The American-European Consensus Conference on ARDS, part 2. Ventilatory, pharmacologic, supportive therapy, study design strategies and issues related to recovery and remodeling

The acute respiratory distress syndrome (ARDS) continues as a contributor to the morbidity and mortality of patients in intensive care units throughout the world, imparting tremendous human and financial costs. During the last ten years there has been a decline in ARDS mortality without a clear explanation. The American-European Consensus Committee on ARDS was formed to re-evaluate the standards for the ICU care of patients with acute lung injury (ALI), with regard to ventilatory strategies, the more promising pharmacologic agents, and the definition and quantification of pathological features of ALI that require resolution. It was felt that the definition of strategies for the clinical design and coordination of studies between centers and continents was becoming increasingly important to facilitate the study of various new therapies for ARDS.

Effect of ranitidine on gastric intramucosal pH in critically ill patients

OBJECTIVE

To determine whether ranitidine a) increases the values of gastric intramucosal pH (pHi) in critically ill patients, as determined by tonometry; b) reduces the variability of these measurements.

DESIGN

Prospective, double blind, randomized, placebo-controlled study.

SETTING

General Intensive Care Unit of a teaching hospital.

PATIENTS

Twenty-five critically ill, mechanically ventilated patients requiring arterial catheter and nasogastric tube.

INTERVENTIONS

Tonometer placement; blind, random administration of intravenous ranitidine (50 mg) or placebo.

MEASUREMENTS AND MAIN RESULTS

Tonometer saline PCO2 (PCO2i), arterial blood gases, gastric juice pH and pHi were determined immediately before, and 2, 4, 6 and 8 h after, ranitidine (12 patients) or placebo (13 patients). Ranitidine significantly increased gastric juice pH, but did not affect PCO2i or pHi; pHi was 7.34 +/- 0.14 before ranitidine, and 7.30 +/- 0.12, 7.31 +/- 0.11, 7.31 +/- 0.14 and 7.31 +/- 0.12-2, 4, 6 and 8 h, respectively, after ranitidine administration (p = 0.55). Ranitidine did not modify the coefficients of variation of PCO2i or pHi, either. No significant changes in gastric juice pH, PCO2i or pHi were observed in the placebo group.

CONCLUSIONS

In critically ill patients, ranitidine has no effect on pHi values, and does not increase the reproducibility of pHi measurements.

Effect of sucralfate on gastric intramucosal pH in critically ill patients

OBJECTIVE

To determine whether sucralfate administration affects the tonometric measurement of gastric intramucosal pH (pHi).

DESIGN

Non-randomized observational study.

SETTING

General intensive care unit of a teaching hospital.

PATIENTS

Twenty critically ill, mechanically ventilated, consecutively admitted patients requiring an arterial catheter and nasogastric tube.

INTERVENTIONS

Tonometer placement and sucralfate administration.

MEASUREMENTS AND MAIN RESULTS

We simultaneously determined tonometer saline PCO2 (PCO2i), arterial blood gases, pH of gastric juice and pHi. These parameters were evaluated immediately before sucralfate administration, and 2 h and 4 h after. We did not detect any change in either PCO2i or pHi after sucralfate administration (PCO2i: basal 6.4 +/- 1.7, 2 h 6.3 +/- 1.7, 4 h 6.3 +/- 1.7; pHi: basal 7.35 +/- 0.13, 2 h 7.36 +/- 0.12, 4 h 7.36 +/- 0.12).

CONCLUSIONS

Sucralfate does not affect the tonometric measurement of PCO2i and pHi.

Assessment of the prognosis of coronary patients: performance and customization of generic severity indexes

STUDY OBJECTIVE

To assess the prognostic performance of general severity systems (APACHE II [acute physiology and chronic health evaluation], simplified acute physiology score [SAPS II], and mortality probability models [MPM II]) in coronary patients and to derive new customized indexes for coronary patients using a reduced number of variables.

DESIGN

Inception cohort.

SETTING

Adult medical and surgical ICUs in 17 hospitals in Catalonia and the Balearic Islands.

PATIENTS

Four hundred fifty-six patients with acute myocardial infarction.

MEASUREMENTS AND RESULTS

The APACHE II, SAPS II, and MPM II variables and survival status at hospital discharge have been collected. Performance of the severity systems was assessed by evaluating calibration and discrimination. Logistic regression was used to customize the MPM II(24) and SAPS II indexes. Discrimination was high enough for all of the models. However, calibration of the MPM II(24) was not as satisfactory as for the other models. The MPM II(24) and SAPS II were both reduced to five variables (MPM II(24 cor:) age, PaO2, continuous vasoactive drugs, urinary output, and mechanical ventilation; SAPS II(cor:) age, PaO2/FI(O2) ratio, systolic BP, Glasgow coma score, and urinary output). Both models showed better calibration and discrimination than the original ones.

CONCLUSIONS

Prognostic indexes developed for multidisciplinary patients show good performance when applied to patients with acute myocardial infarction, but customization can reduce the number of variables necessary to compute them without a loss of, and a possible improvement in, prognostic accuracy.

Hemodynamic and gas exchange responses to inhalation of nitric oxide in patients with the acute respiratory distress syndrome and in hypoxemic patients with chronic obstructive pulmonary disease

OBJECTIVE

Inhalation of nitric oxide (NO) can improve oxygenation and decrease mean pulmonary artery pressure (MPAP) in patients with the acute respiratory distress syndrome (ARDS). It is not known whether inhaled NO exerts a similar effect in hypoxemic patients with chronic obstructive pulmonary disease (COPD).

DESIGN

Prospective clinical study.

SETTING

General intensive care unit in Sabadell, Spain.

PATIENTS

Nine mechanically ventilated COPD patients (mean age 72 +/- 2 years; forced expiratory volume in 1 s 0.91 +/- 0.11 l) and nine ARDS patients (mean age 57 +/- 6 years; mean lung injury score 2.8 +/- 0.1).

MEASUREMENTS AND RESULTS

We measured hemodynamic and gas exchange parameters before NO inhalation (basal 1), during inhalation of 10 ppm NO (NO-10), and 20 min after NO was discontinued (in basal 2) in the ARDS group. In the COPD group, these parameters were measured before NO inhalation (basal 1), during different doses of inhaled NO (10, 20, and 30 ppm), and 20 min after NO was discontinued (basal 2). A positive response to NO was defined as a 20% increment in basal arterial partial pressure of oxygen (PaO2). MPAP and pulmonary vascular resistance (PVR) decreased significantly, while other hemodynamic parameters remained unchanged after NO-10 in both groups. Basal oxygenation was higher in the COPD group (PaO2/FIO2 (fractional inspired oxygen) 190 +/- 18 mmHg) than in the ARDS group (PaO2/FIO2 98 +/- 12 mmHg), (p < 0.01). After NO-10, PaO2/FIO2 increased (to 141 +/- 17 mmHg, p < 0.01) and Qva/Qt decreased (39 +/- 3 to 34 +/- 3%, p < 0.01) in the ARDS group. There were no changes in PaO2/FIO2 and Qva/Qt when the NO concentration was increased to 30 ppm in the COPD group. In both groups, a correlation was found between basal MPAP and basal PVR, and between the NO-induced decrease in MPAP and in PVR. The NO-induced increase in PaO2/FIO2 was not correlated with basal PaO2/FIO2. In the ARDS group, six of the nine patients (66%) responded to NO and in the COPD group, two of nine (22%) (p = 0.05).

CONCLUSIONS

NO inhalation had similar effects on hemodynamics but not on gas exchange in ARDS and COPD patients, and this response probably depends on the underlying disease.

Evaluation of outcome for intubated patients with pneumonia due to Pseudomonas aeruginosa

Thirty consecutively intubated patients with pneumonia due to Pseudomonas aeruginosa (cases) were prospectively observed to establish the attributable mortality rate and the prognostic value of APACHE (Acute Physiological and Chronic Health Evaluation) II scores. Four cases did not receive accurate empirical therapy and were excluded from the study. APACHE II scores were calculated within 24 hours of admission (T0), at the time of the diagnosis of pneumonia (T1), and after 72 hours of therapy (T2). The outcomes for these cases (n = 26) were compared with those for matched controls (n = 52) without pneumonia. Six cases died of causes directly related to pneumonia (group D). Two cases whose conditions clinically improved died of cardiac complications, and 18 cases had clinical resolution (group R); however, only 15 of these cases were alive at discharge. The mean APACHE II score at admission was similar (P > .20) for group R, group D, and controls. In contrast, the mean score at T1 (15.40 +/- 6.07 vs. 20.83 +/- 4.66; P < .05) and the mean score at T2 (10.40 +/- 3.57 vs. 25.50 +/- 3.93; P < .01) differed significantly for groups R and D, respectively. The overall observed and predicted mortality rates among cases and controls were 42.3% and 28.1% and 28.8% and 28.7%, respectively, while the attributable mortality rate among cases was estimated to be 13.5% (95% confidence interval, 1.95%-25.04%). We conclude that the attributable mortality rate among intubated patients with pneumonia due to P. aeruginosa is high. The APACHE II score at admission is not useful as a prognostic factor, while progression of organ dysfunction after the onset of pneumonia is an ominous sign.

Clinical consequences of the implementation of a weaning protocol

OBJECTIVE

To analyze the clinical and economic consequences of the implementation of a weaning protocol in patients mechanically ventilated (MV) for more than 48 h.

DESIGN

Comparative study.

SETTING

General intensive care unit (ICU) in a county hospital covering 360000 inhabitants.

PATIENTS

51 patients weaned by a fixed protocol were studied prospectively and compared with 50 retrospective controls.

MEASUREMENTS

The following variables were assessed: Acute Physiology and Chronic Health Evaluation (APACHE) II score, age, cause of respiratory failure, type of extubation (direct extubation or extubation using a weaning technique), number of days on MV before the weaning trial, weaning time, total duration of MV, complications (reintubations and tracheostomies), length of ICU stay, and mortality.

RESULTS

The groups were comparable in terms of age, APACHE II score, and main cause of acute respiratory failure. Number of days on MV up to the weaning trial were similar in the two groups (8.4 +/- 7.7 in the protocol group vs 7.5 +/- 5.5 in the control group, NS). Most of the patients (80%) in the protocol group were directly extubated without a weaning technique, unlike the control group (10%) (p < 0.01). When a weaning technique was used, the weaning time was similar in both groups (3.5 +/- 3.9 days vs 3.6 +/- 2.2 days in the control group). Duration of MV was shorter in the protocol group (10.4 +/- 11.6 days) than in the control group (14.4 +/- 10.3 days) (p < 0.05). As a result, the ICU stay was reduced by using the weaning protocol (16.7 +/- 16.5 days vs 20.3 +/- 13.2 days in the control group, p < 0.05). We found no differences in reintubation rate (17 vs 14% in the control group) and need for tracheostomies (2 vs 8% in the control group).

CONCLUSION

The implementation of a weaning protocol decreased the duration of MV and ICU stay by increasing the number of safe, direct extubations.

The Logistic Organ Dysfunction system. A new way to assess organ dysfunction in the intensive care unit. ICU Scoring Group

OBJECTIVE

To develop an objective method for assessing organ dysfunction among intensive care unit (ICU) patients on the first day of the ICU stay.

DESIGN AND SETTING

Physiological variables defined dysfunction in 6 organ systems. Logistic regression techniques were used to determine severity levels and relative weights for the Logistic Organ Dysfunction (LOD) score and for conversion of the LOD score to a probability of mortality.

PATIENTS

A total of 13 152 consecutive admission to 137 adult medical/surgical ICUs in 12 countries from the European/North American Study of Severity Systems.

OUTCOME MEASURES

Patient vital status at hospital discharge.

RESULTS

The LOD System identified from 1 to 3 levels of organ dysfunction for 6 organ systems: neurologic, cardiovascular, renal, pulmonary, hematologic, and hepatic. From 1 to 5 LOD points were assigned to the levels of severity, and the resulting LOD scores ranged from 0 to 22 points. Model calibration was very good in the developmental and validation samples (P=.21 and P=.50, respectively), as was model discrimination (area under the receiver operating characteristic curves of 0.843 and 0.850, respectively).

CONCLUSION

The LOD System provides an objective tool for assessing severity levels for organ dysfunction in the ICU, a critical component in the conduct of clinical trials. Neurologic, cardiovascular, and renal dysfunction were the most severe organ dysfunctions, followed by pulmonary and hematologic dysfunction, with hepatic dysfunction the least severe. The LOD System takes into account both the relative severity among organ systems and the degree of severity within an organ system.

The Logistic Organ Dysfunction system. A new way to assess organ dysfunction in the intensive care unit. ICU Scoring Group

OBJECTIVE

To develop an objective method for assessing organ dysfunction among intensive care unit (ICU) patients on the first day of the ICU stay.

DESIGN AND SETTING

Physiological variables defined dysfunction in 6 organ systems. Logistic regression techniques were used to determine severity levels and relative weights for the Logistic Organ Dysfunction (LOD) score and for conversion of the LOD score to a probability of mortality.

PATIENTS

A total of 13 152 consecutive admission to 137 adult medical/surgical ICUs in 12 countries from the European/North American Study of Severity Systems.

OUTCOME MEASURES

Patient vital status at hospital discharge.

RESULTS

The LOD System identified from 1 to 3 levels of organ dysfunction for 6 organ systems: neurologic, cardiovascular, renal, pulmonary, hematologic, and hepatic. From 1 to 5 LOD points were assigned to the levels of severity, and the resulting LOD scores ranged from 0 to 22 points. Model calibration was very good in the developmental and validation samples (P=.21 and P=.50, respectively), as was model discrimination (area under the receiver operating characteristic curves of 0.843 and 0.850, respectively).

CONCLUSION

The LOD System provides an objective tool for assessing severity levels for organ dysfunction in the ICU, a critical component in the conduct of clinical trials. Neurologic, cardiovascular, and renal dysfunction were the most severe organ dysfunctions, followed by pulmonary and hematologic dysfunction, with hepatic dysfunction the least severe. The LOD System takes into account both the relative severity among organ systems and the degree of severity within an organ system.

Ventilatory factors affecting inhaled nitric oxide concentrations during continuous-flow administration

PURPOSE

Inhaled nitric oxide has been reported to be useful in acute respiratory distress syndrome and other lung diseases characterized by pulmonary hypertension and hypoxemia. The best site to inject the NO is still controversial, as is whether it can be affected by changes in ventilatory settings. The objective of this study was to examine the impact of various ventilator settings (tidal volume [Vt], inspiratory-to-expiratory [I:E] ratio, added dead space) in the final NO concentrations reached when NO is administered as a continuous flow near the endotracheal tube.

METHODS

A test lung model was ventilated using a ServoVentilator 300 Siemens with square wave flow. A continuous flow of NO was administered between the Y piece and the endotracheal tube. The flow was adjusted with an NO precision flowmeter (range, 0.2 to 1.5 L/min) attached to a cylinder containing 800 ppm of NO. Actual NO concentrations in the lung model were measured by chemiluminescence (NOX 2000; Seres). The effects of changing Vt (from 300 to 1300 mL) and I:E ratio (from 1:4 to 2:1) and the addition of dead space (100 mL) were examined.

RESULTS

At each step of the study, the measured NO concentration was higher than predicted. Biases from predicted NO concentration due to tidal volume were 17% at 1,300 mL Vt, 21% at 1,100 mL Vt, 25% at 900 mL Vt, 28% at 700 mL Vt, 35% at 500 mL Vt, and 48% at 300 mL Vt. Changes in I:E ratio induced increases in No concentration of 4% at 2:1, 5% at 1:1, 22% at 1:2, and 31% at 1:4. The addition of dead space enhanced these differences: 62% at 2:1, 104% at 1:1, 230% at 1:2, and 322% at 1:4.

CONCLUSION

According to our lung model, continuous-flow administration of NO near the endotracheal tube is influenced strongly by changes in ventilatory settings.

Short-term impact of the European Consensus Conference on the use of selective decontamination of the digestive tract with antibiotics in ICU patients

Because it remained controversial, the use of selective digestive decontamination (SDD) in patients in the intensive care unit (ICU) was chosen as the topic of the first European Consensus Conference in Intensive Care Medicine (ECCICM) in December, 1991. The Consensus Bureau decided to assess the impact of this conference 2 years afterwards. For this purpose, a questionnaire was sent to the members of the European Society of Intensive Care Medicine, the Societé de Réanimation de Langue Française and the Societé Française d'Anesthesie et Réanimation before the conference. The recommendations following the conference discouraged the systematic use of SDD in ventilated patients and urged the monitoring of bacterial resistance and adapting antibiotics to epidemiology of the units. Two years after the conference, the same questionnaire was sent to those physicians who had responded to the first one. Eighteen percent used SDD for all ventilated patients and 17% remain users after 2 years. Among the occasional (32%) or continual (17%) users of SDD, the regimens used were mostly intravenous cefotaxime (60% of systemic antibiotics) and a topical combination of polymixin E, tobramycin, and amphotericin B (62% of overall topical combinations). The antibiotics used were unchanged after 2 years in almost all cases. In conclusion, the short-term impact of the Consensus Conference on SDD in ICU patients has been poor. This may be related to the continuing insufficiency of strong, definite data regarding the impact of this technique upon mortality and the theoretical risk of resistance to antibiotics, thus allowing physicians to stick to their policies until there is new evidence.

Pneumonia in intubated patients: role of respiratory airway care

In order to assess potential risk factors for pneumonia within the first 8 d of ventilation, we studied 83 consecutive intubated patients undergoing continuous aspiration of subglottic secretions (CASS). Multivariate analysis showed the protective effect of antibiotic use (relative risk [RR] = 0.10; 95% confidence interval [CI] = 0.01 to 0.71), whereas failure of the CASS technique (RR = 5.29; 95% CI = 1.24 to 22.64) was associated with a greater risk of pneumonia. In addition, there was a trend toward a higher risk of pneumonia (RR = 2.57; 95% CI = 0.78 to 8.03) among patients with persistent intracuff pressures below 20 cm H2O. The remaining factors analyzed were not significant. Failure of CASS did not influence the development of pneumonia among patients undergoing antibiotic treatment (33.0% versus 38.5%, p > 0.20), but was strongly associated with pneumonia (42.1% versus 8.3%, p < 0.01) among intubated patients not receiving antibiotics. When multivariate analysis was repeated in this subpopulation, failure of CASS (RR = 7.52, 95% CI = 1.48 to 38.07) and persistent intracuff pressure below 20 cm H2O (RR = 4.23, 95% CI = 1.12 to 15.92) were factors independently associated with the development of pneumonia. We conclude that leakage of colonized subglottic secretions around the cuff of the endotracheal tube is the most important risk factor for pneumonia within the first 8 d of intubation. This study confirms the importance of maintaining adequate intracuff pressure and effective aspiration of subglottic secretions in preventing pneumonia in intubated patients not receiving antibiotic treatment.

Use of capnography to detect hypercapnic episodes during weaning from mechanical ventilation

OBJECTIVE

To evaluate the relationship between PaCO2 and end-tidal CO2 tension (PetCO2) before weaning and during a weaning trial and to determine the ability of PetCO2 to identify clinically relevant episodes of hypercapnia.

DESIGN

Open, prospective study.

SETTING

General intensive care unit.

PATIENTS

30 critically ill patients (mean age 63 +/- 2 years; Acute Physiology And Chronic Health Evaluation (APACHE) II of 18.4 +/- 3) who underwent a weaning trial during the recovery phase of acute respiratory failure requiring mechanical ventilation (MV) (8.9 +/- 1 days on MV).

INTERVENTIONS

Weaning trial consisted of 2 h breathing on 5 cmH2O of Continuous Positive Airway Pressure (CPAP).

MEASUREMENTS AND RESULTS

Arterial blood gas values, PetCO2 register and pulse oximetry determinations were recorded in assist/control ventilation before CPAP, after 1 h on CPAP and after 2 h on CPAP (immediately before extubation) or immediately before returning to assist/control mode in patients who failed the weaning trial. Clinically relevant hypercapnic episodes were described as: (1) an increment in PaCO2 > 42 mm Hg in previously normocapnic patients and (2) an increment of > 8 mm Hg from previous PaCO2 in previously hypercapnic patients. Changes in PaCO2 and changes in PetCO2 between MV and the first and second hour of CPAP showed a significant correlation (r = 0.74; p < 0.01). Clinically relevant hypercapnic episodes were detected by increments of > 3 mm Hg in PetCO2 with a sensitivity of 82%, a specificity of 76% and a negative predictive value of 94%. The area under the receiver operating characteristic curve for increments in PetCO2 was 0.90.

CONCLUSIONS

Capnography provided good assessment of hypercapnic episodes during weaning, although the high number of false positives may result in arterial blood sampling in patients who do not present with ventilation failure.

Impact of using an indwelling introducer on diagnosis of Swan-Ganz pulmonary artery catheter colonization

A prospective study was conducted to determine how the use of an indwelling introducer influences the diagnosis of pulmonary artery catheter (PAC) colonization. Sixty-six consecutive PACs and introducers were aseptically removed over a 15-month period. Two segments of the catheter and the catheter tip (a proximal segment from the portion of the catheter beneath the introducer) and two segments of the introducer (a proximal intradermal segment and the introducer tip) were cultured using a semiquantitative technique. Nineteen of 66 (28.7%) PACs showed colonization, representing an incidence of 5.6 episodes per 100 catheterization-days. Catheter tip cultures identified only 68% of colonized PACs; this yield rose to 91% when introducer tip cultures were added. These results indicate a need to evaluate both introducer tip cultures and catheter tip cultures for an accurate diagnosis of PAC colonization when an indwelling introducer is used.

[Selective pulmonary vasodilator effect of inhaled nitric oxide in a patient with pulmonary thromboembolism]

The increase in pulmonary vascular resistences in acute pulmonary thromboembolism (APT) is the consequence of anatomical obstruction and pulmonary artery constriction. The administration of inhaled nitric oxide (NO) may be therapeutically useful in acute pulmonary hypertension by APT given its limited vasodilator effect on pulmonary circulation. A patient with APT in whom this selective vasodilator effect was observed is presented. The authors suggest that the administration of inhaled NO may be a potentially beneficial coadjuvant therapy in acute pulmonary hypertension induced by APT.

A comparison of severity of illness scoring systems for intensive care unit patients: results of a multicenter, multinational study. The European/North American Severity Study Group

OBJECTIVE

To compare the performance of three severity of illness scoring systems used commonly for intensive care unit (ICU) patients in a large international data set. The systems analyzed were versions II and III of the Acute Physiology and Chronic Health Evaluation (APACHE) system, versions I and II of the Simplified Acute Physiology Score (SAPS), and versions I and II of the Mortality Probability Model (MPM), computed at admission and after 24 hrs in the ICU.

DESIGN

A multicenter, multinational cohort study.

SETTING

One hundred thirty-seven ICUs in 12 European and North American countries.

PATIENTS

During a 3-month period, 14,745 patients were consecutively admitted to 137 ICUs enrolled in the study.

INTERVENTIONS

Collection of information necessary to compute the APACHE II and APACHE III scores, SAPS I and SAPS II, and MPM I and MPM II scores. Patients were followed until hospital discharges. Statistical comparison, including indices of calibration (goodness-of-fit) and discrimination (area under the receiver operating characteristic curve).

MEASUREMENTS AND MAIN RESULTS

Despite having acceptable receiver operating characteristic areas, the older versions of the systems analyzed (APACHE II, SAPS, and MPM I computed at admission-MPM I computed after 24 hrs in the ICU) demonstrated poor calibration for the whole database. The new versions of the systems (SAPS II and MPM II) were superior to their older counterparts. This superiority is reflected by larger receiver operating characteristic areas and better fit. The APACHE III system improved its receiver operating characteristic area compared with the APACHE II system, which showed the best fit of the old systems analyzed.

CONCLUSIONS

The new versions of the severity systems analyzed (APACHE III, SAPS II, MPM II) perform better than their older counterparts (APACHE II, SAPS I, and MPM I). APACHE II, SAPS II, and MPM II show good discrimination and calibration in this international database.

Lower respiratory tract infections following cardiac arrest and cardiopulmonary resuscitation

All episodes of lower respiratory tract infection that developed among 96 patients surviving for > 24 hours after cardiac arrest were prospectively studied over an 18-month period. Pneumonia developed in 23 (24.0%) of patients after a mean of 7 days (SD, +/- 6.2 days). The development of four superinfections raised the cumulative incidence to 28.1%. Purulent tracheobronchitis was diagnosed in three instances. The causative agent of pneumonia was identified in 18 episodes, three of which were polymicrobial. Gram-positive cocci represented 57.1% of isolates, and Staphylococcus aureus--the most frequently isolated microorganism in this population--accounted for two-thirds of all gram-positive cocci. Pseudomonas aeruginosa was isolated in six episodes, five of which were associated with previous antibiotic use. Nine (39.1%) of the 23 patients in the group with pneumonia died, but only one of these deaths was considered to be directly related to pneumonia. In conclusion, pneumonia is a common complication of patients surviving cardiac arrest, but, with adequate treatment, its influence on outcome is marginal. Gram-positive cocci are the predominant pathogens, although infection with P. aeruginosa should be considered among patients receiving antibiotics.

The effect of short-term instillation of a mucolytic agent (mesna) on airway resistance in mechanically ventilated patients

STUDY OBJECTIVE

To determine whether bolus instillation of a mucolytic agent (mesna) could diminish airway resistance, endotracheal tube resistance, or both in patients mechanically ventilated for acute respiratory failure.

DESIGN

Randomized, double-blind, placebo-controlled, crossover trial.

SETTING

Medical-surgical ICU of a county hospital covering 350,000 inhabitants.

PATIENTS

Twenty sedated and paralyzed patients with an endotracheal tube (ET) in place more than 72 h.

INTERVENTIONS

Data were recorded in three steps: (1) basal; (2) 10 min after endotracheal instillation of 3 mL of either saline solution or mesna; and (3) 10 min after instillation of the opposite drug. A 2-h washout period was allowed between data collection.

MEASUREMENTS AND RESULTS

We measured tidal volume (VT), inspiratory flow (VI), auto-PEEP, peak pressure (both at airway opening [Pmax.aw] and trachea [Pmax-.tr]) and plateau pressure (Pplat), and we calculated respiratory system compliance (Crs) and the inspiratory resistances of airways+tube (Rmax.aw), airways (Rmax.tr), and ET (Rtube). We found significant differences after the instillation of mesna compared with baseline in the following: airway plus tube resistance (Rmax.aw) (16.9 +/- 7.1 vs 18.9 +/- 7.7 cm H2O); airways resistance (Rmax.tr) (9.8 +/- 6.2 vs 12.0 +/- 6.4 cm H2O), PaO2 (96 +/- 28.5 vs 80 +/- 24.8 mm Hg), PaO2/PAO2 (0.360 +/- 0.152 vs 0.296 +/- 0.127), and PaCO2 (42 +/- 12.9 vs 43 +/- 14.1 mm Hg). We found no changes in compliance, auto-PEEP, and hemodynamics during the study. Instillation of saline solution had no effect on the physiologic variables studied.

CONCLUSIONS

In our patients, bolus tracheal instillation of mesna does not improve airway resistance; in fact, mesna instillation induces episodes of bronchospasm that disappear 2 h later.

Incidence, severity, and mortality of acute respiratory failure in Berlin, Germany

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.

Customized probability models for early severe sepsis in adult intensive care patients. Intensive Care Unit Scoring Group

OBJECTIVE

To develop customized versions of the Simplified Acute Physiology Score II (SAPS II) and the 24-hour Mortality Probability Model II (MPM II) to estimate the probability of mortality for intensive care unit patients with early severe sepsis.

DESIGN AND SETTING

Logistic regression models developed for patients with severe sepsis in a database of adult medical and surgical intensive care units in 12 countries.

PATIENTS

Of 11,458 patients in the intensive care unit for at least 24 hours, 1130 had severe sepsis based on criteria of the American College of Chest Physicians and the Society of Critical Care Medicine (systemic inflammatory response syndrome in response to infection, plus hypotension, hypoperfusion, or multiple organ dysfunction).

RESULTS

In patients with severe sepsis, mortality was higher (48.0% vs 19.6% among other patients) and 28-day survival was lower. The customized SAPS II was well calibrated (P = .92 for the goodness-of-fit test) and discriminated well (area under the receiver operating characteristic [ROC] curve, 0.78). Performance in the validation sample was equally good (P = .85 for the goodness-of-fit test; area under the ROC curve, 0.79). The customized MPM II was well calibrated (P = .92 for the goodness-of-fit test) and discriminated well (area under the ROC curve, 0.79). Performance in the validation sample was equally good (P = .52 for the goodness-of-fit test; area under the ROC curve, 0.75). The models are independent of each other; either can be used alone to estimate the probability of mortality of patients with severe sepsis.

CONCLUSIONS

Customization provides a simple technique to apply existing models to a subgroup of patients. Accurately assessing the probability of hospital mortality is a useful adjunct for clinical trials.

Continuous aspiration of subglottic secretions in preventing ventilator-associated pneumonia

OBJECTIVE

To determine whether continuous subglottic aspiration prevents nosocomial pneumonia in mechanically ventilated patients.

DESIGN

A randomized, controlled, blinded study.

SETTING

Medical-surgical intensive care unit.

PATIENTS

190 patients who were admitted to the intensive care unit during a 33-month period and whose condition suggested the need for prolonged intubation (> 3 days).

INTERVENTION

76 patients were randomly allocated to receive continuous aspiration of subglottic secretions, and 77 control patients were allocated to receive usual care.

MEASUREMENTS

The numbers of cases of ventilator-associated pneumonia, ventilated days, days in intensive care unit, and deaths were recorded. The amount of subglottic secretions aspirated daily and surveillance cultures in the subglottic secretions were also obtained periodically. Etiologic diagnosis was based on the quantitative culture of secretions obtained by protected specimen brush or bronchoalveolar lavage.

RESULTS

The incidence rate of ventilator-associated pneumonia was 19.9 episodes/1000 ventilator days in the patients receiving continuous aspiration of subglottic secretions and 39.6 episodes/1000 ventilator days in the control patients (relative risk, 1.98; 95% CI, 1.03 to 3.82). This difference was due to a significant (P < 0.03) reduction in the number of gram-positive cocci and Haemophilus influenzae organisms in the patients receiving continuous aspiration. However, no differences were observed in the number of Pseudomonas aeruginosa or Enterobacteriaceae organisms. Episodes of ventilator-associated pneumonia occurred later in patients receiving continuous aspiration (12.0 +/- 7.1 days) than in the control patients (5.9 +/- 2.1 days) (P = 0.003). The same microorganisms isolated from protected specimen brush or bronchoalveolar lavage cultures in patients with ventilator-associated pneumonia were previously isolated from cultures of subglottic secretions in 85% of cases. No significant differences in outcome were found.

CONCLUSIONS

The incidence of nosocomial pneumonia in mechanically ventilated patients can be significantly reduced by using a simple method that decreases the chronic microaspirations through the cuff of endotracheal tubes.