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Original Article
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Chaowat Pimratana, M.D.*, Kornkanok Hengsawat, M.D.**
*Department of Surgery, **Department of Anesthesiology, Buri Ram Hospital, Buri Ram 31000, ailand.
The Analgesic Effect of Cryotherapy on Patients
Undergoing Extracorporeal Shock Wave Lithotripsy:
A Randomized Controlled Trial
ABSTRACT
Objective: To compare the degree of pain between cryotherapy and standard preoperative care in the treatment of
urolithiasis with extracorporeal shock wave lithotripsy (ESWL).
Materials and Methods: A total of 180 ESWL patients were randomly assigned to experience the standard
preoperative method, or additional cryotherapy (ice pack application on the ESWL site) for 10 minutes before
ESWL. e primary outcome was the maximum dierence of pain intensity score from baseline during ESWL
and the secondary outcomes, which were analgesic consumption, pulse rate, adverse events, stone free rate, and
complications that were gathered and analyzed.
Results: e maximum change in pain intensity score from baseline during ESWL in the cryotherapy group was
signicantly lower than in the control group (VAS score 4.0±1.9 vs. 5.2±2.7, p=0.002). e cryotherapy group showed
signicantly less total fentanyl consumption than the control group (85.3±22.0 mcg vs. 93.6±25.6, p=0.021). We
found no signicant dierence in stone free rate, adverse events or complications in either group.
Conclusion: Preoperative cryotherapy using ice packs for 10 minutes can provide an eective analgesic for ESWL.
Adequate pain control with cryotherapy should be an option of pain management during ESWL.
Keywords: Cryotherapy; ESWL; pain; urolithiasis (Siriraj Med J 2022; 74: 85-90)
Corresponding author: Chaowat Pimratana
E-mail: pchaowat@gmail.com
Received 20 May 2021 Revised 10 November 2021 Accepted 16 November 2021
ORCID ID: http://orcid.org/0000-0003-3754-774X
http://dx.doi.org/10.33192/Smj.2022.11
INTRODUCTION
Extracorporeal shock wave lithotripsy (ESWL)
has been a less-invasive option for the treatment of the
majority of patients with urolithiasis since 1980.
1
e
advancement of the new-generation lithotripter machines
has made ESWL more eective with minimal morbidity,
making it possible to perform ESWL without the need for
general or spinal anesthesia.
2
However, this procedure
can be painful because the continuous shock waves act
on the cutaneous supercial skin nociceptors and visceral
nociceptors, such as the renal capsule, peritoneal, and
musculoskeletal pain receptors.
3
Adequate pain control is
an important role in achieving successful ESWL treatment.
Opioid and sedative drugs are common analgesics for
ESWL, but certain amounts of opioids may cause nausea,
vomiting, and delayed recovery of patients.
4
Cryotherapy involves cold applications, which
have eects on both the local site around the treatment
area and at the level of the spinal cord via neurologic
and vascular mechanisms.
5
It is hypothesized that cold
applications can control pain by increasing the pain
threshold and tolerance by reducing nerve conduction
velocity, as described by the gate control theory, whereby
pain is transmitted to the dorsal horn of the spinal cord
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via C-bers and Aß bers; C-bers release substance P,
which opens the gate and Aß bers close the gate. Cold
applications activate the Aß bers, thereby stopping the
transmission of pain stimuli.
6,7
Many studies have been
published in regard to cryotherapy for pain reduction,
for example with knee operations, thoracic operations,
gynecologic operations, and abdominal operations.
8–11
However, no previous study has reported the analgesic
eect of cryotherapy on ESWL.
e aim of this study was to evaluate the eectiveness
of cryotherapy regarding pain control during ESWL for
urolithiasis treatment.
MATERIALS AND METHODS
is randomized controlled trial was conducted at
Buri Ram Provincial Hospital, Buri Ram, ailand. e
protocol of this research was reviewed and approved
by the ethical review board of Buri Ram Hospital (BR
0032.102.1/46) and registered in the ai Clinical Trials
Registry (TCTR20201226002). Patients with indication
for ESWL treatment were randomly assigned into two
groups. Patients in the rst group were given ice pack
compression at the skin on the ESWL site while patients
in the second group were given standard preoperative
ESWL. Between October 2020 and March 2021, kidney and
ureteric stone patients scheduled for ESWL aged 18 to 80
years with the American Society of Anesthesiologists (ASA)
physical status of I, II or III were eligible for the study.
is study excluded patients with a history of allergies to
the drugs that were used for the ESWL treatment, patients
with psychological disorders, neurological disorders,
dermatologic disorders (inammation or eczema within
the eld of cold therapy), and patients that were unable
to comprehend or use the visual analog scale (VAS).
Aer obtaining the informed written consent, the
patients that met the criteria were enrolled and divided
into two groups using computer-generated random
numbers and opaque sealed envelopes. e patients in
group I received cryotherapy; ice pack compression before
ESWL. e ice pack was kept at -10°C in a thin cloth bag
ready for future use. e ice pack was then placed on
the skin at the site of the ESWL for 10 minutes before
beginning the procedure. Control group II received standard
preoperative care. Both groups received premedication-1000
mg paracetamol and 5 mg diazepam-orally 30 minutes
before the ESWL. Initial intravenous fentanyl 1 mcg/kg
began ve minutes before the beginning of the ESWL
for every patient from both groups and a supplementary
dose of fentanyl 20 mcg intravenously was given to
patients whose pain score was greater than 4 or whose
pain tolerance was low. All patients underwent ESWL
using a Dornier Delta III Lithotripter machine in a fully
integrated operating room, and the procedure was carried
out using a similar protocol. An anesthetic nurse, who
was not involved in the study, recorded the patients’
perioperative anesthetic parameters every ve minutes.
ese parameters included blood pressure, pulse rate,
respiratory rate, oxygen saturation, sedative score, pain
score, and nausea/vomiting. e pain scores were placed
on an 11-point visual analog scale (VAS) and ranged from
0 to 10, with 0 representing no pain and 10 representing
the worst pain.
e primary outcome was the maximum of changes
in the pain intensity score from baseline during the ESWL,
using the VAS score. e secondary outcomes were total
fentanyl consumption, pulse rate, perioperative nausea/
vomiting, stone free rate at one month aer ESWL, and
any adverse events or complications.
Statistical analysis
A preliminary study containing 40 patients (20 per
group) was conducted. e preliminary study reported
the VAS score at 4.9±2.1 in the control group and
3.8±2.1 in the experimental group. e mean scores
from the preliminary study were used to calculate an
appropriate sample size for the main study. e sample
size calculation for the two independent mean tests using
a power 90% and a signicance level of 0.05 revealed a
minimum sample size of 81 participants in each group.
We added 10% of the subjects in order to accommodate
the projected dropout rate. Continuous variables were
expressed as mean ± standard deviation (SD) or median
(interquartile range, IQR) and were analyzed between
the two groups by using a t-test or the Mann-Whitney U
test. e categorical data were expressed as number and
percentage and were compared using a chi-squared test
or Fisher’s exact probability test. Statistical signicance
was set at p-value <0.05.
RESULTS
One hundred and eighty-two ESWL cases were
enrolled in the study and control groups. Two patients in
our study were excluded. Each group was composed of 90
cases (Fig 1). ere was no dierence in the demographic
data for either group, including age, sex, body mass
index (BMI), ASA physical status, stone location, time
of ESWL, lateralization, or stone size (Table 1). Intra-
operative parameters, base line pain score, pulse rate,
and initial fentanyl doses were not statistically dierent
between the two groups. e maximum of change in the
pain intensity score from baseline during the ESWL in
the cryotherapy group was signicantly lower than in the
Pimratana et al.
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Fig 1. Consort diagram demonstrating the ow of participants through each stage of the randomized trial.
TABLE 1. Knowledge of the warning symptoms of stroke (n=312).
Cryotherapy group Control group p-value
(n=90) (n=90)
Gender
Malen(%) 56(62.2) 56(62.2) 1.00
Age,yearmean±SD 55.5±11.6 55.9±11.0 0.812
BMI, kg/m
2
mean±SD 24.3±3.9 24.4±4.8 0.862
ASA n (%) 0.875
1 29(32.2) 31(34.4)
2 50(55.6) 50(55.6)
3 11(12.2) 9(10.0)
Stone location n (%) 0.414
Renal calculi 61 (67.8) 66 (73.3)
Uretericcalculi 29(32.2) 24(26.7)
Stone lateralization n (%)
Right side 49 (54.4) 45 (50.0) 0.551
Time of ESWL n (%)
Firsttime 32(35.6) 33(36.7) 0.877
More than 1 time 58 (64.4) 57 (63.3)
Stone size, mm median (IQR) 10.0 (10.0,15.0) 10.0 (9.5,15.0) 0.450
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control group (VAS score 4.0±1.9 vs. 5.2±2.7, p=0.002).
e cryotherapy group showed signicantly lower total
fentanyl consumption than the control group (85.3±22.0
mcg vs. 93.6±25.6 mcg, p=0.021). e stone free rate at
one month aer procedure was not dierence between
both groups (58.8% in the cryotherapy group vs. 62.2%
in the control group. We found no signicant dierence
in terms of adverse events regarding nausea/vomiting
and bradycardia in either group (Table 2).
DISCUSSION
e introduction of ESWL has been revolutionary
for the treatment of urolithiasis since 1980
1
, and new-
generation lithotripter machines have made ESWL more
eective with less morbidity, less pain, shorter recovery
time, and shorter hospital stays.
2
Nevertheless, the most
common complaint is pain and discomfort during the
treatment.
3
e pain experienced during ESWL is due
to the continuous shock waves acting on its targets,
whether from cutaneous tissue or deeper aerent nerves.
3
An adequate analgesia is mandatory for maintaining
patient comfort and improving treatment outcomes
12
,
but sometimes the patients discharge from the hospital
is delayed because of persistent sedation, and nausea and
vomiting due to the anesthetic medication administered,
so non-pharmacological methods may attract some
attention.
13
Cryotherapy for pain relief has been used
for many years, based on the gate control theory; cold
application can inhibit cutaneous input to the spinal
cord and reset the pain threshold in the central nervous
system.
6,7,9
By this means, cryotherapy is able to block
pain sensation from urinary calculi, whether its origin is
from the skin or from the deeper structures. However,
the major concern about cryotherapy is the decline in
the patient’s body core temperature and the local eects
on the areas exposed to cryotherapy. e decline in the
patient’s body temperature has harmful physiological
eects, such as Raynaud’s phenomenon, while exposure
to extreme cold can cause cold urticaria and frostbite
of the skin.
14,15
e study by Palmieri et al. showed that
TABLE 2. Outcomes
Cryotherapy group Control group p-value
(n=90) (n=90)
VAS score
At baseline median (IQR) 0.0 (0.0,0.0) 0.0 (0.0,0.0) 0.946
MaximumVASduringESWLmean±SD 4.3±1.7 5.5±2.6 <0.001*
ChangeofmaximumVASfrombaselinemean±SD 4.0±1.9 5.2±2.7 0.002*
Pulse rate mean±SD
At baseline 63.3±9.4 65.7±11.9 0.135
At15minutes 63.2±9.4 65.5±11.6 0.144
At30minutes 61.2±10.7 63.5±11.4 0.170
Initialfentanyldose(mcg)mean±SD 69.9±19.4 74.3±20.3 0.140
Totalfentanylconsumption(mcg)mean±SD 85.3±22.0 93.6±25.6 0.021*
Nauseaandvomitingn(%) 2(2.2) 2(2.2) 1.00
Bradycardian(%) 11(12.2) 9(10.0) 0.635
Skin complication (necrosis or frostbite) n (%) 0 (0) 0 (0) NA**
Stonefreerate(%) 58.8 62.2 0.760
* p-value <0.05
** NA = not applicable
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a cold application at the skin site for 10-20 minutes did
not decline the body core temperature.
16
ienpont
et al. demonstrated that continuous cryotherapy of
not more than 20 minutes did not cause frostbite on
the skin ap aer knee arthroplasty.
15
Further, Natalia
et al. demonstrated that a cryotherapy application of not
more than 20 minutes was safe and not uncomfortable
for any participants.
17
In this study, our protocol applied
10-minute cryotherapy and close monitoring for any
adverse event from cryotherapy during the procedure.
Many studies have used cryotherapy to decrease
pain in musculoskeletal surgery, gynecologic surgery,
cardiothoracic surgery, and abdominal surgery. e
overall results revealed benecial outcomes in terms of
pain reduction and pain management.
8–11
e present
study is the rst to emphasize the eects of cryotherapy
or cold application in ESWL treatment. In addition, this
study used the change of maximum VAS score from
baseline for the primary outcome instead of the patient’s
stated VAS score aer he or she had his/her operation.
Traditionally the VAS score is clinically meaningful from
the patient’s perspective and clinical decisions are made
based on such. However, the VAS mean scores cannot
capture the complete pain experience because pain is
both subjective and multidimensional.
18
us this study
used the change of maximum VAS score from baseline
for the primary outcome, which oers an alternative
measurement of the analgesic eect during the actual
procedure for the main outcome of our study. We found
that the pain intensity score in the cryotherapy group
was signicantly lower than in the control group (VAS
score 4.0±1.9 vs. 5.2±2.7, p=0.002).
Regarding the objective parameter, we used total
fentanyl consumption for the secondary outcome. e
cryotherapy group showed signicantly lower total fentanyl
consumption than the control group (85.3±22.0 mcg vs.
93.6±25.6 mcg, p=0.021).
In our study, bradycardia was a common side eect,
which may have been caused by both opioid usage and
cryotherapy; nevertheless, the pulse rate and bradycardia
events did not dier between the two groups (12.2% in
the cryotherapy group vs. 10.0% in the control group,
p=0.635), as the incidence was likely to be a minor adverse
eect of opioids rather than the eect of cryotherapy.
13
e emetic eect of opioids has been documented; in
our study, there was no signicant dierence in nausea
or vomiting between both groups (2% in the cryotherapy
group vs. 2% in the control group, p=1.000). Local skin
complications from cryotherapy were not present in our
study. Taking into consideration the signicant benet
of pain management from cryotherapy during ESWL, we
believe that cryotherapy is a safe, inexpensive, practical,
and eective adjuvant pain relief method.
ere were some limitations in this study. First,
we could not blind the cold application between the
cryotherapy group and the control group. Secondly, the
VAS score for pain was subjective and multidimensional.
Even though this study used the change of maximum VAS
score from baseline as an alternative measurement, this
measurement is prone to variation regarding the patient’s
pain tolerance level. In our study the stone free rate was
not signicant dierence between both groups. us,
future studies should consider using a more objective
measurement regarding outcome evaluation such as the
success rate of the stone treatment.
3,12,19,20
CONCLUSIONS
In this study we demonstrated that preoperative
cryotherapy using an ice pack for 10 minutes can provide
an eective analgesic for ESWL treatment. Adequate
pain control with cryotherapy should be an option of
pain management during ESWL.
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