Long-term outcomes after treatment of delirium during critical illness with antipsychotics (MIND-USA): a randomised, placebo-controlled, phase 3 trial

BACKGROUND

Delirium is common during critical illness and is associated with long-term cognitive impairment and disability. Antipsychotics are frequently used to treat delirium, but their effects on long-term outcomes are unknown. We aimed to investigate the effects of antipsychotic treatment of delirious, critically ill patients on long-term cognitive, functional, psychological, and quality-of-life outcomes.

METHODS

This prespecified, long-term follow-up to the randomised, double-blind, placebo-controlled phase 3 MIND-USA Study was conducted in 16 hospitals throughout the USA. Adults (aged ≥18 years) who had been admitted to an intensive care unit with respiratory failure or septic or cardiogenic shock were eligible for inclusion in the study if they had delirium. Participants were randomly assigned-using a computer-generated, permuted-block randomisation scheme with stratification by trial site and age-in a 1:1:1 ratio to receive intravenous placebo, haloperidol, or ziprasidone for up to 14 days. Investigators and participants were masked to treatment group assignment. 3 months and 12 months after randomisation, we assessed survivors' cognitive, functional, psychological, quality-of-life, and employment outcomes using validated telephone-administered tests and questionnaires. This trial was registered with ClinicalTrials.gov, NCT01211522, and is complete.

FINDINGS

Between Dec 7, 2011, and Aug 12, 2017, we screened 20 914 individuals, of whom 566 were eligible and consented or had consent provided to participate. Of these 566 patients, 184 were assigned to the placebo group, 192 to the haloperidol group, and 190 to the ziprasidone group. 1-year survival and follow-up rates were similar between groups. Cognitive impairment was common in all three treatment groups, with a third of survivors impaired at both 3-month and 12-month follow-up in all groups. More than half of the surveyed survivors in each group had cognitive or physical limitations (or both) that precluded employment at both 3-month and 12-month follow-up. At both 3 months and 12 months, neither haloperidol (adjusted odds ratio 1·22 [95% CI 0·73-2.04] at 3 months and 1·12 [0·60-2·11] at 12 months) nor ziprasidone (1·07 [0·59-1·96] at 3 months and 0·94 [0·62-1·44] at 12 months) significantly altered cognitive outcomes, as measured by the Telephone Interview for Cognitive Status T score, compared with placebo. We also found no evidence that functional, psychological, quality-of-life, or employment outcomes improved with haloperidol or ziprasidone compared with placebo.

INTERPRETATION

In delirious, critically ill patients, neither haloperidol nor ziprasidone had a significant effect on cognitive, functional, psychological, or quality-of-life outcomes among survivors. Our findings, along with insufficient evidence of short-term benefit and frequent inappropriate continuation of antipsychotics at hospital discharge, indicate that antipsychotics should not be used routinely to treat delirium in critically ill adults.

FUNDING

National Institutes of Health and the US Department of Veterans Affairs.

Haloperidol and Ziprasidone for Treatment of Delirium in Critical Illness

BACKGROUND

There are conflicting data on the effects of antipsychotic medications on delirium in patients in the intensive care unit (ICU).

METHODS

In a randomized, double-blind, placebo-controlled trial, we assigned patients with acute respiratory failure or shock and hypoactive or hyperactive delirium to receive intravenous boluses of haloperidol (maximum dose, 20 mg daily), ziprasidone (maximum dose, 40 mg daily), or placebo. The volume and dose of a trial drug or placebo was halved or doubled at 12-hour intervals on the basis of the presence or absence of delirium, as detected with the use of the Confusion Assessment Method for the ICU, and of side effects of the intervention. The primary end point was the number of days alive without delirium or coma during the 14-day intervention period. Secondary end points included 30-day and 90-day survival, time to freedom from mechanical ventilation, and time to ICU and hospital discharge. Safety end points included extrapyramidal symptoms and excessive sedation.

RESULTS

Written informed consent was obtained from 1183 patients or their authorized representatives. Delirium developed in 566 patients (48%), of whom 89% had hypoactive delirium and 11% had hyperactive delirium. Of the 566 patients, 184 were randomly assigned to receive placebo, 192 to receive haloperidol, and 190 to receive ziprasidone. The median duration of exposure to a trial drug or placebo was 4 days (interquartile range, 3 to 7). The median number of days alive without delirium or coma was 8.5 (95% confidence interval [CI], 5.6 to 9.9) in the placebo group, 7.9 (95% CI, 4.4 to 9.6) in the haloperidol group, and 8.7 (95% CI, 5.9 to 10.0) in the ziprasidone group (P=0.26 for overall effect across trial groups). The use of haloperidol or ziprasidone, as compared with placebo, had no significant effect on the primary end point (odds ratios, 0.88 [95% CI, 0.64 to 1.21] and 1.04 [95% CI, 0.73 to 1.48], respectively). There were no significant between-group differences with respect to the secondary end points or the frequency of extrapyramidal symptoms.

CONCLUSIONS

The use of haloperidol or ziprasidone, as compared with placebo, in patients with acute respiratory failure or shock and hypoactive or hyperactive delirium in the ICU did not significantly alter the duration of delirium. (Funded by the National Institutes of Health and the VA Geriatric Research Education and Clinical Center; MIND-USA ClinicalTrials.gov number, NCT01211522 .).

The impact of hospital-wide use of a tapered-cuff endotracheal tube on the incidence of ventilator-associated pneumonia

BACKGROUND

Aspiration of colonized oropharyngeal secretions is a major factor in the pathogenesis of ventilator-associated pneumonia (VAP). A tapered-cuff endotracheal tube (ETT) has been demonstrated to reduce aspiration around the cuff. Whether these properties are efficacious in reducing VAP is not known.

METHODS

This 2-period, investigator-initiated observational study was designed to assess the efficacy of a tapered-cuff ETT to reduce the VAP rate. All intubated, mechanically ventilated patients over the age of 18 were included. During the baseline period a standard, barrel-shaped-cuff ETT (Mallinckrodt Hi-Lo) was used. All ETTs throughout the hospital were then replaced with a tapered-cuff ETT (TaperGuard). The primary outcome variable was the incidence of VAP per 1,000 ventilator days.

RESULTS

We included 2,849 subjects, encompassing 15,250 ventilator days. The mean ± SD monthly VAP rate was 3.29 ± 1.79/1,000 ventilator days in the standard-cuff group and 2.77 ± 2.00/1,000 ventilator days in the tapered-cuff group (P = .65). While adherence to the VAP prevention bundle was high throughout the study, bundle adherence was significantly higher during the standard-cuff period (96.5 ± 2.7%) than in the tapered-cuff period (90.3 ± 3.5%, P = .01).

CONCLUSIONS

In the setting of a VAP rate very near the average of ICUs in the United States, and where there was high adherence to a VAP prevention bundle, the use of a tapered-cuff ETT was not associated with a reduction in the VAP rate.

Nosocomial pneumonia risk and stress ulcer prophylaxis: a comparison of pantoprazole vs ranitidine in cardiothoracic surgery patients

BACKGROUND

Stress ulcer prophylaxis (SUP) using ranitidine, a histamine H2 receptor antagonist, has been associated with an increased risk of ventilator-associated pneumonia. The proton pump inhibitor (PPI) pantoprazole is also commonly used for SUP. PPI use has been linked to an increased risk of community-acquired pneumonia. The objective of this study was to determine whether SUP with pantoprazole increases pneumonia risk compared with ranitidine in critically ill patients.

METHODS

The cardiothoracic surgery database at our institution was used to identify retrospectively all patients who had received SUP with pantoprazole or ranitidine, without crossover between agents. From January 1, 2004, to March 31, 2007, 887 patients were identified, with 53 patients excluded (pantoprazole, 30 patients; ranitidine, 23 patients). Our analysis compared the incidence of nosocomial pneumonia in 377 patients who received pantoprazole with 457 patients who received ranitidine.

RESULTS

Nosocomial pneumonia developed in 35 of the 377 patients (9.3%) who received pantoprazole, compared with 7 of the 457 patients (1.5%) who received ranitidine (odds ratio [OR], 6.6; 95% confidence interval [CI], 2.9 to 14.9). Twenty-three covariates were used to estimate the probability of receiving pantoprazole as measured by propensity score (C-index, 0.77). Using this score, pantoprazole and ranitidine patients were stratified according to their probability of receiving pantoprazole. After propensity adjusted, multivariable logistic regression, pantoprazole treatment was found to be an independent risk factor for nosocomial pneumonia (OR, 2.7; 95% CI, 1.1 to 6.7; p = 0.034).

CONCLUSION

The use of pantoprazole for SUP was associated with a higher risk of nosocomial pneumonia compared with ranitidine. This relationship warrants further study in a randomized controlled trial.

Regulation of arachidonate remodeling enzymes impacts eosinophil survival during allergic asthma

Although the role of arachidonic acid (AA) metabolism to eicosanoids has been well established in allergy and asthma, recent studies in neoplastic cells have revealed that AA remodeling through phospholipids impacts cell survival. This study tests the hypothesis that regulation of AA/phospholipid-remodeling enzymes, cytosolic phospholipase A(2) alpha(cPLA(2)-alpha, gIValphaPLA(2)) and CoA-independent transacylase (CoA-IT), provides a mechanism for altered eosinophil survival during allergic asthma. In vitro incubation of human eosinophils (from donors without asthma) with IL-5 markedly increased cell survival, induced gIValphaPLA(2) phosphorylation, and increased both gIValphaPLA(2) and CoA-IT activity. Furthermore, treatment of eosinophils with nonselective (ET18-O-CH(3)) and selective (SK&F 98625) inhibitors of CoA-IT triggered apoptosis, measured by changes in morphology, membrane phosphatidylserine exposure, and caspase activation, completely reversing IL-5-induced eosinophil survival. To determine if similar activation occurs in vivo, human blood eosinophils were isolated from either normal individuals at baseline or from subjects with mild asthma, at both baseline and 24 hours after inhaled allergen challenge. Allergen challenge of subjects with allergic asthma induced a marked increase in cPLA(2) phosphorylation, augmented gIValphaPLA(2) activity, and increased CoA-IT activity. These findings indicate that both in vitro and in vivo challenge of eosinophils activated gIValphaPLA(2) and CoA-IT, which may play a key role in enhanced eosinophil survival.

Using local microbiologic data to develop institution-specific guidelines for the treatment of hospital-acquired pneumonia

BACKGROUND

While current guidelines recommend consideration of local microbiologic data when selecting empiric treatment for hospital-acquired pneumonia (HAP), few specifics of how to do this have been offered.

METHODS

We conducted a retrospective analysis of HAP pathogens in 111 consecutive patients who acquired HAP during July to December 2004 and had a corresponding positive culture finding for a bacterial pathogen. These data were used to develop institution-specific guidelines.

RESULTS

The most common bacteria identified were Staphylococcus aureus, Acinetobacter baumannii, and Pseudomonas aeruginosa, which were associated with 38%, 25%, and 19% of pneumonias, respectively. Susceptibility of Gram-negative bacteria to piperacillin-tazobactam and cefepime was 80% and 81%, respectively. The isolation of organisms resistant to piperacillin-tazobactam or cefepime was significantly more frequent in patients who had been hospitalized > or = 10 days. Of Gram-negative isolates resistant to piperacillin-tazobactam or cefepime, ciprofloxacin was active against < 10%, while amikacin was active against > 80%. New treatment guidelines were developed that divided the American Thoracic Society/Infectious Diseases Society of America "late onset/risk of multidrug-resistant pathogens" group of patients into two subcategories: "early-late" pneumonias (< 10 days of hospitalization) and "late-late" pneumonias (> or = 10 days of hospitalization). Guideline-directed treatment regimens would be predicted to provide adequate initial therapy for > 90% of late-onset pneumonias at our institution.

CONCLUSIONS

Current guidelines suggest adding either an aminoglycoside or a fluoroquinolone to beta-lactam therapy for empiric Gram-negative coverage. However, in our institution, adding ciprofloxacin would not appreciably enhance the likelihood of providing initial appropriate antibiotic coverage. This underscores the importance of employing a systematic analysis of local data when developing treatment guidelines.

Diagnosis and Treatment of Ventilator-Associated Pneumonia

Ventilator-associated pneumonia (VAP) is the most common nosocomial infection in the ICU. Patients who acquire VAP have higher mortality rates and longer ICU and hospital stays. Because there are other potential causes of fever, leukocytosis, and pulmonary infiltrates, clinical diagnostic criteria are overly sensitive in the diagnosis of VAP. Employing quantitative cultures of bronchopulmonary secretions in the diagnostic algorithm leads to less antibiotic use and probably to lower mortality. With respect to microbiologic diagnosis, it is not clear that the use of a particular sampling method (bronchoscopic or nonbronchoscopic), when quantitatively cultured, is associated with better outcomes. Delayed administration of adequate antibiotic therapy is linked to an increased mortality rate. Hence, the focus of initial antibiotic therapy should be to rapidly provide antibiotic coverage for all likely pathogens and to then narrow or focus the antibiotic spectrum based on the results of quantitative cultures. Eight days of antibiotic therapy appears equivalent to 15 days of therapy except when treating nonlactose-fermenting Gram-negative organisms. In this latter situation, longer treatment durations appear to reduce the risk of recrudescence after discontinuation of antibiotic therapy. A guideline-based approach using the local hospital or ICU antibiogram can increase the likelihood that adequate initial antibiotic therapy is used and reduce the overall use of antibiotics and the associated selection pressure for multidrug-resistant organisms.

Prospective comparison of bronchoalveolar lavage and quantitative deep tracheal aspirate in the diagnosis of ventilator associated pneumonia

BACKGROUND

Ventilator associated pneumonia (VAP) is common in trauma patients, and accurate diagnosis of VAP may improve survival. With the risk of development of bacterial resistance, we also strive to minimize the use of unnecessary antibiotics. Recent studies suggest that quantitative deep endotracheal aspirate (QDEA) is adequate in VAP diagnosis. We currently use bronchoalveolar lavage (BAL) diagnosis. The purpose of this study was to examine the accuracy of QDEA as compared with BAL in diagnosing VAP in trauma patients.

METHODS

We prospectively compared the results of BAL and QDEA in intubated patients suspected of having VAP during an 8-month period. Indication for BAL was pulmonary infiltrate, systemic inflammatory response syndrome, and C-reactive protein >17 mg/dL at > or =48 hours after admission. Study patients underwent QDEA immediately before BAL, and quantitative cultures were compared for both specimens. The techniques differ in that QDEA involves the direct culture of sputum suctioned from the distal trachea, whereas BAL involves lavage of the bronchoalveolar tree with sterile saline, which is then cultured. VAP was diagnosed on BAL if > or =10(5) cfu/mL was present on culture. The ability of QDEA to diagnose pneumonia was examined at cutoffs of > or =10(5) cfu/mL and > or =10(4) cfu/mL, as compared with BAL at > or =10(5).

RESULTS

Sixty-one patients underwent BAL during this period, and 39 of these underwent both BAL and QDEA for the study. Of the 39 studied patients between March 16, 2002, and November 4, 2002, 20 (51%) were found to have VAP by BAL (> or =10(5) cfu/mL). Using this cutoff for QDEA, 18 of 20 (90%) would have been correctly diagnosed. Using > or =10 cfu/mL for QDEA, the rate of correct diagnosis would increase to 19 of 20 (95%). However, of the 19 who did not have pneumonia according to BAL, 6 (31%) would have been incorrectly diagnosed with VAP using the QDEA cutoff of > or =10(5) cfu/mL. A QDEA cutoff of > or =10 (4) cfu/mL would result in the even higher false-positive rate of 8 of 19 patients (42%).

CONCLUSION

Whereas most patients with pneumonia by BAL would have been diagnosed by QDEA, use of QDEA in treatment decisions would have led to needless antibiotic administration in 31% of VAP-negative patients at a cutoff of > or =10(5) cfu/mL and 42% at > or =10(4) cfu/mL. The use of QDEA in VAP diagnosis is limited because of the rate of over-diagnosis. With the increasing problems associated with excess antibiotic use, we believe these results support the use of BAL over QDEA in the diagnosis of VAP in the ventilated trauma patient.

Impact of a soluble phospholipase A2 inhibitor on inhaled allergen challenge in subjects with asthma

The possible roles of secretory phospholipases A2 (sPLA2) in asthma include the release of arachidonic acid from cellular membranes, generation of lysophospholipids, sPLA2-mediated activation of cPLA2 with increased leukotriene production, and surfactant degradation. LY333013 is a potent inhibitor of sPLA2. This study examined the impact of two doses of LY333013 vs. placebo on allergen-induced bronchoconstriction following inhaled allergen challenge in atopic asthmatics. Fifty subjects were randomly assigned to treatment, and 40 subjects completed the study. A double-blind, placebo-controlled, random order, crossover study design was used. LY333013 had no impact on the primary outcome variables of the areas under the FEV1 response curve early (0-3 hours) (AUC(early)) and late (3-8 hours) (AUC(Iate)) following inhaled allergen challenge. No significant drug-related adverse effects were observed. The response to inhaled allergen challenge was reproducible and confirms the utility of this technique as a model in which to screen compounds for further testing in asthmatic patients.

Surfactant phospholipid changes after antigen challenge: a role for phosphatidylglycerol in dysfunction

In asthma, inflammation-mediated surfactant dysfunction contributes to increased airway resistance, but the mechanisms for dysfunction are not understood. To test mechanisms that alter surfactant function, atopic asthmatics underwent endobronchial antigen challenge and bronchoalveolar lavage (BAL). BAL fluids were sequentially separated into cells, surfactant, and supernatant, and multiple end points were analyzed. Each end point's unique relationship to surfactant dysfunction was determined. Our results demonstrate that minimum surface tension (gamma(min)) of surfactant after antigen challenge was significantly increased with a spectrum of responses that included dysfunction in 6 of 13 asthmatics. Antigen challenge significantly altered the partitioning of surfactant phospholipid measured as a decreased ratio of large surfactant aggregates (LA) to small surfactant aggregates (SA), LA/SA ratio. Phosphatidylglycerol (PG) was significantly reduced in the LA of the dysfunctional asthmatic BALs. There was a corresponding significant increase in the ratio of phosphatidylcholine to PG, which strongly correlated with both increased gamma(min) and decreased LA/SA. Altered surfactant phospholipid properties correlated with surfactant dysfunction as well or better than either increased eosinophils or protein. Secretory phospholipase activity, measured in vitro, increased after antigen challenge and may explain the decrease in surfactant PG. In summary, alteration of phospholipids, particularly depletion of PG, in the LA of surfactant may be an important mechanism in asthma-associated surfactant dysfunction.

Quinine-induced disseminated intravascular coagulation: case report and review of the literature

OBJECTIVE

To describe the clinical course of quinine-induced disseminated intravascular coagulation (DIC) and review all previous cases reported in the medical literature.

DESIGN

Case report/literature review.

SETTING

University teaching hospital medical ICU.

PATIENTS

One patient in whom thrombocytopenia, coagulopathy, intravascular hemolysis, DIC, and acute renal failure temporally followed the ingestion of quinine.

DATA SOURCES

We conducted a computerized free-text MEDLINE database search from 1969 to 2000 using the keywords quinine and thrombocytopenia, quinine and hemolytic-uremic syndrome, and quinine and disseminated intravascular coagulation.

STUDY SELECTION

All reported cases and reviews of quinine-induced thrombocytopenia, hemolytic-uremic syndrome (HUS), and DIC were reviewed. DIC was distinguished from quinine-induced thrombocytopenia or quinine-induced HUS based on the presence of abnormal clotting times, elevated fibrin degradation products, and/or elevated D-dimer levels.

DATA SYNTHESIS

Fifteen previous patients were found to meet the criteria for DIC temporally related to the recent ingestion of quinine. The clinical course and laboratory abnormalities documented for each case are reviewed.

CONCLUSIONS

Quinine-induced DIC is a distinct clinical entity, which may present as unexplained thrombocytopenia, coagulopathy, or renal failure. In susceptible patients, the immune response to quinine may result in the production of not only anti-platelet antibodies but also antibodies against leukocytes, erythrocytes, and endothelial cells. Furthermore, the varying patterns and specificities of antibody production in an individual patient may result in a spectrum of clinical disease from mild, transient thrombocytopenia to overt intravascular hemolysis, renal failure, coagulopathy, and DIC. Early recognition of quinine-induced DIC is paramount, as this diagnosis affords a better prognosis than other adult forms of HUS or DIC.

Self-reported health status, prophylactic medication use, and healthcare costs in older adults with asthma

OBJECTIVES

To examine the relationship between self-reported health status, prophylactic medication use, and healthcare service use in older adults with asthma.

DESIGN

A prospective longitudinal cohort study was conducted over a 2-year postenrollment period in a population of asthmatic older adults enrolled in managed care. Patients completed a comprehensive health-risk screen at time of enrollment in the plan.

SETTING

A Medicare health maintenance organization (HMO) in the southeastern United States with prescription benefit.

PARTICIPANTS

One hundred twenty-nine older adults with asthma using inhaled corticosteroid therapy as prophylaxis and enrolled in a Medicare HMO were available for complete follow-up.

MEASUREMENTS

We measured self-reported health perception, falls, lifestyle, depressive symptomatology, and pre-enrollment healthcare service use using a comprehensive risk screen. We used the Med-Total index and total annual healthcare charges as measures of postenrollment inhaled corticosteroid and healthcare service use.

RESULTS

After adjusting for the effects of other variables, we found that depressive symptomatology at baseline and increased comorbidity severity (using the Charlson comorbidity index) were associated with significant reductions in prophylactic medication possession (27% with depressive symptomatology and 6% with unit increase in Charlson's index, P <.05). Additionally, after adjusting for the effects of baseline health status, we found that a 10% increase in prophylactic medication possession was associated with a nearly 5% decrease in total annual healthcare charges in this population (P <.01).

CONCLUSION

There are strong but not fully explained associations between depressive symptoms at time of enrollment, decreased postenrollment prophylactic medication use and increased postenrollment healthcare service use in older adults with asthma.

Predictors of successful extubation in neurosurgical patients

A respiratory therapist-driven weaning protocol incorporating daily screens, spontaneous breathing trials (SBT), and prompts to caregivers has been associated with superior outcomes in mechanically ventilated medical patients. To determine the effectiveness of this approach in neurosurgical (NSY) patients, we conducted a randomized controlled trial involving 100 patients over a 14-mo period. All had daily screens of weaning parameters. If these were passed, a 2-h SBT was performed in the Intervention group. Study physicians communicated positive SBT results, and the decision to extubate was made by the primary NSY team. Patients in the Intervention (n = 49) and Control (n = 51) groups had similar demographic characteristics, illness severity, and neurologic injuries. Among all patients, 87 (45 in the Control and 42 in the Intervention group) passed at least one daily screen. Forty (82%) patients in the Intervention group passed SBT, but a median of 2 d passed before attempted extubation, primarily because of concerns about the patient's sensorium (84%). Of 167 successful SBT, 126 (75%) did not lead to attempted extubation on the same day. The median time of mechanical ventilation was 6 d in both study groups, and there were no differences in outcomes. Overall complications included death (36%), reintubation (16%), and pneumonia (9%). Tracheostomies were created in 29% of patients. Multivariate analysis showed that Glasgow Coma Scale (GCS) score (p < 0.0001) and partial pressure of arterial oxygen/fraction of inspired oxygen ratio (p < 0.0001) were associated with extubation success. The odds of successful extubation increased by 39% with each GCS score increment. A GCS score > or = 8 at extubation was associated with success in 75% of cases, versus 33% for a GCS score < 8 (p < 0.0001). Implementation of a weaning protocol based on traditional respiratory physiologic parameters had practical limitations in NSY patients, owing to concerns about neurologic impairment. Whether protocols combining respiratory parameters with neurologic measures lead to superior outcomes in this population requires further investigation.

Cell-specific expression of group X and group V secretory phospholipases A(2) in human lung airway epithelial cells

Secretory phospholipase A(2) (sPLA(2)) enzymes contribute to inflammatory injury in human lungs by several mechanisms, including eicosanoid production and hydrolytic damage to surfactant phospholipids. Several distinct sPLA(2) genes have been described in human tissue but little is known regarding their presence, localization, or function(s) within lungs. We hypothesized that sPLA(2)s would have cell-specific distributions within lung. We used reverse transcriptase/polymerase chain reaction to identify sPLA(2) messenger RNAs (mRNAs) in adult human lung tissue. Resulting complementary DNA (cDNA) sequences indicated that total lung extracts contained mRNA for Groups IB, IIA, V, and X sPLA(2). An epithelial cell line, BEAS cells, expressed only Groups IIA, V, and X. We used these cDNAs to clone these enzymes, especially the recently described Group X and Group V enzymes. Digoxigenin-labeled complementary RNA probes were used to determine localization of each sPLA(2) by in situ hybridization of human lung. Hybridization was strongly positive for Group X and Group V in airway epithelial cells, which failed to hybridize Group IB or IIA probes. Although four known mammalian sPLA(2) isotypes were expressed in lung, only Group X and Group V sPLA(2) mRNAs appear uniquely expressed in airway epithelium, suggesting they could provide a mechanism of pulmonary surfactant hydrolysis during lung injury.

Education of physicians-in-training can decrease the risk for vascular catheter infection

BACKGROUND

Procedure instruction for physicians-in-training is usually nonstandardized. The authors observed that during insertion of central venous catheters (CVCs), few physicians used full-size sterile drapes (an intervention proven to reduce the risk for CVC-related infection).

OBJECTIVE

To improve standardization of infection control practices and techniques during invasive procedures.

DESIGN

Nonrandomized pre-post observational trial.

SETTING

Six intensive care units and one step-down unit at Wake Forest University Baptist Medical Center, Winston-Salem, North Carolina.

PARTICIPANTS

Third-year medical students and physicians completing their first postgraduate year.

INTERVENTION

A 1-day course on infection control practices and procedures given in June 1996 and June 1997.

MEASUREMENTS

Surveys assessing physician attitudes toward use of sterile techniques during insertion of CVCs were administered during the baseline year and just before, immediately after, and 6 months after the first course. Preintervention and postintervention use of full-size sterile drapes was measured, and surveillance for vascular catheter-related infection was performed.

RESULTS

The perceived need for full-size sterile drapes was 22% in the year before the course and 73% 6 months after the course (P < 0.001). The perceived need for small sterile towels at the insertion site decreased reciprocally (P < 0.001). Documented use of full-size sterile drapes increased from 44% to 65% (P < 0.001). The rate of catheter-related infection decreased from 4.51 infections per 1000 patient-days before the first course to 2.92 infections per 1000 patient-days 18 months after the first course (average decrease, 3.23 infections per 1000 patient-days; P < 0.01). The estimated cost savings of this 28% decrease was at least $63000 and may have exceeded $800000.

CONCLUSIONS

Standardization of infection control practices through a course is a cost-effective way to decrease related adverse outcomes. If these findings can be reproduced, this approach may serve as a model for physicians-in-training.

Venous air embolism from central venous catheterization: a need for increased physician awareness

OBJECTIVES

To report a series of patients with clinically diagnosed venous air embolism (VAE) and major sequelae as a complication of the use of central venous catheters (CVCs), to survey health care professionals' practices regarding CVCs, and to implement an educational intervention for optimizing approaches to CVC insertion and removal.

SETTING

Tertiary care, university-based 806-bed medical center.

INTERVENTIONS

We surveyed 140 physicians and 53 critical care nurses to appraise their awareness of the proper management and complications of CVCs. We then designed, delivered, and measured the effects of a multidisciplinary educational intervention given to 106 incoming house officers.

MEASUREMENTS AND MAIN RESULTS

Although most physicians (127, 91%) chose the Trendelenburg position for CVC insertion, only 42 physicians (30%) reported concern for VAE. On CVC removal, only 36 physicians (26%) cited concern for VAE. Some physicians (13, 9%) reported elevating the head of the bed during CVC removal, possibly increasing the risk of VAE. Awareness of VAE or its prevention did not correlate with the level of physician training, experience, or specialty. After the educational intervention, concern for and awareness of proper methods of prevention of VAE improved (p < .001). At 6-month follow-up, reported use of the Trendelenburg position continued, but concern cited for VAE had returned to baseline.

CONCLUSIONS

There is inadequate awareness of VAE as a complication of CVC use. Focused instruction can improve appreciation of this potentially fatal complication and knowledge of its prevention, but the effect declines rapidly. To achieve a more sustained improvement, a more intensive, hands-on, periodic educational program will likely be necessary, as well as reinforcement through enhanced supervision of CVC insertion and removal practices.

Nosocomial pneumonia in the ICU--year 2000 and beyond

Diagnostic and treatment strategies in ICU patients with ventilator-associated pneumonia (VAP) remain controversial, largely because of the paucity of well-controlled comparison trials using clinically important end points. Recent studies indicating that early appropriate antibiotic therapy significantly lowers mortality underscore the urgent need for well-designed comparative trials. When quantitatively cultured, bronchial specimens obtained by noninvasive techniques may provide clinically useful information and avoid the higher costs and risks of invasive bronchoscopic diagnostic techniques. Previous antibiotic use before onset of nosocomial pneumonia raises the likelihood of infection with highly virulent organisms, such as Pseudomonas aeruginosa and Acinetobacter sp. Thus, the empiric antibiotic regimen should be active against these Gram-negative pathogens as well as other common Gram-negative and Gram-positive causative organisms. Promising preventive modalities for nosocomial VAP include use of a semirecumbent position, endotracheal tubes that allow continuous aspiration of secretions, and heat and moisture exchangers. Rotating their standard empiric antibiotic regimens and restricting the use of third-generation cephalosporins as empiric therapy may help hospitals reduce the incidence of nosocomial pneumonia caused by resistant Gram-negative pathogens.

Large scale implementation of a respiratory therapist-driven protocol for ventilator weaning

We prospectively investigated the large-scale implementation of a respiratory-therapist-driven protocol (TDP) that included 117 respiratory care practitioners (RCPs) managing 1,067 patients with respiratory failure over 9,048 patient days of mechanical ventilation. During a 12-mo period, we reintroduced a previously validated protocol that included a daily screen (DS) coupled with spontaneous breathing trials (SBTs) and physician prompt, as a TDP without daily input from a physician or "weaning team." With graded, staged educational interventions at 2-mo intervals, RCPs had a 97% completion rate and a 95% correct interpretation rate for the DS. The frequency with which patients who passed the DS underwent SBTs increased throughout the implementation process (p < 0.001). As the year progressed, RCPs more often considered SBTs once patients had passed a DS (p < 0.001), and physicians ordered more SBTs (46 versus 65%, p = 0.004). Overall, SBTs were ordered more often on the medicine than on the surgical services (81 versus 63%, p = 0.001), likely reflecting medical intensivists' prior use of this protocol. Important barriers to protocol compliance were identified through a questionnaire (89 respondents, 76%), and included: Physician unfamiliarity with the protocol, RCP inconsistency in seeking an order for an SBT from the physician, specific reasons cited by the physician for not advancing the patient to a SBT, and lack of stationary unit assignments by RCPs performing the protocol. We conclude that implementation of a validated weaning strategy is feasible as a TDP without daily supervision from a weaning physician or team. RCPs can appropriately perform and interpret DS data more than 95% of the time, but significant barriers to SBTs exist. Through a staged implementation process, using periodic reinforcement of all participants in ventilator management, improved compliance with this large-scale weaning protocol can be achieved.

Radiographic assessment of hyperinflation: correlation with objective chest radiographic measurements and mechanical ventilator parameters

BACKGROUND

Pulmonary barotrauma is a potentially fatal complication of positive pressure ventilation. We previously found that barotrauma occurred in patients with radiographic hyperinflation, but few objective data define the relationships among hyperinflation, objective chest radiograph (CXR) measurements, ventilator parameters, and development of barotrauma.

OBJECTIVES

We sought (1) to assess the relationships among hyperinflation, objective CXR findings, mechanical ventilator parameters, and development of barotrauma. (2) To compare radiographic hyperinflation, ventilator parameters, and incidence of barotrauma in a current group of ICU patients with historical control subjects.

SETTING

Medical and surgical ICU patients in a university hospital.

DESIGN

Prospective blinded observational study; comparison of current series with historical control subjects.

METHODS

One hundred two prospectively enrolled mechanically ventilated medical and surgical ICU patients each received portable supine CXRs that were reviewed independently by three radiologists who made objective measurements and subjectively determined the likelihood of hyperinflation. Ventilator parameters were recorded at the bedside at the time each CXR was obtained. CXR measurements and ventilator parameters were then related to the development of barotrauma during the course of ventilation and compared with findings of a prospective study at our institution 1 year earlier.

RESULTS

Radiographically recognizable hyperinflation occurred in 18 of 102 mechanically ventilated ICU patients (18%) and correlated with lung length (24.7 vs 19.8 cm; p<0.05) and the anterior rib number that intersects the hemidiaphragm (5.4 vs 4.7; p<0.05). Patients with hyperinflation were ventilated at higher tidal volume per kilogram (VT/kg) (11.0 vs 9.4; p=0.0081), but peak airway pressure, plateau pressure, and positive end-expiratory pressure were similar. There were significant decreases in VT (810 vs 739 mL; p=0.015) and VT/kg (11.0 vs 10.1 mL/kg; p<0.001) in these mechanically ventilated ICU patients in comparison to hospital control subjects evaluated during the previous year. Paralleling these changes was a decrease in the frequency of CXR hyperinflation (p=0.003) and the incidence of ventilator-associated barotrauma (6.5% vs 0.98%; p=0.048).

CONCLUSIONS

Ventilation at higher VT/kg is associated with a higher incidence of CXR hyperinflation. Radiographic hyperinflation is associated with lung length > or =24.7 cm and visualization of the sixth anterior rib. Patients with hyperinflation may be at greater risk for developing barotrauma or volutrauma. Ventilatory strategies utilizing lower volumes are associated with a lower incidence of such trauma in the current sample as compared with historical control subjects.

Skin sensitivity to allergen does not accurately predict airway response to allergen

BACKGROUND

Allergen challenge of the asthmatic airway has become widely applied in the study of allergic asthma in humans. Skin sensitivity correlates with inhaled sensitivity in some populations. Skin test titration has been proposed as a useful tool to guide the selection of initial allergen concentration.

OBJECTIVE

To determine the relationship between skin test sensitivity and inhaled reactivity to allergen.

METHODS

We examined the relationship between skin test and inhaled reactivity in 22 allergic asthmatic subjects. Methacholine bronchoprovocation was performed using a standardized tidal breathing technique. Prick skin test titrations were done using serially diluted lyophilized antigen extracts reconstituted in normal saline from 1:100,000 to 1:10. Inhaled allergen challenge was routinely performed in the morning using the same allergen employed in skin test titration.

RESULTS

There was no correlation between skin test threshold and the inhaled concentration required to produce a 20% fall in FEV1 (r = 0.07; P = .78). If subjects who manifested marked cutaneous reactivity (i.e., skin reactivity at dilutions greater than 1:10,000) were excluded from analysis, there was a significant correlation between cutaneous and inhaled reactivity (r = 0.84; P < .001).

CONCLUSION

While a correlation between skin test threshold and inhaled reactivity is present in some subjects with allergic asthma, the relationship is inconsistent.

Phospholipase A2 and arachidonate increase in bronchoalveolar lavage fluid after inhaled antigen challenge in asthmatics

Phospholipases A2 (PLA2) hydrolyze phospholipids resulting in the release of fatty acids including arachidonic acid (AA) and lysophospholipids. AA, in turn, serves as a substrate for the synthesis of leukotrienes which can cause bronchoconstriction and airways edema and appear to be important mediators of clinical asthma. Further, lysophospholipids may be cytotoxic and/or impair the function of surfactant. We examined the release of secretory PLA2 (sPLA2) and AA into the airways after antigen challenge in 16 subjects with allergic asthma. Asthmatic subjects underwent bronchoscopy with bronchoalveolar lavage (BAL) before and after inhaled antigen challenge; in addition, a single BAL, without inhaled antigen, was performed in 10 control subjects. BAL was obtained at 4 h (n = 7), the time of the late asthmatic response (LAR) (n = 5), or 24 h (n = 4) after challenge. There was no difference between normal and asthmatic subjects in either BAL fluid (BALF) sPLA2 activity or AA concentration at baseline. Both sPLA2 and AA increased after antigen challenge (p < 0.01 and 0.05, respectively). These changes were most marked 4 h after challenge (p < 0.03 for both). sPLA2 may play an important role in the generation of AA in patients with asthma.

Effect on the duration of mechanical ventilation of identifying patients capable of breathing spontaneously

BACKGROUND

Prompt recognition of the reversal of respiratory failure may permit earlier discontinuation of mechanical ventilation, without harm to the patient.

METHODS

We conducted a randomized, controlled trial in 300 adult patients receiving mechanical ventilation in medical and coronary intensive care units. In the intervention group, patients underwent daily screening of respiratory function by physicians, respiratory therapists, and nurses to identify those possibly capable of breathing spontaneously; successful tests were followed by two-hour trials of spontaneous breathing in those who met the criteria. Physicians were notified when their patients successfully completed the trials of spontaneous breathing. The control subjects had daily screening but no other interventions. In both groups, all clinical decisions, including the decision to discontinue mechanical ventilation, were made by the attending physicians.

RESULTS

Although the 149 patients randomly assigned to the intervention group had more severe disease, they received mechanical ventilation for a median of 4.5 days, as compared with 6 days in the 151 patients in the control group (P=0.003). The median interval between the time a patient met the screening criteria and the discontinuation of mechanical ventilation was one day in the intervention group and three days in the control group (P<0.001). Complications -- removal of the breathing tube by the patient, reintubation, tracheostomy, and mechanical ventilation for more than 21 days -- occurred in 20 percent of the intervention group and 41 percent of the control group (P=0.001). The number of days of intensive care and hospital care was similar in the two groups. Total costs for the intensive care unit were lower in the intervention group (median, $15,740, vs. $20,890 in the controls, P=0.03); hospital costs were lower, though not significantly so (median, $26,229 and $29,048, respectively; P=0.3).

CONCLUSIONS

Daily screening of the respiratory function of adults receiving mechanical ventilation, followed by trials of spontaneous breathing in appropriate patients and notification of their physicians when the trials were successful, can reduce the duration of mechanical ventilation and the cost of intensive care and is associated with fewer complications than usual care.

Chest X-ray changes in air space disease are associated with parameters of mechanical ventilation in ICU patients

To assess relationships between parameters of mechanical ventilation (MV) and portable chest X-ray (CXR) measurements of lung length (LL) and severity of air space disease, a prospective, randomized, blinded comparison of 102 adults in a university hospital was performed. Each patient received two portable, supine CXRs on different MV breaths within 5 min of one another. Ventilator parameters were recorded. All 204 CXRs were randomly assorted and read independently by three radiologists. Air space disease was considered more severe with pressure support ventilation (PSV) breaths than with intermittent mandatory ventilation (IMV) breaths (p = 0.0003), and its extent correlated inversely with static compliance (p = 0.0001, r = -0.40). Among patients having CXRs on both IMV and PSV breaths, 15 of 67 (22%) had their overall degree of air space disease read differently by one category (mild, moderate, or severe). Increases in LL between the two CXRs were associated with increasing peak (p = 0.0038) or mean (p = 0.0065) airway pressure, tidal volume (VT) (p = 0.022), and VT per kilogram (p = 0.006). We conclude that lung volume changes during MV, typically not noted nor controlled for during portable chest radiography, may substantially alter the interpretation of air space disease and LL. Physicians monitoring intensive care unit (ICU) patients with daily CXRs should be aware of the variables influencing interpretation of portable CXRs of ICU patients.

Pulmonary section development influences general medical house officer interests and ABIM certifying examination performance

To determine whether sectional development in pulmonary and critical care medicine influences medical house officers' (HO) interests and knowledge about respiratory medicine, we reviewed HO performance on the American Board of Internal Medicine (ABIM) certifying examination during 4 years before and 5 years after reorganization of our section. After major changes in the program and introduction of new educational opportunities, HOs more often selected pulmonary consultation electives (68.6% vs 47.8%; p = 0.009) and entered pulmonary fellowships after completion of residency training (12% vs 3%; p = 0.047). Total ABIM examination score did not change, but performance on its respiratory disease component improved from a median national percentile score of 48.5% (1986 to 1989) to 80.0% (1990 to 1994) (p = 0.0365). In relation to other specialty component scores, the rank of the respiratory disease percentile improved from the lowest specialty score to the highest. ABIM examination scores correlated with the cumulative faculty effort directed toward HO teaching (r = 0.70; p = 0.04) and the total number of clinical teachers (faculty and fellows) interacting with HOs (r = 0.73; p = 0.02). Academic development in pulmonary/critical care faculty has an important influence on medical HO interests in and knowledge of that discipline. Plans for the future structure of academic pulmonary/critical care sections must take into account this impact on the training of generalists. Although institutional priorities, resources, and shifting external forces will define how, where, and by whom respiratory medicine will be taught, an appropriate number of faculty members and sufficient commitment of their time to HO education must be preserved.

Comparison of the infusion requirements and recovery profiles of vecuronium and cisatracurium 51W89 in intensive care unit patients

The selection and administration of neuromuscular blocking (NMB) drugs in intensive care unit (ICU) patients remain controversial. We compared the dose-response and recovery pharmacodynamics of a new intermediate-acting NMB drug, cisatracurium besylate, to the intermediate-acting NMB drug, vecuronium (VEC), in a prospective, randomized, double-blind, multicenter study in critically ill adults. After informed consent, 58 mechanically ventilated ICU patients from five medical centers were randomized to receive either cisatracurium or VEC. Fifty-four of the 58 patients received NMB drugs before entering this study but demonstrated at least partial recovery (> or = one twitch) in the train-of-four (TOF) response before initiation of the NMB study drug. NMB drug infusion was titrated by peripheral nerve stimulation to maintain at least one twitch in the TOF response. NMB drugs were infused for 1-5 days. After discontinuation of NMB drug infusion, recovery of neuromuscular transmission was monitored with an accelerometer. NMB drug infusion for 28 cisatracurium patients averaged 2.6 +/- 0.2 (mean +/- SEM) micrograms.kg-1.min-1 with a mean duration of 80 +/- 7 h. After discontinuing cisatracurium administration, recovery to 70% TOF ratio averaged 68 +/- 13 min. The mean infusion rate for 30 VEC patients was 0.9 +/- 0.1 micrograms.kg-1.min-1 with a mean duration of 66 +/- 12 h. Neuromuscular recovery after VEC averaged 387 +/- 163 min, which was significantly longer (P = 0.02) than that after cisatracurium. Prolonged recovery of neuromuscular function after discontinuation of NMB drug infusion (identified by the primary investigator at each medical center) was reported in two cisatracurium patients and 13 VEC patients (P = 0.002), and occurred despite the routine use of neuromuscular twitch monitoring. Seven VEC and one cisatracurium patients died during the infusion of study drug or within 48 h after discontinuation of the NMB drug infusion. In summary, we found recovery of neuromuscular function after discontinuation of NMB drug infusion in ICU patients is significantly faster with cisatracurium than with VEC. In addition, routine neuromuscular monitoring was not sufficient to eliminate prolonged recovery and myopathy in ICU patients.

Education and experience improve transbronchial needle aspiration performance

To determine whether the diagnostic yield of transbronchial needle aspiration (TBNA) improves over time and to obtain insights about factors influencing its performance, we reviewed our experience during a 3-yr period. After serial multifaceted educational interventions directed toward bronchoscopists and their technical staff, TBNA yield increased significantly from 21.4 to 47.6% (p < 0.001). More frequent and more detailed notations in bronchoscopy reports (p < 0.05), a lower frequency of cytopathology specimens contaminated by endobronchial material (p < 0.05), and higher yields in patients with small cell carcinoma (p < 0.01) suggested that bronchoscopists' TBNA proficiency had increased. More frequent diagnoses with small cell carcinoma and fewer cytologically unsatisfactory specimens (p < 0.01) suggested that education of bronchoscopy technicians, and use of a direct smear technique for specimen preparation also contributed to improved TBNA yield. Increased experience with TBNA and focused education regarding its performance can enhance the role of this procedure in diagnosis and staging of patients with lung cancer.

Decision making in nosocomial pneumonia. An analytic approach to the interpretation of quantitative bronchoscopic cultures

Quantitative cultures of specimens obtained at fiberoptic bronchoscopy have been used to diagnose nosocomial pneumonia in research settings, but their clinical role remains controversial. We reviewed the literature comparing these culture techniques with other accepted methods to diagnose pneumonia in mechanically ventilated patients and extracted data to describe the receiver operator characteristics (ROC) of quantitative cultures of protected specimen brush (PSB) and bronchoalveolar lavage (BAL) samples. Analysis of ROCs reveals that these tests have a discriminating power comparable or superior to that of many widely accepted routinely used tests. Current data do not suggest that either culture technique offers an advantage over the other. Since benefits of antibiotic therapy of pneumonia and risks of treatment of noninfected critically ill patients are not well quantified, universally applicable recommendations for appropriate values to define an abnormal test result cannot logically be made. Multiple decision analytic tools show that values lower than those previously recommended are more appropriate in patients suspected of having pneumonia unless the risk of antibiotic therapy is judged to be extreme. On the basis of these findings, we suggest guidelines for clinicians' interpretation of PSB and BAL quantitative culture results.

Effect of chronic theophylline therapy on brain blood flow and function in adult asthmatics

The impact of theophylline therapy on neuropsychological (NP) function in adult asthmatics is unclear. Additionally, whether the previously demonstrated acute reduction in cerebral blood flow (CBF) persists with continued administration of theophylline, or whether accommodation develops, has not been previously reported. We examined the effects of chronic theophylline administration on CBF and NP function in adults with mild to moderate asthma. Sixty adult patients with mild to moderate asthma were entered into this double-blind, placebo-controlled, crossover, random sequence study. Subjects received theophylline or placebo for 6 wk interposed with a 2-wk washout period. At the conclusion of Week 1 and Week 6 of each drug phase, patients received NP testing, and CBF was determined using the 133Xenon washout method. Forty-three patients completed the study. Theophylline administration was associated with small (6%), but statistically significant, reductions in CBF after both 1 and 6 wk of treatment. No differences consequent to theophylline administration were observed in any of the tests of NP function after 1 or 6 wk of therapy. While CBF was decreased after theophylline, the changes were small compared with previously reported decrements in CBF immediately after theophylline administration.

Portable chest radiographs identify mechanical ventilator-associated hyperinflation

OBJECTIVE

Portable chest radiographs (CRs) are obtained routinely in mechanically ventilated patients, but little is known about relationships between CR findings and ventilator parameters. It is unclear whether radiographically apparent hyperinflation correlates with tidal volume (VT), body weight (BW), VT/kg, or levels of peak airway pressure (PAP), positive end-expiratory pressure (PEEP), or pressure support (PS).

DESIGN

Prospective comparison of CR and ventilator parameters in 62 mechanically ventilated patients in surgical and medical intensive care units of a university hospital.

PATIENT SELECTION

All mechanically ventilated adults with portable CR on four separate dates.

METHODS

Chest radiographs were classified by subjective assessments as hyperinflated (H+) or nonhyperinflated (H-), independent of knowledge of patients or their mechanical ventilation. Chest radiographs were reclassified independently as H+, H-, or indeterminate by a radiologist using objective criteria. Ventilator parameters recorded at the time of the CR were obtained and compared.

RESULTS

Patients with CRs classified subjectively as H+ compared with patients with CRs classified as H- had a larger VT/kg (12.0 +/- 0.4 ml/kg [mean +/- SEM] vs 10.2 +/- 0.4; p = 0.004), lower BW (70.8 +/- 2.9 kg vs 81.5 +/- 3.8; p = 0.03), higher PEEP (6.5 +/- 0.5 cm H2O vs 5.0 +/- 0.4; p = 0.01), and higher PAP (38.2 +/- 2.1 cm H2O vs. 33.4 +/- 1.8; p = 0.06). Using objective CR classifications, patients with H+ CRs had a VT/kg of 12.6 +/- 0.4, larger than in the indeterminate (11.1 +/- 0.8) and H- (9.9 +/- 0.3) groups (p < 0.001). The BW differed among objectively classified groups (66.5 +/- 2.7 H+, 68.9 +/- 5.1 indeterminate, and 85.2 +/- 3.7 H-; p < 0.001), but other ventilator parameters did not correlate univariately with the degree of inflation on CR. Multivariate analysis showed that higher VT was predictive of H+ after adjusting for BW in subjective (p = 0.076) and objective (p = 0.017) classifications. PEEP (p = 0.004) and older age (p = 0.021) were also associated with H+ in multivariate analysis. Four of 25 (16 percent) patients with objectively H+ CRs developed barotrauma, while no patient with H- CR had this complication (p = 0.037).

CONCLUSIONS

In mechanically ventilated patients, hyperinflation seen on portable CR is associated with higher VT, VT/kg, and lower BW, and may help predict subsequent barotrauma.

The incidence and effect on outcome of hypoxemia in hospitalized medical patients

The effect on survival of episodic hypoxemia was prospectively studied in 100 patients hospitalized on general medicine services of a large, tertiary care, university hospital. Pulse oximetry monitoring (POM) was initiated within 24 hours of admission and was maintained for approximately 24 hours independent of patient management. Hypoxemia lasting for at least 5 consecutive minutes and resulting in an arterial oxygen saturation of less than 90% occurred in 26 of the 100 patients. No clinical characteristics were found that could reliably distinguish those patients who did develop hypoxemia from those who did not, though the small number of patients in many categories precludes drawing firm conclusions. However, severe desaturation was unlikely to occur in patients with normal chest roentgenograms. During the following 4 to 7 months, 8 patients (32%) suffering episodic hypoxemia died, while only 7 individuals (10%) without hypoxemia died, an increase in mortality that remained significant after adjustment for severity of illness. The relative risk of death associated with desaturation was 3.3 (95% CI 1.41 to 8.2). The severity of hemoglobin oxygen desaturation, expressed as the saturation-time index, correlated inversely with survival time.

A laboratory comparison of three pulmonary artery oximetry catheters

BACKGROUND

Measurement of mixed venous hemoglobin oxygen saturation via catheters employing reflectance spectrophotometry has been available for more than 10 yr. Despite numerous clinical reports that have presented data showing the poor accuracy of these devices when used clinically, they are still widely used in clinical care. The reason for lack of agreement with measurements made using bench spectrophotometry is unclear. The purpose of this study is to define the performance limitations of three hemoglobin oxygen saturation catheters (Oximetrix 3, SAT-2, and HEMOPRO2) in a controlled laboratory environment using a blood flow loop primed with fresh whole human blood as a model. Our hypothesis is that the performance limitations of these devices represent inherent limitations in the technology, not error introduced by patient anatomy and physiology.

METHODS

Blood was equilibrated in a flow loop to four analytic gas mixtures designed to achieve oxygen saturation of approximately 50%, 60%, 70%, and 80%, respectively, with carbon dioxide tension, pH, and temperature held constant. Saturation readings from the catheters were collected on-line by microcomputer. Periodic blood samples were withdrawn from the flow loop for analysis on a bench spectrophotometer and subsequent comparison with catheter-derived values.

RESULTS

By all measures, performances of the Oximetrix 3 and SAT-2 systems were comparable (all data are presented as percent saturation unless otherwise noted); bias +/- precision was 3.20 +/- 2.47 and -1.25 +/- 3.36, respectively, versus -9.97 +/- 7.05 for the HEMOPRO2. The 95% confidence limits based on intracatheter variability were +/- 3.49, +/- 2.90, and +/- 9.13 for the Oximetrix 3, SAT-2, and HEMOPRO2, respectively. The 95% confidence limits based on total variability, although similar for Oximetrix 3 (+/- 4.83) and SAT-2 (+/- 6.59), were larger for the HEMOPRO2 (+/- 13.82). The 95% confidence intervals for agreement between catheter brands were -2.14, 11.04 (Oximetrix 3 - SAT-2); -0.18, 26.52 (Oximetrix 3 - HEMOPRO2) and -5.24, 22.68 (SAT-2 - HEMOPRO2).

CONCLUSIONS

While the Oximetrix 3 and SAT-2 may be acceptable as continuous monitors used to detect changes or trends, none of the three systems is equivalent to conventional bench oximetry for the measurement of hemoglobin oxygen saturation.

Aspiration and acute lung injury

Aspiration is a common clinical entity whose consequences range from the relatively benign to fulminant acute respiratory failure and death. Clinical situations in which airway protection is lost or compromised predispose patients to aspiration. Treatment of aspiration, while generally supportive, depends in part upon the material aspirated and the resulting clinical syndrome. When mechanical ventilatory support is required, the avoidance of iatrogenic complications, including worsening lung injury, becomes especially important. Preventative measures, either to minimize the chances of aspiration, or to reduce the potential for injury consequent to aspiration may be highly effective in reducing the incidence of aspiration syndromes.

Performance characteristics and interanalyzer variability of PO2 measurements using tonometered human blood

We performed a side-by-side comparison of the ability of four blood gas analyzers (IL-1312, Corning-178, AVL-995, and ABL-330) to measure PO2 across a wide range under controlled laboratory conditions. Samples of fresh whole human blood, tonometered with analytic quality gas, were prepared with partial pressures of oxygen from 0 to 283 mm Hg. Fifteen determinations were made at 16 levels of tonometric PO2 (tPO2) on each of the four blood gas analyzers. The bias, precision, and root mean squared error (RMSE) of the PO2 measurement relative to tPO2 were determined for each analyzer at each tPO2 level. Mean bias and precision across the range tested were 2.78 +/- 1.29 mm Hg (IL), -0.35 +/- 1.91 (Corning), 2.14 +/- 1.43 (AVL), and 3.00 +/- 1.47 (ABL). RMSE was 3.28, 2.61, 3.57, and 2.41 for IL, AVL, ABL, and Corning, respectively. Percent RMSE (RMSE/tPO2 x 100%), ranged from 0.9% (AVL at 75 mm Hg PO2 and IL at 283 mm Hg tPO2) to 9.1% (IL at 29 mm Hg tPO2). Three analyzers (AVL, ABL, and Corning) showed a statistically significant (p < 0.0001) correlation between RMSE and tPO2, and no correlation between percent RMSE and tPO2. This demonstrates that, for these instruments, accuracy is a function of the magnitude of the tPO2 value. IL did not show a significant correlation between RMSE and tPO2 but did demonstrate a significant negative correlation (r = -0.78, p > 0.001) between percent RMSE and tPO2, indicating that, for this analyzer, accuracy is not a function of tPO2. The differences in PO2 measurements between pairs of analyzers were also examined.(ABSTRACT TRUNCATED AT 250 WORDS)

A comparison of three pulmonary artery oximetry catheters in intensive care unit patients

OBJECTIVE

To compare the clinical performance of three pulmonary artery oximetry catheters (Oximetrix 3, SAT-2, and HEMOPRO2) in intensive care unit (ICU) patients.

DESIGN

Unblinded comparison of performance over 24 h using an IL-282 CO-oximeter as a criterion standard.

SETTING

Multispecialty adult ICU at a university teaching hospital.

PATIENTS

Thirty critically ill patients selected from those requiring hemodynamic monitoring for medical management.

MEASUREMENTS AND MAIN RESULTS

By all measures, performance of the Oximetrix 3 and SAT-2 systems were comparable; bias +/- precision were -1.98 +/- 3.07 and +1.80 +/- 3.49, respectively, vs -2.28 +/- 5.24 for the HEMOPRO2. The Oximetrix 3 and SAT-2 systems demonstrated consistent performance over the range of saturations tested, though Oximetrix 3 tended to underestimate and SAT-2 tended to overestimate the CO-oximeter value. The HEMOPRO2 underestimated the CO-oximetry-derived saturation, although this was not constant across the range of values tested. The 95 percent confidence limits based on intrasubject variability were similar (+/- 4.59, +/- 5.66, and +/- 6.56 for the Oximetrix 3, SAT-2, and HEMOPRO2, respectively); however, the 95 percent confidence limits based on total variability, while similar for Oximetrix 3 (+/- 6.03) and SAT-2 (+/- 6.86), were larger for the HEMOPRO2 (+/- 10.30). The expected SD was similar for the three systems (2.03, 2.50, and 2.90 for the Oximetrix 3, SAT-2, and HEMOPRO2 systems, respectively). None of the systems equaled or exceeded (p greater than 0.05) the manufacturers' published specifications, which, in all cases, are listed as +/- 2 percent (saturation; 1 SD) when compared with bench oximetry.

CONCLUSIONS

Although each system measures mixed venous oxygen saturation, the Oximetrix 3 and SAT-2 systems demonstrate closer agreement with CO-oximetry. However, none of these catheters provided statistically significant evidence that they would perform within +/- 2 percent of CO-oximetry. As a continuous monitor used to detect changes or trends, any of the three may be acceptable.

Substitution of metered-dose inhalers for hand-held nebulizers. Success and cost savings in a large, acute-care hospital

Administration of beta-agonist bronchodilators by metered-dose inhaler (MDI) is as effective as administration by hand-held nebulizer (NEB). Recent studies have suggested that MDI therapy is less costly to administer and that routine substitution of MDI for NEB would result in considerable savings to patients and to hospitals. To our knowledge, the actual extent to which MDI therapy would replace NEB therapy or the cost savings realized has not been reported previously. We examined the success and impact on hospital costs of the routine substitution of MDI for NEB therapy in a large tertiary-care hospital. Following introduction of this strategy, more than 60 percent of all aerosol therapy was actually given as MDI. The mean amount of time spent by therapists to provide aerosol therapy was significantly reduced by MDI substitution, falling from 1,576 +/- 131 h/mo, to 992 +/- 116 h/mo (p less than 0.002). The total cost to deliver aerosol therapy fell from $27,600 +/- $2,277/mo to $20,618 +/- $2,086/mo (p = 0.008). Potential cost savings of $83,000 annually were achieved by the hospital, and charges to patients were lowered by approximately $300,000 per year. Routine substitution of MDI therapy for NEB therapy can be accomplished with considerable, but not total, success. This approach results in significant reductions in the cost of health care provision.