Department of Anaesthesia and Intensive Care, The Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, NT, Hong Kong SAR, People's Republic of China
* Corresponding author. E-mail: hoamh{at}cuhk.edu.hk
Accepted for publication April 28, 2004.
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Abstract |
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Keywords: analgesia ; anaesthesia, regional ; anaesthetics, local ; complications, coagulopathy ; complications, thrombocytopenia
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Introduction |
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Case reports |
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As the hospital intensive care unit was full, we planned a regional block with post-operative rescue patient-controlled analgesia in order to improve her chance of early tracheal extubation after surgery. Epidural catheterization was contraindicated because of coagulopathy and thrombocytopenia, so we sited a paravertebral catheter instead. We began by inserting an 18-G Tuohy needle 2.53 cm lateral to the most cephalad aspect of the spinous process of T7 on the right-hand side and advanced it perpendicularly to the skin in all planes to contact the transverse process of T8 at a depth of approximately 3 cm.10 We then walked the needle above the transverse process and gradually advanced it until a loss of resistance to air was felt.10 An epidural catheter was then passed through the lumen of the needle until its tip was 4 cm caudal to the needle tip. Radiograph confirmed accurate paravertebral placement (Fig. 1). Upon placement of appropriate monitors, general anaesthesia was induced. Through a right subcostal incision, the surgeons removed her right lobe. At the time when the surgical specimen was removed, a 20 ml bolus of plain bupivacaine 0.5% was injected over 30 min via the paravertebral catheter, followed by an infusion of bupivacaine 0.25% at 8 ml h1, without any effect on arterial pressure. A drain was placed by the surgeon with an exit point at the L1 level in the mid-clavicular line. Overall, surgery and anaesthesia were uneventful. At the end of surgery, the patient's trachea was extubated before the patient was transferred to the recovery room, from where she was later discharged to a regular ward with continuation of the paravertebral infusion and a patient-controlled infusion of morphine.
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Case 2
A 52-yr-old Chinese man (height 156 cm, weight 72 kg) with moderate smoking-related lung disease, hepatitis B and hepatoma, but with no evidence of cirrhosis or malnutrition, presented for hepatectomy. His creatinine was 0.75 mg dl1, bilirubin was 1.1 mg dl1, albumin was 4.1 g dl1, INR was 1.1 (Child's A, Child-Pugh score 5, MELD score 8), APTT was 32.3 s (control 2638) s and platelet count was 125x109 litre1. This patient did not receive prior hepatic vein embolization or transarterial chemoembolization. He received a similar right thoracic paravertebral catheter before the right lobe hepatectomy. The anaesthetic and surgical techniques were otherwise similar to Case 1, and were uncomplicated.
The local anaesthetic bolus and infusion were the same as in Case 1 (started when the surgical specimen was removed) and were without haemodynamic disturbance. He had a block from T3 to T12, as tested 10 h after surgery. Post-operatively, his pain score was 01 at rest, 12 on coughing and 23 on moving to a chair. Cumulative patient-controlled morphine consumption was 10.5 mg at 16 h, 12 mg (or 0.2 mg kg1) at 24 h, 15 mg at 30 h and 18 mg (or 0.3 mg kg1) at 48 h after surgery. His mental status and vital signs were also stable throughout the first 48 h after surgery. The infusion was stopped and the catheter was removed at 48 h after surgery. His post-operative course was complicated only by a low-grade fever (38.038.4°C) between the second and fourth days, and he was discharged eight days after surgery.
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Discussion |
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The risk of spinal haematoma should be negligible with the use of paravertebral block8 9a technique that has been used for pain relief after liver12 and chest13 trauma, in labour,14 after thoracotomy15 and in inguinal,16 breast,17 cardiac18 and vascular19 surgery. Bleeding into the non-compressible thoracic paravertebral space is nonetheless of concern, especially when the technique is associated with vascular puncture in 3.8% of cases.20 As such, our decision to withdraw the paravertebral catheter at 48 h after surgery was contentious and involved avoiding local anaesthetic toxicity and balancing the poorly defined risks of bleeding and infection. On the one hand, any bleeding should tamponade with time, and, to date, there has not been a reported case of neurological injury or fatality directly related to bleeding after thoracic paravertebral block. On the other hand, the risk of infection increases with the duration a catheter remains in situ, and infection in the paravertebral space could be devastating.
Since a unilateral thoracic paravertebral block confers only ipsilateral pain relief and inconsistent block below T12,21 rescue morphine is usually required during the post-operative period. To confirm our impression that the block is morphine-sparing, we obtained institutional ethics approval and retrospectively reviewed all hepatectomy cases at our hospital between October 2002 and February 2003. Of the 54 cases identified, all but one received post-operative patient-controlled analgesia. The pain scores of the 53 patients receiving patient-controlled morphine (mean weight 56 kg (SD 15 kg)) were uniformly 12 at rest and mean morphine consumption was 0.7 (0.3) mg kg1 at 24 h and 1.2 (0.5) mg kg1 at 48 h. While not convincingly so for patient 1's morphine consumption at 24 h, these data are consistent with our clinical impression that our two patients did require less morphine. Morphine consumption of our two patients was also much lower than that found in a study of Western post-hepatectomy patients without a regional block.22 Any real differences in morphine consumption and the quality of analgesia, however, can only be determined through a comparative trial involving similar patients with and without a paravertebral block.
Thoracic epidural block can be associated with marked hypotension. However, if titrated appropriately, sympathetic blockade could be exploited to decrease the central venous pressure and blood loss during hepatectomy. Our anaesthesia group has extensive experience with paravertebral blocks, and has found that significant hypotension rarely occurs.9 13 22 In the absence of this potential advantage, we did not see a great difference between establishing the paravertebral block early or late during surgery. Another difference between an epidural block and a paravertebral block is that the latter does not usually cause urinary retention.9
Systemic accumulation of local anaesthetic may occur after prolonged paravertebral infusion. Although total plasma concentrations of local anaesthetic increase with time, the concentration of free (unbound) local anaesthetic remains unchanged in the post-operative period.23 This may explain why toxicity is rare after post-operative paravertebral infusion. Nevertheless, because of decreased hepatic clearance in patients with compromised liver function, until more data on local anaesthetic pharmacokinetics after thoracic paravertebral infusion is available, continuing an infusion much beyond 48 h after hepatectomy may not be advisable.
Our experience suggests that right thoracic paravertebral block is a possible analgesia option for patients undergoing hepatectomy in whom epidural block is contraindicated. Comparative studies on the use of thoracic paravertebral block in patients undergoing extensive liver resection may be worthwhile.
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References |
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