Regional analgesia for lower leg trauma and the risk of acute compartment syndrome



## Summary
Pain resulting from lower leg injuries and consequent surgery can be severe. There is a range of opinion on the use of regional analgesia and its capacity to obscure the symptoms and signs of acute compartment syndrome. We offer a multi-professional, consensus opinion based on an objective review of case reports and case series. The available literature suggested that the use of neuraxial or peripheral regional techniques that result in dense blocks of long duration that significantly exceed the duration of surgery should be avoided. The literature review also suggested that single-shot or continuous peripheral nerve blocks using lower concentrations of local anaesthetic drugs without adjuncts are not associated with delays in diagnosis provided post-injury and postoperative surveillance is appropriate and effective. Post-injury and postoperative ward observations and surveillance should be able to identify the signs and symptoms of acute compartment syndrome. These observations should be made at set frequencies by healthcare staff trained in the pathology and recognition of acute compartment syndrome. The use of objective scoring charts is recommended by the Working Party. Where possible, patients at risk of acute compartment syndrome should be given a full explanation of the choice of analgesic techniques and should provide verbal consent to their chosen technique, which should be documented. Although the patient has the right to refuse any form of treatment, such as the analgesic technique offered or the surgical procedure proposed, neither the surgeon nor the anaesthetist has the right to veto a treatment recommended by the other. technique, which should be documented. [bib_ref] Regional anesthesia for trauma outside the operating theatre, Choi [/bib_ref] Although the patient has the right to refuse any form of treatment, such as the analgesic technique offered or the surgical procedure proposed, neither the surgeon nor the anaesthetist has the right to veto a treatment recommended by the other. Ideally, consensus should be achieved but, if consensus is not achievable, the role of the anaesthetist as the expert on pain relief should be respected. It is, therefore, the anaesthetist who has the right to offer the patient the range of what they consider to be acceptable analgesic techniques provided they express to the patient the concerns voiced by the surgeon. 7 The available literature suggests that the use of neuraxial or peripheral regional techniques that result in dense blocks of long duration, that is, significantly exceeding the duration of surgery, should be avoided. [bib_ref] Regional anaesthesia for the trauma patient: improving patient outcomes, Gadsden [/bib_ref] The available literature suggests that single-shot or continuous peripheral nerve blocks using lower concentrations of local anaesthetic drugs without adjuncts are not associated with delays in diagnosis provided post-injury and postoperative surveillance is appropriate and effective. 9 Given the lack of reliable, published data on the safety and efficacy of analgesia in patients at risk of ACS, the Working Party recommends that studies that address the use of low-dose regional analgesia, spinal opioid analgesia and wound infusion with local anaesthetic drugs for patients undergoing surgery for tibial fractures be conducted as a matter of urgency. The low incidence of ACS means that prospective, randomised trials would need to be large, and the conduct of prospective audit should therefore be encouraged What other guideline statements are available on this topic?
There are no other guidelines currently available.
Why were these guidelines developed?
Pain resulting from lower leg injuries and consequent surgery can be severe. There is a range of opinion on the use of regional analgesia and its capacity to obscure the symptoms and signs of ACS. However, a systematic review of the available literature is absent. We offer a multiprofessional, consensus opinion based on an objective review of case reports and case series. We aimed to provide pragmatic guidance to enable optimal analgesia and to highlight the need for careful observation for ACS in any patient at risk (irrespective of the mode of analgesia).

## How and why does this statement differ from existing guidelines?
Opinion on the optimal choice of anaesthesia and analgesia is often based on a single case or a small case series in which the impact of the mode of analgesia was poorly understood.
Other evidence is often anecdotal. In the absence of highquality trials, consensus opinion offers the next best guidance and should supplant personal opinion.

# Introduction
Few topics divide orthopaedic surgeons and anaesthetists quite so quickly and reliably as the question of whether This document will limit itself to trauma to the lower leg, while accepting that ACS is by no means restricted to this area of the body, in order to provide an exemplar of the management of similar clinical situations for which there is less supporting information.

## Pathology and diagnosis

## Incidence
Acute compartment syndrome has a reported incidence of 3.1 per 100,000 [bib_ref] Compartment syndrome and regional anaesthesia: critical review, Klucka [/bib_ref] , with a range of 1-7.3 per 100,000 [bib_ref] Acute compartment syndrome. Who is at risk?, Mcqueen [/bib_ref]. It has an incidence in men of 10 times that in women, at 7.3 per 100,000 [bib_ref] Acute compartment syndrome. Who is at risk?, Mcqueen [/bib_ref] , although this difference is accentuated in those who suffer ACS that is associated with fractures, for which the male to female ratio is 13:1 [bib_ref] Compartment syndrome: diagnosis, management and unique concerns in the twenty-first century, Garner [/bib_ref]. Fractures account for 69% of all ACS cases [bib_ref] Acute compartment syndrome of the limbs: current concepts and management, Mabvuure [/bib_ref]. Up to 40% of all ACS episodes involve a tibial shaft fracture, and approximately 4-5% of all tibial fractures result in ACS [bib_ref] Acute compartment syndrome risk in fracture fixation with regional blocks, Ganeshan [/bib_ref]. There is an increased risk in young men aged < 35 y with tibial fractures [bib_ref] Compartment syndrome and regional anaesthesia: critical review, Klucka [/bib_ref] [bib_ref] Acute compartment syndrome of the limbs: current concepts and management, Mabvuure [/bib_ref] [bib_ref] Regional anesthesia for trauma outside the operating theatre, Choi [/bib_ref].
Children are at a theoretically increased risk due to the higher pre-existing compartment pressures. However, the overall incidence in children is lower [bib_ref] Compartment syndrome and regional anaesthesia: critical review, Klucka [/bib_ref]. Acute compartment syndrome is a recognised side-effect of intra osseous access [bib_ref] Compartment syndrome and regional anaesthesia: critical review, Klucka [/bib_ref]. Acute compartment syndrome can occur in the absence of a fracture if there is soft tissue damage.
Additional risk-factors in developing ACS after lower limb trauma include: open fracture; intramedullary nailing; anticoagulation; high energy injury; penetrating trauma; vascular injury; burns; the use of tourniquets; and haemophilia [bib_ref] Compartment syndrome and regional anaesthesia: critical review, Klucka [/bib_ref].

## Pathophysiology
Acute compartment syndrome is the result of an increased pressure in a closed, relatively inelastic osteofascial compartment [bib_ref] Compartment syndrome after total knee arthroplasty: regarding a clinical case, Pinheiro [/bib_ref]. There is then a spiralling action that results in a rapid increase in pressure requiring early action [fig_ref] Recommendations 1: Patients at risk of acute compartment syndrome [/fig_ref] [bib_ref] Regional anaesthesia for the trauma patient: improving patient outcomes, Gadsden [/bib_ref]. The increasing pressure reduces the capillary and venous blood flow, and the resulting tissue ischaemia results in more oedema and release of vaso-active mediators, further increasing the pressure in the compartment.
The above describes the arteriovenous gradient hypothesis. However, there is an alternative hypothesis: the ischaemic-reperfusion mechanism [bib_ref] Case scenario: compartment syndrome of the forearm in patient with an infraclavicular..., Aguirre [/bib_ref]. Within both hypotheses, there is increased pressure resulting in decreased capillary blood flow, decreased oxygen delivery to the tissues and a resulting metabolic deficit. However, the latter hypothesis focuses on free radicals, calcium and vasoactive substrates released under ischaemic conditions resulting in the increased vessel permeability and subsequent increase in extravascular fluid and pressure. In both, the pressure cannot be relieved until the inability of the compartment to expand has been resolved. [fig_ref] Recommendations 1: Patients at risk of acute compartment syndrome [/fig_ref] Pathophysiology of acute compartment syndrome (adapted from [bib_ref] Regional anaesthesia for the trauma patient: improving patient outcomes, Gadsden [/bib_ref].

## Diagnosis
The diagnosis of ACS remains a controversial area.
Historically, it was regarded as a clinical diagnosis, with compartment pressure measurement reserved for cases in which the diagnosis remained unclear after clinical examination. However, several studies have cast doubt on the reliability of diagnosing ACS on clinical signs alone. This uncertainty in diagnostic criteria may lead to a significant variation in rates of fasciotomy between surgeons [bib_ref] Variation in diagnosis of compartment syndrome by surgeons treating tibial shaft fractures, O&apos;toole [/bib_ref].
Classically, six clinical signs or symptoms are attributed to ACS: pain; cold; paraesthesia; paralysis; pulselessness;
and pallor [bib_ref] Acute compartment syndrome of the lower leg: a review, Pechar [/bib_ref]. As perfusion to the affected compartment decreases, the lack of oxygen and the accumulation of Palpation of the suspected compartment has been shown to be unreliable in isolation, with a sensitivity and specificity of 54% and 76% respectively in predicting an increased compartment pressure in children [bib_ref] Pediatric acute compartment syndrome: a systematic review and meta-analysis, Lin [/bib_ref]. In isolation, severe pain gave around only a 25% chance of a correct diagnosis of ACS. However, as the number of clinical signs increases, the likelihood of a positive diagnosis of ACS increases [bib_ref] The clinical diagnosis of compartment syndrome of the lower leg: are clinical..., Ulmer [/bib_ref]. [bib_ref] Continuous compartment pressure monitoring for tibia fractures: does it influence outcome?, Harris [/bib_ref].

## Pressure threshold for fasciotomy
Traditionally, an absolute compartment pressure of  30 mmHg has been regarded as a diagnostic cut-off for ACS requiring fasciotomy [bib_ref] Intracompartmental pressure monitoring of leg injuries. An aid to management, Allen [/bib_ref] [bib_ref] Acute compartment syndromes: diagnosis and treatment with the aid of the wick..., Mubarak [/bib_ref]. When taken in isolation without other clinical suggestions of ACS, this may lead to a rate of fasciotomy of up to 29% after tibial surgery [bib_ref] Skjeldal S Compartment pressure in nailed tibial fractures. A threshold of 30..., Ovre [/bib_ref].
Higher thresholds of up to 45 mmHg have been suggested [bib_ref] Diagnosis and management of compartmental syndromes, Matsen [/bib_ref] , although these too may over-diagnose ACS when taken in isolation [bib_ref] Compartment monitoring in tibial fractures. The pressure threshold for decompression, Mcqueen [/bib_ref]. The differential pressure threshold is the most recognised cut-off for intervention in current use [bib_ref] Tissue pressure measurements as a determinant for the need of fasciotomy, Whitesides [/bib_ref]. Tissue perfusion is affected both by the patient's diastolic blood pressure and intracompartmental pressure.
Patients with an increased diastolic blood pressure can tolerate a greater increase in compartment pressure without muscle or nerve ischaemia from hypoperfusion when compared with patients who are hypotensive. Fasciotomy should usually be performed when the tissue pressure increases to within 10-30 mmHg of the diastolic pressure in a patient with any of the other signs or symptoms of ACS.
When combined with the differential pressure threshold, continuous pressure monitoring in patients after tibial shaft fracture has been reported to have a sensitivity of up to 94%, with an estimated specificity of 98% [bib_ref] Court-Brown CM. The estimated sensitivity and specificity of compartment pressure monitoring for..., Mcqueen [/bib_ref]. Unfortunately, by definition, even this approach may miss some cases of ACS.
There is insufficient prospective evidence for any single sign or investigation that is guaranteed to diagnose or One group has suggested the use of 'three As' to diagnose ACS in children: anxiety; agitation; analgesic requirement [bib_ref] Pediatric acute compartment syndrome, Livingston [/bib_ref].
A recent study found an incidence of ACS after paediatric trauma of 0.02% [bib_ref] Acute compartment syndrome in children: a case series in 24 patients and..., Erd Os [/bib_ref]. This study included [bib_ref] Diagnosis and treatment of acute extremity compartment syndrome, Von Keudell [/bib_ref] [bib_ref] Acute compartment syndrome in children: contemporary diagnosis, treatment, and outcome, Bae [/bib_ref]. Others have argued against this for children aged < 12 y with minimally displaced tibial fractures [bib_ref] Do minimally displaced, closed tibial fractures in children need monitoring for compartment..., Malhotra [/bib_ref]. There were no cases of ACS in 159 children with these fractures whose pain was well controlled and who mobilised in a back slab, with early follow-up following Emergency Department discharge [bib_ref] Do minimally displaced, closed tibial fractures in children need monitoring for compartment..., Malhotra [/bib_ref]. Near infra-red spectroscopy has also been used successfully in young children to diagnose ACS [bib_ref] Compartment Syndrome in children, Hosseinzadeh [/bib_ref]. However, there is currently no agreement on what method of monitoring is best: clinical;
intracompartmental pressure measurement; near infra-red spectroscopy; or a combination of these. Complications after ACS in children are rare. One study found a complication rate of 4.2%, with 87.5% of children who underwent fasciotomy having a secondary closure 1522 of skin and only 12.5% requiring split skin grafting. Mean time from admission to fasciotomy was just under 28 h and ranged from 2.5 h to 99 h [bib_ref] Acute compartment syndrome in children: a case series in 24 patients and..., Erd Os [/bib_ref].
Debate continues regarding the use of regional anaesthesia and patient/nurse-controlled analgesia in children at risk of ACS. Paediatric regional anaesthetists' desire to prove the safety of low-dose peripheral nerve blockade and the absence of convincing case reports linking regional analgesia in children to diagnosis delays led the European Society of Regional Anaesthesia and Pain Therapy (ESRA) and the American Society of Regional

## Pain relief after lower leg trauma
The Declaration of Montreal underscores the widespread view that pain relief is a fundamental human right, and the provision of effective analgesia for patients suffering any form of trauma should therefore be a priority. If the injury suffered is one that is associated with a significant incidence of ACS, this human right is not affected, and the provision of pain relief should remain central to the medical management of the patient. controlled studies of this latter technique do not exist and its use should, therefore, be considered developmental or experimental. Many anaesthetists hold firmly to the view that regional analgesia with local anaesthetic drugs, and in particular single-shot and continuous peripheral nerve blocks, is the most effective form of analgesia available for tibial fractures and surgery to reduce them.
As noted above, most of those anaesthetists who provide regional analgesia for patients undergoing surgery associated with ACS currently choose to use low concentrations of local anaesthetic drugs without adjuncts, thereby preserving some sensation and movement, and allowing the potential for breakthrough pain. It should be noted that severe pain is not always a feature of ACS [bib_ref] Regional anaesthesia for the trauma patient: improving patient outcomes, Gadsden [/bib_ref] [bib_ref] Pain in complex trauma: lessons from Afghanistan, Beard [/bib_ref] [bib_ref] Acute compartment syndrome with an atypical presentation: a useful clinical lesson, Wright [/bib_ref].
It is easy to believe that the choice of analgesia is the surgeon's alone, the anaesthetist's alone or is a consensus between the two when, in reality, it is none of these. As
[fig] Recommendations 1: Patients at risk of acute compartment syndrome (ACS) should be identified on admission to hospital or at the time of surgery, and should be managed within agreed, multidisciplinary protocols. 2 Post-injury and postoperative ward observations and surveillance should be able to identify the signs and symptoms of ACS; these observations should be made at set frequencies by healthcare staff trained in the pathology and recognition of ACS. The use of objective scoring charts is recommended. 3 The equipment necessary to measure intracompartmental pressure should be available on wards caring for patients at risk of ACS. Staff should be trained in its use and there should be standard operating procedures available and implemented that address the performance of such measurements, and the urgent steps to be taken if measurements are abnormal. 4 All patients who have suffered trauma or who have undergone surgery should be offered effective analgesia. 5 Where possible, patients at risk of ACS should be given a full explanation of the choice of analgesic techniques and should provide verbal consent to their chosen [/fig]