Epidural

Introduction

Epidurals involve the insertion of a needle into the epidural space with the injection of the agent, causing desensitisation of nerves in or near the spinal cord. The meninges remains intact. It is usually performed at the lumbosacral junction. Patients can be placed in either lateral or sternal recumbancy so that the wings of ilia can be palpated. The lumbosacral junction is caudal to this and should be palpated between the seventh lumbar vertebra and sacral ridge. The site should be prepared aseptically. The epidural space is reached when a pop is felt, which describes the entry through the ligamentum flavum.

Agents

It is important to use preservative free agents, and those without epinephrine in the preparation.

Opioids

Thought to act at the presynaptic site in the dorsal horn. Here, it prevents substance P release and hyperpolarises nerve cells. This means that there is only loss of sensation rather then an effect on the motor function. ]

Morphine

Morphine is considered the most useful opioid due to its potency and long duration of action.

Pethidine

Used in cats and has a rapid onset of action, but relatively short duration of action.

Local Anaesthetics

Commonly used agents include lidocaine and bupivicaine

Uses

• Multimodal analgesia in small animals.

Advantages

• Good analgesic properties.
• Provide muscle relaxation.
• Reduces the need for a deep anaesthetic for painful procedures.

Disadvantages

• Affects the function of the hindlimbs, depending on the agent used, so cannot be used in the concious patient.
• Requires practice to perform correctly.