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Biomedical subjects

Stephen M Davis

Publications and source records attributed to Stephen M Davis.

65 records · Page 4Linked to original sources
PubMed2002

Lithium neurotoxicity: the development of irreversible neurological impairment despite standard monitoring of serum lithium levels.

We report the case of a 44 year old man who presented with a two-month history of dysarthria, ataxia and leg weakness whilst on maintenance lithium for bipolar disorder. Examination revealed significant cerebellar and pyramidal dysfunction. Serum lithium was 1.5 mmol/l, a moderate elevation above his usual stable levels of 0.4-0.8 mmol/l. The patient's past history included hypertension and chronic renal impairment and the development of neurological symptoms coincided with the recent onset of heart failure. On cessation of lithium he partially recovered, the main residuum being persistent cerebellar ataxia. The case is an example of lithium neurotoxicity developing insidiously in the absence of an overt acute phase syndrome, and highlights the need for keen observation of the patient in the hope of preventing permanent deficits.

Adult↗
PubMed2002

The influence of diabetes mellitus and hyperglycaemia on stroke incidence and outcome.

Diabetes mellitus is a complex metabolic syndrome with significant effects on the systemic and cerebral vasculature. The incidence and severity of ischaemic stroke are increased by the presence of diabetes, and outcome from stroke is poorer. More than one third of patients admitted with acute stroke are hyperglycaemic at presentation. Reasons for the altered prognosis in diabetes associated stroke are multifactorial. A direct influence of hyperglycaemia at the time of ischaemia is likely to be important. The use of novel methods to delineate stroke topography and pathophysiology such as MR spectroscopy, diffusion and perfusion weighted MRI appear helpful in delineating the effects of hyperglycaemia on stroke pathophysiology. Randomised clinical trials to determine optimal management for patients with hyperglycaemia following stroke are ongoing. Such trials will determine if aggressive control of acute hyperglycaemia following stroke has similar benefits to that observed following acute myocardial infarction. Clinicians responsible for stroke patients should be aware of the importance of adequate glycaemic control in both primary and secondary prevention of stroke.

Diabetes Mellitus↗
PubMed2002

Examining the lacunar hypothesis with diffusion and perfusion magnetic resonance imaging.

BACKGROUND: The clinical diagnosis of subcortical cerebral infarction is inaccurate for lesion location and pathogenesis. Clinically suspected small perforating artery occlusions may be embolic infarcts, with important implications for investigation and treatment. New MRI techniques may allow more accurate determination of the stroke mechanism soon after admission. METHODS: In a prospective series of 106 patients evaluated with acute diffusion-weighted MRI (DWI) and perfusion-weighted MRI (PWI) within 24 hours of stroke, we enrolled 19 with a lacunar syndrome. On the basis of the topography, DWI and PWI findings, and outcome T2 MRI, we determined whether the mechanism of infarction was single perforating vessel occlusion or large artery embolism. RESULTS: Thirteen patients had pure motor stroke, 2 had ataxic hemiparesis, and 4 had sensorimotor stroke. Six patients had lacunes on MRI, none with PWI lesions. Four patients had subcortical and distal cortical infarcts on DWI. Nine had solitary restricted striatocapsular infarcts. Seven of these 9 had PWI studies, 5 with PWI lesions. The presence of a PWI lesion reliably differentiated striatocapsular from lacunar infarction for solitary small subcortical infarcts (P=0.03). CONCLUSION: DWI and PWI altered the final diagnosis of infarct pathogenesis from small perforating artery occlusion to large artery embolism in 13 of 19 patients presenting with lacunar syndromes. Lacunes cannot be reliably diagnosed on clinical grounds.

Aged↗
PubMedDate not supplied

Mathematical determination of external defibrillators needed at mass gatherings.

OBJECTIVE: To develop a mathematical formula that assists in determining the number of automated external defibrillators (AEDs) needed at sites of mass gatherings. METHODS: Twenty (10 male, 10 female) healthy volunteers (equally divided between age groups 21-30 and 31-40 years) responded to mock cardiac arrests in a sports stadium. Seven different first-responder scenarios were simulated (ascending and descending three separate stairway slopes (22 degrees, 39 degrees, and 69 degrees ), as well as a response across a horizontal (0 degrees ) surface. To assess the impact of spectator congestion, the same volunteers conducted each scenario in an empty and full stadium. The quantitative relationship between time and distance was then plotted for each situation. Using the quantitative relationship, the area a first responder can cover in a specified time was calculated. RESULTS: The formula for the total number of AEDs needed in a stadium (or other mass gathering site) can be expressed as follows: Total AEDs=[A(1)/(Ds(1)xDh(1))]+[A(2)/(Ds(2)xDh(2))]+[A(3)/(Ds(3)xDh(3))] where A(1), A(2), and A(3) represent the total areas of a stadium with a slight, moderate, or steep stairway slope, respectively; Ds(1), Ds(2), and Ds(3) represent the stairway distance a first responder must ascend or descend for each slope; and Dh(1), Dh(2), and Dh(3) are the horizontal distances a responder can run in the time remaining. CONCLUSION: Given a medical director's targeted response times and goals, the optimal number of AEDs required at a mass gathering can be calculated using time versus distance relationships. Future studies should evaluate the impact of the mathematically derived optimal number of AEDs at mass gatherings.

Adult↗
PubMedDate not supplied

Salvaging the ischaemic penumbra: more than just reperfusion?

1. The ischaemic penumbra is defined as a moderately hypoperfused region that retains structural integrity but has lost function. In animal models of ischaemic stroke, this region is prone to recurrent anoxic depolarization and will become infarcted if reperfusion does not occur. In the macaque model, an ischaemic penumbra has been identified for up to 3 h after ischaemic stroke onset, whereas in selected human patients it may exist for up to 48 h. 2. Although most definitions of the ischaemic penumbra stress a time-brain volume concept, few incorporate the idea that selective and delayed neuronal injury plays an important role. Thus, in addition to necrotic cell death caused by acute injury, it is important to also consider delayed death mediated by caspase-dependent and -independent apoptotic pathways. 3. Salvage of penumbral tissue is possible if reperfusion (e.g. after thrombolysis) occurs. However, neurons within this salvaged region may be still at risk of further delayed neuronal injury. 4. In the present review, we aim to revisit the concept of the ischaemic penumbra and explore the role of selective and delayed neuronal injury in enlargement of the volume of infarction, as well as pathogenic mechanisms of white matter ischaemia. Both animal and human models of cerebral ischaemia imaged using magnetic resonance and positron emission tomography techniques will be discussed.

Animals↗
PubMedDate not supplied

Predictors of stroke during 9-1-1 calls: opportunities for improving EMS response.

OBJECTIVE: Only 31%-52% of stroke calls are accurately identified by 9-1-1 dispatchers according to prior studies. Recognizing the time-dependent nature of acute stroke, better identification of stroke patients at the time of their 9-1-1 calls may allow an improved prehospital response. We sought to identify any words/phrases that 9-1-1 dispatchers could use to identify more stroke calls. METHODS: Potential stroke calls were identified from emergency medical services run sheets, and the discharge diagnosis for each of these patients was obtained. The emergency medical services tapes were independently reviewed by two listeners who were blinded to the final diagnosis. Words/phrases previously associated with 9-1-1 stroke calls mentioned by the caller were recorded. Other pertinent words/phrases were also recorded. Using the final diagnosis of stroke as the gold standard, the sensitivity, specificity, and positive likelihood ratio of each word and phrase were calculated. Cohen's kappa was calculated to assess interrater agreement. Data were collected for runs from October 2003 to July 2004. RESULTS: A total of 176 tapes were reviewed (40 strokes, 136 nonstrokes). The presence of at least one of four criteria predicted 80% of all stroke calls: the word "stroke," facial droop, weakness/fall, and impaired communication. All criterion elements had very good interrater agreement (kappa > 0.7). The word "stroke" was highly predictive of actual stroke (positive likelihood ratio, 2.27). CONCLUSIONS: The majority of stroke patients in this study could be identified by 9-1-1 dispatchers if the caller reported any one of the following four complaints: stroke, facial droop, weakness/fall, or impaired communication.

Cohort Studies↗
PubMedDate not supplied

Laying the cornerstone: an employee-driven customer service program.

In the 21st-century healthcare environment, customer service remains critical to the fiscal viability of healthcare organizations. Continued competition for patients and diminishing reimbursements have necessitated the establishment of customer service programs to attract patients and retain outstanding employees. These programs should increase quality experiences for both internal customers (employees) and external customers (patients). This article describes a unique employee-driven customer service initiative titled Serving Together Achieving Results. Obstacles to implementing a customer service program in a multifaceted academic setting are highlighted, and the use of a novel tool, Q technique, to prioritize employee feedback is discussed.

Consumer Behavior↗