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Biomedical subjects

R L Kirsner

Publications and source records attributed to R L Kirsner.

11 recordsLinked to original sources
PubMed1992

Left ventricular energy in mitral regurgitation: a preliminary report.

Energy exchange based on Newtonian principles is the most appropriate way to express the function of any pump--including the heart. Using information obtained at cardiac catheterisation, we have measured the total work energy (ET) of the left ventricle (LV) (mean 1.63 F) in patients with severe mitral regurgitation (mean regurgitant fraction 0.66). ET was approximately 84% above normal. Of the regurgitant energy (RE) (mean 0.95 F), on average , 3/4 (73.6%) was kinetic (KE) and 1/4 (23.4%) potential (PE). Both components represent wasted LV energy: the kinetic energy associated with turbulence lost as heat, the potential energy responsible for a rise in Left Atrial (LA) pressure. The amount of PE as a percentage of total regurgitant energy (RE) varied considerably from one patient to another (10.5% to 54.4%). Hence, colour flow mapping which detects only KE of turbulent jet flow must underestimate LV energy loss and, because of patient to patient variation, cannot consistently reflect severity of regurgitation. Measurements of PE correlate well with wedge P-wave height. Corresponding non-invasive estimates were made using sphygmodynamometer-calibrated indirect carotid pulse tracings and echocardiographic measurements. These were not significantly different from the invasive measurements. Unfortunately, the calculation of PE is indirect and involves subtraction, so that measurements for individual patients were not accurate enough for clinical use. Part of the non-invasive calculation involved an estimate of left atrial pressure based on the blood pressure measurement and Doppler velocity of regurgitation; this should be a useful measurement in itself.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1991

Validation and evaluation of test for sympathetic cholinergic function in diabetes mellitus.

Skin potential response (SPR), an electrodermal measure of sudomotor nerve function, was shown in this study to examine specifically sympathetic cholinergic fibers by abolition of the response during atropine infusion but not during propranolol infusion. The difference between responses in the left and right arms (SPR-D) was used to assess autonomic nerve function in 136 patients with diabetes and 52 control subjects. In 82% of the diabetic population (112 of 136), SPR-D was greater than 2SD above the mean control response compared with 42% (57 of 137) greater than 2SD below the mean control age-related value for a standard autonomic test predominantly of parasympathetic function, the R-R interval variation with breathing. Of 15 patients with clinical diabetic autonomic neuropathy, SPR wave forms were bizarre or absent in 5 patients compared with 18 of 121 patients' without clinical autonomic neuropathy (chi 2 = 3.5, P = 0.062). Measurement of SPR-D provides an easily determined measure of sympathetic cholinergic nerve function and may be a useful component of a group of tests for autonomic nerve function in diabetes.

Adult↗
PubMed1990

Thin basement membranes in minimally abnormal glomeruli.

The light microscopic, immunofluorescence, and electron microscopic appearances of renal biopsy specimens were reviewed and correlated with the clinical and laboratory findings in 61 patients in whom the findings were initially considered to be either normal or to show only minor non-specific abnormalities. In all cases this reassessment included quantitative measurement of glomerular basement membrane thickness by an orthogonal intercept technique. On the basis of the indication for biopsy, patients were classified into three groups: those with haematuria (group I, n = 41); those with a minor degree of proteinuria (group II, n = 16); and those without any urinary abnormality but in whom possible renal disease as a result of systemic disease was suspected (group III, n = 6). About half of the patients with haematuria had significantly thinner glomerular basement membranes than those in the other two groups, irrespective of the variable selected for assessment, and in three this was confirmed in follow up biopsy specimens. Follow up for up to eight years showed that in patients either with or without thin basement membranes haematuria commonly persisted, but the long term outlook in all three groups was otherwise good and no patient developed impaired renal function.

Anthropometry↗
PubMed1986

Metabolic consequences of prolonged hyperinsulinemia in humans. Evidence for induction of insulin insensitivity.

Hyperinsulinemia is frequently associated with a variety of insulin-resistant states and has been implicated causally in the development of insulin resistance. This study examines the metabolic consequences of prolonged hyperinsulinemia in humans. Basally and 1 h after cessation of a 20-h infusion of insulin (0.5 mU X kg-1 X min-1, aimed at elevating plasma insulin levels to approximately 30 mU/L) or normal saline, subjects were assessed for glucose turnover with 3-[3H]glucose; insulin sensitivity, as measured by either the euglycemic glucose-clamp technique or the intravenous glucose tolerance test (IVGTT) minimal model method of Bergman; and monocyte insulin-receptor binding. Hepatic glucose production (Ra) was suppressed by greater than 95% during each euglycemic clamp and during the 20-h insulin infusion. After the insulin infusion, Ra and glucose utilization rate returned to the initial basal level within 1 h, as did insulin levels. At that time, insulin sensitivity was significantly decreased, as measured by the "insulin action" parameter during the 40- to 80-min phase of the clamp (0.049 +/- 0.003 vs. 0.035 +/- 0.007 min-1, P less than .05) and during the 80- to 120-min phase (0.047 +/- 0.005 vs. 0.039 +/- 0.007 min-1, .05 less than P less than .1).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1979

Assessment of sympathectomy--the skin potential response.

Objective assessment of the results of surgical sympathectomy and sympathetic block (both temporary and permanent) are not widely practised. This article comments briefly on the available methods, and describes the use of the abolition of the skin potential response (formerly known as the psychogalvanic reflex) to assess the abolition of sympathetic function. This method of assessment has proved useful in clinical practice.

Galvanic Skin Response↗
PubMedDate not supplied

An inexpensive r.m.s. ammeter for use with electrosurgical units.

A true r.m.s. reading rf ammeter utilizing low-cost integrated circuits has been developed for use in measurements of the power output and rf leakage of electrosurgical units. The meter is sufficiently accurate for most clinical applications without the drawbacks of the thermal ammeter.

Calibration↗