Pain

Question 1

Intrathecal vs epidural analgesia

Answer 1

Indication: Failed conventional drug therapy or intolerable side effects.

Intrathecal routh, the catheter lies within the subarachnoid space, medication directly access to spinal receptors.

Epidural routh, the catheter lies within the epidural space, medications are distributed by 3 pathways: diffuse through the dura into the CSF, then to the spinal cord or nerve roots; Uptake to vessels then systemic circulation; Store in epidural fat.

Question 2

advantages of intrathecal to epidural

Answer 2

• Ease of catheter placement, particularly in the presence spinal pathology.
• Fewer catheter problems such as catheter migration or tip occlusion.
• Lower dose requirements may reduce side effects and lower drug costs.

Superior analgesia in the following settings:

• Presence of epidural pathology, e.g. metastatic disease, radiation fibrosis, vertebral compression.
• Widespread pain, multiple pain locations, and pain distant from catheter site, especially upper body.
• Pain poorly responsive to high-dose epidural therapy.

Question 3

Pain responsiveness to intraspinal opioids

Answer 3

• continuous somatic pain > continuous visceral > intermittent somatic > intermittent visceral > neuropathic > cutaneous (ulcers or fistulas).
• ADDED local anesthetics (bupivacain) and/or alpha-agonists (clonidine) for treating neuropathic pain.

Question 4

Pain receptors and neuromediators

Answer 4

Question 5

Opioid Poorly-Responsive Pain

Question 6

Wind-up

Answer 6

These neurons synapse on second-order neurons, which carry pain signals to the central nervous system. However, if afferent fibers continue to have a high-level, sustained discharge, the threshold for firing by the second-order cells in the dorsal horn may decrease, causing pain to be experienced even with minimal stimulus (hyperalgesia) or stimuli that ordinarily do not induce pain (allodynia).

Question 7

LE Pain pattern

Answer 7

• Radiation-related neuropathy, Bilateral with diffuse Lower extremity weaknes predominance in L5-S1 distribution. ABSENT knees reflex. pain is UNCOMMON.
• chemotherapy-related neuropathy, would be more likely to present with bilateral, peripheral shooting, stabbing, or numbness in both feet and hands.
• Cauda equina syndrome involves sphincter weaknesses causing urinary retention, decreased anal tone, saddle anesthesia, bilateral leg pain and weakness, and bilateral ABSENT ANKLE reflexes.
• carcinomatous lumbosacral plexopathy;Reflex changes in L1-L4. intense pain in the low back or hip with radiation into the lower extremity, followed by motor weakness or sensory loss. Pain on straight leg raise +ve. NO sphincter incontinence
• sacral plexopathy. L5-S2; Sphincter INCONTINENCE and sensory loss. Aching and dull in sacral area, and a burning or throbbing in the rectum and perineal pain.

Reflex: Knee reflect lumbar; Ankle is sacral.