Ivar Risnes

Mediastinitis After Coronary Artery Bypass Grafting Risk Factors and Long-Term Survival

BACKGROUND Mediastinitis is a severe complication of coronary artery bypass grafting. The aim of the present study was to determine incidence of mediastinitis, its risk factors, and its effect on early and long-term survival. METHODS The study has a dual design, a case-control, and a retrospective cohort, using a source population of 18,532 consecutive patients who underwent coronary artery bypass grafting from January 1989 to December 2000. The closing date was February 1, 2008. Median follow-up was 10.3 (range 8.1 to 18.9) years. Patients with mediastinitis were compared with a random control group without mediastinitis issued from the same source population in a ratio 1:4. The crude effect of mediastinitis was estimated using rate ratio and 95% confidence limits. Adjustment for multiconfounders was done with the Cox model. A logistic model was used to pinpoint risk factors of mediastinitis. Calibration and discrimination of a prognostic model was done. RESULTS One hundred seven patients (0.6%) developed mediastinitis. Diagnosis was made 12 (9 to 19) days postoperatively. Independent risk factors of mediastinitis using the logistic model were advanced age, male gender, left main stenosis, body mass index 30 kg/m(2) or greater, chronic obstructive pulmonary disease, diabetes, and increased amount of blood transfusion. There was no increased risk of early mortality (odds ratio = 0.58; 95% confidence interval 0.13 to 2.61) (p = 0.48) but there was increased risk of morbidity (intraaortic balloon pump, ventricular and supraventricular arrhythmia, stroke, inotrope, and myocardial infarction). Follow-up had a median observation time of 10.3 years. Survival for patients with mediastinitis was 49.5 +/- 5.0% versus 71.0 +/- 2.2% for controls (p < 0.01). Analysis of specific death causes documented that cardiac deaths were significantly more frequent in mediastinitis patients than in control patients. When controlling for the confounding effect of the other variables (age, cardiopulmonary bypass time, body mass index, chronic obstructive pulmonary disease), the hazard ratio associated with mediastinitis on long-term mortality was 1.59, 95% confidence limits (1.16 and 2.70) (p = 0.003). CONCLUSIONS The incidence of mediastinitis in 18,532 patients undergoing coronary artery bypass grafting surgery was low. The major preventable risk factor of mediastinitis was amount of blood transfusion. Mediastinitis had an excess risk of early morbidity and was associated with a significant reduced long-term survival. Most deaths were considered to be cardiac.

Sternal wound infections in patients undergoing open heart surgery: randomized study comparing intracutaneous and transcutaneous suture techniques

BACKGROUND Intracutaneous suture technique has been our standard method for closing sternal wounds in cardiac surgery, mainly for cosmetic reasons. However, an increased rate of postoperative infections has been reported in cosmetic surgery with this method compared with the percutanous or transcutaneous closure technique. A comparison of these two techniques in cardiac surgery is presented. METHODS In a randomized study, 300 patients were selected to intracutaneous suture (n = 150) or percutanous suture (n = 150). The endpoints were superficial and deep sternal wound infections within 6 weeks postoperatively. RESULTS The total infection rate was lower in the percutanous group compared with the intracutaneous group (3% versus 8%) (p = 0.007). The superficial infection rate was lower in the percutaneous group (2.3% versus 6.7%) (p = 0.01), whereas there was no statistically significant difference in the deep infection rate between the groups. CONCLUSIONS The percutaneous suture technique reduces the incidence of superficial wound infections, but not the deep infection rate in open heart surgery. There was no difference in the cosmetic results on a visual scale, assessed by the patients.

Is it possible to predict outcome in cardiac ECMO? Analysis of preoperative risk factors

Serious pulmonary failure may be treated with extracorporeal membrane oxygenation (ECMO) when other treatment has failed. The aim of this study was to analyze pre-operative risk factors of early mortality in patients who underwent either veno-arterial (VA) ECMO or veno-venous (VV) ECMO for pulmonary failure. We studied a total of 26 risk factors in 72 patients with severe pulmonary insufficiency treated with ECMO. All consecutive cases treated at our institution between Sept 1990 and Aug 2007 were included. Univariate analysis and multiple logistic regression analysis were performed on 26 risk factors. The end point was early mortality (any death within 30 days of ECMO treatment). Thirty-six (50%) of the patients died within 30 days of treatment. Age, gender, body mass index(BMI)(adults), cause of pulmonary failure, pre-ECMO treatment with nitric oxide(NO), intra-aortic balloon pump(IABP), and type of ventilation did not significantly influence early mortality. Neither pre-operative blood gas results, oxygenation index or pre-operative PaO2/FiO2 ratio, nor mean ventilator days prior to ECMO gave any indications on early mortality. Liver function did not predict early mortality, but pre-ECMO serum creatinine levels were significantly lower in patients who survived. Treatment with ECMO in patients with severe pulmonary failure may save lives. It is, however, difficult to predict outcome when initiating ECMO. In this analysis, only pre-operative serum creatinine levels correlated with survival. None of the other parameters, including those which were used to select patients for ECMO treatment, could significantly predict the outcome.

Interleukin-6 may predict survival in extracorporeal membrane oxygenation treatment.

The cytokine network and its association with complement activation during cardiac surgery with cardiopulmonary bypass (CPB) is complex. Extracorporeal membrane oxygenation (ECMO) differs from CPB in duration of days to weeks rather than hours. However, few studies have analyzed the levels of inflammatory mediators during ECMO treatment. Plasma samples from 22 patients [nine neonates, one infant, four children and eight adults (14 males and eight female)] who underwent ECMO treatment were collected prior to, during and after treatment, and analyzed for concentrations of inflammatory and anti-inflammatory cytokines and parameters of complement activation. Seven children were treated for cardiac and seven for pulmonary failure and, in the adult group, four were treated for cardiac and four for pulmonary failure. ECMO was performed with veno-arterial (VA) bypass in all children and five adults, and with veno-venous (VV) bypass in three adults. Fourteen patients survived (64%) and eight (36%) patients died during follow-up. A marked (~99%) and rapid (i.e., within two days) decrease in IL-6 was seen in survivors. The non-survivors were characterized by persistently high IL-6 levels throughout the observation period (i.e., until death). C-reactive protein (CRP) levels showed a similar pattern as the IL-6, with higher levels in non-survivors throughout the observation period. However, in contrast to IL-6, the differences between survivors and non-survivors reached statistical significance, but only at the end of the observation period. It is possible that early measurements of IL-6 in ECMO patients could give prognostic information beyond that of CRP.

Leg Wound Closure after Saphenous Vein Harvesting in Patients Undergoing Coronary Artery Bypass Grafting: A Prospective Randomized Study Comparing Intracutaneous, Transcutaneous and Zipper Techniques

Objective : Two prospective randomized studies were undertaken to compare different suture closure techniques with respect to postoperative wound infection rates and cosmetic results after saphenous vein harvesting in patients undergoing coronary artery bypass surgery. Design : A total of 166 patients were included in the first study, in which 85 had their leg wounds closed with transcutaneous and 81 with intracutaneous suture. In the second study, 168 patients were selected to a non-invasive surgical zipper ( n = 78) or intracutaneous suture ( n = 90). Results : In the first study the overall infection rate was 20.5%, 17.6% in the transcutaneous group compared with 23.5% in the intracutaneous group ( p = 0.35). In the second study the infection rate was 19.3%, 15.3% in the zipper group vs 23.3% in the intracutaneous group ( p = 0.20). On a cosmetic scale from 1 to 10, an average score of 8.0 was obtained in the percutaneous (p.c.) group vs 8.3 in the intracutaneous (i.c.) group ( p = 0.35), and 9.0 in the zipper group vs 8.4 in the i.c. group ( p = 0.003). Conclusion : The incidence of leg wound infection after saphenous vein harvesting in coronary artery bypass graft surgery is high. The zipper closing method may give a lower infection rate and a better cosmetic result compared with the intracutaneous suture.

Mediastinitis after coronary artery bypass grafting: the effect of vacuum‐assisted closure versus traditional closed drainage on survival and re‐infection rate

Mediastinitis is treated with either vacuum‐assisted closure (VAC) or traditional closed drainage (TCD) with irrigation. The aim of the study was to determine the effect of the two treatments on mortality and re‐infection rate in a source population, using 21 314 consecutive patients undergoing isolated coronary artery bypass grafting (CABG) from January 1997 to October 2010. Median observation time was 2·9 years in the VAC group and 8·0 years in the TCD group. The epidemiological design was of an exposed (VAC, n = 64) versus non‐exposed (TCD, n = 66) cohort with two endpoints: (1) mortality and (2) failure of sternal wound healing or re‐infection. The crude effect of treatment technique versus endpoint was estimated by univariate analysis. Stratification analysis by the Mantel–Haenszel method was performed to quantify confounders and to pinpoint effect modifiers. Adjustment for confounders was performed using Cox regression analysis. Mediastinitis was diagnosed 6–105 (median 14) days after primary operation in the VAC group and 13 (5–29) days in the TCD group. There was no difference between groups in long‐term survival. Failure of sternal wound healing or re‐infection occurred less frequently in the VAC group (6%) than in the TCD group (21%; relative risk = 0·29, 95% CI = 0·06–0·88, P = 0·01). There are concerns for increase in right ventricle rupture in VAC compared with TCD. There was no difference in survival after VAC therapy and TCD therapy of post‐CABG mediastinitis. Failure of sternal wound healing or re‐infection was more common after TCD therapy.

Complement activation and cytokine and chemokines release during mediastinitis.

BACKGROUND Mediastinitis after open heart operation is an infrequent, but life-threatening complication with a reported incidence rate between 1% and 4%. Hospital mortality is estimated at 10% to 35%. The aim of the present work was to study the systemic inflammatory reaction as judged by complement activation and cytokine and chemokines release in patients with mediastinitis after open heart operation. METHODS Seven patients with clinical signs of mediastinitis were included. Three patients had undergone coronary artery bypass grafting, whereas 4 patients had combined coronary artery bypass grafting, valve replacement, or valvuloplasty. Blood samples were drawn before induction of anesthesia and at the time of reoperation, and thereafter daily during the hospital stay. Controls comprised similar patients with an uneventful postoperative course. RESULTS The terminal SC5b-9 complement complex concentration in the mediastinitis patients was substantially higher compared with the controls (p < 0.001), and the terminal SC5b-9 complement complex values showed no overlap between the two groups. Interleukin-8, stromal cell-derived factor-1alpha and IL-6 concentrations were also significantly higher in the mediastinitis group than in the control group (p < 0.001), but with considerable overlap between the groups. Interleukin-1beta, interleukin-10, and monocyte chemoattractant protein-1 concentrations were slightly higher in the mediastinitis group, and no differences were seen for the tumor necrosis factor-alpha. CONCLUSIONS During mediastinitis, the complement is activated and the cytokines and chemokines, interleukin-6, interleukin-8, and stromal cell-derived factor-1alpha are released. These proteins may be involved in the pathogenesis of this complication. Terminal SC5b-9 complement complex may be an indicator to discriminate mediastinitis patients from those with uneventful course.

Sternal wound closure in patients undergoing open-heart surgery: a prospective randomized study comparing intracutaneous and zipper techniques.

OBJECTIVE A prospective, randomized study was undertaken to compare a non-invasive surgical zipper to intracutaneous suture closure in open-heart surgery with respect to postoperative wound infection rate and cosmetic results. METHODS A total number of 300 patients were included in the study, of which 150 had their skin wound closed with zipper and 150 with intracutaneous suture. The end-points were superficial and deep sternal wound infections within 6 weeks postoperatively. RESULTS The incidence of total infection after 6 weeks was equal in the two groups (6.7 vs. 6.7%) (P=0.94). The superficial infection rate was 5.3% in the zipper group vs. 6.0% in the intracutaneous, and the deep infection rate was 1.4% in the zipper group and 0.7% in the intracutaneous. There was no statistically significant difference between the groups. Only the cosmetic result differed. On a visual scale from 1 (poorest) to 10 (best), an average score of 8.2 was obtained in the intracutaneous group versus 8.9 in the zipper group (P<0.01). CONCLUSION The wound infection rate was equal for the intracutaneous group compared with the zipper group; however, the cosmetic result was judged better by the patients in the zipper group.

Mediastinitis after coronary artery bypass grafting increases the incidence of left internal mammary artery obstruction

Mediastinitis after coronary artery bypass grafting (CABG) gives a longstanding chronic inflammation and has a detrimental negative effect on long‐term survival. For this reason, we aimed to study the effect of mediastinitis on graft patency after CABG. The epidemiologic design was of an exposed (mediastinitis, n = 41) versus non‐exposed (non‐mediastinitis, controls, n = 41) cohort with two endpoints: (i) obstruction of saphenous vein grafts (SVG) and (ii) obstruction of the internal mammary artery (IMA) grafts. The graft patency was evaluated with coronary CT‐angiography examination at a median follow‐up of 2·7 years. The number of occluded SVG in the mediastinitis group was 18·9% versus 15·5% in the control group. Using generalized estimating equations model with exchangeable matrix, and confounding effect of ischaemic time and patients age, we found no significant association between presence of mediastinitis and SVG obstruction [rate ratio (RR) = 0·96, 95% CI (0·52–2·67), P = 0·697]. The number of occluded IMA grafts was 10·5% in the mediastinitis group and 2·4% in the control group. Using the Poisson regression model, we estimated RR = 5·48, 95% CI (1·43–21·0) and P = 0·013. There was a significant association between mediastinitis and IMA graft obstruction, when controlling for the confounding effect of ischaemic time, body mass index, presence of diabetes mellitus and the number of diseased vessels. Presence of mediastinitis increases the risk of IMA graft obstruction. This may confirm the importance of inflammation as a major contributor to the pathogenesis of atherosclerosis and explain the negative effect of mediastinitis on a long‐term survival.