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Biomedical subjects

D J Cook

Publications and source records attributed to D J Cook.

At least 73 records · Page 4Linked to original sources
PubMed1999

The attributable morbidity and mortality of ventilator-associated pneumonia in the critically ill patient. The Canadian Critical Trials Group.

To evaluate the attributable morbidity and mortality of ventilator-associated pneumonia (VAP) in intensive care unit (ICU) patients, we conducted a prospective, matched cohort study. Patients expected to be ventilated for > 48 h were prospectively followed for the development of VAP. To determine the excess ICU stay and mortality attributable to VAP, we matched patients with VAP to patients who did not develop clinically suspected pneumonia. We also conducted sensitivity analyses to examine the effect of different populations, onset of pneumonia, diagnostic criteria, causative organisms, and adequacy of empiric treatment on the outcome of VAP. One hundred and seventy-seven patients developed VAP. As compared with matched patients who did not develop VAP, patients with VAP stayed in the ICU for 4.3 d (95% confidence interval [CI]: 1.5 to 7. 0 d) longer and had a trend toward an increase in risk of death (absolute risk increase: 5.8%; 95% CI: -2.4 to 14.0 d; relative risk (RR) increase: 32.3%; 95% CI: -20.6 to 85.1%). The attributable ICU length of stay was longer for medical than for surgical patients (6. 5 versus 0.7 d, p < 0.004), and for patients infected with "high risk" organisms as compared with "low risk" organisms (9.1 d versus 2.9 d). The attributable mortality was higher for medical patients than for surgical patients (RR increase of 65% versus -27.3%, p = 0. 04). Results were similar for three different VAP diagnostic criteria. We conclude that VAP prolongs ICU length of stay and may increase the risk of death in critically ill patients. The attributable risk of VAP appears to vary with patient population and infecting organism.

Critical Illness↗
PubMed1999

School-based telemedicine: using technology to bring health care to inner-city children.

In the USA, children in low-income, medically understaffed areas have difficulty accessing health care. A pilot telemedicine service was established in Kansas, linking four elementary schools with a local hospital at 128 kbit/s. PC-based videoconferencing systems, a stethoscope, an otoscope and fax machine were installed for each school's nurse. During the first three months of operation, 187 consultations were conducted by a hospital physician over the video-link. Ear, nose and throat problems were the most common reason for referral (29%), followed by dermatological problems (20%) and mandatory school physicals (20%). Prescriptions were issued in 67% of cases. Eighteen per cent of children required referrals for specialist care. The pilot service successfully enabled medically disadvantaged children to receive health care and prompted four additional schools to join the project.

Child↗
PubMed1999

The clinical utility of invasive diagnostic techniques in the setting of ventilator-associated pneumonia. Canadian Critical Care Trials Group.

OBJECTIVE: To evaluate the clinical utility of bronchoscopy with protected brush catheter (PBC) and BAL for patients with ventilator-associated pneumonia (VAP). DESIGN: Prospective cohort study. SETTING: Ten tertiary care ICUs in Canada. PATIENTS: Ninety-two mechanically ventilated patients with a clinical suspicion of VAP who underwent bronchoscopy were compared with 49 patients with a clinical suspicion of pneumonia who did not. INTERVENTIONS: None. MEASUREMENTS AND RESULTS: We compared antibiotic use, duration of mechanical ventilation, ICU stay, and mortality. In addition, for patients who received bronchoscopy, we administered a questionnaire (before and after bronchoscopy) to evaluate the effect of PBC or BAL on (1) physician perception of the probability of VAP, (2) physician confidence in the diagnosis of VAP, and (3) changes to antibiotic management. After bronchoscopy results became available, from the physician's perspective, the diagnosis of VAP was deemed much less likely (p < 0.001), confidence in the diagnosis increased (p = 0.03), and level of comfort with the management plan increased (p = 0.02). Following the results of invasive diagnostic tests, in the group that underwent bronchoscopy, patients were receiving fewer antibiotics (31/92 vs 9/49, p = 0.05) and more patients had treatment with all their antibiotics discontinued (18/92 vs 3/49, p = 0.04) compared with the group that did not undergo bronchoscopy. Duration of mechanical ventilation and ICU stay were similar between the two groups, but mortality was lower in the group that underwent bronchoscopy with PBC or BAL (18.5% vs 34.7%, p = 0.03). CONCLUSIONS: Invasive diagnostic testing may increase physician confidence in the diagnosis and management of VAP and allows for greater ability to limit or discontinue antibiotic treatment. Whether performing PBC or BAL affects clinically important outcomes requires further study.

Anti-Bacterial Agents↗
PubMed1999

Cerebral response to hemodilution during hypothermic cardiopulmonary bypass in adults.

UNLABELLED: We examined the cerebral response to changing hematocrit during hypothermic cardiopulmonary bypass (CPB) in 18 adults. Cerebral blood flow (CBF), cerebral metabolic rate for oxygen (CMRO2), and cerebral oxygen delivery (CDO2) were determined using the nitrous oxide saturation technique. Measurements were obtained before CPB at 36 degrees C, and twice during 27 degrees C CPB: first with a hemoglobin (Hgb) of 6.2 +/- 1.2 g/dL and then with a Hgb of 8.5 +/- 1.2 g/dL. During hypothermia, appropriate reductions in CMRO2 were demonstrated, but hemodilution-associated increases in CBF offset the reduction in CBF seen with hypothermia. At 27 degrees C CPB, as the Hgb concentration was increased from 6.2 to 8.5 g/ dL, CBF decreased. CDO2 and CMRO2 were no different whether the Hgb was 6.2 or 8.5 g/dL. In eight patients in whom the Hgb was less than 6 g/dL, CDO2 remained more than twice CMRO2. IMPLICATIONS: This study suggests that cerebral oxygen balance during cardiopulmonary bypass is well maintained at more pronounced levels of hemodilution than are typically practiced, because changes in cerebral blood flow compensate for changes in hemoglobin concentration.

Aged↗
PubMed1998

Minimum hematocrit at differing cardiopulmonary bypass temperatures in dogs.

BACKGROUND: The purpose of this study was to determine the minimum hematocrit (Hct) supporting cerebral oxygenation over the range clinically relevant cardiopulmonary bypass (CPB) temperatures in dogs. The effect of hemodilution on cerebral blood flow (CBF), cerebral metabolic rate (CMRO2), and cerebral oxygen delivery (CDO2) was determined over a range of Hcts during CPB at 38 degrees C, 28 degrees C, and 18 degrees C. METHODS AND RESULTS: Measurements were obtained at target CPB temperature and after progressive normovolemic hemodilution in 3 groups of 8 anesthetized animals. Dextran 70 (6%) was used as a diluent. CBF was measured by use of the sagittal sinus outflow technique. CMRO2 and CDO2 were calculated by the use of standard formulae. In each temperature group, hemodilution was associated with a reciprocal rise in CBF. As Hct was reduced to 0.10 +/- 0.02 at 38 degrees C, 28 degrees C, and 18 degrees C, CBF increased 260%, 220%, and 160% of the control nonhemodiluted value. Increases in CBF helped compensate for decreased arterial oxygen content and maintain CDO2. With progressive temperature reduction, these compensatory flow increases were reduced and CDO2 was decreased at lesser degrees of hemodilution. Statistical analysis indicated that cerebral oxygen demand was maintained to an Hct of 0.14, 0.11, and < or = 0.10 in the 38 degrees C, 28 degrees C, and 18 degrees C groups; however, physiologically important changes in cerebral oxygen supply occur at Hcts of approximately 0.18, 0.15, and 0.12, respectively, at those temperatures. CONCLUSIONS: This investigation systematically characterizes the critical Hct supporting cerebral oxygenation at differing CPB temperatures. Over a range of CPB temperatures, the curve describing the relationship between Hct and cerebral oxygen balance has a broad plateau, indicating cerebral tolerance for a wide range of Hcts. The minimum Hct that supports cerebral oxygenation is shifted leftward as temperature is reduced, but the reduction in critical Hct is not proportional to the reduction in CMRO2. Although we do not advocate hemodilution to these extreme values, we find that these data provide a physiological foundation for our hemodilution practice and provide some guidance for management of Hct as body temperature changes during CPB.

Animals↗
PubMed1998

Incidence of and risk factors for ventilator-associated pneumonia in critically ill patients.

BACKGROUND: Understanding the risk factors for ventilator-associated pneumonia can help to assess prognosis and devise and test preventive strategies. OBJECTIVE: To examine the baseline and time-dependent risk factors for ventilator-associated pneumonia and to determine the conditional probability and cumulative risk over the duration of stay in the intensive care unit. DESIGN: Prospective cohort study. SETTING: 16 intensive care units in Canada. PATIENTS: 1014 mechanically ventilated patients. MEASUREMENTS: Demographic and time-dependent variables reflecting illness severity, ventilation, nutrition, and drug exposure. Pneumonia was classified by using five methods: adjudication committee, bedside clinician's diagnosis, Centers for Disease Control and Prevention definition, Clinical Pulmonary Infection score, and positive culture from bronchoalveolar lavage or protected specimen brush. RESULTS: 177 of 1014 patients (17.5%) developed ventilator-associated pneumonia 9.0 +/- 5.9 days (median, 7 days [interquartile range, 5 to 10 days]) after admission to the intensive care unit. Although the cumulative risk increased over time, the daily hazard rate decreased after day 5 (3.3% at day 5, 2.3% at day 10, and 1.3% at day 15). Independent predictors of ventilator-associated pneumonia in multivariable analysis were a primary admitting diagnosis of burns (risk ratio, 5.09 [95% CI, 1.52 to 17.03]), trauma (risk ratio, 5.00 [CI, 1.91 to 13.11]), central nervous system disease (risk ratio, 3.40 [CI, 1.31 to 8.81]), respiratory disease (risk ratio, 2.79 [CI, 1.04 to 7.51]), cardiac disease (risk ratio, 2.72 [CI, 1.05 to 7.01]), mechanical ventilation in the previous 24 hours (risk ratio, 2.28 [CI, 1.11 to 4.68]), witnessed aspiration (risk ratio, 3.25 [CI, 1.62 to 6.50]), and paralytic agents (risk ratio, 1.57 [CI, 1.03 to 2.39]). Exposure to antibiotics conferred protection (risk ratio, 0.37 [CI, 0.27 to 0.51]). Independent risk factors were the same regardless of the pneumonia definition used. CONCLUSIONS: The daily risk for pneumonia decreases with increasing duration of stay in the intensive care unit. Witnessed aspiration and exposure to paralytic agents are potentially modifiable independent risk factors. Exposure to antibiotics was associated with low rates of early ventilator-associated pneumonia, but this effect attenuates over time.

Adult↗
PubMed1998

Does quality of reports of randomised trials affect estimates of intervention efficacy reported in meta-analyses?

BACKGROUND: Few meta-analyses of randomised trials assess the quality of the studies included. Yet there is increasing evidence that trial quality can affect estimates of intervention efficacy. We investigated whether different methods of quality assessment provide different estimates of intervention efficacy evaluated in randomised controlled trials (RCTs). METHODS: We randomly selected 11 meta-analyses that involved 127 RCTs on the efficacy of interventions used for circulatory and digestive diseases, mental health, and pregnancy and childbirth. We replicated all the meta-analyses using published data from the primary studies. The quality of reporting of all 127 clinical trials was assessed by means of component and scale approaches. To explore the effects of quality on the quantitative results, we examined the effects of different methods of incorporating quality scores (sensitivity analysis and quality weights) on the results of the meta-analyses. FINDINGS: The quality of trials was low. Masked assessments provided significantly higher scores than unmasked assessments (mean 2.74 [SD 1.10] vs 2.55 [1.20]). Low-quality trials (score < or = 2), compared with high-quality trials (score > 2), were associated with an increased estimate of benefit of 34% (ratio of odds ratios [ROR] 0.66 [95% CI 0.52-0.83]). Trials that used inadequate allocation concealment, compared with those that used adequate methods, were also associated with an increased estimate of benefit (37%; ROR=0.63 [0.45-0.88]). The average treatment benefit was 39% (odds ratio [OR] 0.61 [0.57-0.65]) for all trials, 52% (OR 0.48 [0.43-0.54]) for low-quality trials, and 29% (OR 0.71 [0.65-0.77]) for high-quality trials. Use of all the trial scores as quality weights reduced the effects to 35% (OR 0.65 [0.59-0.71]) and resulted in the least statistical heterogeneity. INTERPRETATION: Studies of low methodological quality in which the estimate of quality is incorporated into the meta-analyses can alter the interpretation of the benefit of intervention, whether a scale or component approach is used in the assessment of trial quality.

Bias↗
PubMed1998

Methodology and reports of systematic reviews and meta-analyses: a comparison of Cochrane reviews with articles published in paper-based journals.

CONTEXT: Review articles are important sources of information to help guide decisions by clinicians, patients, and other decision makers. Ideally, reviews should include strategies to minimize bias and to maximize precision and be reported so explicitly that any interested reader would be able to replicate them. OBJECTIVE: To compare the methodological and reporting aspects of systematic reviews and meta-analyses published by the Cochrane Collaboration with those published in paper-based journals indexed in MEDLINE. DATA SOURCES: The Cochrane Library, issue 2 of 1995, and a search of MEDLINE restricted to 1995. STUDY SELECTION: All 36 completed reviews published in the Cochrane Database of Systematic Reviews and a randomly selected sample of 39 meta-analyses or systematic reviews published in journals indexed by MEDLINE in 1995. DATA EXTRACTION: Number of authors, trials, and patients; trial sources; inclusion and exclusion criteria; language restrictions; primary outcome; trial quality assessment; heterogeneity testing; and effect estimates. Updating by 1997 was evaluated. RESULTS: Reviews found in MEDLINE included more authors (median, 3 vs 2; P<.001), more trials (median, 13.5 vs 5; P<.001), and more patients (median, 1280 vs 528; P<.001) than Cochrane reviews. More Cochrane reviews, however, included a description of the inclusion and exclusion criteria (35/36 vs 18/39; P<.001) and assessed trial quality (36/36 vs 12/39; P<.001). No Cochrane reviews had language restrictions (0/36 vs 7/39; P<.01). There were no differences in sources of trials, heterogeneity testing, or description of effect estimates. By June 1997, 18 of 36 Cochrane reviews had been updated vs 1 of 39 reviews listed in MEDLINE. CONCLUSIONS: Cochrane reviews appear to have greater methodological rigor and are more frequently updated than systematic reviews or meta-analyses published in paper-based journals.

Meta-Analysis as Topic↗
PubMed1998

Benefit of heparin in peripheral venous and arterial catheters: systematic review and meta-analysis of randomised controlled trials.

OBJECTIVE: To evaluate the effect of heparin on duration of catheter patency and on prevention of complications associated with use of peripheral venous and arterial catheters. DESIGN: Critical appraisal and meta-analysis of 26 randomised controlled trials that evaluated infusion of heparin intermittently or continuously. Thirteen trials of peripheral venous catheters and two of peripheral arterial catheters met criteria for inclusion. MAIN OUTCOME MEASURES: Data on the populations, interventions, outcomes, and methodological quality. RESULTS: For peripheral venous catheters locked between use flushing with 10 U/ml of heparin instead of normal saline did not reduce the incidence of catheter clotting and phlebitis or improve catheter patency. When heparin was given as a continuous infusion at 1 U/ml the risk of phlebitis decreased (relative risk 0.55; 95% confidence interval 0.39 to 0.77), the duration of patency increased, and infusion failure was reduced (0.88; 0.72 to 1.07). Heparin significantly prolonged duration of patency of radial artery catheters and decreased the risk of clot formation (0.51; 0.42 to 0.61). CONCLUSIONS: Use of intermittent heparin flushes at doses of 10 U/ml in peripheral venous catheters locked between use had no benefit over normal saline flush. Infusion of low dose heparin through a peripheral arterial catheter prolonged the duration of patency but further study is needed to establish its benefit for peripheral venous catheters.

Adolescent↗
PubMed1998

Evaluation of a ventilation strategy to prevent barotrauma in patients at high risk for acute respiratory distress syndrome. Pressure- and Volume-Limited Ventilation Strategy Group.

BACKGROUND: A strategy of mechanical ventilation that limits airway pressure and tidal volume while permitting hypercapnia has been recommended for patients with the acute respiratory distress syndrome. The goal is to reduce lung injury due to overdistention. However, the efficacy of this approach has not been established. METHODS: Within 24 hours of intubation, patients at high risk for the acute respiratory distress syndrome were randomly assigned to either pressure- and volume-limited ventilation (limited-ventilation group), with the peak inspiratory pressure maintained at 30 cm of water or less and the tidal volume at 8 ml per kilogram of body weight or less, or to conventional ventilation (control group), with the peak inspiratory pressure allowed to rise as high as 50 cm of water and the tidal volume at 10 to 15 ml per kilogram. All other ventilatory variables were similar in the two groups. RESULTS: A total of 120 patients with similar clinical features underwent randomization (60 in each group). The patients in the limited-ventilation and control groups were exposed to different mean (+/-SD) tidal volumes (7.2+/-0.8 vs. 10.8+/-1.0 ml per kilogram, respectively; P<0.001) and peak inspiratory pressures (23.6+/-5.8 vs. 34.0+/-11.0 cm of water, P<0.001). Mortality was 50 percent in the limited-ventilation group and 47 percent in the control group (relative risk, 1.07; 95 percent confidence interval, 0.72 to 1.57; P=0.72). In the limited-ventilation group, permissive hypercapnia (arterial carbon dioxide tension, >50 mm Hg) was more common (52 percent vs. 28 percent, P=0.009), more marked (54.4+/-18.8 vs. 45.7+/-9.8 mm Hg, P=0.002), and more prolonged (146+/-265 vs. 25+/-22 hours, P=0.017) than in the control group. The incidence of barotrauma, the highest multiple-organ-dysfunction score, and the number of episodes of organ failure were similar in the two groups; however, the numbers of patients who required paralytic agents (23 vs. 13, P=0.05) and dialysis for renal failure (13 vs. 5, P= 0.04) were greater in the limited-ventilation group than in the control group. CONCLUSIONS: In patients at high risk for the acute respiratory distress syndrome, a strategy of mechanical ventilation that limits peak inspiratory pressure and tidal volume does not appear to reduce mortality and may increase morbidity.

Barotrauma↗
PubMed1998

The use of glycopyrrolate in a case of intermediate syndrome following acute organophosphate poisoning.

PURPOSE: This report describes a case of organophosphate intoxication refractory to atropine in which glycopyrrolate was used to reduce cholinergic symptoms, and describes the development of intermediate syndrome, an uncommon subacute complication of organophosphate poisoning. CLINICAL FEATURES: A 44-yr-old woman presented in cholinergic crisis following malathion ingestion. Treatment was initiated with atropine and pralidoxime. Despite clinical signs of adequate atropinisation, the patient continued to have profuse bronchorrhoea, which resolved with glycopyrrolate. During her course in the intensive care unit, she displayed a subacute deterioration in neuromuscular and mental status with decrement-increment phenomenon on electromyography consistent with intermediate syndrome. The patient eventually made a complete recovery. CONCLUSION: This case report describes the successful use of glycopyrrolate in organophosphate intoxication and the development of the intermediate syndrome, characterised by onset of weakness of neck flexors, proximal limb muscles, and respiratory muscles within one to four days after poisoning. Recognition of the syndrome is important in light of the potential for respiratory depression requiring ventilatory support.

Acute Disease↗
PubMed1998

Risk factors for death after heart transplantation: does a single-center experience correlate with multicenter registries?

BACKGROUND: Risk factors for death after heart transplantation (Tx) are frequently documented from multicenter registries. Although this information is helpful, it reflects a whole range of experiences and results, and may not translate to a particular center. This study was performed to (1) evaluate pre-Tx factors affecting mortality in a single-center experience, and (2) compare these factors with risk factors obtained from multicenter registry reports. METHODS: Review of our transplant database between January 1984 and December 1995 identified 405 adults who received a primary heart Tx. Multiple factors were analyzed, including demographics, Tx era, cytomegalovirus status, United Network for Organ Sharing status of recipient, presence of pulmonary hypertension, previous cardiac operations, mechanical ventilation or circulatory support, ischemia time, number of rejection episodes, and preoperative flow cytometry crossmatching. RESULTS: One- and 5-year survival rates were 87.8% and 73.4%, respectively (Kaplan-Meier). Contrary to multicenter registry reports, our data indicate that reoperative procedures, left ventricular assist device support, increasing donor and recipient age, and ischemia time up to 4.2 hours are not risk factors for death after Tx. Likewise, mode of donor death is not a risk factor affecting outcome. Significant risk factors for mortality identified by multivariate analysis included early transplant era (1984 to 1989; p = 0.002), female donor (p = 0.042), cytomegalovirus-seropositive donor (p = 0.048), high pulmonary vascular resistance (p = 0.018), and intraaortic balloon pump support (p = 0.03). It also identified a positive B-cell flow cytometry crossmatch (p = 0.015) to be a risk factor with univariate analysis. CONCLUSIONS: Our data identify a group of recipients, reportedly at high risk in multicenter registries, who are not at increased risk of death after Tx. This information supports the growing experience with older donors and recipients and with bridged transplants, and has allowed us to expand our donor pool. These prognostic factors at evaluation allow more liberal selection of patients and donors for transplantation.

Adolescent↗
PubMed1998

Critical cerebral perfusion pressure during tepid heart operations in dogs.

BACKGROUND: The management of blood pressure during cardiopulmonary bypass varies widely. This may be particularly relevant with the trend to warmer bypass temperatures and an older patient population. Therefore, we examined the minimal perfusion pressure that maintains cerebral oxygen delivery during cardiopulmonary bypass at 33 degrees C. METHODS: Ten dogs were placed on bypass and body temperature was reduced to 33 degrees C (alpha-stat pH management). At six randomly ordered mean arterial blood pressures (35, 40, 45, 50, 60, and 70 mm Hg), cerebral blood flow, oxygen delivery, and metabolic rate were determined. RESULTS: Cerebral oxygen delivery was stable if the mean arterial pressure was greater than or equal to 60 mm Hg. If mean arterial pressure was less than or equal to 50 mm Hg, cerebral oxygen delivery decreased, and at less than 45 mm Hg cerebral ischemia was seen. CONCLUSIONS: In a dog without vascular disease, the brain becomes perfusion pressure-dependent at a mean arterial pressure of approximately 50 mm Hg. There is no leftward shift of the cerebral autoregulatory curve during bypass at 33 degrees C. Greater support of mean arterial pressure during "tepid" cardiopulmonary bypass is indicated in the current adult surgical population that is older and has vascular comorbidity.

Animals↗
PubMed1998

Hemodilution and whole body oxygen balance during normothermic cardiopulmonary bypass in dogs.

OBJECTIVE: The purpose of this study was to determine the minimum hematocrit value that can support whole body oxygen consumption during normothermic cardiopulmonary bypass. The effect of hemodilution on peripheral resistance, whole body oxygen delivery, and oxygen consumption was determined over a range of hematocrit values. METHODS: Measurements were obtained during 38 degrees C cardiopulmonary bypass with progressive normovolemic hemodilution (hematocrit value 40% to 9%) in nine dogs. Dextran 70 (6%) was used as a diluent. Anesthesia consisted of high-dose fentanyl and midazolam. A mean arterial pressure of 60 mm Hg was maintained throughout cardiopulmonary bypass via increases in pump flow. RESULTS: Progressive hemodilution was associated with a decreasing total peripheral resistance. During normothermic cardiopulmonary bypass with a whole blood prime, the whole body oxygen consumption approximated values previously reported in dogs under nonbypass conditions. Oxygen delivery and whole body oxygen uptake were maintained between a hematocrit value of 39% and 25%. Significant decreases for both were seen when the hematocrit value was reduced to 18% and below. CONCLUSIONS: A hematocrit level greater than 18% was needed to maintain systemic oxygen delivery and consumption during warm cardiopulmonary bypass. The critical hematocrit value may be higher under bypass than nonbypass conditions because the flow increases that are practical during cardiopulmonary bypass do not approximate those seen in response to hemodilution of the intact circulation. Finally, the critical hematocrit value for the body may be higher than that required for the brain during warm cardiopulmonary bypass.

Animals↗