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Department of Anesthesiology, Faculty of Medicine, Tanta University Hospital, Tanta, Egypt
Accepted for publication October 27, 2009.
* Address correspondence to Dr Amr, Department of Anesthesiology, Tanta University Hospital, Tanta, 31527, Egypt (Email: yasser.amr{at}gmail.com).
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Abstract |
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Methods: Forty patients undergoing posterolateral thoracotomy received TEA either before (preoperative-TEA group) or after (postoperative-TEA group) surgery. Postoperative analgesia was maintained with epidural infusion of bupivacaine and fentanyl. Pain scores, pulmonary functions, arterial blood gases, plasma glucose, cortisol levels and epidural fentanyl consumption were compared for 48 hours after surgery.
Results: The preoperative-TEA group demonstrated significantly reduced pain scores at 2, 4, 8, 12, 24, and 48 hours at rest (p = 0.001, p = 0.002, p = 0.004, p = < 0.001, p = 0.006, and p = 0.001, respectively) and at 4, 8, 12, 24, 48 hours on coughing (p = 0.001, p = 0.001, p = 0.001, p = 0.001, p = 0.004, respectively), and a significant reduction in epidural fentanyl consumption (208.6 ± 49.3 mL, versus 260 ± 28.8 mL, p = 0.001). The preoperative-TEA group showed significant improvement in pulmonary functions as compared with the postoperative-TEA group (p < 0.05), except forced expiratory volume in one second at 24 hours (p = 0.061) and peak expiratory flow rate at 48 hours (p = 0.188). The postoperative-TEA treated patients were more likely to have a higher arterial carbon dioxide pressure at 4, 8, 12, and 24 hours (p = 0.017, p = 0.001, p = 0.003, p = 0.001), respectively. However, we could not demonstrate a statistical difference in oxygenation, cortisol, or glucose level.
Conclusions: Though preemptive TEA appeared to reduce the severity of acute pain, preserve pulmonary function, and reduce analgesic requirements, these statistically significant differences were not enough to conclude a clinical significant difference between groups.
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Introduction |
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The concept of preemptive analgesia to reduce postoperative pain was founded on a series of successful animal experimental studies that demonstrated central nervous system plasticity and sensitization after nociception [4]. Preemptive analgesia is defined as an antinociceptive treatment that prevents the establishment of altered central processing of afferent input, which amplifies postoperative pain [5]. By decreasing the altered central sensory processing, preemptive analgesia is thought to consequently decrease the incidence of hyperalgesia and allodynia after surgery [6]. Whether preemptive analgesic interventions are more effective than conventional regimens in managing acute postoperative pain remains controversial [7]. This study attempts to determine if there is an advantage to giving preoperative TEA compared to postoperative administration after thoracic surgery on postthoracotomy pain, pulmonary function, stress response, and total opioids consumption.
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Material and Methods |
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Forty patients, American Society of Anesthesiologists (ASA) classification II-III, undergoing elective posterolateral thoracotomy, were allocated randomly to one of two groups. A prospective, randomized (sealed envelopes), double-blind design was used, with both patients and postoperative assessors blinded to analgesic management.
Exclusion criteria were age (younger than 18 years), previous opioids, corticosteroids, or nonsteroidal antiinflammatory drugs within one week of surgery, previous chronic anticoagulation therapy, allergy to local anesthetics or opioids, inability to understand or perform verbal or physical assessments or use patient controlled epidural analgesia (PCEA), neurologic disorders, previous surgery to (or severe deformity of) the thoracic spine, and forced expiratory volume in one second (FEV1) less than 60% of the reference value.
After the preoperative visit, all patients received a thoracic epidural catheter placed two hours before operation at the T5-7 interspaces and advanced 3 to 4 cm cephalad. A test dose of 1% lidocaine (10 mL) was used to confirm the location of the catheter. If the epidurals did not function, patients were excluded from this trial; the process of inclusion into the study went on until the requested number of patients was reached. Patients were familiarized with the visual analogue scale (VAS). Patients were allocated randomly to receive one of two analgesic regimens. For the preoperative-TEA group, 8 mL of 0.25% bupivacaine plus fentanyl 50 µg in 2 mL was administered preoperatively. For the postoperative-TEA group, no medication was administered through the epidural catheter preoperatively and intraoperatively.
Twenty minutes after the epidural injection, general anesthesia was induced with an intravenous (IV) administration of fentanyl (2µg/kg), atracurium (0.5 mg/kg), propofol (2 mg/kg), and lidocaine (1.5 mg/kg). Tracheal intubation was with a double lumen tube and anesthesia was maintained with isoflurane in oxygen and nitrous oxide (40% and 60%, respectively). Respiratory rate and tidal volume were adjusted to maintain the end-tidal carbon dioxide level at 35 to 45 mm Hg.
For fluid therapy all patients received balanced salt solution. No additional opioids were given during the operation. Standard monitors included pulse oximetry, electrocardiography, end-tidal carbon dioxide, and noninvasive arterial blood pressure. At the end of surgery, residual neuromuscular block was reversed with neostigmine (0.04 mg/kg) and atropine (0.01 mg/kg), and the endotracheal tube was removed when the patient met the criteria for extubation.
Immediately after arrival to intensive care unit; an epidural infusion of fentanyl was initiated using a continuous basal infusion with a superimposed PCEA bolus dose.
The standard setting used was fentanyl concentration (10 mcg/mL) and bupivacaine (1 mg/mL) [8]. Continuous basal epidural infusion 5 bmL/hour (50 mcg/hour fentanyl plus 5 mg bupivacaine), superimposed PCEA bolus dose of 1 mL (containing 10 mcg fentanyl plus 1mg bupivacaine) every 15 minutes with a 4-hour lockout of 40 mL. Fentanyl infusion was maintained for 48 hours while the patient was placed in the intensive care unit.
Analgesia was assessed at both rest and with cough at 2, 4, 8, 12, 24, and 48 hours after surgery by an observer blinded to treatment groups using a 100 mm VAS. Total amount of fentanyl consumption was recorded.
Pulmonary function tests including forced vital capacity (FVC), FEV1, and peak expiratory flow rate (PEFR) were performed preoperatively as a baseline, 24 and 48 hours after surgery. Arterial blood gases were performed at 4, 8, 12, 24, 36, and 48 hours after surgery. Stress response was assessed by measurement of blood glucose and serum cortisol levels one day preoperatively as a baseline 4, 24, and 48 hours postoperatively.
Statistical Analysis
Data were presented in the form of mean ± SD. Two-way analysis of variance with correction for repeated measurements was used to compare groups. The Mann-Whitney U test was for pain scores.
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Results |
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Thoracotomy resulted in a significant decrease (p < 0.05) of FVC, FEV1, and PEFR. Thereafter, a steady recovery on the second postoperative day of parameters was observed in both groups but complete normalization was not reached within the extended period of observation. The preoperative-TEA group showed a significant improvement in pulmonary functions compared with the postoperative-TEA group (p < 0.05) except for FEV1 at 24 hours (p = 0.061) and PEFR at 48 hours (p = 0.188) (Table 4).
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Four hours after extubation arterial carbon dioxide pressure values (mm Hg) demonstrated significant reduction in the preoperative-TEA group. The significant difference between both groups persisted at 8, 12, and 24 hours after extubation (p < 0.05) (Table 5).
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Comment |
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Provision of effective postoperative analgesia is an integral part of anesthetic practice. Regional analgesia by continuous epidural infusion offers benefits over conventional opioid analgesia, particularly for thoracic surgery [12].
This is a small prospective randomized trial on 40 patients. The authors report statistically significant decreased pain in the group with the preoperative epidural drugs compared with the postoperative. As expected, pulmonary function was significantly decreased at all postoperative measurement times, and the reduction was more in the postoperative epidural group than in the preoperative epidural group. There are several problems with the study. The difference in total epidural fentanyl consumption between the two groups is 52 mL. This is statistically significant but clinically this is a small difference. Similarly, with the VAS scores, the differences are small although clinically significant.
To support the argument that these results are not clinically significant is the finding that there was no clinically significant difference in the pulmonary function testing. We found the FEV1 in the preoperative group was 58% of predicted and 52% of predicted in the postoperative group. This small percent difference is not enough to conclude a clinical significant difference in the two groups. As proof that there is no physiologic advantage and the stated benefits are all statistical is the data on the blood glucose and cortisol levels that do not show any difference.
Oxygenation was satisfactory in all patients during the study. The values of arterial carbon dioxide pressure was significantly higher in the postoperative-TEA group during the first 24 hours after surgery as compared with the preoperative-TEA group.
Senturk and colleagues [2] compared the effects of preoperative and postoperative initiation of TEA. They showed that preoperative initiation of TEA is more effective in controlling acute pain after thoracotomy compared with postoperative initiation.
Obata and colleagues [13] have shown that an epidural block with mepivacaine before surgery reduces acute and long-term postthoracotomy pain. There are two major differences between that study and the present study. Obata and colleagues used only a local anesthetic drug (mepivacaine) for epidural block (without opioid supplementation), and that study included long-term postthoracotomy pain, which is out of the scope of our study.
Akural and colleagues [14] concluded that, preemptive epidural sufentanil administration had a short-term opioid-sparing effect, reduced wound touch, and pain sensitivity in patients with a Pfannenstiel incision, and reduced adrenocorticotropic hormone and cortisol concentrations compared with patients who received epidural sufentanil at the end of surgery. This may be explained by the nature of the surgery as patients in that study were undergoing hysterectomy, while in our study they were undergoing thoracotomy which is characterized by the most severe type of pain.
In contrary, Aguilar and colleagues [15] found that, there was no significant difference between groups, either in PCEA requirements or in VAS scores (either at rest, during mobilization of the ipsilateral arm of surgery, or after cough) in a study carried out by using (mepivacaine) as a preemptive epidural analgesia.
In another study, no significant difference in dynamic pain relief was seen when bupivacaine and morphine were given before and after incision and continued into the postoperative period [16] or when bupivacaine alone was given followed by PCEA with fentanyl and bupivacaine [17]. Two studies have demonstrated a preemptive effect; Wu and colleagues [18] used a mixture of ketamine, bupivacaine, and morphine, and demonstrated a statistically significant improvement in analgesia in the preincisional group after upper abdominal surgery during the first postoperative day. Also, Gottschalk and colleagues [19] demonstrated that, patients recovering from radical prostatectomy, all of whom had an aggressive postoperative epidural analgesic regimen, had significantly less pain in-hospital and 9.5 weeks later if they had epidural fentanyl or bupivacaine administered before surgical incision.
Preemptive TEA appeared to reduce the severity of acute pain, preserve pulmonary function, and reduce analgesic requirements but had no effect on stress response. This statistically significant difference is not enough to conclude a clinical significant difference in the two groups.
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