiotics have significantly led to a reduction in the risk of post-operative surgical site infections (SSI) in orthopaedic surgery. The aim of using antibiotics for this purpose is to achieve serum and tissue drug levels that exceed, for the duration of the operation, the minimum inhibitory concentration of the likely organisms that are encountered. Prophylactic antibiotics reduce the rate of SSIs in lower limb arthroplasty from between 4% and 8% to between 1% and 3%. Controversy, however, still surrounds the optimal frequency and dosing of antibiotic administration.

AIM

To evaluate the impact of introduction of a weight-adjusted antibiotic prophylaxis regime, combined with a reduction in the duration of administration of post-operative antibiotics on SSI incidence during the 2 years following primary elective total hip and knee arthroplasty.

METHODS

Following ethical approval, patients undergoing primary total hip arthroplasty (THA)/total knee arthroplasty (TKA) with the old regime (OR) of a preoperative dose [cefazolin 2 g intravenously (IV)], and two subsequent doses (2 h and 8 h), were compared to those after a change to a new regime (NR) of a weight-adjusted preoperative dose (cefazolin 2 g IV for patients < 120 kg; cefazolin 3g IV for patients > 120 kg) and a post-operative dose at 2 h. The primary outcome in both groups was SSI rates during the 2 years post-operatively.

RESULTS

A total of n = 1273 operations (THA n = 534, TKA n = 739) were performed in n = 1264 patients. There was no statistically significant difference in the rate of deep (OR 0.74% (5/675) vs NR 0.50% (3/598); fishers exact test P = 0.72), nor superficial SSIs (OR 2.07% (14/675) vs NR 1.50% (9/598); chi-squared test P = 0.44) at 2 years post-operatively. With propensity score weighting and an interrupted time series analysis, there was also no difference in SSI rates between both groups [RR 0.88 (95%CI 0.61 to 1.30) P = 0.46].

CONCLUSION

A weight-adjusted regime, with a reduction in number of post-operative doses had no adverse impact on SSI incidence in this population.

Diagnostic efficacy of serum presepsin for postoperative infectious complications: a meta-analysis

Background

Postoperative infectious complications (PICs) are major concerns. Early and accurate diagnosis is critical for timely treatment and improved outcomes. Presepsin is an emerging biomarker for bacterial infections. However, its diagnostic efficacy for PICs across surgical specialties remains unclear.

Methods

In this study, a systematic search on MEDLINE, Embase, Google Scholar, and Cochrane Library was performed on September 30, 2023, to identify studies that evaluated presepsin for diagnosing PICs. PIC is defined as the development of surgical site infection or remote infection. Pooled sensitivity, specificity, and hierarchical summary receiver operating characteristic (HSROC) curves were calculated. The primary outcome was the assessment of the efficacy of presepsin for PIC diagnosis, and the secondary outcome was the investigation of the reliability of procalcitonin or C-reactive protein (CRP) in the diagnosis of PICs.

Results

This meta-analysis included eight studies (n = 984) and revealed that the pooled sensitivity and specificity of presepsin for PIC diagnosis were 76% (95% confidence interval [CI] 68%-82%) and 83% (95% CI 75%-89%), respectively. The HSROC curve yielded an area under the curve (AUC) of 0.77 (95% CI 0.73-0.81). Analysis of six studies on procalcitonin showed a combined sensitivity of 78% and specificity of 77%, with an AUC of 0.83 derived from the HSROC. Meanwhile, data from five studies on CRP indicated pooled sensitivity of 84% and specificity of 79%, with the HSROC curve yielding an AUC of 0.89.

Conclusion

Presepsin exhibits moderate diagnostic accuracy for PIC across surgical disciplines. Based on the HSROC-derived AUC, CRP has the highest diagnostic efficacy for PICs, followed by procalcitonin and presepsin. Nonetheless, presepsin demonstrated greater specificity than the other biomarkers. Further study is warranted to validate the utility of and optimize the cutoff values for presepsin.

Systematic review registration

https://www.crd.york.ac.uk/prospero/, identifier CRD42023468358.

Surgical antibiotic prophylaxis: is the clinical practice based on evidence?

Objective:

To assess the surgical antibiotic prophylaxis.

Methods:

This was a descriptive study performed at a public tertiary care university hospital gathering prescription, sociodemographic and hospitalization data of inpatients admitted in 2014 who used antimicrobial drugs. This data were obtained from the hospital electronic database. The antimicrobial data were classified according to the anatomical, therapeutic chemical/defined daily dose per 1,000 inpatients. An exploratory analysis was performed using principal component analysis.

Results:

A total of 5,182 inpatients were prescribed surgical antibiotic prophylaxis. Of the total antimicrobial use, 11.7% were for surgical antibiotic prophylaxis. The orthopedic, thoracic and cardiovascular postoperative units, and postoperative intensive care unit comprised more than half of the total surgical antibiotic prophylaxis use (56.3%). The duration of antimicrobial use of these units were 2.2, 2.0, and 1.4 days, respectively. Third-generation cephalosporins and fluoroquinolones had the longest use among antimicrobial classes.

Conclusion:

Surgical antibiotic prophylaxis was inadequate in the orthopedic, postoperative intensive care, thoracic and cardiovascular postoperative, gynecology and obstetrics, and otolaryngology units. Therefore, the development and implementation of additional strategies to promote surgical antibiotic stewardship at hospitals are essential.

Changes of the Serum Antibiotic Levels During Open Heart Surgery (ceftazidim, ciprofloxacin, clindamycin)

Background: Wound, mediastinal and intracardiac infections are still very serious complications of open-heart surgey. The incidence of it is still in the range of 0.4%-5%. The aims of our study were to assess the adequacy of regimen using ceftazidim (CTZ), ciprofloxacin (CPF) and clindamycin (CLIN) as prophylactic antibiotics and to verify whether cardiopulmonary bypass (CPB) can modify the time of antibiotic serum concentrations. That is why the serum levels of them were measured during open heart procedures. Methods: The prospective study comprised 75 consequent coronary patients randomized in to three groups receiving 1 g of CTZ or 400 mg of CPF or 900 mg of CLIN i.v. with anesthesia induction. Routine coronary surgery with left internal mammary artery harvesting, moderate body hypothermic (30 °C) CPB with crystaloid cardioplegia was performed. Serum antibiotic levels were determined before application, with skin incision, prior CPB induction, after cardioplegia infusion, every 20 minutes of CPB, prior end of CPB, in time of chest closure. Conventional cylinder – plate microbiological assay was used for antibiotic levelmeasurement. Results: All serum antibiotic concentrations showed a sharp decrease immediately after starting CPB and lasted until CPB ended. After initiating of CPB after cardioplegia administration serum concentrations of CTZ (105 min after initial dose) decreased by, on average 55%, CPF (97 min) by 42% and CLIN (116 min) by 78%. Conclusion: CPB can modify the time course of antibiotic serum concentrations. The serum levels of CTZ at the end of the longest procedures were found to be below the MICs for some of the suspected pathogens. We recommend to use higher antibiotic doses for prophylaxis and to administer the second dose with protamin sulphate to obtain maximum concentration in newly formed blood clots.

Questionnaire Survey Regarding Prevention of Surgical Site Infection after Neurosurgery in Japan: Focus on Perioperative Management and Administration of Surgical Antibiotic Prophylaxis

Various guidelines regarding surgical site infection (SSI) have recently been established. However, perioperative management of the wound and use of antibiotics have never been standardized completely in departments of neurosurgery in Japan. This survey investigated current perioperative management and administration of surgical antibiotic prophylaxis (SAP) and compared with guidelines intended to reduce SSI associated with neurosurgery in Japan. Questionnaires were distributed to members of the conference on Neurosurgical Techniques and Tools and the Japan Society of Aesthetic Neurosurgery via internet. The questionnaires asked about methods of perioperative management. A total of 255 members returned answers to the questionnaires. The questionnaires revealed that partial or no removal of the hair and hair shampooing at the day before surgery were performed in 96.1% and 88.1% of each institute following the World Health Organization (WHO) guidelines. Use of SAP at just before, during, and after surgery were 65.0%, 86.2%, and 63.0%, respectively. The postoperative period of use of intravenous SAP prolonged beyond 24 h in 80.0% against the recommendation of WHO. Perioperative management of wounds and use of SAP varies in institutes in Japan and some procedures were far different from the WHO guidelines. Japanese neurosurgeons should notice the prolonged SAP and comply with the WHO guidelines.

New WHO recommendations on intraoperative and postoperative measures for surgical site infection prevention: an evidence-based global perspective

Surgical site infections (SSIs) are the most common health-care-associated infections in developing countries, but they also represent a substantial epidemiological burden in high-income countries. The prevention of these infections is complex and requires the integration of a range of preventive measures before, during, and after surgery. No international guidelines are available and inconsistencies in the interpretation of evidence and recommendations in national guidelines have been identified. Considering the prevention of SSIs as a priority for patient safety, WHO has developed evidence-based and expert consensus-based recommendations on the basis of an extensive list of preventive measures. We present in this Review 16 recommendations specific to the intraoperative and postoperative periods. The WHO recommendations were developed with a global perspective and they take into account the balance between benefits and harms, the evidence quality level, cost and resource use implications, and patient values and preferences.

Routine Surveillance Versus Independent Assessment by an Outcome Adjudication Committee in Assessing Patients for Sternal Surgical Site Infections After Cardiac Surgery

Based on a cohort of 966 patients, routine surveillance data were not sufficiently accurate for use in clinical trials investigating surgical site infections. Surveillance data can only be used if adequate 90-day follow-up is provided and if cases identified by surveillance are independently reviewed by a blinded outcome adjudication committee.

Effectiveness of a bundled intervention of decolonization and prophylaxis to decrease Gram positive surgical site infections after cardiac or orthopedic surgery: systematic review and meta-analysis

OBJECTIVE

To evaluate studies assessing the effectiveness of a bundle of nasal decolonization and glycopeptide prophylaxis for preventing surgical site infections caused by Gram positive bacteria among patients undergoing cardiac operations or total joint replacement procedures.

DESIGN

Systematic review and meta-analysis.

DATA SOURCES

PubMed (1995 to 2011), the Cochrane database of systematic reviews, CINAHL, Embase, and clinicaltrials.gov were searched to identify relevant studies. Pertinent journals and conference abstracts were hand searched. Study authors were contacted if more data were needed.

ELIGIBILITY CRITERIA

Randomized controlled trials, quasi-experimental studies, and cohort studies that assessed nasal decolonization or glycopeptide prophylaxis, or both, for preventing Gram positive surgical site infections compared with standard care.

PARTICIPANTS

Patients undergoing cardiac operations or total joint replacement procedures. DATA EXTRACTION AND STUDY APPRAISAL: Two authors independently extracted data from each paper and a random effects model was used to obtain summary estimates. Risk of bias was assessed using the Downs and Black or the Cochrane scales. Heterogeneity was assessed using the Cochran Q and I(2) statistics.

RESULTS

39 studies were included. Pooled effects of 17 studies showed that nasal decolonization had a significantly protective effect against surgical site infections associated with Staphylococcus aureus (pooled relative risk 0.39, 95% confidence interval 0.31 to 0.50) when all patients underwent decolonization (0.40, 0.29 to 0.55) and when only S aureus carriers underwent decolonization (0.36, 0.22 to 0.57). Pooled effects of 15 prophylaxis studies showed that glycopeptide prophylaxis was significantly protective against surgical site infections related to methicillin (meticillin) resistant S aureus (MRSA) compared with prophylaxis using β lactam antibiotics (0.40, 0.20 to 0.80), and a non-significant risk factor for methicillin susceptible S aureus infections (1.47, 0.91 to 2.38). Seven studies assessed a bundle including decolonization and glycopeptide prophylaxis for only patients colonized with MRSA and found a significantly protective effect against surgical site infections with Gram positive bacteria (0.41, 0.30 to 0.56).

CONCLUSIONS

Surgical programs that implement a bundled intervention including both nasal decolonization and glycopeptide prophylaxis for MRSA carriers may decrease rates of surgical site infections caused by S aureus or other Gram positive bacteria.

Antibiotic prophylaxis in cardiac surgery: systematic review and meta-analysis

BACKGROUND

Antibiotic prophylaxis is recommended in cardiac surgery. Current debate concerns the type of antibiotic(s), dosing and the duration of prophylaxis.

METHODS

Systematic review of randomized controlled trials comparing one antibiotic regimen versus another in cardiac surgery. We searched The Cochrane Library, PubMed, LILACS, conference proceedings and bibliographies. Two reviewers independently extracted the data. The primary outcome was deep sternal wound infections (DSWIs). Meta-analysis was performed using the Mantel-Haenszel fixed-effect method. Risk ratios (RRs) with 95% confidence intervals (95% CIs) are reported.

RESULTS

Fifty-nine trials were included. There were no significant differences in DSWI or all other categories of surgical site infections (SSIs) for antibiotic prophylaxis with β-lactams comprising a Gram-negative spectrum of coverage versus prophylaxis targeting Gram-positive bacteria, but the former led to a significantly lower rate of post-operative pneumonia (RR 0.68, 95% CI 0.51-0.90) and all-cause mortality (RR 0.66, 95% CI 0.47-0.92). In trials comparing different antibiotic regimens for different durations, prophylaxis duration of ≤24 h post-operation led to higher rates of DSWI (RR 1.83, 95% CI 1.25-2.66), any sternal SSI, surgical interventions for SSI and endocarditis compared with longer duration prophylaxis. There was no advantage of regimens lasting >48 h post-operation. In the comparison of glycopeptides versus β-lactams, an advantage of glycopeptides was observed when comparators were given for similar duration and for β-lactams when given for a longer duration than the glycopeptides. There was no significant advantage of high antibiotic dosing.

CONCLUSIONS

Evidence supports second- or third-generation cephalosporins for cardiac surgery prophylaxis and points at a possible advantage of prophylaxis prolongation up to 48 h post-operatively.

Recent trends in the use of antibiotic prophylaxis in pediatric surgery

AIMS

The use of surgical antibiotic prophylaxis (AP) in children is poorly characterized. The aims of this study were to examine (1) trends in the use of AP for commonly performed operations, (2) appropriateness in the context of available guidelines, and (3) adverse events potentially attributable to AP.

METHODS

We conducted a 5-year retrospective analysis of 22 children's hospitals (January 2005-March 2009) for all patients younger than 18 years who underwent 1 of the 40 commonly performed general and urological procedures. Indications for AP were defined by published specialty-specific guidelines. Clostridium difficile infection and surrogate events for drug allergy (diphenhydramine and epinephrine administrations) were examined as potential antibiotic-associated adverse events.

RESULTS

Procedures of 246,316 were identified, of which 25% met criteria for AP. Eighty-two percent of the children received antibiotics during procedures when AP was indicated (range, 60%-96% by hospital), and 40% of the patients received antibiotics when there was no indication (range, 10%-83%). The likelihood of receiving AP was significantly different between hospitals for all procedures examined (P < .0001 for each procedure). Adverse events were significantly more frequent in children receiving AP than in those who did not (odds ratio [95% confidence interval] C difficile: 18.8 [6.9-51.5], P < .0001; epinephrine: 1.8 [1.7-2.0], P < .0001; diphenhydramine: 6.0 [5.6-6.5], P < .0001).

CONCLUSIONS

Significant variation exists in the use of AP in the pediatric surgical population. Many children do not receive AP when indicated, and an even greater proportion may receive antibiotics when there is no indication. These findings may have profound implications from a public health perspective when extrapolated to all children undergoing surgical procedures.

Continuous Infusion of Nafcillin for Sternal Osteomyelitis in an Infant After Cardiac Surgery

We report the use of the continuous infusion of nafcillin for the treatment of an infant who had methicillinsusceptible Staphylococcus aureus sternal osteomyelitis not responsive to traditional nafcillin dosing. The patient was successfully treated with surgical debridement and the continuous infusion of nafcillin. To our knowledge, this is the first report describing the successful use of the continuous infusion of nafcillin to treat an infant who had sternal osteomyelitis after cardiac surgery.

Prophylactic antibiotics in hip and knee arthroplasty

Prophylactic parenteral antibiotics have contributed to the present low rate of surgical site infections following hip and knee arthroplasty. Over the past decade, there has been a change in the pattern of methicillin-resistant Staphylococcus aureus infections from hospital-acquired to community-acquired. The findings of recent studies on screening programs to identify carriers of methicillin-resistant Staphylococcus aureus have been equivocal, with some studies showing that such programs reduce the rate of infections and others showing no effect on infection rates. Hospitals with antibiogram data that reveal high Staphylococcus resistance should consider use of vancomycin as a prophylactic antibiotic.

A national survey of antimicrobial prophylaxis in adult cardiac surgery across Canada

OBJECTIVE

To characterize national and regional patterns of antimicrobial prophylaxis in adult cardiac surgery across Canada.

DESIGN

Retrospective, cross-sectional analysis.

SETTING

Thirty-three adult cardiac surgical centres across Canada.

INTERVENTIONS

A one-page questionnaire collecting information regarding institutional demographics and antimicrobial prophylaxis regimens for adult cardiac surgical procedures was mailed to all adult surgical centres across Canada. If a response was not received within one month, a second survey was mailed, followed by a telephone reminder within two weeks of the second mailing.

MAIN RESULTS

The Overall response rate was 100%. Prophylactic antimicrobials were used in all the adult cardiac centres; single-agent prophylaxis was used in 97% (32 of 33) of centres; Single-dose antimicrobial prophylaxis was used in only 3% (one of 33) of centres. Preoperative and postoperative antimicrobial prophylaxis regimens varied both between provinces and within provinces across Canada. Cefazolin was the antimicrobial used in 88% (38 of 43) and 87% (33 of 38) of the reported pre-operative and post-operative prophylaxis regimens, respectively. Antimicrobial prophylaxis was initiated in the operating room 72% (26 of 36) of the time and intra-operative supplemental antimicrobial doses were administered for cardiac procedures longer than a median of 4 hours (range 4 to 8 hr). Overall, the median duration of antimicrobial prophylaxis was 36 hours (range 8 to 96 hr).

CONCLUSIONS

Despite the availability of various published guidelines, our survey identified several areas for improvement with respect to antimicrobial prophylaxis in adult cardiac surgery across Canada.

Electronic surveillance system for monitoring surgical antimicrobial prophylaxis

OBJECTIVES

Antimicrobial surgical prophylaxis comprises one third of all antibiotic use in pediatric hospitals and 80% of all antibiotic use in surgery. Previous studies reported that antimicrobial surgical prophylaxis is often inconsistent with recommended guidelines. An electronic surveillance system was developed to measure antimicrobial utilization and to identify opportunities to improve and monitor the administration of antibiotics for surgical prophylaxis.

METHODS

A retrospective cohort study was conducted on patients with selected inpatient surgical procedures performed from May 1999 to April 2000 at 4 US children's hospitals. International Classification of Diseases, Ninth Revision surgical procedure codes were divided into clean or unclean categories, and an electronic surveillance system was designed using antibiotic and microbiologic culture utilization data to measure appropriate antimicrobial use associated with the surgical procedure. A medical chart review was conducted to validate the electronic system.

RESULTS

Ninety percent of cases were classified properly by the electronic surveillance system as confirmed by medical chart review. Surgical antibiotic prophylaxis was not in accordance with the American Academy of Pediatrics (AAP) guidelines for almost half of all procedures. Prolonged antimicrobial administration in clean surgical procedures was the most frequent deviation from guidelines. Statistical differences between the index hospital and the comparison hospitals reflect both over- and underutilization of surgical prophylaxis with significant opportunity to improve prophylaxis for all hospitals.

CONCLUSIONS

Antimicrobial surgical prophylaxis at the children's hospitals studied is not always consistent with published AAP guidelines. This electronic surveillance system provides a rapid, reproducible, and validated tool to measure easily the efforts to improve adherence to AAP surgical prophylaxis guidelines.

Prophylaxis of sternal wound infections with gentamicin-collagen implant: randomized controlled study in cardiac surgery

Postoperative infections may lead to prolonged hospital stay and increased morbidity, mortality and hospital costs, especially in heart surgery. Finding new means to prevent infections would benefit both the patient and society. The aim of this study was to assess if locally administered gentamicin prevents sternal wound infections in coronary artery bypass (CABG) surgery. We randomized 542 consecutive CABG patients to two groups: those who received gentamicin-collagen implant under their sternum before closure (N=272) and controls (N=270). The subjects received routine intravenous antimicrobial prophylaxis (85% cefuroxime, 14% cefuroxime and vancomycin), and were followed-up for three months. The sternal wound infection rate was 4.0% (11/272) in the gentamicin group and 5.9% (16/270) in the control group. The mediastinitis rates were 1.1 and 1.9%, respectively. This treatment was safe and easy to administer, and no side-effects occurred. No statistically significant difference was demonstrated between infection rates in the two groups. This is the first study on the use of gentamicin-collagen sponge as prophylaxis in cardiac surgery. Our data show that infection was reduced slightly in the gentamicin-collagen group compared with the control group, but the study population was too small to draw conclusions. Further evaluation is needed, and the results may warrant another larger, better-powered study.

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.

Glycopeptides are no more effective than beta-lactam agents for prevention of surgical site infection after cardiac surgery: a meta-analysis

A meta-analysis was performed to investigate whether a switch from beta-lactams to glycopeptides for cardiac surgery prophylaxis should be advised. Results of 7 randomized trials (5761 procedures) that compared surgical site infections (SSIs) in subjects receiving glycopeptide prophylaxis with SSIs in those who received beta -lactam prophylaxis were pooled. Neither agent proved to be superior for prevention of the primary outcome, occurrence of SSI at 30 days (risk ratio [RR], 1.14; 95% confidence interval [CI], 0.91-1.42). In subanalyses, beta-lactams were superior to glycopeptides for prevention of chest SSIs (RR, 1.47; 95% CI, 1.11-1.95) and approached superiority for prevention of deep-chest SSIs (RR, 1.33; 95% CI, 0.91-1.94) and SSIs caused by gram-positive bacteria (RR, 1.36; 95% CI, 0.98-1.91). Glycopeptides approached superiority to beta-lactams for prevention of leg SSIs (RR, 0.77; 95% CI, 0.58-1.01) and were superior for prevention of SSIs caused by methicillin-resistant gram-positive bacteria (RR, 0.54; 95% CI, 0.33-0.90). Standard prophylaxis for cardiac surgery should continue to be beta-lactams in most circumstances.

Effect of sevoflurane on human neutrophil apoptosis

BACKGROUND AND OBJECTIVE

Both chronic occupational exposure to volatile anaesthetic agents and acute in vitro exposure of neutrophils to isoflurane have been shown to inhibit the rate of apoptosis of human neutrophils. It is possible that inhibition of neutrophil apoptosis arises through delaying mitochondrial membrane potential collapse. We assessed mitochondrial depolarization and apoptosis in unexposed neutrophils and neutrophils exposed to sevoflurane in vivo.

METHODS

A total of 20 mL venous blood was withdrawn pre- and postinduction of anaesthesia, the neutrophils isolated and maintained in culture. At 1, 12 and 24 h in culture, the percentage of neutrophil apoptosis was assessed by dual staining with annexin V-FITC and propidium iodide. Mitochondrial depolarization was measured using the dual emission styryl dye JC-1.

RESULTS

Apoptosis was significantly inhibited in neutrophils exposed to sevoflurane in vivo at 24 (exposed: 38 (12)% versus control: 28 (11)%, P = 0.001), but not at 1 or 12 h, in culture. Mitochondrial depolarization was not delayed in neutrophils exposed to sevoflurane.

CONCLUSIONS

The most important findings are that sevoflurane inhibits neutrophil apoptosis in vivo and that inhibition is not mediated primarily by an effect on mitochondrial depolarization.

Opioid-induced respiratory depression is associated with increased tidal volume variability

BACKGROUND AND OBJECTIVE

mu-agonistic opioids cause concentration-dependent hypoventilation and increased irregularity of breathing. The aim was to quantify opioid-induced irregularity of breathing and to investigate its time-course during and after an opioid infusion, and its ability to predict the severity of respiratory depression.

METHODS

Twenty-three patients breathing spontaneously via a continuous positive airway pressure (CPAP) mask received an intravenous (i.v.) infusion of alfentanil (2.3 microg kg(-1) min(-1), 14 patients) or pirinitramide (piritramide) (17.9 microg kg(-1) min(-1), nine patients) until either a cumulative dose of 70 microg kg(-1) for alfentanil or 500 microg kg(-1) for pirinitramide had been achieved or the infusion had to be stopped for safety reasons. Tidal volumes (VT) and minute ventilation were measured with an anaesthesia workstation. For every 20 breaths, the quartile coefficient was calculated (Qeff20V(T)).

RESULTS

Both the decrease of minute volume and the increase of Qeff20V(T) during and after opioid infusion were highly significant (P < 0.001, ANOVA). Patients in which the alfentanil infusion had to be terminated prematurely had lower minute volumes (P = 0.002, t-test) and higher Qeff20V(T) (P = 0.034, t-test) than those who received the complete dose. Changes in the regularity of breathing measured as Qeff20V(T) parallel those of minute ventilation during and after opioid infusion.

CONCLUSIONS

Opioids cause a more complicated disturbance of the control of respiration than a mere resetting to higher PCO2. Furthermore, Qeff20V(T) appears to predict the severity of opioid-induced respiratory depression.

Intravenous patient-controlled analgesia after thoracotomy: a comparison of morphine with tramadol

BACKGROUND AND OBJECTIVE

This study examined the quality of analgesia together with the side-effects produced by tramadol compared with morphine using intravenous patient-controlled analgesia during the first 24 h after thoracotomy.

METHODS

Forty-four patients scheduled for thoracotomy were included in the study. Morphine 0.3 mg kg(-1) was given interpleurally 20 min before a standard general anaesthetic. In the postanaesthetic care unit, the patients were randomly allocated to one of two groups to self-administer tramadol or morphine using a patient-controlled analgesia device throughout a 24 h period. The patient-controlled analgesia device was programmed to deliver tramadol 20 mg as an intravenous bolus or morphine 2 mg with a lockout time of 10 min.

RESULTS

Mean cumulative morphine and tramadol consumption were 48.13 +/- 30.23 and 493.5 +/- 191.5 mg, respectively. There was no difference in the quality of analgesia between groups. Five (26.3%) patients in the tramadol group and seven (33%) in the morphine group had nausea, and three of the latter patients vomited. The incidence rate of vomiting with tramadol was 5.2%. All vital signs were within safe ranges. Sedation was less in the tramadol group, but not statistically significant.

CONCLUSIONS

In this clinical setting, which includes interpleural morphine pre-emptively, postoperative analgesia provided by tramadol was similar to that of morphine at rest and during deep inspiration. Side-effects were slight and comparable between the patients receiving morphine and tramadol.

Effects of ropivacaine on human neutrophil function: comparison with bupivacaine and lidocaine

BACKGROUND AND OBJECTIVE

Neutrophils are important both for the immunological defence system and for the inflammatory tissue autoinjury mechanism. However, many local anaesthetics impair certain neutrophil functions. The aim was to assess the effects of ropivacaine, bupivacaine and lidocaine on human neutrophils from adult volunteers.

METHODS

Chemotaxis, phagocytosis, reactive oxygen species production, intracellular calcium ion ([Ca2+]i) concentrations and protein kinase C activity were measured in the absence and presence of ropivacaine, bupivacaine or lidocaine. The lowest concentrations of the local anaesthetics were similar to those clinically observed in the plasma.

RESULTS

Bupivacaine did not affect any neutrophil function (P > 0.05). Ropivacaine failed to change chemotaxis or phagocytosis, while lidocaine suppressed both these neutrophil functions. Ropivacaine (15, 150 microg mL(-1)) and lidocaine (20, 200 microg mL(-1)) impaired neutrophil production of O2-, H2O2 and OH- (P < 0.05) at similar rates (by 7-10%). These same concentrations of ropivacaine and lidocaine suppressed [Ca2+1i elevation. Finally, neither ropivacaine nor bupivacaine inhibited protein kinase C activity, while lidocaine did.

CONCLUSIONS

Suppression of the [Ca2+]i response in neutrophils by ropivacaine may represent one of the mechanisms responsible for the impairment of neutrophil functions. It should be emphasized that the inhibitory effects of ropivacaine are minor and are attained only at high concentrations, which may minimize the clinical implication of ropivacaine-associated impairment of reactive oxygen species production. Further studies using in vivo systems are required to identify the inhibitory effects of ropivacaine on reactive oxygen species production in clinical settings.

Neural nets and prediction of the recovery rate from neuromuscular block

BACKGROUND AND OBJECTIVE

The aim was to train artificial neural nets to predict the recovery of a neuromuscular block during general anaesthesia. It was assumed that the initial/early neuromuscular recovery data with the simultaneously measured physical variables as inputs into a well-trained back-propagation neural net would enable the net to predict a rough estimate of the remaining recovery time.

METHODS

Spontaneous recovery from neuromuscular block (electrically evoked electromyographic train-of-four responses) were recorded with the following variables known to affect the block: multiple minimum alveolar concentration, end-tidal CO2 concentration, and peripheral and central temperature.

RESULTS

The mean prediction errors, mean absolute prediction errors, root-mean-squared prediction errors and correlation coefficients of all the nets were significantly better than those of average-based predictions used in the study. The root-mean-squared prediction error of the net - employing minimum alveolar concentrations from the whole recovery period (the recovery time from E2/E1 = 0.30 to E4/E1 = 0.75; E1 = first response of train-of-four, E2 = second response of train-of-four, etc.)--were significantly smaller than those of other nets, or the same net employing minimum alveolar concentrations only from the initial recovery period (from E2/E1 = 0.30 to E4/E1 = 0.25).

CONCLUSIONS

Neural nets could predict individual recovery times from the neuromuscular block significantly better than the average-based method used here, which was supposed to be more accurate than guesses by any clinician. The minimum alveolar concentration was the only monitored variable that influenced the recovery rate, but it did not aid neural net prediction.

Sevoflurane but not isoflurane can reduce prostacyclin production of endothelial cells

BACKGROUND AND OBJECTIVE

Little is known about the interaction of newer volatile anaesthetics with endothelial eicosanoid production. Sevoflurane may possibly reduce prostacyclin formation. Thus, we compared the influences of sevoflurane and isoflurane on endothelial prostacyclin production.

METHODS

Production of prostacyclin of human umbilical vein endothelial cells was measured by the ELISA technique under basal conditions and after stimulation with calcium ionophore A 23187 10 micromol or histamine 0.1 micromol in the absence and presence of 1 and 2 minimal alveolar concentrations (MAC) of sevoflurane or isoflurane.

RESULTS

The basal production of prostacyclin was unaffected by the volatile anaesthetics. Stimulation of endothelial cells increased prostacyclin formation 3-5-fold. Sevoflurane at 2 MAC, but not at 1 MAC, could reduce stimulated prostacyclin production by about half (P < 0.05). Isoflurane had no inhibitory effect. Inhibition of cyclo-oxygenase function by acetylsalicylic acid abolished the induced burst of prostacyclin formation completely.

CONCLUSIONS

Sevoflurane, but not isoflurane, can reduce stimulated endothelial prostacyclin production in a concentration-dependent manner. Because at least 2 MAC of sevoflurane were required, this effect should be of minor importance under clinical conditions of balanced anaesthesia.

Adsorption of sufentanil to epidural filters and catheters

BACKGROUND AND OBJECTIVE

Stable drug concentrations must be administered to provide adequate patient-controlled epidural analgesia. This study investigated the stability of sufentanil after the epidural delivery system had been flushed with solutions containing the drug.

METHODS

Sufentanil citrate, 5 microg mL(-1) was injected through an epidural catheter system into a glass container. The concentrations of the drug leaving the system, in 1 mL aliquots (1-5 mL) were measured using high-performance liquid chromatography. In the same manner, sufentanil samples were analysed after flushing the filter, as well as after priming the filter and catheter.

RESULTS

ANOVA for repeated measurements demonstrated that sufentanil concentrations remained constant as long as the catheter had been adequately flushed. However, the concentration of sufentanil in the solution exiting the filter was reduced significantly. Hardly any sufentanil could be detected (0.09 +/- 0.01 microg mL(-1), P < 0.001) in the first 1 mL aliquot (probe) leaving the filter. Altogether, 3 mL sufentanil solution was needed to pass through the filter before the baseline values were restored (P > 0.05). The greatest decrease occurred when the whole epidural delivery apparatus (catheter and filter) was primed; to regain baseline values, as much as 4 mL solution was needed to flush the system.

CONCLUSIONS

Sufentanil citrate is adsorbed by the materials used to manufacture systems (catheters, filters) used in epidural anaesthesia. Hence, the epidural catheter system should be primed with sufentanil before connecting it to the patient so as to deliver reliable concentrations.

Nitrous oxide/oxygen mixture and the prevention of pain during injection of propofol

BACKGROUND AND OBJECTIVE

The incidence of pain associated with the injection of propofol still remains a problem. This study sought to examine the analgesic effects of inhaled nitrous oxide in oxygen on the prevention of propofol injection pain.

METHODS

Nitrous oxide in oxygen was compared with a lidocaine (20 mg)-propofol mixture and with propofol alone (control) in a prospective, randomized, observer-blinded study. ASA I and II patients (n = 135) scheduled for elective surgical procedures were studied. A standard propofol injection technique and scoring system to measure the pain on injection was used.

RESULTS

Demographic variables were similar between the study groups. Without analgesia (control) 26 of 45 patients (58%) reported pain on injection compared with 11 of 45 patients (24%) in both the nitrous oxide (95% CI: 14-52%, P = 0.001) and lidocaine groups (95% CI: 14-52%, P = 0.001).

CONCLUSIONS

The inhalation of a nitrous oxide/oxygen mixture significantly reduces the incidence of pain during propofol injection. This therapeutic stratagem was as effective as a lidocaine-propofol mixture.

Effects of repeated anaesthesia on central cholinergic function in the rat cerebral cortex

BACKGROUND AND OBJECTIVE

General anaesthesia may contribute to postoperative cognitive decline in the elderly. The aim was to determine the effects of repeated pentobarbital anaesthesia throughout life on central cholinergic function in the rat.

METHODS

Young Lewis rats were randomly allocated to two groups. The anaesthesia group (n = 15) was anaesthetized with pentobarbital 20 mg kg(-1) intraperitoneally at 6, 8.5, 11, 13.5, 16, 18.5, 21 and 23.5 months of age. The control group (n = 12) was treated identically, apart from the anaesthesia. At 26 months of age, the animals were killed and the brain dissected and stored for analysis. Central cholinergic function in the cortex and hippocampus was assessed by measuring [3H]-epibatidine and [125I]alpha-bungarotoxin binding to nicotinic receptors and choline acetyltransferase (ChAT) activity.

RESULTS

Tissue from nine rats in the anaesthesia group and eight in the control group was available for analysis. There was a significant reduction in alpha-bungarotoxin binding in the anaesthetized compared with the control group in the superior cortex (P < 0.0002) and molecular cortex (P < 0.04). There were no significant differences between the groups for epibatidine binding or ChAT.

CONCLUSIONS

Repeated anaesthesia in rat reduces central nicotinic cholinergic binding in the cortex. The findings may have implications for postoperative cognitive function studies.

Induced arterial hypotension for interventional thoracic aortic stent-graft placement: impact on intracranial haemodynamics and cognitive function

BACKGROUND AND OBJECTIVE

The study investigated the impact of induced arterial hypotension for the facilitation of endovascular stent-graft placement in patients with thoracic aortic aneurysm on cerebral blood flow velocity and neurological/neurocognitive outcome.

METHODS

In 27 ASA III patients, cerebral blood flow velocity was recorded during induced arterial hypotension for endovascular stent-graft placement using transcranial Doppler sonography and the Folstein Mini Mental State Examination and the National Institute of Health Stroke Scale were performed before and after the intervention.

RESULTS

Mean arterial pressure was decreased <50 mmHg, and in 22 patients it was <40 mmHg. Diastolic cerebral blood flow velocity decreased by 59%. Postoperatively, six of 21 patients exhibited changes in the Folstein Mini Mental State Examination and four of these six patients in the National Institute of Health Stroke Scale as indices of new-found neurocognitive dysfunction, but there were no signs of stroke. Loss of the diastolic blood flow profile was detected in two of six patients with new-found neurocognitive dysfunctions and in 18 of 21 patients with no new-found neurocognitive dysfunction. Changes in the Folstein Mini Mental State Examination on postoperative day 1 were correlated to the pre-procedural Folstein Mini Mental State Examination, but not to the time spent with a mean arterial pressure <50 mmHg, <40 mmHg or with a loss of diastolic blood flow profile.

CONCLUSIONS

Transcranial Doppler sonography visualizes the individual effect of induced hypotension and the period of intracranial circulatory arrest during aortic stent-graft placement. However, transient new-found neurocognitive dysfunctions occur independently of the transcranial Doppler data, and are in close correlation to the neurocognitive state before the procedure. The results suggest that induced arterial hypotension is not the major factor for postoperative new-found neurocognitive dysfunction.

Gastric mucosal-to-end-tidal PCO2 difference during major abdominal surgery: influence of the arterial-to-end-tidal PCO2 difference?

BACKGROUND AND OBJECTIVE

Because gastric mucosal PCO2 must be referenced to arterial values via a gastric-to-arterial PCO2 gap (Pg-aCO2), the gastric-to-end-tidal PCO2 difference (Pg-ETCO2) may be proposed as a surrogate method to monitor Pg-aCO2. However, the influence of arterial-to-end-tidal PCO2 (Pa-ETCO2) on its value remains unknown. Pa-ETCO2 may be enhanced by a low cardiac output and subsequent reduced perfusion of the lungs. This study was designed to compare such gaps observed during abdominal surgery in patients with or without preoperative cardiac dysfunction.

METHODS

Haemodynamic, metabolic and tonometric variables were measured in seven patients with Crohn's disease and in five patients with chronic heart failure scheduled for abdominal surgery. Data were collected before skin incision (T0); at extractor placement (T1), 30 (T2) and 60 (T3) min later; at organ extraction (T4), 30 (T5) and 60 (T6) min later, and at the end of surgery (T7).

RESULTS

Gradients appeared larger in the cardiac group. The difference was significant for Pg-ETCO2 during the whole study period, while it was only reached at T1-T2 for Pa-ETCO2 and at T5-T6 for Pg-aCO2. Gaps did not change significantly over the peroperative time points in either group. No major haemodynamic variations were registered in either group.

CONCLUSIONS

In patients with preoperative chronic heart failure, Pg-ETCO2 remained constant throughout a major general surgical procedure and was only moderately influenced by the Pa-ETCO2 gap. In these patients, Pg-ETCO2 may be used as a reliable index of gastrointestinal perfusion after control of PaCO2.

Ondansetron disintegrating tablets of 8 mg twice a day for 3 days did not reduce the incidence of nausea or vomiting after laparoscopic surgery

BACKGROUND AND OBJECTIVE

Although many antiemetic drugs are available for intravenous use in the hospital setting, few are available after patient discharge. Consequently, nausea and vomiting are frequent complaints from patients at home after ambulatory surgery. We tested the hypothesis that the new 8 mg ondansetron disintegrating tablets will decrease the rate of nausea and vomiting at home after laparoscopic surgery.

METHODS

Ninety-six patients were studied in a randomized double-blind study. Starting the first evening after operation and continuing every 12 h for 3 days, patients received either placebo or ondansetron 8 mg disintegrating tablets orally. The patients returned a questionnaire about postoperative nausea and vomiting, other side-effects, e.g. dizziness, headache, nightmare, anxiety and pain, as well as their overall satisfaction at 24 and 72 h after completion of surgery.

RESULTS

The rates of nausea and vomiting were similar in the two groups, both during the first 24 h (28 versus 48%, placebo and ondansetron, respectively (ns) and during the 24-72 h (21 versus 35% (ns)). The incidence rate of vomiting was 8% (placebo) versus 12% (ondansetron) during the first 24 h (ns) and 9 versus 13% respectively in the 24-72 h (ns). No difference between groups was observed in overall satisfaction, incidence of postoperative pain or other side-effects.

CONCLUSIONS

The use of ondansetron disintegrating tablets of 8 mg twice a day for 3 days did not reduce the incidence of nausea and vomiting in patients undergoing outpatient laparoscopic surgery.

Effects of xenon on mesenteric blood flow

BACKGROUND AND OBJECTIVE

The effects of xenon on mesenteric vascular resistance have not been investigated. Because human beings anaesthetized with xenon show good cardiovascular stability, we believed that the agent would have little or no effect on vascular resistance in the splanchnic bed. We determined the effects of different inhaled xenon concentrations on mesenteric blood flow and mesenteric oxygen consumption in pigs sedated with intravenous propofol.

METHODS

Twenty-three minipigs were instrumented with transit time flow probes around the pulmonary and superior mesenteric arteries as well as with pulmonary artery and portal venous catheters. A 14 h recovery was allowed followed by recordings of baseline values. Xenon was then randomly administered in 0.30, 0.50, and 0.70 end-tidal fractions.

RESULTS

The administration of xenon resulted in an 8% (not dose dependent) decrease in mean arterial pressure (from 99 +/- 15 to 91 +/- 19 mmHg; P < 0.05), a 20% decrease in calculated systemic oxygen consumption (from 0.23 +/- 0.07 to 0.19 +/- 0.04L min(-1); P < 0.01), a 20% reduction in mesenteric oxygen delivery (from 41 +/- 12 to 33 +/- 11 mL min; P < 0.001), a 37% reduction in mesentericmetabolic rate of oxygen (from 11.3 +/- 3.6 to 7.1 +/- 3.2 mL min(-1); P < 0.01) and an 8% decrease in mesenteric artery blood flow (0.22 +/- 0.07 to 0.20 +/- 0.07 L min(-1); P < 0.05) in a dose-dependent fashion. Heart rate, cardiac output, systemic vascular resistance, mesenteric vascular resistance, mesenteric oxygen extraction fraction and portal lactate concentration were not significantly altered by xenon.

CONCLUSIONS

Xenon inhalation in the propofol-sedated pig had no measurable effects on mesenteric vascular resistance. This finding may partly explain the well-known cardiovascular stability observed in patients anaesthetized with xenon. Although mesenteric artery blood flow and mesenteric oxygen delivery decreased during xenon administration, unchanged mesenteric oxygen extraction fraction and portal lactate suggest that metabolic regulation of the splanchnic circulation remained unaltered.

Dopamine stabilizes milrinone-induced changes in heart rate and arterial pressure during anaesthesia with isoflurane

BACKGROUND AND OBJECTIVE

Phosphodiesterase-III inhibitors and dobutamine effectively improve cardiac function in patients with cardiac failure, but they are limited by possible hypotensive effects. We tested the hypothesis that dopamine contributes to stabilizing milrinone-induced haemodynamic changes.

METHODS

Nine patients undergoing major surgery were anaesthetized using nitrous oxide and oxygen supplemented with isoflurane 1-2%. After baseline haemodynamics were recorded, milrinone (25 or 50 microg kg(-1)) was administered over 10min, followed by a continuous infusion (0.5 microg kg(-1) min(-1). The second set of haemodynamic values was measured 50 min after beginning the continuous infusion of milrinone. Dopamine (4 microg kg(-1) min(-1)) was then administered with milrinone.

RESULTS

Milrinone significantly increased the heart rate from 81 +/- 8 to 102 +/- 16beats min(-1), but it decreased the mean arterial pressure from 83 +/- 10 to 66 +/- 10 mmHg and systemic vascular resistance (P < 0.05 for each). The pulmonary capillary wedge pressure, cardiac index and pulmonary vascular resistance did not change significantly. The addition of dopamine to the milrinone infusion significantly decreased the heart rate (94 +/- 12 beats min(-1)) and increased the mean arterial pressure (82 +/- 11 mmHg). Dopamine and milrinone, but not milrinone alone, significantly increased the cardiac index and the rate-pressure product.

CONCLUSIONS

The combination regimen of milrinone and dopamine improved cardiac function, and changes in heart rate and mean arterial pressure induced by milrinone were attenuated by dopamine. The results suggest that a combination regimen of milrinone and dopamine rather than milrinone alone should be used to maintain arterial pressure.

A retrospective review of three antibiotic prophylaxis regimens for pediatric cardiac surgical patients

BACKGROUND

Optimal antimicrobial prophylaxis for the pediatric cardiac surgical patient is unknown. We have reviewed our experience with more than 4,000 pediatric cardiac surgical patients at the University of Michigan to evaluate antibiotic prophylaxis regimens.

METHODS

Three antibiotic prophylaxis protocols were serially used during a 6-year period: Protocol 1 (n = 786): cefazolin was administered before operation and continued as long as thoracostomy tubes or central venous catheters were present; Protocol 2 (n = 1095): cefazolin was discontinued 48 hours postoperatively, regardless of the presence of tubes or catheters; Protocol 3 (n = 2039): cefazolin was continued as long as thoracostomy tubes were present, but not for central venous catheters. Patients with an open chest postoperatively received vancomycin and gentamicin until chest closure. This was identical during all three protocols. We retrospectively determined the rate of surgical site infections and unrelated bloodstream infections (the latter for both cardiac medical and surgical patients) for the three protocols.

RESULTS

Surgical site infections per 100 operations for protocols 1, 2, and 3 was 2.04, 6.58, and 1.67, respectively (p < 0.05 for protocol 2 versus protocols 1 and 3). The mean age of patients with a surgical site infection ranged from 12 to 15.4 months. Patients with an open chest had a higher rate of surgical site infection (18.8% for protocol 2 and 9.3% for protocol 3). Bloodstream infections per 1,000 patient days for protocols 1, 2, and 3 were 2.18, 6.51, and 5.02, respectively (p < 0.05 protocol 1 versus protocols 2 and 3).

CONCLUSIONS

These data suggest that pediatric cardiac surgical patients may benefit from prophylactic antibiotics as long as thoracostomy tubes are in place.