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Biomedical subjects

C E Bredenberg

Publications and source records attributed to C E Bredenberg.

At least 55 records · Page 3Linked to original sources
PubMed1983

Effect of positive end-expiratory pressure on lung water in pulmonary edema caused by increased membrane permeability.

Pulmonary edema caused by increased membrane permeability was created in dogs by alloxan and infusion of saline solution. Pulmonary extravascular water volume was measured gravimetrically using the supernatant hemoglobin concentration to estimate red cell mass in the calculation of residual pulmonary blood volume. Three groups were studied for two hours: a control group, a group given alloxan and mechanical ventilation without positive end-expiratory pressure (PEEP), and a group given alloxan and mechanical ventilation with 10 cm H2O of PEEP. After two hours, alloxan caused moderately severe pulmonary edema in the two experimental groups, but PEEP had no effect on the accumulation of pulmonary extravascular water volume. No sustained differences in pulmonary or systemic hemodynamics were present throughout two hours of pulmonary edema. The pulmonary shunt was increased in the group without PEEP but was similar in the control group and the group with PEEP. No significant changes in alveolar dead space were noted among the three groups.

Alloxan↗
PubMed1983

Relation of portal hemodynamics to cardiac output during mechanical ventilation with PEEP.

The relation of portal hemodynamics to cardiac output (CO) during mechanical ventilation with 15 cm H2O PEEP was studied in 12 dogs under pentobarbital anesthesia. Cardiac output was measured by thermal dilution. Portal vein flow (PF) and superior mesenteric artery flow (SMAF) were measured by electromagnetic flow probes. Intraesophageal, intraabdominal, portal vein (PVP) and intrathoracic caval (CVP) pressures, as well as the intraluminal venous pressure gradient across the liver (PVP-CVP) were measured. Intravascular volume was expanded with dextran prior to the addition of PEEP. In nine animals, dextran plus PEEP maintained CO and visceral flows within 3% of control. In three animals, CO and visceral flows fell to the same proportion. There was no increase in hepatic resistance. PF showed a linear correlation with SMAF, and SMAF had a linear correlation with CO. In these experiments, the effect of PEEP on portal hemodynamics system is primarily the consequence of reduced CO.

Animals↗
PubMed1981

Mechanisms of arterial injuries associated with total hip replacement.

Five cases of arterial complications of total hip replacement, all of which can be explained on the basis of intraoperative injury, are reported, with diagrammatic analysis of the intraoperative mechanisms of injury involved. The injuries were manifested as hemorrhage, ischemia, or development of a pulsatile mass. Vascular structures affected include the external iliac, common femoral, medial femoral circumflex, and lateral femoral circumflex arteries. Arterial damage may result from retractor injury, thermal injury from methylmethacrylate, or direct penetration from polymer or gouging during acetabular preparation. An understanding of the mechanisms and location of arterial injury following hip replacement will aid the vascular surgeon in diagnosis, exposure, and repair of these injuries.

Aged↗
PubMed1981

Alternatives in the management of atherosclerotic occlusive disease of aortic arch branches.

The cases of 62 patients with atherosclerotic occlusive disease at the origin of the aortic arch branches were reviewed. Thirty-six were initially without neurologic symptoms and in four (11%) intermittent neurologic symptoms without stroke developed during an average follow-up of 27 months. No patient had limb-threatening ischemia. Twenty-six operations were performed for neurologic symptoms or disabling limb ischemia, with one death. Five-year graft patency by life-table analysis was 81%. Preoperative or late postoperative stroke in three patients with occluded common carotid artery suggests this to be a more dangerous subgroup. We advise surgery for patients with disabling arm symptoms or with ischemic neurologic symptoms associated with multiple-vessel disease or with major lesions in the innominate-carotid circulation. We advocate selective revascularization with priority given to the innominate-carotid flow, isolated subclavian lesions first seen as a single lesion or as the only residual lesion after reconstruction for multiple-vessel disease can be safely left unreconstructed.

Adult↗
PubMed1981

Alveolar function following surfactant deactivation.

In vivo cinemicroscopic studies of subpleural alveoli were conducted in dogs for 4 h after pulmonary lavage with 5% Tween 20 and after lavage with normal saline. Saline-lavaged alveoli showed little change in alveolar size during tidal ventilation, whereas Tween lavage resulted both in alveolar recruitment and marked variation in alveolar size from end expiration to peak inspiration, with total collapse frequently occurring by end expiration. Following Tween, alveolar stability decreased, but alveolar capillary perfusion increased. Marked recovery of stability by 4 h was noted in most alveoli. Wilhelmy balance studies on lung extracts showed a decrease in surfactant function 30 min after Tween and a partial recovery of surfactant activity after 4 h. This study provides in vivo evidence that normal surfactant function is critical to alveolar stability and that alveolar stability is markedly restored 4 h after acute deactivation or displacement by Tween. Surfactant deactivation and loss of alveolar stability are associated with increased alveolar capillary perfusion creating significant ventilation-perfusion ratio abnormalities.

Animals↗
PubMed1981

Portal hemodynamics in dogs during mechanical ventilation with positive end-expiratory pressure.

The effects of 10 and 15 cm H2O positive end-expiratory pressure (PEEP) on portal vein flow (PVF), superior mesenteric artery flow (SMAF), and cardiac output (CO) were studied. Portal vein pressure (PVP) and the intraluminal pressure gradient between portal vein and intrathoracic inferior vena cava (PVP-CVP) were also measured. PEEP caused a fall in CO and SMAF, and the fall in each was proportionately the same. PVF also fell and a linear correlation between PVF and SMAF during PEEP was observed. Although PVP increased relative to atmosphere, no increase in transmural PVP and no change in PVP-CVP gradient was observed with PEEP. These data suggest that the major effect of PEEP on portal hemodynamics is a reduction in portal flow secondary to the reduction of arterial inflow into the gut. These hemodynamic changes do not appear to be the result of an increase in resistance to protal flow at the liver but rather the result of PEEP reducing cardiac output.

Animals↗
PubMed1980

Pulmonary and systemic hemodynamics during hemorrhagic shock in baboons.

The pulmonary and systemic hemodynamic response to four hours of hemorrhagic shock and resuscitation has been studied in 17 baboons using both open and closed chest models. No pulmonary artery (PA) hypertension occurred during shock or resuscitation except for an increase in lft ventricular end diastolic pressure (LVEDP) secondary to intravascular volumee overload with Dextran. Pulmonary vascular resistance (PVR) increased during shock but returned to control levels with reinfusion of shed blood and correction of acidosis. PVR was moderately elevated following reinfusion of shed blood if acidosis was not corrected or if volum resuscitation was inadequate. No increase in gradients occurred between PA pressure and left atrial (LA) pressure or LVEDP and there was no gradients between small pulmonary vein and LA pressure. Arterial PO2 uniformly increased during shock and remained at or above control levels of reinfusion. Gross or histologic evidence of "congestive atelectasis" or "shock lung" was not observed. These observations suggest that in the subhuman primate, hemorrhage alone does not produce significant injury to the lung during shock or the immediate postresuscitation interval. Hemorrhage alone did not produce changes in the lung which would result in increased pulmonary microvascular hydrostatic pressure following appropriate resuscitation.

Animals↗
PubMed1980

The effect of thrombocytopenia on the pulmonary and systemic hemodynamics of canine endotoxin shock.

Dogs were made thrombocytopenic (platelet count less than 12,000) with serial intramuscular injections of goat antiplatelet serum (APS), and the hemodynamic response to 1 mg/kg of E. coli endotoxin administered intravenously was studied. Intramuscularly administered APS rendered dogs thrombocytopenic without major alteration in other blood elements or coagulation parameters. The response of normal dogs to endotoxin was a fall in systemic blood pressure and cardiac output (CO) with an increase in pulmonary artery (PA) pressure and an increase in pulmonary vascular resistance (PVR) to 600% of control with a minimal fall in mean left atrial (LA) pressure and pulmonary artery wedge (PAW) pressure. Thrombocytopenic dogs had an identical fall in systemic pressure and CO, but obliteration of the initial PA hypertensive response. LA and PAW pressures fell slightly as in normal dogs, and the obliteration of the PA hypertension was caused by an attenuation of the increase in PVR to a third of that of normals. Cinemicroscopic studies of the lung in vivo showed marked and prolonged slowing of the microcirculation following endotoxin administration in normal dogs. In thrombocytopenic animals slowing of the pulmonary microcirculation was brief and mild. We conclude that platelets are an essential component for the initial pulmonary hypertensive response to infusion of E. coli endotoxin in dogs.

Animals↗
PubMed1979

Experimental pulmonary edema. The effect of unilateral PEEP on the accumulation of lung water.

The effect of PEEP in retarding the development of pulmonary edema produced by elevation of left atrial (LA) pressure to 25cm water was studied in dogs, Using two synchronized volume respirators connected to a double lumen endotracheal tube, 10 or 25cm H2O PEEP was applied to one lung while the contralateral lung was ventilated with an equal tidal volume without PEEP. LA pressure was then elevated by inflating a Foley catheter ballon in the LA until the desired LA pressure was reached. After three hours of pulmonary edema with ventilation of one lung with PEEP lung water was quantitated by wet-to-dry weights. There were no differences in wet to dry weights of PEEP and nonPEEP lungs at either 10 or 25cm H2O level. Additional blood flow studies showed that 25cm H2O of PEEP reduced blood flow to the PEEP lung by 25% and to the nonPEEP lung by 7%. This study shows that PEEP will not mechanically retard the accumulation of lung water due to increased pulmonary capillary hydrostatic pressure.

Animals↗
PubMed1978

Diagnosis and management of spontaneous aortoenteric fistulas.

Spontaneous aortoenteric fistulas are rare but appear to be increasing. They may occur anywhere from the esophagus to the rectum but most often between the duodenum and an infrarenal abdominal aortic aneurysm. Four patients (two with aortoesophageal, one with aortoduodenal, and one with aortocolic fistulas) are presented. The patient usually presents with the clinical triad of aortic aneurysm, pain suggesting aortic disruption, and gastrointestinal hemorrhage. The final exsanguinating hemorrhage is usually preceded by prodomal hemorrhages of varying severity which may be present for weeks to months. Endsocopy is the most helpful diagnostic procedure. Prompt aggressive surgical therapy is the only hope for survival. Successful reconstruction requires placement of the graft in uninfected tissue--often in an extraanatomic position--and interposition of healthy tissues between the graft and the repaired enteric tract.

Aged↗
PubMed1978

Experimental pulmonary edema: the effect of positive end-expiratory pressure on lung water.

The effect of 10 cm of positive end-expiratory pressure (PEEP) on lung water was studied during pulmonary edema induced in dogs by inflating a Foley balloon placed in the left atrium. Colloid oncotic pressure (COP) was measured directly. Intrapleural pressure (IPP) was measured after surgical closure of the chest. Transmural left atrial (LA) pressure (LA minus IPP) minus COP was considered to be the net force driving water out of the capillaries. LA pressure was elevated so that transmural LA pressure minus COP averaged +7.5 mm Hg. Water accumulation was expressed as the ratio of wet to dry weight. The control ratio of wet to dry lung weight was 4.30 +/- 0.10 (+/- SE). After 2 hours of standardized pulmonary edema and ventilation without PEEP, wet-to-dry lung weight was 5.63 +/- 0.24. In animals ventilated with 10 cm of PEEP through 2 hours of pulmonary edema the ratio was 5.36 +/- 0.14. Animals ventilated with 10 cm of PEEP showed a significant increase in functional residual capacity and decreased intrapulmonary shunt. Ten centimeters of PEEP, however, had no statistically significant effect on water accumulation during experimental pulmonary edema.

Animals↗
PubMed1978

The relationship between transfusion and hypoxemia in combat casualties.

The relationship between transfusion and subsequent hypoxemia was examined retrospectively in the records of combat casualties studied by the first three U.S. Army Surgical Research Teams in Vietnam. There was no evident relationship in 425 casualties studied before anesthesia and operation. In 199 casualties studied preoperatively and on at least two of the first three postoperative days, there was no evident relationship in those with injuries not involving the chest or abdomen. Eighteen such casualties received over ten units of blood each (average 24.5) and exhibited subsequent changes in arterial oxygen tension (PaO2) which were indistinguishable from those transfused lesser amounts or not all. Similar observations were made in casualties with injuries to the abdomen, although there was a tendency to lower PaO2 two days after injury in those heavily transfused. In those with thoracic injury, there was statistically significantly lower PaO2 on the first two postoperative days in those heavily transfused. Two possible interpretations are considered, one that blood transfusion contributed to hypoxemia, and alternatively, that a greater magnitude of the injuries accounted for both the worsened hypoxemia and the need for more transfusions. The latter was thought more likely. The differences in PaO2 related to the type of injury exceeded the differences associated with transfusion.

Adult↗
PubMed1978

Prevention of pulmonary insufficiency through prophylactic use of PEEP and rapid respiratory rates.

This study evaluated the effectiveness of prophylactic positive end-expiratory pressure (PEEP) rapid respiratory rates (RRR), and high tidal volume (HTV) in prevention of congestive atelectasis. Measurements of pulmonary hemodynamics, mechanics, gas exchange, functional residual capacity (FRC), pathology, and cinemicroscopy were performed in 45 anesthetized dogs subjected to hemorrhagic hypotension. Randomly, the animals received control ventilation, HTV (20 ml. per kilogram), RRR (32 breaths per minute), or PEEP (5 cm. of water). Carbon dioxide was added as needed to maintain normocapnia. Control and HTV animals showed characteristic changes of congestive atelectasis (capillary congestion, stasis, interstitial edema, periarterial hemorrhage, alveolar edema, and hemorrhage). These microscopic and cinemicroscopic changes were prevented by PEEP and RRR and correlated with decreased physiological shunting (PEEP 10 percent, RRR 13 percent, HTV 22 percent; p less than 0.01) in the postshock phase. PEEP increased FRC by 40 percent (p less than 0.02) and reduced the pulmonary artery--small pulmonary vein gradient (PA-SPV), suggesting a direct effect on the capillary bed. RRR did not affect FRC but minimized the SPV-LA gradient. This effect on the pulmonary venules theoretically could be mediated by stimulating lymphatic flow, thereby decreasing interstitial edema. Thus PEEP and RRR are beneficial when used prophylactically but may work by widely differing mechanisms.

Animals↗