Current ultrafiltration techniques before, during and after pediatric cardiopulmonary bypass procedures.

Ultrafiltration, which is currently considered as a standard method to remove excess water administered during pediatric cardiopulmonary bypass (CPB), aims to minimize the adverse effects of hemodilution, such as tissue edema and blood transfusion. Three ultrafiltration techniques can be used before, during and after CPB procedures, including conventional ultrafiltration (CUF), modified ultrafiltration (MUF) and zero-balance ultrafiltration (Z-BUF). These methods are widely different, but they have common benefits on hemoconcentration, less requirement for blood products, and reduction of the systemic inflammatory responses (SIRS). The present review attempts to restate these ultrafiltration circuitries, application methods, end-points, and clinical impacts.

Benefits of pulsatile flow in pediatric cardiopulmonary bypass procedures: from conception to conduction.

This review on the benefits of pulsatile flow includes not only experimental and clinical data, but also attempts to further illuminate the major factors as to why this debate has continued during the past 55 years. Every single component of the cardiopulmonary bypass (CPB) circuitry is equally important for generating adequate quality of pulsatility, not only the pump. Therefore, translational research is a necessity to select the best components for the circuit. Generation of pulsatile flow depends on an energy gradient; precise quantification in terms of hemodynamic energy levels is, therefore, a necessity, not an option. Comparisons between perfusion modes should be done after these basic steps have been taken. We have also included experimental and clinical data for direct comparisons between the perfusion modes. In addition, we included several suggestions for future clinical trials for other interested investigators.

Successful treatment of peripartum cardiomyopathy with extracorporeal membrane oxygenation.

A 24-year-old female developed heart failure within four months of delivering her first child. Echocardiogram revealed a moderately dilated left ventricle with severely reduced systolic function. She continued to decompensate, requiring intubation and inotropic support. When the use of an intra-aortic balloon pump failed to stabilize the patient, the decision was made to place her on ECMO. The circuit consisted of a Quadrox D membrane oxygenator and a CentriMag centrifugal pump. After 11 days of support, the patient met the weaning criteria and was successfully removed from ECMO. She was discharged one month after her admission. The new technology available allows for ECMO to be considered as an earlier option for the treatment and management of these patients as a bridge to recovery.

Effect of Carmeda BioActive Surface coating versus Trillium Biopassive Surface coating of the oxygenator on circulating platelet count drop during cardiopulmonary bypass.

An investigation was conducted to evaluate the effect that surface coating of the hollow-fiber membrane oxygenator had on circulating platelet count drop during cardiopulmonary bypass (CPB). Sixty patients undergoing non-emergency myocardial revascularization for coronary artery disease were randomly divided into two groups. Group one (n = 32) received the Carmeda-coated Maxima-Plus PRF oxygenator while the patients in Group two (n=28) received the Trillium-coated Affinity oxygenator during CPB. The net platelet count drops for the pump specimen (15-20 min after the initiation of bypass) for the Carmeda and the Trillium groups were 3.6 +/- 15.8% and 6.2 +/- 10.2%, respectively. The net platelet count drop for the warming specimen for the Carmeda and the Trillium groups were 2.9 +/- 19.4% and 0.5 +/- 11.0%, respectively. There were no statistically significant differences between the groups. The authors conclude that using either the Carmeda-coated Maxima-Plus PRF oxygenator or the Trillium-coated Affinity oxygenator afford similar benefits in regards to preserving circulating platelet counts during bypass.

Albumin in the pump prime: its effect on postoperative weight gain.

An investigation was conducted to determine whether adding albumin to the prime of the cardiopulmonary bypass circuit had any effect on postoperative weight gain. Patients undergoing non-emergency myocardial revascularization for coronary artery disease were divided into two groups. Group I (albumin) received 250 ml of 5% human albumin in their pump prime, whereas group II (control) served as controls. The same surgeon, anesthesia technique, perfusion circuit and conduct, and postoperative management were employed for all patients in the study. No statistically significant differences could be found between the groups for any of the variables studied, including fluid intake during surgery and the first 24 h postoperation, urine output, fluid balance and postoperative weight gain. The authors conclude from this investigation that adding 250 ml of 5% human albumin to the pump prime has no effect on postoperative weight gain. The next step could be to examine the effect of using larger amounts of albumin or plasma volume expanders in the pump prime.

Effect of Trillium Biopassive Surface coating of the oxygenator on platelet count drop during cardiopulmonary bypass.

The new Trillium Biopassive Surface is a coating designed to minimize the adsorption of protein and the attachment of cells. In previous studies, we were able to demonstrate that, by coating the bypass circuit with small amounts of albumin, the drop in circulating platelet count seen with the newer low-prime hollow-fiber membrane oxygenators is eliminated. A study was undertaken to compare the Avecor Affinity oxygenator with albumin in the prime with the Trillium-coated Affinity. Fifty-six patients undergoing nonemergency open-heart surgery were randomly divided into two groups. One group (Albumin) received the Affinity oxygenator with 10 ml of 25% albumin added to the pump prime. The other group (Trillium) received the Trillium-coated Affinity oxygenator. To normalize the data for the effects of hemodilution, the mean net platelet count drop on bypass was calculated for each group. The Albumin group had a net platelet count drop of 0.81+/-9.78%, while the Trillium group had a drop of 1.58+/-13.0%. There was no significant statistical difference between the two groups. From our investigation, we concluded that Trillium Biopassive Surface coating affords the Affinity oxygenator the same protective effects on circulating platelet counts as adding albumin to the prime.

Albumin in the cardiopulmonary bypass prime: how little is enough?

Previous studies have demonstrated high transoxygenator pressures with noncoated hollow-fiber membrane oxygenators. These reports have been associated with dramatic platelet count drops during cardiopulmonary bypass (CPB). It has also been shown that adding human albumin to the prime of the bypass circuit reduces, if not eliminates, these problems. This study was conducted to determine what is the smallest amount of albumin added to the prime that will still display its protective effects. Eighty patients undergoing nonemergency open-heart surgery were randomly divided into four groups. Groups I and II received the Sarns Turbo 440 oxygenator with 0.0375 g of albumin/100 ml of prime and 0.125 g of albumin/100 ml of prime, respectively, added to the pump prime. Groups III and IV received the Medtronic Maxima-PRF oxygenator with 0.0375 g of albumin/100 ml of prime and 0.125 g of albumin/100 ml of prime, respectively, added to the pump prime. Pre-CPB, on CPB (15-20 min after the initiation of bypass) and warming hemoglobin, hematocrit and platelet counts were drawn on all patients. Net platelet count drop, which accounted for hemodilutional effects, was calculated for all specimens and compared to previous results obtained from the test oxygenators without albumin in the prime. The net platelet count drops for the study groups were as follows: Sarns oxygenator with no albumin in the prime = 11.8+/-12.5%; Sarns oxygenator with 0.0375 g of albumin/100 ml prime = -3.7+/-10.8%; Sarns oxygenator with 0.125 g of albumin/100 ml prime = -2.0+/-12.6%; Medtronic oxygenator with no albumin in the prime = 20.1+/-14.5%; Medtronic oxygenator with 0.0375 g albumin/100 ml prime = -6.9+/-8.7%; and Medtronic oxygenator with 0.125 g albumin/100 ml prime = -14.0+/-12.4%. Our results illustrate that adding as little as 0.0375 g albumin/100 ml prime (3 ml of 25% solution/2000 ml of prime) to the pump prime illicits the beneficial effects of surface coating on platelet loss during CPB.

Effect of surface coating on platelet count drop during cardiopulmonary bypass.

This study was designed to investigate the effect of surface coating on platelet count drop during cardiopulmonary bypass (CPB). Sixty patients undergoing open-heart surgery were randomly divided into three groups each receiving a different type of coated hollow-fiber membrane oxygenator. The patients were given either an uncoated oxygenator (noncoated group), an oxygenator coated with Carmeda (Carmeda group) or an uncoated oxygenator with albumin in the priming solution (albumin group). Comparisons were made in platelet count pre-CPB, on bypass (15-25 min) and during the warming period. Calculations were used to account for the effect of hemodilution. The albumin group had significantly lower platelet count drops (-4.8+/-7.1%) than the Carmeda group (11.0+/-8.3%) and the noncoated group (20.3+/-14.5%). Carmeda surface coating demonstrated some beneficial effects, but to a lesser degree than the albumin.

Myocardial preconditioning using adenosine: review and clinical experience.

Adenosine is an endogenous nucleotide and a breakdown product of adenosine triphosphate. Adenosine has been proposed as a mediator of the ischaemic preconditioning phenomenon. Ischaemic reperfusion injury incurred during and following cardiopulmonary bypass contributes to depressed myocardial function after cardiac surgery. It is believed that administering adenosine via the aortic root, immediately following aortic crossclamping as well as just prior to removal of the aortic crossclamp, provides myocardial preconditioning resulting in improved cardiac protection during ischaemic arrest and retarding ischaemic reperfusion injury. A retrospective analysis was done utilizing consecutive patients undergoing coronary artery bypass grafting performed by the same surgeon. Some of the patients received myocardial preconditioning with adenosine. A comparison was made in postoperative cardiac function between patients who underwent myocardial preconditioning and those who did not receive adenosine. Results demonstrate a greater improvement in postoperative cardiac function, when compared to preoperative values, in those patients receiving myocardial preconditioning with adenosine.

Perfusion safety: past, present, and future.

Safe cardiopulmonary bypass has been paramount from its first use in the early 1950s until the present. The original perfusion circuits incorporated complex feedback loops and multiple safety devices. As circuits improved and became simpler to operate, advances in safety did not always keep pace. Surveys have illustrated areas that needed improvement and extra attention has been focused on those problems. As the field of perfusion evolved, so has the perfusionist. Perfusion has progressed from on-the-job training to formalized training, certification, and accreditation, and is now approaching national standardization. As the computer age proceeds, the use of safety devices and feedback mechanisms whose developments have been aided by the newly available technologies increases. As the 21st century approaches, cardiopulmonary bypass will continue to become safer, but the perfusionist must continue to stay up-to-date in education and remain vigilant while in the operating room.

The effect of fast-tracking on neurological complications post-cardiopulmonary bypass.

With the push to get patients through the system in five days, most patients undergoing nonemergency coronary artery bypass grafting (CABG) are being "fast-tracked'. Using this anaesthetic regimen appears to keep patients less anaesthetized (light) during cardiopulmonary bypass (CPB) than when using our previous regimen. This is manifested by higher mean arterial pressures (maintained above 65 mmHg) during CPB. If patients are receiving less anaesthesia during CPB, they may have an increased cerebral metabolism. This could lead to decreased cerebral oxygenation with a resultant neurological deficit postoperatively. A retrospective analysis of 200 patients who underwent nonemergency CABG was conducted to evaluate postoperative neurological complications. The patients were matched by surgeon, procedure and CPB time. They were separated into two groups: group 1 had maintained mean arterial pressures greater than 65 mmHg on CPB (n = 100) and group 2 had pressures less than 65 mmHg (n = 100). Group 1 had two patients (2%) who exhibited neurological complications after CPB (delirium, continuous coma for at least 24 h) with both of these patients previously having noted cerebrovascular disease. Group 2 also had two patients (2%) with postoperative neurological complications (delirium, transient stroke) with one patient having cerebrovascular disease. From our study, we cannot say that fast-tracking increases the risk for postoperative neurological complications. This could be due to the fact that we maintained the mean venous oxygen saturation during CPB above 70%. More specific testing needs to be done to truly rule out any negative postoperative effect.

Potential problem when using the new lower-prime hollow-fibre membrane oxygenators with uncoated stainless steel heat exchangers.

A prospective study was conducted to evaluate the trans-oxygenator pressure gradient across three different hollow-fibre membrane oxygenators during routine cardiopulmonary bypass (CPB). Sixty consecutive open-heart surgery patients were randomly divided into three groups each receiving a different model of membrane oxygenator. Inlet and outlet pressures, as well as patients' pressures, blood flow, revolutions per minute and tympanic membrane temperature were recorded every 15 min during CPB. Within the study groups, there were subsets of patients who exhibited high trans-oxygenator pressures. Although most of these episodes were transient and resolved over a period of time, there were several cases during which the high trans-membrane pressures persisted, resulting in decreasing oxygenator performance. In one such case, oxygenator change-out was required. After extensive analysis and review, the only similarities or correlation that could be made were with the marriage of the newer lower-prime hollow-fibre membrane oxygenators (with corresponding narrow blood path) and the integral uncoated stainless steel heat exchangers. Further study needs to be performed to pinpoint the mechanism and pathophysiology that are involved in this phenomenon.

The effect of low-dose epsilon-aminocaproic acid on patients following coronary artery bypass surgery.

The effect of low-dose epsilon-aminocaproic acid (EACA) on the postoperative course of 46 patients was studied. Patients undergoing coronary artery bypass grafting were randomly selected in two groups. Group 1 (20 patients) received 5 g EACA upon initiation of cardiopulmonary bypass (CPB). Group 2 (26 patients) received no antifibrinolytic drugs prior to CPB. Neither group received antifibrinolytic drugs after CPB. There was no significant difference between the two groups' blood usage on CPB: 0.65 units in Group 1 and 0.60 units in Group 2. After CPB, blood usage significantly differed: 2.2 +/- 1.7 (SD) units in Group 1 and 3.9 +/- 3.0 units in Group 2 (p = 0.033). Significant difference was also demonstrated in postoperative blood loss in the first 24 hours: 1610 +/- 531 ml in Group 1 versus 2025 +/- 804 ml in Group 2 (p = 0.043). Pre-CPB administration of low-dose EACA significantly decreases blood loss and blood usage in the postoperative period.

Coronary artery bypass grafting in a patient with haemophilia B.

Patients with coagulation disorders present the entire open-heart surgical team with an increased challenge. A patient with a known history of moderately severe Factor IX deficiency (2.4% activity) was evaluated for coronary artery disease. Cardiac catheterization revealed a 99% right coronary artery lesion, a long 99% circumflex lesion and normal left ventricular function. Sextuple coronary artery bypass grafting was performed with the aid of aprotinin and Factor IX transfusions. The patient's platelet count after cardiopulmonary bypass was 65,000/mm3, down from a preoperative level of 172,000/mm3, requiring the transfusion of six units of pooled platelets immediately postoperation. The patient was extubated five and a half hours after arriving in the Intensive Care Unit, and his chest-tube drainage after the first 24 hours was 373 ml. Other than a transient episode of atrial fibrillation on the third postoperative day, the patient had an uneventful postoperative course and was discharged on the sixth postoperative day. With the use of aproptinin and the newer monoclonal antibody-purified Factor IX concentrates that have been developed, many of the added risks of performing open-heart surgery on patients with haemophilia B are greatly reduced if not eliminated.

Surface tension effects of heparin coating on arterial line filters.

An investigation was conducted to determine the effects that heparin-coated screen arterial line filters have on the surface tension of cardiopulmonary bypass (CPB) priming solution. Five brands of non-heparin coated arterial line filters (Bard H625, Bentley AF1040, Intersept 40mum, Pall EC3840 and Pall SP3840) and four brands of heparin-coated filters (Bard H640, Bentley AF1040C and AF1040D and Intersept 40mum) were tested in a closed-loop circuit containing two litres of Plasma-Lyte A and pumped at a rate of five litres per minute. Samples were collected at 0.5, 20, 60 and 120 minutes to determine the surface tension of the recirculated solution. The non-heparin coated arterial line filters showed no significant changes in surface tension, either between the individual groups or over time. The benzalkonium-heparin coated filters (Bard H640, Bentley AF1040C and Intersept 40mum) all showed significant decreases in surface tension when compared to zero circulation time or to the noncoated groups. The largest drop in surface tension occurred within the first five minutes of recirculation. The circuit with a Bentley AF 1040D (a new nonbenzalkonium process) coated filter showed no significant change in surface tension.

Hetastarch as a prime for cardiopulmonary bypass.

Hetastarch, a synthetic colloid osmotic plasma volume expander, was employed in a prime for cardiopulmonary bypass in 37 patients undergoing myocardial revascularization. Comparison of laboratory values to those of 42 patients undergoing myocardial revascularization using an albumin-containing prime showed lower postoperative platelet counts (p less than 0.02) with hetastarch. There were no differences in chest tube drainage, blood use, plasma hemoglobin, fibrinogen levels, of coagulation times. The hetastarch prime cost $119.50 per patient, whereas the albumin-containing prime cost $321.35 per patient.