Abdos

Question 1

Nausea and Vomitus

Pathophysiology Brain Structure

Answer 1

Brain Structure

Question 2

Nausea and Vomitus

Pathophysiology Causes

Answer 2

Causes

Question 3

Nausea and Vomitus

Recipere NK Antagonists

Answer 3

NK Antagonist

Question 4

Nausea and Vomitus

Clinical Scenarios

Answer 4

Clnical Scenarios

Question 5

Nausea and Vomitus

Answer 5

The vomiting centre (VC) - this is situated in the brainstem and has histamine H1R, acetylcholine AChR and serotonin 5HT2R (5-hydroxytryptamine 2) receptors.

The chemoreceptor trigger zone (CTZ) - located in an area of the brain that has NO blood-brain barrier, and enables various drugs, toxins and metabolites to access the site, has dopamine D2R and serotonin 5HT3R receptors.

The cerebral cortex - there are multiple receptors which can be triggered by anxiety. Also, mechanoreceptors in the meninges are sensitive to changes in intracranial pressure.

The vestibular system - changes in movement or diseases of the ear may stimulate the ACh or H1 receptors, triggering nausea or vomiting.

P/Naus, Vom]
Antihistamine
Block H1R at vomiting centre.
{Gravol} Dimenhydrinate 25-100mg PO/IV/PR q4-8h
{Antivert} Meclizine 25mg PO q6-12h
{Phenergan} Promethazine 25mg PO/IV q4-6h

Serotonin Antagonists
Block 5HT2R at VC and 5HT3R at CTZ.
{Zofran} Ondansetron 4-8mg PO/IV/SQ BID-TID
{Sancuso} Granisetron 0.5-1mg PO/IV/SQ OD-BID

Antipsychotic
Block D2R in the CTZ
{Haldol} Haloperidol 0.5-2mg PO/IV/SQ q6-12h
{Thorazine} Chlorpromazine 25-50mg PO/IV/PR q6-8h
{Stemetil} Prochlorperazine 5-20mg PO/IV/PR q4-8h
{Nozinan} Methotrimeprazine 2.5-10mg PO/IV/SQ/SL q4-8h
{Zyprexa} Olanzapine 2.5-5mg PO OD

Prokinetic
Block D2R in the CTZ
{Maxeran} Metoclopramide 10-20mg PO/IV/SQ/PR q4-8h
{Motilium} Domperidone 10mg PO q4-8h
Note: Prokinetic effects work through the release of Ach onto the muscarinic receptor M3R of the smooth muscle of the gut. Dopamine inhibits the release of Ach called the “dopaminergic brake”. Serotonin 5HT4 activates the release of Ach.

Domperidone is a peripherally selective dopamine D2 and D3 receptor antagonist. The drug provides relief from nausea by blocking D2R at the CTZ at the floor of the fourth ventricle. It increases motility in the upper gastrointestinal tract to a moderate degree and increases lower esophageal sphincter pressure by blocking dopamine receptors in the gastric antrum and the duodenum.

The antiemetic action of metoclopramide is due to its antagonist activity at D2R in the CTZ in the central nervous systes. At higher doses, 5HT3R antagonist activity at the CTZ may also contribute to the antiemetic effect.

The gastroprokinetic activity of metoclopramide is mediated by muscarinic activity, dopamine D2R antagonist activity and serotonin 5HT4R agonist activity. The gastroprokinetic effect itself may also contribute to the antiemetic effect. Metoclopramide also increases the tone of the lower esophageal sphincter.

Antimuscarinic
Block AchR at VC.
{Transderm-V] Scopolamine patch

Cannabinoids
{Cesamet} Nabilone 1-2mg PO BID
{Marinol} Dronabinol 2.5mg PO BID

Inflammation
{Decadron} Dexamethasone 2-4mg PO/IV/SQ OD-QID

Anticonvulsant
{Tegretol} Carbamazepine 25-50mg PO/IV/PR q6-8h

Question 6

Constipation

Pathophysiology

Answer 6

Constipation

Question 7

Constipation

Answer 7

RECIPERE]

P/Org (gastrointestino)]
First Line
Softener
​{Restoralax, Peg-Lyte} PEG 240mL PO q10min
Lactulose 15-30mL or 10-20g PO daily
{Colace} Docusate 240mg PO daily
Note: Colace reduces surface tension of the oil-water interface of the stool resulting in enhanced incorporation of water and fat allowing for stool softening. Colace not used anymore as an approved softener.

Stimultent
{Senokot} Senna 2 tabs, 1 tsp, 10-15mL PO
{Dulcolax} Bisacodyl 5-15mg PO PRN
Cascara 5mL PO QHS

Second Line
Rectal Suppository and Enema
{Dulcolax} Bisacodyl 10mg PR PRN
{Fleet enema} Sodium Phosphate

Third Line
Manual enema
{Relistor} Methylnaltrexone 38kg-61kg 8mg SQ, if opioid induced constipation

Question 8

Constipation

Oral Laxative Classification

Answer 8

Oral Laxative Classification

Question 9

Recipere

Bowel Obstruction

Answer 9

RECIPERE}

NP/ Nut] NPO, NG tube

P/Poine]
{Buscopan} Scopolamine butylbromide 10-20mg PO/IV q4-6h
Note: Anticholergic and an antispasmatic.
P/Naus, Vom]
Haloperidol 0.5-1.0mg SC/PO q8-12h
P/Org (Gastrointestino)]
Octreotide 100microg SC BID-TID
Note:
P/Infla]
Dexamethasone 2-4mg SC/IV OD-BID

**Avoid the serotonin antagonists, and prokinetics in complete bowel obstruction.

In Partial Bowel Obstruction consider a prokinetic such as Metoclopramide 10-20mg SC/IV q4-6h