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M G Tweeddale

Publications and source records attributed to M G Tweeddale.

At least 19 recordsLinked to original sources
PubMed2001

Teaching old dogs new tricks--a personal perspective on a decade of efforts by a clinical ethics committee to promote awareness of medical ethics.

To incorporate medical ethics into clinical practice, it must first be understood and valued by health care professionals. The recognition of this principle led to an expanding and continuing educational effort by the ethics committee of the Vancouver General Hospital. This paper reviews this venture, including some pitfalls and failures, as well as successes. Although we began with consultants, it quickly became apparent that education in medical ethics must reach all health care professionals--and medical students as well. Our greatest successes came in the formative years of a medical career (i.e., in medical school and residency training programmes), but other efforts were not wasted, particularly among nurses and other health care professionals. Although this is a personal review of the experience in one institution, the lessons learnt in Vancouver are applicable to the further development of medical ethics in the UK.

Awareness↗
PubMed1998

Admission of bone marrow transplant recipients to the intensive care unit: outcome, survival and prognostic factors.

The role of ICU support in BMT patients is controversial. In an era of constrained resources, the use of prognostic factors predicting outcome may be helpful in identifying patients who are most likely (or unlikely) to benefit from this intervention. We attempted to define the survival of patients admitted to ICU following autologous or allogeneic BMT and to identify those factors important in determining patient outcome. A retrospective study of all adult BMT recipients admitted to intensive care over a 6 year study period was performed to determine overall and prognostic indicators of poor outcome. Pre-treatment, pre-ICU admission and ICU admission data were analyzed to identify factors predicting long-term survival. 116 patients were admitted to ICU on 135 separate occasions with the primary reasons for admission being respiratory failure (66%), sepsis associated with hypotension (10%), and cardiorespiratory failure (8%). No pre-ICU characteristics were predictive of survival. Univariate analysis identified the number of support measures required, the need for ventilation or hemodynamic support, the APACHE II score, the year of ICU admission and the serum bilirubin as significant predictors of post-discharge survival. On multivariate analysis the year of ICU admission, the need for hemodynamic support and the serum bilirubin remained significant. The APACHE II score significantly underestimated survival in the 46% of patients with scores less than 35, and could only be used to predict 100% mortality when it exceeded 45. Twenty-three percent of all BMT patients admitted to the ICU and 17% of ventilated patients survived to hospital discharge. Of the 27 patients surviving to leave hospital, 16 remain alive with a median follow-up of 4.2 years and a mean Karnofsky performance status of 90. Although mortality in BMT recipients admitted to ICU is high our results indicate that intensive care support can be lifesaving and that the outcome in patients requiring ventilation and ICU support may not be as poor as has been previously reported. No single variable was identified which could be used to predict futility but patients requiring both hemodynamic support and mechanical ventilation, and those with an APACHE II score greater than 45 have a very poor prognosis and are unlikely to benefit from lengthy ICU support.

Adolescent↗
PubMed1997

Association of mortality with age of blood transfused in septic ICU patients.

PURPOSE: To determine, retrospectively, the age of packed red blood cell (PRBC) units transfused to patients admitted to the ICU with the diagnosis of severe sepsis and to correlate this variable with outcome. METHODS: All patients admitted to the ICU during 1992 with a diagnosis of severe sepsis were selected retrospectively. The criteria for the diagnosis of severe sepsis and septic shock were based on established guidelines. For each patient the total number of PRBC units transfused, the number of units transfused before, during and after the septic episode, and the age of each PRBC unit transfused were recorded. RESULTS: Of the 31 patients admitted to the ICU with severe sepsis, 19 died and 12 survived. No statistical differences between survivors and nonsurvivors were found with respect to age, sex, number of days in ICU, duration of sepsis, incidence of septic shock, admission Apache II score or total number of PRBC units transfused. During sepsis the median age of PRBC units transfused to survivors was 17 days (range 5-35) vs 25 days (range 9-36) for nonsurvivors (P < 0.0001). A negative correlation (r = -0.73) was found between the proportion of PRBC units of a given age transfused to survivors and increasing age of PRBC. CONCLUSION: This is the first study to report a correlation of mortality with the age of PRBC transfused. The cause of this association is unclear. If this association is confirmed by a prospective randomised trial it would have major implications for the use of PRBC in severe sepsis.

Adolescent↗
PubMed1996

Does increasing oxygen delivery improve outcome in the critically ill? No.

The strategy of treating critically ill patients by increasing oxygen delivery and consumption to values previously observed among survivors of critical illness (supranormal values) is based on the belief that (1) tissue hypoxia may persist in critically ill patients despite aggressive early resuscitation to traditional endpoints of adequate tissue perfusion and (2) that increasing oxygen delivery can reverse tissue hypoxia. This article addresses the question of whether increasing oxygen delivery improves outcomes in critically ill patients by reviewing the relationship between whole-body oxygen delivery and consumption and by critically examining the randomized controlled trials that have increased oxygen delivery to supranormal values.

Cell Hypoxia↗
PubMed1994

Blood transfusion as a cause of leucocytosis in critically ill patients.

The diagnosis of infection in the intensive care unit is confounded by the presence of non-infectious causes of leucocytosis. Unless such causes are recognised, time and effort will be spent on unnecessary investigations and treatments. In a prospective study we have shown that the transfusion of blood frequently (45/50 patients) causes an acute leucocytosis in such patients. This effect was not seen in 8 patients who received plasma. Blood transfusion should be added to the list of non-infectious causes of leucocytosis in the critically ill.

Adult↗
PubMed1993

Identification of the critical oxygen delivery for anaerobic metabolism in critically ill septic and nonseptic humans.

OBJECTIVES: To determine the critical oxygen delivery threshold for anaerobic metabolism and to compare its value between septic and nonseptic critically ill patients. DESIGN: Cohort analytic study, consecutive sample. SETTING: Two tertiary care medical and surgical intensive care units in university hospitals. PATIENTS: Nine septic and nine nonseptic critically ill humans. A diagnosis of sepsis was established by the presence of sepsis syndrome, positive cultures obtained within 48 hours of study, and autopsy evidence of a source of infection. METHODS AND INTERVENTIONS: The O2 consumption (determined by indirect calorimetry), O2 delivery (calculated from the Fick equation), and concentration of arterial plasma lactate were simultaneously determined at 5- to 20-minute intervals while life support was discontinued. MAIN OUTCOME MEASURES: Critical O2 delivery, critical O2 extraction ratio, and maximal O2 extraction ratio. RESULTS: In all septic and eight nonseptic patients, O2 delivery and O2 consumption displayed a biphasic relationship over the range of O2 delivery studied. There were no differences in critical O2 delivery threshold (3.8 +/- 1.5 vs 4.5 +/- 1.3 mL.min-1 x kg-1; P > .28), critical O2 extraction ratio (0.61 +/- 0.05 vs 0.59 +/- 0.16; P > .64), and maximal O2 extraction ratio (0.74 +/- 0.08 vs 0.80 +/- 0.11; P > .29) between septic and nonseptic patients. These data have greater than 90% power to detect a difference of 2 mL.min-1 x kg-1 in the critical O2 delivery and 0.1 in the critical and maximal O2 extraction ratios between the septic and nonseptic groups. CONCLUSIONS: The critical O2 delivery for anaerobic metabolism was identified from the biphasic relationship between O2 delivery and O2 consumption in individual humans. The critical O2 delivery is considerably lower than previously reported in humans with the use of pooled group data. Sepsis does not alter the critical O2 delivery for anaerobic metabolism or tissue O2 extraction ability. Interventions to increase O2 delivery to supranormal levels in critically ill humans in the hope of increasing O2 consumption may be inappropriate.

Adult↗
PubMed1993

Oxygen consumption is independent of increases in oxygen delivery by dobutamine in septic patients who have normal or increased plasma lactate.

We asked whether the relationship between oxygen delivery and oxygen consumption is different between patients who have sepsis and normal (n = 6) or increased (n = 8) concentrations of plasma lactate. We determined oxygen consumption using analysis of respiratory gases while increasing oxygen delivery using a dobutamine infusion. The relationship between oxygen delivery and consumption was y = 124 + 0.043 * x in the normal lactate group and y = 131 - 0.003 * x in the high lactate group (95% CI for differences in slopes, -0.003 to 0.096; p < or = 0.05 for slope, normal versus high lactate). In the normal lactate group, direct oxygen consumption increased by only 8 +/- 6 ml/min/m2 after dobutamine infusion (from 144 +/- 26 to 153 +/- 22 ml/min/m2, p < or = 0.02) despite an average increase of 220 +/- 80 ml/min/m2 in oxygen delivery (from 446 +/- 91 to 666 +/- 90 ml/min/m2, p < or = 0.01). The oxygen extraction ratio fell from 0.27 +/- 0.03 to 0.21 +/- 0.02 after dobutamine (p < or = 0.017). In the high lactate group, direct oxygen consumption decreased by 1 +/- 6 ml/min/m2 after dobutamine (from 131 +/- 33 to 130 +/- 35 ml/min/m2, p > 0.60) despite an average increase of 168 +/- 138 ml/min/m2 in oxygen delivery (from 467 +/- 194 to 635 +/- 300 ml/min/m2, p < or = 0.01). The oxygen extraction ratio fell from 0.30 +/- 0.14 to 0.26 +/- 0.12 after dobutamine (p < or = 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Nonvalue of antigen detection immunoassays for diagnosis of candidemia.

We evaluated the Cand-Tec (Ramco Laboratories Inc., Houston, Tex.) and LA-Candida antigen detection system (Immuno-Mycologics Inc., Norman, Okla.) tests as possible rapid alternatives to blood cultures for the identification of patients with candidemia. Tests were performed on sera from (i) 33 patients with candidemia, (ii) 82 patients with fever and risk factors for invasive candidiasis, and (iii) 13 healthy controls. A total of 21 patients had no evidence of invasive candidiasis, as determined by clinical course, blood culture, and/or autopsy; results for 61 patients were indeterminate regarding the presence of invasive candidiasis, or else the patients had invasive candidiasis with organ involvement. By using a threshold positive Cand-Tec titer of greater than or equal to 1:4, the sensitivity in candidemic patients was 49%; the specificity was 43% (patients with true-negative results had neither candidemia nor other evidence of invasive candidiasis). Coexistent disseminated candidiasis in some candidemic patients may have accounted for some positive Cand-Tec tests and possible overestimation of the sensitivity of the test for candidemia. Cand-Tec test results were negative for healthy controls. All test results obtained by the LA-Candida antigen detection system assay were negative. Our findings indicate that neither of these assays reliably identifies patients with candidemia.

Adolescent↗
PubMed1989

Interactions between plasma proteins and pulmonary surfactant: pulsating bubble studies.

The influence of human albumin, alpha-globulin, and fibrinogen on the actions of porcine pulmonary surfactant in a pulsating bubble surfactometer has been investigated. All three proteins detracted from the ability of the surfactant to adsorb to the air-water interface. The proteins also reduced the ability of surfactant to lower the opening pressures of bubbles cycling between different sizes in suspensions of surfactant. This was equivalent to restricting the ability of the surfactant to achieve low surface tension during compression of the surface. Of the three proteins, globulin competed most effectively with surfactant during the adsorption process, and albumin competed the least effectively. The proteins also may have interfered with the processes of surface refinement, which usually yields a monolayer enriched enough in dipalmitoyl phosphatidylcholine to achieve very low surface tension (very low opening pressures in the bubbles). Of the three proteins tested, albumin was least deleterious to surface refining whereas globulin and fibrinogen appeared to be about equally detrimental to the process.

Alpha-Globulins↗
PubMed1988

Interactions between plasma proteins and pulmonary surfactant: surface balance studies.

The influence of human fibrinogen, alpha-globulin, and albumin on the properties of monolayers of pulmonary surfactant under dynamic compression and expansion has been studied at 37 degrees C. Each of the proteins altered some of the properties of the normal compression and expansion isotherms of surfactant such that characteristics deemed desirable for proper lung function were impaired. The order of potency of these effects was fibrinogen greater than globulin greater than albumin. The proteins (a) decreased the maximum surface pressure (equivalent to the minimum surface tension) which the surfactant monolayers attained on compression, (b) decreased the areas occupied per mole of lipid phosphorus when the monolayers were at surface tensions of 20 and 12 mN.m-1, (c) reduced the areas of the hysteresis between compression and expansion isotherms, and (d) decreased the rate of change of surface tension with area at the point of initial expansion of the monolayers. The proteins might compete with surfactant lipid for available space at the interface, especially at low film compression. They might also enhance the desorption of lipid from the monolayer. The findings are consistent with the loss of pulmonary function and presence of edema that occur in adult respiratory distress syndrome being contributed to by plasma proteins interfering with surfactant function.

Alpha-Globulins↗
PubMed1979

Elevated serum uric acid. A cardiovascular risk factor?

A critical survey of the literature suggests that elevated serum uric acid is definitely associated with hypertension and may function as an independent risk factor in the development of this disease. The possible role of an elevated serum uric acid as an independent risk factor for the development of ischemic heart disease remains controversial and the association of these two factors may depend on the relationship between uric acid and hypertension. There is no evidence available to define the metabolic turnover of uric acid in hypertensives. The exact mechanisms underlying elevated serum uric acid values during diuretic treatment are unclear, but depend initially upon diuretic-induced extracellular volume depletion.

Adolescent↗