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Eur J Cardiothorac Surg 2005;28:375-379
© 2005 Elsevier Science NL
Original articles |
Department of Anaesthesiology, Ankara Oncology Hospital, Ankara, Turkey
Received 23 February 2005; received in revised form 13 May 2005; accepted 16 May 2005.
* Corresponding author. Address: Birlik mah. 5. Cad. Yal
apt. No: 27/3, 06610 Çankaya/Ankara, Turkey. Tel.: +90 312 495 85 57; fax: +90 312 345 49 79. (Email: goncatuncel{at}hotmail.com).
Abstract
Objective: The aim of this study was to compare the analgesic efficacy and side effects of continuous epidural infusions of ropivacaine and ropivacaine–sufentanil mixtures after thoracotomy. Methods: Sixty-two patients scheduled for thoracic surgery were allocated in this prospective double-blinded randomised study. They received an epidural catheter inserted from thoracic 5–6 (Th5–6) interspace a day before surgery and were randomly assigned into two groups, sufentanil–ropivacaine group (Group SR, n=31) and ropivacaine group (Group R, n=31). Bolus dose of the study drugs, ropivacaine 0.2% or ropivacaine 0.2% and sufentanil 0.75µg/ml calculated in ml according to the patient's height was given through the epidural catheter before surgery. One hour after anaesthesia induction, another bolus was given and the epidural infusion was started (4.5–8ml). Whenever visual analogue scale (VAS) scores were 
4 during function, the patients received additional boluses and the infusion rate was increased by 1ml/h. If the pain was not relieved after administration of two boluses, the patient was excluded from the study. Results: VAS at rest and during function was lower in ropivacaine–sufentanil group and the need for additional boluses and infusion rate increase was high in ropivacaine group (P<0.05). Ropivacaine–sufentanil infusion rate was decreased due to nausea and vomiting in two patients and due to CO2 retention in one patient. There was no statistically significant difference between the incidences of side effects except pruritus significantly higher in Group SR. The total epidural solution volume was more in Group R (P<0.05). Conclusions: The continuous epidural infusion of ropivacaine with sufentanil provided superior pain relief than ropivacaine alone without causing any severe side effect or post-operative pulmonary impairment.
Key Words: Thoracotomy • Epidural analgesia • opioid • Sufentanil • Local anaesthetic • Ropivacaine
1. Introduction
Thoracotomy is associated with severe post-operative pain, which is thought to be one of the most important factors causing post-operative impairment of respiratory mechanics and gas exchange [1]. The sources of perceived pain are multiple and include the site of the surgical incision, disruption of ribs and intercostals nerves, inflammation of chest wall structures adjacent to the incision, incision or crushing of pulmonary parenchyma or pleura, stretching of shoulder joint and placement of thoracostomy drainage tubes [2]. Specific associated pain syndromes may develop in these patients during the acute and long-term post-operative courses as a result of the surgical or the analgesic techniques [3,4].
Adequate post-operative analgesia must be provided without impairment of respiratory function. Although systemic opioids have traditionally formed the basis for the treatment of post-thoracotomy pain, the continuous epidural administration of analgesics has been shown to provide better pain control [5].
The purpose of this study was to compare the analgesic efficacy and side effects of continuous epidural infusions of ropivacaine or sufentanil–ropivacaine mixtures in patients undergoing thoracotomy.
2. Methods
After receiving approval of the hospital ethics committee and informed consent, 62 American Society of Anaesthesiologists (ASA) physical status I–II patients scheduled for thoracic surgery were allocated in this prospective double-blinded randomised study. All patients had malignant primary or metastatic pulmonary tumours, except one patient with cyst hydatic in both groups, and underwent a classic posterolateral thoracotomy involving the division of latissimus dorsi and serratus anterior muscle after a posterolateral incision at the fifth intercostal space by the same two surgeons. Chest wall reconstructions, mini-thoracotomies and other non-standard incisions were not included in the study. Rib resection was employed if necessary. Other exclusion criteria were coagulation disorders, known allergy to the drugs used, local infection, age <18 or >75yr and patient refusal for the catheter placement. The patients received an epidural catheter inserted from thoracic 5–6 (Th5–6) interspace with a paramedian approach in the lateral decubitis position a day before surgery. They were slightly sedated with IV midazolam during the procedure. The epidural space was identified with the ‘loss of resistance to saline’ technique. The catheters were fixed firmly by a surgical suture to avoid dislodgement. Bilateral sensory blockade was assessed by pinprick 20min after a test dose of 5ml lidocaine 1.5%. The patients were randomly assigned via an envelope system into one of two groups, sufentanil–ropivacaine group (Group SR, n=31) and ropivacaine group (Group R, n=31). On the operation day, bolus dose of the study drugs, 0.2% ropivacaine or 0.2% ropivacaine and sufentanil 0.75µg/ml was given through the epidural catheter to support surgical analgesia, depending on the height of the patient according to the formula: dose (ml)=(height (cm)–100)x10–1. The initial bolus dose given before surgery ranged between 4.5 and 8ml. Thereafter general anaesthesia was induced by fentanyl 1–2µg/kg, vecuronium 0.1mg/kg and thiopental 4–7mg/kg. It was maintained with sevoflurane and 66% N2O in O2. Additional fentanyl doses were used if needed intraoperatively. One hour after anaesthesia induction, another bolus of the study drugs was given and the epidural infusion was started (Acute Pain Manager—APM®, Abbott, USA). The amounts of the drugs given as bolus and as continuous infusion were the same as the initial bolus that was administered before the surgery. The epidural infusion was planned to continue for 3 days. At the end of the surgery, all patients were allowed to resume spontaneous breathing. After extubation, they were observed in the post-operative care unit (PACU) for 24h and thereafter transported to the surgical ward. The patients were routinely administered diclofenac 75mg intramuscularly two times daily. Arterial blood pressure, electrocardiogram, SpO2 and respiratory rate were continuously monitored. Blood gas measurements were made daily to detect any respiratory dysfunction. Pain intensity at rest (VAS-R) and during function (VAS-F) was independently evaluated by the same two anaesthesiologists unaware of the content of the epidural regimen using a 10cm visual analogue scale (VAS) with end points labelled ‘no pain’ and ‘worst possible pain’. Pain during function was assessed by asking patient to breathe deeply or to cough. VAS scores less than four during function were considered satisfactory analgesia. Whenever VAS-F scores were 4, the patients received additional bolus of the study drugs and the infusion rate was increased by 1ml/h. The epidural bolus doses throughout the study were same with the initial doses calculated according to the height. If the pain was not relieved after administration of two boluses at 1-h interval, the patient was excluded from the study and given systemic analgesics. Assessments were made at 1/2 and 1, 2, 4, 6, 12 and 24h and two times daily on the second and third days. Time ‘0’ was taken as the time that each patient regained consciousness in the PACU.
Side effects like pruritus, nausea, vomiting, hypotension, respiratory depression, sedation and numbness or motor weakness in arms were noted. Urinary retention was not assessed because most of the patients had indwelling urinary catheters. Sedation was evaluated by using a four-point scale defined as 0=awake, 1=responds to verbal stimulation, 2=responds to touching, 3=not arousable. A respiratory rate 
10breaths/min and PaCO2 50mmHg was defined as respiratory depression and a decrease of mean arterial blood pressure more than 20% from the basal value as hypotension.
Demographic data, anaesthesia and operation time, intraoperative fentanyl dose, total epidural local anaesthetic use and continuous variables such as blood pressure, heart rate, PaCO2, and SpO2 were compared by t-test. Mann–Whitney U-test was used to compare sedation and VAS pain scores. Side effects were analysed by 
2 test and the requirement for boluses by t-test and Mann–Whitney U-test. P-values below 0.05 were considered significant. Values expressed as means are given with the standard error of the mean.
3. Results
The demographic variables were similar in both groups (Table 1 ). There were no significant differences at the time of anaesthesia and operation. Two patients in both groups needed division of rhomboid muscle and three patients in Group R, four patients in Group SR had rib resection. Intraoperative fentanyl doses were comparable between groups (Table 1). In Group R, one patient was excluded from the study due to inadequate analgesia and administered IV patient-controlled analgesia. One patient had his epidural catheter dislodged at the second day in Group SR. Thirty patients in both groups completed the study and were evaluated for the statistical analysis.
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50mmHg, respiratory rate <10breaths/min), which was easily relieved by discontinuation of the infusion. The epidural infusion was started at a lower rate in the same patient and no further complication was observed. The respiratory rates were lower in Group SR, significant at 0, 12h, second and third days (P<0.05). The PaCO2 was higher than the preoperative values on the first post-operative day in both groups. On the second and third days, PaCO2 in Group R was lower than Group SR, although not significant. The need for intraoperative anaesthetic agents and cardiovascular stability throughout the study period were comparable between groups.
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The present study shows that continuous thoracic epidural analgesia by using ropivacaine with sufentanil provides optimum pain relief with minor side effects after thoracotomy. Most of the patients receiving ropivacaine infusion alone experienced inadequate analgesia and needed boluses and dose arrangements.
Pain in the post-operative period following thoracotomy is frequently associated with clinically important abnormalities of pulmonary function. Although several methods are used for post-thoracotomy pain management, including systemic opioids, non-steroid anti-inflammatory drugs, ketamine, regional techniques such as paravertebral, intercostal and interpleural blocks, thoracic epidural analgesia (TEA) remains the most beneficial approach [6,7]. The role of epidural anaesthesia and analgesia in reducing the incidence and severity of perioperative physiologic derangements, in addition to relieving pain has been reported in several studies [8,9]. TEA plays a pivotal role in multimodal treatment programs, allowing for important advances in recovery from surgery and reductions in overall morbidity and cost [9]. It offers maximal sympathetic blockade of the heart and bowel and promotes coronary perfusion and gastrointestinal motility, while providing freedom from lower extremity motor blockade and opioid-induced side effects [9]. Epidural opioids have been combined with epidural local anaesthetics with the aim of synergistically blocking spinal nociceptive pathways while reducing the dose-related adverse effects of either class alone [5,10].
In this study, we used ropivacaine as the local anaesthetic and sufentanil as the opioid. Ropivacaine was the local anaesthetic of choice because of more differential block allowing for a better separation between sensory and motor block, low toxicity relative to potency and long duration of action, resulting in a low risk of toxicity during continuous infusion [11]. Sufentanil has a rapid onset and potent analgesic effect due to high lipid solubility, an intermediate degree of ionisation, a low molecular weight, a very high µ receptor affinity, and a high therapeutic range [5,12]. The analgesic efficacy of thoracic epidural ropivacaine was clearly enhanced when combined with sufentanil. Most of the patients in Group SR were able to cough and breathe deeply. Only six patients needed additional bolus dose of the study drug while 25 patients received boluses in Group R. Mourisse et al. have found that combination of epidural sufentanil 0.83µg/ml with bupivacaine 0.125% provided superior pain relief both at rest and on exercise. Sufentanil infusion alone resulted in good analgesia only at rest. Most of the patients in bupivacaine group had high VAS scores and there were a high number of dropouts from the study due to inadequate analgesia. Combination of local anaesthetics with opioids has been found to provide better pain control especially during exercise and was offered as an optimum analgesic regimen [5].
Although TEA after thoracic surgery is being increasingly used, reports regarding the use of epidural infusion regimens including ropivacaine and sufentanil for thoracotomy pain are lacking. These drugs have been frequently used for labour analgesia or procedures involving abdomen and lower extremities [13,14]. For thoracotomy pain, sufentanil has been generally administered at doses of 0.83–1µg/ml combined with bupivacaine [5,10,15]. In this study, we obtained adequate analgesia with lower doses of sufentanil (0.75µg/ml) used with ropivacaine, thus we expected the side effects being lower.
Hansdottir et al. [10] have shown that epidural sufentanil analgesia is optimal when tailored to the site of nociceptive input and combined with bupivacaine after thoracotomy. In another study, it was stated that the efficacy of epidural sufentanil in particular would depend on the extent to which it is administered in the vicinity of spinal opioid receptors involved in surgical nociceptive processing. Their pharmacokinetic findings supported the concept that epidural sufentanil analgesia is optimal when administered segmentally and tailored to the surgical incision [16]. In our study, all the epidural catheters were inserted from Th5–6 interspace and the necessary segmental level for the surgery was obtained.
Sufentanil analgesia is short acting, thus it must be given by repeated boluses or continuous infusion. The side effects of sympathetic and motor blockade may restrict the use of local anaesthetics to selected group of patients. Stability of arterial pressure is more easily achieved with a continuous infusion technique [5]. We also used continuous infusion of both drugs and made adjustments of the infusion rates as needed. Intraoperatively, the hemodynamic variables and need for additional anaesthetics were comparable between groups.
There were no differences between the side effects except pruritus in this study. The total number of patients who had one or more side effect did not differ between groups. Although respiratory rates were significantly lower in Group SR, only one patient had respiratory depression on the first post-operative day and was relieved by discontinuation of the infusion. We started the infusion at a lower rate after 2h and she did not develop any other complication. There was no incidence of late respiratory depression. Delayed respiratory depression seems less probable with lypophilic opioids because of their rapid uptake into the lipid-rich areas of the spinal cord, resulting in lower cerebrospinal fluid concentrations [5,17]. Wiebalck et al. have reported early respiratory depression in a patient receiving bupivacaine for post-operative patient-controlled epidural analgesia. This shows that early respiratory depression may occur without the use of an opioid during post-operative pain therapy [17].
Different rates of pruritis have been reported in patients receiving epidural sufentanil [11,15,17]. In the present study, seven patients had pruritus in Group SR, which was not spontaneously described and needed no treatment. The infusion rate of sufentanil–ropivacaine was decreased due to nausea and vomiting in two patients. In Group R, one patient described motor weakness in the arm after the epidural bolus dose and another patient complained of weakness and numbness during the infusion. As more frequent bolus doses and a higher infusion rate had to be administered due to inadequate analgesia in this group, that kind of side effects are more probable to occur. Although TEA with local anaesthetic–opioid mixture is considered as a gold standard for post-thoracotomy pain control, rare but potentially serious complications must be known. Experienced anaesthetists to perform the technique and close follow up of the patients will overcome the possible complications and side effects. We did not have any serious complication except one patient developing respiratory depression discussed above.
Thoracic epidural analgesia with a combination of local anaesthetic and opioid is the most beneficial technique for post-operative pain control. In this study, the continuous epidural infusion of ropivacaine with sufentanil provided superior pain relief than ropivacaine alone without causing any severe side effect or post-operative pulmonary impairment.
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Footnotes
Presented in the XXIII Annual European Society of Regional Anaesthesia and Pain Therapy Congress, Athens, Greece, 2004. 
References
ppana E, Nilsson E, Kalso E. Post-thoracotomy pain after thoracic epidural analgesia: a prospective follow-up study. Acta Anaesthesiol Scand 2003;47:433-438.[CrossRef][Medline]
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