PubMed Health⌕ Search

Biomedical subjects

L F de Figueiredo

Publications and source records attributed to L F de Figueiredo.

10 recordsLinked to original sources
PubMed2001

Initial management of severe hemorrhage with an oxygen-carrying hypertonic saline solution.

We tested the hypothesis that the combination of polymerized bovine hemoglobin (PBHg) with hypertonic saline may be beneficial for the initial management of hemorrhagic shock in 22 mongrel dogs (15 +/- 1 kg) bled to a mean arterial pressure (MAP) of 40 mm Hg in 5 min and maintained at this level for 45 min (shed blood volume approximately 50 ml/kg). Animals were treated with a 4 ml/kg bolus over 4 min of one of the following fluids: whole blood, 7.5% NaCl (HS), 13 g/dl of PBHg, or 7.5% NaCl combined with polymerized bovine hemoglobin (HS-PBHg). No additional intervention was performed, and the animals were followed for 60 min after treatment. PBHg and HS-PBHg produced a sustained, significant increase in MAP. Cardiac output was transiently increased only after HS and HS-PBHg. A partial increase in superior mesenteric artery blood flow was observed, particularly after HS-PBHg. We concluded that small volumes of PBHg alone restore MAP, but not blood flow. The combination of PBHg with hypertonic saline provides improvements in cardiac output and mesenteric blood flow, suggesting a potential benefit for the initial management of major blood loss.

Animals↗
PubMed2001

Effects of hemoglobin-based blood substitutes on vasoactivity of rat aortic rings.

Our objective is to characterize the vasoactive properties of a 10% alphaalpha diaspirin cross-linked human hemoglobin (alphaalphaHb) and to test the hypothesis that sodium nitroprusside (SNP)-induced relaxation is inhibited in the presence of alphaalphaHb. Experiments were performed on aortic rings from 18 Wistar rats; the rings were suspended in aerated Krebs solution. Changes in isometric tension were measured to increasing concentrations of alphaalphaHb (1.8 x 10(-9) to 10(-4) M) on phenylephrine (PE)-induced contraction (3 x 10(-7) M), on acetylcholine (ACh)-induced relaxation (10(-8) to 10(-6) M), on SNP-induced relaxation (10(-9) and 10(-8) M), and on PE-induced contraction with an endothelin-1 (ET1) receptor antagonist, BQ123 (10(-5) M). Control rings received no alphaalphaHb. A concentration-dependent increase of the PE-precontraction (1.3%, 6.8%, 17.4%, and 34%, respectively) as well as the inhibition and reversal of ACh-induced relaxation was observed after alphaalphaHb. The presence of alphaalphaHb decreased the SNP-induced relaxation in the presence or absence of endothelium. The relaxation induced by SNP was reduced with time in the presence, but not in the absence, of alphaalphaHb. In conclusion, although pharmacological modulation of the vasoconstriction is possible with nitric oxide donors, our findings suggest that in the clinical setting, large sustained donor doses may be required.

Animals↗
PubMed1998

Vasoactive properties of synthetic blood substitutes.

There is a great need for the development of a safe and efficient blood substitute, to overcome the important limitations of homologous blood transfusion. Currently available cell-free hemoglobin-based oxygen-carrying solutions present oxygen transport and exchange properties similar to blood and potential benefits over conventional transfusion, including large supply, absence of transfusion reactions, no need for cross-matching, no risk for transmission of disease and long shelf life. Several experimental studies have suggested that cell-free hemoglobin is a vasoactive agent. In animal models of hemorrhagic shock, small doses of cell-free modified hemoglobin restore arterial pressure, promote adequate tissue oxygenation, and improve survival, when compared with fluids with no oxygen-carrying capacity. On the other hand, it has been demonstrated that hemoglobin-induced vasoconstriction may result in decreased cardiac output, reduced blood flow to vital organs and severe pulmonary hypertension. Cell-free hemoglobin solutions cause their pressor effects by binding and scavenging nitric oxide. Although hemoglobin within the red blood cells is the natural scavenger of NO, when the hemoglobin is free in solution, NO is inactivated to a greater extend. Cell-free hemoglobins are on advanced clinical trials, despite the fact that several concerns raised by experimental studies have not been adequately addressed in early clinical trials. The development of a safe and efficient blood substitute depends on the availability of these products for critical evaluation by the scientific community before the widespread clinical use of these blood substitutes.

Animals↗
PubMed1997

Pulmonary hypertension and systemic vasoconstriction may offset the benefits of acellular hemoglobin blood substitutes.

OBJECTIVE: We tested the hypothesis that the pharmacologic properties of a small volume of alpha alpha-cross-linked hemoglobin (alpha alpha Hb) could effectively resuscitate pigs subjected to hemorrhage. METHODS: Fourteen pigs hemorrhaged to a mean arterial pressure (MAP) of 40 mm Hg for 60 minutes were treated with a 4-mL/kg 2-minute infusion of 10 g/dL alpha alpha Hb or 7 g/dL human serum albumin, an oncotically matched control solution. RESULTS: The removal of blood (17 +/- 1.5 mL/kg) caused the typical physiologic responses to hemorrhagic hypovolemia. Infusion of alpha alpha Hb restored mean arterial pressure and coronary perfusion pressure, but cardiac output and mixed venous O2 saturation did not improve significantly. Pulmonary arterial pressure and pulmonary vascular resistance increased markedly and were higher than baseline levels after alpha alpha Hb. Infusion of human serum albumin produced only minor hemodynamic changes. Brain blood flow did improve to baseline values after alpha alpha Hb, but was the only tissue to do so. In the human serum albumin group, superior mesenteric artery blood flow recovered to baseline values, whereas brain blood flow did not. Blood flows to other tissues were similar in both groups. CONCLUSION: Small-volume infusion of alpha alpha Hb restored mean arterial pressure and brain blood flow, but pulmonary hypertension and low peripheral perfusion may offset benefits for trauma patients.

Albumins↗
PubMed1993

Upper-extremity deep venous thrombosis: analysis of 52 cases.

In a review of 52 cases of deep venous thrombosis (DVT) of the upper extremity, the predisposing factors, clinical manifestations, topography of thrombosis, treatment employed, presence of complications, and evolution of the disease were investigated. In all patients, clinical manifestations were confirmed by bilateral phlebography and superior cavography. Thirty-five (67%) of the patients were male; the mean age was 45.4 years. Clinical manifestations were edema in 51 patients (98%), dilated collateral circulation in 37 (71%), and pain in 33 (63%). One patient presented with pulmonary embolism and another with phlegmasia cerulea dolens-like signs in an extremity. The right axillosubclavian segment was involved in 23 patients (44%), the left in 17 (33%), and both left and right segments associated with DVT of the superior vena cava in 11 (21%). One patient had left and right axillosubclavian thrombosis without superior vena cava involvement. The main predisposing factors identified were central venous catheterization in 15 patients (29%) and extrinsic compression, caused mainly by cancer, in 15 (29%). There were three cases of DVT related to effort and three to thoracic outlet syndrome. The majority of patients were treated with systemic heparin therapy followed by oral anticoagulation. During a follow-up of 6 months, nine patients died, one from pulmonary embolism; 21 patients (40%) were symptom-free, 11 (21%) had minimal edema, and seven (13%) had symptomless edema. Four patients (8%) were lost to follow-up. The overall incidence of pulmonary embolism was 4%.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMedDate not supplied

Postnephrectomy arteriovenous fistula.

The development of the postnephrectomy arteriovenous fistula (PNAVF) between the renal vessels stumps is rare. Here we present a case report of PNAVF, and review the diagnosis, treatment and prevention. The most common clinical features include a loud murmur over the previous nephrectomy scar, and heart failure resistant to common medical treatment. A 58-year-old white woman was admitted to the hospital for a complete evaluation of an unexplained congestive heart failure with no response to common medical treatment. She had had a right nephrectomy for pyonephrosis 13 years before. The diagnosis of PNAVF was suspected because over the right lumbar region a definite trill was palpated, and on auscultation a harsh, machinery-like murmur was heard. The diagnosis was confirmed by aortogram and selective renal arteriography. In May 1989, the right arteriovenous was excised through a right subcostal transperitoneal approach. The renal vessel stumps were individually ligated and sutured separately close to aorta and vena cava. The patient's postoperative course was entirely uneventful in the following seven years. We conclude that during nephrectomy, the renal vessels should be ligated separately, and the transfixation in mass of the stumps avoided to prevent arteriovenous fistula.

Arteriovenous Fistula↗
PubMedDate not supplied

Individual strategies of hemostasis for thoracic aortic surgery.

The problem of altered hemostasis remains a major challenge during thoracic aortic surgery. Bleeding is associated with a marked increase in morbidity and mortality. The hemostatic derangements are caused by multiple interrelated factors including interference with the vascular integrity, extensive surgical dissection, transient need for complete inhibition of the normal coagulation process, large blood products and fluid requirements, hemodilution, hypothermia, extensive ischemia and reperfusion, activation of systemic inflammatory responses, interference with fibrinolysis, and the use of extracorporeal circulation systems. Acquired coagulopathy must be specifically diagnosed and treated. Platelet deficiencies, both qualitative and quantitative, are the most predictable and consistent disturbance in the hemostatic function and the most common cause of intraoperative and postoperative bleeding. Precise surgical technique is essential to prevent blood loss. Topical agents should not be used for and cannot correct imperfections in surgical technique. Nonspecific measurements that are useful to decrease intraoperative blood loss include strict control of blood pressure and hemodynamic status, the induction of mild controlled hypotension, and the reversal of hypothermia. Rewarming may produce clear procoagulant effects by improving the efficacy of platelets and clotting factors. Platelet dysfunction can be reduced by several pharmacological interventions including acid aminocaproic, desmopressin and aprotinin; however, efficacy and safety are still being established. The most important factorS regarding safety in thoracic aortic surgery are a secure suture line and the experience of the surgical and anesthesiology teams.

Aortic Dissection↗
PubMedDate not supplied

Natural history of descending and thoracoabdominal aortic aneurysms.

Data on the natural history of descending and thoracoabdominal aneurysms are limited to a few studies. They demonstrated that, independent from the different mechanisms of injury and degeneration affecting the structural integrity of the aortic wall, the biologic fate of all aneurysms is progressive enlargement and rupture. Laminated thrombus and calcification do not prevent this process. The natural history is markedly influenced by size, location, symptoms, and etiology of thoracic aneurysms. They may develop symptoms related to mechanical compression of adjacent structures, but more frequently they are asymptomatic until rupture occurs. Usually, aortic rupture causes death by exsanguination and shock before bleeding can be controlled. Occasionally, rupture can be contained by the parietal pleura or occur towards the mediastinum, esophagus, pulmonary parenchyma, or bronchi. Untreated aneurysms will cause death in the majority of patients because of rupture. Recent data evaluating smaller and asymptomatic thoracic aneurysms with CT scan support nonoperative management and close follow-up of descending and thoracoabdominal aortic aneurysms only when the diameter is less than 5 cm. Patients with Marfan syndrome may be operated upon with smaller aneurysms. Independent of etiology, operative repair is the most effective means to alter the otherwise malignant course of descending and thoracoabdominal aortic aneurysms. The role of endovascular repair of these aneurysms remains to be established; however, it may represent an alternative to treat thoracic aneurysmal disease in very high risk patients.

Aortic Dissection↗