Echocardiography and pulse contour analysis to assess cardiac output in trauma patients.

BACKGROUND: Echocardiography is a valuable technique to assess cardiac output (CO) in trauma patients, but it does not allow a continuous bedside monitoring. Beat-to-beat CO assessment can be obtained by other techniques, including the pulse contour method MostCare. The aim of our study was to compare CO obtained with MostCare (MC-CO) with CO estimated by transthoracic echocardiography (TTE-CO) in trauma patients. METHODS: Forty-nine patients with blunt trauma admitted to an intensive care unit and requiring hemodynamic optimization within 24 hours from admission were studied. TTE-CO and MC-CO were estimated simultaneously at baseline, after a fluid challenge and after the start of vasoactive drug therapy. RESULTS: One hundred sixteen paired CO values were obtained. TTE-CO values ranged from 2.9 to 7.6 L·min(-1), and MC-CO ranged from 2.8 to 8.2 L·min(-1). The correlation between the two methods was 0.94 (95% confidence interval [CI]=0.89 to 0.97; P<0.001). The mean bias was -0.06 L·min(-1) with limits of agreements (LoA) of -0.94 to 0.82 L·min(-1) (lower 95% CI, -1.16 to -0.72; upper 95% CI, 0.60 to 1.04) and a percentage error of 18%. Changes in CO showed a correlation of 0.91 (95% CI=0.87 to 0.95; P<0.001), a mean bias of -0.01 L·min(-1) with LoA of -0.67 to 0.65 L·min(-1) (lower 95% CI, -0.83 to -0.51; upper 95% CI, 0.48 to 0.81). CONCLUSION: CO measured by MostCare showed good agreement with CO obtained by transthoracic echocardiography. Pulse contour analysis can complement echocardiography in evaluating hemodynamics in trauma patients.

Comparison between an uncalibrated pulse contour method and thermodilution technique for cardiac output estimation in septic patients.

BACKGROUND: The purpose of this study was to evaluate the reliability of a new uncalibrated pulse contour method, the MostCare, in determining cardiac output (CO) in septic patients. METHODS: Thirty patients with septic shock admitted to an intensive care unit, receiving a norepinephrine infusion and requiring haemodynamic monitoring with a pulmonary artery catheter, were prospectively enrolled. Thermodilution measurements of CO (ThD-CO) were considered as the 'gold standard'. MostCare was connected to the monitoring system of the radial arterial pressure waveform to obtain a continuous CO calculation (MostCare-CO). ThD-CO and MostCare-CO measurements were recorded at three different haemodynamic states: baseline (T1), after raising mean arterial pressure (MAP) to 90 mm Hg by increasing the norepinephrine infusion (T2), and after returning the MAP to baseline value by decreasing vasopressor therapy (T3). A Bland-Altman and linear regression analyses were performed. RESULTS: A total of 90 paired ThD-CO and MostCare-CO measures were obtained (range 4.1-13.9 litre min(-1) for ThD-CO and 4.5-13.5 litre min(-1) for MostCare-CO). A good correlation between ThD-CO and MostCare-CO was observed (R = 0.93). The mean bias between the two techniques was -0.26 litre min(-1) (sd 0.98 litre min(-1)) and the 95% limits of agreement were -2.22 to 1.70 litre min(-1). The percentage of error was 25%. Pearson's R was 0.94, 0.92, and 0.93 at T1, T2, and T3, respectively. CONCLUSIONS: MostCare-CO and ThD-CO showed a good agreement at each time of the study. The reliability of the MostCare system was not affected by the vascular tone changes produced by a norepinephrine infusion.

Predicting transfusions in cardiac surgery: the easier, the better: the Transfusion Risk and Clinical Knowledge score.

BACKGROUND AND OBJECTIVES: Allogeneic blood products transfusions are associated with an increased morbidity and mortality risk in cardiac surgery. At present, a few transfusion risk scores have been proposed for cardiac surgery patients. The present study is aimed to develop and validate a risk score based on adequate statistical analyses joint with a clinical selection of a limited (five) number of preoperative predictors. MATERIALS AND METHODS: The development series was composed of 8989 consecutive adult patients undergone cardiac surgery. Independent predictors of allogeneic blood transfusions were identified. Subsequently, five predictors were extracted as the most clinically relevant based on the judgement of 30 clinicians dealing with transfusions in cardiac surgery. A predictive score was developed and externally validated on a series of 2371 patients operated in another institution. The score was compared to the other existing scores. RESULTS: The following predictors constituted the Transfusion Risk and Clinical Knowledge score: age > 67 years; weight < 60 kg for females and < 85 kg for males preoperative haematocrit; gender--female; and complex surgery. At the external validation, this score demonstrated an acceptable predictive power (area under the curve 0.71) and a good calibration at the Hosmer-Lemeshow test. When compared to the other three existing risk scores, the Transfusion Risk and Clinical Knowledge score had comparable or better predictive power and calibration. CONCLUSION: A simple risk model based on five predictors only has a similar or better accuracy and calibration in predicting the transfusion rate in cardiac surgery than more complex models.

Pressure recording analytical method (PRAM) for measurement of cardiac output during various haemodynamic states.

BACKGROUND: Cardiac output (CO) can be measured using the pressure recording analytical method (PRAM), which is a new, less invasive technique allowing beat-by-beat stroke volume monitoring from the pressure signals recorded in femoral or radial arteries. METHODS: We investigated PRAM by comparing its cardiac output (PRAM-CO) with paired measurements obtained by electromagnetic flowmetry (EM-CO) and by standard thermodilution (ThD-CO) during various haemodynamic states in a swine model. Nine pigs were monitored with a pulmonary artery catheter and a femoral artery catheter at baseline, in a hyperdynamic state produced by administration of dobutamine and in a hypodynamic state induced by progressive exsanguination. Bland-Altman analysis was used. RESULTS: One hundred and eight paired cardiac output values over a range of EM-CO of 1.8-10.4 litre min(-1) resulted. We found close agreement between the techniques. Mean bias between EM-CO and PRAM-CO was -0.03 litre min(-1) (precision 0.58 litre min(-1)). The 95% limits of agreement were -0.61 to +0.55 litre min(-1). Similar results between ThD-CO and PRAM-CO were found. CONCLUSIONS: In a porcine model we have demonstrated accuracy of PRAM during various haemodynamic states. PRAM is a reliable tool to detect changes in cardiac output in pigs and has ability as a basic research tool.

Optimization of mechanical ventilation support following cardiac surgery.

BACKGROUND: Mechanical ventilation (MV) is essential in the management of patients that underwent cardiac surgery and cardiopulmonary bypass. It has been demonstrated that MV dependence is directly related to morbidity incidence and ICU length of stay, with a strong impact on economic cost. Therefore identification of measures that can reduce MV interval, may reduce the incidence of respiratory complications and length of hospitalization. The aim of this study was to identify weaning indexes and adopt a weaning algorithm in order to optimize ventilatory support after cardiac surgery. METHODS: Forty-nine patients with low and medium Higgins risk score, who underwent, between February and November 1999, elective surgery at our Institution, were enrolled in this study. All patients were randomized into 2 groups: Group I (weaning group - 24 patients), extubated with the aid of a weaning protocol, and Group II (control group - 25 patients), extubated with conservative weaning, dependent on the physician's subjective clinical judgment. All patients were successfully weaned from mechanical support. RESULTS: Intubation time was significantly lower in Group I than Group II and "Fast Track Recovery" group (p=0.05). ICU length of stay was also significantly lower in Group I (p=0.03). Analysis of weaning indexes did not show cut-off points predictive of successful weaning, except for PaO2/FiO2 ratio, which was higher in Group I (p=0.02). CONCLUSIONS: These results confirm that the use of a weaning algorithm enables the MV interval and hospital length of stay to be shortened, suggesting that it should be used in the management following cardiac surgery.

Heparin coating of extracorporeal circuits inhibits cytokine release from mononuclear cells during cardiac operations.

PURPOSE: To evaluate whether the production of interleukin 2 (IL 2), interleukin 6 (IL 6) and interleukin 10 (IL 10) from stimulated peripheral blood mononuclear cells (PBMC) was affected by coating extracorporeal circuits in patients undergoing cardiopulmonary bypass (CPB). In addition, postoperative clinical parameters were compared between patients with heparin-coated and uncoated CPB. DESIGN: Prospective, controlled in vivo/ex vivo study. PROCEDURE: Blood samples were drawn immediately before, at the end and 24 hours after the end of CPB using either a conventional circuit (n=10) or a heparin-coated circuit (n=10) in patients undergoing CPB. Cytokine release on the supernatants of activated PBMC was detected. Cardiopulmonary parameters were measured before CPB, at ICU admission, 3 hours and 24 hours after ICU admission in both groups of patients. Statistical difference intragroups and between groups were investigated with the analysis of variance for repeated measures. RESULTS: IL 6 and IL 10 release was significantly less (p<0.05) in the heparin-coated group. No differences in clinical parameters were observed between the two groups. CONCLUSIONS: These results suggest that with the use of heparin-coated circuits there is a lower production of IL 6 and IL 10 from isolated PBMC than with uncoated circuits.

Inhibition of CD11-CD18 complex prevents acute lung injury and reduces mortality after peritonitis in rabbits.

Acute lung injury is frequent after severe peritonitis. The aim of this study was to investigate whether inhibition of the adhesion molecule CD11-CD18 on polymorphonuclear leukocytes (PMNs) would have any beneficial effects on pulmonary function and mortality in an animal model reproducing these clinical conditions. Acute peritonitis was induced in 36 rabbits by intraperitoneal injection of zymosan (0.6 g/kg) suspended in mineral oil; 20 were pretreated with a murine-specific IgG2a anti-CD18 monoclonal antibody, 16 (controls) with nonspecific purified murine IgG (1 mg/kg). The animals were followed for 10 d, then killed for histologic examination of the lungs. Blood samples were taken on Days 0, 1, 3, 7, and 10 for red blood cell (RBC), white blood cell (WBC), and platelet counts, pH, PO(2), PCO(2), carbon dioxide content (HCO(3)(-)) measurements, and renal and liver tests. Treatment with the anti-CD18 monoclonal antibody reduced mortality by approximately 40% (p < 0.05). PO(2) was higher in these treated animals than in the control animals throughout the study (p < 0.05 on Day 1, 3, and 10). On Day 1 control animals had significant leukopenia, whereas anti-CD18-treated animals had a moderate increase of the number of circulating WBC compared with baseline values (p < 0.05 between groups). The lungs of the anti-CD18-treated animals showed minor signs of inflammation and PMN infiltration whereas controls had interstitial and intra-alveolar edema and a large number of granulocytes. Quantification of PMNs by morphometry showed that there were constantly less granulocytes in the lungs of the animals treated with the anti-CD18 antibody (p < 0.001). PMN infiltration correlated with the levels of PO(2) (p < 0.001). Lung tissue of anti-CD18-treated rabbits contained less malonyldialdehyde, a by-product of membrane lipid peroxidation by PMN oxygen radicals (950 +/- 120 versus 1,710 +/- 450 pM/mg of protein) and, conversely, more of the antioxidant alpha-tocopherol (136 +/- 22 versus 40 +/- 9 ng/mg of protein), than the control rabbits (p < 0.01). In this particular model of ARDS the monoclonal antibody against the CD11-CD18 complex had a beneficial effect, reducing PMN infiltration and oxygen radical release in the lungs, preventing alveolocapillary membrane damage, improving gas exchange and, finally, significantly reducing mortality.

The diagnostic and prognostic value of cardiac Troponin T in bypass surgery.

BACKGROUND: The purpose of this study was to verify the utility of serum Troponin T (TnT) in the diagnosis of myocardial damage after coronary surgery performed using different methods of myocardial protection. The prognostic value of TnT peak for a poor postoperative course was also investigated. METHODS: Forty-three patients were enrolled and randomised in 2 group: Group A (n. 22) receiving warm blood cardioplegia and Group B (n. 21) receiving cold blood cardioplegia. According to TnT peak levels 3 subgroups were identified: Subgroup 1 (TnT peak < than 1 ng/ml); Subgroup 2 (TnT peak between 1 and 3 ng/ml), Subgroup 3 (TnT peak >3 ng/ml). A comparison with the standard criteria for diagnosis of myocardial ischemia was performed for each subgroup of patients. A 12 months follow-up for the patients of subgroups 1 and 2 was also completed in order to evaluate the prognostic value of a higher TnT peak. RESULTS: The overall patients subdivision in subgroup 1, 2 and 3 was 20 (46.5%), 14 (32.5%) and 9 (20.9%) respectively with no statistical difference for Group A or B. Only 7 of the patients of subgroup 3 (87%) matched the WHO diagnostic criteria for myocardial infarction. At the overall follow-up, 2 (14.28%) patients of subgroup 2, and 4 (20.0%) of subgroup 3, revealed a residual ischemia at the ECG-stress test even if none of these needed reoperation. CONCLUSIONS: Our data confirmed the high sensitivity and specificity of TnT measurement in the diagnosis of myocardial infarction and minor myocardial damage. This study, however, failed to show any statistically significant difference of the TnT peak when using different strategies of myocardial protection. The late prognostic value of the TnT increase in the early post-operative course has to be confirmed from a further study.

Heparin-coated circuits for high-risk patients: a multicenter, prospective, randomized trial.

BACKGROUND: Heparin-coated circuits (HCCs) in low-risk cardiac patients who have coronary revascularization have a limited impact on postoperative outcome. In this prospective, randomized investigation, we studied high-risk patients who had cardiac operations with or without HCCs. METHODS: A total of 886 patients who had cardiac operations with cardiopulmonary bypass and at least one patient-related or procedure-related risk factor were enrolled in a multicenter study. They were randomly allocated to have cardiopulmonary bypass with Duraflo II HCCs (HCC group, n = 442) or conventional circuits (control group, n = 444). Postoperative outcome was investigated with respect to the occurrence of organ dysfunction. RESULTS: HCCs are associated with a shorter intensive care unit and postoperative hospital stay and with a lower rate of patients having a severely impaired clinical outcome (stay in intensive care unit for more than 5 days or death) (relative risk 0.66, p = 0.045). Lung dysfunction rate was significantly lower for the patients in HCC group affected by chronic obstructive pulmonary disease or who had mitral procedure (relative risk, respectively, 0.31, p = 0.018 and 0.05, p = 0.02). Renal dysfunction rate was significantly (p = 0.05) lower for diabetics in the HCC group (relative risk 0.28). CONCLUSIONS: When HCCs were used postoperative times decreased and they had a protective effect on lung and kidney function in high-risk patients.

Interleukin 10 production in patients undergoing cardiopulmonary bypass: evidence of inhibition of Th-1-type responses.

The cardiopulmonary bypass (CPB) procedure has long been associated with a generalized immunosuppression. To understand further the cytokine-mediated regulation of the complex physiological and immunological changes induced by CPB, the authors decided to investigate whether CPB affects the release of interleukin (IL)-10, as well as other cytokines, in correlation to the inhibition of T cell responses. Using phytohaemagglutinin (PHA) as mitogen and peripheral blood mononuclear cells (PBMC) isolated from patients undergoing CPB, we investigated whether this procedure has an effect on the secretion of different patterns of cytokines (Th1- and Th2-type) and PBMC proliferation. In all patients, CPB significantly enhances IL-10 and IL-6 production in resting and PHA-stimulated PBMC. On the other hand, IL-2 production, in response to PHA, was significantly diminished. Reduced IL-2 and enhanced IL-10 production were associated with a significant decrease in PBMC proliferation. Immunosuppression was also associated to lymphopenia, while neutrophil counts were significantly enhanced. These results show that after CPB there is a transient but clear unbalanced immune response demonstrated by a differentiated production of Th1- and Th2-type cytokines. The release of different patterns of cytokines observed after CPB may be helpful in understanding and preventing the development of infectious and immune complications in surgical procedure employing CPB.

Reduction of oxidative stress does not affect recovery of myocardial function: warm continuous versus cold intermittent blood cardioplegia.

OBJECTIVE: To compare oxidative stress after cardiac surgery in patients treated with two different methods of myocardial protection: warm continuous versus cold intermittent blood cardioplegia. To correlate oxidative stress with postoperative myocardial dysfunction. DESIGN: Prospective, randomised, double blind, trial. SETTING: Institutional centre of cardiovascular surgery. PATIENTS: 20 patients were selected for coronary artery bypass surgery (CABG) on the following basis: stable angina, ejection fraction > 50%, double or triple vessel disease, no previous CABG or associated disease. Patients were randomised to two groups of 10 patients each. INTERVENTIONS: Patients underwent CABG with one of two different methods of myocardial protection and cardiopulmonary bypass. CBC group: intermittent cold blood antegrade-retrograde cardioplegia with moderate hypothermic cardiopulmonary bypass; WBC group: continuous warm blood antegrade-retrograde cardioplegia with mild hypothermic cardiopulmonary bypass. MAIN OUTCOME MEASURE: The index of oxidative stress used was the alteration of whole blood and plasma glutathione redox status. Samples were collected from the coronary sinus and peripheral vein before anaesthesia (T1), before aortic unclamping (T2), 15 minutes (T3), and 30 minutes (T4) after unclamping. Haemodynamic parameters were measured with thermodilution techniques. RESULTS: Oxidised glutathione and glutathione-cysteine mixed disulphide significantly increased in the coronary sinus plasma in the CBC group, and the overall redox balance of glutathione was decreased (P < 0.01) at T2-T4 versus T1, and compared with the WBC group. Comparable results were obtained for coronary sinus blood. There was no correlation between postoperative haemodynamic measurements and oxidative stress markers. CONCLUSIONS: Oxidative stress was significant in patients undergoing CABG using cold blood cardioplegia, while the warm technique minimised the effects of ischaemia. However, oxidative stress was not correlated with myocardial dysfunction following CABG.

Video-assisted minimally invasive coronary operations without cardiopulmonary bypass: a multicenter study.

OBJECTIVE: The need to avoid the risks associated with cardiopulmonary bypass has led to the interest in coronary operations without cardiopulmonary bypass. PATIENTS AND METHODS: From April 1994 to September 1995, 44 patients (mean age 63.3 +/- 10.0 years, range 43 to 83 years) were selected for video-assisted coronary artery bypass grafting without cardiopulmonary bypass through a small anterior thoracotomy. Mean preoperative ejection fraction was 50.7% +/- 13.4% (range 20% to 65%). Four patients had left ventricular dysfunction (ejection fraction below 35%). Thirty patients had stable angina (26 with class 3 angina) and 14 had unstable angina. One had recurrent angina (redo). In all cases a small (3.5 to 11 cm) anterior thoracotomy (43 left and one right) was performed and the harvesting of the left internal thoracic artery was video-assisted by thoracoscopy. RESULTS: The left internal thoracic artery was used in 43 cases to graft the left anterior descending coronary artery; the right thoracic mammary was used in one case to graft the right coronary artery; the radial artery was used in one case to perform a T-graft to the first diagonal and first marginal branches. We recorded one death (2.3%) and one case of postoperative low cardiac output syndrome (2.3%). Perioperative myocardial infarction occurred in two cases (4.5%). We did not record noncardiac complications (cerebrovascular complications, kidney failure, prolonged ventilatory support, or wound complications). Supraventricular and ventricular arrhythmias were never detected. CONCLUSION: According to our experience, video-assisted coronary bypass through a small anterior thoracotomy is a new promising technique that can be considered an alternative in most cases to angioplasty and complementary to conventional coronary operations.

Total arterial myocardial revascularization without cardiopulmonary bypass.

The risks associated with cardiopulmonary bypass have led to an interest in coronary surgery without the use of such a bypass. Six patients of mean(s.d.) age 62.0(8.0) (range 52-71) years were selected for elective coronary surgery without cardiopulmonary bypass. In five cases a midline sternotomy and in one case a small anterolateral thoracotomy were performed; in the latter case the harvesting of the proximal end of the left internal mammary artery was video-assisted by thoracoscopy. The left internal mammary artery was used in all cases; the right internal mammary artery was used in one case, the radial artery in four, the inferior epigastric artery in two and the right gastroepiploic artery inn one. No patient died or had a stroke. There were no postoperative episodes of low cardiac output syndrome or perioperative myocardial infarction. All patients were extubated within a few hours after surgery. The mean(s.d.) intensive care unit and hospital stays were 1.3(0.5) and 5.0(0.9) days, respectively. Total arterial myocardial revascularization without cardiopulmonary bypass using composite grafts, is a new and promising technique that is feasible with low risks and good early results in selected cases.

Plasma levels of immunosuppressive mediators during cardiopulmonary bypass.

The aim of this study was to evaluate plasma levels of two mediators with immunosuppressive properties, complement fraction C3a (C3a) and transforming growth factor-beta(1) (TGF-beta(1)), during extracorporeal circulation. The proliferation index after phytohaemagglutinin (PHA) stimulation of isolated peripheral blood mononuclear cells was also investigated. Sixteen patients undergoing hypothermic (n = 8, group 1) and normothermic (n = 8, group 2) cardiopulmormry bypass (CPB) were enrolled in this study. As a control, we evaluated four patients undergoing thoracovascular operations without CPB. Blood samples were collected before CPB but after anaesthesia, every 30 min during CPB, at the end of CPB and 10 min after protamine administration. Both C3a and TGF-beta(1) increased significantly during CPB and after protamine administration in the hypothermic as well as the normothermic group. In the latter case the increase of C3a and TGF-beta(1), although more prominent, was not significantl higher than in the former group. Conversely, the proliferation, index of peripheral mononuclear cells had already decreased 30 min after CPB was started and remained depressed throughout the CPB time. These results suggest a possible role of C3a and TGF-beta(1) in the immunological changes occurring during extracorporeal circulation.

Coronary surgery without cardiopulmonary bypass.

The need to obviate the risks associated with cardiopulmonary bypass (CPB) in coronary surgery has led to an interest in coronary artery bypass grafting without CPB. From November 1994 to May 1995, 58 patients (49 males and 9 females, mean age 61.8 +/- 9.3 years, range 40-74) were selected for coronary artery bypass grafting without CPB. Three patients had left main stenosis and 6 had left ventricular dysfunction (ejection fraction < 40%). Stable angina was present in 42 patients (27 with low threshold angina) and unstable angina in 16. In 44 patients a routine median sternotomy and in 14 cases a small anterior thoracotomy were performed: in the latter the proximal harvesting of the left internal mammary artery was video-assisted by thoracoscopy. The left internal mammary artery was used in 53 cases; the saphenous vein was used in 36 cases; the radial artery was used in 4 cases; the inferior epigastric artery was used in 2 cases and the right gastroepiploic artery in 1 case. We recorded 1 death (1.7%) and 1 case of postoperative low cardiac output syndrome requiring counterpulsation (1.7%). Perioperative myocardial infarction occurred in 3 cases (5.8%). We did not record noncardiac complications (cerebrovascular, renal failure, prolonged ventilatory support over 24 hours or sternal wound complications). Supraventricular and ventricular arrhythmias were never detected. Mean intensive care unit and hospital stay were 1.1 +/- 0.5 and 5.1 +/- 1.7 days, respectively. In conclusion, according to our experience, "beating heart" coronary surgery is a new promising technique that can be considered alternative in most cases to percutaneous transluminal coronary angio and complementary to conventional coronary surgery.

In vitro cytokine production and T-cell proliferation in patients undergoing cardiopulmonary by-pass.

Cardiac surgery, employing cardiopulmonary by-pass (CPB), has long been associated with a generalized immunosuppression. To further understand the complex physiological and immunological changes related to CPB, we decided to investigate whether CPB affects the immune response, with regard to T-cell activation and cytokine production. Using phytohaemagglutinin (PHA) as mitogen and peripheral blood mononuclear cells (PBMC) isolated from patients undergoing CPB, we investigated whether this procedure has any effect on interferon-gamma(IFN-gamma) and other cytokine production and/or PBMC proliferation. Comparisons were made between the responsiveness of PBMC obtained before, during and at the end of CPB. In all patients, CPB significantly reduces IFN-gamma and interleukin 2 (IL-2) production in response to PHA. On the other hand, tumour necrosis factor-alpha (TNF-alpha) production was also significantly diminished, while interleukin 6 (IL-6), interleukin 1 beta (IL-1 beta) and interleukin 8 (IL-8) release in response to PHA was not significantly affected. Reduced IFN-gamma, IL-2 and TNF-alpha production was associated with a significant decrease in PBMC proliferation. These results might be related to the mechanical damage on blood cells described during extracorporeal circulation procedures as well as the release of immunosuppressive factors during surgery. The immunosuppression observed during CPB may play an important role in the development of infectious complications after CPB.