Biomedical subjects

P S MacDonald

Publications and source records attributed to P S MacDonald.

8 recordsLinked to original sources

PubMed2002

Patency of superficial femoral vein employed as a crossover femoral artery bypass conduit.

This study assesses the patency of superficial femoral vein used as a crossover femoral artery bypass conduit in patients presenting either with localized groin sepsis, generalized sepsis or in patients with occluded or heavily diseased superficial femoral artery outflow. Twenty patients were followed prospectively with femoral crossover grafts constructed of superficial femoral vein. Twelve patients presented with sepsis and 8 with chronic ischemia from iliac artery occlusion and severely diseased superficial femoral artery outflow. Graft patency was assessed with regular duplex ultrasound examination. There was one perioperative death. Six patients died during the follow-up period. Mean follow-up time was 24.3 months. No graft occluded or required revision. There was no limb loss, graft infection, or graft hemorrhage. Superficial femoral vein offers an effective femoral crossover bypass graft in patients with either localized/generalized sepsis or disadvantaged outflow tracts.

Adult↗

PubMed2001

Incidence of major venous and renal anomalies relevant to aortoiliac surgery as demonstrated by computed tomography.

Preoperative knowledge of the presence of major venous anomalies facilitates the safe performance of aortic surgery. The purpose of the study was to estimate the incidence, as detected by abdominal and pelvic computed tomography (CT), of major venous and renal anomalies related to the abdominal aorta in an adult population. A total of 1822 intravenous contrast-enhanced abdominal and pelvic CT scans done in 1822 patients at two university teaching hospitals were randomly selected and prospectively reviewed (between June 1999 and March 2000) to identify major venous and renal anomalies associated with the abdominal aorta and iliac arteries. An interpreting staff radiologist then indicated on adata sheet whether any of the following anomalies were present or absent: (1) retroaortic left renal vein, (2) circumaortic left renal vein, (3) left-sided inferior vena cava (IVC) without situs inversus, (4) left-sided IVC with situs inversus, (5) duplicate IVC, (6) preaortic confluence of the iliac veins, or (7) horseshoe kidney. The CT scans reviewed had been performed for a wide variety of indications. Thirty-four scans were excluded from the study because either the anomalies we were looking for could not be assessed for technical reasons or the patient had a previous left nephrectomy and therefore assessment of the left renal vein was impossible. From this analysis we found that in an adult population, the prevalence of major venous and renal anomalies related to the abdominal aortaand iliac arteries and detected by CT scan was 5.65%. Prior to aortic surgery, preoperative knowledge of the presence of such anomalies helps with operative planning and may reduce the risk of major venous hemorrhage associated with these anomalies.

Abnormalities, Multiple↗

PubMed1997

Effect of inhaled nitric oxide on normal human left ventricular function.

OBJECTIVES: This study determined the effects of inhaled nitric oxide (NO) on load-independent indexes of normal human left ventricular (LV) function. BACKGROUND: Inhaled NO is a potent and selective pulmonary vasodilator. However, when it is used in patients with congestive heart failure, the decrease in pulmonary vascular resistance (PVR) is often associated with an increase in pulmonary capillary wedge pressure. NO has been shown to have a negative inotropic action, but it is not known whether it affects LV chamber function when delivered by inhalation. METHODS: Eleven subjects (51 to 69 years old) with normal LV function (mean ejection fraction 72% [range 60% to 80%]) were studied. Four patients had concomitant coronary artery disease. Pressure-volume loop recordings were used to determine end-systolic and end-diastolic pressure-volume and preload recruitable stroke work relations. NO was delivered at 20 ppm for 10 min. In an additional group of patients with normal LV function, PVR (n = 5) and NO metabolites (n = 9) were measured. RESULTS: There was no effect of inhaled NO on steady state LV pressures, volumes, contractility, contraction duration, active relaxation (time constant of relaxation, peak negative first derivative of left ventricular pressure), diastolic compliance or PVR. NO metabolites (methemoglobin and nitrate) were present in the LV cavity at the same concentration as right atrial venous blood, suggesting inactivation of free NO before arrival in the LV chamber. This study had a power of 0.995 to detect a 5% change in contractility (slope of preload recruitable stroke work relation) for alpha = 0.05, based on the multiple linear regression model used. CONCLUSIONS: These results indicate that 20 ppm of inhaled NO does not have significant effects on normal LV function. This lack of effect may be due in part to rapid inactivation of free NO in transit to the heart.

Administration, Inhalation↗

PubMed1994

Urinary nitrate excretion is a noninvasive indicator of acute cardiac allograft rejection and nitric oxide production in the rat.

Cytokine induction of calcium-independent nitric oxide synthase is associated with production of large amounts of nitric oxide (NO). NO is a free radical that is rapidly degraded to nitrite and nitrate. Measurement of plasma and urinary nitrate is an indirect marker of NO production and previous studies have demonstrated that plasma nitrate rises with allograft rejection. The purpose of this study was to examine the temporal relationship between the rise in urinary nitrate excretion and the onset of graft rejection, and to determine the effect of conventional immunosuppression on nitrate excretion. The heterotropic model of cardiac transplantation in the rat was used, with Brown-Norway to Lewis allografts and Lewis to Lewis isograft controls. Twenty-four-hour urine specimens were collected before and after transplantation. Urinary nitrate excretion was measured by gas chromatography/mass spectrometry. Each group was treated with (1) no immunosuppression, (2) dexamethasone (3 mg/kg), or (3) CsA (10 mg/kg) on days 0, 1, and 2. Time to rejection for untreated allografts was 5.1 +/- 0.1 days, extending to 8.4 +/- 0.5 and 9.6 +/- 0.4 days with dexamethasone and CsA treatment, respectively. There was a significant rise in nitrate excretion on days 4, 7, and 9 for control, dexamethasone-treated, and CsA-treated allografts, respectively, preceding evidence of rejection. Untreated allograft rejection was associated with a peak in nitrate excretion 8 times that of basal excretion by isografts. Treatment of the allografts with dexamethasone and CsA significantly attenuated peak nitrate excretion compared with untreated allografts with a only a 2- to 3-fold rise preceding rejection. Results indicate that allograft rejection is associated with a dramatic increase in peak urinary nitrate excretion that is attenuated by standard immunosuppressive therapy. An increase in nitrate excretion precedes evidence of graft rejection, and may serve as a noninvasive marker of graft rejection.

Animals↗

PubMed1990

Prostacyclin and vascular function: implications for hypertension and atherosclerosis.

Prostacyclin and endothelium-derived relaxing factor (or nitric oxide) are unstable mediators produced by the vascular endothelium, that are important for local regulation of platelet behavior and blood flow. This review focuses on the basic biochemistry and pharmacology of prostacyclin, its interactions with nitric oxide and nitrovasodilator drugs, and the implications of disturbances in this system for vascular disease, particularly hypertension and atherosclerosis. Prostacyclin and its stable analogs are also finding limited therapeutic applications in preservation of platelet function, pulmonary hypertension, and investigation into the cytoprotective and antiatherosclerotic properties is continuing.

Animals↗

PubMed1989

Rat aortic endothelium antagonizes nitroprusside-induced relaxation by release of the peptide endothelin.

1. The effects of porcine endothelin were examined in rat thoracic aortic rings. 2. Endothelin was a potent contractile agonist (EC50 4.0 +/- 0.6 nmol/L). 3. Endothelin (1 nmol/L) did not affect contractile responses to cumulative concentrations of the thromboxane analogue, U46619. 4. In the presence of U46619, but not phenylephrine, endothelin (1 nmol/L) and endothelium abrogated the vasodilator response to cumulative concentrations of sodium nitroprusside. 5. The inhibitory effect of endothelin on vasodilator responses to nitroprusside in the presence of U46619 was abolished by nifedipine (0.1 mumol/L) but unaffected by indomethacin (3 mumol/L) or haemoglobin (10 mumol/L). 6. These data suggest that endothelin generated by native endothelium exerts a physiological antagonism of sodium nitroprusside in the presence of thromboxane.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗

PubMed1985

Calcitonin gene-related peptide stimulates cyclic AMP formation in rat aortic smooth muscle cells.

In rat aortic smooth muscle cells in culture, calcitonin gene-related peptide stimulated cAMP formation in a dose-dependent manner, half-maximally effective at 0.5 to 1 nM. There was no effect on formation of cGMP, which was increased 300-fold in the same experiments by atriopeptin or sodium nitroprusside. The vasodilator effect of CGRP in rat aorta requires an intact endothelium, indicating that increase in vascular smooth muscle cAMP is not in itself sufficient to bring about relaxation. cAMP is probably a mediator of CGRP action in vascular smooth muscle.

Animals↗

PubMed1985

Aggravation of myocardial ischaemia by nifedipine.

Three cases in which myocardial ischaemia was possibly precipitated by the administration of nifedipine are reported. It is suggested that the initial administration of nifedipine should be undertaken with caution in patients with unstable ischaemic heart disease.

Coronary Disease↗