Volume 26, Issue 1 , Pages 78-82, February 2012
Thoracic Epidural or Paravertebral Catheter for Analgesia After Lung Resection: Is the Outcome Different?
Article Outline
Objective
The aim of this study was to determine whether thoracic epidural analgesia (TEA) or a paravertebral catheter block (PVB) with morphine patient-controlled analgesia influenced outcome in patients undergoing thoracotomy for lung resection.
Design
A retrospective analysis.
Setting
A tertiary referral center.
Participants
The study population consisted of 1,592 patients who had undergone thoracotomy for lung resection between May 2000 and April 2008.
Interventions
Not applicable.
Measurements and Main Results
Patients who received PVBs were younger, had a higher forced expiratory volume in 1 second, had a higher body mass index, a higher incidence of cardiac comorbidity, fewer pneumonectomies, and more wedge resections. A multivariable logistic regression model was used to develop a propensity-matched score for the probability of patients receiving an epidural or a paravertebral catheter. Four patients with an epidural to one with a paravertebral catheter were matched, with 488 patients and 122 patients, respectively. Postmatching analysis now showed no difference between the groups for preoperative characteristics or operative extent. Postmatching analysis showed no significant difference in outcome between the two groups for the incidence of postoperative respiratory complication (p = 0.67), intensive therapy unit (ITU) stay (p = 0.51), ITU readmission (p = 0.66), or in-hospital mortality (p = 0.67). There was a significant reduction in the hospital length of stay in favor of the paravertebral group (6 v 7 days, p = 0.008).
Conclusions
Paravertebral catheter analgesia with morphine patient-controlled analgesia seems as effective as thoracic epidural for reducing the risk of postoperative complications. The authors additionally found that paravertebral catheter use is associated with a shorter hospital stay and may be a better form of analgesia for fast-track thoracic surgery.
Key Words: paravertebral block , thoracic epidural , post-thoracotomy pain
A THORACOTOMY INCISION is widely recognized as being one of the most painful surgical procedures. The incision involves multiple muscle layers and possible rib injury. Acute post-thoracotomy pain is aggravated by the continuous motion as the patient breathes. The effective treatment of acute post-thoracotomy pain after lung resections is particularly important to keep the patient comfortable and to minimize pulmonary complications.1, 2
Thoracic epidural analgesia (TEA) has long been considered the optimal technique for the management of post-thoracotomy pain. A paravertebral block (PVB) is an alternative technique. It has, for some time, been argued that a thoracic PVB may provide an equivalent level of analgesia to that of thoracic epidurals.2, 3 In this study, the relationship between the analgesic technique used and the outcome of patients undergoing thoracotomy with lung resection was analyzed using propensity matching of the populations.
Methods
Patients who underwent thoracotomy for lung resection in the authors' center between May 2000 and April 2008 were examined retrospectively. Patients were offered either a thoracic epidural or a paravertebral catheter with morphine patient-controlled analgesia (PCA) depending on the outcome of the preoperative assessment and dialog between the anesthesiologist and patient regarding benefits and risks of both techniques. All patients were fully informed of the risks and benefits of each technique and gave verbal consent for the analgesic technique that was to be used, as is the usual practice.
Thoracic epidural catheters (TEAs) were inserted before the induction of anesthesia at the level of T7 and secured in place. TEA was used for intraoperative analgesia. The protocol during the period of study was for patients to receive a mixture of 0.1% local anesthetic, initially racemic bupivicaine but later levobupivacaine, combined with 5 μg/mL of fentanyl. This was commenced at 0.1 mL/kg/h but then titrated to provide adequate analgesia.
Paravertebral catheters were inserted under direct vision by the operating surgeon at the end of the procedure and secured in place. Patients received an infusion of plain local anesthetic 0.25%, initially racemic bupivicaine but later levobupivacaine, which was commenced at a maximum dose of 0.1 mL/kg/h, but this also was titrated down if analgesia was adequate.
Intravenous opioids (fentanyl or morphine) were given before the cessation of anesthesia at the anesthesiologist's discretion. Morphine PCA with a 1-mg bolus and 5-minute lockout was connected in recovery and continued into the postoperative period. During working hours, an acute pain nurse and consultant anesthesiologist conducted pain rounds to ensure that pain relief was adequate. After hours, a senior anesthetic resident was available to review analgesia management.
Measured perioperative variables that may have influenced in-hospital patient outcomes were examined. These included preoperative patient characteristics (eg, age, predicted forced expiratory volume in 1 second %, body mass index, smoking status, New York Heart Association classification of dyspnea, hypertension, and cardiac comorbidity) and the extent of surgical resection (eg, pneumonectomy, lobectomy, or wedge resection). Endpoints for the analysis were postoperative outcomes, including respiratory complications (eg, chest infection, atelectasis, sputum retention, and acute lung injury), intensive therapy unit (ITU) readmission, in-hospital mortality, ITU length of stay, and total hospital length of stay.
Continuous variables not normally distributed are shown as a median with 25th and 75th percentiles. Categoric data are shown as percentages. Univariate comparisons were made with Wilcoxon rank sum tests and chi-square tests as appropriate. In all cases, a p value <0.05 was considered significant. Because analgesic treatment assignment was not based on random allocation and other significant differences between the groups might exist, a propensity score method was used to match patients who received epidurals to patients who received paravertebrals. All statistical analyses were performed using SAS for Windows Version 8.2 (SAS, Cary, NC).
Results
A total of 1,592 patients underwent thoracotomy with lung resection during the study period and received either a thoracic epidural or a paravertebral catheter with morphine PCA. As can be seen in Table 1, there were many important differences between those who received an epidural and those who received a paravertebral catheter and PCA. Most notably, patients who received a PVB were younger, had a higher forced expiratory volume in 1 second, a higher body mass index, had fewer pneumonectomies (13.1% compared with 3.9% for paravertebrals), and had more wedge resections (18.3% compared with 33.1% for paravertebrals).
Table 1. Preoperative and Intraoperative Characteristics of All Patients
| Preoperative Characteristics | Paravertebral Catheter (n = 134) | Thoracic Epidural (n = 1,458) | p Value |
|---|---|---|---|
| Median age (IQR) | 63.5 (53-73) | 67(60-73) | 0.002 |
| % predicted FEV1 (IQR) | 82.09(72-97) | 80.70(66-94) | 0.013 |
| BMI (IQR) | 27.09(24-31) | 25.66(23-28) | <0.0001 |
| Current smoker (%) | 25.4 | 31.7 | 0.134 |
| NYHA >2 (%) | 5.4 | 6.7 | 0.553 |
| Hypertension (%) | 38.5 | 36.9 | 0.720 |
| Cardiac comorbidity (%) | 36.2 | 25.2 | 0.006 |
| Extent of resection | <0.0001 | ||
| Lobectomy (%) | 63.1 | 68.6 | |
| Pneumonectomy | 3.9 | 13.1 | |
| Wedge | 33.1 | 18.3 |
Outcome analysis between the two groups before propensity matching showed a significantly lower incidence of respiratory complications and a shorter postoperative length of stay in patients receiving PVB versus TEA (Table 2). A suitable match could not be identified for 12 patients who received a paravertebral catheter, and they were excluded from the propensity scoring. The 4:1 matching produced groups with 488 patients in the epidural group and 122 patients in the paravertebral group (Fig 1).
Table 2. Outcome of All Patients by Analgesia Technique
| Postoperative Outcomes | Paravertebral Catheter (n = 134) | Thoracic Epidural (n = 1,458) | p Value |
|---|---|---|---|
| Respiratory complications (%) | 4.6 | 11.3 | 0.018 |
| Atelectasis (%) | 1.5 | 2.6 | 0.768 |
| Sputum retention (%) | 2.3 | 5.6 | 0.109 |
| Chest infection (%) | 0.8 | 4.4 | 0.039 |
| Bronchoscopy and suction (%) | 1.5 | 4.1 | 0.146 |
| Minitracheostomy (%) | 2.3 | 3.9 | 0.479 |
| Reintubated (%) | 0 | 2.6 | 0.070 |
| All complications (%) | 27.7 | 32.4 | 0.269 |
| ITU readmission (%) | 4.6 | 5.8 | 0.570 |
| In-hospital mortality (%) | 1.5 | 2.4 | 0.765 |
| ITU length of stay (IQR) | 1(1-1) | 1(1-1) | 0.353 |
| Postoperative total LOS (IQR) | 6(5-8) | 8(6-10) | <0.0001 |
Fig 1.
A patient flow diagram.
A propensity score for receiving a PVB was estimated using a multivariate logistic model. All measured covariates were considered. The Hosmer and Lemeshow goodness-of-fit test showed that the model adequately fit the data, and a c-statistic of 0.71 also showed acceptable discriminative power. The propensity score was used to match epidural patients to those who underwent a PVB. This process matched 4 patients with an epidural to 1 with a PVB (increasing the c-statistic of the score) using an identical 8-digit propensity score. If this was not possible, the authors then proceeded to a 7-, 6-, 5-, and finally 4-digit match using a computerized greedy matching technique.
After propensity matching, there were no significant statistical differences between the two groups in respect to patient characteristics or the surgical extent of resection (Table 3). After propensity matching, outcomes were again compared between both groups, and no statistical difference was found regarding respiratory complications (p = 0.24), all complications (p = 0.89), ITU readmission (p = 0.66), in-hospital mortality (p = 0.67), and ITU length of stay (p = 0.51). The paravertebral group had a statistically significant shorter postoperative length of stay compared with the epidural group (6 days v 7 days [p = 0.008], Table 4).
Table 3. Preoperative and Intraoperative Characteristics of Patients After Propensity Matching
| Preop Characteristics | Paravertebral Catheter (n = 122) | Thoracic Epidural (n = 488) | p Value |
|---|---|---|---|
| Median age (IQR) | 65(55-73) | 63(56-71) | 0.638 |
| % predicted FEV1 (IQR) | 81.17(71-96) | 82.24(71-97) | 0.969 |
| BMI (IQR) | 26.82(24-30) | 26.75(24-30) | 0.962 |
| Current smoker (%) | 27.1 | 30.9 | 0.402 |
| NYHA >2 (%) | 5.8 | 7.8 | 0.439 |
| Hypertension (%) | 38.5 | 36.7 | 0.706 |
| Cardiac comorbidity (%) | 36.9 | 35.5 | 0.768 |
| Extent of resection | 0.94 | ||
| Lobectomy (%) | 65.6 | 67.2 | |
| Pneumonectomy (%) | 4.1 | 3.9 | |
| Wedge (%) | 30.3 | 28.9 |
Table 4. Outcome of Patients by Analgesic Technique After Propensity Matching
| Postoperative Outcomes | Paravertebral Catheter (n = 122) | Thoracic Epidural (n = 488) | p Value |
|---|---|---|---|
| Respiratory comp (%) | 4.9 | 8.0 | 0.245 |
| Atelectasis (%) | 1.6 | 2.5 | 0.589 |
| Sputum retention (%) | 2.5 | 4.7 | 0.327 |
| Chest infection (%) | 0.8 | 2.7 | 0.322 |
| Bronchoscopy and suction (%) | 1.6 | 2.9 | 0.751 |
| Minitracheostomy (%) | 2.5 | 2.9 | 0.806 |
| Reintubated (%) | 0 | 2.7 | 0.082 |
| All complications (%) | 28.7 | 28.1 | 0.893 |
| ITU readmission (%) | 4.9 | 5.9 | 0.663 |
| In-hospital mortality (%) | 1.6 | 2.3 | 0.674 |
| ITU length of stay (IQR) | 1(1-1) | 1(1-1) | 0.517 |
| Postoperative total LOS (IQR) | 6(5-8) | 7(6-9) | 0.008 |
Discussion
PVB, which was first performed in 1905 to produce abdominal analgesia,1 is an alternative technique to thoracic epidural analgesia; both being used as methods to control postoperative thoracotomy pain. The classic approach for performing PVBs uses loss of resistance to air or saline as the superior costo-transverse ligament is traversed. The injection of local anesthetic into the paravertebral space by blocking the intercostal nerve, its dorsal ramus, the rami communicantes, and the sympathetic chain produces a dense sensory and sympathetic block.2 The paravertebral catheter also can be inserted under ultrasound guidance.4
An alternative technique for paravertebral insertion is the technique of surgical insertion, which is used at the authors' center. Intraoperatively, a trocar is used, which is passed one space below the thoracotomy wound posteriorly. When its tip is visible in the extrapleural space through the thoracotomy wound, the catheter is passed through the trocar and positioned to lie vertically covering two intercostal spaces. The authors believe this method of insertion offers better pain control because the extrapleural space is closed, and there is coverage of more than one intercostal space.
PVBs performed as single-shot or continuous techniques are useful in providing analgesia after thoracic surgical procedures. Richardson et al5 performed a prospective, randomized comparison of epidural and paravertebral bupivicaine on post-thoracotomy pain, pulmonary function, and stress responses. They found that the paravertebral group had significantly lower visual analog scale scores at rest and with coughing as well as lower morphine requirements. Side effects, such as nausea, vomiting, and hypotension, were more common in the epidural group. Continuous PVBs have also been shown to provide superior postoperative analgesia when compared with single-shot PVBs or intrapleural blocks after thoracotomy.6
In a review of 55 studies, Richardson et al7 examined the effects of analgesia on post-thoracotomy lung function. PVB was the most effective at maintaining spirometric function, with most patients having approximately 75% of their preoperative values in the first 48 hours after surgery, whereas most other techniques produced no better than 55% preservation by 48 hours.
Although it has been reported that a blood vessel is punctured in 2.8% to 11.5% of epidural insertions, usually without any sequelae,8 instrumentation of the epidural space potentially can result in epidural hematoma and paraplegia. The exact incidence of permanent neurologic damage after thoracic epidural catheterization is unknown, but a meta-analysis in 1995 that included both thoracic and lumbar epidural catheterization estimated the incidence of major spinal hematoma at 0.0007%.9 A review that included studies published between 1995 and 2005 with the primary intent of investigating neurologic complications of regional anesthesia estimated the rate of paraplegia after epidural placement at 0.0009% and the rate of cauda equina syndrome at 0.0023%.10 Despite the incidence of blood vessel puncture being reported to be significantly greater during lumbar epidural placement than during TEA, there still remains a potentially significant risk of a neurologic complication because of thoracic epidural placement.11 This risk is increased if the patient has a coagulation disorder or has received any anticoagulant medications, a situation that is increasingly common in today's patient population.12, 13 In addition, epidural abscesses can cause spinal cord compression requiring emergency decompression to avoid permanent neurologic damage.14
Accidental dural puncture, with an incidence of 1% to 5%,15 is also a common complication of thoracic epidural catheterization. Although postdural puncture headaches occur in up to 70% of patients after accidental dural puncture, fortunately, persistent neurologic sequelae are extremely rare.15 Other infrequent neurologic complications of epidural placement include radiculopathies and peripheral neuropathies, with an incidence of 0.0219%.10 Almost all are transient and do not require treatment.16 One of the most devastating complications of regional anesthesia is spinal cord injury, a rare but catastrophic complication that can result from instrumentation of the epidural space.17 PVB carries a significantly lower risk of this complication compared with TEA.15
It must be said that paravertebral catheters are not without drawbacks as well. PVBs also have been associated with neurologic complications. Although uncommon, there is a risk of inadvertent neuraxial placement of the needle or of potentially puncturing a dural sleeve with subsequent intrathecal injection.18 Additionally, nearly 10% of patients have a clinically significant parasympathetic discharge at needle placement, resulting in hypotension, bradycardia, and near-syncope.19 This is less common in the authors' practice because PVBs are placed intraoperatively while patients are anesthetized. Furthermore, continuous paravertebral nerve blocks also may be problematic in patients with spinal anomalies, trauma, or a history of spine surgery.3
Perhaps the ultimate side effect of a PVB is block failure, with both the percutaneous approach and the open technique having a relatively high failure rate of approximately 10%.20 This failure rate might be caused from the interference by the endothoracic fascia. Once the tip of the needle or the catheter is ventral to this fascia, the diffusion of the local anesthetic solution back to the nerve(s) is severely hindered.21
In a meta-analysis by Davies et al,22 the epidural failure rate was still significantly higher than the paravertebral group. Another life-threatening complication of PVB that would be expected with higher doses of local anesthesia medications compared with TEA is drug toxicity,23 which might require rapid resuscitation. In the authors' center, despite starting to insert PVB pre-emptively immediately after a thoracotomy rather than at the end of the procedure because some studies have shown better pain control,24 the authors still believe that TEA provides better control in the first 24 hours after surgery. This should be analyzed by pain scores, but it has been supported by other studies.25 This is important in counseling patients preoperatively for the choice of the type of regional anesthesia.
Many of the unwanted side effects of regional analgesia techniques are secondary to the associated sympathetic, sensory, and motor blockade or the addition of opioids to the local anesthetic solution. Both hypotension and urinary retention are commonly reported sequelae of these methods of regional anesthesia. The perils of hypotension in the thoracic patient can lie as much in the treatment as in the occurrence; excessive fluid administration, especially after pneumonectomy, can lead to elevated pulmonary artery pressures and pulmonary edema. Additionally, vasoconstrictive medications are not without side effects.26 It would be reasonable to expect a higher incidence of these complications with TEA because of the bilateral nature of the associated sympathetic and sensory block in contrast to a unilateral PVB.27
Richardson et al,28 in a prospective, randomized comparison of epidural versus paravertebral bupivicaine in 95 patients, found a significantly higher incidence of both urinary retention (defined as the requirement for catheterization) and hypotension (defined as a decrease in preoperative systolic or diastolic blood pressure of 20% or more) in the epidural group. To improve the effectiveness of epidurals, it is routine practice to combine local anesthetic with low-dose opiates. However, a serious risk of epidural opioids is respiratory depression, with an incidence after conventional dosing regimens of approximately 1%, which is similar to the incidence after conventional dosing of intravenous or intramuscular opioids.29
Although certain factors, such as advanced age and coexisting disease are associated with an increased risk of respiratory depression with epidural opioids, its occurrence largely is unpredictable, and patients generally need closer monitoring in the postoperative setting than patients who have a PVB or who are receiving local anesthetic alone.30 Probably the most common side effect of epidural opioids is pruritus, which can be generalized but more commonly is localized to the face, neck, or upper chest.31 The incidence is related to the type of opioids used, with epidural morphine being implicated more frequently than fentanyl or hydromorphone.32 The group of PVBs in this study was still prone to opioid-induced complications because morphine-based patient-controlled analgesia additionally was used.
Some of the absolute contraindications to epidural insertion do not exclude the use of a paravertebral technique. In the setting of a coagulopathy, when an epidural technique carries the risk of epidural hematoma and subsequent cord compression, the margin of safety is higher with a PVB and the more distensible paravertebral space.33 Nevertheless, PVBs are not void of nerve compression risks in cases of coagulopathy, and this should be weighed against the benefit of better pain control on an individual patient basis.
Difficult thoracic spinal anatomy makes an epidural technique more difficult and more likely to be associated with complications.27 In this situation, a paravertebral technique has the added advantage that it can be placed under direct vision by the surgeon before the end of the surgical procedure. If, after a patient in whom no epidural is inserted before him/her being anesthetized, a decision is made to extend the original procedure because of pathology findings, complications, or poor surgical exposure, a paravertebral catheter still can be placed.34 In contrast, most anesthesiologists are uncomfortable with epidural placement in anesthetized patients although some case series suggest that the practice is not unsafe.35 Local or systemic sepsis and allergy to local anesthetic drugs contraindicate both an epidural block and a PVB.
This study supports the theory of paravertebral analgesia as a safe alternative to epidural analgesia. The additional safety is supported by the fact that they are placed under direct vision by the surgeons. Possible explanations for the shorter length of stay associated with a paravertebral catheter, which was found in the present study, are, first, that there is more cardiovascular stability with less need of vasoconstrictor administration to control hypotension.28 Second, patients with PVBs are more likely to be mobilized earlier by the nurses and physiotherapists, and there is better respiratory reserve with a unilateral block because of less impairment of intercostal muscles.22 Finally, complications of epidural catheters, such as urinary retention,28 also can prolong the length of stay.
Limitations
The limitations of this study are those of a retrospective study despite having a large number. The authors do admit that without a randomized controlled study there can be type II errors, and randomization also would be useful to observe if certain high-risk groups would benefit from an epidural analgesia. Additionally, postoperative pain scores were not obtained to compare efficacy and failure rates of both techniques.
The results of the present study, containing the largest group of patients, should add to the growing bulk of evidence35, 36 for the efficacy of paravertebral catheters and patient-controlled analgesia as a safe alternative to epidural analgesia for post-thoractomy pain after lung resections. The additional information regarding a reduced length of stay also should be encouraging for surgeons and anesthesiologists to imply this technique. The technique now has been more widely accepted in the authors' hospital as a standard of care for analgesia to control post-thoracotomy pain.
Conclusions
In conclusion, PVBs have proved to be as effective as thoracic epidural analgesia for reducing the risk of postoperative complications associated with lung resections. The authors additionally have found that they are associated with an improved length of stay, and they are a better mode of analgesia for fast-tracking patients after thoracic surgery.
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- A prospective randomized comparison of interpleural and paravertebral analgesia in thoracic surgery . Br J Anaesth . 1995;75:405–408
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- Schwander D, Bachmann F: Heparin and spinal or epidural anesthesia: Decision analysis [French]. Ann Fr Anesth Reanim 10:284-296, 199
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- Neurological complications after regional anesthesia: Contemporary estimates of risk . Anesth Analg . 2007;104:965–974
- Extensive application of epidural anesthesia and analgesia in a university hospital: Incidence of complications related to technique . Reg Anesth . 1993;18:34–38
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- . Case report: Epidural abscess in a parturient with pruritic urticarial papules and plaques of pregnancy (PUPPP) . Can J Anaesth . 2006;53:1010–1014
- . Incidence of neurologic complications related to thoracic epidural catheterization . Anesthesiology . 1997;86:55–63
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- Small risk of serious neurologic complications related to lumbar epidural catheter placement in anesthetized patients . Anesth Analg . 2003;96:1547–1552
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- A prospective, randomized comparison of preoperative and continuous balanced epidural or paravertebral bupivacaine on post-thoracotomy pain, pulmonary function and stress responses . Br J Anaesth . 1999;83:387–392
- . Side effects of intrathecal and epidural opioids . Can J Anaesth . 1995;42:891–903
- In defence of paravertebral blockade . Br J Anaesth . 2002;88:743
- . Intrathecal and epidural administration of opioids . Anesthesiology . 1984;61:276–310
- . Comparison of epidural morphine, hydromorphone and fentanyl for postoperative pain control in children undergoing orthopaedic surgery . Paediatr Anaesth . 1999;9:419–422
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PII: S1053-0770(11)00694-X
doi:10.1053/j.jvca.2011.09.019
© 2012 Elsevier Inc. All rights reserved.
Volume 26, Issue 1 , Pages 78-82, February 2012
