Thoracic paravertebral block (PVB) analgesia.
The use of a local anaesthetic as either a bolus injection or a continuous infusion into the paravertebral space to provide analgesia is a long established technique. Thoracic paravertebral blockade was described for use in patients scheduled for obstetric procedures in the 1930s. The local anaesthetic produces a unilateral somatic and sympathetic block which may be of use after unilateral surgery on the chest and abdomen. In the surgical patient the technique may be used prior to the skin incision (pre-emptive), intraoperatively under direct vision by the surgeon or at the end of the surgical procedure when the wound is closed. The use of preincisional paravertebral blockade may also reduce the prevalence of chronic pain after breast surgery (Kairaluoma et al 2006).
Paravertebral space location
The paravertebral space (PVS) is a wedge shaped compartment, bordered above and below by the heads and necks of adjoining ribs, posteriorly by the superior costotransverse ligament, medially it communicates with the epidural (extradural) space through the intervertebral foramen and laterally its apex leads into the intercostal space (Figure 1). In transverse section the PVS is triangular and contains the intercostal nerve, its dorsal primary ramus and the rami communicantes, the sympathetic chain, the intercostal artery and veins as well as fibrous fatty matter. Like the epidural space the PVS is a potential (not a true) space which can be created by fluid distension.
[FIGURE 1 OMITTED]
There is no direct communication between one paravertebral space and another, although spread of local anaesthetic from one paravertebral space to another across the epidural space can occur.
[FIGURE 2 OMITTED]
Uses of thoracic PVB
Thoracic PVB has a variety of uses including:
* relief from myofascial pain (Naja et al 2007)
* relief from the pain of fractured ribs (Karmarkar et al 2003)
* local anaesthesia
* for breast augmentation (Burlacu et al 2007, Cooter et al 2007)
* for percutaneous transhepatic biliary drainage
* postoperative analgesia
* after thoracotomy (Marret et al 2005, Casati et al 2006, Navlet et al 2006, Davies et al 2007)
* after breast surgery (Kairaluoma et al 2006)
* after thoracoabdominal aortic aneurysm repair (Shine et al 2004).
Patient selection criteria
Patients who are scheduled for the above procedures may benefit from thoracic PVB, but this is not a 'stand alone' technique. Therefore parenteral or enteral opioids are usually required. All patients require an explanation of technique's risks and benefits together with consent (RCoA 2006).
Patients unsuitable for epidural analgesia because of local or systemic sepsis or anticoagulation or who refuse to have an epidural inserted because of concerns about potential risks may benefit from PVB. The formation of an epidural haematoma secondary to bleeding associated with epidural catheter insertion or removal may result in spinal cord compression. This may result in a permanent loss of sensation or function below the level of compression and is a risk with epidural analgesia especially at the thoracic or cervical epidural levels. The risk of haematoma formation is increased by the use of thromboprophylaxis (for example, low molecular weight thromboprophylaxis) and anticoagulation/antiplatelet therapy (for example, ticlopidine and clopidogrel) (Horlocker et al 2002). The risk of haematoma formation associated with cardiac surgery and systemic heparinisation is yet to be quantified but may be as high as 1:2,400 (Hemmerling et al 2008). Therefore epidural analgesia insertion and removal timings need to be co-ordinated with thromboprophylaxis timings to reduce the risk of bleeding.
Exclusion criteria for thoracic PVB analgesia may include:
* allergy or sensitivity to local anaesthetic agents including lidocaine (lignocaine), bupivacaine, levobupivacaine or ropivacaine
* septic conditions of the pleural space, for example, empyema
* inflammatory conditions of the pleural space
* complete atrioventricular (AV) node block.
The techniques for single injection and continuous infusion via a catheter are described below. The patient is positioned in the sitting or lateral decubitus position and supported by an assistant. The patient should be encouraged to assume a kyphotic position, similar to the position required for epidural insertion (Figure 2). Nerve stimulators have been used to identify the correct PVS for patients having single PVB injections for chronic pain syndromes. The mean depth from the skin to the PVS has been measured as 55mm (Naja et al 2005).
The spread of the LA solution is determined by the site of injection with injection into the more ventral part of the thoracic PVS resulting in more longitudinal spread (Naja et al 2004). Cheema et al (2003) concluded that repeat injections in chronic pain patients produced varied spreads and that this was most likely due to physical properties and anatomical factors.
In the awake patient, after skin antisepsis (for example, chorhexidine 2% in isopropyl alcohol 70% as recommended by Pratt et al 2007) and draping, skin wheals are raised 4 cm from the midline using a short acting local anaesthetic (for example, lidocaine), opposite the lower borders of the vertebral spines. Through each weal, the needle (a Tuohy type similar to that used for epidural catheter insertion and shown in Figure 3) is inserted perpendicularly to strike bone near the lateral extremity of the transverse process. The needle is then redirected upwards and slightly medially over the upper border of the transverse process. After aspiration to ensure that the needle is not within a vessel or in the intrathecal (subdural) space a local anaesthetic with a long duration of action (for example, levobupivacaine, ropivacaine) is then injected. The injections sites are covered with sterile dressings. The injection sites will require regular observation to assess for bleeding or haematoma formation.
As above, but the PVS is identified using a Seldinger technique and the catheter fed through the Tuohy needle and secured in place with a moisture responsive, clear occlusive dressing. The block is then initiated with a bolus injection and continued using a dedicated pain management infusion device (NPSA 2007). The dressing should remain in situ until the catheter is removed.
Local anaesthetic selection
The choice of local anaesthetic (LA) should be restricted to medicines with a longer duration of action. Shorter acting local anaesthetics such as lidocaine have a shorter onset of action compared to bupivacaine or ropivacaine but also have a shorter duration of action, which is usually only advantageous for procedural pain. The local anaesthetic may be combined with an opioid to enhance analgesia. A meta-analysis of randomised studies revealed that a variety of concentrations of local anaesthetics have been used in published studies (Davies et al 2006). Bupivacaine was the most commonly used LA with concentrations of between 0.125-0.25% as standard.
[FIGURE 3 OMITTED]
Newer amide local anaesthetics such as ropivacaine and levobupivacaine may also be used. These LAs are considered to be potentially 'safer' than bupivacaine if inadvertently administered intravenously (Cox 2007).
There have been reports of cardiac arrest associated with the use of bupivacaine for peripheral nerve blockade where prolonged resuscitative efforts were required before the patient responded. In some instances resuscitation has proven impossible (NPSA 2007). Bupivacaine (like all local anaesthetic medicines) may cause acute toxicity effects on the central nervous and cardiovascular systems if utilised for local anaesthetic procedures resulting in high blood concentrations of the drug. After unintentional intravascular administration, ventricular arrhythmias, ventricular fibrillation, sudden cardiovascular collapse and death have been reported (Astra Zeneca 2005).
Major peripheral nerve blocks like PVB require the administration of a large volume of local anaesthetic into an area with a rich blood supply. This increases the risk of intravascular injection and systemic absorption. Thus, patients must have patent intravenous access (RCoA et al 2004) and blocks should be performed in an appropriately staffed and stocked clinical area.
All institutions providing PVB should have a policy, protocol or guideline detailing the care of patients receiving this form of analgesia. The PVB infusion should be clearly prescribed. This may be performed on a dedicated prescription chart (an example is shown in Figure 4). The catheter and administration set should be clearly labelled. Ideally the infusate should be commercially prepared to reduce the risk of dilution errors (Cox 2007) and should be infused using a dedicated infusion device (NPSA 2007). Some UK centres use yellow administration sets and infusion devices to indicate a regional block, whilst others use a grey infusion pump to signify that the infusion is regional but is not an epidural.
Education and training
Medical, nursing and operating department practitioners' education is an important aspect when utilising any form of 'high tech' analgesia to ensure that benefit outweighs risk. Most institutions require that competency is demonstrable. This should involve targeted education, appropriate to level of expertise, followed by certification. Institutions should provide PVB training in the form of teaching sessions at formal pain study days and also informal sessions organised by the acute pain service within the clinical area. In relation to PVB a practical assessment of clinical skills would be necessary to ensure that staff are deemed competent to safely manage and remove the PVB catheter.
Assessment of competency regarding PVB should include the following:
* basic anatomy and physiology of the paravertebral and epidural spaces
* advantages and disadvantages of the technique
* correct documentation of observations
* correct identification and management of associated complications, such as local anaesthetic systemic toxicity
* the safe removal of the PVB catheter.
Care of the patient receiving thoracic PVB
PVB should not be considered to be a stand alone technique, rather it should be viewed as an opioid sparing technique. An opioid sparing technique is one which reduces the required dose of an opioid hopefully resulting in a reduction in opioid related side effects and enhanced analgesia (lower pain intensity scores). Patients should receive PVB as one constituent of a multimodal approach (based on regular paracetamol, a nonsteroidal anti-inflammatory if not contraindicated, an appropriate opioid if needed). This multimodal approach is also known as 'balanced' analgesia. The patient should also be prescribed rescue analgesia. This may take the form of opioids in an oral or parenteral preparation (for example, patient controlled analgesia) depending on the patient's medical and pain history and the surgical procedure performed.
[FIGURE 4 OMITTED]
In common with all postoperative patients, dynamic pain should be assessed at regular intervals and the effectiveness of interventions recorded. Dynamic pain is pain experienced when the patient is moving. In thoracic surgical patients, pain should be assessed at rest (static pain) and on deep breathing and coughing (dynamic pain). Brown (2008) and McMain (2008) provide additional information about pain assessment elsewhere in this issue.
Sensory block is a term used to describe the degree of sensation loss (for example, to the application of cold) that a patient experiences due to a local anaesthetic. It is a standard observation for patients who have undergone neuraxial analgesia (for example, an epidural infusion or spinal injection). Hura et al (2006) compared the sensory blockade of 70 patients who received a single thoracic PVB injection (at level T4) of bupivacaine or ropivacaine after modified radical mastectomy. Ropivacaine produced a quicker onset of action and a block of sufficient width and intensity with which to commence surgery after only five minutes (53% of patients in the ropivacaine group versus 20% in the bupivacaine group). The regression of the block was similar although sensory block was statistically greater in the ropivacaine group at 24 hours.
The measurement of the level of sensory block to cold is standard care for patients receiving epidural analgesia but is not necessary for patients receiving PVB as the block is unilateral and should not interfere with muscle strength.
Catheter and insertion site
This should be dressed with a clear dressing and inspected and recorded alongside the patient observations. The site should be observed for any signs of inflammation or infection (heat, redness, swelling, discharge). Catheter migration is a frequent cause of PVB failure in research studies and is most likely due to inadequate fixation of the catheter. A filter should be used to connect the catheter to the administration set (Karmakar et al 2001).
Infusion rates and duration of PVB
These will vary depending on the concentration of local anaesthetic and patient factors such as age, weight, comorbidities and the type of surgery. Clinical experience suggests that PVB infusions should continue whilst intercostal or other drains remain in situ, usually 72 hours. Longer infusion times may be suitable in some patient groups but a risk/benefit analysis should be undertaken at regular intervals.
Side effects of PVB
The administration of all types of analgesia is never side effect free. These are related to the route of administration and the pharmacokinetics and pharmacodynamics of the medicine and are listed in Table 1.
A PVB catheter may occlude which is usually indicated by a pump alarm of 'distal occlusion'. The catheter should only be flushed by an appropriately trained member of staff.
Thoracic PVB is a relatively safe and effective mode of providing procedural and postoperative pain management. The block may be performed as a single injection or a catheter may be inserted to allow for the continuous or bolus administration of a long acting local anaesthetic. This mode of analgesia requires additional (usually opioid) analgesia. The paravertebral administration of analgesia is considered to be safer than neuraxial techniques such as epidurals in anti-coagulated patients but patients remain at risk of local anaesthetic toxicity. Staff caring for patients receiving PVB must have undergone an education programme and been assessed as competent.
Association of Anaesthetists of Great Britain & Ireland 2007 Guidelines for the management of severe local anaesthetic toxicity London, AAGBI Available from: www.aagbi.org/publications/guidelines/docs/latoxicity07.pdf [Accessed 8 July 2008]
Astra Zeneca UK Limited 2005 Marcain Polyamp Steripack SPC Available from: www.medicines.org.uk [Accessed 8 July 2008]
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Burlacu CL, Frizelle HP, Moriarty DC, Buggy DJ 2007 Pharmacokinetics of levobupivacaine, fentanyl and clonidine after administration in thoracic paravertebral analgesia Regional Anesthesia and Pain Medicine 32 (2) 136-146
Casati A, Alessandrini P, Nuzzi M et al 2006 A prospective, randomized, blinded comparison between continuous thoracic paravertebral and epidural infusion of 0.2% ropivacaine after lung resection surgery European Journal of Anaesthesiology 23 (12) 999-1004
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Horlockler TT et al 2002 Second Consensus Conference on Neuraxial Anesthesia and Anticoagulation. Regional Anesthesia in the Anticoagulated Patient: Defining the Risks. American Society of Regional Anesthesia and Pain Medicine Park Ridge (Illinois), ASRA
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Royal College of Anaesthetists, Royal College of Nursing, The Association of Anaesthetists of Great Britain & Ireland et al 2004 Good practice in the management of continuous epidural analgesia in the hospital setting London, RCoA Available from: www.britishpainsociety.org/Epid-Analg.pdf Accessed 8 July 2008]
Royal College of Anaesthetists 2006 Risks associated with your anaesthetic. Nerve damage associated with peripheral nerve block London, RCoA Available from: www.rcoa.ac.uk/docs/nerve-peripheral.pdf [Accessed 19 September 2008]
Thavaneswaran P et al 2006 Paravertebral blocks for anaesthesia and analgesia: a systematic review. ASERNIP-S report No.47, Adelaide SA, ASERNIP-S Available from: http://www.library.nhs.uk/Theatres/ViewResource.aspx?resID=257223 [Accessed 19 September 2008]
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About the authors
Senior Nurse, Pain
Royal Brompton and
Harefield NHS Trust
Sister, Pain Management,
Royal Brompton Hospital,
by Felicia Cox and Angela Cousins Correspondence address: Pain Management Service, Royal Brompton & Harefield NHS Trust, Harefield Hospital, Hill End Road, Harefield, UB9 6JH. Email: firstname.lastname@example.org
Table 1 Side effects of thoracic PVB Anticipated, but not usually serious. Observe the patient. * Sympathetic blockade associated with Horner's Syndrome (ptosis, miosis, anhydrosis) * Inadequate analgesia (especially shoulder tip pain secondary to diaphragmatic irritation) Unexpected--potential to be serious. Observe the patient and inform the pain team and/or anaesthetist. * Infection * Pneumothorax * Inadvertent neuraxial analgesia (if epidural or spinal spaces breached) * Hypotension (if neuraxial spread occurs) 'Red flag'--potential to be serious. The infusion must immediately be turned OFF and a review by the pain team/anaesthetist undertaken. * Motor block (indicates that the catheter has migrated) * Local anaesthetic toxicity (twitching, convulsions, perioral numbness, sudden loss of consciousness, cardiovascular collapse) (AAGBI 2007)
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|Author:||Cox, Felicia; Cousins, Angela|
|Publication:||Journal of Perioperative Practice|
|Date:||Nov 1, 2008|
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