Search PubMed⌕ Search

Biomedical subjects

W C Shoemaker

Publications and source records attributed to W C Shoemaker.

At least 19 recordsLinked to original sources
PubMed1999

Physiologic monitoring of circulatory dysfunction in patients with severe head injuries.

Secondary brain insults influence outcome significantly in patients with severe head injuries. Inadequate tissue perfusion should be identified and treated early to avoid such insults. Conventional hemodynamic monitoring (blood pressure, heart rate, urine output) is not a reliable method for evaluating circulatory function in such patients. Invasive monitoring by means of pulmonary artery catheters may offer more precise information on early circulatory abnormalities. The objective of this study was to study the hemodynamic patterns of patients with severe closed head trauma by invasive methods and to correlate the derived information with survival. Fifty-nine consecutive patients with blunt trauma, closed head injuries, and Glascow Coma Scale < 8 were studied. Pulmonary artery catheters were placed in all patients shortly after admission, and flow and flow-derived variables were monitored for 96 hours or patient demise. Survivors had higher cardiac index, oxygen delivery, and oxygen consumption values compared to nonsurvivors during the first 24 hours after injury. Following this period increased values were recorded in both groups. These temporal hemodynamic patterns were similar for patients with isolated head trauma and patients with other associated injuries. Thus initial hemodynamic patterns are associated with final outcome in patients with severe head injuries. Aggressive early hemodynamic monitoring may reveal subtle but significant changes. Further studies are warranted to investigate whether treatment guided by such information can improve survival.

Adult↗
PubMed1998

Circulatory effects of whole blood, packed red cells, albumin, starch, and crystalloids in resuscitation of shock and acute critical illness.

Circulatory deficiencies and the effectiveness of transfusion and fluid therapy may be evaluated by invasive and noninvasive monitoring after high risk surgery, hemorrhage, trauma, and sepsis in the ED, OR, and ICU. Earlier recognition and therapy of circulatory problems in emergency and critically ill patients to achieve optimal goals empirically defined by the survivors' patterns is recommended to improve outcome. WB, Prbc, and colloids markedly and statistically significantly improved pressure, flow, and tissue perfusion and best achieved these goals. Noninvasive monitoring may be used in the ED and OR shortly after admission to identify circulatory deficiencies and to titrate therapy, or they may be used initially as the front-end of subsequent invasive monitoring.

Blood Transfusion↗
PubMed1998

Multicenter study of noninvasive monitoring systems as alternatives to invasive monitoring of acutely ill emergency patients.

BACKGROUND: Recent reports showed lack of effectiveness of pulmonary artery catheterization in critically ill medical patients and relatively late-stage surgical patients with organ failure. Since invasive monitoring requires critical care environments, the early hemodynamic patterns may have been missed. Ideally, early noninvasive hemodynamic monitoring systems, if reliable, could be used as the "front end" of invasive monitoring to supply more complete descriptions of circulatory pathophysiology. OBJECTIVES: To evaluate the accuracy and reliability of noninvasive hemodynamic monitoring consisting of a new bioimpedance method for estimating cardiac output combined with arterial BP, pulse oximetry, and transcutaneous PO2 and PCO2; we compared this system of noninvasive monitoring with simultaneous invasive measurements to evaluate circulatory deficiencies in acutely ill patients shortly after hospital admission where invasive monitoring was not readily available. We also preliminarily explored early differences in temporal hemodynamic patterns of survivors and nonsurvivors. DESIGN AND SETTING: Prospective comparison of simultaneous invasive and noninvasive measurements of circulatory function with retrospective analysis of data in university-run county hospitals, university hospitals and affiliated teaching hospitals, and a community private hospital. PATIENTS: We studied 680 patients, including 139 severely injured or hemorrhaging patients in the emergency department (ED), 129 medical (nontrauma) patients on admission to the ED, 274 high-risk surgical patients intraoperatively, and 138 patients recently admitted to the ICU. RESULTS: A new noninvasive impedance device provided cardiac output estimations under conditions in which invasive thermodilution measurements were not usually applied. There were 2,192 simultaneous bioimpedance and thermodilution cardiac index measurements; the correlation coefficient, r = 0.85, r2 = 0.73, p < 0.001. The precision and bias was -0.124+/-0.75 L/min/m2. Both invasive and noninvasive monitoring systems provide similar information and identified episodes of hypotension, low cardiac index, arterial hemoglobin desaturation, low transcutaneous O2, high transcutaneous CO2, and low oxygen consumption before and during initial resuscitation. The limitations of noninvasive systems were described. CONCLUSIONS: Noninvasive monitoring systems gave continuous displays of physiologic data that provided information allowing early recognition of low flow and poor tissue perfusion that were more pronounced in the nonsurvivors. Noninvasive systems may be acceptable alternatives where invasive monitoring is not available.

Adult↗
PubMed1998

Invasive and noninvasive hemodynamic monitoring of patients with cerebrovascular accidents.

Seventeen patients with hemodynamic instability from acute cerebrovascular accidents were evaluated shortly after arrival at the emergency department of a university-run county hospital with both invasive Swan-Ganz pulmonary artery catheter placement and a new, noninvasive, thoracic electrical bioimpedance device. Values were recorded and temporal patterns of survivors and nonsurvivors were described. Cardiac indices obtained simultaneously by the 2 techniques were compared. Of the 17 patients, 11 (65%) died. Survivors had higher values than nonsurvivors for mean arterial pressure, cardiac index, and oxygen saturation, delivery, and consumption at comparable times. Cardiac index values, as measured by invasive and noninvasive methods, were correlated. We concluded that hemodynamic monitoring in an acute care setting may recognize temporal circulatory patterns associated with outcome. Noninvasive electrical bioimpedance technology offers a new method for early hemodynamic evaluation. Further research in this area is warranted.

Aged↗
PubMed1997

Continuous intraoperative noninvasive cardiac output monitoring using a new thoracic bioimpedance device.

OBJECTIVES: To compare a new noninvasive bioimpedance device with the standard thermodilution method during the intraoperative period in high-risk patients undergoing oncological surgery. DESIGN: Prospectively collected data with retrospective analysis. SETTING: The study was undertaken at a university hospital, single institution. PARTICIPANTS: Twenty-three selected adults undergoing extensive, ablative oncological surgery. INTERVENTIONS: Simultaneous measurements of cardiac output by a new bioimpedance method and the standard thermodilution method during the intraoperative and immediate postoperative periods. MEASUREMENTS AND MAIN RESULTS: The correlation coefficient between the two methods was r = 0.89, p < 0.001. Bias and precision analysis between the two techniques showed a mean bias of 0.1 L/min and SD of the bias [precision] of 1.0 L/min [95% level of agreement +2.1 L/min to -1.9 L/min]. After software enhancement, data from the last 11 monitored patients showed improved correlation between the two methods; r = 0.93, mean bias -0.1 L/min, and precision 0.8 L/min. Electrical and motion-induced interference only transiently impaired the performance of the new impedance method. CONCLUSION: This new impedance device is a safe, reliable, clinically acceptable alternative to the invasive thermodilution method in the operating room environment.

Adult↗
PubMed1996

Noninvasive physiologic monitoring of high-risk surgical patients.

OBJECTIVES: To study the feasibility of multicomponent noninvasive monitoring, consisting of a new bioimpedance method for estimating cardiac output together with routine pulse oximetry and transcutaneous oximetry, and to compare physiologic data obtained noninvasively with hemodynamic and oxygen transport data obtained by standard invasive pulmonary artery thermodilution catheter to evaluate circulatory function in high-risk surgical patients. DESIGN: Prospective descriptive analysis of the time course of physiologic patterns in surgical patients. SETTING: University-run county hospital. PATIENTS: Seventy-one consecutively monitored, high-risk critically ill surgical patients in their perioperative period. OUTCOME MEASURES: Simultaneous measurements by invasive and noninvasive methods to describe and compare the temporal physiologic patterns of survivors and nonsurvivors. RESULTS: The new impedance cardiac output estimations closely approximated those of the thermodilution method (r = 0.82, P < .001). Episodes of hypotension, tachycardia, low cardiac index, arterial hemoglobin desaturation, low transcutaneous oximetry, reduced oxygen delivery, and low oxygen consumption occurred with both groups but were more pronounced in the nonsurvivors than in the survivors. Noninvasive monitoring provided information similar to that of the thermodilution method. Both approaches indicated low flow and poor tissue perfusion (oxygenation) that was worse in the nonsurvivors. CONCLUSIONS: The multicomponent noninvasive monitoring provides continuous online, real-time displays of physiologic data that allow immediate recognition of circulatory dysfunction as well as the means to titrate therapy to appropriate predetermined therapeutic goals. The noninvasive systems are easy to apply, safe, inexpensive, reasonably accurate, and cost-effective.

Adult↗
PubMed1996

Invasive and noninvasive monitoring for early recognition and treatment of shock in high-risk trauma and surgical patients.

The proposed noninvasive monitoring systems provide the essential hemodynamic and oxygen transport information previously available only by invasive thermodilution catheters. More importantly, the noninvasive systems provide continuous on-line real-time displays of data which allow immediate recognition of circulatory abnormalities and provide a means to titrate therapy to appropriate therapeutic goals. The noninvasive systems are easy to apply, safe, inexpensive, and more cost-effective than invasive monitoring.

Emergencies↗
PubMed1996

Oxygen transport and oxygen metabolism in shock and critical illness. Invasive and noninvasive monitoring of circulatory dysfunction and shock.

The common underlying physiologic problem in shock is low flow from hypovolemia or maldistributed microcirculatory flow from uneven vasoconstriction, leading to inadequate tissue perfusion (hypoxia), often in the face of increased metabolic demands. Noninvasive monitoring which was found to provide similar information to that of invasive monitoring, was used in the earliest period of time shortly after admission to the emergency department to provide objective physiologic criteria as therapeutic goals for each of the three major circulatory components: cardiac, pulmonary, and tissue perfusion functions. A clinical algorithm or branch-chain decision tree for high-risk surgical patients was developed from decision rules based on survivor and nonsurvivor patterns, outcome predictors, prospective controlled clinical trials of the oxygen delivery/oxygen consumption (DO2/VO2) concept, and the DO2/VO2 responses of a wide variety of therapeutic agents.

Decision Trees↗
PubMed1996

Noninvasive hemodynamic monitoring of critical patients in the emergency department.

OBJECTIVE: To evaluate the feasibility of multicomponent noninvasive hemodynamic monitoring in critical emergency patients and to compare this technique with simultaneous invasive monitoring by the pulmonary artery thermodilution catheter. METHODS: A prospective observational study was done comparing invasive monitoring and noninvasive monitoring in 60 critically ill or injured patients who required hemodynamic monitoring shortly after entering the ED of a university-affiliated country hospital. Cardiac output (CO) values measured by the standard thermo-dilution pulmonary artery catheter technique were compared with simultaneously obtained measurements using a noninvasive bioimpedance method. Concurrent measurements were made of pulse oximetry to screen pulmonary function and transcutaneous oximetry to assess tissue perfusion. RESULTS: The impedance CO values closely approximated those for the thermodilution method; r 0.81, p < 0.001. Significant circulatory abnormalities, including hypotension, reduced cardiac index, arterial hemoglobin desaturation, tissue hypoxia, reduced O2 delivery, and consumption, were found in 54 of the 60 (90%) patients. The cardiac index decreased in 44% of the patients, the transcutaneous O2 decreased in 39%, and the O2 saturation by pulse oximetry fell in 22% during the observation period in the ED (commonly lasting 2-8 hours). CONCLUSIONS: Noninvasive monitoring can provide hemodynamic and perfusion information previously available only by invasive thermodilution catheters. Such noninvasive monitoring can display continuous on-line real-time data, allowing immediate recognition of circulatory abnormalities and providing a means to titrate therapy to appropriate therapeutic goals.

Adult↗
PubMed1996

Noninvasive cardiac index monitoring in gunshot wound victims.

OBJECTIVE: To evaluate a bioimpedance device for the noninvasive measurement of cardiac index (CI) against standard thermodilution measurements in patients with gunshot wounds. METHODS: A prospective open-label performance evaluation was done using a convenience sample of gunshot wound victims initially treated in the resuscitation area of a high-volume, urban ED. After initial resuscitation, patients had a flow-directed pulmonary artery catheter placed for thermodilution cardiac output (CO) measurements. The CO measurements were made in triplicate and averaged. Estimates of body surface area were used to convert these measurements to CI estimates. Electrodes for bioimpedance measurements were placed as soon as practical after ED arrival. Simultaneous measurements of CI using the bioimpedance device were made as clinically indicated during each patient's hospital course. RESULTS: There were 54 patients studied, with an overall mean (+/- SEM) age of 32 +/- 3 years, Revised Trauma Score of 6.7 +/- 0.4, and Injury Severity Scale score of 22 +/- 3. There were 42 survivors and 12 nonsurvivors. The CI as estimated by bioimpedance correlated well with that measured by thermodilution (r = 0.79, p < or = 0.02). The precision of the invasive and noninvasive measurements was 1.1 L/min/m2; the bias was -0.011 L/min/m2. In 24 patients with thoracic injuries requiring tube thoracostomy or thoracic surgery, the correlation of the 2 devices was r = 0.71 with precision and bias of 1.4 L/min/m2 and -0.018 L/min/m2, respectively. CONCLUSIONS: Cardiac index can be noninvasively estimated in acutely injured patients with gunshot wounds using a bioimpedance device. Further study of bioimpedance measurements as a guide to volume therapy is warranted.

Adult↗
PubMed1996

Resuscitation from severe hemorrhage.

The potential to be successfully resuscitation from severe traumatic hemorrhagic shock is not only limited by the "golden 1 hr", but also by the "brass (or platinum) 10 mins" for combat casualties and civilian trauma victims with traumatic exsanguination. One research challenge is to determine how best to prevent cardiac arrest during severe hemorrhage, before control of bleeding is possible. Another research challenge is to determine the critical limits of, and optimal treatments for, protracted hemorrhagic hypotension, in order to prevent "delayed" multiple organ failure after hemostasis and all-out resuscitation. Animal research is shifting from the use of unrealistic, pressure-controlled, hemorrhagic shock models and partially realistic, volume-controlled hemorrhagic shock models to more realistic, uncontrolled hemorrhagic shock outcome models. Animal outcome models of combined trauma and shock are needed; a challenge is to find a humane and clinically realistic long-term method for analgesia that does not interfere with cardiovascular responses. Clinical potentials in need of research are shifting from normotensive to hypotensive (limited) fluid resuscitation with plasma substitutes. Topics include optimal temperature, fluid composition, analgesia, and pharmacotherapy. Hypotensive fluid resuscitation in uncontrolled hemorrhagic shock with the addition of moderate resuscitative (28 degrees to 32 degrees C) hypothermia looks promising in the laboratory. Regarding the composition of the resuscitation fluid, despite encouraging results with new preparations of stroma-free hemoglobin and hypertonic salt solutions with colloid, searches for the optimal combination of oxygen-carrying blood substitute, colloid, and electrolyte solution for limited fluid resuscitation with the smallest volume should continue. For titrating treatment of shock, blood lactate concentrations are of questionable value although metabolic acidemia seems helpful for prognostication. Development of devices for early noninvasive monitoring of multiple parameters in the field is indicated. Molecular research applies more to protracted hypovolemic shock followed by the systemic inflammatory response syndrome or septic shock, which were not the major topics of this discussion.

Animals↗
PubMed1996

Temporal physiologic patterns of shock and circulatory dysfunction based on early descriptions by invasive and noninvasive monitoring.

In the past, most investigators failed to consider time relationships in their studies of circulatory problems. Because of this, data obtained in middle- or late-stage shock during organ failure are often presented as being characteristic of specific shock syndromes. Even "early" studies are not physiologically early, but instead have often come to mean early after ICU admission or early after life-threatening hypotensive events. The hypotensive episode represents decompensation of protective circulatory mechanisms, not the beginning of circulatory dysfunction. Early monitoring demonstrates that circulatory changes do not start with hypotension, but with the precipitating event, i.e., hemorrhage, trauma, surgery, or sepsis. When monitoring is started after hypotension, the first half of the problem is missed. It is, therefore, appropriate to focus on the earliest period of circulatory dysfunction with noninvasive methods to evaluate pathophysiology, to predict outcome, and to propose therapeutic protocols to improve outcome. Invasive monitoring is generally accepted as the "gold standard" for critically ill patients. The pulmonary artery flotation catheter has translated information to the bedside previously only available in cardiac catheterization laboratories, forever changing the way we treat ICU patients. Newer high-tech hardware and software innovations in the impedance method give more accurate and reliable cardiac index (CI) measurements that now satisfactorily agree with thermodilution in most clinical conditions. Minor disparities are more than made up for by the continuous online display of data. This impedance device, combined with pulse oximetry and transcutaneous oximetry, provides a feasible, noninvasive hemodynamic monitoring system that can be applied in a manner similar to electrocardiogram electrodes in the emergency department, operating room, ICU, hospital floors, and doctor's offices. More importantly, noninvasive monitoring provides a continuous, online, real-time display of hemodynamic data needed to titrate therapy rapidly and expeditiously. This is a major advantage, since therapy is more effective if given prophylactically or early and then titrated to optimal goals. Noninvasive monitoring provides a powerful method for objective evaluation of early, rapidly changing circulatory dynamics beginning with the precipitating event. This gives a new and different view of circulatory failure, exceeding the boundaries of our old concepts of shock based on blood pressure, subjective symptoms, and imprecise signs. Data of survivors revealed increased cardiac function (CI and oxygen delivery) shortly after surgery, trauma, and sepsis; this response is needed to meet the increased metabolic demands defined by the increased oxygen consumption. Nonsurvivors have limited responses to the added metabolic demands of external stressors. Therapy should augment naturally occurring compensations, but it must be given promptly within appropriate time limits.

Hemodynamics↗
PubMed1996

Early physiologic patterns in acute illness and accidents: toward a concept of circulatory dysfunction and shock based on invasive and noninvasive hemodynamic monitoring.

The aim of the present study was to explore methods, concepts, and techniques that provide recognition of circulatory deficiencies at the earliest possible time in the patient's illness. We used both the standard invasive pulmonary artery thermodilution catheter and noninvasive hemodynamic monitoring systems consisting of a new bioimpedance cardiac output device, pulse oximetry, transcutaneous oxygen (PtCO2) and carbon dioxide tensions as well as the transcutaneous oxygen tension/fraction of inspired oxygen ratio (PtCO2/FIO2). These three noninvasive systems were used to evaluate cardiac function, pulmonary function, and tissue perfusion, respectively. This approach to early noninvasive monitoring is based on recent evidence suggesting that poor tissue perfusion and oxygenation initiate circulatory dysfunction that leads to shock and organ failure. We studied 303 acute episodes of circulatory dysfunction and shock in 261 patients in a university-run county hospital; 75 were acute traumatic injuries and 109 acute nontrauma medical emergencies on admission to the emergency department, and 77 ICU patients with an acute illness or exacerbation of their current illness. The study was a prospective, descriptive study to identify early abnormal circulatory patterns reflecting the cardiac, pulmonary, and perfusion functions associated with death and with survival. We described noninvasively monitored patterns in individual illustrative cases, in common etiologic groups, and in physiologic categories representing various abnormal functional patterns. We found that hypotensive shock usually was preceded by episodes of high flow followed by low flow and inadequate tissue perfusion indicated by reduced PtCO2; this frequent pattern was modified by associated co-morbid conditions, especially hypovolemia, limited cardiac reserve capacity, age, hypertensive states, and increased body metabolism from infection, trauma, stress, exercise, temperature, and endocrine disorders. Reduced pulmonary function occurred in 18% of emergency patients; these were usually patients with thoracic trauma, severe hypovolemia, head injuries, chronic obstructive pulmonary disease, asthma, drug overdose, and central nervous system failure (massive stroke and coma). We concluded that noninvasive measurements identify early circulatory problems reliably and provide objective criteria for physiologic analysis as well as for definition of therapeutic goals and titration of therapy.

Adult↗
PubMed1996

Intraoperative maintenance of tissue perfusion prevents ARDS. Adult Respiratory Distress Syndrome.

Patients undergoing prolonged, complex oncological surgery are at increased risk of developing the adult respiratory distress syndrome (ARDS) and other organ failures. Our hypothesis is that maintaining adequate tissue perfusion and oxygenation may prevent tissue hypoxia and acidosis in pulmonary, peripheral, and splanchnic microcirculations. Experimental evidence suggests that the hypoxic, acidotic endothelium stimulates the release of cytokines, kinins, and other mediators. We developed and tested an intraoperative protocol for surgical patients likely to develop ARDS and organ dysfunction; the protocol focuses on the intraoperative period but is not limited to this time. Nitroglycerin and fluids were used to maintain tissue perfusion and prevent tissue hypoxia as reflected by transcutaneous oxygen tension values. In 155 high-risk patients, none developed ARDS. We conclude that maintenance of tissue perfusion and oxygenation in high-risk surgical patients decreases the incidence of ARDS.

Adult↗
PubMed1996

Use of large databases for resolving critical care problems.

Large databases allow for rapid access to large volumes of data. To convert raw data to information, large numbers of data points must be correlated into a descriptive pattern that can be interpreted by the user. Databases must be constructed so as to allow reliable extraction of the raw data into a format that supports analysis of events in a meaningful, objective, and reproducible manner. Databases must be responsive to a variety of users. They must not demand unrealistic amounts of effort on those responsible for data entry. Standard protocols in various stages of development will make databases easier to use and more reliable. Database management tools such as the Internet and the National Library of Medicine will become more integrated into the practice of critical care medicine at all levels, including administration, clinical care, and research. This article provides an overview of the capabilities and difficulties associated with large databases. The major areas of use of large databases in the hospital setting are administration, bibliographic, patient care, research, and education. Each of these areas has different requirements and is supported by different types of databases. The advantages and disadvantages of linear, relational, and object-oriented databases are discussed. Issues relating to methods of data entry and the accuracy and reliability of data are discussed. The challenges involving integration of various sources of data and the interfacing of devices are reviewed.

Critical Care↗