Michael D. Strong

The dose-response relationship of tranexamic acid.

Background: Prophylactic administration of the autifibrinolytic drug tranexamic acid decreases bleeding and transfusions after cardiac operations. However, the best dose of tranexamic acid for this purpose remains unknown. This study explored the dose-response relationship of tranexamic acid for hemostatic efficacy after cardiac operation. Methods: In prospective, randomized, double-blinded fashion, 148 patients undergoing cardiac operation with extracorporeal circulation were divided into six groups: a placebo group and five groups receiving tranexamic -acid in loading doses before incision (range 2.5 to 40 mg-kg -1 ) and one-tenth the loading dose hourly for 12 h. The mass of blood collected by chest tubes over 12 h represented blood loss. Allogeneic transfusions within 12 h and within 5 d of surgery were tallied. Results: The six groups presented similar demographics. Patients receiving placebo had increased postoperative D-dimer concentration compared to groups receiving tranexamic acid. Patients receiving at least 10 mg-kg -1 tranexamic acid followed by 1 mg-kg -1 -h -1 bled significantly less (365, 344, and 369 g-12 h -1 , respectively, for those three groups) compared with patients who received placebo (552 g, P<0.05). Tranexamic dose did not affect transfusions. Only initial hematocrit affected whether a patient received an allogeneic transfusion within 5 days of operation (odds ratio 2.08 for each 3% absolute decrease in hematocrit). Conclusions: Prophylactic tranexamic acid, 10 mg-kg -1 followed by 1 mg-kg -1 -h -1 , decreases bleeding after extracorporeal circulation. Larger doses do not provide additional hemostatic benefit

Hemostatic effects of tranexamic acid and desmopressin during cardiac surgery.

Background Desmopressin-induced release of tissue plasminogen activator from endothelial cells may explain the absence of its hemostatic effect in patients undergoing cardiac surgery. Prior administration of the antifibrinolytic drug tranexamic acid might unmask such an effect, and combination therapy might thereby improve postoperative hemostasis. Methods and Results A double-blinded design randomly allocated 163 adult patients undergoing coronary revascularization, valve replacement, both procedures, or repair of atrial septal defect to four treatment groups: placebo, tranexamic acid given as 10 mg/kg over 30 minutes followed by 1 mg. kg−1. hr−1 for 12 hours initiated before skin incision, desmopressin given as 0.3 μg/kg over 20 minutes after protamine infusion, and both drugs. One surgeon performed all operations. Blood loss consisted of mediastinal tube drainage over 12 hours. Follow-up visits sought evidence of myocardial infarction and stroke. Desmopressin decreased neither the 12-hour blood loss nor the amount of homologous red cells transfused. Tranexamic acid alone significantly reduced 12-hour blood loss, by 30%1 (mean, 318 versus 453 ml; Conclusions Desmopressin exerts no hemostatic effect, with or without prior administration of antifibrinolytic drug. Prophylactic tranexamic acid alone appears economical and safe in decreasing blood loss and transfusion requirement after cardiac surgery.

Does Off-Pump Coronary Artery Bypass Reduce the Incidence of Clinically Evident Renal Dysfunction After Multivessel Myocardial Revascularization?

In this prospective, observational trial, we determined whether off-pump coronary artery bypass (OPCAB) was associated with less postoperative renal dysfunction (RD) compared with coronary bypass surgery with cardiopulmonary bypass (CABG). All patients undergoing primary, isolated coronary surgery at our institution in the year 2000 participated. Data collected on each patient included demographics, preoperative risk factors for RD, perioperative events, and serum creatinine concentrations from date of admission until discharge or death. The criteria for RD was both a ≥50% increase from preoperative creatinine and an absolute postoperative creatinine ≥2.0 mg/dL (177 &mgr;M). Student’s t-test or the Fisher’s exact test was used to compare groups. Stepwise multiple logistic regression identified determinants of RD; P < 0.05 significant. The CABG group (n = 119) differed from the OPCAB group (n = 220) with respect to age (64 ± 13 versus 67 ± 10 yr, P = 0.0074) and number of distal grafts (median 4 versus 3, P = 0.0003). Type of operation did not associate with the presence of postoperative RD: 18 (8.2%) of 220 OPCAB patients versus 12 (10%) of 119 CABG patients (P = 0.55). Our data suggest that choice of operative technique (OPCAB versus CABG) is not associated with reduced renal morbidity.

Cardiac Surgery in Nonagenarians

Abstract Objectives and Background: The purpose of this study was to document our initial experience with patients 90 years of age and older and to determine whether cardiac surgery is justified in this age group. Cardiac surgery in octogenarians has proven to be a successful and worthwhile procedure. A small group of nonagenarians with severe coronary artery disease (CAD) and aortic valve disease refractory to medical therapy have been considered for surgery. Methods: Fourteen patients aged 90 or more underwent cardiac surgery for symptomatic CAD or aortic valvular disease refractory to medical therapy. Eight patients underwent isolated coronary artery bypass grafting (CABG) and six patients underwent aortic valve replacement (AVR). All patients were in NYHA Class IV preoperatively. Results: Hospital mortality occurred in one patient (7%). Hospital morbidity occurred in 10 patients (71%) and included 7 cardiac, 5 neurological, 1 gastrointestinal, 1 infectious, and 1 pulmonary event. All survivors left the hospital symptomatically improved. The mean length of stay was 26 days. Four CABG patients went on to die at a mean of 2 years and 2 months, and 3 remain alive at a mean of 2 years and 4 months. Three AVR patients expired at a mean of 3 years and 4 months, and 3 remain alive at 4 years and 1 month. Conclusions: Cardiac surgery in carefully selected nonagenarians is justified and can be performed with acceptable results.

Three-Dimensional Echocardiography of Intracardiac Masses

We describe two cases in which three‐dimensional echocardiography provided unique anatomical data. This information enhanced the diagnostic power of two‐dimensional echocardiography by improving confidence in interpretation and by providing distinctive spatial insights. (ECHOCARDIOGRAPHY, Volume 21, February 2004)

Aneurysm of Aortocoronary Saphenous Vein Graft

True aneurysms of aortocoronary saphenous vein bypass grafts are a relatively rare complication of bypass surgery, but because the complications of thrombosis, embolization, or rupture are potentially fatal, this condition requires immediate surgical intervention. We describe a 78-year-old man who had undergone coronary bypass 15 years previously and who presented with a saphenous vein graft that was severely degenerated and aneurysmally enlarged throughout its course, measuring as much as 5 to 6 cm in certain locations. Redo coronary artery bypass grafting using the right and left internal thoracic arteries and resection of the aneurysm were performed. We also present a review of the literature regarding diagnosis, management, and treatment of this condition.

Three-dimensional echocardiography of post-myocardial infarction cardiac rupture.

Ventricular septal defects and pseudoaneurysms are two serious complications of acute myocardial infarction and are associated with a high mortality if not surgically treated. Two‐dimensional echocardiography provides excellent diagnostic information in such cases, but three‐dimensional echocardiography may provide superior anatomic data of these potentially fatal complications. We describe two cases in which three‐dimensional echocardiography provided incremental morphological information. (ECHOCARDIOGRAPHY, Volume 21, April 2004)

Failure of four bovine pericardial mitral prostheses

The bovine pericardial valve has a long history of excellent performance in both the aortic and mitral positions, with low rates of both short-term and long-term valverelated events. In two large studies spanning 12 and 15 years, there were no reported occurrences of intraoperative structural failure. Although there are some reports in the literature of early postoperative failure, there are few reported cases of intraoperative failure of bovine pericardial valves. We present 4 instances in 3 patients from two separate institutions of intraoperative structural failure of bovine pericardial mitral bioprostheses.

Spontaneous left main coronary artery dissection, possibly due to cystic medial necrosis found in the internal mammary arteries.

A 55-year-old male without previous medical history developed chest pain. Coronary catheterization showed left main coronary dissection. Coronary artery bypass grafting was performed using bilateral internal mammary arteries, which were very fragile. The specimens of the internal mammary arteries sent for pathology showed cystic medial necrosis.

Haemodynamic consequences of warm cardiac irrigation during cardiac surgery

Following cardiopulmonary bypass (CPB) and prior to closing the chest, some surgeons irrigate the heart and pericardium with warm saline. This prospective study, using each patient as his own control, evaluated the haemodynamic effects of warm (44 ± 5∘ C) irrigation on the heart and pericardium following CPB. Following discontinuation of CPB, a Mon-atherm model 6500 thermocouple monitor measured the myocardial septum and the irrigating fluid temperatures. Immediately before, during and two minutes after irrigation of the heart and pericardium, we measured heart rate (HR), systemic blood pressure (BP), pulmonary artery pressure (PAP), central venous pressure (CVP), thermodilution cardiac output, and calculated systemic vascular resistance (SVR). During warm irrigation, HR increased from 93 ± 75 to 101 ± 13 min−1 and systolic BP increased from 111 ± 17 to 131 ± 27 mmHg. After irrigation, HR decreased to 96 ± 12 min−1 with no change in systolic BP The calculated SVR after irrigation increased to 1117 ± 413 dynes · sec · cm−5 from the pre-irrigation value of 821 ± 243 dynes · sec · cm−5, while cardiac index decreased to 2.4 L · min−1 · m−1 from its preirrigation value of 2.99 L · min−1 · m−2. Warm irrigation of the pericardial pouch causes tachycardic and hypertensive responses in patients undergoing cardiac surgery.RésuméCertains chirurgiens irriguent le coeur et le péricarde avec du liquide chaud après une circulation extracorporelle (CEC) et avant de refermer le thorax. Cette étude prospective évalue les effets hémodynamiques de l’irrigation chaude (44 ± 50) du coeur et du péricarde après CEC, chaque patient étant sa propre référence. Suite à l’arrêt de la CEC, un moniteur thermocouple, modèle Mon-a-therm 6500, mesure les températures du septum myocardique et des liquides d’irrigation. Nous mesurons la fréquence cardiaque (Fc), la pression arterielle systémique (PA), la pression de l’artère pulmonaire (PAP), la pression veineuse centrale (PVC), le débit cardiaque par thermodilution et calculons la résistance vasculaire systémique (RVS) immédiatement avant, pendant, et deux minutes après l’irrigation du coeur et du péricarde. Pendant l’irrigation chaude, la Fc s’accroît de 93 ± 15 à 101 ± 13 min−2 et la PA systolique augmente de 111 + 17 à 131 ± 27 mmHg. Après l’irrigation, la Fc diminue de 96 ± 12 min−1 sans changement de PA systolique. La RVS calculée après l’irrigation atteint 1117 ± 413 dynes · sec · cm−5 à partir de valeur de 821 ± 243 dynes · sec · cm−5, tandis que l’index cardiaque diminue à 2,4 L · min−1 · m−2 à partir de valeur de 2,99 L · min−2 · m−2 avant l’irrigation. L’irrigation chaude de la poche péricardique entraîne une réponse d’hypertension et de tachycardie chez les patients qui subissent une chirurgie cardiaque.