In Genesis, it states that the Lord caused a deep sleep to fall upon Adam so that his rib could be removed to create the female of the species.1 It would, in the current healthcare climate, be interesting to look at outcome studies in both species! It would also seem that it was prophesied that thoracic surgery would be very painful and would require appropriate and effective treatment.
Most anaesthetists would agree that there is considerable pain after thoracotomy and that excellent analgesia is required. However, the ideal method has yet to be developed. What, therefore, are the advantages and disadvantages of current regimens and what does the future hold?
Worldwide, morphine is probably the most commonly used drug despite its well-known disadvantages. However, to be effective, it is recommended that regular doses are given at regular intervals.2 The former is probably attainable while the latter is probably not. In the 1960s and 1970s this approach was used by the majority of anaesthetists. The major problems were that patients were either in pain or asleep and were unable to expectorate secretions from the respiratory tract. Inevitably, a high percentage of these patients returned to the operating theatre for a bronchoscopy to remove retained secretions. Some of these patients developed pneumonia and occasionally died.
It was, therefore, reasoned that the way to achieve the best analgesia was to try to obtain an appropriate and constant blood level of an analgesic agent. Thus, constant i.v. infusions became, and indeed still remain, popular.3 4 These techniques, however, were potentially unreliable because of the apparatus involved in the drug delivery. There was also a concern that any additional top-ups, if and when required, could lead to overdosage and in particular, respiratory depression. Such concerns helped in the development of high dependency units.
The next development was patient controlled analgesia (PCA)5. Although this system worked well, when sleep occurred, drug delivery stopped. The patient subsequently awoke in pain and had difficulty in coughing so that the secretions that had accumulated during the sleep period were not expelled from the respiratory tract.
Therefore, it seemed that the ideal approach might be a background infusion with PCA back up. Such a regimen could produce excellent pain relief despite the possible disadvantages. There is, however, some evidence whereby the patient, usually the more elderly, became confused because of a combination of the drug effects and loss of the natural circadian rhythm. This confusion prevented cooperation with the physiotherapist; sputum retention and occasionally pneumonia ensued.
The increased interest in epidural analgesia in the 1980s, particularly in obstetrics, provided the anaesthetist with an ideal opportunity for dealing with thoracic pain though with an equal potential for disaster in the form of spinal cord damage.6 The development of this method led to robust international debates which revolved around several issues.711
Should the epidural catheter be inserted while the patient is awake or asleep?
Should the epidural be placed in the thoracic or lumbar region?
Should the technique be loss of resistance to air or saline?
Should the drug used be either a local analgesic agent, an opioid, or a mixture of both?12
Where should the patient be looked after in the post operative periodin a HDU/ICU or on a general ward?
There is still no universal agreement but a general theme is beginning to emerge. Many anaesthetists believe that awake insertion is the safest approach as the patient will let the operator know if the needle approaches and touches the dura. There is some evidence that this is not necessarily so and that complications do still arise.13 14
The exact level of placement is in dispute though it is natural to think that a drug works best at the area required. There are those who advocate that the tip of the epidural catheter should be sited around T4T6. When placed in this area, fat-soluble analgesic drugs should be used as they diffuse into the correct segmental area. There are those, however, who prefer to use the lumbar route and thread the epidural catheter cephalad for several centimetres. It would appear in these situations that there is a preference for water-soluble, opioid drugs.
There has been an increasing tendency to use loss of resistance to saline and not air because of the possibility of causing an air embolism. The difficulty is deciding, particularly under sterile operating conditions, whether the liquid coming back from the Tuohy needle is either saline or cerebrospinal fluid. The differentiation is extremely important as it will have considerable bearing on the subsequent injection and actions of the preferred drugs.
There has also been considerable debate concerning the drugs used. On the one hand, local analgesic solutions can lead to a drop in peripheral vascular resistance as a result of sympathetic block. The danger that follows is that an increased fluid load is given intravenously. Occasionally, if excessive fluid is administered particularly after right pneumonectomy, the pulmonary artery pressure rises and pulmonary oedema can ensue.15 16 This has a poor prognosis. On the other hand, when using opioids, there is a danger that there may be patchy analgesia, which requires some form of back up for break through pain. Overdose is, therefore, a possibility. Consequently, a mixture of both is gaining in popularity, for example fentanyl 12.5 µg ml1 and 0.125% bupivacaine in saline (Table 1).
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There are colleagues who recommend that an epidural should be inserted with the patient asleep. After all, similar techniques using local analgesia have been, and continue to be, used in neonates, infants and children where the potential for harm is probably greater and for a longer period of time. Others would argue that the safest method would be to use the lumbar route to avoid possible spinal cord damage. However, a recent editorial has suggested that the anatomy of the lower end of the spinal cord is not constant and that such an assumption may produce a false sense of security.13 Furthermore, another recent study has shown that many anaesthetists cannot accurately identify the interlumbar vertebral spaces.17
Richardson, by contrast, has argued that there is no need to insert an epidural needle, as a catheter appropriately placed beneath the parietal pleura is equally effective.18 19 In his hands, this technique has produced excellent results. However, this technique is not widely used as both surgical and anaesthetic expertise are required to accurately place the catheter and to manage the therapeutic regimen thereafter. There are also other problems, such as hypotension, and for example in the original paper, 10% of patients needed i.v. opioids to cover the break-through pain. In the event of failure of either system, the final fall back would probably be a constant infusion with superimposed PCA. In children, nurse controlled analgesia (NCA) may also be an option.
However, even when these methods are used, there still remains the problem of movement and referred pain, particularly to the shoulder. The use of NSAIDs, either orally or rectally, has become popular and follows on from the original work by Kennan and colleagues and Appadurai and colleagues which showed that similar drugs were good at counteracting movement pain.20 21 Shoulder pain can also be treated by infiltrating the fat pad around the phrenic nerve with 1% lidocaine at the level of the diaphragm after lung resection. It may be that if a long-acting drug such as bupivacaine is used in greater volumes, results could well improve further.
There are, of course, other methods such as cryotherapy,7 constant pleural infusion and the use of regular paravertebral blocks. These methods, however, do not seem popular.
In the early days when using both thoracic and lumbar epidurals for the relief of pain, it was felt that the patient should be nursed postoperatively in either an ICU or HDU. Currently, it would seem that most thoracic units have a HDU for these patients. The question of nursing these patients outside such areas has both advocates and opponents, and could well be a subject of a future editorial particularly when risk management issues are considered.
What therefore does the future hold? There is coming into clinical use a very long-acting preparation based on bupivacaine. In early experiments in man, where the preparation was placed around the appropriate nerves, analgesia lasted for several days. This has great potential in thoracic anaesthesia and other major surgery and will, no doubt, be investigated in the future.22
Ideally, it seems that any regimen used should be able to treat both wound and movement pain, prevent mental confusion and enable the patient to breath deeply and expectorate. Currently, I believe that an epidural solution using a combination of fentanyl 12.5 µg ml1 and 0.125% bupivacaine with either oral or rectal NSAIDs is the most effective. The infiltration of the appropriate phrenic nerve can give an additional dimension.
Sadly, the best regimen will never be agreed because each patient and anaesthetist are different. A double blind clinical trial will be extremely difficult, if not impossible, to conduct. In addition, it would be very difficult to obtain the necessary ethical permission. It may, therefore, be that the answer may evolve from evidence-based anaesthesia. This will undoubtedly include patient choice, informed consent, risk assessment and outcome studies to mention but a few issues.
Finally, it may be prudent to reflect on a lesson learned many years ago from J. Alfred Lee: There is nothing wrong with anaesthesia, it is the anaesthetists that are at fault. Hence, the current philosophy of knowledge, skills, attitudes, and appropriate research will most certainly be a step in the right direction holding the promise of excellent analgesia for patients who have had major thoracic and other surgical procedures.
Ralph S. Vaughan
Department of Anaesthetics
University Hospital of Wales NHS Trust
Heath Park
Cardiff CF14 4XW
UK
References
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