The primary aortoenteric fistula in The Netherlands--the unpublished cases.

OBJECTIVE: Primary aortoenteric fistula is a rare disorder of which only four patients have been reported in the Dutch literature so far. The objective of our study was to obtain more realistic figures on the incidence of this condition, with data on the clinical presentation, diagnostic procedures, treatment and results in a group of patients not previously reported as "case histories". METHODS: A questionnaire was sent to all surgical clinics in The Netherlands. Out of 180 questionnaires, 102 have been returned reporting 27 patients to which data of eight others treated in our own institution were added. RESULTS: In all but one of these 29 patients the fistula was caused by an atherosclerotic aneurysm, the one exception being caused by an ingested cocktail pin. Gastrointestinal haemorrhage was the predominant symptom, being present in 28 of the patients, while the complete triad of haemorrhage, pain and a pulsating mass was found in only eight patients. Twenty-seven patients were treated with an in situ graft of which 14 are doing well at long term follow-up. CONCLUSIONS: Primary aortoenteric fistula is far more common than one would expect from the number of patients reported in literature. A high index of suspicion based on a complete physical examination remains the key to a correct diagnosis. Direct closure of the intestine and in situ grafting of the aorta is the treatment of first choice.

Primary aortoenteric fistula: report of eight new cases and review of the literature.

Primary aortoenteric fistula, a direct communication between the aorta and the intestinal tract, is a rare cause of gastrointestinal hemorrhage. Eight patients who were all treated at one hospital are described, followed by a review of all surgically treated patients reported within the past 10 years. The usual cause is erosion of an atherosclerotic aneurysm into the adherent duodenum, but a wide variety of other causes and localizations have been described. The clinical presentation is usually one of intermittent gastrointestinal hemorrhage resulting in lethal exsanguination within a matter of hours or days. Pain, a pulsatile abdominal mass, or fever may not be present. Endoscopy, arteriography, ultrasound, and CT scan can be useful in the evaluation of these patients, but physical examination and a high index of suspicion remain key to diagnosis. Primary aortoenteric fistula is more often discovered unexpectedly during exploratory laparotomy and is not usually considered as a presumptive preoperative diagnosis. Although contamination is unavoidable, most patients are treated with an in situ vascular graft and primary closure of the intestinal defect with good results.

Abdominal pain as a first symptom of iliac vein thrombosis.

Two patients are described with abdominal pain as a first symptom of primary iliac vein thrombosis. This phenomenon can be regarded to be analogous to the calf tenderness when thrombosis arises from the venous sinusoids in the calf muscles which is the usual localisation. When one is aware of this clinical entity, thrombotic occlusion will be recognized as the cause of the complaints, instead of being regarded to be a complication of another, yet unknown disease.

Venous outflow measurement in the diagnosis of deep vein thrombosis--principles and practice.

Venous outflow measurement (kenoseography) is increasingly applied in the diagnosis of deep vein thrombosis. Performance and interpretation of this examination have a considerable influence on the final result. The influence of congestion pressure, outflow determination, positioning of the patient and the site of measurement are discussed. One should be aware that figures obtained by one institution can not always be applied by others.

Instead of "plethysmography": "kenoseography" and "plesmonegraphy".

The recording of volume changes in health and disease has from old been designated as "Plethysmography". This was supposed to be a correct term for the recording (graphein) of an increase in volume (plethysmos). The present paper shows that the choice of this term was not felicitous, and suggests an alternative. The first "plethysmographic" recordings are ascribed to Glisson (1622) and Swammerdam (1737). Since Glisson and Swammerdam did, in fact, record the volume of muscle to be constant on contraction, their measurements should probably have been referred to as "isography". This, however, is merely a historical matter. Presently venous outflow measurement is a common procedure to establish the diagnosis of deep vein thrombosis. Venous outflow is determined by recording the decrease in volume of a limb which occurs after release of a congestion cuff. As this is quite the opposite of what is meant by "Plethysmography", another indication is needed for this examination. It appears that a suitable alternative can be taken from ancient Greek medical literature.

Caloric vestibular test with the use of air.

In a group of 28 test subjects the vestibular caloric test was performed with the aid of two different methods. In the first method the ears were irrigated for 30 sec with water with a temperature of 30 C and 44 C and later on with airstream with a temperature of 20 C and 50 C. The wet method proved to be a significant stronger stimulus than the dry method. The authors conclude that the water irrigation is the method of choice for the caloric test. The dry method is only useful when the wet method is undesirable.

Synthesis of Isocyanic Acid from Nitric Oxide over Palladium and Iridium Catalysts.

A novel and convenient synthesis of isocyanic acid (HNCO) and its trimer isocyanuric acid has been obtained by the conversion of nitric oxide (NO). Nitric oxide, carbon monoxide, and hydrogen mixed in helium at the level of 0.3 to 5 percent reacted over iridium and palladium catalysts at 280 degrees to 450 degrees C to form HNCO in 60 to 75 percent yield. Major side products were ammonium cyanate at low temperature and ammonia or nitrogen at high temperature. Total conversion of nitrogen from NO to NCO reached 73 percent over palladium and 86 percent over iridium.

Synthesis of ammonium cyanate and urea by reduction of nitric oxide on platinum, rhodium, and ruthenium catalysts.

Nearly quantitative conversion of nitric oxide (NO) into N(2)H(4)CO has been obtained in the reduction of NO with carbon monoxide and hydrogen over platinum and rhodium catalysts. Depending on the temperature of collection, N(2)H(4)CO is isolated as ammonium cyanate or its isomer, urea. The process is an effective way of recovering fixed nitrogen from dilute industrial streams containing NO. Ammonium cyanate may play a role in the reduction of NO in automotive exhaust control.

Hydrogen Cyanide Production During Reduction of Nitric Oxide over Platinum Catalysts: Transient Effects.

The formation of hydrogen cyanide during the catalytic reduction of nitric oxide (NO) with carbon monoxide and hydrogen was studied with a bench-scale flow reactor. The previously reported inhibition by sulfur dioxide of the formation of hydrogen cyanide was found to be counteracted by transient admission of oxygen to the catalyst. These results are discussed in the context of the control of automotive emissions of NO and the prevention of hydrogen cyanide production during such control.

Perovskite oxides: materials science in catalysis.

In a time of growing need for catalysts, perovskites have been rediscovered as a family of catalysts of such great diversity that a broad spectrum of scientific disciplines have been brought to bear in their study and application. Because of the wide range of ions and valences which this simple structure can accommodate, the perovskites lend themselves to chemical tailoring. It is relatively simple to synthesize perovskites because of the flexibility of the structure to diverse chemistry. Many of the techniques of ceramic powder preparation are applicable to perovskite catalysts. In their own right, they are therefore of interest as a model system for the correlation of solid-state parameters and catalytic mechanisms. Such correlations [See figure in the PDF file] have recently been found between the rate and selectivity of oxidation-reduction reactions and the thermodynamic and electronic parameters of the solid. For commercial processes such as those mentioned in the introduction, perovskite catalysts have not yet proven to be practical. Much of the initial interest in these catalysts related to their use in automobile exhaust control. Current interest in this field centers on noble metalsubstituted perovskites resistant to S poisoning for single-bed, dual-bed, and three-way catalyst configurations. The formulations commercially tested to date have shown considerable promise, but long-term stability has not yet been achieved. A very large fraction of the elements that make up presently used commercial catalysts can be incorporated in the structure of perovskite oxides. Conversely, it is anticipated that perovskite oxides, appropriately formulated, will show catalytic activity for a large variety of chemical conversions. Even though this expectation is by no means a prediction of commercial success in the face of competition by existing catalyst systems, it makes these oxides attractive models in the study of catalytic chemical conversion. By appropriate formulation many desirable properties can be tailored, including the valence state of transition metal ions, the binding energy and diffusion of O in the lattice, the distance between active sites, and the magnetic and conductive properties of the solid. Only a very small fraction of possible perovskite formulations have been explored as catalysts. It is expected that further investigation will greatly expand the scope of perovskite catalysis, extend the understanding of solid-state parameters in catalysis, and contribute to the development of practical catalytic processes.

Rare-Earth manganites: catalysts with low ammonia yield in the reduction of nitrogen oxides.

Rare-earth manganites such as La(1-x) Pb(x)MnO(3), with 0.3 x 0.6, and their perovskite-like homologs are active catalysts for the reduction of nitric oxide to molecular nitrogen. At low temperatures, innocuous nitrous oxide rather than anmmonia is the main side product. The activity of single crystalline catalysts and of ceramic catalysts of this type is substantially improved by etching with dilute acids.

Rare-earth oxides of manganese and cobalt rival platinum for the treatment of carbon monoxide in auto exhaust.

The perovskite-like compounds RE(1-X)Pb(5)MnO(3) and RECoO(3), where RE (rare earth) is lanthanum, praseodymium, or neodymium, are active catalysts for the oxidation of carbon monoxide. Crushed single crystals of these compounds compare favorably with commercial platinum catalysts in initial activity and lifetime. Therefore, these compounds are promising substitutes for platinum in devices for the catalytic treatment of auto exhaust.