Mediastinitis after cardiac surgery

Mediastinitis as a complication after cardiac surgery is rare but disastrous increasing the hospital stay, hospital costs, morbidity and mortality. It occurs in 1-3 % of patients after median sternotomy. The purpose of this study was to find out the risk factors and also to investigate new ways to prevent mediastinitis. First, we assessed operating room air contamination monitoring by comparing the bacteriological technique with continuous particle counting in low level contamination achieved by ultra clean garment options in 66 coronary artery bypass grafting operations. Second, we examined surgical glove perforations and the changes in bacterial flora of surgeons' fingertips in 116 open-heart operations. Third, the effect of gentamicin-collagen sponge on preventing surgical site infections (SSI) was studied in randomized controlled study with 557 participants. Finally, incidence, outcome, and risk factors of mediastinitis were studied in over 10,000 patients. With the alternative garment and textile system (cotton group and clean air suit group), the air counts fell from 25 to 7 colony-forming units/m3 (P<0.01). The contamination of the sternal wound was reduced by 46% and that of the leg wound by >90%. In only 17% operations both gloves were found unpunctured. Frequency of glove perforations and bacteria counts of hands were found to increase with operation time. With local gentamicin prophylaxis slightly less SSIs (4.0 vs. 5.9%) and mediastinitis (1.1 vs. 1.9%) occurred. We identified 120/10713 cases of postoperative mediastinitis (1.1%). During the study period, the patient population grew significantly older, the proportion of women and patients with ASA score >3 increased significantly. In multivariate logistic regression analysis, the only significant predictor for mediastinitis was obesity. Continuous particle monitoring is a good intraoperative method to control the air contamination related to the theatre staff behavior during individual operation. When a glove puncture is detected, both gloves are to be changed. Before donning a new pair of gloves, the renewed disinfection of hands will help to keep their bacterial counts lower even towards the end of long operation. Gentamicin-collagen sponge may have beneficial effects on the prevention of SSI, but further research is needed. Mediastinitis is not diminishing. Larger populations at risk, for example proportions of overweight patients, reinforce the importance of surveillance and pose a challenge in focusing preventive measures.

Therapeutic hypothermia after cardiac arrest : Studies on neurological and cardiological outcome and prediction of outcome in hypothermia-treated patients resuscitated from out-of-hospital cardiac arrest

The outcome of the successfully resuscitated patient is mainly determined by the extent of hypoxic-ischemic cerebral injury, and hypothermia has multiple mechanisms of action in mitigating such injury. The present study was undertaken from 1997 to 2001 in Helsinki as a part of the European multicenter study Hypothermia after cardiac arrest (HACA) to test the neuroprotective effect of therapeutic hypothermia in patients resuscitated from out-of-hospital ventricular fibrillation (VF) cardiac arrest (CA). The aim of this substudy was to examine the neurological and cardiological outcome of these patients, and especially to study and develop methods for prediction of outcome in the hypothermia-treated patients. A total of 275 patients were randomized to the HACA trial in Europe. In Helsinki, 70 patients were enrolled in the study according to the inclusion criteria. Those randomized to hypothermia were actively cooled externally to a core temperature 33 ± 1ºC for 24 hours with a cooling device. Serum markers of ischemic neuronal injury, NSE and S-100B, were sampled at 24, 36, and 48 hours after CA. Somatosensory and brain stem auditory evoked potentials (SEPs and BAEPs) were recorded 24 to 28 hours after CA; 24-hour ambulatory electrocardiography recordings were performed three times during the first two weeks and arrhythmias and heart rate variability (HRV) were analyzed from the tapes. The clinical outcome was assessed 3 and 6 months after CA. Neuropsychological examinations were performed on the conscious survivors 3 months after the CA. Quantitative electroencephalography (Q-EEG) and auditory P300 event-related potentials were studied at the same time-point. Therapeutic hypothermia of 33ºC for 24 hours led to an increased chance of good neurological outcome and survival after out-of-hospital VF CA. In the HACA study, 55% of hypothermia-treated patients and 39% of normothermia-treated patients reached a good neurological outcome (p=0.009) at 6 months after CA. Use of therapeutic hypothermia was not associated with any increase in clinically significant arrhythmias. The levels of serum NSE, but not the levels of S-100B, were lower in hypothermia- than in normothermia-treated patients. A decrease in NSE values between 24 and 48 hours was associated with good outcome at 6 months after CA. Decreasing levels of serum NSE but not of S-100B over time may indicate selective attenuation of delayed neuronal death by therapeutic hypothermia, and the time-course of serum NSE between 24 and 48 hours after CA may help in clinical decision-making. In SEP recordings bilaterally absent N20 responses predicted permanent coma with a specificity of 100% in both treatment arms. Recording of BAEPs provided no additional benefit in outcome prediction. Preserved 24- to 48-hour HRV may be a predictor of favorable outcome in CA patients treated with hypothermia. At 3 months after CA, no differences appeared in any cognitive functions between the two groups: 67% of patients in the hypothermia and 44% patients in the normothermia group were cognitively intact or had only very mild impairment. No significant differences emerged in any of the Q-EEG parameters between the two groups. The amplitude of P300 potential was significantly higher in the hypothermia-treated group. These results give further support to the use of therapeutic hypothermia in patients with sudden out-of-hospital CA.

Cardiac function before and after treatment for various types of loading conditions and in myocardial restriction : A prospective study on pediatric patients with two- and three-dimensional echocardiography and measurement of serum natriuretic peptides

Background: The incidence of all forms of congenital heart defects is 0.75%. For patients with congenital heart defects, life-expectancy has improved with new treatment modalities. Structural heart defects may require surgical or catheter treatment which may be corrective or palliative. Even those with corrective therapy need regular follow-up due to residual lesions, late sequelae, and possible complications after interventions. Aims: The aim of this thesis was to evaluate cardiac function before and after treatment for volume overload of the right ventricle (RV) caused by atrial septal defect (ASD), volume overload of the left ventricle (LV) caused by patent ductus arteriosus (PDA), and pressure overload of the LV caused by coarctation of the aorta (CoA), and to evaluate cardiac function in patients with Mulibrey nanism. Methods: In Study I, of the 24 children with ASD, 7 underwent surgical correction and 17 percutaneous occlusion of ASD. Study II had 33 patients with PDA undergoing percutaneous occlusion. In Study III, 28 patients with CoA underwent either surgical correction or percutaneous balloon dilatation of CoA. Study IV comprised 26 children with Mulibrey nanism. A total of 76 healthy voluntary children were examined as a control group. In each study, controls were matched to patients. All patients and controls underwent clinical cardiovascular examinations, two-dimensional (2D) and three-dimensional (3D) echocardiographic examinations, and blood sampling for measurement of natriuretic peptides prior to the intervention and twice or three times thereafter. Control children were examined once by 2D and 3D echocardiography. M-mode echocardiography was performed from the parasternal long axis view directed by 2D echocardiography. The left atrium-to-aorta (LA/Ao) ratio was calculated as an index of LA size. The end-diastolic and end-systolic dimensions of LV as well as the end-diastolic thicknesses of the interventricular septum and LV posterior wall were measured. LV volumes, and the fractional shortening (FS) and ejection fraction (EF) as indices of contractility were then calculated, and the z scores of LV dimensions determined. Diastolic function of LV was estimated from the mitral inflow signal obtained by Doppler echocardiography. In three-dimensional echocardiography, time-volume curves were used to determine end-diastolic and end-systolic volumes, stroke volume, and EF. Diastolic and systolic function of LV was estimated from the calculated first derivatives of these curves. Results: (I): In all children with ASD, during the one-year follow-up, the z score of the RV end-diastolic diameter decreased and that of LV increased. However, dilatation of RV did not resolve entirely during the follow-up in either treatment group. In addition, the size of LV increased more slowly in the surgical subgroup but reached control levels in both groups. Concentrations of natriuretic peptides in patients treated percutaneously increased during the first month after ASD closure and normalized thereafter, but in patients treated surgically, they remained higher than in controls. (II): In the PDA group, at baseline, the end-diastolic diameter of LV measured over 2SD in 5 of 33 patients. The median N-terminal pro-brain natriuretic peptide (proBNP) concentration before closure measured 72 ng/l in the control group and 141 ng/l in the PDA group (P = 0.001) and 6 months after closure measured 78.5 ng/l (P = NS). Patients differed from control subjects in indices of LV diastolic and systolic function at baseline, but by the end of follow-up, all these differences had disappeared. Even in the subgroup of patients with normal-sized LV at baseline, the LV end-diastolic volume decreased significantly during follow-up. (III): Before repair, the size and wall thickness of LV were higher in patients with CoA than in controls. Systolic blood pressure measured a median 123 mm Hg in patients before repair (P < 0.001) and 103 mm Hg one year thereafter, and 101 mm Hg in controls. The diameter of the coarctation segment measured a median 3.0 mm at baseline, and 7.9 at the 12-month (P = 0.006) follow-up. Thicknesses of the interventricular septum and posterior wall of the LV decreased after repair but increased to the initial level one year thereafter. The velocity time integrals of mitral inflow increased, but no changes were evident in LV dimensions or contractility. During follow-up, serum levels of natriuretic peptides decreased correlating with diastolic and systolic indices of LV function in 2D and 3D echocardiography. (IV): In 2D echocardiography, the interventricular septum and LV posterior wall were thicker, and velocity time integrals of mitral inflow shorter in patients with Mulibrey nanism than in controls. In 3D echocardiography, LV end-diastolic volume measured a median 51.9 (range 33.3 to 73.4) ml/m² in patients and 59.7 (range 37.6 to 87.6) ml/m² in controls (P = 0.040), and serum levels of ANPN and proBNP a median 0.54 (range 0.04 to 4.7) nmol/l and 289 (range 18 to 9170) ng/l, in patients and 0.28 (range 0.09 to 0.72) nmol/l (P < 0.001) and 54 (range 26 to 139) ng/l (P < 0.001) in controls. They correlated with several indices of diastolic LV function. Conclusions (I): During the one-year follow-up after the ASD closure, RV size decreased but did not normalize in all patients. The size of the LV normalized after ASD closure but the increase in LV size was slower in patients treated surgically than in those treated with the percutaneous technique. Serum levels of ANPN and proBNP were elevated prior to ASD closure but decreased thereafter to control levels in patients treated with the percutaneous technique but not in those treated surgically. (II): Changes in LV volume and function caused by PDA disappeared by 6 months after percutaneous closure. Even the children with normal-sized LV benefited from the procedure. (III): After repair of CoA, the RV size and the velocity time integrals of mitral inflow increased, and serum levels of natriuretic peptides decreased. Patients need close follow-up, despite cessation of LV pressure overload, since LV hypertrophy persisted even in normotensive patients with normal growth of the coarctation segment. (IV): In children with Mulibrey nanism, the LV wall was hypertrophied, with myocardial restriction and impairment of LV function. Significant correlations appeared between indices of LV function, size of the left atrium, and levels of natriuretic peptides, indicating that measurement of serum levels of natriuretic peptides can be used in the clinical follow-up of this patient group despite its dependence on loading conditions.

Inhibition of Thrombin in Cardiac Surgery : experiments in a porcine model

Cardiac surgery involving cardiopulmonary bypass (CPB) induces activation of inflammation and coagulation systems and is associated with ischemia-reperfusion injury (I/R injury)in various organs including the myocardium, lungs, and intestine. I/R injury is manifested as organ dysfunction. Thrombin, the key enzyme of coagulation , plays a cenral role also in inflammation and contributes to regulation of apoptosis as well. The general aim of this thesis was to evaluate the potential of thrombin inhibition in reducing the adverse effects of I/R injury in myocardium, lungs, and intestine associated with the use of CPB and cardiac surgery. Forty five pigs were used for the studies. Two randomized blinded studies were performed. Animals underwent 75 min of normothermic CPB, 60 min of aortic clamping, and 120 min of reperfusion period. Twenty animals received iv. recombinant hirudin, a selective and effective inbitor of thrombin, or placebo. In a similar setting, twenty animals received an iv-bolus (250 IU/kg) of antithrombin (AT) or placebo. An additional group of 5 animals received 500 IU/kg in an open label setting to test dose response. Generation of thrombin (TAT), coagulation status (ACT), and hemodynamics were measured. Intramucosal pH and pCO2 were measured from the luminal surface of ileum using tonometry simultaneusly with arterial gas analysis. In addition, myocardial, lung, and intestinal biopsies were taken to quantitate leukocyte infiltration (MPO), for histological evaluation, and detection of apoptosis (TUNEL, caspase 3). In conclusion, our data suggest that r-hirudin may be an effective inhibitor of reperfusion induced thrombin generation in addition to being a direct inhibitor of preformed thrombin. Overall, the results suggest that inhibition of thrombin, beyond what is needed for efficient anticoagulation by heparin, has beneficial effects on myocardial I/R injury and hemodynamics during cardiac surgery and CPB. We showed that infusion of the thrombin inhibitor r-hirudin during reperfusion was associated with attenuated post ischemia left ventricular dysfunction and decreased systemic vascular resistance. Consequently microvascular flow was improved during ischemia-reperfusion injury. Improved recovery of myocardium during the post-ischemic reperfusion period was associated with significantly less cardiomyocyte apoptosis and with a trend in anti-inflammatory effects. Thus, inhibition of reperfusion induced thrombin may offer beneficial effects by mechanisms other than direct anticoagulant effects. AT, in doses with a significant anticoagulant effect, did not alleviate myocardial I/R injury in terms of myocardial recovery, histological inflammatory changes or post-ischemic troponin T release. Instead, AT attenuated reperfusion induced increase in pulmonary pressure after CPB. Taken the clinical significance of postoperative pulmonary hemodynamics in patients undergoing cardiopulmonary bypass, the potential positive regulatory role of AT and clinical implications needs to be studied further. Inflammatory response in the gut wall proved to be poorly associated with perturbed mucosal perfusion and the animals with the least neutrophil tissue sequestration and I/R related histological alterations tended to have the most progressive mucosal hypoperfusion. Thus, mechanisms of low-flow reperfusion injury during CPB can differ from the mechanisms seen in total ischemia reperfusion injury.

Pharmacokinetics, efficacy, and safety of pravastatin in children : Studies in children with heterozygous familial hypercholesterolemia and in pediatric cardiac transplant recipients

Background. Hyperlipidemia is a common concern in patients with heterozygous familial hypercholesterolemia (HeFH) and in cardiac transplant recipients. In both groups, an elevated serum LDL cholesterol level accelerates the development of atherosclerotic vascular disease and increases the rates of cardiovascular morbidity and mortality. The purpose of this study is to assess the pharmacokinetics, efficacy, and safety of cholesterol-lowering pravastatin in children with HeFH and in pediatric cardiac transplant recipients receiving immunosuppressive medication. Patients and Methods. The pharmacokinetics of pravastatin was studied in 20 HeFH children and in 19 pediatric cardiac transplant recipients receiving triple immunosuppression. The patients ingested a single 10-mg dose of pravastatin, and plasma pravastatin concentrations were measured up to 10/24 hours. The efficacy and safety of pravastatin (maximum dose 10 to 60 mg/day and 10 mg/day) up to one to two years were studied in 30 patients with HeFH and in 19 cardiac transplant recipients, respectively. In a subgroup of 16 HeFH children, serum non-cholesterol sterol ratios (102 x mmol/mol of cholesterol), surrogate estimates of cholesterol absorption (cholestanol, campesterol, sitosterol), and synthesis (desmosterol and lathosterol) were studied at study baseline (on plant stanol esters) and during combination with pravastatin and plant stanol esters. In the transplant recipients, the lipoprotein levels and their mass compositions were analyzed before and after one year of pravastatin use, and then compared to values measured from 21 healthy pediatric controls. The transplant recipients were grouped into patients with transplant coronary artery disease (TxCAD) and patients without TxCAD, based on annual angiography evaluations before pravastatin. Results. In the cardiac transplant recipients, the mean area under the plasma concentration-time curve of pravastatin [AUC(0-10)], 264.1 * 192.4 ng.h/mL, was nearly ten-fold higher than in the HeFH children (26.6 * 17.0 ng.h/mL). By 2, 4, 6, 12 and 24 months of treatment, the LDL cholesterol levels in the HeFH children had respectively decreased by 25%, 26%, 29%, 33%, and 32%. In the HeFH group, pravastatin treatment increased the markers of cholesterol absorption and decreased those of synthesis. High ratios of cholestanol to cholesterol were associated with the poor cholesterol-lowering efficacy of pravastatin. In cardiac transplant recipients, pravastatin 10 mg/day lowered the LDL cholesterol by approximately 19%. Compared with the patients without TxCAD, patients with TxCAD had significantly lower HDL cholesterol concentrations and higher apoB-100/apoA-I ratios at baseline (1.0 ± 0.3 mmol/L vs. 1.4 ± 0.3 mmol/L, P = 0.031; and 0.7 ± 0.2 vs. 0.5 ± 0.1, P = 0.034) and after one year of pravastatin use (1.0 ± 0.3 mmol/L vs. 1.4 ± 0.3 mmol/L, P = 0.013; and 0.6 ± 0.2 vs. 0.4 ± 0.1, P = 0.005). Compared with healthy controls, the transplant recipients exhibited elevated serum triglycerides at baseline (median 1.3 [range 0.6-3.2] mmol/L vs. 0.7 [0.3-2.4] mmol/L, P=0.0002), which negatively correlated with their HDL cholesterol concentration (r = -0.523, P = 0.022). Recipients also exhibited higher apoB-100/apoA1 ratios (0.6 ± 0.2 vs. 0.4 ± 0.1, P = 0.005). In addition, elevated triglyceride levels were still observed after one year of pravastatin use (1.3 [0.5-3.5] mmol/L vs. 0.7 [0.3-2.4] mmol/L, P = 0.0004). Clinically significant elevations in alanine aminotransferase, creatine kinase, or creatinine ocurred in neither group. Conclusions. Immunosuppressive medication considerably increased the plasma pravastatin concentrations. In both patient groups, pravastatin treatment was moderately effective, safe, and well tolerated. In the HeFH group, high baseline cholesterol absorption seemed to predispose patients to insufficient cholesterol-lowering efficacy of pravastatin. In the cardiac transplant recipients, low HDL cholesterol and a high apoB-100/apoA-I ratio were associated with development of TxCAD. Even though pravastatin in the transplant recipients effectively lowered serum total and LDL cholesterol concentrations, it failed to normalize their elevated triglyceride levels and, in some patients, to prevent the progression of TxCAD.

Late results after paediatric cardiac surgery

Background: Congenital heart defects include a wide range of inborn malformations. Depending on the defect, the life expectancy of a newborn with cardiac anomaly varies from a few days to a normal life span. In most instances surgery, is the only treatment available. The late results of surgery have not been comprehensively investigated. Aims: Mortality, morbidity and the life situation of all Finnish patients who had been operated on for congenital heart defect during childhood were investigated. Methods: Patient and surgical data were gathered from all hospitals that had performed heart surgeries on children. Late mortality and survival data were obtained from the population registry, and the causes of deaths from Statistics Finland. Morbidity of patients operated on during 1953-1989 was assessed by the usage of medicines. The pharmacotherapy data of patients and controls were obtained from the Social Insurance Institute. The life situation of patients was surveyed by mailed questionnaire. Survival, causes of deaths and life situation of patients were compared with those of the general population. Results: A total of 7240 cardiac operations were performed on 6461 children during the first 37 years of cardiac surgery (1953-1989). The number of procedures constantly rose during this period, and the increase continued in later years. The patient material varied over time, as more defects became surgically treatable. During 1953-1989 the operative mortality (death within 30 days of surgery) was 6.9%. In the 1990s a slight rise occurred in early mortality, as increasingly complicated patients were surgically treated. During 2000-2003 practically no defects were beyond the operative range. Thus, the operative mortality of 4.4% was excellent, decreasing even further to 2.0% in 2004-2007. The overall 45-year survival of patients operated on in 1953-1989 was 78%, and the corresponding figure for the general population was 93%. Survival depended on the defect, being worst among patients with univentricular heart. Late survival was also better during the 1990s and at the beginning of the 21st century. Of the 6028 early survivors, 592 died late (>30 days) after surgery. A total of 397 deaths (67%) were related and 185 (31%) unrelated to congenital heart defect. The cause of death was unknown in 10 cases. Of those 5774 patients who survived their first operation and had complete follow-up, 16% were operated on several times. Seventeen percent of patients used medicines for cardiac symptoms (heart failure, arrhythmia, hypertension and coronary disease). Patients risk of using cardiac medicines was 2.16 (Cl 1.97-2.37) times higher than that of controls. Patients also had more genetic syndromes and mental retardation and more often used medicines for asthma and epilepsy. Adult patients who had been operated on as children had coped surprisingly well with their defects. Their level of education was similar and their employment level even higher than expected, and they were living in a steady relationship as often as the general population. Conclusions: Cardiac surgery developed rapidly, and nowadays practically all defects can be treated. The overall survival of all operated patients was 78%, 16% less than that of the general population. However, it was significantly better than the anticipated natural survival. However, many patients had health problems; 16% needed reoperations and 17% cardiac medicines to maintain their condition. Most of the patients assessed their general health as good and lived a normal life.