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Biomedical subjects

D J Cook

Publications and source records attributed to D J Cook.

At least 37 records · Page 2Linked to original sources
PubMed2001

Withdrawing and withholding life support in the intensive care unit: a Spanish prospective multi-centre observational study.

OBJECTIVE: To determine how frequently life support is withheld or withdrawn from adult critically ill patients, and how physicians and patients families agree on the decision regarding the limitation of life support. DESIGN: Prospective multi-centre cohort study. SETTING: Six adult medical-surgical Spanish intensive care units (ICUs). PATIENTS AND PARTICIPANTS: Three thousand four hundred ninety-eight consecutive patients admitted to six ICUs were enrolled. MEASUREMENTS AND RESULTS: Data collected included age, sex, SAPS II score on admission and within 24 h of the decision to limit treatment, length of ICU stay, outcome at ICU discharge, cause and mode of death, time to death after the decision to withhold or withdraw life support, consultation and agreement with patient's family regarding withholding or withdrawal, and the modalities of therapies withdrawn or withheld. Two hundred twenty-six (6.6%) of 3,498 patients had therapy withheld or withdrawn and 221 of them died in the ICU. Age, SAPS II and length of ICU stay were significantly higher in patients dying patients who had therapy withheld or withdrawn than in patients dying despite active treatment. The proposal to withhold or withdraw life support was initiated by physicians in 210 (92.9%) of 226 patients and by the family in the remaining cases. The patient's family was not involved in the decision to withhold or withdraw life support therapy in 64 (28.3%) of 226 cases. Only 21 (9%) patients had expressed their wish to decline life-prolonging therapy prior to ICU admission. CONCLUSIONS: The withholding and withdrawing of treatment was frequent in critically ill patients and was initiated primarily by physicians.

Adult↗
PubMed2001

The attributable mortality and length of intensive care unit stay of clinically important gastrointestinal bleeding in critically ill patients.

OBJECTIVE: To estimate the mortality and length of stay in the intensive care unit (ICU) attributable to clinically important gastrointestinal bleeding in mechanically ventilated critically ill patients. DESIGN: Three strategies were used to estimate the mortality attributable to bleeding in two multicentre databases. The first method matched patients who bled with those who did not (matched cohort), using duration of ICU stay prior to the bleed, each of six domains of the Multiple Organ Dysfunction Score (MODS) measured 3 days prior to the bleed, APACHE II score, age, admitting diagnosis, and duration of mechanical ventilation. The second approach employed Cox proportional hazards regression to match bleeding and non-bleeding patients (model-based matched cohort). The third method, instead of matching, derived estimates based on regression modelling using the entire population (regression method). Three parallel analyses were conducted for the length of ICU stay attributable to clinically important bleeding. SETTING: Sixteen Canadian university-affiliated ICUs. PATIENTS: A total of 1666 critically ill patients receiving mechanical ventilation for at least 48 hours. MEASUREMENTS: We prospectively collected data on patient demographics, APACHE II score, admitting diagnosis, daily MODS, clinically important bleeding, length of ICU stay, and mortality. Independent adjudicators determined the occurrence of clinically important gastrointestinal bleeding, defined as overt bleeding in association with haemodynamic compromise or blood transfusion. RESULTS: Of 1666 patients, 59 developed clinically important gastrointestinal bleeding. The mean APACHE II score was 22.9 +/- 8.6 among bleeding patients and 23.3 +/- 7.7 among non-bleeding patients. The risk of death was increased in patients with bleeding using all three analytic approaches (matched cohort method: relative risk [RR]= 2.9, 95% confidence interval (CI)= 1.6-5.5; model-based matched cohort method: RR = 1.8, 95% CI = 1.1-2.9; and the regression method: RR = 4.1, 95% CI = 2.6-6.5). However, this was not significant for the adjusted regression method (RR = 1.0, 95% CI = 0.6-1.7). The median length of ICU stay attributable to clinically important bleeding for these three methods, respectively, was 3.8 days (95% CI = -0.01 to 7.6 days), 6.7 days (95% CI = 2.7-10.7 days), and 7.9 days (95% CI = 1.4-14.4 days). CONCLUSIONS: Clinically important upper gastrointestinal bleeding has an important attributable morbidity and mortality, associated with a RR of death of 1-4 and an excess length of ICU stay of approximately 4-8 days.

APACHE↗
PubMed2001

Deep vein thrombosis and its prevention in critically ill adults.

BACKGROUND: Our objective was to systematically review the incidence of deep vein thrombosis (DVT) and the efficacy of thromboprophylaxis in critically ill adults, including patients admitted to intensive care units and following trauma, neurosurgery, or spinal cord injury. METHODS: Two authors independently searched MEDLINE, EMBASE, abstract databases, and the Cochrane database. Data were extracted independently in triplicate. RESULTS: Ten percent to 30% of medical and surgical intensive care unit patients develop DVT within the first week of intensive care unit admission. The use of subcutaneous low-dose heparin reduced the rate by 50% compared with no prophylaxis. Approximately 60% of trauma patients developed DVT within the first 2 weeks of admission. Use of unfractionated heparin appears to decrease the incidence of DVT by only 20%, whereas low-molecular-weight heparin decreases the incidence by a further 30%. The estimated prevalence of DVT in neurosurgical patients not given prophylaxis is 22% to 35%. Mechanical prophylaxis is efficacious, with a pooled odds ratio in 5 randomized trials of 0.28. Use of low-molecular-weight heparin has been investigated as an adjunct to mechanical prophylaxis with a pooled odds ratio of 0.59 compared with graduated compression stockings alone. The incidence of DVT without prophylaxis in acute spinal cord injury patients is likely in excess of 50% to 80%. Studies of prophylaxis in these patients are too sparse to come to any definitive conclusion. CONCLUSIONS: Critically ill patients commonly develop DVT, with rates that vary from 22% to almost 80%, depending on patient characteristics. Methods of prophylaxis proven in one group do not necessarily generalize to other critically ill patient groups. More potent prophylactic regimens other than unfractionated or low-molecular-weight heparins alone may be needed with higher-risk groups.

Anticoagulants↗
PubMed2001

Guidelines as rationing tools: a qualitative analysis of psychosocial patient selection criteria for cardiac procedures.

BACKGROUND: Cardiac procedure guidelines often include psychosocial criteria for selecting patients that potentially introduce social value judgements into clinical decisions and decisions about the rationing of care. The aim of this study was to investigate the terms and justifications for and the meanings of psychosocial patient characteristics used in cardiac procedure guidelines. METHODS: We selected English-language guidelines published since 1990 and chapters in textbooks published since 1989. These guidelines amalgamated multiple sources of evidence and expertise and made recommendations regarding patient selection for specific procedures. A multidisciplinary team of physicians and social scientists extracted passages regarding psychosocial criteria and developed categories and conceptual relationships to describe and interpret their content. RESULTS: Sixty-five papers met the criteria for inclusion in the study. Forty-five (69%) mentioned psychosocial criteria as procedure indications or contraindications. The latter fell into several categories, including behavioural and psychological issues, relationships with significant others, financial resources, social roles and environmental circumstances. INTERPRETATION: Psychosocial characteristics are portrayed as having 2 roles in patient selection: as risk factors intrinsic to the candidate or as indicators of need for special intervention. Guidelines typically simply list psychosocial contraindications without clarifying their specific nature or providing any justification for their use. Psychosocial considerations can help in the evaluation of patients for cardiac procedures, but they become ethically controversial when used to restrict access. The use of psychosocial indications and contraindications could be improved by more precise descriptions of the psychosocial problem at issue, explanations regarding why the criterion matters and justification of the characteristic using a biological rationale or research evidence.

Attitude of Health Personnel↗
PubMed2001

Hierarchy of regional oxygen delivery during cardiopulmonary bypass.

BACKGROUND: Relative to the nonbypass state, cardiopulmonary bypass may decrease whole-body oxygen (O2) delivery. We predicted that during cardiopulmonary bypass, a hierarchy of regional blood flow and O2 delivery could be characterized. METHODS: In 8 46.5 +/- 1.2-kg pigs, fluorescent microspheres were used to determine blood flow and O2 delivery to five organ beds before and during 37 degrees C cardiopulmonary bypass at four randomized bypass flows (1.4, 1.7, 2.0, and 2.3 L/min/m2). At completion, 18 tissue samples were obtained from the cerebral cortex (n = 4), renal cortex (n = 2), renal medulla (n = 2), pancreas (n = 3), small bowel (n = 3), and limb muscle (n = 4) for regional blood flow determination. RESULTS: At conventional cardiopulmonary bypass flow (2.3 L/min/m2), whole-body O2 delivery was reduced by 44 +/- 6% relative to the pre-cardiopulmonary bypass state (p < 0.05). Over a range of cardiopulmonary bypass flows (2.3 to 1.7 L/min/m2), brain and kidney maintained their perfusion. Blood flow and O2 delivery to both regions were reduced when the cardiopulmonary bypass flow was reduced to 1.4 L/min/m2. However, perfusion and O2 delivery to other visceral organs (pancreas, small bowel) and skeletal muscle showed pump flow dependency over the range of flows tested. CONCLUSIONS: This study characterizes the organ-specific hierarchy of blood flow and O2 distribution during cardiopulmonary bypass. These dynamics are relevant to clinical decisions for perfusion management.

Animals↗
PubMed2001

Distribution and hierarchy of regional blood flow during hypothermic cardiopulmonary bypass.

BACKGROUND: Cardiopulmonary bypass (CPB) may decrease oxygen delivery relative to the nonbypass state. We predicted that a hierarchy of regional blood flow could be characterized under hypothermic (27 degrees C) CPB. METHODS: Ten pigs underwent bypass at 27 degrees C. Fluorescent microspheres were administered before and during CPB at four randomized flows: 1.9, 1.6, 1.3, and 1.0 L x min(-1) x m(-2). At completion, tissue samples were obtained from brain, renal cortex and medulla, pancreas, small bowel, and limb muscle for regional blood flow determination. RESULTS: Cerebral blood flow remained unchanged between CPB flows of 1.9 and 1.3 L x min(-1) x m(-2). Renal perfusion was stable between flows of 1.9 and 1.6 L x min(-1) x m(-2), whereas perfusion of small bowel decreased linearly with pump flow. Pancreatic perfusion was unchanged over the range of flows studied; muscle blood flow was profoundly reduced at the highest CPB flow and further decreased if pump flow was reduced below 1.6 L x min(-1) x m(-2). CONCLUSIONS: This study characterizes the organ-specific hierarchy of blood flow and oxygen distribution during hypothermic CPB. These dynamics are relevant to clinical decisions for perfusion management.

Animals↗
PubMed2001

Can hypocapnia reduce cerebral embolization during cardiopulmonary bypass?

BACKGROUND: Cerebral embolization is a major cause of central nervous dysfunction after cardiopulmonary bypass. Experimental studies demonstrate that reductions in arterial carbon dioxide tension (PaCO2) can reduce cerebral embolization during cardiopulmonary bypass. This study examined the effects of brief PaCO2 manipulations on cerebral embolization in patients undergoing cardiac valve procedures. METHODS: Patients were prospectively randomized to either hypocapnia (PaCO2 = 30 to 32 mm Hg, n = 30) or normocapnia (PaCO2 = 40 to 42 mm Hg, n = 31) before aortic cross-clamp removal. With removal of the aortic cross-clamp embolic signals were recorded by transcranial Doppler ultrasonography for the next 15 minutes. RESULTS: Despite significant differences in PaCO2, groups did not differ statistically in total cerebral emboli counts. The mean number of embolic events was 107 +/- 100 (median, 80) in the hypocapnic group and 135 +/- 115 (median, 96) in the normocapnic group, respectively (p = 0.315). CONCLUSIONS: Due to the high between-patient variability in embolization, reductions in PaCO2 did not result in a statistically significant decrease in cerebral emboli. In contrast to experimental studies, the beneficial effect of hypocapnia on cerebral embolization could not be demonstrated in humans.

Carbon Dioxide↗
PubMed2001

Carbon dioxide management and the cerebral response to hemodilution during hypothermic cardiopulmonary bypass in dogs.

BACKGROUND: Increases in blood flow support oxygen (O2) delivery with hemodilution. However, with alpha-stat management, the cerebral response to hemodilution is blunted. We tested the hypothesis that carbon dioxide (CO2) management is a primary determinant of the cerebral blood flow (CBF) response to hemodilution during hypothermic bypass. METHODS: Following Animal Care Committee approval, 15 dogs underwent bypass at 18 degrees C (pH-stat, n = 7 or alpha-stat, n = 8). Measurements were obtained after progressive hemodilution, and cerebral blood flow was determined by sagittal sinus outflow. Arterial pressure was maintained at 60 to 70 mm Hg. The CBF response to hemodilution and cerebral metabolic rate were compared in the two groups of animals. RESULTS: In both groups, hemodilution increased CBF. At every hematocrit, CBF and O2 delivery in the pH-stat group exceeded that of alpha-stat group, although O2 demand did not differ between groups. While absolute CBF in the pH-stat group was greater at every hematocrit, the relative change in CBF from control and the slope of the CBF-Hct relationship did not differ between groups. CONCLUSIONS: pH-stat management is associated with a greater absolute CBF and a greater ratio of cerebral O2 supply to demand for any degree of hemodilution. However, over the range of hematocrits common in practice, CO2 management per se does not determine the cerebral response to hemodilution.

Animals↗
PubMed2001

When should an effective treatment be used? Derivation of the threshold number needed to treat and the minimum event rate for treatment.

Clinicians and patients must decide when treatment effects are large enough to more than offset the adverse effects and costs of therapy. Calculation of the number of patients one needs to treat (NNT) in order to prevent one patient from having the target event is one tool to help with this decision. Clinicians should treat patients when the NNT is lower than a threshold NNT at which point the therapeutic risk equals the therapeutic benefit. We aimed: (1) to identify the determinants of the threshold NNT, and (2) to derive equations for the explicit estimation of the threshold NNT and of the minimum expected rate of target event, without treatment, above which treatment is justified. We conceived the threshold number needed to treat to prevent one target event as the point at which the benefits of treating that number of patients equal the negative consequences of treating that same number of patients. After identifying the various elements comprising the treatment impact, we equated the benefits and negative consequences and solved the equation for threshold NNT. We then derived the minimum expected rate of target event which would justify treatment. We derived an equation that relates the threshold NNT to the treatment-attributable adverse event rates (AER) and the relative values (RV) of the adverse events compared to that of the target event prevented. Specifically, the threshold NNT, denoted NNT(T) is given by NNT(T) = 1/(AER(1).RV(1) +...+ AER(n).RV(n)). We also derived a more complex equation which addresses the costs incurred by treatment and costs avoided by preventing target events. Solving the equation that includes costs requires specifying both the value of preventing a target event and the values of adverse treatment effects in economic units. The threshold NNT and the relative risk reduction (RRR) for the target event determine the minimum target event rate above which treatment is justified. This minimum event rate for treatment is 1/(NNT(T).RRR). The values that clinicians and patients use determine the threshold NNT and therefore also the minimum target event rate, without treatment, above which treatment is justified. Quantification of the determinants of the threshold NNT and of the minimum event rate to justify treatment can assist clinicians and patients in the explicit use of underlying values when making treatment decisions.

Cost-Benefit Analysis↗
PubMed2001

Resolution of cis-trans ambiguities between HLA-DRB1 alleles using single-strand conformation polymorphisms and sequencing.

DNA-based typing of HLA alleles occasionally results in the inability to assign a specific allele because of ambiguity in associating two or more polymorphisms to the same or to alternate homologs (cis/trans ambiguity). Since most individuals are heterozygous at a given HLA locus, the highest level of confidence in definition is obtained when the alleles are tested in isolation. By using single-strand conformation polymorphisms (SSCP) to separate heterozygous HLA-DRB1 alleles, followed by sequencing of separated conformers, we have achieved resolution of previously ambiguous assignments without the need for additional probes or primers.

Alleles↗
PubMed2001

Hypogammaglobulinemia after heart transplantation: impact of pre-emptive use of immunoglobulin replacement (CytoGam) on infection and rejection outcomes.

Hypogammaglobulinemia (HGG) in solid organ transplant (SOT) patients confers an increased risk of opportunistic infections and poorer outcomes. Severe HGG (IgG < 350 mg/dL) after heart transplantation may follow intensification of immunosuppressive therapy and the resultant increased risk of opportunistic infections, particularly cytomegalovirus (CMV) disease. Evaluation of the effects of replacement therapy using intravenous immunoglobulin (CMV-IGIV, CytoGam) was conducted in cardiac transplant recipients and the data matched with a historical control group. Patients with severe HGG who received pre-emptive replacement therapy had significantly fewer opportunistic infections (P < 0.001) and episodes of rejection (grade > or = 3; P = 0.03 and grade > or = 2; P = 0.04) compared with the control group.

Adult↗
PubMed2001

Cerebral hyperthermia and cardiac surgery: consequences and prevention.

Temperature management during cardiac surgery deserves considerable attention because it has broad effects, altering virtually every physiologic process, including oxygen demand, blood flow, cardiac output, and coagulation. Temperature is also important in cardiac surgery because virtually all patients undergo significant temperature change. These changes can be unique in mammalian physiology both with regard to their magnitude and rate of change. Furthermore, cardiac surgical patients may be uniquely vulnerable to the effects of temperature. Because of vascular disease and embolization, many patients are at risk for cerebral ischemia. Additionally, their cardiac, pulmonary, and renal reserve is typically limited; and there is risk for perioperative bleeding. Patient temperature can affect all of these processes and has its greatest effect on those who are physiologically most fragile. An appreciation for temperature management is also compelling because, unlike new technologies, procedures, or drugs; temperature management is simple, practical, applicable to every patient, and can be performed with very little cost. This article will show why cerebral hyperthermia should be avoided in cardiac surgery. Second, it will discuss why it occurs and the management steps that may prevent it. Finally, we will highlight recent discussion of postoperative hyperthermia and speculate as to its origin and relevance.

Body Temperature Regulation↗
PubMed2001

Agreement between alternative classifications of acute respiratory distress syndrome.

To examine the agreement between two classifications of acute respiratory distress syndrome (ARDS) that are used interchangeably in clinical practice and clinical research, we classified 118 patients taking part in a randomized trial with respect to the presence of ARDS using the North American-European Consensus Committee (NAECC) and the Lung Injury Severity Score (LISS) criteria. The incidence of ARDS using NAECC criteria was 55.1% (95% confidence interval, 46.1% to 64.1%), and using the LISS criteria 61.9% (95% confidence interval, 53.1% to 70.6%). The p value on the difference between these proportions was 0.07. Raw agreement, chance-corrected agreement (kappa), and chance-independent agreement (phi) on the study occurrence of ARDS using the two classifications were, respectively, 0.73 (95% CI, 0.65 to 0.81), 0.46 (95% CI, 0.32 to 0.61), and 0.63 (95% CI, 0.41 to 0.79). No single component of either index contributed to disagreement to an appreciably greater extent than other components. Baseline characteristics and outcomes were similar among patients who developed ARDS according to either classification. We conclude that NAECC and LISS classifications resulted in similar estimates of the incidence of ARDS in this clinical trial, though patients were frequently classified as having ARDS with only one model. These discordant classifications had no prognostic importance.

Adult↗
PubMed2001

Clinical outcomes in a prison telepsychiatry clinic.

The effectiveness of a prison telepsychiatry service was evaluated from a user perspective. Forty-five inmates (41 male, 4 female) completed the Symptom Rating Checklist-90-Revised (SCL-90-R) on three occasions, once before the teleconsultation and twice during treatment. The psychiatrist completed the Clinical Global Impression Scale--Severity Index (CGI) after each teleconsultation. Forty-nine per cent of inmates were aged under 30 years, 24% were aged between 30 and 39 years, while 27% were aged over 40 years. The inmates' mean SCL-90-R scores decreased over time, indicating less psychiatric distress. The psychiatrist reported patient improvement over time as assessed by the CGI. Telepsychiatry is an effective means of delivering mental health services to the prison population.

Adult↗
PubMed2001

Administrator and provider perceptions of the factors relating to programme effectiveness in implementing telemedicine to provide end-of-life care.

Two large hospice organizations in Kansas and Michigan began a telehospice project with the goal of improving care at the end of life using telemedicine. Hospice nurses provided services using video directly to the homes of hospice patients. The telemedicine equipment operated over ordinary telephone lines. Nursing services included symptom assessment and psychospiritual evaluations. Patients lived in both urban and rural settings. Studies were designed to evaluate utilization patterns, access to care, patient/carer acceptance, medical outcomes and cost. During the first year of the project, telehospice care was initiated at five rural sites (two in Michigan and three in Kansas) and three urban sites (two in Michigan and one in Kansas). There was greater telehospice activity in Michigan than in Kansas, with 118 and 44 patients served, respectively. The urban site in Kansas withdrew from the study after participating for only nine months. In an effort to understand the difference in utilization patterns and reasons for withdrawing from the project, in-depth interviews of key study participants, including hospice administrators, nurses and research personnel, were conducted. Human factors appear to be important in the adoption of novel telemedicine applications.

Attitude of Health Personnel↗