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L Uziel

Publications and source records attributed to L Uziel.

18 recordsLinked to original sources
PubMed1990

Physiopathology and management of coagulation during long-term extracorporeal respiratory assistance.

Thrombohemorrhagic risk is one of the main limiting factors in extracorporeal circulation. We describe here our experience in managing some life-threatening hematological complications in 58 patients with acute respiratory failure treated with long-term extracorporeal assistance. These patients were studied by clinical and laboratory means to assess questions related to heparin monitoring, coagulation complications and bleeding incidence. We found that two clotting tests, activated partial thromboplastin time (APTT) and activated clotting time (ACT) can be easily used to assess the safety of anticoagulant treatment (therapeutic ranges: APTT from 55 to 95 sec and ACT from 170 to 220 sec). A certain degree of coagulation activation, despite heparin, was indicated by the constant finding of thrombin-antithrombin complexes, while fibrinolytic activation, measured as plasminogen activator activity, was confined to the time of bypass connection and was of no clinical consequence. Platelet function was always impaired without relation to the platelet loss. Disseminated intravascular coagulation (DIC) (13 episodes) and severe bleeding (11 episodes) were major complications. DIC was corrected with a good outcome for 8 of 13 patients, while severe bleeding was correlated with a poor outcome in 8 of the 11 patients, probably because of the severity of the underlying disease.

Adolescent↗
PubMed1989

Fibrinolytic response in normal subjects to venous occlusion and DDAVP infusion.

A set of fibrinolytic parameters was measured in 40 healthy subjects before and after a venous occlusion (VO) test lasting 10 min. After VO, plasma levels of tissue-type plasminogen activator (t-PA) antigen increased in all subjects, t-PA activity increased only in 25 subjects who were considered responders and remained unchanged in 15 (non-responders). High levels of plasminogen activator inhibitor (PAI) in the non-responder group explain this discrepancy. The non-responders had basal levels of PAI activity and t-PA antigen higher than responders (p less than 0.0001) and their basal levels of t-PA activity were lower (p less than 0.001). DDAVP infusion elicited good responses in 7 of 9 non-responders to VO with a fall of PAI activity to 0. Our data indicate that a high proportion of healthy subjects do not have a fibrinolytic response after VO, that a lack of fibrinolytic response to VO is due to high plasma levels of PAI and that DDAVP infusion appear to be more selective than VO for detecting non-responders.

Adult↗
PubMed1988

Haemostasis contact system and fibrinolysis in hereditary angioedema (C1-inhibitor deficiency).

Factors of the classical complement pathway, the contact system and fibrinolysis were evaluated both with functional and immunochemical methods, in patients with inherited deficiency of C1-inhibitor. Evaluations were performed under basal conditions, during acute attacks and during prophylaxis with low doses of anabolic steroids. Patients in the basal state showed no significant abnormalities of any of the parameters that we investigated. During acute attacks a slightly reduced prekallikrein concentration was registered. During treatment with low doses of danazol and stanozolol, protein C and plasminogen were found to be increased. Our data suggest that C1-inhibitor deficiency per se does not lead to a derangement of the fibrinolysis and coagulation contact system, and that the kinin system may be involved during acute attacks of angioedema.

Adolescent↗
PubMed1986

Low-frequency positive-pressure ventilation with extracorporeal CO2 removal in severe acute respiratory failure.

Forty-three patients were entered in an uncontrolled study designed to evaluate extracorporeal membrane lung support in severe acute respiratory failure of parenchymal origin. Most of the metabolic carbon dioxide production was cleared through a low-flow venovenous bypass. To avoid lung injury from conventional mechanical ventilation, the lungs were kept "at rest" (three to five breaths per minute) at a low peak airway pressure of 35 to 45 cm H2O (3.4 to 4.4 kPa). The entry criteria were based on gas exchange under standard ventilatory conditions (expected mortality rate, greater than 90%). Lung function improved in thirty-one patients (72.8%), and 21 patients (48.8%) eventually survived. The mean time on bypass for the survivors was 5.4 +/- 3.5 days. Improvement in lung function, when present, always occurred within 48 hours. Blood loss averaged 1800 +/- 850 mL/d. No major technical accidents occurred in more than 8000 hours of perfusion. Extracorporeal carbon dioxide removal with low-frequency ventilation proved a safe technique, and we suggest it as a valuable tool and an alternative to treating severe acute respiratory failure by conventional means.

Acute Disease↗
PubMed1986

Evaluation of tests for heparin control during long-term extracorporeal circulation.

Two coagulation tests, Recalcified Activated Clotting Time (RACT) and Hemochron, were compared with the activated partial thromboplastin time (APTT) in in vitro heparinization experiments and in patients heparinized for long term extracorporeal circulation (ECC) to determine their suitability as guidelines for heparin administration. All tests had good precision, with a small variability between methods. There was satisfactory correlation with the heparin level in vivo (r = 0.77 for RACT; r = 0.80 for Hemochron and r = 0.82 for APTT) too, while the in vitro r was always greater than or equal to 0.94. Nevertheless, APTT values for plasma heparin levels higher than 1.5 U/ml were markedly prolonged, with a large standard deviation, and often "unclottable". The good correlation between the three tests, makes it possible to substitute RACT and Hemochron for APTT, during long-term ECC.

Analysis of Variance↗
PubMed1978

Hepatic function and fibrinolysis in patients with hereditary angioedema undergoing long-term treatment with tranexamic acid.

Prophylactic treatment with antifibrinolytic agents, epsilon-aminocaproic and tranexamic acid, reduces the incidence and severity of attacks in patients with hereditary angioedema. Long-term effectiveness or risk of antifibrinolytic agents has not been established. Sixteen patients needing continuous prophylaxis because of frequency and severity of attacks were treated with tranexamic acid. In four patients this treatment was ineffective and the drug was withdrawn after 2 months. A remission or reduction in the frequency or severity of attacks was observed in 12 patients treated for a period ranging from 8 to 34 months. Hepatic tests and blood fibrinolytic activity were not influenced by long-term oral treatment with tranexamic acid.

Adolescent↗
PubMedDate not supplied

Extracorporeal circulation in sheep with normal bleeding time using a surface heparinized circuit.

Bleeding due to systemic heparinization represents the major side effect of extracorporeal respiratory support. In the present animal study, a surface heparinized system (Carmeda Biological Active Surface) was applied to assess the feasibility of prolonged perfusion at low circulating heparin levels. Eight sheep divided into two groups: group A (5 animals) and group B (3 animals) underwent venovenous bypass using a heparin coated surface circuit. The following protocol was used: a) 24 hours at high heparin dose (30 to 100 U/kg/hr with an ACT [activated coagulation time] three to four times normal); b) 24 hours at low heparin dose (3 to 8 U/kg/hr with an ACT within the normal range); c) 24 hours at high heparin dose. Group B animals also received fresh frozen sheep plasma (14 ml/kg/day). During Period b, the clotting times were within baseline range. The bleeding time showed a dramatic decrease after change from a to b (27.9 +/- 3 minutes vs. 10.2 +/- 5.6 minutes). There was a negative relationship between antithrombin III (AT III) and thrombin coagulase time (TC); the latter is considered to be an aspecific indicator of circulating fibrin(ogen) degradation products. Maintaining AT III over 70%, TC changes were only minor. The use of the bioactive heparin surface allowed the performance of a 24 hour bypass, with normal coagulation times, at low circulating heparin levels.

Animals↗