Renal excretion of fluid, electrolytes and hydrogen ions before and during diamox administration in healthy Nigerians

Abstract

Twenty-four urine specimens of eleven healthy Nigerians taken during the cool rainy season, were examined before and during diamox (acetazolamide) administration. Mean control volume-output was 1.4 litres containing 109.5 mEq Na + , 46.6 mEq K * and 120 mEq CI- ions. Total renal acid excretion was 36-82 partitioned as 14-72 mEq titratable buffer-acid and 22.1 mEq ammonia. During diamox intake, volume-output increased to 2.56 litres with N a + and K * contents of 222-4 and 107 mEq respectively, whilst CI¬- ions, fell to 2-6 mEq. Daily renal acid excretion was reduced by 25% and titratable buffer acid was absent in most samples but ammonia excretion showed a wide scatter with a range of 6.5-60.8 mEq. The probable explanations for the lower potassium and total acid excretions during the control period as well as the pattern of ammonia excretion during diamox therapy are discussed. The pattern of fluid and electrolyte excretion of man in the tropics of necessity differs from that in temperate environs, one major difference being greatly increased losses of fluid and electrolyte due to increased sweat rate. Even in the absence of overt sweating, at ambient temperatures lower than 30"C or 86'F, insensible fluid losses via pulmonary and cutaneous channels may account for as much as 1:71 in the tropics as compared to 1 1 in temperate zones (Tinckler, 1966; Elebute, 1969). However, no electrolytes arc lost with insensible perspiration which is a physical process, essentially beyond physiologic control and governed mainly by changes in ambient temperature and relative humidity. The kidney as the chief custodian of the constancy of the milleur interne, ensures that the volume and composition of urine normally represent what needs to be extracted from this internal environment to keep its composition constant irrespective of obligatory extra-renal losses. Therefore, the characteristics of normal urine vary with dietary habit and external environmental factors such as temperature and relative humidity. Yet in tropical clinical practice, fluid and electrolyte therapy is usually based on figures obtained in temperate environments. Awareness of the attendant dangers associated with this practice has led a few workers in this environment to try and fill the gap. This present study was carried out in Lagos, which for most part of the year is hot and humid. In order to minimize the effect of climate-induced sweating, this investigation was carried out during the coolest part of the year, in the months of June-September when ambient temperature ranged between 70 and 84 F and the relative humidity was between 80 and 95%. This paper is therefore designed to examine renal handling of fluid, electrolytes and hydrogen ions under these environmental conditions and to evaluate the effects of administration of acetazolamide, a carbonic anhydrase inhibitor, on the characteristics of normal urine