Regional Blocks I: An Introduction to Regional Anaesthesia

I am sure by now most readers have been faced with a patient in extreme pain. This can be distressing to any member of the trauma team - it certainly is to patients themselves. In the trauma unit we see everything from small phalanx fractures all the way to polytrauma and extensive burns, as well as everything in between. Managing pain is of the highest priority and should be tackled as aggressively as possible. Pain, after all, is one of the most common presenting complaints in the Emergency Department worldwide.

Now imagine this patient is also hypotensive, elderly, or riddled with co-morbidities that would render our traditional analgesic ladder sub-optimal or even dangerous. Maybe the patient with multiple rib fractures is struggling on face mask oxygen due to pain. What if you need to manipulate a limb but the airway is a possible nightmare? Many situations demand more than the usual paracetamol and opioid knee-jerk combo, and sometimes procedural sedation might not have a favourable benefit-risk ratio. What if we could add another tool to our belt in managing pain? This is where regional anaesthesia comes in.

It has been well established in trauma, emergency medicine, and anaesthesia literature that multi-model analgesia is superior and should be pursued as much as possible. A key difference between the emergency setting and anaesthetic setting to remember is that the goal of this procedure is not complete and total anaesthesia but analgesia. In theatre a block is usually considered “failed” if there is still some sensation, but any reduction in pain in the acute setting should be considered beneficial.

What I want to impart on you today with this article is the kick-starter that might help you safely manage pain in the elderly comorbid patient, potentially save the patient with multiple rib fractures from intubation, or even reduce that limb without subjecting the patient to all the risks of a procedural sedation.

What do I need?

1.      An ultrasound, ideally one with a high frequency linear probe.

2.      A local anaesthetic agent, with or without adjuvants.

3.      A block needle, spinal needle, or an IV cannula with extension tubing and appropriately sized syringes.

4.      A basic sterile pack or “block pack”, depending on your institution.

5.      Monitoring and resuscitation equipment.

Let’s tackle each separately.

Ultrasound

Any ultrasound with a probe that allows you to visualise the needle and tissue planes will do. There's no need for fancy software with needle tracking or bi-plane visualisation. These are often very simple blocks, and we don’t need to overcomplicate things. A high-frequency linear probe is preferable, especially one with a small footprint if blocking the smaller nerves of the forearm, but in some cases a curvilinear probe may be necessary. These have a lower frequency which allows sound waves to penetrate deeper into the body, are so are useful in patients with more soft tissue.

Its also important to optimise your use of the ultrasound. Typically you would hold it with your non-dominant hand, and rest your hand against the patient in such a way that it stabilises your image. Orient the screen in your natural line of vision. Use the gain and depth settings to optimise your image acquisition. Also bear in mind that both needles and nerves are quite anisotropic - their echogenicity is significantly affected by the angle of the ultrasound waves. To see these structures most clearly, the ultrasound needs to be at ninety degrees to the structure (note - this is not necessarily ninety degrees to the skin!) so that sound waves bounce directly back to the transducer. Have a play around next time you're scanning a patient and watch as the nerve appears and disappears as you tilt the probe.

Local anaesthetic

The choice of local anaesthetic is important but not really as hard as you might think. Most units that perform regional anaesthesia on a regular basis will use either ropivacaine or bupivacaine for longer acting blocks or lignocaine if a shorter duration of action is required. The addition of adrenaline (epinephrine if you're American) is a no-brainer as it limits local vascular absorption, prolonging local effect and protects against local anaesthetic systemic toxicity (LAST).  All the other agents you read about in anaesthetic texts or online are probably not available in most EDs or trauma units so no need to worry if you are starting out. What's important to remember is that calculating your maximum dose is crucial. You can use the table below to serve as a guide when doing so:

In addition to adrenaline, consider other adjuvants that prolong the duration of action but have minimal side effects of their own. In our setting, magnesium and dexamethasone are the two agents that tick both those boxes.

Sterile equipment

Most regional anaesthesia literature recommends specialised “block” needles that are more echogenic, and so are easier to see on ultrasound. They also offer more tactile feedback when advancing through fascial planes and have shorter bevels that theoretically lower the chance of inadvertent nerve damage. Some even have built-in extension tubing. All of this comes with extra cost and these may not be readily available. A long IV cannula is often sufficient.

All of the regional anaesthesia articles and statements that I could find agree that one-shot blocks don’t require full patient draping, probe covers, and all the other sterile setup required for the more extensive, multi-pass blocks you might see in theatre. After all, you are simply putting a needle in a space, right? We don’t drape a patient for venepuncture or vaccination, so why complicate this? Properly cleaning the skin and keeping your probe covered before using a sterile needle is more than sufficient. Just remember to mentally map out your needle path and plan your approach - this minimises the need to repeatedly pass the needle and reduces the risk of infection.

Monitoring

It would be remiss of me not to mention that although regional blocks have very low complication rates if done correctly, you do need to be ready for rare but severe complications like anaphylaxis and local anaesthetic systemic toxicity (LAST).

While the risk of latter can be minimised by always calculating your maximum safe local anaesthetic dose, using adrenaline as an adjuvant, aspirating before you inject, and always keeping your needle tip in view, you still need to make sure you are performing the block in an appropriate space, with appropriate monitoring, staff, and resuscitation equipment. Rescue drugs like 20% Intralipid® should be available, and you should know where these are kept (often the operating theatre). Once the block has been placed, remain vigilant for early symptoms and signs of LAST, which is usually heralded by patients complaining of a metallic taste, tingling around their lips, having tinnitus, or you notice them slurring their speech, acting confused, or becoming agitated.

That said - LAST is extremely rare, and with proper precautions, simple blocks have extremely low complication rates, so don’t let this dissuade you from starting out.

Other pitfalls

Remember to perform and document a thorough neurological exam before placing the block, and if you're referring to another specialty who may want to perform their own assessment of neurovascular status, I'd advise you have a dialogue with them about the fact that you intend to perform a block. It may change the speed with which they come to review the patient and avoid unnecessary confusion at a later stage. Once the block is placed, be mindful that you've lost your first early sign of compartment syndrome: pain. If you're performing a block for a high risk injury, like a tibial fracture, adjust your plan for observing the limb.

Other resources

Check out the resources below - these are some of my favourites:

With basic understanding of these principles and a little practice, you have now acquired a whole new trick up your sleeve. Consider whether your next trauma patient may be suitable for a block, and I hope that this has opened up a world of possibilities for you, just as it did for me.

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Dr Marcus Kruger is a senior emergency medicine registrar with a passion for ultrasound, trauma, pain management, and perfecting the smash burger.

He has worked in a number of Emergency Departments in the Gauteng Province, and before that spent his time as a junior doctor in Durban. He loves empowering junior colleagues with new and practical skills.

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References

[1] Local anesthetic systemic toxicity. UpToDate [internet]. Accessed 28th May 2025. Available from: https://www.uptodate.com/contents/local-anesthetic-systemic-toxicity.

[2] Swain A, Nag DS, Sahu S, Samaddar DP. Adjuvants to local anesthetics: current understanding and future trends. World J Clin Cases. 2017;5(8):307-23.

[3] Introduction to ultrasound-guided regional anesthesia. NYSORA [internet]. Accessed 29th May 2025. Available from: https://www.nysora.com/topics/equipment/introduction-ultrasound-guided-regional-anesthesia/