Biomedical subjects
Ellen McDonald
Publications and source records attributed to Ellen McDonald.
Levels of care in the intensive care unit: a research program.
A multidisciplinary research program on levels of care was conducted in 15 adult intensive care units in North America, Europe, and Australia. The program addressed advance directives for cardiopulmonary resuscitation, provision of advanced life support, and clinicians' discomfort with evolving treatment plans. The results indicated that the factors that determined the establishment of directives for advance life support differed from the factors that informed a decision to limit or withdraw support after admission to an intensive care unit. In addition, clinicians' prognoses were imprecise and often an underestimation of the probability of short-term survival. Finally, some degree of discomfort was common in care providers in the intensive care unit, most often because they thought interventions were excessive and not compatible with an acceptable future quality of life. The provision of advanced life support mandates explicit decision making about how life-support measures should be used.
Mechanical thromboprophylaxis in critically ill patients: a systematic review and meta-analysis.
OBJECTIVE: To systematically review the randomized trials, observational studies, and survey evidence on compression and pneumatic devices for thromboprophylaxis in intensive care patients. METHODS: Published studies on the use of compression and pneumatic devices in intensive care patients were assessed. A meta-analysis was conducted by using the randomized controlled trials. RESULTS: A total of 21 relevant studies (5 randomized controlled trials, 13 observational studies, and 3 surveys) were found. A total of 811 patients were randomized in the 5 randomized controlled trials; 3421 patients participated in the observational studies. Trauma patients only were enrolled in 4 randomized controlled trials and 4 observational studies. Meta-analysis of 2 randomized controlled trials with similar populations and outcomes revealed that use of compression and pneumatic devices did not reduce the incidence of venous thromboembolism. The pooled risk ratio was 2.37, indicative of favoring the control over the intervention in reducing the deep venous thrombosis; however, the 95% CI of 0.57 to 9.90 indicated no significant differences between the intervention and the control. A range of methodological issues, including bias and confounding variables, make meaningful interpretation of the observational studies difficult. CONCLUSIONS: The limited evidence suggests that use of compressive and pneumatic devices yields results not significantly different from results obtained with no treatment or use of low-molecular-weight heparin. Until large randomized controlled trials are conducted, the role of mechanical approaches to thromboprophylaxis for intensive care patients remains uncertain.
Dalteparin thromboprophylaxis for critically ill medical-surgical patients with renal insufficiency.
PURPOSE: Thromboprophylaxis with low-molecular-weight heparin (LMWH) may be more effective than unfractionated heparin but also more likely to bioaccumulate and potentially cause bleeding in patients with renal insufficiency. The objectives of this study were to assess, among medical-surgical patients in the intensive care unit receiving dalteparin 5,000 IU daily for thromboprophylaxis, (1) the relationship between renal dysfunction and LMWH bioaccumulation as measured by trough anti-Xa levels, (2) the relationship between renal dysfunction and risk of bleeding as measured by a surrogate marker (peak anti-Xa levels), and (3) the relationship between anti-Xa levels, bleeding events, and thrombotic events. MATERIALS AND METHODS: In this prospective single-center cohort study, we enrolled patients 18 years or older, expected to stay 72 hours or longer, and with a creatinine clearance 30 mL/min or higher at intensive care unit admission. We administered 5,000 IU dalteparin subcutaneously each day. The main phase 1 objective was to detect bioaccumulation of dalteparin by measuring trough anti-Xa levels (22-23 hours post dalteparin). The main phase 2 objective was to examine the relationship between renal dysfunction and peak anti-Xa levels (4 hours post dalteparin). We recorded creatinine clearance daily and bleeding and thrombotic events, blinded to anti-Xa levels. RESULTS: We enrolled 19 patients aged 62.7 (13.2) years with an APACHE II score of 23.5 (9.4). We measured trough anti-Xa levels on 185 occasions in 19 patients; we measured peak anti-Xa levels on 113 occasions in 11 patients. We identified no bioaccumulation of LMWH in this study, as detected by trough anti-Xa levels. Most peak anti-Xa levels were in the conventional prophylactic range. CONCLUSIONS: When administered in prophylactic doses to critically ill patients with a wide range of calculated creatinine clearances, we found no evidence of bioaccumulation of dalteparin. If dalteparin does not bioaccumulate, it may be an attractive alternative agent for thromboprophylaxis.
Deep venous thrombosis: clinically silent in the intensive care unit.
PURPOSE: The reliability of clinical signs and the physical examination in the evaluation of deep venous thrombosis (DVT) in the critically ill is unknown. The purpose of this study was to determine the diagnostic properties of clinical examination for signs of DVT in a cohort of medical-surgical intensive care unit (ICU) patients using screening compression ultrasonography as a reference standard. MATERIALS AND METHODS: We prospectively included patients older than 18 years with an expected length of ICU stay of more than 72 hours. Patients underwent bilateral lower limb screening compression ultrasound twice weekly and structured physical examination twice weekly by 2 independent trained research coordinators blinded to the ultrasonography results. We classified patients according to 2 methods: method 1, a DVT Risk Stratification System of 3 categories and method 2, a DVT Risk Score, both of which use the history and physical examination to stratify patients for their risk of DVT. RESULTS: We included 239 patients in our study, 32 of whom had DVT based on the results of their compression ultrasound. We excluded 7 patients with DVT on ICU admission and 2 who did not undergo any structured examinations. We matched controls with cases (9:1) based on duration of ICU stay. Cases and controls were then allocated to low, moderate, and high risk strata for DVT. Using method 1, the area under the receiver operating characteristic curve (AUC) was 0.57 (95% CI, 0.33-0.78, P = .01). Using method 2, the AUC was 0.59 (95% CI, 0.42-0.75, P = .02). An AUC of 1.0 indicates an ideal test, and AUC of 0.50 indicates a test with no diagnostic utility. CONCLUSIONS: The history and physical examination for DVT are not useful in detecting lower limb DVT in the ICU.
DNR directives are established early in mechanically ventilated intensive care unit patients.
PURPOSE: Setting treatment goals in the intensive care unit (ICU) often involves resuscitation decisions. Our objective was to study the rate of establishing do-not-resuscitate (DNR) directives, determinants, and outcomes of those directives for mechanically ventilated patients. METHODS: In a multicentre observational study, we included consecutive adults with no DNR directives within 24 hr of ICU admission who were mechanically ventilated for at least 48 hr. We identified the rate with which DNR directives were established, and factors associated with these directives. RESULTS: Among 765 patients, DNR directives were established for 231 (30.2%) patients; 143 (62.1%) of these were established within the first week. Factors independently associated with a DNR directive were: patient age [> or = 75 yr (hazard ratio [HR] 2.3, 95% confidence interval 1.5-3.4], 65 to 74 yr (HR 1.8, 1.2-2.7), 50 to 64 yr (HR 1.4, 1.0-2.2) relative to < 50 yr); medical rather than surgical diagnosis (HR 1.8, 1.3-2.5); multiple organ dysfunction score (HR 1.7 for each five-point increment, 1.4-2.0); physician prediction of ICU survival [< 10% (HR 15.0, 6.7-33.6)], 10 to 40% [(HR 5.0, 2.3-11.2), 41 to 60% (HR 4.0, 1.8-9.0) relative to > 90%]; and physician perception of patient preference to limit life support (no advanced life support [(HR 5.8, 3.6-9.4) or partial advanced life support (HR 3.2, 2.2-4.6) compared to full measures]. CONCLUSION: One third of mechanically ventilated patients had DNR directives established early during their ICU stay after the first 24 hr of admission. The strongest predictors of DNR directives were physician prediction of low probability of survival, physician perception of patient preference to limit life support, organ dysfunction, medical diagnosis and age.
Clinician predictions of intensive care unit mortality.
OBJECTIVE: Predicting outcomes for critically ill patients is an important aspect of discussions with families in the intensive care unit. Our objective was to evaluate clinical intensive care unit survival predictions and their consequences for mechanically ventilated patients. DESIGN: Prospective cohort study. SETTING: Fifteen tertiary care centers. PATIENTS: Consecutive mechanically ventilated patients > or = 18 yrs of age with expected intensive care unit stay > or = 72 hrs. INTERVENTIONS: We recorded baseline characteristics at intensive care unit admission. Daily we measured multiple organ dysfunction score (MODS), use of advanced life support, patient preferences for life support, and intensivist and bedside intensive care unit nurse estimated probability of intensive care unit survival. MEASUREMENTS AND MAIN RESULTS: The 851 patients were aged 61.2 (+/- 17.6, mean + SD) yrs with an Acute Physiology and Chronic Health Evaluation (APACHE) II score of 21.7 (+/- 8.6). Three hundred and four patients (35.7%) died in the intensive care unit, and 341 (40.1%) were assessed by a physician at least once to have a < 10% intensive care unit survival probability. Independent predictors of intensive care unit mortality were baseline APACHE II score (hazard ratio, 1.16; 95% confidence interval, 1.08-1.24, for a 5-point increase) and daily factors such as MODS (hazard ratio, 2.50; 95% confidence interval, 2.06-3.04, for a 5-point increase), use of inotropes or vasopressors (hazard ratio, 2.14; 95% confidence interval, 1.66-2.77), dialysis (hazard ratio, 0.51; 95% confidence interval, 0.35-0.75), patient preference to limit life support (hazard ratio, 10.22; 95% confidence interval, 7.38-14.16), and physician but not nurse prediction of < 10% survival. The impact of physician estimates of < 10% intensive care unit survival was greater for patients without vs. those with preferences to limit life support (p < .001) and for patients with less vs. more severe organ dysfunction (p < .001). Mechanical ventilation, inotropes or vasopressors, and dialysis were withdrawn more often when physicians predicted < 10% probability of intensive care unit survival (all ps < .001). CONCLUSIONS: Physician estimates of intensive care unit survival < 10% are associated with subsequent life support limitation and more powerfully predict intensive care unit mortality than illness severity, evolving or resolving organ dysfunction, and use of inotropes or vasopressors.
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.