Real-time continuous injection pressure monitoring during regional anaesthesia administration.

Abstract

In their recent editorial, Barrington and Lirk referred to several of our studies on injection pressure monitoring during regional anaesthesia. Although we agree that provider education, core skills development and situational awareness prevent complications resulting from lack of knowledge and improve accuracy and success rate (particularly when an operator-dependent technique, such as ultrasound guidance, is used), we think that knowledge and expertise are not a universal recipe for safety in interventional medicine. Even in expert hands and under ultrasound and nerve stimulation guidance, many studies have shown that disastrous complications can still occur 1-3. Ultrasound guidance is intrinsically limited by penetration depth during peripheral nerve blockade, but evidence suggests closer approaches to the nerves increase block efficacy and reduce the dose of local anaesthetic agent needed. However, ultrasound is currently not sophisticated enough to distinguish inframillimetric nerve structures and fasciae surrounding the nerves. Moreover, keeping the perfect alignment between the ultrasound beam, the needle and the target at all time is a demanding task, which demands stereotactical skills that imply the possibility of failure/complication 3. Rare but catastrophic complications of regional anaesthesia, such as permanent nerve damage or accidental intravascular injection of local anaesthetics, are too often dismissed as intrinsically non-modifiable factors. As a specialty, however, anaesthesia does not consider any risk rate as acceptable; our professional evolution has passed through a very rapid phase of technical innovation, which now allows for low-risk general anaesthesia in patients that would have been refused anaesthesia, but which has outstripped the pace of development in regional anaesthesia. Safety in the latter demands more than simply needle visualisation. Accurate injection pressure monitoring at the needle tip provides real-time information about the nature of tissues, that is, about their compliance, which complement (but do not substitute) the visual information provided by ultrasound and physiological information provided by nerve stimulation. Injection pressure can indicate intraneural injection, even where ultrasound and nerve stimulation do not, reducing further the likelihood of inaccurate needle tip placement, and therefore catastrophic complication 4. The sensitivity and specificity of real-time injection pressure curves 5 are greatly improved at the needle tip, hence our use of a new system in recent studies which we think is likely to improve the safety of regional anaesthesia still further 6, 7.