Effect of isothermic dialysis on intradialytic hypertension

Abstract

The primary outcome was incidence of intradialytic hypertension (IDH) during standard and cooler isothermic dialysate temperatures. Two pair of haemodialysis sessions were done at 37°C (SHD) and at isothermic temperature (IHD). All the four dialysis were done on the same time of the day to negate the changes due to circadian variation in body temperature. Axillary and tympanic temperatures were measured before start of the dialysis and dialysis temperature was adjusted as per axillary temperature. Sixty patients were enrolled and completed the study. The mean delivered dialysate temperature in the intervention group was 36.5 ± 0.2 achieving a 0.5 ± 0.2°C between-group separation. The incidence of IDH and intradialytic hypotension while on SHD and IHD were 79/120 (66%) vs 44/120 (37%), odds ratio (OR) 3.3, 95% confidence interval (CI) (1.96–5.65) and 45/120 (38%) vs 14/120 (12%), OR 4.5, 95% CI (2.3–8.7), respectively. The 4 h time averaged mean systolic blood pressure (SBP) at IHD and SHD were 154 ± 1.7 and 157.2 ± 1.1 mmHg, respectively, the mean difference in SBP being −3.4 mmHg to −3.1 mmHg, 95% CI, P < 0.001. The standard deviation, a measure of BP variability was lower at IHD than at SHD (P < 0.001). In a subgroup analysis during IHD there was a significant reduction of both SBP and diastolic BP during the entire duration of dialysis in 35 out of 60 patients (systolic 4 h mean 154.96 ± 2.22 vs 164.32 ± 1.99 mmHg), (diastolic 4 h mean 79.24 ± 0.82 vs 82.54 ± 0.68 mmHg) – (rANOVA for systolic and diastolic <0.001). This phenomenon of cooler dialysis causing reduction of BP was reproduced in the same group of patients when the IHD was repeated another time (systolic 4 h mean 157.95 ± 1.88 vs 160.65 ± 1.47), (diastolic 4 h mean 79.27 ± 0.74 vs 82.03 ± 1.07) rANOVA for systolic and diastolic <0.001. The incidence of IDH can be reduced significantly by reducing the dialysate temperature to patients' body temperature. Hypertension during dialysis is related to heat gain during dialysis.

Management of intradialytic hypertension: current evidence and future perspectives

“…Axillary and tympanic membrane temperature were both measured before initiation of dialysis and dialysate temperature was adjusted based on the temperature recorded at the patients’ axilla opposite to the side of the arteriovenous fistula. Mean intradialytic SBP at isothermic and standard dialysis were 154.0 ± 1.7 and 157.2 ± 1.1 mmHg, respectively, and the mean difference in SBP between the groups was −3.4 to −3.1 mmHg, P < 0.001 [36]. The incidence of IDH episodes was significantly lower during isothermic dialysis [66% of standard dialysis sessions versus 37% of isothermic sessions; odds ratio (OR) 3.3, 95% CI 1.96–5.65].…”

Isothermic dialysis-a new panacea for intradialytic hypertension?

“…present their data on a single center randomized cross-over study that adds yet another dimension to our knowledge on IDH by proposing that primary heat gain during standard HD may be contributory. [5] The authors subjected 60 chronic HD patients to two sessions of standard hemodialysis (SHD) with dialysate temperature fixed at 37°C and two sessions of isothermic hemodialysis (IHD) in varying random sequences to primarily study the incidence of IDH. IHD was delivered by matching dialysate temperature to axillary temperature measured at the start of dialysis.…”

“…Data collected from 240 HD sessions showed significantly lesser incidence of IDH in IHD (37%) as compared to SHD (66%). [5] Other benefits of IHD included significantly lower incidence of intradialytic hypotension (12% vs. 38%) and lower intradialytic mean SBP and BP variability. [5] Post hoc classification of patients as “responders” defined as those with ≥5 mmHg drop in SBP with IHD as against the “non-responders” showed no differences in inter dialytic fluid gain and total ultrafiltration (UF) per HD session between the groups.…”

“…[5] Post hoc classification of patients as “responders” defined as those with ≥5 mmHg drop in SBP with IHD as against the “non-responders” showed no differences in inter dialytic fluid gain and total ultrafiltration (UF) per HD session between the groups. [5]…”

“…is probably the first to suggest that heat stress generated from a fixed 37°C dialysate can lead to IDH. [5] The authors speculate that this could be from paradoxical vasoconstriction in response to twin situations of heat stress and hypovolemia as shown in normal human experiments. [57] Regardless of the mechanisms involved, the impressive reduction in incidence of IDH could be generalizable to a high-risk population because study subjects had substantial interdialytic weight gains (~3.4–3.5 kg) with high average UF rate of around 12.4 ml/kg/h making them particularly vulnerable to such complications.…”