Permissive hypercapnia in ARDS: just do it?
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Publications and source records attributed to K Lewandowski.
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Acute respiratory distress syndrome (ARDS) is rare but beset with a high mortality rate. In recent years, however, a trend towards higher survival rates has been observed. High inspiratory oxygen concentrations, large tidal volumes, and high peak inspiratory airway pressures applied during mechanical ventilation have been identified as harmful to the lung and can contribute to the progression of ARDS. This had led to reconsideration of the sequelae of ventilatory therapy. Mechanical ventilation and other adjunctive strategies in ARDS have changed from the conventional approach aiming at normalisation of physiological ventilatory parameters to an elaborated approach that intends to protect the ventilated lung, prevent oxygen toxicity, recruit the infiltrated atelectatic and consolidated lung and reduce the anatomical and alveolar dead space. This new approach consists of various forms of pressure-controlled mechanical ventilation with PEEP and permissive hypercapnia, body position changes, and inhalation of nitric oxide. Should these procedures fail to improve impaired gas exchange, extracorporeal membrane oxygenation is an additional therapeutic option. None of these therapeutic procedures, however, has been tested against traditional standard treatment in a classical randomised controlled trial. The following review focuses on the latest insights into the pathophysiology, diagnosis, and treatment of ARDS.
Nitric oxide (NO) produced in the respiratory tract is released into the respiratory gases of humans, rabbits, guinea-pigs, and rats. We analysed the NO concentrations in the exhaled gas of four awake Asian elephants. Two methods were employed: (1) exhaled gas was sampled from the elephants' trunks with a 1 L syringe and analysed for NO concentrations by chemiluminescence; (2) respiratory gas was continuously aspirated via a thin plastic tube positioned within the trunk and on-line analysed for NO concentrations by chemiluminescence. Syringe sampling (n = 4), when corrected for dilution by ambient air using linear regression analysis, revealed a mean NO concentration of 31 parts per billion (ppb); highest exhalatory concentrations measured during continuous suctioning were 27 and 28 ppb (n = 2). The exhaled NO concentrations in elephants are similar to those found in humans measured with a comparable technique. This supports the hypothesis that a size-independent 'normal value' of endogenous NO is provided in the airways which may contribute to regulation of pulmonary ventilation and perfusion by autoinhalation in some mammals.
The purpose of our study was to determine the effectiveness of 2-CdA in 2-hour intravenous infusions in the treatment of B-CLL. One hundred and ten patients with B-CLL received 1 to 10 courses of 2-CdA (median 2.5) at a dosage of 0.12 mg/kg daily for 5 consecutive days. Eighteen of them were untreated and 92 relapsed or became refractory to previous therapeutic modalities. Complete remission (CR) was achieved in 8 (7.3%) and partial remission (PR) in 35 patients (31.8%) giving an overall response rate of 39.1%. In 3 patients, cross-resistance to fludarabine was noticed. Toxic effects of 2-CdA were more frequently observed in previously treated patients. Hemorrhagic complications due to drug-induced thrombocytopenia were noticed in 25 (22.7%) and severe infections including sepsis in 14 (12.7%) patients.
In 53 patients with recent (< 6 hrs) acute myocardial infarction a study was undertaken to evaluate the safety of conjunctive therapy with streptokinase (1.5 mln U), aspirin (150 mg) and low molecular weight heparin (Fraxiparine). Patients were treated with Fraxiparine 250 U anti-Xa IC/kg/24 hrs iv for 2 days (with bolus 12.5 U anti-Xa IC/kg), and 125 U anti-Xa IC/kg twice a day sc for 5 subsequent days. Clinical course in one-year observation was compared regarding the time the therapy was initiated. In the group undergoing therapy 3-6 hrs after the infarct had occurred 4 (7.5%) patients died (2 during hospitalization, 2 after discharge). In 31 patients treated within 3 hrs of the myocardial infarction there were fewer cases of recurrent myocardial infarction, unstable angina or congestive heart failure necessitating rehospitalization their (9.1%) than in 22 patients included in the treatment regimen between 3 rd and 6th h of the infarction (27.3%). Earlier thrombolysis was also connected with higher left ventricular ejection fraction (55 +/- 8% vs 49 +/- 10%) and more frequent peak CK-MB values 12 hrs after thrombolysis (81% and 68% of patients respectively). Neither symptomatic deep vein thrombosis nor pulmonary embolism was detected. The left ventricular thrombosis was diagnosed by echocardiography in 4 of 20 patients (20%) with the first anterior myocardial infarction. There was neither bleeding requiring blood transfusion nor cerebrovascular stroke. The treatment with Fraxiparine did not induce the prolongation of APTT values. Conjunctive thrombolytic therapy with low molecular weight heparin was safe and followed by a favorable outcome of the acute myocardial infarction, especially if instituted within the first 3 hrs after the onset of infarction.
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The aim of the study was to evaluate the thrombosis free survival in unrelated 24 heterozygous carriers for Leiden mutation and in unrelated 26 patients with "idiopathic" thromboembolic disease. The subjects with coexisting antithrombin III, protein C, S deficiency, obesity, antiphospholipid antibodies, cancer or taking oral contraceptives were excluded from analysis. The clinical manifestations of thrombosis were comparable in both investigated group, similarly the mean age of the first episode occurrence (37.2 vs 41.5 years). The probability for development of thrombosis in Kaplan-Meier analysis was not different between two groups. Moreover, during six months of observation period thrombosis reoccurrence rate was similar (1/24 vs 1/26).
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Continuous intra-arterial blood gas monitoring is a new technique, possibly offering therapeutic advantages through improved monitoring in patients prone to hypoxaemia, hypercapnia and/or respiratory acidosis. Therefore, we studied the clinical applicability, reliability, precision and side effect of long-term continuous intra-arterial blood gas monitoring in patients suffering from severe acute respiratory distress syndrome. In 10 patients continuous intra-arterial blood gas monitoring based on fluorescent optodes technique was performed. At 4 h intervals, arterial blood samples for in vitro blood gas analyses were drawn, stored in ice, and analysed within 3 min. Evaluation of data retrieved from the continuous intra-arterial blood gas monitoring and in vitro blood gas analysis was based on 596 data points using 10 catheters. Average length of insertion was 281 +/- 215 h, max. lengths of stay was 750 h. Arterial blood gas data obtained in vivo were compared to the mean of in vivo and in vitro arterial blood gases. Inter-catheter bias, expressed as percent difference between continuous intra-arterial blood gas and mean in vitro blood gas analysis was 0.19 +/- 0.23% for pH. 1.1 +/- 5.2% for PaCO2 and 1.6 +/- 5.7% for PaO2. No significant gas partial pressure dependent change in precision was demonstrable. There was no significant time dependent drift in sensor precision over the study period. No negative side-effects related to IABG monitoring were observed. We conclude that long-term use of this new device is possible in patients and represents a reliable alternative to conventional in vitro arterial blood gas analysis, when continuous monitoring of blood gases and/or acid-base balance is critical.
A prospective multicenter study was carried out from October 1 to November 30, 1991, to determine the incidence, severity, and mortality of acute respiratory failure (ARF) in Berlin, Germany, a metropolis with a population of 3.44 million. Adult patients from 72 intensive care units (ICUs) were evaluated. ARF was defined as: (1) intubation and mechanical ventilation (I+MV) > or = 24 h; age > or = 14 yr. Incidence of ARF was assessed as the number of patients fulfilling ARF criteria within the 2-mo study period. Severity of ARF was defined as "no lung injury" (NLI), "mild-to-moderate lung injury" (MMLI), and "severe lung injury" (SLI) according to Murray and coworkers' proposals. Mortality was assessed as number of patients with ARF dying during ICU stay. During the study period, 508 patients were diagnosed as having ARF, representing an incidence of ARF of 88.6 per 100,000/yr. Twenty-four h after I+MV, MMLI occurred in 94% and SLI in 3.6% of the ARF patients. Overall mortality rate was 42.7%. Mortality rate in the NLI group was 36.4%; in patients with MMLI, 40.8%; and in patients with SLI, 58.8%. Our data offer novel information on incidence, severity, and mortality of ARF in a major urban population.
STUDY OBJECTIVE: To investigate the initial and long-term effect of nitric oxide (NO) inhalation in patients with severe acute respiratory distress syndrome (ARDS). DESIGN: Retrospective, clinical study. SETTING: University surgical ICU. PATIENTS: Eighty-seven patients with severe ARDS. INTERVENTIONS AND MEASUREMENTS: Thirty of 87 patients with ARDS inhaled low concentrations of NO for more than 48 h in addition to the standard treatment. Initial and long-term effects of NO inhalation on hemodynamics, gas exchange, and methemoglobin formation were determined. Survival of patients treated with inhaled NO was compared with survival in similar patients without NO inhalation. RESULTS: In 83% of the patients, NO increased the ratio of arterial PO2 to the fraction of inspired O2 (PaO2/FIO2) by > or = 10 mm Hg; in 87%, NO reduced venous admixture (QVA/QT) by > or = 10%, and in 63%, NO decreased mean pulmonary artery pressure (PAP) by > or = 3 mm Hg. Daily short interruption of continuous inhalation of NO for a duration of 17 +/- 2.4 days was consistently associated with a decrease in PaO2/FIO2 by 81 +/- 4 mm Hg (p < 0.001). QVA/QT increased by 8.3 +/- 0.4% (p < 0.001) and PAP by 5.3 +/- 0.3 mm Hg (p < 0.001). Over time, we observed neither tachyphylaxis nor a more pronounced effect of inhaled NO. Methemoglobin increased from 0.74 +/- 0.56% to 0.98 +/- 0.02% (p < 0.001). Survival rates in patients treated with NO did not differ from survival rates in patients not treated with NO. CONCLUSION: Beneficial effects of NO inhalation can be observed in most patients with severe ARDS; in some cases, however, it may fail to improve pulmonary gas exchange or to reduce pulmonary hypertension without obvious explanation. To demonstrate a possible increase in survival associated with NO inhalation, large randomized prospective trials are required.
Myelodysplastic syndromes (MDS) comprise a heterogenous group of closely related, acquired stem cell disorders. Various patterns of clinical evolution have been observed in patients with different subtypes according to the FAB (French-American-British) criteria. The marked differences in clinical outcome among MDS patients have encouraged us to search the alternative variables for predicting leukemic transformation and survival. During the past 10 years different prognostic scoring systems based on age combined with blood and bone marrow parameters have been described. This has enabled the identification of patients with better and worse prognosis among different MDS types. Additionally, studies of cytogenic patterns in MDS patients and widespread availability of bone marrow histological specimens extended the possibility of prognosis in this disease. Similarly, the in vitro culture results of hematopoietic cells using growth and differentiation factors have given very promising results. The high prevalence of RAS mutation in patients with MDS has been defined, but its clinical usefulness is under discussion.
The number of treatment modalities for patients with myelodysplastic syndromes (MDS) has increased, but curative options are still limited. For the majority of patients with low risk there is no standard therapy other than appropriate supportive care. In selected patients anabolic steroids, differentiation inducers such as cis-retinoic acid (RA), interferon alpha or gamma have been claimed to be active. Application of growth factors such as granulocyte-macrophage colony stimulating factor (GM-CSF), granulocyte colony stimulating factor (G-CSF), and interleukin 3 (IL-3) improves neutrophil count and diminishes frequency of infectious complications, but responses are incomplete and of short duration. Preliminary results of erythropoietin (Epo) applied in therapeutical doses are disappointing, giving an improvement in 15-20% patients. Epo in large doses produces greater and sustained responses, but this treatment is too expensive. Low-dose cytosine arabinoside (Ara-C) induces a response rate in 25-30% patients, however, no survival advantage has been obtained. Addition of RA or GM-CSF produces response rates comparable to Ara-C alone, but also with no prolongation in survival. Bone marrow transplantation (BMT) offers a good chance of long-term disease-free survival if is performed in an early stage of the disease or in complete remission, however, it is limited to patients below 55 years with an HLA-identical donor. Relatively young, high risk patients not eligible for allogeneic BMT should be considered for treatment with intensive polychemotherapy.
Although patients with thromboembolic disease frequently have family histories of thrombosis, well-defined defects such as inherited deficiencies of anticoagulant proteins are found only in minority of cases. Herein, we present a family study of 42 years old woman with recurrent deep vein thrombosis which occurred first time four years ago during pregnancy, in subclavian vein, in relation to cardiac stimulator implantation because of atrio-ventricular III(0) block. Her laboratory investigation demonstrated normal APTT time, prothrombin time, platelet number, antithrombin III and protein C activity. Plasma antiphospholipid antibodies contents was within the normal range. The result of activated protein C(APC) resistance test was abnormal (R=1.64). Family study revealed similar degree of APC-resistance defect in her DVT symptomatic mother and two healthy young daughters (R=1.73 and 1.54 respectively). Additionally, a slightly reduced total protein S plasma concentration was found in the patient and her two children. The influence of a slightly reduced protein S level on the results of APC-resistance was excluded by evaluation of normalized activated protein C sensitivity ratio (nAPC-SR) as described de Ronde and Bertina.
The aim of this study was to assess the frequency of haemostatic defects in 78 patients with the history of venous thromboembolic disease. In all patients antithrombin III activity and in 50 of them protein C, in 53-protein S, in 49 activated protein C (APC) resistance, plasminogen, alfa-2-antiplasmin were measured. We found 35 patients with haemostatic defect: 3 patients with decreased protein C activity and one case with decrease of protein C both activity and antigen level; 15 patients with decreaced antithrombin III activity; 7 patients with decreased free protein S antigen level; 5 patients with APC resistance. In 4 patients we found more than one defect; 2 patients had decreased concentration of free protein S and APC resistance, one patient had decreased activity of both antithrombin III and protein C, one patient had decreased antithrombin III activity and free protein S antigen level. Plasminogen and alfa-2-antiplasmin levels were within the normal range. Family studies indicated hereditary thrombophilia in 6 families. Screening for thrombophilia is very important for the optimal prophylaxis and treatment of venous thromboembolic disease.
Recent studies and reviews continue to report a high mortality associated with the acute respiratory distress syndrome (ARDS), which involves a severe inflammatory reaction within the whole lung that is frequently associated with multiple-organ failure. Important factors contributing to the poor results in severe ARDS are the aggressive procedures required to maintain sufficient arterial oxygenation, such as mechanical ventilation with high inspiratory pressures and high inspired oxygen concentrations (FiO2) which themselves contribute to the progression of the disease. As no specific therapy that reduces or prevents the general inflammatory reaction is known, current therapy is limited to procedures that minimize peak inspiratory pressures and FiO2. Therefore, pressure- and volume-limited ventilation modes with positive end-expiratory pressure, controlled hypercapnia, differential lung ventilation when appropriate, positioning (particularly prone), and aggressive dehydration are used. Should these procedures fail to improve arterial gas exchange, the patients may be additionally treated by veno-venous extracorporeal gas exchange. To reduce the risk of severe haemorrhagic complications due to high levels of systemic heparinization, systems internally coated with covalently bound heparin, which allow a lower level of systemic anticoagulation, should be used. From April 1989 to August 1993, 89 patients were transferred to our intensive care unit for treatment of severe ARDS; 52 were treated by combining the described conventional methods without artificial gas exchange (survival rate 88%) and 37 additionally underwent artificial gas exchange (survival rate 57%). The overall survival rate was 75%. On the basis of these experiences, we conclude that this step-by-step approach may improve survival in patients with severe ARDS.
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The platelet function as well as parameters of lipid metabolism and glucose tolerance were investigated in 30 men with occlusive atherosclerotic arterial disease of the low extremities (IIIB or IV Fontaine's stage). The platelet aggregation, platelet survival, activity of intraplatelet metabolism of arachidonic acid, radiofibrinogen binding to platelet, circulating platelet aggregates and both the activity of factor VIII and the concentration of von Willebrand factor antigen in the plasma were measured. In the majority of patients the impairment of platelet aggregation with ADP, enhancement of radiofibrinogen binding to platelets and an increase of factor VIII level in the plasma were established. There was an interrelationship between platelet dysfunction and disturbances of lipid metabolism. Platelet survival was shortened in patients with moderate hyperlipidemia and correlated with a concentration of HDL-cholesterol in the serum. The radiofibrinogen binding to platelets was the most pronounced in patients with severe hyperlipidemia and correlated with a concentration of total cholesterol in the serum. The results may suggest the potential usefulness of antiplatelet drugs in patients with occlusive atherosclerotic arterial disease.