Myocardial ischaemia in patients with impaired left ventricular function undergoing coronary artery bypass grafting--milrinone versus nifedipin

BACKGROUND AND OBJECTIVE: Myocardial ischaemia and infarction are major complications immediately after coronary artery bypass grafting. They may be due to incomplete surgical revascularization, perioperative anaesthetic management or vasospasm of arterial grafts, e.g. the internal mammary artery. Infusions of nifedipine or milrinone have been advocated to prevent spasm of the mammary artery. The study compared the incidence of myocardial ischaemia after continuous infusion of either nifedipine (0.2 microg kg(-1) min(-1)) or milrinone (0.375 microg kg(-1) min(-1)) in patients with compromised left ventricular function scheduled for elective coronary artery bypass graft. METHODS: After Institutional Review Board approval, this double-blinded randomized clinical study enrolled 30 adult patients with compromised left ventricular function (ejection fraction < 0.4) scheduled for elective coronary artery bypass grafting after written informed consent had been obtained. Ischaemia was detected by Holter electrocardiographic monitoring. The incidence of myocardial cell death was monitored by serial determinations of the creatine kinase-MB (CK-MB) and troponin-I. RESULTS: New ST elevation > or = 0.2 mV or new ST depression < or = 0.1 mV occurred in five of 15 patients in the milrinone group (33.3%) and in 13 of 15 patients (86.6%) in the nifedipine group (P < 0.05). There were increases in CK-MB and troponin-I in both groups. Twenty-four hours postoperatively, CK-MB (P = 0.003) and troponin-I (P = 0.001) were significantly higher in the nifedipine group. CONCLUSIONS: Perioperative continuous infusion of milrinone, compared with nifedipine, results in a significantly lower incidence of myocardial ischaemia and myocardial cell damage after elective coronary artery bypass grafting.     

A randomized double-blind study of the effect of triiodothyronine on cardiac function and morbidity after coronary bypass surgery.

BACKGROUND: Although triiodothyronine deficiency has been described after cardiopulmonary bypass, data supporting its use have been conflicting. A double-blind, randomized, placebo-controlled study was undertaken to further define the effect of triiodothyronine on hemodynamics and outcome after coronary artery bypass grafting. METHODS: A total of 170 patients undergoing elective coronary artery bypass grafting were enrolled and completed the study from November 1996 through March 1998. On removal of the aortic crossclamp, patients were randomized to receive either intravenous triiodothyronine (0.4 microgram/kg bolus plus 0.1 microgram/kg infusion administered over a 6-hour period, n = 81) or placebo (n = 89). Outcome variables included hemodynamic profile and inotropic drug/pressor requirements at several time points (mean +/- standard error of the mean), perioperative morbidity (arrhythmia/ischemia/infarction), and mortality. RESULTS: Despite similar baseline characteristics, patients randomized to triiodothyronine had a higher cardiac index and lower inotropic requirements after the operation. Subjects receiving triiodothyronine demonstrated a significantly lower incidence of postoperative myocardial ischemia (4% vs 18%, P =.007) and pacemaker dependence (14% vs 25%, P =.013). Seven patients in the placebo group required postoperative mechanical assistance (intra-aortic balloon pump, n = 4; left ventricular assist device, n = 3), compared with none in the triiodothyronine group (P =.01). There were 2 deaths in the placebo group and no deaths in the triiodothyronine group. CONCLUSIONS: Parenteral triiodothyronine given after crossclamp removal during elective coronary artery bypass grafting significantly improved postoperative ventricular function, reduced the need for treatment with inotropic agents and mechanical devices, and decreased the incidence of myocardial ischemia. The incidence of atrial fibrillation was slightly decreased, and the need for postoperative pacemaker support was reduced.     

Intravenous nifedipine to treat hypertension after coronary artery revascularization surgery. A comparison with sodium nitroprusside.

We administered sodium nitroprusside (SNP) or nifedipine intravenously to patients who became hypertensive after elective coronary revascularization and compared their effects on hemodynamics and the electrocardiogram in a parallel, randomized, open-label study. Four of 21 patients treated with nifedipine required the addition of SNP to maintain mean arterial pressure less than 90 mm Hg, compared with 4 of 28 patients in the SNP group who required the addition of nifedipine. The success rates of nifedipine (81%) and SNP (86%) were not significantly different. There was no difference in the incidence of adverse ST-segment changes during drug infusion (4% versus 5%) or perioperative myocardial infarction (9.5% versus 10.7%) in the nifedipine versus SNP groups, respectively. The plasma nifedipine concentration (mean value +/- SD) at steady state for 21 patients receiving nifedipine was 119 +/- 42.5 ng/mL. The pharmacokinetic variables for nifedipine were as follows (mean values +/- SD): systemic clearance, 0.525 +/- 0.228 L.h-1.kg-1; apparent volume of distribution, 0.738 +/- 0.446 L/kg; and elimination half-life, 1.02 +/- 0.51 h. These values are similar to those reported previously in healthy volunteers. We conclude that intravenous nifedipine can be used safely to control hypertension after coronary revascularization but were unable to demonstrate an advantage of nifedipine compared with SNP in preventing postoperative ischemia or infarction in this group of patients who had good left ventricular function.     

Creatine phosphate administration preserves myocardial function in a model of off-pump coronary revascularization

AIM: Off pump coronary artery bypass grafting (OPCAB) involves, and is occasionally impaired by obligatory regional myocardial ischemia, particularly with the use of proximal coronary in-flow occlusion techniques. Intracoronary shunts do not guarantee absence of distal ischemia given their small inner diameter and the presence of proximal coronary stenosis. Additional adjunctive measures to provide short-term myocardial protection may facilitate OPCAB. High-energy phosphate supplementation with creatine phosphate prior to ischemia may attenuate ischemic dysfunction. METHODS: In a rodent model of a transient coronary occlusion and myocardial ischemia, 36 animals underwent preischemic intravenous infusion of either creatine phosphate or saline, 10 minutes of proximal left anterior descending (LAD) occlusion, and 10 minutes of reperfusion. Rats underwent continuous intracavitary pressure monitoring and cellular ATP levels were quantified using a luciferin/luciferase bioluminescence assay. RESULTS: Within 2 minutes of ischemia onset, creatine phosphate animals exhibited statistically significant greater preservation of myocardial function compared to controls, an augmentation which persisted throughout the duration of ischemia and subsequent reperfusion. Furthermore, significantly greater cellular ATP levels were observed among creatine phosphate treated animals (344+/-55 nMol/g tissue, n=5) compared to control animals (160+/-9 nMol/g tissue, n=5)(p=0.014). CONCLUSIONS: A strategy of intravenous high-energy phosphate administration successfully prevented ischemic ventricular dysfunction in a rodent model of OPCAB.     

Tranexamic acid reduces bleeding after off-pump coronary artery bypass grafting

AIM: To assess the ability of tranexamic acid, compared with an untreated control group, to decrease bleeding and transfusion requirements in patients undergoing coronary artery bypass grafting on the beating heart. METHODS: Forty-nine randomly selected patients were enrolled to elective coronary artery bypass grafting without the use of cardiopulmonary bypass. Of these, 23 received tranexamic acid (bolus of 1 g before surgical incision, followed by infusion 200 mg/hour during surgery) and 26 patients were enrolled into a control group. Preoperative hematological variables, postoperative blood loss at 4 and 24 hours, transfusion requirements of packed red blood cells,and postoperative thrombotic events such as a myocardial infarction, stroke and pulmonary embolism were recorded. RESULTS: The two groups were similar in terms of patients' characteristics. Postoperative bleeding was significantly lower in the tranexamic acid group compared with the control group (median [25th-75th percentiles]): 115 [92-148] vs 230 [170-260] mL at 4 hours, p<0.001; 420 [330-523] vs 550 [500-650] mL at 24 hours, p<0.01). Transfusion requirements were lower in the tranexamic acid group compared with the control group (RBC 9% vs 28%), but the difference was not statistically significant. Treatment with tranexamic acid was not associated with a higher incidence of myocardial ischemia or other thrombotic events. CONCLUSION: Tranexamic acid reduces postoperative blood loss after coronary artery bypass grafting on the beating heart. Evaluation of transfusion requirements warrants further study.     

Glucose-insulin-potassium solutions improve outcomes in diabetics who have coronary artery operations

BACKGROUND: This study was undertaken to determine whether glucose-insulin-potassium (GIK) would improve myocardial performance and limit morbidity after coronary artery bypass grafting in diabetic patients. METHODS: Forty consecutive coronary artery bypass grafting patients with medically treated diabetes mellitus were prospectively randomly assigned to either a GIK group (n = 20; 500 mL D5W + 80 U regular insulin + 40 mEq KCl 30 mL/hour) or a no-GIK group (n = 20; D5W at 30 mL/hour). The GIK was begun at anesthetic induction and continued for 12 hours postoperatively. RESULTS: Patients treated with GIK had higher postoperative cardiac indices (2.88 +/- 0.50 versus 2.20 +/- 0.39 L/minute per square meter; p < 0.0001), lower inotrope scores (0.40 +/- 0.68 versus 1.25 +/- 1.44; p = 0.05), less weight gain (5.80 +/- 3.76 versus 13.85 +/- 6.52 pounds; p < 0.0001), and had shorter times of ventilator support (8.35 +/- 2.60 versus 13.45 +/- 7.33 hours; p = 0.0128). They had a significantly lower prevalence of atrial fibrillation (15% versus 60%; p = 0.003), and shorter hospital stays (6.70 +/- 1.52 versus 10.15 +/- 6.62 days; p = 0.02). CONCLUSIONS: Substrate enhancement with GIK in diabetic patients improved myocardial performance and resulted in faster recovery after coronary artery bypass grafting.     

Intravenous nifedipine for prevention of myocardial ischaemia after coronary revascularization

We sought to determine the pharmacokinetic and pharmacodynamic behaviour of a continuous infusion of nifedipine given for prevention of myocardial ischaemia following coronary artery bypass graft (CABG) surgery. Patients scheduled for elective CABG, who had good left ventricular function, were included. Only normotensive patients who did not require treatment with vasoactive drugs and were bleeding less than 100 ml.hr-1 following surgery were included. The patients were randomly distributed into two groups: a control group not receiving any treatment and a treated group receiving a bolus (3 micrograms.kg-1.min-1 for 5 min) and maintenance (0.2 micrograms.kg-1.min-1) infusion of nifedipine, starting upon arrival in the recovery room and continuing for four hours. Patients given nifedipine were compared with control patients in order to determine the effects of nifedipine on haemodynamic function and on the postoperative incidence of hypotension, hypertension, myocardial ischaemia and infarction. Continuous 2-lead Holter monitoring was used to detect myocardial ischaemia. Infarction was diagnosed by 12-lead ECGs and by assessment of the MB-isoenzyme creatine kinase. The infusion of nifedipine rapidly achieved and maintained plasma concentrations between 30 and 40 ng.ml-1. The pharmacokinetic studies revealed a systemic clearance of nifedipine of 0.371 +/- 0.101 L.hr-1.kg-1, an apparent volume of distribution of 0.764 +/- 0.288 L.kg-1 and an elimination half-life of 1.4 +/- 0.6 hr. No correlation was found between plasma concentration of nifedipine and mean arterial pressure (MAP). The incidence of postoperative hypotension (MAP < 70 mmHg) and hypertension (MAP > 100 mmHg) was comparable between the groups. All haemodynamic variables were similar in both groups during the study period. Of 23 patients who received nifedipine, none showed evidence of ischaemia within six hours of starting the infusion. During the same period, five of 24 patients in the control group had ST-segment deviation suggestive of myocardial ischaemia (P = 0.05, Fisher's exact test). Three patients in the control group and none in the nifedipine group suffered perioperative myocardial infarction (P = NS). In conclusion, the continuous infusion of nifedipine used in this study is safe and reduces the incidence of myocardial ischaemia in normotensive patients with good left ventricular function following CABG. Further studies of larger number of patients are required to determine the role of calcium entry blockers following coronary artery surgery.     

Reduction of myocardial injury with verapamil before aortic cross-clamping

The effect of verapamil administered before aortic cross-clamping was assessed in 40 patients undergoing elective coronary artery bypass grafting. Myocardial protection consisted of cold blood potassium cardioplegia, topical ice slush, and moderate (28 degrees C) systemic hypothermia. Patients were randomly divided into two groups: group 1 (18 patients) received verapamil (0.1 mg/kg up to 10 mg) intravenously three to five minutes before aortic cross-clamping; group 2 (22 patients) did not (control). Myocardial injury was assessed by cumulative release of the cardiac-specific isoenzyme of creatine kinase (CK-MB) after release of the aortic cross-clamp. Release of CK-MB was significantly lower in the verapamil group (44.9 +/- 6.2 versus 72.2 +/- 9.0 IU at 24.5 hours, p = 0.005). Calculated total infarct size was also lower in the verapamil group (6.0 +/- 0.9 versus 8.9 +/- 1.0 g-Eq, p = 0.035). Individual CK-MB release curves showed either one or two peaks. The two-peak pattern was more frequent in control patients (18 of 21 control patients versus 6 of 18 verapamil patients, p = 0.001) and was associated with a larger infarct size. Atrioventricular pacing was not required in any verapamil patient, but was needed in 1 control patient. We conclude that verapamil administered before aortic cross-clamping protects against myocardial injury during coronary artery bypass grafting with no increase in the incidence of atrioventricular block.     

Cardiomyocyte apoptosis and ischemic preconditioning in open heart operations

BACKGROUND: The aim of the present study was to ascertain the percentage of left apical myocardial apoptosis in three-vessel coronary artery bypass grafting patients quantitatively and the impact of ischemic preconditioning. METHODS: Twenty-one patients with three-vessel disease who had elective coronary artery bypass grafting were randomized in a ratio of 2:1 to ischemic preconditioning (n = 14) or a control group (n = 7). The ischemic preconditioning protocol was established by two cycles of ascending aorta occlusion for 2 minutes followed by 3 minutes of reperfusion. Myocardial samples from the apex of the left ventricle were taken using a Tru-Cut needle before aortic cross-clamping and immediately after declamping. The percentage of apoptosis was analyzed by TUNEL methods. Data on hemodynamics and biochemical markers were collected. RESULTS: Low levels of myocardial apoptosis were found before the operation (0.01% +/- 0.00%). During the early reperfusion period, the percentage of myocardial apoptotic cells significantly increased (0.15% +/- 0.05%, p = 0.008). Ischemic preconditioning significantly improved cardiac index and right ventricular ejection fraction recovery after the operation (p = 0.036 and 0.001 respectively, repeated measure) but had no effect on myocardial apoptosis before and after the operation (0.01 +/- 0.00 versus 0.01 +/- 0.00, p = 0.658 and 0.12% +/- 0.04% versus 0.23% +/- 0.14%, p = 0.302). CONCLUSIONS: Cardioplegic myocardial ischemia during open heart operation was associated with induction of cardiomyocyte apoptosis in humans. Attenuation of postoperative cardiac dysfunction by ischemic preconditioning appeared to be independent of apoptosis.     

Intermittent antegrade warm myocardial protection compared to intermittent cold blood cardioplegia in elective coronary surgery--do we have to change?

OBJECTIVE: Intermittent antegrade warm blood cardioplegia (IAWBC) is a simple and cost-effective method of myocardial preservation. However, there are only few prospective trials comparing this type of cardioplegia to established cardioplegic strategies in elective on-pump coronary surgery with respect to myocardial protection and outcome. METHODS: In a prospective, randomized trial IAWBC (33 degrees C) (n=100) was compared to intermittent antegrade cold (4 degrees C) blood cardioplegia (n=100), regarding clinical outcome and myocardial protection using cardiac troponin-I (cTNI) and creatine kinase MB isoenzyme (CK-MB) measurements to assess ischemia. RESULTS: Preoperative parameters were comparable in both groups. Results demonstrated no differences in-between the groups regarding mortality (2.0% both), incidence of perioperative myocardial infarction (2 versus 3%), need for intra-aortic balloon pump (3 versus 4%), length of ICU stay (2.0+/-2.5 versus 2.1+/-3.0 days) and incidence of postoperative atrial fibrillation (41 versus 34%). However, the necessity of defibrillation after cardiac arrest (18 versus 43%, P<0.001) was significantly less frequent and of lower intensity (3.4+/-10.8 versus 10.8+/-20.6 J, P<0.001) in the IAWBC-group. Postoperatively the ischemia markers were significantly lower in the IAWBC-group, cTNI within the first 72 h (from P<0.001 to P=0.013) and even CK-MB within the first 24 h (from P=0.004 to P<0.011). CONCLUSION: IAWBC is a safe and simple method in elective on-pump coronary artery bypass surgery. Significantly lower ischemic markers suggest an improved myocardial protection compared to cold blood cardioplegia in these patients.     

Increased creatine kinase MB level predicts postoperative mortality after cardiac surgery independent of new Q waves

BACKGROUND: Recent consensus statements recommend cardiac enzyme release as the essential criterion for diagnosing myocardial infarction. However, the outcome implications of cardiac enzyme release in patients undergoing coronary artery bypass grafting are controversial. METHODS: Eight hundred patients were followed for 30 days after elective on-pump coronary artery bypass grafting in a multicenter, prospective, randomized trial of the anti-C5 complement antibody pexelizumab. Data from centralized electrocardiography and creatine kinase MB analyses were examined for any association with death or severe left ventricular dysfunction. RESULTS: More than half of the 800 patients had peak creatine kinase MB levels of more than 5 times the upper limit of 5 ng/mL set by the core laboratory. The median peak value was 29 ng/mL. The incidence of the combined outcome (death or severe left ventricular dysfunction) was 1.7% if the peak creatine kinase MB level was less than 25 ng/mL and 18.0% if 100 ng/mL or greater (P < .01). Similarly, the incidence of new Q-wave myocardial infarction was 3.9% if the peak creatine kinase MB level was less than 25 ng/mL and 30.6% if 100 ng/mL or greater (P < .01). In a multivariate analysis that included preoperative and intraoperative factors, as well as peak enzyme release and Q-wave myocardial infarction, the strongest predictor of the combined outcome was a peak creatine kinase MB level of 100 ng/mL or greater. New Q-wave myocardial infarction did not significantly predict the combined outcome. CONCLUSIONS: Increased postoperative peak creatine kinase MB level, especially when 20 times or more of the upper limit of normal, indicates increased risk of severe postoperative left ventricular dysfunction and mortality within 30 days of coronary artery bypass grafting. High peak enzyme level is a stronger predictor of adverse outcomes than is postoperative Q-wave myocardial infarction in this population.     

Magnesium infusion dramatically decreases the incidence of atrial fibrillation after coronary artery bypass grafting

BACKGROUND: Atrial fibrillation (AF) is one of the most common complications of cardiac surgery. Magnesium, like several other pharmacologic agents, has been used in the prophylaxis of postoperative AF with varying degrees of success. However, the dose and the timing of magnesium prophylaxis need to be clarified. The purpose of this study was to assess the effect of intermittent magnesium infusion on postoperative AF. METHODS: A total of 200 consecutive patients who had elective, isolated, first-time coronary artery bypass grafting were prospectively randomized to two groups. Patients in the magnesium group (n = 100) received 6 mmol MgSO4 infusion in 100 mL 0.9% NaCl solution (25 mL/h) the day before surgery, just after cardiopulmonary bypass, and once daily for 4 days after surgery. Patients in the control group (n = 100) received only 100 mL 0.9% NaCl solution (25 mL/h) at the same time points. RESULTS: Postoperative AF occurred in 2 (2%) patients in the magnesium group and in 21 (21%) patients in the control group (p < 0.001). Atrial fibrillation started, on average, 49.4 +/- 16.8 hours postoperatively. The postoperative length of hospital stay was not significantly different in patients with AF (7.4 +/- 8.0 days) compared with patients without AF (5.4 +/- 1.1 days; p = 0.236). CONCLUSIONS: The use of magnesium in the preoperative and early postoperative periods is highly effective in reducing the incidence of AF after coronary artery bypass grafting.     

Significance of right bundle branch block in the diagnosis of myocardial ischemia in patients undergoing coronary artery bypass grafting.

BACKGROUND: Perioperative diagnosis of myocardial ischemia following cardiac surgical procedures remains a challenging problem. Particularly, the role of new conduction disturbances as markers of postoperative ischemia is still questionable. The goal of this study was to elucidate the diagnostic significance of new postoperative right bundle branch block (RBBB) for the detection of perioperative myocardial ischemia in patients undergoing elective coronary artery bypass grafting (CABG). METHODS: In 169 consecutive patients, three-channel Holter monitoring and serial assessment of serum enzymes were performed for 48 h, and 12-lead ECG repeated for up to 5 days postoperatively. Postoperative events were classified as either myocardial infarction (MI), transient ischemic events (TIE) or various conduction disturbances. RESULTS: Transient (n=9) or permanent (n=4) RBBB occurred in 13 patients (8%); 14 patients (8%) showed signs of perioperative MI and 18 patients (11%) evidence of TIE. Peak activity of creatine-kinase (CK, 561+/-135 vs. 316+/-19, P<0.05) and CK-MB (22.7+/-3.2 vs. 13.4+/-0.8, P<0.01) were higher in patients with RBBB than in patients without perioperative ischemic events. Peak CK-MB levels were significantly higher in patients with MI as compared to those with RBBB (33.4+/-7.6 vs. 22.7+/-3.2, P<0. 05). Patients with TIE had similar perioperative enzyme levels as patients with no events. CONCLUSION: It is concluded that the combined assessment of repeated 12-lead ECG, continuous Holter monitoring and enzyme analysis allows a reliable diagnosis of perioperative myocardial ischemia and conduction disturbances. The occurrence of new RBBB following elective CABG is indicative of perioperative myocardial necrosis and thus serves as a valuable tool for the diagnosis of new, perioperative ischemic events.     

Off-pump coronary artery bypass grafting surgery in early stage myocardial infarction treatment

We evaluated the surgical results of off-pump coronary artery bypass grafting (OPCAB) performed within the first 12 h of infarction in patients with acute myocardial infarction. From January 2005 to January 2007, emergency coronary artery bypass grafting without cardiopulmonary bypass was performed in 56 patients with acute coronary syndromes. The mean age was 62.9 (range, 51-86) years. All patients underwent OPCAB via sternotomy. An average of 2.5 +/- 1.1 grafts per patient were performed. The mortality rate was 7.1% (4 of 56 patients). One patient suffered from postoperative stroke (1.7%), and 3 (5.3%) needed hemofiltration for acute renal failure. Postsurgery elective coronary angiography (n = 21) showed no significant stenosis. These results indicate that emergency OPCAB can be applied to patients with acute myocardial infarction with low morbidity and mortality and excellent early results.     

Emergency aortocoronary bypass after failed angioplasty

One thousand two hundred fourteen percutaneous transluminal coronary angioplasties were performed over a 38-month period. Sixty patients required immediate emergency coronary artery bypass grafting after angioplasty failure; 7 of these had evidence of acute myocardial infarction before angioplasty and were excluded from the study. Of the 53 patients remaining, 27 (51%) had electrocardiographic and enzyme evidence of postoperative myocardial infarction. Two patients died (4%), and 10 had postoperative complications (19%). No statistical significance was noted comparing age, sex, incidence of prior myocardial infarction or myocardial dysfunction, time for revascularization, or average number of grafts completed in those with single-vessel (n = 21) versus multiple-vessel (n = 32) coronary artery disease. Postoperatively, those with multiple-vessel disease required intraaortic balloon pump support (p = 0.06) and antiarrhythmic medications more frequently than single-vessel patients (p less than 0.01) and had a higher complication rate (p less than 0.05). Although not reaching statistical significance, the data also suggest a higher death and postoperative myocardial infarction rate in patients with multiple-vessel disease. Emergency coronary artery bypass grafting after failed percutaneous transluminal coronary angioplasty carries a higher morbidity and mortality than elective coronary artery bypass grafting, particularly for patients with multiple-vessel coronary artery disease.     

Myocardial metabolism and hemodynamics during coronary surgery without cardiopulmonary bypass

BACKGROUND: Although renewed interest has recently been shown in coronary artery bypass grafting without cardiopulmonary bypass, no reports are available on myocardial metabolism and hemodynamics during temporary coronary occlusion and rotation of the contracting heart. METHODS: Changes in myocardial energy metabolism and hemodynamics were monitored in 12 patients undergoing elective coronary artery bypass grafting without cardiopulmonary bypass, and the postoperative efflux of creatine kinase-MB mass and troponin T were also determined. RESULTS: There was a significant increase in myocardial production of ATP degradation products (p = 0.026) and lactate (p = 0.004) during the operation. Myocardial oxygen extraction decreased (p = 0.012) in correlation with use of the short-acting beta-blocker, esmolol (r = -0.71). Apart from a decrease in mean arterial blood pressure (p = 0.002), there were no significant hemodynamic changes during the operation. The overall postoperative troponin T and creatine kinase-MB mass changes remained nonsignificant during the first two postoperative days. One patient had a myocardial infarction, diagnosed by electrocardiography, on the second postoperative day, but otherwise there were no major complications. CONCLUSIONS: Coronary artery bypass grafting without cardiopulmonary bypass seems to be well tolerated as only minor changes in myocardial energy metabolism and hemodynamics are observed during the operation.     

Perioperative use of tirofiban hydrochloride (Aggrastat) does not increase surgical bleeding after emergency or urgent coronary artery bypass grafting.

BACKGROUND: The platelet glycoprotein IIb/IIIa inhibitor tirofiban hydrochloride improves outcome in patients with acute coronary syndrome. Nevertheless, a considerable number of patients require emergency or urgent coronary artery bypass grafting and may be at increased risk of postoperative bleeding after treatment with this molecule. The aim of this study is to evaluate the incidence of bleeding complications among patients undergoing bypass grafting after treatment with tirofiban. METHODS: We investigated the influence of the molecule on postoperative bleeding after cardiac surgery, comparing 2 groups of patients undergoing emergency or urgent coronary artery bypass grafting: group A (n = 20) received tirofiban, and group B (n = 68) received conventional therapy with intravenous heparin up until the operation. A total of 88 patients underwent coronary artery bypass surgery within 2 hours of ceasing the hemodynamic study. Clinical outcome, chest tube outputs, bleeding complications, transfusion requirements, platelet and hemoglobin counts, and clinical complications were examined. RESULTS: Bleeding differences were noted between the 2 groups at 8, 16, and 24 hours postoperatively. The incidence of blood, platelet, and fresh frozen plasma transfusions was higher in the control group. Postoperative thrombocytopenia was preserved in group A (199.5 +/- 70.4 vs 150.6 +/- 33.4 10(3)/mL, P <.01). No significant differences were noted between the 2 groups in the incidence of perioperative myocardial infarction, but significant differences were noted in enzyme levels, length of stay in the intensive care unit, and length of stay in the hospital. No deaths were observed. Hospital morbidity was increased in group B because of factors that were not apparently linked with tirofiban infusion. CONCLUSIONS: Patients may safely undergo coronary artery bypass surgery after treatment with tirofiban hydrochloride. This molecule, administered in the immediate preoperative period, has no adverse clinical effects and does not seem to negatively influence the incidence of perioperative myocardial infarction. Although extracorporeal circulation can modify platelet numbers and function, our ongoing data could show significant reduction in the loss of platelets induced by cardiopulmonary bypass, minor postoperative bleeding, and a minor transfusion requirement in general.     

Improved myocardial recovery after cardioplegic arrest with an oxygenated crystalloid solution

Possible enhancement of myocardial protection by oxygenation of a crystalloid cardioplegic solution was evaluated in a three-part study. In Part I, canine hearts underwent ischemia followed by heterogeneous cardioplegic arrest for 45 to 60 minutes. Oxygenation led to improved recovery in the left anterior descending region (47% versus 86% recovery, p less than 0.05) (15 minutes of ischemia) and in the circumflex region (9.5% versus 52% recovery, p less than 0.05) (30 minutes of ischemia). Part II was a blind prospective randomized study in 12 patients. It examined creatine kinase, myoglobin, and lactate as well as coronary sinus flow, oxygen consumption, and cardiac work 1 hour after aortic cross-clamping during atrial and during ventricular pacing. No significant difference was demonstrable between control and oxygenated solutions. In Part III, 57 coronary bypass patients were protected with a nonoxygenated solution while 94 patients received an identical oxygenated solution. Twelve-hour creatine kinase levels were similar in the nonoxygenated (9.5 +/- 16 IU, +/- standard deviation) and oxygenated (11 +/- 22 IU) groups if the cross-clamp interval was 28 minutes or less. In patients subjected to longer than 28 minutes of arrest, the 12 hour creatine kinase MB levels were more than twice as high in the nonoxygenated group (26.5 +/- 26 IU) compared to the oxygenated group (9.9 +/- 14 IU, p less than 0.05). In this canine model of heterogeneous cardioplegia and in the routine conduct of coronary bypass operations, oxygenated crystalloid cardioplegia is superior to an identical nonoxygenated solution.     

The supportive value of pre-bypass L-glutamate loading in patients undergoing coronary artery bypass grafting

AIM: Experimental studies have demonstrated that an exogenous supply of glutamate improves mechanical function and recovery of ischemic myocardium. The aim of the present study was to investigate the effect of myocardial pre-bypass loading with glutamate on myocardial protection during global ischemia and reperfusion of patients undergoing coronary artery bypass grafting (CABG). METHODS: The study was double blinded. Twenty patients undergoing elective CABG were randomized to receive L-glutamate (n = 10) or normal saline (n = 10). Intracellular levels of glutamate, ATP and lactate were measured in left ventricular biopsies collected 10 min after aortic clamp release. Hemodynamic data, and postoperative release of CK-MB and troponin T were also measured. RESULTS: Pre-bypass administration of glutamate resulted in myocardial glutamate loading since glutamate levels were significantly higher in the glutamate group of patients than in controls (18.6 +/- 3.1 versus 8.7 +/- 1.2 microg/g tissue, P < 0.001). In the same group ATP levels were also significantly higher (2.4 +/- 0.7 versus 1.5 +/- 0.4 microg/g tissue, P < 0.05) and lactate levels significantly less than in controls (6.9 +/- 1.9 versus 12.0 +/- 2.1 microg/g tissue, P < 0.001). Glutamate patients had statistically significantly superior post-bypass hemodynamic performance (cardiac index, left ventricular stroke work index, systemic vascular resistance and pulmonary vascular resistance). Statistically significantly lower levels of CK-MB (6 h postoperative), total and peak CK-MB, troponin T (24 h postoperative), and total troponin T were found in the glutamate group. CONCLUSIONS: The results of this preliminary study indicate that pre-bypass intravenous administration of glutamate in patients undergoing CABG has a supportive effect on myocardial metabolism during global ischemia and reperfusion, improves patients' postoperative hemodynamic performance and reduces postoperative cardiac enzyme release.     

Tranexamic acid reduces bleeding and the need for blood transfusion in primary myocardial revascularization

BACKGROUND: The objective of this study was to study the effect of low-dose tranexamic acid (TA) on postoperative bleeding and coagulation variables after coronary artery bypass grafting operation. METHODS: Fifty patients undergoing primary coronary artery bypass grafting were randomly assigned to receive either placebo (0.9% NaCl; n = 25) or 10 mg/kg TA followed by infusion of 1 mg/kg per hour during the operation (n = 25). Data measured included blood loss, transfusion, reoperation, fibrinogen level, fibrinogen split products, platelet size, and platelet function. Measurements were made after induction of anesthesia, after heparin administration, during patient warming, after skin closure, and 24 hours after operation. RESULTS: Patients in the TA study group weighed less. Other demographic characteristics were similar between groups. Postoperative bleeding was less in the TA group (194 +/- 135 mL versus 488 +/- 238 mL, p < 0.001), whereas blood requirement was higher in the control group (1.68 +/- 1 versus 0.52 +/- 0.9 U of packed cells per patient, p < 0.001). The percent of patients exposed to blood products was significantly less in the TA group (36% versus 100%, p < 0.001). Fibrinogen split products were lower in the TA group during bypass (p < 0.001). Fibrinogen levels fell in both groups during cardiopulmonary bypass. Platelet number and function were reduced equally in both groups by cardiopulmonary bypass. Other test results were not different between groups. CONCLUSIONS: The use of low-dose TA during coronary artery bypass grafting significantly reduced the coagulopathy-induced postoperative bleeding and allogeneic blood products requirement. The low levels of fibrinogen split products during bypass in the study group reflect the inhibiting effect of TA in fibrinolysis. Tranexamic acid had no effect on platelet function during cardiopulmonary bypass.