Continuous servo-controlled replacement of urinary sodium loss in conscious dogs.
A method for continuous servo-controlled infusion of sodium chloride to dogs is reported. The servo system consists of a sodium-sensitive electrode, a modified commercial flowmeter, a thermistor, a control unit, and a pump. Based on analog inputs from electrode, flowmeter, and thermistor, the control unit generates appropriate numbers of voltage steps, which drive the pump infusing a concentrated solution of sodium chloride. Inputs from the thermistor are necessary to correct for the influence of fluctuations in urine temperature. The sodium servo system has been tested together with a weight servo mechanism in conscious water-diuretic dogs. Furosemide (1 microgram.kg-1.min-1) was infused to change the rate of sodium excretion by a factor of 17 from 3 +/- 1 to 50 +/- 15 mumols/min. Within this range, the apparatus replaced the sodium losses with great accuracy. From seven experiments the average system response in micromoles per minute (NaIn) measured in 10-min periods against mean renal excretion of sodium (NaEx) was NaIn = 0.98.NaEx - 1.37. The servo system provides a tool for accurate maintenance of body sodium irrespective of large changes in the rate of sodium excretion.
Andersen
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SE
Department of Medical Physiology C, Panum Institute, University of Copenhagen, Denmark.
Bie
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D000818:Animals; D004231:Diuresis / Q000187:drug effects; D004285:Dogs; D005260:Female; D005665:Furosemide / Q000494:pharmacology; D009318:Natriuresis / Q000187:drug effects; D010827:Physiology / Q000295:instrumentation / Q000379:methods*; D011188:Potassium / Q000097:blood / Q000652:urine; D012044:Regression Analysis; D012964:Sodium / Q000008:administration & dosage* / Q000097:blood
D005665:Furosemide; D012964:Sodium; D011188:Potassium