Bryan K. Lee

Thromboelastogram fails to predict postoperative hemorrhage in cardiac patients

To determine the clinical usefulness of the thromboelastogram in the prediction of postoperative hemorrhage in cardiac patients, we related the results of routine coagulation tests (RCTs) and thromboelastography with the amount of chest tube drainage postoperatively in 101 patients requiring cardiopulmonary bypass. Our data indicated that there was no correlation between RCT results and thromboelastographic variables. No single variable of RCTs and thromboelastography correlated well with the amount of chest tube drainage postoperatively. Before the onset of cardiopulmonary bypass, the most frequent abnormalities detected by thromboelastograms were fibrinolysis and hypocoagulability resulting from factor deficiency. Hypercoagulability detected by thromboelastograms occurred in 13% of patients after cardiopulmonary bypass and usually was not detected by RCTs. The incidence of false-negative thromboelastograms and RCT results in patients who had excessive hemorrhage of unknown cause was 46% and 52%, respectively. The incidence of fibrinolysis as detected by thromboelastograms was similar before and after bypass, but only 2 of the 18 patients with fibrinolysis had excessive hemorrhage postoperatively. Our results indicate that neither RCTs nor thromboelastography predicts the likelihood of excessive hemorrhage in patients after cardiopulmonary bypass. The thromboelastographic results should be interpreted cautiously because of the high rate of unreliable results.

Assessment of Myocardial Perfusion during CABG Surgery with Two-dimensional Transesophageal Contrast Echocardiography

No reliable, quantifiable index of tissue perfusion is currently available to assess the efforts of coronary artery bypass graft (CABG) surgery. We used two-dimensional transesophageal contrast echocardiography with sonicated Renografin-76 microbubbles to determine the distribution of myocardial blood flow during coronary artery bypass graft surgery in 15 patients. Sonicated Renografin-76 contrast agent was injected into the aortic root of all patients after institution of cardiopulmonary bypass and application of the aortic occlusive clamp. Eight patients had contrast agent injected directly into the free proximal end of the vein-CABG anastomosis. All patients again received aortic root injections during reperfusion after anastomosis of the proximal aortovein and distal coronary artery. Echocardiographic images of the left ventricle short axis at the level of the papillary muscles were obtained in real time and analyzed retrospectively from videotape. Injection of contrast provided information about the magnitude and geometric distribution of coronary artery-vein bypass run-off and enabled identification of poorly perfused myocardial regions. When predicted myocardial perfusion patterns, based on preoperative evaluation of epicardial vessel distribution derived from coronary angiography, were compared to actual perfusion patterns assessed with intraoperative echocardiography, contrast regional myocardial perfusion patterns were predicted 84% of the time (71-97%, 95% confidence limit). Regional myocardial perfusion deficits detected after coronary bypass grafting were associated with regional wall motion abnormalities detected after separation from cardiopulmonary bypass. Our technique makes possible on-line visualization of changes in regional blood flow in the heart before, during, and after CABG.(ABSTRACT TRUNCATED AT 250 WORDS)

Assessment of retrograde cardioplegia distribution using contrast echocardiography

Retrograde cardioplegia has gained popularity in coronary and noncoronary cardiac operations. We have used contrast echocardiography in the open-chest canine model to compare the distribution of cardioplegia delivered antegrade in the aortic root versus retrograde through the coronary sinus, and to determine the effect of coronary occlusion on that delivery. With no coronary occlusion, antegrade cardioplegia was distributed to the entire left ventricle and septum whereas retrograde cardioplegia was distributed to the left ventricular free wall but had inconsistent delivery to the septum. Acute occlusion of the left circumflex coronary artery resulted in 57.06% +/- 9.52% of the left ventricle not being perfused by antegrade cardioplegia and occlusion of both the left circumflex and anterior descending coronary arteries caused a 65.46% +/- 18.5% reduction in perfusion by antegrade cardioplegia. Acute coronary occlusion had no effect on retrograde cardioplegia distribution. We conclude that retrograde cardioplegia is less homogeneous than antegrade cardioplegia in the intact coronary circulation but that retrograde cardioplegia preserves cardioplegia distal to acutely occluded coronary arteries. Furthermore, contrast echocardiography is a useful method of assessing myocardial perfusion and may have useful clinical applications.

Retrograde-delivered cardioplegia is not distributed equally to the right ventricular free wall and septum

Right ventricular myocardial protection during cardiac surgery continues to be a challenge. Retrograde delivery of cardioplegia has been shown to perfuse left ventricular regions subtended by critical coronary stenosis and not adequately protected by antegrade delivery. However, the distribution of cardioplegia from the coronary sinus to the right ventricle remains in question. A reliable means for assessing such flow distribution intraoperatively is provided by contrast echocardiography. It was hypothesized that conventional use of coronary sinus catheters for retrograde cardioplegia delivery does not reliably perfuse the myocardial region subtended by the right coronary artery. Six patients scheduled to undergo elective coronary artery bypass surgery were evaluated with contrast echocardiography to determine the distribution of retrograde-delivered cardioplegia into the right ventricle. Sonicated Renografin-76 (Squibb Diagnostics, Princeton, NJ) was injected during retrograde delivery of cold crystalloid cardioplegia solution and continuous two-dimensional ultrasound imaging of the heart. On-line videodensitometric analysis was performed with a digital ultrasound system. The area under the curve and peak pixel intensity were determined for the anterior septum, the posterior septum, and the right ventricular free wall for each contrast injection. Recorded VHS videotape images of contrast-enhanced perfusion patterns were also reviewed and scored. On-line acoustic-densitometric analysis showed that right ventricular posterior and anterior septal peak pixel intensities were 4.8 ± 3.2 and 7.3 ± 1.5, respectively, compared with only 1.6 ± 1.2 ( P ≤ 0.05) in the right ventricular free wall. Visual assessment of contrast enhancement within the identical regions of interest showed similar results. It is concluded that retrograde-delivered cardioplegia through a balloon-tip coronary sinus catheter does not reliably perfuse the right ventricular free wall. If right ventricular protection is a clinical priority, other techniques should be employed to ensure optimal preservation during ischemic arrest.

Assessing Myocardial Perfusion With Albunex During Coronary Artery Bypass Surgery: Technical Considerations and Safety of Aortic Root Injections

OBJECTIVE To test the safety and report on limiting technical considerations, including optimal dosing of Albunex (Molecular Biosystems, Inc, Mallinckrodt Medical, St. Louis, MO) for myocardial opacification after intra-aortic root injections during cardiac surgery. DESIGN This was a prospective randomized study with a control group who did not receive Albunex and a group who received intra-aortic root injections of Albunex. SETTING Multicenter (two) independent university hospitals. PARTICIPANTS 32 patients scheduled for elective coronary artery bypass surgery were evaluated after individual informed consent was obtained. INTERVENTIONS 2 to 8 mL of Albunex were injected before and after coronary revascularization. MEASUREMENTS AND MAIN RESULTS Quality of enhancement in each of four regions of the left ventricle was assessed from a short-axis mid-papillary ultrasound image by three experienced observers blinded to dose. Electrocardiogram (ECG), creatine phosphokinase (CPK) (MB fraction), and hemodynamics were evaluated at baseline and throughout the study period for up to 72 hours. No differences were noted between groups with respect to preoperative and postoperative CPK enzymes (CPK-MB fraction), ECG changes, hemodynamics, requirements for separation from CPB, need for postoperative inotropes, time to extubation, and time to discharge from the intensive care unit. The average total dose of Albunex injected was 19 mL +/- 4 (0.25 mL/kg). A single dose of 4.2 +/- 1.2 mL (0.05 mL/kg) appeared to offer optimal enhancement of contrast effect for myocardial perfusion assessment. CONCLUSION Albunex is safe and easy to use for myocardial opacification when administered via an antegrade cardioplegia catheter into the aortic root during CPB.

A 73-Year-Old Man With Hypertension and Syncope

A 73-year-old man presented to the University of Chicago Hospital Emergency Department on April 9, 1995, with a syncopal episode. The patient had been in his usual state of health until earlier that morning when he experienced an acute loss of consciousness during micturition. He fell and hit the left side of his head but sustained no other injuries. He was unable to tell how long he had been unconscious, although he thought that it had only been a few seconds. The event was not witnessed. He did not remember any premonitory symptoms such as palpitations, chest pain, dyspnea, headache, visual changes, or olfactory sensations or any confusion, grogginess, or bowel incontinence after the event. The patient had not noted any recent or remote episodes of dyspnea on exertion, orthopnea, paroxysmal nocturnal dyspnea, dizziness, numbness or weakness, nausea, vomiting, diarrhea, fever, chills, cough, abdominal pain, back pain, or lower-extremity claudication. One month before this admission, the patient had experienced a similar episode of micturition syncope, but he had not sought medical attention. The previous episode also occurred immediately after awakening and was not preceded by any unusual symptoms. His past medical history was significant for long-standing systemic hypertension, chronic atrial fibrillation, a cerebral vascular accident in 1983 without any residual defects, and a bowel obstruction due to volvulus that required surgery in 1992. He was a retired maintenance worker and part-time minister. He did not smoke, drink alcohol, or use recreational drugs. He was not taking any prescription or over-the-counter medications. His family history is significant for atherosclerosis, with his mother and father dying of myocardial infarction at ages 60 and 70 years, respectively. On physical examination, the patient was alert and oriented. He was 6 ft tall and weighed 69 kg. His vital signs included a temperature of 38.1°C, …

Retrograde-Delivered Cardioplegia Is Not Distributed Equally to the Right Ventricular Free Wall and Septum

Right ventricular myocardial protection during cardiac surgery continues to be a challenge. Retrograde delivery of cardioplegia has been shown to perfuse left ventricular regions subtended by critical coronary stenosis and not adequately protected by antegrade delivery. However, the distribution of cardioplegia from the coronary sinus to the right ventricle remains in question. A reliable means for assessing such flow distribution intraoperatively is provided by contrast echocardiography. It was hypothesized that conventional use of coronary sinus catheters for retrograde cardioplegia delivery does not reliably perfuse the myocardial region subtended by the right coronary artery. Six patients scheduled to undergo elective coronary artery bypass surgery were evaluated with contrast echocardiography to determine the distribution of retrograde-delivered cardioplegia into the right ventricle. Sonicated Renografin-76 (Squibb Diagnostics, Princeton, NJ) was injected during retrograde delivery of cold crystalloid cardioplegia solution and continuous two-dimensional ultrasound imaging of the heart. On-line videodensitometric analysis was performed with a digital ultrasound system. The area under the curve and peak pixel intensity were determined for the anterior septum, the posterior septum, and the right ventricular free wall for each contrast injection. Recorded VHS videotape images of contrast-enhanced perfusion patterns were also reviewed and scored. On-line acoustic-densitometric analysis showed that right ventricular posterior and anterior septal peak pixel intensities were 4.8 +/- 3.2 and 7.3 +/- 1.5, respectively, compared with only 1.6 +/- 1.2 (p < or = 0.05) in the right ventricular free wall.(ABSTRACT TRUNCATED AT 250 WORDS)

Problems Associated with Coagulation Monitoring during Cardiovascular Surgery

Despite the success of cardiac surgery and the improvement of cardiopulmonary bypass (CPB) instruments, life-threatening bleeding after CPB remains a serious problem that necessitates transfusion of blood components in a high percentage of patients and sometimes requires re-exploration. The incidence of hemorrhage is 5% to 18% in patients who have undergone open-heart procedures (1-4). Many different disorders can occur in patients undergoing CPB; this complicates the identification of specific causes and often delays effective treatment. The modification of routine coagulation tests and the application of new methods of detecting and treating coagulation abnormalities are focused on the reduction of morbidity and mortality in CPB patients. Thromboelastography (TEG) has been utilized for guiding the therapy of postoperative hemorrhage in cardiac patients (5). A system for quantitative determination of heparin concentration is now commercially available, which may obviate the disadvantages of the routine activated clotting time (ACT) measurement. It has recently been reported that, because of the anticoagulation effects of aprotinin, the need for heparin can be reduced in patients given aprotinin (6).

Validity of Continuous Cardiac Output Measured by a Doppler Pulmonary Artery Catheter Versus Thermodilution, and Effect of Distal Angle on the Variance Between Methods

Continuous monitoring of cardiac output in patients with cardiac dysfunction or hemodynamic instability is desirable, especially if the patient is in critical condition. For the anesthesiologist, continuous monitoring of cardiac output may be helpful because it provides information which may allow more appropriate management of events during critical periods, such as weaning from cardiopulmonary bypass in cardiac surgery, or cross-clamping and declamping of the aorta in vascular surgery. A pulmonary artery catheter that allows both intermittent and continuous Doppler measurements of cardiac output has been developed (Flocath, Cardiometrics Inc., CA). In high-risk patients, we tested the hypothesis that the Doppler-estimated cardiac output (DECO) was identical to the thermodilutional cardiac output (TDCO), and that the DECO changed similarly in direction and magnitude when the TDCO changed. Further, we investigated the change in cardiac output with both techniques when the distal angle of the Flocath was altered.