Steltzer H

The acute respiratory distress syndrome: definitions, severity and clinical outcome An analysis of 101 clinical investigations

ObjectiveTo determine possible changes in outcome from acute respiratory distress syndrome (ARDS) and to compare severity of lung injury and methods of treatment from 1967 to 1994.Data sourcesComputerized (Medline, Current Contents) and manual (Cumulated Index Medicus) literature search using the key word and/or title ARDS.Study selectionOnly clinical studies published as full papers reporting data on both patient mortality (survival) and oxygenation index (PaO2/FIO2) were included. Single case reports, abstracts, reviews and editorials were excluded from evaluation.Data extractionRelevant data were extracted in duplicate, followed by quality checks on approximately 80% of data extracted.Data synthesis101 papers reporting on 3264 patients were included: 48 studies (2207 patients) were performed in the USA, 43 studies (742 patients) in Europe and 10 studies (315 patients) elsewhere. Mortality reported in these studies was 53±22% (mean±SD), with no apparent trend towards a higher survival (1994: 22 studies, mortality 51±19%). The mean PaO2/FIO2 ratio remained unchanged throughout the observation period (118±47 mmHg). No correlation could be established between outcome and PaO2/FIO2 or lung injury score. Patients who underwent pressure-limited ventilation had a significantly lower mortality (35±20%) than patients on volume-cycled ventilation (54±22%) or patients for whom there was no precise information on ventilatory support (59±19%). Significantly lower PaO2/FIO2 ratios (61±17 mmHg) were observed in patients prior to extracorporeal lung assist, together with mortality rates in the range of those for conventionally treated patients (55±22%).ConclusionsThe mortality of ARDS patients remained constant throughout the period studied. Therefore, the standard for outcome in ARDS should be a mortality in the 50% range. Neither PaO2/FIO2 ratio nor lung injury score was a reliable predictor for outcome in ARDS. Patients might benefit from pressure-limited ventilatory support, as well as extracorporeal lung assist. Since crucial data were missing in most clinical studies, thus preventing direct comparison, we emphasize the importance of using standardized definitions and study entry criteria.

Bilateral lung transplantation with intra- and postoperatively prolonged ECMO support in patients with pulmonary hypertension

OBJECTIVEnLung transplantation for pulmonary hypertension (PH) is usually performed on cardiopulmonary bypass, with the disadvantage of full systemic anticoagulation, uncontrolled allograft reperfusion and aggressive ventilation. These factors can be avoided with intra- and postoperatively prolonged extracorporeal membrane oxygenator (ECMO) support.nnnPATIENTS AND METHODSnBetween February 1999 and March 2001, 17 consecutive patients with PH (systolic pulmonary artery pressure >70 mmHg) of different etiologies underwent bilateral lung transplantation (BLTX). There were 11 females and six males in the age range from 7 to 50 years (mean age, 28.4+/-12.9 years). Six patients were preoperatively hospitalized, four in the intensive care unit (ICU), one was on ECMO for 3 weeks pretransplantation, and one was resuscitated and bridged with ECMO for 1 week until transplantation. Femoral venoarterial ECMO support with heparin-coated circuits was set up after induction of anesthesia and discontinued at the end of surgery (n=3) or extended for 12 h median into the postoperative period (n=14). Postoperative ventilation pressure was kept below 25 mmHg. Allograft function at 2 h after discontinuation of ECMO, outcome and adverse events were monitored in all patients. Mean follow up time was 18+/-11.4 months.nnnRESULTSnThe perioperative mortality was 5.9% (n=1). Arterial oxygen pressure measured 2 h after weaning from ECMO, and under standard mechanical ventilation with a peak pressure of 25 mmHg and inspired oxygen fraction of 0.4, was 157+/-28 mmHg. The mean pulmonary artery pressures were reduced to 29+/-3,4 from 66+/-15 mmHg before transplantation. Postoperative complications included rethoracotomy due to bleeding (n=4) and temporary left ventricular failure (n=4). Median ICU stay was 12 days. Incidence of rejection within the first 100 days was 0.4 per patient.nnnCONCLUSIONnBLTX with intraoperative and postoperatively prolonged ECMO support provides excellent initial organ function due to optimal controlled reperfusion and non-aggressive ventilation. This results in improved outcome even in advanced forms of PH.

Changes in lung parenchyma after acute respiratory distress syndrome (ARDS): assessment with high-resolution computed tomography

The aim of this study was to evaluate the appearance, extent, and distribution of parenchymal changes in the lung after acute respiratory distress syndrome (ARDS) as a function of disease severity and therapeutic procedures. High-resolution computed tomography (HRCT), clinical examination, and lung function tests were performed in 15 patients, 6–10xa0months after ARDS. The appearance and extent of parenchymal changes were compared with the severity of ARDS, as well as with clinical and therapeutic data. Lung parenchymal changes resembling those found in the presence of pulmonary fibrosis were observed in 13 of 15 patients (87%). The changes were significantly more frequent and more pronounced in the ventral than in the dorsal portions of the lung (p<0.01). A significant correlation was observed between the extent of lung alterations and the severity of ARDS (p<0.01), and the duration in which patients had received mechanical ventilation either with a peak inspiratory pressure greater than 30xa0mmHg (p<0.05), or with more than 70% oxygen (p<0.01). Acute respiratory distress syndrome frequently is followed by fibrotic changes in lung parenchyma. The predominantly ventral distribution of these changes indicates that they may be caused by the ventilation regimen and the oxygen therapy rather than by the ARDS.

Detection of graft nonfunction after liver transplantation by assessment of indocyanine green kinetics

I ndocyanine green dye (ICG) has been used in tests for a global measure of liver perfusion and excretory function for more than three decades (1) and has shown good correlation with the severity of hepatic disease as well as with outcome in liver transplant recipients (2-5). We report a case of the early detection of graft nonfunction after orthotopic liver transplantation (OLT) using a bedside monitoring device for fiberoptic assessment of ICG plasma disappearance rate (ICG PDR) (normal value 20%-30%) (2) in a 43-yr-old woman who underwent OLT because of cholangiocellular carcinoma. Retransplantation was performed, and the patient was dismissed from the hospital 3 wk after the first OLT.

The relationship between oxygen delivery and uptake in the critically ill : is there a critical or optimal therapeutic value ? A meta-analysis

In order to identify a critical or an optimal therapeutic value for oxygen delivery and oxygen uptake, we analysed data from 40 publications concerning the relationship between oxygen delivery and consumption in patients with adult respiratory distress syndrome, trauma or during sepsis, and in nonseptic controls. According to the outcome, the patients were allocated to either group 1 (survivors) or group 2 (nonsurvivors). While oxygen delivery and uptake (mean, SEM) were significantly higher in patients with adult respiratory distress syndrome (636, SEM 31 ml.min‐1.m‐2and 155, SEM 5 ml.min‐1.m‐2), trauma (782, SEM 77 ml.min‐1.m‐2 and 167, SEM 10 ml.min‐1.m‐2) and sepsis (654, SEM 28 ml.min‐1.m‐2 and 163, SEM 5 ml.min‐1.m‐2) than in nonseptic controls (452, SEM 18 ml.min‐1.m‐2 and 126, SEM 3 ml.min‐1.m‐2, p < 0.05), there were no significant differences in these parameters between survivors and nonsurvivors. Although therapeutic manoeuvres were effective in increasing both oxygen delivery and consumption, these improvements were not parallelled by an increase in survival rate. The correlation between oxygen delivery and uptake is generally a result of the use of pooled data and therefore prone to mathematical coupling. This is true particularly for patients with adult respiratory distress syndrome and sepsis. Thus, our study failed to identify either an optimal or a critical value of oxygen delivery or oxygen consumption in critically ill patients.

Perioperative liver graft function: the role of oxygen transport and utilization.

To assess the evolution of satisfactory neohepatic graft function or failure, hemodynamic variables, along with data for oxygen delivery and utilization, were analyzed retrospectively in 99 patients undergoing orthotopic liver transplantation. Caval cross-clamping without venovenous bypass initiated a series of hemodynamic events, characterized by decreases in pulmonary artery pressures, cardiac output, and arterial pressures and increases in systemic vascular resistance, with reciprocal changes after unclamping. Concerning oxygen transport, the increased oxygen delivery after caval unclamping led to increases of mixed venous oxygen tension, decreases of oxygen extraction, and the arteriovenous oxygen content difference. The most striking result, however, was that with similar values for oxygen delivery, the patients with primary nonfunction (n = 9) had both lower anhepatic oxygen consumption, much smaller increases in oxygen consumption, and lower ratios of oxygen extraction during reperfusion of the liver than the patients with normal initial graft function (n = 90). Thus, distinct increases in total body oxygen consumption were found to be indicative of the onset of hepatocellular function and satisfactory neohepatic graft function. The authors conclude that perioperative measurements of whole-body oxygen consumption are important in reflecting early allograft viability during orthotopic liver transplantation without anhepatic venovenous bypass.

Right ventricular function and oxygen transport patterns in patients with acute respiratory distress syndrome

We investigated the impact of right ventricular performance on oxygen kinetics in 15 consecutive patients with acute respiratory distress syndrome. Six hundred and twenty‐two complete assessments of haemodynamics, right ventricular function and oxygenation were used for evaluation. Patients were grouped as survivors (n = 8) and nonsurvivors (n = 7) and studied during four phases of lung failure. Oxygen delivery and consumption were significantly higher in survivors compared to nonsurvivors despite comparable arterial oxygen saturation. Right ventricular end‐diastolic volumes were similar for both groups, while end‐systolic volumes were significantly higher in nonsurvivors due to depressed ejection fraction (40.5 (SD 1.2) versus 34.4 (SD 2.8)%) during all phases of lung failure. No clinically relevant differences in right ventricular function or oxygenation were observed between periods of moderate or severe pulmonary hypertension. Nonsurvivors have depressed cardiac function caused by reduced contractility and not by inadequate right ventricular end‐diastolic volume (preload) or increased pulmonary artery pressure (afterload). Maintenance of oxygen delivery in ARDS is predominantly a function of cardiac performance and not of pulmonary gas exchange.

Bilateral lung transplantation via two sequential anterolateral thoracotomies

OBJECTIVEnBilateral anterior trans-sternal thoracotomy (clam shell incision) is the standard approach used for bilateral sequential lung transplantation (BLTX). The morbidity of this large incision can be considerable. Two separate sequential anterolateral thoractomies represent a less invasive approach.nnnMETHODSnThe value of this approach was investigated in a prospective series of 22 consecutive patients who received BLTX between June 1997 and July 1998. Their underlying diseases were COPD (n = 16), cystic fibrosis (n = 4) and other (n = 2). All patients underwent BLTX through two anterolateral thoracotomies, without the use of cardiopulmonary bypass. The anterior mediastinum and the sternum with all the surrounding tissue were left completely intact. Twenty-one patients underwent spirometrical examination during the postoperative in-hospital stay. Follow-up is 7+/-4 months (range: 3 to 15).nnnRESULTSnThe only intraoperative complication was severe reperfusion edema of the first transplanted lung seen in one patient at the end of the operation, which required pneumonectomy during the same session. All other operations were uneventful. The difference between the cold ischemic time of the first and second transplanted lung was 83+/-17 min. Median intubation duration, ICU- and in-hospital-stay were 1.5, 5 and 20 days, respectively (ranges: 1 to 96, 2 to 96 and 15 to 96, respectively). One major perioperative complication occurred and was due to gross donor/recipient size mismatch: the patient required lobectomy of the consolidated right upper lobe 11 days after transplantation. In 19 patients (86.4%), this less extensive incision allowed early postoperative mobilization, which resulted in good ventilatory performance, with VC of 53+/-15 and FEV1 of 60+/-20% of the predicted, respectively, at the first spirometry, 3 weeks after the operation. Three months survival was 100%.nnnCONCLUSIONnThe bilateral sequential anterolateral thoracotomy represents a safe and minimal invasive approach for BLTX compared with the clam shell incision. It minimizes the operative trauma, improves postoperative functional recovery and prevents the potential spread of unilateral complications to the other pleural cavity.

Optimal values for oxygen transport during hypothermia in sepsis and ARDS

Mild hypothermia (33 °C to 35. 5 °C) is reported to improve oxygenation and survival in patients with lung failure (1). Although hypermetabolism may account for about 50% of the ventilatory demand in ARDS patients, the concept of reducing oxygen consumption (VO2) by lowering metabolic rate, has only recently gained attention (2). Our study was aimed to test whether mild hypothermia established by continuous veno‐venous haemofiltration (CVVHF), could optimize values for oxygen kinetics in ARDS patients.

Severity and Outcome of ARDS: The Present Place of Extracorporeal Lung Assist (ECLA)

Within the last decade extracorporeal lung assist has been recommended for the treatment of acute respiratory distress syndrome. However, this recommandation was challenged by several recent clinical studies and reviews. The goal of our analysis was therefore to investigate data on outcome and severity of gas exchange disturbance published from patients treated with ECLA. These data were compared to a historical control group consisting of ARDS patients treated conventionally. Computerized (MEDLINE 1967-95) literature search using the keywords ARDS, ECLA, ECMO, ECCO2R and HUMAN was performed. Only clinical studies published as full papers reporting data on both, patients mortality and oxygenation index (PaO2/FiO2) were included. Overall mean mortality reported was 53±22% in 17 studies (419 patients), with no apparent trend towards a higher survival within the last decade with a mean PaO2/FIO2 (14 papers; 61±17 mmHg). However, mean mortality rates of ARDS patients requiring ECLA was 52.3% and 44.9% if patients undergoing ECMO were excluded (3 papers). Therefore the mortality of these patients with severe lung injury was in the range of patients treated conventionally. Patient outcome observed in our analysis is in accordance with the mortality rates from the European ECLA centres published recently (49% in 1993). Therefore, we conclude that the mean mortality rate of patients suffering from severe ARDS treated with ECLA is in the 50% range and does not differ significantly from those of patients treated conventionally, despite significantly poorer pulmonary function.