Theoretical and experimental intravascular gas embolism absorption dynamics.

Multifocal cerebrovascular gas embolism occurs frequently during cardiopulmonary bypass and is thought to cause postoperative neurological dysfunction in large numbers of patients. We developed a mathematical model to predict the absorption time of intravascular gas embolism, accounting for the bubble geometry observed in vivo. We modeled bubbles as cylinders with hemispherical end caps and solved the resulting governing gas transport equations numerically. We validated the model using data obtained from video-microscopy measurements of bubbles in the intact cremaster microcirculation of anesthetized male Wistar rats. The theoretical model with the use of in vivo geometry closely predicted actual absorption times for experimental intravascular gas embolisms and was more accurate than a model based on spherical shape. We computed absorption times for cerebrovascular gas embolism assuming a range of bubble geometries, initial volumes, and parameters relevant to brain blood flow. Results of the simulations demonstrated absorption time maxima and minima based on initial geometry, with several configurations taking as much as 50% longer to be absorbed than would a comparable spherical bubble.     

Cerebral fat embolism.

An unusual presentation of fat embolism is reported. Forty-eight hours after severe trauma to her legs the patient became stuporous and her right arm weak. A computerized tomography scan showed diffuse brain swelling. Although the petechiae, thrombocytopenia and lipuria characteristic of the fat embolism syndrome were present, at no time was there any evidence of pulmonary involvement.     

Cerebral hemodynamics during microgravity.

As one of the causes of the space adaptation syndrome, an increased intracranial pressure due to the cephalad fluid shift is suggested. In the present study, we measured intracranial pressure (ICP), aortic pressure and cerebral flow velocity (CFV) in anesthetized rats (n=5) during 4.5 sec of microgravity induced by free drop. The rats were set at horizontal prone (Flat) and 30-degree head-up whole body tilting (HU) positions to examine the effect of gravitational pressure gradient. Then, arterial pressure at the eye level (APeye), cerebral perfusion pressure (CPP; CPP=APeye-ICP), and CPP-CFV relationship was calculated. In HU position, ICP, APeye, and CPP increased by 2.2 +/- 0.4, 12.3 +/- 2.0, and 10.1 +/- 1.7 mmHg respectively. However, CFV did not change significantly. In Flat position, none of these variables did not change significantly. In HU position the slope of CPP-CFV relationship decreased, suggesting the increased cerebral flow resistance. However, it did not change in Flat position. These results can be understood by the disappearance of gravitational pressure gradient by microgravity and the cerebral autoregulation.     

Fatal fat embolism during ritual initiation.

A young Coast Salish Indian woman became fatally ill during ritual Initiation into the Native Winter Spirit Dancing Society. She died from massive fat emboli associated with subcutaneous bruises that appeared clinically unimportant and were not associated with fractures or other underlying injury. The liver showed extreme fatty metamorphosis.     

Copper-sodium linkage during intestinal absorption: inhibition by amiloride.

The possible association between copper and sodium small intestinal absorption in the rat was investigated in the presence or absence of the electrolyte transport inhibitors amiloride, acetazolamide, and furosemide, at pharmacologic concentrations, using an in situ perfusion procedure. Amiloride (1 mM) produced a significant decrease in copper, net water, and sodium absorption, in solutions with sodium. Copper tissue retention was not altered, but was much higher in the absence of sodium. Acetazolamide and furosemide (1 mM), in separate experiments, had no effect on copper removal from the lumen, but generally reduced sodium and water transport. The presence or absence of sodium in the perfusate influenced rates of copper uptake. These data are compatible with a more effective passage of copper across the enterocyte basolateral membrane in the presence of sodium than in its absence.     

Chest diseases: benefits of hyperbaric oxygen therapy in infectious disease

The Scientific Board of the California Medical Association presents the following inventory of items of progress in chest diseases. Each item, in the judgment of a panel of knowledgeable physicians, has recently become reasonably firmly established, both as to scientific fact and important clinical significance. The items are presented in simple epitome and an authoritative reference, both to the item itself and to the subject as a whole, is generally given for those who may be unfamiliar with a particular item. The purpose is to assist busy practitioners, students, research workers, or scholars to stay abreast of these items of progress in chest diseases that have recently achieved a substantial degree of authoritative acceptance, whether in their own field of special interest or another.The items of progress listed below were selected by the Advisory Panel to the Section on Chest Diseases of the California Medical Association and the summaries were prepared under its direction.