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Biomedical subjects

A M Davison

Publications and source records attributed to A M Davison.

At least 91 records · Page 5Linked to original sources
PubMed1991

Cationic colloidal gold--a novel marker for the demonstration of glomerular polyanion status in routine renal biopsies.

Investigations of glomerular anionic charge status in human renal biopsies have previously been restricted, by the techniques and markers used, to staining of sites in pre-embedded tissue. The introduction of a novel marker, cationic colloidal gold, which demonstrates fixed anionic sites in hydrophilic resin (LR Gold)-embedded, ultrathin tissue sections, has now enabled glomerular charge to be evaluated in routine biopsy material. The cationic gold marker detects components which express anionic charge under different pH conditions. The patterns of staining in tissue showing minor glomerular pathology and low proteinuria, together with enzyme-digestion studies indicate that anionic sites are normally associated with heparan sulphate proteoglycans, glycocalyx sialoproteins, hyaluronic acid, and other GBM components which have not yet been characterised. Several charge aberrations involving different pathological mechanisms have been identified using cationic gold. These aberrations may be categorised according to the pathological basis of the charge pattern defect, rather than glomerular disease classification, as a prelude to the precise identification of the anionic sites and their functional importance in relation to the glomerular charge selectivity barrier. The categories which have been defined are: (1) 'Normal', (2) interrupted, (3) neutralised, (4) structurally disorganised, and (5) depleted. As sites are further characterised sub-categorisation is likely. We anticipate that this approach will help to elucidate both the participation of charged components in disease pathogenesis and their role in relation to glomerular proteinuria.

Adolescent↗
PubMed1991

Tumour necrosis factor does not increase during routine cuprophane haemodialysis in healthy well-nourished patients.

Serum tumour necrosis factor (TNF) was measured by both bioassay and immunoassay (ELISA) during routine cuprophane acetate haemodialysis in 17 asymptomatic patients. In 14 (82%) there was no change in the serum values during haemodialysis. TNF was found to increase, using both assays, in three patients, the responders. These patients differed from the others in terms of body mass index, mean index 16.8 kg/m2 (range 14.8-18.2), compared to the non-responders, mean 24.1 kg/m2 (range 19.6-33.1), P less than 0.05, and had an increased serum calcium, mean 2.9 mmol/l (range 2.6-3.2) compared to the non-responders, mean 2.4 mmol/l (range 1.7-2.8), P less than 0.05. Two of the TNF responders subsequently died of cachexia and respiratory infection. The third underwent a successful parathyroidectomy, and when retested after an increase in body-weight with a normal serum calcium concentration no longer showed an increase in TNF during haemodialysis.

Adult↗
PubMed1991

Hyaluronic acid in end-stage renal failure treated by haemodialysis: clinical correlates and implications.

Serum hyaluronic acid was measured in 176 adults and 15 children receiving regular dialysis therapy. Hyaluronic acid was elevated to greater than 80 micrograms/l in more than 90%, with median value 182 micrograms/l (range 39-898 micrograms/l). Concentrations did not correlate with serum creatinine, but showed a significant correlation with duration of dialysis and serum beta 2-microglobulin. Values greater than 400 micrograms/l were frequent in patients whose clinical condition deteriorated, but in others, hyaluronic acid remained stable over 4-15 months. Serum hyaluronic acid is mainly in a high-molecular-weight form, which in the presence of normal hepatic function suggests that there is a metabolic disorder involving connective tissue and/or vascular endothelium that increases with progressive loss of renal function. Hyaluronic acid may also be a biochemical marker of patients whose condition deteriorates despite renal replacement therapy.

Adult↗
PubMed1991

Adverse effects on cerebral perfusion of prostacyclin administered directly into patients with fulminant hepatic failure and acute renal failure.

Prior to commencing renal replacement therapy, 8 patients with fulminant hepatic failure and acute renal failure were treated with an infusion of prostacyclin, 5 ng/kg/min, for 30 min, administered directly into the femoral vein. During this period, several adverse effects were noted. There was a reduction in mean arterial blood pressure from a median of 82 (range 65-93) to 67 mm Hg (55-80), p less than 0.01; and an increase in intracranial pressure from a median of 14 (6-33) to 17 mm Hg (6-42), p less than 0.05; with a consequent reduction in cerebral perfusion pressure from a median of 63 (43-77) to 43 mm Hg (15-74), p less than 0.05. There was a reduction in arterial oxygen tension from a median of 19 (13-28) to 16 kPa (12-27), p less than 0.05; and no change in cardiac output, from a median of 6.7 (4.9-11.2) to 6.5 l/min/m2 (3.8-11.0), p greater than 0.05). The administration of prostacyclin into this group of critically ill patients, at risk of death due to cerebral oedema/hypoxia, produced both a reduction in cerebral perfusion pressure and a reduction in total cerebral oxygen delivery.

Acute Kidney Injury↗
PubMed1991

Hyperlactataemia and metabolic acidosis during haemofiltration using lactate-buffered fluids.

We have investigated the effect of an exogenous lactate load given during machine haemofiltration treatment in 22 patients with acute renal failure and 12 patients with chronic renal failure, without any overt evidence of liver disease. Hyperlactataemia occurred in all patients, but the expected changes in acid base status, an increase in bicarbonate and a reduction in arterial hydrogen ions were observed in less than 40% of the treatments in the acute renal failure group. Ultrafiltrate losses of lactate and bicarbonate could not alone explain the changes in acid-base status. There was a positive correlation between the increase in arterial lactate and hydrogen ion concentrations, r = 0.52, p less than 0.01. Lactate accumulation in patients at, or close to, their threshold for lactate utilisation may result in further depression of cardiac function and peripheral lactate utilisation. Hyperlactataemia due to use of lactate-based dialysis/haemofiltration solutions in critically ill patients may result in a worsening of the acid-base status, and arterial pH should be monitored so that bicarbonate solutions can be substituted if the changes are progressive.

Acidosis, Lactic↗
PubMed1991

Prevalence of Helicobacter pylori in patients with end-stage renal failure and renal transplant recipients.

The prevalence of Helicobacter pylori was determined using an ELISA technique for IgG antibodies to H. pylori in 76 patients with end-stage renal failure who were receiving regular haemodialysis and 202 patients with functioning renal transplants. Twenty-seven (34%) of the haemodialysis group and 58 (29%) of the transplant group were positive for H. pylori IgG antibodies, and the prevalence did not differ significantly from that in 247 age-matched healthy controls. In the haemodialysis group, patients positive for H. pylori were older, median age 60 years (range 22-73), compared to those patients without H. pylori antibodies, median age 52 years (range 22-75), p less than 0.05, more suffered from dyspeptic symptoms, 35 vs. 10% (p less than 0.01), yet fewer had been prescribed aluminium-containing antacids, 38 vs. 78% (p less than 0.01). In the transplanted group, those positive for H. pylori were more symptomatic for dyspepsia, 30 vs. 11% (p less than 0.01), and had lower serum creatinine values, 136 +/- 10 mumol/l (mean +/- SEM) vs. 172 +/- 12 mumol/l (p less than 0.05), compared to those without H. pylori antibodies. Almost all the transplant patients with H. pylori antibodies were taking steroids (98%) compared to 84% of those without antibodies (p less than 0.05). The prevalence of antibodies to H. pylori in this study was increased in symptomatic dyspeptic subjects and reduced in those patients prescribed aluminium-containing phosphate binders.

Adult↗
PubMed1991

Detection of glomerular anionic sites in post-embedded ultra-thin sections using cationic colloidal gold.

We detected glomerular anionic sites in fixed, LR Gold-embedded ultra-thin tissue sections using cationic colloidal gold. Manual and computer-assisted quantitation were compared, and the influence of pH and glycosaminoglycan-degrading enzymes on site expression was examined. Both quantitation methods produced similar results. Alteration of pH within a narrow range (pH 2.5-3.0) markedly affected the staining pattern. At pH 2.5, epithelial and endothelial glycocalyx and regular sites restricted to the lamina rara externa were stained. At pH 3.0 and above, glycocalyx was unstained but intracellular and nuclear staining was present; glomerular basement membrane (GBM) and mesangial matrix sites were abundant. After chondroitinase ABC or hyaluronidase digestion, GBM staining was eliminated at pH 2.0 and reduced at pH 7.0 (p less than 0.001), suggesting that degraded sites are associated with chondroitin sulfate or hyaluronic acid. By contrast, prolonged heparitinase I digestion was ineffective at either pH. Digestion of purified substrates revealed crossreactivity of heparitinase towards chondroitin sulfate and of chondroitinase towards hyaluronic acid. Since tissue sites were reduced by chondroitinase but not heparitinase, we suggest that degradation is due to hyaluronidase activity of chondroitinase and the anionic sites are associated with hyaluronic acid. However, the influence of pH indicates that lamina rara externa sites are structurally distinct from other GBM anionic sites.

Animals↗
PubMed1991

The prognostic use of a lactate infusion in patients with severe hepatorenal failure.

We have used machine hemofiltration (MHF) with lactate-buffered hemofiltration replacement solution in the management of four patients with severe hepatorenal failure. Hyperlactatemia developed in all four patients. However, consecutive treatments were associated with increasing blood lactate values postfiltration in the two patients who died and with a fall in the lactates in the two patients who survived. The survivors had lower postfiltration blood lactates 3.2 +/- 0.2 mmol/L (mean +/- SEM) compared to the nonsurvivors, 5.3 +/- 0.5 mmol/L (p less than 0.01). This suggests that the measurement of blood lactate following a lactate challenge may be of prognostic significance in patients with severe hepatorenal failure.

Adult↗
PubMed1991

Volumetric control of continuous haemodialysis in multiorgan failure.

The authors have developed a system for volumetric control of continuous haemodialysis. The article describes this system and reports its successful use in providing renal support in the intensive care unit to 10 patients with multiorgan failure. In addition to providing effective treatment of uraemia, it permits the precise control of fluid balance in a prospective manner ("dial-up" fluid balance) while reducing nursing workload.

Acute Kidney Injury↗
PubMed1991

The effect of prostacyclin on intracranial pressure in patients with acute hepatic and renal failure.

Prostacyclin was administered on 20 occasions to 12 patients with fulminant hepatic failure complicated by acute renal failure prior to commencing dialysis at a dose of 5 ng/kg.min. Intracranial pressure was noted to increase during the infusion from a median of 12 mmHg (95% confidence limits 9-14) to 17 mmHg (12-25), p less than 0.01, at the same time the mean arterial blood pressure declined from 79 mmHg (65-82) to 64 (56-70), p less than 0.01, and the cerebral perfusion pressure from 62 mmHg (53-67) to 44 mmHg (41-55), p less than 0.01. The changes were greater for those patients who subsequently died from cerebral edema. Patients with fulminant hepatic and acute renal failure are at risk of dying from cerebral edema. The direct administration of prostacyclin, used for extracorporeal anticoagulation, may cause a further increase in intracranial pressure and reduce cerebral perfusion, thus resulting in patient morbidity and mortality.

Acute Kidney Injury↗
PubMed1991

Aluminium mobilization following renal transplantation and the possible effect on susceptibility to bacterial sepsis.

We monitored urinary aluminium excretion in 60 renal allograft recipients for the first 6 months following transplantation. Plasma and urinary aluminium values steadily decreased during the study period. Patients who suffered two or more bacterial infections during this period excreted more urinary aluminium than those with only one or no infections. Twenty patients experienced a two-fold or greater sudden unexpected increase in urinary aluminium excretion: 14 of these patients (60 per cent) had evidence of infection (10 bacterial and four viral), at this time. Both urinary aluminium and fractional aluminium excretion were greater in the 10 patients with bacterial infection than in the other 10 patients. Thus, patients who suffered bacterial infections had higher base-line urinary aluminium excretion, suggesting a higher body burden of aluminium. In addition, bacterial sepsis was associated with aluminium release from tissue stores with an associated increase in urinary aluminium excretion. This implies that patients with an increased body burden of aluminium are more prone to bacterial sepsis, and that aluminium excretion is increased during sepsis.

Adult↗
PubMed1990

Adverse effects of prostacyclin administered directly into patients with combined renal and respiratory failure prior to dialysis.

We infused prostacyclin into 11 critically ill patients for 30 min at a rate of 5 ng/kg.min, prior to commencing prostacyclin haemodialysis. All patients had combined respiratory and renal failure and required intropic support. Despite the previous correction of hypovolaemia, prostacyclin produced a decrease in mean arterial pressure, pulmonary and systemic vascular resistances and cardiac filling pressures. There was no compensatory increase in cardiac output and due to an increase in pulmonary ventilation/perfusion mismatch an overall decrease in tissue oxygen delivery from a median of 560 ml/min.m2 to 370 ml/min.m2 was noted p less than 0.05, with a corresponding reduction in tissue oxygen uptake from 140 ml/min.m2 to 125 ml/min.m2. This was associated with an increase in both arterial hydrogen ion and lactate concentrations in 8 of the 11 patients studied, suggesting a deterioration in tissue oxygen supply/oxygen requirement. Prostacyclin should not be infused directly into patients unless monitored to assess the therapeutic/adverse effects on an individual patient basis.

Acute Kidney Injury↗
PubMed1990

Early changes in intracranial pressure during haemofiltration treatment in patients with grade 4 hepatic encephalopathy and acute oliguric renal failure.

We measured the intracranial pressure (ICP), using a subdural catheter in nine patients admitted with grade 4 hepatic encephalopathy due to fulminant hepatic failure complicated by oliguric renal failure. Six patients received daily machine haemofiltration and four patients were treated with continuous arteriovenous haemofiltration (CAVHF). The mean ICP increased during the first hour of machine haemofiltration from 9 +/- 1.4 mmHg to 13 +/- 1.8 mmHg (P less than 0.05), and there was a reduction in the mean arterial pressure from 92.4 +/- 2.7 mmHg to 81 +/- 3.2 mmHg (P less than 0.05) resulting in a reduction in cerebral perfusion pressure of up to 30%. The group treated by CAVHF, although having a greater mean ICP prior to treatment (19 +/- 4.8 mmHg) and a lower mean arterial pressure (66 +/- 3.6 mmHg) and consequently a lower cerebral perfusion pressure, did not show any increase in ICP or reduction in mean arterial or cerebral perfusion pressure. There was a significant reduction in serum osmolality during the first hour of treatment in the machine haemofiltration group (314 +/- 4 mOsm/kg to 309 +/- 4 mOsm/kg, P less than 0.05), whereas there was no corresponding change in the CAVHF group. This suggests that CAVHF is to be preferred for the treatment of acute renal failure in such patients who are at considerable risk of developing cerebral oedema.

Acute Kidney Injury↗
PubMed1990

Paradoxical increase in arterial hydrogen ion concentration in patients with hepatorenal failure given lactate-based fluids.

We have investigated lactate intolerance in nine patients with acute hepatorenal failure during 21 machine haemofiltration treatments using a lactate based replacement solution. In all cases hyperlactataemia occurred, the mean arterial lactate increased from 1 +/- 0.2 mmol/l (mean +/- SEM) prior to treatment to 3.2 +/- 0.3 mmol/l at 1 h (P less than 0.01), 4.2 +/- 0.4 mmol/l at 2 h (P less than 0.01), 4.2 +/- 0.4 mmol/l at 3 h (P less than 0.01) and 3.9 +/- 0.4 mmol/l (P less than 0.01) post-treatment. There were correlations between the maximum increase in blood lactate and both the change in arterial hydrogen ion concentration (r = 0.71, P = 0.001) and the mean arterial blood pressure prior to starting treatment (r = -0.57, P = 0.007). During eight of the treatments (38%), the arterial hydrogen ion concentration increased. This group showed increased lactate intolerance in association with a lesser pretreatment mean arterial pressure. The administration of exogenous lactate to patients with hepatorenal failure who are at, or near to, the threshold of their own endogenous lactate metabolism can result in an increase in hydrogen ion concentration rather than the expected decrease, and therefore lactate-based dialysate solutions are best avoided.

Acid-Base Equilibrium↗
PubMed1990

Effect of posture on intracranial pressure and cerebral perfusion pressure in patients with fulminant hepatic and renal failure after acetaminophen self-poisoning.

We measured the effect of posture on intracranial pressure (ICP) and cerebral perfusion pressure (CPP) in eight patients admitted with grade 4 hepatic coma due to fulminant hepatic failure complicated by renal failure. Upward head elevation greater than 20 degrees did not consistently reduce ICP; instead, ICP increased in three patients who later died of cerebral edema. CPP was reduced significantly by elevation greater than 20 degrees, falling to less than 50 mm Hg in those patients who subsequently died of cerebral edema. Our study does not support the current practice of nursing patients with hepatic coma, who are at risk of dying from cerebral edema, in head-upright postures greater than 20 degrees.

Acetaminophen↗