ORIGINAL ARTICLE
The effects of topical heat therapy on chest pain in patients with acute coronary syndrome: a randomised double-blind placebo-controlled clinical trial Ali Mohammadpour, Batol Mohammadian, Mehdi Basiri Moghadam and Mahmoud Reza Nematollahi
Aims and objectives. To investigate the effects of local heat therapy on chest pain in patients with acute coronary syndrome. Background. Chest pain is a very common complaint in patients with acute coronary syndrome. It is managed both pharmacologically and nonpharmacologically. Pharmacological pain management is associated with different side effects. Design. This was a randomised double-blind placebo-controlled clinical trial conducted in 2013. Methods. A convenience sample of 66 patients with acute coronary syndrome was selected from a coronary care unit of a local teaching hospital affiliated to Gonabad University of Medical Sciences, Gonabad, Iran. Patients were randomly assigned to either the experimental or the placebo group. Patients in the experimental and the placebo groups received local heat therapy using a hot pack warmed to 50 and 37 °C, respectively. We assessed chest pain intensity, duration and frequency as well as the need for opioid analgesic therapy both before and after the study. The study instrument consisted of a demographic questionnaire, the McGill Pain Questionnaire, and a data sheet for documenting pain frequency and duration as well as the need for analgesic therapy. Findings. The placebo heat therapy did not significantly decrease the intensity, the duration and the frequency of pain episodes. However, pain intensity, duration and frequency in the experimental group decreased significantly after the study. Moreover, the groups differed significantly in terms of the need for opioid analgesic therapy neither before nor after the intervention. Conclusion. Local heat therapy is an effective intervention for preventing and relieving chest pain in patients with acute coronary syndrome. Relevance to clinical practice. Effective pain management using local heat therapy could help nurses play an important role in providing effective care to patients with acute coronary syndrome and in minimising adverse effects associated with pain medications.
What does this paper contribute to the wider global clinical community?
• The findings of this study suggest
•
•
that local heat therapy is an effective intervention for preventing and relieving chest pain in patients with acute coronary syndrome (ACS). Effective pain management using local heat therapy can help nurses play an important role in providing effective care to patients with ACS. Effective pain management using local heat therapy can help minimising adverse effects and financial burden associated with pain medications.
Key words: acute coronary syndrome, chest pain, local heat therapy Accepted for publication: 25 February 2014 Authors: Ali Mohammadpour, PhD, BSN, MSN, Associate Professor, Social Determinates of Health Research Center, Department of Nursing, Faculty of Nursing and Midwifery, Gonabad University of Medical Science; Batol Mohammadian, BSN, MSN, Lecturer, Faculty of Nursing and Midwifery, Gonabad University of Medical Science; Mehdi Basiri Moghadam, BSN, MSN, Lecturer, Department of Nursing, Faculty of Nursing and Midwifery, Gonabad
© 2014 John Wiley & Sons Ltd Journal of Clinical Nursing, doi: 10.1111/jocn.12595
University of Medical Science; Mahmoud Reza Nematollahi, MD, Cardiologist, Gonabad University of Medical Science, Gonabad, Iran Correspondence: Batol Mohammadian, Lecturer, Faculty of Nursing and Midwifery, Gonabad University of Medical Science, Gonabad, Iran. Telephone: +98 533 7223028. E-mail: [email protected]
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Introduction Cardiovascular disease – with a mortality rate of 35% – is a major health problem and a major cause of death worldwide. The mortality rate of the disease in high- and lowincome countries is 40 and 28%, respectively (Fauci et al. 2012). Coronary artery disease is the most prevalent type of cardiovascular disease and the leading cause of death worldwide. In our country, Iran, about 46% of all deaths result from coronary artery disease (Sharifnia et al. 2013). Acute coronary syndrome (ACS), an important type of coronary artery disease, is a highly prevalent heart disease worldwide (Monro 2009). The term ‘ACS’ refers to a wide and diverse range of heart problems – from slight chest discomfort and atypical electrocardiogram changes to ST-segment elevation, myocardial infarction and cardiogenic shock (Scirica 2010) – that result from a same pathologic mechanism (Chen et al. 2005). The underlying pathologic mechanism of ACS is reduced myocardial oxygen supply (e.g. in atherosclerosis and coronary artery spasm) or increased myocardial oxygen demand (e.g., in tachycardia and severe anaemia) or both (Fauci et al. 2012). The clinical manifestations of ACS included, but not limited to, chest pain, sweating, dyspnoea, tachycardia, blood pressure fluctuations, anxiety, and senses of suffocation and death (Fauci et al. 2012).
Background Chest pain is the most common complaint of patients with ACS (Karampurian & Imeni 2003). Chest pain results from myocardial ischaemia and injury secondary to decreased blood flow to the myocardium. The injured tissues secrete bradykinin and histamine, which stimulate pain receptors and cause pain. Chest pain, in turn, increases sympathetic activity and myocardial oxygen demand, which finally result in the progression of ischaemia and injury (Asgari & Soleimani 2006). Unrelieved chest pain can cause different physiological and psychological problems such as general discomfort, anxiety, respiratory distress, increased vascular resistance, increased blood pressure and cardiac dysrhythmias (Karampurian & Imeni 2003). These conditions increase cardiac workload and myocardial oxygen demand, resulting in the exacerbation of myocardial ischaemia and injury and the aggravation of chest pain (Fauci et al. 2012). Consequently, effective chest pain management has a top priority in providing care to patients with ACS (Fauci et al. 2012). Chest pain is managed both pharmacologically and nonpharmacologically. Pain medications such as nitrates,
2
beta-blockers and opioid analgesics are widely used for pharmacologic chest pain management (Fauci et al. 2012). However, alongside therapeutic effects, pain medications also bring about different side effects. Moreover, pharmacological pain management imposes a significant financial burden on patients, families and the healthcare system. Consequently, nonpharmacological strategies have been developed for the management of pain. One of the nonpharmacological pain management strategies is heat therapy. Heat increases the blood flow to injured and inflamed tissues. Improved tissue perfusion relieves pain through promoting tissue oxygenation and facilitating the removal of inflammatory mediators such as bradykinin and histamine from the injured tissues (Gale et al. 2006). Moreover, according to the gate control theory, heat relieves pain by stimulating nonpain receptors in the skin and thereby closing pain pathways (Habananda 2004). There are different methods for administrating heat therapy including, but not limited to, local heat therapy, sauna therapy and bathing. Miyata and Tei (2010) reported that sauna therapy improves haemodynamic status, vascular and autonomic nervous system function and general health in patients with congestive heart failure. They also reported that sauna therapy regulates the electrical activity of the heart as well as the secretion of neurotransmitters and hormones. Sobajima et al. (2011) also found that repeated sauna therapy improves myocardial function through increasing the blood levels of nitric oxide, stimulating the formation of myocardial collateral blood vessels and increasing myocardial perfusion. However, given the haemodynamic instability in patients with ACS, sauna therapy and whole-body heat therapy are contraindicated. Consequently, local heat therapy may help relieve chest pain in these patients. Local heat therapy using hot pack is one of the many techniques for applying heat to the body surface. Hot pack is a silicate gel bag that is warmed using an electric water heater and then is applied directly to skin to provide humid heat to the body (Gale et al. 2002). Yaghobi et al. (2012) found that local heat therapy applied to lumbar area using hot pack significantly decreased the intensity and the duration of herniated disc-related pain. Behmanesh et al. (2008) also reported that perineal and lumbar heat therapy significantly reduced the intensity and the duration of labour pains. Moreover, Yildirim et al. (2009) found heat therapy to be effective in relieving pain and joint stiffness and improving physical function in patients with knee osteoarthritis. However, to the best of our knowledge, the effect of local heat therapy with hot pack on chest pain in patients © 2014 John Wiley & Sons Ltd Journal of Clinical Nursing
Original article
with ACS has not yet been examined. Moreover, despite the potential effects of heat therapy on pain, chest pain is still managed mainly pharmacologically. Consequently, we conducted this study to examine the effectiveness of local heat therapy in relieving chest pain in patients with ACS.
Effect of topical heat therapy on chest pain
(Z1a/2 = 258), the sample size was determined to be 32 patients in each group. Given the probability of attrition, we recruited 66 patients to the study – 33 patients in each group.
Randomisation and masking Aim The aim of this study was to investigate the effects of local heat therapy on chest pain in patients with ACS. The research question was, ‘What is the effect of local heat therapy on chest pain in patients with ACS?’ Specific research questions were: 1 What is the effect of local heat therapy on the intensity, the duration and the frequency of chest pain episodes in patients with ACS? 2 What is the effect of local heat therapy on the need for opioid analgesic therapy?
After recruitment to the study, patients were randomly assigned to either the experimental or the placebo groups using the permuted block randomisation method. The block size was equal to 42 patients for each group. Accordingly, we generated a list of 17 four-sized blocks using the PERMUTATION RANDOMIZATION SOFTWARE PROGRAM (SAS Institute Inc., Cary, NC, USA) and allocated the patients to either of the study groups according to the list. All the patients were blinded to the study interventions. The chief researcher generated the random allocation list. The study intervention and data collection were performed by two separate research assistants who were both blind to the study interventions.
Methods Instrument Design and sample We conducted this randomised double-blind placebo-controlled clinical trial in 2013 – from March–October. The study setting was a coronary care unit (CCU) of a local teaching hospital affiliated to Gonabad University of Medical Sciences, Gonabad, Iran. The study population consisted of all patients with ACS referring to the study setting. The inclusion criteria were having a definitive diagnosis of ACS as established by attending cardiologists, having a normal haemodynamic status as evident from vital signs, having no history of drug or alcohol addiction, having no history of gastrointestinal or chest musculoskeletal diseases or psychological disorders, having the ability to speak and understand Persian, having no swelling, bruising, oedema or wound on chest and having a body mass index of 185–25. The exclusion criteria were transportation to other clinical settings or development of haemodynamic instability. We recruited the eligible patients to the study using the convenience sampling method. The study sample size was calculated using the findings of the pilot study and the following formula: ðZ þ Z Þ2 ðS21 þ S22 Þ g ¼ 1a=2 ðl1b . The pilot study was conducted on 2 1 l2 Þ ten patients meeting the inclusion criteria. The primary outcome variable was chest pain intensity. The mean and the standard deviation of the pre- and postintervention pain intensity in the experimental group were 286 309 and 820 135, respectively. Accordingly, with a power of 80% (Z1b = 084) and a confidence interval of 99% © 2014 John Wiley & Sons Ltd Journal of Clinical Nursing
The study instrument consisted of a demographic questionnaire, the McGill Pain Questionnaire (MPQ), and a data sheet for documenting the frequency and the duration of pain episodes as well as the need for opioid analgesic therapy. The MPQ consists of 20 sets of words on sensory, affective, evaluative and miscellaneous dimensions of pain. In each set, there are words describing the intensity and the quality of pain. The sensory dimension – word sets number 1 to 10 – included words on spatial, temporal, thermal and pressure-related properties of pain. The affective dimension – word sets number 11 to 15 – examines the affective properties of pain such as fear and tension. The word set number 16 relates to the evaluative dimension of pain and measures its overall subjective intensity. The word set numbers 17–20 relate to other aspects of pain not included in the first three dimensions. The total score of MPQ ranges from 0–78. Higher scores indicate more intense pain and vice versa (Ebrahimi Nejad et al. 2004). Nikravan et al. (2009) assessed the content validity and the reliability of the Persian version of MPQ. They reported a Cronbach’s alpha of 086 for the questionnaire. A research assistant measured the duration of each pain episode – in minutes – using a chronometer.
Intervention At the time of admission to CCU, patients meeting the inclusion criteria were recruited to the study and allocated
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to either of the study groups. During the first two hours after admission, all patients in both the study groups received the routine care of the study setting attending and were assessed for chest pain intensity, duration and frequency as well as the need for opioid analgesic therapy. Two hours after admission, we administered local heat therapy to patients in the experimental group. The hot pack was first warmed to 75 °C and placed exactly on patients’ chest. To prevent patients from burning and also hot pack from losing heat, we wrapped hot pack in a towel provided by the manufacturer. Consequently, patients received heat therapy at 50 °C. We administered the heat therapy to patients every 12 hours for two subsequent days – four sessions altogether. Each heat therapy session lasted for 23 minutes. After 23 minutes, the hot pack temperature decreased to below 44 °C. According to the hot pack manufacturer, temperatures below 44 °C have no therapeutic effects. Patients in the placebo group were also treated similarly. However, the pack was warmed only to 37 °C. After each heat therapy session, we closely monitored patients for chest pain. Accordingly, if patients developed chest pain, we assessed and documented the intensity and the duration of pain as well as the need for opioid analgesic therapy. Moreover, the total number of pain episodes happened after the intervention, that is, pain frequency, was also documented.
Data analysis Data analysis was performed using the Statistical Package for Social Sciences (SPSS, version 16.0; SPSS Inc., Chicago, IL, USA). Initially, we calculated a total mean for the pain intensity and pain duration of pre- and postintervention pain episodes and used these new total mean variables for the final data analysis. We employed the descriptive statistics measures such as mean, standard deviation and absolute and relative frequency values to describe the study data. The study groups were compared in terms of demographic characteristics using the independent-samples t-test and the chi-square test. The Kolmogorov–Smirnov test was also used to examine the distribution of the study variables. Accordingly, variables that had normal distribution were analysed using parametric statistical tests such as the paired- and the independent-samples t-tests. These variables were preintervention pain intensity in both groups and postintervention pain intensity in the control group. On the other hand, we analysed variables having non-normal distribution as well as the nominal and ordinal variables using nonparametric statistical tests such as the chi-square test, the Fisher’s exact test, the McNemar test, the Mann–Whit-
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ney U-test and the Wilcoxon signed rank test. These variables included of postintervention pain intensity in the experimental group as well as pre- and postintervention pain frequency, pain duration and the need for opioid analgesic therapy in both the study groups. Moreover, as the preand postintervention time episodes were not the same in length (two vs. 48 hours), the number of postintervention pain episodes was inevitably greater than the preintervention pain episodes. Accordingly, we only performed between-groups comparison for the variable ‘pain frequency’. p-Values less than 005 were considered significant.
Ethical considerations The Ethics Committee of Gonabad University of Medical Sciences, Gonabad, Iran, approved the study. In addition, the Iranian Registry of Clinical Trials registered the study. We provided the study participants with information about the aim and the process of the study. Moreover, they were ensured that both participation in and withdrawal from the study were voluntary. Finally, we obtained a written informed consent from each individual participant.
Findings Figure 1 shows the flow of participants. The study participants ranged in age from 31–90 years. The mean and the standard deviation of patients’ age in the experimental and placebo groups were 6661 1279 and 6230 1394, respectively. Most of the study participants were female patients (591%). The results of the chi-square and the independent-samples t-tests revealed that there was no statistically significant difference between the study groups in terms of demographic characteristics such as age, gender, marital status, history of hospitalisation, family history of heart disease and the type of current heart problem (p > 005; Table 1). The results of the paired-samples t-test and the Wilcoxon signed rank test reflected that the placebo heat therapy did not significantly decrease the intensity, the duration and the frequency of pain episodes. However, the results of this test revealed that after the study, pain intensity, duration and frequency in the experimental group decreased significantly (p < 0001; Table 2). The results of the Mann–Whitney U-test showed that before the study, there was no statistically significant difference between the study groups in terms of the duration and the frequency of pain episodes. However, the results of this test revealed that after the study, the duration and the frequency of pain episodes in the experimental group were © 2014 John Wiley & Sons Ltd Journal of Clinical Nursing
Original article
Effect of topical heat therapy on chest pain
(p = 1 and 026, respectively; Table 2). Moreover, the results of the McNemar test showed that after the study, the need for opioid analgesic therapy did not decrease significantly in the study groups (p > 005; Table 2).
A convenience sample of 66 eligible patients
Random allocation
Discussion 33 allocated to the placebo group
33 allocated to the experimental group
Routine care and use of placebo
Routine care and local heat therapy
Measurment of frequency of pain episodes, pain duration, pain severity and need for analgesic
66 patients (33 in each group) completed the study and were included in data analysis Figure 1 Flow of participants.
significantly lower than the placebo group (p < 005; Table 2). On the other hand, the results of the same test illustrated that before the study, the pain intensity in the experimental group was significantly higher than in the placebo group (p = 003; Table 2). After the study, the pain intensity in the experimental group decreased so much so that it became significantly lower than in the placebo group (p < 0001; Table 2). Finally, the results of the Fisher’s exact test revealed that neither before nor after the study, the groups differed significantly in terms of the need for opioid analgesic therapy
The aim of this study was to investigate the effects of local heat therapy on chest pain in patients with ACS. The study findings revealed that chest local heat therapy decreased the intensity, the duration and the frequency of chest pain episodes in patients with ACS. Moreover, findings showed that compared with the patients in the placebo group, patients receiving local heat therapy needed opioid analgesic therapy less frequently. The main cause of chest pain in patients with ACS is impaired myocardial perfusion and oxygenation (Fauci et al. 2012). Local heat therapy seems to prevent and relieve chest pain through dilating the coronary arteries, accelerating the angiogenesis process and hence increasing myocardial perfusion. Increased perfusion, in turn, promotes myocardial oxygenation and facilitates the removal of inflammatory mediators such as bradykinin and histamine from the injured myocardium. Moreover, local heat therapy may also stimulate the secretion of endorphins – endogenous morphine-like compounds – that help relieve pain. Previous studies have also demonstrated the effectiveness of local heat therapy in relieving herniated disc-related pain (Yaghobi et al. 2012), arthritis-related pain and stiffness (Michlovitz et al. 2004, Yildirim et al. 2009), and delivery pains (Behmanesh et al. 2008). On the other hand, the humid heat provided by hot pack alleviates patients’ anxiety and hence decreases sympathetic activity, reduces cardiac workload, prevents the progression of ischaemia and finally relieves chest pain. Moreover, humid heat stimulates nonpain receptors and relieves pain through the gate control mechanism. Sobajima et al. (2011) noted that repeated sauna therapy after myocardial infarction
Table 1 Patients’ characteristics and outcomes comparison between groups Patients’ characteristics
Experimental group (n = 33)
Age [years: mean (SD)] Gender (F/M), n (%) Marital status (Ma/S), n (%) History of hospitalisation (N/Y), n (%) Family history of heart disease (N/Y), n (%) Kind of heart disease (MI/U.A), n (%)
21 20 15 22 10
6661 1279 (636)/12 (364) (606)/13 (394) (455)/18 (545) (667)/11 (333) (303)/23 (697)
Placebo group (n = 33) 18 23 15 24 5
6230 1394 (545)/15 (455) (697)/10 (303) (455)/18 (545) (727)/9 (273) (152)/28 (848)
p-Value 019* 045† 062† 1† 059† 014†
F, female; M, male; Ma, married; S, single; N, no; Y, yes; n, number; MI, myocardial infarction; U.A, unstable anjina. *Results of the independent-sample t-test. † Results of the chi-squared test.
© 2014 John Wiley & Sons Ltd Journal of Clinical Nursing
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A Mohammadpour et al. Table 2 Chest pain intensity, duration, frequency and need for opioid analgesic therapy in both the study groups
Variables
Groups
Frequency
Placebo group Experimental group
p-Value Pain Duration p-Value Pain Severity
Placebo group Experimental group Placebo group Experimental group
p-Value
Need for analgesic
Before the intervention Mean SD
After the intervention Mean SD
100 050 103 030 077* 2597 1718 2536 1663 074* 4227 936 4738 905 002§
093 154 027 052 002* 2591 1593 348 734
The effects of topical heat therapy on chest pain in patients with acute coronary syndrome: a randomised double-blind placebo-controlled clinical trial Ali Mohammadpour, Batol Mohammadian, Mehdi Basiri Moghadam and Mahmoud Reza Nematollahi
Aims and objectives. To investigate the effects of local heat therapy on chest pain in patients with acute coronary syndrome. Background. Chest pain is a very common complaint in patients with acute coronary syndrome. It is managed both pharmacologically and nonpharmacologically. Pharmacological pain management is associated with different side effects. Design. This was a randomised double-blind placebo-controlled clinical trial conducted in 2013. Methods. A convenience sample of 66 patients with acute coronary syndrome was selected from a coronary care unit of a local teaching hospital affiliated to Gonabad University of Medical Sciences, Gonabad, Iran. Patients were randomly assigned to either the experimental or the placebo group. Patients in the experimental and the placebo groups received local heat therapy using a hot pack warmed to 50 and 37 °C, respectively. We assessed chest pain intensity, duration and frequency as well as the need for opioid analgesic therapy both before and after the study. The study instrument consisted of a demographic questionnaire, the McGill Pain Questionnaire, and a data sheet for documenting pain frequency and duration as well as the need for analgesic therapy. Findings. The placebo heat therapy did not significantly decrease the intensity, the duration and the frequency of pain episodes. However, pain intensity, duration and frequency in the experimental group decreased significantly after the study. Moreover, the groups differed significantly in terms of the need for opioid analgesic therapy neither before nor after the intervention. Conclusion. Local heat therapy is an effective intervention for preventing and relieving chest pain in patients with acute coronary syndrome. Relevance to clinical practice. Effective pain management using local heat therapy could help nurses play an important role in providing effective care to patients with acute coronary syndrome and in minimising adverse effects associated with pain medications.
What does this paper contribute to the wider global clinical community?
• The findings of this study suggest
•
•
that local heat therapy is an effective intervention for preventing and relieving chest pain in patients with acute coronary syndrome (ACS). Effective pain management using local heat therapy can help nurses play an important role in providing effective care to patients with ACS. Effective pain management using local heat therapy can help minimising adverse effects and financial burden associated with pain medications.
Key words: acute coronary syndrome, chest pain, local heat therapy Accepted for publication: 25 February 2014 Authors: Ali Mohammadpour, PhD, BSN, MSN, Associate Professor, Social Determinates of Health Research Center, Department of Nursing, Faculty of Nursing and Midwifery, Gonabad University of Medical Science; Batol Mohammadian, BSN, MSN, Lecturer, Faculty of Nursing and Midwifery, Gonabad University of Medical Science; Mehdi Basiri Moghadam, BSN, MSN, Lecturer, Department of Nursing, Faculty of Nursing and Midwifery, Gonabad
© 2014 John Wiley & Sons Ltd Journal of Clinical Nursing, doi: 10.1111/jocn.12595
University of Medical Science; Mahmoud Reza Nematollahi, MD, Cardiologist, Gonabad University of Medical Science, Gonabad, Iran Correspondence: Batol Mohammadian, Lecturer, Faculty of Nursing and Midwifery, Gonabad University of Medical Science, Gonabad, Iran. Telephone: +98 533 7223028. E-mail: [email protected]
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Introduction Cardiovascular disease – with a mortality rate of 35% – is a major health problem and a major cause of death worldwide. The mortality rate of the disease in high- and lowincome countries is 40 and 28%, respectively (Fauci et al. 2012). Coronary artery disease is the most prevalent type of cardiovascular disease and the leading cause of death worldwide. In our country, Iran, about 46% of all deaths result from coronary artery disease (Sharifnia et al. 2013). Acute coronary syndrome (ACS), an important type of coronary artery disease, is a highly prevalent heart disease worldwide (Monro 2009). The term ‘ACS’ refers to a wide and diverse range of heart problems – from slight chest discomfort and atypical electrocardiogram changes to ST-segment elevation, myocardial infarction and cardiogenic shock (Scirica 2010) – that result from a same pathologic mechanism (Chen et al. 2005). The underlying pathologic mechanism of ACS is reduced myocardial oxygen supply (e.g. in atherosclerosis and coronary artery spasm) or increased myocardial oxygen demand (e.g., in tachycardia and severe anaemia) or both (Fauci et al. 2012). The clinical manifestations of ACS included, but not limited to, chest pain, sweating, dyspnoea, tachycardia, blood pressure fluctuations, anxiety, and senses of suffocation and death (Fauci et al. 2012).
Background Chest pain is the most common complaint of patients with ACS (Karampurian & Imeni 2003). Chest pain results from myocardial ischaemia and injury secondary to decreased blood flow to the myocardium. The injured tissues secrete bradykinin and histamine, which stimulate pain receptors and cause pain. Chest pain, in turn, increases sympathetic activity and myocardial oxygen demand, which finally result in the progression of ischaemia and injury (Asgari & Soleimani 2006). Unrelieved chest pain can cause different physiological and psychological problems such as general discomfort, anxiety, respiratory distress, increased vascular resistance, increased blood pressure and cardiac dysrhythmias (Karampurian & Imeni 2003). These conditions increase cardiac workload and myocardial oxygen demand, resulting in the exacerbation of myocardial ischaemia and injury and the aggravation of chest pain (Fauci et al. 2012). Consequently, effective chest pain management has a top priority in providing care to patients with ACS (Fauci et al. 2012). Chest pain is managed both pharmacologically and nonpharmacologically. Pain medications such as nitrates,
2
beta-blockers and opioid analgesics are widely used for pharmacologic chest pain management (Fauci et al. 2012). However, alongside therapeutic effects, pain medications also bring about different side effects. Moreover, pharmacological pain management imposes a significant financial burden on patients, families and the healthcare system. Consequently, nonpharmacological strategies have been developed for the management of pain. One of the nonpharmacological pain management strategies is heat therapy. Heat increases the blood flow to injured and inflamed tissues. Improved tissue perfusion relieves pain through promoting tissue oxygenation and facilitating the removal of inflammatory mediators such as bradykinin and histamine from the injured tissues (Gale et al. 2006). Moreover, according to the gate control theory, heat relieves pain by stimulating nonpain receptors in the skin and thereby closing pain pathways (Habananda 2004). There are different methods for administrating heat therapy including, but not limited to, local heat therapy, sauna therapy and bathing. Miyata and Tei (2010) reported that sauna therapy improves haemodynamic status, vascular and autonomic nervous system function and general health in patients with congestive heart failure. They also reported that sauna therapy regulates the electrical activity of the heart as well as the secretion of neurotransmitters and hormones. Sobajima et al. (2011) also found that repeated sauna therapy improves myocardial function through increasing the blood levels of nitric oxide, stimulating the formation of myocardial collateral blood vessels and increasing myocardial perfusion. However, given the haemodynamic instability in patients with ACS, sauna therapy and whole-body heat therapy are contraindicated. Consequently, local heat therapy may help relieve chest pain in these patients. Local heat therapy using hot pack is one of the many techniques for applying heat to the body surface. Hot pack is a silicate gel bag that is warmed using an electric water heater and then is applied directly to skin to provide humid heat to the body (Gale et al. 2002). Yaghobi et al. (2012) found that local heat therapy applied to lumbar area using hot pack significantly decreased the intensity and the duration of herniated disc-related pain. Behmanesh et al. (2008) also reported that perineal and lumbar heat therapy significantly reduced the intensity and the duration of labour pains. Moreover, Yildirim et al. (2009) found heat therapy to be effective in relieving pain and joint stiffness and improving physical function in patients with knee osteoarthritis. However, to the best of our knowledge, the effect of local heat therapy with hot pack on chest pain in patients © 2014 John Wiley & Sons Ltd Journal of Clinical Nursing
Original article
with ACS has not yet been examined. Moreover, despite the potential effects of heat therapy on pain, chest pain is still managed mainly pharmacologically. Consequently, we conducted this study to examine the effectiveness of local heat therapy in relieving chest pain in patients with ACS.
Effect of topical heat therapy on chest pain
(Z1a/2 = 258), the sample size was determined to be 32 patients in each group. Given the probability of attrition, we recruited 66 patients to the study – 33 patients in each group.
Randomisation and masking Aim The aim of this study was to investigate the effects of local heat therapy on chest pain in patients with ACS. The research question was, ‘What is the effect of local heat therapy on chest pain in patients with ACS?’ Specific research questions were: 1 What is the effect of local heat therapy on the intensity, the duration and the frequency of chest pain episodes in patients with ACS? 2 What is the effect of local heat therapy on the need for opioid analgesic therapy?
After recruitment to the study, patients were randomly assigned to either the experimental or the placebo groups using the permuted block randomisation method. The block size was equal to 42 patients for each group. Accordingly, we generated a list of 17 four-sized blocks using the PERMUTATION RANDOMIZATION SOFTWARE PROGRAM (SAS Institute Inc., Cary, NC, USA) and allocated the patients to either of the study groups according to the list. All the patients were blinded to the study interventions. The chief researcher generated the random allocation list. The study intervention and data collection were performed by two separate research assistants who were both blind to the study interventions.
Methods Instrument Design and sample We conducted this randomised double-blind placebo-controlled clinical trial in 2013 – from March–October. The study setting was a coronary care unit (CCU) of a local teaching hospital affiliated to Gonabad University of Medical Sciences, Gonabad, Iran. The study population consisted of all patients with ACS referring to the study setting. The inclusion criteria were having a definitive diagnosis of ACS as established by attending cardiologists, having a normal haemodynamic status as evident from vital signs, having no history of drug or alcohol addiction, having no history of gastrointestinal or chest musculoskeletal diseases or psychological disorders, having the ability to speak and understand Persian, having no swelling, bruising, oedema or wound on chest and having a body mass index of 185–25. The exclusion criteria were transportation to other clinical settings or development of haemodynamic instability. We recruited the eligible patients to the study using the convenience sampling method. The study sample size was calculated using the findings of the pilot study and the following formula: ðZ þ Z Þ2 ðS21 þ S22 Þ g ¼ 1a=2 ðl1b . The pilot study was conducted on 2 1 l2 Þ ten patients meeting the inclusion criteria. The primary outcome variable was chest pain intensity. The mean and the standard deviation of the pre- and postintervention pain intensity in the experimental group were 286 309 and 820 135, respectively. Accordingly, with a power of 80% (Z1b = 084) and a confidence interval of 99% © 2014 John Wiley & Sons Ltd Journal of Clinical Nursing
The study instrument consisted of a demographic questionnaire, the McGill Pain Questionnaire (MPQ), and a data sheet for documenting the frequency and the duration of pain episodes as well as the need for opioid analgesic therapy. The MPQ consists of 20 sets of words on sensory, affective, evaluative and miscellaneous dimensions of pain. In each set, there are words describing the intensity and the quality of pain. The sensory dimension – word sets number 1 to 10 – included words on spatial, temporal, thermal and pressure-related properties of pain. The affective dimension – word sets number 11 to 15 – examines the affective properties of pain such as fear and tension. The word set number 16 relates to the evaluative dimension of pain and measures its overall subjective intensity. The word set numbers 17–20 relate to other aspects of pain not included in the first three dimensions. The total score of MPQ ranges from 0–78. Higher scores indicate more intense pain and vice versa (Ebrahimi Nejad et al. 2004). Nikravan et al. (2009) assessed the content validity and the reliability of the Persian version of MPQ. They reported a Cronbach’s alpha of 086 for the questionnaire. A research assistant measured the duration of each pain episode – in minutes – using a chronometer.
Intervention At the time of admission to CCU, patients meeting the inclusion criteria were recruited to the study and allocated
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to either of the study groups. During the first two hours after admission, all patients in both the study groups received the routine care of the study setting attending and were assessed for chest pain intensity, duration and frequency as well as the need for opioid analgesic therapy. Two hours after admission, we administered local heat therapy to patients in the experimental group. The hot pack was first warmed to 75 °C and placed exactly on patients’ chest. To prevent patients from burning and also hot pack from losing heat, we wrapped hot pack in a towel provided by the manufacturer. Consequently, patients received heat therapy at 50 °C. We administered the heat therapy to patients every 12 hours for two subsequent days – four sessions altogether. Each heat therapy session lasted for 23 minutes. After 23 minutes, the hot pack temperature decreased to below 44 °C. According to the hot pack manufacturer, temperatures below 44 °C have no therapeutic effects. Patients in the placebo group were also treated similarly. However, the pack was warmed only to 37 °C. After each heat therapy session, we closely monitored patients for chest pain. Accordingly, if patients developed chest pain, we assessed and documented the intensity and the duration of pain as well as the need for opioid analgesic therapy. Moreover, the total number of pain episodes happened after the intervention, that is, pain frequency, was also documented.
Data analysis Data analysis was performed using the Statistical Package for Social Sciences (SPSS, version 16.0; SPSS Inc., Chicago, IL, USA). Initially, we calculated a total mean for the pain intensity and pain duration of pre- and postintervention pain episodes and used these new total mean variables for the final data analysis. We employed the descriptive statistics measures such as mean, standard deviation and absolute and relative frequency values to describe the study data. The study groups were compared in terms of demographic characteristics using the independent-samples t-test and the chi-square test. The Kolmogorov–Smirnov test was also used to examine the distribution of the study variables. Accordingly, variables that had normal distribution were analysed using parametric statistical tests such as the paired- and the independent-samples t-tests. These variables were preintervention pain intensity in both groups and postintervention pain intensity in the control group. On the other hand, we analysed variables having non-normal distribution as well as the nominal and ordinal variables using nonparametric statistical tests such as the chi-square test, the Fisher’s exact test, the McNemar test, the Mann–Whit-
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ney U-test and the Wilcoxon signed rank test. These variables included of postintervention pain intensity in the experimental group as well as pre- and postintervention pain frequency, pain duration and the need for opioid analgesic therapy in both the study groups. Moreover, as the preand postintervention time episodes were not the same in length (two vs. 48 hours), the number of postintervention pain episodes was inevitably greater than the preintervention pain episodes. Accordingly, we only performed between-groups comparison for the variable ‘pain frequency’. p-Values less than 005 were considered significant.
Ethical considerations The Ethics Committee of Gonabad University of Medical Sciences, Gonabad, Iran, approved the study. In addition, the Iranian Registry of Clinical Trials registered the study. We provided the study participants with information about the aim and the process of the study. Moreover, they were ensured that both participation in and withdrawal from the study were voluntary. Finally, we obtained a written informed consent from each individual participant.
Findings Figure 1 shows the flow of participants. The study participants ranged in age from 31–90 years. The mean and the standard deviation of patients’ age in the experimental and placebo groups were 6661 1279 and 6230 1394, respectively. Most of the study participants were female patients (591%). The results of the chi-square and the independent-samples t-tests revealed that there was no statistically significant difference between the study groups in terms of demographic characteristics such as age, gender, marital status, history of hospitalisation, family history of heart disease and the type of current heart problem (p > 005; Table 1). The results of the paired-samples t-test and the Wilcoxon signed rank test reflected that the placebo heat therapy did not significantly decrease the intensity, the duration and the frequency of pain episodes. However, the results of this test revealed that after the study, pain intensity, duration and frequency in the experimental group decreased significantly (p < 0001; Table 2). The results of the Mann–Whitney U-test showed that before the study, there was no statistically significant difference between the study groups in terms of the duration and the frequency of pain episodes. However, the results of this test revealed that after the study, the duration and the frequency of pain episodes in the experimental group were © 2014 John Wiley & Sons Ltd Journal of Clinical Nursing
Original article
Effect of topical heat therapy on chest pain
(p = 1 and 026, respectively; Table 2). Moreover, the results of the McNemar test showed that after the study, the need for opioid analgesic therapy did not decrease significantly in the study groups (p > 005; Table 2).
A convenience sample of 66 eligible patients
Random allocation
Discussion 33 allocated to the placebo group
33 allocated to the experimental group
Routine care and use of placebo
Routine care and local heat therapy
Measurment of frequency of pain episodes, pain duration, pain severity and need for analgesic
66 patients (33 in each group) completed the study and were included in data analysis Figure 1 Flow of participants.
significantly lower than the placebo group (p < 005; Table 2). On the other hand, the results of the same test illustrated that before the study, the pain intensity in the experimental group was significantly higher than in the placebo group (p = 003; Table 2). After the study, the pain intensity in the experimental group decreased so much so that it became significantly lower than in the placebo group (p < 0001; Table 2). Finally, the results of the Fisher’s exact test revealed that neither before nor after the study, the groups differed significantly in terms of the need for opioid analgesic therapy
The aim of this study was to investigate the effects of local heat therapy on chest pain in patients with ACS. The study findings revealed that chest local heat therapy decreased the intensity, the duration and the frequency of chest pain episodes in patients with ACS. Moreover, findings showed that compared with the patients in the placebo group, patients receiving local heat therapy needed opioid analgesic therapy less frequently. The main cause of chest pain in patients with ACS is impaired myocardial perfusion and oxygenation (Fauci et al. 2012). Local heat therapy seems to prevent and relieve chest pain through dilating the coronary arteries, accelerating the angiogenesis process and hence increasing myocardial perfusion. Increased perfusion, in turn, promotes myocardial oxygenation and facilitates the removal of inflammatory mediators such as bradykinin and histamine from the injured myocardium. Moreover, local heat therapy may also stimulate the secretion of endorphins – endogenous morphine-like compounds – that help relieve pain. Previous studies have also demonstrated the effectiveness of local heat therapy in relieving herniated disc-related pain (Yaghobi et al. 2012), arthritis-related pain and stiffness (Michlovitz et al. 2004, Yildirim et al. 2009), and delivery pains (Behmanesh et al. 2008). On the other hand, the humid heat provided by hot pack alleviates patients’ anxiety and hence decreases sympathetic activity, reduces cardiac workload, prevents the progression of ischaemia and finally relieves chest pain. Moreover, humid heat stimulates nonpain receptors and relieves pain through the gate control mechanism. Sobajima et al. (2011) noted that repeated sauna therapy after myocardial infarction
Table 1 Patients’ characteristics and outcomes comparison between groups Patients’ characteristics
Experimental group (n = 33)
Age [years: mean (SD)] Gender (F/M), n (%) Marital status (Ma/S), n (%) History of hospitalisation (N/Y), n (%) Family history of heart disease (N/Y), n (%) Kind of heart disease (MI/U.A), n (%)
21 20 15 22 10
6661 1279 (636)/12 (364) (606)/13 (394) (455)/18 (545) (667)/11 (333) (303)/23 (697)
Placebo group (n = 33) 18 23 15 24 5
6230 1394 (545)/15 (455) (697)/10 (303) (455)/18 (545) (727)/9 (273) (152)/28 (848)
p-Value 019* 045† 062† 1† 059† 014†
F, female; M, male; Ma, married; S, single; N, no; Y, yes; n, number; MI, myocardial infarction; U.A, unstable anjina. *Results of the independent-sample t-test. † Results of the chi-squared test.
© 2014 John Wiley & Sons Ltd Journal of Clinical Nursing
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A Mohammadpour et al. Table 2 Chest pain intensity, duration, frequency and need for opioid analgesic therapy in both the study groups
Variables
Groups
Frequency
Placebo group Experimental group
p-Value Pain Duration p-Value Pain Severity
Placebo group Experimental group Placebo group Experimental group
p-Value
Need for analgesic
Before the intervention Mean SD
After the intervention Mean SD
100 050 103 030 077* 2597 1718 2536 1663 074* 4227 936 4738 905 002§
093 154 027 052 002* 2591 1593 348 734
