bluuebunny/crossref_metadata_2025 huggingface dataset:
Modeling and Predicting Hearing Aid Outcome
Authors: Humes Larry E.
Published: March 2006

Following a brief tutorial on the application of factor analysis to hearing aid outcome measures, three studies of hearing aid outcome measures in elderly adults are presented and analyzed. Two of the studies were completed at Indiana University (IU-1 and IU-2), and one was a collaborative multisite study by the Veterans Administration and the National Institute of Deafness and other Communication Disorders (NIDCD/VA). IU-1 measured hearing aid outcome in 173 elderly wearers of single-channel, linear, in-the-ear hearing aids with output-limiting compression, whereas IU-2 obtained the same extensive set of outcome measures from 53 elderly wearers of two-channel, wide-dynamic-range compression, in-the-canal hearing aids. In the NIDCD/VA study, 333 to 338 participants wore three single-channel circuits in succession, with each circuit housed within an in-the-ear shell. The three circuits included in that study and in this analysis were: (1) linear with peak clipping, (2) linear with output-limiting compression, and (3) single-channel, wide-dynamic-range compression. Evaluation of the many outcome measures completed in each study using principal components factor analysis revealed that from three (both IU studies) to five (NIDCD/VA study) principal components captured the individual differences in hearing aid outcome. This was independent of hearing aid type (in-the-ear or in-the-canal) and circuitry. Subsequent multiple regression analyses of individual differences in performance along each dimension of hearing aid outcome revealed that these individual differences could be accounted for reasonably well by various prefit variables for some dimensions of outcome, but not others. In general, measures of speech recognition performance were well accounted for by prefit measures, with the best predictors being hearing loss, cognitive performance, and age. Measures of hearing aid usage were less well accounted for by prefit measures, with the most accurate predictor of current hearing aid use being prior hearing aid use. The outcome dimension accounted for most poorly was that associated with hearing aid satisfaction, with subjective measures of aided sound quality being the best predictor of performance along this dimension of hearing aid outcome. Additional multicenter, large-scale studies are needed to develop more complete models of hearing aid outcome and to identify the variables that influence various aspects of hearing aid outcome. It is only through this additional research that it will be possible to optimize outcome for hearing aid wearers.
Reconsidering the Concept of the Aided Threshold for Nonlinear Hearing Aids
Authors: Kuk Francis , Ludvigsen Carl
Published: March 2006

The aided threshold (and functional gain) has been discussed in the context of linear hearing aids since the early 1960s. The use of nonlinear hearing aids, however, could change the meaningfulness of this verification tool because of their unique characteristics. The interpretation of the aided threshold (and functional gain) as it pertains to linear and nonlinear hearing aids is reviewed. Also discussed are the ideas of an optimal aided threshold, factors that may affect its magnitude, and a comparison between functional gain and insertion gain measures. Finally, how to improve the accuracy of the aided thresholds (and functional gain) through the use of in-situ unaided threshold measurements is discussed.
Hearing Aid Satisfaction: What Does Research from the Past 20 Years Say?
Authors: Wong Lena L. N. , Hickson Louise , McPherson Bradley
Published: March 2006

Hearing aid satisfaction is a pleasurable emotional experience as an outcome of an evaluation of performance. Many tools have been designed to measure the degree of satisfaction overall, or along the dimensions of cost, appearance, acoustic benefit, comfort, and service. Various studies have used these tools to examine the relationships between satisfaction and other factors. Findings are not always consistent across studies, but in general, hearing aid satisfaction has been found to be related to experience, expectation, personality and attitude, usage, type of hearing aids, sound quality, listening situations, and problems in hearing aid use. Inconsistent findings across studies and difficulties in evaluating the underlying relationships are probably caused by problems with the tools (eg, lack of validity) and the methods used to evaluate relationships (eg, correlation analyses evaluate association and not causal effect). Whether satisfaction changes over time and how service satisfaction contributes to device satisfaction are unclear. It is hoped that this review will help readers understand current satisfaction measures, how various factors affect satisfaction, and how the way satisfaction is measured may be improved to yield more reliable and valid data.
Trends in Cochlear Implants
Authors: Zeng Fan-Gang
Published: March 2006

More than 60,000 people worldwide use cochlear implants as a means to restore functional hearing. Although individual performance variability is still high, an average implant user can talk on the phone in a quiet environment. Cochlear-implant research has also matured as a field, as evidenced by the exponential growth in both the patient population and scientific publication. The present report examines current issues related to audiologic, clinical, engineering, anatomic, and physiologic aspects of cochlear implants, focusing on their psychophysical, speech, music, and cognitive performance. This report also forecasts clinical and research trends related to presurgical evaluation, fitting protocols, signal processing, and postsurgical rehabilitation in cochlear implants. Finally, a future landscape in amplification is presented that requires a unique, yet complementary, contribution from hearing aids, middle ear implants, and cochlear implants to achieve a total solution to the entire spectrum of hearing loss treatment and management.
Hearing Aids and Music
Authors: Chasin Marshall , Russo Frank A.
Published: March 2006

Historically, the primary concern for hearing aid design and fitting is optimization for speech inputs. However, increasingly other types of inputs are being investigated and this is certainly the case for music. Whether the hearing aid wearer is a musician or merely someone who likes to listen to music, the electronic and electro-acoustic parameters described can be optimized for music as well as for speech. That is, a hearing aid optimally set for music can be optimally set for speech, even though the converse is not necessarily true. Similarities and differences between speech and music as inputs to a hearing aid are described. Many of these lead to the specification of a set of optimal electro-acoustic characteristics. Parameters such as the peak input-limiting level, compression issues—both compression ratio and knee-points—and number of channels all can deleteriously affect music perception through hearing aids. In other cases, it is not clear how to set other parameters such as noise reduction and feedback control mechanisms. Regardless of the existence of a “music program,” unless the various electro-acoustic parameters are available in a hearing aid, music fidelity will almost always be less than optimal. There are many unanswered questions and hypotheses in this area. Future research by engineers, researchers, clinicians, and musicians will aid in the clarification of these questions and their ultimate solutions.
Music Perception with Cochlear Implants: A Review
Authors: McDermott Hugh J.
Published: March 2006

The acceptance of cochlear implantation as an effective and safe treatment for deafness has increased steadily over the past quarter century. The earliest devices were the first implanted prostheses found to be successful in compensating partially for lost sensory function by direct electrical stimulation of nerves. Initially, the main intention was to provide limited auditory sensations to people with profound or total sensorineural hearing impairment in both ears. Although the first cochlear implants aimed to provide patients with little more than awareness of environmental sounds and some cues to assist visual speech-reading, the technology has advanced rapidly. Currently, most people with modern cochlear implant systems can understand speech using the device alone, at least in favorable listening conditions. In recent years, an increasing research effort has been directed towards implant users’ perception of nonspeech sounds, especially music. This paper reviews that research, discusses the published experimental results in terms of both psychophysical observations and device function, and concludes with some practical suggestions about how perception of music might be enhanced for implant recipients in the future. The most significant findings of past research are: (1) On average, implant users perceive rhythm about as well as listeners with normal hearing; (2) Even with technically sophisticated multiple-channel sound processors, recognition of melodies, especially without rhythmic or verbal cues, is poor, with performance at little better than chance levels for many implant users; (3) Perception of timbre, which is usually evaluated by experimental procedures that require subjects to identify musical instrument sounds, is generally unsatisfactory; (4) Implant users tend to rate the quality of musical sounds as less pleasant than listeners with normal hearing; (5) Auditory training programs that have been devised specifically to provide implant users with structured musical listening experience may improve the subjective acceptability of music that is heard through a prosthesis; (6) Pitch perception might be improved by designing innovative sound processors that use both temporal and spatial patterns of electric stimulation more effectively and precisely to overcome the inherent limitations of signal coding in existing implant systems; (7) For the growing population of implant recipients who have usable acoustic hearing, at least for low-frequency sounds, perception of music is likely to be much better with combined acoustic and electric stimulation than is typical for deaf people who rely solely on the hearing provided by their prostheses.
Challenges and Recent Developments in Hearing Aids: Part I. Speech Understanding in Noise, Microphone Technologies and Noise Reduction Algorithms
Authors: Chung King
Published: March 2006

This review discusses the challenges in hearing aid design and fitting and the recent developments in advanced signal processing technologies to meet these challenges. The first part of the review discusses the basic concepts and the building blocks of digital signal processing algorithms, namely, the signal detection and analysis unit, the decision rules, and the time constants involved in the execution of the decision. In addition, mechanisms and the differences in the implementation of various strategies used to reduce the negative effects of noise are discussed. These technologies include the microphone technologies that take advantage of the spatial differences between speech and noise and the noise reduction algorithms that take advantage of the spectral difference and temporal separation between speech and noise. The specific technologies discussed in this paper include first-order directional microphones, adaptive directional microphones, second-order directional microphones, microphone matching algorithms, array microphones, multichannel adaptive noise reduction algorithms, and synchrony detection noise reduction algorithms. Verification data for these technologies, if available, are also summarized.
Challenges and Recent Developments in Hearing Aids
Authors: Chung King
Published: March 2006

This is the second part of a review on the challenges and recent developments in hearing aids. Feedback and the occlusion effect pose great challenges in hearing aid design and usage. Yet, conventional solutions to feedback and the occlusion effect often create a dilemma: the solution to one often leads to the other. This review discusses the advanced signal processing strategies to reduce feedback and some new approaches to reduce the occlusion effect. Specifically, the causes of three types of feedback (acoustic, mechanical, and electromagnetic) are discussed. The strategies currently used to reduce acoustic feedback (i.e., adaptive feedback reduction algorithms using adaptive gain reduction, notch filtering, and phase cancellation strategies) and the design of new receivers that are built to reduce mechanical and electromagnetic feedback are explained. In addition, various new strategies ( i.e.,redesigned sound delivery devices and receiver-in-the-ear-canal hearing aid configuration) to reduce the occlusion effect are reviewed. Many manufacturers have recently adopted laser shell-manufacturing technologies to overcome problems associated with manufacturing custom hearing aid shells. The mechanisms of selected laser sintering and stereo lithographic apparatus and the properties of custom shells produced by these two processes are reviewed. Further, various new developments in hearing aid transducers, telecoils, channel-free amplification, open-platform programming options, rechargeable hearing aids, ear-level frequency modulated (FM) receivers, wireless Bluetooth FM systems, and wireless programming options are briefly explained and discussed. Finally, the applications of advanced hearing aid technologies to enhance other devices such as cochlear implants, hearing protectors, and cellular phones are discussed.
Auditory Neuropathy/Dys-synchrony and Its Perceptual Consequences
Authors: Rance Gary
Published: March 2006

Auditory neuropathy/dys-synchrony is a form of hearing impairment in which cochlear outer hair cell function is spared but neural transmission in the auditory pathway is disordered. This condition, or group of conditions with a common physiologic profile, accounts for approximately 7% of permanent childhood hearing loss and a significant (but as yet undetermined) proportion of adult impairment. This paper presents an overview of the mechanisms underlying auditory neuropathy/dys-synchrony-type hearing loss and the clinical profile for affected patients. In particular it examines the perceptual consequences of auditory neuropathy/dys-synchrony, which are quite different from those associated with sensorineural hearing loss, and considers currently available, and future management options.
Principles of Digital Dynamic-Range Compression
Authors: Kates James M.
Published: March 2006

This article provides an overview of dynamic-range compression in digital hearing aids. Digital technology is becoming increasingly common in hearing aids, particularly because of the processing flexibility it offers and the opportunity to create more-effective devices. The focus of the paper is on the algorithms used to build digital compression systems. Of the various approaches that can be used to design a digital hearing aid, this paper considers broadband compression, multi-channel filter banks, a frequency-domain compressor using the FFT, the side-branch design that separates the filtering operation from the frequency analysis, and the frequency-warped version of the side-branch approach that modifies the analysis frequency spacing to more closely match auditory perception. Examples of the compressor frequency resolution, group delay, and compression behavior are provided for the different design approaches.
The WHO-DAS II: Psychometric Properties in the Measurement of Functional Health Status in Adults With Acquired Hearing Loss
Authors: Chisolm Theresa H. , Abrams Harvey B. , McArdle Rachel , Wilson Richard H. , Doyle Patrick J.
Published: March 2006

The World Health Organization's (WHO) Disability Assessment Scale II (WHO-DAS II) is a generic health-status instrument firmly grounded in the WHO's International Classification of Functioning, Disability and Health (WHO-ICF). As such, it assesses functioning for six domains: communication, mobility, self-care, interpersonal, life activities, and participation. Domain scores aggregate to a total score. Because the WHO-DAS II contains questions relevant to hearing and communication, it has good face validity for use as an outcome measure for audiologic intervention. The purpose of the present study was to determine the psychometric properties of the WHO-DAS II on a sample of individuals with adult-onset hearing loss, including convergent validity, internal consistency, and test-retest stability. Convergent validity was established by examining correlations between the WHO-DAS II (domain and total scores) and the Abbreviated Profile of Hearing Aid Benefit (APHAB) and the Hearing Aid Handicap for the Elderly (HHIE), two disease-specific measures, as well as with the Short Form-36 for veterans (SF-36V), a second generic measure. Data on all four measures were collected from 380 older individuals with adult-onset hearing loss who were not hearing aid users. The results of the convergent validity analysis revealed that the WHO-DAS II communication domain score was moderately and significantly correlated with scores on the APHAB and the HHIE. WHO-DAS II interpersonal and participation domain scores and the total scores were also moderately and significantly correlated with HHIE scores. These findings support the validity of using the WHO-DAS II for assessing activity limitations and participation restrictions of adult-onset hearing loss. Several WHO-DAS II domain scores and the total score were also significantly and moderately-markedly correlated with scores from the SF-36V. These findings support the validity of the WHO-DAS II as a generic health-status instrument. Internal consistency reliability for all the domain scores was adequate for all but the interpersonal domain. Test-retest stability for all the domain scores was adequate. Critical difference values were calculated for use in clinical application of the WHO-DAS II. From these findings, we concluded that the WHO-DAS II communication, participation, and total scores can be used to examine the effects of adult-onset hearing loss on functional health status. Further work examining the utility of the WHO-DAS II as an outcome measure for hearing aid intervention is warranted.
The WHO-DAS II: Measuring Outcomes of Hearing Aid Intervention for Adults
Authors: McArdle Rachel , Chisolm Theresa H. , Abrams Harvey B. , Wilson Richard H. , Doyle Patrick J.
Published: March 2006

The World Health Organization's Disability Assessment Scale II (WHO-DAS II) is a generic health-status instrument that provides six domain scores and a total, aggregate score. Two of the domain scores, communication and participation, and the total score, have good validity, internal-consistency reliability, and test-retest stability in individuals with adult-onset hearing loss. As such, these two domain scores and the total WHO-DAS II score may be useful as generic outcome measures to assess the effectiveness of hearing aid intervention for this population. Before the use of the WHO-DAS II in hearing aid clinical trials, however, the responsiveness of the instrument and the short- and long-term outcomes to hearing aid intervention had to be determined. Responsiveness and outcomes were assessed in 380 veterans (approximately half received hearing aids and half served as controls) by examining group differences, effect-size estimates, and individual differences as a function of hearing aid intervention. For comparison, data also were obtained on two disease-specific measures, the APHAB and the HHIE. The WHO-DAS II communication domain and total scores were sufficiently responsive to hearing aid intervention for use in future studies in which group differences are to be detected. The WHO-DAS II participation domain was not sufficiently responsive to hearing aid intervention. The APHAB and HHIE, both disease-specific measures, were more sensitive to hearing aid intervention than the generic measure. The short- and long-term outcomes of hearing aid intervention were also examined in the present study. Group outcomes for hearing aid intervention can be expected to be stable for at least 6 months when measured by WHO-DAS II total score and for at least 12 months when measured by the WHO-DAS II communication domain scores. Effect-size estimates and examination of the number of individuals exhibiting change scores exceeding 90% critical differences for true changes in scores indicate that for clinical applications, disease-specific instruments are more useful than the WHO-DAS II. The findings of this study support the use of the WHO-DAS II as a generic measure in hearing aid trials research so as to allow for comparisons of health-status outcomes across different diseases or disorders.
The DSL Method for Pediatric Hearing Instrument Fitting: Historical Perspective and Current Issues
Authors: Seewald Richard , Moodie Sheila , Scollie Susan , Bagatto Marlene
Published: March 2006

The Desired Sensation Level (DSL) Method was originally developed in the early 1980s to provide clinicians with a systematic, science-based approach to pediatric hearing instrument fitting that ensures audibility of amplified speech by accounting for factors that are uniquely associated with the provision of amplification to infants and young children who have hearing loss. This review identifies and describes several of the primary factors that have been considered in the development of the DSL Method. Specifically, the issues discussed relate to: (1) the definition and measurement of relevant acoustic, electroacoustic and audiometric variables; (2) how the external ear acoustics of infants and young children are accounted for in the DSL Method for both audiometric assessment and in the fitting of amplification; and (3) how the DSL Method has evolved concurrently with developments in hearing instrument and electroacoustic measurement technologies. Finally, current issues in the field are identified that have motivated the development of version 5.0 of the DSL Method for hearing instrument fitting.
The Desired Sensation Level Multistage Input/Output Algorithm
Authors: Scollie Susan , Seewald Richard , Cornelisse Leonard , Moodie Sheila , Bagatto Marlene , Laurnagaray Diana , Beaulac Steve , Pumford John
Published: March 2006

The Desired Sensation Level (DSL) Method was revised to support hearing instrument fitting for infants, young children, and adults who use modern hearing instrument technologies, including multichannel compression, expansion, and multimemory capability. The aims of this revision are to maintain aspects of the previous versions of the DSL Method that have been supported by research, while extending the method to account for adult-child differences in preference and listening requirements. The goals of this version (5.0) include avoiding loudness discomfort, selecting a frequency response that meets audibility requirements, choosing compression characteristics that appropriately match technology to the user's needs, and accommodating the overall prescription to meet individual needs for use in various listening environments. This review summarizes the status of research on the use of the DSL Method with pediatric and adult populations and presents a series of revisions that have been made during the generation of DSL v5.0. This article concludes with case examples that illustrate key differences between the DSL v4.1 and DSL v5.0 prescriptions.
Clinical Protocols for Hearing Instrument Fitting in the Desired Sensation Level Method
Authors: Bagatto Marlene , Moodie Sheila , Scollie Susan , Seewald Richard , Moodie Shane , Pumford John , Liu K. P. Rachel
Published: March 2006

A discussion of the protocols used particularly in the clinical application of the Desired Sensation Level (DSL) Method is presented in this chapter. In the first section, the measurement and application of acoustic transforms is described in terms of their importance in the assessment phase of the amplification fitting process. Specifically, the implications of individual ear canal acoustics and their impact on accurately defining hearing thresholds are discussed. Detailed information about the statistical strength of the real-ear-to-coupler difference (RECD) measurement and how to obtain the measure in young infants is also provided. In addition, the findings of a study that examined the relationship between behavioral and electrophysiologic thresholds in real-ear SPL is described. The second section presents information related to the electroacoustic verification of hearing instruments. The RECD is discussed in relation to its application in simulated measurements of real-ear hearing instrument performance. In particular, the effects of the transducer and coupling method during the RECD measurement are described in terms of their impact on verification measures. The topics of insertion gain, test signals, and venting are also considered. The third section presents three summary tables that outline the hearing instrument fitting process for infants, children, and adults. Overall, this chapter provides both clinical and scientific information about procedures used in the assessment and verification stages of the DSL Method.
BIS Monitoring: Awareness and Catastrophic Events
Authors: Adam Naureen , Sebel Peter S.
Published: March 2006

The bispectral index is an electroencephalogram-based monitoring tool to help anesthesiologists determine depth of anesthesia. The bispectral index indicates both the potential for awareness and of relative hypnotic overdose, but it does not predict movement or hemodynamic responses to stimulation, and it cannot predict the exact moment consciousness returns. The bispectral index has been assessed for its relationship to awareness, and bispectral index monitoring appears to be generally associated with a low incidence of awareness. The bispectral index has also has been noted to detect periods of cerebral ischemia. It is also being used in intensive care units to help quantify the level of sedation in patients and as an outcome predictor in patients with brain injuries. Low values of the bispectral index often occur during catastrophic, ischemic, events but the use of this technology for the routine monitoring of such events is unproven.
Perioperative Detection of Brain Oxygenation and Clinical Outcomes in Cardiac Surgery
Authors: Murkin John M.
Published: March 2006

Awareness of the high incidence of subtle central nervous system dysfunction after cardiopulmonary bypass, when it leads to increased vigilance in monitoring and diagnosis, remains the most important factor in the detection of postoperative injury. Preliminary data from an ongoing prospective study indicates that the use of noninvasive cerebral oximetry may be associated with a decreased length of stay in patients who have had coronary artery bypass grafting.
Risk Factors for Cardiac Surgery: The High-Risk Patient
Authors: Hammon John W.
Published: March 2006

The demographics of cardiac surgical patients are changing. The average age at operation has risen 10 years since 1980, and the risk of surgery related to severe atherosclerosis of the aorta and its branches is increasing. Although cardiac risk is increasing, operative techniques to minimize cardiac risk have placed the emphasis on comorbid conditions. Patients with preexisting unstable cerebral, vascular, renal, and hepatic disease are at a markedly increased risk and should be carefully evaluated preoperatively.
Intraoperative Echocardiography: Support for Decision Making in Cardiac Surgery
Authors: Iglesias Ivan , Bainbridge Daniel , Murkin John
Published: March 2006

Intraoperative echocardiography (including transesophageal echocardiography, epiaortic ultrasound and epicardial echocardiography) is commonly performed in North American hospitals during cardiac anesthesia. Several authors have reported on the positive impact of intraoperative echocardiography on patients’ outcomes. Transesophageal echocardiography is useful in identifying anatomic and functional abnormalities either before or after cardiopulmonary bypass and helps to make decisions in the care of high-risk and unstable patients. In minimally invasive and robotically assisted surgery, transesophageal echocardiography is essential in order to guide cannulation of venous and arterial vessels for cardiopulmonary bypass and in providing immediate assessment of the quality of the performed repair. Intraoperative echocardiography can also detect complications associated with the performed procedure and can be an excellent hemodynamic monitor in unstable patients. In this paper different scenarios where intraoperative echocardiography is useful are reviewed, some clinical cases are shown to illustrate, and a review of related literature is reported.
A Critical Review of the Role of Carotid Disease and the Outcomes of Staged and Synchronous Carotid Surgery
Authors: Naylor A. R.
Published: March 2006

Few subjects are as enduring as the management of patients with combined carotid and cardiac disease. This paper reviews the available evidence supporting and refuting the role of carotid artery disease in the pathophysiology of stroke after coronary artery bypass grafting surgery and analyzes the results of systematic reviews of staged and synchronous carotid reconstruction. The available data suggest that only about 40% of strokes (at most) could be directly attributable to ipsilateral carotid artery disease. The rate of death and stroke following staged or synchronous carotid surgery in all published series was 6% and 9%, respectively. Unfortunately, natural history data are inadequate to determine whether a policy of prophylactic carotid endarterectomy reduces the risk of stroke after cardiac surgery.
Treatment of Inoperable Coronary Disease and Refractory Angina: Spinal Stimulators, Epidurals, Gene Therapy, Transmyocardial Laser, and Counterpulsation
Authors: Svorkdal Nelson
Published: March 2006

Intractable angina from refractory coronary disease is a severe form of myocardial ischemia for which revascularization provides no prognostic benefit. Inoperable coronary disease is also accompanied by a “vicious cycle” of myocardial dystrophy from a chronic alteration of the cardiac sympathetic tone and sensitization of damaged cardiac tissues. Several adjunctive treatments have demonstrated efficacy when revascularization is either unsuccessful or contraindicated. Spinal cord stimulation modifies the neurologic input and output of the heart by delivering a very low dose of electrical current to the dorsal columns of the high thoracic spinal cord. Neural fibers then release CGRP and other endogenous peptides to the coronary circulation reducing myocardial oxygen demand and enhancing vasodilation of collaterals to improve the myocardial blood flow of the most diseased regions of the heart. Randomized study has shown the survival data at five years is comparable to bypass for high-risk patients. Transmyocardial laser revascularization creates small channels into ischemic myocardium in an effort to enhance flow though studies have shown no improvement in prognosis over medical therapy alone. Enhanced external counterpulsation uses noninvasive pneumatic compression of the legs to improve diastolic filling of the coronary vessels and promote development of collateral flow. The compressor regimen requires thirty-five hours of therapy over a seven-week treatment period. Therapeutic angiogenesis requires injection of cytokines to promote neovascularization and improve myocardial perfusion into the regions affected by chronic ischemia. Phase 3 trials are pending. High thoracic epidural blockade produces a rapid and potent sympatholysis, coronary vasodilation and reduced myocardial oxygen demand in refractory coronary disease. This technique can be used as an adjunct to bypass surgery or medical therapy in chronic or acute unstable angina. Epidurals are easy to perform and often available for outpatient or inpatient use. The rapid anti-ischemic effect may complement therapeutic angiogenesis or other interventions with delayed onset to clinical benefit. A new era for interventional and implant cardiology is beginning to emerge as more clinicians, including cardiologists, gradually learn new procedures to safely provide more therapeutic options for patients suffering refractory angina.
Monitoring the Electroencephalogram During Bypass Procedures
Authors: Gugino Laverne D. , Aglio Linda S. , Yli-Hankala Arvi
Published: March 2006

Electroencephalographic monitoring has been performed since the early days of cardiopulmonary bypass. Despite this long experience, the technology has never been widely used for cardiac operations. This review examines the reasons for the limited use and describes technological advances that may alter this pattern.
Evoked Potentials during Cardiac and Major Vascular Operations
Authors: Stecker Mark M.
Published: March 2006

Somatosensory evoked potentials are widely used in spine surgery to prevent injury to the spinal cord. However, their application in cardiac and major vascular surgery is largely unappreciated. This paper will review the unique stresses placed on peripheral nerves, spinal cord, and brain during these operations. In addition, the potential benefits of perioperative somatosensory evoked potentials monitoring are described in detail.
Electrophysiologic Monitoring during Surgery to Repair the Thoracoabdominal Aorta
Authors: Sloan Tod B.
Published: March 2006

The repair of aneurysms and dissections that involve the thoracoabdominal aorta represent a major stress to the cardiovascular surgery team because of the feared complication of paraplegia. Here, the etiology of this complication is explained through a description of the relevant surgical anatomy and characteristics of hemodynamic support. In addition, recent advances in the neurophysiologic assessment of the descending motor pathways and their application to perioperative monitoring are discussed.
Intraoperative Transcranial Ultrasonic Monitoring for Cardiac and Vascular Surgery
Authors: Doblar Dennis D.
Published: March 2006

The brain is the only organ not routinely monitored by any direct method during the administration of anesthesia. Anesthesiologists rely primarily on indirect physiologic evidence provided by blood pressure, peripheral pulse oximetry, heart rate, and respiratory and anesthetic gas concentrations to determine that brain blood flow and oxygenation are adequate. The reasons for this practice are that: (1) after millions of anesthetics significant numbers of adverse neurologic outcomes have not occurred, (2) the interpretation of transcranial Doppler, electroencephalogram, and near-infrared cerebral oximetry requires experienced personnel, and (3) the evidence of cost-benefit to support monitoring is limited. Brain monitoring generally has been confined to procedures where the brain is exposed to unique insults and risks specific to the procedures and where reliance on indirect physiologic evidence of cerebral integrity has been proven to be unreliable. Transcranial Doppler monitoring is valuable in the assessment of established surgical techniques, refinement of recent surgical techniques, and development of new techniques and instrumentation. Brain monitoring with transcranial Doppler is of particular value when deviations from established surgical or anesthetic techniques may place the brain at risk for cerebral hyper-or hypoperfusion, gaseous or particulate embolization, or their combined effects. This paper discusses applications of transcranial Doppler in coronary artery bypass surgery, aortic arch procedures, pediatric cardiac surgery, carotid endarterectomy, and a few other special cases. The insight into cerebral physiology is unique to the continuous window on the brain that transcranial Doppler provides.
Perioperative Multimodality Neuromonitoring: An Overview
Authors: Murkin John M.
Published: March 2006

Neurologic damage after cardiac surgery remains an important cause of postoperative morbidity. In addition to a wide variety of procedural risks, patient-specific factors such as the presence of extracranial or intracranial atherosclerotic disease, either alone or together, have a fundamental impact on the risk of brain injury developing after cardiovascular surgery. A variety of neurophysiologic monitoring techniques have been used during cardiovascular surgery in hopes of averting neurologic injury. In this issue of Seminars, the strengths and weaknesses of each are discussed by a group of highly experienced clinical investigators. The ultrasound techniques of epiaortic scanning and continuous transcranial Doppler insonation of large intracranial arteries can alter perfusion management and surgical habits to markedly decrease the delivery of atherosclerotic, lipoidal, and gaseous microemboli to the brain and other vital organs. Cerebral hypoperfusion from unrecognized cerebral venous obstruction, inadequate mean arterial pressure, or hypocapnic cerebral alkalosis can be identified by transcranial near-infrared spectroscopy, electroencephalogram, and sensory evoked potentials. Compromise of spinal cord perfusion during the repair of thoracoabdominal aneurysms may be identified and corrected with the guidance provided by transcranial electric motor-evoked potentials. Quantitative electroencephalogram and auditory evoked potential indices also appear beneficial in producing objective measures of the hypnotic component of anesthesia. These neuromonitoring methods, particularly when used in concert, can improve overall patient outcome and reduce hospital length of stay.
Pulmonary Complications After Cardiac Surgery
Authors: Weissman Charles
Published: March 2006

Over the past two decades there has been a steady evolution in the practice of adult cardiac surgery with the introduction of “off-pump” surgery. However, respiratory complications remain a leading cause of postcardiac surgical morbidity and can prolong hospital stays and increase costs. The high incidence of pulmonary complications is in part due to the disruption of normal ventilatory function that is inherent to surgery in the thoracic region. Furthermore, patients undergoing such surgery often have underlying illnesses such as intrinsic lung disease (e.g., chronic obstructive pulmonary disease) and pulmonary dysfunction secondary to cardiac disease (e.g., congestive heart failure) that increase their susceptibility to postoperative respiratory problems. Given that many patients undergoing cardiac surgery are thus susceptiple to pulmonary complications, it is remarkable that more patients do not suffer from them during and after cardiac surgery. This is to a large degree because of advances in anesthetic, surgical and critical care that, for example, have reduced the physiological insults of surgery (e.g., better myocardial preservation techniques) and streamlined care in the immediate postoperative period (e.g., early extubation). Moreover, the development of minimally invasive surgery and nonbypass techniques are further evidence of the attempts at reducing the homeostatic disruptions of cardiac surgery. This review examines the available information on the incidences, consequences, and treatments of postcardiac surgery respiratory complications.
Renal Insufficiency After Cardiac Surgery
Authors: Garwood Susan
Published: March 2006

The new millennium ushered in a number of changes in cardiac surgery. Off-pump coronary artery bypass surgery became technically easier so that multivessel surgery became less of a challenge and cardiologists were supplied with new catheters that accessed lesions that were previously thought of as being unapproachable. New drugs were introduced that made the management of heart failure patients feasible on an outpatient basis, and new devices extend the bridging period to transplantation. However, these advances have not necessarily been attended by significant improvements in outcome, possibly because the less challengng a procedure becomes, the sicker the patients that can be managed. This observation is particularly true with the incidence and outcome of renal failure after cardiac surgery. Bypass factors have been manipulated without much effect, and the traditional drugs that were found to increase renal blood flow in animal experiments did not translate into clinical improvement in renal outcome. Recent research has given us insight into the pathophysiology of ischemic acute renal failure, and it has been found that the paradigm was not as simple as previously thought, possibly accounting for the failure of the more traditional renal drugs (dopamine, mannitol and diuretics). However, these new insights open up the possibility of novel targets for renal protection and repair.
Abdominal Organ Injury After Cardiac Surgery
Authors: Hessel Eugene A.
Published: March 2006

Gastrointestinal complications occur in about 2.5% of patients undergoing cardiac surgery, are associated with a high mortality (about 33%), and account for nearly 15% (and perhaps increasing) of all postoperative deaths. The various complications and risk factors are reviewed. Splanchnic ischemia prior to, during, and especially postoperatively appears to be an important cause of these complications. In addition, splanchnic ischemia is hypothesized to be one cause of the systemic inflammatory response syndrome and multiorgan failure that may follow cardiac surgery. The physiology of splanchic perfusion and the effects of cardiac surgery, including cardiopulmonary bypass, on it are reviewed. Finally, possible methods to minimize splanchnic ischemia and reduce the incidence of abdominal complications are discussed.
Transfusion of Blood Products Affects Outcome in Cardiac Surgery
Authors: Spiess Bruce D.
Published: March 2006

There remains controversy as to when patients undergoing cardiac surgery should receive a transfusion and whether a low hematocrit and its treatment with a transfusion of red cells influences outcome. The data related to this controversy are reviewed. Although the risk of known viral transmission is currently low, stored red cells do not function normally, and each unit contains activated inflammatory cells and mediators. These changes cause limited oxygen release, impaired microcirculatory flow, and immune suppression. A number of studies have observed decreased survival associated with transfusions in trauma, coronary artery bypass grafting, and intensive care unit patients. Studies that show an adverse outcome associated with low hematocrit are not definitive, because they fail to distinguish between the impact of low hematocrit per se and the possible adverse effects of transfusion, for what the low hematocrit may simply be a surrogate. The observation that a low hematocrit is associated with an adverse outcome does not necessarily prove that “treatment” of the anemia with a red cell transfusion will improve the outcome. Stored platelets contain a highly activated mixture of platelets with storage lesions and inflammatory mediators. Two retrospective post hoc multifactorial analyses suggest that platelet transfusions are associated with substantial increased morbidity and mortality. Clearly, large prospective studies are required to define the proper trigger for blood product transfusion to balance the adverse effects of anemia and platelet deficiency or dysfunction with the adverse effects of transfusion of blood products on morbidity and mortality associated with cardiac surgery and anesthesia.
Does Gender Influence the Likelihood or Types of Complications Following Cardiac Surgery?
Authors: Fox Amanda A. , Nussmeier Nancy A.
Published: March 2006

Over 410,000 cardiac surgeries are performed in American women each year. Women having coronary artery bypass graft (CABG) and valve surgery do so at an older age and with more cardiovascular risk factors than men. Women's smaller body size may also increase risk by increasing the technical difficulty of surgical procedures. Female CABG patients appear to have higher perioperative mortality and cardiac morbidity, although studies of neurologic outcomes in female CABG patients have produced equivocal findings. Women undergoing CABG tend to consume more hospital resources than men do in terms of blood transfusion, mechanical ventilation, and length of intensive care unit and overall hospital stay. With regard to valve surgery, women appear to have worse outcomes than men if the surgery is combined with a CABG operation. Women and men undergoing isolated aortic valve surgery have similar mortality, but little is known about gender differences in mitral and tricuspid valve surgery outcomes. Women who require heart transplantation tend to have idiopathic cardiomyopathy rather than the ischemic cardiomyopathy that is more common in male heart transplant candidates. Although female heart transplant recipients seem to have a stronger immunologic response after transplantation, which manifests in more frequent acute rejection episodes, it is not clear whether this increases women's mortality risk. Men appear to have a greater incidence of posttransplant vasculopathy than women. Further research is needed to identify risk factors for perioperative morbidity and mortality in women undergoing cardiac surgery and to develop medical interventions to mitigate these risks.
Predictive Genomics of Adverse Events After Cardiac Surgery
Authors: Fox Amanda A. , Shernan Stanton K. , Body Simon C.
Published: March 2006

Significant, yet highly individual, thrombotic and inflammatory responses to surgery provide an excellent opportunity for insight into the genomic impact upon a patient's postoperative course. Cardiac surgery elicits the most profound perioperative disturbance and is associated with the highest incidence of adverse outcomes of any elective surgical procedure. Thus, cardiac surgical patients are an ideal population in which to evaluate the influence of complex traits on perioperative morbidity and mortality. This review describes the application of fundamental genetics upon the occurrence of adverse outcomes after cardiac surgery and cardiac transplantation. Specific emphases include a brief primer of the principles of genetics concentrating on the effects of variation within the human genome upon clinical outcomes and the differences between so-called Mendelian traits and complex traits. Four important clinical diseases dealt with in this review as examples of the impact of genetic factors on clinical outcomes are the genetics of heparin-induced thrombocytopenia, heart transplantation rejection and vasculopathy, atrial fibrillation, and infection.
Acute Lung Injury and Acute Respiratory Distress Syndrome After Pulmonary Resection
Authors: Grichnik Katherine P. , D'Amico Thomas A.
Published: March 2006

The occurrence of acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) after thoracic surgery are perplexing and persistent problems. Variously described as postpneumonectomy pulmonary edema, noncardiogenic pulmonary edema, and postlung resection pulmonary edema, ALI and ARDS may be considered a single entity, with ALI being the less severe form of ARDS. It is characterized by the acute onset of hypoxemia with radiographic infiltrates consistent with pulmonary edema, without elevations in the pulmonary capillary wedge pressure. Although this syndrome does not occur frequently and is usually without identifiable cause, the mortality is high. However, the phenomenon has not been rigorously studied owing to the low incidence, with primarily retrospective case series reported. Thus, the nomenclature, risks, and pathogenesis are not well defined. Interest in this syndrome has recently been renewed as the rate of other perioperative complications has declined. ALI/ARDS is reviewed with a focus on potential etiologies and the spectrum of available interventions.