An Improved Bladder for Pump Control During ECMO Procedures

A new inline reservoir called the Better-Bladder™, now FDA-cleared for long term use, overcomes some disadvantages of the silicone bladder and bladder box used in extracorporeal membrane oxygenation circuits. The Better-Bladder™ provides compliance in the venous line and allows for noninvasive pressure measurements. Both features are useful for controlling pump speed as a function of venous line pressure. Bench tests showed that the Better-Bladder™ measures pressure noninvasively within ±4% of invasive (i.e., liquid contacting) pressure measurements in a range from −200 to +500 mmHg and at temperatures from 10°C to 37°C. After 60 days, the error in noninvasive pressure measurement with the Better-Bladder™ was less than ±3%. The Better-Bladder™ withstood pressurization to 1700 mmHg for ten days without leaking or failing in other ways. The advantages of the Better Bladder™, along with its accuracy and durability, suggest its use for short and long term pumping applications

Evaluation of Blood Cardioplegia Administration Systems

Four different blood cardioplegia administration systems (CAS) were evaluated for ease of use, cooling capacity, uniformity of mixing and blood flow capability. The CAS were one single pass (SP) and three recirculating CAS (RC). Each of the RC had a different reservoir; the first a cardiotomy reservoir (CARD), the second a transfer bag, and the third the GISH system. Each CAS was primed and debubbled with crystalloid. For RC, blood was collected, potassium added, and the solution cooled to 10°C. With SP, the infusate temperature at the field was measured at different flows and oxygenator temperatures. Hematocrit and potassium were measured at the start and end of cardioplegia administration. Single pass had the least tubing, lowest priming volume and the simplest design. For RC, l0°C infusate temperature was obtained fastest with the heat exchanger at the pump outlet and slowest at the reservoir inlet. For SP, the temperature at the field increased as either the oxygenator temperature and/or the cardioplegia flow rate increased. Only RC with CARD produced nonuniform mixing (initial potassium and hematocrit compared to the end of infusion were 16 percent lower and 36 percent higher respectively). At 10°C infusate temperature, RC allowed higher flow rates than SP. The GISH administration tubing had high resistance (800 mmHg at 500 mllmin). GISH is flow-limited by resistance and SP by cooling capacity. Clinically, if oxygenator temperature and infusion flows are such that SP can be used it is preferred. Otherwise, RC with low resistance tubing and heat exchanger within the reservoir is optimal

Concentration of Blood in the Extracorporeal Circuit Using Ultrafiltration

During cardiopulmonary bypass (CPB) the concentration of blood components is controlled by fluid administration and diuresis. However, diuresis is not always adequate and at the end of CPB the diluted pump blood, unless processed by expensive and cumbersome RBC saving techniques, is usually discarded. To control “diuresis” during CPB and to concentrate all blood components of the diluted pump blood post CPB, we evaluated ultrafiltration as a technique to extract plasma water from the extracorporeal circuit in 17 patients. At the end of each case, the blood left in the CPB circuit was circulated through a hollow fiber dialyzer (TriEx-3, Extracorporeal). At a transmembrane pressure of 430 torr, plasma water was extracted at 29 cc/min. Extracting plasma water decreased the initial pump volume by 50% causing the initial concentration of blood components to increase as follows: hemoglobin 80%, platelets 53%, fibrinogen 79%, total protein 75%, and plasma hemoglobin 294%. Following concentration, the high activated partial thromboplastin, prothrombin and thrombin times obtained for the pump blood decreased towards normal. There were no clinically significant changes in the plasma concentration of electrolytes. The concentrated blood was transfused to the patient within 2 hours of collection without any adverse effects. As compared to the increase in hemoglobin, the smaller increase in platelets and larger increase in plasma hemoglobin indicates that the dialyser caused some platelet loss and red blood cell damage. However, the concentrated blood did provide whole blood for the patient without the risks associated with donor blood

Conversion of Dilute Pump Blood to Whole Blood by Single Pass Ultrafiltration

Ultrafiltration (UF) effectively reverses hemodilution. However, when used to concentrate pump blood post-bypass, the recirculation method does not make concentrated blood available until all the blood has been processed. To make concentrated whole blood immediately available, we have investigated the use of a single pass ultrafiltration (SPUF) technique in 7 patients. By reducing the blood flow, the concentration of the blood components at the outlet of the ultrafilter (UF) was sufficient to allow direct transfusion. After bypass, the blood in the oxygenator (1664 ± 112 ml) was pumped (153 ± 12 mllmin) through an UF device and into a transfusion bag. Suction (- 480 torr) applied to the device extracted plasma water (82 ± 3 ml/min). SPUF concentrated the diluted pump blood as follows (mean ± standard error of the means): WBC from 8.5 ± 1.2 to 16.3 ± 2.5 × 103/ul, hemoglobin (6.5 ± 0.2 to 13.2 ± 0.5 gr/dl), platelets (135 ± 14 to 224 ± 32 × 103/ul), albumin (2.9 ± 0.2 to 7.6 ± 0.6 gr/dl) and fibrinogen (114 ± 9 to 274 ± 26 mg/dl). For heparin neutralized plasma, there was a decrease towards normal in prothrombin time (17.9 ± 0.6 to 14.1 ± 0.3 sec) and activated partial thromboplastin time (46 ± 2 to 32 ± 2 sec). There was no net increase in plasma free homoglobin. Red cell indices tended to normalize. Following transfusion of the concentrated blood there were increases in albumin (3.4 ± 0.2 to 3.9 ± 0.2 gr/dl) and hemoglobin (8.5 ± 0.6 to 9.5 ± 0.6 gr/dl). There were no statistically significant changes in white blood cells, platelets, prothrombin and activated partial thromboplastin time. Conclusion: SPUF is an efficient, useful, safe, simple and rapid method for obtaining whole blood for immediate transfusion

New Roller Pump Disposable Provides Safety and Simplifies Occlusion Setting

A new disposable insert for the arterial roller pump, the Better-Header™, provides safety and functionality beyond what standard tubing provides. It automatically limits pump outlet pressure to a level determined by the user and provides a self-contained, simple means to set pump occlusion. The Better-Header™ consists of a Starling-like pressure relief valve connected across standard header tubing. As long as arterial line pressure at the pump outlet remains below a set limit, the valve is closed. If line pressure approaches the pressure limit, the valve opens, preventing overpressurization by shunting blood from pump outlet to inlet. The BetterHeader ™ can also be used to set occlusion by the “dynamic method” to obtain nonocclusive settings. The Better-Header™ was evaluated in the lab for its pressure-flow characteristics. Even when the arterial line was completely clamped at a pump flow of 7 Llmin, line pressure was limited to a safe level and all circuit connections were preserved. The Better-Header™ has been used successfully at North Shore University Hospital in over 500 clinical cases covering a wide range of patients and procedures. In several instances, the user was alerted to high pressure situations by fluid flow through the valve and by an audible alarm, allowing rapid correction of the source of pressure. Compared to the standard setup, the Better-Header™ maintains outlet pressure within safe, user-settable limits, and permits consistent, nonocclusive settings with predictable retrograde flow

Errors in Flow and Pressure Related to the Arterial Filter Purge Line

The purge line is a necessary component on arterial filters, although its presence may affect the amount of flow reaching the patient as well as the pump outlet pressure in the extracorporeal circuit. In-vitro and clinical studies conducted to investigate these effects with a commonly used purge line showed that at flows less than 1.5 L/min, rates for pediatric or infant patients, the purge line diverts as much as 40% of the intended pump flow away from the patient. A small diameter resistance tube connected in series with the purge line reduced purge flow such that over 80% of the pump flow reached the patient. Pressure monitored at the arterial filter port with the purge line open could be as much as 45 mmHg lower than the pressure measured with the purge line closed to the filter. Studies should be done to determine if the arterial filter purge line compromises flow to the patient, and if an additional resistance to the purge line is appropriate to reduce the flow through it

Effects of the Memo-Concentrator on Blood

A high flux, non-traumatic ultrafilter (UF) can be useful for controlling the volume in the cardiopulmonary bypass circuit. Recently three such devices have been made available. It is the purpose of this work to describe the direct effects of ultrafiltration with one of these devices, the HemoConcentrator, on blood. The effects were determined by calculating the net changes in blood components due to hemoconcentration of pump blood at the end of bypass. The net changes were calculated from measurements taken before and after the concentration process. Samples taken pre and post-transfusion of the concentrated blood to the patient were also compared. The blood volume left in the circuit, 2050 ± 136 cc was concentrated by circulation through the UF and a total of 1083 ± 74 cc of plasma water extracted at a rate of 87 ± 3cc/min. The % net change for glucose, chloride, CO2 , potassium, sodium, BUN, creatinine, and phosphorous approximated the net loss of the plasma water. There were no losses in hemoglobin, albumin, and fibrinogen and only 2.5% losses in white blood cells*