T. Gourlay

Laboratory evaluation of the Pall LG6 leukocyte depleting arterial line filter

The Pall LG6 arterial line filter has been designed to remove free circulating leukocytes from the arterial line of the extracorporeal circuit employed in openheart surgery. The filter was evaluated and compared to a control filter (Pall Stat-Prime) in terms of its general blood handling characteristics, particularly with regard to the associated level of leukocyte removal. The gross air handling characteristics of the filters were also assessed together with pressure drop. It was found that the filters differed little in terms of all factors studied other than the level of leukocyte depletion. The LG6 filter was associated with substantial levels of leukocyte depletion, particularly the depletion of neutrophils. Over the 90 minute perfusion period the LG6 filter was found to be associated with a neutrophil depletion rate of around 70% while preferentially sparing lymphocytes. This compared to a 10-20% depletion rate in the control filter. This was achieved without apparently compromising the performance of the filter in terms of the other factors studied.

Pulsatile Flow Compatibility of a Group of Membrane Oxygenators

The use of pulsatile flow during extracorporeal perfusion for cardiac surgical procedures has been demonstrated to be superior to conventional continuous flow with regard to many haemodynamic, metabolic and histological factors.’-’’ The pulsatile properties of arterial flow and pressure have been shown to influence the exchange rate between interstitial fluid and lymph, maintain normal capillary flow and kidney function, and the exchange of cerebrospinal fluid.I6 Recent studies have demonstrated that normal hepatic blood flow is also maintained when pulsatile flow is employed.” There also exists much evidence supporting the employment of membrane oxygenating systems for these procedures as opposed to the more conventional bubble Over the past few years, significant advances have been made in the design of both the pulsating pump and the membrane oxygenator to the extent that both are now considered to be extremely ~ser-fr iendly.~’-~~ Some controversy still exists however as to the compatibility of membrane oxygenators with pulsatile flow. Many users feel that the inclusion of a membrane oxygenator in the arterial line of the extracorporeal circuit may represent a significant

The effects of pulsatile flow on the leukocyte depleti ng qualities of the Pall LG6 leukocyte depleting arterial line filter: a laboratory investigation

The Pall LG6 arterial line filter has, in a previous publication, demonstrated its inherent leukocyte depleting qualities. This initial study was however carried out under continuous flow conditions. The present study was designed to assess the effectiveness of the LG6 filter in performing this leukocyte removal function under the more dynamic conditions of pulsatile flow. In addition to leukocyte depletion, the general blood handling and degree of energy absorbtion associated with the LG6 and Stat-Prime filters was also assessed. The results demonstrated that the LG6 filter was unaffected by the flow regime employed in terms of leukocyte removal and platelet depletion. There was a higher level of measured haemolysis associated with the use of pulsatile rather than nonpulsatile flow, however, this was the case with both filter types and was not found to be the case when generated values were computed. The LG6 filter absorbed more energy than the Stat-Prime filter as reflected by energy equivalent pressure (EEP) measurement, but this difference did not reach a level which was considered to be clinically significant.

Evaluation of a range of arterial line filters: Part II

In this, the first part of our filter evaluation programme, we shall be concentrating on two aspects of extracorporeal arterial line filtration performance. These aspects are the haemodynamic and haematological properties of a range of arterial line filters. A wide range of filters has evolved, all designed to meet the general selection criteria for arterial line filtration devices. There has been some concern expressed by the perfusion community regarding the possibility of damage to formed blood elements by the complicated fluid pathways within these filters and also to the potential resistance to flow exhibited by these filters. However, despite these concerns, the employment of arterial line filtration devices in clinical perfusion practice is unquestionably on the increased As a result of this increase in interest in arterial line filtration the number of commercially available filters has also increased to the extent that currently the potential user has a staggering number of devices to choose from. These devices vary in terms of filtration method, pore size and method of gas removal. This particular study concentrated on 13 different types of arterial line filter including one depth filter. These were:

Evaluation of a range of extracorporeal membrane oxygenators

Over several decades, blood gas exchange devices (oxygenators) have evolved which are designed to fulfil the gas exchange requirements of the patient undergoing open-heart surgery. In the early years these devices took the form of rotating discs, then bubble oxygenators and more recently membrane oxygenators. This study deals with the membrane oxygenator group which typically consists of ’sheet’ and hollow-fibre oxygenators. Previously published work has focused mainly on the clinical use of such devices 1-14 leading many authors to conclude that there are some considerable advantages to be gained from the use of these devices when compared to the more traditional bubble oxygenators. Reported advantages have been, in the main, in the areas of predictability of gas exchange, improved blood handling and in terms of microbubble handling characteristics. Some level of end-organ protection has also been associated with the employment of membrane oxygenators.ls-22 Over the past few years, the number of membrane oxygenators available to the cardiac surgical community has increased, with all of the new devices claiming essentially the same benefits. It

The role of arterial line filters in perfusion safety

in the very early days of extracorporeal perfusion for open-heart cardiac surgical procedures. The presence of emboli in extracorporeal perfusion circuits detected by ultrasound and other methods was noticed in conjunction with a relatively high incidence of neurological dysfunction after operation at a very early stage in development of cardiac surgery. Many observers noted that a very high percentage of patients surviving open-heart surgery displayed behavioural abnormalities and in the case of one particular study in 1970 the incidence of behavioural abnormalities was reported to be in excess of 40% .’ In this same study, 90% of patients who died during or after openheart surgery were reported to have multiple lesions throughout the brain. These findings were obviously important in relation to perfusion safety and led to the development of filters designed to

Evaluation of Carmeda® Bioactive Surface (CBAS®), Duraflo II and a novel nonspecific protease-modified surface using a new in vitro model simulating cardiopulmonary bypass

patible interface in which the cellular and protein cascade components of blood are kept in an inactivated state. The extracorporeal circuit circulates blood through the artificial heart and lung machine during CPB, but its surface lacks the blood biocompatibility of the endothelium. As a consequence, both cellular and humoral activation of blood components occurs. Although biomaterials currently used in cardiac surgery exhibit tolerable haemocompatability characteristics, it is, nevertheless, desirable to develop

Performance characteristics of a new arterial line filter

A new 40 micron polyester screen arterial line filter with integral automatic blood gas separator has been designed with the potential for improved removal characteristics for gas microbubbles and massive air. A simple in vitro evaluation has been carried out comparing the new filter (Pall EC+) against a standard widely-used reference arterial line filter (Pall EC 3840). The filters have been compared in terms of their haemodynamic performance, specifically pressure drop at incremental flow rates and haemolysis characteristics measuring generated plasma free haemoglobin. In addition, the relative abilities of the test and reference filters to remove gaseous microbubbles, and also to vent massive air introduced into the test circuits have been assessed using an ultrasound based microbubble detection system. The results of the studies indicate that the test and reference filters are identical in terms of haemodynamics, with maximal pressure drops of 30 mmHg at 4-5 litres mean flow rate. Neither filter is associated with significant haemolysis in bovine blood test circuits flowing at 4 I/min for 60 minutes. However, the EC+ filter has significantly superior performance over the reference EC 3840 filter in both microbubble removal and in removal of nitrogen gas introduced directly into the test circuit at up to 5 litres gas/min (p < 0.01). The new EC+ filter appears to offer safety in terms of haemodynamics and haemolysis, while providing maximal protection against massive arterial gas embolism.

Evaluation of the Sorin Monolyth membrane oxygenator.

Monolyth membrane oxygenator under a number of laboratory test situations. This membrane oxygenator, like many of the recent products in this area, is of the open reservoir integral type (Figure 1). The membrane consists of hollow fibres with blood flowing on the outside of the fibre lumen. The heat exchanger is on the venous side of the device and is constructed of pleated stainless steel with a surface area of 0.17m2. The

Clinical experience with the Sarns pulsatile pump during open-heart surgery:

more recently developed systems for open-heart surgery is the Sarns 7400 pulsatile pump which is a modified roller pump. Previous studies by the authors and others have shown the clinical acceptability of modified roller pump pulsatile systems in routine open-heart surgical practice. 1 3 With the availability of the new Sarns pulsatile pump system a simple clinical trial was undertaken with detailed haematological studies for evidence of haemolysis and platelet depletion being carried out in a subset of