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Biomedical subjects

E J Guilbeau

Publications and source records attributed to E J Guilbeau.

15 recordsLinked to original sources
PubMed1990

Thermoelectric enzyme sensor for measuring blood glucose.

A new calorimetric sensor has been developed which employs a thin-film thermopile in association with an immobilized enzyme. The thermopile detects the minute temperature rise that occurs when a specific chemical substrate is catalyzed by the enzyme. A prototype sensor is described which generates an equivalent proportional voltage response to glucose concentrations present in either buffer solution or blood. These sensors have remained useful for up to 18 days when operated intermittently for measuring glucose in buffer solutions, or for up to 4 days when operated continuously. When implanted inside cardiovascular shunts on anesthetized dogs, the sensors responded appropriately to changes in the blood glucose concentration.

Animals↗
PubMed1987

Perioperative right heart failure: etiology and pathophysiology.

A considerable amount of literature has been devoted to compromise of the right ventricle in spontaneous myocardial infarction. Little information is available regarding disproportionate dysfunction of the right ventricle associated with cardiac operation and the recovery period therefrom. Recognition of the problem is of paramount importance, if support measures are to be implemented. A great deal has yet to be learned regarding the appropriate support for the acutely failing right ventricle. Much remains to be accomplished regarding the assessment of right ventricle reserve, defining the role of risk factors, and quantitating the value of measures to optimally protect the right ventricle from injury during the perioperative period. Recognizing that the integrity of the right ventricle can be altered by numerous preoperative, perioperative and postoperative factors will provide an enlightened disposition on the part of the surgical team. Awareness of these considerations in the planning and conduct of surgical procedures should reduce morbidity and mortality from perioperative right ventricular failure. The imposition of new or unexpected morbidity during operation on a relatively unrelated problem represents surgical imperfection. Appropriate effort toward minimizing insult of the right ventricle could result in significantly decreasing the incidence and severity of perioperative right ventricular failure before the impetus of the continuing clinical problem dictates improvement in techniques to more appropriately treat this frequently preventable problem.

Coronary Disease↗
PubMed1985

Acute right ventricular failure is caused by inadequate right ventricular hypothermia.

The hypothesis of this study was that inadequate right ventricular hypothermia contributes to the right ventricular dysfunction occasionally observed after cardiac operations. Dogs were placed on cardiopulmonary bypass, and 60 minute periods of hypothermic myocardial ischemia were imposed. Left ventricular temperature was always maintained at 15 degrees C and right ventricular temperatures were maintained at 15 degrees C (Group I, n = 8), 25 degrees C (Group II, n = 8), and 35 degrees C (Group III, n = 8). These temperatures were produced by infusion of hypothermic crystalloid cardioplegic solution and appropriate topical cooling and heating of the left and right ventricles, respectively. Multiple indices of ventricular function were obtained 15, 30, 45, and 60 minutes after bypass and compared to prebypass control values. In all Group I animals (left ventricular temperature = 15 degrees C, right ventricular temperature = 15 degrees C), postischemic indices of right ventricular function were not different from control values (p = NS). In Group II (left ventricular temperature = 15 degrees C, right ventricular temperature = 25 degrees C), two animals died 30 and 45 minutes after bypass, respectively, of right ventricular failure. In the other six animals in Group II, all indices of right ventricular function were significantly reduced (p less than 0.05) except for right ventricular systolic pressure. In Group III (left ventricular temperature = 15 degrees C, right ventricular temperature = 35 degrees C), two animals could not be weaned from cardiopulmonary bypass because of right ventricular akinesia. Six animals were weaned from bypass, but two died 15 minutes, one died 30 minutes, and one 45 minutes after bypass. Two animals lived 60 minutes, but all indices of right ventricular function were decreased. Failure to maintain right ventricular temperatures below 25 degrees C during 1 hour of cardiac ischemia in the dog can result in fatal right ventricular failure.

Animals↗
PubMed1976

Experimental and theoretical analysis of oxygen transport in fetal brain.

Based on the results obtained in this study and the results of others it seems safe to conclude the following: 1) Fetal brain PO2 values are considerably lower than those found in adult brain. 2) Administration of 100% oxygen to the mother can (but not always) significantly raise the PO2 at a specific point in the fetal cortex. 3) The response of fetal brain PO2 to changes in maternal arterial PO2 is delayed by a finite quantity of time of the order of magnitude of 38 seconds. 4) The time required for the fetal brain PO2 to reach a minimum following a decrease in the PO2 of maternal arterial blood coincides closely with the time required for the maternal arterial PO2 to reach its minimum plus the pure transport delay time (38 seconds). 5) The fetus has available a control mechanism which acts to compensate for periods of reduced PO2 in the microenvironment of the fetal cortex.

Animals↗
PubMedDate not supplied

Total pericardial replacement. Design and preliminary evaluation in greyhounds.

Existing pericardial substitutes, used for the prevention of pericardial and pleural adhesions to the epicardium, are in the form of a patch. To improve on this concept, an elastic, anatomically correct, implantable sac has been developed for total pericardial replacement. Total pericardial substitutes fabricated from Silastic silicone rubber and Mitrathane polyetherurethane urea were implanted in greyhound dogs and harvested at 8 weeks. Pericardial adhesions were prevented by the substitutes that remained intact. Fibrous tissue formation had occurred on the epicardium underlying the substitutes, the extent being more severe in response to the Silastic compared with the Mitrathane. However, the Silastic was superior to the Mitrathane in retention of its tensile strength and elastic modulus over the implant period (p less than 0.05). Further development of total pericardial substitutes from different materials shows promise.

Animals↗
PubMedDate not supplied

Performance of a hydrogel composite pericardial substitute after long-term implant studies.

A novel composite patch has been tested as a pericardial substitute to reduce adhesion formation after cardiac surgery. The patch consists of poly 2-hydroxyethyl methacrylate (pHEMA) hydrogel reinforced with a polyethylene terephthalate (PET) mesh. The hydrogel-PET composite pericardial patches were implanted in canines for 6, 9, and 12 months. Upon termination, adhesion formation and epicardial reaction to the implant were rated. No adhesions formed between the patch and the native pericardium or epicardium. A thin fibrous layer on the epicardium progressively developed where the patch contacted the heart. The coronary anatomy remained visible. Histologically, the response to the implant was fibrous in nature. No significant signs of cellular inflammation were found. The gross appearance of the retrieved patches was nearly identical to that of preimplant patches. Mechanical tests showed no significant changes (alpha = 0.05) in patch strength or stiffness. Hydrogel water content initially increased during implantation. The thickness of the patch did not change significantly (alpha = 0.05) throughout the study. Scanning electron microscopy (SEM) revealed unequal layers of hydrogel on either side of the PET mesh and cracks in the hydrogel surfaces of retrieved patches. Both SEM and light microscopic observation of the patches showed traces of calcification in patches in the 9 and 12 month studies.

Animals↗
PubMedDate not supplied

In vivo results of hydrogel composite pericardial substitutes.

In this study, two improved pericardial patches were developed and evaluated for their efficacy as pericardial substitutes. The patches are composites consisting of a hydrogel (PHEMA) that coats an underlying mesh (either ETFE or PET). Studies were conducted using subcutaneous implants in rats and pericardial patch implants in greyhound dogs. Adhesions between the substitute and pericardium and the epicardium were minimal. The ETFE composite patch caused an unacceptable epicardial reaction. The PET patch results were encouraging; the epicardium was largely unaffected by the patch.

Animals↗
PubMedDate not supplied

A hydrogel pericardial patch.

Patients undergoing repeat cardiac operations are higher operative risks than those undergoing an initial cardiac procedure because adhesion formation can occur if the native pericardium is not closed. A unique composite patch that may be used to augment the pericardial tissue when primary closure is not possible has been developed. The patch is made of a hydrogel, poly (2-hydroxyethyl methacrylate), reinforced with an ethylene tetrafluoroethylene (ETFE) mesh. The mesh provides the needed mechanical properties, whereas the patch's surface properties are comparable to the hydrogel. Two types of patches were fabricated: one with the mesh weave at a perpendicular orientation and one at 45 degrees to the principle loading direction. The patches were mechanically tested and compared with canine pericardium. Ultimate tensile strength of the patches is not significantly different from canine pericardium (p less than 0.05), are the patch suture strength is nearly twice that of canine pericardium. The perpendicular patch is stiffer than canine pericardium, whereas the 45 degree patch is not (p less than 0.05). The 45 degree patch shows considerable promise as a pericardial substitute because it closely matches the properties native canine pericardium.

Animals↗