The empirical validity of straight-line responses on a clinical evaluation form.

PURPOSE: Many preceptors fill out students' clerkship-performance forms with all items marked with the maximum value. Because items are usually designed to measure somewhat specific behaviors, the authors questioned the validity of straight-line five (SL5) responses, and conducted an empirical validity study to investigate the measurement properties of these SL5 forms. METHOD: In 1999-00 the authors undertook a correlation study and a generalizability study to assess the measurement characteristics of the SL5 forms. For the correlation study, they calculated mean scores for each of 168 students across forms, excluding the SL5 forms, then correlated this mean with the proportion of straight-line forms the student received. They conducted a generalizability analysis with and without the straight-line forms to determine the impact on score reliability. RESULTS: The proportion of SL5 forms was significantly correlated (r =.48, p <.0001) with the mean student score. Inclusion of the SL5 forms did not negatively affect the reliability of the mean score. CONCLUSION: The SL5 forms appear to be valid ratings of students' performances. An informal comparison of the comments on SL5 forms and those not displaying this format supported this conclusion.     

Cellular mechanisms of orexin actions on paraventricular nucleus neurones in rat hypothalamus

Using whole-cell patch clamp techniques we have examined the cellular mechanisms underlying the effects of orexin A (OX-A) on electrophysiologically identified magnocellular and parvocellular neurones in the rat hypothalamic paraventricular nucleus (PVN). The majority of magnocellular neurones (67 %) showed concentration-dependent, reversible depolarizations in response to OX-A. These effects were abolished in tetrodotoxin (TTX), suggesting them to be indirect effects on this population of neurones. OX-A also caused increases in excitatory postsynaptic current (EPSC) frequency and amplitude in magnocellular neurones. The former effects were again blocked in TTX while increases in mini-EPSC amplitude remained. Depolarizing effects of OX-A on magnocellular neurones were also found to be abolished by kynurenic acid, supporting the conclusion that these effects were the result of activation of a glutamate interneurone. Parvocellular neurones (73 % of those tested) also showed concentration-dependent, reversible depolarizations in response to OX-A. In contrast to magnocellular neurones, these effects were maintained in TTX, indicating direct effects of OX-A on this population of neurones. Voltage clamp analysis using slow voltage ramps demonstrated that OX-A enhanced a non-selective cationic conductance with a reversal potential of -40 mV in parvocellular neurones, effects which probably explain the depolarizing effects of this peptide in this subpopulation of PVN neurones. These studies have identified separate cellular mechanisms through which OX-A influences the excitability of magnocellular and parvocellular PVN neurones.     

Environmental conditions for treatment of burned patients by the exposure method.

The influence of the thermal environment on evaporation and heat loss from patients with severe burns treated by exposure has been studied. Simple heat transfer equations can be used to predict changes resulting from alterations in environmental conditions and these have been tested using phantoms. The method relies upon the derivation of surface diffusion resistances to describe the moisture properties of burn wounds. Clinical measurements revealed wide variations in evaporation rates and diffusion resistances for different wounds. Evaporation rates changed by less than 30 per cent during the first 5-6 days following injury, after which evaporation from partial skin thickness wounds gradually fell whereas that from full skin thickness wounds tended to remain higher. Raising ambient temperature can compensate for increased evaporation heat losses. Patients can be treated at ambient temperatures of 32-35 degrees C in the intensive care room with a specially designed airflow system. However, raising the temperatures of standard wards with no special airflow or temperature control facilities often caused patients to sweat, further increasing heat loss.     

Deliberate self-poisoning with dapsoneA case report and summary of relevant pharmacology and treatment

We report the case of a 14-year-old girl who deliberately ingested 8–9 g of dapsone and presented with severe methaemoglobinaemia and altered mental status. Prompt treatment with repeated doses of methylene blue and organ support brought about control of the methaemoglobinaemia and averted organ failure.     

Hemodynamic consequences of right ventricular isolation: the contribution of the right ventricular free wall to cardiac performance

Surgical isolation of the right ventricular free wall was performed in 10 dogs to evaluate both the hemodynamic effects of the procedure and the postoperative contribution of right ventricular free wall contraction to overall cardiac performance. Following the procedure, there was no significant differences in peak right ventricular systolic pressure, right atrial pressure, right ventricular stroke volume, or cardiac index. Cardiac index remained at preoperative levels over a wide range of filling pressures. However, there was a significant decrease in right ventricular stroke work (6.0 +/- 1.3 gm-m/m2 to 5.1 +/- 0.5 gm-m/m2; p less than 0.05). Pacing the isolated right ventricular free wall resulted in marked hemodynamic improvement compared with an electrically silent right ventricular free wall. Cardiac index increased from 1.7 +/- 0.2 L/min/m2 to 2.6 +/- 0.2 L/min/m2 (p less than 0.0005), and right ventricular stroke work went from 3.0 +/- 0.6 gm-m/m2 to 6.4 +/- 0.9 gm-m/m2 (p less than 0.0005). Right ventricular performance was also significantly related to the timing of right ventricular free wall contraction. Thus, the right ventricular free wall played an important role in the maintenance of normal cardiac hemodynamics.     

Sequential metabolic studies of pancreas allograft function in type 1 diabetic recipients.

We have previously shown that the loss of acute first phase insulin secretion precedes pancreas allograft rejection and development of glucose intolerance in Type 1 diabetic patients. In order to examine whether there is a progressive loss of phases of insulin secretion and beta-cell function in technically successful pancreas transplants during the first year, we measured glucose, insulin, and C-peptide responses to physiological (mixed meal) and pharmacological (IV glucose and IV glucagon) stimulation in 27 glucose-tolerant, insulin-independent allograft recipients at 3, 6, and 12 months. Mean +/- SE fasting serum glucose levels were normalized throughout the study period. Postprandial serum glucose profiles tended to increase by 12 months compared to 3 and 6 months, although peak glucose levels were not statistically different. Following pancreas transplantation, basal serum insulin levels were high at 3 months (163 +/- 17 pM), 6 months (165 +/- 22 pM), and 12 months (248 +/- 54 pM, p = NS) in the Type 1 diabetic pancreas allograft recipients when compared to normal (25 +/- 3 pM). We observed slight elevations in postprandial insulin and C-peptide profiles at 12 months compared to 3 and 6 months. Following IV glucose and glucagon stimulation, serum insulin and C-peptide levels as well as phases of insulin release did not differ over the 12-month study period. Similarly, the glucose decay constant (KG) was nearly identical at 3, 6, and 12 months. In summary, 1 year following successful whole cadaveric, heterotopic pancreas transplantation in Type 1 diabetic recipients, fasting serum glucose remains normalized, while postprandial glucose tends to rise.(ABSTRACT TRUNCATED AT 250 WORDS)