Introduction Whilst recognising that altered coagulation may be associated with sepsis, polytrauma, liver disease, uraemia and massive transfusion, for the purposes of this manuscript, I will confine my discussion to the issue of peripheral nerve block (PNB) in patients on antithrombotic or antiplatelet drugs. Antithrombotic and antiplatelet drugs transcend medical practice and the use of these agents in our patients has become ubiquitous. This has made the decision making process of performing a PNB in the presence of altered coagulation increasingly difficult. There are in effect no guidelines directing the practice of PNB in patients with altered coagulation.

Questions Given that ultrasound guided regional anaesthesia (USGRA) allows identification of vascular structures and the avoidance of puncturing these structures is important in this cohort, several questions arise:

1. Does the use of USGRA protect from inadvertent vascular administration of local anaesthesia?

2. Is the use of USGRA associated with fewer vascular punctures?

The risk The use of PNB in the setting of altered coagulation may be associated with both morbidity and mortality. Retroperitoneal haematoma following lumbar plexus blockade in the setting of enoxaparin or clodpidogrel administration have been reported.^{1 2}

Bickler et al describe three cases of bleeding post total knee replacement (TKR) associated with femoral and sciatic catheters removal in the setting of low molecular weight heparin (enoxaparin 40 mg daily). In one case, the removal of catheters on day three, resulted in massive thigh ecchymosis with a subsequent 2-day delay in discharge. There was no neurological injury in any case.³

Furthermore, Steinfeldt and colleagues demonstrated in a porcine model that perineural injection of 50ml of autologous blood resulted in significant myelin inflammation and nerve damage in sciatic nerves. It remains unclear whether perineural haematoma is innocuous in humans.⁴

1. Does the use of USGRA protect from inadvertent vascular administration of local anaesthesia?

Given that ultrasound allows the identification of vascular structures, it would seem reasonable to assume that USGRA would reduce the incidence of inadvertent vascular punctures. There are several papers documenting accidental inadvertent intravascular administration despite using ultrasound.^{5 6}

Guidelines: 3rd Regional Anaesthesia in Patients Receiving Antithrombotic or Thrombolytic therapy ASRA consensus guidelines – 2010

Whilst the guidelines concerning neuraxial block and antithrombotic therapy were extensive, the role of PNB in this setting received scant attention. With respect to PNB the following statement was included: ‘For patients undergoing deep plexus or peripheral block we recommend the recommendations regarding neuraxial techniques be similarly applied (grade IC).’

Whilst recognising that this may be more restrictive than necessary, it is noteworthy that the guideline makes no recommendation with respect to more superficial PNB techniques. Neither does it define what are superficial and deep blocks.⁷

Regional Anaesthesia and Antithrombotic agents: recommendation of the European Society of Anaesthesia guideline – 2010

These guidelines again made limited recommendations with respect to PNB. They reference the Austrian guidelines, which suggests that PNB may be performed for superficial blocks (axillary, femoral, distal sciatic) with the proviso the interval between LMWH administration and that insertion or removal of a catheter should follow the neuraxial guidelines.⁸

4th ASRA consensus guidelines – 2018

The guideline made the following statement with respect to PNB: ‘For patients undergoing other plexus or peripheral techniques, we suggest management (performance, catheter maintenance, and catheter removal) based on site compressibility, vascularity, and consequences of bleeding, should it occur (grade 2C).’

It remains uncertain what is meant by this statement and what the nature of the management recommendations are.

Evidence The evidence for the use of PNB in the setting of altered coagulation is limited and largely confined to case reports, retrospective or observational studies.

Buckenmaier reported a series of 187 continuous peripheral nerve blocks in combatant casualties receiving Enoxaparin 40mg twice daily. In no case was bleeding a complication.¹⁰ In a retrospective study, Chelly reported the removal of lumbar plexus catheter in 607 patients receiving warfarin as thromboprophylaxis post total hip replacement (THR). All catheters were removed on day 2 without reference to the INR. 35% of all patients had an INR of 1.4 or greater at the time of removal. One patient had a bleeding complication. the INR in this case was > 3 at the time of catheter removal. Site pressure was sufficient to control the bleeding.¹¹ Chelly also reported on thromboprophylaxis and PNBs in patients undergoing joint arthroplasty. He reported 6935 blocks in 3588 patients. Patients received both deep and superficial blocks. No perineural haematoma was recorded in any case.¹² Idestrup reported on an observational study of 504 patients with continuous femoral catheters following TKA whilst receiving Rivaroxaban. In no case did haematoma formation cause neurovascular compromise. He reported a 12% incidence of ecchymosis.¹³ Chelly’s group again reported a series of 766 patients undergoing joint arthroplasty with Rivaroxaban. Some 1104 blocks were performed (both superficial and deep). No major bleeding was recorded associated with PNB.¹⁴

2. is the use of USGRA associated with fewer vascular punctures?

Given that bleeding is the consequences of PNB in this patient group and that ultrasound allows the identification of the vascular structures, it would seem reasonable to presume that the use of USGRA results in fewer vascular punctures.

A meta-analysis by Abrahams et al comparing USGRA and peripheral nerve stimulation (PNS) included some 1000 patients in 13 studies. This review showed evidence in favour of USGRA vs PNS in reducing inadvertent vascular puncture.¹⁵ This finding was supported by Barrington et al who carried out an audit of more than 7000 blocks from the Australian Regional Anaesthesia register. the use of ultrasound was associated with a statistically significant reduction in unintentional vascular puncture when compared to PNS.¹⁶

A consensus statement of the Orthopaedic Pain and Rehabilitation Society on the use of peripheral nerve blocks in patients receiving thromboprophylaxis was published in 2014. They reported only 4 cases of major bleeding between 1997 and 2012 in patients who received PNB whilst receiving prophylaxis. They concluded that there was no evidence that PNB in the setting of thromboprophylaxis increased the risk of major bleeding than either treatment alone.¹⁷

Case reports There are an increasing number of case reports and case series documenting the successful use of PNB in anticoagulated patients. It is likely that there are many more unreported cases of this kind.^{18 19}

In 2013, the Association of Anaesthetists of Great Britain and Ireland in association with Regional Anaesthesia UK and the Obstetric Anaesthetic Association produced a guideline for Regional Anaesthesia in patients with abnormalities of coagulation. of value, they included a risk classification of PNBs depending on whether the block was deep and superficial.²⁰

More recently, Joubert et al carried out a systemic review of bleeding complications following PNB in patients on antiplatelet or anticoagulant agents. They reported 80 bleeding complications following some 9738 blocks. This translated to an incidence of 0.82%. They concluded that bleeding complications post PNB are rare in patients on these agents.²¹

Conclusions

1. PNB in the setting of altered coagulation is not without risk.

2. The current evidence base for the use of PNB in patients with altered coagulation relies on case series, observational or retrospective reports. the evidence base for this practice is therefore weak.

3. USGRA does not protect from inadvertent intravascular administration.

4. USGRA reduces the risk of inadvertent vascular puncture.

5. The AAGBI guideline classifies deep versus superficial block. There is a clear consensus amongst many national societies that for deep blocks the same recommendations for neuraxial blockade applies (e.g. lumbar plexus, paravertebral)

6. The same risks do not apply for superficial blocks as they are invariably in a compressible site.

7. The risk associated with PNB in the setting of thromboprophylaxis is less than those in an anticoagulated patient.

8. The incidence of bleeding post PNB in this cohort of patients is 0.82%.

9. Ultimately the decision to perform a PNB in a patient with altered coagulation will depend on the risk benefit assessment for each individual patient.

References

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