Antonio Ditta

Risk factors for renal dysfunction after coronary surgery: the role of cardiopulmonary bypass technique:

We studied 316 patients undergoing cardiopulmonary bypass for coronary artery surgery in order to determine perioperative risk factors for postoperative renal dysfunction A preliminary univariate analysis was performed by χ2 analysis for categorical data and Mann-Whitney U-test for continuous variables to detect significant correlations between each risk factor and the occurrence of moderate or severe renal dysfunction. Subsequently, a multiple logistic regression was applied to the three risk factors identified as predictive for severe renal dysfunction. Low cardiac output syndrome and need for banked blood transfusions combined with a low haematocrit value during cardiopulmonary bypass increase the probability of severe renal dysfunction in the postoperative course.

Surgical Reexploration After Cardiac Operations: Why a Worse Outcome?

BACKGROUND Surgical reexploration due to postoperative bleeding occurs in 2% to 6% of cardiac surgical patients and is accompanied by increased morbidity and mortality. In this study, we addressed the postoperative course of patients needing surgical reexploration, with specific respect to the timing of reexploration and the transfusional needs as determinants of morbidity and mortality. METHODS This was a retrospective study of 232 patients having undergone surgical reexploration owing to postoperative bleeding after cardiac operations, compared with a control, propensity-matched group. RESULTS Patients in the surgical reexploration group had greater morbidity (low cardiac output, acute renal failure, sepsis) and longer mechanical ventilation time and intensive care unit stay than did control patients, and a significantly higher mortality rate (14.2% versus 3.4%, p = 0.001). The timing of surgical reexploration was not associated with morbidity or mortality. The amount of packed red cells transfused was significantly associated with increased morbidity (acute renal failure, low cardiac output syndrome, sepsis), with mechanical ventilation time and intensive care unit stay, and with the mortality rate (0.25% increase for each unit transfused). CONCLUSIONS The main determinant of morbidity and mortality for patients requiring a surgical reexploration after cardiac operations is the amount of packed red cells transfused. Delaying the timing of reexploration may represent a risk factor only when the delay creates the need for an excessive use of allogeneic blood products, or in the presence of clinical signs of cardiac tamponade.

Postoperative antithrombin levels and outcome in cardiac operations

Objective:During cardiac operations with cardiopulmonary bypass surgery, antithrombin is consumed and low levels of antithrombin activity are commonly observed at admission to the intensive care unit (ICU). This study investigates the association between antithrombin activity at admission to the ICU (ICU-antithrombin activity) and various outcome variables. Design:The authors conducted a prospective, observational cohort study. Setting:The study was conducted at a university hospital. Patients:The study consisted of 647 consecutive patients who had undergone cardiac surgery with cardiopulmonary bypass. Measurements and Main Results:ICU-antithrombin activity significantly (p < .001) decreased with respect to preoperative values. As seen with univariate analysis, low levels of ICU-antithrombin activity were significantly associated with higher blood loss, prolonged mechanical ventilation time and ICU stay, a higher incidence of allogeneic blood products use, surgical reexploration, low cardiac output syndrome, adverse neurologic events, thromboembolic events, renal dysfunction, and hospital mortality. When corrected for the other explanatory variables, low levels of ICU-antithrombin activity remained independently associated with a prolonged ICU stay (p = .003) and with a higher incidence of surgical reexploration (p = .023), adverse neurologic events (p = .001), and thromboembolic events (p = .036). An ICU-antithrombin activity value of <58% was found to be predictive of prolonged ICU stay, with a sensitivity of 67% and a specificity of 83%. Conclusions:Low levels of ICU-antithrombin activity are associated with a poor outcome in cardiac surgery; ICU-antithrombin activity is predictive of prolonged ICU stay.

Beneficial effects of duraflo II heparin-coated circuits on postperfusion lung dysfunction

BACKGROUND Heparin coating of the cardiopulmonary bypass circuit reduces the activation of the terminal part of the complement cascade. Conflicting data are reported concerning neutrophil activation and postoperative lung dysfunction. In this study, we compared three different types of oxygenator: a bubble oxygenator, a conventional hollow-fiber oxygenator, and a heparin-coated oxygenator and circuit. METHODS Sixty patients undergoing myocardial revascularization were randomly assigned to one of three oxygenator groups. All the patients were free from preoperative lung dysfunction. Lung function was studied with repeated measurements of respiratory index, intrapulmonary shunt, alveolar dead space, ventilation/perfusion ratio, and static thoracopulmonary compliance. RESULTS Immediately after cardiopulmonary bypass, the intrapulmonary shunt and respiratory index values in the bubble oxygenator and hollow-fiber oxygenator groups increased more than those in the heparin-coated oxygenator group. In the intensive care unit, the between-group difference in intrapulmonary shunt disappeared, but the within-group difference in respiratory index (from baseline) remained for the bubble oxygenator group. The other three variables did not significantly differ between groups. Intubation time and stay in the intensive care unit did not differ between groups. CONCLUSIONS Heparin-coated circuits exert a protective effect on pulmonary function. However, their use did not modify the postoperative clinical course of patients with normal lung function preoperatively.

Different patterns of heparin resistance: therapeutic implications.

Heparin resistance (HR) during cardiac operations is a common feature. Its aetiology often recognizes a decrease in circulating antithrombin III (AT III) due to a preoperative heparin treatment. Nevertheless, some papers highlighted the existence of HR in patients with normal values of AT III. This paper was designed in order to identify this subgroup of AT III-independent heparin-resistant patients. Five hundred consecutive patients scheduled for coronary revascularization with cardiopulmonary bypass were enrolled in this prospective trial. HR was identified in 104 (20.8%) patients. Thirty-six of them (7.2% of the total population) had a preoperative AT III activity ≥100%, and were defined as AT III-independent heparin-resistant patients. This subgroup significantly differs from the AT III-dependent heparin-resistant group being affected by a less severe degree of HR and including less patients pretreated with heparin. Unlike the other heparin-resistant patients, these subjects do not respond to AT III supplementation aimed at reaching supranormal AT III activity values.

A Systematic Review of Biocompatible Cardiopulmonary Bypass Circuits and Clinical Outcome

This systematic review and meta-analysis explores the clinical efficacy of biocompatible surfaces for cardiopulmonary bypass in adults. Thirty-six randomized controlled trials were retrieved for a total of 4360 patients. Patients treated with biocompatible circuits had a lower rate of packed red cells transfusions and atrial fibrillation, and shorter durations of stay in the intensive care unit. When the analysis was limited to high-quality studies, only a reduction in atrial fibrillation rate and a shorter stay in the intensive care unit remained significantly associated with the use of biocompatible surfaces. Using biocompatible surfaces without other measures to contain blood activation results in a limited clinical benefit.

Normothermic perfusion and lung function after cardiopulmonary bypass: effects in pulmonary risk patients

Fifty patients at risk for postoperative lung dysfunction and undergoing elective coronary revascularization have been randomly assigned to receive normothermic (36°C) perfusion with warm heart protection (NP group) or hypothermic (28°C) perfusion with cold heart protection (HP group). Lung function before and after cardiopulmonary bypass (CPB) was studied through the determination of the intrapulmonary shunt (Qs/Qt), the alveolo-arterial oxygen gradient (A-aΔO2), and the artero-alveolar carbon dioxide gradient (a-AΔCO2). The Q s /Q t after CPB was significantly lower in the NP group (27.1 ± 2.6 vs 35.7 ± 2.3) as well as the A-aΔO2 (50.2 ± 1.5 vs 57.6 ±2.4); both data returned to comparable between the groups after 3 h in the intensive care unit. The a-AΔCO2 was significantly lower after CPB in the NP group (5.2 ± 0.74 vs 8.2 ± 0.8). Hospital stay and mortality were comparable in the two groups; intubation time and rate of early extubation showed a trend in favour of the NP group; the rate of patients suffering hypoxia and/or hypercapnia after extubation was significantly lower in the NP group (12%) versus the HP group (44%). Normothermia seems to exert a protective effect against lung dysfunction after CPB. The absence of a rewarming injury associated with reperfusion, a limitation of the hypothermic-induced vasoconstriction due to local cooling of the lung and a better compliance of the normothermic lung are hypothesized as beneficial effects of the ‘all-warm’ strategy.

Determinants of antithrombin consumption in cardiac operations requiring cardiopulmonary bypass

Antithrombin (AT) is a natural anticoagulant that is consumed during cardiac operations with cardiopulmonary bypass (CPB). This study is an observational trial aimed at identifying the factors determining the magnitude of the AT consumption during cardiac operations. Two hundred and fifty consecutive adult patients undergoing cardiac operations with CPB were admitted to the study. Preoperative and intraoperative variables were tested with respect to their role in determining AT activity at the end of the operation. At a univariate analysis, eight predictors of AT activity at the end of the operation have been identified: preoperative AT activity; age; diabetes on medication; preoperative haematocrit value; preoperative dialysis; combined operation; CPB duration; lowest temperature on CPB. A multivariate predictive model was created, and five factors remained as independent predictors of AT activity at the end of the operation: preoperative AT activity (p = 0.001); age (p = 0.015); combined operation (p = 0.014); diabetes (p = 0.013) and CPB duration (p = 0.001). On this basis, predictive tables of AT consumption have been established for different combinations of risk factors.

Effects of priming volume reduction on allogeneic red blood cell transfusions and renal outcome after heart surgery

Introduction: Excessive hemodilution during cardiopulmonary bypass (CPB) is associated with an increased rate of red blood cell (RBC) transfusion and acute kidney injury (AKI). Minimization of the oxygenator priming volume is a measure to contain hemodilution. In this study, we evaluated the new oxygenator, Sorin Inspire 6™, with respect to its ability to limit hemodilution, RBC transfusion rate and postoperative AKI rate. Methods: A retrospective study on a consecutive series of 1,724 adult patients receiving heart surgery with CPB. Patients treated with the Inspire 6™ were assigned to the low priming volume oxygenator (LPVO) group (N=383) and patients treated with conventional oxygenators to the conventional group (N=1,341). Dynamic priming volume, time course of the hematocrit, RBC transfusions and AKI rate were compared between the groups. Results: Priming volume was significantly (p=0.001) lower in the LPVO group (624±113 mL) vs. the conventional group (775±150 mL), with higher values of hematocrit during and after CPB. After correction for other confounders, patients in the LPVO group had a significantly lower RBC transfusion rate (odds ratio 0.68, 95% confidence interval 0.52-0.90, p=0.006) and AKI rate (odds ratio 0.55, 95% confidence interval 0.32-0.93, p=0.032). Conclusion: The Inspire 6™ oxygenator allows a significant containment of hemodilution during CPB, reducing the risk of RBC transfusions and postoperative AKI.

Transfusions during cardiopulmonary bypass: better when triggered by venous oxygen saturation and oxygen extraction rate

During cardiopulmonary bypass (CPB), red blood cell transfusions may be required to correct dilutional anemia. The decision-making process for transfusions is usually based on the level of hemoglobin.This study investigates the hypothesis that oxygen-derived variables (mixed venous oxygen saturation, SvO2, and oxygen extraction rate, O2ER) may be more reliable predictors of the efficacy of the transfusion. Thirty-six patients for 41 transfusion episodes during CPB were retrospectively analyzed. For each patient, oxygen-derived variables, including SvO2 and O2ER, were measured before and after the transfusion. No changes in pump flow were allowed between the two measurements. The efficacy of transfusion was defined as an increase in SvO2 of at least 5%. We identified 11 transfusion episodes leading to an efficacious SvO 2 increase. Factors associated with the efficacy of the transfusion were a low SvO2 and a high O2ER. No association was found with hemoglobin values, unless for a trend for efficacy of transfusion in patients with very low (<6 g/dL) hemoglobin values. Cut-off values of 68% for SvO2 and 39% for O2ER were predictive for the efficacy of red blood cell transfusions, with a high accuracy (c-statistics 0.856 and 0.848, respectively) and negative and positive predictive values exceeding 82%. In conclusion, SvO2 and O2ER are better than the hemoglobin value for guiding the decision-making process of red blood cell transfusions to correct hemodilutional anemia during CPB.