Use of Transcutaneous Postoperative 0. Bayindir,
MD, T. Paker,
Electrical Nerve Stimulation in the Control Chest Pain After Cardiac Surgery
MD, B. Akpinar,
MD, S. Erenturk,
The effect of continuous transcutaneous electrical nerve stimulation (TENS) on postoperative pain following median sternotomy was evaluated in 89 patients with severe chest pain who underwent cardiac surgery in a prospective, randomized, blinded trial. Pain was assessed by visual analog pain scores before and during treatment in each group. In the active TENS group, 79% of the patients were completely free of chest pain during rest at the end of 180 minutes (P < 0.001). Among the remaining patients with TENS, 16% had slight pain not needing narcotic analgesics and 5% still had chest pain requiring narcotics. In the control group in which
C
ONTROLLING postoperative pain after intrathoracic and abdominal operations is essential to maintain early mobilization and reduce pulmonary complications. Although the potent analgesic capabilities of the opioid drugs are well known, they decrease central respiratory drive and cough; cause mental clouding, nausea, vomiting, and constipation; and, with continued use, produce tolerance and physical dependence. These unwanted effects of narcotics have stimulated the search for alternative modes of pain control. In 1965, Melzack and Wall presented the gate control theory of pain transmission and this theory led to the concept of using transcutaneous electrical nerve stimulation (TENS) for analgesia.’ Hymes et al* first suggested that TENS might be used to control acute postoperative pain. Previous studies have shown that the use of TENS after intraabdominal and intrathoracic operations has decreased the incidence of pulmonary complications including atelectasis and pneumonia, and reduced the pain score and stay in the intensive care unit.3.4 Cooperman et al have also shown that the use of TENS after intraabdominal operations significantly reduced narcotic analgesia requirements.5 The goal of the present study was to evaluate the direct and placebo effects of TENS in controlling chest pain after median sternotomy for cardiac surgery in a prospective, randomized, double-blinded trial in which pain was assessed by visual analog pain scores.6.7
MATERIALS
AND METHODS
Eighty-nine adult patients who underwent cardiac surgery via a median sternotomy were selected for this study. Because patients having internal mammary artery implantation were expected to suffer greater postoperative pain, they were not included in the study. Fifty-nine patients received active TENS, whereas the other 30 patients constituted the control group and received inactive TENS. Before the operation, the patients were informed about the character of pain they might suffer in the early postoperative period. The postoperative application of TENS and the unwanted side effects of narcotic analgesics were also discussed. This interview was carefully structured to avoid any suggestion of the outcome of postoperative TENS. The patients were told that if TENS was not effective, postoperative pain medication with narcotic analgesics would be available. They were also informed
Journalof Cardiofhoracic and VascularAnesthesia,
MD, D. Askin,
MD, and
A. Aytac,
of
MD
inactive TENS was used, the intensity of pain was reduced in 44% of the patients at the end of 90 minutes (P < 0.001). However, this early placebo effect was noted to diminish with time and at the end of 180 minutes, 80% of the patients complained of severe chest pain and needed narcotics. These data suggest that TENS can be effective in controlling postoperative chest pain due to median sternotomy after cardiac surgery and its continuous application in the early postoperative period can reduce the need for narcotics. Copyright o 199 1 by W. 6. Saunders Company
about the importance of correctly scoring their intensity of pain on the scale because this would avoid unnecessary narcotic use. Anesthesia was induced with fentanyl, 6 pg/kg, thiopental, 3 pg/kg, pancuronium, 0.1 mgikg, and 50% nitrous oxide. During the operatian, anesthesia was maintained with fentanyl, pancuronium, 50% nitrous oxide, and 0.5% to 1% isoflurane. The patients entered the study in the intensive care unit just after extubation. The mean duration of time until extubation was 4 ? 1.5 hours. The routine protocol for pain relief was started as soon as the patient arrived in the intensive care unit (metamisolum natrium, 1 g, 3 times daily, a nonnarcotic analgesic). Patients with chest pain after extubation were first asked to score their pain on a visual analog pain score. Very severe pain was scored as 4, severe pain as 3, moderate pain as 2, slight pain as 1, and no pain as 0. Only patients with pain scores of 3 or 4 were included in the study. In the active TENS group, two electrodes were placed on each side of the sternotomy incision over the area of maximum pain. An IT0 dual-channel TENS device (model 1207, ITO, Co., Ltd., Japan) was adjusted to the burst mode, applying 10 pulses/burst, and 2 bursts/s, with a pulse width of 50 to 60 microseconds. The intensity was increased until the patient felt the sensation on the chest wall and was then continuously applied. The same electrodes were applied with the same TENS device, but without a battery to the control (inactive TENS) group. During the interview that took place before the operation, all the patients were told that they may or may not feel any sensation on their chest wall during TENS application and this would not necessarily mean that the treatment was not effective. TENS was applied for 180 minutes in both groups and patients were asked to score their pain on the pain scale every 15 minutes. Narcotic analgesics were administered only for patients continuing to have pain at the end of 180 minutes (morphine infusion at 0.6 pg/kg/min). In order to avoid interference on the electrocardiogram (ECG) monitor, ECG electrodes were placed as far as possible from the TENS electrodes. External pacemaker wires were isolated to avoid contact with the TENS electrodes and patients with demand pacemakers were excluded from the study. The statistical results were evaluated with the Student’s t test. RESULTS
The mean ages of the patients in the active and inactive TENS groups were 57.3 and 58.4 years, respectively. The
From the Department of Cardiac Anesthesia, Institute of Cardiology, University of Istanbul, Haseki, Turkey. Address reprint requests to B. Akpinar, MD, O.L. V.R. Ziekenhuis, Cardiovasculaire Heelkunde, 9300~AALST, Belgium. Copyright 0 1991 by W.B. Saunders Company 1053-077019110506-0012$03.00/0
Vol5, No 6 (December), 1991:
pp 589-591
589
BAYINDIR i;’ i.
590
Table 1. Patient Demographics Actwe TENS Group
Control Group
Mean age (yr)
57.3
56.4
Mean weight (kg)
72.5
73.2
67133
66134
Sex (M/F, %)
?
Surgical procedure CABG
64
62
Valve
36
38
Abbreviations:
CABG, coronary
b%-
artery bypass graft; Valve, valve
replacement or repair procedures.
I
min.
mean weight was 72.5 kg in the active TENS group and 73.2 kg in the inactive TENS group. Sixty-seven percent of the active TENS group were men, whereas 66% of the inactive TENS group were men. The patients in both groups underwent coronary revascularization or valvular heart procedures (Table 1). In the active TENS group at the end of 165 minutes, 79% of the patients were completely free of pain with a pain score of 0, 16% had a pain score of 1, 3% had a score of 2, and 2% still had a pain score of 3 or 4. The decrease in the percentage of patients having severe pain was statistically significant (P < 0.001; Fig 1). At the end of 180 minutes, only 5% of the patients had pain scores ranging between 2 and 4 and needed narcotic analgesics. In the control group in which inactive TENS was used, 6% of the patients were completely free of pain at the end of 90 minutes. Thirteen percent of the patients had a pain score of 1, 23% had a pain score of 2, and 58% had pain scores of 3 and 4 at 90 minutes. In sum, the pain score was reduced in 44% of the patients in the control group that received inactive TENS (P < 0.001) at the end of 90 minutes. However, after 90 minutes the number of patients with severe chest pain started to increase again and at the end of 180 minutes 80% of the control group had severe pain requiring narcotics (Fig 2). Figure 3 shows the percent of patients with severe pain and the significant difference between groups after 90 minutes (P < 0.001). There were no complications related to TENS in both groups.
Fig 2. The distribution of pain scores in the control group. Note the increase of patients with severe pain after 90 minutes. 0, score 3 and 4; ?? , score 2; a, score 1; B. score 0.
DISCUSSION
The use of TENS in the control of postoperative pain has been reported previously. Although it is known that median sternotomy incisions cause less discomfort than thoracotomy or abdominal incisions, they can necessitate the use of narcotic analgesics in some patients. To the authors’ knowledge, the application of TENS in patients with a median sternotomy has not been reported previously. The present results show that in the active TENS group chest pain during rest was completely eliminated in 79% of the patients at the end of 165 minutes, while 16% had slight pain not needing narcotic analgesics. In total, 95% of the patients in this group did not need any narcotics for pain, which suggests that TENS can be very effective in reducing pain after median sternotomy and cardiac surgery. These results suggest that TENS can be an alternative to pharmacological therapy when begun in the early postoperative period before the pain starts and applied continuously. In the inactive TENS group, the 44% decline in patients
nin. Fig 1. The distribution of pain scores at the end of 180 minutes in the active TENS group. 0, score 3 and 4; ?? , score 2; ?3, ?score 1; ?,? score 0.
Fig 3. The decrease in the percentage of patients with severe chest pain in both groups. ?? , TENS; 0, control.
MANAGEMENT
OF POSTOPERATIVE
591
CHEST PAIN WITH TENS
having pain scores of 3 or 4 at the end of 90 minutes also was found to be significant, which can be explained by the placebo effect of TENS (Fig 2). In spite of this, the decline in the percentage of patients having high pain scores was significantly less than the active TENS group (Fig 3). In addition, the number of patients with severe pain started to increase again after 90 minutes in the control group and reached 80% of the population at the end of 180 minutes, whereas there was a steady decline in the number of
patients with severe pain with time in the active TENS group. These results suggest that TENS can be very effective in reducing the use of narcotic analgesics in the majority of the patients when it is applied continuously before the pain starts. Low cost, lack of undesirable side effects, and ease of application can make TENS an acceptable method of reducing postoperative chest pain after median stemotomy and cardiac surgery.
REFERENCES 1. Melzack R, Wall PD: 150:971-979,1965
Pain mechanism: A new theory. Science
2. Hymes AC, Raab DE, Yonehiro EG, et al: Electrical surface stimulation for control of acute postoperative pain and prevention of ileus. Surg Forum 24:447-449,1973 3. Ali J, Yaffe CS, Serrette C: The effect of transcutaneous nerve stimulation on postoperative pain and pulmonary function. Surgery 89:507-512,198l 4. Wartield
CA, Stein JM, Frank HA: The effect of transcutane-
ous electrical nerve stimulation on pain after thoracotomy. Ann Thorac Surg 39:462-465,1985 5. Cooperman AM, Hall B, Mikalacki K, et al: Use of transcutaneous electrical nerve stimulation in the control of postoperative pain: Results of a prospective randomized controlled study. Am J Surg 133:185-187,1977 6. Huskisson EC: Measurement of pain. Lancet 2:1127-1131, 1974 7. Revill SI, Robinson JO, Rosen M, et al: The reliability of a linear analogue for evaluating pain. Anesthesia 31:1191-1198, 1976
MD, T. Paker,
Electrical Nerve Stimulation in the Control Chest Pain After Cardiac Surgery
MD, B. Akpinar,
MD, S. Erenturk,
The effect of continuous transcutaneous electrical nerve stimulation (TENS) on postoperative pain following median sternotomy was evaluated in 89 patients with severe chest pain who underwent cardiac surgery in a prospective, randomized, blinded trial. Pain was assessed by visual analog pain scores before and during treatment in each group. In the active TENS group, 79% of the patients were completely free of chest pain during rest at the end of 180 minutes (P < 0.001). Among the remaining patients with TENS, 16% had slight pain not needing narcotic analgesics and 5% still had chest pain requiring narcotics. In the control group in which
C
ONTROLLING postoperative pain after intrathoracic and abdominal operations is essential to maintain early mobilization and reduce pulmonary complications. Although the potent analgesic capabilities of the opioid drugs are well known, they decrease central respiratory drive and cough; cause mental clouding, nausea, vomiting, and constipation; and, with continued use, produce tolerance and physical dependence. These unwanted effects of narcotics have stimulated the search for alternative modes of pain control. In 1965, Melzack and Wall presented the gate control theory of pain transmission and this theory led to the concept of using transcutaneous electrical nerve stimulation (TENS) for analgesia.’ Hymes et al* first suggested that TENS might be used to control acute postoperative pain. Previous studies have shown that the use of TENS after intraabdominal and intrathoracic operations has decreased the incidence of pulmonary complications including atelectasis and pneumonia, and reduced the pain score and stay in the intensive care unit.3.4 Cooperman et al have also shown that the use of TENS after intraabdominal operations significantly reduced narcotic analgesia requirements.5 The goal of the present study was to evaluate the direct and placebo effects of TENS in controlling chest pain after median sternotomy for cardiac surgery in a prospective, randomized, double-blinded trial in which pain was assessed by visual analog pain scores.6.7
MATERIALS
AND METHODS
Eighty-nine adult patients who underwent cardiac surgery via a median sternotomy were selected for this study. Because patients having internal mammary artery implantation were expected to suffer greater postoperative pain, they were not included in the study. Fifty-nine patients received active TENS, whereas the other 30 patients constituted the control group and received inactive TENS. Before the operation, the patients were informed about the character of pain they might suffer in the early postoperative period. The postoperative application of TENS and the unwanted side effects of narcotic analgesics were also discussed. This interview was carefully structured to avoid any suggestion of the outcome of postoperative TENS. The patients were told that if TENS was not effective, postoperative pain medication with narcotic analgesics would be available. They were also informed
Journalof Cardiofhoracic and VascularAnesthesia,
MD, D. Askin,
MD, and
A. Aytac,
of
MD
inactive TENS was used, the intensity of pain was reduced in 44% of the patients at the end of 90 minutes (P < 0.001). However, this early placebo effect was noted to diminish with time and at the end of 180 minutes, 80% of the patients complained of severe chest pain and needed narcotics. These data suggest that TENS can be effective in controlling postoperative chest pain due to median sternotomy after cardiac surgery and its continuous application in the early postoperative period can reduce the need for narcotics. Copyright o 199 1 by W. 6. Saunders Company
about the importance of correctly scoring their intensity of pain on the scale because this would avoid unnecessary narcotic use. Anesthesia was induced with fentanyl, 6 pg/kg, thiopental, 3 pg/kg, pancuronium, 0.1 mgikg, and 50% nitrous oxide. During the operatian, anesthesia was maintained with fentanyl, pancuronium, 50% nitrous oxide, and 0.5% to 1% isoflurane. The patients entered the study in the intensive care unit just after extubation. The mean duration of time until extubation was 4 ? 1.5 hours. The routine protocol for pain relief was started as soon as the patient arrived in the intensive care unit (metamisolum natrium, 1 g, 3 times daily, a nonnarcotic analgesic). Patients with chest pain after extubation were first asked to score their pain on a visual analog pain score. Very severe pain was scored as 4, severe pain as 3, moderate pain as 2, slight pain as 1, and no pain as 0. Only patients with pain scores of 3 or 4 were included in the study. In the active TENS group, two electrodes were placed on each side of the sternotomy incision over the area of maximum pain. An IT0 dual-channel TENS device (model 1207, ITO, Co., Ltd., Japan) was adjusted to the burst mode, applying 10 pulses/burst, and 2 bursts/s, with a pulse width of 50 to 60 microseconds. The intensity was increased until the patient felt the sensation on the chest wall and was then continuously applied. The same electrodes were applied with the same TENS device, but without a battery to the control (inactive TENS) group. During the interview that took place before the operation, all the patients were told that they may or may not feel any sensation on their chest wall during TENS application and this would not necessarily mean that the treatment was not effective. TENS was applied for 180 minutes in both groups and patients were asked to score their pain on the pain scale every 15 minutes. Narcotic analgesics were administered only for patients continuing to have pain at the end of 180 minutes (morphine infusion at 0.6 pg/kg/min). In order to avoid interference on the electrocardiogram (ECG) monitor, ECG electrodes were placed as far as possible from the TENS electrodes. External pacemaker wires were isolated to avoid contact with the TENS electrodes and patients with demand pacemakers were excluded from the study. The statistical results were evaluated with the Student’s t test. RESULTS
The mean ages of the patients in the active and inactive TENS groups were 57.3 and 58.4 years, respectively. The
From the Department of Cardiac Anesthesia, Institute of Cardiology, University of Istanbul, Haseki, Turkey. Address reprint requests to B. Akpinar, MD, O.L. V.R. Ziekenhuis, Cardiovasculaire Heelkunde, 9300~AALST, Belgium. Copyright 0 1991 by W.B. Saunders Company 1053-077019110506-0012$03.00/0
Vol5, No 6 (December), 1991:
pp 589-591
589
BAYINDIR i;’ i.
590
Table 1. Patient Demographics Actwe TENS Group
Control Group
Mean age (yr)
57.3
56.4
Mean weight (kg)
72.5
73.2
67133
66134
Sex (M/F, %)
?
Surgical procedure CABG
64
62
Valve
36
38
Abbreviations:
CABG, coronary
b%-
artery bypass graft; Valve, valve
replacement or repair procedures.
I
min.
mean weight was 72.5 kg in the active TENS group and 73.2 kg in the inactive TENS group. Sixty-seven percent of the active TENS group were men, whereas 66% of the inactive TENS group were men. The patients in both groups underwent coronary revascularization or valvular heart procedures (Table 1). In the active TENS group at the end of 165 minutes, 79% of the patients were completely free of pain with a pain score of 0, 16% had a pain score of 1, 3% had a score of 2, and 2% still had a pain score of 3 or 4. The decrease in the percentage of patients having severe pain was statistically significant (P < 0.001; Fig 1). At the end of 180 minutes, only 5% of the patients had pain scores ranging between 2 and 4 and needed narcotic analgesics. In the control group in which inactive TENS was used, 6% of the patients were completely free of pain at the end of 90 minutes. Thirteen percent of the patients had a pain score of 1, 23% had a pain score of 2, and 58% had pain scores of 3 and 4 at 90 minutes. In sum, the pain score was reduced in 44% of the patients in the control group that received inactive TENS (P < 0.001) at the end of 90 minutes. However, after 90 minutes the number of patients with severe chest pain started to increase again and at the end of 180 minutes 80% of the control group had severe pain requiring narcotics (Fig 2). Figure 3 shows the percent of patients with severe pain and the significant difference between groups after 90 minutes (P < 0.001). There were no complications related to TENS in both groups.
Fig 2. The distribution of pain scores in the control group. Note the increase of patients with severe pain after 90 minutes. 0, score 3 and 4; ?? , score 2; a, score 1; B. score 0.
DISCUSSION
The use of TENS in the control of postoperative pain has been reported previously. Although it is known that median sternotomy incisions cause less discomfort than thoracotomy or abdominal incisions, they can necessitate the use of narcotic analgesics in some patients. To the authors’ knowledge, the application of TENS in patients with a median sternotomy has not been reported previously. The present results show that in the active TENS group chest pain during rest was completely eliminated in 79% of the patients at the end of 165 minutes, while 16% had slight pain not needing narcotic analgesics. In total, 95% of the patients in this group did not need any narcotics for pain, which suggests that TENS can be very effective in reducing pain after median sternotomy and cardiac surgery. These results suggest that TENS can be an alternative to pharmacological therapy when begun in the early postoperative period before the pain starts and applied continuously. In the inactive TENS group, the 44% decline in patients
nin. Fig 1. The distribution of pain scores at the end of 180 minutes in the active TENS group. 0, score 3 and 4; ?? , score 2; ?3, ?score 1; ?,? score 0.
Fig 3. The decrease in the percentage of patients with severe chest pain in both groups. ?? , TENS; 0, control.
MANAGEMENT
OF POSTOPERATIVE
591
CHEST PAIN WITH TENS
having pain scores of 3 or 4 at the end of 90 minutes also was found to be significant, which can be explained by the placebo effect of TENS (Fig 2). In spite of this, the decline in the percentage of patients having high pain scores was significantly less than the active TENS group (Fig 3). In addition, the number of patients with severe pain started to increase again after 90 minutes in the control group and reached 80% of the population at the end of 180 minutes, whereas there was a steady decline in the number of
patients with severe pain with time in the active TENS group. These results suggest that TENS can be very effective in reducing the use of narcotic analgesics in the majority of the patients when it is applied continuously before the pain starts. Low cost, lack of undesirable side effects, and ease of application can make TENS an acceptable method of reducing postoperative chest pain after median stemotomy and cardiac surgery.
REFERENCES 1. Melzack R, Wall PD: 150:971-979,1965
Pain mechanism: A new theory. Science
2. Hymes AC, Raab DE, Yonehiro EG, et al: Electrical surface stimulation for control of acute postoperative pain and prevention of ileus. Surg Forum 24:447-449,1973 3. Ali J, Yaffe CS, Serrette C: The effect of transcutaneous nerve stimulation on postoperative pain and pulmonary function. Surgery 89:507-512,198l 4. Wartield
CA, Stein JM, Frank HA: The effect of transcutane-
ous electrical nerve stimulation on pain after thoracotomy. Ann Thorac Surg 39:462-465,1985 5. Cooperman AM, Hall B, Mikalacki K, et al: Use of transcutaneous electrical nerve stimulation in the control of postoperative pain: Results of a prospective randomized controlled study. Am J Surg 133:185-187,1977 6. Huskisson EC: Measurement of pain. Lancet 2:1127-1131, 1974 7. Revill SI, Robinson JO, Rosen M, et al: The reliability of a linear analogue for evaluating pain. Anesthesia 31:1191-1198, 1976
