Nocturnal but not Short Hours Quotidian Hemodialysis Requires an Elevated Dialysate Calcium Concentration FAYEZ AL-HEJAILI, CLAUDE KORTAS, ROSEMARY LEITCH, A. PAUL HEIDENHEIM, LAURIE CLEMENT, GIHAD NESRALLAH, and ROBERT M. LINDSAY Optimal Dialysis Research Unit, London Health Sciences Centre and The University of Western Ontario, London, Ontario, Canada. Abstract. Interest in quotidian (daily) hemodialysis (HD) is grow- ing. Some advocate short-hours high-efficiency daily HD (SDH) and others long-hours slow-flow nocturnal HD (NH) while the patient is asleep, both being used 5 to 7 d/week. The London Daily/Nocturnal Hemodialysis Study was the first attempt to obtain data of SDH and NH that may be compared with conven- tional thrice weekly HD (CH). This was a 4-yr observational study designed to enter and follow 40 patients: 10 receiving SDH, 10 receiving NH, and 20 receiving CH. The CH patients were cohort control subjects matched for each SDH and NH patient by age, gender, comorbidity, and original dialysis modality (in-center, home, self-care, or satellite HD). All SDH and NH treatments were at home. Data collection to December 2001 was analyzed. Then enrollment had been completed and all patients had been followed for 15 mo, eight SDH plus six NH for 18 mo, seven SDH plus six NH for 21 mo, and seven SDH and five NH for 24 mo. This report gives data on calcium and phosphorus metabolism in these patients. All patients were initially dialyzed against a 1.25-mmol/L calcium bath. Predialysis serum calcium levels be- came lower in NH versus SDH patients by the first month and at 9 mo were 2.67  0.25 mmol/L (M  SD) in SDH, 2.40  0.16 mmol/L in NH, and 2.52  0.21 mmol/L in CH (SDH versus NH, P = 0.038; SDH versus CH versus NH, NS). Predialysis phos- phorus levels were better controlled by NH than by SDH or CH, and with NH, all phosphate binders were discontinued. By 12 mo, a rise in bone alkaline phosphatase was seen in NH patients (but not in SDH or CH patients), which peaked at 15 to 18 mo (NH 191 IU/L  70; SDH 82  34; CH 80  36; P  0.002) and similarly with intact parathyroid hormone (iPTH) levels (NH 159 pmol/L  75; SDH 13.1  10; CH 18  18; P  0.00001). Because of these changes, the dialysate calcium concentration was increased to 1.75 mmol/L for the NH patients. Postdialysis cal- cium then rose to 2.57  0.21, and alkaline phosphatase and iPTH normalized completely by 21 mo. These observations prompted mass balance studies that showed that a 1.25-mmol/L calcium dialysate was associated with a mean net calcium loss of 2.1 mmol/h of dialysis time, whereas 1.75-mmol/L calcium dialysate provides a net gain of 3.7 mmol/h. In addition, the mass balance studies showed that phosphate removal by NH (43.5  20.7 mmol) was significantly (P  0.05) higher than by SHD (24.2  13.9 mmol) but not by CH (34.0  8.7 mmol) on a per-treatment basis. With the increased frequency of treatments provided by quotidian dialysis, the weekly phosphorus removal (261.2  124.2 mmol) by NH was significantly higher than by SDH (P = 0.014) and CH (P = 0.03). This allowed the discontinuation of P binders in the NH group, which in turn eliminated approx- imately 8 g elemental Ca/wk oral intake. This, together with a 4 g elemental Ca/wk dialysate loss induced by a 1.25- mmol/L Ca bath, explains the changes in Ca, alkaline phos- phatase, and iPTH seen in the NH patients. The SDH pa- tients have weekly dialysis times similar to CH and still require P binders and do not become Ca deficient using 1.25-mmol/L Ca dialysate. With NH but not SDH, an ele- vated dialysate Ca concentration is required. The interest in high-efficiency short-hours daily hemodialysis (SDH) and slow long-hours nocturnal hemodialysis (NH) has experienced a resurgence in recent years. The effects of these dialysis modalities on calcium and phosphorus metabolism have been described to some extent (1,2), but direct compari- sons between SDH and NH have not yet been made in this regard. Before the advent of calcium-based phosphorus bind- ers, patients were dialyzed against a 1.5- to 1.75-mmol/L calcium bath to prevent calcium depletion. With the wide- spread use of calcium-containing phosphorus binders, this practice changed, and a 1.25-mmol/L bath became the standard. In this article, we describe the effect of this latter bath calcium concentration on calcium balance in SDH and NH, as well as the influence of dialysate composition and dialysis time on net cal- cium shift and on intact parathyroid hormone (iPTH) levels. Materials and Methods The Daily/Nocturnal HD Study This was a 4-yr observational study to follow 40 patients: 10 receiving SDH, 10 receiving NH, and 20 receiving conventional thrice weekly hemodialysis (CH). The CH patients were cohort control Received January 31, 2002. Accepted May 20, 2003. Correspondence to Dr. Robert Lindsay, London Health Sciences Centre, 800 Commissioners Road East, London, Ontario, Canada, N6A 4G5. Phone: 519- 685-8349; Fax: 519-685-8395; E-mail: Robert.Lindsay@lhsc.on.ca 1046-6673/1409-2322 Journal of the American Society of Nephrology Copyright © 2003 by the American Society of Nephrology DOI: 10.1097/01.ASN.0000083044.42480.C1 J Am Soc Nephrol 14: 2322–2328, 2003