Flow dynamics of a novel counterpulsation device characterized by CFD and PIV modeling.

BACKGROUND: Historically, single port valveless pneumatic blood pumps have had a high incidence of thrombus formation due to areas of blood stagnation and hemolysis due to areas of high shear stress. METHODS: To ensure minimal hemolysis and favorable blood washing characteristics, particle image velocimetry (PIV) and computational fluid dynamics (CFD) were used to evaluate the design of a new single port, valveless counterpulsation device (Symphony). The Symphony design was tested in 6-h acute (n=8), 5-day (n=8) and 30-day (n=2) chronic experiments in a calf model (Jersey, 76 kg). Venous blood samples were collected during acute (hourly) and chronic (weekly) time courses to analyze for temporal changes in biochemical markers and quantify plasma free hemoglobin. At the end of the study, animals were euthanized and the Symphony and end-organs (brain, liver, kidney, lungs, heart, and spleen) were examined for thrombus formations. RESULTS: Both the PIV and the CFD showed the development of a strong moving vortex during filling phase and that blood exited the Symphony uniformly from all areas during ejection phase. The laminar shear stresses estimated by CFD remained well below the hemolysis threshold of 400 Pa inside the Symphony throughout filling and ejection phases. No areas of persistent blood stagnation or flow separation were observed. The maximum plasma free hemoglobin (<10mg/dl), average platelet count (pre-implant = 473 ± 56 K/µl and post-implant = 331 ± 62 K/µl), and average hematocrit (pre-implant = 31 ± 2% and post-implant = 29 ± 2%) were normal at all measured time-points for each test animal in acute and chronic experiments. There were no changes in measures of hepatic function (ALP, ALT) or renal function (creatinine) from pre-Symphony implantation values. The necropsy examination showed no signs of thrombus formation in the Symphony or end organs. CONCLUSIONS: These data suggest that the designed Symphony has good washing characteristics without persistent areas of blood stagnation sites during the entire pump cycle, and has a low risk of hemolysis and thrombus formations.

A new method of monitoring recovery and weaning the Thoratec left ventricular assist device.

BACKGROUND: Recent scientific and clinical data suggest that chronic mechanical ventricular unloading may lead to myocardial recovery. Evaluating and monitoring patients for myocardial recovery and the optimal methods of weaning the left ventricular assist device are not well defined. METHODS: Six patients with advanced heart failure and severe mitral regurgitation have undergone successful bridge to recovery using a Thoratec left ventricular assist device. Data that details their monitoring for myocardial recovery and weaning from the left ventricular assist device were prospectively collected. RESULTS: Clinical data collected during the recovery phase included chest roentgenogram, echocardiography, plasma norepinephrine, tumor necrosis factor-alpha, bioimpedance, and cardiopulmonary exercise testing (peak oxygen consumption). Normalization of these variables with a 10% increase in the peak oxygen consumption was obtained before weaning. The Thoratec device rate and percent systole were manipulated to allow gradual reloading of the ventricle. The weaning process occurred for more than 5 to 10 days to allow time for observation of the ventricle and its response to the increasing workload. CONCLUSIONS: Select patients with advanced congestive heart failure and severe mitral insufficiency can benefit from mechanical device support. We describe our technique of monitoring for myocardial recovery using clinical variables. Our technique of weaning allows for gradual reloading of the ventricle and a longer period of observation before device removal. Additional research is needed to determine which variables will accurately predict long-term myocardial recovery and the optimal weaning method.

Surgical management of heart failure.

Surgical therapy for congestive heart failure can offer gratifying results in selected elderly patients. Several trials have shown a survival advantage for surgical revascularization compared with medical therapy in the treatment of ischemic cardiomyopathy. Aortic valve replacement is highly effective in treating elderly patients with heart failure caused by severe aortic stenosis, and stentless aortic valves seem to provide a survival advantage in elderly patients with low-gradient aortic stenosis. Mitral valve repair with or without coronary revascularization has been used successfully in patients with severe mitral regurgitation. Transplantation is a viable but rarely used option for elderly patients with congestive heart failure. Totally implantable ventricular assist devices are an exciting new option for elderly patients with congestive heart failure who are not heart transplantation candidates.

An unusual case of hypoxia from benzocaine-induced methemoglobinemia.

Hypoxemia during bronchoscopy occurs frequently. It can usually be managed by supplemental oxygen and bronchodilators or, in some cases, occasionally stopping the procedure. Benzocaine spray is commonly used as a topical anesthetic agent during bronchoscopy. However, it has been associated with the development of methemoglobinemia. The following is a case report of hypoxia during bronchoscopy from benzocaine-induced methemoglobinemia and its management.

Modified minimally invasive technique for greater saphenous vein harvesting.

A technique is described for minimally invasive harvesting of the greater saphenous vein. This technique requires no new or disposable equipment, thus adding no additional cost to the procedure. It is rapid and reliable, and it can be performed in the majority of patients requiring greater saphenous vein for coronary artery bypass grafting.

Coronary bypass grafting for single-vessel coronary artery disease: a 17-year review with short- and long-term follow-up.

STUDY OBJECTIVES: We reviewed our short- (30 days) and long-term (up to 17 years) experience with surgical revascularization for patients with angiographically documented isolated single-vessel coronary artery disease. DESIGN: Retrospective study of single-vessel coronary artery bypass procedures performed from January 1980 through June 1996. During this time, 100 consecutive patients underwent a single-vessel coronary artery bypass. All patients were men with a mean age of 59+/-9 years (range, 35 to 78 years) and a mean ejection fraction of 56+/-8% (range, 35 to 77%). The vessels bypassed included the left anterior descending in 66 (66%), right coronary artery in 31 (31%), and the obtuse marginal in 3 (3%). RESULTS: Short-term results reveal no deaths and six (6.0%) complications. Long-term follow-up by chart review and telephone survey was available in 87 (87%) patients at a mean of 46.9 months (range, 12 to 151 months). Cumulative freedom from angina and repeated revascularization was 93% and 98% at 1 year and 55% and 81% at 10 years, respectively (Kaplan-Meier). CONCLUSION: Single-vessel coronary artery bypass for isolated single-vessel disease can be performed with minimal morbidity and no mortality and provides excellent long-term relief of angina.

Abdominal complications after lung transplantation.

BACKGROUND: Serious abdominal complications after heart and heart-lung transplantation have been a well-documented source of morbidity and mortality in this patient population. This report reviews the incidence and spectrum of abdominal complications occurring in lung transplant recipients at a single institution. METHOD: Between January 1988 and July 1993, 75 patients underwent lung transplantation (58 single lung, 16 bilateral single lung, and 1 double lung) at the University of Minnesota. RESULTS: Twelve patients (16%) sustained 20 abdominal complications. There were 11 early abdominal complications (< or = 30 days after transplantation) including prolonged adynamic ileus (4), diaphragmatic hernia after omental wrap (3), ischemic bowel (2), colitis with hemorrhage (1), and splenic injury after colonoscopy (1). There were nine late abdominal complications (range, 32 days to 28 months after transplantation) including colonic perforation (4), cholelithiasis/choledocholithiasis (2), development of a mesenteric pseudoaneurysm (1), fungal hepatic abscess (1), and intraabdominal hemorrhage (1). Twenty-six procedures were performed for management of the abdominal complications including: colonoscopy (7), colectomy (5), repair of diaphragmatic hernia (3), colostomy takedown (4), small-bowel resection (2), open cholecystectomy with common bile duct exploration (1), open cholecystectomy (1), splenectomy (1), mesenteric arterial pseudoaneurysm embolization (1), and percutaneous liver biopsy (1). Four patients died of causes attributable to their abdominal complications. CONCLUSIONS: In each case in which a death occurred, there was a delay between the onset of symptoms and diagnosis and intervention of more than 6 days. Abdominal complications accounted for 22% of all deaths in our lung transplantation group. A high index of suspicion and early recognition and intervention will decrease the morbidity and mortality caused by abdominal complications in lung transplant patients.

Pediatric heart transplantation: results of 2- and 5-year follow-up.

Pediatric heart transplantation has become an accepted method of treatment for certain pediatric heart disease. From July 1986 to January 1993, we performed 25 orthotopic pediatric heart transplantations at the University of Minnesota Hospital and Clinics in 16 male patients and nine female patients. The average age was 8.5 years with a range from 7 days to 18 years. Three of the patients were younger than 1 year of age. The indications for transplantation included congenital heart disease in six patients and cardiomyopathy in 19 patients. Four of the patients with congenital heart disease had previously undergone a cardiac surgical procedure. Two patients with cardiomyopathy had mechanical assist devices in place at the time of transplantation. Donor age ranged from 2 months to 36 years. The donor organ ischemic time ranged from 60 minutes to 329 minutes, with an average of 191 minutes. Follow-up ranged from 6 to 84 months. Overall, there were seven deaths (28%) in the patients undergoing transplantation. Of the seven deaths, four (16%) were early (within 30 days) and three (14.3%) were late. The four early deaths were a result of donor organ failure, and the three late deaths a result of acute rejection. The 2-year survival for patients with a minimum 24-month evaluation was 79% (15 of 19). Of 12 patients available for 5-year assessment, 75% (9 of 12) were alive and doing well at the time this article was written. Pediatric heart transplantation can provide good intermediate and long-term survival for selected pediatric patients.

Internal mammary artery for arterial pressure monitoring after pediatric cardiac operations.

Establishing and maintaining arterial access in pediatric cardiac operations is a frequent and sometimes frustrating problem. We have modified a procedure commonly used in our research laboratory for arterial pressure monitoring and applied it successfully to the pediatric cardiac surgical patient. The internal mammary artery can provide reliable arterial access in the postoperative period.

A fifteen-year wound surveillance study after coronary artery bypass.

Wound infections after coronary artery bypass operations have been continuously monitored at the Minneapolis Veterans Affairs Hospital for 15 years. All patients were followed up for 30 days. From 1977 to 1991, 2,402 coronary artery bypass operations were performed, and wound infections developed in 125 (5%) patients. There were 71 (3%) chest infections of which 33 (1.4%) were major and 38 (1.6%) superficial. Greater than 94% of these grew only a single organism, of which 74% were Staphylococcus species. There were 63 (2.6%) leg wound infections. More than 50% of these grew multiple organisms, of which 68% were enteric in origin. Nine (0.4%) patients had simultaneous chest and leg infections. Wound infections were diagnosed an average of 15.3 +/- 6.7 (range, 4 to 30) days postoperatively, with 50% occurring after discharge from the hospital. Of 14 variables evaluated by multivariate logistic regression analysis, only steroids (p = 0.005) and diabetes (p = 0.003) were identified as independent risk factors for wound infections. Patients taking steroids or with diabetes tended to have chest infections, whereas obese patients tended to have more leg infections (p = 0.08). During an interval in the surveillance program, a trend toward increasing infections was identified and successfully reversed.

Aortic diameter as a function of age, gender, and body surface area.

BACKGROUND: An aortic aneurysm is defined as a 50% or greater increase in diameter compared with normal levels or the level of the left renal vein. However, normal diameters for many aortic segments are not known, and the aortic segment at the left renal vein may be enlarged. The purpose of this study was to determine normal diameters of the thoracic and abdominal aortas in relationship to age, gender, and body size. METHODS: Aortic diameters (ADs) were determined at four anatomic levels: thoracic aorta, abdominal aorta at the celiac axis, renal arteries, and midway between the renal arteries and the bifurcation. ADs were determined with the use of a video analyzer and an electronic caliper. Computed tomographic scans (n = 389) obtained for nonvascular diagnoses were analyzed according to gender, age, height, weight, and body surface area (BSA). RESULTS: At all levels and in each decade the AD is significantly greater in men than in women (p < 0.0001). BSA is a better predictor of size than height or weight. AD increased with age at all levels, and there was a positive correlation between the AD and BSA and gender. Expected ADs for each aortic segment may be calculated according to regression equations. Age-, gender-, and BSA-matched patients with abdominal aortic aneurysms revealed significant enlargements in all proximal aortic segments. CONCLUSIONS: AD at a given level is a function of gender, age, and BSA. When these variables are known, it is possible to calculate an expected AD. The AD is greater at all levels in patients with abdominal aortic aneurysms and in men compared with women.

Extracorporeal membrane oxygenation after lung or heart-lung transplantation.

Extracorporeal membrane oxygenation (ECMO) has proven to be life-saving in cases of reversible lung injury. One potential application of ECMO in the field of lung transplantation is the support of the patient with acute pulmonary failure immediately after transplantation until the transplanted lung has resumed satisfactory gas transfer function. The authors have had experience with ECMO in three patients who have had acute pulmonary failure and inadequate oxygenation after bilateral single lung (BSLT) or heart-lung transplantation (HLT). Patient 1 is a 47-year-old woman with alpha-1 antitrypsin deficiency who underwent a HLT and experienced fulminant pulmonary edema secondary to an intraoperative coagulopathy that required massive transfusion. Patient 2 was a 45-year-old man with a patent ductus arteriosus (PDA) that resulted in Eisenmenger's complex. Patient 2 underwent an HLT and experienced acute pulmonary failure. Patient 3 is a 58-year-old woman with an atrial septal defect (ASD) and pulmonary hypertension who underwent repair of the ASD and BSLT. Patient 3 experienced complete atelectatic collapse of the right lung and pulmonary edema of the left lung. These three patients had PO2 measurements of 23, 39, and 23 mmHg, respectively, despite receiving 100% FiO2 and maximal ventilatory support. All three patients were subsequently placed on ECMO and had improvement of their oxygenation. Patients 1 and 3 were successfully weaned from ECMO and extubated on post-operative day (POD) 21 and 16, respectively. Patient 2 had significant improvement in oxygenation but died on POD 4 of persistent mediastinal hemorrhage.(ABSTRACT TRUNCATED AT 250 WORDS)

Infiltrating syringomatous adenoma of the nipple.

Infiltrating syringomatous adenoma of the nipple is a distinct, benign clinical entity. It is similar histologically to a syringoma, a benign tumor originating in the ducts of the dermal sweat glands. When located in the nipple, this lesion has been mistaken for nipple duct adenoma or tubular carcinoma. Infiltrating syringomatous adenoma of the nipple is locally infiltrating but does not metastasize. Appropriate local management depends on an accurate diagnosis. Following is a case report, review of the literature, and therapeutic options for infiltrating syringomatous adenoma of the nipple.

Hemodynamic monitoring in respiratory care.

Continuous, invasive hemodynamic monitoring of patients in respiratory failure is an important aspect of total respiratory care. Understanding both the technical and physiological principles underlying hemodynamic monitoring is therefore important for respiratory care practitioners. This review is designed to meet this need by (1) addressing the technical aspects of hemodynamic monitoring (catheters, transducers, and monitors), (2) discussing the determinants of commonly measured hemodynamic variables (intravascular pressures and cardiac output), and (3) offering an orderly approach to hemodynamic data that allows for rapid determination of the patient's physiologic state and appropriate diagnostic possibilities. These principles are illustrated by five examples.