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B D Spiess

Publications and source records attributed to B D Spiess.

At least 19 recordsLinked to original sources

Perfluorocarbon emulsion in the cardiopulmonary bypass prime reduces neurologic injury.

BACKGROUND: Perfluorocarbon emulsion has proved beneficial in the prevention and amelioration of experimental air embolism. We examined whether the addition of perfluorocarbon to the prime solution could lead to a reduction in the incidence and severity of neurologic injury after the formation of a massive air embolism during cardiopulmonary bypass. METHODS: Fourteen pigs underwent bypass in which either a crystalloid prime solution or a perfluorocarbon prime solution (10 mL/kg) was used. Ten minutes into bypass a bolus (5 mL/kg) of air or saline (control) was delivered via the carotid artery. The resulting cerebral infarcts were graded on the basis of the findings in triphenyltetrazolium chloride-stained cerebral sections. Colored microspheres were used to measure cerebral blood flow. Bitemporal electroencephalography was used to evaluate cerebral function. RESULTS: Cerebral infarction was not found in the perfluorocarbon-air group (0 to 5 animals), as compared with its occurrence in 3 of the 5 animals in the crystalloid-air group. Cerebral blood flow was also maintained or increased in the perfluorocarbon-air group (p < 0.05), and the electroencephalogram total power showed less of a decrease and recovered more completely (p < 0.05) than it did in the crystalloid-air group. CONCLUSIONS: The addition of perfluorocarbon emulsion to the cardiopulmonary bypass prime solution leads to a reduction in the incidence and severity of neurologic injury after the formation of a massive air embolism during bypass.

Animals

Endothelial cell injury in cardiovascular surgery: the procoagulant response.

The vascular endothelium plays a critical role in the regulation of coagulation through the constitutive expression and release of anticoagulants and the inducible expression of procoagulant substances. Cardiopulmonary bypass dysregulates this process by activating endothelial cells, initially promoting bleeding and then thrombosis. Endothelial cell activation in response to circulating inflammatory mediators leads to the initiation of coagulation when tissue factor is expressed throughout the intravascular space. This results in the widespread consumption of coagulation factors. Additionally, there is a cardiopulmonary bypass-related qualitative platelet defect that is exacerbated by thrombocytopenia as platelets are consumed from the circulation by clot and adherence to the cardiopulmonary bypass circuit. Finally, cardiopulmonary bypass results in the endothelial release of plasminogen activators, which lead to an increase in systemic fibrinolysis. The diffuse generation of thrombin, driven by the inducible intravascular expression of tissue factor, plays a major role in all of these processes. Efforts to understand the critical role of the endothelium in coagulation may lead to novel therapies to prevent bleeding or thrombosis in cardiovascular surgery patients.

Blood Coagulation

The agreement between ventricular volumes and ejection fraction by transesophageal echocardiography or a combined radionuclear and thermodilution technique in patients after coronary artery surgery.

OBJECTIVES: To study the reproducibility of and agreement between perioperative transesophageal echocardiographic (TEE) and radionuclide (RN) assessment of ventricular volumes and ejection fraction (EF). DESIGN: A prospective, blinded comparison of two methods of measurement. SETTING: A surgical intensive care unit in a university hospital. PARTICIPANTS: Patients after coronary artery bypass surgery. INTERVENTIONS: Left ventricular volumes and ejection fraction were simultaneously measured by radionuclide ventriculography and transesophageal echocardiography. Two sets of measurements were made in rapid succession with a third set after an interval. RESULTS: Reproducibilities of EF and ventricular volumes by TEE and RN were similar. At each set of measurements, the bias for radionuclide EF and TEE Simpson's rule EF, 0.03 +/- 0.05, 0 +/- 0.06, -0.01 +/- 0.07, respectively, for radionuclide EF and TEE area length EF 0.01 +/- 0.05, -0.01 +/- 0.05, -0.03 +/- 0.08, respectively, were significantly less than for radionuclide EF and TEE FAC 0.07 +/- 0.05, 0.05 +/- 0.05, 0.03 +/- 0.09. Poor agreement was observed between RNTD-EDV, and both of the TEE EDV measurements. CONCLUSION: EF measured by TEE area length and Simpson's rule method are as reproducible as TEE FAC and are more accurate estimates of RN EF. Poor agreement between methods of measuring end-diastolic volume was observed.

Aged

Perfluorocarbon emulsions and cardiopulmonary bypass: a technique for the future.

Artificial blood has been sought for a considerable period of time and two major lines of research have led to FDA testing of some possible compounds. The two major types of compounds are polymerized hemoglobin moieties and perfluorocarbon emulsions (PFC). Polymerized hemoglobin preparations have the ability to carry oxygen and release it in a manner similar to the oxyhemoglobin dissociation curve of whole blood. PFCs carry oxygen, nitrogen and carbon dioxide, as well as all other non-polar gases, by enhanced chemical solubility. Therefore, all dissolved gases are available for metabolic utilization and no sinusoidal release curve of oxygen is encountered. Early PFC emulsions had problems with toxicity of the emulsifier and were difficult to get into their emulsion for infusion. Furthermore they were very dilute in the active ingredient for gas transport. Today there are second generation PFCs becoming available that have a 40% concentration of the PFC and therefore the potential for gas transport is greatly increased. The PFC emulsions have a very small size, 0.1 microns, so the surface for gas exchange is massively increased as well as the potential increased for perfusion into areas of potentially sludged erythrocytes. Work with the PFCs has shown them now to be able to carry adequate oxygen to work as blood substitutes. They have shown protection from air embolism in a number of animal and end-organ models. What makes the PFCs unique is their ability to carry/absorb nitrogen and therefore protect from gas embolization. There are data in animal models showing significant cerebral protection in cardiopulmonary bypass models. The new PFCs should sometime in the not-too-distant future be tested in human bypass with assessments of neuropsychiatric dysfunction and stroke.

Animals

Ischemia--a coagulation problem?

The causes of perioperative ischemia and myocardial infarction (MI) in coronary artery bypass graft (CABG) patients are almost certainly multifactorial, although not well understood. Ultimately, outcome after CABG is dependent on myocardial preservation and prevention of further myocardial ischemia. The largest number of ST-T-wave events come immediately after protamine is given, suggesting that re-establishment of coagulation function after cardiopulmonary bypass (CPB) may be an important event. CPB induces an inflammatory state that involves platelet-endothelial-cell interactions and vasospastic responses that result in low flow states in the coronary vasculature. The fibrinolytic system is activated during CPB, with raised tissue plasminogen activator (tPA) levels and related falls in plasminogen activator inhibitor (PAI-1). PAI-1 levels rise during the postoperative period. There is a huge variability in human response. However, the patients with the highest tPA surge are not the same patients who have the highest PAI surge. It could be postulated that patients with high PAI-1 levels are at highest risk for early ischemia. New data just being evaluated from the Multicenter Study of Perioperative Ischemia (McSPI) Research Groups' database in San Francisco may support the hypothesis that coagulation influences perioperative ischemia. The study of approximately 2,400 patients undergoing CABG surgery at 24 major institutions in the United States revealed that intensive care unit (ICU) entry hematocrit was significantly related to the risk for postoperative MI. Patients entering the ICU with hematocrits below 24% had the lowest MI rate (3.7%), whereas those with hematocrits greater than 34% had the highest rate (8.1%). Patients with ICU entry hematocrits below 18% had a zero incidence of perioperative MI. One possible explanation for these findings is that platelets are involved. As red cells stream down vessels, they marginate the smaller formed elements of the blood. As hematocrit is increased, the number of platelets moved to the outer sides of the vessels increases. Therefore, the number of endothelial-platelet interactions would increase over time with higher hematocrits.

Blood Coagulation

Changes in transfusion therapy and reexploration rate after institution of a blood management program in cardiac surgical patients.

A retrospective study was performed to determine the impact of a coagulation and transfusion management program on blood utilization in 1,079 sequential patients for myocardial revascularization and open ventricle or combined procedures. Four hundred and eighty-eight patients (group 1) before, and 591 patients (group 2) after institution of thromboelastography (TEG)-guided coagulation were studied and compared for transfusion requirements, donor exposure, and the incidence of reoperation for hemorrhage. Group 2 patients had a significantly lower incidence of overall transfusion (78.5% v 86.3%) during hospitalization and in total transfusion in the operating room (57.9% v 66.4%). The incidence of each transfusion subtype was also significantly lower in group 2 patients. Actual total median donor exposure was 8 in group 1 patients and 6 exposures in group 2 patients. Mediastinal reexploration for hemorrhage was 5.7% before institution of TEG-based coagulation monitoring and 1.5% in TEG-monitored patients. Use of TEG monitoring before reexploration has decreased the cost and potential risk for patients undergoing CABG surgery.

Blood Coagulation

Perfluorocarbon emulsions: one approach to intravenous artificial respiratory gas transport.

The PFC emulsions have had a developmental history of promise as yet unfulfilled. Today, second-generation PFC emulsions are poised with the right gas-carrying capabilities to be able to make significant contributions to oxygen transport and delivery. The dream of stable, safe, easily transportable intravenous fluid, with universal rapid application is not yet at hand. However, we appear to be a great deal closer than in the mid 1980s. If these 40% volume-to-volume emulsions prove safe, then an entirely new realm of therapeutic options will become available. Not only will the uses for trauma and acute blood loss replacement become a reality, but extremes of euvolemic hemodilution may become possible. The use of these compounds for prevention of stroke, ischemic organ salvage, and prevention of air embolism or decompression sickness are particularly exciting. It is clear from the recent developments in PFC technology that some product will come to market in the not-too-distant future. How such a PFC will be utilized as compared with hemoglobin preparations is yet to be discerned, but the two concepts are quite different. Each will have its own specific indications.

Animals

Thromboelastography and cardiopulmonary bypass.

The TEG tracks postoperative hemorrhage after CPB and is useful in guiding therapy. Its ability to characterize the overall interaction of all procoagulant participants in a final outcome (clot strength) is unique. Much work in the future is needed to establish the particular applications for TEG monitoring in CPB patients

Adult

Cardiac anesthesia risk management. Hemorrhage, coagulation, and transfusion: a risk-benefit analysis.

Transfusion risks include the possibility of ABO/Rh incompatibility, sepsis, febrile reactions, immunosuppression, and viral transmission; incidences and consequences of these complications are reviewed. Predonation of autologous blood generally reduces the need for homologous blood by about 30% to 40%, but relatively few coronary artery bypass surgery (CABG) patients predonate blood. Drug products to decrease blood use include 1-deamino-8-D-arginine vasopressin (DDAVP), tranexamic acid, epsilon-aminocaproic acid, and aprotinin. A recent study suggests that a subgroup of patients with abnormal platelet function may benefit from a platelet therapy such as DDAVP. The prophylactic use of tranexamic acid reduces cardiac surgery postoperative blood loss, as measured by chest-tube output, by about 30%; unfortunately, data demonstrating a reduction in transfusion requirements are not available. Aprotinin use is associated with major reductions in blood transfusion requirements. Aprotinin provides platelet protection during cardiopulmonary bypass. Duration of stay in the intensive care unit was not increased by use of aprotinin, thus alleviating some concerns that aprotinin might promote coronary thrombosis. A recent report cites early graft closure as a major concern with aprotinin therapy, but data from other studies show no significant differences in rates of graft closure between patients receiving and those not receiving aprotinin. Routine use of a thromboelastogram with all cardiopulmonary bypass surgery at the University of Washington Hospital has reduced use of blood products by 30%.

Blood Coagulation Disorders

Pulmonary artery and noninvasive hemodynamics during lung lavage in primary alveolar proteinosis.

Noninvasive hemodynamic monitoring by bioimpedance has been compared to cardiac output measured by thermodilution. The technology of bioimpedance does allow for monitoring of static thoracic impedance, a measurement thought to be affected by extravascular lung water. No contemporary studies (in the last 20 years) have examined the effectiveness of that parameter in measuring changes in lung water. This case report notes hemodynamics and examines thoracic impedance in a patient undergoing unilateral lung lavage. The hemodynamic data measured by bioimpedance and thermodilution correlated well (r = 0.97 for cardiac output). The changes in static impedance were compared to thoracic compliance during infusion of saline solution and evacuation. The changes in both parameters followed each other closely. Further work is required in patients with pulmonary edema or effusions before bioimpedance can be used to monitor such clinical events.

Adult

Bioimpedance hemodynamics compared to pulmonary artery catheter monitoring during orthotopic liver transplantation.

Simultaneous cardiac output measurements were obtained using bioimpedance (BI) and thermodilution (TD) methods in 10 patients undergoing orthotopic liver transplantation (OLT). BI and TD data were collected during five intraoperative phases of OLT. Linear regression revealed significant correlation between BI and TD (r = 0.8, P = 0.001) with a slope of regression of 0.64. Bias analysis demonstrated a negative of BI (-0.26) when compared with TD.Sv-O2 correlated poorly with cardiac index determined by TD (r = 0.41) or BI (r = .47). BI is an accurate reproducible method for measuring cardiac output and may be a useful adjunct to the pulmonary artery catheter for hemodynamic monitoring during OLT.

Adult

Oxygen consumption and mixed venous oxygen saturation monitoring during orthotopic liver transplantation.

Mixed venous oxygen saturation (SvO2) monitoring has been advocated for some critically ill patients. Patients with end-stage hepatic failure have oxygen consumption rates that are lower than normal. Using the Fick equation, oxygen consumption may be calculated if mixed venous and arterial oxygen tensions (and saturations), hemoglobin, and cardiac output are determined simultaneously. This report describes a unique pattern of changes in SvO2 and oxygen consumption in 7 patients undergoing liver transplantation. A previous study correlated plasma carbohydrate (glucose) levels with early hepatic graft survival. After induction, the 7 patients reported here had low oxygen consumption and high SvO2 values. The oxygen consumption rates decreased to the lowest point during the anhepatic phase and rose above baseline by the end of the case. The SvO2 and oxygen consumption data reported here follow the presence of presumed hepatic metabolic activity (increased CO2 and ionized calcium). Further research must be completed to determine whether these measurements indicate early hepatic nonfunction.

Adult