Post-Operative Pain Management (POPM) is an important part of the patient’s management. It is the most common reason for a patient’s dissatisfaction, and it is the most common reason for an otherwise unjustified prolongation of hospital stay. It must be done well. For some reason, however, it often seems to fall between two stools, the surgeon and the anaesthesiologist. Each one thinks the other one is taking care of it, so nobody does it. Or, rather, it falls onto the junior doctors and the nurses in the ward, who follow the hospital guidelines. Some of these guidelines are reasonable, some are not. This seems to happen everywhere, in too many hospitals in the world, good and bad. Specifically, in the UK, both in the NHS and, incredibly, also in the many private hospitals, it is common to see the same guidelines applied, which have been in use in the NHS for the last 50 years: oral opioids.
Why is this happening? One of the reasons, perhaps, is that in the UK private system (like in many other countries) many senior doctors work in private hospitals only part-time. Typically, they work in an NHS teaching hospital 3-4 days a week, and in one or more private hospitals the other days of the week. The style and culture of the NHS is something they bring with them into the private sector. If the NHS has always been driven by cost-containment, for obvious reasons, this is even more evident now, because of the change in demographics, and the increased offering of medical care – both in terms of increasingly sophisticated pharmacology, and in terms of increasingly sophisticated medical devices. All of this has been given a final blow by the recent Covid-19 pandemic. The private sector often offers more in terms of accessibility to good surgery and good medical care; and in terms of hotel accommodation (private rooms, good meals). But not necessarily in terms of post-surgical aftercare, specifically POPM.
This is a shame, because, beyond the psychological damage inflicted by post-operative pain, it prolongs hospital stay, it delays the start of physical rehabilitation and it reduces motility, which in turn increases the risk of complications.
Post-Operative Pain can vary in intensity and duration. These are normally dependant on many factors. To mention but a few, individual, existential, psychological, physical, and pre-existing medical conditions. Most importantly, it depends on the type of tissue traumatised by the surgery (for example, the bone is one of the most sensitive tissues, because of the high level of innervation of the periosteum), the duration of surgery, and the amount of tissue traumatised.
For example, a two-level TLIF is known to be one of the most painful types of surgery, because of the level of manipulation of the vertebrae, and the amount of tissue traumatised by the operation, including three vertebrae, and the surrounding tissues – ligaments, articular facets, muscles, tendons.
A TLIF (Trans-foraminal Lumbar Interbody Fusion) is one of the most common and effective types of vertebral fusion (Spondylosyndesis). It involves a posterior approach to the spine for the removal of fragments of the damaged disc(s) from the interbody spaces, the foramina and the spinal nerve emergence. This is followed by the insertion of titanium expandable spacers in the interbody spaces, together with bone fragments (autograft or allograft from bone bank) and/or Hydroxyapatite to facilitate the fusion of the vertebral bodies.
The main causes of pain are (a) the spacers that separate by force two vertebral bodies which have been adjacent for years; (b) the screws in the vertebral bodies, and the rods connecting them; and (c) the extra-vertebral portion of the screws and the rods that lie in the middle of the muscular planes of the Erector Spinae.
TLIF is just an extreme example of orthopaedic surgery; but all types of surgery cause Post-Operative Pain, to various extent, and of various type. Knee replacement surgery is, for example, known to be painful for several days.
Acute Post-Operative Pain normally lasts for 48-72 hours and must be managed aggressively, with the right drugs and for the right duration of time, dependant on the type of surgery. The most common mistake is to treat it too weakly and, consequently, for longer than necessary.
Proper post-operative analgesia should always be multi-modal, consisting of a combination of local, loco-regional, spinal and systemic approaches; not all are always and consistently used.
- The standard local approach consists of the injection of long-acting local anaesthetics (LA) in the surgical site, both the skin and the lower planes. The effectiveness of this approach is limited in time, because the duration of action of local anaesthetics is never longer than 7-8 hours and can be prolonged to a maximum of 12-18 hours by the addition of adrenaline and the carry-over effect. Continuous Wound Infusion (CWI) through a fenestrated catheter for 48 -72 hours is ideal, because it reduces the need for systemic drugs (and all the side effects connected with them), but is complex to manage. Device delivering the right dose of a long-acting local anaesthetic, in the right place, for 48-72 hours, can be the ideal solution. These can be elastomeric pump, electronic pumps, or more modern disposable and pre-filled devices such as the Readyfusor.
- The standard loco-regional approach consists of the injection of local anaesthetics in the tissues surrounding the appropriate section of the afferent nerves (nerve block). Normally performed by the anaesthesiologist. It can only be used in some areas of the body, though. Otherwise, the injection of long-acting local anaesthetics in a deep muscular plane is often a viable option and can be very effective. Common examples are the Transversus Abdominis Plane (TAP) Block, for the analgesia of the anterior abdominal wall, or the Quadratus Lumborum Block, or also the Erector Spinae Block, for the analgesia of the posterior abdomen / lumbar area. This is normally done either by the surgeon or the anaesthesiologist under ultrasound guidance. Usually the long-acting Local Anaesthetics (LA: Bupivacaine or Ropivacaine) are combined with Adrenaline, which causes vaso-constriction and prolongs the effect of the LA.
- The standard spinal approach consists of the injection of a combination of local anaesthetics and opioids (and occasionally other drugs) in the extra-dural (= “epidural”) or intra-dural (= “intrathecal” = subarachnoid) space of the spinal cord. This option, always performed by the anaesthesiologist, is highly effective but difficult and can only be used for the lower part of the body (pelvic area, lower limbs).
- Systemic approaches can be either intravenous (IV administration of opioids, in a continuous fashion or in bolus when needed; IV administration of non-opioid painkillers, such as NSAIDs or paracetamol) or oral (again, both opioids and non -opioids are regularly used). A more modern technique of IV infusion of opioids is now in widespread use, the PCA (Patient-Controlled-Analgesia), where the patient presses a button of a portable device (with a reservoir) when analgesic effect is needed. This was initially done in the 1980s with elastomeric pumps and is now almost exclusively performed by electronic pumps with an on-demand switch. The big advantage is that in this way the number of opioids consumed has been shown to be much lower; this has a positive impact on the common side effects of systemic opioids (respiratory depression, constipation, etc.)
High levels of pain can persist, however, for many weeks after orthopaedic surgery. This can be defined as Sub-Acute Post-Operative Pain. For this type of pain, on top of oral systemic therapy, in some cases a more sophisticated, loco-regional approach becomes appropriate. This consists of the insertion of a fenestrated catheter either closed to the afferent nerve (long-term nerve block) or in a deep fascial plane, already at the time of surgery. The catheter can deliver long-acting Local Anaesthetics, and can offer long-lasting and effective analgesia for the whole duration of the Post-Operative Pain. The procedure is similar to the one used for the Peri-operative Fascial Plane Block, a very effective type of loco-regional anaesthesia; but, instead of a bolus injection, it requires long-term electronic pumps, or disposable pre-filled devices replaced every 48 hours.
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