Joseph J. Sistino

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.

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.

Cerebral Blood Flow during Low-flow Hypeithermic Cardiopulmonary Bypass in Baboons

BackgrortndNeurologic 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. MethodsAfter induction of general anesthesia in seven baboons, CPB was instituted. a-Stat management of arterial blood gases was used. Animals were cooled at a pump flow rate of 2.51·min−1 m−2 until tympanic membrane temperature decreased to l8°C. CPB flow was then reduced to 0.51 min−1 m−2 and maintained constant for at least 77 min. Thereafter, CPB flow was increased to 2.51· 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. ResultsLow-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. ConclrtsionsAlthough 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 lowflow conditions.

Perfusion bioreactor for vascular tissue engineering with capacities for longitudinal stretch.

Arterial growth during embryonic vascular development is associated with longitudinal strain. The longitudinal strain is an important element of the embryonic vascular mechanical environment (EVME). Thus, a perfusion bioreactor for vascular tissue engineered constructs must include the functional capacity for longitudinal strain. To accomplish this goal, a perfusion bioreactor with the capacity for longitudinal strain was developed. The bioreactor includes two media perfusion systems: one for the inside perfusion and one for the outside perfusion of the cardiovascular engineered tubular construct (CETC). The watertight perfusion chamber allows periodic changing of longitudinal strain of the construct during mechanical conditioning. The range of the longitudinal strain is 0% to 200%. The biomechanical properties of the CETC are controlled by a pressure transducer and a digital TV camera. The pressure transducer and TV camera are connected to a computer. This allows the recording of a relationship between the radius of the VTEG and pressure in both static and dynamic regimens. This bioreactor can perform biomechanical conditioning with longitudinal strain.

Review of ventricular rupture: key concepts and diagnostic tools for success.

Although a rare complication of acute myocardial infarction (AMI), ventricular rupture is a serious event associated with significant mortality and morbidity. Patients normally present with hemodynamic instability, often in cardiogenic shock. Despite improvements in surgical techniques and diagnostic tools, post-myocardial infarction ventricular rupture remains a difficult therapeutic challenge. There are three categories of ventricular rupture: free wall rupture (FWR), ventricular septal rupture (VSR), and papillary muscle rupture (PWR). The incidence of FWR occurs following up to 10% of myocardial infarctions. VSR and PWR have a lower incidence of 1-2% and 0.5-5%, respectively. Patients often present with single-vessel coronary artery disease and usually do not have a positive history for a previous myocardial infarction. The incidence of post infarction angina in these patients is significantly greater than in patients without ventricular rupture. Delay in treatment and continued physical activity post infarction increases the risk of ventricular rupture. Diagnostic tools such as two-dimensional echocardiography and cardiac catheterization confirm the diagnosis of ventricular rupture in only 45-88% of cases. Knowledge of the disease progression is necessary to insure accurate and timely diagnosis. Due to the rapid deterioration of these patients, there is a 50-80% mortality rate within the first week if untreated. With surgical correction, patients can extend their 5-year survival rates to 65%. A good example of the complex course of ventricular rupture is the case of a 71-year-old patient at our institution. The patient presented in cardiogenic shock following an AMI. Preoperative diagnosis was unsuccessful in determining the extent of the ventricular rupture. The correct diagnosis was determined in the operating room, and both a mitral valve replacement and closure of a ventricular septal defect were completed. The patient was successfully treated with this difficult pathology.

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 (n5 /3), continuous veno-venous hemofiltration (CVVH) (n 5 /7), intraoperative dialysis (n 5 /8), and intraoperative dialysis with fluid removal (n 5 /3) techniques will be presented for review.

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.

Epidemiology of cardiovascular disease in the last decade: treatment options and implications for perfusion in the 21st century

Cardiovascular disease (CVD) rates determine, to a large extent, the adult patient population that undergoes heart surgery. Many new treatment options have surfaced over the last decade which delay surgical intervention. The purpose of this study is to review the epidemiology of CVD in the USA over the past decade and project treatment patterns for the future. This information is important for the perfusion profession because it will influence the numbers of perfusionists required to staff open-heart centers in this country. Discharge data from hospitals in the USA were reviewed to determine numbers and rates of patients treated for CVD referenced to age and specific types of CVD. Operative procedure codes were reviewed to determine the volume and rates of cardiac surgical procedures, including catheterization and angioplasty, in the USA between 1990 and 2000. The results of this epidemiological review demonstrate that the surgical treatment rates for ischemic heart disease have not increased significantly over the past 10 years, except in the over-65 population. The large increase in the number of patients admitted for congestive heart failure (CHF) (39.4%) during this time period due to an aging population afford the perfusion profession an opportunity to become more involved in treatment options, such as cardiac assist devices. Cardiac surgeons are facing many of the same challenges that we face as perfusionists due to interventional cardiology, and should focus more attention on improving treatment for the heart failure population in the next decade. The continuation of perfusion education programs at their current rate of output seems justified, based on population projections and the increased incidence of CVD in the elderly population.

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.