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Biomedical subjects

W C Shoemaker

Publications and source records attributed to W C Shoemaker.

At least 181 records · Page 10Linked to original sources
PubMed1983

Use of physiologic monitoring to predict outcome and to assist in clinical decisions in critically ill postoperative patients.

A predictive index based on cardiorespiratory-monitored values of an earlier series of postoperative critically ill patients was tested in prospective clinical trials and found to be reasonably accurate, sensitive, and specific. The hypothesis was tested that the median values of patients who survived life-threatening postoperative conditions, rather than the norms of unstressed, healthy volunteer subjects, constitute a first approximation to the optimal therapeutic goals for critically ill postoperative patients. In a prospective series of 223 consecutive, critically ill postoperative patients, normal values were used as the therapeutic goals of the control patients, whereas the median values of surviving patients were used as the goals of therapy for the protocol group. The clinical conditions of the protocol group were at least as severe as those of the control group, but the mortality was significantly less in the protocol group (12.5 percent) than in the control group (35 percent); the number of life-threatening complications were also greater in the control group. These data suggest that at least half and possibly as much as two thirds of postoperative deaths may be due to physiologic problems that can be identified, described, predicted, and prevented. Therapy for the critically ill patient should be defined by physiologic criteria, and administration of therapy should be monitored to attain prophylactically optimal physiologic goals rather than giving therapy after a deficiency has occurred to attain normal values.

Clinical Trials as Topic↗
PubMed1983

Use of a transcutaneous PO2 regional perfusion index to quantify tissue perfusion in peripheral vascular disease.

In order to develop transcutaneous oxygen tension (PtcO2) measurements into a practical method for assessing peripheral vascular disease, the relationships between extremity and chest wall PtcO2 were examined in subjects with and without systemic atherosclerotic disease. The ratio of extremity to chest PtcO2, or transcutaneous regional perfusion index (RPI) assessed limb oxygenation more reliably than did direct PtcO2 measurement by obviating the effects of changes in systemic oxygen delivery upon local PtcO2. The authors find that transcutaneous oximetry can be used during treadmill exercise testing and that the RPI is unchanged by exercise in all normal subjects. PtcO2 and RPI were then measured during rest, position change, and exercise testing in patients with intermittent claudication. Whereas normal subjects maintain a constant thigh and calf RPI during exercise, patients with intermittent claudication consistently manifested large decreases in RPI in these areas when they were exercised until symptomatic. The authors find no overlap between the responses of normal subjects and patients with claudication; positive findings are, therefore, highly specific for exercise-induced limb ischemia. Since transcutaneous RPI exercise testing is easily performed and highly reproducible, it is well suited to clinical use in the diagnosis and documentation of intermittent claudication. Furthermore, since limb ischemia can be quantified, this method lends itself both to grading the severity of disease and to evaluating clinical progression of disease. It is suggested that such a quantitative approach to evaluation of intermittent claudication may allow refinement and extension of the indications for operative intervention in patients with intermittent claudication.

Adult↗
PubMed1983

Hemodynamic and colloid osmotic pressure alterations in the surgical patient.

Colloid osmotic pressure (COP) was measured simultaneously with cardiorespiratory measurements in 103 surgical patients suspected of having circulatory problems. In a small subset of 28 patients, measurements were taken before, during, and after surgical operations. Similarly, data sets were taken before, during, and after infusions of colloids and crystalloids to assess the interactions of these variables during the stress of surgery and the administration of fluid therapy. COP was found to decrease during and shortly after surgical operations despite reasonably well-maintained pressure, volume, and flow variables. Concentrated (25%) albumin and plasma protein fraction (PPF) increased COP, cardiac index (CI), CVP, pulmonary capillary wedge pressure (WP), and blood volume, whereas crystalloids transiently increased CI, CVP, and WP but did not significantly change COP and blood volume. Low COP values were weakly related to survival, and COP-WP differences less than or equal to 3 mm Hg were roughly related to ARDS and pulmonary edema.

Blood Physiological Phenomena↗
PubMed1983

Use of transcutaneous O2 monitoring in the intraoperative management of severe peripheral vascular disease.

Transcutaneous O2 (PtcO2) and CO2 (PtcCO2) monitoring has been used in infants, in critically ill adults, and more recently, in peripheral vascular disease. The present report compares values of centrally placed chest (PtcO2 and PtcCO2) sensors with values of peripherally placed calf (Ptc'O2 and Ptc'CO2) sensors in a patient with severe peripheral vascular disease during performance of an axillofemoral bypass graft. The calf Ptc'O2 values may be expressed as a ratio of their corresponding PaO2 values or as a percentage of the chest PtcO2, i.e., calf Ptc'O2/chest PtcO2 X 100. The ratio reflects local tissue perfusion in the face of fluctuating PaO2 and central PtcO2 values. The data demonstrate that PtcO2 sensors reflect tissue blood flow and oxygenation and, therefore, are useful measures of tissue perfusion, especially during limb revascularization.

Arterial Occlusive Diseases↗
PubMed1983

Clinical trial of an emergency resuscitation algorithm.

Clinical trials of a resuscitation algorithm for patients entering the Surgical Emergency Department (ED) with acute hypotension were conducted for a 30-month period. The intent was not to compare good management with bad, but rather university-run county hospital services with and without an algorithm. The study group was comprised of 603 hypotensive patients out of 6833 consecutive admissions. The effects of the policy of using a resuscitation algorithm were evaluated by the outcomes of the patients who were treated by residents given the algorithm (protocol group) versus those treated by residents not given the algorithm (control group). The efficacy of the algorithm, per se, was evaluated by outcomes of patients whose management was in satisfactory compliance with the algorithm as compared with those whose management deviated from the algorithm. The patients were also evaluated by the primary cause of their hypotension and the presence of severe associated illnesses. Outcomes of patients treated by residents given the algorithm were as good and in a number of respects better than those of patients treated by residents without the algorithm. The mean resuscitation time of the protocol group was markedly and significantly less than that of the control group indicating that the policy of using the algorithm facilitated resuscitation even though it was not always properly followed. Patients with trauma, hemorrhage, and sepsis, whose care was in satisfactory compliance with the algorithm had shorter resuscitation times, lower MAP-time deficits, and less shock-related complications. The algorithm which is primarily directed toward fluid resuscitation did not appear to be efficacious for patients whose trauma was primarily head injury, where fluid restriction may be the therapy of choice.

Adolescent↗
PubMed1983

Clinical aspects of resuscitation with and without an algorithm: relative importance of various decisions.

Clinical description was made of a series of hypotensive patients resuscitated with and without an algorithm. Of 603 hypotensive patients, there were 114 (19%) deaths and 169 (28%) patients with complications; the average low MAP was 53 +/- 25 mm Hg. Of 169 patients with complications, 48 (28%) had shock-related (SR) complications; 25 (52%) of these patients died. There were 265 (44%) patients who had severe associated diseases and these patients comprised the group most vulnerable to complications and death; in this group, there were 41 patients with SR-complications who had significantly higher mortality, longer resuscitation times, lower MAP, more deviations from the algorithm, and more delays in resuscitation than did those with nonshock-related complications. Multiple deviations from the algorithm were associated with longer resuscitation times, and higher incidence of SR complications. Most of the delays in resuscitation of these patients and most of the SR complications could have been prevented. Seventeen percent of hypotensive patients entering the emergency department (ED) normally carried low arterial pressures, which averaged 75 +/- 3 (SD) mm Hg; this was more common, but not confined to young females. Of the 603 patients who actually were hypotensive, 6% were admitted in arrest (phase I), 18% in severe shock (phase II, MAP less than 60 mm Hg), 52% in moderate shock (phase III, MAP less than 80 mm Hg), and 24% were normotensive but subsequently became hypotensive (phase IV). The importance of various decision nodes of the algorithm were evaluated. The present algorithm, designed for these hypotensive emergency patients, provides a framework for fluid management that expedites resuscitation and reduces complications related to shock. We conclude that: (a) delays in resuscitation can be clearly related to an increased incidence of SR complications; (b) when the algorithm was satisfactorily followed, there was faster resuscitation and less SR complications; and (c) when the algorithm was satisfactorily followed in patients with severe associated illnesses, there was also shorter ICU stay, shorter hospitalization and decreased mortality.

Adolescent↗
PubMed1983

Sequential cardiorespiratory patterns of anesthetic induction with ketamine in critically ill patients.

Hemodynamic and O2 transport effects of ketamine anesthesia were evaluated in 22 critically ill patients. After placement of radial and pulmonary artery catheters, simultaneous measurement were made of cardiac output, intravascular pressures, arterial and mixed venous gases, saturations, pH, and Hct; cardiorespiratory values then were calculated for a preinduction control period and sequentially at frequent intervals over a 15-min observation period. In general, there was an early progressive increase in HR, cardiac index (CI), arterial and venous pressures, stroke work, and O2 delivery (DO2); O2 consumption (VO2) and O2 extraction (O2 Ext) decreased. In general, ketamine produced an inotropic cardiac response, but these responses were not uniform; a relatively small percentage had reduced pressures, flow, and reduced myocardial performance that were related to hypovolemia and associated medical conditions.

Anesthesia↗
PubMed1983

Sequential cardiorespiratory patterns in septic shock.

Sequential hemodynamic and oxygen transport monitoring was performed in 33 patients with septic shock to define the temporal pattern of physiologic events. Measurements taken over a 24-h period before the hypotensive crisis, defined as the lowest initial mean arterial pressure (MAP), were compared to those taken during the 48 h thereafter. In the 24-h period before the hypotensive crisis, there were increases in cardiac index (CI), central venous pressure (CVP), pulmonary capillary wedge pressure (WP), pulmonary vascular resistance index (PVRI), and pulmonary shunt (Qsp/Qt), but decreases in MAP, systemic vascular resistance index (SVRI) and oxygen delivery (Do2). When sequential cardiorespiratory patterns were examined, oxygen consumption (VO2) fell transiently to significantly low values 12 h before as well as at the time of the hypotensive crisis. SVRI fell and CI rose to values significantly different from normal in the 4 h before the low MAP. During the subsequent 48 h after the hypotensive crisis, CI, CVP, WP, PVRI and Qsp/Qt remained elevated. Values for MAP, SVRI, DO2, and VO2 were significantly reduced. These results demonstrate the existence of antecedent cardiorespiratory alterations that precede the hypotensive episode in septic shock and suggest that flow maldistribution in the systemic circulation is an early event with possible pathogenic significance.

Adult↗
PubMed1983

Method for continuous conjunctival oxygen monitoring during carotid artery surgery.

A new device for measuring conjunctival oxygen tension (PcjO2) was used for intraoperative monitoring during carotid endarterectomy. The PcjO2 measures local tissue oxygenation and, thus, reflects the oxygen delivery to the areas supplied by the internal carotid artery. PcjO2 was found to be sensitive to manipulation, clamping, and obstruction of the carotid artery; it provided a useful monitoring system for assessment of the cerebral circulation during carotid surgery.

Aged↗
PubMed1983

Calcium homeostasis in patients with acute pancreatitis.

Calcium homeostasis was studied serially in six patients admitted to the surgical intensive care unit because of acute pancreatitis. All developed ionized hypocalcemia. Serial assays of serum parathyroid hormone (PTH) revealed a prompt response to this hypocalcemia (1143 +/- 239 versus 574 +/- 24 pg/ml, P less than 0.05). Serum 1,25-dihydroxyvitamin D (1,25(OH)2D) levels rose from 26 +/- 8 to 104 +/- 17 pg/ml (P less than 0.01) in the expected time frame subsequent to the PTH peak, confirming the biologic significance of the PTH increases observed. Despite these significant elevations of PTH and 1,25(OH)2D, the expected prompt return of ionized calcium concentrations to normal levels was not seen. Also, urinary cyclic adenosine monophosphate production was not stimulated. These results suggest an acute functional resistance of bone to physiologic levels of PTH stimulation during the acute phase of pancreatitis. Fluid sequestration and hypovolemia are marked at this time. We suggest that pancreatitic hypocalcemia may occur when oligemic bone cannot respond normally to PTH and 1,25(OH)2D stimulation. As such, it may represent an end organ failure syndrome associated with shock and poor tissue perfusion.

Acute Disease↗
PubMed1983

Physiologic determinants of operative survival after portacaval shunt.

Twenty cirrhotic patients with bleeding from esophageal varices were studied before, during, and after portacaval shunt. There were 12 survivors and eight nonsurvivors. Preoperative determination of hepatic function and classification by Child's criteria correctly predicted outcome only in those with very good and those with very poor hepatic function. However, the majority of patients had intermediate liver function, and their operative survival could not be predicted on this basis. Other parameters, however, did distinguish between survivors and nonsurvivors. Survivors had better preoperative cardiac contractility, shorter operations, less severe preoperative and intraoperative blood loss, and fewer emergency operations. Intraoperatively, survivors maintained cardiac index and oxygen delivery while nonsurvivors did not. After operation, survivors had increased cardiac index, oxygen delivery, and oxygen consumption above preoperative values, while nonsurvivors failed to attain this. Analysis of these data suggests that determination of preoperative hepatic function alone will not provide accurate prediction of outcome from portacaval shunt, because there are multiple factors that determine outcome. The determinants identifed in this study were 1) preoperative hepatic function, 2) degree of hemodynamic compensation from preoperative bleeding and shock, 3) magnitude of the intraoperative oxygen deficits, 4) hemodynamic reserve allowing for the compensatory postoperative state, and 5) nutritional status.

Adult↗
PubMed1982

Physiologic responses to massive intraoperative hemorrhage.

In five patients who had massive, sudden, intraoperative hemorrhage, defined as loss of more than 1 L of blood in less than ten minutes, mean arterial pressure was initially maintained, and there were early increases in both systemic and pulmonary vascular resistance; however, cardiac output and oxygen delivery decreased. During control of hemorrhage and replacement of blood, wedge pressure and central venous pressure increased, and mean arterial pressure was maintained; however, cardiac output and oxygen delivery decreased, and oxygen consumption decreased below prehemorrhage levels. Three patients died postoperatively of multiple organ failure. The data indicate that anesthesia and operation affect both cardiopulmonary performance and peripheral oxygen transport, such that the ordinary physiologic response to hemorrhage are lessened. The absence of compensatory increase in oxygen consumption after resuscitation may have contributed to the high postoperative mortality.

Adult↗
PubMed1982

Use of crystalline hemoglobin as replacement of RBC mass.

Replacement of a circulatory RBC mass was performed isovolemically in experimental dogs using either 7% crystalline hemoglobin solution with a low P50 (the oxygen tension necessary to produce 50% saturation of hemoglobin at pH 7.4 and 37 degrees C) or with an albumin solution. Progressive RBC depletion caused increased cardiac output in both groups. Oxygen delivery was better preserved after using the crystalline hemoglobin solution, and, under conditions of extreme anemia, oxygen transport using this solution enabled dogs to survive the otherwise lethal insult. Although administration of crystalline hemoglobin preserved oxygen transport, oxygen off-loading was at a lower tension because of the lower P50. Decreased mixed venous oxygen tension, which presumably reflects lower tissue oxygen tension, was associated with systemic vasoconstriction. The administration of oxygen-carrying solutions with low P50 values results in a relatively vasoconstricted state. This vascular response is mediated by changes in tissue oxygen tension, rather than by impaired tissue oxygen consumption.

Animals↗
PubMed1982

Sequential perioperative lactate determination. Physiological and clinical implications.

Sequential arterial blood lactate concentrations were determined pre-, intra-, and postoperatively in 12 high risk surgical patients. These levels were correlated with simultaneous measurements of arterial blood pressure, cardiac index (CI), and oxygen consumption (VO2). There was a marked increase in lactate values intraoperatively. This increase did not correspond to decreases in either mean arterial pressure (MAP) or CI, but did appear to correlate with decreased intraoperative VO2. Postoperatively, lactate levels remained elevated, and this elevation appeared to correlate with an estimation of intraoperative oxygen deficit. CI and VO2 were increased postoperatively; the data support the hypothesis that these postoperative increases in CI and VO2 represent physiological compensations for intraoperative oxygen deficits. Clinically, determinations of lactate values may prove useful in titrating postoperative therapy to support needed physiological compensations.

Adult↗
PubMed1982

Hemoglobin solution in the treatment of hemorrhagic shock.

The major physiological effects of hemorrhage are hypovolemia and anemia. The administration of an oxygen-carrying plasma expander, such as crystalline hemoglobin solution (CHb), can restore both of these deficits while avoiding many of the logistical problems entailed in the use of blood. The authors have used Chb to treat severe hypovolemia and anemia in separate canine models and found it to be highly effective. CHb acts as a colloid plasma expander to resuscitate intravascular volume in hypovolemia and supplements oxygen-carrying capacity in anemia. CHb can support oxygen transport essentially in the absence of red blood cells. Hemodynamic responses to low P50 CHb, however, suggest that oxygen offloading at the tissue level is compromised by the high oxygen affinity of unmodified CHb. Whereas such oxygen offloading deficits may be compensated for in the chronic situation, they may be of crucial importance in severe trauma where oxygen transport is often limited by arterial desaturation, low cardiac output, maldistribution of perfusion and interstitial water overload. The development of a lower-affinity CHb is, therefore, of the essence.

Animals↗
PubMed1982

Clinical trial of an algorithm for outcome prediction in acute circulatory failure.

The authors evaluated prospectively an index for outcome prediction previously developed retrospectively from the cardiorespiratory data of a series of 113 critically ill postoperative general surgical patients. A predictive score generated by nonparametric multivariate analysis of the observed value for each cardiorespiratory variable and the frequency distributions of survivors' and nonsurvivors' values of that variable at each stage of postoperative shock. An overall global predictive index was then generated from the sum of the weighted predictive scores in each variable. This predictive index was tested prospectively in a new series of 156 operations and was found to be 94% accurate for the values of the last available data set, suggesting that the method satisfactorily predicts outcome. This index may be used as an objective measure of the severity of illness; i.e., it may be used to track the clinical course of postoperative general surgical patients during periods of critical illness. It was concluded that the predictive index aids in evaluation of monitored cardiorespiratory variables, improves interpretation of physiologic alternation, and facilitates clinical decision-making of critically ill patients at the bedside.

Adult↗
PubMed1982

Clinical trial of survivors' cardiorespiratory patterns as therapeutic goals in critically ill postoperative patients.

The hypothesis was tested that the median values of survivors of life-threatening postoperative conditions, rather than the norms of unstressed healthy volunteers, are the appropriate therapeutic goals for critically ill postoperative patients. The authors studied prospectively a series of 100 consecutive critically ill postoperative patients; normal values were used as the therapeutic goals of the control patients, while the median values of survivors were used as the goals of therapy for the protocol group. The age, sex, primary illness, surgical operation, lowest mean arterial pressure (MAP), time in hypotension incidence of severe hypotension (MAP greater than 50 mm Hg), and presence of associated severe medical illnesses (defined by predetermined criteria) were comparable in the control and protocol groups; i.e., clinical conditions of the protocol group were at least as severe as those of the control group. The mortality was significantly less in the protocol group (13%) than in the control group (48%); the number of life-threatening complications were also greater in the control group. These data suggest that the cardiorespiratory pattern of survivors are the appropriate goals of therapy for critically ill patients.

Adult↗