The hemodynamic and respiratory effects of cuirass ventilation in healthy volunteers: Part 1.

OBJECTIVE: Negative-pressure ventilation (NPV) by external cuirass (RTX; Deminax Medical Instruments Limited, London, UK) in intubated patients after cardiac surgery improves hemodynamics measured by pulmonary artery catheter (PAC)-based methods, with an increased cardiac output (CO) and stroke volume (SV), without changing the heart rate (HR). The less-invasive pressure recording analytical method (PRAM) (Mostcare; Vytech Health srl, Padova, Italy) allows radial artery-based monitoring of the CO, SV, SV variation, and cardiac cycle efficiency (CCE). The authors investigated the hypothesis that NPV improves PRAM-based hemodynamics and arterial blood gas analysis in spontaneously breathing subjects. DESIGN: A clinical investigation. SETTING: A teaching hospital. PARTICIPANTS: Ten healthy volunteers. INTERVENTIONS: Subjects underwent 5 consecutive experimental ventilation modalities lasting 5 minutes: (1) baseline (no cuirass ventilation), (2) mode 1: cuirass ventilation with a continuous negative pressure of -20 cmH(2)O, (3) first rest period (no cuirass ventilation), (4) mode 2: cuirass ventilation in control mode of 12 breaths/min at -20 cmH(2)O, and (5) second rest period. MEASUREMENTS AND MAIN RESULTS: PRAM parameters were analyzed throughout the final minute of each experimental modality, which concluded with arterial blood gas sampling. Both NPV modes significantly reduced HR without changing CO or systemic vascular resistance. Mode 1 significantly increased CCE and decreased SVV. PO(2) decreased in both rest modes compared with baseline. This was prevented by NPV. In 5 smokers, PO(2) significantly increased in the control mode compared with first rest period. The control mode NPV improved oxygenation with a reduced PCO(2) and reciprocally increased pH. CONCLUSIONS: Five minutes of NPV improves hemodynamics and oxygenation in healthy subjects.

The hemodynamic and respiratory effects of continuous negative and control-mode cuirass ventilation in recently extubated cardiac surgery patients: Part 2.

OBJECTIVE: Negative-pressure ventilation (NPV) by external cuirass (RTX; Deminax Medical Instruments Limited, London, UK) in intubated patients after cardiac surgery improves hemodynamics measured by pulmonary artery catheter (PAC)-based methods with increased cardiac output (CO) and stroke volume (SV) without changing the heart rate (HR). The less-invasive pressure recording analytical method (PRAM) (MostCare; Vytech Health srl, Padova, Italy) allows radial artery monitoring of CO, SV, SV variation, and cardiac cycle efficiency (CCE). The authors investigated the hypothesis that NPV improves PRAM-based hemodynamics and arterial blood gas analysis in extubated cardiac surgery patients. DESIGN: A clinical investigation. SETTING: A teaching hospital. PARTICIPANTS: Twenty recently extubated cardiac surgery patients. INTERVENTIONS: Five consecutive experimental ventilation modalities lasted 5 minutes: (1) baseline (no cuirass ventilation), (2) mode 1 (cuirass ventilation with a continuous negative pressure of -20 cmH(2)O), (3) rest 1 (no cuirass ventilation), (4) mode 2 (cuirass ventilation in the control mode of 12 breaths/min at -20 cmH(2)O, and (5) rest 2. MEASUREMENTS AND MAIN RESULTS: PRAM parameters were analyzed throughout the final minute of each experimental modality, concluding with arterial blood gas sampling. NPV was well tolerated. HR was unchanged. Mode 2 SV was higher than baseline and rest 2. Mode 2 CO was higher than rest 2. Rest 2 systolic blood pressure was lower than rest 1 and mode 2. Increased CCE with NPV was not significant (p = 0.0696). Oxygenation and PCO(2) were unchanged although mode 2 pH increased. CONCLUSIONS: Extubated sedated cardiac surgery patients comfortably tolerated NPV with unchanged HR. SV and pH increased.

Recruitment maneuver in prevention of hypoxia during percutaneous dilational tracheostomy: randomized trial.

BACKGROUND: Percutaneous dilational tracheostomy (PDT) can potentially lead to hypoxia and alveolar derecruitment. The aim of this prospective study was to evaluate the efficacy of performing a recruitment maneuver (RM) before tracheostomy, in order to improve oxygenation. METHODS: We enrolled 29 eligible trauma patients with acute lung injury criteria requiring tracheostomy in a university ICU. Subjects were ventilated on volume controlled mechanical ventilation (tidal volume of 6 mL/kg) and F(IO(2)) set at 1.0. Subjects were randomized into 2 groups: RM group (subjects who underwent RM 10 min before PDT, 15 subjects) and no-RM group (subjects without application of RM before PDT, 14 subjects). RM was performed by imposition of continuous positive airway pressure of 40 cm H(2)O for 40 seconds. We collected gas exchange, respiratory, and hemodynamic data 5 times: 1 hour before RM, 5 min after RM, 5 min after PDT, 30 min after PDT, and 6 hours after PDT. RESULTS: Subjects who underwent RM had a significant increase in P(aO(2)); 5 min after the maneuver, P(aO(2)) increased from 222.6 ± 33.4 mm Hg to 341.3 ± 33.1 mm Hg (P < .01) and was always significantly maintained throughout the following times of the study, compared to the no-RM group: in the RM and no-RM groups, respectively, 260.7 ± 35.4 mm Hg vs 108.5 ± 36.9 mm Hg 5 min after PDT; 285.6 ± 29.1 mm Hg vs 188.4 ± 21.4 mm Hg 30 min after PDT; and 226.3 ± 24.8 mm Hg vs 147.6 ± 42.8 mm Hg 6 h after PDT (P < .01). CONCLUSIONS: Our study suggests that application of RM before PDT could be useful to avoid hypoxemia following such procedure, by reducing fall in P(aO(2)) and preventing the decrease in oxygenation values below baseline at 6 hours.

A simple clinical model for planning transfusion quantities in heart surgery.

BACKGROUND: Patients undergoing heart surgery continue to be the largest demand on blood transfusions. The need for transfusion is based on the risk of complications due to poor cell oxygenation, however large transfusions are associated with increased morbidity and risk of mortality in heart surgery patients. The aim of this study was to identify preoperative and intraoperative risk factors for transfusion and create a reliable model for planning transfusion quantities in heart surgery procedures. METHODS: We performed an observational study on 3315 consecutive patients who underwent cardiac surgery between January 2000 and December 2007. To estimate the number of packs of red blood cells (PRBC) transfused during heart surgery, we developed a multivariate regression model with discrete coefficients by selecting dummy variables as regressors in a stepwise manner. Model performance was assessed statistically by splitting cases into training and testing sets of the same size, and clinically by investigating the clinical course details of about one quarter of the patients in whom the difference between model estimates and actual number of PRBC transfused was higher than the root mean squared error. RESULTS: Ten preoperative and intraoperative dichotomous variables were entered in the model. Approximating the regression coefficients to the nearest half unit, each dummy regressor equal to one gave a number of half PRBC. The model assigned 4 units for kidney failure requiring preoperative dialysis, 2.5 units for cardiogenic shock, 2 units for minimum hematocrit at cardiopulmonary bypass less than or equal to 20%, 1.5 units for emergency operation, 1 unit for preoperative hematocrit less than or equal to 40%, cardiopulmonary bypass time greater than 130 minutes and type of surgery different from isolated artery bypass grafting, and 0.5 units for urgent operation, age over 70 years and systemic arterial hypertension. CONCLUSIONS: The regression model proved reliable for quantitative planning of number of PRBC in patients undergoing heart surgery. Besides enabling more rational resource allocation of costly blood-conservation strategies and blood bank resources, the results indicated a strong association between some essential postoperative variables and differences between the model estimate and the actual number of packs transfused.

Current and future role of ultrafiltration in CRS.

Ultrafiltration has been used in patients with decompensated HF and volume overload refractory to diuretics. Criteria for the initiation of renal replacement therapy (RRT) in the ICU are oliguria, anuria, urea, creatinine, Na and K blood concentrations, pulmonary edema unresponsive to diuretics, uncompensated metabolic acidosis, temperature >40°C, uremic complication, and overdose with a dialyzable toxin. Moreover, the treatment of acute renal failure requires a different style and philosophy from renal replacement therapy for chronic renal failure. The degree and the location of renal lesion, the entity, the gravity of the concomitant acute or chronic cardiac damage, the weight of a trauma, surgical stress, or septic complication they determine a variability of clinical picture that can modify the prescription and the timing of RRT and the monitoring technology. In the presence of cardiac alterations due to a condition of chronic heart failure, all the acute events contribute to the progression of the cardiac insufficiency and the patient will always have as a result an ulterior reduction in the cardiac function. It derives the opportunity to put more precociously in action everything of it how much serves for a real cardioprotection. A valid hemodynamic monitoring is essential to reach the lowest possible value of pressure of left ventricular filling, without reduction in the cardiac output, increase in the cardiac frequency or the ulterior activation of the neurohormones. An early ultrafiltration allows a more easy control of the circulating mass but also an effective neurohormonal purification and of all the inflammation mediators.

An adjusted EuroSCORE model for high-risk cardiac patients.

OBJECTIVE: To verify the accuracy and precision of the logistic European system for cardiac operative risk evaluation (EuroSCORE) in high-risk cardiac surgery patients and to develop and externally validate a new system of recalibration. METHODS: The development series included 4279 high-risk patients who had undergone cardiac operations at the IRCCS Policlinico S. Donato. Performance, accuracy, and precision of the logistic EuroSCORE were assessed in this series, using a deciles-based comparison between expected and observed mortality rates, a receiver operating characteristic analysis, and a Hosmer-Lemeshow test for calibration. Differences between predicted and observed mortality rates were mathematically evaluated to develop an adjusted logistic EuroSCORE. This adjusted risk score was subsequently validated with the same approach on an external series of 1459 high-risk patients who had undergone cardiac operations at the Siena hospital. RESULTS: The adjusted logistic EuroSCORE was based on five different correction factors applied to the crude logistic EuroSCORE depending on its value. At the external validation, this model provided a good performance, with observed mortality rates not significantly different from the expected in 8 out of 10 deciles of risk distribution. The adjusted EuroSCORE had the same moderate balanced accuracy of the crude logistic EuroSCORE (area under the curve: 0.695), with a better precision (Hosmer-Lemeshow calibration test: chi(2): 3.6, p=0.891). CONCLUSIONS: Recalibration of the logistic EuroSCORE in high-risk patients is needed due to its tendency to overestimate the mortality risk. The application of a variable correction factor results in a better performance, increased precision, with unaltered balanced accuracy.

Predictive role of pretransplant serum CXCL10 for cardiac acute rejection.

BACKGROUND: The detection of acute rejection in heart transplantation remains an important feature of transplant management, especially in the early phase. Frequent surveillance with endomyocardial biopsy is necessary, even though it is an invasive procedure and carries a certain risk. Hence, noninvasive biomarkers able to predict acute rejection could be a further helpful tool in patient management. The interferon-gamma-inducible chemokine CXCL10 is required for initiation and development of graft failure caused by acute or chronic rejection. It has been reported that CXCL10 serum level is predictive of graft loss in kidney graft recipients. In the present study, we investigated whether pretransplant CXCL10 serum level may be a predictive noninvasive biomarker in heart transplant (HTx) recipients, as well. METHODS: Sera from 143 patients undergoing orthotopic heart transplantation were collected before surgery and tested for CXCL10 and CCL22 and compared with serum samples from healthy subjects. RESULTS: We found that basal CXCL10 serum levels in HTx recipients were significantly higher than in healthy subjects, whereas no difference was seen in CCL22 levels. Among HTx recipients, CXCL10 serum levels of rejectors were significantly higher than in nonrejectors. Our results showed that CXCL10 was a significant independent risk factor of several variables and had the highest predictive value for early acute heart rejection, with 160 pg/mL cutoff value. CONCLUSIONS: In HTx recipients, measurement of pretransplant CXCL10 serum levels could be a clinically useful tool for predicting cardiac acute rejection, especially in the early posttransplant period.

A comparative analysis of predictive models of morbidity in intensive care unit after cardiac surgery - part II: an illustrative example.

BACKGROUND: Popular predictive models for estimating morbidity probability after heart surgery are compared critically in a unitary framework. The study is divided into two parts. In the first part modelling techniques and intrinsic strengths and weaknesses of different approaches were discussed from a theoretical point of view. In this second part the performances of the same models are evaluated in an illustrative example. METHODS: Eight models were developed: Bayes linear and quadratic models, k-nearest neighbour model, logistic regression model, Higgins and direct scoring systems and two feed-forward artificial neural networks with one and two layers. Cardiovascular, respiratory, neurological, renal, infectious and hemorrhagic complications were defined as morbidity. Training and testing sets each of 545 cases were used. The optimal set of predictors was chosen among a collection of 78 preoperative, intraoperative and postoperative variables by a stepwise procedure. Discrimination and calibration were evaluated by the area under the receiver operating characteristic curve and Hosmer-Lemeshow goodness-of-fit test, respectively. RESULTS: Scoring systems and the logistic regression model required the largest set of predictors, while Bayesian and k-nearest neighbour models were much more parsimonious. In testing data, all models showed acceptable discrimination capacities, however the Bayes quadratic model, using only three predictors, provided the best performance. All models showed satisfactory generalization ability: again the Bayes quadratic model exhibited the best generalization, while artificial neural networks and scoring systems gave the worst results. Finally, poor calibration was obtained when using scoring systems, k-nearest neighbour model and artificial neural networks, while Bayes (after recalibration) and logistic regression models gave adequate results. CONCLUSION: Although all the predictive models showed acceptable discrimination performance in the example considered, the Bayes and logistic regression models seemed better than the others, because they also had good generalization and calibration. The Bayes quadratic model seemed to be a convincing alternative to the much more usual Bayes linear and logistic regression models. It showed its capacity to identify a minimum core of predictors generally recognized as essential to pragmatically evaluate the risk of developing morbidity after heart surgery.

A comparative analysis of predictive models of morbidity in intensive care unit after cardiac surgery - part I: model planning.

BACKGROUND: Different methods have recently been proposed for predicting morbidity in intensive care units (ICU). The aim of the present study was to critically review a number of approaches for developing models capable of estimating the probability of morbidity in ICU after heart surgery. The study is divided into two parts. In this first part, popular models used to estimate the probability of class membership are grouped into distinct categories according to their underlying mathematical principles. Modelling techniques and intrinsic strengths and weaknesses of each model are analysed and discussed from a theoretical point of view, in consideration of clinical applications. METHODS: Models based on Bayes rule, k-nearest neighbour algorithm, logistic regression, scoring systems and artificial neural networks are investigated. Key issues for model design are described. The mathematical treatment of some aspects of model structure is also included for readers interested in developing models, though a full understanding of mathematical relationships is not necessary if the reader is only interested in perceiving the practical meaning of model assumptions, weaknesses and strengths from a user point of view. RESULTS: Scoring systems are very attractive due to their simplicity of use, although this may undermine their predictive capacity. Logistic regression models are trustworthy tools, although they suffer from the principal limitations of most regression procedures. Bayesian models seem to be a good compromise between complexity and predictive performance, but model recalibration is generally necessary. k-nearest neighbour may be a valid non parametric technique, though computational cost and the need for large data storage are major weaknesses of this approach. Artificial neural networks have intrinsic advantages with respect to common statistical models, though the training process may be problematical. CONCLUSION: Knowledge of model assumptions and the theoretical strengths and weaknesses of different approaches are fundamental for designing models for estimating the probability of morbidity after heart surgery. However, a rational choice also requires evaluation and comparison of actual performances of locally-developed competitive models in the clinical scenario to obtain satisfactory agreement between local needs and model response. In the second part of this study the above predictive models will therefore be tested on real data acquired in a specialized ICU.

Lowest hematocrit on cardiopulmonary bypass impairs the outcome in coronary surgery: An Italian Multicenter Study from the National Cardioanesthesia Database.

Severe hemodilutional anemia on cardiopulmonary bypass increases morbidity and mortality after coronary surgery. The present study focuses on the lowest hematocrit values during extracorporeal circulation and on allogenic blood transfusions as mortality and morbidity risk factors. The records of 1,766 consecutive adult patients undergoing isolated coronary artery bypass graft surgery at 3 institutions have been analyzed retrospectively for in-hospital mortality and adverse outcomes. Clinical data were from the Italian National Cardioanesthesia Database. Multivariate analysis and analysis of receiver operating characteristic curves were applied. The lowest hematocrit value on cardiopulmonary bypass was an independent risk factor for postoperative low-output syndrome and renal failure. The hematocrit cutoff values were similar for renal failure (23%) and low-output syndrome (24%). Blood transfusions were significantly associated with both renal failure and low-output syndrome. The risk of renal failure doubled when the nadir-on-cardiopulmonary-bypass hematocrit occurred in transfused patients. Anemia upon cardiopulmonary bypass was not associated with death. Our findings confirm that both severe anemia and blood transfusions were significantly associated with renal failure and low-output syndrome.

A multivariate Bayesian model for assessing morbidity after coronary artery surgery.

INTRODUCTION: Although most risk-stratification scores are derived from preoperative patient variables, there are several intraoperative and postoperative variables that can influence prognosis. Higgins and colleagues previously evaluated the contribution of preoperative, intraoperative and postoperative predictors to the outcome. We developed a Bayes linear model to discriminate morbidity risk after coronary artery bypass grafting and compared it with three different score models: the Higgins' original scoring system, derived from the patient's status on admission to the intensive care unit (ICU), and two models designed and customized to our patient population. METHODS: We analyzed 88 operative risk factors; 1,090 consecutive adult patients who underwent coronary artery bypass grafting were studied. Training and testing data sets of 740 patients and 350 patients, respectively, were used. A stepwise approach enabled selection of an optimal subset of predictor variables. Model discrimination was assessed by receiver operating characteristic (ROC) curves, whereas calibration was measured using the Hosmer-Lemeshow goodness-of-fit test. RESULTS: A set of 12 preoperative, intraoperative and postoperative predictor variables was identified for the Bayes linear model. Bayes and locally customized score models fitted according to the Hosmer-Lemeshow test. However, the comparison between the areas under the ROC curve proved that the Bayes linear classifier had a significantly higher discrimination capacity than the score models. Calibration and discrimination were both much worse with Higgins' original scoring system. CONCLUSION: Most prediction rules use sequential numerical risk scoring to quantify prognosis and are an advanced form of audit. Score models are very attractive tools because their application in routine clinical practice is simple. If locally customized, they also predict patient morbidity in an acceptable manner. The Bayesian model seems to be a feasible alternative. It has better discrimination and can be tailored more easily to individual institutions.

Anaerobic metabolism during cardiopulmonary bypass: predictive value of carbon dioxide derived parameters.

BACKGROUND: Hyperlactatemia during cardiopulmonary bypass (CPB) is a common event and is associated to a high morbidity and mortality after cardiac operations. The present study is aimed to identify the possible predictors of hyperlactatemia during CPB among a series of oxygen and carbon dioxide derived parameters measured during CPB. METHODS: This is a prospective observational study on 54 patients undergoing cardiac surgery with CPB. Hyperlactatemia was defined as an arterial lactate concentration higher than 3 mMol/L. Serial blood lactate assays have been performed during CPB, and their association to a number of oxygen and carbon dioxide derived parameters was explored. RESULTS: Arterial blood lactate concentration was positively correlated to the CPB duration, the carbon dioxide elimination, and the respiratory quotient, and negatively correlated to the presence of the aortic cross-clamping, the body surface area, the ratio between the oxygen delivery and the carbon dioxide production, and the arterial oxygen saturation. Predictors of hyperlactatemia during CPB are a carbon dioxide production higher than 60 mL.min(-1).m(-2), a respiratory quotient higher than 0.9, and a ratio between oxygen delivery and carbon dioxide production lower than 5. CONCLUSIONS: Carbon dioxide derived parameters are representative of hyperlactatemia during CPB, as a result of the carbon dioxide produced under anaerobic conditions through the buffering of protons by the bicarbonate system. The carbon dioxide elimination rate measured at the exhaled site of the oxygenator may be used for an indirect assessment of the metabolic state of the patient.

Systemic arterial waveform analysis and assessment of blood flow during extracorporeal circulation.

BACKGROUND: The pressure recording analytical method (PRAM) is a method for real-time beat-to-beat quantification of peripheral blood flow based on the analysis of arterial waveform morphology. Since PRAM can be implemented in any conditions of flow, whether physiological or artificial, we assessed its accuracy in patients undergoing cardiac surgery during extracorporeal circulation (ECC), using the roller-pump device as the reference gold standard. METHODS: We prospectively studied 32 patients undergoing elective coronary surgery. Flow values obtained by PRAM from the radial artery were compared with simultaneous values by thermodilution in physiological conditions of flow and with the roller-pump device readings during ECC. RESULTS: Before and after ECC, the overall estimates of flow measured by PRAM closely agreed with thermodilution (mean difference 0.07 +/- 0.40 L/min). During ECC, PRAM estimates of flow also closely correlated with simultaneous pump readings (mean difference 0.11 +/- 0.33 L/min). At time of weaning from ECC, two patterns of hemodynamic adaptation were documented by PRAM following resumption of cardiac contraction: in most patients (n =26; 80%), cardiac output (CO) was stable (reduction < or = 10% compared to the steady ECC phase); six patients (20%) showed a fall in CO exceeding 10% and up to 38%. CONCLUSIONS: PRAM provided accurate, continuous quantification of peripheral blood flow during each phase of cardiac surgery, including ECC, and allowed early recognition of patients with low CO during weaning from the pump.

Cardiac output monitoring by pressure recording analytical method in cardiac surgery.

OBJECTIVE: A less-invasive method has been developed that may provide an alternative to monitor cardiac output from arterial pressure: beat-to-beat values of cardiac output can be obtained by pressure recording analytical method (PRAM). The purpose of this study was to assess the reliability of cardiac output determination by PRAM in cardiac surgery. METHODS: Cardiac output was measured in 28 patients undergoing coronary artery bypass grafting at 15 min after anaesthesia induction, 30 min after extracorporeal circulation, 1 and 3 h after arrival in the intensive care unit using thermodilution (ThD) method through a pulmonary artery catheter and PRAM. ThD cardiac output was calculated as the mean of five separate measurements. PRAM provided beat-by-beat cardiac output data continuously throughout the study and the cardiac output values displayed on a dedicated personal computer at each time point were recorded. Correlations were calculated and differences were compared by Bland-Altman analysis. RESULTS: A total of 112 measurements were obtained. Cardiac output ranged from 2.3 to 7.4 l/min, and a good linear correlation (R2=0.78, P<0.0001) was found between ThD and PRAM. The highest degree of correlation (R2=0.86) was obtained at 3 h after arrival in the intensive care unit. The lower degree of correlation (R2=0.70) was obtained 30 min after extracorporeal circulation. At Bland-Altman analysis, the overall estimates of cardiac output measured by PRAM closely agreed with ThD (mean difference, 0.027; standard deviation, 0.43; limits of agreement, -0.83 and +0.89). CONCLUSIONS: Under the studied conditions, our results demonstrate good agreement between PRAM data and ThD measurements, and this new method has shown to be accurate for real-time monitoring of cardiac output in cardiac surgery. Further studies will be required to assess this method in higher-risk patients and in the setting of haemodynamic instability or arrhythmias. This is the first study designed to assess the accuracy of PRAM in cardiac surgery.

Cerebral autoregulation after hypothermic circulatory arrest in operations on the aortic arch.

BACKGROUND: The purpose of this study was to determine whether patients who undergo thoracic aorta repairs with the aid of hypothermic circulatory arrest experience impairments in cerebral autoregulation, and to ascertain the influence of three different techniques of cerebral protection on autoregulatory function. METHODS: Sixty-seven patients undergoing elective aortic arch procedures with hypothermic circulatory arrest were tested for cerebral dynamic autoregulation using continuous transcranial Doppler velocity and blood pressure recordings. Twenty-three patients were treated using hypothermic circulatory arrest without adjuncts (group 1), 25 using antegrade cerebral perfusion (group 2), and 19 using retrograde cerebral perfusion (group 3). RESULTS: There were no hospital deaths. Two major strokes occurred in this series; 9 patients experienced temporary neurologic dysfunction: in all these patients severe impairment of cerebral autoregulation was observed. Cerebral autoregulation in the immediate postoperative period was preserved only in patients treated with antegrade cerebral perfusion. Severe impairments were observed in the other two groups in which the degree of autoregulatory response was inversely correlated to the duration of the cerebral protection time during hypothermic circulatory arrest. Postoperative improvement of autoregulatory function was observed in the majority of patients. Our data suggest the exposure to brain damage in the presence of autoregulation impairment, thus indicating that postoperative hypotensive phases may further contribute to neurologic impairment. CONCLUSIONS: The status of cerebral autoregulation in the postoperative period after hypothermic circulatory arrest procedures is profoundly altered. The degree of impairment is influenced by the cerebral protection technique. This study indicates the beneficial role of antegrade perfusion during hypothermic circulatory arrest for the preservation of this function and suggests that postoperative cerebral autoregulation impairment can be regarded as an expression of central nervous system injury.

Myocardial and lung injury after cardiopulmonary bypass: role of interleukin (IL)-10.

BACKGROUND: Proinflammatory cytokines, such as tumor necrosis factor-alpha (TNF-alpha), interleukin (IL)-6, and IL-8 play a key role in the inflammatory cascade after cardiopulmonary bypass (CPB) and may induce cardiac and lung dysfunction. Antiinflammatory cytokines such as IL-10 may also significantly limit these complications. Corticosteroid administration before CPB increases blood IL-10 levels and prevents proinflammatory cytokine release. This study examined the association of increased release of IL-10, stimulated by steroid pretreatment, with reduced myocardial and lung injury after CPB. METHODS: Twenty patients undergoing coronary artery bypass grafting (CABG) received either preoperative steroid (n = 10, protocol group) or no steroid (n = 10, control group). Perioperative care was standardized, and all caregivers were blinded to treatment group. Seven intervals of blood samples were obtained and assayed for TNF-alpha, IL-6, IL-8, and IL-10. Various hemodynamic and pulmonary measurements were obtained perioperatively. Levels of MB isoenzyme creatine kinase (CK-MB) were also measured. RESULTS: In the protocol group, proinflammatory cytokines were significantly reduced while IL-10 levels were much higher after CPB. The protocol group had a lower alveolar-arterial oxygen gradient and higher ratio of arterial oxygen pressure to fraction of inspired oxygen after CPB. Creatine kinase (CK) and CK-MB were reduced in the patients treated with steroid. Correlations were found between plasma cytokines levels and cardiac index, and CK-MB. CONCLUSIONS: This study confirms that corticosteroids abolish proinflammatory cytokines release and increase blood IL-10 levels after CPB. Our findings demonstrate a greater release of IL-10 induced by steroid pretreatment, and better heart and lung protection after CPB.

Nonocclusive intestinal ischemia in patients with acute aortic dissection.

BACKGROUND: In aortic dissection, visceral complications that result from aortic branch compromise have been described extensively, whereas intestinal ischemia not associated with the false lumen anatomy has rarely been discussed. The aim of this report is to identify clinical factors that may contribute to the development of this form of acute mesenteric ischemia, to profile the patients at greatest risk, and to review diagnostic and treatment methods that emerged from our experience. METHODS: With a computerized database, we identified 371 patients who underwent treatment in our institution with a diagnosis of aortic dissection between July 15, 1985, and January 10, 2001. Mesenteric ischemia was present in 73 patients (19%). In 36 patients (9%), bowel ischemia was not associated with a false lumen anatomy or an extension of the dissection process. From a general analysis of the determinants of mesenteric ischemia in aortic dissection, we investigated, with univariate and multivariate analysis, the specific characteristics of these patients with nonocclusive ischemia. A retrospective analysis of the oxygen metabolic profile of patients who underwent operation also was performed. RESULTS: The mortality rate in patients with nonocclusive mesenteric ischemia was 86%; sepsis and multiple organ failure were the causes of death in all nonsurvivors. Surgical treatment was beneficial only in the early phases of the disease. The results of the multivariate analysis showed the multifactorial origin of nonocclusive mesenteric ischemia; cerebral ischemia, thrombosis of the false lumen, severe coagulation disorders, chronic obstructive pulmonary disease, aortic calcinosis, prolonged hypotension, chronic renal insufficiency, and low cardiac output were independent predictors of the condition. In patients who underwent operation, the significant risk factors were severe coagulation disorders, postoperative cerebral ischemia, maximal oxygen extraction rate of more than 0.40, aortic calcinosis, chronic obstructive pulmonary disease, thrombosis of the false lumen, inotropic support, and chronic renal insufficiency. An oxygen extraction rate of more than 0.4 at 6 hours after operation was found to be an index of intestinal damage sufficient to initiate an evaluation for visceral ischemia. Significant differences with occlusive ischemia also were evidenced with this study. CONCLUSION: In aortic dissection, nonocclusive mesenteric ischemia shows some unique clinical and individual predisposing factors. Most instrumental investigations are of poor diagnostic value, and prognosis is poor, especially when mesenteric gangrene had already taken place. Prevention can be exercised only with a heightening of our awareness of this condition and with timely correction of metabolic disturbances. In suspected cases, an aggressive surgical attitude may represent the only means for reducing mortality.