The value of pretest probability and modified clinical pulmonary infection score to diagnose ventilator-associated pneumonia

PURPOSE

The aim of the study was to assess the utility of pretest probability and modified clinical pulmonary infection score CPIS in the diagnosis of late-onset ventilator-associated pneumonia (VAP).

MATERIALS AND METHODS

In 740 adults enrolled in a multicenter randomized trial, intensivists prospectively rated the pretest probability of VAP as low, moderate, or high based on their clinical judgment. The modified CPIS was calculated without considering culture results. Ventilator-associated pneumonia diagnosis was determined by 2 adjudicators using standardized definitions. We analyzed the relationship between pretest likelihood, CPIS, and VAP diagnosis.

RESULTS

Among the 739 patients analyzed, 14.5%, 39.6%, and 45.9% had low, moderate, and high pretest probability of VAP. Patients with high pretest probability had a lower PaO2/FiO2 ratio and a larger volume of secretions. High or moderate vs low pretest probability had high sensitivity (0.88; 95% confidence interval [CI], 0.87-0.89) and positive predictive value (0.87; 95% CI, 0.86-0.88) but low specificity (0.27; 95% CI, 0.21-0.35) and negative predictive value (0.29; 95% C,: 0.22-0.37) for the diagnosis of VAP. Therefore, 71% of patients who had a low pretest probability were actually infected (1 - negative predictive value). The area under the receiver operating characteristic curve for the modified CPIS was not significant (0.47; 95% CI, 0.42-0.53), meaning that no score threshold was clinically useful.

CONCLUSIONS

Pretest probability and a modified CPIS, which excludes culture results, are of limited utility in the diagnosis of late-onset VAP.

Ventilator-associated pneumonia caused by multidrug-resistant organisms or Pseudomonas aeruginosa: prevalence, incidence, risk factors, and outcomes

PURPOSE

The aim of this study was to clarify the prevalence and incidence of, risk factors for, and outcomes from suspected ventilator-associated pneumonia (VAP) associated with the isolation of either Pseudomonas or multidrug-resistant (MDR) bacteria ("high risk" pathogens) from respiratory secretions.

MATERIALS AND METHODS

Data were collected as part of a large, multicentered trial of diagnostic and therapeutic strategies for patients (n = 739) with suspected VAP.

RESULTS

At enrollment, 6.4% of patients had Pseudomonas species, and 5.1% of patients had at least 1 MDR organism isolated from respiratory secretions. Over the study period, the incidence of Pseudomonas and MDR organisms was 13.4% and 9.2%, respectively. Independent risk factors for the presence of these pathogens at enrollment were duration of hospital stay >or=48 hours before intensive care unit (ICU) admission (odds ratio, 2.37 [95% CI, 1.40-4.02]; P = .001] and prolonged duration of ICU stay before enrollment (odds ratio, 1.50 [95% CI, 1.17-1.93]; P = .002] per week. Fewer patients whose specimens grew either Pseudomonas or MDR organisms received appropriate empirical antibiotic therapy compared to those without these pathogens (68.5% vs 93.9%, P < .001). The isolation of high risk pathogens from respiratory secretions was associated with higher 28-day (relative risk, 1.59 [95% CI, 1.07-2.37]; P = .04] and hospital mortality (relative risk, 1.48 [95% CI, 1.05-2.07]; P = .05), and longer median duration of mechanical ventilation (12.6 vs 8.7 days, P = .05), ICU length of stay (16.2 vs 12.0 days, P = .05), and hospital length of stay (55.0 vs 41.8 days, P = .05).

CONCLUSIONS

In this patient population, the incidence of high-risk organisms newly acquired during an ICU stay is low. However, the presence of high risk pathogens is associated with worse clinical outcomes.

Correlates of clinical failure in ventilator-associated pneumonia: insights from a large, randomized trial

PURPOSE

Our objective was to determine clinical variables measured at baseline and day 3 that may relate to failure of resolution of ventilator-associated pneumonia (VAP).

MATERIALS AND METHODS

In patients with confirmed VAP derived from a large, randomized controlled trial comparing different modalities for the diagnosis and treatment of VAP, we identified risk factors associated with clinical failure. Clinical failure was prospectively defined in this trial as death, persistence of clinical and radiographic features of infection throughout the study period requiring additional antibiotics, superinfection, or relapsing infection. We examined the relationship between VAP resolution and clinical characteristics measured both at study enrollment and at day 3. We used logistic regression to identify independent factors associated with clinical failure and conducted a sensitivity analysis focusing only on patients who met the definition for clinical failure but who nonetheless survived until day 28.

RESULTS

Of 563 subjects with VAP, 179 (31.8%) were classified as clinical failures. Death was the most common reason for clinical failure. At baseline, clinical failure patients were older, more severely ill, had been on mechanical ventilation for a longer period, and had higher Clinical Pulmonary Infection Score values and lower Pao2/Fio2 ratios. By day 3, patients defined as clinical failures remained more severely ill and continued to have worse oxygenation. In multivariate analysis, 4 factors were independently associated with clinical failure: older age, duration of ventilation before enrollment, presence of neurologic disease at admission, and failure of the Pao2/Fio2 ratio to improve by day 3. Repeating this multivariable model in only surviving patients suggested that persistence of fever was the only variable associated with clinical failure.

CONCLUSIONS

Clinical characteristics correlate with eventual outcomes in VAP. Failure of the Pao2/Fio2 ratio and fever to improve are independently associated with clinical failure. We suggest that clinicians follow these measures and consider integrating them in their decisions as to when to reevaluate persons with VAP who are not improving.

Comparison and modeling of the adsorption of two microcystin analogues onto powdered activated carbon

The presence of cyanobacterial toxins, such as microcystins, in drinking water supplies is a major concern for water authorities worldwide due to possible adverse health effects associated with exposure to these compounds. Adsorption onto powdered activated carbon in the water treatment process offers an effective treatment option for the removal of these compounds. However, for the efficient use of powdered activated carbon, knowledge of the appropriate dose to apply is required. In this study the adsorption of two microcystin analogues, microcystin-LR and microcystin-LA, onto powdered activated carbon was studied for two waters. Analysis of batch kinetic and equilibrium adsorption data showed that the homogeneous surface diffusion model could successfully predict the adsorption kinetics of the two toxins. The application of the homogeneous surface diffusion model is extremely useful to water treatment plant operators as it can be used to predict the powdered activated carbon dose for the removal of algal toxins based on the analogue(s) present, influent toxin concentration and powdered activated carbon contact time. Adsorption was also found to be different for the two toxin analogues, and dependent on the water character. Microcystin-LR was much more easily removed than microcystin-LA in both waters, and adsorption of both analogues was lower in the water with a higher dissolved organic carbon concentration.

Detecting myocardial infarction in critical illness using screening troponin measurements and ECG recordings

INTRODUCTION

To use screening cardiac troponin (cTn) measurements and electrocardiograms (ECGs) to determine the incidence of elevated cTn and of myocardial infarction (MI) in patients admitted to the intensive care unit (ICU), and to assess whether these findings influence prognosis. This is a prospective screening study.

MATERIALS AND METHODS

We enrolled consecutive patients admitted to a general medical-surgical ICU over two months. All patients underwent systematic screening with cTn measurements and ECGs on ICU admission, then daily for the first week in ICU, alternate days for up to one month and weekly thereafter until ICU death or discharge, for a maximum of two months. Patients without these investigations ordered during routine clinical care underwent screening for study purposes but these results were unavailable to the ICU team. After the study, all ECGs were interpreted independently in duplicate for ischaemic changes meeting ESC/ACC criteria supporting a diagnosis of MI. Patients were classified as having MI (elevated cTn and ECG evidence supporting diagnosis of MI), elevated cTn only (no ECG evidence supporting diagnosis of MI), or no cTn elevation.

RESULTS

One hundred and three patients were admitted to the ICU on 112 occasions. Overall, 37 patients (35.9 per cent) had an MI, 15 patients (14.6 per cent) had an elevated cTn only and 51 patients (49.5 per cent) had no cTn elevation. Patients with MI had longer duration of mechanical ventilation (p < 0.0001), longer ICU stay (p = 0.001), higher ICU mortality (p < 0.0001) and higher hospital mortality (p < 0.0001) compared with those with no cTn elevation. Patients with elevated cTn had higher hospital mortality (p = 0.001) than patients without cTn elevation. Elevated cTn was associated with increased hospital mortality (odds ratio 27.3, 95 per cent CI 1.7 - 449.4), after adjusting for APACHE II score, MI and advanced life support. The ICU team diagnosed 18 patients (17.5 per cent) as having MI on clinical grounds; four of these patients did not have MI by adjudication. Thus, screening detected an additional 23 MIs not diagnosed in practice, reflecting 62.2 per cent of MIs ultimately diagnosed. Patients with MI diagnosed by the ICU team had similar outcomes to patients with MI detected by screening alone.

CONCLUSION

Systematic screening detected elevated cTn measurements and MI in more patients than were found in routine practice. Elevated cTn was an independent predictor of hospital mortality. Further research is needed to evaluate whether screening and subsequent treatment of these patients reduces mortality.

Venous thromboembolism and bleeding in critically ill patients with severe renal insufficiency receiving dalteparin thromboprophylaxis: prevalence, incidence and risk factors

BACKGROUND

Critically ill patients with renal insufficiency are predisposed to both deep vein thrombosis (DVT) and bleeding. The objective of the present study was to evaluate the prevalence, incidence and predictors of DVT and the incidence of bleeding in intensive care unit (ICU) patients with estimated creatinine clearance <30 ml/min.

METHODS

In a multicenter, open-label, prospective cohort study of critically ill patients with severe acute or chronic renal insufficiency or dialysis receiving subcutaneous dalteparin 5,000 IU once daily, we estimated the prevalence of proximal DVT by screening compression venous ultrasound of the lower limbs within 48 hours of ICU admission. DVT incidence was assessed on twice-weekly ultrasound testing. We estimated the incidence of major and minor bleeding by daily clinical assessments. We used Cox proportional hazards regression to identify independent predictors of both DVT and major bleeding.

RESULTS

Of 156 patients with a mean (standard deviation) creatinine clearance of 18.9 (6.5) ml/min, 18 had DVT or pulmonary embolism within 48 hours of ICU admission, died or were discharged before ultrasound testing - leaving 138 evaluable patients who received at least one dose of dalteparin. The median duration of dalteparin administration was 7 days (interquartile range, 4 to 12 days). DVT developed in seven patients (5.1%; 95% confidence interval, 2.5 to 10.1). The only independent risk factor for DVT was an elevated baseline Acute Physiology and Chronic Health Evaluation II score (hazard ratio for 10-point increase, 2.25; 95% confidence interval, 1.03 to 4.91). Major bleeding developed in 10 patients (7.2%; 95% confidence interval, 4.0 to 12.8), all with trough anti-activated factor X levels </= 0.18 IU/ml. Independent risk factors for major bleeding were aspirin use (hazard ratio, 6.30; 95% confidence interval, 1.35 to 29.4) and a high International Normalized Ratio (hazard ratio for 0.5-unit increase, 1.68; 95% confidence interval, 1.07 to 2.66).

CONCLUSION

In ICU patients with renal insufficiency, the incidence of DVT and major bleeding are considerable but appear related to patient comorbidities rather than to an inadequate or excessive anticoagulant from thromboprophylaxis with dalteparin.

Randomized Trials in Vulnerable Populations

Many persons enrolled in clinical trials can be considered vulnerable, and such trials often raise concerns because of the diminished ability of vulnerable persons to consider and protect their own interests. However, this research is necessary to answer important questions, such as which interventions are effective, which have no impact, and which do more harm than good. In this article, we identified six specific challenges associated with randomized clinical trials in vulnerable populations and have suggested several potential solutions to overcome these challenges. First addressed were macro issues, such as the scope of the problem, and research capacity in terms of funding and investigators. Next, we have addressed research ethics review, informed consent, regulatory hurdles, and serious adverse event reporting. As clinical trials are expanding globally, all stakeholders (investigators, granting agencies, REBs, DSMBs, regulatory bodies, universities, hospitals, clinicians, patients, and family members) should be aware of the challenges we have outlined, and work collaboratively toward effective solutions that improve the quality, quantity, safety, and relevance of clinical trials for vulnerable persons around the world. Clinical Trials 2008; 5: 61—69. http://ctj.sagepub.com

Relationship between the endophyte Embellisia spp. and the toxic alkaloid swainsonine in major locoweed species (Astragalus and Oxytropis)

Locoweeds (Astragalus and Oxytropis spp. that contain the toxic alkaloid swainsonine) cause widespread poisoning of livestock on western rangelands. There are 354 species of Astragalus and 22 species of Oxytropis in the US and Canada. Recently, a fungal endophyte, Embellisia spp., was isolated from Astragalus and Oxytropis spp. and shown to produce swainsonine. We conducted a survey of the major locoweeds from areas where locoweed poisoning has occurred to verify the presence of the endophyte and to relate endophyte infection with swainsonine concentrations. Species found to contain the fungal endophyte and produce substantial amounts of swainsonine were A. wootoni, A. pubentissimus, A. mollissimus, A. lentiginosus, and O. sericea. Astragalus species generally had higher concentrations of swainsonine than Oxytropis. Swainsonine was not detected in A. alpinus, A. cibarius, A. coltonii, A. filipes, or O. campestris. The endophyte could not be cultured from A. mollissimus var. thompsonii or A. amphioxys, but was detected by polymerase chain reaction, and only 30% of these samples contained trace levels of swainsonine. Further research is necessary to determine if the endophyte is able to colonize these and other species of Astragalus and Oxytropis and determine environmental influences on its growth and synthesis of swainsonine.

Comparison of direct and indirect sampling methods for tarnished plant bug (Hemiptera: Miridae) in flowering cotton

A complex of hemipterans, especially the tarnished plant bug, Lygus lineolaris (Palisot de Beauvois) (Hemiptera: Miridae), has become a major target of insecticides in flowering cotton, Gossypium hirsutum L., in the mid-southern United States. Sampling protocols for this complex during this period of cotton development are poorly established, resulting in uncertainty about when infestations warrant treatment. Nine direct and indirect sampling methods were evaluated for bias, precision, and efficiency in cotton throughout the Mid-South during 2005 and 2006. The tarnished plant bug represented 94% of the bug complex in both years. Sweep-net and black drop-cloth methods were more efficient than other direct sampling methods, but they were biased toward adults and nymphs, respectively. Sampling dirty blooms was the most efficient indirect sampling method. The sweep-net, whole-plant, and dirty-bloom methods were more accurate than the other sampling methods evaluated based on correlations with other sampling methods. Variability attributed to the person collecting the sample was significant for all sampling methods, but least significant for the dirty-square method. Further research is needed to establish thresholds based on sweep-net, drop-cloth, dirty-square, and dirty-bloom sampling methods as these methods provide the best combinations of accuracy and efficiency for sampling tarnished plant bugs in cotton.

A model browser for biosimulation

The complexities of biological simulation present difficulties with modeling and experimenting. Simulators process models represented as code, whereas biologists think about abstract models. Our ModelBrowser addresses this difficulty through interactive visualization. Variables and equations appear as a directed graph of nodes and edges, and the user can search and browse this graph by performing queries on metadata associated with the variables and the connectivity of the edges. The browser also supports a hierarchical categorization of the variables, such as by an ontology. We believe that the ModelBrowser will help biologists reason about code in the context of the abstract model, so that they can understand and modify others' code and debug their own.

Clinical practice guidelines in the intensive care unit: a survey of Canadian clinicians’ attitudes

PURPOSE

To understand clinicians' perceptions regarding practice guidelines in Canadian intensive care units (ICUs) to inform guideline development and implementation strategies.

METHODS

We developed a self-administered survey instrument and assessed its clinical sensibility and reliability. The survey was mailed to ICU physicians and nurses in Canada to determine local ICU guideline development and use, and to compare physicians' and nurses' attitudes and preferences towards guidelines.

RESULTS

The survey was completed by 51.6% (565/1095) of potential respondents. Although less than half reported a formal guideline development committee in their ICU, 81.0% reported that guidelines were developed at their institutions. Of clinicians who used guidelines in the ICU, 70.2% of nurses and 42.6% of physicians reported using them frequently or always. Professional society guidelines (with or without local modification) were reportedly used in most ICUs, but physicians were more confident than nurses of their validity (P<0.001). Physicians considered endorsement of guidelines by a colleague more relevant for enhancing guideline use than did nurses (P<0.001). Nurses considered low risk of the guideline and whether the guideline is consistent with their practice (P<0.001) to be more relevant to guideline uptake than did physicians (P<0.001). Lack of agreement with recommendations was a more important barrier to use of guidelines for physicians than for nurses (P<0.001).

CONCLUSIONS

Many Canadian institutions locally develop guidelines, and many ICU physicians and nurses report using them. Planning implementation strategies according to clinician preferences may increase guideline use. The nature of the differences in attitudes towards guidelines between nurses and physicians, and their impact on clinician adherence to guidelines requires further exploration.

Facilitating clinician adherence to guidelines in the intensive care unit: A multicenter, qualitative study*

OBJECTIVE

To determine perceived facilitators and barriers to guideline implementation and clinician adherence to guidelines in the intensive care unit (ICU).

DESIGN

Multicenter qualitative study in three university-affiliated ICUs in Canada.

METHODS

We conducted individual semistructured interviews of 44 ICU clinicians (12 intensivists, two physician directors, 12 nurses, three nurse educators, three nurse managers, nine respiratory therapists, and three respiratory therapist educators). We elicited attitudes and perceptions regarding the facilitators and barriers to adherence to guidelines in the ICU. We transcribed all interviews and analyzed data in duplicate using grounded theory to identify themes and develop a model to describe clinicians' views.

MAIN RESULTS

The presence of a culture within the ICU that enabled guideline implementation and clinician adherence to guidelines was considered essential. Central to this culture was an ICU team that believed guidelines would reduce practice variation, help implement research findings at the bedside, and result in a more rapid implementation of best practice. Effective leadership and positive interprofessional team dynamics were deemed requisites for this culture. Important strategies identified by the participants to overcome potential barriers to clinician adherence to guidelines were: the presence of effective leaders to promote adoption of the guideline and its adherence, education tailored to the learning preferences of different professional groups, and repeated educational interventions, reminders, and audit and feedback. Participants suggested that the use of strategies to select and prioritize guidelines, simple guideline formats, and electronic media to implement guidelines may further contribute to successful guideline programs.

CONCLUSIONS

Complex ICU practices and unique interprofessional team dynamics influence clinician adherence to guidelines. Initiatives that employ an approach addressing these issues may optimize guideline uptake and adherence. The optimal approach and its effectiveness may be guideline-dependent and requires further study.

Fresh frozen plasma transfusion in critically ill patients

OBJECTIVES

Although guidelines for fresh frozen plasma (FFP) use have been published, many transfusions are considered inappropriate. Current guidelines suggest few circumstances in which FFP transfusion to critically ill patients is warranted. The objectives of this study were to evaluate the consistency of Canadian guidelines for FFP administration to critically ill patients and to examine factors associated with inappropriate FFP transfusions.

DESIGN

Retrospective cohort study.

SETTING

15-bed medical surgical intensive care unit in a teaching hospital.

PATIENTS

254 consecutive adults admitted during 1 yr expected to stay in intensive care for more than 72 hrs.

INTERVENTION

None.

MEASUREMENTS AND MAIN RESULTS

Patient demographics, illness severity, life support, intensive care and hospital length of stay, and survival were prospectively collected. All FFP orders were identified from the hospital laboratory information system. For each order, coagulation parameters, planned invasive interventions, recent or current bleeding, and bleeding severity were retrospectively collected. Three observers independently adjudicated whether transfusions were consistent with guidelines, inconsistent but appropriate for the intensive care context, or inappropriate. Of 254 patients, 76 (29.9%) received FFP, accounting for 225 orders to transfuse 547 units. Of 225 orders, 73 (32.4%) were consistent with guidelines, 45 (20.0%) were inconsistent but appropriate, and 107 (47.6%) were inappropriate. Considering transfusions clustered within patients, chance-independent agreement on whether transfusions were inappropriate or not was high (phi 0.73, 0.64-0.81). Independent determinants of inappropriate FFP were the presence of less severe coagulopathy as indicated by lower international normalized ratios (p < .0001) and the absence of bleeding (p < .0001) of planned invasive procedure (p = .0001).

CONCLUSIONS

Critically ill patients frequently receive inappropriate FFP transfusions. Many transfusions may be appropriate for the intensive care setting, although they are inconsistent with expert recommendations, highlighting that further studies are needed to assess the effectiveness and safety of FFP transfusion in critical illness.