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Biomedical subjects

D J Cook

Publications and source records attributed to D J Cook.

At least 163 records · Page 9Linked to original sources
PubMed1996

Once-daily aminoglycoside dosing in immunocompetent adults: a meta-analysis.

OBJECTIVE: To compare the efficacy, nephrotoxicity, and ototoxicity of once-daily aminoglycoside dosing with those of standard aminoglycoside regimens in immuno-competent adults. DATA SOURCES: A structured MEDLINE search from 1966 to April 1995 using the keywords aminoglycosides, drug administration schedule, and adult; bibliographic searching of review articles, position papers, and references of the selected articles; contact with primary authors of selected articles to obtain information not in the published reports and lists of potentially relevant articles. STUDY SELECTION: Randomized, controlled trials that 1) compared an intravenous once-daily aminoglycoside regimen with a standard aminoglycoside regimen in infected immunocompetent adults and 2) examined efficacy, mortality, or toxicity. DATA EXTRACTION: For each selected study, two independent reviewers assessed methodologic quality and abstracted data. The heterogeneity of individual study risk ratios was assessed and data were pooled using a random-effects model. RESULTS: Forty-two studies were reviewed for possible inclusion. Thirteen independent studies met the selection criteria, and their results were pooled. The trials had a mean methodologic quality score of 0.69 (range, 0.50 to 0.91). Heterogeneity exists among the individual risk ratios for clinical cure (P = 0.07); significant heterogeneity does not exist for the other outcomes. For the pooled efficacy outcomes, the risk ratio for bacteriologic cure is 1.02 (95% CI, 0.99 to 1.05), and the risk ratio for mortality is 0.91 (CI, 0.63 to 1.31). For the pooled toxicity outcomes, the risk ratio for nephrotoxicity is 0.87 (CI, 0.60 to 1.26), and the risk ratio for ototoxicity is 0.67 (CI, 0.35 to 1.28). CONCLUSIONS: Standard and once-daily aminoglycoside dosing regimens are equivalent with regard to bacteriologic cure, and once-daily dosing shows a trend toward reduced mortality and toxicity. However, additional studies are needed for more precise estimates of mortality and toxicity risk ratios. The equivalency of the dosing regimens, the ease of administration, reduced nursing time, and reduced variability in the timing of drug administration that are associated with once-daily dosing may mean that the once-daily regimen is clinically advantageous.

Adult↗
PubMed1996

Effect of calcium supplementation on pregnancy-induced hypertension and preeclampsia: a meta-analysis of randomized controlled trials.

OBJECTIVE: To review the effect of calcium supplementation during pregnancy on blood pressure, preeclampsia, and adverse outcomes of pregnancy. DATA SOURCE: We searched MEDLINE and EMBASE for 1966 to May 1994. We contacted authors of eligible trials to ensure accuracy and completeness of data and to identify unpublished trials. STUDY SELECTION: Fourteen randomized trials involving 2459 women were eligible. DATA EXTRACTION: Reviewers working independently in pairs abstracted data and assessed validity according to six quality criteria. DATA SYNTHESIS: Each trial yielded differences in blood pressure change between calcium supplementation and control groups that we weighted by the inverse of the variance. The pooled analysis showed a reduction in systolic blood pressure of -5.40 mm Hg (95% confidence interval [CI], -7.81 to -3.00 mm Hg; P<.001) and in diastolic blood pressure of -3.44 mm Hg (95% CI, -5.20 to -1.68 mm Hg; P<.001). The odds ratio for preeclampsia in women with calcium supplementation compared with placebo was 0.38 (95% CI, 0.22 to 0.65). CONCLUSIONS: Calcium supplementation during pregnancy leads to an important reduction in systolic and diastolic blood pressure and preeclampsia. While pregnant women at risk of preeclampsia should consider taking calcium, many more patient events are needed to confirm calcium's impact on maternal and fetal morbidity.

Blood Pressure↗
PubMed1996

Effects of dietary calcium supplementation on blood pressure. A meta-analysis of randomized controlled trials.

OBJECTIVE: To review the effect of supplemental calcium on blood pressure. DATA SOURCE: We searched MEDLINE and EMBASE for 1996 to May 1994. We contacted authors of eligible trials to ensure accuracy and completeness of data and to identify unpublished trials. STUDY SELECTION: We included any study in which investigators randomized people to calcium supplementation or placebo and measured blood pressure for at least 2 weeks. Fifty-six articles met the inclusion criteria, and 33 were eligible for analysis, involving a total of 2412 patients. DATA EXTRACTION: Two pairs of independent reviewers abstracted data and assessed validity according to six quality criteria. DATA SYNTHESIS: We calculated the differences in blood pressure change between the calcium supplementation group and the control group and pooled the estimates, with each trial weighted with the inverse of the variance using a random-effects model. Predictors of blood pressure reduction that we examined included method of supplementation, baseline blood pressure, and the methodological quality of the studies. The pooled analysis showed a reduction in systolic blood pressure of -1.27 mm Hg (95% confidence interval [CI], -2.25 to -0.29 mm Hg; P=.01) and in diastolic blood pressure of -0.24 mm Hg (95% CI, -0.92 to 0.44 mm Hg; P=.49). None of the possible mediators of blood pressure reduction explained differences in treatment effects. CONCLUSIONS: Calcium supplementation may lead to a small reduction in systolic but not diastolic blood pressure. The results do not exclude a larger, important effect of calcium on blood pressure in subpopulations. In particular, further studies should address the hypothesis that inadequate calcium intake is associated with increased blood pressure that can be corrected with calcium supplementation.

Blood Pressure↗
PubMed1996

Infrared emission spectra of candidate interstellar aromatic molecules.

Interstellar dust is responsible, through surface reactions, for the creation of molecular hydrogen, the main component of the interstellar clouds in which new stars form. Intermediate between small, gas-phase molecules and dust are the polycyclic aromatic hydrocarbons (PAHs). Such molecules could account for 2-30% of the carbon in the Galaxy, and may provide nucleation sites for the formation of carbonaceous dust. Although PAHs have been proposed as the sources of the unidentified infrared emission bands that are observed in the spectra of a variety of interstellar sources, the emission characteristics of such molecules are still poorly understood. Here we report laboratory emission spectra of several representative PAHs, obtained in conditions approximating those of the interstellar medium, and measured over the entire spectral region spanned by the unidentified infrared bands. We find that neutral PAHs of small and moderate size can at best make only a minor contribution to these emission bands. Cations of these molecules, as well as much larger PAHs and their cations, remain viable candidates for the sources of these bands.

Extraterrestrial Environment↗
PubMed1996

Impaired gastric emptying in mechanically ventilated, critically ill patients.

OBJECTIVE: To measure gastric emptying in critically ill patients using an acetaminophen absorption model and determine which variables are associated with impaired gastric emptying. DESIGN: A prospective, cohort study. SETTING: A medical/surgical ICU at a tertiary care hospital: Hamilton General Hospital, Hamilton, Ontario. PATIENTS AND PARTICIPANTS: We recruited 72 mechanically ventilated patients expected to remain in the ICU for more than 48 h. Our results were compared to those in healthy volunteers. INTERVENTION: Within 48 h of admission to the ICU, 1.6 g acetaminophen suspension were administered via a nasogastric tube into the stomach. Blood samples were drawn a t = 0, 30, 60, 90, and 120 min for measurement of plasma acetaminophen levels determined by the enzymatic degradation method. MEASUREMENTS AND RESULTS: Maximal concentration of acetaminophen was 94.1 (75.3) mumol/l compared to 208.4 (33.1) mumol/l in a control population (p < 0.0001). The time to reach the maximal concentration was 105 min (60-180) compared to 30 min (15-90) in controls (p < 0.0001). The area under the time-acetaminophen concentration curve t = 120 was 9301 (7343) mumol/min per l compared to 11644 (1336) mumol/min per l in the controls (p = 0.28). The variables associated with delayed gastric emptying were age, sex and use of opioids for analgesia and sedation. CONCLUSIONS: Gastric emptying is delayed in critically ill patients. The important consequences of this phenomenon include intolerance to enteral nutrition and gastric colonization. Strategies to minimize the use of narcotics may improve gastric emptying. Studies to examine the effect of gastrointestinal prokinetic agents on gastric emptying are needed.

Acetaminophen↗
PubMed1996

Discrimination and abuse in internal medicine residency. The Internal Medicine Program Directors of Canada.

OBJECTIVE: To survey the extent to which internal medicine housestaff experience abuse and discrimination in their training. DESIGN: Through a literature review and resident focus groups, we developed a self-administered questionnaire. In this cross-sectional survey, respondents were asked to record the frequency with which they experienced and witnessed different types of abuse and discrimination during residency training, using a 7-point Likert scale. PARTICIPANTS: Internal medicine housestaff in Canada. MEASUREMENTS AND MAIN RESULTS: Of 543 residents in 13 programs participating (84% response rate), 35% were female. Psychological abuse, as reported by attending physicians (68%), patients (79%), and nurses or other health workers (77%), was widespread. Female residents experienced gender discrimination by attending physicians (70%), patients (88%), and nurses (71%); rates for males were 23%, 38%, and 35%, respectively. Females reported being sexually harassed more often than males, by attending physicians (35% vs 4%, p < .01), peers (30% vs 6%, p < .01), and patients (56% vs 18%, p < .01). Physical assault by patients was experienced by 40% of residents. Half of the residents surveyed reported racial discrimination and homophobic remarks in the workplace, perpetrated by all groups of health professionals. CONCLUSIONS: Psychological abuse, gender discrimination, sexual harassment, physical abuse, homophobia, and racial discrimination are prevalent problems during residency training. Housestaff, medical educators, allied health workers, and the public need to work together to address these problems in the training environment.

Adult↗
PubMed1996

Does successful bridging with the implantable left ventricular assist device affect cardiac transplantation outcome?

OBJECTIVES: We sought to determine whether cardiac transplant recipients who required a bridge to transplantation with an implantable left ventricular assist device had a different outcome than patients who underwent transplantation without such a bridge. METHODS: A retrospective study of 256 cardiac transplants from 1992 to 1996 included 53 patients who received the HeartMate left ventricular assist device and 203 patients who had no left ventricular assist device support. RESULTS: Left ventricular assist device transplants increased from 8% of all transplants in 1992 (n = 63) to 32% in 1995 (n = 65) and 43% in 1996 (n = 14 year to date). Patients with and without left ventricular assist device had similar age and sex distributions. Left ventricular assist device recipients were larger (body surface area 1.96 vs 1.86 m2, p = 0.004). They were more likely to have ischemic cardiomyopathy (70% vs 45%, p = 0.001) and type O blood group (51% vs 34%, p = 0.06). All patients with left ventricular assist device and 42% of those without had undergone previous cardiac operations by the time of transplantation (mean number per patient 1.5 vs 0.3, p < 0.001). More patients in the left ventricular assist device group had anti-HLA antibodies before transplantation (T-cell panel reactive antibody level > 10% in 66% of left ventricular assist device group vs 15% of control group, p < 0.0001). Waiting time was longer for the left ventricular assist device than for patients in status I without a left ventricular assist device (median 88 vs 37 days, p = 0.002). There was no difference in length of posttransplantation hospital stay (median 15 days for each) or operative mortality (3.8% vs 4.4%). Mean follow-up averaged 22 months. No significant difference was found in Kaplan-Meier survival estimates. One-year survival was 94% in the left ventricular assist device group and 88% in the control group (difference not significant). Comparison of posttransplantation events showed no significant difference in actuarial rates of cytomegalovirus infection (20% vs 17%) or vascular rejection (15% vs 12%) at 1 year of follow-up. Similar percentages of patients were free from cellular rejection at 1 year of follow-up (12% vs 22%, p = 0.36). CONCLUSIONS: Left ventricular assist device support intensified the donor shortage by including recipients who otherwise would not have survived to transplantation. Bridging affected transplant demographics, favoring patients who are larger, have ischemic cardiomyopathy, have had multiple blood transfusions and complex cardiac operations, and are HLA sensitized. Successfully bridged patients wait longer for a transplant than do UNOS status I patients without such a bridge, but they have similar posttransplantation hospital stay, operative mortality, and survival to those of patients not requiring left ventricular assist device support.

Adult↗
PubMed1996

The relationship between cerebral blood flow and transcranial Doppler blood flow velocity during hypothermic cardiopulmonary bypass in adults.

A noninvasive, simple, and continuous method to assess cerebral perfusion during cardiopulmonary bypass (CPB) could help prevent cerebral ischemia. Transcranial Doppler sonography (TCD) allows a noninvasive, on-line measurement of blood flow velocity in cerebral arteries. The correlation of TCD-estimated and actual cerebral blood flow (CBF) has not been well studied during CPB. We determined the correlation of middle cerebral artery (MCA) mean velocity and CBF determined by the Kety-Schmidt method during nonbypass and two hypothermic bypass flow conditions. Sixteen patients undergoing hypothermic (27 degrees C) CPB for coronary artery bypass grafting and/or valve replacement surgery were enrolled in the study. We were able to determine MCA velocity in only 12 patients. We determined CBF and MCA velocity in each patient during four 15-min study periods: 1) prebypass after sternotomy before aortic cannulation; 2) hypothermic (27 degrees C) CPB with 1.2 L.min-1.m-2 pump flow; 3) hypothermic CPB with 2.4 L.min-1.m-2 pump flow, and 4) 30 min after weaning from CPB. There was no difference in the mean arterial pressure between the two CPB pump blood flows. The pooled change in MCA velocity and CBF as percentage of baseline (prebypass) for all patients and at all time points had a correlation of 0.33 (r). A decrease or increase in MCA velocity did not necessarily indicate a corresponding decrease or increase in CBF. This technology may be of limited usefulness during the circulatory condition of hypothermic, nonpulsatile CPB.

Aged↗
PubMed1996

Evidence based critical care medicine; what is it and what can it do for us? Evidence Based Medicine in Critical Care Group.

OBJECTIVE: To describe the philosophy and approach to patient care called evidence based medicine, and to highlight how it can enhance the practice of intensive care. DATA SOURCES: We searched MEDLINE, reference lists, and our personal files to identify relevant literature. STUDY SELECTION: Articles on intensive care practice, critical appraisal, clinical research, and healthcare delivery were selected for discussion. DATA SYNTHESIS: We summarize the rationale for evidence based medicine, its applications and future developments, and suggest several methods for intensivists to use evidence based medicine in their practice and teaching. CONCLUSIONS: Evidence based medicine can complement other foundation disciplines in intensive care. This is the first article in a series entitled "Evidence Based Critical Care Medicine" which will demonstrate how this approach can be used at the bedside.

Clinical Competence↗
PubMed1996

Maximizing oxygen delivery in critically ill patients: a methodologic appraisal of the evidence.

OBJECTIVE: To systemically review the effect of interventions designed to achieve supraphysiologic values of cardiac index, oxygen delivery (DO2), and oxygen consumption (VO2) in critically ill patients. DATA SOURCES: Computerized bibliographic search of published research, citation review of relevant articles, and contact with primary investigators. STUDY SELECTION: We included all randomized clinical trials of adult intensive care unit (ICU) patients that evaluated interventions (fluids, inotropes, and vasoactive drugs) designed to achieve supraphysiologic values of cardiac index, DO2, and/or VO2. Independent review of 64 articles identified seven relevant studies of 1,016 patients. DATA EXTRACTION: We abstracted data on the population, interventions, outcomes, and methodologic quality of the studies by duplicate independent review. Agreement was high (weighed kappa 0.73); differences were resolved by consensus. DATA SYNTHESIS: Targeting therapy to achieve supraphysiologic end points in critically ill patients is associated with a nonstatistically significant trend toward decreased mortality rates (relative risk 0.86, 95% confidence intervals 0.62 to 1.20). For the two studies in which supraphysiologic goals were initiated preoperatively, the relative risk was 0.20 (95% confidence intervals 0.07 to 0.55). This value differed significantly from the combined estimate of the remaining studies, in which the intervention was started after ICU admission (relative risk 0.98, 95% confidence intervals 0.79 to 1.22; p<.01). However, there are several methodologic problems with the primary studies. In no trials were caregivers or outcome assessors blinded to treatment allocation. Only three of seven trials analyzed patients according to the group to which they were allocated. None adequately controlled for cointerventions, and there was considerable crossover between groups (patients in the control group achieved the goals of the intervention group and vice versa). CONCLUSIONS: Interventions designed to achieve supraphysiologic goals of cardiac index, DO2, and VO2 did not significantly reduce mortality rates in all critically ill patients. However, there may be a benefit in those patients in which the therapy is initiated preoperatively. Methodologic limitations weaken the inferences that can be drawn from these studies and preclude any evidence-based clinical recommendations.

Adult↗
PubMed1996

Economic evaluations in the critical care literature: do they help us improve the efficiency of our unit?

OBJECTIVE: To determine the extent to which economic evaluations published in the critical care literature provide information that can help us to improve the efficiency of our unit. DATA SOURCES: We searched computerized bibliographic databases and manually searched key critical care journals to retrieve all economic evaluations. STUDY SELECTION: We included economic evaluations that dealt with clinical problems relevant to the practice of adult critical care and that compared competing healthcare interventions. DATA ABSTRACTION: Included articles were further evaluated using criteria for minimal methodologic soundness, adopted from the literature, and criteria that we developed to assess the generalizability of results to our clinical setting. DATA SYNTHESIS: We screened 4,167 papers manually and > 450 abstracts and titles in our computer search. One hundred fifty-one papers were retrieved for further evaluation; 29 papers met our inclusion criteria. Of these 29 papers, only 14 (48%) adequately described competing healthcare interventions, 17 (59%) provided sufficient evidence of clinical efficacy, six (21%) identified, measured, and valuated costs appropriately, and three (10%) performed a sensitivity analysis. None of the papers met all four of these criteria for a minimum level of methodologic soundness. Four (14%) of 29 studies which adequately dealt with issues of cost and efficacy were evaluated using our generalizability criteria. Different costing methods precluded the application of the results of three of the four studies to our intensive care unit. CONCLUSIONS: In the critical care literature, very little useful economic information exists to help decision-makers maximize efficiency in their own setting.

Adult↗
PubMed1996

How to keep up with the critical care literature and avoid being buried alive.

OBJECTIVE: To provide practical suggestions for accessing, utilizing, and storing the rapidly expanding literature on critical care. DATA SOURCES: Original research on information sources for clinicians and techniques for keeping up with the literature, found through bibliographic searches, our personal files, and consultation with critical care colleagues. DATA SYNTHESIS: Suggestions for keeping up with the critical care literature include: 1) focus the clinical question; 2) locate literature using bibliographic databases; 3) use original journal articles; 4) use systematic reviews with confidence; 5) use text-books with caution; 6) read the preappraised literature; 7) abandon advertisements; 8) throw away the throwaways; 9) teach yourself critical appraisal; 10) be wary of overinterpretation of substitute end points; 11) teach yourself basic clinical statistics; 12) engage in effective browsing; 13) store useful articles; 14) invest in informatics; and 15) implement evidence-based practice guidelines. CONCLUSION: Efficient access, appraisal, and application of the literature on intensive care are basic skills for intensivists, who have adopted a variety of resourceful and pragmatic methods for "keeping up."

Critical Care↗
PubMed1996

Ultrasound guidance for placement of central venous catheters: a meta-analysis of the literature.

OBJECTIVE: To evaluate the effect of real-time ultrasound guidance using a regular or Doppler ultrasound technique for placement of central venous catheters. DATA SOURCES: We searched for published and unpublished research using MEDLINE, citation review of relevant primary and review articles, conference abstracts, personal files, and contact with expert informants. STUDY SELECTION: From a pool of 208 randomized, controlled trials of venous and arterial catheter management, eight published randomized, controlled trials were identified. DATA EXTRACTION: In duplicate, independently, we abstracted data on the population, intervention, outcome, and methodologic quality. DATA SYNTHESIS: Ultrasound guidance significantly decreases internal jugular and subclavian catheter placement failure (relative risk 0.32; 95% confidence interval 0.18 to 0.55), decreases complications during catheter placement (relative risk 0.22; 95% confidence interval 0.10 to 0.45), and decreases the need for multiple catheter placement attempts (relative risk 0.60; 95% confidence interval 0.45 to 0.79) when compared with the standard landmark placement technique. CONCLUSIONS: When used for vessel location and catheter placement real-time, ultrasound guidance or Doppler ultrasound guidance improves success rates and decreases the complications associated with internal jugular and subclavian venous catheter placement.

Catheterization, Central Venous↗
PubMed1996

Introducing Critical Appraisal to studies of animal models investigating novel therapies in sepsis.

OBJECTIVES: To discuss theoretical and practical aspects relating to the design of animal studies investigating the efficacy of novel therapeutic agents for the treatment of sepsis, and to make explicit the process whereby these studies can be evaluated for the purpose of designing clinical trials in humans. DATA SOURCES: Relevant articles from the pertinent literature were reviewed. STUDY SELECTION: Studies relevant to an evidence-based assessment of clinical studies on therapeutic efficacy, and studies relevant to the design of animal models of sepsis were selected. DATA EXTRACTION: Concepts relevant to an evidence-based assessment of the animal literature were extracted. DATA SYNTHESIS: Articles were reviewed and an evidence-based framework for the assessment of animal studies was developed. In this process, we discuss the steps that are necessary to assess the internal validity of an individual study and review topics relevant to the application of animal data to the design of clinical trials. CONCLUSIONS: The success of clinical trials of sepsis therapies is predicated on the generation and interpretation of sound preclinical data. In this review, we have attempted to outline an evidence-based approach to the assessment of preclinical animal studies evaluating novel therapeutic interventions in sepsis.

Animals↗
PubMed1996

Cisapride improves gastric emptying in mechanically ventilated, critically ill patients. A randomized, double-blind trial.

We conducted a randomized, double-blind, placebo-controlled trial in mechanically ventilated intensive care unit (ICU) patients to evaluate the effect of cisapride on gastric emptying using an acetaminophen absorption model. We enrolled 72 patients expected to remain in the ICU for more than 48 h; 39% were female; the average age was 54.0 +/- 19.1 yr; 47% were postoperative, 83% were receiving narcotics, and the mean simplified acute physiology score (SAPS) was 9.5 +/- 3.0. Within 72 h of admission to ICU, 1.6 g of acetaminophen suspension was administered via a nasogastric tube into the stomach (Day 1). Blood samples were drawn at baseline, 30, 60, 90, 120, and 180 min for measurement of plasma acetaminophen levels. The following morning (Day 2), patients were randomized to receive 20 mg of cisapride or placebo and gastric emptying was again assessed. The difference (Day 2-Day 1) in the maximal plasma concentration was 49.1 mumol/L in the cisapride groups compared with 12.3 mumol/L in the placebo group (p = 0.005) and the time to reach maximal concentration was significantly shorter in the cisapride group (-40.8 min versus -4.2 min, p = 0.02). The difference in area under the time-acetaminophen concentration curve was also greater in the patients receiving cisapride (5,534 versus 2,832, p = 0.09). We conclude that cisapride enhances gastric emptying in critically ill patients. Studies to examine the effect of cisapride on tolerance to enteral nutrition, infectious morbidity, and other clinically important outcomes are warranted.

Acetaminophen↗