Vomiting Flashcards
VOMITING PHASES
Nausea Retching Expulsion
PHASE 1 – NAUSEA
Or … Prodromal Phase Clinical Signs
Ptyalism
Hiding
Seeking attention
Yawning
Shivering Tachycardia Pallor
PHASE 2 - RETCHING
Abdominal muscles, chest wall and diaphragm all contract without any expulsion of gastric contents
Retrograde contractionduodenal contents into stomach
Deep inspiratory movements Respiratory center is inhibited
PHASE 3 – FORCEFUL EXPULSION
Stomach does not actively expel
Stomach, esophagus, and & sphincters relaxed during vomiting
Force that expels arises from the contraction of the diaphragm & abdominal muscles
What is the pathway for vomiting?
PHYSIOLOGY OF VOMITING
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 BBBstimulated by ‘emetogens’
Kinetosis’
Motion sickness = ‘Kinetosis’
Inner ear/labyrinth stimulationdopamine and serotonin released from CRTZ activationAch released from emetic center
Drugs such as chemo-agents
5-HT3 Serotonergic Receptors & CRTZ
ACUTE VOMITING & ‘NOT ILL’
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
WHY SYMPTOMATIC TREATMENT ?
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
H2 RECEPTOR ANTAGONISTS
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
PROTON PUMP INHIBITOR
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
ANTIEMETIC MEDICATIONS
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
M1-CHOLINERGIC RECEPTOR ANTAGONISTS
Scopalamine – crosses BBB, causes excitement in cats Phenothiazines (Chlorpromazome, Prochlorpromazone) Propantheline & isopropamide – peripheral/PNS action
Not Used Often Sedation Hypotension
HISTAMINE ANTAGONISTS
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)
D2-DOPAMINERGIC ANTAGONIST
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
5-HT3-SEROTOIN ANTAGONISTS
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)
NK-1 RECEPTOR ANTAGONISTS
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)
Sucralfate (CARAFATE)
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
5-HT4 RECEPTOR ACTIVATOR
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
MACROLIDE ANTIBIOTIC
Stimulates Motilin Promotes intestinal motility
Initiates phase III of migrating myoelectric complex which propels ingesta
Example: Erythromycin
0.5-1 mg/kg PO TID
Cyproheptadine
H1 receptor blocker
Serotonin antagonist
MIRTAZAPINE
Tetracyclic Antidepressant Increases NE and thus appetite
5-HT3 antagonist H1-histamine antagonist
Example: MIRTAZAPINE
SEs: Polyphagia, sedation or excitement
What is the mechanism by which Cerenia works?
Substance P compeitor at NK-1 receptor
