Major sternal wound infection after open-heart surgery: a multivariate analysis of risk factors in 2,579 consecutive operative procedures

Variables predicting adverse outcome in patients with deep sternal wound infection

BACKGROUND

Mortality after deep sternal wound infection (DSWI) ranges between 5% and 47%. Variables predicting hospital mortality and prolonged hospital stay are still to be assessed.

METHODS

Among 13,420 patients who underwent cardiac surgery in our institution between 1979 and 1999, DSWI developed in 112 cases (0.8%). Multiple variables were recorded prospectively and analyzed retrospectively as predictors of hospital death and prolonged (>30 days) hospital stay. The analyzed variables were divided into three groups: (1) related to the patient, including demographic variables and preoperative conditions; (2) related to cardiac operation; and (3) related to infection. Predictive variables were assessed by univariate and multivariate logistic regression analysis.

RESULTS

Hospital mortality was 16.9%. The hospital stay of the 93 discharged patients ranged between 16 and 180 days (mean 31.3 +/- 15.2). Length of cardiac operation, length of stay in intensive care unit, interval between symptoms of DSWI and wound debridement were found to be the most significant predictors of bad outcome following DSWI.

CONCLUSIONS

In our study demographic variables and preoperative conditions did not affect the prognosis of DSWI. Lower mortality rate and shorter hospital stay could be achieved with earlier and aggressive treatment of DSWI.

Comparison of standard coronary artery bypass grafting and minimary invasive direct coronary artery bypass grafting. Early and mid-term result

OBJECTIVES

We studied indications and problems involved in minimally invasive coronary artery bypass grafting (MIDCAB).

METHODS

We compared patients profiles, graft patency, stenosis severity, morbidity, mortality, long-term survival and freedom from cardiac accidents in 174 patients undergoing elective standard coronary artery bypass grafting (CABG) and 128 undergoing between January 1996 and March 1999.

RESULTS

No statistically difference was seen in gender, diabetes mellitus, renal failure, cerebrovascular accident, multi-vessel disease ratios, or left main trunk stenosis between 2 groups. Internal thoracic artery graft patency was 97% (114/118) and the rate of anastomotic stenosis (> 50%) was 9% (10/118) compared to 96% (213/221) in the MIDCAB group. The 3-year survival rate was 91% in the MIDCAB group and 92% in the CABG group and freedom from cardiac accidents, most involving pericutaneus transluminal coronary angioplasty retreatment, was 66% in the MIDCAB group and 88% in the CABG group.

CONCLUSION

Although patency and stenosis incidence did not differ between 2 groups, freedom from cardiac accidents was lower in the MIDCAB group.

Ten-year experience with Mersilene-reinforced sternal wound closure

BACKGROUND

We were interested in reviewing our experience with Mersilene-reinforced sternal wound closure to evaluate its overall morbidity and its impact on patient management.

METHODS

We reviewed our experience with 1,039 patients undergoing median sternotomy with Mersilene-reinforced sternal wound closure over the past 10 years. Major wound complications, which were categorized into two groups, required in-hospital management and operative intervention. Group 1 had a sternal dehiscence alone. Group II had a major sternal infection or mediastinitis.

RESULTS

The incidence of wound morbidity was 2.4% (n = 25). There were 6 (0.58%) sternal dehiscences (Group I) and 19 (1.8%) sternal wound infections (Group II). Patients taken to the operating room for repair of their sternal dehiscence or sternal infection were noted to have two completely intact sternal halves.

CONCLUSIONS

While wound related morbidity with Mersilene tape closure is equivalent to the historical results of conventional wire closure, dehiscence occurs in a more controlled fashion with less bony destruction. The reduction in tissue damage associated with sternal wound dehiscence and sternal infection after Mersilene-reinforced sternal wound closure makes treatment of these potentially devastating complications easier and more efficient.

Coagulase-negative staphylococci and sternal infections after cardiac operation

BACKGROUND

Coagulase negative staphylococci (CoNS) have been recognized as important pathogens in nosocomial infections, especially in connection with implanted foreign materials. In cardiac operation they are among the most common pathogens isolated from infected sternal wounds. The definition of the infection is very important. In this study we focus on deep postoperative chest infections.

METHODS

By studying 33 infected patients retrospectively and comparing them to 33 matched uninfected controls, we studied the characteristics and costs of the infections.

RESULTS

Typical for these infections is the late and insidious onset, and that the infections initially give only minor symptoms such as pain, redness, and serous secretion. We found the following risk factors for infection: number of preoperative days in a hospital, the total length of the operation, and if the patient had undergone an early reoperation due to causes other than infection. This kind of infection more than doubled the hospital costs for the patients affected.

CONCLUSIONS

Coagulase negative staphylococci are the most important pathogens in deep postoperative infections in this material. They cause infections that are difficult to recognize since they give only discrete symptoms and start well after the patients leave the hospital. The risk factors for patients with CoNS infections are mostly associated with a long exposure to the hospital environment. The treatment is often difficult and costly because of multiresistant bacteria and frequent need for repeated surgical revisions.

Nosocomial pneumonia in patients undergoing heart surgery

OBJECTIVE

To determine the risk factors related to the presence of postsurgical nosocomial pneumonia (NP) in patients who had undergone cardiac surgery.

DESIGN

A case-control study.

SETTING

Postcardiac surgical intensive care unit at a university center.

PATIENTS

A total of 45 patients with NP and 90 control patients collected during a 4-yr period.

INTERVENTIONS

Pre-, intra-, and postoperative factors were collected and compared between two groups of patients (cases vs. controls) to determine their influence on the development of NP. The diagnosis of NP was always microbiologically confirmed as pulmonary specimen brush culture of > or =10(3) colony-forming units/mL or positive blood culture/pleural fluid culture by the growth of identical microorganisms isolated at the lung. For each patient diagnosed with NP, we selected control cases at a ratio of 1:2.

MEASUREMENTS AND MAIN RESULTS

The incidence of NP was 6.5%. Multivariate analysis found a probable association of the following variables with a greater risk for the development of NP: reintubation (adjusted odds ratio [AOR], 62.5; 95% confidence interval [CI], 8.1-480; p = .01); nasogastric tube (AOR, 19.7; 95% CI, 3.5-109; p = .01), transfusion of > or =4 units of blood derivatives (AOR, 12.8; 95% CI, 2-82; p = .01) and empirical treatment with broad-spectrum antibiotics (AOR, 6.6; 95% CI, 1.2-36.8; p = .02). Culture results showed 13.3% of the NP to be of polymicrobial origin, whereas 77.3% of the microorganisms isolated were Gram-negative bacteria. The mortality (51 vs. 6.7%, p < .01) and the length of stay in the intensive care unit (25+/-14.8 days vs. 5+/-5 days, p < .01) were both greater in patients with NP.

CONCLUSIONS

We conclude that the surgical risk factors, except the transfusion of blood derivatives, have little effect on the development of NP. Reintubation, nasogastric tubing, previous therapy with broad-spectrum antibiotics, and blood transfusion are factors most likely associated with NP acquisition.

New Technique for Reinforced Sternal Closure

A simplified method of reinforced sternal closure is described. Figure-of-8-shaped sutures of no. 5 stainless steel wire are inserted with 2 Sterna-Bands between them. The advantages of this technique are simplicity, effectiveness, and speed.

The endogenous pathway is a major route for deep sternal wound infection

OBJECTIVE

Deep wound infections pose an increasing problem in cardiac surgery patients. Prospective infection monitoring is thus a means of identifying possible risk factors.

METHODS

Within a period of 5 months, a total of 376 adult patients, 260 men and 116 women, with a mean age of 62.6 years (range 18-88), underwent coronary bypass grafting (n=281) or other cardiac surgery procedures (n=95). Nasal cultures were taken preoperatively from every patient, as well as cultures of the wound during surgery and when dressings were changed thereafter. In addition, nasal cultures were taken from all the medical and nursing staff. To differentiate endogenous and exogenous infection pathways, DNA fingerprint analysis was performed.

RESULTS

A total of 38 patients (10.1%) developed a wound infection, in 14 patients this happened to be a deep wound infection, in 24 patients a superficial one. Five sternal wound infections were associated with mediastinitis (1.3%). The occurrence of a wound infection overall resulted in prolonged hospitalization (29.4+/-24 vs. 11.9+/-6.9 days, P=0.001), but not in increased hospital mortality (4.4% vs. 3.9%). Obesity, diabetes mellitus and nasal carriage of Staphylococcus aureus proved to be independent risk factors with an odds ratio of 2.07, 2.26 and 2.28, respectively. In all but one of the sternal colonizations with S. aureus, DNA fingerprint analysis demonstrated an identical pattern of S. aureus from the patient's nose and sternum, indicating an endogenous infection pathway.

CONCLUSIONS

The determination of the endogenous pathway for severe wound infection makes prevention possible by means of preoperative local S. aureus eradication.

Modifiable risk factors associated with deep sternal site infection after coronary artery bypass grafting

OBJECTIVE

Our objective was to identify risk factors for deep sternal site infection after coronary artery bypass grafting at a community hospital.

METHODS

We compared the prevalence of deep sternal site infection among patients having coronary artery bypass grafting during the study (January 1995-March 1998) and pre-study (January 1992-December 1994) periods. We compared any patient having a deep sternal site infection after coronary artery bypass graft surgery during the study period (case-patients) with randomly selected patients who had coronary artery bypass graft surgery but no deep sternal site infection during the same period (control-patients).

RESULTS

Deep sternal site infections were significantly more common during the study than during the pre-study period (30/1796 [1.7%] vs 9/1232 [0.7%]; P =.04). Among 30 case-patients, 29 (97%) returned to the operating room for sternal debridement or rewiring, and 2 (7%) died. In multivariable analyses, cefuroxime receipt 2 hours or more before incision (odds ratio = 5.0), diabetes mellitus with a preoperative blood glucose level of 200 mg/dL or more (odds ratio = 10.2), and staple use for skin closure (odds ratio = 4.0) were independent risk factors for deep sternal site infection. Staple use was a risk factor only for patients with a normal body mass index.

CONCLUSIONS

Appropriate timing of antimicrobial prophylaxis, control of preoperative blood glucose levels, and avoidance of staple use in patients with a normal body mass index should prevent deep sternal site infection after coronary artery bypass graft operations.

Risk factors for surgical wound infection and bacteraemia following coronary artery bypass surgery

BACKGROUND

There has been no consensus from previous studies of risk factors for surgical wound infections (SWI) and postoperative bacteraemia for patients undergoing coronary artery bypass graft (CABG) surgery.

METHODS

Data on 15 potential risk factors were prospectively collected on all patients undergoing CABG surgery during a 12-month period.

RESULTS

Of 693 patients, 62 developed 65 SWI using the Centres for Disease Control definition: 23 were sternal wound infections and 42 were arm or leg wound infections at the site of conduit harvest. There were 19 episodes of postoperative bacteraemia. Multivariate analysis revealed that: (i) diabetes, obesity and previous cardiovascular procedure were independent predictors of SWI; and (ii) obesity was an independent risk factor for postoperative bacteraemia.

CONCLUSIONS

These findings suggest that improved diabetic control and pre-operative weight reduction may result in a decrease in the incidence of SWI. But further prospective studies need to be undertaken to examine (i) whether the increased SWI risk in diabetes occurs with both insulin- and non-insulin-requiring diabetes, and whether improved peri-operative diabetes control decreases SWI; and (ii) what degree of obesity confers a risk of SWI and postoperative bacteraemia, and whether pre-operative weight reduction, if a realistic strategy in this patient group, results in a decrease in SWI.

Computed tomography of the sternum and mediastinum after median sternotomy

BACKGROUND

Computed tomography is used in our hospital to diagnose complications after median sternotomy, but its efficiency is unknown. Nor is the computed tomographic appearance of normal healing of a median sternotomy known. Computed tomography was evaluated for its ability to diagnose mediastinitis and sternal dehiscence, and a reference material of normally healing median sternotomies was created.

METHODS

In a prospective study, 20 patients with a normally healing median sternotomy were examined 1 week, 1 month, 3 months, and 6 months after operation. In a retrospective study, 87 scans from 65 patients that were made because a postoperative complication was suspected were reviewed.

RESULTS

In the prospective study, all patients had clinically uneventful healing. None of the computed tomographic scans showed radiologic signs of healing at 3 months. At 6 months, half of the patients had healed completely. In the retrospective study, 49 scans were performed on suspicion of infection; 7 of them indicated mediastinitis, 2 were false-positive, while mediastinitis was present in a total of 16 of the scans. Thirty-eight scans were made because of sternal pain or suspected dehiscence; after 21 of the scans, recovery was uneventful, and in 11, the definite diagnosis was dehiscence or pseudarthrosis.

CONCLUSIONS

Clinical healing of the sternotomy does not correlate with the computed tomographic image. Computed tomography is not a sensitive tool for diagnosing mediastinitis, and in patients with sternal pain, it adds little information.

Mechanical analysis of midline sternotomy wound closure

OBJECTIVE

Unstable median sternotomy closure can lead to postoperative morbidity. This study tests the hypothesis that separation of the sternotomy site occurs when physiologic forces act on the closure.

METHODS

Median sternotomy was performed in 4 human cadavers (2 male) and closed with 7 interrupted stainless steel wires. The chest wall was instrumented to apply 4 types of distracting force: (1) lateral, (2) anterior-posterior, (3) rostral-caudal, and (4) a simulated Valsalva force. Forces were applied in each direction and were limited to physiologic levels (< 400 N). Four sets of sonomicrometry crystals were placed equidistantly along the sternum to measure separation at the closure site.

RESULTS

Sternal separation occurred as a result of the wires cutting through the bone. Less force was needed to achieve 2.0-mm distraction in the lateral direction (220 +/- 40 N) than in the anterior-posterior (263 +/- 74 N) and rostral-caudal (325 +/- 30 N) directions. More separation occurred at the lower end of the sternum than the upper. During lateral distraction, xiphoid and manubrial displacement averaged 1.85 +/- 0.14 and 0.35 +/- 0.12 mm, respectively. Anterior-posterior distraction caused 1.99 +/- 0.04-mm xiphoid displacement and 0.26 +/- 0.12-mm manubrial displacement. During a simulated Valsalva force, more separation occurred in the lateral (2.14 +/- 0.11 mm) than in the anterior-posterior (0.46 +/- 0.29 mm) or rostral-caudal (0.25 +/- 0.15 mm) directions.

CONCLUSIONS

These data suggest that sternal dehiscence can occur under physiologic loads and that improved sternal stability may be readily achieved via mechanical reinforcement near the xiphoid. Closure techniques designed to minimize wire migration into the sternum should also be developed.

Muscle flap reconstruction for the treatment of major sternal wound infections after cardiac surgery: a 10-year analysis

Infection of a median sternotomy wound is a rare though potentially fatal complication. Despite early diagnosis and proper treatment, prognosis is poor because of the chance of mediastinal spread of the infection and the poor physical state of these patients. Muscle repair is superior to more conservative surgical options such as sternal resuturing with mediastinal irrigation. During the last 10 years, complications--including sternal infections and dehiscences--have been encountered in 172/4725 median sternotomy wounds after cardiac surgery procedures (4%). Thirty-four patients (of whom 30 had acute sternal infections and four chronical sternal infections) underwent aggressive sternal debridement followed by muscle flap closure. Seventy-two muscle flaps were carried out, a pectoralis major bilateral muscle flap being the most common either alone or in combination with a rectus abdominis muscle flap. Five perioperative deaths (15%) were recorded. Of the 29 surviving patients, 25 patients (74%) were free of infection and four (12%) developed recurrence of the infection after a mean follow up of 3 years (range 49 days-8 years). We conclude that although muscle repair is not free of complications, it is reliable in reducing mediastinitis-related morbidity and mortality.

Is mediastinitis a preventable complication? A 10-year review

BACKGROUND

The incidence of mediastinitis after cardiac surgical intervention is reported to be between 0.15% and 5% and is a major cause of postoperative morbidity. A number of risk factors have been identified, most of which are not modifiable. It is our contention that this complication can be reduced to a minimum by the consistent application of good operative technique and postoperative management.

METHODS

We reviewed the records of all 9,771 patients who underwent cardiac surgical procedures between 1987 and 1997. All operations were performed using a common skin preparation, draping, and antibiotic prophylaxis. Cases of mediastinitis were defined according to Centers for Disease Control and Prevention criteria and were identified from three sources: medical records database, hospital infection control, and the Society of Thoracic Surgeons database. Risk factors were assessed using chi2 and Fisher's exact tests.

RESULTS

Of 24 patients identified as having deep sternal wound infection (incidence, 0.25%), 2 died (mortality rate, 8.3%), 18 required reoperation (75%), and only 4 needed pectoral muscle flaps. Statistical analysis revealed only the presence of chronic obstructive pulmonary disease as a significant risk factor (p < 0.01). Other factors, including diabetes, renal failure, smoking, sex, age, reoperation, morbid obesity, and steroid use, were not significant. The use of internal mammary arteries (single or bilateral) was not associated with mediastinitis. Postoperative complications, including prolonged ventilation, inotropic support, and the need for blood products, were not significant risk factors. The patients who developed mediastinitis were more likely to be readmitted to the hospital (p < 0.005) and more likely to require reoperation (p < 0.005).

CONCLUSIONS

In a large patient series we found a low incidence of mediastinitis (0.25%) and an even lower incidence of required reoperation (0.19%). Except for the use of bone wax and the use of bilateral mammary arteries in diabetic patients, none of the previously identified risk factors are modifiable. We believe that with strict adherence to perioperative aseptic technique, attention to hemostasis, and precise sternal closure, a very low incidence of mediastinitis can be achieved.

Reduction of wound healing problems after median sternotomy by use of retention sutures

Obese people have a higher risk of sternal wound dehiscence resulting from traction of suprasternal tissue. In such patients we recommend the use of retention sutures with extracorporeal plates to improve tissue connection and to disburden fascia and skin sutures. This augmented closure is simple and effective and, since 1996, has prevented wound healing problems in more than 50 patients with a body mass index greater than 27.

Morbidity, cost, and six-month outcome of minimally invasive direct coronary artery bypass grafting

BACKGROUND

Minimally invasive direct coronary artery bypass grafting (MIDCABG) promises to reduce the morbidity of coronary bypass, but this has not been proved.

METHODS

This retrospective study compares the morbidity, mortality, cost, and 6-month outcome of patients less than 80 years old undergoing elective left internal mammary artery to left anterior descending artery bypass grafting via MIDCABG (n = 60) or sternotomy (n = 55) between January 1995 and December 1996. There were no differences between the groups in mean age, sex distribution, or preoperative risk level. The left internal mammary artery was mobilized from the fifth costal cartilage to the subclavian artery in all patients. The anastomoses were done with a beating heart in the MIDCABG group and with cardioplegic arrest in the sternotomy group.

RESULTS

There were no operative deaths in either group. The MIDCABG patients had a lower transfusion incidence (10/60 [17%] versus 22/55 [40%]; p< or =0.02) and a shorter postoperative intubation time (2.1+/-4.2 versus 12.6+/-9 hours; p< or =0.0001). One patient in each group was reexplored for bleeding. Three sternotomy patients (3/55, 5%) required ventilatory support for greater than 48 hours, but no MIDCABG patient was ventilated for more than 24 hours. Median postoperative length of stay was 4 days for MIDCABG and 7 days for sternotomy. Estimated hospital costs were $11,200+/-3100 for MIDCABG and $15,600+/-4200 for CABG (p < 0.001). The reduced morbidity and cost of MIDCABG was found mostly in high-risk patients. At 6-month follow-up, 5 MIDCABG patients (5/60, 8%) had evidence of recurrent ischemia involving the left anterior descending artery, primarily the result of anastomotic stricture.

CONCLUSIONS

This analysis shows that MIDCABG reduces the initial morbidity and cost of coronary bypass, but some patients require subsequent reintervention. Long-term follow-up is needed before MIDCABG can be judged better than traditional bypass, but the initial results are promising, especially in high-risk patients.

Biomechanical study of sternal closure using rigid fixation techniques in human cadavers

BACKGROUND

We believe rigid plate fixation may be superior to wire fixation in sternal closure, as rigid fixation used in the craniofacial skeleton has shown greater stability, lower postoperative pain, and accelerated bone healing. We hypothesize that sterna fixed with titanium plates are more stable mechanically than sterna fixed with wires.

METHODS

The sterna from human cadavers were used in this two-phased study. Phase I compared wires to four-hole titanium straight plates. Phase II compared wires to four-hole titanium custom H plates. The sterna were tested biomechanically using all fixation methods.

RESULTS

Phase I showed no statistically significant difference in the stiffness or lateral displacement between the wired and straight plated sterna. Phase II showed a statistically significant greater stiffness (p < 0.05) and less lateral displacement (p < 0.05) in the custom plated sterna over the wired sterna.

CONCLUSIONS

Our results showed that custom titanium H plates were superior to wire fixation. Furthermore, our results established the importance of plate configuration in sternal fixation. Our study may have beneficial clinical implications, as decreased motion at the sternotomy site could mean less postoperative pain, a decreased incidence of infection, and accelerated bone healing.

Deep sternal wound infection: risk factors and outcomes

BACKGROUND

Deep sternal wound infection (DSWI) is a serious complication of cardiac operations performed by median sternotomy. We attempted to define the predictors of DSWI and to describe the outcomes of two treatment strategies used at our institution.

METHODS

Retrospective review was performed using prospectively gathered data on 12,267 consecutive cardiac surgical patients from 1990 to 1995. Chart review was performed on all patients in whom DSWI developed, and follow-up was obtained on 100% of these patients.

RESULTS

Deep sternal wound infections developed in 92 patients (incidence 0.75%). Multivariable predictors for development of DSWI in all patients were (odds ratios and 95% confidence intervals in parentheses) (1) diabetes mellitus (2.6; 1.7 to 4.0) and (2) male sex (2.2; 1.3 to 3.9). In patients receiving coronary artery bypass grafting alone, independent predictors were (1) bilateral internal thoracic artery grafts (3.2; 1.1 to 8.9), (2) diabetes (2.7; 1.6 to 4.3), and (3) male sex (1.8; 0.9 to 3.7). For all other patients, predictors were (1) age more than 74 years (3.3; 1.1 to 10.1), (2) male sex (3.0; 1.1 to 8.1), and (3) diabetes (2.3; 0.9 to 5.8). Bilateral internal thoracic artery grafts increased the risk of DSWI in all subgroups of coronary artery bypass graft patients, particularly in diabetics who had a 14.3% incidence of DSWI after bilateral internal thoracic artery grafting. Patients with DSWIs received either sternal debridement with primary closure (n=45) or sternectomy with flap reconstruction (n=46). The 6-month freedom from adverse event rate (ie, readmission, reoperation, or death) was 76% for both groups of patients.

CONCLUSIONS

Male sex and diabetes are predictors of DSWI in all cardiac surgical patients. Bilateral internal thoracic artery grafting may be contraindicated in diabetic patients.

Postcardiac surgery infections

Infections following cardiac surgery, although generally uncommon, are associated with difficult management decisions and significant morbidity and mortality. They often present while the patient is either in a critical care unit, or requires CCU management. This review analyzes infections related to median sternotomy wounds, prosthetic heart valves, transvenous permanent pacemakers, automatic implantable cardioverter-defibrillators, and left ventricular assist devices. The diagnosis, microbiology, treatment and outcome of each is also discussed.

Treatment of mediastinitis: early modified Robicsek closure and pectoralis major advancement flaps

BACKGROUND

The treatment of sternal wound complications is controversial. It is our practice to combine early aggressive debridement, a modified Robicsek sternal closure, and bilateral pectoralis major advancement flaps with or without closed irrigation in a single procedure. We reviewed our experience to determine the efficacy of this approach.

METHODS

Grade II to IV mediastinitis (dehiscence and infection) developed in 47 patients 3 to 14 days after routine open heart operations between 1990 and 1995. Culture-positive infection was identified in 60% (n = 28); 62% (n = 29) had septicemia. Thirty patients underwent incision, drainage, and surgical assessment of the wound. Once systemic signs of infection were under control (no pyrexia, normal white blood cell count), formal single-stage debridement of all infected soft tissues and bones was performed. Sternal stability was achieved using a modified Robicsek closure and bilateral pectoralis major advancement flaps. Seventeen patients were treated with staged procedures.

RESULTS

Early sternal closure and coverage with pectoralis major advancement flaps can be associated with a low mortality (0%), low morbidity (13%; n = 4: three superficial wound infections, one seroma), and shortened hospital stay (median, 22 days, compared with a median of 82 days in patients managed with conservative staged treatment; p < 0.05). Sternal stability with excellent functional and aesthetic results has been achieved in all patients.

CONCLUSIONS

The combination of aggressive early surgical debridement, sternal closure, and the placement of bilateral pectoralis major advancement flaps is a simple procedure associated with a low mortality and morbidity and a short hospital stay.

Mediastinitis after cardiovascular operations: a case-control study of risk factors

BACKGROUND

An analysis of risk factors for postoperative mediastinitis can lead to a better understanding of the pathogenesis of this complication and to more effective preventive measures.

METHODS

This case-control study of 37 patients and 74 matched controls evaluated 54 potential risk factors.

RESULTS

Nine variables were significantly associated with increased risk of postoperative mediastinitis: total operation time (p = 0.0013), high body-mass index (p = 0.0033), use of beta-adrenergic drugs before the onset of infection (p = 0.0037), long cardiopulmonary bypass time (p = 0.0072), long aortic cross-clamp time (p = 0.0075), presence of diabetes (p = 0.0122), high body weight (p = 0.0130), and use and duration of temporary pacing wires (p = 0.0293 and p = 0.0241 respectively). In a conditional logistic regression analysis, use of beta-adrenergic drugs before the onset of infection (p = 0.0058; odds ratio 19.7; 95% confidence limits, 2.37 and 163.7) and body mass index (p = 0.0082; odds ratio 1.27; 95% confidence limits, 1.06 and 1.52) were independently associated with a significantly increased risk of postoperative mediastinitis.

CONCLUSIONS

Obesity and use of beta-adrenergic drugs, which is indicative of obstructive respiratory problems, were the most important risk factors suggesting that mechanical strain on the sternotomy and sternal instability may precede infection. Targeted preventive measures for these groups could be justified.

Blood transfusion and bone allografts. Effect on infection and outcome

Intraoperative and postoperative blood replacement have been implicated in increased rates of wound infection, decreased rates of renal allograft transplant rejection, and increased rates of local recurrence and metastasis of certain kinds of tumors, all presumably on the basis of some alteration in the immune system. Because patients who have bone allograft surgery for tumors often require transfusion and because the procedure is associated with a high rate of failure (20%), infection (9%-10%), and local recurrence (10% for high grade tumors), the effect of transfusion (range, 0-4750 ml) was studied for 264 patients who had proximal humeral, proximal or distal femoral resections, and massive cadaveric allografts but who did not have adjuvant chemotherapy or radiation. An attempt was made to statistically correlate the tumor and allograft outcome and rate of infection with patient age and gender, anatomic site, diagnosis, stage, type of graft, number of subsequent procedures, surgical margins, perioperative transfusions, blood loss, duration of operative procedures, and number of pregnancies. Of the variables studied, only blood loss, transfusion, and duration of surgery had an effect on outcome and, more specifically, on infection rate and time to union. No effect was observed on metastasis, recurrence, or the ultimate outcome of the procedure.

Rehabilitation following redo revascularization and repaired sternotomy

Currently there are no guidelines for exercise prescription for cardiac patients with repaired sternotomy. This study reports good results in a 63-yr-old patient with prolonged course of hospitalization following mediastinitis and discusses considerations required for safe participation in competitive sports.

Hemorrhage and the use of blood products after adult cardiac operations: myths and realities

BACKGROUND

Several patient-, procedure-, and prescriber-related factors are thought to influence the decision to administer allogeneic blood products. We reexamine a number of assertions applied commonly to the practice of transfusion in cardiac operations.

METHODS

More than 50 original articles including a total of more than 10,000 patients from 70 centers were reviewed. Data from 5,426 patients operated on between 1990 and 1994 at the Montreal Heart Institute are presented.

RESULTS

From our review of the literature, we conclude that postoperative mediastinal fluid drainage averages 917 mL and that aspirin therapy increases drainage by less than 300 mL in most studies, which should not increase use of blood products, insofar as a strict transfusional protocol is adhered to. Across centers, transfusions can vary eightfold for the same postoperative drainage. Data from our institution show that postoperative mediastinal drainage per se is not influenced by reoperation or by the type of operation. However, total blood losses and transfusion requirements remain increased in reoperative and complex procedures. Excessive mediastinal drainage resulting in increased transfusions occurs in 29% of patients.

CONCLUSIONS

Exposure to allogeneic transfusions remains institution dependent. Constant reevaluation of local practice is essential to implement efficient blood conservation strategies.

Video-assisted cardiac surgery. Preliminary experience in reoperative mitral valve surgery

OBJECTIVES

Video-assisted endoscopic techniques had been applied in the surgical correction of patent ductus arteriosus, vascular ring, or coronary artery disease. However, it has been used only recently in the correction of reoperative mitral valve lesions.

DESIGN

Video-assisted cardiac operations were performed on four patients who had received surgical interventions on their mitral valves and needed emergent reoperation.

PATIENTS

Four patients (3 men and 1 woman) received emergency surgery from September to December 1995 for thrombosis of mechanical mitral prosthesis (2 patients) and severe mitral regurgitation with previously failed mitral valve repair (2 patients). Six previous operations had been performed on these mitral valves. Patient ages ranged from 26.7 to 68.1 years (mean, 47.3 years). Preoperatively, acute pulmonary edema occurred in two patients, cerebral emboli occurred in one patient, and sepsis was found in one patient. Mechanical ventilatory support was used in two patients before operation.

INTERVENTION

The operations were performed through right anterior minithoracotomy, guided by video-assisted endoscopic techniques with femoro-femoral extracorporeal circulation. The operative procedures were thrombectomy of mitral prosthesis in two patients, mitral valve repair in one patient, and mitral valve replacement in one patient.

RESULTS

The duration of extracorporeal circulation was 166 to 320 min (222 +/- 67 min) and the operation time was 4.6 to 6.8 h (6.1 +/- 1.0 h). All patients recovered from the operations rapidly with uneventful postoperative courses except 1 patient who had sepsis preoperatively and died 2 months later.

CONCLUSION

Our experience demonstrates that video-assisted cardiac surgery is technically feasible and could be performed in reoperation of the mitral valve.

Factors predisposing to median sternotomy complications. Deep vs superficial infection

STUDY OBJECTIVES

Median sternotomy infections are a serious complication of cardiac surgery. The purpose of this study was to determine the patient characteristics and operative variables that predict incidence of sternal infection, and possibly its severity.

DESIGN

Univariate and multivariate retrospective analysis comparing patient, operative, and post-operative data in patients with and without sternal infections.

SETTING

Cardiac surgery program of a 580-bed private hospital in Toledo, Ohio.

PATIENTS

We studied 2,317 consecutive (June 1991 to December 1994) patients undergoing cardiac surgery.

RESULTS

Forty-one sternal infections were documented. Of these, 21 (0.91%) were deep infections with mediastinal involvement and 20 (0.86%) were superficial. Two patients with deep infections died (2/41, 5%). Ten variables were associated with infection by univariate analysis (p < 0.05), and of these, five were independent predictors by multivariate logistic regression. These predictors were obesity (p < 0.001), insulin-dependent diabetes (p < 0.001), use of internal mammary artery grafts (p = 0.02), surgical reexploration of the mediastinum (p = 0.003), and postoperative transfusions (p = 0.01). Predictors of deep and superficial sternal infection did not differ. Length of hospitalization was substantially longer for patients with deep (32 +/- 21 days) vs superficial infection (13 +/- 10 days).

CONCLUSIONS

The present study confirms previous findings that obesity, insulin-dependent diabetes, and internal mammary artery grafting (especially bilaterally) increase the risk of sternal infection. In addition, chest surgical reexploration and blood transfusions were postoperative factors that predisposed patients with median sternotomy to infection. Unlike their associated morbidity and mortality, predictors of deep and superficial sternal infections are similar.

Nosocomial infections in patients having cardiovascular operations: a multivariate analysis of risk factors

A total of 970 adult patients undergoing cardiovascular operations during a 1-year period were eligible for a case-control study on the risk factors for nosocomial infection. Cases were defined as patients in whom a postoperative infection developed. Every case was paired with one uninfected subject. Nosocomial infection occurred in 89 (9.2%) patients. A total of 120 episodes of infection were diagnosed (1.3 episodes per patient). The infection ratio was 12.4%. Surgical site infection was the most common (5.6%), followed by pneumonia (3.2%), urinary tract infection requiring the use of intravenous antibiotics (1.8%), deep surgical site (0.9%), and bacteremia (0.7%). Advanced age, urgent intervention, duration of surgical procedure, blood transfusion, and use of invasive procedures (urinary catheter, chest tubes, nasogastric tube passage) were significantly associated with infection in the bivariate analysis. Nosocomial infection resulted in a significant increase in the length of hospital stay. Cases showed an almost fivefold greater risk of death than controls (odds ratio, 4.73; 95% confidence interval, 1.11 to 6.83; p = 0.009). Age older than 65 years, female sex, and mode of surgical intervention were selected in the multivariate analysis for patients undergoing cardiac operations, whereas general anesthesia or assisted ventilation, central venous catheter, and blood transfusion were the variables selected for patients undergoing operation for vascular disorders. In summary, the recognition of risk factors for postoperative infection in patients undergoing cardiovascular surgical procedures may contribute to improve their prognosis and to more organized surveillance and control activities in the hospital environment.

Risk factors for deep sternal wound infection after sternotomy: a prospective, multicenter study

Several risk factors for deep sternal wound infection after sternotomy remain unclear. To assess and compare risk factors among units, a prospective study included 1830 patients in 10 units during a 4-month period: 960 underwent coronary artery bypass grafting and 870 underwent other procedures. According to the Centers for Disease Control and Prevention definitions, 2.3% of patients (42/1830) acquired a deep sternal wound infection. Independent risk factors for deep sternal wound infection were obesity, coronary artery bypass grafting, reoperation, and postoperative inotropic support. Independent risk factors after coronary artery bypass grafting were obesity, bilateral internal thoracic artery grafting, reoperation, and postoperative inotropic support. In all five of the units usually performing bilateral internal thoracic artery graftings, this procedure was associated with high risk of deep sternal wound infection. Duration of operation was a major risk factor in comparison of the unit with the highest risk of deep sternal wound infection with the other nine units; this suggests that parameters related to the perioperative period were involved. Multicenter surveillance is useful to determine reliable risk factors for deep sternal wound infection, to define a high-risk population before operation, and to assess unit-specific risk factors.

Reexploration for bleeding is a risk factor for adverse outcomes after cardiac operations

OBJECTIVE

Although previous studies have included early reexploration for bleeding as a risk factor in analyzing adverse outcomes after cardiac operations, reexploration for bleeding has not been systematically examined as a multivariate risk factor for increased morbidity and mortality after cardiac surgery. Furthermore, multivariate predictors of the need for reexploration have not been identified. Accordingly, we performed a retrospective analysis of 6100 patients requiring cardiopulmonary bypass from January 1, 1986, to December 31, 1993.

METHODS

Eighty-five patients who had ventricular assist devices were excluded from further analysis because of the prevalence of bleeding and the significant morbidity and mortality associated with placement of a ventricular assist device, unrelated to reexploration. In the remaining 6015 patients, potential adverse outcomes analyzed included operative mortality, mediastinitis, stroke, renal failure, adult respiratory distress syndrome, prolonged mechanical ventilation, sepsis, atrial arrhythmias, and ventricular arrhythmias. To control for the confounding effects of other risk factors, we performed a multivariate logistic regression analysis. Potential covariates considered in the logistic model included age, sex, race, history of reoperation, urgency of the operation, congestive heart failure, prior myocardial infarction, renal failure, diabetes, hypertension, chronic obstructive pulmonary disease or stroke, and the bypass and crossclamp time.

RESULTS

The overall incidence of reexploration was 4.2% (253/6015). Four independent risk factors--increased patient age (p < 0.001), preoperative renal insufficiency (p = 0.02), operation other than coronary bypass (p < 0.001), and prolonged bypass time (p = 0.0.3)--were identified as predictors of the need for reexploration. The preoperative use of aspirin, heparin, or thrombolytic agents and the bleeding time were not identified as predictors. Reexploration for bleeding was identified as a strong independent risk factor for operative mortality (p = 0.005), renal failure (p < 0.0001), prolonged mechanical ventilation (p < 0.0001), adult respiratory distress syndrome (p = 0.03), sepsis (p < 0.0001), and atrial arrhythmias (p = 0.006).

CONCLUSION

These data indicate that meticulous attention to surgical hemostasis and possibly application of recently developed modalities designed to facilitate perioperative correction of coagulopathy could improve outcomes after cardiac operations.

Postoperative mediastinitis: classification and management

Although the incidence of mediastinal wound infection in patients undergoing median sternotomy for cardiopulmonary bypass is less than 1%, its associated morbidity, mortality, and "cost" remain unacceptably high. There is considerable lack of consensus regarding the ideal operative treatment of complicated median sternotomy wounds. The aim of this article is to review the current preventive, diagnostic, and therapeutic techniques offered to patients with mediastinitis. We also propose a new classification for postoperative mediastinitis. Data from the English-language literature suggest that the type of mediastinitis and direct assessment of the mediastinum under general anesthesia are the main determinants of the nature of subsequent operative treatment. Wound debridement and removal of foreign materials are essential steps of whatever procedures are applied. Closed mediastinal irrigation can be successful in type I mediastinitis, whereas major reconstructive operation is probably the treatment of choice for patients with mediastinitis types II to V. Refinement of the current diagnostic tools and further evaluation of the benefits of primary sternal fixation in combination with a reconstructive procedure in mediastinitis types I to III could improve the outcome of this dreaded complication.

Allogeneic transfusion risks in the surgical patient

The risk of blood transfusion-associated complications has been reduced in the past 10 years through technical advances in testing of blood, viral inactivation of noncellular blood components, enforcement of stringent donor selection criteria, and the use of alternatives to allogeneic transfusion. Even so, a zero-risk blood supply is unfeasible. The general public perceives infectious complications to be the most significant risk: although the greatest fear is associated with transmission of human immunodeficiency virus (HIV), at least three hepatitis viruses are transmissible by all blood components. Human immunodeficiency virus accounts for < 20 cases per year of transfusion-related acquired immunodeficiency syndrome in the United States. The three important noninfectious complications are alloimmunization, which is common but clinically insignificant; immunosuppression, the clinical significance of which is controversial; and graft-versus-host disease, a lethal complication most likely to affect patients who are immunosuppressed, have cancer, or are recipients of bone marrow transplants.

Poststernotomy mediastinitis treated by transposition of the greater omentum

Due to its anatomical structure and physiological properties, omental tissue has proven to be beneficial when transposed to the thorax to treat severe mediastinal infections. Between April 1987 and July 1994, 17,005 open heart operations were performed at our institution. One hundred and forty patients who developed mediastinitis or serious wound infections postoperatively were treated by transposition of the greater omentum into the retrosternal space. These patients were compared with a control group of 100 patients operated in the same period, who did not develop infectious complications postoperatively. Significant differences were found in several risk factors, such as obesity, type, and duration of primary operation, ejection fraction < 30% (< 0.01), as well as the incidence of low cardiac output syndrome treated by insertion of an intra-aortic balloon pump (p < 0.05). However, no significant differences were observed in factors such as diabetes mellitus, emergency operation, reoperation, degree of postoperative bleeding, and duration of aortic cross-clamp time. The mortality of mediastinitis largely depended on the type of primary operation. It was 19.2% in patients who underwent coronary surgery, and 52.2% in patients who underwent transplantation (overall mortality 35.7%). Only in 2% of the patients did we find complications related to the creation of the omental pedicle and its translocation. Today, serious disturbances in sternal wound healing, especially involving mediastinitis, are rare complications in cardiac surgery. Nevertheless, they continue to be associated with high mortality and prolonged hospitalization.

Mediastinitis after coronary artery bypass graft surgery. Risk factors and long-term survival

BACKGROUND

Mediastinitis is a severe complication of coronary artery bypass graft surgery (CABG). The purpose of the present study was to determine preoperative and intraoperative variables that predict mediastinitis and to determine the impact of this complication on long-term survival.

METHODS AND RESULTS

Data on 20 preoperative and intraoperative variables were collected prospectively on 6459 consecutive patients who underwent CABG between January 1987 and January 1994. Eighty-three patients (1.3%) developed mediastinitis postoperatively, and a total of 24 patients (29%) died. Multivariate analysis identified 4 of the 20 variables as highly significant independent predictors for the development of mediastinitis: obesity (P = .0002), New York Heart Association congestive heart failure class (P = .002), previous heart surgery (P = .008), and duration of cardiopulmonary bypass (P = .05). A comprehensive review of the literature identified 13 other studies that evaluated 48 factors as predictors of mediastinitis; these data were critically analyzed and compared with the results from this series. In this series, postoperative interval mortality during the first 90 days after surgery for the patients with mediastinitis was 11.8% compared with 5.5% for the patients without mediastinitis. Interval mortality between 1 and 2 years after surgery remained high for the mediastinitis group (8.1%) relative to the nonmediastinitis group (2.3%). These differences were not eliminated by adjusting for important variables that influenced late survival in this population.

CONCLUSIONS

The present study and a review of the literature suggest that obesity and duration of surgery are the most important predictors of mediastinitis. Furthermore, although the early increase in mortality has been well described, the present study documents for the first time that mediastinitis has a significant negative influence on long-term survival independent of the patient's preoperative condition.

Potential for reduction in morbidity and cost with total leucocyte control for cardiac surgery

The economics of health care in the USA and abroad has caused a shift in the focus on therapeutic interventions that transcend issues of safety and clinical efficacy. Now, cost justification is emerging as a major consideration to influence clinical practice. This brief review of the medical literature attempts to identify leucocyte-mediated adverse reactions that develop in open-hear surgery, quantify the costs incurred to manage such reactions and infer the savings that may accrue by controlling the burden of leucocytes presented to the open-heart surgical patient using commercially available leucocyte reducing filtration technology.

Re-inventing the wheel; the use of autologous and fresh donor blood in cardiac surgery

From the opening of a new cardiac surgical programme in November 1992, autologous and fresh donor blood (FDB) were used rather than cold stored blood (CSB) wherever possible in patients undergoing operations involving the use of cardiopulmonary bypass (CPB). In the first 250 consecutive patients, autologous blood was used in 168 (67.2%), fresh blood was used in 188 (75.2%). A total of 740 units of fresh blood were obtained on the day of operation (mean 3.9 +/- 1.6 units per patient able to supply donors; 4.9 +/- 1.7 units in the 147 who received fresh blood) and 728 units of stored blood were used (mean 3.08 +/- 1.84 units per patient where fresh blood was used; 6.2 +/- 2.5 units in the 114 where no fresh blood was used). The use of autologous blood significantly reduced FDB and CSB requirements (p < 0.001), was associated with a shorter intensive care and total postoperative stay (p = 0.006 and p = 0.033 respectively), even though there were more urgent and emergency cases in this group (p = 0.009) and no significant difference in chest drainage. Coagulopathy developed in 41 patients (16.4%) and was significantly associated with bypass time (p = 0.0001) and preoperative renal dysfunction (p = 0.005), although not with advanced age, sex, redo operation, diabetes or glucose-6-phosphate dehydrogenase deficiency. Patients with coagulopathy had significantly more transfused blood and blood products (p = 0.0001) and longer intensive care and total postoperative stays (p = 0.0001). In terms of blood conservation, the use of autologous blood was of primary importance.(ABSTRACT TRUNCATED AT 250 WORDS)

The haemostatic effectiveness of autologous platelet rich plasma sequestered after heparin administration and institution of cardiopulmonary bypass

Preoperative harvesting and postoperative reinfusion of autologous platelet rich plasma (PRP) has been reported to decrease blood loss as well as the requirement for homologous blood transfusion following cardiopulmonary bypass (CPB). We have developed a technique of intraoperative PRP sequestration which occurs during the initial period of CPB after the patient's circulation is supported and heparin has been given (PRP+). This process does not require any additional hardware, personnel or expense and it is performed without difficulty or complication. To evaluate the effect of PRP+ sequestration and reinfusion on blood loss and homologous blood requirement after CPB, we randomly assigned 126 consecutive patients undergoing elective open heart surgery into the experimental group 1 (PRP+) (n = 64) or the control (no platelet pheresis) group 2 (n = 52). A third group (n = 10) were not included in the randomization. Patients in group 3 had PRP prepared by conventional techniques (PRPc) prior to heparin administration and given to the patient after protamine infusion. Aggregation and activation studies were performed on the PRP+, PRPc, and blood bank platelets (BBP). Per cent aggregation of PRP in response to ADP was superior to that of BBP. There were no significant differences in ADP induced aggregation between PRP+ and PEPc. There was no significant difference in platelet activation (CD62) or number between the three groups. Patients infused with PRP+ showed significantly increased aggregation to ADP when compared with untreated patients 120 minutes after return to the ICW. Furthermore, more homologous haemostatic components (platelets/fresh frozen plasma) were required in the control group. We have demonstrated that collection of autologous PRP+ after administration of heparin does not interfere with its haemostatic effectiveness compared with PRPc prepared before the initiation of bypass. Moreover, this can be performed universally in haemodynamically unstable patients without any additional costs.

Escherichia coli sternal osteomyelitis after open heart surgery

Deep-seated infections after open-heart surgical procedures, fortunately, are uncommon with appropriate prophylactic antibiotics and careful aseptic technique. When serious infection, such as sternal osteomyelitis, does occur, the effects are devastating and usually require one or more debridement procedures. The organisms usually implanted in postoperative sternal infections are primarily Staphylococcus aureus and aquatically based gram-negative bacilli. Common gram-negative pathogens such as Escherichia coli are very unusual in this setting. We report a case of E. coli sternal osteomyelitis in a diabetic patient after coronary artery bypass grafting.

Transfusion-associated bacterial sepsis

The incidence of sepsis caused by transfusion of bacterially contaminated blood components is similar to or less than that of transfusion-transmitted hepatitis C virus infection, yet significantly exceeds those currently estimated for transfusion-associated human immunodeficiency and hepatitis B viruses. Outcomes are serious and may be fatal. In addition, transfusion of sterile allogenic blood can have generalized immunosuppressive effects on recipients, resulting in increased susceptibility to postoperative infection. This review examines the frequency of occurrence of transfusion-associated sepsis, the organisms implicated, and potential sources of bacteria. Approaches to minimize the frequency of sepsis are discussed, including the benefits and disadvantages of altering the storage conditions for blood. In addition, the impact of high levels of bacteria on the gross characteristics of erythrocyte and platelet concentrates is described. The potentials and limitations of current tests for detecting bacteria in blood are also discussed.