Biomedical subjects

R Calderwood

Publications and source records attributed to R Calderwood.

3 recordsLinked to original sources

PubMed2004

Ruptured abdominal aortic aneurysm. Is it possible to predict outcome?

AIM: Mortality after ruptured abdominal aortic aneurysm (rAAA) remains high. Hardman et al. suggested that the following factors predict perioperative death: age >76 years, loss of consciousness, ECG confirmed ischemia, creatinine over 180 micromol/l and hemoglobin below 9 g/dl. A score of 3 or more had 100% mortality. A retrospective study was performed to validate this and determine if modification is required. METHODS: Retrospective analysis of the 5 Hardman Index factors along with preoperative systolic blood pressure at presentation, after resuscitation and during surgery was performed. RESULTS: A total of 137 cases were reviewed with overall mortality of 56.2%. Of Hardman's criteria: age, ECG ischemic changes, creatinine and hemoglobin levels were significant in predicting outcome (p=0.0007, 0.0152, 0.0001 and 0.0213, respectively). Loss of consciousness was not significant (p=0.9054). Hardman scores of 0, 1, 2, 3, and 4 scored mortality percentages of 40.4%, 46.4%, 76.7%, 91.7% and 100%, respectively. Systolic blood pressure was significantly predictive at 100 mmHg and 120 mmHg on presentation (p=0.0008 and 0.0017, respectively) and 100 mmHg and 120 mmHg after resuscitation (p=0.0001 and 0.0510, respectively). A modified score replaced loss of consciousness with systolic blood pressure below 100 mmHg with scores of 0, 1, 2, 3, and 4 had mortality of 22.2%, 46.8%, 66.7%, 83.9% and 100%, respectively. CONCLUSION: Our data supports the effectiveness of the Hardman Index in predicting successful surgery. However loss of consciousness was not a significant predictor. We proposed review of predictive indices, but resources should be channelled into screening to prevent rAAA.

Aortic Aneurysm, Abdominal↗

PubMed2004

Screening men for aortic aneurysm.

AIM: Ruptured abdominal aortic aneurysm (rAAA) accounts for 10000 deaths annually in the UK. Deaths occur in the 6th and 7th decades with loss of potential years of life. Mortality rates of 5% to 8% are reported for elective AAA repair, but no significant improvement in emergency outcome, with community mortality remaining at 80% and operative mortality at 50%. Patients surviving have several years life expectancy, regardless of age, and good quality of life. The difference suggests that overall emergency mortality could be significantly reduced by earlier diagnosis with widespread screening of the at risk population. Previous studies suggest screening men over 65 years significantly reduces incidence of rupture and aneurysm related death. Patients with abdominal aortic aneurysm (AAA) have a high prevalence of coronary artery disease (CAD) and vice versa. There is mounting evidence that screening men for AAA reduces rAAA mortality, especially in high-risk groups. A limited screening study of CABG patients was introduced. METHODS: Patients on the waiting list for coronary artery bypass grafting (CABG) (n=118) had a single duplex scan of the abdominal aorta. Aortic diameter of >2.6 cm was considered abnormal. RESULTS: Eighteen AAAs were detected (15.3%), 5 required surgery, 13 underwent surveillance. Mean age at detection was 64.8 years with a range of ages between 60 and 72 years. CONCLUSION: Patients with symptomatic CAD have a high incidence of AAA, with significant risk of rupture in the perioperative period post-CABG. Screening should form part of the routine work-up for coronary revascularisation. Staged repair should be considered with AAA greater than 5.5 cm diameter.

Aged↗

PubMed1983

Resource allocation and the attentional demands of letter encoding.

The idea that familiar events can be encoded automatically has gained general acceptance in cognitive psychology since Posner and Boies (1971) first reported that reaction times to a secondary probe were not interfered with by letter encoding. More recently, Ogden, Martin, and Paap (1981) used a more valid control for estimating baseline probe performance and found secondary task interference, suggesting that letter encoding does require attentional resources. The present series of experiments began with the aim of evaluating Ogden et al's evidence against automaticity when the first letter was not terminated after a brief exposure, as was done in their study. In the first set of experiments we found evidence of encoding interference when the interval between the two letters was varied (50 to 1,000 msec), but this interference disappeared when there was a constant 1,000-msec interval between the letters. On the basis of these findings, we hypothesized that changes in the primary task (e.g., the exposure duration of the first letter or the interval between the two letters) may influence the momentary allocation of resources between the primary and secondary tasks. More specifically, we hypothesized that any momentary reduction in the resources demanded by the primary tasks results in a reallocation of resources to the secondary task, which in turn reduces the sensitivity of the secondary task to the demands of the primary task, that is, probe performance is moved into the data-limited region of processing (Norman & Bobrow, 1975). This idea was tested by reducing resource allocation to the probe task at the time of encoding by reducing the expectancy (i.e., the probability) of probes in the temporal proximity of the first letter. The results showed that this manipulation produced a large and significant increase in encoding interference. Moreover, when the intensity of the tone (probe) was decreased from 70 to 60 dB, the magnitude of encoding interference was further increased. In regard to the specific issue of automaticity, the findings suggest that encoding familiar events does require resources, which will result in secondary task interference given that the secondary task is in the resource-limited region of processing. More important, the findings suggest that the magnitude of secondary task interference is dependent on within-trial changes in resource allocation between the primary and secondary tasks. This possibility has general implications for dual-task methodology and the measurement of attentional demands.

Adult↗