CDU Washington Editor
WASHINGTON – The idea of patient safety is not a novel concept, but in the years since the publication of the 1999 report by the Institute of Medicine (IOM; Washington) that laid the blame for 44,000 to 98,000 hospital deaths each year on deficient medical care, patient safety has taken on an urgency perhaps not seen since Hippocrates issued the imperative “First, do no harm.”
Thus it was that the Foundation for the Advancement of CardioThoracic Surgical Care (Washington) and the Medical Education Collaborative (Golden, Colorado) sponsored the 2006 edition of Cardiothoracic Surgical Critical Care last month to review the latest in a variety of procedures commonly undertaken in emergency and urgent care settings. Dozens of presentations targeted – and debated – the various aspects of clinical practice care for patient safety and best outcomes in these and related settings.
Higher-risk patients riskier
In opening remarks, Nevin Katz, MD, of the George Washington University Medical Center (Washington) pointed out that “the techniques we have now allow us to operate on patients we would not have operated on in the past,” thus providing a substantial patient benefit but also opening the possibilities for new difficulties in these high-risk patients.
Modern critical care patients tend to be older and partly, as a consequence, often present with more advanced states of myocardial infarction, congestive heart failure (CHF) and arrhythmias. Pulmonary and esophageal diseases are also presenting more frequently and more severely, creating serious dilemmas for providers under circumstances that are already very difficult.
This confluence of forces is driving a need for a more comprehensive understanding of how the body’s various systems interact and a more tightly woven multi-disciplinary approach to critical care to produce the best outcomes and prevent avoidable errors.
CHF perioperative management
John Conte Jr., MD, director of heart and lung transplantation at Johns Hopkins Medical Institutions (Baltimore), reviewed some of the issues and most effective procedures in the preoperative management of CHF.
Opening his discussion, Conte offered a variety of sobering figures. He reminded the audience that roughly 5 million Americans suffer from CHF with an additional 70,000 diagnoses each year. And he cited figures from the U.S. Census Bureau that project an increase in the numbers of Americans with CHF from 4.7 million Americans in 2000 to 10.3 million by 2010. According to his estimates, one in five are expected to lose their lives within a year of diagnosis at a cost to the economy of $60 billion.
Conte remarked that transplantation is still the gold standard for dealing with a failed heart, offering “about a 20% survival rate over 20 years,” with roughly 85% surviving the first year after a transplant. However, he pointed out that “we don’t have transplants for everyone.” While the number of transplants in 2005 added up to roughly 2,000, Conte said that he expected the number to fall in part because of a lack of healthy available hearts.
Pinpointing a key issue, he said the most prevalent problem with donor hearts is right ventricular dysfunction. Secondary mitral regurgitation, according to Conte, affects “up to 60% of CHF patients,” but those undergoing mitral valve repair/replacement enjoyed a survival rate of 80% over five years, “a dramatically improved outcome” as compared to medical care alone.
Conte discussed a passive heart assist device, the CorCap made by Acorn Cardiovascular (St. Paul, Minnesota), designed to support left ventricular diastolic function and to “reverse progressive dilation” by restricting myocardial stretch. The company’s clinical trial showed some efficacy, including a reduction in the need for major cardiac procedures as compared to medical care alone, but FDA’s circulatory system device panel did not recommend that the agency approve the device in a June 2005 hearing. The device remains under investigational status.
Ventricular restriction, or SVR, also came up in Conte’s discussion. “What we aim to do is reduce the volume in the anterior and the septa of the ventricles,” with the hope of also correcting any mitral valve regurgitation. He described a minimally invasive path in which “[w]e’ve actually gone in through the groin” to remodel a heart.
However, the procedure is not for everyone. The ideal candidate for SVR should have “good” right ventricle function and should demonstrate “acceptable function of basal portion of the heart and lateral well.”
Assisting to bridging
Conte discussed several bridge ventricular assist devices, including the Heartmate flow pump by Thoratec (Pleasanton, California), which was the subject of the REMATCH trial. The Heartmate survival rate for the first year was 50% vs. 25% for medical therapy alone, but Conte said that the data were not adjusted to reflect that some of the controls switched to the other study arm, which might have dropped the survival numbers for those in medical therapy.
The second generation of axillary flow pumps are now available, and some are much more compact than their antecedents. One of these, the DeBakey VAD manufactured by MicroMed (Houston), is the fruit of a collaboration between the legendary Michael DeBakey, MD, George Noon, MD, and NASA engineer David Saucier, on whom the two surgeons operated in 1984. The DeBakey, which NASA helped to fund, employs a small turbine to drive blood, a radical design departure from earlier models.
DeBakey is the director of the DeBakey Heart Center at Baylor and Methodist Hospital and Noon is the chief of the division of transplant surgery and assist devices at Baylor College of Medicine (Waco, Texas).
Here, in terms of follow-on problems, Conte said that “bleeding is the main issue” with most VADs. Some of this is attributed to renal and hepatic congestion, but coagulation problems also plague some recipients. As many as 20% of patients eventually require assist devices for the right ventricle, but those with second-generation devices require less frequent intervention for the right ventricle.
Conte made the case that hospitals might expect to see a drop in bypass procedures as other devices and technologies come online, but that stays in cardiac intensive care units may lengthen. “These patients will take up more beds for a longer time” in the years to come.
AF often defined by decision to treat
James Rawn, MD, the director of the cardiac surgery intensive care unit at Brigham & Women’s Hospital (Boston), opened his discussion on atrial fibrillation (AF) by stating that “it’s hard to come up with a consistent definition” of the condition, and usually ends up being defined by a physician’s decision to intervene.
To highlight the confusion over diagnosis of AF, he offered a chart that depicted the incidence of AF in patients who had undergone bypass graft surgery as determined in several journal articles. The low end of these estimates was just over 15% with the high end of the range at almost 35%. Some of the preoperative indicators of risk for AF include age, sex (males at higher risk), hypertension, prior AF, and congestive heart failure.
Rawn presented a risk index published by Mathew, et al in the 2004 edition of the Journal of the American Medical Association, which assigned risk points to a variety of factors for post-operative AF, including negative risk scores for the use of beta blockers and ACE inhibitors. The risk factors stack up to a failing score quickly.
Beta blocker use both before and after surgery reduce the cumulative risk score by seven points, but in marked contrast, their use only post-operatively reduces risks scores by 11 points. Potassium supplementation cuts risk scores by five points and the use of non-steroidal anti-inflammatories knocks the risk score down by seven.
In this scale, low risk is defined as a total of less than 14 points. Some of the risk factors are a previous history of AF (7 points) and chronic obstructive pulmonary disease (4 points). Age as a risk factor starts out at 6 points for those under the age of 30, 12 points for ages 30-39, and 18 points for those in their forties.
The drug-effect risks
In discussing prevention of AF, Rawn offered a few points from a joint guideline on prevention and management of post-operative AF, penned by the American College of Cardiology (Bethesda, Maryland), the American Hospital Association (Chicago) and the European Society of Cardiology (Sophia Antipolis, France). Among the recommendations in that guideline is that patients who have been diagnosed Class II-a (patients for whom the “weight of evidence/opinion is in favor of usefulness/efficacy”) should be “treated with sotalol or amiodarone prophylactically,” given their status as patients at increased risk of developing post-operative AF.
Rawn pointed out that amiodarone, an important antiarrhythmic used for treatment and for prevention of AF, can create problems of its own. It is known to affect pulmonary function, already a sore spot for many with reduced cardiac function. He stated that pulmonary toxicity often surfaces within two weeks of administration.
He offered a slide describing the side effects of amiodarone, including impacts on thyroid hormone levels, corneal microdeposits, sleep disturbances and erectile dysfunction. Because of these problems, Rawn recommended careful use of amiodarone, remarking that if one is “too aggressive in rhythm control, you only induce a lot of toxicity.” Metoprolol, marketed by Novartis (Basel, Switzerland) as Lopressor, is a beta blocker for which Rawn expressed a preference over amiodarone.
“It’s not too unusual to overreact” to any hints of AF, which are not uncommon when “there are a lot of people in white coats” milling around the patient’s bed discussing the problem, Rawn added. As for the devices used at the bedside, Rawn made the case that biphasic defibrillators “work a whole lot better with half the energy” introduced into the patient’s body.
According to an undated white paper by Michael Gold, PhD, chief of the division of cardiology at the Medical University of South Carolina (Charleston), the medical community may harbor a “misconception that biphasic shocks [greater than] 200J [joules] are damaging,” but such devices may offer “improved shock efficacy with decreased risk of shock-induced cardiac damage when compared with traditional monophasic” technology. Gold writes further that using joules as the primary unit of measure of electricity in this application may be “limiting and misleading” because this parameter describes “how much work must be done to generate the pulse of current,” but that “the energy setting is not indicative of the actual amount of energy delivered” by some defibrillators.
Rawn discussed anti-coagulation therapy for “patients who have been in atrial fibrillation for more than 24 hours or have multiple sustained episodes,” recommending the use of warfarin “in the absence of contraindications.”
He recommended further that warfarin not be administered in patients who may require a pacemaker and that heparin be considered in patients who have a low ejection fraction or a history of stroke or transient ischemic attacks. Unless contraindicated, “all patients should receive metoprolol” to reduce the risk of post-operative fibrillation, according to Rawn.