Measurement of emboli in extracorporeal perfusion systems

Does pharmacotherapy influence the inflammatory responses during cardiopulmonary bypass in children?

Cardiopulmonary bypass (CPB) induces a systemic inflammatory response syndrome (SIRS) by factors such as contact of the blood with the foreign surface of the extracorporeal circuit, hypothermia, reduction of pulmonary blood flow during CPB and endotoxemia. SIRS is maintained in the postoperative phase, co-occurring with a counter anti-inflammatory response syndrome. Research on the effects of drugs administered before the surgery, especially in the induction phase of anesthesia, as well as drugs used during extracorporeal circulation, has revealed that they greatly influence these postoperative inflammatory responses. A better understanding of these processes may not only improve postoperative recovery but also enable tailor-made pharmacotherapy, with both health and economic benefits. In this review, we describe the pathophysiology of SIRS and counter anti-inflammatory response syndrome in the light of CPB in children and the influence of drugs used on these syndromes.

Bilateral sudden sensorineural hearing loss following non-otologic surgery

Hearing loss as a complication of non-otological surgery is rare. The majority of described cases have followed cardiac bypass surgery. To date there have been only 25 reported cases of non-otological surgery associated hearing loss (NOSAHL) which have not involved cardiopulmonary bypass. Only two cases of bilateral NOSAHL have been previously described, and neither resulted in permanent severe bilateral hearing deficit. We describe a case of permanent bilateral severe hearing loss following metatarsal pinning in a patient with pre-existing non-operated otosclerosis.

Audiovestibular complications of non-otological surgery

Post-operative dizziness or imbalance is often regarded as 'trivial' and self-limiting and vaguely ascribed to the drugs used in anaesthesia or to haemodynamic changes. While hearing loss after anaesthesia has been documented in several studies, very little attention has been paid to a possible vestibular cause for post-operative dizziness. Twelve patients with post-operative vestibular disorders, with or without concomitant hearing loss, and one patient with tinnitus are described. As effective management for vestibular dysfunction exists, the importance of identifying this potential cause of dizziness is emphasized.

Comparison of bubble release from various types of oxygenators. An in vivo investigation

The present study compares the creation of free gas bubbles in five different bubble oxygenators and one membrane oxygenator, by use of Doppler ultrasound technique. The study was carried out on groups of male patients undergoing coronary artery bypass surgery. The results show that the bubble oxygenators produce a considerable amount of free gas bubbles, with variances based on type. The membrane oxygenator showed virtually no counts at all.

Sudden sensorineural hearing loss: operative complication in non-otologic surgery

Sudden sensorineural hearing loss is a well recognized phenomenon in otologic practice with both viral and vascular etiologies being supported. However, sudden hearing loss as a complication of non-otologic surgical procedure is a seldom reported and rare phenomenon. Five cases of unilateral sudden sensorineural hearing loss which are time related and probably causally related to non-otologic surgery are presented. Two cases underwent open heart surgery and support previous reports of hearing loss secondary to cardiopulmonary bypass procedures. Three noncardiac cases are also reviewed. None of these patients had prior otologic disease which would predispose to a sudden hearing loss, and no intraoperative or postoperative complication was specifically noted as a cause of the hearing loss. The literature is reviewed and attention is drawn to the problem. We wish to encourage further reports and to recommend early identification and treatment in those cases related to cardiopulmonary bypass.

The effect of thromboresistent surfaces on the development of blood emboli and hemolysis

Heparinized dog blood was sheared in conicylindrical test cells which had been coated with thrombo-resistant materials. Hemolysis and blood emboli formation in the coated cells were as great or greater than in uncoated polycarbonate cells. These results suggest that materials which resist the buildup of thrombi may still be stimulating emboli formation and red cell damage.

Plasma administration to defibrinogenated dogs during extracorporeal circulation

Plasma, in an amount corresponding to 0.05 gm fibrinogen/Kg of body weight, was administered during one hour to defibrinogenated dogs subjected to extracorporeal circulation. Four blood filters included in the extracorporeal circuit were removed one by one at 30-minute intervals. The prefilter pressures rose gradually during the whole experiment. Scanning electron microscopy of the filter surface revealed equal amounts of deposits before, during and after the infusion of plasma. Only minimal amounts of fibrin were found on the filter surfaces by immunoelectrophoresis. Mean arterial pressure, arterial blood gases, fibrinogen concentration, platelet count and leukocyte count were followed before, during and after plasma infusion and showed no significant changes. Thus, it is possible to administer limited amounts of plasma to defibrinogenated dogs subjected to extracorporeal circulation.

The effect of shear, specific surface, and air interface on the development of blood emboli and hemolysis

Heparinized dog blood was exposed to shear and foreign surfaces in conicylindrical test cells. The cells were injection molded from polycarbonate and were filled using a technique that avoided contact of the blood with air. Particulate-matter formation was measured and was found to be dominated by the surface-to-blood-volume ratio and to be independent of shear rate. Hemolysis was also measured and was found to vary linearly with shear rate and to increase with increasing surface-to-blood volume ratio. Thus, at low shear rates and high specific surface conditions, the degree of hemolysis was found to be minimal while particulate-matter formation was high. The results suggest that the safety of extracoporeal perfusion procedures cannot be inferred from hemolysis measurements alone. In one series of tests, a gas-blood interface was generated at a rate equivalent to the rate of surface renewal in conventional disc oxygenators. The gas-blood interface failed to contribute significantly to the damage indices, which suggests that the apparent superiority of membrane oxygenators may be a result of factors other than the absence of a blood-gas interface.

Thrombus formation and microaggregate removal during prolonged extracorporeal circulation using a capillary membrane oxygenator. A scanning electron microscope study

Despite adequate heparinization, thrombus formation occurs at the blood/foreign material interface. Depending on the part of the device, the material and the blood flow, the amount and the components of thrombi vary greatly. This is not dangerous by itself but clots can be expelled downstream and damage the lungs, brain, kidney and retina. Interposition of a filter may prevent risks of embolization. The present paper reports the scanning electron microscope study carried out on the Awad oxygenator after use during prolonged extracorporeal circulation on 13 dogs. No filter has been inserted in the circuit for the first six experiments. A screen filter (4) or a polyurethane foam filter (3) was employed in the following ones.

Events related to microembolism during extracorporeal perfusion in man: effectiveness of in-line filtration recorded by ultrasound

Microparticle generation during cardiopulmonary bypass was monitored continuously in 60 adult patients who underwent open-heart operations. Echo-ultrasound transducers of 5 mHz frequency were interposed in a bubble oxygenator arterial line proximal and distal to a commercially available micropore filter. Ordinary perfusion events correlated with an increase in embolic counts and were recorded graphically. Calculation of filter efficiency revealed that all filters decreased measurable embolic counts. Platelet and leukocyte determinations and plasma hemoglobin values were not altered beyond limits ordinarily encountered during perfusion without filters. No patient in any filter group experienced postoperative respiratory distress, diffuse pulmonary infiltrate, or low PaO2. The 20 mu woven nylon mesh filter and the Dacron-wool filter showed greater than 90% effectiveness in removing recorded particles. Insertion of a cardiotomy filter did not appreciably alter recorded embolic counts distal to the arterial line filter.