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.

Phase 1A safety assessment of intravenous amitriptyline

The antidepressant amitriptyline is used as an adjuvant in the treatment of chronic pain. Among its many actions, amitriptyline blocks Na+ channels and nerves in several animal and human models. As perioperative intravenous lidocaine has been suggested to decrease postoperative pain, amitriptyline, because of its longer half-life time, might be more useful than lidocaine. However, the use of intravenous amitriptyline is not approved by the US Food and Drug Administration. We therefore investigated the adverse effects of preoperative intravenous amitriptyline in a typical phase 1A trial. After obtaining written Food and Drug Administration and institutional review board approval, we obtained written consent for preoperative infusion of amitriptyline in an open-label, dose-escalating design (25, 50, and 100 mg, n=5 per group). Plasma levels of amitriptyline/nortriptyline were determined, and adverse effects were recorded in a predetermined symptom list. Infusion of 25 and 50 mg amitriptyline appears to be well tolerated; however, the study was terminated when 1 subject in the 100-mg group developed severe bradycardia. Intravenous infusion of amitriptyline (25 to 50 mg over 1 hour) did not create side effects beyond dry mouth and drowsiness, or dizziness, in 2 of our 10 otherwise healthy participants receiving the 25- to 50-mg dose. An appropriately powered future trial is necessary to determine a potential role of amitriptyline in decreasing postoperative pain.

PERSPECTIVE

Amitriptyline potently blocks the persistently open Na+ channels, which are known to be instrumental in various pain states. As this occurs at very low plasma concentrations, a single preoperative intravenous infusion of amitriptyline could provide long-lasting pain relief and decrease the incidence of chronic pain.

Emergency room management of patients with blunt major trauma: evaluation of the multislice computed tomography protocol exemplified by an urban trauma center

BACKGROUND

The early clinical management of patients with major trauma still represents a challenge. To clinically evaluate the full extent of a patient's injuries is difficult, especially when the patient is unconscious. Before December 2002, trauma patients admitted to our emergency room (ER) underwent a diagnostic protocol including physical examination, conventional radiography (CR), sonography and further procedures if necessary. After the installation of a MSCT scanner, all trauma patients underwent the "MSCT protocol" immediately after admission. The aim of the study was to compare the "MSCT-protocol" as it is performed at our institution, with the "Pre-MSCT-protocol".

METHODS

We compared 185 patients undergoing the "Pre MSCT-protocol" with 185 patients undergoing "MSCT protocol". We evaluated the efficacy, speed and accuracy of the "MSCT protocol" using several variables. Time periods from admission to the ER to admission to the intensive care unit were compared as well as outcome parameters such as length of ICU stay, ventilation period and rates of organ. Dichotomous data were analyzed by Chi-square analysis; continuous data were analyzed by Student's t test. Any values of p < 0.05 were considered significant for any test.

RESULTS

No significant differences were found regarding demographic data. The full extent of injuries was definitively diagnosed after 12 +/- 9 minutes in 92.4% of the "MSCT protocol" cohort. In only 76.2% of "Pre-MSCT protocol" cohort definitive diagnosis was possible after 41 +/- 27 minutes. Total ER time was 104 +/- 21 minutes with the "Pre-MSCT protocol" and 70 +/- 17 minutes with "MSCT protocol" (p < 0.05). "Pre-MSCT protocol" patients had a significantly longer ICU stay than "MSCT protocol" patients (p < 0.05). "MSCT protocol" patients had significantly fewer ventilation days (14.3 vs. 10.9 days). Furthermore, rates of organ failure were lower in patients undergoing the "MSCT protocol".

CONCLUSION

We could demonstrate that immediate MSCT in patients with blunt major trauma leads to more accurate and faster diagnosis, and reduction of early clinical time intervals. We also observed a reduction in ventilation, ICU, and hospital days, and in organ failure rates, though this might have been partly due to small differences in case mix. The "MSCT protocol" algorithm seems to be safe and effective.

Phase Ia and Ib Study of Amitriptyline for Ulnar Nerve Block in Humans

Background

The antidepressant amitriptyline is used as an adjuvant in the treatment of chronic pain conditions. Among its many actions, this drug also blocks ion channels, such as Na channels. Preliminary animal studies suggested that amitripty-line would be a longer-lasting local anesthetic than bupivacaine, with potentially fewer side effects. Therefore, the authors investigated the adverse effects and effectiveness of this drug when given for ulnar nerve blockade in human volunteers.

Methods

After obtaining written institutional review board approval and informed consent, a typical phase Ia trial was conducted by administration to the ulnar nerve at the level of the wrist in an open-label, dose-escalating fashion. Amitripty-line hydrochloride, 4 ml, at concentrations of 5, 10, and 20 mM (n = 4-9/group) was used for each volunteer. If no major side effects and nerve block were encountered, comparison in a randomized, double-blinded trial of amitriptyline (20 mM) to placebo and bupivacaine (4 mM) (n = 4-9/group), was to follow. A blunt needle was used to grade the pain, and motor blockade was assessed by the Froment test.

Results

There was no significant statistical difference in terms of side effects (pain, swelling, erythema, and sedation) among any groups. The analgesic effects of 20 mM amitriptyline and 4 mm bupivacaine solution were significantly higher than those of the placebo solution.

Conclusions

Because of the lack of evidence that amitripty-line provides better nerve blockade than current local anesthetics and the potential for neurotoxicity, its use for peripheral nerve blockade in humans seems limited.

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

The 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 license. 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.

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, 6-10 months 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 30 mmHg ( 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.

[Knowledge-based diagnosis and therapeutic recommendations with fuzzy-set theory methods in patients with acute lung failure (ARDS)]

OBJECTIVE

Since the treatment of patients with severe ARDS using the extracorporal lung assist (ECLA) methods remains a cost intensive and speculative procedure, a knowledge based computer system should be created and evaluated in order to support clinical decisions.

METHODS

The model was based on the fuzzy set theory and therefore able to give decisions between yes and no, that means that a criterion could also be fulfilled to 35% or 80% for example. The development of this computer program consists of two steps: first, the entry criteria for the ECLA therapy were established within a framework of an international evaluation of clinical data from 3 centres (Berlin, Marburg, Vienna). Here, inherent vagueness, uncertainty of the occurrence and limited availability of medical data are to be considered to establish a useful tool. Secondly, this was done by grouping and weighting of parameters by the system and the status of each patient or patient group was assigned by the percentage of fulfillment of the criterion.

RESULTS

By using a mixed sample of patients from these three centres, the fulfillment of entry criteria according either to definitions of Berlin or to definition of Marburg was different (68% versus 36%). Other differences (36% vs. 22% and 68% vs. 60%) were found between the fuzzy based score and the crisp score which represents the usually performed method.

CONCLUSIONS

This now preevaluated minimal data set to describe severe ARDS patients based on the fuzzy set theory may be useful to evaluate patients for ECLA therapy or for another controlled ARDS-therapy.

Antioxidant status in patients with acute respiratory distress syndrome

OBJECTIVES

Reactive oxygen species (ROS) have been implicated in the pathophysiology of ARDS. We investigated the pattern of antioxidants in plasma and ROS production by neutrophils in patients with ARDS over 6 days.

DESIGN

Observational study. Blood samples were taken when the diagnosis was made (D0) and after 3 (D3) and 6 days (D6) during therapy.

SETTING

Intensive care units at a University Hospital.

PATIENTS

Eight patients with ARDS were investigated, 17 healthy volunteers served as controls.

MEASUREMENTS AND RESULTS

Plasma levels of ascorbate, alpha-tocopherol, retinol, beta-carotene, selenium and lipid peroxidation products (MDA) were determined and the activities of the antioxidative enzymes catalase (CAT), superoxide dismutase (SOD) and glutathione-peroxidase (GSH-PX) in erythrocytes were measured. In addition, ROS production (superoxide anion and hydrogen peroxide) in activated neutrophils was assessed. Plasma levels of alpha-tocopherol, ascorbate, beta-carotene and selenium were reduced from the onset of illness. MDA plasma levels were increased throughout the illness. ROS generation from neutrophils was normal on D0 and decreased to D6 in ARDS patients.

CONCLUSION

The antioxidative system is severely compromised in patients with ARDS. Plasma levels of alpha-tocopherol, ascorbate, beta-carotene and selenium are decreased. Elevated MDA levels provide further evidence of massive oxidative stress. The routine replacement of micronutrients according to recommended daily allowances was inadequate to compensate for the increased requirements.

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 degrees C-32 degrees C) using PaCO2 measured at 37 degrees 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 PaCO2 to adjust ventilation (alpha-stat acid-base regimen). Body core temperature was reduced without surgical intervention to 32 degrees C by surface cooling. Continuous PETCO2 was monitored with a mainstream PETCO2 module. The PA-ETCO2 was calculated using the uncorrected and corrected PaCO2 values. During body temperature reduction from 36 degrees C to 32 degrees 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 degrees C-32 degrees C) on the gradient between PaCO2 and PETCO2 (PA-ETCO2). 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.

Pulmonary function and radiographic abnormalities related to neurological outcome after aneurysmal subarachnoid hemorrhage

OBJECT

This observational study is based on a consecutive series of 207 patients with aneurysmal subarachnoid hemorrhage who were treated within 7 days of their most recent bleed. The purpose of the study was to evaluate the effect of respiratory failure on neurological outcome.

METHODS

Pulmonary function was assessed by determination of parameters describing pulmonary oxygen transport and exchange, by using composite scores for quantification of lung injury (lung injury score [LIS]) and mechanical ventilator settings (PIF score). Pulmonary function was related to the Hunt and Hess (H & H) grade assigned to the patient at hospital admission (p < 0.001). The pattern and time course of lung injury differed significantly between patients with H & H Grade I or II, Grade III, and Grade IV or V. Hunt and Hess grade, Fisher computerized tomography grade, intracranial pressure, cerebral perfusion pressure, LIS, ratio of PaO2 to the fraction of inspired oxygen (FiO2), and the ratio of the alveolar-minus-arterial oxygen tension difference (AaDO2) to FiO2 were related to neurological outcome (p < 0.001). The LIS on the day of maximum lung injury remained an independent predictor of outcome (p = 0.01) in a stepwise logistic regression analysis. The probability of poor neurological outcome significantly increased with both decreasing cerebral perfusion pressure and increasing severity of lung injury.

CONCLUSIONS

The overall mortality rate was 22.2% (46 of 207 patients). Subarachnoid hemorrhage and its neurological sequelae accounted for the principal mortality in this series. Medical (nonneurological and nontreatment-related) complications accounted for 37% of all deaths. Systemic inflammatory response syndrome with associated multiple organ dysfunction syndrome was the leading cause of death from medical complications. The authors conclude that respiratory failure is related to neurological outcome, although it is not commonly the primary cause of death from medical complications.

The UpsherScope in routine and difficult airway management: a randomized, controlled clinical trial

The UpsherScope, a rigid fiberoptic laryngoscope, may facilitate tracheal intubation. We performed a randomized, controlled trial of tracheal intubation using the UpsherScope and compared the success rate with that of direct laryngoscopy. Three hundred patients were randomly assigned to either fiberoptic oral intubation using the UpsherScope (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 +/- 41 s for the US group compared with 23 +/- 13 s for the DL group (P < 0.05). We found no advantage of the UpsherScope 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 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.

[Subdural, extra-arachnoid block as a complication of stellate ganglion block: documentation with ultrasound]

We present a patient who developed a high central neural block after stellate-ganglion-blockade. The underlying pathophysiology was assessed via sonographic imaging. Stellate ganglion block was performed in a 19-year old patient according to the standard technique. Multiple aspiration tests were negative and a test dose of 3 ml bupivacaine 0.25% was injected. After a 3 min interval another 5 ml were injected. Two minutes after the local anaesthetic administration the patient reported nausea and sensations in the upper extremity. Spontaneous respiration efforts stopped, and the patient became unconscious. Tracheal intubation was performed, and the patient was ventilated in a controlled mode for two hours. Heart rate as well as blood pressure remained within the normal range. Neurologic recovery occurred rapidly and extubation was performed about two and a half hours after the event. Our sonographic studies demonstrated a local anaesthetic depot directly at the root of C 6, with a mean diameter of 10 mm and a length of 5 to 6 cm (about a third smaller than expected). Sonographic studies and clinical symptoms of our patient are most likely to occur with a subdural extra-arachnoidal block. Ultrasonographic guided puncture enhances the patient's safety by the opportunity to directly visualise transverse process, nerval root as well as local anaesthetic depot. In case of depot formation directly at the nerval root, injection may be stopped and the needle repositioned. Furthermore, direct visualisation of the great vessels (A. vertebralis) prevents intravascular injection and haematoma formation.

Bronchoscopy via a redesigned Combitube in the esophageal position. A clinical evaluation

BACKGROUND

The esophageal-tracheal Combitube (Kendall-Sheridan Catheter Corp., Argyle, NY) is an effective device for providing adequate gas exchange. However, tracheal suctioning is impossible with the Combitube placed in the esophageal position. To eliminate this disadvantage, the Combitube was redesigned by creating an enlarged hole in the pharyngeal lumen that allows fiberoptic access, tracheal suctioning, and tube exchange over a guide wire.

METHODS

The two anterior, proximal perforations of regular Combitubes were replaced by a larger, ellipsoid-shaped hole. After the study was approved by the institutional review board, 20 patients with normal airways (Mallampati I or II) were studied. During general anesthesia, patients were esophageally intubated with the Combitube. A flexible bronchoscope was inserted and guided via the modified hole and glottic opening down the trachea. For the replacement procedure, a J tip guide wire was introduced through the bronchoscope. The bronchoscope and the Combitube were removed and a standard endotracheal tube was advanced over a guide catheter.

RESULTS

Bronchoscopic evaluation of the trachea and guided replacement of the Combitube by an endotracheal tube was successful in all 20 study patients. The average time needed to perform airway exchange was 90 +/- 20 s (mean +/- SD). Arterial oxygen saturation and end-tidal carbon dioxide levels remained normal in all patients. No case of laryngeal trauma was observed during intubation or the airway exchange procedure.

CONCLUSIONS

The redesigned Combitube enables fiberoptic bronchoscopy, fine-tuning of its position in the esophagus, and guided airway exchange in patients with normal airways. Further studies are warranted to demonstrate its value in patients with abnormal airways.

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.

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: PaO2 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.

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

OBJECTIVE

To 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 SOURCES

Computerized (Medline, Current Contents) and manual (Cumulated Index Medicus) literature search using the key word and/or title ARDS.

STUDY SELECTION

Only 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 EXTRACTION

Relevant data were extracted in duplicate, followed by quality checks on approximately 80% of data extracted.

DATA SYNTHESIS

101 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%).

CONCLUSIONS

The 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.

Effectiveness of nitric oxide inhalation in septic ARDS

STUDY OBJECTIVE

To evaluate the percentage of nitric oxide (NO) responders in septic shock patients with ARDS. Additionally, to investigate long-term NO effects on cardiac performance and oxygen kinetic patterns in NO responders vs nonresponders.

DESIGN

Prospective cohort study.

SETTING

ICU of a university hospital.

PATIENTS

Twenty-five consecutive patients with a diagnosis of septic shock and established ARDS requiring inotropic and vasopressor support.

INTERVENTIONS

After diagnosis of ARDS, NO was administered at 18 or 36 ppm. Patients demonstrating a NO-induced rise of arterial oxygen tension of 20% or more and/or a fall in mean pulmonary artery pressure of 15% or more were grouped as NO responders; others were grouped as nonresponders.

MEASUREMENTS AND RESULTS

Ten patients (40%) were NO responders, while 15 patients (60%) were nonresponders. Mortality was 40% in NO responders and 67% in nonresponders (NS). NO responders developed a significantly lower mean pulmonary artery pressure (28 +/- 6 vs 33 +/- 6 mm Hg; p < 0.05), lower pulmonary vascular resistance (PVR: 258 +/- 73 vs 377 +/- 163 dyne.s.cm-5.m-2; p < 0.05), and higher PaO2/FIO2 ratio (192 +/- 85 vs 144 +/- 74 mm Hg; p < 0.05) within the study period. In responders, NO-induced afterload reduction resulted in increased right ventricular ejection fraction (RVEF: 40 +/- 7 vs 35 +/- 9%; p < 0.05), significantly higher cardiac index (CI: 4.5 +/- 1.1 vs 4.0 +/- 1.2 L.min-1.m-2; p < 0.05) and oxygen delivery (DO2: 681 +/- 141 vs 599 +/- 160 mL.min-1.m-2; p < 0.05) compared with nonresponders. In NO nonresponders, RVEF was correlated with PVR, CI, DO2, mixed venous oxygen saturation (SvO2), and oxygen extraction ratio (O2ER) (r = +/- 0.60 to +/- 0.69; p < 0.05). No significant correlation between RVEF and any of these parameters was observed in responders. SvO2 (75 +/- 7 vs 69 +/- 8%; p < 0.05) and O2ER (0.24 +/- 0.06 vs 0.27 +/- 0.06; p < 0.05) were significantly different between responders and nonresponders, while no difference in oxygen consumption was observed (161 +/- 41 vs 153 +/- 43 mL.min.m-2).

CONCLUSIONS

Inhaled NO is effective in only a subgroup of septic ARDS patients, with a higher, but insignificantly different percentage of survivors in the responder group. NO responders were characterized by increased RVEF accompanied by higher CI, DO2, and lower O2ER. In nonresponders, RVEF remained depressed, with a close correlation between RVEF and CO as well as DO2 and O2ER. Thus, nonresponders seem to suffer from impaired cardiac reserves and correspondingly lower oxygen transport variables.

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 recommendation 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.

Optimal values for oxygen transport during hypothermia in sepsis and ARDS

Mild hypothermia (33 degrees C to 35.5 degrees 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. Overall, we recruited 27 patients with ARDS and sepsis. Prior initiation of CVVHF patients had to meet the following criteria: a) Murray score > 2.5, and hypoxaemia with PaO2/FIO2 < 200, b) hyperthermia of > 38 degrees C, c) cardiovascular instability requiring inotropic support. Evaluation of cardio-respiratory data was performed within four different phases (I = before, II + III during and IV = after CVVHF) every 6 hours. Core temperature as derived from the thermistor of pulmonary artery catheter was aimed to be between 35.0 degrees C and 36.5 degrees C. Optimal values for oxygen delivery (DO2) (> 550 mL/min/m2) and VO2 (> 160 mL/min/m2) were defined according to Shoemaker and achieved by fluid loading, transfusion and inotropic support (3). Septic shock occurred in 10 of 14 nonsurvivors (nons) and 2 of 13 survivors (surv). Mean values for DO2 and VO2 were calculated at different body temperature ranges. While at 37 degrees C DO2 was identical between surv and nons, (663 +/- 128 versus 666 +/- 127 means +/- SD) moderate hypothermia led to a small decrease of DO2 in surv and a significant decrease in nons (632 +/- 134 versus 605 +/- 128 mL/min/m2) at 35 degrees C. Concerning VO2 during hypothermia, there was a significant drop in nonsurvivors while in survivors the decrease was less pronounced. We could demonstrate a decrease in DO2 and VO2 during mild hypothermia during CVVHF. However, decreases in nonsurvivors were more pronounced than in survivors. These results suggest that the inability to achieve optimal values for DO2 and VO2 during mild hypothermia induced by CVVHF could serve as a prognostic sign for fatal outcome. Although oxygen consumption is decreased during hypothermia, hypoxaemia may result due to alterations of the oxygen transport on a cellular basis. The relationship between oxygen transport and temperature during CVVHF therefore deserves further studies.

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 45 min 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.