Peter Fridrich

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.

The effects of long-term prone positioning in patients with trauma-induced adult respiratory distress syndrome

Prone positioning improves gas exchange in some patients with adult respiratory distress syndrome (ARDS), but the effects of repeated, long-term prone positioning (20 h duration) have never been evaluated systemically. We therefore investigated 20 patients with ARDS after multiple trauma (Injury Severity Score [ISS] 27.3 +/- 10, ARDS score 2.84 +/- 0.42). Patients who fulfilled the entry criteria (bilateral diffuse infiltrates, severe hypoxemia, pulmonary artery occlusion pressure [PAOP] < 18 mm Hg, and PaO2/fraction of inspired oxygen [FIO2] < 200 mm Hg at inverse ratio ventilation with positive end-expiratory pressure [PEEP] > 8 mm Hg for more than 24 h) were turned to the prone position at noon and were turned back to the supine position at 8:00 AM on the next day. Thus, only two turns per day were necessary, and the risk of disconnecting airways or medical lines was minimized. Prone positioning was repeated for another 20 h if the patients fulfilled the entry criteria. Except for FIO2, the ventilator settings remained unchanged during the study period. All patients were sedated and, if needed, paralyzed to minimize patient discomfort. One hour before and after each position change, ventilator settings and pulmonary and systemic hemodynamics were recorded and blood was obtained for blood gas analysis. Derived cardiopulmonary and ventilatory variables were calculated using standard formulas. Overall mortality was 10%. Oxygenation variables improved significantly each time the patients were placed prone. Immediately after the first turn from the supine to the prone position the following changes were observed: PaO (2) increased from 97 +/- 4 to 152 +/- 15 mm Hg, intrapulmonary shunt (Qva/Qt) decreased from 30.3 +/- 2.3 to 25.5 +/- 1.8, and the alveolar-arterial oxygen difference decreased from 424 +/- 24 to 339 +/- 25 mm Hg. All these changes were statistically significant. Most of these improvements were lost when the patients were turned supine, but could be reproduced when prone positioning was repeated after a short period (4 h) in the supine position. Short periods in the supine position were necessary to allow for nursing care, medical evaluation, and interventions, such as placement of central lines. No position-dependent changes of systemic hemodynamic variables were observed. We conclude that, in trauma patients with ARDS undergoing long-term positioning treatment, lung function improves significantly during prone position compared to short phases of conventional supine position during which the beneficial effects are partly lost. (Anesth Analg 1996;83:1206-11)

The UpsherScope[trademark symbol] in Routine and Difficult Airway Management: A Randomized, Controlled Clinical Trial

The UpsherScope[trademark symbol], a rigid fiberoptic laryngoscope, may facilitate tracheal intubation.We performed a randomized, controlled trial of tracheal intubation using the UpsherScope[trademark symbol] and compared the success rate with that of direct laryngoscopy. Three hundred patients were randomly assigned to either fiberoptic oral intubation using the UpsherScope[trademark symbol] (Group US, n = 148) or to direct laryngoscopy (Group DL, n = 152). No significant differences in airway variables were observed between the groups. US intubation was successful in 129 of 148 patients (87%). A second or third attempt was required in 15% and 3%, respectively, of the patients successfully intubated with US. The remaining patients were intubated using DL (n = 17) or the flexible fiberoptic bronchoscope (n = 2). The success rate of DL was significantly higher (97%; P < 0.05), with a second or third attempt required in only seven patients. Time needed to perform successful intubation was 50 +/- 41s for the US group compared with 23 +/- 13 s for the DL group (P < 0.05). We found no advantage of the UpsherScope[trademark symbol] over direct laryngoscopy during routine and difficult airway management. Time needed, number of attempts required to perform intubation, and incidence of failure were significantly longer and higher in group US. Implications: We studied tracheal intubation using the fiberoptic UpsherScope[trademark symbol] and compared the success rate with that of a control group of patients intubated using conventional laryngoscopy. No advantages of the new device were found. On the contrary, time needed, number of attempts required, and incidence of failure were even longer and higher. (Anesth Analg 1997;85:1377-81)

The arterial to end-tidal carbon dioxide gradient increases with uncorrected but not with temperature-corrected Paco2 determination during mild to moderate hypothermia

End-tidal carbon dioxide (PETCO2) monitoring is recommended as a basic standard of care and is helpful in adjusting mechanical ventilation. Gas solubility changes with temperature, which might affect the PaCO2 and thereby the gradient between Paco2 and PETCO2 (PA-ETCO2) under hypothermic conditions. We investigated whether the PA-ETCO2 changes during mild to moderate hypothermia (36[degree sign]C-32[degree sign]C) using PaCO2 measured at 37[degree sign]C (uncorrected PaCO2) and PaCO2 corrected to actual body temperature. We preoperatively investigated 19 patients. After anesthesia had been induced, controlled ventilation was established to maintain normocarbia using constant uncorrected PaCO (2) to adjust ventilation (alpha-stat acid-base regimen). Body core temperature was reduced without surgical intervention to 32[degree sign]C by surface cooling. Continuous PETCO2 was monitored with a mainstream PETCO2 module. The PA-ETCO (2) was calculated using the uncorrected and corrected PaCO2 values. During body temperature reduction from 36[degree sign]C to 32[degree sign]C, the gradient between PETCO2 and uncorrected PaCO2 increased 2.5-fold, from 4.1 +/- 3.7 to 10.4 +/- 3.8 mm Hg (P < 0.002). The PA-ETCO2 remained unchanged when the corrected Paco2 was used for the calculation. We conclude that when the alpha-stat acid-base regimen is used to adjust ventilation, the PA-ETCO2 calculated with the uncorrected PaCO2 increases and should be added to the differential diagnosis of widened PA-ETCO2. In contrast, when the corrected PaCO2 is used for the calculation of the PA-ETCO2, the PA-ETCO2 remains unaltered during hypothermia. Implications: We investigated the impact of induced hypothermia (36[degree sign]C-32[degree sign]C) on the gradient between PaCO2 and PETCO2 (PA-ETCO (2)). The PA-ETCO2 increased 2.5-fold when CO2 determinations were not temperature-corrected. Hypothermia should be added to the differential diagnosis of an increased PA-ETCO2 when the alpha-stat acid-base regimen is used. (Anesth Analg 1998;86:1131-6)

Maßnahmen durch Ersthelfer am Unfallort Eine prospektive, epidemiologische Studie im Raum Wien

SummaryThe object of this prospective, epidemiological study was to determine whether bystanders provided necessary first aid measures in the prehospital trauma setting, whether they performed these measures correctly, and whether the level of first aid training affected the quality of first aid measures performed. Data were collected by means of a questionnaire, which was filled out between March and July 2000 for all cases attended to by the Vienna Ambulance Service. A total of 2812 cases were documented. The most frequent causes of trauma were falls from heights less than 1 meter (50%) and traffic accidents (17%). The most frequent injuries were injuries to the extremities (59%) and head and traumatic brain injuries (42%). Most patients were “moderately” or “severely” injured (69% and 29%,. respectively), but life-threatening injuries were rare (2%). Bystanders were present in 57% of the cases. The most frequently required first aid measures were “application of a dressing” and “positioning” of the patient, “Control of haemorrhage”, “ensuring accident site safety” and “extrication” of the patient were less frequently required. “Clearing of the airway”, “precautions against hypothermia” and cardio-pulmonary resuscitation were very rarely required. Bystanders were most frequently policemen, relatives or friends of the patient, and strangers. The vast majority of bystanders had no training in first aid or had only attended the first aid course required to attain a driving licence. We found a clear relationship between the level of first aid training and the quality of first aid measures provided. It would be advisable to offer an increased amount of refresher courses in first aid to improve bystander trauma care.ZusammenfassungZiel dieser prospektiven, epidemiologischen Studie war es, zu erheben, ob Erste-Hilfe-Maßnahmen am Unfallort notwendig waren und ob sie von Ersthelfern geleistet und korrekt durchgeführt wurden. Weiters sollten Angaben zu den Ersthelfern erhoben und festgestellt werden, ob der Ausbildungsstand die Qualität der Erste-Hilfe-Maßnahmen beeinflusst. Die Erhebung erfolgte mittels eines Fragebogens, der zwischen März und Juli 2000 bei allen Einsätzen der Wiener Rettung ausgefüllt wurde. Insgesamt wurden 2812 Einsätze erfasst. Die häufigsten Unfallursachen waren Sturz aus <1 m Höhe (50%) und Verkehrsunfälle (17%). Die häufigsten Verletzungen waren Extremitätenverletzungen (59%) und Schädel- und Schädel-Hirn-Traumen (42%). Die meislen Patienten waren „mäßig schwer” (69%) oder „schwer” (29%) verletzt, aber lebensbedrohliche Verletzungen waren selten (2%). Ersthelfer waren in 57% der Unfälle anwesend. Die am häufigsten indizierten Erste-Hilfe-Maßnahmen waren „Anlegen eines Verbands” und „Lagerung”. Seltener waren „Stillung einer Bluttung”, „Absicherung der Unfallstelle” und „Bergung” indiziert „Freimachen der Atemwege”, „Schutz gegen Unterkühlung” und „Atemspende und Herzmassage” waren sehr selten indiziert. Die häufigsten Ersthelfer waren Polizisten. Verwandte oder Freunde des Verunfallten, und Unbetelligte. Die überwiegende Mehrzahl aller Ersthelfer hatte keine Erste-Hilfe-Ausbildung oder nur den für den Erwerb des Führerscheins notwendigen Kurs. Es bestand ein deutlicher Zusammenhang zwischen Ausbildungsstand und Qualität der Erste-Hilfe-Maßnahmen. Es wäre sinnvoll, vermehrt Wiederholungskurse anzubieten, um bestehende Defizite zu beheben.

Cardiovascular and catecholamine response to surgery in brain‐dead organ donors

Eleven brain‐dead organ donors were studied during surgery. Plasma levels of adrenaline and noradrenaline were measured before and after skin incision, upon sternotomy and 15, 30 and 45min thereafter. Haemodynamic changes were measured continuously throughout the observation period. Blood pressure and heart rate increased after skin incision, remained high at sternotomy then decreased towards the end of the observation period in six of the 11 patients. Plasma catecholamines increased promptly with the onset of surgical stimuli. We conclude that surgical stress can evoke an excessive rise of plasma adrenaline and noradrenaline and thus could impair allograft function.

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.

Clinical trial of a new device for fiberoptic orotracheal intubation (Augustine Scope).

Blind oral intubation using the Augustine Guide is helpful for intubating the trachea of patients presenting with difficult airways. This device has been modified by adding a fiberoptic scope with a built-in battery-powered light. We studied this Augustine Scope in 104 patients (Group AS) and compared the results with 96 patients managed by direct laryngoscopy (Group DL). No significant differences in Mallampati class, thyromental distance, laryngoscopic view, and patients height or weight were observed between the two groups. The Augustine Scope provided conditions for successful intubation in 102 of 104 patients (98%), compared with a 97% success rate in the group where DL was used. The three patients who failed DL were successfully intubated with AS. The mean +/- SD time needed to perform intubation was 19 +/- 10 s in Group AS and 21 +/- 13 s in Group DL (P = not significant). No traumatizing effects were observed. We conclude that the Augustine Scope is an effective and safe device for orotracheal intubation in routine and difficult airways.

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.