The effect on pulmonary ultrastructure of dacron-wool filtration during cardiopulmonary bypass

Haematological effects of a depth absorption arterial line filter during extracorporeal circulation

An arterial line filter (Swank High Flow 6000) was used during extracorporeal circulation (ECC) in 21 of 45 patients undergoing coronary artery bypass grafting, to study haematological effects. The mean age was 60 (41-69) years. All patients had obstructions of at least three coronary artery branches. Average ECC and aortic crossclamp times, drainage via chest tubes until the first day after surgery, total transfusions of blood products and haemolysis did not differ in the two groups. After 90 minutes of ECC, leukocyte counts were significantly lower in the filter group whereas haematocrit, counts of erythrocytes, lymphocytes and platelets, platelet volume, fibrinogen concentration and fibrinopeptide A were similar. Release of β-thromboglobulin and platelet factor 4 were significantly higher in the filter group. No clinically significant adverse haematological effects were observed with use of the arterial line filter, although there were indications of more pronounced platelet damage in the filter group.

Analysis of microembolic particles originating in extracorporeal circuits

Silicone tubing is utilised increasingly in extracorporeal circulation (ECC), particularly for prolonged bypass in cases of left ventricular failure following open heart surgery. We compared the spectrum of particle formation in the EC circuit, due to roller pump damage, resulting from wear of silicone tubing with that of polyvinyl chloride (PVC) tubing. The EC circuit was primed with plasmalyte solution for pump runs of up to 24 hours. Samples of the perfusate were taken from either system at prefixed times. Number and size of the particles were determined by means of a Coulter counter, while their chemical composition was analysed by X-ray dispersion (EDXA). The tubing was examined by scanning electron microscopy. When using PVC tubing, the amount of particles of all sizes rose above acceptable standards shortly after activating the roller pump. Following this early upsurge, the number of particles continued to increase for the remainder of the pump run, albeit at a more moderate rate. The silicone tubing continuously generated a marked quantity of particular matter at a steadily increasing rate. Electron microscopic examination of the silicone tubing revealed multiple particles emanating from the inner surface of the tube. The results suggest that filtration of the initial priming fluid may be advisable before connecting the patient to an EC circuit using PVC tubing. The multitude of particles liberated by the silicone tubing implies that its usage in ECC should be curtailed. Utilisation of noncrushing head pumps is recommended in ECC.

The use of leucocyte-depleting and conventional arterial line filters in cardiac surgery: a systematic review of clinical studies

Although various forms of arterial line filter have been available for use during cardiopulmonary bypass (CPB) for 30 years, their use is not universal. The aim of this review was to seek evidence of the clinical benefit of using conventional or leucocyte-depleting arterial line filters during bypass. A literature search revealed 28 relevant clinical studies. Despite the wide variety of patient populations, types of filter and outcome measures utilized in studies, a few conclusions are possible. Whereas conventional filtration has the definite effect of reducing neuropsychological deficit post-CPB, the results of studies using the leucocyte-depleting filter are less clear cut. Leucocyte-depleting filters have potential for reducing inflammatory mediated heart and lung injury, however it is recommended that any additional benefit of leucocyte-depleting filters over conventional filters should be further tested by randomized controlled trials of sufficient size.

Spallation performance of extracorporeal membrane oxygenation tubing

During the prolonged roller pump use of extracorporeal membrane oxygenation (ECMO), tubing wear generates spallation. The spallation performance of Tygon S-65-HL was measured and compared with a potential new ECMO tubing, LVA (Portex 800-500-575). Spallation was measured by on-line laser diode particle counting (HIAC) during simulated ECMO. The effects of differing levels of occlusion and pump speed were examined, as was the effect of spallation over time. The spallation produced by Tygon S-65-HL was less than that seen with LVA during 24 h of simulated ECMO (p < 0.001), and after 72 h had fallen almost to zero. Spallation with Tygon tubing increases with increasing pump speed and decreases over time. There appears to be only a weak correlation with occlusion, which is surprising. The spallation performance of Tygon S-65-HL was variable and under some conditions exceeded that of LVA. Overall, however, Tygon S-65-HL produced less spallation than LVA. Therefore, LVA cannot be recommended for clinical ECMO use.

Impact of pleurotomy, continuous positive airway pressure, and fluid balance during cardiopulmonary bypass on lung mechanics and oxygenation

OBJECTIVE

To determine effects of surgical pleurotomy, continuous positive airway pressure, and fluid balance during cardiopulmonary bypass (CPB) on lung mechanical properties and indices of oxygenation.

DESIGN

Prospective, descriptive, and interventional study.

SETTING

Cardiothoracic service at a major university referral center.

PARTICIPANTS

Eighteen anesthetized-paralyzed patients undergoing elective coronary artery bypass grafting requiring CPB.

INTERVENTIONS

During CPB, continuous positive airway pressure (CPAP) was applied to nine patients, in nine others, no CPAP was applied.

MEASUREMENTS AND MAIN RESULTS

From measurements of airway and esophageal pressures and flow, lung resistance and elastance were determined before sternotomy and after sternal reapproximation. Measurements were made during forced ventilation over a physiologic range of tidal volumes and frequencies, and frequency and volume dependences of lung resistance and elastance were additionally identified. In all patients, lung resistance and elastance increased after CPB, consistent with models of pulmonary edema. Multiple regression analysis showed that these increases were relatively less in patients with intact pleurae (p < 0.05) or net negative fluid balance (p < 0.05); however, no difference in these increases was noted between patients receiving CPAP and those receiving no CPAP. Increases in lung resistance were positively correlated to net fluid balance, and negatively correlated to frequency and tidal volume (p < 0.05). Increases in lung elastance were positively correlated to tidal volume (p < 0.05). Absolute change in alveolar-arterial oxygen gradient was negatively correlated with net fluid balance, whereas percentage change was positively correlated to changes in lung elastance (p < 0.05).

CONCLUSIONS

These findings suggest that pleurotomy before CPB and positive fluid balance during CPB enhance postbypass pulmonary edema and/or atelectasis, as demonstrated by acute changes in respiratory mechanics and indices of oxygenation. Low levels of CPAP applied during CPB did not significantly change either mechanical properties or oxygenation.

Massive blood transfusion: the blood bank perspective

The pathophysiology and support of the massively transfused patient from the vantage of a blood banker is reviewed. Hypothermia, acidosis and shock must be reversed if blood component therapy is to be effective. Algorithms which employ ratios of various blood components have not proved themselves, nor are screening coagulation tests of value until they are remarkably abnormal. Thrombocytopenia, thrombocytopathy, and hypofibrinogenemia appear to be the parameters which predispose to continued bleeding and microvascular hemorrhage in these patients. A large part of the impaired hemostasis is due to a consumption coagulopathy rather than the anecdotal assumption that dilution of the hemostatic elements is to blame. Hypocalcemia, hypomagnesemia and hyperkalemia are rarely observed nor do they pose a problem for this group of individuals. The logistics of blood supply to the clinical areas are addressed by describing one system that has proved itself.

Brain embolic phenomena associated with cardiopulmonary bypass

Various biologic and non-biologic materials may be embolized to the brain after the use of cardiopulmonary bypass (CPB) pumps during open heart surgery but their relative frequency and importance are uncertain. Among the nonbiologic materials, Antifoam A, which contains organosilicates and silicon, continues to be employed as an additive to prevent frothing. Recent improvements in filtration and oxygenation techniques have clearly reduced the incidence of large emboli and complications like stroke but other neurologic sequelae following open heart surgery are common and in many cases poorly explained. A recently developed histochemical technique for the demonstration of the endothelial alkaline phosphatase (AP) was employed in a post-mortem study of brains from 8 patients and 6 dogs dying within a few days after open heart surgery employing cardiopulmonary bypass perfusion. Brains from 38 patients and 6 dogs who were not subjected to heart surgery were studied as controls with the same technique. The AP-stained slides are suitable for both light microscopic examination of the thick celloidin sections as well as a subsequent processing for high-resolution microradiography. Small capillary and arteriolar dilatations (SCADs) were seen in the test subjects/animals but not controls. SCADs were seen in all parts of the brain. Approximately 50% of the SCADs showed birefringence when examined with polarized light. SCADs are putative embolic phenomena and the exact nature and source of the embolic material is under investigation. A glycolipid component is indicated by preliminary studies. SCADs are difficult to find in routine paraffin sections and most if not all of the offending material seems to be dissolved during processing.(ABSTRACT TRUNCATED AT 250 WORDS)

Quantitation of particulate microemboli during cardiopulmonary bypass: experimental and clinical studies

An electronic particle-size analyzer (Coulter Counter ZM) was used to quantitate particulate microemboli 15 to 80 microns in size during cardiopulmonary bypass. Through both laboratory studies and clinical research, we confirmed three main causes of microemboli: (1) infusion of banked blood stored for more than 3 days; (2) use of cardiotomy reservoirs; and (3) use of bubble oxygenators. The regression equation between number of particles and blood storage time was Y = 3.7262X + 10.244 (r = 0.886; p < 0.01). The number of microemboli from cardiotomy reservoirs was 2.8 to 5.1 times that from other sources (p < 0.01). The number of solid particles from bubble oxygenators was 1.8 to 3.2 times that from membrane oxygenators (p < 0.01). Electron microscopy showed that a large number of solid particles more than 20 microns in size were formed during heart-lung bypass. They obstructed the microcirculation and damaged pulmonary capillary endothelial and alveolar epithelial cells. The degree of histological damage was related to the number and size of microemboli and the duration of pulmonary microcirculatory obstruction.

Lung extravascular volume during venovenous bypass with extracorporeal CO2-removal in dogs

Extracorporeal circulation can cause lung damage, which would be especially counterproductive during extracorporeal gas exchange for the treatment of acute respiratory failure. To test the hypothesis that partial venovenous bypass with extracorporeal CO2-removal combined with low-frequency positive pressure ventilation (ECCO2R-LFPPV) can adversely affect lung fluid balance, extravascular thermal lung volume (ETV) and hemodynamics were assessed before, during and after ECCO2R-LFPPV in normal closed chest dogs. In series I dogs (n = 6) subjected to 10 h of ECCO2R-LFPPV, ETV did not change significantly from control (7.1 ml/kg +/- 0.99 SE) during or after bypass. Gravimetric extravascular lung water and lung histology after bypass were found to be normal. In series II dogs (n = 5), subjected to shorter periods of ECCO2R-LFPPV, ETV also remained unchanged. In contrast to previous reports using sheep, pulmonary arterial hypertension during bypass was not observed. Thus, ECCO2R-LFPPV was not associated with increased lung water, pulmonary hypertension or morphological lung changes under the conditions studied and does not seem to cause lung damage in normal lungs.

Continuous airway pressure with oxygen minimizes the metabolic lesion of 'pump lung'

Water distribution and energy status of the lung were measured in ten rabbits at two hours of hypothermic cardiopulmonary bypass (CPB) with left heart venting and incision of the parietal pleurae. During CPB, half the animals had their airways open to room air at ambient atmospheric pressure (ZEEP), and the remainder had their lungs inflated (CPAP) at a pressure of 5 cms H2O with the oxygen-enriched (70-75 per cent) gas mixture exiting from the disc oxygenator. In both the ZEEP and CPAP groups, there was more than doubling of the pulmonary extravascular sodium-free water (intracellular) space and reciprocal reduction of the pulmonary extravascular sodium (extracellular) space, compared with 12 control animals not undergoing CPB. In the ZEEP group, there was an 18-fold increase in the pulmonary lactate/pyruvate (L/P) ratio compared with controls, and the pulmonary energy charge (E.C.) was significantly less than in controls (0.74 +/- 0.02 vs. 0.89 +/- 0.01). In the CPAP group the pulmonary L/P ratio was 2 1/2 times control values and the pulmonary E.C. was virtually identical with that of the control group. These data suggest that CPB results in a shift of fluid from the pulmonary interstitium into the pulmonary intracellular compartment with no net increase in total pulmonary extravascular water. The data also suggest that pulmonary deflation during CPB results in a significant pulmonary energy deficit which can be prevented by keeping the lung inflated with an oxygen-enriched gas mixture during CPB.

Microemboli observed in deaths following cardiopulmonary bypass surgery: silicone antifoam agents and polyvinyl chloride tubing as sources of emboli

Refractile foreign particles within clear vacuoles were observed in capillaries of 17 patients who underwent cardiopulmonary bypass surgery, died, and were autopsied at the George Washington University Hospital from December 1978 through April 1981. The postoperative survival time ranged from less than one day to more than eight months. The approximate maximal diameter of the individual particles was 10 micrometer and that of the vacuoles 60 micrometer. The particle-droplet complexes showed affinity for hydrophobic stains. In all 17 cases, the kidneys were involved in combination with several other organs. In two patients, the emboli were associated with microinfarcts in one or more organs. Scanning electron microscopy (SEM) of the polyvinyl chloride tubing used during four cardiopulmonary bypasses showed spallation and shredding of the luminal surface in the areas exposed to the roller pump heads. This suggested that fragments of polyvinyl chloride might be the particles in the emboli. Another possible source was the antifoam agent used in the bubble oxygenator. Scanning electron microscopy x-ray microprobe analysis of the foreign material within capillaries of several organs showed it to be strongly positive for silicon but not for chlorine. Therefore, it was concluded that the microemboli were droplets of antifoam agent, the refractile particles corresponding to the particulate silica component and the vacuoles corresponding to the dimethylpolysiloxane liquid component. Since x-ray microprobe analysis of the microemboli did not reveal a strong chloride peak, there is as yet no evidence that polyvinyl chloride fragments were involved in the microembolism. The morphologic findings reported here indicate that antifoam microembolization continues to complicate cardiopulmonary bypass surgery and must, therefore, be considered a potential cause of postoperative morbidity. The consequence of the fragments of polyvinyl chloride tubing released into the circulation remains to be established.

Stroke in coronary bypass surgery

A retrospective review of 253 patients who underwent coronary bypass surgery was performed. Eight (3.2%) had suffered a stroke either intra-operatively (4) or during the early post-operative period (4). A comparison of pre-operative and intra-operative variables between the stroke group and the stroke-free group showed a significant difference only for the hemoglobin level (p less than 0.01). All intraoperative strokes occurred in patients who had undergone femoral cannulation; it is suggested that this may have been a source of embolic material in these patients. An embolic origin for most of the strokes (both intra-operative and post-operative) is postulated on the basis of clinical and pathological findings.

The effect of a nylon mesh blood filter in the arterial line during extracorporeal circulation

Forty patients with different cardiac diseases underwent perfusion with the Shiley bubble oxygenator without a filter in the arterial line (Group A). This group was compared with a similar group of patients (Group B), in whom an Intersept nylon mesh filter was used in the arterial line. There were no differences according to age, weight or duration of perfusion between the two groups. The average postoperative bleeding via the chest tubes was 361 ml/m2 B.S.A./24 hours in group A compared with 414 in group B (p less than 0.05). One patient in the filter group died on the table because of myocardial failure, while the remaining 79 patients could leave hospital alive. One patient in each group showed impaired consciousness, but no other neurological complications were recorded in the patients. There were no significant differences in haematocrit, B-haemoglobin or leucocyte counts after 15 min, 1 hour, at the end of perfusion or 1 hour, respectively 24 hours postoperatively. The platelet count after 1 hour of perfusion was 55.8 x 10(9)/l in the filter group compared with 80.4 x 10(9)/l in group A (p less than 0.05), there were, however, no significant differences in B-platelet counts at the end of perfusion or later. Our study showed that a nylon mesh filter in the arterial line can reduce the platelet count. As no measureable advantages were found in the filter group we cannot recommend an arterial line filter.

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.

A role of extracorporeal circuit in the post-perfusion thrombocytopenia: a scanning electronmicroscopic observation

Thrombocytopenia is one of the adverse effects of extracorporeal circulation (ECC) but the mechanism of which has not been fully understood. Blood-gas interface, mechanical agitation, rough surface of extracorporeal circuit and sequestration in the liver have been considered to be a cause of platelet loss. Extracorporeal circuit which provides large artificial surface for contact of blood has been blamed as the site of platelet destruction during oxygenation. However, the part of the oxygenator responsible for platelet loss has bot been located. This study was designed to identify the sites of extracorporeal circuit responsible for platelet loss during ECC with scanning electron microscopy (SEM) of the post-perfusion circuit. The accumulation of platelet aggregates was most pronounced at the defoaming net and blood filter where a sudden changes in velocity of blood flow take place. The aggregates were considered to be formed locally at these sites. However, there were no accumulation and/or adherence of platelet aggregates of significant degree at the other parts of the circuit, namely venous and arterial tubings, venous colum and arterial reservoir. Platelets seem to be removed from the circulation during each passage by defoaming net and blood filter. However the other parts of the circuit seem to be less blamed for the platelet loss. It was not possible to conclude whether the formation and trapping of platelet microaggregates at the defoaming net and blood filter or the destruction by oxygen bubbles is mainly responsible for the plateletloss during ECC.

Microcirculatory changes in the gastrointestinal tract of the hypoxic puppy: an electron microscope study

Hypoxia and hypovolemia result in similar ultrastructural changes. These changes are characterized by aggregation of platelets and leukocytes in the vascular space, focal endothelial cell disruption, and appearance of increased amounts of perivascular edema, and loss of ultrastructural organization of the mucosal cell. These changes appear to relate to variations in blood flow to the mucosa of different areas of the bowel and to follow the distribution observed for necrotizing enterocolitis in the human infant.

Clinical effects of membrane lung support for acute respiratory failure

Extrapulmonary support in respiratory failure has become possible for prolonged periods with clinical application of the membrane lung oxygenator. The membrane lung may be perfused in a venovenous circuit, in which case it functions by prepulmonary venous oxygenation, or it may be pumped in venoarterial perfusion as partial or total cardiopulmonary bypass. Four patients were placed on venovenous membrane lung (GE-Peirce) perfusion for periods ranging from 6 to 112 hours. In oxygenating blood flows of less than 50% of the cardiac output, a viable PaO2 (mean, 52 mm Hg) was obtained in 2 patients with 60% FIO2, including 1 survivor who was weaned from the membrane lung. The remaining 2 patients had heart failure and insufficient venovenous membrane lung flows to improve systemic oxygenation (mean PaO2, 45 mm Hg on 100% FIO2). Four other patients were placed on venoarterial membrane lung (GE-DuaLung) bypass for 18 to 110 hours. With 40 to 85% of the cardiac output bypassed through the membrane oxygenator, immediate improvement was seen in systemic oxygenation (mean PaO2, 75 mm Hg), effective compliance (mean increase of 75%), and reduction in pulmonary hypertension (mean decrease, 15 mm Hg). These changes during bypass allowed the lungs to be put at rest with a decrease in FIO2 and positive end-expiratory pressures. This clinical experience indicates that venoarterial membrane lung bypass may be both supportive and therapeutic, decompressing the pulmonary circuit and maintaining systemic oxygenation. Membrane lung supported by either mode of perfusion has been shown to be clinically effective in patients suffering acute respiratory failure.

Cardiopulmonary bypass. Microembolization and platelet aggregation

Particulate microemboli and in vitro platelet aggregation were studied in blood of patients during cardiac operations with an electronic particle size analyzer. A small gradient of microemboli developed on passage of blood through a bubble oxygenator but not through a membrane oxygenator. However, with both types of oxygenators, there was a sustained increase in the volume of microemboli in cardiotomy return blood which was much greater than in aterial blood. After cardiopulmonary bypass with both oxygenators, there was a comparable reduction in the volume of circulating platelets which exceeded that of the hemoglobin concentration, indicating platelet loss exceeded that that expected from hemodilution alone. However, the total volume and mean size of platelet aggregates induced in blood of patients after membrane oxygenation was significantly greater than similar measurements after bubble oxygenation. This study shows that membrane oxygenation reduces particulate microembolization and preserves platelet function in patients undergoing cardiac operations when compared to bubble oxygenation.

Platelet aggregation: effects of cardiopulmonary bypass

This study was designed to determine whether reduction in platelet aggregate microembolization during the first 30 minutes of cardiopulmonary bypass is due to thrombocytopenia or to decreased ability of platelets to aggregate. The total volume of platelet aggregates induced in blood by adenosine diphosphate (ADP) was measured with a Coulter counter. The volume of platelets in blood was calculated by multiplying hemocytometry platelet counts by the mean platelet volume. Immediately before cardiopulmonary bypass, the total volume of aggregates induced in blood by ADP (2muM) was reduced when compared to normal donors because of (1) a slight fall in the volume of platelets, and (2) reduction in the percentage by volume of platelets which aggregated. After 30 minutes on bypass, the volume of both platelets and aggregates fell, but a greater percentage of platelets aggregated. This indicates that reduction of platelet aggregate formation during cardiopulmonary bypass is due to thrombocytopenia. It also suggests that anesthesia, surgical trauma and heparinization alter platelet reactivity more than cardiopulmonary bypass.