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Analgesia for thoracotomy
Thoracic
Analgesia for thoracotomy
careful attention to protecting pressure points. Surgical drains must be placed to minimize postoperative irritation and pain. The aetiology of ipsilateral shoulder tip pain, which is seen in up to 75% of thoracotomy cases, is not clearly understood. Possible mechanisms include referred pain from phrenic stimulation and direct strain on the glenohumeral joint secondary to positioning and retraction. Pain may be a manifestation of underlying pathology, including recurrence of tumour, infection, bleeding or persistent air leak. The patient’s background and preoperative mindset also affect postoperative pain scores, emphasizing the importance of good communication and effective anti-anxiety medication.
Bevan Hughes Jonathan Mackay
Abstract Thoracotomy is one the most painful surgical incisions. Surgical exposure to the thoracic cavity causes damage to multiple nociceptive structures in the chest wall and cardiopulmonary viscera. There is a high incidence of both acute and chronic postoperative pain, which can delay recovery and cause long-term disability. Prevention of pain after thoracotomy is challenging and may require a variety of interventions.
Impact of pain Severe, acute post-thoracotomy pain may delay recovery. Impaired inspiration and ineffective cough may cause hypoxaemia and retained pulmonary secretions. Reluctance to mobilize also increases the risk of thromboembolic events and pressure sores. Chronic post-thoracotomy pain syndrome (PTPS) is defined as persistent pain at least 2 months after the procedure. PTPS is usually characterized as burning or stabbing with neuropathic features including allodynia and hyperaesthesia. Up to 80% of patients will report some residual pain along a thoracotomy incision at 3 months. PTPS may interfere with normal life in half these patients. Although acute pain is certainly decreased in patients undergoing VAT procedures, there is controversy as to whether the long-term incidence of PTPS is any less than after open techniques. Frozen shoulder is another potential consequence of reduced mobility due to persistent shoulder pain.
Keywords chronic post-thoracotomy pain syndrome; intercostal block; post-thoracotomy pain; thoracic epidural anaesthesia; thoracic paravertebral block; thoracotormy; video-assisted thoracoscopy
Mechanisms of pain Thoracotomy pain is transmitted primarily via the intercostal, vagus and phrenic nerves. Shortly after exiting the intervertebral foramen through the dorsal root, the intercostal nerve gives off posterior, ventral and visceral divisions made up of both somatic Aδ fibres and visceral C fibres. The latter include afferent sympathetic fibres, which combine with input from multiple spinal levels in the paravertebral sympathetic trunk. Intercostal nerves are vulnerable to surgical damage by the incision, cautery, retractors and chest drains. Thoracotomy pain is transmitted to higher cranial segments by parasympathetic vagal fibres and the phrenic nerve, which innervates the mediastinum, pericardium and diaphragm. The standard incision is via a posterolateral approach along one of the mid-thoracic intercostal spaces. Retraction of the ribs often results in fractures, ligamentous disruption of costochondral and costovertebral joints and distraction of intercostal nerves. Latissimus and serratus muscle layers may be incised or torn. The impact of surgical modifications including minimally invasive video-assisted thoracoscopy (VAT) and muscle-sparing techniques is often only equivocal. Lateral positioning requires
Treatment modalities Perioperative treatment modalities can be roughly divided into either regional nerve blockade or pharmacological intervention. Table 1 outlines the main categories used in thoracic anaesthesia.
Regional techniques Epidural block The gold standard for pain control after thoracotomy is thor acic epidural analgesia (TEA) using solutions of dilute local anaesthetic, with or without the addition of an opioid. Dilute local anaesthetic (0.1% bupivacaine) limits the likelihood of motor blockade, and lipophilic opioids (fentanyl) have been shown to improve the effectiveness of the block without increased sedation. TEA has been shown to significantly reduce perioperative pain, improve pulmonary function, reduce the stress response to surgery and attenuate sympathetic activation, thereby limiting perioperative cardiac complications. Mid-thoracic placement of the catheter, as close as possible to the dermatomes involved in the planned procedure, is most effective. TEA is technically challenging owing to the anatomy of the thoracic spine. Compared with the lumbar level, thoracic posterior processes are steeper, intravertebral foramina are smaller and the epidural space is narrower. Although lumbar catheters were previously advocated, the higher volumes of infusate required and wider familiarity with the thoracic approach have reduced
Bevan Hughes, MD, FRCPC, is Consultant Anaesthetist and Clinical Instructor at Vancouver General and University of British Columbia Hospitals, Canada. He is currently completing a cardiothoracic fellowship at Papworth Hospital, Cambridge, UK, and has a special interest in thoracic anaesthesia and transplantation. Conflicts of interest: none declared. Jonathan Mackay, MRCP, FRCA, is a Consultant Anaesthetist at Papworth Hospital, Cambridge, UK. His special interests are cardiothoracic anaesthesia and resuscitation. Conflicts of interest: none declared.
ANAESTHESIA AND INTENSIVE CARE MEDICINE 9:12
527
© 2008 Elsevier Ltd. All rights reserved.
Thoracic
The main treatment modalities used in thoracic anaesthesia
Needle position for paravertebral block
Regional techniques Epidural block Paravertebral block Extrapleural block Intercostal block Intrathecal injection Brachial plexus block Phrenic infiltration
Anterior division Spinal cord
Vertebra
Pharmacological categories Opioid Non-opioid Non-steroidal anti-inflammatory drugs Analgesic (paracetamol) Anticonvulsant (gabapentin, pregabalin) N-methyl-d-aspartic acid antagonists (ketamine, dextromethorphan) α2 adrenergic agonists (clonidine, dexmedetomidine)
Sympathetic chain Spinal process Dorsal root ganglion
Optimal needle position in relation to the transverse process of the vertebra and the nervous structures of the thoracic paravertebral space.
Table 1
Redrawn with permission from Richardson J, Lonnquist PA. Thoracic paravertebral block. Br J Anaesth 1998; 81: 230–8.
their usage. Similarly, because of the perceived increased risk of complications as a result of direct needle trauma, in particular catastrophic spinal cord cannulation, most practitioners advocate avoidance of placing thoracic epidural catheters in anaesthetized patients. The risks associated with neuroaxial techniques include direct nerve injury, dural puncture and paraplegia resulting from abscess or haematoma. Patients’ reluctance may preclude their acceptance and time should be taken to ensure truly informed consent. Excessive sympathetic and motor blockade may result in postoperative management issues such as orthostatic hypotension, decreased mobility and urinary retention. For this reason, thoracic epidurals require close monitoring by nursing staff and follow-up by anaesthetists to ensure that the catheters and infusions are managed appropriately.
Figure 1
Recent meta-analysis suggests that PVB offers equivalent pain relief with a lower incidence of hypotension than thoracic epidurals. Although some anaesthetists claim that failure rates for PVB and epidural blocks are similar at ∼10%, other anaesthetists who use PVB less regularly believe that PVB failure rates are higher and reserve PVB as a ‘back-up’ for situations in which TEA is not possible. The anatomy of the paravertebral space is not as well delineated as the epidural space and the presence of septation by endothoracic fascia may explain some cases of ‘resistance to catheter insertion’ and inconsistent blockade. Intercostal block Intercostal blocks are usually reserved for use in VAT procedures, though some claim very good pain control in open thoracotomy when adjuvant intravenous opioids are included. This technique seeks to block the intercostal nerve, which is found in the neurovascular bundle along the inferior border of each rib. Injection should be aimed somewhere behind the posterior axillary line as this will usually ensure that the take-off of the lateral cutaneous branch of the nerve is not missed. It is recognized that this technique will not block the dorsal ramus of the nerve, which splits off in the paravertebral space, and thus will not provide analgesia to the posterior structures of the thorax. Here again, blockade can be achieved either with individual injections or by using a catheter for continuous infusion. Intercostal nerve blocks require a large volume of local anaesthetic and as such are among the highest risk regional techniques for systemic toxicity. They also pose a substantial risk for ipsilateral pneumothorax; however, this is mitigated in the post-thoracotomy patient by the presence of a post-surgical chest drain. In an effort to prolong the efficacy of intercostal blockade, some surgeons
Paravertebral block Paravertebral injections (PVBs) seek to block neuronal transmission of the ipsilateral intercostal nerves at the level of the dorsal root, which is found in the paravertebral space. This space can be accessed just behind the transverse process with a percutaneous approach (Figure 1), or in the extrapleural paravertebral gutter via an intrathoracic (surgical) approach. A single dermatome is blocked with each injection and as such multiple levels should be targeted to account for chest drain sites and sutures (usually two segments above and two below). Single-shot PVB after VAT procedures has been shown to modestly improve pain control, without impact on pulmonary function. The use of a catheter allows for continuous infusion of anaesthetic solutions into the paravertebral space, extending the duration and range of effective blockade. The main advantages of PVBs over epidural analgesia are unilateral blockade, lower incidences of hypotension and neurological injury together with preserved bladder and lower limb function.
ANAESTHESIA AND INTENSIVE CARE MEDICINE 9:12
Rib
528
© 2008 Elsevier Ltd. All rights reserved.
Thoracic
have used cryoneurolysis to ablate axonal conduction for up to 3 months. Although this has been shown to reduce pain control requirements in the short term, long-term outcomes reveal a high incidence of chronic pain, persistent dysaesthesia and paralysis.
blood loss due to platelet dysfunction should be carefully considered in patients at risk. Controversy still surrounds the use of more selective COX-2 inhibitors as some high-profile drugs in this category have been proven to increase the risk of perioperative cardiac complications. The use of NSAIDs in patients undergoing pleurodesis is inadvisable as they may interfere with the efficacy of pleural adhesion. Other drugs with proven opioid-sparing effects include the anticonvulsant medications gabapentin and pregabalin. Although their use in thoracic analgesia has not been studied widely, growing evidence of anti-neuropathic properties suggests that they may be ideal for post-thoracotomy pain. N-Methyl-d-aspartic acid (NMDA) antagonists such as ketamine have analgesic properties and are especially useful in patients with pre-existing chronic pain or opioid dependence. Dosage should be kept low (10–20 mg/h) in order to avoid unpleasant dysphoric reactions common with higher doses. Finally, some practitioners advocate the use of centrally active α2 adrenergic agonists, which have analgesic properties attributed to reduced noradrenaline release in peripheral sympathetic afferents. Side effects such as increased sedation and postural hypotension limit their widespread use. Effective management of post-thoracotomy pain is best achieved with a multimodal approach, which uses both regional and pharmacological interventions. This is to target as many nociceptive pathways and receptors as possible, while minimizing side effects associated with any one therapy alone. The ideal perioperative strategy will probably also include some form of pre-emptive analgesia aimed at reducing sensitization and windup at the spinal cord level. This technique has been shown to improve outcomes in animal models of pain, and there is some evidence that it may help to reduce the incidence of long-term post-thoracotomy pain syndromes. Ultimately, the best regimen will need to be tailored to the unique needs of each patient and the exact nature of his or her surgical procedure. ◆
Other blocks Intrathecal injection of hydrophilic opioids (such as morphine) reduces post-thoracotomy pain, although the technique is less effective than neuroaxial blocks using local anaesthetics. There is also a significant risk of respiratory depression, which is especially undesirable in this population. In many centres, an extrapleural catheter is used to provide more effective intercostal nerve blockade. The extrapleural space is a potential space lying between parietal pleura and chest wall. A catheter can be placed by the surgeon during thoracotomy or VAT using direct disection. Continuous infusion of local anaesthetic will provide analgesia over several thoracic segments. Attempts to address the major problem posed by shoulder tip pain after thoracotomy have involved a number of novel approaches. While direct cervical plexus blockade of the shoulder does not appear to offer much benefit, studies aimed at phrenic nerve block have been more effective. This involves either direct infiltration of the periphrenic fat before surgical closure, or the use of brachial plexus blockade at the interscalene level. Studies have shown that pain scores are improved without significantly undermining postoperative pulmonary function in spite of the resultant unilateral diaphragmatic paralysis.
Pharmacological analgesia The most effective alternative to good regional analgesia for post-thoracotomy pain is an opioid-based administration system. Although non-intravenous administration is an option, the optimal way to titrate treatment is to provide intravenous delivery of patient-controlled analgesia (PCA). Indeed, patients’ satisfaction with PCA has been shown to be almost equivalent to thoracic epidural techniques in spite of troublesome side effects. Although PCA limits some of the risk of overdose inherent with the use of potent opioids, careful monitoring is still required owing to the high incidence of side effects including sedation, decreased respiratory drive, vomiting, gastroparesis and pruritus. In order to reduce the risk of some of these side effects, there are a number of other pharmacological adjuvants that have been shown to be effective at reducing the use of opioid after thoracotomy. Non-opioid analgesics such as paracetamol have few side effects and should be administered regularly. Nonsteroidal anti-inflammatory drugs (NSAIDs) are extremely useful for opioid sparing, although their use is not completely innocuous. Acute renal failure, gastrointestinal irritation and increased
ANAESTHESIA AND INTENSIVE CARE MEDICINE 9:12
Further reading Davies RG, Myles PS, Graham JM. A comparison of the analgesic efficacy and side-effects of paravertebral vs. epidural blockade for thoracotomy: a systematic review and meta-analysis of randomized trials. Br J Anaesth 2006; 96: 418–26. Gerner P. Post thoracotomy pain management problems. Anesthesiol Clin 2008; 26: 355–67. Gottschalk A, Cohen S, Yang S, Ochroch A. Preventing and treating pain after thoracic surgery. Anesthesiology 2006; 104: 594–600. Richardson J, Lonnquist PA. Thoracic paravertebral block. Br J Anaesth 1998; 81: 230–8.
529
© 2008 Elsevier Ltd. All rights reserved.
Analgesia for thoracotomy
careful attention to protecting pressure points. Surgical drains must be placed to minimize postoperative irritation and pain. The aetiology of ipsilateral shoulder tip pain, which is seen in up to 75% of thoracotomy cases, is not clearly understood. Possible mechanisms include referred pain from phrenic stimulation and direct strain on the glenohumeral joint secondary to positioning and retraction. Pain may be a manifestation of underlying pathology, including recurrence of tumour, infection, bleeding or persistent air leak. The patient’s background and preoperative mindset also affect postoperative pain scores, emphasizing the importance of good communication and effective anti-anxiety medication.
Bevan Hughes Jonathan Mackay
Abstract Thoracotomy is one the most painful surgical incisions. Surgical exposure to the thoracic cavity causes damage to multiple nociceptive structures in the chest wall and cardiopulmonary viscera. There is a high incidence of both acute and chronic postoperative pain, which can delay recovery and cause long-term disability. Prevention of pain after thoracotomy is challenging and may require a variety of interventions.
Impact of pain Severe, acute post-thoracotomy pain may delay recovery. Impaired inspiration and ineffective cough may cause hypoxaemia and retained pulmonary secretions. Reluctance to mobilize also increases the risk of thromboembolic events and pressure sores. Chronic post-thoracotomy pain syndrome (PTPS) is defined as persistent pain at least 2 months after the procedure. PTPS is usually characterized as burning or stabbing with neuropathic features including allodynia and hyperaesthesia. Up to 80% of patients will report some residual pain along a thoracotomy incision at 3 months. PTPS may interfere with normal life in half these patients. Although acute pain is certainly decreased in patients undergoing VAT procedures, there is controversy as to whether the long-term incidence of PTPS is any less than after open techniques. Frozen shoulder is another potential consequence of reduced mobility due to persistent shoulder pain.
Keywords chronic post-thoracotomy pain syndrome; intercostal block; post-thoracotomy pain; thoracic epidural anaesthesia; thoracic paravertebral block; thoracotormy; video-assisted thoracoscopy
Mechanisms of pain Thoracotomy pain is transmitted primarily via the intercostal, vagus and phrenic nerves. Shortly after exiting the intervertebral foramen through the dorsal root, the intercostal nerve gives off posterior, ventral and visceral divisions made up of both somatic Aδ fibres and visceral C fibres. The latter include afferent sympathetic fibres, which combine with input from multiple spinal levels in the paravertebral sympathetic trunk. Intercostal nerves are vulnerable to surgical damage by the incision, cautery, retractors and chest drains. Thoracotomy pain is transmitted to higher cranial segments by parasympathetic vagal fibres and the phrenic nerve, which innervates the mediastinum, pericardium and diaphragm. The standard incision is via a posterolateral approach along one of the mid-thoracic intercostal spaces. Retraction of the ribs often results in fractures, ligamentous disruption of costochondral and costovertebral joints and distraction of intercostal nerves. Latissimus and serratus muscle layers may be incised or torn. The impact of surgical modifications including minimally invasive video-assisted thoracoscopy (VAT) and muscle-sparing techniques is often only equivocal. Lateral positioning requires
Treatment modalities Perioperative treatment modalities can be roughly divided into either regional nerve blockade or pharmacological intervention. Table 1 outlines the main categories used in thoracic anaesthesia.
Regional techniques Epidural block The gold standard for pain control after thoracotomy is thor acic epidural analgesia (TEA) using solutions of dilute local anaesthetic, with or without the addition of an opioid. Dilute local anaesthetic (0.1% bupivacaine) limits the likelihood of motor blockade, and lipophilic opioids (fentanyl) have been shown to improve the effectiveness of the block without increased sedation. TEA has been shown to significantly reduce perioperative pain, improve pulmonary function, reduce the stress response to surgery and attenuate sympathetic activation, thereby limiting perioperative cardiac complications. Mid-thoracic placement of the catheter, as close as possible to the dermatomes involved in the planned procedure, is most effective. TEA is technically challenging owing to the anatomy of the thoracic spine. Compared with the lumbar level, thoracic posterior processes are steeper, intravertebral foramina are smaller and the epidural space is narrower. Although lumbar catheters were previously advocated, the higher volumes of infusate required and wider familiarity with the thoracic approach have reduced
Bevan Hughes, MD, FRCPC, is Consultant Anaesthetist and Clinical Instructor at Vancouver General and University of British Columbia Hospitals, Canada. He is currently completing a cardiothoracic fellowship at Papworth Hospital, Cambridge, UK, and has a special interest in thoracic anaesthesia and transplantation. Conflicts of interest: none declared. Jonathan Mackay, MRCP, FRCA, is a Consultant Anaesthetist at Papworth Hospital, Cambridge, UK. His special interests are cardiothoracic anaesthesia and resuscitation. Conflicts of interest: none declared.
ANAESTHESIA AND INTENSIVE CARE MEDICINE 9:12
527
© 2008 Elsevier Ltd. All rights reserved.
Thoracic
The main treatment modalities used in thoracic anaesthesia
Needle position for paravertebral block
Regional techniques Epidural block Paravertebral block Extrapleural block Intercostal block Intrathecal injection Brachial plexus block Phrenic infiltration
Anterior division Spinal cord
Vertebra
Pharmacological categories Opioid Non-opioid Non-steroidal anti-inflammatory drugs Analgesic (paracetamol) Anticonvulsant (gabapentin, pregabalin) N-methyl-d-aspartic acid antagonists (ketamine, dextromethorphan) α2 adrenergic agonists (clonidine, dexmedetomidine)
Sympathetic chain Spinal process Dorsal root ganglion
Optimal needle position in relation to the transverse process of the vertebra and the nervous structures of the thoracic paravertebral space.
Table 1
Redrawn with permission from Richardson J, Lonnquist PA. Thoracic paravertebral block. Br J Anaesth 1998; 81: 230–8.
their usage. Similarly, because of the perceived increased risk of complications as a result of direct needle trauma, in particular catastrophic spinal cord cannulation, most practitioners advocate avoidance of placing thoracic epidural catheters in anaesthetized patients. The risks associated with neuroaxial techniques include direct nerve injury, dural puncture and paraplegia resulting from abscess or haematoma. Patients’ reluctance may preclude their acceptance and time should be taken to ensure truly informed consent. Excessive sympathetic and motor blockade may result in postoperative management issues such as orthostatic hypotension, decreased mobility and urinary retention. For this reason, thoracic epidurals require close monitoring by nursing staff and follow-up by anaesthetists to ensure that the catheters and infusions are managed appropriately.
Figure 1
Recent meta-analysis suggests that PVB offers equivalent pain relief with a lower incidence of hypotension than thoracic epidurals. Although some anaesthetists claim that failure rates for PVB and epidural blocks are similar at ∼10%, other anaesthetists who use PVB less regularly believe that PVB failure rates are higher and reserve PVB as a ‘back-up’ for situations in which TEA is not possible. The anatomy of the paravertebral space is not as well delineated as the epidural space and the presence of septation by endothoracic fascia may explain some cases of ‘resistance to catheter insertion’ and inconsistent blockade. Intercostal block Intercostal blocks are usually reserved for use in VAT procedures, though some claim very good pain control in open thoracotomy when adjuvant intravenous opioids are included. This technique seeks to block the intercostal nerve, which is found in the neurovascular bundle along the inferior border of each rib. Injection should be aimed somewhere behind the posterior axillary line as this will usually ensure that the take-off of the lateral cutaneous branch of the nerve is not missed. It is recognized that this technique will not block the dorsal ramus of the nerve, which splits off in the paravertebral space, and thus will not provide analgesia to the posterior structures of the thorax. Here again, blockade can be achieved either with individual injections or by using a catheter for continuous infusion. Intercostal nerve blocks require a large volume of local anaesthetic and as such are among the highest risk regional techniques for systemic toxicity. They also pose a substantial risk for ipsilateral pneumothorax; however, this is mitigated in the post-thoracotomy patient by the presence of a post-surgical chest drain. In an effort to prolong the efficacy of intercostal blockade, some surgeons
Paravertebral block Paravertebral injections (PVBs) seek to block neuronal transmission of the ipsilateral intercostal nerves at the level of the dorsal root, which is found in the paravertebral space. This space can be accessed just behind the transverse process with a percutaneous approach (Figure 1), or in the extrapleural paravertebral gutter via an intrathoracic (surgical) approach. A single dermatome is blocked with each injection and as such multiple levels should be targeted to account for chest drain sites and sutures (usually two segments above and two below). Single-shot PVB after VAT procedures has been shown to modestly improve pain control, without impact on pulmonary function. The use of a catheter allows for continuous infusion of anaesthetic solutions into the paravertebral space, extending the duration and range of effective blockade. The main advantages of PVBs over epidural analgesia are unilateral blockade, lower incidences of hypotension and neurological injury together with preserved bladder and lower limb function.
ANAESTHESIA AND INTENSIVE CARE MEDICINE 9:12
Rib
528
© 2008 Elsevier Ltd. All rights reserved.
Thoracic
have used cryoneurolysis to ablate axonal conduction for up to 3 months. Although this has been shown to reduce pain control requirements in the short term, long-term outcomes reveal a high incidence of chronic pain, persistent dysaesthesia and paralysis.
blood loss due to platelet dysfunction should be carefully considered in patients at risk. Controversy still surrounds the use of more selective COX-2 inhibitors as some high-profile drugs in this category have been proven to increase the risk of perioperative cardiac complications. The use of NSAIDs in patients undergoing pleurodesis is inadvisable as they may interfere with the efficacy of pleural adhesion. Other drugs with proven opioid-sparing effects include the anticonvulsant medications gabapentin and pregabalin. Although their use in thoracic analgesia has not been studied widely, growing evidence of anti-neuropathic properties suggests that they may be ideal for post-thoracotomy pain. N-Methyl-d-aspartic acid (NMDA) antagonists such as ketamine have analgesic properties and are especially useful in patients with pre-existing chronic pain or opioid dependence. Dosage should be kept low (10–20 mg/h) in order to avoid unpleasant dysphoric reactions common with higher doses. Finally, some practitioners advocate the use of centrally active α2 adrenergic agonists, which have analgesic properties attributed to reduced noradrenaline release in peripheral sympathetic afferents. Side effects such as increased sedation and postural hypotension limit their widespread use. Effective management of post-thoracotomy pain is best achieved with a multimodal approach, which uses both regional and pharmacological interventions. This is to target as many nociceptive pathways and receptors as possible, while minimizing side effects associated with any one therapy alone. The ideal perioperative strategy will probably also include some form of pre-emptive analgesia aimed at reducing sensitization and windup at the spinal cord level. This technique has been shown to improve outcomes in animal models of pain, and there is some evidence that it may help to reduce the incidence of long-term post-thoracotomy pain syndromes. Ultimately, the best regimen will need to be tailored to the unique needs of each patient and the exact nature of his or her surgical procedure. ◆
Other blocks Intrathecal injection of hydrophilic opioids (such as morphine) reduces post-thoracotomy pain, although the technique is less effective than neuroaxial blocks using local anaesthetics. There is also a significant risk of respiratory depression, which is especially undesirable in this population. In many centres, an extrapleural catheter is used to provide more effective intercostal nerve blockade. The extrapleural space is a potential space lying between parietal pleura and chest wall. A catheter can be placed by the surgeon during thoracotomy or VAT using direct disection. Continuous infusion of local anaesthetic will provide analgesia over several thoracic segments. Attempts to address the major problem posed by shoulder tip pain after thoracotomy have involved a number of novel approaches. While direct cervical plexus blockade of the shoulder does not appear to offer much benefit, studies aimed at phrenic nerve block have been more effective. This involves either direct infiltration of the periphrenic fat before surgical closure, or the use of brachial plexus blockade at the interscalene level. Studies have shown that pain scores are improved without significantly undermining postoperative pulmonary function in spite of the resultant unilateral diaphragmatic paralysis.
Pharmacological analgesia The most effective alternative to good regional analgesia for post-thoracotomy pain is an opioid-based administration system. Although non-intravenous administration is an option, the optimal way to titrate treatment is to provide intravenous delivery of patient-controlled analgesia (PCA). Indeed, patients’ satisfaction with PCA has been shown to be almost equivalent to thoracic epidural techniques in spite of troublesome side effects. Although PCA limits some of the risk of overdose inherent with the use of potent opioids, careful monitoring is still required owing to the high incidence of side effects including sedation, decreased respiratory drive, vomiting, gastroparesis and pruritus. In order to reduce the risk of some of these side effects, there are a number of other pharmacological adjuvants that have been shown to be effective at reducing the use of opioid after thoracotomy. Non-opioid analgesics such as paracetamol have few side effects and should be administered regularly. Nonsteroidal anti-inflammatory drugs (NSAIDs) are extremely useful for opioid sparing, although their use is not completely innocuous. Acute renal failure, gastrointestinal irritation and increased
ANAESTHESIA AND INTENSIVE CARE MEDICINE 9:12
Further reading Davies RG, Myles PS, Graham JM. A comparison of the analgesic efficacy and side-effects of paravertebral vs. epidural blockade for thoracotomy: a systematic review and meta-analysis of randomized trials. Br J Anaesth 2006; 96: 418–26. Gerner P. Post thoracotomy pain management problems. Anesthesiol Clin 2008; 26: 355–67. Gottschalk A, Cohen S, Yang S, Ochroch A. Preventing and treating pain after thoracic surgery. Anesthesiology 2006; 104: 594–600. Richardson J, Lonnquist PA. Thoracic paravertebral block. Br J Anaesth 1998; 81: 230–8.
529
© 2008 Elsevier Ltd. All rights reserved.