Blood pressure and serum potassium levels in hypertensive patients receiving or not receiving antihypertensive treatment.

Objective: Serum potassium has a fundamental role in blood pressure (BP) regulation, and there is evidence highlighting the importance of potassium homeostasis in hypertension. The aim of this study was to determine the relationship between serum potassium levels and office BP in untreated essential hypertensives and the effect of antihypertensive medication on serum potassium levels.

Setting And Participants: In a retrospective analysis, we collected data for consecutive patients first visiting our Hypertension Clinic from 1999-2004. From this population, we first selected patients who were not taking any antihypertensive medication. Patients who had conditions that could affect potassium metabolism, such as history of arrhythmias treated with digitalis, diabetes mellitus under insulin treatment, and hypo- and hyperthyroidism, were excluded from the study. From the remaining patients, those who had impaired renal function (serum creatinine > or = 1.6 mg/dL for men and > or = 1.4 mg/dl for women) and patients with secondary forms of hypertension were also excluded. The final population consisted of 817 subjects. Multivariate linear regression analysis was applied, and models were created associating serum potassium with systolic BP, diastolic BP, mean BP, or pulse pressure. The population for the second part of the study consisted of patients first visiting our Hypertension Clinic who were on one antihypertensive agent. This second group included 757 patients, 218 of whom were on beta-blockers, 42 on diuretics, 187 on angiotensin-converting enzyme (ACE) inhibitors, 287 on calcium channel blockers (CCBs), and 28 on angiotensin receptor blockers (ARBs).

Results: After adjusting for age, gender, and body mass index, significant negative correlations were found between serum potassium levels and systolic BP (R = -0.093, p = 0.007), diastolic BP (R = -0.078, p = 0.03), mean BP (R = -0.122, p = 0.002), and pulse pressure (R = -0.071, p = 0.044). The levels of potassium were found to be significantly lower among patients receiving diuretics than those receiving one of the other four drug categories of antihypertensive (p < 0.05 for beta-blockers, ACE inhibitors, and CCBs; p < 0.001 for ARBs). In addition, hypokalemia was found to be significantly more prevalent in the group using diuretics than the other groups.

Conclusions: The observed reverse relation between serum potassium and BP supports a close pathophysiological connection between serum potassium and essential hypertension. Moreover, diuretic therapy is a significant cause of hypokalemia and requires systematic monitoring.