Vol.5, No.2, 253-258 (2013) Health
http://dx.doi.org/10.4236/health.2013.52034
Effect of thermal therapy using hot water bottles on
brain natriuretic peptide in chronic hemodialysis
patients
Yoko Uchiyama-Tanaka*
Yoko Clinic, Kitakyushu, Japan;
Received 14 May 2011; revised 15 August 2012; accepted 28 August 2012
ABSTRACT
Introduction: The use of repeated thermal the-
rapy for improving the symptoms of chronic
heart failure (CHF) has been recently demon-
strated. Usually, thermal therapy requires an in-
frared dry sauna. However, it is difficult for small
clinics to acquire such an expensive and exten-
sive sy stem. The author assessed the efficacy of
its substitution with hot water bottles. Moreover,
there are no prior studies demonstrating the
efficacy of thermal therapy in hemodialysis pa-
tients with chronic heart failure. Methods: The
author evaluated plasma brain natriuretic pep-
tide (BNP) levels in 98 hemodialysis p atients in a
clinic. A total of nine patients w hose BNP levels
were more than 500 pg/mL agreed to be enrolled
in this study and received thermal therapy using
hot water bottles. Results: Plasma BNP levels, a
potential marker for CHF, tended to decrease
(891 ± 448 pg/mL to 680 ± 339 pg/mL), but the
difference was not significant (P = 0.0845). The
oral temperature changed from 36.44˚C ± 0.45˚C
to 37.04˚C ± 0.48˚C (+0.597˚C, P < 0.0001). No
side effect s were experie nced during the t herapy.
Moreover, most patients had an improvement in
their symptoms and the ability to perform activi-
ties of daily living. Conclusion: Thermal therapy
using hot water bottles is very safe and tends to
reduce plasma BNP levels in hemodialysis pa-
tient s with CHF.
Keyw ords: BNP; Brain Natriure t i c Pe p t i de; Chronic
Heart Failure; Chronic Kidney Disease;
Hemodialysis; Hot Water Bottle Thermal Therapy
1. INTRODUCTION
Chronic heart failure (CHF) is a major serious com-
plication for hemodialysis patients [1-3]. Kihara et al.
and Miyata et al. recently reported that repeated thermal
therapy could improve hemodynamics and symptoms in
patients with CFH [4-6]. The therapy requires an infra-
red-ray dry sauna because the temperature needs to be
maintained evenly at 60˚C. Unfortunately, it is difficult
for small clinics to acquire such an expensive and exten-
sive system. Tei et al. [4-6] proposed warm water baths
as a substitute for saunas, which can warm the body
without overloading the heart.
This study assessed whether thermal therapy for CHF
using hot water bottles can be used as a substitute for
infrared-ray dry sauna. Moreover, the author also as-
sessed whether thermal therapy is useful for hemodialy-
sis patients with CHF as there have been no studies
demonstrating the efficacy of thermal therapy in this
patient population. BNP is a superior parameter for as-
sessing left ventricular (LV) function rather than volume
overload of heart failure patients with normal kidney
function [7]. Hemodialysis patients are loading of vo-
lume every day. This study used BNP as parameter for
assessing LV function.
2. MATERIALS AND METHODS
2.1. Study Design and Participants
The study procedures were in accordance with the
guidelines of the 2000 Declaration of Helsinki for human
experimentation. All subjects provided informed consent.
Nine out of 98 inpatients undergoing hemodialysis treat-
ment in November 2007 at the Hosoe clinic, and whose
BNP levels were more than 500 pg/mL were enrolled in
this study. Patients with arterial ventricular stenosis and
other outflow obstacle heart disease were excluded, as
such thermal therapy is contraindicated in these condi-
tions [4,5]. None of the nine patients had any signs,
symptoms, or history of cancer or any active inflamma-
tory disease.
2.2. Laboratory Measurements
To evaluate brain natriuretic peptide (BNP) levels after
*The author declares no conflict of interest.

Y. Uchiyama-Tanaka / Health 5 (2013) 253-258
254
hemodialysis, blood samples of the patients were col-
lected in the supine position. Plasma samples were pre-
pared within 30 minutes after collection using a pre-
cooled centrifuge. Extracted plasma samples were frozen
immediately and stored at −20˚C until analysis. Plasma
BNP concentrations were measured by an immunoradi-
ometric assay specific for human BNP using a commer-
cial kit (Shionogi BNP kit; Shionogi Co. Ltd., Osaka,
Japan). The author again collected blood samples 3
months later at the end of the follow-up period. Oral
temperature was measured before and after each therapy
session.
2.3. Thermotherapy Using Hot Water Bottles
The author interviewed and evaluated the ability to
perform activities of daily living (ADL), and classified
the heart failure using the classification of New York
Heart Association (NYHA) before and after this study.
Before this study, all patients were treated with beta-
blockers, angiotensin II-converting enzyme inhibitors,
and angiotensin II-receptor blockers according to the
treatment guideline for the evaluation and management
of CHF [8]. Drug treatment was continued throughout
the study. After an examination that involved measuring
patients’ dry weight, and assessing X-ray images and
other clinical parameters, such as blood pressure, patients
received thermal therapy using hot water bottles. This
therapy is derived from the thermal therapy using an in-
frared-ray dry sauna invented by Kihara et al. and Mi-
yata et al. [4,5]. Initially, patients received a hot water
foot bath (44˚C) for 30 minutes. Subsequently, patients
were then asked to lie down on a bed with hot water bot-
tles and were wrapped in a blanket for another 30 min-
utes. This procedure was repeated three times per week
after hemodialysis for a total follow-up period of 3
months.
2.4. Statistical Analysis
Values are expressed as the mean ± SD. Student’s
t-test was used for all comparisons. P-values less than
0.05 were considered significant.
3. RESULTS
Demographic and clinical characteristics of the pa-
tients are summarized in Tables 1 and 2, respectively.
Before the study, the author assessed the ability of pa-
tients to perform ADL. If, despite high BNP levels, the
patients did not complain of NYHA-defined heart fail-
ure-related symptoms, it was speculated that it might
have been difficult for hemodialysis patients with many
other aches and joint problems to notice the symptoms
related to heart failure. Each patient underwent the ther-
mal therapy three times per week after hemodialysis for
3 months. The nine patients who were included in the
analysis (two men and seven women; mean age, 74.2 ±
14.6 years old; average duration of hemodialysis, 8.3 ±
6.2 years) were able to continue thermotherapy and were
observed for 3 months. Plasma BNP levels in the periph-
eral blood changed from 891 ± 448 pg/mL (range 419 -
1627 pg/mL) to 680 ± 339 pg/mL (range 208 - 1100
pg/mL) after 3 months (P = 0.0845). The change in
plasma BNP levels was not significant, but the levels
tended to decrease. The oral temperature changed from
36.44˚C ± 0.45˚C to 37.04˚C ± 0.48˚C (+0.597˚C, P <
0.0001). After 3 months of thermal therapy, the ADL
score was improved in all patients (Table 2).
Other clinical parameters, such as blood pressure, dry
weight, anemia, and cardiothoracic ratio did not change
significantly (data not shown). Results of the echocar-
diogram tests conducted before and after the study period
revealed no significant change in the ejection fraction
and other associated parameters (data not shown). No
side effects were experienced during the therapy.
Table 1. Demographic characteristics, and present heart disease and other conditions of the study population.
Case Age (years) Sex Duration of hemodialysis (years) Heart disease
1 79 Female 5.0 SN/AR moderate
2 79 Male 6.0 CGN/MR mild
3 53 Female 15.0 DM/LVH
4 83 Female 3.0 DM/OMI
5 73 Female 13.0 PKD/MR and LVH mild
6 80 Female 5.0 DM/MR and AR
7 47 Male 6.0 SN/MR
8 90 Female 2.0 MR/AR and LVH
9 84 Female 20.0 PKD/MR
AF atrial fibrillation, AR aortic valve regurgitation, CGN chronic glomerular nephropathy, DM diabetic nephropathy, LV H left ventricular hypertrophy, MR
mitral valve regurgitation, OMI old myocardial infarction, PKD polycystic kidney disease, SN sclerosis nephropathy.

Y. Uchiyama-Tanaka / Health 5 (2013) 253-258 255
Table 2. Demographic characteristics of the study population and the experienced symptom change.
Case Age
(years) Sex Ability to perform ADL† Change in ability to perform ADL NYHA heart failure classification change
1 79 Female Pain in the right knee* Disappeared II → I
2 79 Male No symptoms No change II → I
3 53 Female Chill, heart palpitation at rest Disappeared (both symptoms) II → I
4 83 Female No symptoms No change I → I
5 73 Female
Right hand sclerosis (10/10); abdominal
pain after abdominal surgery (10/10); pain
in the left knee (10/10); could not perform
housework
Improvement in hand movement
(6/10), abdominal pain (3/10), knee
pain (5/10); could perform some
housework‡
NA
6 80 Female Back pain Disappeared§ NA
7 47 Male Could not speak after brain hemorrhage Became more alert and started
speaking¶ NA
8 90 Female Pain in both knees Disappeared** NA
9 84 Female Pain in the left shoulder, toothache Disappeared†† NA
ADL activities of daily living, NYHA New York Heart Association. *The duration of knee pain was over a year; †Symptoms were assessed on a scale from 1
(minimal) - 10 (maximum); ‡The patient could not walk for 100 meters because of knee pain; after the study the patient could walk 3 km; §The patient could not
walk and used a wheelchair; after the study the patient could walk with a cane; ¶The patient could not speak to complain of any symptoms for 5 years, after the
study the patient could speak; **The patient could not walk because of knee pain and used a wheelchair; after the study the patient can walk with a cane; ††The
patient is bedridden.
4. DISCUSSION
Results of this study suggest that the ability to perform
ADL of hemodialysis patients can be improved with the
use of hot water bottle thermal therapy, and that such
therapy can help to decrease plasma BNP levels. This is
the first study to demonstrate that mild thermal therapy is
an effective, relatively safe, and easy way to improve the
ability to perform ADL, and may also improve LV func-
tion in CHF patients.
Thermal therapy, also known as Waon therapy, is de-
fined as “therapy in which the entire body is warmed in
an evenly heated chamber for 15 min at a temperature
that soothes the mind and body, and after the deep body
has increased by approximately 1.0˚C - 1.2˚C, the sooth-
ing warmth continues at rest for an additional 30 min,
with fluids supplied at the end to replace the loss from
perspiration” [4].
According to Tei [4-6], although medical progress in
the 20th century has been outstanding, there is still no
way of determining the magnitude of a patient’s internal
suffering and conflict. Medical staff cannot understand
the extent of pain, tension, and stress experienced by
patients who receive life-saving therapies, especially
CHF patients ineligible for operation. Kihara et al. and
Miyata et al. developed thermal therapy for such patients,
and it has been found to improve hemodynamics and
decrease serum BNP levels, arrhythmia, and sympathetic
nervous system activity, which occurs with severe car-
diac failure [4-6]. Moreover, this method is an effective
treatment for Sjogren disease and other lifestyle-related
diseases, such as hypertension, diabetes mellitus, hyper-
lipidemia, obesity, and smoking-related diseases [9,10].
Warming the body has been shown to relieve the
sympathetic nervous system [5-7]. Furthermore, it has
been shown that it might also improve the immune sys-
tem [11-13]. Warming the body using hot water bottles
warms the patient slowly and does not burden weak pa-
tients [11]. In the current medical practice, the medical
staff often does not have the sufficient time to see and
talk to patients. Talking and listening to a suffering pa-
tient enables them to relax and develop a trusting rela-
tionship with the medical team. The time spent with the
patient by the medical staff during the thermal treatment
might be the most important and effective part of this
therapy.
In the present study, most patients reported alleviation
of pain and the symptoms impacting the ability to per-
form ADL during the thermal therapy. Warming de-
creases activity of the sympathetic nervous system and
opens peripheral blood vessels, resulting in relaxation of
tendons and muscles [4-6]. Reducing the pain also de-
creases activity of the sympathetic nervous system and
increases the patient’s trust in the medical staff, resulting
in more efficient medical care.
There are no previous studies on the appropriate dura-
tion of the thermal treatment. The effect of sauna therapy
after 2 - 4 weeks has been reported [4-6], and the authors
suggest that the therapy was effective for improving the
ability to perform ADL in severe heart failure patients
when performed once a day for 3 - 4 days a week. In
addition, this method is very easy to implement; hence,
the length of each session can vary as required.
Measuring BNP levels is the established parameter for
assessing LV function with normal kidney function [7].
However, there are conflicting results concerning as-

Y. Uchiyama-Tanaka / Health 5 (2013) 253-258
256
sessing chronic renal function, especially in dialysis pa-
tients. Many reports recommend using the BNP level as a
possible prognostic marker for cardiac disease even in
chronic kidney disease (CKD) [14-17]. Park et al. re-
cently reported that the BNP level is a useful marker for
assessing the risk of new cardiac events in patients with
CKD [18]. There are few reports recommending BNP
levels as a prognostic marker for CHF in CKD because
BNP levels in hemodialysis patients vary within a large
range. Moreover, the level of BNP in hemodialysis pa-
tients can change daily [14,19]. Although a few reports
suggest that the normal BNP level is below 100 pg/dL
even in hemodialysis patients [20], other reports most
commonly suggest a range of 150 - 300 pg/dL for pa-
tients without heart disease, but this level is not consis-
tently reported and is based on cross-sectional studies
[21,22].
There have been no reports on longitudinal BNP levels
in hemodialysis patients. In the present study, the author
evaluated BNP levels in hemodialysis patients by means
of a longitudinal study. In most people without CKD,
BNP enhanced LV systolic and diastolic functions. How-
ever, the most precise and convenient method for the
evaluation of diastolic LV function remains controversial.
It is difficult to evaluate diastolic LV function by general
ultrasonography [23]. Echocardiography was performed
for all patients in the present study, but patients’ ability to
perform ADL was very poor and correct posture could
not be obtained. Some patients also had lung disease
with severe calcifications. Among patients on hemodi-
alysis, there are numerous patients with normal ejection
fraction, who also have restricted function of left ventri-
cle because of chronic volume overload, volume change,
hypertension, and/or amyloidosis.
The timing for measuring the BNP level is very im-
portant. In the present study, the author compared BNP
levels in the same patients at different times. Before
hemodialysis, weight gain (water volume) values dif-
fered each time, but after hemodialysis, dry weight va-
lues were fixed for each patient. The BNP level was
found to have less of a relationship to water volume, but
the levels were measured before and after hemodialysis,
and were clearly different. The author evaluated the BNP
levels after hemodialysis. This might be the reason that
there was no significant change in BNP levels before and
after the study. Interestingly, the BNP level could be used
as a marker for LV function in some patients, as shown
in the two patients whose BNP levels clearly decreased
in the present study (Figure 1). However, there is no
consensus on the best time to measure the BNP levels in
hemodialysis patients, whether it is at the start or end of
the week, or pre- or post-hemodialysis. The author de-
cided to measure BNP levels after hemodialysis when
weights were fixed and other parameters were stable. It
was difficult to find the most convenient and valid pa-
rameter to determine heart function in hemodialysis pa-
tients. BNP levels decreased in this study, but the de-
crease was not statistically significant; however, some
patients experienced significant decreases in BNP (Fig-
ure 1).
There were several limitations to this study. The num-
ber of patients was very limited and the increase of body
Figure 1. BNP levels before and after the present study of the two patients whose BNP clearly decreased. BNP brain
natriuretic peptide.

Y. Uchiyama-Tanaka / Health 5 (2013) 253-258 257
temperature in the study was 0.597˚C, less than 1.0˚C
suggested by Tei’s et al. Furthermore, the renal impair-
ment of hemodialysis patients in the present study may
lead to accumulation of levels of N-terminal proBNP [7,
15,24,25]. Moreover, this study included a small popula-
tion that was followed up for a very limited duration.
5. CONCLUSION
Using such a convenient and simple method for ther-
mal therapy, the author demonstrated an improvement in
patients who suffered from pain and experienced diffi-
culty with mobility. The therapy also could be conducted
without the side effects associated with other effective
therapies. The author concludes that thermal therapy
using hot water bottles is very safe and tends to decrease
plasma BNP levels in hemodialysis patients with CHF.
6. KEY SUMMARY POINTS
 The author assessed the efficacy of substituting infra-
red dry sauna with hot water bottle thermal therapy.
 A total of nine patients whose brain natriuretic pep-
tide (BNP) levels were more than 500 pg/mL agreed
to be enrolled in this study and received thermal
therapy using hot water bottles.
 Plasma BNP levels tends to decrease (891 ± 448
pg/mL to 680 ± 339 pg/mL), but there was no signi-
ficant difference (P = 0.0845). The oral temperature
changed 36.44˚C ± 0.45˚C to 37.04˚C ± 0.48˚C
(+0.597˚C, P < 0.0001).
 Most patients showed an improvement in their symp-
toms and ability to perform activities of daily living.
 The author concludes that thermal therapy using hot
water bottle is a very safe and tends to reduce plasma
BNP levels in hemodialysis patients with chronic
heart failure.
7. ACKNOWLEDGMENTS
Dr. Uchiyama-Tanaka is the guarantor for this article, and takes re-
sponsibility for the integrity of the work as a whole.
Open Access. This article is distributed under the terms of the Crea-
tive Commons Attribution Noncommercial License which permits any
noncommercial use, distribution, and reproduction in any medium,
provided the original author(s) and source are credited.
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