Aortic stenosis with end-stage liver disease: prioritizing surgical and anesthetic therapies.

A 48-year-old man with end-stage liver disease and aortic stenosis (AS), was being evaluated for liver transplantation. This report focuses on the question of which medical problem to correct first, the end-stage liver disease or the AS. Risk factors for surgical correction of AS and liver transplantation are reviewed and discussed, and the surgical and anesthetic management strategies for this patient are outlined.

Availability of records in an outpatient preanesthetic evaluation clinic.

OBJECTIVE: Despite efforts to develop electronic access to medical records, there are few data on availability of past evaluations. Typical analyses assess only availability of paper charts. We studied the availability of prior internal and external medical documentation in the preanesthetic clinic of our tertiary teaching institution, which has had access to hospital-wide electronic records for five years. METHODS: Residents and clerks answered questions on availability of desired pre-existing records either in a physical chart delivered to our clinic by computer terminal, at the start of the physician interview, and on later success in obtaining desired records not available at start of interview. Patient interview lengths were calculated. RESULTS: 397 responses from 19-9-96 through 25-10-96 were available after 718 patient encounters. The surgeon's history & physical was unavailable in 11%. For 114/397 patients (29%) the anesthesiologist desired more preexisting information than was available in either paper or electronic format. For 32/397 patients (8%), the desired information resided outside the institution ("MISSING EXTERNAL"); for 89/397 (22%), it was within the institution ("MISSING INTERNAL"). Additional information was desired for 41% of ASA 3/4 patients, and for 23% of ASA 1/2 patients. Some or all of desired information was not found for 45% of MISSING INTERNAL, and for 78% (p = 0.12 NS) of MISSING EXTERNAL. MISSING EXTERNAL of any ASA status required significantly longer evaluations (70+/-39 min) than even ASA 3/4 patients missing no information (51.4+/-35.7 min, p 0.03). The surgeries of only eight patients (2%) were postponed in the preanesthetic evaluation clinic; half of the postponements were to obtain pre-existing records. CONCLUSIONS: Anesthesiologists retrieved, and added to the perioperative evaluation, information from previous encounters for 16% of patients. Despite our hospital-wide electronic records, internal information was missing for 22% of patients. Uneven deployment, and reliance on transcription may contribute to failures. A national electronic medical records system would benefit the 8% (one out of twelve) of outpatients missing external records identified in this study. For many patients, optimal medical understanding was not achieved during the planned preanesthetic evaluation.

The Internet and electronic transmission of medical records.

OBJECTIVE: To review, from a legal perspective the potential for using the Internet for inter-institutional transfer of patient medical records. METHODS: Basic issues and recent legislation that relate to protection of both medical data, and those transferring that data over public network systems is reviewed. RESULTS: Many laws already in existence can be applied to Internet transmission, but questions of jurisdiction remain. Providing signatures on requests for information, which are in essence contracts, is a problem. Signatures must both prove the identity of the participants and provide for non-repudiation of the agreement. Cryptographic digital signatures appear secure and effective, but their use is difficult to implement. Simpler methods are fraught with risks, yet are more easily accomplished. The patient's rights of privacy must be balanced against the need for access by government, physician, or healthcare institutions to confidential information. In general, information holders must put forth reasonable efforts to keep information confidential. The development of acknowledged standards will provide guidance. Multiple laws provide some deterrence and hence some reassurance to healthcare institutions, for example, by criminalizing acts of electronic interception of patient records in transit. CONCLUSION: Some believe the expense of secure transfer of medical records by electronic means is a major obstacle; this is false: such transfers are now technologically quite easy. The greatest obstacle to electronic transfer of medical records at this point is the development of workable standards for signing agreements and protecting transmissions, but the perceived advantages will likely drive the necessary developments.

Anesthesia information-management systems: their role in risk-versus cost assessment and outcomes research.

Computerized clinical information systems clearly have a role in this era of managed care when outcomes research and cost/benefit analyses are becoming crucial. Despite anesthesiologists' leadership in developing physician-entry systems, automated recordkeeping systems have been underused. This report reviews the problems and possible solutions associated with establishing more effective and user-friendly systems in the anesthesia specialty. A key feature of any cost/benefit analysis or outcome study is the precise definition of data to be collected. Redesign of anesthesia information systems will be required to assist users to enter events according to standardized definitions. To filter the vast amount of data collected by electronic medical-records systems in the ordinary course of care that are not applicable to a specific study, some form of filtering or data reduction on transfer to research or administrative databases will be needed. To allow careful analysis of possible correlations of outcome to care choices requires both the capture of the clinical context-a detailed description of all relevant conditions extending well beyond merely the objective vital signs-throughout a specific medical episode and the establishment of postoperative evaluation systems to allow outcomes capture. Connections to new as well as existing outcome data will provide vast new opportunities for outcomes research.

Computerized pre-anesthetic evaluation results in additional abstracted comorbidity diagnoses.

OBJECTIVE: To study the impact of information from a physician-entry computerized preanesthetic evaluation system on the coding of International Classification of Diseases (ICD-9-CM) diagnoses and on hospital reimbursement due to alterations in diagnosis-related group (DRG) codes. METHODS: Nonrandomized, unblinded trial conducted at a 570-bed university tertiary care hospital. First without and then with reference to information contained on computer-based preanesthetic evaluation reports, medical charts were coded by the study institution's usual professional codes for ICD-9-CM discharge diagnoses and DRG assignment. RESULTS: For 22 of 180 charts studied (12%, 95% confidence limits 7.4% to 16.7%), at least one ICD-9-CM diagnosis was added. Three of 84 DRG-based reimbursements were altered, increasing hospital reimbursement by 1.5%. CONCLUSIONS: Supplemental information from a physician-entered, problem-oriented, computerized preanesthetic evaluation system improved discovery of diagnoses in the population studied.

Evaluation of electrosurgical interference to low-power spread-spectrum local area net transceivers.

OBJECTIVE: To study whether an electrosurgery device interferes with the operation of a low-power spread-spectrum wireless network adapter. METHODS: Nonrandomized, unblinded trials with controls, conducted in the corridor of our institution's operating suite using two portable computers equipped with RoamAbout omnidirectional 250 mW spread-spectrum 928 MHz wireless network adapters. To simulate high power electrosurgery interference, a 100-watt continuous electrocoagulation arc was maintained five feet from the receiving adapter, while device reported signal to noise values were measured at 150 feet and 400 feet distance between the wireless-networked computers. At 150 feet range, and with continuous 100-watt electrocoagulation arc five feet from one computer, error-corrected local area net throughput was measured by sending and receiving a large file multiple times. RESULTS: The reported signal to noise (N = 50) decreased with electrocoagulation from 36.42+/-3.47 (control) to 31.85+/-3.64 (electrocoagulation) (p < 0.001) at 400 feet inter-adapter distance, and from 64.53+/-1.43 (control) to 60.12+/-3.77 (electrocoagulation) (p < 0.001) at 150 feet inter-adapter distance. There was no statistically significant change in network throughput (average 93 kbyte/second) at 150 feet inter-adapter distance, either transmitting or receiving during continuous 100 Watt electrocoagulation arc. CONCLUSIONS: The manufacturer indicates "acceptable" performance will be obtained with signal to noise values as low as 20. In view of this, while electrocoagulation affects this spread spectrum network adapter, the effects are small even at 400 feet. At a distance of 150 feet, no discernible effect on network communications was found, suggesting that if other obstructions are minimal, within a wide range on one floor of an operating suite, network communications may be maintained using the technology of this wireless spread spectrum network adapter. The impact of such adapters on cardiac pacemakers should be studied. Wireless spread spectrum network adapters are an attractive technology for mobile computer communications in the operating room.

Use of data from a hospital online medical records system by physicians during preanesthetic evaluation.

OBJECTIVE: There is no data on the use of hospital-wide online medical record (OLMR) systems by anesthesiologists. We measured how often anesthesiologists accessed the OLMR database maintained by the hospital, how often data was copied from this database into the clinic's computer system, and how much data was copied. METHODS: In a preanesthetic evaluation clinic that has a computerized evaluation system designed for physician-entered data, a graphical user-interface prototype link provided access to the hospital OLMR database for users and was studied over a 37-day period. The software allowed the user to search the OLMR system by patient name, retrieve a text listing of the patient's record, and then copy and paste desired information into the forms of the preanesthetic system. Using embedded routines, we recorded how many times physicians searched for and retrieved medical records from the hospital OLMR database, as well as how many times they copied data to the preoperative database. As a measure of how much data was copied, the number of characters was also recorded. RESULTS: Of 1,080 patients evaluated in the clinic during the study period, electronic searches of the hospital OLMR database for 221 patients (20.5%) were noted. Of these searches, 208 (94.1%, or 19.3% of 1,080 patients) successfully retrieved data from the patient's record. Data was copied for 170 patients - 81.7% of the successful searches. Of 7,525,153 characters retrieved, 262,269 were copied-an average of 1,543 characters per instance of copying. CONCLUSION: We conclude that anesthesiologists, given even crude graphical access to a hospital OLMR data-base, will retrieve and copy data, potentially increasing the accuracy of the medical records and saving time.

Magnetron-based inline microwave fluid warmer.

OBJECTIVE: To develop an in-line microwave fluid warming system that eliminates the difficulties of uneven heating that are characteristic of batch-mode microwave fluid warmers. METHODS: Using a commercial microwave oven, we developed a method for warming fluid as it flowed through tubing along a defined path in the oven's cavity. Algorithms utilizing either proportional or adaptive control were used to control microwave heating cycles by varying the heating pulse-width during 3-second epochs. Methods of fluid entry and exit were devised to minimize microwave leakage. Heating performance was tested using icewater at multiple flow rates from 18 mL/min to 105 mL/min. RESULTS: In all warming tests, the system achieved temperature control without exceeding the maximum temperature allowable based on American Association of Blood Banks requirements. The adaptive control maintained the set temperature, with peak-to-peak oscillations of 2 degrees C or less. Microwave leakage was below the commercially required limit for home microwave appliances. CONCLUSIONS: The combination of proportional and adaptive control is successful in controlling the permanent magnet magnetron microwave energy to heat the icewater tested. The in-line microwave warmer has the potential to become a successful medical fluid warmer. More study is needed to determine the stability of the control system under clinical conditions, and to evaluate its utility for warming blood.

The efficiency of preoperative evaluation: a comparison of computerized and paper recording systems.

OBJECTIVE: We designed and implemented a preoperative evaluation record system with seven networked computers for use by physicians and other medical staff. This study compared the efficiency of the new computerized system with that of the paper system. METHODS: We reviewed data from preoperative evaluations completed from November 1990 through December 1992. Data were analyzed automatically (Borland C program) for two intervals: (1) the waiting period, defined as the time the patient entered the waiting room until he or she entered the examination room; and (2) the examination period, defined as the time the patient entered the examination room until an evaluation form was printed. Data were obtained for 2,511 evaluations on paper and 8,342 by computer. RESULTS: The average waiting period with the paper system was 56.1 +/- 44.8 min; the average waiting period with the computerized system was 59.1 +/- 47.0 min. The average examination period was nearly identical for both systems: 27.5 +/- 23.6 min for the paper system; 28.5 +/- 22.7 min for the computerized system. CONCLUSION: The computerized system required no more examination time than the manual system. In addition, we speculate that time is saved at other points of patient care by the legible, instantly retrievable preoperative evaluations that the computerized system produces.

Real-time automated computerized detection of venous air emboli in dogs.

OBJECTIVE: My objective was to develop a real-time pattern recognition system to monitor the precordial Doppler and end-tidal CO2 for characteristic changes of venous air emboli. The system also must check the adequacy of the input signals, to allow for unattended operation. The sensitivity of the precordial Doppler monitoring of the resulting system was the focus of this study. METHODS: The computerized system electronically sampled systolic sounds, the amplitude envelope of Doppler pulsations, and, optionally, end-tidal CO2. Features were defined and calculated from the samples, the means and standard deviations of which were also calculated. During real-time test administrations of intravenous air in anesthetized dogs, each new sample was compared with previous statistics and, when parameters changed beyond calculated limits, an alarm was activated. RESULTS: The sensitivity of the on-line system to an intravenous air injection of 0.025 ml/kg was 33%; to 0.05 ml/kg, 73%; to 0.1 ml/kg, 90%; and to 0.2 ml/kg, 100%. A confounding factor, air lodging in the veins, was detected in the smaller injections; when this was corrected, the sensitivity of the system improved beyond these results. CONCLUSION: An on-line, real-time system, developed for continuous observation of precordial Doppler, has a sensitivity comparable to human observers. This system may improve clinical monitoring particularly in situations where the occurrence of a venous air embolism is not a high probability and, therefore, monitoring is not currently used because of its requirement for human observation. Systems such as the one described may allow many more patients to be monitored for this complication.

A method for evaluation of enhancement operations in two-dimensional echocardiographic images.

A means of estimating the degree of enhancement of structure and suppression of background noise in filtered two-dimensional echocardiographic images is described. The method is termed the peak-to-background ratio. To test the method, two-dimensional short-axis echocardiographic images were enhanced with Laplacian operations of increasing mask size. There was excellent correlation between the calculated peak-to-background ratio and the subjective opinion of trained echocardiographers. Furthermore, radial length measurements made from images that were thought to be optimally enhanced by the peak-to-background ratio calculation showed the lowest interobserver mean differences. We conclude that the peak-to-background ratio does reflect improvement in characteristics of the image that favor more precise measurement (amplification of peaks and suppression of background) and can be used to help guide a dynamic approach to image processing.

Applications of cross-correlation techniques to the quantitation of wall motion in short-axis two-dimensional echocardiographic images.

Echocardiography is now a mainstay in the diagnosis of cardiovascular disease. Rapid methods for quantitation of the images would provide an effective tool for the diagnosis of change in left ventricular function. The purpose of this article is to show the feasibility of using the cross-correlation technique to quantify change in left ventricular function over time in two-dimensional short-axis echocardiographic images. Radial histograms of radial distance versus the number of probable specular targets are formed in eight sectors on each frame during the cardiac cycle. These histograms are then shifted to a position of best correlation. The number of radial bins through which the histograms at end systole are shifted to correlate with those of the frame at end diastole defines the regional motion. The methods are described and preliminary findings are presented.

Computer-assisted Doppler monitoring to enhance detection of air emboli.

Currently, two of the most sensitive clinical approaches commonly used to monitor for venous air embolism, i.e., precordial Doppler audio and capnography, require the attention of the anesthesiologist's eye or ear, which is a distraction from other aspects of care. To assess the feasibility of allowing the computer to relieve the necessity for continuous human monitoring, we developed a computer algorithm for monitoring the precordial Doppler audio. This algorithm extracted (1) the amplitude of certain higher-frequency components of the Doppler audio, (2) a measure of the average value of the envelope of Doppler audio, and (3) the ratio between the average value of the Doppler envelope and the amount of envelope signal variation at heart rate frequency and its multiples. These three features were monitored by an adaptive pattern recognition algorithm that compared each new value for each feature with the previously developed mean and standard deviation for that feature. If the changes in the three features exceeded a detection threshold, an alarm (indicating suspected air embolism) was activated. Implemented as a prototype system, the algorithm was given preliminary testing in 2 dogs and activated alarms at levels of air well below those reported to cause clinically significant hemodynamic changes in dogs. While decreasing the distraction for the anesthesiologist, this early prototype alarm system alerts its user to the need for analysis of the Doppler signals when it senses an air embolus.

Augmentation of cerebral blood flow induced by hemodilution in stroke patients after superficial temporal-middle cerebral arterial bypass operation.

Experimental hemodilutional therapy has been shown to raise collateral perfusion to acutely ischemic brain regions distal to occluded internal carotid (ICA) and middle cerebral (MCA) arteries and to reduce infarct size. Superficial temporal (STA)-MCA anastomosis surgically establishes additional regional collateralization, and this bypass angiographically enlarges over time. Despite bypass patency verification by Doppler recording made at the edge of the craniectomy, the microsurgical STA-MCA anastomosis in 11 stroke patients did not produce early changes in cerebral perfusion parameters in the MCA territory of either hemisphere as determined by 133xenon inhalation. Therefore, hemodilution was initiated in an effort to increase cerebral perfusion during this marginal period when the STA was beginning to dilate progressively. Incremental venesections with equal intravenous volume replacement with 5% human serum albumin caused a significant lowering of the hematocrit from 40 +/- 1 to 33 +/- 1%. This isovolemic hemodilutional therapy resulted in significant mean regional cerebral blood flow (rCBF) elevations of 23 +/- 5% (SE) in the bypassed MCA territory and of 25 +/- 6% in the opposite MCA region. The mean gray flow (F1) in the involved and homologous MCA regions significantly increased 27 +/- 8% and 30 +/- 11%, respectively. Similarly, the initial slope index (ISI2) significantly rose by 17 +/- 5% in the bypassed MCA territory and by 18 +/- 6% in the homologous region. These data objectively support the premise that reductions in hematocrit without intravascular volume expansion augment cerebral blood flow, probably by reducing blood viscosity.(ABSTRACT TRUNCATED AT 250 WORDS)

Quantitative EEG alterations after isovolemic-hemodilutional augmentation of cerebral perfusion in stroke patients.

Eleven patients with ischemic neurologic deficits in the middle cerebral arterial (MCA) territory and ipsilateral slowing on initial EEG underwent venesection and equal volume replacement with intravenous 5% human serum albumin. As the mean hematocrit was reduced by 19%, the mean cerebral blood flow (CBF) in the MCA territory of the affected and contralateral hemisphere determined by the 133Xenon inhalation technique increased 18 and 21%, respectively. Similarly, CBF in the contralateral occipital region increased 17%. The percentage total slow-wave EEG activity (fractional sum of theta and delta activity, 1.0 to 7.5 Hz) determined by fourier analysis was reduced significantly in the affected MCA territory and in the contralateral occipital region within 1 to 2 hours after isovolemic hemodilution. Using quantitative EEG analysis, rapid improvement in background EEG activity can be demonstrated following the diffuse elevation in CBF by hemodilution.