Gender, low Kt/V, and mortality in Japanese hemodialysis patients: Opportunities for improvement through modifiable practices

Abstract

Guidelines have recommended single pool Kt/V > 1.2 as the minimum dose for chronic hemodialysis (HD) patients on thrice weekly HD. The Dialysis Outcomes and Practice Patterns Study (DOPPS) has shown that "low Kt/V" (<1.2) is more prevalent in Japan than many other countries, though survival is longer in Japan. We examined trends in low Kt/V, dialysis practices associated with low Kt/V, and associations between Kt/V and mortality overall and by gender in Japanese dialysis patients. We analyzed 5784 HD patients from Japan DOPPS (1999-2011), restricted to patients dialyzing for >1 year and receiving thrice weekly dialysis. Logistic regression models estimated the relationships of patient characteristics with Kt/V. Logistic models also were used to estimate the proportion of low Kt/V cases attributable to various treatment practices. Multivariable Cox regression was used to estimate the associations of low Kt/V, blood flow rate (BFR), and treatment time (TT), with all-cause mortality. From 1999 to 2009, the prevalence of low Kt/V declined in men (37-27%) and women (15-10%). BFR <200 mL/min, TT <240 minutes, and dialyzate flow rate (DFR) < 500 mL/min were common (35, 13, and 19% of patients, respectively) and strongly associated with low Kt/V. Fifteen percent of low Kt/V cases were attributable to BFR <200 and 13% to TT <240, compared to only 3% for DFR <500. Lower Kt/V was associated with elevated mortality, more so among women (hazard ratio [HR] = 1.13 per 0.1 lower Kt/V, 95% CI: 1.07-1.20) than among men (HR = 1.06 per 0.1 lower Kt/V, 95% CI: 1.00-1.12). The relatively large proportion of low Kt/V cases in Japanese facilities may potentially be reduced 30% by increasing BFR to 200 mL/min and TT to 4 hours thrice weekly in HD patients. Associations of low Kt/V with elevated mortality suggest that modification of these practices may further improve survival for Japanese HD patients.

The impact of blood flow rate during hemodialysis on all-cause mortality

“…In Canada and other Europe, the patients with BFR ≥ 250 mL/min take about 98% of the HD patients [9]. However, in Japan, the patients with BFR ≥ 250 mL/min account for 18% and BFR prescribed usually 200 mL/min for a typical HD treatment [6,9]. …”

“…Some investigators proposed that the use of low BFR in Japan may contribute the longer survival compared other countries because the lower BFR may help facilitate the maintenance of high rate of AVF. Some investigators suggest that the use of low BFR may contribute the longer survival by facilitating the maintenance of high rate of AVF [6,8]. On the contrary, other studies demonstrated that increased BFR is important for optimizing dialysis dose [2,5] and inadequate dialysis dose is associated with increased mortality [1].…”

“…Japan DDOPS study reported that low Kt/V was more strongly associated with short dialysis treatment time than low BFR [6]. Short dialysis treatment time is associated with low Kt/V and independent risk factor for sudden death [3,6]. Furthermore, DOPPS showed longer HD patients survival with longer dialysis treatment time [7].…”

“…Japan Dialysis Outcomes and Practice Patterns Study (DOPPS) reported that patients with a mean prescribed BFR < 180 mL/min had higher mortality compared with reference group of BFR 180 to 210 mL/min [6]. However, it is uncertain whether these results can be generalized to other country groups because the prescribed BFRs in Japanese HD patients is usually 200 mL/min, which are lower than those in other countries with 250 to 350 mL/min [6,7].…”

“…However, it is uncertain whether these results can be generalized to other country groups because the prescribed BFRs in Japanese HD patients is usually 200 mL/min, which are lower than those in other countries with 250 to 350 mL/min [6,7]. Furthermore, some investigators proposed that the use of low BFR in Japan may contribute the longer survival compared other countries because the lower BFR may help facilitate the maintenance of high rate of arteriovenous fistula (AVF) [6,8]. …”