diatrizoate were studied. The dose employed (5 ml. 45% hypaque per kg body weight) is equal to twice the maximum recommended dosage for excretion.
Medical Research Society appear in which calibrations have been placed on records of velocity in human arteries determined transcutaneously by this method. This study critically examines the performance of one such instrument (Sophia) and reports the errors that have been found and that are important in clinical usage. The Schlieren technique was used to visualize the ultrasound beam. Its shape, width and volume from which information would be received at various angles of incidence of the beam with a vessel, were defined. Transmission of the beam,without apparent reflection occurred through a dog aortic wall. The system was calibrated in a flow rig which produced steady velocity with a flat velocity profile. The output voltage was linearly related to the flow velocity only up to 25 cmlsec, above which aliearity appeared so that the true velocity was grossly underestimated. The frequency response of the instrument tested with a sinusoidal flow velocity within the linear range showed that at 1 cycle/sec the amplitude response was down by 20% and the phase shift was 23"(transit time 43 ms); the reference comparison was with an electromagnetic flowmeter using a cannulating probe. These characteristics precluded the quantitation of pulsatile velocity patterns in arteries, even if the velocity profile was known to be flat. Can the mean forward velocity be determined in a human brachial artery? The angle of the probe and beam to the vessel could be defined to within 2'. Electronic and biological zeros coincided. The mean velocity fluctuated in a manner that could not have been physiological as the subject lay quietly with the arm outstretched. It is concluded that this type of instrumentation, though useful qualitatively, cannot be used at present for quantitative measurements in man. 7. THE URINARY EXCRETION OF THYROID
HORMONES VIVIANCHAN,G. M. BesseR and J. LANDON The Medical Professorial Unit and Department of Chemical Pathology, St Bartholomew's Hospital, London, E.C.l
Recently a saturation analysis technique for thyroxine (T4) and a radioimmunoassay for tri-iodothyronine (T3)have been applied, for the first time, to determine the concentration of these thyroid hormones in urine. Urinary T3 and T4 values are similar in both ambulant and hospitalized euthyroid subjects and in women who are pregnant or are receiving oral ovulation inhibitors. Distinct differences are found between these groups and patients with hypo- and hyperthyroidism. Serial 24 h urinary T4 levels over a period of 28 consecutive days were found to lie within relatively narrow limits in healthy, euthyroid men and show a transient increase during menstruation in women. A
1 3 ~
transient but marked increase in urinary T4 levels was observed during oestrogen withdrawal in all women receiving oral ovulation inhibitors and in all healthy euthyroid men given ethinyl oestradiol (20 pg/day) for 3 days. The rise was maximal within 1-3 days and levels had returned to normal within 6 days of oestrogen withdrawal. Urinary T4 excretion remained relatively constant throughout the day and decreased significantly during sleep in all euthyroid subjects not receiving oestrogens. Preliminary results indicate the probable value of urinary thyroid hormone assays in dynamic test procedures. Thus there was a marked and rapid increase in urinary T, excretion following the administration of thyrotrophin releasing hormone and of thyroid stimulating hormone to euthyroid subjects. The clinical value of assessing the suppression of urinary T3 during the oral administration of T4 is being investigated. 8. TOXICITY STUDIES ON EXCRETION UROGRAPHY IN EXPERIMENTAL RENAL FAILURE
I. F. MosereY, W.R. CATTELL and C. S. MCINTOGH, I. b R Y FRY Department of Nephrology. St Bartholomew's Hospital, London, E. C.1
Although excretion urography is of great diagnostic value in acute renal failure, doubts have been expressed regarding the safety of infusing high doses of contrast media into patients with severe renal damage. Using two wellestablished models of acute renal failure in the rat-the glycerol and the mercuric chloride models-the effects of the infusion of sodium diatrizoate were studied. The dose employed (5 ml 45% hypaque per kg body weight) is equal to twice the maximum recommended dosage for excretion urography in man. To exclude any adverse effect due to the sodium load infused or to the anaesthetic required for the intravenous infusion, control studies were carried out on anaesthetized, non-infused animals and in animals given an equimolar saline injection. The results clearly show that the infusion of sodium diatrizoate does not increase the mortality in experimental acute renal failure. 9. LONG-TERM OXYGEN THERAPY FOR COR PULMONALE
P. B. ANDERSON,R. M. CAYTON, P. J. HOLTand P. HOWARD Department of Medicine, University of Shefield, l 3 e Royal Hospital, Shefield
The prognosis for recurrent pulmonary heart failure associated with obstructive airways disease is poor (mean survival 43 months from the first attack; Ude
