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Biomedical subjects

M Holtz

Publications and source records attributed to M Holtz.

At least 19 recordsLinked to original sources
PubMed1990

Measurements of plasma colloid osmotic pressure, total protein and sodium concentration during haemodialysis: can single-pool sodium modelling explain the results?

Considering the plasma colloid osmotic pressure (COP) as a possible parameter for the monitoring of dialysis treatment compatibility, a characteristic time course was found. The COP and the total protein concentration very often do not increase significantly during the first treatment hour in spite of ultrafiltration. An increase in the plasma sodium concentration, which was higher than expected, was found to be the reason for a plasma dilution effect. This can be explained by a transcapillary sodium transfer coefficient which is not infinitely high as assumed in single-pool sodium modelling. From a 2-pool model considering the plasma volume as a separate pool and including capillary filtration time courses for plasma sodium, total protein concentration and COP could be calculated, which was very similar to the measured curves.

Blood Proteins↗
PubMed1988

[Determination of clearance for urea-controlled hemodialysis].

Through a simple variant of the urea model the qualitative influence of the dialyzer-clearance on the individual dialysis guidance is elucidated. Realization of the respective Kdtd/V-value require an exact knowledge of the in-vivo-urea-clearance of all available dialyzer types and their manipulation with the aid of blood flow. The theoretical connections are explained and possible parameters affecting the in-vivo-clearance are discussed. The results concerning the dependence of urea-clearance on the blood flow are presented in an urea-guided dialysis patient pool for all in the GDR customary in the trade or temporary available dialyzers. It is shown, that in MLW-dialyzers an influence on the urea-clearance about the blood flow is small because of their relatively thick-walled membrane. Therefore, the development of dialysis membranes with superior diffusible permeability is necessary.

Blood Flow Velocity↗
PubMed1987

A clinical study on different cellulosic dialysis membranes.

A controlled clinical study was performed over a period of 8 weeks in two dialysis centres (Rostock, GDR, and Munich, FRG). The aim was to compare a dialysis membrane made of modified cellulose (Hemophan) with classical regenerated cellulose (Cuprophan). Dialysers containing these membranes, together with a cellulose acetate dialyser, were therefore incorporated in a cross-over programme and clinical and biochemical investigations undertaken. The efficacy of the modified cellulosic membrane with respect to urea and creatinine clearance was shown to be comparable to that of regenerated cellulose and cellulose acetate. However, modified cellulose showed an increased clearance for inorganic phosphate, significantly different from that demonstrated by both regenerated cellulose and cellulose acetate. Blood compatibility studies, which included the assessment of C3a activation and the reduction of white blood cell (WBC) and platelet count, clearly demonstrated that in comparison to regenerated cellulose, modified cellulose resulted in significantly less complement activation and WBC reduction. Similarly in comparison to cellulose acetate, modified cellulose showed reduced complement-activating and WBC-reducing properties. The reason for the improved blood compatibility of modified cellulose is not, as was originally assumed, related to binding of complement-inhibiting heparin, but appears instead to be due to the substitution of hydroxyl groups of regenerated cellulose.

Biocompatible Materials↗
PubMed1986

Experiments with continuous hemofiltration and hemofiltrate regeneration in the rat.

Experimental studies were made with continuous hemofiltration treatment for bilaterally nephrectomized rats and initial observations regarding the effects of such treatment on leukocyte and thrombocyte counts are reported. Hemofiltration of unanesthetized rats able to move freely within their cage could be continued for up to 30 h using a pump-driven ECC system. Blood parameters recorded during this treatment indicate that the detoxification was effective. In another series of experiments the water and electrolyte reabsorption capacity of the colon ascendens of healthy rats was tested by continuously supplying NaCl solution into the colon via a fistula. A large proportion, if not all, of the hemofiltrate can be discharged into the colon without diarrhoea. A final series of experiments showed that the three-stage operation (implantation of permanent catheters, connection of a permanent intestinal fistula and bilateral nephrectomy) is possible with the rat.

Animals↗
PubMed1985

Shoulder forearm support for the subluxed shoulder.

Subluxation of the shoulder is a common problem in patients who have had a stroke. Of the shoulder supports that are being used, many do not reduce the subluxation, and patients continue to complain of shoulder pain. The shoulder support designed for this study reduces subluxation, is custom fit, costs less, and is more comfortable than conventional slings. The sling is difficult to don but patients are able to perform self-ROM exercises without removing the sling. The sling consists of two parts: a shoulder support and forearm support. Both portions are worn when the patient is ambulating or standing. Only the shoulder support is worn when the patient is sitting with a lapboard. X-rays confirmed the reduction of subluxation, and patients reported decreased shoulder pain.

Cerebrovascular Disorders↗
PubMed1984

[Information content of endogenous creatinine parameters for kidney function diagnosis in glomerulonephropathies].

The functional-diagnostic findings, namely serum creatinine level, 24-h creatinine clearance, 1-h (morning) creatinine clearance and inulin clearance, of 58 glomerulo-nephropathy patients were evaluated using regression and correlation analysis. For clinical nephrology it is recommended not to measure 24-h creatinine clearance. For the purpose of diagnosing kidney function the information content of the serum creatinine level is sufficient if the hyperbolic relation to the GFR is taken into account. For clinical-scientific nephrology standardized short-term creatinine estimation in combination with direct or indirect GFR measurement (and other parameters of kidney function) is advisable.

Creatinine↗
PubMed1983

Heparin binding and release properties of DEAE cellulose membranes.

Two cellulose-based membranes, containing 5 and 20% N, N-diethyl-aminoethyl cellulose (DEAE) respectively, were investigated for ionic attachment of heparin and heparin release. Heparinization was achieved by recirculation of a heparin-containing glycine buffer over each membrane. Heparin was determined by chemical analysis or by 99mTc labelling. The heparin uptake was shown to be linearly dependent on the heparin content in the contacting fluid. Heparin release was studied by contacting heparinized membranes with saline, glycine buffer, phosphate buffer and plasma. Incubation with plasma brought about the release of 50% of the attached heparin. Crosslinking of the heparinized membrane with glutaraldehyde reduced the heparin release by one half. The release reaction is more critical in the case of increased heparin uptake and a more efficient immobilization of heparin appears necessary.

Cellulose↗
PubMed1983

[Possibilities for using extracorporeal circulation in the rat].

An extracorporal system of freely mobile, unanaesthetized rats is presented. This model was used in experiments on the biocompatibility of silicone rubber and new types of hollow membranes. The results confirm a sensitive reaction of haematological parameters to various test substances, thus indicating that the model is very suitable. Carrying out a membrane plasma separation in rats makes it possible also to use rats for studies on detoxification and thus to use the advantages offered by this experimental animal to the full.

Animals↗
PubMed1983

[What is the current outlook for an implantable artificial kidney?].

Considering the homeostatic demands made by the organism on an artificial eliminating substitute kidney system, it seems that the haemofiltrative principle for transporting matter is the most suitable for simulating the natural glomerular kidney function in an implantable artificial kidney. Biophysical laws can be used to influence long-term filtrative efficiency and the blood-flow in the haemofilter system can be controlled by technical feedback regulation. Endogenically, the filtration process is, in terms of energy, driven by the aterial blood pressure (specifically, by the trans-membrane pressure thus generated). The definitive ultrafiltrate treatment takes place by intestinal reabsorption and elimination of the end products, whereby these functions may be assisted by the use of sorbents etc. or an adequate substitution therapy if reabsorption is insufficient. These processes can reasonably be triggered by neurohormonal feedback regulation if the homeostasis situation is greatly disturbed by the haemofiltration process. The implantable artificial kidney is thus a biochemical hybrid kidney.

Animals↗
PubMed1983

[Experimental development of hollow cellulose membranes for blood detoxification].

In recent years there have been repeated demands in medical circles for new membranes for various purposes. At present attention is focussed on the development of membranes for the detoxification of blood. Using available technology and resources, it seemed appropriate to develop such hollow membranes out of cellulose by the viscose process. It is possible to give the membrane a suitable structure according to the use intended. The transport of matter and ultrafiltration can be influenced by varying the influence parameter in the spinning process via changes in the pore structure. In this way it is possible to produce hollow membranes for dialysis or ultrafiltration, with varying grades of permeability, out of cellulose by the viscose process.

Blood↗
PubMed1982

Selection of filters and evaluation in vitro of the selective dual filtration artificial kidney, SEDUFARK.

Transport properties of different artificial kidney membranes have been studied employing substances with molecular weights ranging from 60 daltons (urea) to 62,000 daltons (dextran). The results from these studies were used to select filters for the SElective DUal Filtration ARtificial Kidney, SEDUFARK. Selection criteria for filters to be used in long-term clinical trials with SEDUFARK were based on biological tests showing toxicity of large molecular weight substances in uremic blood plasma and clinical advantages of returning middle molecular weight substances to the patient. The filters selected were used for evaluation in vitro of the complete SEDUFARK system. The results confirmed a theoretical analysis of this system, demonstrating that selective removal of substances within given molecular weight ranges from uremic blood plasma is feasible with a combination of commercial filters. The efficiency of the system, however, is limited due to the "cut-off" characteristics and hydraulic permeabilities of membrane types currently available.

Biological Transport↗
PubMed1982

Utilization of a silastic sheet in tendon repair of the foot.

Specific reparative processes often dictate the function of a tendon upon completion of healing. At times the surgeon must improvise when the results of a previous traumatic or iatrogenic insult to a tendon produced a less than desirable result. The following is a case in which the authors utilized Silastic sheeting as a pseudosheath in the repair of an iatrogenic laceration of the extensor hallucis longus tendon in a previous surgery.

Adult↗