Hypotension is the most common complication of outpatient hemodialysis sessions, with a reported prevalence of 4% to 31%, depending on which definition has been used and whether patients are symptomatic and nursing interventions were required. Dialysis centers which mix the dialysate in the dialysis machine have the opportunity to individualize the composition of the dialysate for patients. This permits a choice of dialysate sodium, potassium, calcium, magnesium, bicarbonate, acetate, and citrate concentrations and temperature. Studies have reported a higher intradialytic systolic blood pressure and fewer episodes of intradialytic hypotension when using a higher dialysate sodium, calcium, magnesium concentrations and lower temperature, but no clinical advantage for changing the potassium, bicarbonate, or citrate for acetate concentrations. The introduction of newer technology allowing real time measurements of plasma electrolyte concentrations will potentially allow changing the dialysate composition to reduce the risk of intradialytic hypotension without increasing the risk of positive electrolyte balances.

The osmolar gap increases with kidney failure. A number of equations have been proposed to calculate serum osmolality, allowing determination of the osmolar gap by comparison with measured osmolality. As glucose and icodextrin absorption can potentially interfere with the laboratory measurement of serum sodium, a key component in equations calculating osmolality, we reviewed the performance of 14 equations used to calculate serum osmolality compared to the measurement of serum osmolality in 144 patients with peritoneal dialysis (PD); 81 (56.3%) males, 76 (52.5%) diabetics, mean age of 64.4 ± 16.3 years, 115 (79.9%) prescribed icodextrin and 38 (26.4%) 22.7 g/L glucose dialysates. Measured serum osmolality was 311 (304–320) mosmo/kg (mmol/kg), whereas calculated osmolality for the 14 equations ranged from a median of 274 (269–284) mosmo/kg to 307 (300–316) mosmo/kg. Bland–Altman mean bias showed that measured serum osmolality was greater than the calculated osmolality ranging from 4.0 mosmo/kg to 36.2 mosmo/kg between the 14 equations, with wide 95% limits of agreement (LoA) ranging from −27.1 mosmo/kg to 19.4 mosmo/kg and from −58.5 mosmo/kg to −13.8 mosmo/kg. Only 2 of the 14 equations gave a mean osmolar gap of <10 mosmo/kg and showed no systematic bias, median serum osmolality of 307 (300–316) and 303 (298–312) mosmo/kg, Spearman ρ of 0.57, 0.62, both p < 0.001, respectively. Our study would suggest that only 2 of the 14 equations we compared with measured serum osmolality showed no systematic bias, but still had too great a bias to be useful in clinical practice. As such we propose a new equation to calculate serum osmolality in patients with PD.

Advanced glycosylation end‐products (AGEs) are reported to be a risk factor for cardiovascular mortality in hemodialysis (HD) patients. As serum AGEs can change with dialysis, measurement of AGEs deposited in the skin by autofluorescence (SAF) is now a recognized method of measuring AGEs. An arteriovenous fistula (AVF) is the preferred way to access blood in HD patients, and as the creation of an AVF changes blood flow distribution in the arm, we wished to determine whether this affected SAF deposition in the skin. SAF was measured using the AGE reader, which directs ultraviolet light at an intensity range of 300‐420 nm (peak 370 nm) in the arms of HD patients dialyzing with an AVF. We measured SAF in 267 patients, 60.3% male, 46.1% diabetic, median duration of dialysis 34.7 (15.1‐64.2) months with AVF. The median SAF was lower in the AVF arm (median 3.4 (2.9‐4.2) vs. 3.7 (3.2‐4.5) AU, P < .001), and for the 160 patients with an upper arm AVF (3.5 (2.9‐4.3) vs. 3.8 (3.2‐4.5) AU, P < .001), but not for the 107 patients dialyzing with a forearm AVF ((3.4 (2.8‐4.2) vs. 3.6 (3.0‐4.5) AU, P = .085). Blood flow was greater for upper arm AVF compared to forearm AVFs (1190 (770‐1960) vs. (930 (653‐1250) mL/min, P = .007), but there was no association between blood flow and SAF (P > .05). AVF alters blood flow in the arm, and we found that SAF measurements were lower in the arm with AVF. We suggest that SAF measurements are made in the non‐AVF arm.