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What causes
Nausea and Vomiting ?
Both nausea and vomiting
result from stimulation of the vomiting centre located in
the brain stem. This centre can be activated in two ways
- chemically and neurally. Chemical activation is
mediated via the chemoreceptor trigger zone
(CTZ) that is sensitive to the presencd of toxins and
poisons in the blood stream. Neural activation occurs as
a result of information coming directly from the frontal
lobes of the brain, the digestive tract and balancing
mechanism of the inner ear.
Stimulation of the vomiting
centre causes hypo-motility and reverse- motility of the
digestive tract. The diaphragm presses down on the
stomach and the abdominal walls move inwards, forcing the
stomach contents out through the oesophagus. As this
happens, the epiglottis clamps down upon the voice-box,
thus preventing vomit from entering the wind-pipe.
Identification
of Cause.
The seriousness of vomiting
depends upon its cause. It may be caused by overeating or
drinking too much or by a viral infection. Alternatively,
it may follow head injury or poisoning. Careful attention
has to be paid in the following situations:
* Head injury
* Blood in the vomit
* Temperature is more than
38degreeCelcius
* Diarrhoea and continuous
stomach pain
* Stomach pain not relieved
by vorniting
* Chronic and unresponsive
Situation &
Conditions to be suspected
Overindulgence in food, drinks or intake
of drugs -- Gastric Irritation.
Consumption of bad food; similar symptoms
seen in those who shared the food -- Food Poisoning
Diarrhoea with or without rise in
temperature -- Gastoentiritis
Vomit contains blood or brown-black
material resembling coffee grounds -- Bleeding in the
Gastroentestinal tract.
Abdominal pain not relieved by vomiting --
Appendicitis, Perforation of duodenal ulcer,
Pancreatitis.
Colicky pain -- Gall Stones.
Jaundice -- Hepatitis
Headache, drowsiness, difficulty in
looking towards light; pain when bending the neck --
Meningitis
Pain in and around one eye with blurred
vision -- Glaucoma.
Young woman who has missed her period --
Pregnancy
While travelling -- Motion Sickness
Accident, trauma -- Head Injury, hematoma
in the stomach
Vomiting during pregnancy
usually begins in the sixth week and peaks during the
tenth week. Drug therapy should be avoided as far as
possible. In severe cases, promethazine and
doxylamine can be used as they are
apparently free from teratogenic effects.
Drugs that commonly
cause nausea and vomiting
Allopurinol
Antibiotics
Bromocriptine
Cytotoxics
Digoxin
Gold
Iron
Levopa
NSAIDS( Nonsteroid anti inflamatory drugs)
Oestrogens
Opiates
Penicillamine
Quinidine
Sulphasalazine
Theophyline
Thiazides
.
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NAUSEA is the
sensation that precedes vomiting.
VOMITING is the
involuntary foreem expulsion of stomach contents through
the mouth. In most cases, the explanation is simp le like
irritation of the stomach by food or overindulgence in
food and alcohol. Both are common complaints and are
usually self-limiting. However, attention has to be paid
to fluid balance and referral to hospital should be
considered in case of dehydration and weight loss. If
symptoms persist, a full examination of the patient is
mandatory to look for serious underlying pathologies.
Stimulation of the vomiting centre causes
hypo-motility and reverse- motility of the digestive
tract. The diaphragm presses down on the stomach and the
abdominal walls move inwards, forcing the stomach
contents out through the oesophagus. As this happens, the
epiglottis clamps down upon the voice-box, thus
preventing vomit from entering the wind-pipe.
Management
The patient must be asked not
to eat any solid food until nausea and vomiting subsides.
He must be en couraged to take small sips of water to
prevent dehydration. When the stomach settles, he should
be advised to eat dry food like biscuits and toast before
resuming normal diet. Attention has to be paid to fluid
and electrolyte balance. Signs of dehydration include
severe thirst, dry lips and tongue, sunken eyes , loss of
skin elasticity, increased heart and respiratory rate,
muscle cramps, lethargy, confusion and headache. If
patient cannot take anything by mouth, intravenous fluids
should be considered and the water salt balance should be
carefully monitored by blood tests.
Medication
Drugs to manage nausea and
vomiting are of two types: those that act directly on the
digestive tract and those that act centrally. Drugs that
act on the digestive tract increase intestinal
contraction and accelerate transit. Centrally acting
agents act at the vomiting centre or chemoreceptor
trigger zone (CTZ) located in the brainstem and block
impulses that induce nausea and Vomiting.
DOPAMINE ANTAGONISTS
(prochlorperazine, metoclopramide,
domperidone) act against D2 receptors in
the brain stem (CTZ).
Prochlorperazine is a
phenothazine possessing powerful antiernetic activity. In
addition to CTZ, it also acts at the vomi ting centre. It
is used for nausea and vomiting due to various causes
including migraine. Metoclopramide has a peri- pheral
action on the gut and enhances gastric hurrying in
addition to its effect on CTZ. Domperidone, unlike
metoclopramide, does not cross the blood-brain barrier
and may cause fewer extrapyramidal side-effects at high
doses, eg. dystonia in children and parkinsonism in
elderly.
ANTIHISTAMINES
(promethazine, diphenhydramine,
cyclizine, cinnarizine)
act on the vestibular apparatus of the inner ear and are
useful in motion sickness and vomiting due to vestibular
disease.
ANTISEROTONIN
agents like ondansetron act on
peripheral and central serotonin Acceptors and are
valuable in the management of nausea and voming not
relieved by conventional, less expensive agents.
ANTICHOLINERGICS
act on the vomiting centre and digestive tract and reduce
gastrointestinal hyperactivity. They help in the
management of mo- tion sickness but can cause dry mouth,
drowsiness and blurred vision. All motion sickness drugs
are effective if given before the journey. Once the
sickness has started, the symptoms are more difficult to
control.
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