Evaluating the potential risks of bubble studies during echocardiography.

OBJECTIVE: Cardiac shunts are often identified using bubble studies in echocardiography, with agitated saline. Previous studies have recommended various safe amounts of agitated saline. This poses a potential risk for air microembolism. The purpose of this study was to quantify the bubbles created by various quantities of agitated saline. METHODS: A closed circuit was constructed with a HeartMate pneumatic ventricular assist pump and a cardiotomy reservoir to remove air during recirculation. One empty 10 mL syringe and one 10 mL syringe containing 1 mL of air and 9 mL of saline were attached to a three-way stopcock. The air/saline bolus was then agitated between the two syringes five times to create bubbles and injected into the tubing proximal to the HeartMate. An EDAC bubble detector sensor was attached prior to the saline injection site and distal to the HeartMate I to measure the size and volume of the bubbles. This technique was repeated using 0.5 mL of air and 9.5 mL of saline bolus and 2 mL of air and 8 mL of saline bolus. Each bolus was tested 20 times. RESULTS: This study identifies the potential risks of air administration and proposes a safer air volume to agitate for the administration of a bubble study. CONCLUSIONS: Further studies should be conducted to create either a guideline or a standard for agitated saline administration by the Intersocietal Commission for the Accreditation of Echocardiography Laboratories (ICAEL) in order to minimize the risk of air microembolism.

Evidence-based medicine and myocardial protection--where is the evidence?

OBJECTIVE: Myocardial protection with cardioplegia is an integral component of most cardiac surgical procedures, providing protection of the heart by limiting metabolic activity and increasing the myocardium's capacity to withstand ischemia for prolonged periods of time. Cardioplegia has greatly affected the landscape of cardiothoracic surgery since its introduction in the 1960s, but, to this day, there continues to be a debate over what the ideal cardioplegic solution should be. The goal of this analysis is to describe current practices in cardioplegia and to point out the lack of quality human research and subsequent publications that prevent best practices from being utilized. METHODS: This study is a systematic review of journal publications pertaining to the composition of commonly used cardioplegic solutions. Four main types of cardioplegia were assessed to give a narrower field of examination; specifically, microplegia, del Nido, Custodiol HTK, and 4:1 blood cardioplegia. Other combinations of cardioplegia, including St. Thomas's Solution and the University of Wisconsin (UW) Solution, were considered when applicable according to the context of the publication being reviewed. Factors being assessed consisted of scientific validity, nature of the test subject (isolated organ vs. animal vs. human studies), experimental setup (retrospective trials vs. randomized clinical trials) and patient outcomes. RESULTS: There are very few randomized clinical trials with human subjects comparing commonly used cardioplegic solutions. Numerous retrospective studies exist, but often show similar intraoperative and postoperative outcomes between the solutions. Some solutions, del Nido cardioplegia in particular, were found to have few or no significant human trials to back the rigor required in such a highly specialized field as cardiovascular surgery. A wide variation in the types of surgeries and primary outcomes were included in the publications, so it is difficult to perform an accurate systematic review of the topic. CONCLUSION: Uniform variables among different studies would be preferable for analysis of this topic; thus, it is the researchers' recommendation that the collection of multicenter data be undertaken in order to more fully answer this research question.Comparative effectiveness studies to associate commonly used solutions are needed. Without this research, surgeon preference remains the primary determining factor for deciding which cardioplegic solution to use. Cardioplegia selection should rely more on higher scientific research, using evidenced-based medicine and ranking of clinical studies.

A systematic review of cerebral oxygenation-monitoring devices in cardiac surgery.

OBJECTIVE: Cerebral oxygenation monitoring via near-infrared spectroscopy (NIRS) during cardiopulmonary bypass (CPB) is increasingly becoming an accepted and valued component of intraoperative monitoring. In recent years, new devices have become available which all make different claims. The purpose of this study is to examine the research on these individual devices to establish the levels of evidence for each and formulate a research path for further evaluation of this technology in cardiac surgery. METHODS: This study is a systematic review of published research on cerebral oximetry. We searched PubMed, CINAHL and Scopus for full-length, peer-reviewed articles containing original data resulting from the study of patient neurologic outcomes based on the use of FDA-approved near-infrared spectroscopy devices. The studies were then grouped and classified based on the device used and the levels of evidence each study provided. RESULTS: Only a very limited number of high-level clinical evidence research papers are currently available, with nearly all of those papers based on the INVOS system. This is likely due to the different lengths of time each device has been on the market and its availability for use in clinical trials. Challenges to testing include the expense of testing various devices, the lack of a globally accepted gold standard for cerebral oxygenation saturation, the limited availability of patient frontal surface area and the gradual adoption of this technology. Despite these limitations, significant results have been identified in relation to patient outcomes. CONCLUSION: At this time, there is limited high-level evidence available for all of the NIRS devices on the market despite significant outcomes found in these studies. Additional prospective randomized studies should be conducted in order to establish the potential role NIRS may play in patient monitoring as well as assessing the efficacy of the multiple devices on the market.

Attention deficit/hyperactivity disorder after neonatal surgery: review of the pathophysiology and risk factors.

There are many factors that influence the long-term neurological outcomes in children following cardiac surgery. Because there is also complex interaction between these many factors, it is difficult to assess which are primary and modifiable and which can be used to make improvements in outcomes. As survival after complex neonatal heart surgery has increased, the number of children with long-term neurological deficits is becoming more evident and this affects quality of life for children and their families. One area of long-term assessment is the incidence of attention deficit/hyperactivity disorder (ADHD). The incidence rate for ADHD following pediatric cardiac surgery is significantly higher than the normal rate for children of the same age. Because this is a measureable long-term outcome, it can be used to evaluate methods for cerebral protection during surgery as well as the timing of surgical procedures to maximize cerebral oxygen levels. This paper will review the pathophysiological basis for ADHD in this population, based on the similarities between neonatal cardiac surgical patients and pre-term infants. Both populations have an increased risk for ADHD and the etiology and pathological changes in pre-term infants have been widely investigated over the past 25 years. The rate of ADHD in this population is a window into the effects of these pathological changes on long-term outcomes. Reducing the incidence of ADHD in the future in this population should be a primary goal in developing and assessing new cerebral protective strategies during cardiac surgery.

Incorporating high fidelity simulation into perfusion education.

The new Perfusion Simulation Center at the Medical University of South Carolina provides a new level of high fidelity simulation training for perfusion students. A key component is the Orpheus Perfusion Simulator which is a computer-driven simulator integrated with the mechanical connections of the heart-lung machine to allow for real time operative procedures and perfusion incidents. Due to the ability to consistently reproduce cardiac surgical scenarios, it is possible to develop both basic perfusion skills as well as advanced emergency skills more effectively than with animal models. The purpose of this paper is to provide details about advanced simulation for perfusionists and to illustrate how simulation can be used to promote the assets of good communication, team work, and surgical awareness. Two sets of four cardiac surgical scenarios were recorded in the perfusion simulation operating room. Scenario team member roles included a cardiac surgeon, an anesthesiologist, a perfusionist and an operating room nurse. The scripted surgical scenarios were viewed by a focus group of students charged with identifying key personality traits of different members of the operating team and to characterize them using a list of descriptive words adapted from the Medical University of South Carolina's Peer Review Tool. In the first set of scenarios, initial scores were negative, with irresponsibility, impatience, and carelessness listed as the top behavioral characteristics leading to human error. In the second set of scenarios, logical, clear-thinking, and attentive were the most common personality traits observed of the effective team members. Simulation has become an invaluable tool for perfusion education and the goal of improving patient safety during cardiopulmonary bypass. The opportunities for advanced training in the perfusion simulation environment will certainly expand in the future.

Renal dysfunction in cardiac surgery: identifying potential risk factors.

Aprotinin has been associated with increased renal failure and mortality when used in cardiac surgery. The purpose of this retrospective study was to compare the incidence of renal failure and mortality in our patient population to the published rates, accounting for risk factors associated with renal failure. After IRB approval; using the STS Database and cardiopulmonary bypass pump records, a total of 2292 cardiac patients were identified from January 2004 through June 2008. Forty-nine patients were excluded because they were on renal dialysis preoperatively. There were 1226 coronary artery bypass patients. Patients were separated into groups, according to which antifibrinolytic agent was used. This study included a total of 716 patients, divided into three groups; aprotinin (n = 436), tranexamic acid (n = 61), and off-pump coronary artery bypass (OPCAB) (n = 219). Epsilon aminocaproic acid (AMICAR) was given by the anesthesiologist to the majority of the remaining 510 patients and was not recorded on the bypass record. Therefore, patients given AMICAR were not included in this study. Outcomes included renal dialysis after surgery and mortality. Risk factors were identified and compared to patients in a study published by Mangano in the New England Journal of Medicine (N Engl J Med 2006; 354: 353-365). Aprotinin vs. control group showed no significant difference in risk factors for diabetes mellitus, hypertension, creatinine level above 1.3 mg/dl, or low ejection fraction. The percentage of patients requiring renal dialysis and mortality was less in Medical University of South Carolina (MUSC) patients than the other published study. Overall, the patients in the MUSC study had greater risk factors for renal failure, with the exception of patients with preoperative serum creatinine of >1.3 mg/dl (8.3 vs. 15.1%). This study does not show the same risk for renal failure associated with aprotinin that has been published elsewhere.

Perioperative perfusion strategies for optimal fluid management in liver transplant recipients with renal insufficiency.

Renal Insufficiency (RI) is a common finding in patients suffering from end-stage liver disease. The causes of RI are reported to be multifactorial and the degree of RI can range from early functional impairment to hepatorenal syndrome (HRS). The process of liver transplantation is highly likely to exacerbate the symptoms and sequelae of renal dysfunction. RI continues to be a cause of morbidity and mortality in the intraoperative and postoperative periods. With careful evaluation and monitoring in addition to appropriate intervention, a uniformly good outcome may be possible even for these most complicated patients. This paper will describe successful perfusion interventions carried out during the three phases of liver transplantation: pre-anhepatic, anhepatic and reperfusion at our institution for a three-year period. Intraoperative plasmapheresis (n = 3), continuous veno-venous hemofiltration (CVVH) (n = 7), intraoperative dialysis (n = 8), and intraoperative dialysis with fluid removal (n = 3) techniques will be presented for review.

Aortopulmonary collateral flow in the Fontan patient: does it matter?

BACKGROUND: The effects of aortopulmonary collaterals (APCs) on the outcome of a Fontan procedure are unclear. We undertook this study to define the incidence and extent of APC flow, identify risk factors for APC flow, and determine if APC flow has a measurable effect on the outcome of a Fontan procedure. METHODS: The APC flow was directly measured in 32 patients undergoing Fontan procedures from July 1997 to September 2000. The APC flow was measured in the operating room during total cardiopulmonary bypass, and was expressed as a percentage of total bypass pump flow. RESULTS: The APC flow ranged from 9% to 49% of total pump flow (median, 18%). Higher preoperative systemic oxygen saturation, pulmonary artery oxygen saturation, pulmonary to systemic flow ratio, and angiographic APC grade correlated with higher APC flow. There were no operative deaths; there was one Fontan takedown (APC flow = 14%). The APC flow had no significant effects on postoperative Fontan pressure, common atrial pressure, transpulmonary gradient, duration of effusions, or resource utilization after the Fontan procedures. CONCLUSIONS: In patients undergoing a Fontan procedure, APC flow is omnipresent, although its extent varies widely. Increased APC flow has no significant effect on the outcome of a Fontan procedure. This conclusion applies to patients who are well prepared for a Fontan procedure, but may not extend to patients at higher risk.

Coronary artery bypass grafting with and without cardiopulmonary bypass: a comparison analysis.

Coronary artery bypass grafting (CABG) using stabilization devices in place of the heart-lung machine is being performed on a wide range of patients. This study retrospectively compared the performance of off-pump coronary artery grafting bypass (OPCAB) with conventional bypass patients over the same 6-month period at The Medical University of South Carolina. Data were collected and compared from the National Cardiac Database of the Society of Thoracic Surgeons (STS). Parameters studied included age, gender, left ventricular ejection fraction (LVEF), previous myocardial infarction (MI), disease severity, number of grafts, complications, blood usage, ventilation times, operating room (OR) time, and hospital length of stay (LOS). There were no significant difference between the patient groups with regard to age, gender, LVEF, previous MI, predicted mortality, and LOS. Operative mortality was also similar in the two groups: conventional bypass 4/117 (3%) and OPCAB 2/86 (2%). The conventional bypass patients (CPB) had significantly (p < 0.05) more diseased vessels (2.9 vs. 2.6) and distal grafts (4.1 vs. 2.7), as compared to the OPCAB group. OPCAB procedures resulted in significantly (p < 0.05) lower mean OR time (365 min vs. 406 min) and reduced mean postoperative ventilation hours (3.4 vs. 8.3 hours), as compared to conventional bypass. There were significantly (p < 0.05) fewer blood transfusions in the OPCAB group (1.1 units vs. 2.4 units), and the percentage of patients transfused blood was significantly less (34.9% vs. 57.3%). Nine out of 95 (9.5%) of patients who presented for OPCAB were converted to conventional bypass. Although there may be potential benefits to OPCAB, further studies must be directed at determining those patients who would benefit most from CABG using the off-pump technique.

In-vitro evaluation of the hemolytic effects of augmented venous drainage.

Augmentation of venous drainage with either kinetic-assisted drainage (KAVD) or vacuum-assisted (VAVD) has been used clinically in order to overcome added venous resistance due to smaller venous cannulae or tubing. This in-vitro study evaluates the extent of hemolysis and sub-lethal red blood cell membrane damage than occurs with augmented (kinetic or vacuum) when compared to conventional gravity drainage. Four trials were conducted using each test circuit. The circuits were primed with 6 liters of fresh heparinized bovine blood, which was diluted to a hematocrit of 32% and was recirculated at 5 L/min for 8 hours. Hemolysis was determined by the change in plasma free-hemoglobin (Hb), hematocrit, and potassium at two hour intervals. The red cell osmotic fragility index was used to quantify the sub-lethal red blood cell membrane damage and was also measured every two hours. After 8 hours, the mean +/- SD of the plasma free-Hb were: 96.27 +/- 69.45 mg/dl for gravity, 83.87 +/- 48.14 mg/dl for vacuum-assist, and 134.45 +/-83.78 mg/dl for kinetic-assist. Two-hour increases in the plasma free-Hb revealed the following median values (mg/dL/2 h): 16.90 for gravity, 13.75 for vacuum-assist, and 19.40 for kinetic-assist. Analysis of the two-hour increases in plasma free-Hb with Kruskal-Wallis One-Way ANOVA did not reveal a significant difference among the groups. After 8 hours, the red cell osmotic fragility test results at the 0.55% sodium chloride concentration were compared. The medians of the percent hemolysis were 52.67% for gravity, 49.8% for vacuum-assist, and 57.2% for kinetic-assist. Analysis with the Kruskal-Wallis Wallis One-Way ANOVA did not reveal a significant difference among the groups. Therefore, there is no significant increase in hemolysis or sub-lethal red blood cell membrane damage associated with the use of augmented venous drainage.

Systemic inflammatory response syndrome (SIRS) following emergency cardiopulmonary bypass: a case report and literature review.

A complication of emergency resuscitation is the development of the Systemic Inflammatory Response Syndrome (SIRS). In the past, this has been identified as multiple organ failure, with symptoms similar to sepsis. The hallmark of this syndrome is peripheral vasodilation, which is associated with a breakdown of capillary membranes and the accumulation of excess interstitial fluid. This case report discusses the development of SIRS in a patient following emergency cardiopulmonary bypass (CPB). The patient was a 53 year old male with significant left main coronary artery disease who developed sudden bradycardia and hypotension in the operating room and was emergently placed on cardiopulmonary bypass. During CPB, the patient was peripherally vasodilated, and required continuous alpha-adrenergic support to maintain normal systemic vascular resistance. In addition, metabolic acidosis was present despite high flow rates, high hematocrit, addition of colloids, and hemoconcentration. Despite excellent neurological and myocardial recovery following surgery, the patient died one week later in renal and hepatic failure. Several mechanisms for the development of this syndrome have been hypothesized. One of these theories is that the ischemic injury in the gastrointestinal tract disturbs the gut barrier function and allows enteric bacterial endotoxins to pass into the circulation producing sepsis-like symptoms. Other theories relate to the release patterns of cytokines associated with CPB. These mechanisms and the treatment of SIRS with new pharmacological agents and perfusion techniques are reviewed.

Hematological effects of a low-prime neonatal cardiopulmonary bypass circuit utilizing vacuum-assisted venous return in the porcine model.

Limiting hemodilution in neonates is difficult when extracorporeal circuits require priming volumes that are 2 to 3 times the blood volume of the newborn patient. This extreme hemodilution contributes to the development of significant postbypass coagulation disturbances. The purpose of this project was to design a low-prime neonatal bypass circuit and evaluate the coagulation status after reduced hemodilution. The null hypothesis stated there is no significant difference in the measured coagulation parameters between the low-prime circuit and the standard high-prime circuit. Four neonatal piglets (2-4 kg) were divided into two groups and placed on cardiopulmonary bypass using either a low- (200 ml) or high-prime (500 ml) circuit. Both groups were cooled to 20 degrees C, and, following cardioplegic arrest, underwent circulatory arrest for 20 minutes. The low-prime circuit used vacuum-assisted venous drainage, which permitted the circuit to be at the patient level. The high-prime circuit required fresh washed donor red blood cells to maintain the hematocrit in the desired range of 15-20%. The platelet count on bypass decreased by 60 +/- 1.0% in the low-prime group versus 79.6 +/- 0.1% in the high-prime group. Following bypass, the platelet count was reduced by 38.3 +/- 14.3% in the low-prime versus 60.2 +/- 2.6% in the high-prime group. During rewarming, the mean heparinase activated clotting time (ACT) increased 5.1% above baseline in the low-prime group and 53.5% above baseline in the high-prime group. Mean plasma-free hemoglobin levels increased 40.4 mg/dl in the low-prime group versus 62.1 mg/dl in the high-prime group during bypass. This laboratory evaluation of a low-prime neonatal circuit demonstrates that coagulation disturbances often present in neonates can be reduced with the use of a low-prime circuit.

The additive effects of antifibrinolytics: dangers in the OR.

The use of antifibrinolytic agents in recent years had been heralded as a major breakthrough in the prevention of postoperative bleeding. However, whenever the delicate balance between coagulation and fibrinolysis is altered, the potential exists for disaster. There have been a number of complications reported in the literature related to the use of antifibrinolytics. With the availability of oral epsilon aminocaproic acid (EACA) as treatment for the symptoms of hemophilia and other secondary bleeding disorders, the possibility exists that a patient presenting for heart surgery may already be receiving antifibrinolytic therapy. A 72 year-old female underwent double valve replacement which was complicated by postoperative bleeding. Her medical history included gastrointestinal bleeding which was being treated with oral EACA. The patient was heparin resistant with a dose response of 55 sec/unit/ml. Heparin was administered during cardiopulmonary bypass to maintain the ACT between 400-500 seconds using a heparin-coated bypass circuit. In spite of this, the patient became thrombocytopenic and bled excessively in the postoperative period. Administration of additional antifibrinolytic agents in the operating room may be contraindicated when the patient is receiving this therapy preoperatively, and may contribute to the development of a procoagulant state during bypass.

Foetal bypass: concepts and controversies.

One of the most controversial and challenging surgical undertakings of the next century promises to be foetal cardiac surgery. Animal studies have been underway for several years to gain an understanding of the physiological mechanisms required to achieve this undertaking. Not since the days of crosscirculation has there been a maternal risk associated with open-heart surgery. The diagnosis of congenital heart defects with foetal ultrasound can now be made as early as 12 weeks gestation. Simple cardiac abnormalities, such as valvular stenosis or atresia, alter intracardiac flow patterns and affect normal cardiac chamber development. Without early intervention, these complex lesions often require major surgical reconstruction, beginning in the neonatal period. Foetal cardiac bypass techniques have evolved from the use of roller pumps and bubble oxygenators primed with maternal blood to the use of an axial flow pump incorporated in a right atrial to pulmonary artery or aortic shunt. Because the blood entering the right atrium is oxygenated by the placenta, an oxygenator in the bypass circuit is probably not needed. The low prime axial flow pump system avoids the dilution of the foetus with the maternal adult haemoglobin and improves the outcome. A major focus of research has concentrated on maintenance of placental blood flow with the use of vasodilators and cyclooxygenase inhibitors. Investigation with primates will be necessary to confirm the placental physiology before human operations can be performed. As the foetal bypass challenges are overcome, there is the potential for a reduction in the number of complex cardiac lesions requiring early surgical intervention in the twenty-first century.

Monitoring aortic root effluent during retrograde cardioplegia delivery.

Continuous monitoring of myocardial protection during aortic crossclamping is not always performed, due to limitations with current technology. The purpose of this study was to use readily available technology to evaluate the effectiveness of retrograde cardioplegia delivery by monitoring the aortic root vent effluent. The CDI 400, a commonly used blood monitoring device, was used to monitor changes in temperature, pO2, pCO2, and pH by placing a 1/4-inch CDI Quick Cell and probe in the aortic root vent line prior to each case. Twenty adult patients undergoing coronary bypass surgery were involved in the study, which resulted in 48 doses of retrograde cardioplegic solution. The study revealed a significant correlation between the temperature of the cardioplegia solution and the temperature of the aortic root effluent (p < 0.001. r = 0.88). The cardioplegia temperature did not correlate with the change in effluent pO2 (p = NS) or the degree of effluent temperature change (p = NS). Furthermore, the change in effluent temperature was not influenced by the amount of cardioplegia solution delivered (p = NS), or the time between administrations (p = NS). Both the decreasing and increasing trends of the effluent pO2 significantly correlated with the cardioplegia solution flow rate (p = 0.034, r = 0.32 and p = 0.013, r = 0.37, respectively), but not with the time between doses (p = NS) or volume of cardioplegia solution delivered (p = NS). The increase in effluent pO2 did correlate with the coronary sinus pressure (p < 0.001, r = 0.48). Measuring aortic root vent effluent may be used to assure the successful delivery of retrograde cardioplegic solution and aid in the detection of various procedural problems. Once the trends from this technique are established by the surgical team, they may be used to adjust cardioplegic solution administration and provide documentation of myocardial protection.

Experience with right ventricular assist devices for perioperative right-sided circulatory failure.

BACKGROUND: Right-sided circulatory failure remains a significant source of morbidity and mortality for both cardiac transplant and left ventricular assist device recipients. METHODS: We reviewed our experience with 11 patients who required a right ventricular assist device (RVAD) after either orthotopic heart transplantation or left ventricular assist device implantation. Variables analyzed included total time of RVAD support, hemodynamic and hematologic parameters, and parameters of end-organ perfusion. These were assessed at five time points: (1) at least 2 weeks before RVAD implantation, (2) intraoperatively just before RVAD insertion, (3) while on RVAD support, and, for those who survived, (4) just before RVAD explantation, and (5) off RVAD support. Survival was assessed as the ability to be weaned successfully from RVAD support. Urine output and serum transaminase levels were recorded throughout the period of RVAD support. RESULTS: Five patients received an ABIOMED 5000 BVS RVAD, and 6 received a Bio-Medicus centrifugal pump. Nine patients in the study underwent orthotopic heart transplantation and had development of right-sided circulatory failure from 0 to 96 hours after donor organ insertion, and 2 patients underwent left ventricular assist device implantation 12 to 48 hours before RVAD support. The mean time of RVAD support for survivors was 133.6 +/- 33.6 hours (range, 107 to 190 hours). Six patients were successfully separated from RVAD support, and 5 patients died while on RVAD support. Causes of death included sepsis (2), biventricular failure (2), and coagulopathy (1). Continuous arteriovenous hemodialysis was employed in 3 of 6 survivors and 1 of 5 nonsurvivors. CONCLUSIONS: Right ventricular assist devices work most effectively if implanted early enough to avoid significant, potentially irreversible end-organ injury. We liberally employ continuous arteriovenous hemodialysis, minimize the use of heparin immediately postoperatively, keep patients sedated, and continue RVAD support until the patient displays signs of hemodynamic and end-organ recovery as heralded by (1) a decrease in central venous pressure and, more importantly, a decrease in pulmonary artery diastolic pressure, (2) an increase in urine output, and (3) a decrease in serum transaminase levels.

Cerebral blood flow is determined by arterial pressure and not cardiopulmonary bypass flow rate.

BACKGROUND: During cardiopulmonary bypass, global hypoperfusion of the brain has been shown to result in ischemic insult and subsequent neurologic injury. Furthermore, outcome after focal cerebral ischemia depends on collateral circulation, which is determined by the parameters of global perfusion. We therefore measured cerebral blood flow during independent manipulations of arterial blood pressure and pump flow rate to determine which of these hemodynamic parameters regulates cerebral perfusion during cardiopulmonary bypass. METHODS: Seven anesthesized baboons were placed on cardiopulmonary bypass and cooled to 28 degrees C. Pump flow rate and arterial blood pressure were altered in varied sequence to each of four conditions: (1) full flow (2.23 +/- 0.06 L.min-1.m-2, mean +/- standard deviation) at high pressure (61 +/- 2 mm Hg), (2) full flow (2.23 +/- 0.06 L.min-1.m-2) at low pressure (24 +/- 3 mm Hg), (3) low flow (0.75 L.min-1.m-2) at high pressure (62 +/- 2 mm Hg), and (4) low flow (0.75 L.min-1.m-2 at low pressure (23 +/- 3 mm Hg). During each of these hemodynamic conditions cerebral blood flow was measured by washout of intracarotid xenon. RESULTS: Cerebral blood flow was greater at high blood pressure than at low pressure during cardiopulmonary bypass both at low flow (34 +/- 8.3 versus 14.1 +/- 3.7 mL.min-1 x 100 g-1) and full flow (27.6 +/- 9.9 versus 16.8 +/- 3.7 mL.min-1 x 100 g-1) (p < 0.01). At comparable mean arterial blood pressures alteration of pump flow rate produced no changes in cerebral blood flow. CONCLUSIONS: These results indicate that cerebral blood flow during moderately hypothermic cardiopulmonary bypass is regulated by arterial blood pressure and not pump flow rate.

Use of a pulsatile right ventricular assist device and continuous arteriovenous hemodialysis in a 57-year-old man with a pulsatile left ventricular assist device.

BACKGROUND: Despite advances in the perioperative treatment of both heart transplant and left ventricular assist device recipients, right-sided circulatory failure refractory to medical management remains a major source of morbidity in the immediate postoperative period. In addition, hypervolemia is a frequent complication encountered in the treatment of these patients because of their large fluid intake requirements and relative potential for kidney failure. METHODS: Previous reports have documented the use of continuous-flow devices to support the failing right-sided circulation of patients after both left ventricular assist device insertion and orthotopic heart transplantation. However, such continuous-flow devices may carry the attendant risks of hemolysis and bleeding and may further require 24-hour monitoring by trained personnel. We report the temporary-use pulsatile Abiomed BVS 5000 right ventricular assist device and continuous arteriovenous hemodialysis in the recipient of a pulsatile TCI HeartMate 1000 IP left ventricular assist device both after left ventricular assist device implantation and after orthotopic heart transplantation. RESULTS: The patient was well at 13 months follow-up. CONCLUSIONS: The use of right ventricular assist devices and continuous arteriovenous hemodialysis in both transplant and left ventricular assist device recipients undoubtedly will remain important as the popularity of these two therapeutic modalities continues to grow.

Cerebral blood flow during low-flow hypothermic cardiopulmonary bypass in baboons.

BACKGROUND: Neurologic injury after cardiopulmonary bypass (CPB) is a frequent and devastating complication of cardiothoracic surgery. Disordered cerebral hemodynamics during CPB has been implicated as an important factor in the etiology of these injuries. Evidence of disordered cerebral hemodynamics includes reports of a progressive time-dependent decrease in cerebral blood flow (CBF) during stable full-flow CPB. Low-flow hypothermic CPB has become a preferred technique for the management of pediatric patients undergoing surgical repair of complex cardiac lesions. Because CBF is already substantially reduced with the onset of low-flow CPB, we determined if a similar progressive decline in CBF occurs during the low-flow state. METHODS: After induction of general anesthesia in seven baboons, CPB was instituted. alpha-Stat management of arterial blood gases was used. Animals were cooled at a pump flow rate of 2.5 l.min-1.m-2 until tympanic membrane temperature decreased to 18 degrees C. CPB flow was then reduced to 0.5 l.min-1.m-2 and maintained constant for at least 77 min. Thereafter, CPB flow was increased to 2.5 l.min-1.m-2 and baboons rewarmed to normal temperature. CPB was discontinued after return of cardiac function. CBF was measured before, during and after CPB by washout of intraarterial xenon 133. RESULTS: Low-flow CPB resulted in a decrease in CBF to about 50% of the prebypass rate and about 30% of the value measured during full-flow CPB. Sequential measurements of CBF at 30-min intervals during low-flow CPB showed no time-dependent change in cerebral perfusion. CONCLUSIONS: Although systemic flow is reduced to 20% of full-flow during low-flow CPB, CBF reduced by half is disproportionately preserved relative to systemic flow. Furthermore, there is no time-dependent change in CBF under these low-flow conditions.