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Biomedical subjects

R D Dowling

Publications and source records attributed to R D Dowling.

53 records · Page 3Linked to original sources
PubMed1991

Argon beam coagulation is superior to conventional techniques in repair of experimental splenic injury.

Present management of splenic trauma focuses on splenic preservation. However, conventional operative techniques for splenic salvage are time consuming and frequently ineffective. The purpose of this study was to assess the efficacy of the argon beam coagulator (ABC) in the management of experimental splenic injury. Ten adult miniature pigs were randomized to treatment with either conventional surgical techniques (topical Surgicel, electrocautery, suture-ligation, digital pressure) or splenic repair with the ABC. Three standard splenic injuries were made in each pig: capsular avulsion, splenic laceration, and hemisplenectomy. The ABC was more effective in treating all three types of splenic injury. The time required to achieve hemostasis and total operative time were significantly less in the group treated with the ABC for all three types of splenic injuries (p less than 0.05, Student's t-test, two sided). Operative blood loss was significantly less in the group treated with ABC for avulsion and hemisplenectomy (p less than 0.05, Student's t-test, two sided). Recurrent bleeding was significantly higher in the group treated with conventional techniques (p less than 0.001, Fisher's exact test, two-sided). We conclude that the argon beam coagulator is more effective than conventional techniques in treating experimental splenic injuries. The ABC provides more rapid and reliable hemostasis. Clinical trials using the ABC for splenic injury are warranted.

Animals↗
PubMed1990

Disruption of the aortic anastomosis after heart-lung transplantation.

Disruption of the aorta at the anastomotic site occurred in 4 of 66 consecutive heart-lung transplant recipients and was associated with a 100% mortality. In 3 of these patients, Candida either was cultured from the suture line or was seen in the wall of the aorta at postmortem examination. In 2 of these 3 patients, cultures of material from the donor trachea taken at the time of explanation grew Candida species. Two patients were seen with sudden massive hemorrhage on postoperative day 26 and postoperative day 28. One patient experienced acute decompensation due to right ventricular outflow tract obstruction on postoperative day 30, and the remaining patient was seen 7 months postoperatively with obstruction of both the left main bronchus and the right pulmonary artery caused by extrinsic compression by an aortic pseudoaneurysm. A high index of suspicion should be maintained when transplanting lungs containing Candida species, as we believe there is substantial evidence of donor transmission of the fungal agents. We now include amphotericin B in our antibiotic prophylactic regimen in an attempt to prevent fungal infection because previous treatment has been uniformly unsuccessful. Furthermore, we wrap both the trachea and the aorta with omentum to lessen the likelihood of mediastinal spread of infection to the aortic suture line.

Adolescent↗
PubMed1990

Aerosolized cyclosporine as single-agent immunotherapy in canine lung allografts.

Current systemic immunosuppressive regimens are unable to prevent lung allograft rejection consistently and are associated with significant morbidity and death. Acute rejection has occurred in 40% and chronic rejection in 50% of our lung recipients. We hypothesized that regional immunotherapy with aerosolized cyclosporine would prevent or reduce lung allograft rejection while allowing for low systemic drug delivery. In a canine model of unilateral lung allotransplantation, aerosolized cyclosporine was delivered directly to the allograft. Acute rejection was prevented or reduced in all treated recipients. All control animals had severe acute rejection. Intragraft cyclosporine concentration was high and systemic drug delivery was low, as evidenced by low whole-blood cyclosporine levels and low tissue cyclosporine levels in skeletal muscle. Ninety-five percent of whole-blood trough cyclosporine levels were less than 150 ng/ml. Aerosolized cyclosporine was able to prevent or reduce acute pulmonary rejection and resulted in minimal systemic drug delivery.

Aerosols↗
PubMed1989

Organ procurement for pulmonary transplantation.

Selection of suitable donors is critical to the success of clinical pulmonary transplantation. Requirements for lung donors, management before explantation, and methods of preservation were reviewed for the 70 heart-lung, eight double-lung, and two single-lung transplantations performed at the University of Pittsburgh since 1982. Careful observation of trends of hyperoxygenation studies, chest roentgenograms, and Gram stain and culture results of tracheal secretions, as well as findings on bronchoscopy, can help identify which lungs not only have adequate function but are acceptable for transplantation. In spite of the rigid criteria used, 76% of tracheal cultures from donors deemed acceptable grew organisms. The presence of oropharyngeal flora has been shown to correlate with the development of early intrathoracic infections in the recipient. Prophylactic broad-spectrum antibiotic treatment of the donor is desirable to treat microbial contamination that could cause focal injury to the donor lung and predispose to infection in the recipient. Acceptance of less than ideal donors is ill-advised even though rejection of such donors conflicts with the current shortage of organs.

Graft Survival↗
PubMed1989

Infections in mortally ill cardiac transplant recipients.

A total of 351 cardiac transplantations performed between June 1, 1980, and Sept. 30, 1987, were reviewed to determine if infectious complications were more frequent in those patients requiring preoperative intravenous inotropic support, placement of an intraaortic balloon pump, or mechanical support with a left ventricular assist device or total artificial heart. One hundred forty-nine transplants (45%) were performed in these mortally ill patients. There was no statistically significant difference between patients with and without infection within each support group for the following: the number of in-patient days awaiting a donor heart, the number of days receiving support, the percent of patients with preoperative tracheal intubation, the length of the operation, and the percent of patients requiring reoperation for bleeding. The need for invasive methods of support (intraaortic balloon pump, left ventricular assist device, or total artificial heart) in patients awaiting heart transplantation increases the prevalence of perioperative nonviral infection. Preoperative mechanical support with a left ventricular assist device or total artificial heart significantly increases the risk of infection-related mortality.

Adult↗
PubMed1989

[New trends in combined transplantation of the heart and lungs].

Heart-lung transplantation is a surgical alternative for patients with end-stage lung disease with associated right heart failure. While the procedure is very promising, the morbidity and mortality remain high. The current understanding of the proper selection of candidates, procurement and preservation of donor organs, operative procedure and postoperative care continues to evolve. At the University of Pittsburgh, 70 heart-lung transplantations have been performed since 1982. Early infection and chronic rejection are the major factors influencing survival. Early (less than 2 weeks) intrathoracic infection occurred in 43% of heart-lung transplant recipients, with pneumonia being the most frequent infection. The incidence of pneumonia in heart-lung transplant recipients is twice that in a comparable group of heart recipients. Subclinical pneumonitis in the donor lung, abnormal muco-ciliary clearance and altered allogenic response in the transplanted lung are significant factors associated with the increased incidence of early infections. Chronic rejection, manifested as bronchiolitis obliterans, has occurred in 54% of heart-lung transplantation recipients. Infection caused by cytomegalovirus, Epstein-Barr virus and Pneumocystis carinii have been shown to increase the incidence of bronchiolitis obliterans, as have episodes of acute rejection. Recent reports of a 61% 2-year survival rate represent a substantial improvement over earlier trials. With a better understanding of the pathogenesis of infection in the transplanted lung as well as improved immunosuppressive agents, further improvements in survival can be expected.

Heart-Lung Transplantation↗
PubMedDate not supplied

Clinically available extracorporeal assist devices.

Mechanical circulatory support has been shown to be of benefit to allow recovery after conventional heart surgery and as a successful bridge to heart transplantation. Recent clinical trials with implantable left ventricular assist devices (LVADs) have been completed with these devices showing restoration of normal hemodynamics and successful bridge to transplantation. A major advantage of the implantable devices is the ability for the patient to be discharged and followed up at an outpatient setting. However, multiple advantages to extracorporeal devices still remain, which are the focus of this review. One advantage of the extracorporeal devices is that they can be placed in much smaller patients than currently available implantable LVADs. Also, because of differences in design of the assist devices, the extracorporeal devices can be placed without the need for the cardiopulmonary bypass and with decreased operative time and dissection. Perhaps the biggest advantage of the extracorporeal devices is that they can provide a support for both the right and left side of the heart as opposed to the implantable LVADs, which are only used as left ventricular assist devices. This article describes in detail the advantages and disadvantages of the extracorporeal devices as well as the operative techniques used to implant them. As the number of patients with heart failure continues to rise, so will the need for mechanical circulatory support. Though the majority of these patients will be served by a long-term implantable device, there will remain a subset of patients that will be best suited for treatment with extracorporeal devices.

Assisted Circulation↗
PubMedDate not supplied

Initial experience with the AbioCor implantable replacement heart at the University of Louisville.

Potential benefits of heart transplantation are limited by the severe donor organ shortage. The AbioCor implantable replacement heart has been developed as a potential alternative to heart transplantation. We report our initial experience with the AbioCor in a bovine model. A right thoracotomy was performed for access to the heart and great vessels. After initiation of cardiopulmonary bypass, excision of the native ventricles was followed by orthotopic placement of the IRH and complete implantation of the transcutaneous energy transfer coil, controller, and battery pack. Invasive monitoring of IVC, SVC, carotid artery, pulmonary artery, and left atrial (LA) pressures was performed in all animals. Twelve calves have undergone implantation of the AbioCor. There were three early deaths, one from bleeding, one from respiratory failure, and one from neurodysfunction from low flow during CPB. Nine animals have had a normal recovery and survived a mean of 24.5 days (range, 4-48 days). All the animals have demonstrated excellent hemodynamics with the maintenance of normal pressures in the LA, SVC, IVC, pulmonary artery, and aorta. Adjustment of the right-sided internal hydraulic fluid shunt has allowed for control of right-left balance and, thereby, manipulation of left and right side filling pressures. Late morbidity has consisted of neck wound infection and sepsis, pneumonia, and bleeding. Successful orthotopic implantation of all components of the AbioCor has been achieved in a bovine model. This device has demonstrated restoration of normal hemodynamics and excellent function of the atrial hydraulic shunt to achieve right-left balance.

Animals↗
PubMedDate not supplied

Blood lactic acid levels after artificial heart implantation.

The aim of this study is to investigate blood lactic acid levels after the placement of the AbioCor implantable replacement heart to determine whether circulatory support with the AbioCor device results in adequate tissue perfusion. Tissue perfusion may not be adequate during cardiac surgery, especially with the use of cardiopulmonary bypass (CPB). Inadequate perfusion is usually associated with anaerobic metabolism, metabolic acidosis, and lactate accumulation. Ten calves had implantation of the AbioCor by means of a right thoracotomy. Standard cardiopulmonary bypass was performed during surgery. Lactic acid levels and blood gas analyses were measured. All animals were monitored for pressures in the aorta, pulmonary artery, and left and right atria. The output of the AbioCor was calculated based on beat rate and stroke volume. All animals were rapidly weaned off cardiopulmonary bypass to full AbioCor support and had normal hemodynamics with normal filling pressures. The lactic acid levels were elevated after surgery, peaked at 8 to 12 hours, and then gradually decreased to the normal range 24 hours after surgery. There was a positive relationship between lactate levels, oxygen consumption, and extraction rate, that is, the lactic acid levels were higher in the presence of increased oxygen consumption and increased oxygen extraction rate. There was a negative relationship between lactate levels and oxygen delivery, and arterial and venous oxygen content, that is, the lactic acid levels were higher when oxygen delivery and arterial and venous oxygen contents were low. The pathophysiology of lactic acidosis is uncertain, but is most likely due to inadequate perfusion during cardiopulmonary bypass, and lactate washout after adequate perfusion has been established. The return to aerobic metabolism with clearance of lactate demonstrates that the AbioCor is able to provide complete circulatory support with normal tissue perfusion.

Acidosis, Lactic↗
PubMedDate not supplied

Intraoperative assessment of acute hemodynamic changes after partial left ventriculectomy.

Partial left ventriculectomy (PLV) has been introduced as an alternative surgical therapy for patients with end-stage dilated cardiomyopathy. The physiological benefits of PLV are relatively unknown. Therefore, the objective of this study was to determine the acute effects of PLV by measuring cardiac function before and after PLV. Aortic and left ventricular pressures and aortic flow were measured in eight patients. Continuous, beat-to-beat data were recorded and compared pre-PLV and post-PLV with and without inferior vena cava (IVC) occlusions. PLV increased cardiac output (0.93+/-0.5, p = 0.01) as a result of increased stroke volume (5.12+/-4.24, p = 0.06) and heart rate (14.5+/-8.44, p = 0.02). Contractility (+/- dP/dt, 240.33+/-74.28, p = 0.001) and external work (650.8+/-320.4, p = 0.01) were also improved. Left ventricular end-diastolic elastance (0.15+/-0.14, p = 0.10) nearly doubled after PLV. Our results indicated an improved cardiac function as measured by increased cardiac output, stroke volume, ejection fraction (EF), and contractility.

Cardiac Output↗
PubMedDate not supplied

Intermediate-term results of partial left ventriculectomy.

Partial left ventriculectomy (PLV) has been introduced as an option for patients with end-stage dilated cardiomyopathy. We report the result of a prospective trial of PLV in patients with idiopathic dilated cardiomyopathy, left ventricular end-diastolic diameter (LVEDD) > 7 cm, refractory New York Heart Association (NYHA) Class IV symptoms, and depressed exercise oxygen consumption studies. Sixteen patients underwent a PLV with a mean follow-up of 13 months. Fourteen patients were male. Mean age was 49.6+/-10.5 years (range 30 to 67 years). Left ventricular ejection fraction (LVEF) improved after surgery from 13.9+/-5.6 to 21.0+/-8.4, and this improvement persisted for up to 12 months after operation. LVEDD and NYHA Class also were significantly improved after surgery and for up to 12 months of follow-up. Operative mortality was 6.25%. Twelve-month survival was 86% by Kaplan-Meier analysis. Four (25%) of 16 patients that had initial improvement after PLV developed recurrent heart failure and were listed for transplantation. Freedom from need for listing for heart transplantation was 65% at 12 months. Freedom from death or the need for relisting at 12 months was 56%. PLV can be performed with acceptable early and 12-month mortality. Significant improvements in LVEF, LVEDD, and NYHA Class are seen at up to 12 months of follow-up. Some patients will develop recurrent heart failure and require relisting for heart transplantation.

Adult↗
PubMedDate not supplied

Partial left ventriculectomy: the 2nd International Registry Report 2000.

BACKGROUND: Partial left ventriculectomy (PLV) has been performed without standardized inclusion or exclusion criteria. METHODS: An international registry of PLV was expanded, updated, and refined to include 287 nonischemic cases voluntarily reported from 48 hospitals in 11 countries. RESULTS: Gender, age, ventricular dimension, etiology, ethnology, myocardial mass, operative variation, presence or absence of mitral regurgitation, and transplant indication had no effects on event-free survival, which was defined as absence of death or ventricular failure that required a ventricular assist device or listing for transplantation. Preoperative patient conditions, such as duration of symptoms (> 9 vs < 3 years; p = 0.001), New York Heart Association (NYHA) class (Class IV vs < Class IV; p = 0.002), depressed contractility (fractional shortening [FS] < 5% vs > 12%; p = 0.001), and refractory decompensation that required emergency procedure (p < 0.001) were associated with reduced event-free survival. Five or more cases in each hospital led to significantly better outcomes than the initial four cases. Rescue procedures for 14 patients nonsignificantly improved patient survival (2-year survival 52%) over event-free survival (2-year survival 48%; p = 0.49), with improved NYHA class among survivors (3.6 to 1.8; p < 0.001). Outcome was better in 1999 than in all series before 1999 (p = 0.02) most likely due to patient selection, which was refined to avoid known risk factors such as reduced proportion of patients in NYHA Class IV, FS < 5%, and hospitals with experience in 10 or less cases. A combination of these risk factors could have stratified 17 high-risk patients with 0% 1-year survival and 26 low-risk patients with 75% 2-year event-free survival. CONCLUSION: Avoidance of risk factors appears to improve survival and might help stratify high- or low-risk patients. Although less symptomatic patients with preserved contractility had better results after PLV, change of indication requires prospective randomized comparison with medical therapies or other approaches.

Adolescent↗
PubMedDate not supplied

Intermediate-term results after partial left ventriculectomy for end-stage dilated cardiomyopathy: is there a survival benefit?

BACKGROUND: The mortality of congestive heart failure remains high despite advances in medical therapy. Partial left ventriculectomy (PLV) has been advocated as a surgical alternative for select patients with dilated cardiomyopathy. METHODS: A prospective clinical trial of PLV for patients with end-stage idiopathic dilated cardiomyopathy was performed. Inclusion criteria were left ventricular end-diastolic diameter (LVEDD) greater than 7 cm, refractory New York Heart Association (NYHA) Class IV symptoms, and severely depressed exercise oxygen consumption. RESULTS: Twenty patients underwent PLV with mean follow-up of 21.1 months. Sixteen were male; mean age was 50.1 years +/- 12.0 years (range 25-67 years). Left ventricle (LV) ejection fraction improved after surgery from 14.1% +/- 4.7% to 24.1% +/- 3.1% (p < 0.05, t-test) and this improvement persisted up to 3 years after operation. LVEDD and NYHA Class also were notably improved. There were two early deaths for an operative mortality of 10% (2 of 20 patients). Nine patients after initial improvement in clinical status and LV function developed worsening congestive heart failure (CHF). Six of the 9 ultimately died of complications secondary to CHF. One-, 2-, and 3-year survival rates were 84%, 64%, and 40%, respectively, by Kaplan-Meier analysis. The other three patients required listing for transplantation because of recurrent NYHA Class IV symptoms. Freedom from death or the need for listing for transplantation at 1, 2, and 3 years was 65%, 53%, and 33%, respectively. The remaining nine patients all had improvement in their NYHA classification. CONCLUSIONS: PLV can be performed with acceptable early and intermediate term mortality; survival compares favorably to reports of similar groups of patients treated with medical therapy alone.

Adult↗
PubMedDate not supplied

Influence of the donor lung on development of early infections in lung transplant recipients.

Infection of the lung allograft is the greatest cause of morbidity and mortality after heart-lung transplantation. To better understand the pathogenesis of these infections, we compared the results from cultures of the donor tracheas with the type and prevalence of early intrathoracic infections in the recipients. In the last 37 recipients, intrathoracic infections occurred within 2 weeks of operation in 16 (43%). Organisms isolated from the donor tracheal cultures were different from those associated with early infections, except for three of four recipients with heavy growth of Candida in donor tracheal cultures, in whom fatal invasive candidiasis developed caused by the same species of Candida isolated from the donor culture. Comparisons were made between recipients with (n = 16) and without early infection (n = 21) for age of donors and recipients, ischemic time, length of donor stay in an intensive care unit, donor arterial oxygen pressure, duration of recipient intubation, sterile donor tracheal culture or culture with presence of mouth flora, bacterial pathogens, or Candida, method of lung preservation, and antibiotic prophylaxis of donor. The only factor significantly associated with the onset of early infection was the presence of mouth flora in the donor tracheal culture (p = 0.004, Fisher's exact test, two sided). Multiple logistic regression was performed to test the additional contribution of other covariates after adjusting for the presence of mouth flora. None of the other covariates contributed to the occurrence of early infection. Recipients with early infection had a significantly lower survival compared with those without early infection (p = 0.04) by the Kaplan-Meier survival analysis.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗