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B D Spiess

Publications and source records attributed to B D Spiess.

At least 37 records · Page 2Linked 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↗

Horseradish peroxidase as a histological indicator of mechanisms of porcine retinal vascular damage and protection with perfluorocarbons after massive air embolism.

BACKGROUND AND PURPOSE: This laboratory has previously shown that a second-generation perfluorocarbon emulsion (PFE) reduces the severity of cerebral injury induced by air embolism during cardiopulmonary bypass (CPB). Horseradish peroxidase examines vascular permeability and was used in this study of the mechanisms of cellular protection afforded by the PFE. METHODS: Twenty domestic pigs underwent CPB with a prime of standard crystalloid or PFE (5 mg/kg) and crystalloid. After 10 minutes on CPB, a 5-mL/kg bolus of room air or saline (control) was delivered via the right carotid artery. The air insult was delivered as either a single bolus or double bolus. After 1 hour of CPB and 1 hour of spontaneous reperfusion, horseradish peroxidase was injected intravenously and circulated for 15 minutes. After euthanasia, both eyes were removed, and the retinas were isolated for histological analysis. RESULTS: Total length of retinal vessels exhibiting horseradish peroxidase extravasation was significantly less in PFE pigs (P < .05). Vascular spasm and red blood cell hemorrhages were unaffected by PFE. PFE pigs exhibited mild to moderate vascular nonperfusion and red blood cell sludging; crystalloid groups demonstrated severe nonperfusion and sludging. CONCLUSIONS: Histological staining with horseradish peroxidase indicated that mechanisms of cerebral air embolism include vascular endothelial leakage, vascular nonperfusion, and red blood cell sludging and hemorrhage. Pretreatment with PFE prevented some sequelae associated with massive air embolism and CPB.

Animals↗

A comparison of thromboelastography with heparinase or protamine sulfate added in vitro during heparinized cardiopulmonary bypass.

Thromboelastography (TEG) has been used after cardiopulmonary bypass (CPB) to diagnose excessive postoperative hemorrhage. Conventional TEG during CPB is not possible due to the sensitivity of the TEG to even small amounts of heparin, which produces a nondiagnostic tracing. The purpose of this study was to compare heparin neutralization using heparinase or protamine in TEG blood samples obtained during CPB. TEG testing was performed on 48 patients before, during and after CPB. Tissue plasminogen activator activity and antigen were measured on a subset of 32 patients. We found: 1) heparinase neutralized at least 10 IU/ml heparin while 1.6 ug/ml protamine neutralized up to 7 IU/ml heparin, 2) in samples with complete heparin neutralization by both methods, there was no significant difference in the R values, 3) while there was good correlation for other TEG parameters between heparinase and protamine treated samples, heparinase treatment produced shorter K values and higher angle, MA and A60, 4) while fibrinolysis was detected using both methods, heparinase treatment suppressed fibrinolysis in the TEG in both samples from patients and after in vitro addition of tissue plasminogen activator, 5) TEG was not a sensitive indicator of t-PA activity, detecting only 21% of samples with increased t-PA activity during bypass, and 5) heparinase was at least 100 times more expensive than protamine. We conclude that while both heparinase and protamine can be used to neutralize heparin in TEG samples obtained during CPB, protamine neutralization is more sensitive to fibrinolysis and less expensive, but the protamine dose must be carefully selected to match the heparin level used at individual institutions.

Adult↗

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↗