A reply

Abstract

We thank Drs Biswas and Ó Riain for their interest in our letter [1]. The point they made regarding difficulty in aspirating before injection when using a single-handed technique is well founded, which is why we clearly stated in our letter that we do not routinely aspirate before injection when using a single-handed injection technique. We also stated that we only inject very small volumes of anaesthetic in any one place, which makes significant intravenous injection unlikely. Indeed, in our experience, on several occasions when ultrasound has detected intravenous injection (hypoechoic expansion of the tissues, or visible uptake into veins) prior aspiration has been negative. If the needle is not placed within a large enough vein, aspiration will often be negative. We suggest direct observation with ultrasound is a sensitive detector of intravenous injection. Drs Biswas and Ó Riain correctly state that the first letter (regarding the ‘Jedi grip’) pictured a 10-ml syringe [2]; however, they are mistaken in stating that we also pictured a 10-ml syringe, and we would direct them again to our letter and image, which shows a 20-ml syringe. The size of syringe an operator is capable of manipulating with one hand will, of course, depend on the size of their hands. We have not found a 20-ml syringe particularly difficult to handle. Regarding the pressure exerted and the detection of intraneural needle placement, ultrasound has been shown to be a sensitive detector of intraneural injection of local anaesthetic, whereas peripheral nerve stimulation and injection pressure may be less reliable [3,4]. We suggest direct observation with ultrasound is more reliable than manually perceived injection pressure for detection of intraneural injection of local anaesthetic. We would repeat that single-handed injection has reduced the amount of local anaesthetic we are routinely administering by allowing the operator immediate feedback on needle position in relation to the nerve, so no anaesthetic is wasted. Finally, we would also stress that single-handed injection requires more skill and is therefore suited only to experienced operators. We have been developing our skills in ultrasound-guided regional anaesthesia for nearly ten years. Ultrasound is an excellent imaging technique in regional anaesthesia but is only as good as the operator who is using it. Remember Dr A. Winnie’s words of caution: “When there are problems with any regional technique, look for the cause first on the proximal end of the needle” [5].