Inmaculada Alía

A COMPARISON OF FOUR METHODS OF WEANING PATIENTS FROM MECHANICAL VENTILATION

BACKGROUND: Weaning patients from mechanical ventilation is an important problem in intensive care units. Weaning is usually conducted in an empirical manner, and a standardized approach has not been developed. METHODS: We carried out a prospective, randomized, multicenter study involving 546 patients who had received mechanical ventilation for a mean (+/- SD) of 7.5 +/- 6.1 days and who were considered by their physicians to be ready for weaning. One hundred thirty patients had respiratory distress during a two-hour trial of spontaneous breathing. These patients were randomly assigned to undergo one of four weaning techniques: intermittent mandatory ventilation, in which the ventilator rate was initially set at a mean (+/- SD) of 10.0 +/- 2.2 breaths per minute and then decreased, if possible, at least twice a day, usually by 2 to 4 breaths per minute (29 patients); pressure-support ventilation, in which pressure support was initially set at 18.0 +/- 6.1 cm of water and then reduced, if possible, by 2 to 4 cm of water at least twice a day (37 patients); intermittent trials of spontaneous breathing, conducted two or more times a day if possible (33 patients); or a once-daily trail of spontaneous breathing (31 patients). Standardized protocols were followed for each technique. RESULTS: The median duration of weaning was 5 days for intermittent mandatory ventilation (first quartile, 3 days; third quartile, 11 days), 4 days for pressure-support ventilation (2 and 12 days, respectively), 3 days for intermittent (multiple) trials of spontaneous breathing (2 and 6 days, respectively), and 3 days for a once-daily trial of spontaneous breathing (1 and 6 days, respectively). After adjustment for other covariates, the rate of successful weaning was higher with a once-daily trial of spontaneous breathing than with intermittent mandatory ventilation (rate ratio, 2.83; 95 percent confidence interval, 1.36 to 5.89; P < 0.006) or pressure-support ventilation (rate ratio, 2.05; 95 percent confidence interval, 1.04 to 4.04; P < 0.04). There was no significant difference in the rate of success between once-daily trials and multiple trials of spontaneous breathing. CONCLUSIONS: A once-daily trial of spontaneous breathing led to extubation about three times more quickly than intermittent mandatory ventilation and about twice as quickly as pressure-support ventilation. Multiple daily trials of spontaneous breathing were equally successful.

Airway pressures, tidal volumes, and mortality in patients with acute respiratory distress syndrome

Objective:To determine the usual practice for setting tidal volume and other ventilatory parameters in patients with acute respiratory distress syndrome (ARDS) in the late 1990s and to determine the independent effects of these practices on intensive care unit mortality. Design:Subanalysis of a prospective observational study. Multivariable logistic regression was used to analyze the effects of ventilatory management on mortality. Setting:A total of 361 intensive care units in 20 countries in March 1998. Patients:A total of 467 mechanically ventilated patients with ARDS. Interventions:None. Measurements and Main Results:The mean tidal volume used in the first week of ARDS was 8.8 mL/kg measured body weight, and there was great variability in these tidal volumes (sd = 2.0). Tidal volumes were significantly lower in patients with (n = 265) than without (n = 202) a recorded plateau pressure (8.6 vs. 9.1 mL/kg, p = .01). The overall intensive care unit mortality rate was 60.2%. In addition to the strong influence of organ failures and higher levels of inspired oxygen, late-onset ARDS (onset after >48 hrs of mechanical ventilation; odds ratio, 2.09) was independently associated with mortality. In addition, lower levels of positive end-expiratory pressure were independently associated with higher mortality (odds ratio, 0.91; 1 cm of H2O increments). Neither inspiratory pressures nor tidal volumes were independently associated with mortality, and there was no evidence of increased mortality with the use of lower inspiratory pressures. Conclusions:This descriptive study demonstrated considerable interpatient variability in tidal volumes during the study period. In addition to traditional prognostic indicators, timing of ARDS onset and the use of low levels of positive end-expiratory pressure or no positive end-expiratory pressure during the first week may adversely influence outcome in ARDS patients.

Weaning from mechanical ventilation

Practice guidelines on weaning should be based on the results of several well-designed randomized studies performed over the last decade. One of those studies demonstrated that immediate extubation after successful trials of spontaneous breathing expedites weaning and reduces the duration of mechanical ventilation as compared with a more gradual discontinuation of ventilatory support. Two other studies showed that the ability to breathe spontaneously can be adequately tested by performing a trial with either T-tube or pressure support of 7 cmH2O lasting either 30 or 120 min. In patients with unsuccessful weaning trials, a gradual withdrawal for mechanical ventilation can be attempted while factors responsible for the ventilatory dependence are corrected. Two randomized studies found that, in difficult-to-wean patients, synchronized intermittent mandatory ventilation (SIMV) is the most effective method of weaning.

Efficacy of Corticosteroid Therapy in Patients With an Acute Exacerbation of Chronic Obstructive Pulmonary Disease Receiving Ventilatory Support

BACKGROUND Randomized trials assessing the effect of systemic corticosteroids on chronic obstructive pulmonary disease (COPD) exacerbations excluded patients who were mechanically ventilated or admitted to the intensive care unit (ICU). Critically ill patients constitute a population of persons who are prone to develop complications that are potentially associated with the use of corticosteroids (eg, infections, hyperglycemia, ICU-acquired paresis) that could prolong the duration of mechanical ventilation and even increase mortality. METHODS A double-blind placebo-controlled trial was conducted to evaluate the efficacy and safety of systemic corticosteroid treatment in patients with an exacerbation of COPD who were receiving ventilatory support (invasive or noninvasive mechanical ventilation). A total of 354 adult patients who were admitted to the ICUs of 8 hospitals in 4 countries from July 2005 through July 2009 were screened, and 83 were randomized to receive intravenous methylprednisolone (0.5 mg/kg every 6 hours for 72 hours, 0.5 mg/kg every 12 hours on days 4 through 6, and 0.5 mg/kg/d on days 7 through 10) or placebo. The main outcome measures were duration of mechanical ventilation, length of ICU stay, and need for intubation in patients treated with noninvasive mechanical ventilation. RESULTS There were no significant differences between the groups in demographics, severity of illness, reasons for COPD exacerbation, gas exchange variables, and corticosteroid rescue treatment. Corticosteroid treatment was associated with a significant reduction in the median duration of mechanical ventilation (3 days vs 4 days; P = .04), a trend toward a shorter median length of ICU stay (6 days vs 7 days; P = .09), and significant reduction in the rate of NIV failure (0% vs 37%; P = .04). CONCLUSION Systemic corticosteroid therapy in patients with COPD exacerbations requiring mechanical ventilation is associated with a significant increase in the success of noninvasive mechanical ventilation and a reduction in the duration of mechanical ventilation. TRIAL REGISTRATION clinicaltrials.gov Identifier: NCT01281748.

Enteral Vancomycin Controls Methicillin-resistant Staphylococcus Aureus Endemicity in an Intensive Care Burn Unit: A 9-Year Prospective Study

Objective:The aim of this study was to assess the efficacy and safety of enteral vancomycin in controlling MRSA endemicity in an intensive care burn unit. Summary Background Data:MRSA is a serious clinical and epidemiologic problem. It is not uncommon that the traditional maneuvers, detection and isolation of carriers, fail to control endemicity due to MRSA. Methods:All patients admitted to an Intensive Care Burn unit from January 1995 to February 2004 have been included in this prospective cohort study comprised 2 different periods. During period 1 (January 1995 to January 2000), barrier and isolation measures were enforced. During period 2 (February 2000 to February 2004), patients received enteral vancomycin 4 times daily in addition to selective digestive decontamination. Results:A total of 777 patients were enrolled into the study: 402 in period 1, and 375 in period 2. There were no significant differences in the characteristics of patients between the 2 periods, except for the total body surface burned area, 30.3% in period 1 and 25.61% in period 2 (P = 0.009). There was a significant reduction in the incidence of patients who acquired MRSA from 115 in period 1 to 25 in period 2 (RR, 0.22; 95% confidence interval [CI], 0.15–0.34). Similar reductions were observed in the number of patients with wound (RR, 0.20; 95% CI, 0.12–0.32), blood (RR, 0.13; 95% CI, 0.04–0.35), and tracheal aspirate (RR, 0.07; 95% CI, 0.03–0.19), samples positive for MRSA. There was no emergence of either vancomycin-resistant enterococci or Staphylococcus aureus with intermediate sensitivity to glycopeptides in period 2. Conclusions:Enteral vancomycin is an effective and safe method to control MRSA in intensive care burn units without VRE.

Comparison of one versus two bronchodilators in ventilated COPD patients

ObjectiveTo compare the bronchodilating effect of a single drug, ipratropium bromide (IBr), with that of its combination with fenoterol (IBr+F).DesignThe study was triple blind and randomized.SettingMedical-surgical intensive care unit.Patients12 patients with acute exacerbation of chronic obstructive pulmonary disease (COPD) requiring mechanical ventilation for severe respiratory failure.InterventionsBefore administering each drug, peak airway pressure (Ppeak), end inspiratory pressure (Pei), resistive pressure (Pres), and auto positive — end expiratory pressure (auto-PEEP) were measured. Inspiratory system resistance (Rins) and dynamic respiratory system compliance (C) were calculated. Arterial pH and blood gas determinations were made. These measurements were repeated 60 min after administration of each therapeutic regimen. For ipratropium bromide alone the dose was 0.04 mg. When the combination of drugs was used, the doses were 0.04 mg for ipratropium bromide and 0.1 mg for fenoterol.Measurements and resultsWith the combination of both drugs, all the pressures in the airway, as well as the auto-PEEP and the Rins were significantly reduced (p<0.05) with respect to baseline values. With ipratropium bromide alone, no significant changes were observed either in the pressures or in the inspiratory resistance. No significant changes were observed either in the pH or blood gases with any of the treatments. The combination of both drugs produced significantly reduction in Pei and auto-PEEP when compared with ipratropium bromide alone.ConclusionsThe combination of both drugs is more effective than ipratropium bromide alone at the doses used in this study.

Pronóstico de una cohorte de enfermos en ventilación mecánica en 72 unidades de cuidados intensivos en España

La utilizacion de sistemas para establecer el pronostico de los pacientes es habitual en las unidades de cuidados intensivos. Su capacidad predictiva es variable y depende de la poblacion a la que se aplica. Entre las poblaciones en las que han demostrado una menor exactitud se encuentra la de los enfermos ventilados mecanicamente Estudio de cohortes de 1.103 pacientes ventilados mecanicamente. Con un analisis de particiones recursivas se determinaron las variables asociadas a la mortalidad, y con un analisis de regresion logistica se construyeron dos modelos predictivos: el primero con el SAPS II y las variables previas al inicio de la ventilacion mecanica, y el segundo con el SAPS II y las variables previas y aparecidas durante la ventilacion mecanica. Para evaluar la prediccion de la mortalidad se realizo una medida de calibracion con el metodo de Lemeshow y Hosmer y una medida de discriminacion calculando el area bajo la curva ROC La mortalidad observada fue de un 42% (IC del 95%, 39-45) frente a una predicha por el SAPS II de un 36%. En el analisis de particiones recursivas, las variables asociadas a la mortalidad fueron: fracaso renal agudo, shock, PaO2/FiO2 En una cohorte de enfermos ventilados mecanicamente, el SAPS II fue un mal predictor de la mortalidad hospitalaria. La inclusion de factores previos al inicio y aparecidos durante la ventilacion mecanica mejora discretamente la exactitud predictiva