Introduction In recent decades the high thoracic epidural analgesia (HTEA) has been increasingly replaced as the gold standard in minimal invasive surgical procedures. We strongly believe however it still is a viable (and maybe even essential) technique in major open surgery.1 Adequate placement of a HTEA is difficult art to master.2 Although published failure rates average from moderate to high, the lack of standardized definition of failure hampers a clear view on the problem.3 Due to reduced caseloads since the (r)evolution of minimal invasive surgical techniques training and competence proficiency have also diminished seriously.4Fascial plane blocks (FPB), although extremely popular due to the advancement of ultrasound guided block techniques and the laparoscopic/thoracoscopic/robotic approaches have failed to be a valid alternative for major surgery. The lack of visceral pain coverage, limited duration of analgesia and dermatome coverage are the main drawbacks of almost all FPB’s. Examining the relevance and correct implementation of HTEA, while debunking some myths and exploring the possible solutions for the lack of training is the primary objective of this article.5
Discussion Although major open surgical techniques like abdominal, thoracic and vascular surgery have steadily decreased over the years they will remain an important part of care in more specialized healthcare institutes. Major surgery has a significant morbidity and mortality and should therefore be thoroughly managed. Despite controversy about the influence of the HTEA on morbidity and inflammation there is still more than enough evidence of its potential beneficial effect.6
Surgical safety has increased dramatically over the years so impact of a single intervention like HTEA analgesia on morbidity is naturally much more difficult to prove. The impact on pulmonary function, cardiovascular system and inflammation although proven, have diminished with enhanced recovery programs and multimodal approaches. The analgesic effect, complication rate and educational training problems are somewhat easier topics to dive into.
Analgesic effect and side-effects.
The HTEA not only covers somatic pain via blocking of the spinal nerves, but also has a profound effect on visceral pain. This visceral coverage leads in turn to a dampening of the inflammation cascade.7Non inferiority analysis of other analgesic techniques has almost always failed except the paravertebral block (PVB).8,9 For unilateral procedures like thoracotomy this makes the PVB of course a very interesting alternative. It is less compelling when bilateral catheters, especially because they have a higher rate of displacement.10
Of course, this highly effective pain relief comes at a cost. A HTEA will always produce an effect on hemodynamics. Hypotension has been one of the major issues urging anesthetists to stop using HTEA as a gold standard.11 However, in modern day anesthesia with goal-directed fluid therapy or more moderate fluid replacements the use of inotropes or vasopressors has become a routine part of any tailored anesthesia approach. Using low percentage local anesthetic concentrations for postoperative infusion will allow to reduce and stop any hemodynamic medication postoperatively. It is therefore imperative to use the lowest concentration of local anesthetics (LA) for infusion rate while ensuring adequate analgesia.12
There is no reason to use high concentrations, being 0,5% of any LA, because 0,2% provides equivalent analgesia with less hypotension.13 In certain HTEA high-volume centers (like the University Hospitals of Leuven) low concentrations of 0,125% levobupivacaine have been routinely used for infusions during at least 10 years with no effect on patient satisfaction or pain control, while minimizing systemic hemodynamic repercussions. In addition, HTEA has been proven to increase intestinal blood flow which has a potential for anastomotic blood flow increase and reduction of postoperative ileus. These two effects make a compelling case for enhancing the role of epidurals in major open surgery.
Thislow concentration of LA will also allow early mobilization and enhance recovery. Especially when the thoracic epidural is placed at the correct (high) level.14 It is a persistent and sad misconception that low to mid thoracic epidurals are easier to place (quite the contrary). The myth that HTEA impedes enhanced recovery and hinders walking has in turn also hurt its implementation. In fact, very recent literature showed even better mobilization when HTEA was used compared to opioids alone.15
Safety Neurological complications of the epidural although rare (estimated between 1:1000 and 1:14000) can be extremely devastating in case of hematomas and permanent neurological injury.16 Abscesses, meningitis and more solitary segmental nerve injuries are also rare but almost equally damaging in their consequences. For use in major surgery when adequate risk assessment is in place and proper techniques are used, these risks can be kept at a minimum.
For scheduled major surgery anticoagulant therapy is interrupted, making most patients eligible for HTEA. Of course, precautions on resumption of antithrombotic medication are extremely important, as well as exact knowledge of drug doses time till restart and stopping. Recent literature details all the essentials and an online application, developed by the European Society of Regional anesthesia, can quickly guide you through the maze of options.17
Reliability Failure rates have been quoted as being moderate to high throughout literature. The definitions of failure have nonetheless never been validated.18,19 In contrast relatively good failure rate definitions for lumbar epidurals in obstetrics were established.20,21 Interestingly, if the exact same criteria were used for most of the fascial plane blocks, the success rate would be close to zero for most of these blocks. Mechanical failures like catheter leakage, unintended catheter loss or even stretching tearing should be kept to a minimum if correct bandages and regular follow-up is in place with an acute pain service. Technical failure should be addressed by adequate knowledge of spine anatomy and training and we will address them in the last part of this article. Miscellaneous problems like unilateral block, inadequate dermatome coverage or inappropriate level of block can be addressed in a tailored individual approaches, by withdrawing the catheter, topping up or even re-insertion if needed.
Training Diminishing caseloads have led to decreased training possibilities. However, epidural placement is considered a core competence as it is still the standard for anesthesia in caesarian sections and analgesia for child labor. Thoracic epidurals are not necessarily more difficult but require a more secure knowledge of spine anatomy. Next to teaching, anatomy simulators, online tools, webinars, video tutorials can aid in increasing competence and knowledge.
Although there is no thoracic epidural simulator (as far as we know) a few extremely well designed lumbar epidural fantoms are available for purchase and have good value for money.22 Video-based learning systems are also available and might yield some benefit when incorporated in training schedules.2 Online tools like Virtual Spine: lumbar anatomy, 3D model, vertebra, spinal cord, dura, meninges, cauda equina, ultrasound (utoronto.ca) can further enhance knowledge and should be actively promoted.
In the modern era of ultrasound we should also not forget to use this valuable tool to at least identify the midline or identify the exact spinal level. Real-time ultrasound guidance is a possibility, although it is difficult, time and resource consuming.23
Increasing and consolidating success.
Due to the controversy surrounding failure rates, ascertaining success is imperative. Fluoroscopy is an extremely valuable and powerful tool for lowering dislodgement of catheters while improving success rates, however, it is not practical to implement.
There is little evidence for waveform analysis in the form of an auditive sound adapter or by using a pressure transducer to evaluate pulsatility.24 Probably the best way to assess correct catheter placement is the so-called ‘Tsui test’ or epidural electrical stimulation test.25 Unfortunately it is not widely known or used.
Conclusion HTEA is the best and most complete regional analgesic technique at our disposal. It should be reserved for major surgery as it has drawbacks and side-effects. Nevertheless, it has a positive impact on pulmonary and functional recovery and reduces the need for opioids in a spectacular fashion. Unfortunately, it requires a lot of training to master and good follow-up with investment in an acute pain service team is essential. It should be actively promoted, trained and taught in secondary and tertiary centers with major open thoracoabdominal surgery.
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