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Biomedical subjects

E D Verrier

Publications and source records attributed to E D Verrier.

At least 73 records · Page 4Linked to original sources
PubMed1993

An in vitro protocol for evaluation and comparison of membrane oxygenators.

With the trend in open heart surgery toward normothermic bypass and warm blood cardioplegia, greater demand is being placed on the perfusionist to select an oxygenator that will perform safely and efficiently under a variety of conditions. While manufacturers report performance parameters for their products, the data is often not comparable due to widely differing conditions. Recent in vitro evaluation techniques employed to characterize membrane oxygenators do not simulate the actual oxygenator conditions observed during cardiopulmonary bypass. Biocompatibility and drug delivery are reported but comparisons of different oxygenator performance parameters are not completely addressed. We have designed a test circuit and an evaluation protocol to simultaneously characterize the performance of multiple oxygenators under identical conditions. The test circuit is designed to simulate clinical conditions and to evaluate gas exchange, blood path pressures, gas path pressures, and hemolysis. Previously reported studies have relied on a comparison of a single membrane oxygenator and a single bubble oxygenator. Our protocol will compare multiple membrane oxygenators, in vitro, under similar clinically relevant conditions. Such testing would be done prior to animal or clinical trials. Furthermore in vitro tests should be more reproducible and more discriminating than are ex vivo tests.

Equipment Design↗
PubMed1993

Differential collagen distribution in the mitral valve and its influence on biomechanical behaviour.

Surgical repair of the mitral valve primarily involves endogenous valve tissue, however, the intrinsic mechanical behaviour of the tissue is not well described. To address this issue, porcine mitral valve leaflets were examined histologically and engineering concepts were applied to understand the mechanical behaviour of the layered tissue. Rectangular portions were excised from the anterior and posterior leaflets, either parallel or perpendicular to the annulus, and sections were stained for collagen (Masson's trichrome). The cross sectional layers of the valve (atrialis/spongiosa, fibrosa, and ventricularis) were identified by differences in cellularity and collagen density. The fibrosa is composed of dense collagen, while the atrialis/spongiosa and ventricularis are composed of loose collagen. Layer thicknesses were recorded digitally across the section. These values were averaged within tissue groups to determine changes in layer thickness over the length of the sample and average thickness of each layer. In all tissue groups, the fibrosa was the thickest layer, and the atrialis/spongiosa layer was thicker than the ventricularis layer. The total and fibrosa layer thicknesses of the anterior leaflet were significantly thicker than in the posterior leaflet. Mechanical engineering analysis of the layered structures under tension indicated that the anterior leaflet would be able to support greater tensile loads than the posterior leaflet. The layered arrangement was then examined as a beam in bending, and was shown to decrease the resistance of leaflets to bending, and decrease the overall bending stresses on the leaflet. This type of analysis may be extrapolated to gain insight into changes in function in diseased valves as well.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Finite element analysis of the mitral valve.

A finite element model was developed to examine deformation and stress patterns in the mitral valve under systolic loading conditions. This is the first three-dimensional finite element model of the mitral valve, incorporating all essential anatomic components, regional tissue thickness, collagen fiber orientation and related anisotropic material properties. A non-linear, transient, dynamic analysis was performed which included time-dependent loading, leaflet and chordal mass inertial effects and chordal element bi-linearity. The model was first analyzed without either annular or papillary muscle contraction and then with either or both. The hypothesis was that the combination of annular and papillary muscle contraction would have a beneficial effect on valve function. In all models, the computed anterior leaflet principal stresses were tensile and of greater magnitude than those in the posterior leaflet. The principal stress directions were observed to correlate well with collagen fiber orientation. Earlier leaflet coaptation was demonstrated with annular contraction, promoting valve closure, while papillary muscle contraction increased the stress on the chordae tendineae and both leaflets, tending to pull the latter apart. The combination of the two combined these effects, and showed the most even stress distribution. The effects of annular and papillary muscle contraction on valve function were shown to be beneficial by this model, and they can be further elucidated by varying the extent and timing of the individual contractions. This model can be used to examine the effects of pathologic changes, surgical manipulations and proposed material replacements. It can thus aid both the surgeon and the biomedical engineer in improving the materials and techniques available for the repair and/or replacement of mitral valve system components.

Animals↗
PubMed1993

Infusion of autologous platelet rich plasma does not reduce blood loss and product use after coronary artery bypass. A prospective, randomized, blinded study.

Prior nonblinded studies have suggested dramatic hemostatic effects and decreased plasma after cardiopulmonary bypass. Platelet rich plasma (8 to 10 ml/kg total body weight) was obtained (Haemonetics Plasma Saver; Haemonetics Corp., Natick, Mass.) from 51 patients undergoing primary coronary artery bypass grafting before heparinization. After double-blinded randomization, the platelet rich plasma was reinfused immediately in the control group or after heparin reversal in the treatment group. Homologous blood product usage, blood loss, and the surgeon's intraoperative subjective assessment of coagulation were evaluated. Additionally, thromboelastography, prothrombin time, partial thromboplastin time, activated clotting time, fibrinogen, platelet counts, and hematocrit values were evaluated before the operation, after heparin reversal, after infusion of platelet rich plasma or control solution, and 2 hours after infusion. The surgeon's subjective assessment of coagulation was not different between control and treatment groups (p = 0.78). According to specific predetermined transfusion guidelines, no statistically significant differences were found in the use of whole blood (p = 0.07), packed red blood cells (p = 0.62), platelets (p = 0.11), total units of blood products (p = 0.45), or in the percentage of patients receiving transfusions (control group 70%, treatment group 71%, p = 0.97). Cumulative amount of blood shed through the chest tube was not significantly different between the groups at any interval but tended toward significance at 4, 6, and 12 hours (p = 0.09, 0.07, and 0.09). The prothrombin time immediately after reinfusion of platelet rich plasma was significantly lower in the treatment group (p = 0.03), but all other laboratory studies were similar at each time interval. Infusion of platelet rich plasma after cardiopulmonary bypass in patients having uncomplicated primary coronary artery bypass grafting has minimal effects on the surgeon's assessment of coagulation, total transfusion requirements, mediastinal drainage, and laboratory studies of coagulation.

Aged↗
PubMed1992

Fetal cardiac bypass alters regional blood flows, arterial blood gases, and hemodynamics in sheep.

Successful fetal cardiac bypass might allow prenatal correction of some congenital heart defects. However, previous studies have shown that fetal cardiac bypass may result in impaired fetal gas exchange after bypass. To investigate the etiology of this impairment, we determined whether fetal cardiac bypass causes a redistribution of fetal regional blood flows and, if so, whether a vasodilator (sodium nitroprusside) can prevent this redistribution. We also determined the effects of fetal cardiac bypass with and without nitroprusside on fetal arterial blood gases and hemodynamics. Eighteen fetal sheep were studied in utero under general anesthesia. Seven fetuses underwent bypass without nitroprusside, six underwent bypass with nitroprusside, and five were no-bypass controls. Blood flows were determined using radionuclide-labeled microspheres. After bypass without nitroprusside, placental blood flow decreased by 25-60%, whereas cardiac output increased by 15-25%. Flow to all other fetal organs increased or remained unchanged. Decreased placental blood flow after bypass was accompanied by a fall in PO2 and a rise in PCO2. Nitroprusside improved placental blood flow, cardiac output, and arterial blood gases after bypass. Thus fetal cardiac bypass causes a redistribution of regional blood flow away from the placenta and toward the other fetal organs. Nitroprusside partially prevents this redistribution. Methods of improving placental blood flow in the postbypass period may prove critical to the success of fetal cardiac bypass.

Animals↗
PubMed1992

The safety and efficacy of ten percent pentastarch as a cardiopulmonary bypass priming solution. A randomized clinical trial.

Ten percent pentastarch is a low-molecular-weight hydroxyethyl starch with greater oncotic pressure and shorter intravascular persistence than 6% hetastarch. To evaluate its safety and efficacy as a component of cardiopulmonary bypass priming solution, we prospectively studied 90 patients undergoing coronary artery bypass grafting or valve replacement necessitating cardiopulmonary bypass (bubble oxygenator and moderate systemic hypothermia). Sixty patients were randomized to receive 75 gm of either 10% pentastarch (group P) or 25% albumin (group A), and 30 patients received lactated Ringer's solution alone (group C). Intravascular colloid osmotic pressure during cardiopulmonary bypass was highest with either of the colloid primes (15-minute measurement: group P, 15.7 +/- 2.2 mm Hg (mean +/- standard deviation); group A, 15.2 +/- 2.0 mm Hg; group C, 11.3 +/- 1.7 mm Hg; p less than 0.05, groups P and A compared with group C). This was associated with a lower volume requirement during cardiopulmonary bypass to maintain the venous reservoir (group P, 333 +/- 318 ml; group A, 483 +/- 472 ml; group C, 1332 +/- 1013 ml; p less than 0.05, groups P and A compared with group C). Urine output during cardiopulmonary bypass was similar in each group. Net intraoperative fluid balance was lowest in the colloid groups (groups P and A, 5.7 +/- 1.4 L; group C, 6.9 +/- 1.3 L; p less than 0.05, groups P and A compared with group C). Cardiac index shortly after weaning from cardiopulmonary bypass was greatest in group P (group P, 3.2 +/- 0.9; group A, 2.8 +/- 0.8; group C, 2.7 +/- 0.6 dyne.sec.cm-5; p less than 0.05, group P compared with group C). Changes in alveolar-arterial oxygen gradients, shunt fraction, and effective compliance were similar in all groups. During cardiopulmonary bypass, pentastarch appeared to cause the greatest degree of hemodilution, as suggested by the lowest hemoglobin, factor VII and IX levels and platelet count. The activated partial thromboplastin time was significantly prolonged during and immediately after cardiopulmonary bypass in group P relative to groups A and C (p less than 0.05), although there were no significant differences in the activated clotting time before cardiopulmonary bypass, during cardiopulmonary bypass, or after heparin neutralization. As well, clinical indices of hemostasis, including mediastinal drainage, red cell, platelet, and fresh frozen plasma requirements, and reoperation for excessive postoperative bleeding, were similar. We conclude that pentastarch, when used in cardiopulmonary bypass prime, is as safe as either albumin or Ringer's solution alone.(ABSTRACT TRUNCATED AT 400 WORDS)

Blood Coagulation↗
PubMed1991

Measurement of left ventricular contractility using transesophageal echocardiography in patients undergoing coronary artery bypass grafting. The Study of Perioperative Ischemia (SPI) Research Group.

Optimal assessment of left ventricular function requires the use of load-independent indices of myocardial contractility, which often are difficult to obtain in patients undergoing coronary artery bypass graft (CABG) surgery. We have investigated whether the relation between left ventricular end-systolic stress (ESS) (derived from high-fidelity intraventricular pressure measurements and transesophageal-derived wall thickness) and end-systolic area (ESA) (derived from transesophageal echocardiography [TEE]) could provide a load-independent index of left ventricular function. We studied seven men undergoing coronary revascularization. Multiple data points at varied loading conditions were generated for each patient by infusions of sodium nitroprusside and phenylephrine during the period immediately after induction of general anesthesia and preceding surgical incision. While peak systolic blood pressure was pharmacologically altered between 78 and 204 mm Hg, the correlations between ESS and ESA were excellent for all patients (range r = 0.90 to 0.99). Additionally, the slopes of these relations showed a close correlation to their respective baseline thermodilution cardiac indices (r = 0.85, p = 0.02). Appropriate shifts of the ESS/ESA relationships were documented during postextrasystolic potentiation. The authors conclude that the left ventricular ESS/ESA correlation, derived using TEE and intraventricular pressure measurements, may provide a load-independent index of left ventricular inotropic state in patients undergoing CABG surgery.

Aged↗
PubMed1991

Anterior sternal retraction for reoperative median sternotomy.

The incidence of reoperative median sternotomy for repeat cardiac surgery is increasing. Reoperative median sternotomy is associated with a higher morbidity and mortality than first-time cardiac surgery. A portion of this morbidity and mortality may be due to direct injury to the heart and great vessels in the process of reopening the sternum. We report a new technique utilizing anterior sternal retraction that allows division of adhesions between the undersurface of the sternum and the heart and great vessels under direct vision. This technique enables the surgeon to minimize the risk of serious injury to these underlying structures during reoperative cardiac surgery.

Cardiac Surgical Procedures↗
PubMed1990

Treatment of traumatic rupture of the thoracic aorta. A 15-year experience.

Traumatic rupture of the thoracic aorta is increasing in incidence and remains a highly lethal injury. The morbidity associated with this injury also remains high. We retrospectively reviewed the records of all patients admitted to our emergency department with ruptured thoracic aortas during a 15-year period to determine the reason for this persistently high morbidity and mortality and to identify any factors that might improve the outcome. We found that patients who are in unstable condition on arrival in the emergency department or who become unstable before reaching the operating room are not likely to survive. Patients who are injured in automobile accidents have a greater chance of survival than do those injured in motorcycle accidents or car-pedestrian accidents. Patients who are in hemodynamically stable condition after aortic injury survive only if diagnosis and treatment are prompt. Major complications of repair following thoracic aortic injury relate primarily to the length of cross-clamp time, and every effort should be devoted to keeping the cross-clamp time less than 30 minutes.

Adult↗
PubMed1990

Reduced-size lung transplantation in neonatal swine: technique and short-term physiological response.

Lung transplantation is now a clinical reality in adults but is limited by the scarcity of appropriate donors. The donor shortage is even more acute for neonatal and pediatric patients. Reduced-size lung grafts would expand the pool of appropriate cadaveric donors and allow HLA-matched living related lobar or segmental lung transplants. To evaluate this experimentally, we developed a model of pulmonary lobar transplantation in neonatal pigs and studied the acute hemodynamic response after transplanting the left lower lobe from a more mature donor to a neonatal recipient. Technical considerations included using the recipient atrial appendage for the pulmonary venous anastomosis. Nine pairs of pigs underwent left lateral thoracotomy. The recipient left atrial and pulmonary arterial pressures, cardiac output, and pulmonary vascular resistance were measured before pneumonectomy and after left lower lobe transplantation. Although the left atrial and pulmonary arterial pressures remained unchanged after transplantation, there was a 15% increase in pulmonary vascular resistance and a 23% reduction in cardiac output. Neither change was statistically significant. The distribution of blood flow through the left and right pulmonary arteries was unchanged after transplantation. We conclude that lobar transplantation is technically feasible in immature animals and that the pulmonary venous anastomosis to the left atrial appendage facilitates the procedure. This model may prove useful in studying lung transplantation in immature recipients and expedite implementation of reduced-size lung transplantation in neonatal and pediatric patients.

Anastomosis, Surgical↗
PubMed1990

Pulmonary vascular resistance in neonatal swine: response to right pulmonary artery occlusion, isoproterenol, and prostaglandin E1.

The pulmonary physiological response of adults to unilateral pulmonary artery (PA) occlusion has been well-characterized as resulting in a decrease in the pulmonary vascular resistance (PVR), in order to maintain the same PA pressure and accommodate the entire cardiac output (CO). We evaluated the response of the neonate to unilateral PA occlusion and how this response is altered by infusions of Isoproterenol (Isuprel) and prostaglandin E1 (PGE1) in the neonatal swine model. Twenty farm piglets (five at 1 day, three at 5 days, seven at 14 days, and five at 60 days as controls) underwent left lateral thoracotomy and measurement of PA and left atrial (LA) pressures, CO, and PVR with the right PA open and occluded. To determine if neonatal PVR could be influenced by a vasodilator (indicating the vascular capacity is not fixed) or by an inotrope (indicating the lung is not maximally recruited) this experiment was then repeated with infusions of PGE1 (a vasodilator) at doses of 0.1, 0.5, and 1.0 micrograms/kg/min and subsequently with Isuprel (an inotrope and vasodilator) at doses of 0.1, 0.5, 1.0 micrograms/kg/min. Control measurements taken without unilateral PA occlusion showed that PVR is high at 1 day of age but progressively decreases to a level 89% lower by 60 days of age. The vascular capacity of the neonatal lung is fixed and responds to unilateral PA occlusion with a dramatic increase in PVR. This response cannot be altered by either a vasodilator (PGE1) or an inotrope (Isuprel) thereby limiting the utility of these drugs in treating neonatal pulmonary hypertension.(ABSTRACT TRUNCATED AT 250 WORDS)

Alprostadil↗
PubMed1990

Complete heart block in fetal lambs. I. Technique and acute physiological response.

Prenatally diagnosed complete heart block (CHB), without associated cardiac anomalies, is often refractory to attempts to increase heart rate and cardiac output by medical therapy, and results in fetal death. We developed a model of CHB in fetal lambs in order to evaluate the acute physiological consequences of CHB and to assess the feasibility of fetal cardiac ventricular (V) and atrioventricular (AV) pacing. After hysterotomy and fetal sternotomy AV-sequential pacing leads were placed on the right atrium and ventricle (RV). Electromagnetic flow transducers were placed around the pulmonary artery and the ascending aorta to measure combined ventricular output (CVO) in normal sinus rhythm (NSR), CHB, AV, and V pacing. CHB block was successfully induced in 19 of 21 (90%) fetal lambs at 100 to 110 days' gestation by injection of formalin into the interventricular septum. Two fetuses were refractory to CHB despite multiple injections. The mean ventricular escape rate was 52 +/- 3 (+/- SEM) beats/min (range, 45 to 60 beats/min). CHB lasted for the period of study (1 to 8 hours), and spontaneously reverted to NSR in one fetus after 3 hours. Combined ventricular output in NSR was 470 +/- 31 mL/min (+/- SEM), which fell to 213 +/- 13 mL/min in CHB, 45% of normal CVO (P less than .0001). CVO during AV-sequential and V pacing was 77% (P = .02) and 62% (P less than .001), respectively, of combined ventricular output in NSR. Both RV (27%) and left ventricles (LV) (37%) showed compensatory increase in stroke volume during CHB.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Etiology of intestinal damage in gastroschisis, II. Timing and reversibility of histological changes, mucosal function, and contractility.

Previous work in the fetal lamb examined the relative effects of amniotic fluid and bowel constriction in the etiology of bowel damage in gastroschisis. The present study used the same model to assess the timing and reversibility of these changes during gestation. Gastroschisis was created at 80 days' gestation, and a tape was placed around the bowel to cause gradual constriction with growth. Lambs were killed at 100 days, 120 days, and term. Bowel damage was assessed using histology, mucosal enzyme activity, and in vitro motility. In an additional "repaired" group, the constrictor was removed at 120 days, a silastic pouch placed over the bowel, and bowel damage assessed at term. Normal fetuses at each gestational age were used as controls. A fibrous peel was observed at all gestational ages. Mucosal villous atrophy and mesenteric venous and lymphatic dilation were mild at 100 and 120 days, but severe at term. These changes were present but mild in repaired animals at term. Mucosal enzyme activity decreased gradually with gestational age; inhibition of maltase activity was maximal at term, and was significantly reversed by repair, whereas inhibition of aminooligopeptidase activity was maximal at 120 days, and was not affected by repair. Protein/DNA, DNA/weight, and protein/weight ratios showed that repaired mucosal cells were significantly more proliferative, smaller, and less mature than control or gastroschisis cells. In vitro motility studies demonstrated a mild decrease in contractility at 100 and 120 days, and a large decrease at term. This deleterious effect at the end of gestation was only partially reversed by repair in utero.(ABSTRACT TRUNCATED AT 250 WORDS)

Abdominal Muscles↗
PubMed1990

Rapid diagnosis of thoracic aortic transection using intravenous digital subtraction angiography.

Rupture of the thoracic aorta associated with blunt trauma remains a frequently lethal injury. Although increasing numbers of patients with ruptured aortas are surviving to reach the hospital, the in-hospital mortality attending this injury remains high. Death due to transected aorta has been related to a delay in diagnosis. In an attempt to decrease the time necessary for diagnosis of this injury, we studied 50 patients using intravenous digital subtraction angiography (IVDSA) and conventional biplane angiography. We found that IVDSA was significantly faster than conventional biplane angiography, and that when IVDSA films are of diagnostic quality, they are sufficient to reliably demonstrate the presence of traumatic aortic transection. Our study was too small to establish whether IVDSA is a sufficiently sensitive test to exclude aortic injury. Further studies in this area need to be performed.

Angiography, Digital Subtraction↗
PubMed1990

Pulmonary lobar transplantation in neonatal swine: a model for treatment of congenital diaphragmatic hernia.

Congenital diaphragmatic hernia (CDH) babies born with severe pulmonary hypoplasia are unsalvageable despite maximal therapy including extracorporeal membrane oxygenation (ECMO). Lung transplantation is a potential treatment for these otherwise doomed infants using ECMO as a bridge to transplantation. Cadaveric, or living related donation of a more mature reduced size lung (pulmonary lobe or segment) may help solve the critical donor shortage problem. We evaluated the physiological response of mature left lower lobe (LLL) transplants in neonatal swine with the hemodynamic conditions of CDH simulated by occlusion of the right pulmonary artery (PA), and also studied the pulmonary function of the mature lobar graft compared with the neonatal lung. LLL transplantation was well tolerated and resulted in minimal alteration in hemodynamic parameters. The response to right PA occlusion was similar pre- and posttransplantation with a fall in cardiac output and a significant rise in pulmonary vascular resistance. Compared with the contralateral native lung, the lobar graft was preferentially ventilated with resultant higher pH (7.65 +/- 0.17 v 7.41 +/- 0.08, P less than .01) and lower pCO2 (17 +/- 6 v 36 +/- 5, P less than .001). The more mature lobar graft was preferentially ventilated due to the increased compliance compared with the neonatal right lung (8.16 +/- 1.28 v 5.48 +/- 0.82 mL/cm, P less than .0001). Reduced size lung transplantation is technically feasible and may help solve the donor problem for severe CDH neonates for whom no effective therapy is currently available.

Animals↗
PubMed1989

Esophageal perforation.

Sixty-nine patients with perforation of the esophagus were treated at the University of California, San Francisco, from 1977 to 1988. The perforation was iatrogenic in 33 (48%) of the patients, spontaneous in 8 (12%), and a result of external trauma in 23 (33%). Clinical findings included chest pain in 36 (52%) of 69 patients, subcutaneous emphysema in 22 (32%) of 59 patients, and pneumomediastinum in 21 (36%) of 59 patients. Esophagograms demonstrated the perforation in 40 (93%) of 43 patients. Treatment delays of more than 24 hours occurred in about half of spontaneous and iatrogenic perforations, but when the perforation was due to external trauma, treatment was delayed infrequently. Operative therapy in 59 (86%) of the patients included primary closure in 44 patients, drainage alone in 9 patients, and Celestin tube placement in 1 patient. Four patients with benign strictures had esophagectomy, and 4 patients with achalasia had Heller myotomy in addition to closure of the perforation. Eight (12%) of the patients were treated nonoperatively. For thoracic perforations, nonoperative treatment was reserved for patients who were diagnosed late but who had minimal evidence of sepsis. Seven (10%) of the patients died. Factors that influenced outcome included cause of perforation, anatomic location, and patient age. Our study shows that a high index of suspicion, aggressive use of esophagography, and individualized treatment are necessary for the best results when treating esophageal perforation.

Adolescent↗
PubMed1989

Systemic-to-pulmonary artery shunt using the internal mammary artery.

Systemic-to-pulmonary artery shunts may be useful for palliation of cyanotic congenital heart disease. We report the case of a 5-year-old boy in whom the internal mammary artery was used to create a systemic-to-pulmonary artery shunt after failure of a previous Blalock-Taussig shunt. This technique may have distinct advantages in selected cases and should be considered as an alternative during investigation of the older child who requires a systemic-to-pulmonary artery shunt.

Anastomosis, Surgical↗