PubMed Health⌕ Search

Biomedical subjects

W Dietz

Publications and source records attributed to W Dietz.

At least 19 recordsLinked to original sources
PubMed1992

Cavitation of mechanical heart valves under physiologic conditions.

Cavitation has recently entered the discussion of factors leading to blood and material damage after implantation of mechanical heart valves. Since direct evidence for this phenomenon cannot yet be demonstrated in vivo, an in vitro method had to be developed to permit the investigation whether cavitation actually occurs under (simulated) physiologic conditions and to clarify its clinical relevance. Previous studies have shown that different types of commercially available mechanical valves exhibit different tendencies to generate cavitation in vitro. The present study presents a test protocol for the assessment of cavitation generated by different replacement valves under simulated physiologic conditions. Comparative investigations were performed in order to transfer the in vitro results in vivo conditions. Although mechanical valves with an overlapping closing body/valve ring configuration tend to create cavitation earlier, cavitation could not be demonstrated for any investigated mechanical valve type under simulated resting conditions. The danger of continuous cavitation damage is therefore low. Certain valve types exhibit cavitation only at higher heart rates (more than 120-140 beats/min). Some valve types do not show cavitation even during heavy exercise. Based on mathematical models and experimental investigations, it is very likely that if cavitation does occur, blood and material damage may be expected.

Blood↗
PubMed1991

[Chronic purulent, draining, indolent pancreatic head pancreatitis with extrahepatic cholestasis].

Over the period of two weeks a 19-year-old man developed gradually increasing painless jaundice with dark urine and light-coloured soft stools (6-7 times daily), as well as loss of appetite, nausea and nagging itch. Biochemical tests indicated marked cholestasis (alkaline phosphatase 800 U/l, gamma-GT 206 U/l). Abdominal ultrasound examination revealed high-grade stenosis of the distal choledochal duct caused by an enlargement of the head of the pancreas and computed tomography confirmed a tumour in this location. Endoscopic retrograde cholangiopancreatography demonstrated filiform stenosis of the major pancreatic duct and prepapillary stenosis of the choledochal duct. Several needle biopsies failed to establish a definitive diagnosis. A Whipple operation was performed: the stomach was preserved but about 40% of pancreatic tissue resected. Histologically there was chronic suppurative pancreatitis of the head of the pancreas. The patient was symptom-free 6 months after the operation. The case illustrates that it is not always possible in a painless pancreatic tumour to distinguish between pancreatitis and malignant tumour.

Adult↗
PubMed1991

Controlled clinical trials and cross-sectional studies with plasma histamine measurements and histamine receptor antagonists: solving the problem of preoperative H1- + H2-prophylaxis by asking new questions?

The problem of a preoperative histamine H1- + H2 - prophylaxis was tackled by a group of new studies including randomized controlled clinical trials and cross-sectional studies with plasma histamine measurements and administration of H1- + H2 - antagonists to a control group. The first study demonstrated serial histamine release in the induction of anaesthesia up to 4 times in a single patient. Basal plasma histamine levels in resting subjects fell below 100 pg/ml during the time necessary for preparation of the surgical patient. Hence, spikes of elevated plasma histamine concentrations corresponded to histamine release. Although this histamine release very often was less than 1 ng/ml plasma histamine, it created systemic reactions after atracurium. The cut-off point of 1 ng/ml for such anaphylactoid reactions does no longer exist, also lower plasma levels are of patho-physiological significance. The clinical signs of histamine release in the induction of anaesthesia vary from drug to drug. Sometimes tachycardia and hypertension produce the highest likelihood ratio, sometimes tachy- and bradycardia, but no changes in blood pressure as in the case of atracurium. It is concluded that the reasons why histamine release in anaesthesia and surgery is so much underreported and under-estimated include the present paradigms about plasma histamine levels and the "classical picture" of histamine release. Both are no longer valid and need a re-assessment.

Adolescent↗
PubMed1991

[Stress ulcer or pneumonia: effect of prevention with H2 blockers on gastric juice pH].

In a study with 30 consecutive ventilated patients in a surgical ICU, the course of gastric pH was measured for 24 h. Cimetidine, 1.2 g per 24 h, was given to prevent stress bleeding. In the course of the evaluation period complete alkalization was found in only 4/30 patients (high responders); 10/30 patients showed no alkalization of gastric juice to above pH 4; and in 16/30 patients irregular pH changes were observed. These results suggest that the risk of developing pneumonia under this regimen will only be elevated in the high responder group. Although the alkalization of gastric juice was incomplete in our group, we saw no evidence of upper gastrointestinal bleeding. There is evidence that alkalization is not the only mechanism involved in successful prevention of bleeding.

Adult↗
PubMed1990

Plasma histamine levels in polytraumatized patients.

In a prospective clinical trial, plasma histamine levels were measured in 28 polytrauma patients on day 1, 5 and 14 after trauma. Only those subjects who died were drop-outs. All patients had severe polytrauma with at least 3 body regions involved. The median plasma histamine levels at all three time points were significantly higher than in patients with single trauma of the extremities or before selective orthopaedic surgery but still in the normal range (less than 1 ng/ml). However, all patients with plasma levels above 1 ng/ml on days 1 and 5 died, as did all patients with levels above 0.5 ng/ml on day 1. Thus the elevation of plasma histamine levels, for whatever reason, appears to be a prognostic factor for bad outcome in polytrauma patients.

Adolescent↗
PubMed1990

[Acute acalculous cholecystitis. A stress-induced complication].

The acute acalculous cholecystitis is a stress induced complication following surgery and trauma. A totally different disease is a large atonic gallbladder during parenteral nutrition. The symptoms of the acalculous cholecystitis are similar to acute cholecystitis in patients with cholelithiasis. The diagnosis can be very difficult, because in the postoperative period patients are usually very sick, treated with analgetic and antibiotic drugs and therefore the symptoms are mostly lacking or equivocal. Typical signs are fever and leucocytosis. An ultrasound scan should be performed at the intensive care unit. Although the disease is rare according to the literature, in future it may be diagnosed more frequently because of extended surgical intensive care, higher age of patients, modern methods of surgery and early ultrasound scans in equivocal cases. Having the possibility of postoperative and posttraumatic acute acalculous cholecystitis in mind, surgeons may be able to make the right diagnosis earlier than the pathologist.

Acute Disease↗
PubMed1987

[Ultrastructure of the distal ureter in congenital malformations in childhood].

Ultramicroscopical examinations were performed in ten children with reflux or obstructive megaureter. Resected parts of ureters were used for investigation in connection with reconstructive procedures. Whereas in case of an obstructive megaureter an intramural and juxtavesical localised functionless narrow ureteral segment is characterised by "nexus close contacts" and dissociation of muscle cells with interposition of fibrous tissue, progredient pathonexual changes in the sense of a reversible nexus-distension and irreversible nexus-rupture were seen in megaureters with reflux. Dissociation of muscle cells is combined with typical epithelial and adventitial pathological structures. In congenital megaureter, disturbances in the electric syncytium occur in connection with nexus injury, followed by pathological innervation. Interruption of muscle autonomy and innervation in the wall structure of such congenital ureteral malformations play an ominous role in the sequence of pathogenetic factors.

Child↗
PubMed1986

[Instructions for the complete preparation of the larynx].

A method of preparing the larynx in forensic cases is described especially when death occurs by strangulation (manually or using some form of ligature). After the usual dissection of the hyoid bone and the upper horns of the thyroid cartilage, the complete larynx is clipped and fixed in formaldehyde overnight. The first part of dissection after that is to cut away the thyroid gland and the remaining muscles in front of the larynx, except for the cricothyroid muscle and the esophagus and hypopharynx from the back of the larynx. The complete thyroid cartilage is dissected out, and then a horizontal cut is made through the cricoid cartilage. Median-sagittal halving of the remaining larynx completes the gross dissection. Arytenoid cartilages are exposed by dissection of the arytenoid muscles and opening the cricoarytenoid joints. Now all parts of the laryngeal skeleton and all articulations are examined, and all muscles and soft tissues are visible and can be clipped for histological examination.

Asphyxia↗
PubMed1986

Induced histidine decarboxylase in endotoxic shock: identification of the enzyme in rat liver and influence of its inhibitors on survival parameters.

The hypothesis of a causal relationship between a progressive and unrestrained increase of tissue histamine formation by activation of an inducible histidine decarboxylase (HDC) and lethality in endotoxic shock (Schayer's 'induced histamine concept') was tested in a standardized rat endotoxic shock model. Initial enzyme identification studies in the rat shock liver (8 hrs after endotoxin challenge) clearly demonstrate that the 'induced' histidine decarboxylase is an acid (specific) HDC. The succeeding randomized, controlled study with appropriate inhibitors of the enzyme, alpha-methyl-histidine (competitive inhibitor) and alpha-fluoromethyl-histidine (irreversible inhibitor) using doses of 2, 20 or 100 mg/kg showed no significant effect on the survival rate of rats in endotoxin shock. The survival rate of the non-treated endotoxin control group (NaCl) was 25%; all methylprednisolone treated rats (50 mg/kg) survived. Thus, the 'induced' histamine is not a predominant factor (necessary or sufficient determinant) for the lethal outcome in rat endotoxic shock. The protective effect of MP is not predominantly due to the inhibition of the 'induced' histidine decarboxylase. The use of HDC-inhibitors as the appropriate instruments for evaluation of the significance of this mechanism is discussed.

Animals↗
PubMed1982

Plasma histamine levels in patients in the course of several standard operations: influence of anaesthesia, surgical trauma and blood transfusion.

A prospective controlled clinical trial was conducted on changes in plasma histamine and catecholamine levels during 5 standard operations. This communication, as the first part of the trial, deals only with the feasibility of such a trial and the changes in plasma histamine levels. Elevated histamine concentrations corresponding to histamine-release responses of greater than 1 ng/ml occurred in 8 of 25 operations. In an explorative analysis these responses were associated with distinct phases of anaesthesia or the surgical procedure. Blood transfusion carried the risk of infusion of "free histamine" into the patient--especially when administered under pressure. Since during operations "free histamine" enters the circulation with a rather high incidence and may cause harmful effects, premedication with H1-+H2-receptor antagonists seems worth consideration.

Adult↗
PubMed1982

[Radiographic investigation during medico-legal autopsies (author's transl)].

During the last 13 years (1968-1980), 427 radiographic examinations were carried out during the course of medico-legal autopsies at the Institute of Forensic Medicine at the Free University of Berlin. Important problems were the demonstration of retained foreign bodies resulting from shooting, stabbing or blunt trauma, bone injuries, identification, and the question of life in neonates. An historical survey is given and 12 cases with special forensic problems are illustrated and discussed, and further means of investigation are described.

Adult↗
PubMed1979

Parenteral feeding in the management of children with cancer.

Total parenteral nutrition TPN has been used to treat or prevent malnutrition in 65 children with a variety of solid tumors and leukemia in the past 7 years. TPN was used in 58 patients with gastrointestinal complications of surgery, chemotherapy, or radiation; in 2 patients for preoperative correction of malnutrition; and in 8 who were entered into a prospective study. During TPN, general nutrition and appearance improved in all patients. Weight gain was noted in most. Despite gastrointestinal complications, which usually require the interruption of chemotherapy and radiation, treatment could be continued at full dose in 31 children with nutritional support by TPN. TPN was discontinued in 6 patients when blood cultures became positive. Sepsis was treated successfully by removal of the central venous catheter in all 6 and administration of antibiotics in 3. TPN appears to be safe and effective means of combating malnutrition which may occur with cancer and its therapy.

Adolescent↗
PubMed1979

Comparison of alterations in the histamine-diamine oxidase system during acute intestinal ischaemia in pigs, dogs and rabbits; evidence for a uniform pathophysiological mechanism?

Among various vasoactive substances histamine was also suggested to induce circulatory arrest following superior mesenteric artery occlusion. Thus the involvement of the histamine-diamine oxidase system was studied in intestinal ischaemia using three animal species. In pigs, dogs and rabbits aminoguanidine, the specific inhibitor of diamine oxidase, shortened the survival time after mesenteric infarction. Under these conditions the diamine oxidase activity in the intestinal wall was reduced in animals treated by saline whereas the histamine content was not altered significantly. Plasma histamine levels were increased considerably in the portal vein of pigs during the revascularization period if the animal were pretreated by aminoguanidine. Similar findings were obtained in dogs. It was concluded that in all three species investigated the diamine oxidase protects the organism against the deleterious effects of at least one of its vasoactive substrates-histamine.

Amine Oxidase (Copper-Containing)↗
PubMed1979

Lung alterations in newborn rabbits after maternal thrombin-shock. I. Morphological alterations.

Alterations of the lung structure, especially of the pneumocytes type II, of asphyxied newborn rabbits were investigated. Experiments were carried out on pregnant does shocked by thrombin- and Pamba-applications on the 28th, 29th and 30th day of gestation and on their newborns delivered by caesarian section at these days and killed after one or five hours life-time. Histologically, adult rabbits show characteristic alterations in an early phase of the shock. Lung alterations are the main findings in the newborns. Atelectases and, additionally, disturbances of circulation, permeability and also hyaline thrombi are seen. Lamellar bodies within the pneumocytes type II show a significant decrease of the lamellae and the whole osmiophilic material. The alterations of immature newborns are more severe than those of mature animals and also more severe after the longer life-time. These alterations are considered as a result of decreased synthesis of surface active phospholipids.

Animals↗