Vomiting

Question 1

VOMITING PHASES

Answer 1

Nausea Retching Expulsion

Question 2

PHASE 1 – NAUSEA

Answer 2

Or … Prodromal Phase Clinical Signs

Ptyalism
Hiding
Seeking attention

Yawning

Shivering Tachycardia Pallor

Question 3

PHASE 2 - RETCHING

Answer 3

Abdominal muscles, chest wall and diaphragm all contract without any expulsion of gastric contents

Retrograde contractionduodenal contents into stomach

Deep inspiratory movements Respiratory center is inhibited

Question 4

PHASE 3 – FORCEFUL EXPULSION

Answer 4

Stomach does not actively expel

Stomach, esophagus, and & sphincters relaxed during vomiting

Force that expels arises from the contraction of the diaphragm & abdominal muscles

Question 5

What is the pathway for vomiting?

Answer 5

Question 6

PHYSIOLOGY OF VOMITING

Answer 6

Activation of chemoreceptors & mechanoreceptors
Stimulation of visceral afferent receptors (5-HT3; NK-1)
Direct stimulation of the cerebral cortex & limbic system – fear, stress, trauma Vestibular system stimulation (M1-cholinergic; H1-histaminergic)

CRTZ (Chemoreceptor Trigger Zone)
Simulated by vestibular system
Many receptors
Free nerve endings bathed in CSF - lacks BBBstimulated by ‘emetogens’

Question 7

Kinetosis’

Answer 7

Motion sickness = ‘Kinetosis’

Inner ear/labyrinth stimulationdopamine and serotonin released from CRTZ activationAch released from emetic center

Drugs such as chemo-agents
5-HT3 Serotonergic Receptors & CRTZ

Question 8

ACUTE VOMITING & ‘NOT ILL’

Answer 8

Medical Management

Antacid +/- fluid therapy and time

Anti-nausea can suppress normal vomiting response to expel FB Don’t mask with meds

Water and food

No water for 6-8 hours then small frequent amounts working back to normal over 24-48 hours

If no vomiting, small meals every 4-6 hours for day 1 with bland diet (i.e. chicken and rice or cooked beef and rice) or prescription diet

Question 9

WHY SYMPTOMATIC TREATMENT ?

Answer 9

We don’t always have the immediate answer -support while we embark of diagnostic process

Dehydration
-can be progressive & debilitating

Patient comfort
-nausea, abdominal pain

Electrolyte imbalances
-can lead to systemic consequences if left untreated

Question 10

H2 RECEPTOR ANTAGONISTS

Answer 10

Affects gastric parietal cell receptors
Limits acid secretion (antacid) with mild to little affect on pH

Famotidine
0.5 - 1 mg/kg PO BID

Ranitidine (also prokinetic)
1-2 mg/kg IV, PO, SQ, IM BID-TID 2.5 (IV) -3.5 (PO) mg/kg BID

Cimetidine – more Rx interactions than above 2

Question 11

PROTON PUMP INHIBITOR

Answer 11

Gastric proton pump inhibitor antacid

Inhibits transport of hydrogen ions into the stomach

Inhibits the hepatic cytochrome P-450 mixed function oxidase system

Must check for drug interactions

Pantoprazole – IV 0.7-1 mg/kg IV SID

Omeprazole - PO 0.5-1 mg/kg SID-BID

Question 12

ANTIEMETIC MEDICATIONS

Answer 12

Block/compete with neurotransmission at the receptor sites associated with emesis

Many off-label – veterinary studies are VERY limited Examples:

Anticholinergics Antihistamines Dopamine antagonists Serotonin antagonists Phenothiazines
NK-1 receptor inhibitors

Question 13

M1-CHOLINERGIC RECEPTOR ANTAGONISTS

Answer 13

Scopalamine – crosses BBB, causes excitement in cats Phenothiazines (Chlorpromazome, Prochlorpromazone) Propantheline & isopropamide – peripheral/PNS action

Not Used Often Sedation Hypotension

Question 14

HISTAMINE ANTAGONISTS

Answer 14

Not helpful for cats – no histamine receptors on CRTZ

EXAMPLES: Diphenhydramine

2.2 mg/kg PO BID-TID or IM Meclizine

4 mg/kg PO once daily
12.5 mg – 50 mg per dog PO SID 6.25-12.5 mg PO per cat PO SID

Cyproheptadine (used more for appetite stimulation)

Question 15

D2-DOPAMINERGIC ANTAGONIST

Answer 15

METOCLOPRAMIDE
Stimulus on movement of distal esophagus cats >> dogs Antiemetic dog >> cat (fewer CNS dopamine receptors) Multiple drug interactions
5-HT3 antagonist & 5-HT4 agonist

SEs: constipation, mentation change
DOSE: IV CRI 1-2mg/kg per DAY (over 24 hours)

PO 0.2-0.5 mg/kg PO, SQ, IM BID-QID

Question 16

5-HT3-SEROTOIN ANTAGONISTS

Answer 16

Work in GI tract & CRTZ

SEs: constipation, fatigue, dry mouth

Examples:
Dolasetron = Anzemet

DOSE: 0.6-1 mg/kg PO, SQ, IV SID Ondansetron = Zofran

DOSE: 0.2-1 mg/kg IV or PO BID-QID (lower IV)

Question 17

NK-1 RECEPTOR ANTAGONISTS

Answer 17

Competes with substance-P Peripherally & centrally

EXAMPLE: Maropitant

SE: ataxia, anorexia, diarrhea, injection soreness, bradycardia w/ high dose

DOSE
Vomiting for any cause

1mg/kg IV SID or 1-2 mg/kg PO SID Higher doses needed for motion sickness

8 mg/kg PO SID
Labeled for 5 days only (SAFE LONGER but OFF LABEL)

Question 18

Sucralfate (CARAFATE)

Answer 18

Sucralfate (CARAFATE)
Stimulates PG E2 & I1 - cytoprotective

Reacts with HCl to form paste which sticks to ulcers Inactivates pepsin & binds bile acids
Binds gastrointestinal phosphorous
Weak antacid

Dose
250-1 gram/pet PO TID-QID
Give 2 hours before or after other meds & food

Question 19

5-HT4 RECEPTOR ACTIVATOR

Answer 19

Gastric emptying & GI motility
Stimulate release of acetylcholine into the enteric n.s LES, stomach, colon

 Examples:
 Cisapride

SEs: V, D, QT interval prolongation  DOSE

Dog 0.1-0.5 mg/kg PO BID-TID, 30 minutes before eating

Cat 2.5 mg PO BID to start (up to 7.5mg PO TID documented)  Metoclopramide

Question 20

MACROLIDE ANTIBIOTIC

Answer 20

Stimulates Motilin Promotes intestinal motility

Initiates phase III of migrating myoelectric complex which propels ingesta

Example: Erythromycin

0.5-1 mg/kg PO TID

Question 21

Cyproheptadine

Answer 21

H1 receptor blocker

Serotonin antagonist

Question 22

MIRTAZAPINE

Answer 22

Tetracyclic Antidepressant Increases NE and thus appetite

5-HT3 antagonist H1-histamine antagonist

Example: MIRTAZAPINE

SEs: Polyphagia, sedation or excitement

Question 23

What is the mechanism by which Cerenia works?

Answer 23

Substance P compeitor at NK-1 receptor