Sreekumar Kunnumpurath, MBBS, MD, FCARCSI, FRCA, FFPMRCA
Ronan is a 45-year-old truck driver who is scheduled for right shoulder reconstruction. He has been admitted in your hospital for the last week following a road traffic accident. During this accident, he sustained extensive damage to his right shoulder joint along with fractures of ribs and lung contusion. At the time of admission to the emergency department, it was noted that he had developed pneumothorax and this was treated with the insertion of a chest tube. The surgeon is keen to proceed with the surgery as early as possible. His pain control has been an issue because he could not tolerate morphine secondary to severe nausea.
Over the week, his pneumothorax resolves and he is currently on acetaminophen and ibuprofen along with codeine phosphate PRN that he uses occasionally for fear of side effects. The surgeon has specifically requested you to anesthetize this patient as you are well known for your proficiency in regional anaesthesia.
Summarize the issues regarding anesthesia and pain management for this patient? Regarding anesthetic management, Ronan is recovering from a recent pneumothorax and so a general anesthetic with positive pressure ventilation carries the potential risk of a further air leak into the pleural space. The second issue is managing postoperative pain. Using potent long-acting opioids such as morphine or hydromorphone in the form of PCA is not ideal as he had side effects due to these drugs. On the day before the scheduled surgery, you visit Ronan. After obtaining a detailed clinical history, you make a thorough clinical examination and go through the lab results and X-rays. This time you notice that the chest drain has been removed and the lungs have expanded back to normal without any evidence of residual air or fluid in the pleural cavity. His right shoulder has extensive soft tissue and bone injuries. All his laboratory values are within normal limits, except for the coagulation panel that shows an INR of 1.2.
What would be your anesthetic management for this patient?
There are two key issues in this situation. The first is a potentially for the recurrence the pneumothorax. This could be addressed by administering an effective brachial plexus block through the interscalene route combined with sedation if the patient is worried about being wide awake during the procedure. The second issue is managing postoperative pain in the presence of opioid intolerance, which could possibly be the result of high-opioid requirement in the presence of uncontrolled pain. This could be addressed by adapting a multimodal approach to pain management, namely extending the regional anesthetic technique for postoperative analgesia along with acetaminophen and NSAIDs. Opioid could be reserved for breakthrough pain by PRN administration together with an antiemetic.
You explain your anesthetic technique to Ronan. You describe how you are going to do the interscalene block. You mention that you are going to put a needle in his neck to inject local anesthetic solution and then leave a catheter near the nerve plexus. Ronan is very unhappy about your anesthetic plan. He tells you that he had an unpleasant experience with a nerve block which he had for his knee surgery about 10 years ago. More than the needle, he remembers and worries about electric shocks used by the anesthetist to stimulate and identify the nerves which were very painful and made his limb jerk uncontrollably. Moreover, the block did not work properly and he had to have a general anesthetic, and the postoperative pain was "bad" as well.
How will you explain the advantages of US-guided nerve block to Ronen? You explain to Ronan that using electrical nerve stimulation for identification of individual nerves is probably outdated. Instead, you are going to use high-resolution ultrasound scanner to identify and block the individual nerve roots as they come out of the spinal canal. Advantages of US are the precision with which you can visualize and identify the needle, nerves, blood vessels, and other structures. It helps you to see the local anesthetic spread around the nerves. So there is less chance of any damage to nerves or pleura with the needle and less risk of injecting the local anesthetic into a blood vessel. You would be able to pass the specialized catheter under direct image guidance and leave it close to the nerve plexus for postoperative pain relief. US-guided techniques have higher success rates. The other advantage is that it is least distressing to the patient as he will not be experiencing any of the uncomfortable and painful shocks and muscle jerks.
You stress the importance of avoiding a general anesthetic and the need for an effective and side effect-free postoperative pain relief so that his recovery is hastened without any respiratory complication due to inadequate pain control. Ronan agrees for an ultrasound-guided interscalene block.
What are the disadvantages of ultrasound-guided nerve block?
Sometimes nerves and tendons may have similar echo patterns making their identification difficult. Bones can cast acoustic shadows under it, obscuring the view of underlying structures. On occasions, abnormal anatomy may confuse the operator. Proficiency in this technique will require training and practice. Moreover, the cost of the equipment such as the ultrasound scanner, specialized echogenic needles, and catheters is another drawback.
How can you overcome these difficulties?
Resolution of ultrasound can be increased by using higher frequency ultrasound waves. Penetration to visualize deeper structures can be increased by using lower frequencies (these two properties are in conflict). Penetration and resolution can be adjusted on the ultrasound machine. Echogenic needles have specialized patterns on their surface, thereby reflecting back the sound waves. One of the techniques to make catheters echogenic is to incorporate tiny air bubbles into them during fabrication, thereby creating air-surface interfaces.
Satisfied with your reasoning and explanation, Ronen undergoes surgery with a successful ultrasound-guided interscalene brachial plexus block. A catheter is passed for continuous infusion of local anesthetic for postoperative analgesia. You administer target-controlled propofol infusion to keep him sedated during the procedure.
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