Lamivudine for the treatment of membranous glomerulopathy secondary to chronic Hepatitis B infection

Membranous glomerulopathy is a well-recognized extrahepatic manifestation of chronic hepatitis B virus (HBV) infection. The authors report two cases of HBV-related nephrotic syndrome treated with lamivudine. A 46-year-old Chinese man had a hepatitis B e antigen seroconversion along with improvement in his nephrotic syndrome after lamivudine therapy. Two years after treatment was discontinued, a reactivation of HBV was successfully treated again with lamivudine. A 44-year-old Chinese woman, who was intolerant of interferon, was treated with lamivudine for 15 months without a virological response. However, two years after completing lamivudine, her nephrotic syndrome resolved. Implications for the treatment of HBV-related glomerulopathy and a review of the literature are presented.

Hyperhomocyst(e)inemia and the prevalence of atherosclerotic vascular disease in patients with end-stage renal disease

Hyperhomocyst(e)inemia is now recognized as an independent risk factor for atherosclerotic cardiovascular disease in patients with normal renal function. Hyperhomocyst(e)inemia is common in patients with chronic renal failure. This study is designed to look for an association between hyperhomocyst(e)inemia and atherosclerotic vascular disease in patients with end-stage renal disease (ESRD). Two hundred eighteen patients undergoing hemodialysis were enrolled onto the study and had predialysis bloodwork performed for total homocyst(e)ine, red blood cell folate, and vitamin B(12) levels. A history of clinically significant atherosclerotic vascular disease (ischemic heart disease, cerebrovascular disease, or peripheral vascular disease) was elicited by patient questionnaire and verified by careful inpatient and outpatient chart review. Atherosclerotic vascular disease was present in 45.9% of patients. Mean homocyst(e)ine concentration was 26.7 micromol/L (95% confidence interval [CI], 25.0 to 28.4) overall. Mean homocyst(e)ine concentration was 28.6 micromol/L (95% CI, 25.6 to 31.7) and 25.0 micromol/L (95% CI, 23.2 to 26.8) in patients with and without atherosclerotic disease, respectively (P = 0.036). The adjusted odds ratio for atherosclerotic disease was 2.12 (95% CI, 1.03 to 4.39) for those subjects with a homocyst(e)ine level in the highest quartile compared with the lowest 3 quartiles. In the 126 men, the adjusted odds ratio for atherosclerotic disease was 3.4 (95% CI, 1. 24 to 9.42) for those with homocyst(e)ine levels in the highest quartile compared with the lowest 3 quartiles. No association was found between homocyst(e)ine level and atherosclerotic disease in women. In conclusion, there is an association between hyperhomocyst(e)inemia and atherosclerotic vascular disease in patients undergoing dialysis. Prospective studies need to further examine the relationship between homocyst(e)ine level and atherosclerosis in women with ESRD.

Arterial versus venous changes in vascular capacitance during nitroprusside infusion: a vascular modelling study

The distributions of nitroprusside (NP) induced changes in vascular capacitance, arterial versus venous, are unknown. We measured canine ileal arterial and venous pressures and total (isolated loop) vascular volumes (scintigraphy), before and during NP infusion. NP sufficient to decrease perfusion pressure by 30% increased total vascular volume to 111 +/- 3% (+/- SEM) of control (p < 0.01). Increasing flow to restore perfusion pressure increased volume 4% more (p < 0.01). Assuming a two-compartment model and on the basis of the literature data, changes in venous capacitance were estimated and compared with arterial capacitance. During constant-flow perfusion, NP increased venous volume by 10.0% (vs. 18.1%, arterial). When flow was increased to restore pressure, venous volume increased by another 3.7% (vs. 2.6%, arterial). Assuming an original arterial to venous volume ratio of 133/1033, the final, constant-pressure increase in venous volume was almost 4 times the arterial increase. In conclusion, the increase in vascular volume during NP infusion was due primarily to similar-magnitude, active increases in venous and arterial capacitances (i.e., rightward shifts in pressure-volume relations). However, as venous volume is so much larger than arterial, the NP-induced increase in venous volume was greater.

Hyperhomocysteinemia, anticardiolipin antibody status, and risk for vascular access thrombosis in hemodialysis patients

BACKGROUND

Vascular access failure is an important cause of morbidity in end-stage renal failure patients on hemodialysis. Currently, little is known about risk factors that predispose certain hemodialysis patients to recurrent access thrombosis. Hyperhomocysteinemia (common in patients with renal failure) predisposes people with normal renal function to recurrent and early-onset venous thrombosis, although the effect on vascular access thrombosis is currently unknown. Previous studies have suggested that high titers of IgG anticardiolipin antibody (IgG-ACA) predispose hemodialysis patients to access thrombosis. This cross sectional study was designed to assess for an association between two predictive variables, hyperhomocysteinemia and elevated titers of IgG-ACA, and vascular access thrombosis in patients undergoing chronic hemodialysis.

METHODS

Risk factors for vascular access thrombosis were documented, and the number of episodes of access thrombosis was recorded for the previous three years in patients undergoing hemodialysis. Midweek predialysis total homocysteine and IgG-ACA levels were measured in all subjects.

RESULTS

Of the 118 patients who were enrolled, 75.4% had a native arteriovenous fistula. Episodes of vascular access thrombosis were recorded for the previous three years; 34 (28.8%, 95% CI 20.9 to 37.9%) patients had 72 episodes of access thrombosis over the period of risk. Mean homocysteine levels were not significantly different between these 34 patients (28.6 micromol/liter, 95% CI 24.5 to 32.7) and the patients who had no episodes of graft thrombosis (29.8 micromol/liter, 95% CI 26.7 to 32.9). Sixty-seven unselected patients had IgG-ACA levels drawn for analysis, and all assays were negative. The only variable that was associated with a higher risk for graft thrombosis was the type of vascular access placed (odds ratio 4.0, 95% CI 1.6 to 9.6 for patients with a synthetic graft compared with those with an arteriovenous fistula).

CONCLUSIONS

No association was found between homocysteine levels or anticardiolipin antibody and vascular access thrombosis in our patient population.

Measurement of intestinal vascular capacitance in dogs: an application of blood pool scintigraphy

To define relative changes in intestinal vascular capacitance, we developed a model that allowed us to construct intestinal vascular pressure-volume relationships (PVR). Thirteen alpha-chloralose-anesthetized and splenectomized dogs were studied using a pneumatic constrictor and a small catheter to change and measure portal venous pressure. A small lead sheet was placed beneath the abdominal wall. Relative changes in intestinal blood volume (IBV) were determined by in vivo blood pool scintigraphy with 99mTc-labeled erythrocytes and were expressed as percentages corrected for specific activity and abdominal wall radioactivity. PVRs were constructed using data recorded during graded inflations of the portal venous constrictor. The abdominal wall contributed 32.4 +/- 7.7% (SD) of the total counts. During a 4-h control period, PVRs varied by no more than 6% (of IBV). In the isolated intestinal circulation, the change in IBV was precisely proportional to the volume of blood added, indicating that this method can detect very small changes in volume (< or = 5 ml). Nitroglycerin (25 micrograms.kg-1.min-1) increased capacitance by 20%. Although it measures only relative changes, the model is stable and sensitive, provides reproducible measurement of intestinal PVRs, and, with adaptation, may prove useful in patient studies.

Abdominal compressions during CPR: hemodynamic effects of altering timing and force

To determine the optimal method of applying abdominal compressions during cardiopulmonary resuscitation (CPR), 3 levels of pressure (25, 50, and 100 torr) were applied to the abdomen a) continuously and b) as 500 msec pulses at 10 different phases during the CPR cycle in 8 anesthetized dogs. Thoracic aortic (Ao) and right atrial (RA) pressures were measured and PAo-PRA was calculated as the coronary perfusion gradient. A pneumatic piston device provided external chest compression (60/min, 120 lbs, for 50% of the cycle) and ventilation (80% O2, 12/min, at 20cm, H2O). Another identical device provided abdominal compression (AC) via an air-filled bladder. High-pressure (100 torr) AC applied for 500 msec commencing 200 msec prior to chest compression demonstrated the best overall profile, raising mean aortic pressure 26 torr (P less than 0.001) and peak coronary perfusion gradient pressure 17 torr (P less than 0.02) from control values during standard CPR of 58 and 41 torr, respectively. We conclude that applying high-pressure, 500-msec pulses of AC 200 msec before chest compressions significantly improves CPR hemodynamics.

The right and left ventricular intracavitary and transmural pressure-strain relationships

The magnitude of pericardial pressure and therefore the shape of the right ventricular end-diastolic transmural pressure-volume relationship remains controversial. To investigate ventricular compliance, eight dogs anesthetized with fentanyl were instrumented as follows. Right and left ventricular intracavitary pressures were measured with micromanometer-tipped catheters. Right and left ventricular free wall segment lengths were measured by sonomicrometry. Pericardial pressure was measured over the right and left ventricles by means of flat liquid-containing balloon transducers, and transmural pressures were calculated as the difference between intracavitary and pericardial pressures. After defining the pressure-segment length relationship by vena caval constriction followed by release and blood transfusion, the pericardium and chest were opened widely and the cardiac volume manipulation was repeated; this allowed direct measurement of transmural right ventricular end-diastolic pressure for each level of strain recorded with the chest and pericardium closed. When intracavitary right or left ventricular end-diastolic pressure was raised from zero to 20 mm Hg, the respective transmural pressures increased from 0.2 +/- 0.6 (SD) mm Hg to 2.5 +/- 1.8 mm Hg and from 0.3 +/- 0.7 mm Hg to 6.0 +/- 2.5 mm Hg. Ventricular segmental strain increased by 7.0 +/- 0.8% and 6.0 +/- 0.2%, respectively. No statistically significant differences were found between right ventricular calculated (intracavitary minus pericardial pressure) and measured (open pericardium, open chest) transmural pressures at a given strain, thereby confirming the accuracy of our pericardial pressure measurements.(ABSTRACT TRUNCATED AT 250 WORDS)

Experimental instrumentation and left ventricular pressure-strain relationship

Pericardial pressure measurement with a balloon transducer requires opening and reapproximating the pericardium. If this instrumentation significantly compromises pericardial volume, the heart may be constrained, exaggerating the magnitude of pericardial pressure and thus altering the left ventricular end-diastolic pressure-volume relationship. In open-chest dogs, we studied the effects of opening the pericardium, inserting a pericardial balloon transducer and myocardial sonomicrometer crystals, and reapproximating the pericardium on the left ventricular end-diastolic pressure-strain relationship (LVEDPSR). After a thoracotomy, sonomicrometer crystals were inserted through small holes (less than 3 mm) in the pericardium to measure LV segment length. A micromanometer with a reference lumen was used to measure LV pressure. LVEDPSRs were recorded in the following situations: 1) before the pericardium was opened (but after the crystals were inserted); 2) after the pericardium was opened, the heart was instrumented (4 pairs of crystals and 1 balloon), and the pericardium was reapproximated with interrupted sutures; and 3) after the pericardium was removed. For each dog, a cubic regression equation was fitted to the data obtained before opening the pericardium, and the 95% confidence intervals for the individual data points were determined. In each case, the LVEDPSR obtained after instrumentation was similar to the LVEDPSR described before opening the pericardium. Furthermore, data obtained after instrumentation were uniformly located within the confidence intervals of the LVEDPSR obtained before opening the pericardium and instrumenting the heart.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of nitroglycerin on pulmonary vascular capacitance in dogs

In this study we investigated the hypothesis that the decrease in pulmonary vascular pressures observed after administration of nitroglycerin is in part due to a shift in the pulmonary vascular pressure-volume relationship. The experiments were done in six closed-chest dogs anesthetized with pentobarbital, in which pulmonary, cardiac, and intestinal relative blood volumes were determined by equilibrium blood pool scintigraphy. Nitroglycerin (30 micrograms/kg/min) caused 7% (p less than 0.02) and 12% (p less than 0.02) reductions in pulmonary and total cardiac blood volume, respectively, and a 7% (p less than 0.01) increase in intestinal blood volume. This shift of blood from the heart and the pulmonary circulation to the systemic (intestinal) circulation was accompanied by reductions in mean pulmonary artery pressure from 16 +/- 2 mm Hg to 12 +/- 1 mm Hg (p less than 0.01), in mean pulmonary capillary wedge pressure from 11 +/- 2 mm Hg to 6 +/- 1 mm Hg (p less than 0.01), and in mean portal pressure from 9 +/- 1 mm Hg to 8 +/- 1 mm Hg (p less than 0.01). The position of the pulmonary vascular pressure-blood volume relationship was unaffected by nitroglycerin, whereas the portal pressure-intestinal blood volume relationship was shifted to the left and upward. These changes suggest that pulmonary vascular tone remained unchanged, whereas intestinal vascular tone decreased during administration of nitroglycerin. In conclusion, nitroglycerin decreased pulmonary vascular pressures through a passive emptying of the pulmonary circulation as a result of increased systemic (intestinal) vascular capacitance.

Assessment of the splanchnic vascular capacity and capacitance using quantitative equilibrium blood-pool scintigraphy

A series of human and animal experiments were carried out to assess the usefulness of equilibrium blood pool scintigraphy (EBPS) to study acute changes of the splanchnic vascular capacity and the splanchnic vascular pressure-volume (P-V) relationship. Corrected regional abdominal count rate changes, before and after various pharmacologic interventions, were used to assess regional splanchnic vascular volume changes. Animals were instrumented to manipulate and record splanchnic venous pressures. In patients, splanchnic vascular capacity increased by 5.2 +/- 6.9% (p less than 0.001) after 0.6 mg sublingual nitroglycerin while no significant change was noted after sugar pills (0.9 +/- 5.2%, p greater than 0.3). In dogs, splanchnic vascular capacity decreased by a mean of 16% during infusion of angiotensin (p less than 0.001) and increased by a mean of 32% during infusion of nitroprusside (p less than 0.001). The splanchnic vascular P-V curve was shifted rightwards during nitroglycerin administration. Thus, using the radionuclide technique we detected the expected qualitative and quantitative shifts in splanchnic capacity and capacitance. We conclude that EBPS is a useful method to assess acute changes of 1) the splanchnic vascular P-V relationship, in invasive animal studies, and 2) the splanchnic vascular capacity in noninvasive human and animal studies.

Increased pulmonary vascular capacitance with beta-adrenergic receptor stimulation: an experimental study of the effect of isoproterenol on the pulmonary vascular volume-pressure relationship

The present study is an investigation of the effect of beta-adrenergic receptor stimulation by isoproterenol on pulmonary vascular capacitance. The experiments were done in six intact-chest, anaesthetized dogs in which pulmonary and cardiac blood volumes were assessed by blood pool scintigraphy. Isoproterenol (0.150 microgram.kg-1.min-1) significantly (p less than 0.005) lowered pulmonary capillary wedge pressure (PPCW) and pulmonary artery pressure (PPA) but did not significantly change pulmonary blood volume (PBV). Left ventricular end-diastolic pressure and total cardiac volume both significantly (p less than 0.005) decreased. Pulmonary vascular volume-pressure (V-P) relationships before and during isoproterenol were described by means of blood transfusions and hemorrhage. In individual dogs the PBV-PPCW and the PBV-(PPCW + PPA)/2 relationships were significantly shifted upward by isoproterenol (p less than 0.05 or less); slope changes were variable. Pooled data from all dogs also showed a significant (p less than 0.001) upward shift in the pulmonary vascular V-P relationship regardless of which measure of distending pressure was used. These results suggest that beta-receptor stimulation by isoproterenol increases pulmonary vascular capacitance by increasing the unstressed volume.

Modulation of vascular capacitance by angiotensin and nitroprusside: a mechanism of changes in pericardial pressure

The aim of the present study was to test the hypothesis that vasoactive drugs may modify left ventricular diastolic function by shifting blood between the systemic vascular bed and the heart, thereby changing pericardial and left ventricular pressure. The experiments were done in 10 open-chest, anesthetized, previously splenectomized dogs in which changes in pericardial surface pressure in response to intravenous sodium nitroprusside and angiotensin were related to changes in blood volume in the abdominal region. Blood volume was determined by blood pool scintigraphy (99mTc) and regions of interest were drawn in the liver and in the mesenteric area. Angiotensin was infused at rates that were adjusted to increase mean aortic pressure by 20 and 30 mm Hg, and nitroprusside was infused at rates to decrease mean aortic pressure by 30 and 50 mm Hg. Angiotensin increased pericardial pressure by 3 and 5 mm Hg at the respective doses and there were increments in left ventricular end-diastolic pressure (LVEDP) and left ventricular diameter (sonomicrometry). Angiotensin decreased blood volume in the mesenteric region by 14% and 17%, but did not significantly change blood volume in the liver region. Angiotensin increased portal venous pressure and decreased mesenteric blood volume, suggesting decreased mesenteric venous compliance. Nitroprusside had opposite effects: pericardial pressure was decreased by 5.5 and 6.5 mm Hg by the respective doses. The doses of nitroprusside increased blood volume in the mesenteric region by 14% and 20%, but did not significantly change blood volume in the liver region.(ABSTRACT TRUNCATED AT 250 WORDS)

Nonuniformity of pericardial surface pressure in dogs

Previously, we have shown that pericardial constraint cannot be measured by true (hydrostatic) pressure except when an excess of pericardial fluid is present and that a device such as a balloon (which reflects radial contact stress as well as hydrostatic pressure) must be used. Since radial contact stress is the major component of the constraint exerted by the pericardium when little pericardial liquid is present, it follows that the pressure measured by the balloon might be different over different parts of the heart. In an attempt to test this hypothesis, in 11 anesthetized dogs we placed pericardial balloons over the right and left ventricular free walls, instrumented the animals to measure ventricular dimensions (sonomicrometry) and pressure, mounted pneumatic constrictors on the aortic and pulmonary artery, reapproximated the pericardium, and closed the chest under suction. We studied the transient effects of constrictions of the ascending aorta and pulmonary artery and of angiotensin infusion before and after intravenous saline infusion. Aortic constriction and, to a lesser degree, angiotensin increased pericardial pressure over the left ventricle more than over the right ventricle. Pulmonary artery occlusion increased pericardial pressure over the right ventricle but significantly decreased pericardial pressure over the left ventricle. We conclude that there are significant local differences in pericardial pressure (recorded by balloon) over the lateral ventricular surfaces during acute changes in afterload. These observations may be explained in part by decreased venous return to the contralateral ventricle, the tendency of the heart to resist lateral displacement, and the limited mobility of the pericardium.