Side Effects
In addition to blocking the nerves which carry pain, local anaesthetic drugs in the epidural space will block other types of nerves as well, in a dose-dependent manner. Depending on the drug and dose used, the effects may last only a few minutes or up to several hours. Epidural typically involves using the opiates fentanyl or sufentanil, with bupivacaine, Fentanyl is a powerful opioid with a potency 80 times that of morphine and side effects common to the opiate class. Sufentanil is another opiate, 5 to 10Xs more potent than Fentanyl. Bupivacaine is markedly toxic, causing excitation: nervousness, tingling around the mouth, tinnitus, tremor, dizziness, blurred vision, or seizures, followed by depression: drowsiness, loss of consciousness, respiratory depression and apnea. Bupivacaine has caused several deaths by cardiac arrest when epidural anaesthetic has been accidentally inserted into a vein instead of the epidural space.
Sensory nerve fibers are more sensitive to the effects of the local anaesthetics than motor nerve fibers. This means that an epidural can provide analgesia while affecting muscle strength to a lesser extent. For example, a labouring woman may have a continuous epidural during labour that provides good analgesia without impairing her ability to move. If she requires a Caesarean section, she may be given a larger dose of epidural local anaesthetic.
The larger the dose used, the more likely it is that side effects will be evident. For example, very large doses of epidural anaesthetic can cause paralysis of the intercostal muscles and thoracic diaphragm (which are responsible for breathing), and loss of sympathetic nerve input to the heart, which may cause a significant decrease in heart rate and blood pressure. This may require emergency intervention, which may include support of the airway in addition to the cardiovascular system.
The sensation of needing to urinate is often significantly diminished or even abolished after administration of epidural local anaesthetics and/or opioids. Because of this, a urinary catheter is often placed for the duration of the epidural infusion. People with continuous epidural infusions of local anaesthetic solutions typically ambulate only with assistance, if at all, in order to reduce the likelihood of injury due to a fall.
Large doses of epidurally administered opioids may cause troublesome itching, and respiratory depression.
Read more about this topic: Epidural
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