Search

An increasing number of patients are presenting for cardiac surgery with renal impairment. A simplified technique for dialysis during cardiopulmonary bypass (CPB) was designed and evaluated in the laboratory. The system has successfully been applied to patient care.

Mixed venous oxygen content is commonly used to determine the adequacy of oxygenation during cardiopulmonary bypass (CPB). Due to the shift in the oxyhemoglobin disassociation curve during hypothermia, it is unknown whether PvO2or SvO2is the best indicator of adequate perfusion. The purpose of this study was to determine if there were any differences in blood flow, calculated base deficit, total fluids, hematocrit and oxygen consumption for dogs in the following two groups: PvO2between 35–45mmHg and SvO2between 65–75%. Blood flow was managed in fourteen animals randomly assigned to the PvO2and SvO2group during hypothermic CPB. PvO2management required significantly higher blood flows and total fluids (p<0.05). Hematocrit was significantly higher in the SvO2group (p<0.05). No differences were detected between the two techniques in base deficit or oxygen consumption (p>0.4). These results suggest that in the canine model SvO2monitoring during hypothermic CBP is a better indicator of tissue perfusion because of lower blood flows, fluid requirement, and higher hematocrits.

A new membrane oxygenator has been introduced by Travenol Laboratories with continued development carried out by Sarns Inc. The polypropylene hollow fibers are wound in a pattern perpendicular to the blood flow path and serve as the conduit for the ventilating gas. The membrane surface area is 1.8 M2. The device contains an integral stainless steel bellows heat exchanger and a temperature probe well built into the blood outlet. The oxygenator is held by a wire frame holder that can be mounted in any direction on the heart lung machine. A selection of various size collapsible PVC venous reservoir bags is available to meet individual patient needs. The venous inlet connector of the bag contains a temperature probe port and a connector for the cardiotomy drain line as well as a recirculation line that attaches to the oxygenator.

The purpose of this study is to compare the effectiveness of an alternative method of oxygenating a crystalloid cardioplegic solution to the use of a bubble oxygenator. Five hundred milliliters of 100% oxygen was introduced, using sterile technique, into 100 ml bags of Ringer's solution at varying temperatures (20°, 10°, and 4°C). The contents of the bags were shaken for one minute by hand and then cooled to 4°C or maintained at that temperature using a Shiley CSD 103 Cardioplegia Delivery Set. This method of oxygenation was compared to constant bubbling of 100% oxygen into Ringer's solution in a Shiley S70 bubble oxygenator at 4°C.

A new oxygenator, developed by Shiley Laboratories, uses microporous polypropylene membrane material in a parallel plate design. The device has an integral heat exchanger and built-in temperature ports.

(J. Extra-Corpor. Technol20(2):67-71, 39 references) Reported cases of the pregnant patient during cardiopulmonary bypass are rare but not unique. This case report of the pregnant patient during cardiopulmonary bypass is unique for two reasons. First, the patient was also a Jehovah’s Witness and refused blood products. Secondly, this case report provides a literature review and specific cardiopulmonary bypass considerations pertinent to the perfusionist.

(J. Extra-Corpor. Technol. 20[1]: p. 40–45, 44 references, Spring Issue) Over the past three decades improvements have been made to many of the components of the extracorporeal circulation system resulting in decreased blood damage. However, the cardiotomy suction return sub-circuit, recognized as one of the most injurious components of heart-lung bypass, has remained relatively unchanged. The purpose of this study was to investigate the amount of blood damage that occurred with different cardiotomy suction designs. The five test designs compared two different suction tips with various air-mixing techniques, in vitro. Significant blood damage was observed in the air-containing designs as compared to the airless and control circuits. A minimal flow rate capable of excluding air was demonstrated as being the most important factor for blood protection, irrespective of aspirator tip design.

Blood from seven male patients undergoing coronary bypass surgery was mixed with four priming agents (hydroxyethyl starch (HES), low molecular weight dextran (LMWD), lactated Ringer’s solution (LRS), and 5 percent normal serum albumin (ALB), at concentrations of I percent, 10 percent, 20 percent, and 30 percent. Each sample was then assayed for erythrocyte sedimentation rate (ESR), and blood and plasma viscosities.

The activated clotting time (ACT) has become an important tool for monitoring the status of coagulation potential in patients undergoing cardiopulmonary bypass (CPB). Variability in results leads to confusion in interpretation of results. This study examined several CPB variables that may affect the ACT.

Patients undergoing cardiopulmonary bypass (CPB) using hemodilution are subjected to large reductions in colloid osmotic pressure (COP). The purpose of this investigation was to determine the course of COP during CPB and to compare these values to critical ranges for COP as cited in the literature.

Post-pump hemoconcentration is currently accomplished by centrifugation and saline washing, the product being packed red cells suspended in saline. This study was designed to compare centrifugation with ultrafiltration by an artificial kidney, the product of this method being whole blood.

Using an in vitro placental perfusion apparatus, the diffusion of oxygen and antipyrene across the human placenta was studied. At varying levels of maternal pO2there was no equilibration of fetal pO2across the placenta. Antipyrene diffusion was relatively slow. It is suggested that this apparatus is not physiologically accurate and that any further data from these in vitro methods be accompanied by measurements of other physiological parameters.

Although standard methods of heparin management have proven adequate in routine cardiopulmonary bypass procedures there are, occasionally, extraordinary cases in which special management is necessary. When a patient's blood is introduced to the extracorporeal circuit the non-endothelial surface precipitates platelet adhesion and aggregation. One of the factors released at this time is Platelet Factor IV which acts to neutralize the anticoagulant effect of the heparinantithrombin III complex. The purpose of this investigation was to relate platelet count to heparin requirement. Patients with thrombocytosis were studied. Heparin was managed as per usual except that additional heparin had to be given either before initiating bypass (after the three mg/kg loading dose failed to safely prolong the activated clotting time) or immediately after initiation of bypass due to a dangerously shortened coagulation time. Based upon the results of this study it is recommended that careful monitoring is necessary in thrombocytotic patients.

This study quantitatively investigates two methods of temperature correcting P02 values during hypothermic cardiopulmonary bypass. The magnitude of error associated with the linear temperature correction technique increased steadily with decreasing blood temperature, whereas the Kelman-Nunn correction technique closely estimated the reference PO2in all cases.

This study compares the management of heparin and protamine administration during cardiopulmonary bypass by a protocol assuming a constant heparin degradation rate with management by an activated coagulation time dose-response method.

Recent studies indicate that Streptokinase therapy early in Acute Myocardial Infarction can successfully produce coronary thrombolysis in approximately 80% of such patients. Reperfusion is frequently accompanied by relief of chest pain and normalization of ST segments. Cineangiography has shown myocardial salvage of the infarct region, improved LV function, and lowered mortality rates. The untoward effects of Streptokinase treatment appear to be manageable and the benefits of recanalization with Streptokinase outweigh the risks and side effects involved.

The physiochemical characteristics of hydroxyethyl starch make it suitable for use as a colloidal blood plasma substitute. In high doses, this drug may interfere with blood coagulation. Because of its effectiveness and low cost, we have used hydroxyethyl starch rather than albumin in the priming fluid for cardiopulmonary bypass: 500 ml of 6% hydroxyethyl starch and 2,000 ml of lactated Ringer’s solution. To determine if excessive bleeding has been associated with the use of hydroxyethyl starch, we reviewed 760 cardiac operations. The patients were 49.9 ± 0.5 years old (mean ± SEM) and weighed 73 ± 1 kg. Blood loss during the first postoperative day was 578 ± 25 ml, and 4.0 ± 0.2 units of bank blood were utilized in the perioperative period. We have used an improved method of administering heparin and protamine for the past 3 years. In the 461 patients operated upon since then, blood loss was 437 ± 21 ml, 2.9 ± 0.1 units of bank blood were used, and excessive postoperative bleeding necessitated re-exploration in nine patients (2.0%). These results compare favorably with other recently published series in which hydrobyethyl starch was not used in the pump prime. Thus the dose of hydroxyethyl starch in our priming fluid does not appear to be associated with excessive bleeding. In view of its safety and low cost, hydroxyethyl starch is a suitable colloidal blood plasma substitute for use during cardiopulmonary bypass.

We have studied pulmonary hemodynamics after right ventricular bypass in dogs. Manipulations of pulmonary vascular resistance and transpulmonary blood pressure difference (ΔPP) made it possible to increase pulmonary blood flow. Decreasing resistance by raising arterial pH from 7.25 to 7.38 increased flow by 24.9%. Infusion of homologous blood to increase right atrial pressure from 10 to 30 mm Hg lowered resistance 41.5% and raised flow 183%. Left ventricular bypass (left atrium to aorta) lowered left atrial pressure, increased arteriovenous pressure gradient by 41.4%, and raised flow 32.8%. These experiments support earlier clinical observations of the importance of low pulmonary vascular resistance and of good left ventricular function both in selection of patients and in postoperative management after right ventricular bypass. Attention to the principles we discuss may permit right ventricular bypass operation in some patients who would not be operable by current criteria.

The ideal priming fluid for cardiopulmonary bypass is not known. We designed a study to determine whether there are important differences in the clinical effects of hydroxyethyl starch versus albumin when used in priming fluid, and in the clinical effects of colloid versus crystalloid priming fluid. We prospectively randomized 83 adult patients undergoing coronary artery bypass or valve replacement. All patients were managed by standardized protocol, and they received one of three priming fluids for bypass: hydroxyethyl starch (HES), 26 patients; albumin (ALB), 28 patients, and lactated Ringer’s solution (LRS), 29 patients. The groups were stratified by body weight and type of operation. We measured 41 variables relating to operative time factors, fluid balance, bleeding, and organ function (renal, cardiac, and pulmonary) at several time intervals. The LRS group had a significantly lower colloid osmotic pressure than the other two groups, and the HES group had a substantially higher blood viscosity. Although the prothrombin time was significantly lower in the LRS group (p < 0.05), the differences were very small and not clinically important The platelet count in the HES group was significantly lower than in the other two groups immediately after bypass, but it was not different by the time the patients left the operating room. There were no differences among the groups in chest tube drainage, blood bank usage, or fluid balance. Postoperatively, the pulmonary shunt fraction was significantly greater in the LRS group. Body weight increased more in the LRS than in the HES and ALB groups (p = 0.01). No adverse reaction to the prime solutions was noted. The differences between the HES and ALB groups—prothrombin time, platelet count, and blood viscosity—had no apparent clinical effects; thus, the two may be considered clinically equivalent. The greater somatic and pulmonary fluid accumulation in the LRS group suggests that colloid is preferable to crvstalloid in priming fluid.