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Evaluation of computer-aided monitoring of patients after heart surgery
Evaluation of computer-aided monitoring of patients after heart surgery The medical and economic benefits of a computer-aided monitoring system were evaluated in a prospective, randomized study of 810 patients after open-heart surgery. The design of the study separated benefits of systematized postoperative care from benefits unique to the computer system and established measurable criteria by which computer-aided monitoring systems could be objectively evaluated. Criteria for comparison included the rapidity, safety, and smoothness of convalescence and time spent for various nursing activities. The study showed that the computer-aided monitoring system did not provide discernible medical benefits nor favorably affect nursing activities. Downtime of the system averaged 1 day per week. Reliability and accuracy of the system were inadequate and the benefit/cost ratio was low. Future development of computer-aided monitoring systems for open cardiac surgery should stress reliability, accuracy, and relevance of the monitored measurements.
L. Henry Edmunds, Jr., M.D., Horace MacVaugh 1lI, M.D., Janet Stevens, M.S. (by invitation), Alfred B. Wechsler, Sc. D. (by invitation), and Gwendolyn M. Worthington (by invitation), Philadelphia, Pa., and Cambridge, Mass.
Conceptually, utilization of computer-aided monitoring systems after open cardiac surgery offers many advantages. Some measurements can be made automatically and frequently; data are easily stored, printed, and displayed; data can be processed into calculations, tables, or graphs; and alarms can signal undesirable deviations of multiple measurements.l" Potentially, computer-aided postoperative care systems may be programmed to analyze data, such as arrhythmias or combinations of pressure measurements,":? and to provide therapeutic recommendations." Eventually, computer-controlled systems may automatically carry out preprogrammed therapeutic recommendations without human intervention. Already, sophisticated systems provide means for automatic drug, fluid, and blood infusions according to a combination of current measurements and programmed instructions. '0 The present study was designed to evaluate the medical and economic advantages of a commercially availFrom the Department of Surgery, University of Pennsylvania, Philadelphia, Pa. 19104, and Arthur D. Little, Inc., Cambridge, Mass. 02140. Supported by Grant RI8 HS 01467 from the National Center for Health Services Research, Health Resources Administration. Rockville. Md. 20852. Read at the Fifty-seventh Annual Meeting of The American Association for Thoracic Surgery, Toronto, Ontario, Canada, April 18, 19, and 20, 1977.
890
able computer-aided monitoring system in the care of patients after open-heart surgery. Criteria were developed to assess the rapidity, safety, and smoothness of convalescence. Activity studies were carried out to determine time spent for various professional activities. Lastly, service records and downtime experience of the computer were recorded. The advantages and disadvantages of computer-aided monitoring were compared with those of conventional monitoring in a prospective, randomized control study of 810 patients who had open cardiac surgery at the Hospital of the University of Pennsylvania in the 22 months preceding February, 1977.
Methods Description of the computer-aided monitoring system. Roche Medical Electronics -Inc, (Cranbury, N. J.), a subsidiary of Hoffman-La Roche Inc., installed their computer-based intensive care system in the Surgical Intensive Care Unit of the Hospital of the University of Pennsylvania in January, 1975. The initial installation served two beds and included a Digital Equipment Corporation (Maynard, Mass.) PDP 11/45 compu ter, teletypewriter, Centronics 301 line printer (Hudson, N. H.), and a single bedside unit which contained two Roche closed-loop bedside systems with one keyboard and a character generator (computer display screen). In January, 1976, a second bedside unit was installed to serve two additional beds. The com-
Volume 74 Number 6 December. 1977
puter, teletypewriter, and printer were located 75 feet away in a separate room opposite the blood gaselectrolyte laboratory. A keyboard in the laboratory permitted direct entry of laboratory values into the computer system. Each patient was monitored by a separate front-end unit (Roche Model 4000 series) which contained electrocardiographic, temperature, and four pressure modules. The unit included an oscilloscope for constant display of the electrocardiogram and pressure measurements, an alarm system, and metered pressure gauges. Output from this unit was connected to the computer system. Load cells, from which separate containers for urine and chest drainage were suspended, and two occlusive roller infusion pumps with bubble detectors were connected directly to the computer system. The bedside unit of the computer system served two adjacent beds and included a keyboard, character generator, and two-channel strip-chart recorder. The relationship of the components of the system are diagramed in Fig. I. Front-end units, load cells, infusion pumps, bedside keyboards, and character generators were serviced by Roche Medical Electronics Inc. The computer, teletypewriter, and printer were serviced through Roche by Digital Equipment Corporation. Equipment was warranted for 30 months. On-site technicians set up transducers, load cells, and infusion pumps and replaced malfunctioning front-end modules. Computer software was provided by Roche and was not modfied. The system did not include arrhythmia analysis or medication entries. The computer operated in real time; measurements were made continuously and were time-averaged and displayed every 2 minutes. Programming permitted designation of a safe range or "limits" for each continuously monitored measurement. 4. 11 A flashing light signaled measurements outside of predetermined ranges. Blood infusion pumps infused blood in 20 m!. increments according to a computer program based on left atrial pressure measurements, amounts of chest drainage, and a preselected ratio of replacement to blood drainage. Crystalloid was infused in 20 m!. boli under computer control according to a program based on preselected fluid measurements. The 32 character bedside keyboard permitted staff-computer interaction and entry of certain laboratory data such as blood gas values, serum electrolytes, and hematocrit values. Safe range "limits," instructions for infusion pumps, requests for review, and graphic and tabular displays of monitored data from current to 24 hours past were en-
Computer-aided monitoring systems
89 1
Fig. l. Diagram of the four bed computer-aided monitoring system. tered through the keyboard. Accumulated monitored data at 5 minute intervals were automatically printed every 4 hours. Data outside preselected safe range limits were automatically printed. The system contained various safeguards, including continued operation of front-end equipment if the computer malfunctioned and manual override of infusion pumps. Description of study. A total of 810 patients who had open-heart surgery between March, 1975, and February, 1977, entered the study. Patients were randomized into control or computer-monitored groups by a two factorial by two factorial randomization scheme. No more than four patients per day entered the study, and no assignment to either group was made if a computer-monitored bed was not available. Postoperative care was systematized in both groups by using upper and lower "limits" to define the safe range for both continuously monitored and intermittent measurements. "Limits" were set for heart rate; systolic, diastolic, and mean arterial pressure; central venous pressure; left atrial or pulmonary wedge pressure; and rectal temperature. Desired ranges for chest drainage, urine volume, arterial blood gases, serum potassium, and hematocrit value were also indicated. When a measurement was outside of the desired range or "limits" the doctor was called. The doctor, after review of the patient, either instituted new therapy designed to restore the measurement within "limits" or changed the "limits." For control patients, a special bedside sheet was developed (Fig. 2). Each measurement for which "limits" were written headed a single column. All observations including laboratory values, fluid in and out, medications, and nursing notes (recorded on the back)
The Journal of
Edmunds et al,
892
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Fig. 2. Photograph of the bedside chart used to record data in the intensive care unit. This chart whenfolded once fits into the conventional hospital record. Nurses notes are recorded on the back of the folded sheet. This is the only record used in the intensive care unit for patients who have had heart surgery.
were entered chronologically. A new sheet was started when time entries reached the bottom of the page. Sheets permitted staff personnel to review recorded measurements, laboratory values, fluid balances, and medications easily by looking at the current sheet and the ones immediately preceding it. "Limits" were entered at the top of the first sheet by the doctor in red. When a "limit" was changed, the new range was written in the appropriate column in chronologie sequence. Nurses could review current "limit" instructions by looking over the sheets in appropriate columns. For computer-monitored patients, "limits" were entered at the keyboard by the doctor. A flashing message light on the bedside computer display screen indicated measurements outside of prescribed limits. Laboratory values were entered via keyboard, but medications could not be entered. Current measurements and past measurements in tabular or graphic form could be displayed through the keyboard. The Medical Board of the Hospital of the University of Pennsylvania required bedside sheets for all patients, including computermonitored patients. The computer system did not provide means to record nursing notes or medications. All patients received postoperative care in a thirteen-unit surgical intensive care unit. Eight beds were positioned along a wall facing the nursing station. Four computer-monitored beds were flanked by two pairs of control beds. Electronics for Medicine Model
IR-4 bedside modules were used to monitor control patients. Evaluation. Arthur D. Little, Inc., Cambridge, Massachusetts, conducted the evaluation. Unselected records of 430 patients who entered the study were reviewed. Eighty records were excluded because data entries were incomplete or because the patient was transferred to another hospital following discharge from the intensive care unit. Evaluations were based on records from 350 patients-l 75 in each group. The similarity of the two groups was assessed by patient age, percentage male, operation category, and pump time. Complications that delayed discharge from the surgical intensive care unit for more than 48 hours were recorded. These included discharge-delaying arrhythmias, stroke, respiratory insufficiency, reoperation for bleeding, renal problems, low cardiac output, and cardiac arrest-resuscitation. Time to extubation, length of stay in the intensive care unit, duration of hospital stay, and deaths were also recorded. Duration of measurements outside of "limits" were also recorded for each continuously monitored measurement. The percentage of time out of "limits" was calculated by dividing hours out of "limits" by total time the function was monitored. Bedside sheets of both groups of patients, rather than the computer printout, were used for evaluation of the time out of "limits." Activity and computer use evaluations were con-
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December, 1977
ducted by on-site observations made in April/May, 1975, March/April, 1976, and January/February, 1977. A total of 668 hours of patient care was observed. Activities of the nursing and physician staff were recorded during all three work shifts. Broad activity classifications included measurements and observations, direct patient care, clerical, indirect patient care, communication, and maintenance of the intensive care unit. Computer use sampling included type of use and user. Time spent by nurses in recording measurements on bedside sheets for computer-monitored patients was adjusted in activity compilations. Careful service records were kept to determine the frequency and duration of breakdowns of individual components of the system. On-site technicians were first called to service apparent malfunctions. If service was not restored, the technician usually consulted by phone with a service representative, or else a service call was made and the duration of the malfunction was recorded. Until backup modules were provided on site (last 6 months), malfunction of front-end modules required transfer of individual patients to another monitoring system but did not shut down the computer system.
Results After installation of the system, a 2 month shakedown period was used to attain smooth operation of the system and to train nurses, house staff, and faculty in the use of the computer-aided monitoring system. After 2 additional months, the fluid infusion system was abondoned in favor of a manual system using a Soluset (Abbott Laboratories, North Chicago, II!.). Small, inconsequential bubbles (in patients without right-to-Ieft shunts) frequently stopped the infusion system, and considerable effort was required to clear and remount the tubing. More importantly, intravenously administered drugs such as potassium, calcium, and bicarbonate could not be given safely because the system pumped in 20 m!. aliquots at irregular intervals. The Soluset and continuous-drip infusions permitted easier and safer administration of drugs that did not require constant-infusion pumps. Furthermore, the bedside chart, which listed each vascular infusion catheter separately, facilitated measurements and calculations of fluids and colloids. The staff was unanimous in their rejection of the fluid infusion system. The accuracy and reliability of the chest drainage and urine output measurement were inconsistent. Receptacles were vulnerable to mechanical trauma, and vibrations produced by stripping chest tubes affected load cells. Although load cells were easily and repro-
Table I. Description of the 350 patients reviewed for quantitative comparison between control and computer-aided postoperative care Monitored patients
Control patients
108 59 8 73.1 53.1 84
108 60 7 73.7 53.5 79
Operative category CABG Valve Other Sex (percent male) Age (yr.) Pump time (min.)
Legend: CABG, Coronary artery bypass graft.
Table II. Deaths, complications, and intervals between operation and three postoperative milestones in the two groups (data based upon records of 350 patients)
SICD stay (days) Hospital stay (days) Extubation time (hr., min.) Complications Deaths
Monitored patients
Control patients
1.9 ± 1.6 14.0 ± 7.6 7'40" ± 10'32"
2.0 ± 1.9 14.0 ± 6.7 9'7" ± 15'41"
20
24 6
2
Legend: SICU. Surgical intensive care unit.
ducibly calibrated, marked discrepancies between amounts in receptacles and numbers displayed occurred intermittently. The cause of these occasional discrepancies, sometimes as large as 500 ml., was never discovered despite intense effort by Roche engineers. Because of these problems, calibrated receptacles were hung from the strain gauges to permit visual checks of computer measurements of chest drainage and urine output. The blood infusion program was used sparingly for several reasons. The program requires accurate, continuous measurement of left atrial pressure and chest drainage. The left atrial catheter was considered superfluous in many patients who did not have heart failure and received only aorta-coronary artery venous grafts; routine insertion in these patients was stopped after the introduction of the Swan-Ganz catheter, which permitted quick measurement of pulmonary wedge pressures if postoperative arrhythmias or myocardial infarctions developed. Because of these reasons and the undependable automated measurement of chest drainage, the blood infusion system was not evaluated adequately. As indicated by age, sex, pump time, and operations
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Thoracic and Cardiovascular Surgery
25
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et
20
I
~Control
f:h\H Monitored
15 10
5 Heort Rate
Systolic Pressure Diastolic Pressure Central Venous Pressure
Temperature
Fig. 3. Percentageof monitored time that indicated measurements were outside prescribed "limits." Noneof the differences between computed monitored and control patients is significant. In all instances standard deviations exceed the mean.
~Control
hAm;}) Monitored 3
Hours
6
4 Hours
2
2
Time to <100 mI /hr.
Time to < 30 mllhr.
Fig. 4. Time after operation required for chest drainage to reach two different milestones. Differences between control and computer-monitored patients were not significant. performed, the two groups of 175 patients each were comparable (Table I). Complications, deaths, and the interval between operation and various milestones are presented in Table II. Computer-aided monitoring did not cause a significant difference in any of these parameters. Type of operation did alter these factors. Patients with aorta-coronary artery vein grafts had no deaths, fewer complications, and reached all milestones faster than did patients who had valvular and other cardiac operations. The most common complications, which delayed discharge from intensive care, were low cardiac output and arrhythmias. 15 The percentage of time that various continuous measurements were outside of prescribed limits is illustrated for each group in Fig. 3. None of the differences between the two groups was significant (p > 0.05). Likewise, mean time for chest drainage to reach two end points did not differ between the two groups (Fig. 4). Activity of the nursing staff for both groups of patients for each of the three work-sampling periods is presented in Table III. The computer system was expected to reduce time spent in making, recording, and
communicating measurements. Initially, in 1975, nurses spent more time in these activities with computer-monitored patients, probably because of the novelty of the system. In 1976 nurses used I. 69 hours less time for these activities in computer-monitored patients, but the difference was not significant. However, in 1977 computer-monitored patients required slightly more time than did control patients; thus no time saving for nursing activities could be demonstrated. Patients who had valve operations required more nursing (2.4 hours per patient per day) than did patients who had aorta-coronary bypass grafts. The computer system was used by physicians largely to obtain information. In 1976 physicians accounted for 39.3 percent of the total computer usage, and nurses used the machine 32.1 percent of the total time the machine was used. Others (technicians, students, and aides) accounted for 28.6 percent of the usage. "Demand data" was the most frequent usage (2.9 uses per patient hour); "setup" was second. Only a small amount of time was used to review tabular data or graphics (0.39 uses per patient hour). Service experience was divided into three periods for analysis. The first period between March 19, 1975, and June 19, 1975, occurred after 2 months of shakedown trials and began when engineers and investigators felt confident about equipment performance and staff training. The last 6 months from Aug. I, 1976, to Feb. I, 1977, reflect the multiple efforts made to reduce component downtime. Service experience does not include a 7 week period in the autumn of 1975 when the system was substantially damaged by a flood. Downtime owing to problems with front-end equipment was reduced to zero by availability of on-site backup modules (Table IV). In the last 6 months, backup modules were used thirty times. Every component of the computer system failed at least once. The most common malfunctions were due to locking
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Computer-aided monitoring systems
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of the keyboard, malfunction of the teletypewriter, and failure of the high-speed printer to print. In the last 6 months downtime averaged 1 day per week. Current cost of the Roche computer-aided monitoring system as described for four beds without the fluid infusion system and with the blood infusion system is $152,670 (includes series 7000 front-end units and installation, but excludes tax and shipping). The price includes parts and labor for 12 months. A service contract to service all components of the system, calculated at 8.5 percent of the purchase price per annum, is $12,977. By use of these figures, the cost of computer-aided monitoring was calculated for different periods of depreciation and different annual clinical loads (Table V). Costs of backup modules and technicians are not included. Additional detailed information about the evaluation and results is available. 12
Table III. Activities of the nursing staff in hours per patient per 24 hours
Discussion
Legend: All three work shifts were sampled. A total of 192.8 patient hours
The computer-aided monitoring system evaluated in this study made frequent measurements, processed signals from front-end units, and stored, displayed, and printed data. Because of intermittent inaccuracies of chest drainage and urine volume measurements, data monitored by the computer system sometimes were the same as data monitored by conventional bedside machines. Efferent functions (e.g., fluid and blood infusion) were not evaluated for very practical reasons. As presently developed, the fluid infusion system was less flexible and more cumbersome than available manual systems. Although the blood infusion system was useful for some patients, many did not require left atrial catheters for safe postoperative management. In these patients, insertion of a left atrial catheter represented "extra surgery" which offset potential benefits of the blood infusion system. Had chest drainage measurements been consistently accurate and reliable, the blood infusion system would have been used more, particularly in patients with some degree of left-sided heart failure. Thus the computer system evaluated in this study processed only afferent or incoming functions and either was not or could not be used safely for efferent or computer-directed functions. This system was designed for "turnkey" application, was not reprogrammed during the study, and did not offer the calculating power, therapeutic recommendations, or efferent functions of other systems. 7, 8. 10 Computer-aided monitoring requires systematized postoperative care and the use of prescribed safe ranges or "limits. "4. 11 Use of "limits" is not unique to the computer system, but it is a prerequisite. The prospec-
~ M
C
2.63
1.99
1.68
1.19
1.73
1.61
Subtotal Direct patient care Patient care. other Maintain SICD
Measurements and observations Patient care clerical Communication
Total
M
M
C
2.39
2.65
2.22
1.04
1.72
1.21
1.14
0.66
0.27
0.57
0.35
0.36
5.43
4.38
2.99
4.68
4.21
3.72
5.03
5.00
4.96
4.69
4.74
4.57
0.37
0.47
0.20
0.23
0.32
0.41
1.14
0.73
0.59
0.54
0.41
0.21
11.97
10.58
8.74
10.14
9.68
8.91
C
were observed in 1975. 189.3 in 1976. and 285.6 in 1977. Actual time spent for "patient care. clerical" for computer-monitored patients was reduced 25 percent to compensate for manual recording of measurements made by the computer system. M. Computer monitored patients. C. Control patients.
tive, randomized design of the study prevented crediting the computer system for general advances in postoperative care. A nonrelevant comparison between systematized care with a computer and unsystematized care without a computer was avoided by using "limits" for control patients and by developing a practical bedside chart. The bedside chart made review of all data easier than calling up data from the computer and reduced the need for tabular and graphic reviews. The design of this study and the use of the log-entry bedside chart separated the effects of computer-aided monitoring from the effects of systematized postoperative care and advances in medical practice. The data clearly show that computer-aided monitoring of patients who have had heart surgery, as utilized in this study, does not influence morbidity or mortality and does not significantly alter nursing activities. Several reasons can be offered as explanation of this conclusion, but only two will be discussed. The reliability and accuracy of the present system were inadequate for critically ill patients. Every component failed at least once. Although patients could still be monitored with the front-end equipment alone, the computer system was nonoperative for an average of I day per week and required an outside technician for service. In addition, the accuracy and reliability of the urine volume and chest drainage measurements were unsatisfactory. This "turnkey" system was designed for "off-the-shelf' application by medical profession-
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Table IV. Service experience of the computer-aided monitoring system Initial 3 months
Front end No. instances module repl. Downtime of front-end unit (hr.) Downtime due to lack of back up (hr.) Computer system Keyboard Teletypewriter Centronics printer Computer Other
I
Total hours
49 175 364
3.24 6.74
30 0 0
264 154 87 172 120*
4.89 2.85 1.61 3.19 2.22
376 0 246 16 5t
Total hours
2 3 2
0.25 0.17
0 0 84 69 0
0 0 7.00 5.75 0
Totals
13.17
I
Avg. hours/ week
Avg. hours/ week
Total hours
Last 6 months
/2.5 months
I
24.74
Avg. hours/ week
0 0 14.46 0 9.46 0.62 0.19 24.73
Legend: The number of hours and average hours per week each component of the system was inoperative is presented for three evaluation periods. *Graphic hot box. tBurning transformer in power supply.
Table V. Estimated costs of computer-aided monitoring in dollars per patient* Patients /year Depreciation period
300
3 years 5 years 10 years
198 136 90
/.000 148 102 67
119 82 54
79 54 36
'Estimates include a service contract computed at 8.5 percent of the purchase price for each year after the first. For 1,000 patients annually. calculations are based on an eight bed unit costing $202,670.
als given a minimum of instruction. At the University of Pennsylvania the system did not function satisfactorily; however, in the absence of comparable data we must assume that other systems in a similar price range cannot perform better. To minimize downtime, presently used systems require backup components and on-site technicians capable of "trouble shooting" the entire system." 3. 8. 13, 14 This stopgap measure is unsatisfactory and adds expense which is not included in the purchase price and service contract. More reliable and accurate computer-aided monitoring systems are required, and attention must be paid to every component, particularly sensors and transducers.P" " The hospital is a hostile environment for sophisticated electronics. Equipment is operated by multiple users whose attention is primarily directed toward patients. Components are exposed to mechanical injury, occasional surges of electrical power, and even water damage. The system is expected to operate continuously. Therefore, all components must be built and
packaged to withstand rough use and occasional abuse. A second reason for the failure of this study to show an important difference between computer-aided and manual monitoring is that only afferent functions were processed and the system was underutilized. Unfortunately, the twin problems of reliability and accuracy affect most computer applications. The printout cannot be accepted for the medical record if measurements are sometimes questionable or absent. Similarly, efferent or computer-directed functions, such as blood, fluid, or drug infusions, are based upon accurate, dependable incoming measurements.t'': 17 The computer does not discriminate between important and transitory deviations of incoming signals, artifacts, and malfunctions of sensors and transducers. Therefore, a nurse prompted by an alarm must make this discrimination. Efficient use of computer-directed functions requires that incoming signals, needed by the program of the efferent function, be relatively free of artifacts and transitory deviations. . In patients who have had surgery, monitored measurements must be relevant and accurately reflect the patient's clinical condition. "Limits" must be realistic to prevent nuisance alarms or serious deviations in monitored measurements. Fortunately, existing technology provides sufficient sensors and transducers to make postoperative computer-aided monitoring feasible in patients who have had heart surgery. Future development of continuous measurements of cardiac output;" regional blood flow to vital organs, arterial blood gases;" and certain chemicals will make computer-aided monitoring even more safe and applicable to more patients. As computer-aided monitoring
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Computer-aided monitoring systems
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develops, investigators, designers, and engineers must concentrate on relevant measurements and calculations and meaningful efferent functions that offer real advantages over manual methods. This study does not show a realistic benefit/cost ratio for computer-aided monitoring of patients after cardiac surgery. The study does establish measurable criteria by which the contributions of computer-aided monitoring systems can be objectively evaluated. The study indicated the absolute requirement of accuracy and reliability in all. components of monitoring systems for critically ill patients. It would be shortsighted to conclude, on the basis of this study, that computer-aided monitoring is not worthwhile. The potential for computer-aided monitoring exists, particularly for patients who have had heart surgery. For these patients a constellation of continuous and intermittent measurements quite accurately defines the patient's clinical condition and permits systematic care which is a prerequisite for computer-aided monitoring. Further development of technology, with emphasis on accuracy, reliability, and relevance in the hospital environment and invention of new sensors and transducers to directly measure the most important and bellweather physiological functions, will earn computer-aided monitoring systems an important place in the postoperative care of patients: We thank the nurses, house officers, and technicians in the surgical intensive care unit for their valuable contributions to this study. REFERENCES
2
3
4
5
6
Barnett, G. 0.: Computers in Patient Care, N. Eng!. J. Med. 279: 1321, 1968. Osborn, J. J., Beaumont, J. 0., Raison, J. C. A., Russell, J., and Gerbode, F.: Measurement and Monitoring of Acutely III Patients by Digital Computer, Surgery 64: 1057, 1968. Robicsek, F., Masters, T. N. , Reichertz, P. L., Daugherty, H. K., and Cook, J. W.: Three Years' Experience With Computer-Based Intensive Care of Patients Following Open Heart and Major Vascular Surgery, 81: 12, 1977. Shepherd, L. C., Kouchoukos, N. T., Kurtts, M. A., and Kirklin, 1. W.: Automated Treatment of Critically III Patients Following Operation, Ann. Surg. 168: 596, 1968. Shubin, H., and Weil, M. H.: Efficient Monitoring With a Digital Computer of Cardiovascular Function in Seriously III Patients, Ann. Intern. Med. 65: 453, 1966. Warner, H. R., Gardner. R. M., and Toronto, A. F.: Computer-Based Monitoring of Cardiovascular Functions in Postoperative Patients, Circulation 36: 263, 1967 (Suppl, II).
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7 Gerbode, F.: Computerized Monitoring of Seriously III Patients.J. THoRAc. CARDIOVASC. SURG. 66: 167, 1973. 8 Risso, W. L., Jr., Kempner, K. M., Owens, D. c., Gorlen, K. E., Holsinger, W. P., Mcintosh, C. L., and Syed, D.: A Postsurgical Intensive Care Computer System at the National Institutes of Health, in Computer in Cardiology, Long Beach, Calif., 1975, IEEE Computer Society, pp. 10 1-108. 9 Sheppard, L. c.. Kouchoukos, N. T., and Kirklin, J. W.: The Digital Computer in Surgical Intensive Care Automation, Computer 6: 29, 1973. 10 Shepherd, L. C., Kouchoukos, N. T., Shotts, J. F., and Wallace, F. D.: Regulation of Mean Arterial Pressure by Computer Control of Vasoactive Agents in Postoperative Patients, in Computers in Cardiology, Long Beach, Calif., 1975, IEEE Computer Society, pp. 91-94. II Kirklin, J. W.: Systems Analysis in Surgical Patients With Particular Attention to the Cardiac and Pulmonary System, Fifteenth MacEwen Memorial Lecture, University of Glasgow, Glasgow, Scotland, 1970. 12 Arthur D. Little, Inc.: An Evaulation of the ComputerAided Patient Monitoring System at the Hospital of the University of Pennsylvania, Cambridge, Mass., 1977. 13 Arthur D. Little, Inc.: A Review of the Patient Monitoring System at the University of Alabama Medical Center, Appendix C, Cambridge, Mass., 1973. 14 Arthur D. Little, Inc.: Evaluation of Computer-Based Patient Monitoring Systems: Final Report, Appendix D. A Review of the Medlab System in the Thoracic Surgery Intensive Care Unit at Latter Day Saints Hospital, Cambridge, Mass., 1973. 15 Maloney, J. V.: The Trouble with Patient Monitoring, Ann. Surg. 168: 605, 1968. 16 Evans, T. R., and Clark, T. J. H.: Reliability of Patient Monitoring Apparatus, Br. Med. J. 2: 734, 1971. 17 Morgan, A., Anderson, W., Bevilacqua, R., Cohn, L., Moore, F. D., and Collins, J. J., Jr.: Effects of Computer-Controlled Transufusion on Recovery From Cardiac Surgery, Ann. Surg. 178: 391,1973. 18 Williams, B. T., Sancho-Fornos, S., Clarke, D. B., Abrams, L. D., and Schenk, W. G., Jr.: Continuous LongTerm Measurement of Cardiac Output After Open-Heart Surgery, Ann. Surg. 174: 357, 1971. 19 Veasy, L. G., Clark, J. S., Jung, L., and Jenkins, J. L.: A System for Computerized Automated Blood Gas Analysis, Pediatrics 48: 5, 1971.
Discussion DR. JAMES R. PLUTH Rochester. Minn.
I wish to congratulate the authors on this interesting and very provocative paper and to thank them for the opportunity to review their manuscript. They have certainly pinpointed the many pitfalls that can occur in the problem of computerized monitoring and have underscored the numerous arguments against its use. Intuitively, however, some of us still
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8 9 8 Edmunds et at.
believe that if reliability of the system can be achieved, the care and safety of the patient can be optimized. Many of the problems that they underlined are merely technical and can be overcome. I rise mainly for the purpose of briefly commenting on our own experience which I hope reflects a somewhat more optimistic viewpoint. We possess a rather unique good fortune of having two postoperative intensive care units which are virtually identical in all respects except for the capability of computerizing monitoring in one of these. [Slide] This unit was developed in conjunction with IBM and consists of a System 7 computer located adjacent to the intensive care unit. There are two additional System 7 computers located adjacent to the coronary care unit and also to the catheterization laboratory which are backed up by a System 370/135 unit from which data can be retrieved in the event of breakdown time of either of the System 7 computers. This configuration has provided remarkable reliability. Over the past year we have had a total of 92 1/ 2 hours of downtime, or 0.4 percent. A third of this downtime was scheduled downtime for the addition or deletion of computer programs. Approximately 11/ 2 years ago we completed a 6 months' evaluation of this system, during which time nearly 800 patients were randomized to either the standarized or the computerized units. We were indeed disappointed, like the authors, to find that there was no clear-cut mandate favoring computerized care. However, at the level of 0.05 significance, it was highly suggested that serious arrhythmias and "code" conditions could be reduced by computerized care. In addition, mortality rate secondary to arrhythmia was reduced in the computerized unit as compared to the standardized unit. Utilization of blood in the computerized care unit was one-half unit less than in patients receiving standard care. In addition, free time of the nurses was increased 25 percent. I suggest to the authors that, with the excellent standard postoperative care presently available, 350 or even 800 patients, as in our study, are inadequate to demonstrate the superiority of one system or another. I still suspect, however, that reduction in mortality rate may be real and savings in manpower and in improved supervision of postoperative care may be realistically achieved. DR. RICHARD E. CLARK St. Louis, Mo.
Dr. Edmunds' critical eye and experience have shown three facets of computerized monitoring with which we agree. First, they have used a data-logging system, that is, a computer system which periodically pulls numbers from various beds, and have compared it to a paper and pencil system. I would submit to you that the best system is a paper and pencil one. No present computer and probably no future computer system can beat the human computer, a welldesigned data flow sheet, and a very sharp pencil. Second, we agree that when data-logging and treatment protocols are the same in both a paper and pencil system and a
computer system, one should get identical results in terms of length of stay or any other milestone. Third, we agree that when reliability and accuracy are poor, no instrument, no computer, and no person will be found to be of value in an ICU setting. What, then, is the role for the computer in the care of cardiothoracic patients? Our 4 year experience has demonstrated the computer to be of value when one tailors the computer to the need. We have tailored our system to a philosophy of care, to the particular institution, and to the environment. We have identified two primary ways in which our system is of value. First, it is of value when a low nursepatient ratio exists; that is, one nurse to care for four patients after open-heart surgery, each on a ventilator. Second, it is of value in presenting patient data to the nurse in a highly and easily recognizable form. We have used the computer to continuously measure, analyze, and warn on a beat-by-beat basis as opposed to intermittently sampling data which has already been measured at the front end. Second, we use the computer to display information that will be competent, accurate, and easily recognized by us. Like Dr. Pluth at Rochester, we have found that our elapsed time from ventricular fibrillation to defibrillation is remarkably short because of a display system which alerts a nurse rapidly. Although Dr. Edmunds' experience has not been good, I would suggest that not all monitoring systems using a computer are alike and that each must be tailored to a need, not the need tailored to the computer. DR. FRANCIS ROBICSEK Charlotte. N. C.
I enjoyed the presentation of Henry Edmunds. Our experience can serve as a control, because in Charlotte we are using equipment very similar to his. The application of computers in medicine is logical and predictable. I find it very ironic that hospitals buy multimillion dollar machines which at the whim of any accounting clerk can spit out the outstanding account of any patient, but the surgeon has to crawl under the bed, leaf through pounds of paper or charts, or wake up the sleepy resident to get his information. Clinically effective, low cost computer monitoring has been reported from San Francisco, Rochester, Birmingham. and Stockholm. The experience which Harry Daugherty and I have been involved in, reaches now into the fourth year and comprises 1,400 patients, has also been gratifying. Our computer downtime in the past 6 months averages I hour per week, and the cost is only $100 to $150 per patient, I to 3 percent of the total hospital bill. The computer made our work much easier and put our nurses back where they belong, in direct patient care. Our computer not only does routine monitoring, but also provides automatic infusion and transfusion. We are happy with both programs. It also gives complex clinical and biochemical analysis, simple standard orders, and complicated medical recommendations. On the other hand, we also have to recognize that computer
Volume 74 Number 6 December, 1977
monitoring is still at the beginning stage. The initiation of such a program requires the same time, patience, and compassion as the initiation of a young surgeon or a beginning nurse. It is not enough to study whether or not a computer works; you have to make it work yourself. This requires not only electronic know-how, but continuous personal interest, fascination, deep commitment, and the infusion of your own surgical philosophy and time into the program. If this attitude is not present, the machine is going to hang around your neck like a 500 pound electronic albatross. DR. FRANK GERBODE
Computer-aided monitoring systems
899
new hospital and have learned a good deal about taking care of seriously ill patients, I cannot say that using the computer has been the major cause of the improvement. I will say that all the personnel who work with the computer are thoroughly convinced they do not want to work without it any longer. Nurses sometimes leave us go to another hospital where computer monitoring is not being used, but they usually come back and stay. They like to work with this type of support. You might draw a parallel between this and flying an airplane. Once you learn how to fly an airplane with the use of instruments, you never want to fly it again with the seat of your pants.
San Francisco, Calif.
It is worthwhile to hear Dr. Edmunds bring out some of the disadvantages of computerized monitoring. Certainly, using a computer is like buying an automobile that is mechanically not satisfactory or any sort of a machine which you do not quite understand and perhaps are using for the wrong purpose. For one thing, having been in this business for a long time, we decided that closing the loop probably was going to be unsatisfactory for most patients, contrary to the program in Alabama. If the physician closes the loop and tries to use automated treatment, he may encounter many complications which can be avoided simply by ignoring that entirely. I do not believe that our aim in the immediate future is to treat a patient automatically with a computer. Our objective has been to use the computer to furnish accurate, physiological information about the patient so that the surgeon or the nurse can make a more intelligent decision. This has changed nursing in our unit from an old-fashioned method of taki ng care of sick people to one in which the nurse is almost a physician. She becomes intelligent about complications and hospital complications and the use of the computer. In fact, most often she knows more about what is happening than the physician, particularly the young one. It is very hard to measure the advantages. There are so many factors in taking care of seriously ill patients. Even the staff involved in the Mayo Clinic study may have some doubts about the validity of their controlled experiment. Our morbidity and mortality rates have decreased steadily in the past 5 years. However, since we have moved into a
DR. ED M U N D S (Closing) I would like to thank the discussers for their comments and for reporting their experience. I will try to answer their questions and the points raised collectively rather than individually. I note that at the Mayo Clinic, in St. Louis, in San Francisco, and in Charlotte, the computer system comes equipped with backup components or, lacking that, with an on-site computer engineer. That is a little bit like buying a new car and having a mechanic in the passenger seat. We cannot afford backup systems or on-site engineers in Philadelphia, and I am not so sure that others can afford them either. The second point-and I think this is a important point-is that this technology is in its infancy. It is extremely important to try to find out how we can use sophisticated technology to help us take care of critically ill patients. The system that we evaluated was a "turnkey" system or "off the shelf." The system was designed and built to be used with minimal instruction. What we found is that this kind of machine is not ready for the intensive care unit or for patients who have had heart surgery. I would like to close by emphasizing two points: First, critically ill postoperative patients deserve at least the same reliability and accuracy of their monitoring system that airline passengers deserve of their aircraft. Second, systematized postoperative care has many, many benefits. That is the reason we need to have prospective, randomized control studies when we are going to evaluate future computer technology.
L. Henry Edmunds, Jr., M.D., Horace MacVaugh 1lI, M.D., Janet Stevens, M.S. (by invitation), Alfred B. Wechsler, Sc. D. (by invitation), and Gwendolyn M. Worthington (by invitation), Philadelphia, Pa., and Cambridge, Mass.
Conceptually, utilization of computer-aided monitoring systems after open cardiac surgery offers many advantages. Some measurements can be made automatically and frequently; data are easily stored, printed, and displayed; data can be processed into calculations, tables, or graphs; and alarms can signal undesirable deviations of multiple measurements.l" Potentially, computer-aided postoperative care systems may be programmed to analyze data, such as arrhythmias or combinations of pressure measurements,":? and to provide therapeutic recommendations." Eventually, computer-controlled systems may automatically carry out preprogrammed therapeutic recommendations without human intervention. Already, sophisticated systems provide means for automatic drug, fluid, and blood infusions according to a combination of current measurements and programmed instructions. '0 The present study was designed to evaluate the medical and economic advantages of a commercially availFrom the Department of Surgery, University of Pennsylvania, Philadelphia, Pa. 19104, and Arthur D. Little, Inc., Cambridge, Mass. 02140. Supported by Grant RI8 HS 01467 from the National Center for Health Services Research, Health Resources Administration. Rockville. Md. 20852. Read at the Fifty-seventh Annual Meeting of The American Association for Thoracic Surgery, Toronto, Ontario, Canada, April 18, 19, and 20, 1977.
890
able computer-aided monitoring system in the care of patients after open-heart surgery. Criteria were developed to assess the rapidity, safety, and smoothness of convalescence. Activity studies were carried out to determine time spent for various professional activities. Lastly, service records and downtime experience of the computer were recorded. The advantages and disadvantages of computer-aided monitoring were compared with those of conventional monitoring in a prospective, randomized control study of 810 patients who had open cardiac surgery at the Hospital of the University of Pennsylvania in the 22 months preceding February, 1977.
Methods Description of the computer-aided monitoring system. Roche Medical Electronics -Inc, (Cranbury, N. J.), a subsidiary of Hoffman-La Roche Inc., installed their computer-based intensive care system in the Surgical Intensive Care Unit of the Hospital of the University of Pennsylvania in January, 1975. The initial installation served two beds and included a Digital Equipment Corporation (Maynard, Mass.) PDP 11/45 compu ter, teletypewriter, Centronics 301 line printer (Hudson, N. H.), and a single bedside unit which contained two Roche closed-loop bedside systems with one keyboard and a character generator (computer display screen). In January, 1976, a second bedside unit was installed to serve two additional beds. The com-
Volume 74 Number 6 December. 1977
puter, teletypewriter, and printer were located 75 feet away in a separate room opposite the blood gaselectrolyte laboratory. A keyboard in the laboratory permitted direct entry of laboratory values into the computer system. Each patient was monitored by a separate front-end unit (Roche Model 4000 series) which contained electrocardiographic, temperature, and four pressure modules. The unit included an oscilloscope for constant display of the electrocardiogram and pressure measurements, an alarm system, and metered pressure gauges. Output from this unit was connected to the computer system. Load cells, from which separate containers for urine and chest drainage were suspended, and two occlusive roller infusion pumps with bubble detectors were connected directly to the computer system. The bedside unit of the computer system served two adjacent beds and included a keyboard, character generator, and two-channel strip-chart recorder. The relationship of the components of the system are diagramed in Fig. I. Front-end units, load cells, infusion pumps, bedside keyboards, and character generators were serviced by Roche Medical Electronics Inc. The computer, teletypewriter, and printer were serviced through Roche by Digital Equipment Corporation. Equipment was warranted for 30 months. On-site technicians set up transducers, load cells, and infusion pumps and replaced malfunctioning front-end modules. Computer software was provided by Roche and was not modfied. The system did not include arrhythmia analysis or medication entries. The computer operated in real time; measurements were made continuously and were time-averaged and displayed every 2 minutes. Programming permitted designation of a safe range or "limits" for each continuously monitored measurement. 4. 11 A flashing light signaled measurements outside of predetermined ranges. Blood infusion pumps infused blood in 20 m!. increments according to a computer program based on left atrial pressure measurements, amounts of chest drainage, and a preselected ratio of replacement to blood drainage. Crystalloid was infused in 20 m!. boli under computer control according to a program based on preselected fluid measurements. The 32 character bedside keyboard permitted staff-computer interaction and entry of certain laboratory data such as blood gas values, serum electrolytes, and hematocrit values. Safe range "limits," instructions for infusion pumps, requests for review, and graphic and tabular displays of monitored data from current to 24 hours past were en-
Computer-aided monitoring systems
89 1
Fig. l. Diagram of the four bed computer-aided monitoring system. tered through the keyboard. Accumulated monitored data at 5 minute intervals were automatically printed every 4 hours. Data outside preselected safe range limits were automatically printed. The system contained various safeguards, including continued operation of front-end equipment if the computer malfunctioned and manual override of infusion pumps. Description of study. A total of 810 patients who had open-heart surgery between March, 1975, and February, 1977, entered the study. Patients were randomized into control or computer-monitored groups by a two factorial by two factorial randomization scheme. No more than four patients per day entered the study, and no assignment to either group was made if a computer-monitored bed was not available. Postoperative care was systematized in both groups by using upper and lower "limits" to define the safe range for both continuously monitored and intermittent measurements. "Limits" were set for heart rate; systolic, diastolic, and mean arterial pressure; central venous pressure; left atrial or pulmonary wedge pressure; and rectal temperature. Desired ranges for chest drainage, urine volume, arterial blood gases, serum potassium, and hematocrit value were also indicated. When a measurement was outside of the desired range or "limits" the doctor was called. The doctor, after review of the patient, either instituted new therapy designed to restore the measurement within "limits" or changed the "limits." For control patients, a special bedside sheet was developed (Fig. 2). Each measurement for which "limits" were written headed a single column. All observations including laboratory values, fluid in and out, medications, and nursing notes (recorded on the back)
The Journal of
Edmunds et al,
892
h _..y~
Thoracic and Cardiovascular Surgery
-- ....
. I i 1& /Ij i~ I~
• I •
c I
:II:
.-
LA.
-- 1110'
I
I
J
~
s
/
/
IT
-:
IV'.
COli_lIS
HANGING
-,--
--,
-.
--
-
----------------~~-
f-- .
Fig. 2. Photograph of the bedside chart used to record data in the intensive care unit. This chart whenfolded once fits into the conventional hospital record. Nurses notes are recorded on the back of the folded sheet. This is the only record used in the intensive care unit for patients who have had heart surgery.
were entered chronologically. A new sheet was started when time entries reached the bottom of the page. Sheets permitted staff personnel to review recorded measurements, laboratory values, fluid balances, and medications easily by looking at the current sheet and the ones immediately preceding it. "Limits" were entered at the top of the first sheet by the doctor in red. When a "limit" was changed, the new range was written in the appropriate column in chronologie sequence. Nurses could review current "limit" instructions by looking over the sheets in appropriate columns. For computer-monitored patients, "limits" were entered at the keyboard by the doctor. A flashing message light on the bedside computer display screen indicated measurements outside of prescribed limits. Laboratory values were entered via keyboard, but medications could not be entered. Current measurements and past measurements in tabular or graphic form could be displayed through the keyboard. The Medical Board of the Hospital of the University of Pennsylvania required bedside sheets for all patients, including computermonitored patients. The computer system did not provide means to record nursing notes or medications. All patients received postoperative care in a thirteen-unit surgical intensive care unit. Eight beds were positioned along a wall facing the nursing station. Four computer-monitored beds were flanked by two pairs of control beds. Electronics for Medicine Model
IR-4 bedside modules were used to monitor control patients. Evaluation. Arthur D. Little, Inc., Cambridge, Massachusetts, conducted the evaluation. Unselected records of 430 patients who entered the study were reviewed. Eighty records were excluded because data entries were incomplete or because the patient was transferred to another hospital following discharge from the intensive care unit. Evaluations were based on records from 350 patients-l 75 in each group. The similarity of the two groups was assessed by patient age, percentage male, operation category, and pump time. Complications that delayed discharge from the surgical intensive care unit for more than 48 hours were recorded. These included discharge-delaying arrhythmias, stroke, respiratory insufficiency, reoperation for bleeding, renal problems, low cardiac output, and cardiac arrest-resuscitation. Time to extubation, length of stay in the intensive care unit, duration of hospital stay, and deaths were also recorded. Duration of measurements outside of "limits" were also recorded for each continuously monitored measurement. The percentage of time out of "limits" was calculated by dividing hours out of "limits" by total time the function was monitored. Bedside sheets of both groups of patients, rather than the computer printout, were used for evaluation of the time out of "limits." Activity and computer use evaluations were con-
Volume 74 Number 6
Computer-aided monitoring systems
893
December, 1977
ducted by on-site observations made in April/May, 1975, March/April, 1976, and January/February, 1977. A total of 668 hours of patient care was observed. Activities of the nursing and physician staff were recorded during all three work shifts. Broad activity classifications included measurements and observations, direct patient care, clerical, indirect patient care, communication, and maintenance of the intensive care unit. Computer use sampling included type of use and user. Time spent by nurses in recording measurements on bedside sheets for computer-monitored patients was adjusted in activity compilations. Careful service records were kept to determine the frequency and duration of breakdowns of individual components of the system. On-site technicians were first called to service apparent malfunctions. If service was not restored, the technician usually consulted by phone with a service representative, or else a service call was made and the duration of the malfunction was recorded. Until backup modules were provided on site (last 6 months), malfunction of front-end modules required transfer of individual patients to another monitoring system but did not shut down the computer system.
Results After installation of the system, a 2 month shakedown period was used to attain smooth operation of the system and to train nurses, house staff, and faculty in the use of the computer-aided monitoring system. After 2 additional months, the fluid infusion system was abondoned in favor of a manual system using a Soluset (Abbott Laboratories, North Chicago, II!.). Small, inconsequential bubbles (in patients without right-to-Ieft shunts) frequently stopped the infusion system, and considerable effort was required to clear and remount the tubing. More importantly, intravenously administered drugs such as potassium, calcium, and bicarbonate could not be given safely because the system pumped in 20 m!. aliquots at irregular intervals. The Soluset and continuous-drip infusions permitted easier and safer administration of drugs that did not require constant-infusion pumps. Furthermore, the bedside chart, which listed each vascular infusion catheter separately, facilitated measurements and calculations of fluids and colloids. The staff was unanimous in their rejection of the fluid infusion system. The accuracy and reliability of the chest drainage and urine output measurement were inconsistent. Receptacles were vulnerable to mechanical trauma, and vibrations produced by stripping chest tubes affected load cells. Although load cells were easily and repro-
Table I. Description of the 350 patients reviewed for quantitative comparison between control and computer-aided postoperative care Monitored patients
Control patients
108 59 8 73.1 53.1 84
108 60 7 73.7 53.5 79
Operative category CABG Valve Other Sex (percent male) Age (yr.) Pump time (min.)
Legend: CABG, Coronary artery bypass graft.
Table II. Deaths, complications, and intervals between operation and three postoperative milestones in the two groups (data based upon records of 350 patients)
SICD stay (days) Hospital stay (days) Extubation time (hr., min.) Complications Deaths
Monitored patients
Control patients
1.9 ± 1.6 14.0 ± 7.6 7'40" ± 10'32"
2.0 ± 1.9 14.0 ± 6.7 9'7" ± 15'41"
20
24 6
2
Legend: SICU. Surgical intensive care unit.
ducibly calibrated, marked discrepancies between amounts in receptacles and numbers displayed occurred intermittently. The cause of these occasional discrepancies, sometimes as large as 500 ml., was never discovered despite intense effort by Roche engineers. Because of these problems, calibrated receptacles were hung from the strain gauges to permit visual checks of computer measurements of chest drainage and urine output. The blood infusion program was used sparingly for several reasons. The program requires accurate, continuous measurement of left atrial pressure and chest drainage. The left atrial catheter was considered superfluous in many patients who did not have heart failure and received only aorta-coronary artery venous grafts; routine insertion in these patients was stopped after the introduction of the Swan-Ganz catheter, which permitted quick measurement of pulmonary wedge pressures if postoperative arrhythmias or myocardial infarctions developed. Because of these reasons and the undependable automated measurement of chest drainage, the blood infusion system was not evaluated adequately. As indicated by age, sex, pump time, and operations
The Journal of
894
Edmunds et al.
Thoracic and Cardiovascular Surgery
25
...c:: ~
et
20
I
~Control
f:h\H Monitored
15 10
5 Heort Rate
Systolic Pressure Diastolic Pressure Central Venous Pressure
Temperature
Fig. 3. Percentageof monitored time that indicated measurements were outside prescribed "limits." Noneof the differences between computed monitored and control patients is significant. In all instances standard deviations exceed the mean.
~Control
hAm;}) Monitored 3
Hours
6
4 Hours
2
2
Time to <100 mI /hr.
Time to < 30 mllhr.
Fig. 4. Time after operation required for chest drainage to reach two different milestones. Differences between control and computer-monitored patients were not significant. performed, the two groups of 175 patients each were comparable (Table I). Complications, deaths, and the interval between operation and various milestones are presented in Table II. Computer-aided monitoring did not cause a significant difference in any of these parameters. Type of operation did alter these factors. Patients with aorta-coronary artery vein grafts had no deaths, fewer complications, and reached all milestones faster than did patients who had valvular and other cardiac operations. The most common complications, which delayed discharge from intensive care, were low cardiac output and arrhythmias. 15 The percentage of time that various continuous measurements were outside of prescribed limits is illustrated for each group in Fig. 3. None of the differences between the two groups was significant (p > 0.05). Likewise, mean time for chest drainage to reach two end points did not differ between the two groups (Fig. 4). Activity of the nursing staff for both groups of patients for each of the three work-sampling periods is presented in Table III. The computer system was expected to reduce time spent in making, recording, and
communicating measurements. Initially, in 1975, nurses spent more time in these activities with computer-monitored patients, probably because of the novelty of the system. In 1976 nurses used I. 69 hours less time for these activities in computer-monitored patients, but the difference was not significant. However, in 1977 computer-monitored patients required slightly more time than did control patients; thus no time saving for nursing activities could be demonstrated. Patients who had valve operations required more nursing (2.4 hours per patient per day) than did patients who had aorta-coronary bypass grafts. The computer system was used by physicians largely to obtain information. In 1976 physicians accounted for 39.3 percent of the total computer usage, and nurses used the machine 32.1 percent of the total time the machine was used. Others (technicians, students, and aides) accounted for 28.6 percent of the usage. "Demand data" was the most frequent usage (2.9 uses per patient hour); "setup" was second. Only a small amount of time was used to review tabular data or graphics (0.39 uses per patient hour). Service experience was divided into three periods for analysis. The first period between March 19, 1975, and June 19, 1975, occurred after 2 months of shakedown trials and began when engineers and investigators felt confident about equipment performance and staff training. The last 6 months from Aug. I, 1976, to Feb. I, 1977, reflect the multiple efforts made to reduce component downtime. Service experience does not include a 7 week period in the autumn of 1975 when the system was substantially damaged by a flood. Downtime owing to problems with front-end equipment was reduced to zero by availability of on-site backup modules (Table IV). In the last 6 months, backup modules were used thirty times. Every component of the computer system failed at least once. The most common malfunctions were due to locking
Volume 74 Number6 December. 1977
Computer-aided monitoring systems
895
of the keyboard, malfunction of the teletypewriter, and failure of the high-speed printer to print. In the last 6 months downtime averaged 1 day per week. Current cost of the Roche computer-aided monitoring system as described for four beds without the fluid infusion system and with the blood infusion system is $152,670 (includes series 7000 front-end units and installation, but excludes tax and shipping). The price includes parts and labor for 12 months. A service contract to service all components of the system, calculated at 8.5 percent of the purchase price per annum, is $12,977. By use of these figures, the cost of computer-aided monitoring was calculated for different periods of depreciation and different annual clinical loads (Table V). Costs of backup modules and technicians are not included. Additional detailed information about the evaluation and results is available. 12
Table III. Activities of the nursing staff in hours per patient per 24 hours
Discussion
Legend: All three work shifts were sampled. A total of 192.8 patient hours
The computer-aided monitoring system evaluated in this study made frequent measurements, processed signals from front-end units, and stored, displayed, and printed data. Because of intermittent inaccuracies of chest drainage and urine volume measurements, data monitored by the computer system sometimes were the same as data monitored by conventional bedside machines. Efferent functions (e.g., fluid and blood infusion) were not evaluated for very practical reasons. As presently developed, the fluid infusion system was less flexible and more cumbersome than available manual systems. Although the blood infusion system was useful for some patients, many did not require left atrial catheters for safe postoperative management. In these patients, insertion of a left atrial catheter represented "extra surgery" which offset potential benefits of the blood infusion system. Had chest drainage measurements been consistently accurate and reliable, the blood infusion system would have been used more, particularly in patients with some degree of left-sided heart failure. Thus the computer system evaluated in this study processed only afferent or incoming functions and either was not or could not be used safely for efferent or computer-directed functions. This system was designed for "turnkey" application, was not reprogrammed during the study, and did not offer the calculating power, therapeutic recommendations, or efferent functions of other systems. 7, 8. 10 Computer-aided monitoring requires systematized postoperative care and the use of prescribed safe ranges or "limits. "4. 11 Use of "limits" is not unique to the computer system, but it is a prerequisite. The prospec-
~ M
C
2.63
1.99
1.68
1.19
1.73
1.61
Subtotal Direct patient care Patient care. other Maintain SICD
Measurements and observations Patient care clerical Communication
Total
M
M
C
2.39
2.65
2.22
1.04
1.72
1.21
1.14
0.66
0.27
0.57
0.35
0.36
5.43
4.38
2.99
4.68
4.21
3.72
5.03
5.00
4.96
4.69
4.74
4.57
0.37
0.47
0.20
0.23
0.32
0.41
1.14
0.73
0.59
0.54
0.41
0.21
11.97
10.58
8.74
10.14
9.68
8.91
C
were observed in 1975. 189.3 in 1976. and 285.6 in 1977. Actual time spent for "patient care. clerical" for computer-monitored patients was reduced 25 percent to compensate for manual recording of measurements made by the computer system. M. Computer monitored patients. C. Control patients.
tive, randomized design of the study prevented crediting the computer system for general advances in postoperative care. A nonrelevant comparison between systematized care with a computer and unsystematized care without a computer was avoided by using "limits" for control patients and by developing a practical bedside chart. The bedside chart made review of all data easier than calling up data from the computer and reduced the need for tabular and graphic reviews. The design of this study and the use of the log-entry bedside chart separated the effects of computer-aided monitoring from the effects of systematized postoperative care and advances in medical practice. The data clearly show that computer-aided monitoring of patients who have had heart surgery, as utilized in this study, does not influence morbidity or mortality and does not significantly alter nursing activities. Several reasons can be offered as explanation of this conclusion, but only two will be discussed. The reliability and accuracy of the present system were inadequate for critically ill patients. Every component failed at least once. Although patients could still be monitored with the front-end equipment alone, the computer system was nonoperative for an average of I day per week and required an outside technician for service. In addition, the accuracy and reliability of the urine volume and chest drainage measurements were unsatisfactory. This "turnkey" system was designed for "off-the-shelf' application by medical profession-
The Journal of
89 6
Edmunds et at.
Thoracic and Cardiovascular Surgery
Table IV. Service experience of the computer-aided monitoring system Initial 3 months
Front end No. instances module repl. Downtime of front-end unit (hr.) Downtime due to lack of back up (hr.) Computer system Keyboard Teletypewriter Centronics printer Computer Other
I
Total hours
49 175 364
3.24 6.74
30 0 0
264 154 87 172 120*
4.89 2.85 1.61 3.19 2.22
376 0 246 16 5t
Total hours
2 3 2
0.25 0.17
0 0 84 69 0
0 0 7.00 5.75 0
Totals
13.17
I
Avg. hours/ week
Avg. hours/ week
Total hours
Last 6 months
/2.5 months
I
24.74
Avg. hours/ week
0 0 14.46 0 9.46 0.62 0.19 24.73
Legend: The number of hours and average hours per week each component of the system was inoperative is presented for three evaluation periods. *Graphic hot box. tBurning transformer in power supply.
Table V. Estimated costs of computer-aided monitoring in dollars per patient* Patients /year Depreciation period
300
3 years 5 years 10 years
198 136 90
/.000 148 102 67
119 82 54
79 54 36
'Estimates include a service contract computed at 8.5 percent of the purchase price for each year after the first. For 1,000 patients annually. calculations are based on an eight bed unit costing $202,670.
als given a minimum of instruction. At the University of Pennsylvania the system did not function satisfactorily; however, in the absence of comparable data we must assume that other systems in a similar price range cannot perform better. To minimize downtime, presently used systems require backup components and on-site technicians capable of "trouble shooting" the entire system." 3. 8. 13, 14 This stopgap measure is unsatisfactory and adds expense which is not included in the purchase price and service contract. More reliable and accurate computer-aided monitoring systems are required, and attention must be paid to every component, particularly sensors and transducers.P" " The hospital is a hostile environment for sophisticated electronics. Equipment is operated by multiple users whose attention is primarily directed toward patients. Components are exposed to mechanical injury, occasional surges of electrical power, and even water damage. The system is expected to operate continuously. Therefore, all components must be built and
packaged to withstand rough use and occasional abuse. A second reason for the failure of this study to show an important difference between computer-aided and manual monitoring is that only afferent functions were processed and the system was underutilized. Unfortunately, the twin problems of reliability and accuracy affect most computer applications. The printout cannot be accepted for the medical record if measurements are sometimes questionable or absent. Similarly, efferent or computer-directed functions, such as blood, fluid, or drug infusions, are based upon accurate, dependable incoming measurements.t'': 17 The computer does not discriminate between important and transitory deviations of incoming signals, artifacts, and malfunctions of sensors and transducers. Therefore, a nurse prompted by an alarm must make this discrimination. Efficient use of computer-directed functions requires that incoming signals, needed by the program of the efferent function, be relatively free of artifacts and transitory deviations. . In patients who have had surgery, monitored measurements must be relevant and accurately reflect the patient's clinical condition. "Limits" must be realistic to prevent nuisance alarms or serious deviations in monitored measurements. Fortunately, existing technology provides sufficient sensors and transducers to make postoperative computer-aided monitoring feasible in patients who have had heart surgery. Future development of continuous measurements of cardiac output;" regional blood flow to vital organs, arterial blood gases;" and certain chemicals will make computer-aided monitoring even more safe and applicable to more patients. As computer-aided monitoring
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develops, investigators, designers, and engineers must concentrate on relevant measurements and calculations and meaningful efferent functions that offer real advantages over manual methods. This study does not show a realistic benefit/cost ratio for computer-aided monitoring of patients after cardiac surgery. The study does establish measurable criteria by which the contributions of computer-aided monitoring systems can be objectively evaluated. The study indicated the absolute requirement of accuracy and reliability in all. components of monitoring systems for critically ill patients. It would be shortsighted to conclude, on the basis of this study, that computer-aided monitoring is not worthwhile. The potential for computer-aided monitoring exists, particularly for patients who have had heart surgery. For these patients a constellation of continuous and intermittent measurements quite accurately defines the patient's clinical condition and permits systematic care which is a prerequisite for computer-aided monitoring. Further development of technology, with emphasis on accuracy, reliability, and relevance in the hospital environment and invention of new sensors and transducers to directly measure the most important and bellweather physiological functions, will earn computer-aided monitoring systems an important place in the postoperative care of patients: We thank the nurses, house officers, and technicians in the surgical intensive care unit for their valuable contributions to this study. REFERENCES
2
3
4
5
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Barnett, G. 0.: Computers in Patient Care, N. Eng!. J. Med. 279: 1321, 1968. Osborn, J. J., Beaumont, J. 0., Raison, J. C. A., Russell, J., and Gerbode, F.: Measurement and Monitoring of Acutely III Patients by Digital Computer, Surgery 64: 1057, 1968. Robicsek, F., Masters, T. N. , Reichertz, P. L., Daugherty, H. K., and Cook, J. W.: Three Years' Experience With Computer-Based Intensive Care of Patients Following Open Heart and Major Vascular Surgery, 81: 12, 1977. Shepherd, L. C., Kouchoukos, N. T., Kurtts, M. A., and Kirklin, 1. W.: Automated Treatment of Critically III Patients Following Operation, Ann. Surg. 168: 596, 1968. Shubin, H., and Weil, M. H.: Efficient Monitoring With a Digital Computer of Cardiovascular Function in Seriously III Patients, Ann. Intern. Med. 65: 453, 1966. Warner, H. R., Gardner. R. M., and Toronto, A. F.: Computer-Based Monitoring of Cardiovascular Functions in Postoperative Patients, Circulation 36: 263, 1967 (Suppl, II).
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7 Gerbode, F.: Computerized Monitoring of Seriously III Patients.J. THoRAc. CARDIOVASC. SURG. 66: 167, 1973. 8 Risso, W. L., Jr., Kempner, K. M., Owens, D. c., Gorlen, K. E., Holsinger, W. P., Mcintosh, C. L., and Syed, D.: A Postsurgical Intensive Care Computer System at the National Institutes of Health, in Computer in Cardiology, Long Beach, Calif., 1975, IEEE Computer Society, pp. 10 1-108. 9 Sheppard, L. c.. Kouchoukos, N. T., and Kirklin, J. W.: The Digital Computer in Surgical Intensive Care Automation, Computer 6: 29, 1973. 10 Shepherd, L. C., Kouchoukos, N. T., Shotts, J. F., and Wallace, F. D.: Regulation of Mean Arterial Pressure by Computer Control of Vasoactive Agents in Postoperative Patients, in Computers in Cardiology, Long Beach, Calif., 1975, IEEE Computer Society, pp. 91-94. II Kirklin, J. W.: Systems Analysis in Surgical Patients With Particular Attention to the Cardiac and Pulmonary System, Fifteenth MacEwen Memorial Lecture, University of Glasgow, Glasgow, Scotland, 1970. 12 Arthur D. Little, Inc.: An Evaulation of the ComputerAided Patient Monitoring System at the Hospital of the University of Pennsylvania, Cambridge, Mass., 1977. 13 Arthur D. Little, Inc.: A Review of the Patient Monitoring System at the University of Alabama Medical Center, Appendix C, Cambridge, Mass., 1973. 14 Arthur D. Little, Inc.: Evaluation of Computer-Based Patient Monitoring Systems: Final Report, Appendix D. A Review of the Medlab System in the Thoracic Surgery Intensive Care Unit at Latter Day Saints Hospital, Cambridge, Mass., 1973. 15 Maloney, J. V.: The Trouble with Patient Monitoring, Ann. Surg. 168: 605, 1968. 16 Evans, T. R., and Clark, T. J. H.: Reliability of Patient Monitoring Apparatus, Br. Med. J. 2: 734, 1971. 17 Morgan, A., Anderson, W., Bevilacqua, R., Cohn, L., Moore, F. D., and Collins, J. J., Jr.: Effects of Computer-Controlled Transufusion on Recovery From Cardiac Surgery, Ann. Surg. 178: 391,1973. 18 Williams, B. T., Sancho-Fornos, S., Clarke, D. B., Abrams, L. D., and Schenk, W. G., Jr.: Continuous LongTerm Measurement of Cardiac Output After Open-Heart Surgery, Ann. Surg. 174: 357, 1971. 19 Veasy, L. G., Clark, J. S., Jung, L., and Jenkins, J. L.: A System for Computerized Automated Blood Gas Analysis, Pediatrics 48: 5, 1971.
Discussion DR. JAMES R. PLUTH Rochester. Minn.
I wish to congratulate the authors on this interesting and very provocative paper and to thank them for the opportunity to review their manuscript. They have certainly pinpointed the many pitfalls that can occur in the problem of computerized monitoring and have underscored the numerous arguments against its use. Intuitively, however, some of us still
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believe that if reliability of the system can be achieved, the care and safety of the patient can be optimized. Many of the problems that they underlined are merely technical and can be overcome. I rise mainly for the purpose of briefly commenting on our own experience which I hope reflects a somewhat more optimistic viewpoint. We possess a rather unique good fortune of having two postoperative intensive care units which are virtually identical in all respects except for the capability of computerizing monitoring in one of these. [Slide] This unit was developed in conjunction with IBM and consists of a System 7 computer located adjacent to the intensive care unit. There are two additional System 7 computers located adjacent to the coronary care unit and also to the catheterization laboratory which are backed up by a System 370/135 unit from which data can be retrieved in the event of breakdown time of either of the System 7 computers. This configuration has provided remarkable reliability. Over the past year we have had a total of 92 1/ 2 hours of downtime, or 0.4 percent. A third of this downtime was scheduled downtime for the addition or deletion of computer programs. Approximately 11/ 2 years ago we completed a 6 months' evaluation of this system, during which time nearly 800 patients were randomized to either the standarized or the computerized units. We were indeed disappointed, like the authors, to find that there was no clear-cut mandate favoring computerized care. However, at the level of 0.05 significance, it was highly suggested that serious arrhythmias and "code" conditions could be reduced by computerized care. In addition, mortality rate secondary to arrhythmia was reduced in the computerized unit as compared to the standardized unit. Utilization of blood in the computerized care unit was one-half unit less than in patients receiving standard care. In addition, free time of the nurses was increased 25 percent. I suggest to the authors that, with the excellent standard postoperative care presently available, 350 or even 800 patients, as in our study, are inadequate to demonstrate the superiority of one system or another. I still suspect, however, that reduction in mortality rate may be real and savings in manpower and in improved supervision of postoperative care may be realistically achieved. DR. RICHARD E. CLARK St. Louis, Mo.
Dr. Edmunds' critical eye and experience have shown three facets of computerized monitoring with which we agree. First, they have used a data-logging system, that is, a computer system which periodically pulls numbers from various beds, and have compared it to a paper and pencil system. I would submit to you that the best system is a paper and pencil one. No present computer and probably no future computer system can beat the human computer, a welldesigned data flow sheet, and a very sharp pencil. Second, we agree that when data-logging and treatment protocols are the same in both a paper and pencil system and a
computer system, one should get identical results in terms of length of stay or any other milestone. Third, we agree that when reliability and accuracy are poor, no instrument, no computer, and no person will be found to be of value in an ICU setting. What, then, is the role for the computer in the care of cardiothoracic patients? Our 4 year experience has demonstrated the computer to be of value when one tailors the computer to the need. We have tailored our system to a philosophy of care, to the particular institution, and to the environment. We have identified two primary ways in which our system is of value. First, it is of value when a low nursepatient ratio exists; that is, one nurse to care for four patients after open-heart surgery, each on a ventilator. Second, it is of value in presenting patient data to the nurse in a highly and easily recognizable form. We have used the computer to continuously measure, analyze, and warn on a beat-by-beat basis as opposed to intermittently sampling data which has already been measured at the front end. Second, we use the computer to display information that will be competent, accurate, and easily recognized by us. Like Dr. Pluth at Rochester, we have found that our elapsed time from ventricular fibrillation to defibrillation is remarkably short because of a display system which alerts a nurse rapidly. Although Dr. Edmunds' experience has not been good, I would suggest that not all monitoring systems using a computer are alike and that each must be tailored to a need, not the need tailored to the computer. DR. FRANCIS ROBICSEK Charlotte. N. C.
I enjoyed the presentation of Henry Edmunds. Our experience can serve as a control, because in Charlotte we are using equipment very similar to his. The application of computers in medicine is logical and predictable. I find it very ironic that hospitals buy multimillion dollar machines which at the whim of any accounting clerk can spit out the outstanding account of any patient, but the surgeon has to crawl under the bed, leaf through pounds of paper or charts, or wake up the sleepy resident to get his information. Clinically effective, low cost computer monitoring has been reported from San Francisco, Rochester, Birmingham. and Stockholm. The experience which Harry Daugherty and I have been involved in, reaches now into the fourth year and comprises 1,400 patients, has also been gratifying. Our computer downtime in the past 6 months averages I hour per week, and the cost is only $100 to $150 per patient, I to 3 percent of the total hospital bill. The computer made our work much easier and put our nurses back where they belong, in direct patient care. Our computer not only does routine monitoring, but also provides automatic infusion and transfusion. We are happy with both programs. It also gives complex clinical and biochemical analysis, simple standard orders, and complicated medical recommendations. On the other hand, we also have to recognize that computer
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monitoring is still at the beginning stage. The initiation of such a program requires the same time, patience, and compassion as the initiation of a young surgeon or a beginning nurse. It is not enough to study whether or not a computer works; you have to make it work yourself. This requires not only electronic know-how, but continuous personal interest, fascination, deep commitment, and the infusion of your own surgical philosophy and time into the program. If this attitude is not present, the machine is going to hang around your neck like a 500 pound electronic albatross. DR. FRANK GERBODE
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new hospital and have learned a good deal about taking care of seriously ill patients, I cannot say that using the computer has been the major cause of the improvement. I will say that all the personnel who work with the computer are thoroughly convinced they do not want to work without it any longer. Nurses sometimes leave us go to another hospital where computer monitoring is not being used, but they usually come back and stay. They like to work with this type of support. You might draw a parallel between this and flying an airplane. Once you learn how to fly an airplane with the use of instruments, you never want to fly it again with the seat of your pants.
San Francisco, Calif.
It is worthwhile to hear Dr. Edmunds bring out some of the disadvantages of computerized monitoring. Certainly, using a computer is like buying an automobile that is mechanically not satisfactory or any sort of a machine which you do not quite understand and perhaps are using for the wrong purpose. For one thing, having been in this business for a long time, we decided that closing the loop probably was going to be unsatisfactory for most patients, contrary to the program in Alabama. If the physician closes the loop and tries to use automated treatment, he may encounter many complications which can be avoided simply by ignoring that entirely. I do not believe that our aim in the immediate future is to treat a patient automatically with a computer. Our objective has been to use the computer to furnish accurate, physiological information about the patient so that the surgeon or the nurse can make a more intelligent decision. This has changed nursing in our unit from an old-fashioned method of taki ng care of sick people to one in which the nurse is almost a physician. She becomes intelligent about complications and hospital complications and the use of the computer. In fact, most often she knows more about what is happening than the physician, particularly the young one. It is very hard to measure the advantages. There are so many factors in taking care of seriously ill patients. Even the staff involved in the Mayo Clinic study may have some doubts about the validity of their controlled experiment. Our morbidity and mortality rates have decreased steadily in the past 5 years. However, since we have moved into a
DR. ED M U N D S (Closing) I would like to thank the discussers for their comments and for reporting their experience. I will try to answer their questions and the points raised collectively rather than individually. I note that at the Mayo Clinic, in St. Louis, in San Francisco, and in Charlotte, the computer system comes equipped with backup components or, lacking that, with an on-site computer engineer. That is a little bit like buying a new car and having a mechanic in the passenger seat. We cannot afford backup systems or on-site engineers in Philadelphia, and I am not so sure that others can afford them either. The second point-and I think this is a important point-is that this technology is in its infancy. It is extremely important to try to find out how we can use sophisticated technology to help us take care of critically ill patients. The system that we evaluated was a "turnkey" system or "off the shelf." The system was designed and built to be used with minimal instruction. What we found is that this kind of machine is not ready for the intensive care unit or for patients who have had heart surgery. I would like to close by emphasizing two points: First, critically ill postoperative patients deserve at least the same reliability and accuracy of their monitoring system that airline passengers deserve of their aircraft. Second, systematized postoperative care has many, many benefits. That is the reason we need to have prospective, randomized control studies when we are going to evaluate future computer technology.