Blood Pressure Evaluation among Older Living Kidney Donors

With more patients reaching end-stage renal disease, the demand for living kidney donation is increasing rapidly. Many potential donors are now in older age groups. The effects of increasing BP with age and the measurement criteria for hypertension in this group are not well defined. A total of 238 potential donors between 18 and 72 yr of age were prospec- tively studied, with a comparison of "clinic" BP values mea- sured in the outpatient clinic with an oscillometric recorder (Dinamap; Critikon), ambulatory BP monitoring (ABPM) find- ings, and standardized BP values determined by nurses using American Heart Association criteria. Renal function was eval- uated on the basis of iothalamate clearance (GFR) and urinary protein and microalbumin excretion. Ninety-six percent of subjects were Caucasian. All subjects exhibited normal GFR and urinary protein excretion. Three age groups were defined (group I, 35 yr, n 64; group II, 36 to 49 yr, n 109; group III, 50 yr, n 65). BP increased with age, as determined with all methods. Subjects 50 yr of age exhibited the highest clinic readings (145 2/83 1 mmHg, compared with 129 2/76 1 mmHg for group I, P 0.01). Awake ABPM and nurse-determined BP measurements were lower than clinic readings, including those for group III (131 2/80 1 mmHg, compared with 145 2/83 1 mmHg in the clinic, P 0.001). With the use of systolic BP values of 140 mmHg and/or diastolic BP values of 90 mmHg, 36.7% of subjects were initially considered hypertensive; this proportion de- creased to 11% overall with awake ABPM findings (135/85 mmHg). Measurement variability (SD in ABPM) and the ef- fects of misclassification were greatest for donors 50 yr of age. Multivariate regression indicated that GFR of both donors and recipients decreased with age, but regression identified no independent effect of BP. Recipient outcomes for up to 2 yr were equally good for donor kidneys considered normotensive or hypertensive on the basis of clinic BP measurements. These data indicate that higher arterial BP with age can lead to misclassification of many older living kidney donors. Sixty- two subjects with excellent kidney function were misclassified as hypertensive with clinic oscillometric measurements alone. Detailed evaluations of ABPM findings, GFR, and urinary protein levels are warranted for Caucasian subjects with high clinic BP readings who are otherwise suitable potential donors.