Positive blood aspiration with ultrasound-guided peripheral blocks, do we all do the same?
Regional anesthesia techniques, either alone or in combination with general anesthesia, have gained popularity across the world. In the last two decades, the widespread use of ultrasound guidance improved both safety and quality of regional techniques.1
Nevertheless, the incidence of unintended puncture of venous (0.06%) and arterial vessels (0.12%) cannot be neglected.2 In this regard, one of the most feared complications is the local anesthetic systemic toxicity (LAST), with an incidence of 2.6/10 000 for ultrasound-guided blocks.3
In addition to the use of ultrasound, there are other measures recommended in literature to identify and decrease the occurrence of these events. Recently, Macfarlane et al. summarized the proper conduct to safely perform peripheral nerve blocks, which also includes (1) performing the technique in awake patients; (2) incremental injection of local anesthetics; (3) considering the use of adrenaline as a marker of intravascular administration; (4) aspiration before injection.4
Although current recommendations are aimed to decrease the incidence of adverse events, they do not address how to proceed after confirmed vessel puncture (positive aspiration of blood and/or direct visualization of the needle inside the lumen). In our perspective, there are three possible ways to deal with this problem: (1) perform the peripheral block in a different location; (2) reposition the needle and proceed with the block in the same location, when it is not an area of great vascularization; (3) abort the technique and proceed with another peripherical block or neuroaxial block if suitable.
We´ve realized that there is a great diversity of attitudes when a positive aspiration is verified. Perhaps common sense makes us think that we would all perform in the same way, but in different situations we have not seen a cautious attitude as expected.
Interestingly, we have not found any evidence or guidelines regarding this topic, and this could be the reason for discrepancy in clinical practice.
We believe that performing the block in the same location after vascular puncture might be risky. With the rupture of the vessel wall, there is a theoretical risk of systemic absorption of local anesthetic due to either passive diffusion or pressure gradient favoring entry in blood vessels (increased interstitial pressure during the injection or hematoma formation).
In our understanding, when a vascular puncture is identified, it would be safer, in most cases and if feasible, to cancel the technique and perform the peripheral block in another location. In this regard, other questions are raised: (1) Should we still perform the block despite the potential nerve injury associated with vascular damage?; (2) What is the ideal distance from the puncture to perform the block safely?; (3) Would a second puncture be safer proximal or distal to the first puncture?; (4) Would this second approach reduce the risk of a new bloody tap?; (5) Should a second puncture be considered for deep / vascularized locations?
Although we strongly advocate for peripheral nerve blocks in our practice as an important component of a multimodal strategy, regional anesthesia shouldn’t be compulsory and must be carefully considered weighing the pros and cons, risks and benefits after the occurrence of such (and another) complication.
Therefore, we want to emphasise the importance of reporting vascular puncture during regional anesthesia techniques and how anaesthesiologists manage them. We believe this would encourage the development of guidelines and standardization of clinical practice.
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