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* From the Department of Anesthesia and Intensive Care (Drs. Karmakar, Critchley, Ho, and Gin) and the Cardiothoracic Division (Drs. Lee and Yim), Department of Surgery, The Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, New Territories, Hong Kong.
Correspondence to: Manoj K. Karmakar, MD, Associate Professor, The Chinese University of Hong Kong, Department of Anesthesia and Intensive Care, Prince of Wales Hospital, Shatin, New Territories, Hong Kong; e-mail: karmakar{at}cuhk.edu.hk
| Abstract |
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Design: Prospective nonrandomized case series.
Setting: Multidisciplinary tertiary hospital.
Patients: Fifteen patients with unilateral MFR.
Interventions: Insertion of a catheter into the thoracic paravertebral space. We administered an initial injection of 0.3 mL/kg (1.5 mg/kg) bupivacaine 0.5% with 1:200,000 epinephrine followed 30 min later by an infusion of bupivacaine 0.25% at 0.1 to 0.2 mL/kg/h for 4 days.
Measurements and results: The following parameters were measured during the initial assessment before thoracic paravertebral block (TPVB), 30 min after the initial injection, and during follow-up on day 1 and day 4 after commencing the infusion of bupivacaine: visual analog pain score at rest and during coughing; respiratory rate; arterial oxygen saturation (SaO2); bedside spirometry (ie, FVC, FEV1, FEV1/FVC ratio, and peak expiratory flow rate [PEFR]); arterial blood gas measurements; and O2 index (ie, PaO2/fraction of inspired oxygen ratio). There were significant improvements in pain scores (at rest, p = 0.002; during coughing, p = 0.001), respiratory rate (p < 0.0001), FVC (p = 0.007), PEFR (p = 0.01), SaO2 (p = 0.04), and O2 index (p = 0.01) 30 min after the initial injection, which were sustained for the 4 days that the thoracic paravertebral infusion was in use (p < 0.05). PaCO2 did not change significantly after the initial injection, but on day 4 it was significantly lower than the post-TPVB value (p = 0.04). One patient had an inadvertent epidural injection, and another developed transient ipsilateral Horner syndrome with sensory changes in the arm. No patient exhibited clinical signs of inadvertent intravascular injection or local anesthetic toxicity.
Conclusion: Our results confirmed that continuous thoracic paravertebral infusion of bupivacaine is a simple and effective method of providing continuous pain relief in patients with unilateral MFR. It also produced a sustained improvement in respiratory parameters and oxygenation.
Key Words: analgesia anesthetic technique blunt chest trauma bupivacaine pain control paravertebral anesthetic paravertebral catheter regional anesthetic rib fracture trauma
| Introduction |
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Thoracic paravertebral block (TPVB), which produces multidermatomal, ipsilateral, somatic, and sympathetic nerve blockade,1 2 is one of the therapeutic options for managing pain in patients with MFR.3 4 5 6 7 A single, large-volume (ie, 20 to 30 mL), percutaneous, thoracic paravertebral injection of bupivacaine 0.5% provides effective analgesia and improves respiratory parameters and arterial blood gas tension in patients with unilateral MFR.4 This approach, although effective, is limited by the resurgence of pain and deterioration in respiratory parameters, necessitating repeated paravertebral injections.4 This may not be considered an optimal analgesic regimen and may be overcome by a continuous TPVB. Several case reports have described the use of continuous TPVB, as regular bolus injections3 7 or as a continuous infusion6 of local anesthetic via an indwelling paravertebral catheter,3 6 7 for pain control in patients with MFR. However, the effects of continuous TPVB on respiratory function and oxygenation in patients with MFR have not been described. We now report our experience using a continuous thoracic paravertebral infusion of bupivacaine for pain management in patients with unilateral MFR.
| Materials and Methods |
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IV access was established prior to the TPVB, although no fluid preload was administered. ECG, arterial oxygen saturation (SaO2), and noninvasive BP were monitored throughout the procedure. TPVB was performed under aseptic conditions with the patient in the sitting position using the technique described by Eason and Wyatt.3 The spinal level chosen for the paravertebral injection was either two segments below the uppermost fractured rib or midway between the uppermost and lowest fractured rib. The skin and underlying tissue was infiltrated with a 1% lidocaine solution 2.5 cm lateral to the cephalad aspect of the selected spinous process. A 16-gauge Tuohy needle (Minipack; Portex; Hythe, UK) then was inserted perpendicular to the skin in all planes and was advanced until the rib or transverse process was contacted. Once bone was felt, the needle was walked above the rib or transverse process and gently advanced until there was loss of resistance to the injection of air, indicating that the needle tip had traversed the superior costotransverse ligament to enter the thoracic paravertebral space. An epidural catheter then was inserted through the Tuohy needle and was advanced 2 to 3 cm into the paravertebral space. The catheter was tunneled subcutaneously and was secured to the back with adhesive dressings, and the patient was returned to the supine position. We graded the ease with which the catheter was inserted as easy, some resistance encountered, difficult, and impossible. After negative aspiration through the catheter, 0.3 mL/kg (1.5 mg/kg) bupivacaine 0.5% with 1:200,000 solution of epinephrine was injected slowly for > 3 min in small aliquots with the patient in the supine position. BP and heart rate were recorded every 5 min for the next 30 min. Any procedure-related complication was noted, and the dermatomal distribution of loss of sensation to cold (ice) was determined after 30 min.
A continuous infusion of bupivacaine 0.25% then was commenced at 0.1 mL/kg/h. Regular oral diclofenac (75 mg every 12 h) or dextropropoxiphene chloride, 32.5 mg, with paracetamol, 320 mg (Dolpocetmol; Synco Ltd; Hong Kong), was coadministered (2 tablets every 6 h) in patients with contraindications to the use of nonsteroidal analgesic agents. Patients were managed in the thoracic surgical ward, and no additional monitoring or nursing care was ordered. One of the investigators or a member of our pain team reviewed the patients twice daily for 4 days. During follow-up, the paravertebral infusion rate was increased (1 to 2 mL/h each time to a maximum infusion rate of 0.2 mL/kg/h) if the visual analog scale (VAS) pain score (0, no pain; 100, worst imaginable pain) on coughing was > 40 or if the patient requested additional analgesia. The rate adjustment was preceded by the administration of a bolus of 3 to 4 mL bupivacaine 0.25%. All patients were encouraged to perform breathing exercises using an incentive deep-breathing exerciser (Triflo II; Sherwood Medical; St. Louis, MO) and received regular chest physiotherapy.
The following parameters were measured pre-TPVB, at 30 min post-TPVB, on post-TPVB day 1, and on post-TPVB day 4: VAS pain score at rest and on coughing; respiratory rate; arterial oxygen saturation (SaO2); bedside spirometry (ie, FVC, FEV1, FEV1/FVC ratio, and peak expiratory flow rate) using a ventilometer (VM1; Clement Clarke; Harlow, UK); fraction of inspired oxygen (FIO2) in patients who were receiving O2; and arterial blood gas tension. The inspired oxygen concentration was kept constant before and after TPVB, and subsequently, on days 1 and 4, the FIO2 delivered via a Venturi mask was recorded. The O2 index (ie, PaO2/FIO2 ratio) was calculated from the above data. Patient cooperation with bedside spirometry often was limited by pain and discomfort.
The data were analyzed using a statistical software package (SPSS for Windows, version 10; SPSS Inc; Chicago, IL). A Kolmogorov-Smirnov test was used to test the normality of the data recorded. The data are presented as the mean (SD) when normally distributed or as the median (range) when not normally distributed. Appropriate parametric (paired t test) and nonparametric tests (Wilcoxon signed ranks test) were used. A p value of < 0.05 was considered to be statistically significant.
| Results |
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TPVBs were successful in all patients, and the initial injection of bupivacaine produced a median ipsilateral loss of sensation to cold of > 5 dermatomes (range, 3 to 11 dermatomes). The median distribution of the loss of cold sensation was 1.5 dermatomes (range, 1 to 3 dermatomes) above and 2.5 dermatomes (range, 0 to 9 dermatomes) below the level of injection (Fig 1 ). In a number of patients (cases 3, 5 and 12), few segments of contralateral sensory loss (3 to 6 dermatomes) were present. In one patient (case 9), bilateral symmetrical anesthesia (ipsilateral, T3 to T11; contralateral, T3 to T8) was present. The patient also developed hypotension that required treatment with IV fluid (1 L normal saline solution) and a vasopressor (metaraminol, 2 mg [total]). Subsequently, inadvertent epidural injection was confirmed radiologically (Fig 2 ), and the patient was treated as having an epidural block with a continuous infusion of bupivacaine 0.125% and fentanyl, 2.5 µg/mL at 0.1 to 0.2 mL/kg/h. This case was excluded from our final statistical analysis of TPVB characteristics. In the remaining 14 patients who were managed using the continuous thoracic paravertebral infusion, the infusion rate had to be increased in 10 patients (71.4%) such that the mean infusion rates on days 1, 2, and 4 were 7 mL (1.17 mL) [range, 6 to 10 mL], 8 mL (1.92 mL) [range, 6 to 12 mL], and 8 mL (1.70 mL) [range, 6 to 12 mL], respectively.
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| Discussion |
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Like Eason and Wyatt,3 we also found TPVB placement technically simple and easier to perform than thoracic epidural placement. Patients with MFR are often uncooperative during catheter placement due to pain, which makes the less risky paravertebral technique more desirable.
Unlike epidural catheter insertion, we frequently encountered resistance during paravertebral catheter insertion. Other researchers also have reported resistance and have suggested either rotating the Tuohy needle3 9 or injecting saline solution.2 The reason for this resistance is unclear, but it may reflect the limited size of the thoracic paravertebral space or the catheter being impeded by the endothoracic fascia.2 10
We also found blood-stained fluid in the catheter aspirate in 4 of 15 cases, which we could flush clear with saline solution, indicating that the catheter was not intravascular. In patients without MFR, blood is seldom aspirated, the reported incidence of vascular puncture being 3.8%.11 Thus, we believe that this increase in incidence represents free blood tracking back from the fracture site.
In the series by Gilbert and Hultman,4 TPVB was performed by a single-shot percutaneous technique, with a mean (SD) dose of 25 mL (5 mL) bupivacaine 0.5% being injected, which provided analgesia lasting for a mean duration of 9.9 h (1.2 h). They needed to repeat the block in 7 of the 10 patients studied.4 They justified the use of a repeated single-shot TPVB, instead of a continuous technique, because the block was easy to perform.4 In contrast, when using a continuous technique, we were able to provide continuous pain relief with a sustained improvement in respiratory parameters and oxygenation throughout the 4-day study period.
A segmental contralateral block was present in three of our patients (Fig 1) . Lönnqvist et al11 reported a lower incidence (1.1%). The exact etiology of this contralateral spread is not known but may be attributable either to epidural spread12 or to prevertebral spread5 6 13 to the contralateral paravertebral space.
Hypotension is a common occurrence after thoracic epidural anesthesia. In contrast, following TPVB hemodynamic stability was maintained in all our patients. Hypotension is unlikely to follow TPVB in normovolemic patients because of the unilateral nature of the sympathetic blockade.1 However, TPVB may cause hypotension in the inadequately resuscitated and hypovolemic patient. Therefore, we agree with Gilbert and Hultman4 that patients should not be offered TPVB unless they have been adequately resuscitated and cardiovascular stability has been established for several hours.
In one of our patients, a bilateral symmetrical block with accompanying hypotension indicative of an epidural block developed. This is rarely reported following TPVB but may occur due to extensive epidural spread,14 injection via a medially directed needle,15 16 inadvertent injection into a dural sleeve,15 or if an excessively large volume of local anesthetic is used.17 However, we injected relatively small bolus volumes of local anesthetic via the indwelling paravertebral catheter. Furthermore, an inadvertent intrathecal injection was unlikely because of the absence of motor blockade. Therefore, we must conclude that extensive epidural spread must have occurred. Some minor degree of epidural spread has been reported after 70% of TPVBs.14 However, this is usually unilateral,14 the volume involved being small,18 and somatic and sympathetic nerves are blocked unilaterally.1 14 When radiopaque contrast medium is injected into the thoracic paravertebral space, it produces a typical longitudinal or cloud-like spread of contrast medium that is localized to the paravertebral region, as seen on anteroposterior chest radiographs.6 19 In case 9, the lack of this thoracic paravertebral spread and the preferential epidural spread of contrast medium (Fig 2) suggested an epidural rather than paravertebral injection.
Despite using a high infusion rate of bupivacaine (20 mg/h) for 4 days, none of our patients exhibited clinical signs of local anesthetic toxicity. Currently, there are no published data on the pharmacokinetics and possible toxicity of bupivacaine in patients with MFR who are receiving TPVB. However, systemic toxicity appears to be rare during continuous TPVB,2
despite the use of higher amounts of bupivacaine than that used in our series.2
8
Although the total bupivacaine plasma level steadily increased in surgical patients receiving postoperative infusion, the free bupivacaine level remained unchanged.20
A postoperative rise in
1-acid glycoprotein, which binds to the bupivacaine, appears to offer protection against toxicity.20
The same may be true in patients with MFR due to trauma.21
Other than aberrant blockade, one inadvertent epidural injection, and one instance of Horner syndrome, there were no other major complications of TPVB in our series. However, due to the limited sample size (15 patients), we were unable to draw any definite conclusions about clinical safety. Published data would suggest that the complication rate is low (2.6 to 10%).11 22 Lönnqvist et al11 evaluated 367 paravertebral blocks, both thoracic and lumbar, and found the following rates: vascular puncture, 3.8%; hypotension, 4.6%; pleural puncture, 1.1%; and pneumothorax, 0.5%. Inadvertent pleural puncture may not necessarily result in a pneumothorax and is usually managed conservatively.2 Other rare complications include inadvertent intravascular injection, pulmonary hemorrhage, spinal anesthesia, postural headache, and intercostal nerve trauma.2 No fatality from TPVB has yet been reported.
We conclude that continuous thoracic paravertebral infusion of bupivacaine is a simple and effective method of providing continuous pain relief in patients with unilateral MFR. Patients also enjoy sustained improvement in respiratory parameters and oxygenation.
| Acknowledgements |
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| Footnotes |
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This research was funded locally by the Department of Anesthesia and Intensive Care, The Chinese University of Hong Kong.
Received for publication July 12, 2001. Accepted for publication July 16, 2002.
| References |
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This article has been cited by other articles:
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E. Marret, B. Bazelly, G. Taylor, N. Lembert, A. Deleuze, J.-X. Mazoit, and F. J. Bonnet Paravertebral Block With Ropivacaine 0.5% Versus Systemic Analgesia for Pain Relief After Thoracotomy Ann. Thorac. Surg., June 1, 2005; 79(6): 2109 - 2113. [Abstract] [Full Text] [PDF] |
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A. M.-H. Ho, M. K. Karmakar, M. Cheung, and G. C. S. Lam Right thoracic paravertebral analgesia for hepatectomy Br. J. Anaesth., September 1, 2004; 93(3): 458 - 461. [Abstract] [Full Text] [PDF] |
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