Albert Benzing

Extracorporeal membrane oxygenation: a ten-year experience

BACKGROUND Extracorporeal membrane oxygenation (ECMO) is a supportive therapy used for severe acute respiratory distress syndrome (ARDS). We present outcome, clinical parameters, and complications in a cohort of 245 ARDS patients of whom 62 were treated with ECMO. METHODS Data of all ARDS patients were prospectively collected between 1991 and 1999. Outcome and clinical parameters of patients treated with and without ECMO were evaluated. RESULTS One hundred thirty-eight patients were referred from other hospitals, 107 were primarily located in our hospital. About one fourth of these patients were treated with ECMO. The survival rate was 55% in ECMO patients and 61% in non-ECMO patients. CONCLUSIONS ECMO is a therapeutic option for patients with severe ARDS, likely to increase survival. However, a randomized controlled study proving its benefit is still awaited. Until the development of a causal or otherwise superior therapy ECMO should be used in selected patients.

Inhaled nitric oxide reduces pulmonary transvascular albumin flux in patients with acute lung injury.

Background In acute lung injury, when pulmonary microvascular permeability is enhanced, transvascular fluid filtration mainly depends on pulmonary capillary pressure. Inhaled nitric oxide has been shown to decrease pulmonary capillary pressure. Therefore, the effect of inhaled nitric oxide at a concentration of 40 ppm on pulmonary transvascular albumin flux was studied in nine patients with acute lung injury.

Incidence of pneumonia in mechanically ventilated patients treated with sucralfate or cimetidine as prophylaxis for stress bleeding : bacterial colonization of the stomach

Retrograde colonization of the oropharynx from the stomach by microaspiration of gastric fluid is a recently recognized phenomenon associated with increased gastric pH that may result in pneumonia during ventilation therapy. In a prospective study we investigated 104 mechanically ventilated patients in the intensive care unit who were receiving sucralfate (n = 49) or cimetidine (n = 55) for stress ulcer prophylaxis. The incidence of pneumonia was 45.5% (25 patients) in the cimetidine group and 26.5% (13 patients) in the sucralfate group (95% confidence interval 0.98 to 6.97; odds ratio 2.61; p = 0.0549). Mortality rates were 18.4% (9 patients) in the sucralfate group versus 25.5% (14 patients) in the cimetidine group (p = 0.48). The mean pH values of gastric aspirates were significantly lower in patients treated with sucralfate than in patients receiving cimetidine (p = 0.044). The number of colony-forming units of Enterobacteriaceae in gastric aspirates was also significantly lower in the sucralfate group (p = 0.0037).

Application of a new method for analysis of exhaled gas in critically ill patients

Objective: Application of a new method for analysis of exhaled gas in critically ill patients. Design: Open study. Setting: Surgical intensive care unit of an university hospital. Patients: Thirty-seven consecutive, critically ill, mechanically ventilated patients. Interventions: None. Measurements and results: Chemical analysis of the patients exhaled gas was based upon substance adsorption and concentration onto activated charcoal, microwave desorption and gas chromatographic separation. Patients with acute respiratory distress syndrome (ARDS) exhaled less isoprene than those without ARDS [9.8 (8.2–21.6) vs 21.8 (13.9–41.4) nmol/m2 per min [median (95 % confidence interval)], p = 0.04]. In patients who developed pulmonary infection, pentane elimination increased from 0.4 (0.0–5.4) to 2.7 (0.6–6.1, p = 0.05) nmol/m2 per min and isoprene elimination decreased from 5.2 (0–33) to 5.0 (0–17, p = 0.05) nmol/m2 per min, resulting in a significant increase in pentane/isoprene ratio from 0.1 (0–0.3) to 0.4 (0–15, p = 0.007) when compared to patients without pulmonary infection. Conclusions: The new method allows quantitative analysis of human gas samples with low substance concentrations and is well suited for clinical studies which involve the investigation of metabolic processes in the lung and the body.

Thiopental Inhibits the Activation of Nuclear Factor κB

Background Thiopental is frequently used for the treatment of intracranial hypertension after severe head injury. Its long-term administration increases the incidence of nosocomial infections, which contributes to the high mortality rate of these patients. However, the mechanism of its immunosuppressing effect remains unknown. Methods The effect of thiopental (200–1000 &mgr;g/ml) on the activation of the nuclear transcription factor &kgr;B (NF-&kgr;B; electrophoretic mobility shift assays), on NF-&kgr;B–driven reporter gene activity (transient transfection assays), on the expression of NF-&kgr;B target genes (enzyme-linked immunoassays), on T-cell activation (flow cytometric analyses of CD69 expression), and on the content of the NF-&kgr;B inhibitor I&kgr;B-&agr; (Western blotting) was studied in human T lymphocytes in vitro. Results Thiopental inhibited the activation of the transcription factor NF-&kgr;B but did not alter the activity of the cyclic adenosine monophosphate response element binding protein. Other barbiturates (methohexital), anesthetics (etomidate, propofol, ketamine), or opioids (fentanyl, morphine) did not affect NF-&kgr;B activation. Thiopental-mediated suppression of NF-&kgr;B could be observed in Jurkat cells and in primary CD3+ lymphocytes from healthy volunteers, was time- and concentration-dependent, occurred at concentrations that are clinically achieved, and persisted for hours after the incubation. It was associated with an inhibition of NF-&kgr;B–driven reporter gene activity, of the expression of interleukin-2, -6, and -8, and interferon &ggr;, and of the activation of CD3+ lymphocytes. Suppression of NF-&kgr;B appeared to involve reduced degradation of I&kgr;B-&agr;. Conclusion The results demonstrate that thiopental inhibits the activation of NF-&kgr;B and may thus provide a molecular mechanism for some of the immunosuppressing effects associated with thiopental therapy.

Breathing pattern associated with respiratory comfort during automatic tube compensation and pressure support ventilation in normal subjects

Background: Automatic tube compensation (ATC) is a new option to support spontaneously breathing tracheally intubated patients. We have previously demonstrated an increased respiratory comfort compared to pressure support ventilation (PSV) in volunteers. Here we characterized the breathing pattern during ATC associated with respiratory comfort in comparison to PSV. Furthermore, we studied whether ATC can be substituted by a simple modification of PSV.

Method for analysis of exhaled air by microwave energy desorption coupled with gas chromatography-flame ionization detection-mass spectrometry

A method for chemical analysis of volatile constituents in exhaled air of mechanically ventilated patients is described. Exhaled substances are adsorbed and concentrated onto activated charcoal, desorbed by microwave energy and transferred into a gas chromatograph for separation without prior cryofocusing. Substances are identified by flame ionisation detection and mass spectrometry. This method yields reproducible results and is well suited for clinical studies.

Volume-dependent compliance and ventilation-perfusion mismatch in surfactant-depleted isolated rabbit lungs.

ObjectiveVolume-dependent alterations of lung compliance are usually studied over a very large volume range. However, the course of compliance within the comparably small tidal volume (intratidal compliance-volume curve) may also provide relevant information about the impact of mechanical ventilation on pulmonary gas exchange. Consequently, we determined the association of the distribution of ventilation and perfusion with the intratidal compliance-volume curve after modification of positive end-expiratory pressure (PEEP). DesignRepeated measurements in randomized order. SettingAn animal laboratory. SubjectsIsolated perfused rabbit lungs (n = 14). InterventionsSurfactant was removed by bronchoalveolar lavage. The lungs were ventilated thereafter with a constant tidal volume (10 mL/kg body weight). Five levels of PEEP (0–4 cm H2O) were applied in random order for 20 mins each. Measurements and Main Results The intratidal compliance-volume curve was determined with the slice method for each PEEP level. Concurrently, pulmonary gas exchange was assessed by the multiple inert gas elimination technique. At a PEEP of 0–1 cm H2O, the intratidal compliance-volume curve was formed a bow with downward concavity. At a PEEP of 2 cm H2O, concavity was minimal or compliance was almost constant, whereas higher PEEP levels (3–4 cm H2O) resulted in a decrease of compliance within tidal inflation. Pulmonary gas exchange did not differ between PEEP levels of of 0, 1, and 2 cm H2O. Pulmonary shunt was lowest and perfusion of alveoli with a normal ventilation-perfusion was highest at a PEEP of 3–4 cm H2O. Deadspace ventilation did not change significantly but tended to increase with PEEP. ConclusionsAn increase of compliance at the very beginning of tidal inflation was associated with impaired pulmonary gas exchange, indicating insufficient alveolar recruitment by the PEEP level. Consequently, the lowest PEEP level preventing alveolar atelectasis could be detected by analyzing the course of compliance within tidal volume without the need for total lung inflation.

Large increase in cardiac output in a patient with ARDS and acute right heart failure during inhalation of nitric oxide

Background Inhaled nitric oxide (NO), a selective pulmonary vasodilator, reduces pulmonary artery pressure in patients with acute respiratory distress syndrome (ARDS). In spite of the reduction of right ventricular afterload, the effect of NO on cardiac output remains unclear.

Intratidal compliance-volume curve as an alternative basis to adjust positive end-expiratory pressure: a study in isolated perfused rabbit lungs.

Objective Repeated collapse and reopening of alveoli have been shown to aggravate lung injury, which could be prevented by positive end-expiratory pressure (PEEP). Yet, how to adjust optimum PEEP is a matter of debate. We suggest a new strategy to adjust PEEP, which is based on the analysis of the intratidal compliance-volume curve. This approach was compared with a strategy based on the static pressure-volume curve. Furthermore, two other ventilator settings were investigated. One served as a negative control likely to provoke atelectasis, and the other was expected to induce overdistension. Design Prospective, randomized block design. Setting Laboratory. Subjects Isolated, perfused, and ventilated rabbit lungs. Interventions Tidal volumes of 8 mL/kg of body weight were used throughout. After stabilization, the lungs were randomized to one of four protocols (lasting 120 mins; n = 6 per group). Group 1 was ventilated at zero end-expiratory pressure. In group 2, PEEP was set above the lower inflection point of the static pressure-volume curve. In group 3, adjustment of PEEP was based on the intratidal compliance-volume curve, as determined by the slice method. In group 4, increasing PEEP levels ensured a plateau airway pressure of 20–25 cm H2O likely to provoke overdistension. Measurements and Main Results The ventilation/perfusion (&OV0312;a/&OV0422;) distribution was analyzed by the multiple inert gas elimination technique. Alveolar derecruitment was indicated by shunt and low &OV0312;a/&OV0422; areas as observed in group 1. In groups 2 and 3, &OV0312;a/&OV0422; data initially indicated full recruitment. In contrast to group 3, shunt increased in group 2 near completion of the experiments. Group 4 showed complete recruitment, but the &OV0312;a/&OV0422; distribution included high &OV0312;a/&OV0422; areas. Conclusions The intratidal compliance-volume curve represents a rational basis for adjusting PEEP in the isolated lung model. Because this strategy does not require invasive measures and facilitates continuous assessment of ventilator settings, it may be of clinical interest.