Glycemic control in the ICU: a multicenter survey

BACKGROUND

Intensive insulin therapy has recently been shown to decrease morbidity and mortality in the critically ill population in a large randomized clinical trial.

OBJECTIVE

To determine the beliefs and attitudes of ICU clinicians about glycemic control.

DESIGN

Self-administered survey.

PARTICIPANTS

ICU nurses and physicians in five university-affiliated multidisciplinary ICUs.

RESULTS

A total of 317 questionnaires were returned from 233 ICU nurses and 84 physicians. The reported clinically important threshold for hypoglycemia was 4 mmol/l (median, IQR 3-4 mmol/l). In non-diabetic patients, the clinically important threshold for hyperglycemia was 10 mmol/l (IQR 9-12 mmol/l); however, nurses had a significantly higher threshold than physicians (difference of 0.52 mmol/l (95% CI 0.09-0.94 mmol/l, P=0.018). In diabetic patients, the clinically important threshold for hyperglycemia was also 10 mmol/l (IQR 10-12 mmol/l), and again nurses had a significantly higher threshold than physicians (0.81 mmol/l, 95% CI 0.29-1.32 mmol/l, P=0.0023). Avoidance of hyperglycemia was judged most important for diabetic patients (87.7%, 95% CI 84.1-91.3%), patients with acute brain injury (84.5%, 95% CI 80.5-88.5%), patients with a recent seizure (74.4%, 95% CI 69.6-79.3%), patients with advanced liver disease (64.0%, 95% CI 58.7-69.3%), and for patients with acute myocardial infarction (64.0%, 95% CI 58.7-69.3%). Physicians expressed more concern than nurses about avoiding hyperglycemia in patients with acute myocardial infarction ( P=0.0004). ICU clinicians raised concerns about the accuracy of glucometer measurements in critically ill patients (46.1%, 95% CI 40.5-51.6%).

CONCLUSIONS

Attention to these beliefs and attitudes could enhance the success of future clinical, educational and research efforts to modify clinician behavior and achieve better glycemic control in the ICU setting.

Influence of perceived functional and employment status on cardiopulmonary resuscitation directives

BACKGROUND

Perceptions about functional and employment status before admission to the intensive care unit (ICU) may influence how patients and clinicians make decisions about cardiopulmonary resuscitation.

OBJECTIVE

To examine the relationship between cardiopulmonary resuscitation directives established within 24 hours of admission to the ICU and clinical perceptions of premorbid functional and employment status.

DESIGN

Prospective observational study in 15 university-affiliated centers in Canada, the United States, Australia, and Sweden.

PATIENTS

A total of 1,008 ICU patients aged 18 years or older expected to stay in the ICU at least 72 hours.

MEASUREMENTS

By using multinomial logistic regression, we examined the relationship between functional status and employment status perceived by the ICU team 1 month before ICU admission (the independent variables) and resuscitation status (the dependent variable). Each patient had either an explicit resuscitation directive (to resuscitate or not to resuscitate), or an implicit resuscitation directive to resuscitate.

RESULTS

On average, patients were 61.7 years (+/-17.4 y) old with an Acute Physiology and Chronic Health Evaluation (APACHE) II score of 21.5 (+/-8.7); 846 (83.9%) were ventilated mechanically within 48 hours and 345 (34.2%) died in the ICU. Most patients (793, 78.7%) had no explicit resuscitation directive; 98 (9.7%) had an explicit plan to resuscitate, whereas 117 (11.6%) had an explicit plan of do-not-resuscitate. Of 1,008 patients, 98 (9.7%) were severely functionally limited, 217 (21.5%) were somewhat limited, 628 (62.3%) were totally independent, and 65 (6.4%) had unknown functional status 1 month before ICU admission. Severe functional status impairment was associated moderately with an explicit plan to resuscitate (odds ratio, 2.2 relative to no explicit directive) and associated strongly with an explicit do-not-resuscitate plan (odds ratio, 6.2 relative to no explicit directive, P value on the difference =.011). This relationship was not influenced by age, sex, APACHE II score, medical or surgical status, admission diagnosis, employment status, or city. However, severe functional status was associated strongly and significantly with an explicit do-not-resuscitate directive among those who could not participate in decision making (odds ratio, 8.2; 95% confidence interval, 4.5-15.0), and more weakly associated in those who could participate (odds ratio, 1.7; 95% confidence interval, 0.3-8.6). Being unemployed was associated with an increased odds of an explicit resuscitation directive versus no explicit directive (odds ratio, 5.5; 95% confidence interval, 2.2-13.4).

CONCLUSIONS

Functional status impairment perceived by the ICU team is associated clearly with do-not-resuscitate directives in patients unable to participate in decision making. However, the association appears much weaker in patients able to participate in decision making. PATIENTS' perceived employment status also may influence resuscitation decisions. Our results emphasize the challenges of ensuring that crucial resuscitation decisions are not affected adversely by patients' inability to participate in decisions, and by their functional and employment status.

Dying in the ICU: strategies that may improve end-of-life care

PURPOSE

Since 10 to 20% of adult patients admitted to the intensive care unit (ICU) in Canada die, addressing the needs of dying critically ill patients is of paramount importance. The purpose of this article is to suggest some strategies to consider to improve the care of patients dying in the ICU.

SOURCE

Data sources were randomized clinical trials, observational studies and surveys. We purposively selected key articles on end-of-life care to highlight eight initiatives that have the potential to improve care for dying critically ill patients. These initiatives were presented at the International Consensus Conference on End-of-Life Care in the ICU on April 24-25, 2003 in Brussels, Belgium.

PRINCIPAL FINDINGS

We describe eight strategies that, if adopted, may positively impact on the end-of-life care of critically ill patients: 1) promote social change through professional initiatives; 2) legitimize research in end-of-life care; 3) determine what dying patients need; 4) determine what families of dying patients need; 5) initiate quality improvement locally; 6) use quality tools with care; 7) educate future clinicians; and 8) personally engage in end-of-life care. Most of these strategies have not been subjected to rigorous evaluation.

CONCLUSION

Adoption of some of these strategies we describe may lead to improved end-of-life care in the ICU. Future studies should include more formal evaluation of the efficacy of end-of-life interventions to help us ensure high quality, clinically relevant, culturally adapted care for all dying critically ill patients.

Prevention of venous thromboembolism in critically ill medical patients: a Franco-Canadian cross-sectional study

BACKGROUND

Medical intensive care unit (ICU) patients are at moderate risk of venous thromboembolism (VTE) and prophylaxis against VTE is recommended.

OBJECTIVES

To observe the range and frequency of VTE prophylaxis administered to medical ICU patients and to determine factors associated with different strategies in French and Canadian ICUs.

DESIGN

Prospective cross-sectional observational study.

RESULTS

113/251 (45.0%) French and 29/30 (96.6%) Canadian ICUs agreed to participate. Of 1,222 critically ill medical patients, most were mechanically ventilated (62.5%). Overall, heparin VTE prophylaxis was administered to 63.9% patients, similarly between the 2 countries. Excluding patients with contraindications to heparin and those receiving therapeutic anticoagulation, 91.7% of medical ICU patients appropriately received either low dose unfractionated heparin (UFH) or low molecular weight heparin (LMWH) prophylaxis. Independent predictors of heparin prophylaxis were invasive mechanical ventilation (odds ratio [OR]; 95%CI, 2.4 (1.4-4.3) and obesity (OR 3.1; 1.1-8.8). LMWH was less likely to be prescribed for patients with renal failure (OR 0.1; 0.0009-0.9), or receiving antiembolic stockings (OR 0.4, 0.1-0.9), and much more likely to be prescribed in French ICUs (OR 9.2; 5.0-16.9); however, among patients receiving LMWH, high doses were more likely to be prescribed in Canadian ICUs (OR 8.7; 2.0-37.6). Patients who were pregnant or postpartum (OR 7.7, 1.3-44.3), had neurologic failure (OR 2.1, 1.3-3.4), or were Canadian (OR 3.0, 2.1-4.4) were most likely to receive mechanical VTE prophylaxis (with antiembolic stockings or pneumatic compression devices), whereas those who were already receiving heparin were less likely to receive mechanical prophylaxis (OR 0.5, 0.3-0.7).

CONCLUSIONS

In this binational cross-sectional observational study of medical ICU patients, we found that 92% of eligible patients received either UFH or LWMH for VTE prophylaxis. Differences in prescribing between countries include significantly greater use of LMWH in France, but use of lower doses than in Canada, and greater use of mechanical VTE prophylaxis in Canada. More randomized trials of VTE prophylaxis in critically ill medical patients would better inform practice.

Polymerase chain reaction aids in the diagnosis of an unusual case of Aspergillus niger endocarditis in a patient with acute myeloid leukaemia

Endocarditis secondary to Aspergillus niger has not been described in a leukaemic patient. We describe a case of A. niger endocarditis in a patient with acute myeloid leukaemia and refractory fever. The microbiological cause of his endocarditis was initially misdiagnosed because he fulfilled the Duke criteria for enterococcal endocarditis. A polymerase chain reaction test utilizing pan-fungal primers detected a product from an Aspergillus sp. The DNA was subsequently sequenced and was found to have 100% homology with A. niger. A postmortem revealed fungal endocarditis secondary to disseminated aspergillosis, without evidence of bacterial endocarditis. The patient was found to have a lung aspergilloma that was possibly occupationally acquired, and may have been long standing.

Withdrawal of mechanical ventilation in anticipation of death in the intensive care unit

BACKGROUND

In critically ill patients who are receiving mechanical ventilation, the factors associated with physicians' decisions to withdraw ventilation in anticipation of death are unclear. The objective of this study was to examine the clinical determinants that were associated with the withdrawal of mechanical ventilation.

METHODS

We studied adults who were receiving mechanical ventilation in 15 intensive care units, recording base-line physiological characteristics, daily Multiple Organ Dysfunction Scores, the patient's decision-making ability, the type of life support administered, the use of do-not-resuscitate orders, the physician's prediction of the patient's status, and the physician's perceptions of the patient's preferences about the use of life support. We examined the relation between these factors and withdrawal of mechanical ventilation, using Cox proportional-hazards regression analysis.

RESULTS

Of 851 patients who were receiving mechanical ventilation, 539 (63.3 percent) were successfully weaned, 146 (17.2 percent) died while receiving mechanical ventilation, and 166 (19.5 percent) had mechanical ventilation withdrawn. The need for inotropes or vasopressors was associated with withdrawal of the ventilator (hazard ratio, 1.78; 95 percent confidence interval, 1.20 to 2.66; P=0.004), as were the physician's prediction that the patient's likelihood of survival in the intensive care unit was less than 10 percent (hazard ratio, 3.49; 95 percent confidence interval, 1.39 to 8.79; P=0.002), the physician's prediction that future cognitive function would be severely impaired (hazard ratio, 2.51; 95 percent confidence interval, 1.28 to 4.94; P=0.04), and the physician's perception that the patient did not want life support used (hazard ratio, 4.19; 95 percent confidence interval, 2.57 to 6.81; P<0.001).

CONCLUSIONS

Rather than age or the severity of the illness and organ dysfunction, the strongest determinants of the withdrawal of ventilation in critically ill patients were the physician's perception that the patient preferred not to use life support, the physician's predictions of a low likelihood of survival in the intensive care unit and a high likelihood of poor cognitive function, and the use of inotropes or vasopressors.

Adaptation to the Intensive Care Environment (ATICE): Development and validation of a new sedation assessment instrument

OBJECTIVE

To develop a valid, reliable, and responsive bedside instrument assessing Adaptation to the Intensive Care Environment (ATICE) in mechanically ventilated adult intensive care unit (ICU) patients.

DESIGN

Instrument development and prospective clinimetric evaluation.

SETTING

University-affiliated medical ICU.

PATIENTS

Consecutive patients with expected mechanical ventilation of >/=12 hrs.

INTERVENTIONS

Administration of ATICE.

MEASUREMENTS AND MAIN RESULTS

Item generation for the ATICE involved focus groups and literature review. The ATICE consists of five items: Awakeness and Comprehension combined in a Consciousness domain, and Calmness, Ventilator Synchrony, and Face Relaxation combined in a Tolerance domain. Clinical sensibility of the ATICE assessed by ten ICU physicians and 20 ICU nurses not involved in the development of the ATICE was rated highly (median values 5-7 on a 7-point scale). The ATICE was administered to 80 patients during a total of 152 assessments. Each assessment was performed by three raters (ICU physician, ICU nurse, research nurse), concomitantly with independent scoring of four scales (Ramsay Scale, Riker Scale, Glasgow Coma Scale, and Comfort Scale) and six visual analog scales. Internal consistency was high, as reflected by Cronbach's alpha for the Consciousness and Tolerance domains of .87 and .67, respectively. Intraclass correlation coefficients for the Consciousness and the Tolerance domains ranged from .92 to .99, indicating high interrater reliability. Cross-sectional and longitudinal validity was confirmed for the overall ATICE and the Consciousness and Tolerance domains, as reflected by strong correlations between ATICE and the relevant items or domains of the Ramsay Scale, Riker Scale, Glasgow Coma Scale, Comfort Scale, each of the visual analog scales, and the amounts of sedatives and analgesics administered.

CONCLUSIONS

The ATICE measures the adaptation of mechanically ventilated patients to the ICU environment. After rigorous multidisciplinary development, we demonstrated high reliability, validity, and responsiveness of this instrument.

4-Aryl-3-(hydroxyalkyl)quinolin-2-ones: novel maxi-K channel opening relaxants of corporal smooth muscle targeted for erectile dysfunction

Novel 4-aryl-3-(hydroxyalkyl)quinoline-2-one derivatives were prepared and evaluated as openers of the cloned maxi-K channel hSlo expressed in Xenopus laevis oocytes by utilizing electrophysiological methods. The effect of these maxi-K openers on corporal smooth muscle was studied in vitro using isolated rabbit corpus cavernosum. From this study, a potent maxi-K opener was identified as an effective relaxant of rabbit corporal smooth muscle and shown to be active in an in vivo animal model of male erectile function.

Complementary use of radiological skeletal survey and bone scintigraphy in detection of bony injuries in suspected child abuse

AIM

To compare the effectiveness of radiological skeletal survey and bone scintigraphy for the detection of bony injuries in cases of suspected child abuse.

METHODS

All cases with a discharge diagnosis of child abuse that presented to the Royal Children's Hospital between 1989 and 1998 were retrieved, and those children that had undergone both skeletal survey and bone scintigraphy (radioisotope bone scan) within a 48 hour period were included in this study. Both examinations followed rigid departmental protocols and protocols remained identical throughout the timeframe of the study. The reports of the skeletal surveys and bone scans were retrospectively reviewed by a paediatric radiology fellow and consultant paediatric radiologist.

RESULTS

The total number of bony injuries identified was 124 in 30 children. Of these, 64 were identified on bone scan and 77 on skeletal survey. Rib fractures represented 60/124 (48%) of the bony injuries and were present in 16/30 children (53%), of which 62.5% had multiple rib fractures. Excluding rib fractures, there were 64 (52%) bony injuries, of which 33% were seen on both imaging modalities, 44% were seen on skeletal survey only, and 25% were seen on bone scans alone. Metaphyseal lesions typical of child abuse were present in 20 cases (31%) on skeletal survey; only 35% of these were identified on bone scan. Six children (20%) had normal skeletal surveys, with abnormalities shown on bone scan. There were three children (10%) with normal bone scans who were shown to have injuries radiographically.

CONCLUSIONS

Skeletal survey and bone scintigraphy are complementary studies in the evaluation of non-accidental injury, and should both be performed in cases of suspected child abuse.

2001 SCCM/ESICM/ACCP/ATS/SIS International Sepsis Definitions Conference

OBJECTIVE

In 1991, the American College of Chest Physicians (ACCP) and the Society of Critical Care Medicine (SCCM) convened a "Consensus Conference," the goals of which were to "provide a conceptual and a practical framework to define the systemic inflammatory response to infection, which is a progressive injurious process that falls under the generalized term 'sepsis' and includes sepsis-associated organ dysfunction as well. The general definitions introduced as a result of that conference have been widely used in practice, and have served as the foundation for inclusion criteria for numerous clinical trials of therapeutic interventions. Nevertheless, there has been an impetus from experts in the field to modify these definitions to reflect our current understanding of the pathophysiology of these syndromes.

DESIGN

Several North American and European intensive care societies agreed to revisit the definitions for sepsis and related conditions. This conference was sponsored by the Society of Critical Care Medicine (SCCM), The European Society of Intensive Care Medicine (ESICM), The American College of Chest Physicians (ACCP), the American Thoracic Society (ATS), and the Surgical Infection Society (SIS).

METHODS

29 participants attended the conference from Europe and North America. In advance of the conference, subgroups were formed to evaluate the following areas: signs and symptoms of sepsis, cell markers, cytokines, microbiologic data, and coagulation parameters. The present manuscript serves as the final report of the 2001 International Sepsis Definitions Conference.

CONCLUSION

1. Current concepts of sepsis, severe sepsis and septic shock remain useful to clinicians and researchers. 2. These definitions do not allow precise staging or prognostication of the host response to infection. 3. While SIRS remains a useful concept, the diagnostic criteria for SIRS published in 1992 are overly sensitive and non-specific. 4. An expanded list of signs and symptoms of sepsis may better reflect the clinical response to infection. 6. PIRO, a hypothetical model for staging sepsis is presented, which, in the future, may better characterize the syndrome on the basis of predisposing factors and premorbid conditions, the nature of the underlying infection, the characteristics of the host response, and the extent of the resultant organ dysfunction.

2001 SCCM/ESICM/ACCP/ATS/SIS International Sepsis Definitions Conference

OBJECTIVE

In 1991, the American College of Chest Physicians (ACCP) and the Society of Critical Care Medicine (SCCM) convened a "Consensus Conference," the goals of which were "to provide a conceptual and a practical framework to define the systemic inflammatory response to infection, which is a progressive injurious process that falls under the generalized term 'sepsis' and includes sepsis-associated organ dysfunction as well." The general definitions introduced as a result of that conference have been widely used in practice and have served as the foundation for inclusion criteria for numerous clinical trials of therapeutic interventions. Nevertheless, there has been an impetus from experts in the field to modify these definitions to reflect our current understanding of the pathophysiology of these syndromes.

DESIGN

Several North American and European intensive care societies agreed to revisit the definitions for sepsis and related conditions. This conference was sponsored by the SCCM, The European Society of Intensive Care Medicine (ESICM), The American College of Chest Physicians (ACCP), the American Thoracic Society (ATS), and the Surgical Infection Society (SIS).

METHODS

The conference was attended by 29 participants from Europe and North America. In advance of the conference, five subgroups were formed to evaluate the following areas: signs and symptoms of sepsis, cell markers, cytokines, microbiologic data, and coagulation parameters. The subgroups corresponded electronically before the conference and met in person during the conference. A spokesperson for each group presented the deliberation of each group to all conference participants during a plenary session. A writing committee was formed at the conference and developed the current article based on executive summary documents generated by each group and the plenary group presentations. The present article serves as the final report of the 2001 International Sepsis Definitions Conference.

CONCLUSION

This document reflects a process whereby a group of experts and opinion leaders revisited the 1992 sepsis guidelines and found that apart from expanding the list of signs and symptoms of sepsis to reflect clinical bedside experience, no evidence exists to support a change to the definitions. This lack of evidence serves to underscore the challenge still present in diagnosing sepsis in 2003 for clinicians and researchers and also provides the basis for introducing PIRO as a hypothesis-generating model for future research.

Treatment options for microcystin toxins: similarities and differences between variants

Over sixty variants of the blue-green algal toxin microcystin have been identified. The two microcystin variants LR and LA vary in only one amino group ie. arginine for microcystin LR and alanine for microcystin LA. In the literature to date, the general consensus has been that m-LR and m-LA should respond similarly to a range of water treatment processes. This is the case for ozonation and biodegradation by organisms colonising granular activated carbon filters; there is negligible difference in the response to these processes between the two variants. However, the adsorption of m-LR onto activated carbon is significantly higher than that of m-LA. This result is surprising as m-LA has a lower molecular weight, and is more hydrophobic, factors that would be expected to favour the adsorption of this compound over m-LR. This trend is also seen for the variants RR and YR. The effect is seen on both negatively and positively charged carbons, indicating that the difference between the variants is not caused by electrostatic interactions with the carbon surface. Electrostatic shielding experiments suggest that electrostatic repulsion between the adsorbed m-LA molecules, with a net charge of -2, may be responsible for the low adsorption. The other variants tested have a lower net charge and therefor experience lower intermolecular repulsion in the adsorbed state.

One-year outcomes in survivors of the acute respiratory distress syndrome

BACKGROUND

As more patients survive the acute respiratory distress syndrome, an understanding of the long-term outcomes of this condition is needed.

METHODS

We evaluated 109 survivors of the acute respiratory distress syndrome 3, 6, and 12 months after discharge from the intensive care unit. At each visit, patients were interviewed and underwent a physical examination, pulmonary-function testing, a six-minute-walk test, and a quality-of-life evaluation.

RESULTS

Patients who survived the acute respiratory distress syndrome were young (median age, 45 years) and severely ill (median Acute Physiology, Age, and Chronic Health Evaluation score, 23) and had a long stay in the intensive care unit (median, 25 days). Patients had lost 18 percent of their base-line body weight by the time they were discharged from the intensive care unit and stated that muscle weakness and fatigue were the reasons for their functional limitation. Lung volume and spirometric measurements were normal by 6 months, but carbon monoxide diffusion capacity remained low throughout the 12-month follow-up. No patients required supplemental oxygen at 12 months, but 6 percent of patients had arterial oxygen saturation values below 88 percent during exercise. The median score for the physical role domain of the Medical Outcomes Study 36-item Short-Form General Health Survey (a health-related quality-of-life measure) increased from 0 at 3 months to 25 at 12 months (score in the normal population, 84). The distance walked in six minutes increased from a median of 281 m at 3 months to 422 m at 12 months; all values were lower than predicted. The absence of systemic corticosteroid treatment, the absence of illness acquired during the intensive care unit stay, and rapid resolution of lung injury and multiorgan dysfunction were associated with better functional status during the one-year follow-up.

CONCLUSIONS

Survivors of the acute respiratory distress syndrome have persistent functional disability one year after discharge from the intensive care unit. Most patients have extrapulmonary conditions, with muscle wasting and weakness being most prominent.

Maintaining updated DNA-based HLA assignments in the National Marrow Donor Program Bone Marrow Registry

The National Marrow Donor Program (NMDP) has instituted an approach to address the impact of new alleles on the DNA-based HLA assignments obtained during volunteer donor typing. This approach was applied to the DRB typing results from 371,187 donors received from 14 laboratories in 1999. Samples were tested with a standardized set of sequence specific oligonucleotide reagents and the positive and negative hybridization results transmitted electronically to the NMDP. A software program interpreted the primary data into HLA assignments and rejected assignments which did not produce a result at the specified level of resolution. Comparison of the HLA assignments derived by the NMDP software to the assignments made by the laboratories using several local software prograins showed 90.5% of the assignments to be identical. Differences in assignments were explained by varying levels of typing resolution, variation in the inclusion of the second expressed DRB loci, disparity arising when alternative assignments were summarized, and failure to submit correct information. When the primary data collected in 1999 were interpreted into HLA assignments using the set of alleles defined in July 2000, 74% of the HLA-DRB assignments were altered by the description of new alleles, justifying the development of this software.

Seasonal serum concentrations of melatonin in cycling and noncycling mares

To determine whether secretory patterns of melatonin change throughout the seasons in mares, blood samples were drawn byvenipuncture from nine mares at noon and midnight for five successive days at monthly intervals from August through July at the University of Missouri in Columbia, MO. In addition, during September, December, March, and June, blood samples were drawn from indwelling catheters at 2-h intervals for 48 or 72 h. Mares were predominantly Quarter Horses weighing approximately 450 kg and ranged from 3 to 12 yr of age. Mares were housed in outdoor paddocks with three-sided run-in sheds for shelter. During the noon and midnight bleeding period, mares were placed in a larger open-sided barn with outside runs. Mares remained outdoors with the barn being used as a shelter in the event of inclement weather. All lights in the shed were converted to red light. Often, moonlight provided enough illumination to collect blood samples. Mares were returned to their normal paddock after each sampling period. For analysis of data, a mare was considered to be cycling if serum concentrations of progesterone were greater than 1 ng/ mL. For a mare to be classified as exhibiting a nocturnal rise of melatonin, serum concentrations of melatonin had to be at least two times greater at midnight than at noon. By month, a relationship did not exist (chi2; P > 0.05) among mares that were exhibiting estrous cycles and exhibiting nocturnal rises of melatonin. Likewise, examination of serum profiles of melatonin taken at 2-h intervals for 48 h revealed considerable variation among mares throughout the seasons. A nocturnal rise in serum melatonin was observed only in June (P < 0.02). In March and December, serum melatonin was greater in cycling mares than noncycling mares, but the elevation was not associated with light-dark periods (P < 0.01). Two of the mares exhibited estrous cycles throughout the seasons but melatonin secretion in these two mares were similar to that observed in the seven mares that demonstrated seasonal anestrous. From these results, it does not appear that changes in serum concentrations of melatonin are used as a cue to regulate cyclic activity in the mare throughout the seasons.

Effect of air filtration systems on asthma: a systematic review of randomized trials

STUDY OBJECTIVES

To systematically review the evidence of randomized trials evaluating the effects of residential air filtration systems on patients with asthma.

DATA SOURCES

We searched for published and unpublished studies using MEDLINE, the Cumulative Index to Nursing and Allied Health Literature, and the Cochrane Collaboration. We reviewed all reference lists for additional articles of relevance, and contacted experts in the field and air filter manufacturers.

STUDY SELECTION

We identified 10 relevant randomized controlled trials that examined the influence of a residential air filtration system on patients with asthma.

DATA EXTRACTION

In duplicate and independently, we abstracted data on the methodologic quality, population, intervention, and outcomes.

DATA SYNTHESIS

Five of 10 studies enrolled adults only. One study included children only. The sample size ranged from 9 to 45 participants in each study, for a total of 216 patients across all studies. Two studies reported a statistically significant decrease in airway responsiveness associated with air filter utilization. Air filters were associated with significantly lower total symptom scores (weighted mean difference of 0.47; 95% confidence interval [CI], 0.69 to 0.25) on a 10-point scale, and lower sleep disturbance score (weighted mean difference of 0.93; 95% CI, 1.44 to 0.42); however, heterogeneity of results weakens the inferences from these trials. Air filtration systems were not associated with any differences in medication use or morning peak expiratory flow values. None of these trials employed validated scales to measure clinical symptoms or quality of life.

CONCLUSIONS

Among patients with allergies and asthma, use of air filters is associated with fewer symptoms. Rigorous sufficiently powered randomized clinical trials are needed to more precisely define the influence of air filtration on health-related quality of life and symptom control for asthmatic patients.