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Ann Thorac Surg 2004;77:1951-1955
© 2004 The Society of Thoracic Surgeons

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Original article: general thoracic

Acute postoperative pain in lung transplant recipients

^a Department of Anesthesiology, Montreal University Medical Center, Hôpital Notre-Dame, Montreal, Canada
^b Department of Surgery, Montreal University Medical Center, Hôpital Notre-Dame, Montreal, Canada
^c Department of Medicine, Montreal University Medical Center, Hôpital Notre-Dame, Montreal, Quebec, Canada

Accepted for publication December 2, 2003.

^* Address reprint requests to Dr Girard, Department of Anesthesiology, CHUM, Hôpital Notre-Dame, 1560 Sherbrooke E, Montreal, Quebec, Canada H2L 4M1
e-mail: francois.girard.chum{at}ssss.gouv.qc.ca

	Abstract

Top Abstract Introduction Patients and methods Results Comment References

 
BACKGROUND: This retrospective study was designed to assess the quality of postoperative pain control and the facility of transition from epidural to oral analgesia in lung transplant recipients.

METHODS: After institutional review board approval, data were collected from the charts of all patients who underwent lung transplantation at our institution between 1998 and 2002. The study group consisted of the patients for whom an epidural was the first postoperative pain management modality. To serve as a control group we reviewed the charts of 30 patients, randomly selected over the same period, who underwent a thoracotomy for indications other than transplantation and who received postoperative epidural analgesia.

RESULTS: Eighty-three patients were available for analysis. Unilateral and bilateral lung transplant recipients had equivalent quality of pain control. However, lung transplant recipients had a lower incidence of adequate pain relief than patients undergoing thoracotomy for other indications (73% vs 87%, p < 0.05). Lung transplant recipients also had a higher incidence of epidural to oral analgesia transition failure (47% vs 20%, p < 0.01).

CONCLUSIONS: This is the first study to assess the quality of postoperative pain control and success of transition from epidural to oral analgesia in lung transplant recipients. Prospective studies are needed to assess the impact of our findings on patients' outcome.

	Introduction

Top Abstract Introduction Patients and methods Results Comment References

 
Thoracic surgery incisions such as the posterolateral thoracotomy or bilateral thoracosternotomy (clamshell) are associated with severe postoperative pain [1–3]. In this field of surgery, the quality of pain relief is intimately correlated with the success of the intervention. Pain control allows for a better ventilation and early ambulation, each contributing to the return to normal activities and a better quality of life [4]. Thoracic pain prevents deep breathing and coughing, possibly resulting in pulmonary complications such as atelectasis or infections [5]. In fact, pain is the most important factor responsible for the decrease of respiratory function in the postoperative period [6] and there is evidence of a significant relationship between the intensity of acute postoperative pain following thoracotomy, and the development of chronic pain [7]. Lubenow and colleagues [8] have demonstrated that epidural analgesia provides excellent pain relief with minimal adverse effects in postthoracotomy patients. Epidural analgesia has therefore become a technique of choice in thoracic surgery.

To date, we have found no study that has assessed the quality of postoperative pain relief in lung transplant recipients. This population of patients is usually severely debilitated before the surgery. In the postoperative period, high doses of steroids and immunosuppressive agents place the patients at high risk of developing pulmonary complications. Adequate pain control is therefore mandatory to facilitate mechanical ventilation weaning and to promote appropriate breathing and adequate handling of bronchial secretions once the patient is extubated. In addition, we found no study that assessed the facility of transition from postoperative epidural analgesia to oral analgesics in lung transplant patients. This information is in fact not at all available in the thoracic anesthesia literature. Our clinical experience leads us to believe that this transition is a challenge in lung transplant patients. The main objective of the present study was to evaluate the quality of postoperative pain relief after lung transplantation and to assess the transition to oral analgesics following epidural analgesia. Based on our clinical experience, we hypothesized that the quality of pain relief obtained using epidural analgesia is not as good in lung transplant recipients as it is in patients undergoing thoracotomy for other indications. We also hypothesized that transition to oral analgesia was more difficult to achieve in this patient population.

	Patients and methods

Top Abstract Introduction Patients and methods Results Comment References

 
Following institutional review board approval, we reviewed the charts of every patient who underwent a unilateral or bilateral lung transplantation at CHUM Hoital Notre-Dame between 1998 and 2002. One hundred and seven charts were examined. The study group consisted of the patients who had an epidural as the first postoperative pain management modality. Patients who required sedation and intravenous (IV) analgesia for a maximum of 48 hours before the epidural was performed in order to correct perioperative coagulopathy were also included. As per routine, epidural catheters are inserted at the level of the surgical incision in our institution. Patients undergoing a single lung transplantation were approached using a standard posterolateral thoracotomy through the fifth intercostal space. The posterior arc of the sixth rib is divided and the chest wall is opened using a rib spreader. At the end of transplantation, two 32 FR large bore chest tubes are left in the pleural space and the incision is closed in a standard fashion using resorbable pericostal sutures and running resorbable sutures on the muscle fascia and subcutaneous tissue.

Bilateral lung transplants were carried out through a transverse, submammary thoracosternotomy. The pleural cavities are entered through the fifth intercostal space without sectioning the ribs. The sternum is divided transversely at the same level. The incision is closed in a fashion similar to the posterolateral thoracotomy with the addition of two to three sternal wires and two chest tubes on each side.

The data were compiled directly from the patients' charts. We specifically looked for the following information.

1. The duration of epidural analgesia, and the reason why it was stopped.
   
2. The level of global pain relief during the postoperative period using a ten point verbal rating scale (VRS), with 0 meaning no pain at all, and 10 the worst possible pain (good pain control: VRS 0 to 3, moderate pain control: VRS 3.1 to 6, inadequate pain control: VRS 6.1 to 10) [9]. We used the average VRS score for the entire period during which the patient was under epidural analgesia. Verbal rating scales were always collected by a registered nurse trained in pain management including methods of pain assessment with verbal rating scale.
   
3. Transition from epidural analgesia to oral medication: the postoperative day at which it occurred and an evaluation of the success of the transition. The transition was considered successful when a patient received only oral medication with no parenteral analgesia following epidural discontinuation.
   

To serve as a control group we reviewed the charts of 30 patients who underwent a thoracotomy with epidural analgesia in our institution for various indications other than transplantation between 1998 and 2002. The charts were randomly selected by an archive technician. The composition of the control group in terms of percentage of patients taken from each of the years of the study period matched the repartition of lung transplant patients. The same data as above were extracted from the charts. In this postthoracotomy control group (n = 30), 1 patient was transferred to a patient controlled analgesia pump before the transition to oral analgesia. This left us with 29 patients who had a direct trial to oral analgesia after termination of their epidural.

Data were stored in an Excel (Microsoft Corp., Redmond, WA) spread sheet. Results are expressed as mean ± standard deviation (SD) except when stated otherwise. Differences between and within the groups were sought using the ² test and two-tailed unpaired Student's t test for nonparametrical and parametrical variables, respectively [10]. A p less than 0.05 was considered significant.

	Results

Top Abstract Introduction Patients and methods Results Comment References

 
Eighty-three patients who underwent unilateral or bilateral lung transplantation were available for analysis in this study. The demographic data are summarized in Table 1. Patient diagnosis included cystic fibrosis (n = 22), emphysema (n = 41), and others (n = 20). Table 2 shows the percentage of patients who had good, moderate, and inadequate postoperative pain relief. No differences were found between unilateral and bilateral lung transplant patients. However, thoracotomy patients had better pain relief than unilateral (p = 0.07) or bilateral lung transplant patients (p = 0.008). This difference between each group in terms of quality of postoperative pain control persisted after controlling for the type of epidural drug mixture in the subgroup who received bupivacaine 0.0625% (Table 3). There were not enough patients in the subgroups who received bupivacaine 0.1% and bupivacaine 0.125% to make similar comparisons. The proportion of patients who received the different concentration of bupivacaine was similar in the three study groups.

	Comment

Top Abstract Introduction Patients and methods Results Comment References

The surgical approach in terms of length of cutaneous incision, need for exposure, and costotomy is not significantly different between unilateral lung transplantation and a thoracotomy for another indication. The duration of surgery, however, is usually longer for lung transplant. A longer duration of rib retraction for surgical exposure might lead to greater postoperative pain, although no study could be found in the literature to sustain this argument.

The incision used for bilateral lung transplantation, bilateral thoracosternotomy (clamshell), is a greatly different surgical approach when compared with the traditional posterolateral thoracotomy. Bilateral thoracosternotomy was used for all bilateral lung transplants in this study. It has already been noted that this surgical incision is more painful than a sternotomy for bilateral lung and heart-lung transplantation [2].

When compared with the usual thoracic surgery population, lung transplant recipients constitute a special group of patients. It has already been shown that lung transplant patients have unique and important implications for psychiatric management [11]. In fact, these patients with end-stage respiratory disease have a predicted life span of 18 months or less to become eligible for lung transplant. They usually are severely debilitated with a forced expiratory volume (FEV₁) less than 25% to 30% of predicted, resting hypoxia (PaO₂ < 55 mm Hg), or hypercapnia [12]. In addition, their anxiety level is high since the preoperative period is tinged with uncertainty and future concerns. Craven and colleagues [11] have found that 21% of candidates awaiting lung transplantation developed a psychiatric disorder. The factors given to explain this finding include the stress related to the long period of time before the transplant associated with a decrease in their health condition, moving closer geographically to the transplant center, and the risk of dying on the waiting list.

It is well documented that psychological instability can lead to more suffering. Scott and colleagues [13] have found that state anxiety is a significant predictor of postoperative pain. These psychological characteristics may help explain the greater percentage of moderate to inadequate pain relief found in lung transplant patients when compared to that found in the literature and in our control group of thoracotomy patients.

The lower prevalence of use of coanalgesics during epidural analgesia for the transplant patients (27%) compared to postthoracotomy patients (100%, p < 0.05), may also be a reason for the lower incidence of adequate postoperative pain relief experienced by transplant recipients. The most commonly used drugs for coanalgesia in our center are acetaminophen and indomethacin. As the patients are maintained hypovolemic in the early recovery period, and as the immunosuppressive drugs are nephrotoxic, nonsteroidal antiinflammatory drugs (NSAID), such as indomethacin, are avoided postoperatively in lung transplant recipients. The NSAIDs are potent coanalgesics and replacement with other drugs such as acetaminophen may not always lead to equivalent analgesia.

Successful transition to oral analgesia after termination of epidural infusion is more difficult to achieve in lung transplant recipients than in postthoracotomy patients. This lower rate of success in both unilateral and bilateral transplant patients could be the result of the preexisting condition of the patients combined with their specific psychological profile. We could find no data in the literature indicating that lung transplant patients are at risk of suffering from preexisting chronic pain before their surgery and therefore this could not explain the difficulties in the management of postoperative pain found in this group of patients.

The difference in the success of transition to oral analgesia between the transplant and thoracotomy patients could be a result of the higher incidence of inadequate postoperative pain relief with epidural analgesia found in the transplant patients. To explain this we can assume that the inadequate pain control resulted from the temporal summation of afferences from the A-delta and C fibers. These noxious stimulations can induce prolonged changes in central neural function (neuroplasticity) that may contribute to a greater level of postoperative pain and, hence, a need for higher doses of analgesics [14].

Finally, either the choice or the dosage of medication for the transition to oral analgesia may not be adequate. For example, an inappropriate choice of dosage could easily lead to the prescription of parenteral medication instead of trying to adjust the oral medication. However, there was no difference in the choice of postoperative analgesic between the three study groups.

A hastier transition to oral analgesia in this patient population could possibly result in an earlier discharge from hospital. This issue is important to help protect the immunocompromised transplant recipient from the high risk of hospital-acquired infections [15]. These patients are often hospitalized before their surgery and suffer a great deal of anxiety and depression. It certainly is an advantage to send them home as quickly as possible. In addition, oral analgesics are thought to provide a more uniform level of analgesia than parenteral drugs. When the dosage of oral medication is adequate, it leads to less variability in the control of pain, because the changes in plasmatic concentrations of the drug are minimized.

There are some limitations to the present study. Because of the retrospective nature of our study, a single person could not collect all the pain scores for each patient. However, since the implementation of an acute pain service in our institution in 1997, every registered nurse has received continuous training in pain management including methods of pain assessment with verbal rating scale. In addition, we evaluated global pain control over the entire period the patient was under epidural analgesia to decrease the influence of an eventual interindividual variability. Our results are then as valid as possible with the known limitations of a retrospective study. A prospective study with a more precise tool to evaluate the level of pain could possibly lead to different results.

Retrospective studies can also be contaminated by unknown selection biases. However, because of the small number of lung transplants performed and the precariousness of the health status of lung recipients, a prospective study specifically dealing with acute postoperative pain control would obviously be hard to perform. Finally, the small number of patients included in this study precluded any outcome assessment such as duration of hospitalization, incidence of chronic pain, respiratory complications, and survival.

In conclusion, this study shows that unilateral and bilateral lung transplant recipients have a lower incidence of adequate pain relief than postthoracotomy patients. The transition from epidural to oral analgesia is also more difficult to achieve in this patient population. Further studies are needed to confirm our findings and assess their influence on the patient's outcome and the development of chronic pain.

	References

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12. Ochoa L.L., Richardson G.W. The current status of lung transplant: a nursing perspective. AACN Clin Issues 1999;10:229-239.[Medline]
13. Scott L.E., Clum G.A., Peoples J.B. Preoperative predictors of postoperative pain. Pain 1983;15:283-293.[Medline]
14. Katz J., Kavanagh B.P., Sandler A.N., et al. Preemptive analgesia. Clinical evidence of neuroplasticity contributing to postoperative pain. Anesthesiology 1992;77:439-446.[Medline]
15. Lanuza D.M., McCabe M.A. Care before and after lung transplant and quality of life research. AACN Clin Issues 2001;12:186-201.[Medline]

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