Kenneth Hawkins

Tracheostomy timing and the duration of weaning in patients with acute respiratory failure

IntroductionThe effect of various airway management strategies, such as the timing of tracheostomy, on liberation from mechanical ventilation (MV) is uncertain. We tested the hypothesis that tracheostomy, when performed prior to active weaning, does not influence the duration of weaning or of MV in comparison with a more selective use of tracheostomy.Patients and methodsIn this observational prospective cohort study, surgical patients requiring ≥ 72 hours of MV were followed prospectively. Patients undergoing tracheostomy prior to any active weaning attempts (early tracheostomy [ET]) were compared with patients in whom initial weaning attempts were made with the endotracheal tube in place (selective tracheostomy [ST]).ResultsWe compared the duration of weaning, the total duration of MV and the frequency of fatigue and pneumonia. Seventy-four patients met inclusion criteria. Twenty-one patients in the ET group were compared with 53 patients in the ST group (47% of whom ultimately underwent tracheostomy). The median duration of weaning was shorter (3 days versus 6 days, P = 0.05) in patients in the ET group than in the ST group, but the duration of MV was not (median [interquartile range], 11 days [9–26 days] in the ET group versus 13 days [8–21 days] in the ST group). The frequencies of fatigue and pneumonia were lower in the ET group patients.DiscussionDetermining the ideal timing of tracheostomy in critically ill patients has been difficult and often subjective. To standardize this process, it is important to identify objective criteria to identify patients most likely to benefit from the procedure. Our data suggest that in surgical patients with resolving respiratory failure, a patient who meets typical criteria for a trial of spontaneous breathing but is not successfully extubated within 24 hours may benefit from a tracheostomy. Our data provide a framework for the conduct of a clinical trial in which tracheostomy timing can be assessed for its impact on the duration of weaning.ConclusionTracheostomy prior to active weaning may hasten liberation from ventilation and reduce complications. However, this does not reduce the overall duration of MV.

Alternative case definitions of ventilator-associated pneumonia identify different patients in a surgical intensive care unit.

Diagnostic criteria that define ventilator-associated pneumonia (VAP) remain controversial. The purpose of this study was to evaluate common definitions of VAP and determine their relationship to each other and clinical treatment. This study prospectively evaluated several diagnostic criteria that define VAP in a cohort of 255 consecutive SICU patients ventilated for < 48 h. Definitions evaluated include the CDC definitions, the Johanson definitions which do not rely on culture data, the Physicians Probable diagnosis which relies on positive quantitative cultures, and the antibiotic treatment group. Forty-four patients (17%) received antibiotic treatment for VAP. Depending on the definition evaluated, criteria were met for a diagnosis of VAP from as low as 4% of patients by the Johanson definition to as high as 48% of patients by the CDC definition. There was poor agreement among the definitions in their ability to select the same patient as having VAP. Besides duration of mechanical ventilation and tube feeding, which were risk factors that predicted meeting the criteria for all groups, risk factors predicting VAP varied among the definitions. This study demonstrates that in a surgical ICU, the candidate definitions of pneumonia evaluated show little agreement. The particular case definition chosen to diagnose VAP will determine the incidence rate of pneumonia, the time to onset of pneumonia, and the risk factors of the type of patient treated.

Applicability of the National Healthcare Safety Network's surveillance definition of ventilator-associated events in the surgical intensive care unit: A 1-year review

BACKGROUND In 2012, the National Healthcare Safety Network presented a new surveillance definition for ventilator-associated events (VAEs) to objectively define worsening pulmonary status in ventilated patients. VAE subcategories, ventilator-associated condition (VAC), infection-related VAC, and probable ventilator-associated pneumonia (PrVAP), were vetted predominantly in medical intensive care units. Our goal was to evaluate how well VAE criteria characterize pulmonary complications in surgical intensive care unit (SICU) patients. METHODS Since September 2012, all intubated SICU patients were screened prospectively for VAE and monitored for sustained respiratory dysfunction that did not meet VAE criteria. We diagnosed ventilator-associated pneumonia (VAP) using a clinical definition: Clinical Pulmonary Infection Score (CPIS) greater than 6 and catheter-directed bronchoalveolar lavage cultures with 104 or more colony-forming units per milliliter of pathogenic organisms. RESULTS We admitted 704 intubated patients. A total of 437 were intubated for two or more days (mean [SD], age 46 [18] years; 65% male; median ventilator days, 4 [range, 2–9]; median Sequential Organ Failure Assessment [SOFA] score, 8 [range, 5–10]). Using VAE criteria, we identified 37 patients with VAC, 31 with infection-related VAC, and 22 with PrVAP. While the remaining 400 patients did not meet VAE criteria, we identified 111 patients (28%) with respiratory deterioration and diagnosed 99 additional pneumonias. Of the 111 patients, 85 (77%) never had a period of stable/decreasing oxygenation, requiring elevated vent settings upon initiation of ventilation preventing them from meeting VAE criteria. Of the 99 pneumonia patients, 10% had sustained respiratory deterioration treated with elevations in mean airway pressure; they did not meet VAE criteria as the positive end-expiratory pressure or FIO2 was not elevated. Twenty-seven percent never had a period of stable/decreasing oxygenation. Fifty-eight percent had less than 2 days of respiratory deterioration. Agreement between PrVAP and clinical VAP was 77.3% (&kgr; = 0.243, p < 0.001). CONCLUSION The applicability of the new National Healthcare Safety Network categories of VAE to critically ill surgery patients is limited. Agreement between PrVAP and clinical VAP in SICU patients is poor. Most surgical patients are not well categorized by this new definition; a better method of surveillance should be created for this patient population. LEVEL OF EVIDENCE Diagnostic study, level III.

Examination with Next-Generation Sequencing Technology of the Bacterial Microbiota in Bronchoalveolar Lavage Samples after Traumatic Injury

BACKGROUND We examined the microbiota of bronchoalveolar lavage (BAL) samples with next-generation sequencing (NGS) technology to determine whether its results correlate with those of standard culture methods or affect patient outcome or both. METHODS We collected BAL samples in the surgical intensive care unit (SICU) as part of the standard of care for intubated individuals who had a Clinical Pulmonary Infection Score (CPIS)≥6 points. A portion of the BAL fluid was sequenced for the 16S region of ribosomal deoxyribonucleic acid (rDNA) with the Roche 454 FLX Titanium sequencer. Sequences were analyzed through a data-analysis pipeline to identify the appropriate taxonomic designation (∼species) of each 16s sequence. The bacterial microbiota of each BAL sample was compared with the bacteria identified in the sample through standard culture methods. Correlations between the taxonomic diversity of the microbiota and clinical outcome were examined through linear regression and Pearson correlation. RESULTS Bronchoalveolar lavage samples from 12 individuals in the SICU who had a CPIS≥6 points were examined through 454 pyrosequencing. The number of phylotypes (∼species) in the samples ranged from 15 to 129. The number of phyla in the BAL samples ranged from 3 to 14. There was little correlation between the bacteria identified by NGS and those identified with standard culture methods. The same predominant bacterial strain was identified by both culture and sequencing in only a single sample. The correlation between patient days on a ventilator and the number of species in BAL samples was significant (r=0.7435, p=0.0056; r2=0.5528). CONCLUSIONS Increasing diversity of the bacterial microbiota in BAL samples correlates with the duration of mechanical ventilation. Bacteria identified through standard culture methods were not well correlated with the findings of NGS.

Early nonbronchoscopic bronchoalveolar lavage: predictor of ventilator-associated pneumonia?

BACKGROUND Ventilator-associated pneumonia is a problem in trauma and emergency general surgery patients. Our hospital-acquired infection prevention committee approved the use of early nonbronchoscopic bronchoalveolar lavage (screening-BAL) in the surgical intensive care unit (SICU) to identify ventilated patients with bronchiolar bacteria before 48 hours. We reviewed the results of this quality improvement initiative. METHODS All ventilated patients in the SICU (March 2011 to June 2012) underwent a screening-BAL 36 hours to 48 hours after intubation; quantitative culture results (>5 × 104 colony-forming unit per milliliter) were used to identify positive specimens. Clinical pneumonia was defined as clinical pulmonary infection score greater than 6 with a subsequent positive diagnostic-BAL result. Sequential organ failure assessment scores were averaged for the first 48 hours in the SICU. Continuous and dichotomous data were compared, and a multivariate regression analysis was performed on the screening-BAL and pneumonia results. RESULTS Screening-BALs were performed in 150 patients (99 trauma and 51 emergency general surgery patients), 72 of these specimens had positive findings. Fifty-three clinical pneumonias were diagnosed, and 45 (positive predictive value, 0.85) identified the same organism as the screening-BAL. Clinical pneumonia developed in eight patients with a negative screening-BAL (negative predictive value, 0.85). Antibiotic therapy at the time of the screening-BAL was associated with a negative screen (odds ratio, 0.44; p = 0.026). Pneumonia developed on median postintubation Day 4 (2–15 days) in patients with a positive screening-BAL results as compared with day 7.5 in the patients with a negative screening-BAL results (3.5–15 days; p = 0.007). Field intubation is an independent risk factor (odds ratio, 3.5; p = 0.004). CONCLUSION Positive screening-BAL results in trauma and emergency general surgery patients are associated with the development of ventilator-associated pneumonia by the same organism and may play a role in identifying patients at risk for pneumonia. Further studies must be conducted to evaluate the role of screening-BAL in this patient population. LEVEL OF EVIDENCE Diagnostic/prognostic study, level III.

Immediate effects of positive end-expiratory pressure and low and high tidal volume ventilation upon gas exchange and compliance in patients with acute lung injury

BACKGROUND Protective ventilation, in general, includes low tidal volume ventilation and maintaining end-inspiratory plateau pressures less than 35 cmH2O. Recent clinical studies have determined that such an approach results in improved survival in patients with moderate to severe acute lung injury and acute respiratory distress syndrome. However, experimental evidence suggests that repeated end-expiratory collapse and reexpansion contributes to ventilator-induced lung injury. We sought to determine the immediate effects of specific tidal volume-PEEP combinations upon oxygenation and static compliance in patients with moderate to severe acute lung injury. METHODS Fourteen patients were prospectively studied and were treated with each of 10 tidal volume-PEEP combinations, applied in random order. After 5 minutes at each tidal volume-PEEP combination, PaO2/FIO2 and static compliance were recorded. Comparisons were made between low and high tidal volume ventilation as well as across five PEEP levels. RESULTS At both low (6 mL/kg) and high (10 mL/kg) tidal volume ventilation, PaO2/FIO2 increased with increasing PEEP, up to 20 cmH2O. Similar changes in static compliance were not evident. Static compliance was highest at PEEP of 10 and 15 cmH2O, regardless of tidal volume. With PEEP set at 5 cmH2O, static compliance was significantly lower with 6 mL/kg than with 10 mL/kg tidal volumes. Overall, static compliance was lowest for both tidal volume conditions with PEEP set at 25 cmH2O. CONCLUSION Low tidal volume ventilation with PEEP set at 5 cmH2O results in poor oxygenation and compliance in patients with moderate to severe acute lung injury. Similarly, PEEP set at 25 cmH2O did not improve oxygenation or compliance.

Guiding the management of intubated patients with pneumonia and ventilator-associated events using serial catheter-directed bronchoalveolar lavage

BACKGROUND We evaluated the role of serial catheter-directed bronchoalveolar lavage (CDBAL) in the diagnosis and management of pneumonia in ventilated surgical intensive care unit patients. METHODS Intubated surgical intensive care unit patients were prospectively evaluated with serial CDBALs from September 1, 2012, to May 31, 2013. Initial CDBALs were performed if patients developed the following signs of pneumonia: white blood cell count greater than 11 or less than 4, temperature greater than 38.5°C or less than 36°C, qualitative purulent sputum, worsening oxygenation, or new infiltrate on plain chest x-ray. Subsequent CDBALs were performed every 4 days. Pneumonia was diagnosed using a Clinical Pulmonary Infection Score of greater than 6 and CDBAL cultures with greater than or equal to 104 colony-forming units of pathogenic organisms. Patients were also evaluated for sustained (≥48 hours) respiratory deterioration (increased FIO2 or positive end-expiratory pressure) corresponding to the National Healthcare Safety Network definition of ventilator-associated event (VAE). RESULTS A total of 159 patients were intubated for 5 days or longer, of whom 80 patients were diagnosed with clinical pneumonia. Of these patients, 67 had serial CDBALs performed, and 81 ventilator-associated pneumonias (VAPs) were diagnosed in these patients. Of the patients with VAP, 16 also met the National Healthcare Safety Network criteria for VAE. Patients with VAP that had sustained respiratory deterioration demonstrated resolution of their compromise 60 hours (interquartile range [IQR], 41–107 hours) after starting antibiotics. Of the patients with pneumonia, 66 (81%) had resolution of the pathogenic bacteria in subsequent CDBAL cultures or were extubated within 4 days (IQR, 4–5 days) after starting antibiotics. The duration of antibiotic therapy in this group was 8 days (IQR, 7–9 days). The remaining 15 patients had multiple positive serial CDBAL cultures that isolated the same organism despite antibiotic treatment. The duration of antibiotic therapy was 14 days (IQR, 10–19 days) in these patients. The culture results were used to adjust antibiotic regimens a median of one time (IQR, 1–2 times) in 13 (87%) and two or more times in 6 (40%) of these patients. CONCLUSION Serial CDBALs help guide antibiotic treatment duration in patients with pneumonia and VAE. Patients with sustained hypoxia or persistent bacterial growth may require prolonged therapy. LEVEL OF EVIDENCE Diagnostic test, level III. Therapeutic study, level IV.

Indicators of Fatigue and of Prolonged Weaning from Mechanical Ventilation in Surgical Patients

Abstract. Indicators of weaning success have been tested primarily in patients who have been ventilated for short periods of time, and they may not be as accurate in cases where support has been required for longer than a few days. In patients requiring longer periods of support it is difficult to estimate the likelihood of successful liberation. Therefore we evaluated established weaning indices for their accuracy in surgical patients who required ≥ 72 hours of mechanical ventilation. Surgical patients who required mechanical ventilation for ≥ 72 hours were prospectively followed (over 6 months). We obtained standard indices of ventilatory function daily once patients were ready to wean. These indices included the respiratory rate/tidal volume ratio (RSBI), the maximal inspiratory pressure, and the minute ventilation. The duration of weaning and explicitly defined episodes of fatigue were the outcomes of interest. Statistical analyses evaluated the multiple factors that might influence the duration of weaning. Ninety-five patients (66% trauma; 34% surgery) survived to begin weaning, and 93% were liberated. The median duration of mechanical ventilation prior to weaning was 4 days (range 3–16 days), and the median duration of weaning was 3 days (range 0–56 days). Fatigue occurred in 36 patients and was not reliably predicted by any of the weaning measurements. However, a RSBI of >105 on the first day of weaning was associated with prolonged weaning. By multivariate analysis, an RSBI of >105 on the first day of weaning predicted prolonged weaning (hazard ratio 1.9; p= 0.03). After 72 hours of mechanical ventilation, clinical fatigue and successful liberation are not reliably predicted by standard indices of respiratory muscle strength and reserve. However, an RSBI of >105 observed once the patient is ready to wean is associated with prolonged weaning.