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© 2001 International Anesthesia Research Society
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Abstract |
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Patients receiving effective thoracic epidural analgesia for postthoracotomy pain may still complain of severe ipsilateral shoulder pain. The etiology of this pain is unclear. In this randomized, double-blinded, placebo-controlled study, we investigated the effect of phrenic nerve infiltration with lidocaine or saline on postoperative shoulder pain in 48 patients. After completion of a lung resection, patients received either 10 mL of 1% lidocaine or 10 mL of 0.9% saline infiltrated into the periphrenic fat pad at the level of the diaphragm. Shoulder pain was experienced by 33% of patients receiving lidocaine, compared with 85% of patients receiving saline (P < 0.008). Overall pain scores were lower with lidocaine (P < 0.05). PaCO2 values were not significantly higher with lidocaine in the first 2 h. We conclude that pain transmitted via the phrenic nerve and referred to the shoulder is the most likely explanation for the ipsilateral shoulder pain experienced by patients receiving epidural analgesia for postthoracotomy pain.
IMPLICATIONS: Ipsilateral shoulder pain after thoracotomy is common and may be severe, even in the presence of a functioning thoracic epidural. We have shown that infiltration of the phrenic nerve with local anesthetic significantly and safely reduces this shoulder pain, potentially allowing the ideal goal of a pain-free thoracotomy.
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Introduction |
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Thoracic epidural analgesia provides excellent postoperative pain relief and may even be associated with an improved outcome after thoracotomy (1,2). However, despite excellent pain relief in the dermatomes related to the incision, many patients still complain of severe ipsilateral shoulder pain. Although this pain is well recognized, few studies have defined the incidence and character of this pain. Burgess et al. (3), in a simple observational study, reported 19 of 45 patients having moderate to severe shoulder pain after pulmonary resection. The pain seems to be relatively resistant to IV opioids, and increasing the epidural infusion rate to achieve adequate analgesia may result in an unacceptable level of sedation and hypotension. Nonsteroidal antiinflammatory drugs in relatively large doses may be effective, but these drugs have been associated with an increased risk of renal failure in this predominantly elderly population undergoing major surgery (4,5).
There have been a number of suggestions as to the etiology of this shoulder pain after thoracotomy. Burgess et al. (3) suggested that the shoulder pain is likely to be related to transection of a major bronchus, but they were unable to suggest a mechanism. Distraction of the posterior thoracic ligaments by surgical retraction or stretching the brachial plexus, the shoulder joint, or both as a result of intraoperative positioning have also been suggested as possible mechanisms (6,7).
The phrenic nerve arises mainly from the fourth cervical nerve and provides the sensory innervation for the mediastinal and diaphragmatic pleura and the pericardium. The fourth cervical nerve also provides the cutaneous innervation for the skin over the shoulder. Disruption of the pericardial or diaphragmatic pleural surface during lung resection, or irritation of the pleural surface by chest drains, may provoke pain, which is referred to the shoulder and conducted via the phrenic nerve. If postthoracotomy shoulder pain is the result of pain referred in this way, then blocking the pathway by infiltrating the phrenic nerve with local anesthetic may alleviate this difficult postoperative problem. The aim of this study was to assess the efficacy and safety of phrenic nerve infiltration with local anesthetic on the incidence of ipsilateral shoulder pain after thoracotomy.
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Methods |
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The local Research Ethics Committee approved this double-blinded placebo-controlled study, and written, informed consent was obtained from the patients. We investigated 48 patients undergoing thoracotomy and receiving thoracic epidural analgesia. Patients were excluded if they had preexisting shoulder pain or were unable to fully understand the visual analog scale (VAS) scoring system despite preoperative coaching.
Patients were premedicated with oral diazepam 0.15 mg/kg. On arrival in the anesthetic room, a 14-gauge venous cannula, a 20-gauge radial arterial cannula, and a midthoracic epidural were inserted under local anesthesia. Patients received a 3-mL epidural test dose of 0.5% bupivacaine with 1:200,000 epinephrine. An arterial blood gas sample was taken before the induction of anesthesia. After preoxygenation, general anesthesia was induced with propofol 2–3 mg/kg. Neuromuscular block was achieved with atracurium 0.6 mg/kg, a double-lumen endobronchial tube was inserted, and its position was checked with a fiberoptic bronchoscope. Anesthesia was maintained with isoflurane in oxygen. Neuromuscular block was maintained with further boluses of atracurium.
Patients received a 0.1 mL/kg epidural bolus of 10 µg/mL fentanyl in 0.1% bupivacaine solution before the surgical incision. Intra- and postoperative analgesia was maintained by an epidural infusion of the solution at 0.1 mL · kg-1 · h-1. Intraoperative arterial blood pressure was maintained by altering the inhaled concentration of isoflurane and administering boluses of ephedrine as required.
Patients were placed in the lateral position, with the upper arm flexed by <90° to avoid excessive distraction of the shoulder joint. Chest tube placement was standardized. One tube was directed apically and the other inferiorly toward the posterior diaphragmatic angle. Patients having pneumonectomy received a single posterior chest drain. A standard surgical technique and retraction was used in all patients.
Before the induction of anesthesia, patients were randomized to one of two groups by use of sealed, shuffled envelopes. Patients assigned to Group L received 10 mL of 1% lidocaine infiltrated at the level of the diaphragm by using a 20-gauge spinal needle into the periphrenic fat pad just before chest closure. Care was taken to avoid intraneural injection. Patients assigned to Group S received 10 mL of 0.9% saline infiltrated in the same manner. The anesthetist and the surgeon were blinded as to which solution the patient had received. The site of the periphrenic infiltration is shown in Figure 1. At this site, the nerve is ensheathed by a fat pad. This fat pad is a reproducible site for infiltration, it acts as a reservoir for local anesthetic, and it reduces the risk of damage to the nerve because of intraneural injection.
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An observer who was blinded to the study group assessed patients at 0.5, 1, 2, 3, 4, 5, and 6 h after surgery. During each assessment period, the efficacy of the epidural was determined by mapping the dermatomal block to temperature and pinprick. The overall pain score was assessed with a VAS (0 mm = no pain and 100 mm = worst pain imaginable) and a five-point verbal ranking score (VRS) (0 = no pain, 1 = mild pain, 2 = moderate pain, 3 = severe pain, 4 = horrible pain). Patients were asked if they had any shoulder pain, and they were asked to point to the area of the pain they had to differentiate shoulder pain from wound pain. An arterial blood gas sample was obtained at each assessment period. For each patient, the volume of epidural solution used during the entire study period was recorded.
If at any assessment period, patients complained of severe pain in dermatomes related to the wound, an additional 0.1 mL/kg of epidural solution was administered, and the infusion rate increased. If severe wound pain remained after an epidural bolus, the patient was withdrawn from the trial. These patients were offered a replacement of their epidural or a patient-controlled analgesia pump containing morphine. The authors were reluctant to administer nonsteroidal drugs to this group of elderly patients. However, patients complaining of severe shoulder pain received ketorolac 10 mg IV. Mild or moderate shoulder pain was not treated in this manner.
Data from published accounts of postthoracotomy shoulder pain contained insufficient detail as to the exact incidence and severity to permit a meaningful power analysis before the study. The Shapiro-Francia W test was used to test for normality of the data. Given the nonnormality of some of the data, both the VAS scores and PCO2 measurements were subjected to analysis of variance for repeated measures of ranked data (Friedman’s analysis). Pairwise comparisons at each time interval were made with a correction for multiple comparisons. Binary data, such as sex or the presence or absence of shoulder pain, were analyzed with the test of two proportions. P values of <0.05 were taken to be significant. VRSs were analyzed by Wilcoxon’s ranked sum tests.
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Results |
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Forty-eight patients were entered into the study. Seven patients were excluded. Three patients, one from Group L and two from Group S, all of whom had undergone a pneumonectomy, were excluded from the study when it was apparent that the phrenic nerve had been excised during surgical dissection. Although they were withdrawn from the study, it is of note that none of these patients experienced any shoulder pain. Four patients were withdrawn because of incomplete dermatome block with the epidural (two Lidocaine, two Saline), despite additional boluses of epidural solution. The epidural was replaced in three of these patients with good effect, and the fourth received PCA with morphine.
The demographic data for the patients in the study and control groups who completed the study were comparable and are shown in Table 1. The types of operation undergone by patients in the two groups were broadly similar and are shown in Table 2.
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Immediately after surgery, 7 of the 21 patients in Group L experienced shoulder pain, compared with 17 of the 20 patients in Group S. This difference in proportions was highly significant (P < 0.008). Figure 2 shows the proportions with shoulder pain over the entire study period. Figure 3 shows the VAS scores for total pain experienced by both groups. Total pain scores were significantly (P < 0.05) lower in the Lidocaine group over the first two postoperative hours. VRS scores demonstrated significantly lower pain scores in Group L patients for the first two postoperative hours (P = 0.0028 at 0.5 h, P = 0.016 at 1 h, P = 0.0018 at 2 h, and P = 0.673 at 3 h).
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Between the two groups, there was no significant difference in the total volume of epidural solution used during the operative and study periods. The mean volume (95% confidence interval [CI]) of epidural solution used in the lidocaine group was 49 (43–54) mL, and the mean volume (95% CI) of epidural solution used in the saline group was 54 (44–49) mL.
Figure 4 shows a comparison of the arterial PCO2 by group during the study period. Although the mean PCO2 values are slightly higher over the first 2 h in the Lidocaine Group, the difference between the groups was not statistically different at any time. No patients required postoperative ventilatory support.
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Discussion |
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TopAbstractIntroductionMethodsResultsDiscussionReferences |
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This is the first prospective study in patients receiving epidural analgesia to establish the incidence and severity of ipsilateral postthoracotomy shoulder pain. Eighty-five percent of the Control (S) group experienced shoulder pain. This incidence is similar to that reported by other workers (3). Patients in the study had no difficulty in distinguishing shoulder pain from wound pain in the presence of a functioning epidural. Continuous infusion of the epidural solution provides excellent analgesia of the dermatomes related to the incision, and this was confirmed by eliciting changes in pinprick and temperature sensation in both groups. When shoulder pain does occur, it may be severe and distressing to the patient, detracting from the benefits of an effective dermatome block with the epidural. When shoulder pain is absent or prevented by phrenic infiltration, patients report remarkably little pain. The combination of epidural and ipsilateral phrenic nerve blocks therefore approaches the ideal goal of pain-free thoracotomy.
Although we cannot exclude a contribution from stress on the shoulder joint or posterior thoracic ligaments, all patients were carefully positioned and padded to minimize this problem. Resection of a major bronchus has also been suggested as a factor in the etiology of shoulder pain (1). However, in this study, operations involving bronchial resection were similarly distributed in both study groups. The marked reduction in the incidence of shoulder pain after lidocaine infiltration of the phrenic nerve strongly supports our hypothesis that irritation of the pericardium or mediastinal and diaphragmatic pleural surfaces results in pain that is referred to the shoulder via the phrenic nerve.
It is of note that some patients in the Lidocaine group experienced shoulder pain. There are a number of possible explanations for this. First, the blockade may have been too low to be fully effective. The phrenic nerve supplies sensory fibers to the fibrous pericardium and the parietal layer of the serous pericardium. Both of the two patients in the Lidocaine group who underwent an intrapericardial pneumonectomy experienced shoulder pain. This may have been because of stimulation of the phrenic nerve proximal to the site of lidocaine infiltration at the level of the diaphragm. A higher block might be more appropriate in these patients, with care to avoid intraneural injection because there is less periphrenic fat proximally. The use of a long 20-gauge spinal needle facilitates the injection. Second, the technique relies on the retention of lidocaine by the periphrenic fat pad, which may be insubstantial in some patients.
When the study was designed, we were aware of the possibility that phrenic nerve infiltration may adversely affect ventilation. Phrenic nerve paresis after interscalene block is associated with a 25% reduction in both vital capacity and forced vital capacity (8,9). In another study, altered respiratory sensation or mild dyspnea was reported by a third of healthy patients receiving an interscalene block (10). Because of our concern, we used lidocaine, a short-acting local anesthetic, to block the phrenic nerve. We measured PaCO2 as a marker of respiratory adequacy. Although more sensitive markers of diaphragmatic paralysis are available, they are less readily measurable in the immediate postoperative period. It is of note that the PaCO2 in the lidocaine group tended to be slightly higher during the first two postoperative hours. Although the difference was neither clinically or statistically significant in our random sample of patients presenting for thoracotomy, the importance may be increased in the severely compromised patient. It should also be noted that phrenic nerve paresis may confer some benefit to the patient by reducing space in the hemithorax, especially after a pneumonectomy.
In considering the risks of adverse effects, alternative therapies need to be considered. Nonsteroidal antiinflammatory analgesics, such as ketorolac, represent another therapeutic possibility and may be effective. Burgess et al. (3) recommended 30–60 mg ketorolac IM, followed by 15–30 mg IM every six hours. However, there is concern that these drugs may cause renal failure in this elderly population, who may be prone to hypovolemia (11,12). For this reason, a maximum of 10 mg of ketorolac was administered in this study, and its use was restricted to patients with severe shoulder pain.
In conclusion, ipsilateral shoulder pain after thoracotomy with epidural analgesia is common and may be severe. The most likely explanation is that irritation of the pericardium or mediastinal and diaphragmatic pleural surfaces result in pain referred to the shoulder via the phrenic nerve. Infiltration of the phrenic nerve at the level of the diaphragm significantly reduces the incidence of shoulder pain for up to two hours compared to infiltration with placebo. Phrenic infiltration was not associated with adverse effects in our study population. Further studies are required to assess the duration of action of longer acting local anesthetics, such as bupivacaine or ropivacaine, in this application.
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Footnotes |
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Presented in part to European Society of Regional Anaesthesia 18th Annual Congress, Istanbul, September 30, 1999.
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References |
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Rawal N, Sjostrand U, Christoffersson E, et al. Comparison of intramuscular and epidural morphine for postoperative analgesia in the grossly obese: influence on postoperative ambulation and pulmonary function. Anesth Analg 1984; 63: 583–92.
[Abstract/Free Full Text] - Burgess FW, Anderson DM, Colonna D, Cavanaugh DG. Thoracic epidural analgesia with bupivacaine and fentanyl for postoperative thoracotomy pain. J Cardiothorac Vasc Anesth 1994; 8: 420–4.[Medline]
- Burgess FW, Anderson DM, Colonna D, et al. Ipsilateral shoulder pain following thoracic surgery. Anesthesiology 1993; 78: 365–8.[Web of Science][Medline]
- Appadurai IR, Power I. NSAIDS in the postoperative period: use with caution in elderly people [letter]. BMJ 1993; 307: 257.
- Gibson P, Weadington D, Winney RJ. NSAIDS in the postoperative period: clinical experience confirms risk [letter]. BMJ 1993; 306: 257–8.
- Holt M. Ipsilateral shoulder pain following thoracic operations [letter]. Anesthesiology 1993; 79: 192.
- Mark JBD, Brodsky JB. Ipsilateral shoulder pain following thoracic operations [letter]. Anesthesiology 1993; 79: 192.
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Urmey WF, McDonald M. Hemidiaphragmatic paresis during interscalene brachial plexus block: effects on pulmonary function and chest wall mechanics. Anesth Analg 1992; 74: 352–7.
[Abstract/Free Full Text] - Pere P, Pitkanen M, Rosenberg PH, et al. Effect of continuous interscalene brachial plexus block on diaphragm motion and on ventilatory function. Acta Anaesthesiol Scand 1992; 36: 53–7.[Web of Science][Medline]
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Urmey WF, Talts KH, Sharrock NE. One hundred percent incidence of hemidiaphragmatic paresis associated with interscalene brachial plexus anesthesia as diagnosed by ultrasonography. Anesth Analg 1991; 72: 498–503.
[Abstract/Free Full Text] - Palmer BF, Henrich WL. Clinical acute renal failure with nonsteroidal anti-inflammatory drugs. Semin Nephrol 1995; 15: 214–27.[Web of Science][Medline]
- Pugliese F, Cinotti GA. Nonsteroidal anti-inflammatory drugs (NSAIDs) and the kidney. Nephrol Dial Transplant 1997; 12: 386–8.[Abstract]
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