Clinical problem solving: multidisciplinary case review.
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Ethics, Medical↗
Biomedical subjects
J E Reedy
Publications and source records attributed to J E Reedy.
Understanding ventricular assist devices: a self-study guide.
Considerable progress has been made over the past several decades in development of ventricular assist device (VAD) technology. Initially, failure to wean from cardiopulmonary bypass was the primary indication for VAD support. However, VAD role has expanded to include patients with ventricular failure due to myocardial infarction and patients awaiting cardiac transplantation. A greater number of nurses, both in the intensive care and general floors, are required to care for patients supported with VADs. Therefore, a self-study guide was developed to facilitate learning. Heart failure physiology, mechanical device descriptions, patient selection, potential complications, and nursing care of patients who require VAD support are reviewed.
Bandages↗
Nursing care of the patient on mechanical circulatory support.
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Assisted Circulation↗
Bridging to cardiac transplantation with mechanical circulatory support.
During the last decade, it has been clearly demonstrated that mechanical assist devices are capable of supporting patients in the interim before cardiac transplantation. The use of these devices prior to transplantation has provided an important window of opportunity to evaluate critically the devices and their potential for adaptation to permanent systems. The overall survival rates in the bridge-to-transplant patient population have improved. This is in part due to lessons learned in the past several years with regard to better patient selection and applicability of the devices. This review focuses on selected papers published in the past year that have made significant contributions to the evolution of mechanical support.
Decision Making↗
Nursing care of the patient with an intravascular oxygenator.
Conventional therapy in the management of adult respiratory distress syndrome is often associated with an increased mortality rate. Several methods to improve survival in patients with severe respiratory insufficiency are under evaluation. One recently developed method of treatment is an implantable intravascular oxygenator, which provides supplemental gas exchange for failing lungs. This device can provide temporary ventilatory support in patients with acute, potentially reversible respiratory insufficiency. Reduction in ventilator settings such as airway pressure, oxygen concentration, positive end-expiratory pressure and minute volume can be achieved, decreasing the likelihood of oxygen toxicity and barotrauma. Success of the intravascular oxygenator in adult respiratory distress syndrome is dependent in part on critical care staff expertise. Therefore, a thorough understanding of the operation of this device and its role in acute respiratory failure is necessary for optimal care.
Adult↗
Effects of intraaortic balloon position on renal artery blood flow.
Debate continues over what happens to renal blood flow when intraaortic balloons are adjacent to the renal arteries. Fourteen dogs were prepared by implanting instruments to measure heart rate; right atrial, pulmonary arterial, carotid arterial, and femoral arterial pressures; cardiac index; mixed venous oxygen saturation; urine output; and left and right renal blood flows. A 12-mL intraaortic balloon was inserted through the left (n = 9) or right (n = 5) femoral artery. The position of the balloon was randomized so that it was initially placed in either the control (thoracic) or renal position (at the level of the renal arteries). Intraaortic balloon pumping was performed for 4 hours in each position. In 8 dogs, at least one of the renal arteries had partial occlusion, 23% to 98% decrease in flow (mean decrease, 66%), while the intraaortic balloon was in the renal position. An intraaortic balloon in the renal position results in lower renal blood flow as well as a high risk (57%) of selective renal artery occlusion. Decreased renal blood flow is not apparent using conventional monitoring, as hemodynamics do not change.
Animals↗
Hemodynamic predictors for weaning patients from ventricular assist devices (VADs).
In order to find hemodynamic parameters that can accurately predict whether patients can be successfully weaned from ventricular assist devices (VADs), we studied data from 17 patients supported with Pierce-Donachy VADs [11 left VAD (LVAD); 6 right VAD (RVAD)] following cardiogenic shock for periods from 1.3 to 22 days (mean 5.4). Myocardial recovery was determined by daily measurements of "pump on pump off" parameters, and the data from the 8 LVAD patients and 3 RVAD patients whose hearts recovered were compared to the data from those whose did not. In this study, daily pump on pump off hemodynamic measurements were found to be predictive of success for weaning patients from VADs. In particular, the most significant predictors were: increases in mixed venous oxygen saturation, cardiac index, mean arterial pressure and ventricular ejection fraction, as well as decreases in atrial pressures. An index for measuring hemodynamic function with the VAD off is proposed, as are models of recovery. Seventy percent of the patients weaned from VADs survived, indicating that patients appropriately weaned from VAD support have a reasonable chance for survival.
Equipment Design↗
Mechanical cardiopulmonary support for refractory cardiogenic shock.
From February 1982 to February 1990, 38 patients (30 male patients and 8 female patients) ranging in age from 10 to 78 years (mean 49.4 years) have been supported with arteriovenous extracorporeal membrane oxygenation (ECMO) at St. Louis University Medical Center as a resuscitative system for cardiac arrest or cardiogenic shock. All patients were unresponsive to conventional resuscitative measures including an intraaortic balloon pump in 25 patients. Patients were resuscitated in the intensive care unit, cardiac catheterization laboratory, or the emergency department. Diagnosis varied from acute myocardial infarctions (12 patients), ischemic disease (15 patients), end-stage cardiomyopathy (7 patients), congenital heart disease (3 patients), or postoperative cardiac transplant graft rejection (1 patient). Three patients could not be resuscitated with ECMO because of low flow, but the remaining 35 (92%) achieved hemodynamic stability with ECMO flows greater than 2 L/min/m2. Duration of support ranged from 0.5 to 130 hours (mean 28 hours). Twenty-four patients were successfully weaned from ECMO support after coronary artery bypass (five patients), cardiac transplantation (two patients), or ventricular assist device insertion (eight patients), or with inotropic support (nine patients). Of the 14 patients not weaned, three were inadequately resuscitated, two had percutaneous transluminal coronary angioplasty while receiving ECMO, and nine were not candidates for further intervention. Nine (24%) patients were discharged and are long-term survivors. Our results indicate that resuscitative ECMO is useful for intervals of 12 to 24 hours and can best be applied with (1) patients younger than 60 years of age; (2) patients having acute events (failed percutaneous transluminal coronary angioplasty) amenable to surgical intervention; and (3) candidates for cardiac transplantation who could be switched to more sophisticated devices within 12 to 24 hours of ECMO insertion. With these criteria, ECMO, when used as a resuscitative system, can result in increased survival in selected patients with refractory cardiogenic shock or cardiac arrest.
Acute Kidney Injury↗
T cells in ventricular assist device patients.
Levels of T lymphocytes were measured in 20 consecutive patients, 18 men and two women, supported with ventricular assist devices or an artificial heart. Indications for support were bridge to transplantation (n = 10), postcardiotomy cardiogenic shock (n = 8), and acute myocardial infarction shock (n = 2). Control levels were from healthy volunteers not undergoing cardiac operation. Preoperatively, numbers of total lymphocytes and subclasses CD3, CD4, and CD8, as well as the interleukin-2 receptors (IL2R), were the same as controls (cells/microliters): lymphocytes, 1,940; CD3, 1,413 +/- 410; CD4, 894 +/- 318; CD8, 490 +/- 185; IL2R, 96. From implant to postoperative day 5, levels were below control values (p less than 0.001), reaching a nadir on postoperative day 2 (lymphocytes, 896 +/- 599; CD3, 489 +/- 267; CD4, 309 +/- 207; CD8, 183 +/- 107; IL2R, 43 +/- 47). Data from 10 patients (group 1) who survived (four weaned from cardiopulmonary bypass, six transplanted) were compared with those from 10 patients (group 2) who died of multiorgan failure, sepsis, or both. From preimplant through postoperative day 6, levels did not differ between groups. However, from postoperative day 7 to the last day of ventricular support (group 1, 24-90 days; group 2, 7-29 days), group 1 levels (lymphocytes, 2,364 +/- 618; CD3, 1,825 +/- 553; CD4, 1,013 +/- 187; CD8, 796 +/- 402) were significantly above (p less than 0.01) group 2 levels (lymphocytes, 1,290 +/- 463; CD3, 746 +/- 295; CD4, 534 +/- 253; CD8, 221 +/- 106). These data indicate that lymphocytes and particularly T cells 1) decrease after ventricular assist device insertion, reaching a nadir at postoperative day 2, 2) return to control values after patients whose clinical status improves, and 3) remain low in severely ill patients. T-cell depression in ventricular assist device patients is related to the severity of the patient's condition rather than the presence of the device.
Adult↗
Team approach to circulatory support.
A multidisciplinary approach to circulatory support is discussed in this article. The clinical, educational, and investigational responsibilities of each team member are presented.
Ancillary Services, Hospital↗
Thromboembolic complications with the Pierce-Donachy ventricular assist device.
Pierce-Donachy ventricular assist devices (VADs) were used to support 54 patients. None of the 27 patients supported less than 4 days had any visible thrombi in the VAD at explant. Of the 27 patients supported longer than 4 days, nine patients had visible thrombi. In this group of 27 patients, 19 received VAD support pending myocardial recovery, and anticoagulation consisted of dextran (4-15 days) and heparin during the weaning phase (1-2 days). The other eight patients had VADs implanted as bridges to cardiac transplantation. These patients also received dextran postoperatively (1-5 days), but were switched to a regimen of oral warfarin and dipyridamole. Duration of support for the nine patients in whom thrombi were found ranged from 4-27 days (mean, 12 days). The etiology of thrombus was probably related to mechanical problems in four patients, inadequate anticoagulation in two patients, sepsis in two patients, and unknown causes in one patient. Four of these patients suffered cerebral or peripheral injuries, which were probably embolic in two, and possibly embolic in two. One of these four patients survived, and two patients with thrombi but no emboli survived. One patient suffered a stroke, but no evidence of thrombi was found. Our incidence of thrombus with this VAD was 17%. Thrombi were related to inadequate anticoagulation, interrupted flow, or sepsis, but not to duration of support.
Female↗
The incidence of isolated left ventricular failure in bridge-to-transplant candidates.
Twenty-one patients (pts) were supported with mechanical devices as a bridge to cardiac transplantation (Tx). Ventricular function was assessed by a combination of angiography, echocardiography, nuclear scans, hemodynamics, and visual inspection at the time of device insertion. Twelve pts had biventricular failure (BVF) and 11 received biventricular support with extracorporeal membrane oxygenation (two pts), biventricular assist devices (VAD) (eight pts), or an artificial heart (one pt). One BVF pt received a left VAD (LVAD) and drug support for severe right ventricular failure (RVF), which resolved after 48 hr. The remaining nine pts had left ventricular failure (LVF), with only mild to moderate RVF, and received LVADs with minimal drugs. Eleven pts were tx, with nine survivors. A comparison of pts with LVF vs BVF revealed no differences in age, gender, device flows, duration of support, diagnosis, number tx, or number survived. The incidence of LVF was 43% vs 57% BVF in bridge-to-transplant pts. LVAD support alone is often successful in pts with mild or moderate BVF, but is rarely successful in pts with severe BVF.
Adult↗
The importance of patient mobility with ventricular assist device support.
Patients bridged to transplantation with ventricular assist devices (VADs) often require prolonged support. To reduce complications associated with bed rest, the authors developed a program to mobilize patients with VADs. Between August 1986 and May 1992, 25 men and 7 women aged 12-65 years (mean: 42.4 years) were bridged for possible transplantation. The 32 patients were supported with either a Novacor (n = 9) or a Thoratec (n = 23) VAD. Thirty-one patients were turned within 2-12 hr of VAD insertion and received range of motion therapy. Twenty-six patients sat in a chair 2-16 days (mean: 5 days) after VAD insertion. Twenty-one patients used a stationary bicycle, and 23 patients were ambulatory 3-57 days (mean: 11 days) after VAD insertion. Two patients were transplanted within 72 hr of device insertion. Twenty-one of the 23 ambulatory patients were successfully transplanted or weaned from the VAD and discharged from the hospital. Two ambulatory patients who were difficult to rehabilitate (ambulatory 22 and 57 days, respectively, after VAD insertion) died before transplantation. In conclusion, VAD patients should be mobilized early because the VAD can improve exercise capability and survival rate.
Adolescent↗
Status I heart transplant patients: conventional versus ventricular assist device support.
Since 1985, 59 United Network for Organ Sharing status I patients have been considered for heart transplantation. Thirty-four patients were supported with drugs and/or intraaortic balloon pump (IABP) (group I). Twenty-five patients were supported with ventricular assist devices (VADs, group II). Forty percent of the patients in each group died before transplantation. Of the 20 group I patients who underwent transplantation, all received inotropic drugs, and five also required IABPs. All 14 group II patients who underwent transplantation were bridged with VADs. No difference was found in age, sex, or cause of disease between the groups. Complications after transplantation were more common in group I. Fourteen group I patients (70%) and 14 group II patients (100%) were discharged from the hospital (p = 0.03). One year after transplantation, mean left ventricular ejection fraction by cardiac catheterization was 53% in group I (12 patients) and 72% in group II (11 patients; p = 0.0008). Although VAD support does not insure transplantation, it strongly favors transplantation survival in status I patients. These data further suggest an advantage of VAD support for long-term survival.
Actuarial Analysis↗
Device related infections in patients supported with mechanical circulatory support devices for greater than 30 days.
Mechanical circulatory support with systems that require transcutaneous cannulas or drive lines are associated with a high incidence of device related infections. The development of infection often is related to the duration of support. Data were reviewed on 10 patients (nine men and one woman) supported with assist devices (Thoratec-five, Nova-cor-three, Sarns-one, Jarvik-one) for longer than 30 days (range, 31-440; mean, 137 days). Seven patients had device related infections. Five also had positive blood cultures with the same organisms responsible for the device related infection. Two had mediastinitis from an ascending infection (one cannula and one drive line). Eight patients were transplanted, with seven survivors. One patient was weaned and survived, and one died during support. These data show that device related infections are common and severe, but they do not preclude successful transplantation, weaning, or survival.
Anti-Bacterial Agents↗
Importance of ventricular arrhythmias in recovery patients with ventricular assist devices.
The effect of ventricular arrhythmias (VA) on survival was retrospectively reviewed in 41 patients (33 men, 8 women) who were supported with Thoratec ventricular assist devices (VAD [Thoratec Medical Inc., Berkeley, CA]) (17 left, 9 right, and 15 biventricular). Ages ranged from 15 to 71 years (mean, 56 years), and duration of support was 0.1-17 days (mean, 4.7 days). There was no significant difference in age, gender, or type of support between survivors and nonsurvivors, and no correlation between the type of support and incidence of VA. Only two patients (both on left ventricular assist devices [LVAD]) died as a direct result of VA. There was no significant difference in the occurrence of VA before or during VAD support between survivors and nonsurvivors. These data show that evidence of VA is not a predictor of survival in patients in whom myocardial recovery is expected.
Adolescent↗
Cost and reimbursement rates for investigational circulatory support.
The clinical evaluation of investigational circulatory support devices has, for the most part, been financed with private funds. St. Louis University initiated a system in 1986 to bill for investigational circulatory support devices and care related to their use. Charges for hospitalization and rates of reimbursement were reviewed in 32 patients who received Thoratec (Thoratec Laboratories Corp., Berkeley, CA [N = 26]), Novacor (Baxter Healthcare Corp., Oakland, CA [N = 4]), or Symbion (Symbion Inc., Tempe, AZ [N = 2]) total artificial heart devices. Duration of support ranged from 0.2 to 440 days (mean 32). Total charges ranged from $43,115 to $1,335,691 (mean $221,716). Charges for the devices and technical support relating directly to their use ranged from $10,305 to $96,030 (mean $28,246). The mean percentage of reimbursement (total charges/total paid) was 67%. Whereas it was uncertain in some patients whether or not the devices were paid for, commercial insurers are willing to reimburse at a high percentage for the total cost of care.
Costs and Cost Analysis↗
Univentricular versus biventricular assist device support.
Controversy continues over whether patients should receive selective univentricular assist devices (UVADs) or biventricular assist devices (BVADs). Data from 39 patients supported for more than 2 days with Thoratec VADs were analyzed to compare mortality and morbidity between those receiving UVAD versus BVAD. Twenty-three patients received UVADs and 16 BVADs. Age, gender, and duration of support did not differ significantly between the two groups. Morbidity in VAD patients does not differ between UVAD and BVAD support. Survival is determined by the reversibility of pre-VAD myocardial damage or the eligibility for transplantation, rather than by the number of devices used. These data do not support the use of BVAD in all patients; they support a selective approach based on hemodynamic requirements.
Cardiac Surgical Procedures↗