Department of Anaesthesia and Intensive Care, The Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, NT, Hong Kong, Peoples Republic of China*Corresponding author
Accepted for publication March 19, 2001
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Abstract |
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Br J Anaesth 2001; 87: 31216
Keywords: anaesthetic techniques, regional, paravertebral; anatomy, endothoracic, retroperitoneal, paravertebral space
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Introduction |
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Case report |
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After discussion with the patient, he requested to have the thoracic paravertebral catheter resited. Using the same technique the right thoracic paravertebral space was accessed one interspace lower at the T89 level and 3 cm of catheter was inserted into the thoracic paravertebral space. The catheter was tunneled subcutaneously and safely secured to the back. A total of 10 ml of 0.5% bupivacaine with 1:200 000 epinephrine was injected via the catheter over a 2-min period with the patient in the supine position. The patient once again became pain free. Thirty minutes following the injection, the VAS was 0 at rest and 20 on coughing and ipsilateral cutaneous anaesthesia to temperature (cold) was elicited from T7L3 dermatomes. There were no significant haemodynamic changes or evidence of motor blockade in the distribution of the lumbar spinal nerves bilaterally as judged by normal hip flexion, knee extension and hip adduction.
To confirm the position of the catheter and demonstrate the spread of the paravertebral injection 10 ml of Iopamiro-300 (Iopamidol-300 mg ml1, Bracco s.p.a., Milano, Italia) was injected via the indwelling paravertebral catheter distal to the bacterial filter. Immediately following this injection an anteroposterior chest x-ray was taken (Fig. 1). Ipsilateral paravertebral spread of contrast from the ninth thoracic to the second lumbar segment below the diaphragm was noted on the chest x-ray (Fig. 1).
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Discussion |
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There is controversy whether low thoracic paravertebral block can extend into the lumbar region. Lönnqvist and Hildingsson examined the caudal limit of the thoracic paravertebral space in eviscerated cadavers by approaching the thoracic paravertebral space internally from the thoracic cavity.2 Based on observations made after probing and dye injection, they concluded that the origin of the psoas major muscle completely sealed off the thoracic paravertebral space below the level of the 12th thoracic vertebra, and proposed that spread of a thoracic paravertebral block below this level through the paravertebral space was unlikely.2 However ipsilateral thoraco-lumbar anaesthesia,1 35 radiological spread of contrast below the diaphragm9 and thoraco-lumbar spread of coloured dye in cadavers6 has been described,1 46 9 challenging the concept of lumbar nerve sparing following thoracic paravertebral block.2
The incidence of ipsilateral thoraco-lumbar anaesthesia after thoracic paravertebral block is not known but published data suggest that it is more common after low thoracic paravertebral injections.1 35 Richardson et al. report ipsilateral L1 spinal nerve involvement in three of the ten patient studied after paravertebral injection of 1.5 mg kg1 bupivacaine 0.5% at T6 and T10 level respectively.3 Cheema et al. performed paravertebral injections at a mean level of T910 (range T78 to T1011) and report mean ipsilateral anaesthesia of five dermatomes (range 18), with upper and lower limits of T6 and L3, after 15 ml of bupivacaine 0.5%.1 Saito et al. report broad unilateral anaesthesia extending from the left T4 to L3 after injection of local anesthetic through an epidural catheter, which was inadvertently inserted in the left T11 paravertebral space.5 More recently, Saito et al., in a cadaveric study, demonstrated ipsilateral retroperitoneal lumbar paravertebral spread of crimson dye along the endothoracic fascia and fascia transversalis through the medial and lateral arcuate ligament, after thoracic paravertebral injection at T11.6 The dye stained the ipsilateral subcostal, iliohypogastric, ilioinguinal, genitofemoral and lateral femoral cutaneous nerve in all 12 cadavers studied, and in two cases the dye also reached the femoral nerve.6 On average, spread extended from the 6th intercostal nerve to the lateral femoral cutaneous nerve (T6L2).6 All of these reports of ipsilateral thoraco-lumbar anaesthesia1 35 and paravertebral spread6 9 in vivo1 35 9 and in cadavers6 suggests that there is a fascial plane of communication between the ipsilateral thoracic paravertebral space and the retroperitoneal space. Review of the literature shows that such an anatomical plane of communication exists which may account for ipsilateral thoraco-lumbar anaesthesia.
The endothoracic fascia, also referred to as the internal thoracic fascia, is a fibroelastic structure that forms the deep fascia of the thorax and lines the internal surface of the intercostal muscle, the intervening ribs, and the diaphragm.12 At the diaphragm, the endothoracic fascia is very thin,6 13 being thinnest at the upper surface and thickest at its edges.6 Inferiorly the endothoracic fascia is continuous with the fascia transversalis (Fig. 2),6 12 13 which is the deep fascia of the abdomen. This continuity occurs dorsal to the diaphragm through the medial and lateral arcuate ligament (lumbo-costal arch) and the aortic hiatus.6 12 13 The fascia transversalis blends medially with the anterior layer of the quadratus lumborum fascia and the psoas fascia (psoas sheath) (Fig. 3).14 The subcostal (T12), iliohypogastric (L1) and ilioinguinal (L1) nerves course anterior to and in contact with the quadratus lumborum,15 while the genitofemoral nerve (L1, L2) descends on the ventral surface of the psoas major muscle and the lateral femoral cutaneous nerve (L2, L3) crosses the lateral border of the psoas muscle at the level of the inferior margin of L4 vertebra15 in this fascial plane.
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Based on the fascial anatomy described, an injection in the lower thoracic paravertebral space posterior to the endothoracic fascia can spread caudally via the medial and lateral arcuate ligament to the retroperitoneal space in the abdomen.4 Since this results in spread anterior to the surface of the quadratus lumborum and psoas major muscle, the subcostal, iliohypogastric, ilioinguinal, genitofemoral and the lateral femoral cutaneous nerve may be involved.6 This is the anatomical basis of the technique of extended unilateral anaesthesia4 and may also be the mechanism involved in our patient.
In summary, this case report demonstrates that ipsilateral thoraco-lumbar anaesthesia and paravertebral spread can occur after low thoracic paravertebral injection. Based on current evidence and anatomical knowledge the mechanism for this observation is an extended subendothoracic fascial spread from the thoracic paravertebral space to the retroperitoneal space in relation to the anterior surface of the psoas major and quadratus lumborum muscle where it affects the lumbar spinal nerves. This may have clinical application in the management of acute and chronic pain of unilateral thoraco-lumbar origin.
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References |
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