Heparin Coating of Extracorporeal Circuits Inhibits Cytokine Release from Mononuclear Cells during Cardiac Operations

Purpose

To evalute whether the production of interleukin 2 (IL 2), interlukin 6 (IL 6) and interlukin 10 (IL 10) from stimulated peripheal 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.

Net mineral requirements for growth of Saanen goat kids in early life are similar among genders

The current mineral requirements for growing goat kids are based on sheep and cattle studies without differentiating between the stages of development or gender. The aims of this study were to determine the net requirements for growth of Ca, P, Mg, Na and K of Saanen goat kids during the initial stages of growth and to analyse the effect of gender on the net requirements for growth of these macrominerals. Eighteen female, 19 intact male and 10 castrated male Saanen goat kids were studied. The kids were selected applying a completely randomized design and slaughtered when their body weight (BW) reached approximately 5, 10 and 15 kg to determine the mineral requirements for growth at these stages. The net mineral requirements for growth were similar among genders. The goat kids had slightly increased net requirements of Ca, P and Mg for growth with increasing BW from 5 to 15 kg. The net requirements for growth of Ca, P, Mg, Na and K ranged from 9.61 to 9.67 g/kg of BW gain, 7.14 to 7.56 g/kg of BW gain, 0.34 to 0.37 g/kg of BW gain, 1.26 to 1.13 g/kg of BW gain, 1.88 to 1.82 g/kg of BW gain as the animals grew from 5 to 15 kg respectively. In conclusion, when formulating diets for Saanen goat kids in early growth stage mineral levels do not need to adjusted based on gender.

Relationship between N-terminal pro-B-type natriuretic peptide (Nt-proBNP) and cardiac cycle efficiency in cardiac surgery

N-terminal pro-B-type natriuretic peptide (Nt-proBNP) is a peptide released from myocardium in response to ventricular wall stress and dysfunction. Nt-proBNP plasma levels are elevated in a variety of cardiovascular disorders and are largely used for diagnosis and treatment of cardiac diseases. The cardiac cycle efficiency (CCE) is a haemodynamic variable that represents the left ventricle wall stress and the heart's effort to maintain an adequate blood flow to tissues. We investigated the relationship between Nt-proBNP and CCE values in patients undergoing cardiac surgery. Twenty-five patients undergoing aortic valve replacement were studied. Plasma Nt-proBNP concentrations were performed by electroluminescence immunoassay before starting surgery (t0), at the end of extracorporeal circulation (t1) and 3 hours after surgery (t2). CCE measurements were acquired at the same intervals and correlations with Nt-proBNP levels were calculated. Nt-proBNP plasma concentration was 1430 ± 341 pg/ml at t0, peaked significantly at t1 (2129 ± 561 pg/ml, p<0.001) and moderately decreased at t2 (1924 ± 477 pg/ml, p<0.05). A direct correlation between Nt-proBNP measured at t0 and t1 was found (r=0.91, p<0.001). Overall, a negative correlation between CCE and proBNP values was found (r=-0.89, p<0.01). Correlations between CCE and Nt-proBNP were -0.91, -0.83 and -0.88, at t0, t1 and t2, respectively (p<0.01). Nt-proBNP levels reflect the severity of left ventricle dysfunction in patients undergoing cardiac surgery. CCE correlated well with serum Nt-proBNP levels and seems to be a useful variable to monitor the left ventricular stress and recovery during the various phases of surgery.

Fenoldopam to prevent renal replacement therapy after cardiac surgery. Design of the FENO-HSR study

INTRODUCTION

Acute kidney injury requiring renal replacement therapy is a serious complication following cardiac surgery associated with poor clinical outcomes. Until now no drug showed nephroprotective effects. Fenoldopam is a dopamine-1 receptor agonist which seems to be effective in improving postoperative renal function. The aim of this paper is to describe the design of the FENO-HSR study, planned to assess the effect of a continuous infusion of fenoldopam in reducing the need for renal replacement therapy in patients with acute kidney injury after cardiac surgery.

METHODS

We're performing a double blind, placebo-controlled multicentre randomized trial in over 20 Italian hospitals. Patients who develop acute renal failure defined as R of RIFLE score following cardiac surgery are randomized to receive a 96-hours continuous infusion of either fenoldopam (0.025-0.3 µg/kg/min) or placebo.

RESULTS

The primary endpoint will be the rate of renal replacement therapy. Secondary endpoints will be: mortality, time on mechanical ventilation, length of intensive care unit and hospital stay, peak serum creatinine and the rate of acute renal failure (following the RIFLE score).

CONCLUSIONS

This trial is planned to assess if fenoldopam could improve relevant outcomes in patients undergoing cardiac surgery who develop acute renal dysfunction. Results of this double-blind randomized trial could provide important insights to improve the management strategy of patients at high risk for postoperative acute kidney injury.

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.

NT-proBNP changes, oxidative stress, and energy status of hypertrophic myocardium following ischemia/reperfusion injury

N-terminal pro-B-type natriuretic peptide (NT-proBNP) is a sensitive functional marker in heart disease, including left ventricular hypertrophy (LVH) secondary to valvular aortic stenosis (AS). We evaluated the association between NT-proBNP changes, oxidative stress, energy status and severity of LVH in patients with AS. Ten patients undergoing aortic valve replacement for AS were studied. Plasma NT-proBNP concentrations were performed by electroluminescence immunoassay 15min after the induction of anesthesia (t0), before aortic cross-clamping (t1), before clamp removal (t2), 15min after myocardial reperfusion (t3), and 24h after surgery (t4). Heart biopsies were obtained and high energy phosphates (ATP, ADP, AMP) were analyzed by capillary electrophoresis (CE). In plasma samples from the coronary sinus, nitrate plus nitrite (NOx) concentrations were also analyzed by CE. Echocardiographic measurements were acquired and correlations between biochemical markers and severity of AS were assessed. NT-proBNP peaked significantly at t4 (p<0.001). A linear correlation between NT-proBNP values measured at t0 and t4 was found (R(2)=0.89; p<0.001). A negative correlation between NT-proBNP production and phosphorylation potential (ATP/ADP ratio) was observed (R(2)=0.62; p<0.01). NOx values positively correlated with NT-proBNP levels (p<0.01). NT-proBNP inversely correlated with aortic valvular area (r=81, p<0.01), positively correlated with mean (r=0.82, p<0.01) and maximum left ventricle-to-aortic gradients (r=0.80, p<0.01), and with left ventricular mass (r=0.69, p<0.01). NT-proBNP is a useful marker of LVH and severity of AS. It may complement echocardiographic evaluation of patients with AS in identifying the optimum time for surgery.

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.

Infective endocarditis due to Staphylococcus aureus involving three cardiac valves. A case study

A 20-year-old woman, diagnosed with coarctation of the aorta, situs viscerum inversus, and bicuspid aortic valve, underwent corrective surgery for the coarctation. After a postoperative neurological state that suggested a spinal lesion, corticosteroid therapy was initiated and the patient was discharged early from the unit to begin a motor rehabilitation program. Following the dehiscence of the thoracotomy surgical wound, a severe infective clinical picture, sustained by methicillin-resistant S. Aureus (MRSA), became evident with a diagnosis of bacterial endocarditis involving the aortic, mitral and tricuspid valves and caused the patient's death due to septic shock complicated by ARDS. According to the authors, the early discharge of the patients after such a complex operation, the eccessive lengthening of the steroid therapy that would have contribuited to delay the diagnosis, causing the lack of preventing identification of the first signs of infection and the impossibility for the patient to have another operation (involving 3 valves) are conclusive elements that led to the above mentioned complications.

Relationships between hemodynamic parameters and myocardial energy and antioxidant status in heart transplantation

The relationships between high-energy phosphate levels, oxidative insult and mechanical function represent a key point in heart transplantation and related post-ischemic functional recovery. We evaluated myocardial purine compounds and glutathione antioxidant defence mechanism during 19 heart transplant operations. Heart biopsies were taken before harvesting on beating heart (t1), at the end of cold static preservation (t2) and 30 min after implantation and reperfusion (t3); perchloric extracts of the tissue were analyzed by capillary electrophoresis (CE). Correlation analyses were performed with hemodynamic parameters evaluated 90 min after aortic declamping (T90), 6 h following admission in intensive care unit (T6A) and 1 d post-operation (D1). We evidenced that AMP levels measured at T1 negatively correlate with both cardiac index (CI) and oxygen delivery index (DO2I) evaluated at T6A, respectively. The same behavior was evident plotting IMP levels measured at T3 with CI and DO2I evaluated at D1. After t2 the nucleotide/(nucleoside + base) ratio was in positive correlation with hemodynamic parameters at T6A. Energy charge and GSH/GSSG ratio measured before harvesting were in positive correlation with DO2I evaluated at T90. The present research shows that despite the complexity of the high-energy phosphate metabolism and that of the events associated to a clinical heart transplantation, there are some parameters that, besides reflecting the degree of myocardial preservation, also represents predictive parameters for the following organ functional recovery. It also suggests that heart preservation strategies should carefully take into account the sub-optimal nature of the donor heart at the time of procurement, through a broad spectrum of purine compound and glutathione antioxidant system measurements.

Cardiac surgery: myocardial energy balance, antioxidant status and endothelial function after ischemia-reperfusion

Myocardial and endothelial damage is still a widely debated problem during the ischemia-reperfusion sequence in heart surgery. We evaluated myocardial purine metabolites, antioxidant defense mechanisms, oxidative status and endothelial dysfunction markers in 14 patients undergoing coronary artery by-pass graft (CABG). Heart biopsies were taken before aortic cross-clamping (t1), before clamp removal (t2) and 30 min after reperfusion (t3); perchloric extracts of the tissue were analyzed for glutathione, NAD, nucleotide nucleoside and base content by capillary electrophoresis (CE). In plasma samples from the coronary sinus we evaluated: nitrate and nitrite concentrations by CE, plasma glutathione peroxidase (plGPx) by ELISA, endothelin-1 (ET-1) by RIA and reactive oxygen metabolites (ROM) by colorimetric assay. During the ischemic period (t2) we observed a reduction in cellular NAD and GSH levels, as well as nitrate, nitrite and plGPx. ATP and GTP levels decreased and their catabolic products AMP, GMP, IMP, adenosine, inosine and hypoxanthine accumulated. The energy charge, ATP/ADP ratio, and nucleotide/(nucleoside + base) ratios decreased. At t3, levels of plasma ET-1 increased and monophosphate nucleotides tended to return to basal values. The energy charge did not increase but the nucleotide/(nucleoside + nucleobase) ratio recovered to some extent. Levels of nitrates plus nitrites continued to decrease. No significant variation in ROM levels was observed. Our data indicate that oxidative stress and endothelial damage are major events during CABG, overwhelming the scavenging capacity of the myocyte and preventing restoration of the normal energy balance for 30 min after reperfusion. The AMP deaminase pathway leading to IMP production is active during ischemia and adenosine is not the main compound derived from ATP break-down in the human heart. The possible role of extracorporeal circulation is also discussed.

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.

Capillary electrophoresis in the evaluation of ischemic injury: simultaneous determination of purine compounds and glutathione

An understanding of tissue energy metabolism and antioxidant status is of major interest in the field of organ preservation for transplantation. Nucleotide and glutathione are indicators of cell damage occurring during ischemia and reperfusion. A high performance capillary electrophoresis (HPCE) method with UV detection (185 nm) for the simultaneous analysis of intracellular free ribonucleotides, nucleosides, bases and glutathione (oxidized and reduced form) in myocardial tissues is described. The method does not involve thiol derivatization. The separations were carried out in an uncoated fused-silica capillary, 60 cm long, 52.5 cm to detector, 75 microm ID, with 20 mM Na-borate buffer, pH 10.00, at 20 kV voltage and reading at 185 nm. Injection was hydrostatic for 12 s and total analysis time was 20 min. The technique enables optimum separation of all the compounds examined and has a resolution similar to that of HPLC analysis, with the advantage of fast simultaneous measurement of cell nucleotide metabolism and redox state, not possible with HPLC.

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.

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.

Myocardial metabolism studied during warm blood antero-retrograde reperfusion in ischaemic human hearts

We propose modified warm blood antegrade-retrograde reperfusion (WBARR) of arrested hearts as a metabolic model with which to study substrate exchange and energy metabolism during the recovery phase after 90 min of ischaemia in man. Eleven anaesthetized patients undergoing aorto-coronary bypass were studied during WBARR. The protocol was designed as follows: period 1, a warm blood reperfusion with potassium (3 min); period 2, a warm blood reperfusion without potassium (2 min). The perfusion flow rate averaged 250+/-2 ml/min at the beginning of period 1 and 218+/-19 ml/min at the beginning and at the end of period 2; the perfusion was performed antegradely and retrogradely in the arrested hearts. Samples were simultaneously taken from the coronary venous sinus (CVS) and from the aortic root needle (AR). At the beginning of WBARR lactate release was 85+/-44 micromol/min and at the end it had significantly decreased to 21+/-99 micromol/min (P<0.03). Simultaneously, non-esterified fatty acids (NEFA) and beta-hydroxy-butyrate were initially released (71+/-61 and 22+/-66 micromol/min, respectively), while at the end of the WBARR there was an uptake of both NEFA (20+/-22 micromol/min; P<0.01) and beta-hydroxy-butyrate (12+/-35 micromol/min; P=0.290). Alanine, glycerol and branched chain amino acid balance across the heart did not significantly change. In summary after 90 min of ischaemia the heart energy metabolism is mainly anaerobic and based on glucose consumption, with lactate, NEFA and amino acids, which are mainly released. After 5 min of WBARR (recovery from ischaemia), lactate release is significantly reduced and NEFA becomes the energy supply of the heart. In conclusion, (1) WBARR is a valuable method with which to study myocardial metabolism in anaesthetized humans and may be combined with the use of tracers; (2) the study of myocardial metabolism in arrested hearts eliminates the imprecisions arising from the noncontinuous coronary blood flow; (3) NEFA become an important source of energy utilized by human hearts in the recovery phase from ischaemia.

Myocardial ischemic injury and purine metabolism in patients undergoing coronary artery bypass

OBJECTIVES

High-energy phosphates and their catabolic products were determined in myocardium during coronary artery bypass surgery with blood cardioplegic reperfusion in order to evaluate the effects of aortic cross-clamping and reoxygenation on myocardial purine metabolism.

DESIGN AND METHODS

Transmural left ventricular biopsy specimens were taken with ITu-Cut biopsy needles, before aortic cross-clamping, before cross-clamp removal and after 30' of reperfusion; perchloric extracts of the material were analyzed for nucleotide content by capillary zone electrophoresis (CZE). The CZE procedure used separates the complete spectrum of purine metabolites in myocardial extracts obtained from 0.6-8.6 mg biopsy material.

RESULTS

The basal values of ATP/ADP ratio and energy charge were low, IMP content was high. After the ischemic period, ATP levels further decreased and IMP, nucleosides and bases accumulated. After reperfusion, nucleoside and base basal levels, but not energy charge, were restored to some extent.

CONCLUSIONS

The study arises the problem of myocardial preservation during heart surgery. In this investigation, capillary electrophoresis was an extremely adaptable technique for the evaluation of ischemic injury and could be useful in studying the effects of cardioplegic solutions.

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.

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.

Myocardial function in early hours after coronary artery bypass grafting: comparison of two cardioplegic methods

The theoretical advantages of retrograde blood cardioplegia combined with anterograde blood cardioplegia and warm reperfusion before aortic unclamping during coronary surgery were evaluated in 41 patients (group 2). The early postoperative myocardial function of this group was compared with that of 55 patients (group 1) in whom cold crystalloid cardioplegia was administered. The following variables were measured and analyzed by multivariate statistical analysis: heart rate, left atrial pressure, systemic arterial pressure, cardiac index, left ventricular stroke work index, ventricular function, oxygen delivery, hemoglobin, partial oxygen pressure in mixed venous blood, arteriovenous oxygen difference, carbon dioxide production per square meter, and cardiac isoenzyme of creatine-kinase. The myocardial function improved progressively and cardiac enzymatic release was low for both groups 9 hours after admission to the intensive care unit. However, group 2 had significantly higher oxygen delivery, carbon dioxide production per square meter, cardiac index, left ventricular stroke work index, and ventricular function and significantly lower left atrial pressure and mean systemic arterial pressure than that of group 1. The best separation of group 2 from group 1 occurred at the ninth hour, with a probability of correct recognition of 92.1%.

Epicardial damage induced by topical cooling during paediatric cardiac surgery

OBJECTIVE

To study electrocardiographic changes in infants and children in whom topical cooling was used during surgical repair of congenital heart defects.

DESIGN

A retrospective study of all patients who had surgical repair of congenital heart disease during cold blood cardioplegia and topical cooling from January to August 1990. Eleven patients (group 1) had topical cooling with ice and 15 (group 2) with cold saline.

PATIENTS

All 36 paediatric patients operated on during this period. All the available electrocardiographic records were analysed. Ten patients in whom reliable records were not available were excluded. Twenty six patients entered in this retrospective study.

INTERVENTIONS

Topical cooling with ice or with a slush of cold saline.

MAIN OUTCOME MEASURE

Recordings from all the precordial leads were examined and scored as the sum of the maximum ST elevation (mV) in each precordial lead. The score obtained for each electrocardiogram was recorded together with the timing of the electrocardiogram (preoperative, arrival in intensive care unit immediately after surgery, postoperatively in the intensive care unit, and at discharge).

RESULTS

There were no differences between the two groups in terms of demographic data, diagnosis, duration of ischaemia, and postoperative myocardial performance. There was temporary ST elevation during the first 48 postoperative hours in all the children in group 1 but in only seven of the 15 children in group 2 (Fisher's test, p less than 0.005). The mean (SD) score for maximum ST elevation was 1.34 (0.83) mV in group 1 and 0.52 (0.64) mV in group 2 (Student's t test, p less than 0.01).

CONCLUSIONS

These temporary electrocardiographic changes in the presence of adequate myocardial performance were attributed to epicardial damage induced by hypothermicosmotic injury. The use of ice for topical cooling may damage the epicardium in children.

Hypermetabolic response after hypothermic cardiopulmonary bypass

Sixteen patients undergoing hypothermic cardiopulmonary bypass for open heart surgery were studied prospectively. Oxygen consumption and CO2 production showed a marked increase during the first 6 h postoperatively. Consequently, the measured resting energy expenditure was markedly elevated compared to the predicted energy expenditure. This hypermetabolic response occurred simultaneously with maximum spontaneous rewarming after the end of surgical procedures. Ventricular function was low throughout the postoperative period, and no cardiac response to increased energy requirements was recorded. On the contrary, marked increases in arteriovenous oxygen and CO2 difference were observed during the period of highest resting energy expenditure. We conclude that the first hours after hypothermic cardiopulmonary bypass represent the period of highest risk for decompensation. The continuous monitoring of CO2 production is suggested as a useful clinical method to detect postoperative changes in metabolic rate.

[Anesthesia problems in thoracic and lung surgery; the use of althesin as an alternative solution]

Cardiocirculatory stability and arterial blood oxygenation represent the major problems in chest and lung surgery. The need to cut ventilation off from one of the lungs, or from a segment of a lung, may lead to dangerous haemodynamic and respiratory changes. The use of neuroleptoanalgesia guarantees marked cardiocirculatory stability but problems arise out of the need to administer high percentage nitrogen protoxide with consequent hypoxaemia. The use of Althesin surmounted this inconvenience and made it possible to keep basic haemodynamic parameters (heart stroke volume, peripheral resistances, lung resistances) and respiratory parameters (partial pressure in O2 and CO2 in the arterial and venous blood) stable.