Anaesthesia & Intensive Care Medicine

Lower limb nerve blocks Publication date: Available online 14 March 2019 Source: Anaesthesia & Intensive Care Medicine Author(s): Calum R.K. Grant Abstract The proliferation of ultrasound use is changing the approach to regional anaesthesia of the lower limb. Techniques are being developed that provide high-quality postoperative analgesia while minimizing associated motor block that may impair mobilization. Regional anaesthetic techniques also provide significant opioid-sparing benefits (e.g. less sedation, nausea and urinary retention) that are key principles of current enhanced recovery protocols. Ultrasound-guided nerve localization offers several potential advantages when performing femoral, adductor canal, sciatic and ankle blocks; however, neurostimulation remains a useful and widely used aid to lower limb regional anaesthesia practice.

Complications of regional anaesthesia Publication date: Available online 14 March 2019 Source: Anaesthesia & Intensive Care Medicine Author(s): Alasdair Taylor, Calum R.K. Grant Abstract Complications of regional anaesthesia can be divided into those specific to central neuraxial blockade, those specific to peripheral nerve blockade, and those that pertain to both. Fortunately, severe complications, namely spinal cord damage, vertebral cord haematoma and epidural abscess are rare. Here we have given an overview of these complications, with reference to incidences available following the 3rd National Audit Project of the Royal College of Anaesthetists. A thorough knowledge of anatomy and pharmacology, and a meticulous, unhurried technique are key to reducing the risk of such complications. When considering the use of a regional anaesthetic technique, the risks and benefits for the individual patient should be assessed on a case-by-case basis, and set against the risks and benefits of alternatives.

Systemic toxic effects of local anaesthetics Publication date: Available online 13 March 2019 Source: Anaesthesia & Intensive Care Medicine Author(s): Heather N. Sheppard, Ravi Anandampillai Abstract Local anaesthetics are widely used in the provision of local/regional anaesthesia and the management of acute and chronic pain. Their mechanism of action temporarily inhibits voltage gated sodium channels in neuronal plasma membranes. Local anaesthetic systemic toxicity (LAST) is a serious yet largely preventable complication that can occur by any of the multiple routes of administration. LAST predominantly affects the central nervous and cardiovascular systems. Awareness of LAST and vigilance during administration of local anaesthetics may help in early recognition and successful management of the toxicity. Intralipid emulsion (ILE) infusions have been successfully used in reversing local anaesthetic-induced cardiotoxicity. Since 2007 in the UK, ILE infusion has been incorporated into the safety guidelines for management of LAST.

Practical aspects of ultrasound-guided regional anaesthesia Publication date: Available online 8 March 2019 Source: Anaesthesia & Intensive Care Medicine Author(s): Pavan Kumar BC. Raju, Calum RK. Grant Abstract Ultrasound-guided regional anaesthesia is increasingly popular, offering the user a number of advantages over alternative methods of nerve localization (neurostimulation or paraesthesia). These include a more accurate understanding of individual patient anatomy, identification of needle tip position and the ability to assess local anaesthetic spread in relation to a target nerve. An understanding of the basic principles and commonly used terminologies of ultrasound scanning is a fundamental requirement when using this technology. The aim of this article is to outline these basic principles and explain the practical aspects of performing nerve blocks, using ultrasound, in order to achieve quick, safe and effective block performance with minimal procedural discomfort for the patient.

Omics and anaesthesia: pharmacogenomics, proteomics and metabolomics Publication date: Available online 8 March 2019 Source: Anaesthesia & Intensive Care Medicine Author(s): Thomas E.F. Walton, Jonathan N. Rajan Abstract The inter-individual response to medications and the presence of genetic polymorphisms which impact the safe conduct of anaesthesia and analgesia are of paramount importance to the anaesthetist, intensivist and pain physician. The frequency of these phenomena is not reflected in the attention afforded them in undergraduate or postgraduate curricula. In order to appreciate how these issues may affect our clinical practice, it is crucial to have a working understanding of the concepts that underpin the relevant fields within the collection of disciplines we term the 'omics'.

Upper limb nerve blocks Publication date: Available online 8 March 2019 Source: Anaesthesia & Intensive Care Medicine Author(s): Pavan Kumar B.C. Raju, James S. Bowness Abstract Brachial plexus blockade is used for a variety of upper limb surgical procedures. Ultrasound guidance is generally considered to be the gold-standard technique, although large-scale studies examining efficacy and complications of ultrasound-guided techniques compared with nerve stimulation are still needed. Interscalene block remains the approach of choice for shoulder surgery, although phrenic nerve blockade is common even using low volumes of local anaesthetic. Of the currently available studies comparing the other approaches, there seems to be little difference in efficacy between axillary, supraclavicular and infraclavicular approaches for elbow, forearm and hand surgery when equivalent levels of expertise are used. The major features influencing block choice and performance are discussed.

Action potential: generation and propagation Publication date: Available online 8 March 2019 Source: Anaesthesia & Intensive Care Medicine Author(s): Allan Fletcher Abstract In the normal resting state, the plasma membrane of nerve and muscle cells generates a transmembrane electrical potential difference – the intracellular surface of the membrane being approximately 70–80 mV negative to the extracellular surface. This is a result of markedly different concentrations of ions inside and outside the cell, together with different membrane permeabilities to different ions that permits K+ to flow down their concentration gradient from inside to outside the cell. Nerve and muscle cells are 'excitable' because they can react to external stimuli by generating an extremely rapid change in transmembrane electrical potential difference known as the action potential. This comprises an initial explosive increase in membrane Na+ permeability that allows these ions to flood down their concentration gradient into the cell, thereby depolarizing the membrane such that the potential difference is transiently reversed to a positive value. However, in nerve and skeletal muscle this lasts for only a millisecond, at which time the membrane potential is just as rapidly restored to its resting negative value (repolarization). These events are controlled by the brief opening and closing of voltage-activated sodium and potassium channels in the membrane. The key features of the action potential are that it is: (i) an all-or-none event, rather than a graded response; (ii) it is self-propagating, such that the wave of depolarization travels rapidly along the plasma membrane; and (iii) it is transient, such that membrane excitability is quickly restored. These features of the action potential allow rapid transfer of information along nerve axons in the nervous system.

Nerve cell function and synaptic mechanisms Publication date: Available online 7 March 2019 Source: Anaesthesia & Intensive Care Medicine Author(s): Allan Fletcher Abstract Nerve cells (neurones) are 'excitable' cells that can transduce a variety of stimuli into electrical signals, continuously sending information about the external and internal environment (in the form of sequences of action potentials) to the central nervous system (CNS). Interneurones in the CNS integrate this information and send signals along output (efferent) neurones to various parts of the body for the appropriate actions to be taken in response to environmental changes. Networks of neurones have been arbitrarily classified into various nervous systems that gather and transmit sensory information and control skeletal muscle function and autonomic function, etc. The junctions between neurones (synapses) are either electrical or chemical. The former permit the direct transfer of electrical current between cells, whereas the latter utilize chemical signalling molecules (neurotransmitters) to transfer information between cells. Neurotransmitters are mainly amino acids, amines or peptides (although other molecules such as purines and nitric oxide are utilized by some cells), and can be excitatory or inhibitory. Individual neurones within the CNS may receive synaptic inputs from thousands of other neurones. Therefore, each neurone 'integrates' this vast complexity of inputs and responds accordingly (either by remaining silent or firing action potentials to other neurones). Adaptations in the function and structure of chemical synapses in particular (synaptic plasticity) are thought to underlie the mechanisms mediating cognitive functions (learning and memory).

Peripheral nerve catheter techniques Publication date: Available online 7 March 2019 Source: Anaesthesia & Intensive Care Medicine Author(s): Ayman H.M. Mustafa Abstract Peripheral nerve catheters (PNC) or perineural catheters are used synonymously to describe placing a catheter in close proximity to nerve plexuses or individual nerves for the provision of continuous pain relief. The indications of PNCs extend beyond upper and lower extremity orthopaedic surgery to perioperative analgesia in patients undergoing a wide range of surgical procedures (e.g. abdominal, vascular, thoracic, breast and trauma surgeries). PNC use can facilitate early mobilization after surgery by providing high quality analgesia that in turn leads to reduced opioid consumption and associated opioid related side effects. Perioperative PNC analgesia can result in reduced length of in-hospital stay and improved rates of patient satisfaction. Insertion of peripheral nerve catheters can be done by either anaesthetist or surgeon. Long term benefits are still to be ascertained. Risks are similar to peripheral nerve block although catheter dislodgement remains a specific problem.

Intravenous regional anaesthesia Publication date: Available online 7 March 2019 Source: Anaesthesia & Intensive Care Medicine Author(s): Alastair J.M. Baird, Colin B. Donald Abstract Intravenous regional anaesthesia, or Bier's block, is a useful and safe technique for anaesthetizing distal limbs for short surgical procedures. It is most commonly used for reduction of forearm fractures within the emergency department and can be a useful method of providing anaesthesia in patients who may be unsuitable for a general anaesthetic, or when skills or equipment for other forms of regional anaesthesia are unavailable. When performed as recommended it has a proven safety record.