Anaesthesia for orthopaedic procedures should blunt the stress response to surgery, and provide muscle relaxation and profound perioperative analgesia. Surgical trauma is an injury, and the body reacts locally (inflammation) and systemically (endocrine and metabolic activation). Central neuraxial blockade (epidural anaesthesia, spinal anaesthesia) modulates both endocrine and metabolic responses: a single dose inhibiting the stress response for only few hours, a 24 hours epidural analgesia for few days postoperatively. The influence of peripheral blocks on stress response to surgery appears to be negligible, however they provide effective long lasting analgesia.
Good knowledge of the technique and the use of dedicated material decrease the incidence of side effects and complications during regional anaesthesia: Tuohy needles and Loss-Of-Resistance technique for epidurals, nerve locator and dedicated needles for peripheral blocks, and care in selecting the drug and the dose to be administered should be used. Regional techniques can also lead to early mobilization, early oral intake and early discharge from the practice. In some patients the administration of analgesics through a long term epidural catheter can provide better analgesia during functional recovery and/or physiotherapy.
Local anaesthetics bupivacaine, ropivacaine and levobupivacaine can be safely used for epidural and spinal anaesthesia. Lidocaine should be better avoided because of its neurotoxicity. Duration of the block depends from the drug and the dose used. Morphine can be used to provide long lasting analgesia distant to the site of injection, due to its unique ability to spread cranially in the CSF. However, this may potentially lead to respiratory depression, therefore the dose should be carefully titrated according to patient’s need. Although fentanyl does not cause delayed respiratory depression, it is shorter lasting and does not provide distant analgesia. Central neuraxial alpha-2 agonists provide analgesia and do not cause respiratory depression, however they may cause bradycardia, and hyper- or hypo- tension. Only local anesthetics and alpha-2 agonists (as an adjunct to LA) have been shown to be effective for peripheral blockade.
Although general anaesthesia may limit the perception of the injury, it is now well established that this may not be associated with blunting of the stress response. Although high plasma levels of opioids may transiently alter stress response to surgery, they are associated to side effects and complication including bradycardia, respiratory depression, etc. During balanced anaesthesia inhalational agents are used to provide unconsciousness, while opioids, alpha-2 agonists, ketamine and NSAIDs to provide analgesia. NeuroMuscular Blocking Agents (NMBAs) can be used to provide muscle relaxation during general anaesthesia, however positive pressure ventilation is required and close monitoring of recovery of neuromuscular function is mandatory to avoid ventilatory depression at emergence from anaesthesia. NMBAs provide less effective muscle relaxation compared to regional techniques.
