Thomas J. Vander Salm

Reduction of bleeding after heart operations through the prophylactic use of epsilon-aminocaproic acid

UNLABELLED Excessive postoperative bleeding after heart operations continues to be a source of morbidity. This prospective double-blind study evaluated epsilon-aminocaproic acid as an agent to reduce postoperative bleeding and investigated its mode of action. One hundred three patients were randomly assigned to receive either 30 gm epsilon-aminocaproic acid (51 patients) or an equivalent volume of placebo (52 patients). In a subset of these patients (14 epsilon-aminocaproic acid, 12 placebo), tests of platelet function and fibrinolysis were performed. RESULTS By multivariate analysis, three factors were associated with decreased blood loss in the first 24 hours after operation: epsilon-aminocaproic acid versus placebo (647 ml versus 839 ml, p = 0.004), surgeon 1 versus all other surgeons (582 ml versus 978 ml, p = 0.002), and no intraaortic balloon versus intraaortic balloon pump use (664 ml versus 1410 ml, p = 0.02). No significant differences in platelet function could be demonstrated between the two groups. Inhibited fibrinolysis, as reflected by less depression of the euglobulin clot lysis and no rise in D-dimer levels, was significant in the epsilon-aminocaproic acid group compared with the placebo group. CONCLUSION The intraoperative use of epsilon-aminocaproic acid reduces postoperative cardiac surgical bleeding.

Evaluation of right atrial and biatrial temporary pacing for the prevention of atrial fibrillation after coronary artery bypass surgery

OBJECTIVES The purpose of this study was to determine if atrial pacing is effective in reducing postoperative atrial fibrillation (AF). BACKGROUND Atrial fibrillation after coronary artery bypass grafting (CABG) is a common problem for which medical management has been disappointing. Atrial-based pacing has become an attractive nonpharmacologic therapy for the prevention of AF. METHODS Sixty-one post-CABG patients (mean age = 65 years) were randomized to one of three groups: no atrial pacing (NAP), right atrial pacing (RAP) or biatrial pacing (BAP). Each patient had one set of atrial wires attached to both the right and left atria, respectively, at the conclusion of surgery. Patients in the RAP and BAP groups were continuously paced at a rate of 100 pulses per minute for 96 h or until the onset of sustained AF (>10 min). All patients were monitored with Holter monitors or full disclosure telemetry to identify the onset of AF. The primary end point of the study was the first onset of sustained AF. RESULTS There was no significant difference in the proportion of patients developing AF in the three groups (NAP = 33%; RAP = 29%; BAP = 37%; p > 0.7). However, for the subset of patients on beta-adrenergic blocking agents after CABG, there was a trend toward less AF in the paced groups. There were no serious complications related to pacing, although in three patients the pacemaker appeared to induce AF by pacing during atrial repolarization. CONCLUSIONS Continuous right or biatrial pacing in the postoperative setting is safe and well tolerated. We did not find that post-CABG pacing prevented AF in this pilot study; however, the role of combined pacing and beta-blockade merits further study.

Investigation of noninvasive in vivo blood hematocrit measurement using NIR reflectance spectroscopy and partial least-squares regression

Hematocrit (Hct), the volume percent of red cells in blood, is monitored routinely for blood donors, surgical patients, and trauma victims and requires blood to be removed from the patient. An accurate, noninvasive method for directly measuring hematocrit on patients is desired for these applications. The feasibility of noninvasive hematocrit measurement by using near-infrared (NIR) spectroscopy and partial least-squares (PLS) techniques was investigated, and methods of in vivo calibration were examined. Twenty Caucasian patients undergoing cardiac surgery on cardiopulmonary bypass were randomly selected to form two study groups. A fiber-optic probe was attached to the patients forearm, and NIR spectra were continuously collected during surgery. Blood samples were simultaneously collected and reference Hct measurements were made with the spun capillary method. PLS multivariate calibration techniques were applied to investigate the relationship between spectral and Hct changes. Single patient calibration models were developed with good cross-validated estimation of accuracy (∼ 1 Hct%) and trending capability for most patients. Time-dependent system drift, patient temperature, and venous oxygen saturation were not correlated with the hematocrit measurements. Multi-subject models were developed for prediction of independent subjects. These models demonstrated a significant patient-specific offset that was shown to be partially related to spectrometer drift. The remaining offset is attributed to the large spectral variability of patient tissue, and a significantly larger set of patients would be required to adequately model this variability. After the removal of the offset, the cross-validated estimation of accuracy is 2 Hct%.

Effects of long-term amiodarone therapy on the defibrillation threshold and the rate of shocks of the implantable cardioverter-defibrillator

The effects of long-term amiodarone therapy on the defibrillation thresholds and the rate of shocks were evaluated in 62 patients who had implantation of an automatic cardioverter-defibrillator (n = 53) or prophylactic implantation of patch electrodes (n = 9) who were survivors of sudden cardiac death (n = 34) or had refractory rapid ventricular tachycardia (n = 28). There were 53 men and 9 women, with ages ranging from 18 to 76 years (mean +/- SD, 60 +/- 12). Coronary artery disease occurred in 50 patients (80.6%), cardiomyopathy occurred in six (9.7%), valvular heart disease developed in two (3.2%), primary electrical disease developed in two (3.2%), hypertensive heart disease materialized in one (1.6%), and Ebsteins anomaly occurred in one (1.6%). The left ventricular ejection fraction varied from 10% to 75% (mean, 37 +/- 17%). All patients had failed a mean of 3.9 +/- 1.6 antiarrhythmic drugs prior to implantation of the device. Twenty-eight patients (45%) were taking amiodarone up to the time of surgery, with a mean daily dose of 406 +/- 147 mg (range 200 to 800) and for a mean duration of 6.0 +/- 6.7 months (range 1 to 36 months). The mean defibrillation threshold (DFT) was 12.0 +/- 4.4 joules (range 5 to 20) in the group taking amiodarone and was not significantly different from that of the group not taking amiodarone (n = 32) (mean DFT 12.3 +/- 5.5 joules, range 5 to 30; p = 0.77).(ABSTRACT TRUNCATED AT 250 WORDS)

Prevention of Lower Extremity Ischemia During Cardiopulmonary Bypass via Femoral Cannulation

Prolonged cardiopulmonary bypass requiring femoral arterial cannulation may lead to ipsilateral leg ischemia. A technique described of femoral cannulation via an end-to-side femoral artery graft allows distal femoral perfusion and eliminates the complication of leg ischemia.

Noninvasive, near infrared spectroscopic-measured muscle pH and PO2 indicate tissue perfusion for cardiac surgical patients undergoing cardiopulmonary bypass

ObjectiveTo determine whether near infrared spectroscopic measurement of tissue pH and Po2 has sufficient accuracy to assess variation in tissue perfusion resulting from changes in blood pressure and metabolic demand during cardiopulmonary bypass. DesignProspective clinical study. SettingAcademic medical center. SubjectsEighteen elective cardiac surgical patients. InterventionCardiac surgery under cardiopulmonary bypass. Measurements and Main ResultsA near infrared spectroscopic fiber optic probe was placed over the hypothenar eminence. Reference Po2 and pH sensors were inserted in the abductor digiti minimi (V). Data were collected every 30 secs during surgery and for 6 hrs following cardiopulmonary bypass. Calibration equations developed from one third of the data were used with the remaining data to investigate sensitivity of the near infrared spectroscopic measurement to physiologic changes resulting from cardiopulmonary bypass. Near infrared spectroscopic and reference pH and Po2 measurements were compared for each subject using standard error of prediction. Near infrared spectroscopic pH and Po2 at baseline were compared with values during cardiopulmonary bypass just before rewarming commenced (hypotensive, hypothermic), after rewarming (hypotensive, normothermic) just before discontinuation of cardiopulmonary bypass, and at 6 hrs following cardiopulmonary bypass (normotensive, normothermic) using mixed-model analysis of variance. Near infrared spectroscopic pH and Po2 were well correlated with the invasive measurement of pH (R2 = .84) and Po2 (R 2 = .66) with an average standard error of prediction of 0.022 ± 0.008 pH units and 6 ± 3 mm Hg, respectively. The average difference between the invasive and near infrared spectroscopic measurement was near zero for both the pH and Po2 measurements. Near infrared spectroscopic Po2 significantly decreased 50% on initiation of cardiopulmonary bypass and remained depressed throughout the bypass and monitored intensive care period. Near infrared spectroscopic pH decreased significantly during cardiopulmonary bypass, decreased significantly during rewarming, and remained depressed 6 hrs after cardiopulmonary bypass. Diabetic patients responded differently than nondiabetic subjects to cardiopulmonary bypass, with lower muscle pH values (p = .02). ConclusionsNear infrared spectroscopic-measured muscle pH and Po2 are sensitive to changes in tissue perfusion during cardiopulmonary bypass.

Effectiveness of bi-atrial pacing for reducing atrial fibrillation after coronary artery bypass graft surgery.

Atrial fibrillation (AF) is common after cardiac surgery and adds significant cost and morbidity. The use of prophylactic pacing strategies to prevent post-operative AF has been controversial. We previously performed a pilot study which suggested that the combination of beta-blockers and bi-atrial pacing (BAP) may reduce AF after cardiac surgery.We prospectively randomized 118 patients to continuous BAP for up to 96 hours post-operatively versus standard therapy. All patients were treated with beta-blockers as tolerated. Patients were paced in the AAI mode at a rate of 100 pulses per minute. The primary endpoint of the study was the occurrence of sustained AF (>10 minutes).There was a significant reduction in the incidence of AF in the BAP group among patients undergoing coronary artery bypass graft surgery with or without aortic valve replacement (35% vs. 19% AF; OR=0.38, 95% CI 0.15, 0.93; p <0.05). Including patients undergoing isolated aortic valve surgery (n=7), there remained a strong trend toward a reduction of AF with pacing (no atrial pacing [NAP] vs. BAP; 35% vs. 21% AF; OR=0.48, 95% CI 0.21, 1.11; p=0.08). Patients age 70 or greater benefited most from pacing (NAP vs. BAP; 55 vs. 25% AF; p<0.05), while those less than 70 years of age did not (17 vs. 18% p=NS). There was a significant reduction in the amount of time spent in the intensive care unit among patients receiving BAP (50±40 vs. 37±25[emsp4 ]h; p<0.05).BAP together with beta-blockade after coronary artery bypass graft surgery reduces the incidence of post-operative atrial AF. Elderly patients (age 70 or greater) appear to benefit most, and may be a group to whom this therapy should be targeted.

Prolonged bradyarrhythmias after isolated coronary artery bypass graft surgery

To evaluate clinical and electrocardiographic (ECG) characteristics that may predict the occurrence of bradyarrhythmias after isolated coronary artery bypass graft (CABG) surgery, 1614 consecutive patients who had this procedure performed at our institution from January 1988 to December 1990 were reviewed. Thirteen (0.8%, 7 males and 6 females) patients had prolonged (mean 10.5 +/- 6.5 days) postoperative bradyarrhythmias and required insertion of a permanent pacemaker. Complete heart block occurred in eight patients and sinus node dysfunction in five. These 13 patients (group A) were compared with a group of 490 arbitrarily selected CABG patients (group B) without bradyarrhythmias whose preoperative ECGs were reviewed. Patients in group A were older (mean 69.2 vs 62.8 years; p = 0.0004) and had concomitant left ventricular (LV) aneurysmectomy more frequently (p = 0.02) and internal mammary graft revascularization less frequently (p = 0.022) than group B patients. Review of preoperative ECGs revealed a higher occurrence of complete left bundle branch block (LBBB) (5 of 13 vs 6 of 490; p < 0.0001) and a borderline, more leftward frontal plane QRS axis (-5.3 vs 13.1 degrees, p = 0.068) in group A patients. There were no differences between the groups with respect to gender, number of bypass grafts, location of prior myocardial infarction, and preoperative ECG intervals (PR, QRS, QTc). Multivariate analysis identified the presence of a preoperative LBBB, concomitant LV aneurysmectomy and age > 64 years as independent predictors of severe and prolonged postoperative bradyarrhythmias, mainly complete heart block.(ABSTRACT TRUNCATED AT 250 WORDS)

Mitral Annular Calcification: A New Technique for Valve Replacement

Many dangers attend mitral valve replacement in the presence of dense posterior annular calcification. The procedure described has been successful in 4 patients. The major elements of this procedure include complete ultrasonic debridement of the calcification, reconstitution of the disassembled atrioventricular groove, and retention of the mitral valve leaflets.

Internal mammary artery grafts: The shortest route to the coronary arteries

Inadequate length can limit the use of the internal mammary artery (IMA) for coronary revascularization. By following the shortest route from its origin to the recipient coronary artery, IMA use can be maximized. Seven cadavers were studied to determine that shortest route for the left and right IMAs. The shortest route for the left IMA to the left anterior descending coronary, diagonal, and circumflex coronary arteries was through the pericardium (p less than or equal to 0.01). For the right IMA, the significantly shortest routes were across the anterior heart for the left anterior descending and diagonal arteries, through the right pericardium for the right coronary artery or posterior descending artery, and through the pericardium and transverse sinus for the circumflex artery. Thus, any coronary artery can be reached with an in situ IMA, and the route through the pericardium is markedly shorter to ipsilateral coronary arteries.