Biomedical subjects
J R Pepper
Publications and source records attributed to J R Pepper.
Gastrointestinal complications in 4473 patients who underwent cardiopulmonary bypass surgery.
Thirty-nine gastrointestinal complications occurred in 35 of 4473 patients (0.78 per cent) who underwent surgery involving cardiopulmonary bypass during an 8-year period. The mortality rate when one of these complications occurred was 22 (63 per cent) representing 11.5 per cent of the 191 deaths from all causes in the series. The relative risk of developing a gastrointestinal complication was 1:249 when the heart was not opened, 1:66 when it was and 1:5 after cardiac transplantation. Gastrointestinal bleeding (n = 20) was the most common complication of whom nine (45 per cent) died, followed by intestinal infarction (n = 12) with eight (67 per cent) deaths and acute pancreatitis (n = 6) all of whom died. There was one death after surgery for gastrointestinal bleeding (n = 7). No patient survived bowel infarction without operation but resection was possible in five of the eight who underwent surgery, four of whom survived. The results demonstrate that surgical intervention is not associated with undue mortality but inappropriate conservative therapy is poorly tolerated in this high-risk group.
Vascular reactivity of human internal mammary and gastroepiploic arteries.
Patency rates of bypass graft conduits are thought to be influenced by the determinants of vascular tone. This study has comparatively examined the response of the human internal mammary and gastroepiploic arteries to potassium, noradrenaline, dopamine, 5-hydroxytryptamine, thromboxane, and histamine. The response to potassium was significantly greater in the gastroepiploic artery (Emax = 79.5 +/- 9.6 mN) than in the internal mammary artery (Emax = 27.0 +/- 6.4 mN). Dose-related constrictions were observed in both vessels to all agonists except histamine, which was ineffective in the gastroepiploic artery. Noradrenaline and dopamine produced comparable dose-related constrictions in each vessel, with similar EC50 and Emax (expressed as a percentage of potassium response) values, but 5-hydroxytryptamine (Emax, gastroepiploic = 10.8% +/- 1.9%; internal mammary = 71.8% +/- 21.2%) and thromboxane (Emax, gastroepiploic = 116.7% +/- 4.0%; internal mammary = 169.6% +/- 19.4%) were more efficacious in their constriction of the mammary artery; the potencies were similar. We conclude that there is a heterogeneity of response to some vasoconstrictors between the human internal mammary and gastroepiploic arteries. The internal mammary artery may be more predisposed to events that initiate vasospastic disorders.
False aneurysm of the right internal mammary artery.
False aneurysm of the internal mammary artery is an uncommon complication of median sternotomy. Clinical and radiological findings of 2 such cases are presented. At operative exploration neither was directly related to the presence of a sternal wire.
Experimental model of left ventricular failure.
A model of chronic cardiac failure has undergone extensive hemodynamic investigation. Under anesthesia the homonymous and second diagonal coronary arteries of sheep have been ligated. The resulting myocardial infarction caused significant acute hemodynamic impairment (paired two-tailed t tests), mean pulmonary artery pressure increasing from 7.31 +/- 0.94 to 13.80 +/- 1.19 mm Hg (p less than 0.001), pulmonary artery diastolic pressure increasing from 4.94 +/- 1.03 to 11.13 +/- 1.27 mm Hg (p less than 0.001), and directly measured left ventricular end-diastolic pressure increasing from 9.31 +/- 1.52 to 17.42 +/- 1.82 mm Hg (p less than 0.001) after infarction documented with invasive monitoring. There was a hemodynamically significant left ventricular aneurysm (paired two-tailed t tests) in animals studied 3 months later, with increased mean pulmonary artery pressure from 7.20 +/- 1.15 to 13.80 +/- 2.00 mm Hg (p = 0.009), an increase in pulmonary artery diastolic pressure from 4.60 +/- 1.30 to 12.10 +/- 2.06 mm Hg (p = 0.006), and an increase in left ventricular end-diastolic pressure from 11.00 +/- 1.94 mm Hg before infarction to 17.00 +/- 2.69 mm Hg (p = 0.038). We conclude that this is a useful model of chronic left ventricular failure that is reproducible and applicable to investigations of therapeutic options in chronic heart failure.
Right ventricular dynamic cardiomyoplasty: an experimental model.
The effectiveness of dynamic cardiomyoplasty as a means of haemodynamic support in heart failure remains controversial. We have undertaken a study of right ventricular dynamic cardiomyoplasty in sheep using intravenous propranolol to provoke heart failure. Muscle conditioning was performed with cardiomyostimulators following a previously established protocol. We performed multiple invasive measurements of haemodynamic parameters including arterial blood pressure, cardiac output, pulmonary artery capillary wedge pressure, right ventricular dp/dt and end diastolic pressures. These were performed before induction of heart failure, after induction of heart failure, and with pacing of the cardiomyoplasty flap in established heart failure. Our results confirm that we were able to establish significant heart failure and that subsequent pacing of the conditioned muscle flap was able to return cardiac output and right ventricular function to their pre-failure control levels.
Bronchoalveolar lavage in the prediction of post-thoracotomy chest infection.
A prospective study was carried out on 75 patients undergoing pulmonary surgery to determine the relationship between perioperative lung flora and postoperative infections. Seventy-five patients having pleurectomy or pneumonectomy received cefuroxime prophylaxis; 1.5 g i.v. at induction followed by 6 further doses of 0.75 g i.v. over 48 h. Bronchoalveolar lavage samples were taken perioperatively via bronchoscopy in pleurectomy patients and from excised lung in patients undergoing lung resection. Patients were monitored for development of chest infection during the first 10 days after operation. Bacterial pathogens were cultured from 12 out of 54 lavage samples. The most common pathogen was Haemophilus influenzae and all the organisms were sensitive to cefuroxime. Eight patients (10.7%) developed postoperative chest infection. The likelihood of developing postoperative chest infection was 42% (5 out of 12 patients) in those patients whose lavage culture was positive for bacterial pathogens compared to 4.8% (2 out of 42 patients) for those whose culture was negative (chi 2 test, p less than 0.001). These results suggest that the culturing of bacterial pathogens from lavage samples from resected lung is a significant predictor of postoperative chest infection in patients undergoing pulmonary resection.
Development of mock circulation models for the assessment of counterpulsation systems.
STUDY OBJECTIVE: This study entailed the development of mock circulation models to assess and compare the haemodynamic efficacy of extra-aortic counterpulsation (using trained skeletal muscle wrapped around the proximal descending aorta) and conventional intra-aortic balloon counterpulsation. DESIGN AND EXPERIMENTAL MATERIALS: Hydraulic Windkessel type lumped parameter models were used either in conjunction with native skeletal muscle or as a dynamic simulation of counterpulsation. The haemodynamic performance of the wrapped latissimus dorsi muscle of the normal sheep was assessed using an artificial load to simulate the pressurised proximal descending aorta. Mock circulation models of counterpulsation comprised Windkessel compliance chambers, laminar flow resistors, a blood analogue, a prosthetic blood pump, and a purpose made hydraulic counterpulsator. MEASUREMENTS AND MAIN RESULTS: An electrically stimulated muscle wrap, 5 cm in length, previously trained for 2 weeks at 3 V and 35 Hz, was assessed for haemodynamic performance in a mock circulation: volume of fluid displaced = 14.1(SD 1.8) ml; pressure increase from 100 mm Hg = 14.9(2.1) mm Hg; external work per contraction cycle = 180(70)mJ; external mean power = 800(100) mW. In a simulation of intra-aortic balloon counterpulsation, haemodynamic benefit (ie, an increase in proximal flow rate and endocardial viability ratio and a reduction in left ventricular stroke power) was assessed with respect to defined parameters. CONCLUSIONS: This paper demonstrates the potential of the mock circulation models both for the investigation of muscle wrap performance and for the comparison of extra-aortic muscle with intra-aortic balloon counterpulsation.
Spontaneous rupture of the oesophagus (Boerhaave's syndrome): conservative versus surgical management.
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False-negative dye-test findings in a case of fatal toxoplasmosis associated with cardiac transplantation.
False-negative dye-test results were recorded in a case of fatal toxoplasmosis associated with cardiac transplantation. Serological and histological data require individual consideration in cases of suspected toxoplasma infection of the immunocompromised.
Noninvasive monitoring of human cardiac allograft rejection.
The frequency of donor-reactive cytolytic T lymphocytes was measured in the peripheral blood mononuclear cell population of a group of 12 cardiac allograft recipients immediately before and at various time points after transplantation. At each of the time points after transplantation the donor heart was biopsied and the rejection status of the graft was determined by applying standard histological criteria. The results of this study showed that the preoperative frequency of donor-reactive cytolytic T lymphocytes in the blood was not predictive of a future tendency toward graft rejection. However, when all the data were examined it was apparent that the frequency of donor-reactive cytolytic T lymphocytes was significantly higher (P less than 0.05) in blood samples from patients whose simultaneous biopsy showed histological evidence of acute cardiac allograft rejection than in blood samples from transplant patients showing no evidence of rejection.
Skeletal muscle ventricles in circulation as aortic diastolic counterpulsators: twelve-month update.
In previous studies, we have shown that canine skeletal muscle ventricles (SMVs) of various designs could develop stroke work intermediate between that of the canine left and right ventricle. We have subsequently reported that SMVs could be used as aortic diastolic counterpulsators. In some animals the SMVs pumped blood effectively for several weeks. Thromboembolism, however, caused renal failure, which was responsible for the demise of the longest surviving animals. More recently, we have studied a group of 15 dogs that had skeletal muscle ventricles constructed from their latissimus dorsi muscle and lined with autogenously derived tissues, either pleura, pericardium or fibrous tissue induced by a Teflon mandrel. We now report on one of those animals, that has survived more than 1 year. She remains active and in apparent good health with no clinical evidence of thromboemboli. Her SMV continues to generate effective aortic diastolic counterpulsation.
Leaking thoraco-abdominal aortic aneurysm presenting with a massive left haemothorax: a clinical trap.
A case is described in which a patient, who had had an aortic aneurysm repair 10 years previously, presented with a thoraco-abdominal aortic aneurysm which ruptured immediately above the previous graft. The implications for the management of patients with an abdominal aortic aneurysm repair are discussed.
Boerhaave's syndrome.
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Class II major histocompatibility complex antigens on cardiac endothelium: an early biopsy marker of rejection in the transplanted human heart.
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Surgical treatment of hypertrophic obstructive cardiomyopathy.
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Post-infarction ventricular septal defect: the importance of site of infarction and cardiogenic shock on outcome.
Sixty-eight patients operated upon for post-infarction VSD from 1980-1987 have been reviewed to identify incremental risk factors which influence survival. Univariate and multivariate analysis was performed on 19 parameters and showed the following in decreasing order of importance to be significantly associated with non-survival: (1) operation within 24 h of occurrence of the VSD; (2) inferior infarct preceding the VSD; (3) requirement for inotropic support preoperatively; (4) preoperative cardiogenic shock; (5) a lower mean pulmonary artery pressure; (6) a lower mean wedge pressure; (7) a lower mean systolic pressure. The presence of a graft to the right coronary artery was associated with a better prognosis. Age, sex, diastolic blood pressure, balloon pumping, mean plasma urea, right atrial pressure, extent of coronary disease, number of coronary grafts, grafts to the left coronary system and method of myocardial preservation had no influence on survival.
Prediction of neurological damage after cardiopulmonary bypass surgery. Use of the cerebral function analysing monitor.
Sixty-five patients who had coronary artery graft surgery were subjected to detailed neuropsychometric assessment before operation and twice again within 7 days after operation. They were monitored continuously with a cerebral function analysing monitor during the operation. The results of the peroperative cerebral monitoring were compared on completion of the study with the neuropsychometric assessments. Seventy-six percent of the patients with a significant neuropsychometric deficit after operation also showed significant peroperative changes on the analysing monitor; the majority occurred immediately after the start of perfusion. Twenty-eight patients failed to demonstrate any evidence of neuropsychometric deficit and six (21%) of these also showed significant peroperative changes. All patients whose traces demonstrated more than one significant change during the peroperative course had a significant neuropsychometric deficit afterwards.