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Biomedical subjects

W C Shoemaker

Publications and source records attributed to W C Shoemaker.

At least 19 recordsLinked to original sources
PubMed1992

Hemodynamic and oxygen transport patterns for outcome prediction, therapeutic goals, and clinical algorithms to improve outcome. Feasibility of artificial intelligence to customize algorithms.

A generalized decision tree or clinical algorithm for treatment of high-risk elective surgical patients was developed from a physiologic model based on empirical data. First, a large data bank was used to do the following: (1) describe temporal hemodynamic and oxygen transport patterns that interrelate cardiac, pulmonary, and tissue perfusion functions in survivors and nonsurvivors; (2) define optimal therapeutic goals based on the supranormal oxygen transport values of high-risk postoperative survivors; (3) compare the relative effectiveness of alternative therapies in a wide variety of clinical and physiologic conditions; and (4) to develop criteria for titration of therapy to the endpoints of the supranormal optimal goals using cardiac index (CI), oxygen delivery (DO2), and oxygen consumption (VO2) as proxy outcome measures. Second, a general purpose algorithm was generated from these data and tested in preoperatively randomized clinical trials of high-risk surgical patients. Improved outcome was demonstrated with this generalized algorithm. The concept that the supranormal values represent compensations that have survival value has been corroborated by several other groups. We now propose a unique approach to refine the generalized algorithm to develop customized algorithms and individualized decision analysis for each patient's unique problems. The present article describes a preliminary evaluation of the feasibility of artificial intelligence techniques to accomplish individualized algorithms that may further improve patient care and outcome.

Algorithms↗
PubMed1992

Monitoring and management of acute circulatory problems: the expanded role of the physiologically oriented critical care nurse.

The intensive care unit is set apart from other hospital patient care areas by (1) physiological instrumentation that permits better assessment and more effective therapy and (2) more intensive nursing. These capabilities allow nurse and physician intensivists to evaluate tissue perfusion and tissue oxygenation by the temporal patterns of oxygen delivery and oxygen consumption, as well as hemodynamics. Such evaluation provides important insight into the functional impairment of hemorrhagic, traumatic, septic, and postoperative shock. Using artificial intelligence-based systems, complex clinical algorithms--tailored to specific patient conditions--have been developed and are described. These algorithms are based on both invasive and noninvasive monitoring systems and on clinical experience with a large series of high-risk surgical patients.

Algorithms↗
PubMed1979

Cardiorespiratory monitoring in postoperative patients: I. Prediction of outcome and severity of illness.

An index for prediction of outcome for use as a measure of the severity of illness was developed by a nonparametric multivariate analysis of cardiorespiratory data from 113 critically ill postoperative general surgical patients. This severity (predictive) index was based on a computerized algorithm that compares a given observed value with the frequency distributions of survivors and nonsurvivors. The difference in the mean values of this index for survivors and nonsurvivors was statistically significant (p less than 0.001) during each stage of shock. Sensitivity of the index in prediction of survival ranged from 70-93% depending upon stage, the specificity of the index ranged from 76-92%, and the predictive accuracy ranged from 87-96%. The severity index is used as a process measure to track the course of critically ill patients and to evaluate the efficacy of alternative therapies.

Cardiovascular System↗
PubMed1979

Cardiorespiratory monitoring in postoperative patients: II. Quantitative therapeutic indices as guides to therapy.

Immediate (proximate) and late (optimal) therapeutic goals for critically ill postoperative general surgical patients were based on the frequency distributions of cardiorespiratory data of the survivors immediately after resuscitation and in the late stage of shock, respectively. An algorithm was developed which expresses in quantitative terms the distance from observed values for each variable to both of these therapeutic goals. Further, composite indices were also made of related cardiorespiratory variables that reflect the important aspects of acute circulatory failure and its therapy; i.e., volume, flow, tissue perfusion, oxygen transport, and bodily response to stress. The therapeutic indices of nonsurvivors were found to have greater mean deficits that survivors (p less than 0.05) during all but the middle stage of shock. The therapeutic indices greatly aid in the organization and display of monitored cardiorespiratory variables by expressing the circulatory defects in easily understood indices that can be related to therapeutic interventions. Moreover, the interactions of the various aspects of cardiorespiratory function before and after therapy may be easily observed.

Cardiovascular System↗
PubMed1978

Resuscitation algorithm for management of acute emergencies.

Assuming that unrecognized or inadequately corrected hypovolemia results in higher mortality and morbidity rates, we developed a systematic approach to resuscitation that would: 1) identify criteria to aid in the recognition of hypovolemia and ensure the expeditious correction of this defect without interfering with diagnostic workup and management; 2) define criteria to prevent fluid overload which may jeopardize the patient's course, and 3) express these criteria in an explicit, systematic, patient care algorithm, ie, protocol, useful to both the resident and the practicing physician. We are now conducting prospective clinical trials with one service using the algorithm and the others acting as the control group. Preliminary results comparing patient outcomes suggest that the algorithm improves patient care by shortening resuscitation time and results in fewer hospital days, intensive care unit days, febrile days, and days on mechanical ventilation as well as reduced mortality. The algorithm provides a systematic plan to organize patient care so that the most urgently needed procedures are not delayed or overlooked.

Algorithms↗
PubMed1978

Physiologic monitoring goals for the critically ill patient.

Definition of the appropriate therapeutic goals for physiologic monitoring of patients postoperatively was approached by analyzing more than 50,000 values of the 20 most commonly monitored variables in a series of 113 critically ill patients throughout their immediate postoperative course. In general, normal values were poor criteria for monitoring, since normal values were restored in an average of 75 per cent of the survivors and 76 per cent of the nonsurvivors for the five most frequently measured variables; that is, arterial pressure, heart rate, central venous pressure, wedge pressure and cardiac output. Moreover, an average of 56 per cent of the 20 most commonly monitored variables of nonsurvivors was restored to the normal range. Furthermore, 34 per cent of all the nonsurvivors' values were within the normal range; this was only 2.4 per cent less than the percentage of normal values for the survivors. The empirically determined median value of the survivors taken in the late stage during periods remote from therapy was found to be a better criterion for therapeutic goals for most variables, including blood flow, oxygen transport and most intravascular pressures. However, normal values were satisfactory for arterial pressure, peripheral resistance, pH, mixed venous oxygen tension and arterial carbon dioxide tension, largely because of the biphasic patterns of these variables.

Blood Chemical Analysis↗
PubMed1978

Comparison of cardiorespiratory effects of crystalline hemoglobin, whole blood, albumin, and Ringer's lactate in the resuscitation of hemorrhagic shock in dogs.

We studied the time course and interactions of hemodynamic, oxygen transport, colloid osmotic pressure (COP), and blood volume responses to 500 ml of crystalline hemoglobin (Hgb), 500 ml of whole blood (WB), 1,000 ml of Ringer's lactate (RL), and 500 ml of plasma protein fraction (PPF) given in random order to 12 mongrel dogs subjected to hemorrhagic shock by the standard Wiggers' technique. In general, hemodynamic and oxygen transport responses were greater and more prolonged after the colloids than after RL. These responses were related to concomitant improvement in blood volume and COP. Of the colloids, Hgb appeared to produce somewhat greater hemodynamic and oxygen transport changes. This was particularly evidenced by comparison of these responses when each fluid was the first agent used after the hemorrhage. By virtue of its capacity to increase COP and plasma volume and to carry oxygen, Hgb improved both the gross circulation and the tissue perfusion, as indicated by cardiovascular hemodynamics and bulk oxygen transport variables.

Animals↗
PubMed1978

Optimal hematocrit value in critically ill postoperative patients.

Failling hematocrit values are traditionally used to observe the course of active bleeding, since hematocrit values usually reflect acute blood losses. However, evidence from the literature suggests that, after volume replacement, some degree of normovolemic hemodilution may be desirable and that return to normal hematocrit values is not necessarily the appropriate goal of transfusion therapy. The optimal hematocrit value was defined empirically by three methods in a series of 94 critically ill postoperative patients. First, the mortality rates of postoperative patients were lowest with hematocrit values between 27 and 33 per cent. Second, mortality rates were examined when both hematocrit values and the important cardiorespiratory variables were reduced; significantly increased mortalties occurred when hematocrit values were less than an average of 32 per cent. Finally, oxygen availability and oxygen consumption increased significantly after whole blood and packed red cell transfusions were given when hematocrit values were less than 32 per cent but not above 33 per cent. When accurate blood volume measurements are not available, hematocrit values of 32 per cent are optimal; when volume therapy is indicated, blood may be given with hematocrit values less than 32 per cent, crystalloids or colloids are preferred with hematocrit values greater than 32 per cent.

Adult↗
PubMed1977

Relative hemodynamic effectiveness of whole blood and plasma expanders in burned patients.

In a series of nine fatally burned patients, hemodynamic and oxygen transport measurements were made before, during and after 56 administrations of 500 milliliters of whole blood or colloids and 1,000 milliliters of crystalloids. To enhance comparability, 38 of these studies were conducted at intervals on the same patient, the patient serving as his own control. The data indicate greater hemodynamic responses to colloids than to whole blood and greater responses to whole blood than to crystalloids when the latter was given at twice the volume as well as at four times the volume of the colloid. The data suggest that, in addition to replenishing salt and water, restoration of hemodynamic and oxygen transport variables may be accomplished by expansion of plasma volume with colloids and whole blood. Adequate nutrition is also needed for the increased metabolic needs of the burned patient. Without supplemental nutrition, high grade plasma proteins and tissue proteins may be expended as energy substrates; the lowering of plasma proteins tends to redistribute water from the plasma to the interstitial phase, which increases further the peripheral edema.

Blood Pressure↗
PubMed1976

Interorgan transport of amino acids in hemorrhagic shock.

Arterial concentrations and net organ metabolism of amino acids (AA), O2, CO2, H+, and glucose (Glc) were measured in two dogs before and during hemorrhage and after blood replacement. Shock caused increased splanchnic and decreased peripheral blood flow and O2 consumption. Po2 decreased more in hepatic venous than in mixed venous blood. pH fell in hemorrhage and increased with retransfusion. Increased liver output and arterial concentration of Glc were observed during hemorrhage. Differences between animals correlated with nutritional status. Blood concentrations of most AA showed little change during hemorrhage but increased after retransfusion. In contrast, arginine concentrations declined sharply. Peripheral output and hepatic uptake of most AA occurred during the control period. During shock, peripheral output and hepatic uptake of total AA and most individual AA declined progressively; after retransfusion peripheral uptake and hepatic output of many AA occurred. By contrast, peripheral output and hepatic uptake increased for alanine, glutamine, serine, phenylalanine, and tyrosine. After retransfusion net transport of some compounds occurred from periphery to liver; others, from liver to periphery. During shock, hepatic protein catabolism increased. and this catabolism, accompanied by decreased hepatic uptake (increased hepatic output), seemed the main cause of increased blood AA concentrations. Protein catabolism in peripheral tissue was not a cause of increased blood concentrations. Pathological changes in pH, Po2, and blood flow, occurred early in hemorrhage. In contrast, changes in AA movements and concentrations were within normal limits until late in shock.

Amino Acids↗
PubMed1976

Effects of transfusion on surviving and nonsurviving postoperative patients.

In the pretransfusion control period, generally, the cardiorespiratory values of the nonsurviving patients were worse than those of the surviving patients. Moreover, the responses of nonsurvivors to a standardized test of therapy generally were less than those of survivors. The increase in oxygen availability to the tissues after blood transfusion in nonsurvivors was almost as great as that of survivors, but the increase in oxygen consumed by nonsurvivors was only about one-half that of survivors. This is of particular importance in the critically ill patient, as reduction in oxygen transport represents a major physiopathologic problem in postoperative deaths.

Blood Pressure↗