ABSTRACT
The effects of two diuretics (hydrochlorothiazide and furosemide) on arterial blood pressure (BP) and electrolytes in 80 Nigerians (40 newly diagnosed untreated hypertensives and 40 sex-matched normotensives) aged between 32 and 80 years, were investigated. The objectives of this study were to assess baseline BPs, serum and urine electrolytes as well as creatinine clearance and then determine the effects of the two drugs on the above outcome measures, comparing data in normotensives with hypertensives.
A questionnaire was used to obtain participants’ demographic data and history of hypertension. Each subject gave his/her informed consent and Ethical Committee approval was obtained before they were all investigated on outpatient basis. A stadiometer was used to determine height and a beam balance was used to measure weight. In both normotensives and hypertensives; BPs were measured with a standard mercury sphygmomanometer. Mean Arterial Pressure (MAP) was calculated using the formula: MAP = Diastolic BP + 1/3 Pulse Pressure. Serum from 10mls of blood from each subject was used to determine serum electrolytes (sodium (Na+), potassium (K+), chloride (Cl-) using ion selective electrolyte analyzer (Biolyte 2000) and serum creatinine using Jaffe’s method. A 24 hour urine collection from each participant was measured and 10mls was used to determine urinary electrolytes (Biolyte 2000) and urinary creatinine (Jaffe’s method). Creatinine clearance was calculated from the 24 hour urine volume, serum and urinary creatinine. After noting the baseline values, the normotensives and hypertensives were both divided into two subgroups of 20. One subgroup in both control and hypertensives was given hydrochlorothiazide 25mg tablet daily for 21 days and the other was administered furosemide 40mg tablet daily for the same period. The participants collected 3 successive 24 hour urine samples on days 7, 14, and 21 and on each day the urine volume and BP were measured; blood samples were taken and analysed as usual for electrolytes and creatinine.
It was observed that baseline as well as treatment serum and urine Na+ and Cl- were significantly higher in hypertensives than normotensives (p < 0.0001). The baseline serum K+ was significantly lower in hypertensives than normotensives (p < 0.0006) and it was negatively correlated with MAP (r = -3481, p < 0.0277. Urinary K+ loss was higher in hypertensives (p < 0.0001). Baseline urine volume was higher in hypertensives than normotensives (p < 0.0006) and during treatment with both drugs diuresis, which was maximal on day 7 with furosemide and on day 14 with hydrochlorothiazide, was more profound in hypertensives (p < 0.0001). There was a positive correlation between urine volume and urinary Na+ in hypertensives (r = 0.3490, p < 0.027) and in controls (r = 0.5099, p<0.0008). The reduction in MAP by both drugs was more significant in hypertensives than normotensives (p < 0.0001); and on day 14, serum Na+ was positively correlated with MAP (r = 0.3490, p < 0.0273 in hypertensives; r = 0.5099, p < 0.0008 in controls). There was no significant difference in baseline and treatment creatinine clearance between hypertensives and controls. The study supports the compelling evidence that electrolytes are implicated in the pathophysiology of essential hypertension and indicates that salt restriction and high K+ diet are important in the management of the condition; and also confirms that the two diuretics are effective as monotherapy in Nigerians, especially the elderly. The suggestion of impaired renal ability to excrete Na+ in hypertensive Africans is not supported by the study.
