Current Status of Mechanical Circulatory Assistance

Management of Patients With Left Ventricular Assist Devices Requiring Teeth Extraction: Is Halting Anticoagulation Appropriate?

PURPOSE

An increasing number of patients with end-stage heart failure are supported with left ventricular assist device (LVAD) implantation and must be maintained on a consistent anticoagulation regimen. Pre-emptive extraction of carious teeth in these patients is necessary to prevent seeding of the implanted device and endocarditis. Thus, the objective of this study was to evaluate bleeding complications after minor oral surgery, specifically teeth extractions, in this unique patient population requiring long-term anticoagulation.

MATERIALS AND METHODS

This study was a retrospective single-center review. Adult patients supported on an implanted continuous-flow LVAD from January 1, 2007 to December 31, 2016 were included. Baseline characteristics were collected by retrospective chart review and the institutional LVAD registry. All extractions were performed in the operating room under local anesthesia with moderate sedation or general anesthesia with nasal intubation, and LVAD settings were monitored by a trained perfusionist. Preoperative and postoperative hematology laboratory values, such as hemoglobin and international normalized ratio (INR), were collected by chart review. Continuous variables were presented as mean ± standard deviation and compared using the Student t test. Categorical variables were presented as proportion and percentage and compared using the χ² test or Fisher exact test as appropriate. Statistical significance was established at a P value less than .05.

RESULTS

After screening 798 patients, 32 (4%) were found to have undergone dental extractions after LVAD implantation. The sample was composed of 32 patients with a mean age of 60.13 years and 81.25% were men. The average time from LVAD implantation to extraction was 445.19 ± 1,108.53 days. Average preoperative INR was 1.76 ± 0.47. Preoperative fresh frozen plasma was not administered to any patients. Twenty-eight patients (87.5%) were on Coumadin (warfarin) preoperatively. In 11 of these 28 patients (39.3%), Coumadin was held preoperatively. The average postoperative change in hemoglobin level was -0.79 ± 1.45. Only 1 patient (3%) required postoperative blood transfusion for a hemoglobin level of 7.6 that responded appropriately. There were no reoperations for bleeding.

CONCLUSIONS

Minor oral surgical procedures can be performed safely for patients being supported on LVAD therapy. With primary closure of the gingiva at the site of extraction, dental extractions can be performed without the full reversal of anticoagulation.

Systematic Design of a Magnetically Levitated Brushless DC Motor for a Reversible Rotary Intra-Aortic Blood Pump

The IntraVAD is a miniature intra-aortic ventricular assist device (VAD) designed to work in series with the compromised left ventricle. A reverse-rotation control (RRc) mode has been developed to increase myocardial perfusion and reduce ventricular volume. The RRc mode includes forward rotation in systole and reverse rotation in diastole, which requires the IntraVAD to periodically reverse its rotational direction in synchrony with the cardiac cycle. This periodic reversal leads to changes in pressure force over the impeller, which makes the entire system less stable. To eliminate the mechanical wear of a contact bearing and provide active control over the axial position of the rotor, a miniature magnetically levitated bearing (i.e., the PM-Coil module) composed of two concentric permanent magnetic (PM) rings and a pair of coils-one on each side-was proposed to provide passive radial and active axial rotor stabilization. In the early design stage, the numerical finite element method (FEM) was used to optimize the geometry of the brushless DC (BLDC) motor and the maglev module, but constructing a new model each time certain design parameters were adjusted required substantial computation time. Because the design criteria for the module had to be modified to account for the magnetic force produced by the motor and for the hemodynamic changes associated with pump operation, a simplified analytic expression was derived for the expected magnetic forces. Suitable bearings could then be designed capable of overcoming these forces without repeating the complicated FEM simulation for the motor. Using this method at the initial design stage can inform the design of the miniature maglev BLDC motor for the proposed pulsatile axial-flow VAD.

Effects of Sevoflurane and Propofol on Organ Blood Flow in Left Ventricular Assist Devices in Pigs

The aim of this study was to assess the effect of sevoflurane and propofol on organ blood flow in a porcine model with a left ventricular assist device (LVAD). Ten healthy minipigs were divided into 2 groups (5 per group) according to the anesthetic received (sevoflurane or propofol). A Biomedicus centrifugal pump was implanted. Organ blood flow (measured using colored microspheres), markers of tissue injury, and hemodynamic parameters were assessed at baseline (pump off) and after 30 minutes of partial support. Blood flow was significantly higher in the brain (both frontal lobes), heart (both ventricles), and liver after 30 minutes in the sevoflurane group, although no significant differences were recorded for the lung, kidney, or ileum. Serum levels of alanine aminotransferase and total bilirubin were significantly higher after 30 minutes in the propofol group, although no significant differences were detected between the groups for other parameters of liver function, kidney function, or lactic acid levels. The hemodynamic parameters were similar in both groups. We demonstrated that, compared with propofol, sevoflurane increases blood flow in the brain, liver, and heart after implantation of an LVAD under conditions of partial support.

Management of patients with implanted ventricular assist devices for noncardiac surgery: a clinical review

While originally primarily used as bridge to cardiac transplantation and bridge to recovery, more commonly ventricular assist devices (VADs) are being inserted as destination therapy. These patients are being discharged from transplant and mechanical assist centers, living as outpatients, and thus the pool of community-dwelling patients with VADs continues to expand. Not infrequently they present for surgical procedures either directly related to the device itself or more often incidental to the fact that they have a VAD. This scenario may be more common in patients with VADs placed for destination therapy because these patients tend to be older and have more comorbidities and are living longer with their device. Thus, it is important for all anesthesiologists to be aware of the special anesthesia needs of patients with VADs requiring noncardiac surgery.

Advances and future directions for mechanical circulatory support

Although cardiac transplant remains the gold standard for the treatment of end-stage heart failure, limited donor organ availability and growing numbers of eligible recipients have increased the demand for alternative therapies. Limitations of first-generation left ventricular assist devices for long-term support of patients with end-stage disease have led to the development of newer second-generation and third-generation pumps, which are smaller, have fewer moving parts, and have shown improved durability, allowing for extended support. The HeartMate II (second generation) and HeartWare (third generation) are 2 devices that have shown great promise as potential alternatives to transplantation in select patients.

Feasibility of robotic-assisted laparoscopic nephroureterectomy in left ventricular assist device patient

Left ventricular assist devices (LVADs) have revolutionized management options for patients with advanced heart failure. It is not uncommon for patients treated with these devices to present with noncardiac surgical conditions including urologic problems. Maintaining perioperative hemodynamic and hematologic stability is a special challenge. The minimally invasive surgery provides well-documented advantages over the open approach including a less operative blood loss and faster convalescence. In carefully selected patients, robotic-assisted surgery can be utilized in the management of patients with complex urologic diseases in a dire need for these benefits. We present the first case of robotic-assisted laparoscopic nephroureterectomy (RANU) with retroperitoneal lymph node dissection for upper tract transitional cell carcinoma (TCC) in a patient treated with LVAD.

Perioperative mechanical circulatory support in children with critical heart disease

OPINION STATEMENT

The treatment of cardiovascular failure in the perioperative period with the use of mechanical circulatory support is a well-recognized, well-developed, and commonly utilized treatment modality. Regardless of the exact circumstances of initiation, the use of a support device is a "bridge." Where there has been an acute myocardial insult, short-term assist devices can serve as a "bridge to immediate survival," a "bridge to recovery," or even a "bridge to the next decision." Mechanical circulatory support can serve as a treatment of cardiovascular decompensation caused by myocarditis, acute myocardial insult, low cardiac output following surgery, and congenital heart disease. The utilization of such support carries significant risks such as bleeding, infection, and thrombosis. However, these can be minimized in order to allow for the safe and effective deployment of this therapeutic strategy. One specific therapeutic domain in which these devices provide immediate impact is during cardiac arrest. Although outcomes of cardiac arrest remain poor, use of a mechanical device as an intervention has allowed salvage of otherwise certain mortality. However, it is important to note that the utility of support was most pronounced in patients that were not on either extreme of the survival prediction curve. This can be best summarized by the concept of "not too early, not too late." Therefore, it is the responsibility of the entire care team to find the appropriate patient population in which to "pull the trigger" on mechanical support as a therapy. This decision point is supported by a monitoring strategy that can be utilized to predict deterioration and intervene adequately. Most importantly, an effective monitoring strategy allows the practitioner to judge the effectiveness of treatment and support strategies and make adjustments in a timely manner, potentially with mechanical support in the perioperative period.

A review of clinical ventricular assist devices

Given the limited availability of donor hearts, ventricular assist device (VAD) therapy is fast becoming an accepted alternative treatment strategy to treat end-stage heart failure. The field of mechanical ventricular assistance is littered with novel and unique ideas either based on volume displacement or rotary pump technology, which aim to sufficiently restore cardiac output. However, only a select few have made the transition to the clinical arena. Clinical implants were initially dominated by the FDA approved volume displacement Thoratec HeartMate I, IVAD, and PVAD, whilst Berlin Heart's EXCOR, and Abiomed's BVS5000 and AB5000 offered suitable alternatives. However, limitations associated with an inherently large size and reduced lifetime of these devices stimulated the development and subsequent implantation of rotary blood pump (RBP) technology. Almost all of the reviewed RBPs are clinically available in Europe, whilst many are still undergoing clinical trial in the USA. Thoratec's HeartMate II is currently the only rotary device approved by the FDA, and has supported the highest number of patients to date. This pump is joined by MicroMed Cardiovascular's Heart Assist 5 Adult VAD, Jarvik Heart's Jarvik 2000 FlowMaker and Berlin Heart's InCOR as the axial flow devices under investigation in the USA. More recently developed radial flow devices such as WorldHeart's Levacor, Terumo's DuraHeart, and HeartWare's HVAD are increasing in their clinical trial patient numbers. Finally CircuLite's Synergy and Abiomed's Impella are two mixed flow type devices designed to offer partial cardiac support to less sick patients. This review provides a brief overview of the volume displacement and rotary devices which are either clinically available, or undergoing the advanced stages of human clinical trials.

Anesthesia management of a patient with a ventricular assist device for noncardiac surgery

Congestive heart failure represents a severe health condition with unfavourable long-term prognosis despite all the progress in pharmacological therapy of heart failure. Another therapeutic option is represented by mechanical cardiac support devices. Ventricular assist devices (VAD) constitute largest subgroup of these devices. Patients supported with VAD carry many considerations which are important for successful perioperative management of these patients for noncardiac surgery. The general perioperative considerations include consultation with VAD management personnel, detailed assessment of end-organ dysfunction before surgery, appropriate antibiotic prophylaxis, deactivation of implantable cardioverter-defibrillator for the time of surgical procedure, and the choice between general and regional anesthesia. Intraoperative monitoring depends primarily on the type of blood flow generated by VAD. For devices generating pulsatile blood flow, standard monitoring arrangements are needed. In the patients supported by devices which provide nonpulsatile blood flow, pulse oximetry and noninvasive blood pressure measurement are not reliable monitoring methods, and placement of intra-arterial catheter is warranted. In all the patients supported with VAD, transesophageal echocardiography is extremely useful method for monitoring the function of VAD itself, and in the case of univentricular VAD for monitoring the function of nonsupported cardiac ventricle. The most important issue in hemodynamic management of the patients with VAD is avoiding hypovolemia because it can cause inadequate VAD output with resulting low cardiac output and hypotension. All the patients with VAD need some degree of anticoagulation, and for noncardiac surgery the question of interrupting or decreasing the level of anticoagulation should be discussed among members of the caring team.

Anesthesia for noncardiac procedures for children with a Berlin Heart EXCOR Pediatric Ventricular Assist Device: a case series

OBJECTIVES

To report our experience of providing anesthesia for noncardiac procedures in children with in situ Berlin Heart EXCOR Pediatric ventricular assist devices and to suggest principles of anesthetic management.

BACKGROUND

With the initiation of the first North American training and support center for Berlin Heart at our institution in 2006, we have been asked to provide anesthesia for noncardiac procedures to these children. No current anesthetic approach to these children has been reported.

METHODS/MATERIALS

Anesthetic records for all noncardiac procedures for children with Berlin Heart between August 2006 and February 2009 in a tertiary care pediatric hospital were retrospectively reviewed. Charts were reviewed for demographic and clinical data, perioperative management, and occurrence of hypotension.

RESULTS

Twenty-nine procedures were performed on 11 patients. Hypotension was a common occurrence with all anesthetic induction and maintenance agents even at low doses. Ketamine induction, however, was less likely to produce hypotension, odds ratio for hypotension 0.1333 (95% confidence range 0.021-0.856). Hypotension was responsive to fluid bolus (60%) and alpha-receptor agonists (100%). Preoperative stability and presence of biventricular ventricular assist device (BiVAD) did not predict intraoperative hemodynamic course.

CONCLUSIONS

Unlike patients with other ventricular assist devices, these children do not tolerate reductions in systemic vascular resistance (SVR) because of the relatively fixed cardiac output of this device. Agents that reduce SVR should be avoided where possible. Preoperative stability is not predictive. Fluids and alpha-agonists should be first-line response to hypotension in this population. Further study of this unusual population is warranted to further delineate best anesthetic practice.

Conventional radiography and computed tomography of cardiac assist devices

Patients intended for circulatory support by cardiac assist devices (CAD) usually suffer from end-stage acute or chronic heart failure. Since the introduction of CAD in 1963 by DeBakey and coworkers, the systems have gone through a substantial evolution and have been increasingly used in the intervening decades. The spectrum of CAD includes a variety of systems serving to assist the systolic function of the left ventricle, the right ventricle, or both. Conventional radiography and multislice spiral computed tomography (CT) are the most commonly used radiological techniques for imaging patients with a CAD. CT is very useful for evaluating CAD systems by using both two- and three-dimensional reconstructions of the volumetric data sets. The two techniques together allow for the comprehensive assessment of patients with devices by imaging the in- and outflow cannulae, the anastomoses, the position of the pump, as well as associated complications. A close collaboration with cardiac surgeons with expertise in the field of circulatory support is deemed necessary for adequate image interpretation. This article describes the technical diversity of the currently available CAD systems. The imaging characteristics on conventional radiography and multislice spiral CT as well as the typical complications of their use are demonstrated.

Impact of new technologies on metabolic care in the intensive care unit

PURPOSE OF REVIEW

Technological innovations in the ICU have lead to extraordinary advances in modern critical care. Renal replacement therapy (RRT) innovations and ventricular assist devices (VAD) are now becoming common interventions in the ICU environment. The purpose of this article is to describe the impact of RRT and VAD on critical care medicine with particular reference to metabolic care.

RECENT FINDINGS

Continuous venovenous hemofiltration and slow low efficient daily dialysis are effective modalities of RRT in hemodynamically unstable patients. These continuous forms of RRT can result in accentuated protein and nutrient losses but also provide an opportunity for intradialytic parenteral nutrition support. VAD patients typically have cardiac cachexia and develop chronic critical illness syndrome. Intensive metabolic support, incorporating trophic, concentrated, semielemental enteral nutrition, supplemental parenteral nutrition, and intensive insulin therapy is a rational strategy to implement in VAD patients. Unfortunately, there is insufficient evidence at this time to support the routine use of these nutritional interventions with RRT and VAD.

SUMMARY

Patients requiring RRT or VAD are at high nutritional risk, which negatively affects ICU outcome. Prompt nutritional risk assessment and early optimization of metabolic care is crucial in this patient population.

Update on ventricular assist device management in the ICU

PURPOSE OF REVIEW

Mechanical circulatory support has a progressively increasing impact in the treatment of heart failure. The results of mechanical circulatory support are limited not only by the severity of the disease, which necessitated initiation of support, but also by the serious device-related adverse events. Optimized patient selection, improved patient management, and advanced device technology are interdependent key factors that contributed to the recently improved outcomes. The aim of this article is to summarize the current experience in application of mechanical circulatory support, focusing on the ICU management.

RECENT FINDINGS

Management should aim to prevent rather than treat serious complications and adverse events. Timing of intervention, optimization of the preimplantation patient status, patient and device management to ensure optimal hemodynamics, infection prevention, nutritional support, careful anticoagulation, and vigilance for early recognition and prompt treatment of 'minor' events before progression into major complications are essential elements of successful treatment.

SUMMARY

Critical patient care is a valuable adjunct to successful application of mechanical circulatory support, but it cannot counterbalance a late intervention, neither can it be fruitful in treating irreversible organ damage. Current management includes careful application of treatment protocols adjusted to recent experience, and also individualized care by a specialized team.

Assisting the failing heart

Anesthesiologists increasingly encounter patients who have a spectrum of heart failure ranging from stable chronic heart failure to acute heart failure to cardiogenic shock. Improved medical therapy has increased the survival of patients who have chronic heart failure but not of patients who have acute heart failure. New surgical techniques and mechanical devices may offer alternatives to certain patients who have refractory heart failure This article provides an overview of established and newer pharmacologic and nonpharmacologic therapies and surgical interventions to manage patients who have heart failure, including the perioperative management of heart transplantation and ventricular assist devices.