Emboli generation by the Medtronic Maxima hard-shell adult venous reservoir in cardiopulmonary bypass circuits: a preliminary report.

Increases in right common carotid artery Doppler ultrasound signals typical of emboli were found in cardiopulmonary bypass patients when the Medtronic Maxima hard-shell adult combined venous and cardiotomy reservoir was operated at reservoir blood volumes near the manufacturer;s recommended minimum of 300 ml. The signals were reduced by increasing the reservoir blood volume. Possible microembolus generation in the top- and bottom-entry versions of this reservoir was investigated using an in vitro circuit and a colour flow Doppler monitor that was interfaced with a microprocessor to count the signals. The reservoir blood volume was progressively lowered in 100 ml increments below 1000 ml, and signals were counted over five minutes at each new level. Signal counts downstream of the reservoir increased exponentially after the volume was decreased below 1000 ml in the bottom-entry version, and 700 ml in the top-entry version. Ultrasonic monitoring, both upstream and downstream of the reservoir, showed that the source of these signals was the reservoir itself, and that recirculation of emboli around the circuit accounted for only a small proportion of the measured increase. Changes in circuit blood prime haematocrit within the range 0.11-0.31 did not alter the signal counts. However, counts were profoundly affected by exposure of the circuit to nitrous oxide via a membrane oxygenator; this showed that the emboli were bubbles. Bubble formation may occur where venous blood enters the reservoir as this results in a fountaining effect when the reservoir volume is low. This effect appears to have been serendipitously reduced, but not eliminated, in the design of the top-entry version. It is recommended that perfusionists should not operate these reservoirs at volumes below 1000 and 700 ml in the bottom- and top-entry versions respectively.

Ocular infections and the industrial use of microscopes.

A cluster of ocular infections occurred in one area of a computer fabrication facility that relied on the use of industrial microscopes. A questionnaire was administered to all employees in this area. Microscope oculars were cultured and compared with control microscopes from a nonindustrial setting. Risk of infection was correlated with the number of hours of microscope use per day and subjective indicators of cleanliness. Bacterial cultures confirmed increased colony counts in industrial oculars compared with control oculars. Hygienic practices were instituted similar to those employed in medical settings. No further outbreaks of conjunctivitis have been reported in a 1-year follow-up.

Tension pneumopericardium following blunt chest trauma.

A 12-year-old victim of an automobile-pedestrian accident appeared to develop severely compromised cardiac output shortly after intubation and positive pressure ventilation. Anteroposterior and lateral chest films showed air within the pericardial sac. After pericardiocentesis and withdrawal of air, cardiac function improved markedly as evidenced by a rise in blood pressure and a slowing of the pulse. A catheter was left in the pericardial sac for several days. The patient remained hemodynamically stable throughout the hospital stay and was subsequently discharged. Documentation of this degree of tamponade from air in the pericardium is quite uncommon.

Modifications in the technique of gastric lavage.

A simple experimental model was used to demonstrate the effects of water temperature and mechanical agitation in removing pills during gastric lavage. It was nearly impossible to remove pills from an artificial stomach using room temperature water and no mechanical agitation, Using warm tap water and repetitive compressions of the artificial stomach, the pills were consistently removed with ease. We recommend that gastric lavage for poisoning victims include two phases, the first using traditional lavage technique, and the second using larger aliquots, warm lavage fluid, and massage of the epigastrium.