|
Chronic Refractory Angina |
||||||||||||||
PARAVERTEBRAL BLOCK FOR THE TREATMENT OF CHRONIC REFRACTORY ANGINATreatmentTo improve the quality of life through the alleviation of symptoms. IntroductionParavertebral block was first described in 1905 by Sellheim of Leipzig as a replacement for spinal anaesthesia1 and is used for surgical procedures(2,3), management of both benign and malignant neuralgia and complex regional pain syndromes(4. Up until the 1950's paravertebral injection of alcohol was a common treatment for angina pectoris in patients who were too ill to undergo a cervico-thoracic sympathectomy(5,6,7). However with advances in cardiothoracic surgery and developments in medical therapy both of these techniques lost favour. With an increasing number of patients with post-revascularisation angina, these forgotten therapies are being evaluated to try and ameliorate their symptoms. The theoretical basis for temporary sympathectomy is described in the article on temporary sympathectomy. AnatomyIn two thirds of patients, the cardiac sympathetic nerves relay at the stellate ganglion, hence local anaesthetic injection at this level can alleviate angina(8). In the remainder, the connections seem to be at a lower thoracic level which cannot be reached by stellate ganglion block even with larger volumes of injectate. Thus in these patients paravertebral blockade is appropriate. The paravertebral space is a triangular area which contains the intercostal nerve (and its dorsal ramus), the rami communicantes and the sympathetic chain. Posteriorly is the costotransverse ligament, anteriorly the parietal pleura, medially the postero-lateral aspect of the vertebra and laterally the posterior intercostal membrane. Local anaesthetic injection into this space produces both a somatic and sympathetic block over several dermatomes(9). ProcedureWritten informed consent is obtained and a peripheral cannula is sited to ensure there is intravenous access. Patients sit upright, resting their arms on a pillow on their laps. Throughout the procedure they are attached to a pulse oximeter and a Holter monitor, a full resuscitation trolley is close at hand and there are always two qualified medical practitioners trained in advanced cardiac life support present. The back is prepared with cleaning solution and the spinous processes palpated to locate T3-4. Local anaesthetic is infiltrated two fingersbreadth (3-4cm) to the left of this point to the depth of the transverse process. A Tuohy needle is then inserted perpendicularly to the skin planes until it contacts the bone. Then it is re-angled superiorly and advanced until it slips over the upper border of the transverse process. At this point a low friction syringe is connected to the needle and using the loss of resistance technique, the paravertebral space is located. There may be a click as the needle passes through the costotransverse ligament. Following negative aspiration, 15mls of 0.5% bupivacaine is injected and then the needle is removed. Patients are allowed home later the same day. In patients who find the benefits of this treatment short-lasting, then a catheter can be inserted into the paravertebral space by the same technique. A 72 hour infusion of ropivacaine has produced greater symptom alleviation in some of our patients. Treatment of patients who are anticoagulatedThere is a group of patients with ischaemic heart disease who are anticoagulated, either because of atrial fibrillation or following valve replacement. We recommend that patients stop their warfarin for the three days prior to the procedure as long as they do not have a metal valve replacement. As long as their INR is lower than 1.5, paravertebral block can be safely performed. For patients who are cannot have warfarin stopped, they must be admitted and temporarily switched to intravenous heparin. This is stopped for one hour prior to the paravertebral block. RepeatabilityIn our experience, beneficial amelioration of angina can be achieved with repeated blocks. There does not appear to be any predictability in the length of time a patient remains pain-free after successive blocks. ComplicationsIt is estimated that minor complications occur in less than 5% of cases10 and tend to occur during injection or shortly afterwards. In a large series of patients having mainly perioperative blocks, the main complications were hypotension in 4.6%, vascular puncture in 3.8%, pleural puncture in 1.1% and pneumothorax in 0.5%(11). Accidental extradural or intrathecal injection is rare and due to taking too medial an approach. Total spinal anaesthesia has been reported, with no long-term sequelae(12). Nursing guidelinesThe major central nervous system complications tend to occur during injection or shortly afterwards. Therefore we observe patients in a fully equipped resuscitation area for at least 15 minutes prior to them returning to their bed. Thereafter, the patient is monitored by qualified nursing staff who record the pulse and blood pressure every 15 minutes for the first hour and then every 30 minutes for the next four hours. SummaryParavertebral block with local anaesthetic is a safe procedure, which is making a Ïcome-backÓ in anaesthetic practice(13). In patients with refractory angina, who do not benefit from stellate ganglion block and have no changes in their HRV suggestive of cardiac sympathetic interruption, paravertebral injection of local anaesthetic has a role. Epidural anaesthesia is also effective and is almost certainly works by a similar mechanism. When temporary sympathetic blockade fails.References
|
|||||||||||||||
All pages copyright © angina.org. Last Revision: August 15 2002 |