Management of major tracheobronchial injuries: a 28-year experience

BACKGROUND

Tracheobronchial injuries are rare but potentially life threatening. Their successful diagnosis and treatment often require a high level of suspicion and surgical repairs unique to the given injury.

METHODS

We reviewed our experience with 32 patients with tracheobronchial injuries treated over the past 28 years.

RESULTS

Forty-one percent (13/32) of the injuries were due to blunt trauma and 59% (19/32), to penetrating trauma. Most penetrating injuries were located in the cervical trachea (74%), whereas blunt injuries were more commonly located close to the carina (62%). Fifty-nine percent of the patients required urgent measures to secure the airway. Penetrating injuries were usually diagnosed by clinical findings or at surgical exploration. The diagnosis of blunt injuries was more difficult and required a high index of suspicion and the liberal use of bronchoscopy. The majority of the injuries were repaired primarily using techniques specific to the injury, and most patients returned to their normal activity soon after discharge.

CONCLUSIONS

A high level of suspicion and the liberal use of bronchoscopy are important in the diagnosis of tracheobronchial injury. A tailored surgical approach is often necessary for definitive repair.

Beta-adrenergic augmentation of flecainide-induced conduction slowing in canine Purkinje fibers

BACKGROUND

This study was undertaken to test the hypothesis that beta-adrenergic stimulation in the setting of membrane depolarization will potentiate flecainide-induced conduction slowing.

METHODS AND RESULTS

To elucidate the potential mechanism for the flecainide proarrhythmia observed in CAST, the voltage dependence of beta-adrenergic modulation of impulse propagation in eight flecainide-superfused canine Purkinje fibers was examined with a dual-microelectrode technique. At physiological membrane potentials (Vm) ([K+]o=5.4 micromol), 1 micromol flecainide decreased Vmax from 698+/-55 to 610+/-72 V/s (P=.003) and squared conduction velocity (theta2) from 2.11+/-1.1 to 1.72+/-0.9 (m/s)2 (P=.001). With K+ depolarization to Vm=-70 mV, flecainide further reduced Vmax from 306+/-101 to 245+/-65 V/s and theta2 from 1.12+/-0.4 to 0.99+/-0.6 (m/s)2, producing a 2.0-mV hyperpolarizing shift of apparent Na+ channel availability curves derived from theta2. The addition of 1 micromol isoproterenol to flecainide-superfused fibers at physiological Vm increased theta2 by 8% to 1.84+/-0.6 (m/s)2 (P<.01) without altering Vmax. At -70 mV, the addition of isoproterenol magnified the flecainide-induced reduction of Vmax an additional 24% to 185+/-52 V/s (P<.01) and theta2 by 17% to 0.82+/-0.5 (m/s)2 (P=.04), producing an additional 1.8-mV (P=.002) and 1.9-mV (P=.002) hyperpolarizing shift in the apparent Na+ channel inactivation curves generated from Vmax and theta2, respectively. At physiological Vm, the action potential duration (APD95) was reduced from 307+/-35 to 269+/-27 ms (P<.001) by flecainide and subsequently to 217+/-4 ms (P<.001) with isoproterenol addition. With 12 mmol/L K+, APD95 decreased from 198+/-23 to 182+/-17 ms (P=.005) with flecainide and to 164+/-10 ms (P=.004) with isoproterenol.

CONCLUSIONS

At depolarized Vm, isoproterenol amplified the flecainide-induced reduction of Vmax and theta2, suggesting a further adrenergic-mediated reduction of Na+ current. Consequently, the synergy between catecholamines and flecainide at depolarized Vm and the shortened APD95 could facilitate arrhythmogenesis in the presence of underlying ischemia.

Impact of volume loading and load reduction on ventricular refractoriness and conduction properties in canine congestive heart failure

OBJECTIVES

This investigations was undertaken to examine the alteration of electrophysiologic properties, including refractoriness, strength-interval relations and conduction, with the development of heart failure and to characterize the impact of volume loading on these indexes in the cardiomyopathic setting.

METHODS

Electrophysiologic properties in eight dogs with pacing-induced dilated cardiomyopathy were compared with those in six control dogs before and after rapid infusion of 800 ml of intravenous saline.

RESULTS

The right ventricular (RV) and left ventricular (LV) effective refractory period (ERP) and absolute refractory period (ARP) were significantly longer in dogs with pacing-induced cardiomyopathy than in control dogs: RV ERP 181 +/- 11 ms versus 138 +/- 7 ms (mean +/- SD) (p < 0.0001) and anterior LV ERP 177 +/- 13 ms versus 128 +/- 11 ms (p < 0.0001), respectively; ARP 159 +/- 14 ms versus 114 +/- 7 ms (p < 0.0001) at the RV site and 153 +/- 12 versus 117 +/- 5 ms (p < 0.0001) at the anterior LV site. After volume loading in cardiomyopathic animals, posterior and anterior LV ERPs became prolonged to 178 +/- 5 ms (p = 0.004) and 189 +/- 14 ms (p = 0.065), respectively, shifting the strength-interval relation in the direction of longer S1S2 coupling intervals. Anterior LV monophasic action potential durations at 90% repolarization also became prolonged from 192 +/- 10 ms to 222 +/- 23 ms (p < 0.012) with volume loading. These findings were not altered by subsequent sodium nitroprusside. Local conduction times parallel and perpendicular to fiber orientation were not altered by development of cardiomyopathy or volume alterations.

CONCLUSIONS

The development of dilated cardiomyopathy results in significant prolongation of refractoriness and repolarization that is increased further by volume augmentation but is not reversed by pharmacologic load reduction. Although these abnormalities may contribute to the environment needed for a non-reentrant, triggered or stretch-mediated arrhythmogenic process in cardiomyopathic states, additional studies will be required to demonstrate such a focal mechanism conclusively.

Residential treatment for youngsters with difficult-to-manage insulin dependent diabetes mellitus

A descriptive outcome study of 52 children with insulin-dependent diabetes mellitus (IDDM) admitted to a residential treatment program over 6 years. Criteria for admission included repeated hospitalizations for diabetes-related problems, excessive school absences, and/or familial disruption. Residential treatment included individual, group, and family psychotherapy, diabetes education, and close medical supervision. The design included collection of data before, during and after treatment. Children admitted to the residential unit were compared to a population of pediatric IDDM outpatients from the same geographical area. Treatment was associated with a reduction in diabetes-related hospitalizations, improved school attendance, decreased glycosylated hemoglobin levels, weight gain, individualized insulin changes, improved knowledge about diabetes, and a normalization of attitudes towards this disease.

Improved separation and immunodetection of rat cytochrome P450 4A forms in liver and kidney

In the study of tissues that contain several forms of one cytochrome P450 subfamily, it is useful to develop immunoblotting techniques so that the various individual members of the family can be distinguished. This paper describes improvements in the immunoblotting technique to distinguish members of the rat cytochrome P450 4A subfamily, 4A1, 4A2, and 4A3, as they are present in Sprague-Dawley rat liver microsomes. This procedure was used to investigate differences in the cytochrome P450 4A forms observed under various conditions such as: untreated versus peroxisome proliferator treated rats, Sprague-Dawley versus Fischer 344 male versus female rats, and liver versus kidney microsomes. In liver microsomes of male Sprague-Dawley rats, forms 4A1, 4A2, and 4A3 were induced by the peroxisome proliferators, clofibrate, di-(2-ethylhexyl) phthalate, dehydroepiandrosterone, aspirin, and ibuprofen. Expression of the 4A forms shows strain specificity. A comparison of the cytochrome P450 4A forms in male Sprague-Dawley and Fischer 344 rats treated with peroxisome proliferators demonstrated that three distinct protein bands are visible on immunoblots of liver microsomes of Sprague-Dawley rats, whereas only two distinct protein bands are detectable in liver microsomes of Fischer 344 rats. The two protein bands in liver microsomes of male Fischer 344 rats migrate in positions corresponding to the 4A2 and 4A3 bands in male Sprague-Dawley rats. There did not appear to be a protein band corresponding to the 4A1 band of Sprague-Dawley rats. Expression of the 4A forms also shows gender specificity. In liver microsomes of female Sprague-Dawley rats, expression of the P450 4A2 form was not observed after treatment with a peroxisome proliferator. Expression of the 4A forms also shows tissue specificity. In kidney, 4A2 is the major protein band in male Sprague-Dawley rats with minor amounts of the 4A3 protein, whereas two prominent protein bands (4A2 and 4A3) are seen in male Fischer 344 rats.

Efficacy of prehospital surgical cricothyrotomy in trauma patients

OBJECTIVE

The use of surgical cricothyrotomy (SC) in the prehospital setting is controversial, and the need to teach this procedure to paramedics and intermediate emergency medical technicians remains unclear. The purpose of this study is to define the efficacy, complication rate, and overall survival after SC performed in the prehospital setting.

METHODS

In our region, emergency medical technicians receive training in this technique using an animal model with bi-annual updates required. We retrospectively reviewed data in our regional trauma register (15,686 injured patients) for the years 1991-1995.

RESULTS

Prehospital emergency airway intubation was required in 376 patients, 56 of whom received SC. The primary indications for SC were facial fractures and deformities (32%) and blood in the airway (30%). In 79% of the patients requiring SC, attempted orotracheal intubation prior to SC was unsuccessful, with a mean of 1.9 attempts per patient. SC was judged to provide an adequate airway in the field in 89% of attempts. Complications at the scene included six failed attempts, one case of excessive bleeding, and one adverse patient reaction (agitation). When patients arrived at the trauma center, the SC was judged to be acceptable in 64%, whereas 16% were functioning with some question of adequacy and required airway manipulation (most commonly a mainstem bronchial intubation). Overall survival to hospital discharge was 27%; however, survival to emergency department discharge (an indicator of emergency airway adequacy) was 62%. Using TRISS methodology, there were five unexpected survivors and six unexpected deaths. Only three patients were discharged with a "good neurologic recovery."

CONCLUSION

(1) Prehospital SC can be performed effectively with few complications after training on animal models (2) Good neurologic outcome is rare after the use of this procedure. (3) Although it is effective, clear indications must be developed and followed for the prehospital use of SC.

Mechanism of lethal proarrhythmia observed in the Cardiac Arrhythmia Suppression Trial: role of adrenergic modulation of drug binding

A variety of recent in vivo studies have sought to clarify the mechanism underlying the proarrhythmic response of flecainide in the Cardiac Arrhythmia Suppression Trial (CAST). Increased inducibility of relatively stable ventricular arrhythmias in subacute and chronic postinfarction models has been universally observed. The arrhythmogenesis has been explained in part by drug induced modulation of anisotropic conduction in persistently ischemic tissue, increased durations of vulnerable windows, enhanced generation of unidirectional block with the introduction of extrastimuli, variability of repolarization within the ventricular wall, and the creation of stable reentrant circuits with narrow central zones of propagation. While these data explain arrhythmogenesis in general, malignant ventricular arrhythmia capable of producing the excess sudden or arrhythmic death mortality in the CAST trial have not been universally observed, nor have the proported beneficial effects of beta-blockade seen in the CAST trial and other studies been explained. Additional studies examining the adrenergic modulation of flecainide binding have shown reversal of flecainide effects in normal tissue, but paradoxical amplification of flecainide induced conduction slowing in depolarized tissue. This variable effect in normal versus abnormal tissue produces significant dispersions of conduction with an expected increased propensity for conduction failure in response to ectopy, increased liminal length for impulse propagation, enhanced vulnerability to premature extrastimuli, and completed reentrant circuits in regions of depressed membrane potentials. This, along with the decrease in action potential duration and accompanying refractoriness in the setting of adrenergic modulation may favor more malignant double wavelet or unstable ventricular arrhythmias.

Generic database design for patient management information

Patient management information tracks general facts about the location of the patient and the providers assigned to care for the patient. The Clinical Data Repository at Columbia Presbyterian Medical Center employs a generic schema to record patient management events. The schema is extremely simple, yet can support several different views of patient information, as required by different applications: a longitudinal view of patient visits, including both inpatient and outpatient encounters; a visit-oriented view, to record facts related to a current encounter; a location-based view to provide a census of a nursing ward; and a provider-based view to give a list of the patients currently being cared for by a given clinician. All of these views can be supported in a highly efficient manner by the use of appropriate indexes.

Dual-inflow great vessel aneurysm: delayed presentation after penetrating trauma

Aneurysms constitute uncommon sequelae of injuries to the thoracic outlet. Most such aneurysms are secondary to blunt trauma and usually involve the great vessels at their take-off from the aortic arch. Penetrating injuries are more often identified in the more distal vessels and only very rarely present as pseudoaneurysms. Reported here is a single case of a chronic posttraumatic pseudoaneurysm arising from both the right common carotid artery and the right subclavian artery. The workup and surgical approach provide practical lessons, complemented with illustrations that aid in the understanding of the case. It is an unusual case because of the dual-inflow nature of the aneurysm.

Essential fatty acid deficiency and predisposition to lung disease in cystic fibrosis

Essential fatty acid (EFA) deficiency is a predisposing factor for pulmonary infection with Staphylococcus aureus and Pseudomonas aeruginosa, the two major pathogenic microorganisms in cystic fibrosis (CF).

OBJECTIVE

The goal of this study was to investigate the essential fatty acid status of CF patients from infancy to 20 years old.

MATERIALS AND METHODS

Plasma fatty acid profiles for phospholipid (PL) were determined for cord (n = 6), 4 months (n = 40), 16 months (n = 25), 3 y (n = 8), 5-10 y (n = 10), and 10-20 y (n = 10) aged CF patients and compared to their respective control; cord (n = 22), 1-36 months (n = 38) and adult (n = 100). Significance was established by Student's t-test (p < 0.05).

RESULTS

The plasma PL fatty acid profile for all CF patients, except cord, revealed consistent deficiency in omega 3 and omega 6 EFAs. These deficiencies were most marked at infancy and more pronounced for patients with meconium ileus.

CONCLUSIONS AND RELEVANCE

EFA deficiency may contribute to the predisposition of CF infants to develop respiratory disease and to the excess cytotoxic activity found in bronchoalveolar lavage fluid at 2 months of age in the majority of screened infants.

Design of a clinical event monitor

The issues and implementation of a clinical event monitor are described. An event monitor generates messages for providers, patients, and organizations based on clinical events and patient data. For example, an order for a medication might trigger the generation of a warning about a drug interaction. A model based on the active database literature has as its main components an event (which triggers a rule to fire), a condition (which tests whether an action ought to be performed), and an action (often the generation of a message). The details of implementing such a monitor are described, using as an example the Columbia-Presbyterian Medical Center clinical event monitor, which is based on the Arden Syntax for Medical Logic Modules.

Integrating data from natural language processing into a clinical information system

Demographic data extracted from discharge summaries by natural language processing was compared to data gathered by a conventional hospital admitting system. Discrepancies in data were noted in names, age, sex, race, and ethnicity. Some differences are attributable to errors in collection: interaction with patient, dictation, transcription, and data entry. Very few differences were due to errors in natural language processing. Other differences can be used to critique existing data, or to enhance data with more detailed information. Discrepancies in data as elementary as patient demographics raise the issue of resolving conflicts when neither source of data is known to be more reliable. Clinical repositories can represent conflicting data from multiple sources, but clinical information systems must bear the cost of increased complexity in the application programs that will use the data.

Generic data modeling for clinical repositories

OBJECTIVE

To construct a large-scale clinical repository that accurately captures a detailed understanding of the data vital to the process of health care and that provides highly efficient access to patient information for the users of a clinical information system.

DESIGN

Conventional approaches to data modeling encourage the development of a highly specific data schema in order to capture as much information as possible about a given domain. In contrast, current database technology functions most effectively for clinical databases when a generic data schema is used. The technique of "generic data modeling" is presented as a method of reconciling these opposing views of clinical data, using formal operations to transform a detailed schema into a generic one.

RESULTS

A complex schema consisting of hundreds of entities and representing a rich set of constraints about the patient care domain is transformed into a generic schema consisting of roughly two dozen tables. The resulting database design is efficient for patient-oriented queries and is highly flexible in adapting to the changing information needs of a health care institution, particularly changes involving the collection of new data elements.

CONCLUSION

Conventional approaches to data modeling can be used to develop rich, complex models of clinical data that are useful for understanding and managing the process of patient care. Generic data modeling techniques can successfully transform a detailed design into an efficient generic design that is flexible enough to meet the needs of an operational clinical information system.

Homograft patch repair for hemorrhagic mediastinitis

Hemorrhage from the heart and great vessels is a potentially lethal complication of post-sternotomy mediastinitis. We report 2 cases in which a cryopreserved descending thoracic aortic homograft was used successfully to repair defects of the ascending aorta and right ventricle in the setting of active mediastinal infection. An overview of mediastinitis and management strategies for life-threatening mediastinal bleeding is included.

Penetrating intrapericardial wounds: clinical experience with a surgical protocol

BACKGROUND

From 1972 to 1977, a treatment protocol was developed at our institution for patients with suspected penetrating intrapericardial wounds. It consists of immediate transport to the operating room, pericardial decompression by subxiphoid pericardial window under local or light general anesthesia in patients in stable condition, and median sternotomy and operative repair with limited use of cardiopulmonary bypass.

METHODS

The records of 79 consecutive patients with acute penetrating intrapericardial injury who underwent operation from March 1978 to July 1991 were reviewed. There were 59 patients (75%) with stab wounds and 20 (25%) with gunshot wounds. Wound location was as follows: right ventricle, 33 (42%); left ventricle, 28 (35%); multiple sites, 8 (10%); atrium, 5 (6%); and great vessels, 5 (6%).

RESULTS

Subxiphoid pericardial window was performed under local or light general anesthesia in 53 patients (67%). Cardiopulmonary bypass was required in only 4 patients. Overall mortality was 6%.

CONCLUSION

Approach to a trauma victim must be systematic. We believe one treatment protocol for patients with suspected penetrating intrapericardial wounds is effective.

Unlocking clinical data from narrative reports: a study of natural language processing

OBJECTIVE

To evaluate the automated detection of clinical conditions described in narrative reports.

DESIGN

Automated methods and human experts detected the presence or absence of six clinical conditions in 200 admission chest radiograph reports.

STUDY SUBJECTS

A computerized, general-purpose natural language processor; 6 internists; 6 radiologists; 6 lay persons; and 3 other computer methods.

MAIN OUTCOME MEASURES

Intersubject disagreement was quantified by "distance" (the average number of clinical conditions per report on which two subjects disagreed) and by sensitivity and specificity with respect to the physicians.

RESULTS

Using a majority vote, physicians detected 101 conditions in the 200 reports (0.51 per report); the most common condition was acute bacterial pneumonia (prevalence, 0.14), and the least common was chronic obstructive pulmonary disease (prevalence, 0.03). Pairs of physicians disagreed on the presence of at least 1 condition for an average of 20% of reports. The average intersubject distance among physicians was 0.24 (95% Cl, 0.19 to 0.29) out of a maximum possible distance of 6. No physician had a significantly greater distance than the average. The average distance of the natural language processor from the physicians was 0.26 (Cl, 0.21 to 0.32; not significantly greater than the average among physicians). Lay persons and alternative computer methods had significantly greater distance from the physicians (all > 0.5). The natural language processor had a sensitivity of 81% (Cl, 73% to 87%) and a specificity of 98% (Cl, 97% to 99%); physicians had an average sensitivity of 85% and an average specificity of 98%.

CONCLUSIONS

Physicians disagreed on the interpretation of narrative reports, but this was not caused by outlier physicians or a consistent difference in the way internists and radiologists read reports. The natural language processor was not distinguishable from the physicians and was superior to all other comparison subjects. Although the domain of this study was restricted (six clinical conditions in chest radiographs), natural language processing seems to have the potential to extract clinical information from narrative reports in a manner that will support automated decision-support and clinical research.

Echocardiography in the evaluation of thoracic trauma

Echocardiography has become a useful diagnostic modality in the evaluation of cardiovascular injury after thoracic trauma. Valuable information about cardiac wall motion, valvular function, pericardial effusions, and ventricular volume status can be obtained without significant risk. More recent application for the diagnosis of traumatic aortic disruption provides a safer, easier, less expensive, and more accurate method for detecting these injuries. Cardiac evaluation with TTE is unsuccessful in approximately 20% of examinations and is unable to provide the image resolution of the more invasive transesophageal approach.

The relationship between faculty ward evaluations, OSCE, and ABSITE as measures of surgical intern performance

BACKGROUND

This study determined the degree to which ward evaluations, the American Board of Surgery In-Training Examination (ABSITE), and an Objective Structured Clinical Examination (OSCE) provide equivalent information about intern performance.

METHODS

Twenty-two general surgery interns completed both the ABSITE and a 17-problem, 35-station OSCE. Faculty members completed several 12-item ward evaluations for each intern. Pearson product-moment correlations were employed to determine the degree of association among the various evaluation measures.

RESULTS

The total OSCE score correlated with both the total ABSITE score and the overall ward evaluations, but the latter two measures did not correlate with each other. The ward evaluations identified the performance of 1 of the 22 interns (5%) as deficient, the ABSITE identified 9 (41%) as deficient in knowledge, and the OSCE 8 (36%).

CONCLUSIONS

In the future, performance-based testing methods such as the OSCE should become more important as an evaluative parameter in assessing the clinical performance of postgraduate surgical trainees.

Patients with anorexia nervosa demonstrate deficiencies of selected essential fatty acids, compensatory changes in nonessential fatty acids and decreased fluidity of plasma lipids

The objective of this study was to assess the essential fatty acid status of patients with anorexia nervosa. Blood was collected from eight fasting female anorexia nervosa patients with a mean of 81% ideal body weight. Fatty acid composition of phospholipids, nonesterified fatty acids, triglycerides and cholesteryl esters of plasma were determined by capillary gas chromatography to indicate polyunsaturated fatty acids status compared with 19 healthy female adults < 25 y old. Subjects with anorexia nervosa showed polyunsaturated fatty acid deficiencies in plasma phospholipids different from simple nutritional essential fatty acid deficiency or chronic malnutrition. The phospholipid profile showed significantly lower (n-6) and (n-3) elongation and desaturation products, and elevated short-chain saturated, short-chain monounsaturated, branched-chain and odd-chain fatty acids. These elevations indicate enhancement of biosynthesis of alternative fatty acids that only partially compensated for the loss of polyunsaturated fatty acids in providing membrane "fluidity." Calculated mean melting point of the fatty acids of phospholipids in patients with anorexia nervosa was elevated 7.7 degrees C above normal values. These results demonstrate that patients with anorexia nervosa have deficiencies of selected essential fatty acids, compensatory changes in nonessential fatty acids and decreased fluidity of plasma lipids.

Transesophageal echocardiography in the diagnosis of traumatic rupture of the aorta

BACKGROUND

Rupture of the aorta is a major cause of death after motor vehicle accidents. Survival depends on early diagnosis, and emergency aortography is the standard imaging method. Although transesophageal echocardiography is noninvasive and can provide high-resolution images of the aorta, information about its value in patients with trauma is limited. We conducted this study to assess prospectively the value of transesophageal echocardiography in the emergency evaluation of patients at risk for aortic injury.

METHODS

Transesophageal echocardiography of the aorta was attempted in 101 patients admitted to the emergency room with a diagnosis of possible traumatic rupture of the aorta. Echocardiography and aortography personnel were notified simultaneously of the arrival of the patient, and the two tests were performed sequentially by operators who were blinded to the results of the other test. The sensitivity and specificity of transesophageal echocardiography were calculated on the basis of the results of aortography of the arch, surgery, or autopsy.

RESULTS

Transesophageal echocardiography was attempted in 101 patients. The study was successfully performed in 93 patients but could not be completed in 8 because of lack of cooperation on the part of the patient (7 patients) or maxillofacial trauma (1 patient). Despite a high injury-severity score (mean, 29.6), transesophageal echocardiography was performed without complications, and within a mean (+/- SD) of 29 +/- 12 minutes. Eleven of the 93 studies (12 percent) demonstrated rupture of the aorta near the isthmus. The findings were confirmed in 10 of the 11 patients by aortography (9 patients), surgery (9 patients), or autopsy (1 patient), yielding a sensitivity of 100 percent and specificity of 98 percent for the detection of injury to the aorta. There was one false positive echocardiogram.

CONCLUSIONS

Transesophageal echocardiography is a highly sensitive and specific method of detecting injury to the thoracic aorta. This technique can be used safely and quickly in critically injured patients with suspected traumatic rupture of the aorta and compares favorably with arch aortography.

Applying a controlled medical terminology to a distributed, production clinical information system

To maximize the value of computerized medical records systems, an organizing structure is needed. That structure can be provided by a controlled medical terminology (CMT). At Columbia-Presbyterian Medical Center, we have been employing a controlled medical terminology, our Medical Entities Dictionary (MED), to mediate the storage and retrieval of patient data and enable decision support applications. This paper describes how the MED is actually used for data management in our distributed clinical information systems environment. Our system tools which access the MED for production purposes facilitate the mapping of terms from many sources to a uniform representation of concepts and also return information about the relationships between concepts. Applications which access a CMT for production purposes should be optimized for performance in high volume settings, fault tolerant, synchronizable, extensible, portable, and maintainable. We briefly describe our system architecture and then demonstrate how we utilize the MED for translation and semantic information as data is moved into and out of our patient database. We discuss our current tools and present a preview of the next generation of applications which will manage access to the MED for our production systems.

Medical decision support: experience with implementing the Arden Syntax at the Columbia-Presbyterian Medical Center

We began implementation of a medical decision support system (MDSS) at the Columbia-Presbyterian Medical Center (CPMC) using the Arden Syntax in 1992. The Clinical Event Monitor which executes the Medical Logic Modules (MLMs) runs on a mainframe computer. Data are stored in a relational database and accessed via PL/I programs known as Data Access Modules (DAMs). Currently we have 18 clinical, 12 research and 10 administrative MLMs. On average, the clinical MLMs generate 50357 simple interpretations of laboratory data and 1080 alerts each month. The number of alerts actually read varies by subject of the MLM from 32.4% to 73.5%. Most simple interpretations are not read at all. A significant problem of MLMs is maintenance, and changes in laboratory testing and message output can impair MLM execution significantly. We are now using relational database technology and coded MLM output to study the process outcome of our MDSS.