Ultrasound applications for regional anaesthetists – thinking outside the box

Abstract

Deposition of local anaesthetic in the proximity of nerves, plexi, within fascial planes, in the paravertebral, epidural or subarachnoid space, is the ever expanding core activity of a regional anaesthetist. Advantages of using ultrasound in this clinical setting include detection of anatomic variants, reduction of volume of local anaesthetic needed with the implication of a lower potential for systemic toxicity, faster onset, real-time assessment of needle advancement avoiding key structures such as blood vessels or pleura, and observation of local anaesthetic spread patterns, all of which are key elements of block success and safety [1]. In addition, we have developed approaches aimed at reducing or quantifying side effects, such as sparing the phrenic nerve when performing an interscalene block [2,3] or assessing the degree of the resulting diaphragm paralysis [4].From the preoperative to the postoperative period, there appear to be many more opportunities for ultrasound users to improve patient assessment and management in the ultimate hope of improved perioperative outcomes.Recent guidelines on vascular access recommend the use of ultrasound guidance for all routes of access where the vessel cannot be directly seen or palpated [5]. Routine use of ultrasound had been previously documented for internal jugular central venous catheterisation (unless in emergency or other unusual situations), and early in other procedures (arterial and peripheral venous), if difficult. Clearly, ultrasound makes many steps safer including: evaluation of puncture site, eliminating seeker needles, needle guidance, verification of guidewire/catheters in a vessel, information on central catheter tip position and recognition of complications [5].As an emerging application, ultrasound has been shown to aid airway evaluation and management with obvious potential benefits for both clinician and patient. Ultrasound can identify vocal cord dysfunction and pathology before induction of anaesthesia thus highlighting potential difficulties. It may be utilized to determine airway size and predict the appropriate diameter of single-and double-lumen endotracheal tubes as well as tracheostomy tubes [6]. It appears to reliably differentiate between tracheal, oesophageal, and bronchial intubation. Taken a step forward, ultrasonography of the neck can accurately locate the cricothyroid membrane for emergency airway access and identify tracheal rings for ultrasound-guided tracheostomy. Upper airway point-ofcare ultrasound has thus the potential to become the firstline non-invasive adjunct assessment tool in airway management [6].Much has been published in recent years on the utility of ultrasound for evaluation of gastric content. Inhalation of gastric content during induction, maintenance or emergence from anaesthesia has devastating consequences leading to significant morbidity and mortality. Therefore, evaluation of gastric contents is most helpful in order to inform an assessment of aspiration risk and thus guide anaesthetic management at the be...