Homer R. Warner

The HELP system.

Development of a comprehensive computer system for acquiring medical data and implementing medical decision logic has been ongoing for over 15 years at the University of Utah and the LDS Hospital in Salt Lake City, Utah. This system is known as HELP and is currently operational at LDS Hospital, which is a 550-bed tertiary care hospital serving the needs of the intermountain west. This hospital also serves as one of the primary teaching centers for the University of Utah Medical School. Having been developed in this environment, the design of the HELP system was required to meet the administrative, clinical, teaching, and research needs of hospitals, as well as provide the decision-making capability.

Effect of Combined Sympathetic and Vagal Stimulation on Heart Rate in the Dog

A set of equations is described which permit prediction of the time course of heart rate in a dog anesthetized with pentobarbital from the time course of frequency of stimuli applied to the distal cut ends of vagus and sympathetic efferent nerves to the heart. These equations, although based on assumptions as to the physiological mechanisms involved, were only tested for their ability to describe the kinetic relationship involved. The time course of heart rate resulting from combined vagus and sympathetic nerve stimulation (HRSV) is given by the equation: HRSV = HRV + (HRS − HR0) (HRV − HRmin)/(HR0 − HRmin), where the subscripted terms are heart rate values due to vagus stimulation (v), sympathetic stimulation (s), no stimulation (0) and the minimum (min) heart rate achievable by vagus stimulation alone. Clearly the vagus influence is capable of dominating the sympathetic in the control of heart rate.

The Frequency-Dependent Nature of Blood Pressure Regulation by the Carotid Sinus Studied with an Electric Analog

Amplification of carotid sinus activity of a dog is brought about through the use of an electric analog of the carotid sinus applied in parallel with this element of the dogs own pressure regulating system. Sinusoidal excursions in arterial pressure in response to corresponding variations, between fixed limits, in rate of stimulus of one vagus nerve were larger with carotid sinus amplification than without it. Evidence presented supports the concept that because of the delay in the response of arteriolar smooth muscle, effective buffering of sudden variations in arterial pressure cannot be accomplished by variations in resistance, but can be through variations in flow.

A replicable method for blood glucose control in critically Ill patients.

Context:To ensure interpretability and replicability of clinical experiments, methods must be adequately explicit and should elicit the same decision from different clinicians who comply with the study protocol. Objective:The objective of this study was to determine whether clinician compliance with protocol recommendations exceeds 90%. Design:We developed an adequately explicit computerized protocol (eProtocol-insulin) for managing critically ill adult patient blood glucose. We monitored clinician compliance with eProtocol-insulin recommendations in four intensive care units in four hospitals and compared blood glucose distributions with those of a simple clinical guideline at one hospital and a paper-based protocol at another. All protocols and the guideline used intravenous insulin and 80 to 110 mg/dL (4.4–6.1 mmol/L) blood glucose targets. Setting:The setting for this study was four academic hospital intensive care units. Patients:This study included critically ill adults requiring intravenous insulin. Intervention:Intervention used in this study was a bedside computerized protocol for managing blood glucose. Main Outcome Measure:The main outcome measure was clinician compliance with eProtocol-insulin recommendations. Results:The number of patients was 31 to 458 and the number of blood glucose measurements was 2,226 to 19,925 among the four intensive care units. Clinician compliance with eProtocol-insulin recommendations was 91% to 98%. Blood glucose distributions were similar in the four hospitals (generalized linear model p = .18). Compared with the simple guideline, eProtocol-insulin glucose measurements within target increased from 21% to 39%, and mean blood glucose decreased from 142 to 115 mg/dL (generalized linear model p < .001). Compared with the paper-based protocol, eProtocol-insulin glucose measurements within target increased from 28% to 42%, and mean blood glucose decreased from 134 to 116 mg/dL (generalized linear model p = .001). Conclusions:The 91% to 98% clinician compliance indicates eProtocol-insulin is an exportable instrument that can establish a replicable experimental method for clinical trials of blood glucose management in critically ill adults. Control of blood glucose was better with eProtocol-insulin than with a simple clinical guideline or a paper-based protocol.

Development of a computerized infectious disease monitor (CIDM)

At the LDS Hospital in Salt Lake City, an interface was developed between the microbiology laboratory computer system and the HELP integrated central hospital computer system. The HELP system includes medical information from most clinical care support areas. The microbiology data are translated from the laboratory computer file structure to a hierarchical data structure on the HELP system. A knowledge base was created with the help of infectious disease experts, and became part of a Computerized Infectious Disease Monitoring system (CIDM). The knowledge base is automatically activated when specific microbiology data are entered into a patients computer file (data driven), thus decisions are made automatically with no additional effort required of medical personnel. The CIDM was designed to inform infectious disease personnel when a patient has one of the following conditions: a hospital-acquired infection, an infection at a normally sterile body site, an infection due to a bacteria with an unusual antibiotic sensitivity pattern, an infection for which the patient is not receiving an antibiotic to which the offending bacteria is sensitive, an infection that could be treated with a less expensive antibiotic, an infection which is required by law to be reported to state and national health authorities, and those patients receiving prophylactic antibiotics longer than is medically indicated. All of the microbiology data are now extensively reviewed by nurses and physicians from terminals at nursing stations or intensive care units. The CIDM is currently being used for hospital-acquired infection surveillance at LDS Hospital.

Regulation of Cardiac Output Through Stroke Volume

Heart rate was controlled by direct stimulation of the right ventricle of a dog previously subjected to complete A-V block in order to study the effect of this variable on cardiac output. Measurements of cardiac output were made at various heart rates in unanesthetized dogs, both at rest and walking on a treadmill. Except at the extremes, cardiac output was independent of heart rate at rest and during mild exercise. This finding emphasizes the fact that cardiac output may be regulated to provide required flow through changes in stroke volume alone, even though adjustment of heart rate is the usual means for obtaining this end.

The characteristic sequence for the onset of contraction in the normal human left ventricle.

The sequence for the onset of segmental contraction of the left ventricle was studied in 25 normal patients by analyzing sequential frames obtained at 16.7-msec intervals of right anterior oblique (RAO) ventriculograms by two independent methods. In the first method, we compared the times of onset of contraction of the hemidiameters associated with each of 54 segments with the time of onset of contraction of the average of all the hemidiameters for the ventricular contour. In the second method we used a radial coordinate system and determined relative phase relationships by plotting the motion of each of 54 segments against the average motion of all segments.The resulting pattern showed that, on the average, the midregion of the inferior wall began to contract 25 msec before the apex and the midregion of the anterior wall began contraction 18 msec before the apex. In 12 of 25 patients the interior and anterior walls both began to contract before the apex. In only one of 25 patients did the apex begin to contract first. This sequence of contraction corresponds to the reported sequence of electrical activation for normal human left ventricles.

AN ANALYSIS OF GRANULOCYTE KINETICS IN BLOOD AND BONE MARROW

Technics for labeling granulocytes in human blood and bone marrow with tritiated thymidine ( H3-Th) , P32-labeled sodium phosphate (radiophosphate) and diisopropylfluorophosphate ( DFP32) have now been developed to the point where further analysis of the experimental results in terms of a model of granulocyte dynamics seems justified. The purpose of this report is to present a mathematical model of granulocyte kinetics which will describe the time course of radioactivity in blood granulocytes obtained in human subjects following the administration of these labels.

Computer-based ICU data acquisition as an aid to clinical decision-making.

The critically ill patient places tremendous mental challenges and crucial time demands on intensive care nurses and physicians. Computers can ease these demands by automatically acquiring, storing, and displaying patient data. However, the computer can more effectively serve the staff if medical-decision protocols are implemented. This paper describes the use of a computer system designed to optimize medical care for the acutely ill patient.

Computer-based Monitoring of Cardiovascular Functions in Postoperative Patients

INDUSTRIAL application of computers to complex control problems has led to speculation among the members of the medical profession regarding the possibility of computers monitoring acutely ill patients. A system directed toward this ultimate end has been in operation in the Latter-day Saints Hospital in Salt Lake City, Utah, since March, 1966. To date, 215 patients have been monitored with this system. Many of these patients developed complications which were detected by the computer system earlier than would have been the case by the usual methods of monitoring. Decisions regarding change of therapy were often made as a result of information gathered through the monitoring system. The system, operating 24 hours a day, seven days a week, has now established itself as an integral part of the postoperative care of open-heart surgery patients in this hospital and is well received by the patient, nurse, and physician alike. The purpose of this paper is to describe the goals of this project, techniques currently being used to achieve these goals, and experience with the system to date.