7.16 (13.4) visceral pain

Question 1

define visceral pain

Answer 1

pain arising from in or around internal organs

Question 2

Visceral nerves are predominantly which types of nerves

Answer 2

Unmyelinated C fibers and some thinly myelinated A fibers

Question 3

The CNS receives information from visceral organs through afferent nerves that run in parallel with what type of other nerves?

Answer 3

efferent automonic nerves (parasympathetic and sympathetic)

Question 4

The vagus nerve conveys info from and to what organs?

Answer 4

visceral organs in the chest and abdomen (up to the level of the proximal colon)

Question 5

The pelvic nerve conveys info from and to what organs?

Answer 5

lower bowel and pelvic organs

Question 6

The celiac plexus conveys info from and to what organs?

Answer 6

upper abdo organs

Question 7

Where do primary afferents from visceral organs synapse in the spinal cord?

Answer 7

second order neurons in the dorsal horn

Question 8

List three differences between somatic nociception and visceral nociception*

Answer 8

1. Innervation density is much lower for visceral than somatic nerves
2. Visceral and somatic sensory afferents may converge on same second order neuron in the dorsal horn, but visceral sensory afferents may project to a larger number of levels in the cord and contralateral side
3. one visceral sensory neuron may innervate multiple organs (especially in the pelvis)

Question 9

List four stimuli that may trigger a visceral nociceptive afferent nerve

Answer 9

distension
ischemia
inflammation
noxious substances - bradykinin, capcaisin
torsion
electricity

FS:
Mechanical - distention
Thermal - inflammation
Chemical - noxious substance
Ischemia
Electricity

Question 10

Name and explain 3 broad types of visceral pain mechanisms

Answer 10

1. Peripheral activitation - stimuli (distension, ischemic, inflammation, etc.) that arise in viscera activate visceral nociceptors
2. Peripheral sensitization - changes in functioning of a primary afferent nerve (due to inflammation or nerve trauma) that may include reduced threshold to peripheral activtation, spontaneous activation or increase in magnitude of a response
3. Central sensitization - amplification of neural signalling within CNS

Question 11

Describe the quality of visceral pain involving:

1. Hollow viscus
2. Solid organs or organ capsules
3. Esophageal and bladder

Answer 11

1. Hollow viscus - poorly localized/vague, crampy, gnawing
2. Solid organs or organ capsules - better localized, sharp, stabbing
3. Esophageal and bladder - burning

Question 12

Why does visceral pain get referred to other areas of the body?

Answer 12

Visceral and somatic afferent fibres converge on same laminae in dorsal horn so visceral nociceptive impulses may be processed by higher brain as coming from corresponding somatic site

Question 13

What is “cross organ sensitivity” in visceral pain

Answer 13

The concept that visceral pain may be referred to other visceral organs. Afferents from different visceral organs can converge at the spinal, brainstem or thalamic levels

Question 14

Where is pain from the following organs experienced - name 2 each

liver and gallbladder
lung and diaphragm
heart
pancreas
stomach
kidney

Answer 14

Figure 7.16.1 (13.4.1)
liver and gallbladder - RUQ, right shoulder
lung and diaphragm - ipslilateral shoulder and neck
heart - neck, chest, and left arm
pancreas - epigastrium, mid thoracic back
stomach - epigastrium, left thoracic back
kidney - flank to groin

Question 15

What is the main source of visceral pain in patients with heme malignancies?

What substance cause cause enlarged LNs in patients with lymphoma?

Answer 15

Lymphadenopathy

ETOH drinking

Question 16

Name 3 radiation-related visceral pain syndromes

Answer 16

1. Radiation enteritis
2. Radiation proctitis
3. Radiation prostatitis

FS: esophagitis, cystitis

Question 17

What is the mainstay of therapy for visceral pain

Answer 17

opioids (oxycodone may be better)

Question 18

What are some non-opioid pain medication for:
1. Bowel obstruction
2. Biliary colic
3. Bladder spasm

Answer 18

1. Bowel obstruction - hyoscine butylbromide (buscopan), hyoscine hydrobromide (scopolamine), glycopyrrolate
2. Biliary colic - NSAIDs
3. Bladder spasm - Oxybutynin

Question 19

What 2 categories of interventional pain procedures can help visceral pain?

Answer 19

1. Neuraxial analgesia - placement of intrathecal or epidural catheter for long term infusion of compounds (opioids, local anesthetic, clonidine and others)
2. Peripheral neural blockage (nerve block) - non-neurolytic or neurolytic (phenol or alcohol), block afferent input from a painful site

Question 20

2 ways to perform celiac plexus block?

Answer 20

CT guided percutaneous injection
US guided transesophageal injection

Question 21

List four blocks (and their indication) that can be offered for visceral pain

Answer 21

celiac plexus block (upper abdo pain)

superior hypogastric nerve block (pelvic and intra-abdo pain)

ganglion impar block (perineal pain)

sacral nerve root block (perineal pain)

saddle blocks (perineal pain)

Question 22

List 3 other techniques (and their indication) that can be used for visceral pain

Answer 22

radiation (hep mets, pancreatic cancer, gyne cancer)

T10 myelotomy (pelvic visceral pain) neuraxial

spinal cord stimulation via implanted device (chronic pancreatitis, angina, testicular pain) neuraxial

radiofrequency ablation of peripheral nerve (bladder and rectal cancer pain)