lec 8 Nausea and vomiting Flashcards
The risk factors for PONV include
female gender,
history of motion sickness or PONV,
non-smoking status, and
use of opioids in the postoperative period
Postoperative nausea and vomiting (PONV) occurs in
30% of surgical patients , and in up to 70% of highrisk patient
↑ risk of Postoperative nausea and vomiting (PONV) due to
- disturbing the vagus nerve
- the choice of anesthetic agents
- the duration of surgery.
disturbing the vagus nerve leading to
gastric motility abnormalities
Pregnancy-associated nausea and vomiting is common, affecting
70% to 85% of pregnant women, especially
early in pregnancy
hyperemesis gravidarum due to
raised levels of human chorionic gonadotrophin
lifethreatening condition of prolonged nausea, vomiting
malnutrition weight loss, dehydration
drugs causes nausea and vomiting including
1.Cancer chemotherapy agents
2.Radiation therapy→ abdominal malignancies.
3.Oral contraceptives, hormone therapy, oral hypoglycemic agents, anticonvulsants,
and opiates
4.digoxin and theophylline (bronchodilator
5.Ethanol
Nausea and vomiting stages:
- Nausea
2) retching
(3) vomiting.
Nausea
feeling of a need to vomit
accompanied by autonomic symptoms
autonomic symptoms such as
pallor,
tachycardia,
diaphoresis, and
salivation
Retching
- can occur without vomiting
2.produces the pressure gradient needed for vomiting
no gastric contents are expelled.
Vomiting is a
reflexive,
rapid, and
forceful oral expulsion of upper gastrointestinal contents
Vomiting is due to
First: powerful and sustained contractions in the abdominal and thoracic musculature.
Second: reverse peristalsis accompanied by
Third: relaxation of esophageal sphincters.
Four muscle groups are stimulated in synchronous order to produce vomiting.
- Inspiratory Muscles
- Abdominal Muscles
- Esophageal, gastric, and duodenal muscles
- Esophageal sphincter
Inspiratory Muscles
1.Deep inspiration
↓
negative thoracic pressure to facilitate upchuckingت
Abdominal Muscles
positive intra-abdominal pressure
Esophageal, gastric, and duodenal muscles all undergo
reverse peristalsis.
Esophageal sphincter (LES and UES) must
relax for vomiting to occur.
Regurgitation
- is a passive process without involvement of the abdominal wall and diaphragm
- wherein gastric or esophageal contents move into the mouth
In patients with gastro-esophageal reflux disease (GERD), one hallmark symptom is
acid regurgitation
Autonomic Discharge occurs with vomiting.
Combined
sympathetic / parasympathetic on salivary glands causes hyper-salivation
Chemoreceptor trigger zone (CTZ) located
outside the blood–brain barrier (BBB) in the area postrema of the fourth ventricle of the brain
Chemoreceptor trigger zone (CTZ) is exposed to
to cerebrospinal fluid and blood
Chemoreceptor trigger zone, is easily stimulated by
uremia, acidosis, and the circulation of toxins such as
chemotherapeutic agents
The CTZ has
serotonin type 3 (5-HT3)و neurokinin-1 (NK1),dopamine (D2)
Visceral vagal nerve fibers are rich in
5-HT3 receptors, neurokinin-1 (NK1), and
dopamine (D2) receptor.
Visceral vagal nerve fibers respond to
gastrointestinal distention, mucosal irritation,
and infection
Motion sickness is caused by
stimulation of the vestibular system
the vestibular system contains many
histaminic (H1) and muscarinic cholinergic
receptors
The higher brain (i.e., cerebral cortex) is affected by
sensory input such as sights, smells, or emotions that can lead to vomiting
