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Biomedical subjects

W C Shoemaker

Publications and source records attributed to W C Shoemaker.

At least 217 records · Page 12Linked to original sources
PubMed1980

Hemodynamic, blood volume, and oxygen transport responses to albumin and hydroxyethyl starch infusions in critically ill postoperative patients.

Hemodynamic, plasma volume, and oxygen transport effects were measured after administration of 500 ml of 5% albumin or 6% hydroxyethyl starch (HES) in hypovolemic postoperative patients using a prospectively randomized crossover design. Both agents produced marked and significant improvement in plasma volume and flow as well as small transient increases in arterial and venous pressures, urine output, colloidal osmotic pressure (COP), and oxygen transport. The authors conclude that HES is a safe, inexpensive, effective plasma expander that has hemodynamic effects similar to those of other colloids. It was apparent from these and other studies that clinically stable postoperative patients may have appreciable blood volume deficits. Routine vital signs correlated poorly with the preinfusion control hemodynamic values or the changes in blood volume status after volume loading. Normal cardiac output, central venous pressure (CVP), and pulmonary arterial wedge pressure (WP) values are commonly seen in critically ill postoperative patients who, nevertheless, may be hypovolemic. Measurement of changes in these variables after a fluid challenge is a useful way to assess plasma volume status.

Adult↗
PubMed1980

Continuous transcutaneous oxygen monitoring during respiratory failure, cardiac decompensation, cardiac arrest, and CPR. Transcutaneous oxygen monitoring during arrest and CPR.

The transcutaneous oxygen sensor (PtcO2), which has been used to predict PaO2 in neonates, recently has been shown to follow changes in oxygen delivery, rather than PaO2 during shock and hypoxia in dogs. Six preterminal patients were continuously monitored with PtcO2 and monitored hemodynamically at frequent intervals during cardiac decompensation, arrest, and cardiopulmonary resuscitation (CPR). The weighted mean correlation coefficients between PtcO2 and O2 delivery as well as between PtcO2 and cardiac output were 0.94 and 0.96, respectively. Five patients died of severe ARDS and 1 patient died intraoperatively of hemorrhagic shock. Four patients were monitored 1-7 days before shock occurred. The correlation between PtcO2 and PaO2 was 0.91 during periods of normal cardiac output in the preterminal period. During cardiac decompensation, the cardiac output, PtcO2, and mixed venous oxygen tension (PcO2) of 25 torr was reached, the PtcO2 fell below the PvO2. This also corresponded to a decrease in VO2. The mean VO2 was 142 +/- 24 ml/min x M2 for PtcO2 values > torr, and 75 +/- 15 ml/min x M2 for PtcO2 < 25 torr (p < 0.01). A PtcO2 of > 40 torr corresponded to normal cardiac index, O2 delivery, VO2, PvO2, and arterial pH (pHa) while a PtcO2, of < 25 torr corresponded to large reductions of these variables. A PtcO2 of < 25 torr preceded cardiac arrest by 43 +/- 28 min.

Cardiac Output↗
PubMed1980

Pathogenesis of respiratory failure (ARDS) after hemorrhage and trauma: I. Cardiorespiratory patterns preceding the development of ARDS.

To evaluate clinical and physiologic determinants of adult respiratory distress syndrome (ARDS), we studied 152 consecutively monitored patients with trauma and hemorrhage: 60 developed ARDS. The cardiorespiratory patterns of hemorrhage and trauma patients who did not develop ARDS were compared to those who subsequently did develop ARDS, but before the time of their ARDS. Comparisons also were made in the patients with trauma and those with hemorrhage, as well as in those who survived and those who did not. Hemorrhage and trauma patients who developed ARDS had greater reductions in blood volume, red cell mass, PaCO2 and O2 delivery throughout all stages, as well as greater pulmonary vascular resistance index (PVRI) and pH in the early and middle stages. Nonsurvivors of ARDS had greater deficits in blood volume and red cell mass, higher PVRI and pH, as well as lower central venous pressure (CVP), hemoglobin (Hgb), and PaCO2 than did ARDS survivors. Hemorrhage patients had lower blood volume, left ventricular function, O2 delivery and VO2, as well as higher systemic vascular resistance index (SVRI), PVRI, and O2 extraction than either the trauma patients or normal subjects. Description of the temporal cardiorespiratory patterns before the clinical appearance of ARDS showed the progressive appearance of these deficits beginning 36 h before the hypoxemia was observed. The data are consistent with the concept that ARDS after hemorrhage and trauma is preceded by hypovolemia, reduced myocardial performance, inadequate O2 delivery, and inadequate O2 extraction needed to maintain VO2 at the elevated levels demanded by the increased metabolic requirements of the injured patients. Thus, the so-called shock lung is a complication of shock associated with hypovolemia, hypoxemia, and inadequate cardiac compensatory responses to increasesd O2 demands.

Female↗
PubMed1980

Pathogenesis of respiratory failure (ARDS) after hemorrhage and trauma: II. Cardiorespiratory patterns after development of ARDS.

Hemodynamic and oxygen transport variables were studied in a series of 60 patients who sustained adult respiratory distress syndrome (ARDS) from hemorrhage and trauma; measurements were made during the period of their ARDS and in survivors after their recovery from ARDS. In general, cardiac index (CI) and myocardial performance were increased over normal values; they were greater in trauma patients than in hemorrhage patients and greater in the survivors than in nonsurvivors. The mean pulmonary artery pressure (MPAP) and pulmonary vascular resistance index (PVRI) were high in all groups. Blood volume and hemoglobin (Hgb) concentrations were reduced especially in the nonsurviving hemorrhage patients; hemoglobin saturation (SaO2) and oxygen tension (PaO2) were low initially, but usually responded to therapy; oxygen consumption (VO2) was normal or high in all groups, and was greater in survivors than in nonsurvivors, and greater in trauma than in hemorrhage. Thus, the patient with post-traumatic ARDS has circulatory and metabolic needs which are greater than normal values defined by values from healthy unstressed volunteers and also somewhat greater than hemorrhage and trauma patients without ARDS. Optimal blood volume, hemodynamic and oxygen transport values defined by the survivor's values as well as the standard respiratory care are recommended as goals for preventive or ealy therapy of these patients. Volume therapy should be given provided it does not elevate the pulmonary arterial wedge pressure (WP) above 18 mm Hg to avoid overloading the pulmonary vascular bed and causing pulmonary edema.

Female↗
PubMed1980

Effect of hypercarbia and shock on transcutaneous carbon dioxide at different electrode temperatures.

Transcutaneous CO2 tension (PtcCO2) was measured with heated and nonheated transcutaneous carbon dioxide electrode sensors during hypercarbia and standardized hypovolemic shock in anesthetized dogs. The 95% response times of the PtcCO2 electrode, measured during step increases in FICO2 at four electrode temperatures: 37, 39, 41, and 44 degrees C, were 15, 7.5, 5, and 3.5 min, respectively. During experiments with normal cardiac output, the PtcCO2 correlated well with PaCO2 (r = 0.96). Three PtcCO2 electrode temperatures were tested for response to hypovolemic shock. Data from all PtcCO2 electrodes failed to correlate with PaCO2 during shock. PtcCO2 values rose as cardiac output decreased; there was a good negative correlation (r = -0.95). The 37 and 42 degrees C electrodes were affected by shock at cardiac index values below 2 L/min.M2; but the 44 degrees C probe was not affected until a cardiac index of 1.5 L/min.M2 was reached. Values from the 44 degrees C electrode rapidly returned to preshock values after fluid resuscitation. The response to resuscitation lagged in the 37 and 42 degrees C electrodes and did not return the preshock values until the cardiac index had been normalized for more than 15 min. It was concluded that a PtcCO2 electrode heated to 44 degrees C would be more useful in adult patients because of its faster response to hypercarbia, shock, and resuscitaton. The PtcCO2 values are higher than the corresponding PaCO2 values but they correlate well until the cardiac index (CI) falls below 1.5 L/min.M2; then PtcCO2 values have a strong negative correlation with the corresponding CI values.

Animals↗
PubMed1980

Myocardial performance in critically ill patients: response to whole blood transfusion as a prognostic measure.

The standardized stroke work, which is derived from the left ventricular stroke work (LVSW) and the pulmonary capillary wedge pressure (WP), is presented as a convenient index for tracking changes in the overall cardiac function and relating these changes to other cardiorespiratory variables. This index and its response to whole blood transfusion were used to assess cardiac function in 102 critically ill patients with hemorrhagic or traumatic shock. Survivors had greater mean values of the standardized stroke work before, during, and after transfusion than did the nonsurvivors (p < 0.05). Moreover, the maximal change in standardized stroke work in response to transfusion was greater in survivors than in nonsurvivors (p < 0.05): this response was found to be dependent on the stage of shock. The experience of the authors with this index suggests that it is a useful way to follow changes in myocardial performance in critically ill patients over time, and in quantitating changes in myocardial function after whole blood transfusion or other forms of volume therapy.

Adult↗
PubMed1980

Hemodynamic and oxygen transport effects of a perfluorochemical blood substitute, fluosol-DA (20%).

Cardiorespiratory measurements were made in a severely anemic patient (hemoglobin concentration of 3.5 g/dl) who was preoperatively given the perfluorochemical blood substitute (Fluosol-DA, 20%). Hemodynamic and oxygen transport variables were monitored, including arterial and mixed venous oxygen content (CaO2 and CVO2) before, during, and after infusion of 1000 ml of Fluosol as well as throughout the intraoperative period. Blood samples revealed a maximum of 2.7% of the perfluorochemical. The CaO2 increased 37% above the CaO2 calculated without Fluosol; i.e., 5.8 +/- 0.1 to 8.1 +/- 0.6 ml/dl, p < 0.01. The cardiac index (CI) decreased from 7.2 +/- 0.2 to 5.9 +/- 0.8 L/min . M2 and the left ventricular stroke work decreased from 67 +/- 6 to 58 +/- 13 g . M/M2, while the oxygen delivery increased, and the total body oxygen consumption (VO2) remained essentially unchanged.l Intraoperatively, 27% of the O2 delivery and 51% of the VO2 were transported by Fluosol. No adverse effects of the fluosol were noted.

Adult↗
PubMed1980

Cardiovascular effects of anesthetic induction with ketamine.

Anesthetic induction with ketamine has been reported to maintain or improve cardiovascular performance in severely ill patients. Using invasive cardiovascular monitoring, we studied physiologic responses to a single dose of ketamine in 12 critically ill patients. Six patient demonstrated decreases in ventricular contractility, and four had decreases in cardiac output. Mean arterial blood pressure decreased in four patients. Pulmonary venous admixture increased in four of six patients, while oxygen consumption decreased in eight of 11 patients. Thus, a single dose of ketamine produced decreases in cardiac and pulmonary performance and in peripheral oxygen transport in this group of patients. It is proposed that in severely ill patients, preoperative stress may alter the usual physiologic responses to ketamine administration, and adverse effects may predominate. Ketamine, therefore, should be used with caution for induction of anesthesia in critically ill and in acutely traumatized patients until additional studies and further information on cardiovascular responses to ketamine are available.

Anesthesia↗
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↗