Nighttime blood pressure is the blood pressure

Role of circadian rhythms in potassium homeostasis

It has been known for decades that urinary potassium excretion varies with a circadian pattern. In this review, we consider the historical evidence for this phenomenon and present an overview of recent developments in the field. Extensive evidence from the latter part of the past century clearly shows that circadian potassium excretion does not depend on endogenous aldosterone. Of note is the recent discovery that the expression of several renal potassium transporters varies with a circadian pattern that appears to be consistent with substantial clinical data regarding daily fluctuations in urinary potassium levels. We propose the circadian clock mechanism as a key regulator of renal potassium transporters, and consequently renal potassium excretion. Further investigation into the regulation mechanism of renal potassium transport by the circadian clock is warranted to increase our understanding of the clinical relevance of circadian rhythms to potassium homeostasis.

Ambulatory blood pressure monitoring: recent evidence and clinical pharmacy applications

Conventional office blood pressure readings are a well-established surrogate for the prediction of cardiovascular risk. It is assumed that these readings reflect an underlying average level of blood pressure exposure occurring in an individual over a period of time. But because blood pressure is not static, important additional prognostic information about the diurnal blood pressure profile, including within-day and between-day variability, is not easily ascertained from conventional measurements. Ambulatory blood pressure monitoring provides a more thorough depiction of the underlying blood pressure level and predicts cardiovascular risk more robustly than do conventional blood pressure measurements. Although the technology has been available for more than 30 years, there has been an expansion of the research base in the past decade supporting its role in the evaluation and management of patients with hypertension and as an important surrogate in research trials. This review summarizes recent evidence supporting the predictive ability of ambulatory blood pressure monitoring and briefly highlights opportunities for clinical pharmacists to adopt this important clinical and research tool.

The circadian clock in the kidney

Circadian variations in renal function were first described in the 19th century, and GFR, renal blood flow, urine production, and electrolyte excretion exhibit daily oscillations. These clinical observations are well established, but the underlying mechanisms that govern circadian fluctuations in kidney are not fully understood. Here we provide a brief overview of the machinery governing the circadian clock and examine the clinical and molecular evidence supporting a critical role for circadian rhythm in the kidney. There is a connection between BP oscillation and renal disease that supports the use of chronotherapy in the treatment of hypertension or correction of nondipping BP. Such studies support a developing model of clock controlled sodium and water transport in renal epithelial cells. Recent advances in identifying novel clock-controlled genes using rodent and cellular models also shed light on the molecular mechanisms by which the circadian clock controls renal function; however, the field is new and much more work remains.

Pharmacist-physician comanagement of hypertension and reduction in 24-hour ambulatory blood pressures

BACKGROUND

Pharmacist-physician comanagement of hypertension has been shown to improve office blood pressures (BPs). We sought to describe the effect of such a model on 24-hour ambulatory BPs.

METHODS

We performed a prospective, cluster-randomized, controlled clinical trial, enrolling 179 patients with uncontrolled hypertension from 5 primary care clinics in Iowa City, Iowa. Patients were randomized by clinic to receive pharmacist-physician collaborative management of hypertension (intervention) or usual care (control) for a 9-month period. In the intervention group, pharmacists helped patients to identify barriers to BP control, counseled on lifestyle and dietary modifications, and adjusted antihypertensive therapy in collaboration with the patients' primary care providers. Patients were seen by pharmacists a minimum of every 2 months. Ambulatory BP was measured at baseline and at study end.

RESULTS

Baseline and end-of-study ambulatory BP profiles were evaluated for 175 patients. Mean (SD) ambulatory systolic BPs (SBPs), reported in millimeters of mercury, were reduced more in the intervention group than in the control group: daytime change in (Δ) SBP, 15.2 (11.5) vs 5.5 (13.5) (P < .001); nighttime ΔSBP, 12.2 (14.8) vs 3.4 (13.3) (P < .001); and 24-hour ΔSBP, 14.1 (11.3) vs 5.5 (12.5) (P < .001). More patients in the intervention group than in the control group had their BP controlled at the end of the study (75.0% vs 50.7%) (P < .001), as defined by overall 24-hour ambulatory BP monitoring.

CONCLUSION

Pharmacist-physician collaborative management of hypertension achieved consistent and significantly greater reduction in 24-hour BP and a high rate of BP control. Trial Registration  clinicaltrials.gov Identifier: NCT00201045.

Indication-specific 6-h systolic blood pressure thresholds can approximate 24-h determination of blood pressure control

Ambulatory blood pressure monitoring (ABPM) is an accurate method for evaluating hypertension, yet its use in clinical practice may be limited by availability, cost, and patient inconvenience. The objective of this study was to investigate the ability of a 6-hour ABPM window to predict blood pressure control, based on that of the full 24-hour ABPM session across several clinical indications in a cohort of 486 patients referred for ABPM. Sensitivities and specificities of the 6-hour systolic blood pressure mean to accurately classify patients as hypertensive were determined using a fixed reference point of 130 mmHg for the 24-hour mean. For four common indications in which ABPM was ordered, prediction tables were constructed varying the thresholds for the 6-hour mean to find the optimal value that best predicted the 24-hour hypertensive status as determined from the full 24-hour interval. Using a threshold of 137 mmHg for the indications of borderline hypertension, evaluation of current antihypertensive regimen and suspected white-coat hypertension, sensitivity and specificity ranged from 0.83–0.88 and 0.80–0.88, respectively, for the ability of 6-hour ABPM to correctly categorize hypertensive status. Using 133 mmHg as the threshold for treatment resistance resulted in a sensitivity and specificity of 0.93 and 0.83, respectively. We conclude that a shortened ABPM session of 6 hours can be used to accurately classify blood pressure as controlled or not, based on the results of a 24-hour session. The optimal 6-hour threshold for comparison depends upon indication for referral.