Anaesthetics, local Opioids

Epidural and intrathecal opioids are widely used for postoperative and obstetric analgesia. In contrast to local anaesthetics, spinal opioids cause minimal sympathetic efferent and motor blockade. Pethidine, which has local anaesthetic activity, can produce sensory and motor blockade. Because remifentanil is formulated with glycine as a vehicle, it should not be used epidurally or intrathecally, since glycine is neurotoxic. 

Relief of pain after surgery can be achieved with a variety of techniques. An epidural infusion of a mixture of local anaesthetic and opioid provides excellent pain relief after major surgery such as laparotomy. Parenteral morphine, given intermittently by a nurse or by a patient-controlled system, will also relieve moderate or severe pain but has the attendant risk of nausea, vomiting, sedation and respiratory depression. The addition of regular paracetamol and a NSAID, given orally or rectally, will provide additional pain relief and reduce the requirement for morphine. NSAIDs are contraindicated if there is a history of gastrointestinal ulceration of if renal blood flow is compromised. 

Non-steroidal Anti-inflammatory Drugs Opioid Systems Local Anaesthetics Voltage-dependent Na+ Channels... 

Because epidural opioids are usually ineffective in controlling pain during the final stages of labour they are commonly combined with a low concentration of a local anaesthetic, e.g. 0.125% bupivacaine. There has been speculation that epidural opioids may reactivate herpes simplex in pregnant patients. The aetiology is unclear. Herpes simplex after delivery is potentially dangerous because of the risk of herpes encephalitis in the infant. Spinal opioids should therefore be avoided in the parturient with a history of recurrent herpes simplex. 

Extradural (epidural) anaesthesia is used in the thoracic, lumbar and sacral (caudal) regions. Lumbar epidurals are used widely in obstetrics and low thoracic epidurals provide excellent analgesia after laparotomy. The drug is injected into the extradural space where it acts on the nerve roots. This technique is less likely to cause hypotension than spinal anaesthesia. Continuous analgesia is achieved if a local anaesthetic, often mixed with an opioid, is infused through an epidural catheter. 

RECEPTOR ANTAGONIST (channel-blocking at NMDA receptors). It is an OPIOID ANALGESIC, (dissociate) GENERAL ANAESTHETIC, PSYCHOTROPIC and ANTICONVULSANT. It iS a drug of abuse and has been withdrawn from human clinical use. etidocaine [ban, inn, usan] (Duranest ) is an amide series LOCAL ANAESTHETIC, used by injection for infiltration and regional pain relief. 

Chloroprocaine can reduce the efficacy of epidural morphine and fentanyl analgesia. Bupivacaine may enhance the local anaesthetic effect of fentanyl, but does not appear to affect respiration. Similarly, Udocaine does not appear to increase respiratory depressant effects of morphine. However, two cases of respiratory depression have been reported with Udocaine and opioids. Morphine given as an intravenous bolus does not alter Udocaine serum levels given as a continuous intravenous infusion. 

Local anaesthetics are synergistic with intrathecal opioids and intensify sensory block without increasing sympathetic block. The combination makes it possible to achieve spinal anaesthesia with otherwise inadequate doses of local anaesthetic. 

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