CHAPTER 25. Postoperative Nausea and Vomiting
Susan Jane Fetzer
OBJECTIVES
At the conclusion of this chapter, the reader will be able to:
1. Differentiate nausea, vomiting, and retching.
2. Describe the phases of perianesthesia-related nausea and vomiting.
3. Determine a patient’s risk of experiencing postoperative nausea and vomiting (PONV).
4. Describe the difference between prophylactic and rescue therapy for PONV.
5. List five categories of PONV drugs that work on the chemoreceptor zone.
6. List five nursing interventions in the care of the patient at high risk for PONV or postdischarge nausea and vomiting (PDNV).
7. Describe the importance of risk-adjusted multimodal therapy for PONV.
I DEFINITIONS
A Nausea
1. Subjective sensation in back of throat or epigastrium
2. Conscious cortical activity
3. Conscious awareness of the need to vomit
4. No expulsive muscular movements
5. May not culminate in vomiting
6. Synonyms: sick to my stomach, upset stomach, butterflies, queasy
B Vomiting
1. Objective forceful evacuation of gastric contents through oral or nasal cavity
2. Autonomic reflex directed by brainstem
3. May or may not be preceded by nausea
4. Coordinated muscular movements
5. Associated with physiological changes
a Increased heart rate
b Increased respiratory rate
c Sweating
6. Synonyms
a Pitching
b Barfing
c Ralphing
d Upchucking
e Puking
C Retching
1. An attempt to vomit
2. Nonproductive
3. Synonyms
a Dry heaves
b Gagging
D Vomiting and retching also termed emetic episodes
E PONV
1. Defined as nausea, vomiting, and retching separately or combined
2. Occurs within first 24 hours after inpatient surgery
3. Early PONV: First 2 to 6 hours after surgery
4. Late PONV: After transfer to the postoperative unit, 6 to 24 hours after surgery
F PDNV
1. Occurs after discharge from health care facility
G Delayed PDNV
1. Occurs 24 hours after surgery
II CONSEQUENCES OF PONV
A Physiological
1. Surgical site disruption
2. Esophageal tears
3. Gastric herniation
4. Fatigue
5. Dehydration
6. Electrolyte imbalance
7. Airway compromise with aspiration
8. Increased intracranial pressure
9. Increased ocular pressure
B Delay of oral nutrition and drug therapy
1. Poor pain management
2. Interference with diabetic and antihypertensive drug regimens
3. Potential for dehydration
C Increased costs
1. Each vomiting episode delays discharge from post anesthesia care unit by an average of 20 minutes.
2. Cost of treating vomiting is three times greater than cost of treating nausea.
3. Readmission
4. Increased length of stay
5. Increased cost of complications
6. Delay in resuming activities of daily living
7. Increased nursing time
D Patient satisfaction
1. PONV is among top 10 most undesirable outcomes after surgery.
III ETIOLOGY OF PONV
A Nature of PONV is multifactorial.
B Vomiting center (VC)
1. Located in the lateral reticular formation, medulla (mid brainstem) of the brain
2. Composed of three major nuclei
a Nucleus tractus solitarius
b Dorsal motor nucleus of the vagus nerve
c Nucleus ambiguous involved with coordination of motor activity during vomiting
3. Stimulated by multiple afferent sensory inputs
a Chemoreceptor triggering zone (CTZ)
b Pharyngeal nerve input
(1) Stimulated by mechanical irritation
(2) Gagging can result in retching and vomiting.
c Vagus mucosal pathways from gastrointestinal system
(1) Mechanical receptors in stomach sensitive to distention and contraction
(2) Chemoreceptors in duodenum and stomach sensitive to noxious substances
(3) Vagal afferents also located in eye and oropharynx
(a) Manipulation of the eye can result in VC stimulation.
(b) Oropharyngeal suctioning can result in VC stimulation.
d Midbrain afferent pathways
(1) Stimulated by increased intracranial pressure
e Neuronal pathways from vestibular apparatus
(1) Direct stimulation from cranial nerve VIII
f Reflex afferent pathways from the cerebral cortex
(1) Learned response of anticipatory nausea and vomiting
(2) Cortical afferent stimulation
(a) Emotional: stress, anxiety, fear
(b) Sights and sounds of surgical suite
4. Chemoreceptors located in VC
a Cholinergic
b Histaminic
c Opioid (mu)
d Neurokinin 1 (NK1)
5. Response of VC to multiple inputs is activation of efferent motor pathways of vomiting reflex.
a Gastric efferent response
b Respiratory efferent response
C CTZ
1. Located in area postrema on floor of fourth ventricle of brain
2. Adjacent to VC
3. Very vascular, making it sensitive to decreased blood flow (e.g., hypotension)
4. Outside the blood-brain barrier, making it responsive to emetogenic substances in blood or spinal fluid such as:
a Uremia, hypercalcemia
b Antineoplastic drugs
c Blood sugar fluctuations
d Hormonal influences
e Serum narcotic level
f Inhalation anesthetics
g Levels of dopamine and serotonin
5. Sensitive to intracerebral pressure
6. Contains chemoreceptors
a Serotonin type 3 (5-hydroxytryptamine, 5-HT 3)
b Dopamine type 2 (D 2)
c Histamine type 1 (H 1)
d Muscarinic cholinergic type 1 (M 1)
e Mu opioid
f Stimulation of CTZ chemoreceptors results in stimulation of VC
7. Point of entry of vagal afferent nerve pathways
a Receives vagal stimulation resulting from noxious substances in gut and stomach
b Vagal stimulation triggers serotonin receptors.
c Stimulation of vagal afferents during perianesthesia period creates PONV through CTZ.
(1) Opioids delay gastric emptying, promoting distention and vagal stimulation.
(2) Handling abdominal contents during surgery promotes vagal stimulation.
(3) Pneumoperitoneum secondary to laparoscopic procedures results in vagal stimulation.
(4) Intestinal ischemia creates vagal stimulation.
(5) Vagal stimulation results in serotonin release in GI tract.
8. Point of entry for vestibular afferent pathways
a Changes in motion and pressure increase vestibular activity.
b Vestibular apparatus of inner ear triggers histamine receptors.
(1) Mechanism that creates motion sickness
(2) Mechanism that results in PONV during rapid position changes
c Believed mechanism initiated by nitrous oxide
9. Point of entry for cortical afferent pathways
a Cortical emotional input & stress, anxiety, depression, fear, cognitive overload
b Physiological & hypoxia, pain, hypotension, intracranial pressure
c Sensory input & sight, sound, smell
d Nucleus tractus solitarius (NTS)
10. Physical proximity to CTZ
11. Major site of vagal afferents from vestibular apparatus
12. Contains chemoreceptors
a D 2
b 5-HT 3
c H 1
d M 1
e Vomiting reflex
1. Efferent output of VC
14. Vomiting occurs in three phases.
a Preejection phase
(1) Increase in salivation and swallowing
(2) Decrease in gastric tone
(3) Pallor, diaphoresis
(4) Tachycardia
(5) Regurgitation of small intestine content into stomach
(6) Mediated by vagus nerve and acetylcholine
b Ejection phase
(1) Respiratory inhibition
(2) Closure of glottis to prevent aspiration
(3) Elevation of soft palate
c Postejection phase
(1) Associated with relief of nausea
IV INCIDENCE OF PONV
A PONV occurs in one third of all patients undergoing surgery with anesthesia.
B Up to 80% incidence among patients with predetermined risk factors
C Incidence of PDNV up to 50%
D Patients with PONV are four times more likely to have PDNV.
E More than one third of patients with PDNV will not have PONV.
V RISK FACTORS FOR PONV
A Independent risk factors
1. Independent predictors of PONV
2. Gender
a Females at two to four times higher risk starting at puberty
b No gender difference before puberty
c Unknown relationship of PONV to progesterone, estrogen, and gonadotropin hormonal levels
d Hormonal fluctuation in menstrual cycle may be responsible for PONV differences among women.
e Research has disapproved increased susceptibility during first week of menstrual cycle.
3. Positive history of motion sickness or previous PONV
a Riding in car, plane flight, boat travel
b History of PONV in parent or sibling may be a risk factor.
c Patients with motion sickness appear to have a well-developed vestibular reflex arc.
d Increases risk of PONV two to three times
4. Smoking status
a Nonsmokers at 1.5 to 2.5 times higher risk
b Chemical composition of cigarettes believed to increase hepatic enzyme activity to increase metabolism of anesthesia.
5. Use of postoperative opioids
a Long-acting opioids appear to increase risk.
b Morphine associated with more PONV than fentanyl
B Associated patient risk factors
1. Factors that are not strong enough to predict PONV but are associated with an increased risk
2. Age
a Risk of vomiting in children up to 42%
b Risk increases in children older than 2 years.
c Higher risk in school-age children aged 6 to 16 years, up to 51%
d Female gender adds greater risk after puberty.
e Risk stabilizes in adulthood and is decreased after age 70.
3. Presence of delayed gastric emptying/increased gastric volume
a Pregnancy
b Neurological disease
c Diabetes
d Measurement of delayed emptying is unavailable.
e Degree of PONV risk is not known.
f Obesity (body mass index) has been disproved as a PONV risk factor.
4. American Society of Anesthesiologists (ASA) status
a Healthier patients appear to be at higher risk.
b ASA 1 greater risk than ASA 3
5. Anxiety
a Preoperative anxiety is a weak predictor of PONV.
b Increased circulating levels of catecholamines may stimulate receptors.
c Air swallowing increases gastric volume and decreases gastric motility.
d Anxiety has not been shown to be a risk factor for children.
6. Pain
a Excessive pain increases the risk of PONV.
b Use of nonsteroidal anti-inflammatory agents to reduce need for opioids can lower risk of PONV.
c History of migraine is a possible risk for postoperative nausea.
7. Preoperative fasting
a More liberal criteria for clear liquids appear to reduce incidence of PONV.
b Positive relationship exists between length of liquid fast and incidence of PONV.
c ASA recommendations allowing healthy adults to drink clear liquids as little as 2 hours before surgery are beneficial in PONV.
d A 35% reduction in systolic blood pressure during anesthesia induction is associated with an increased incidence of PONV.
C Associated surgical risk factors
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1. Factors not strong enough to predict PONV but associated with an increased risk
2. Surgery duration
a Longer duration of surgery increases the risk.
b Each 30-minute increase in outpatient surgical time increases baseline risk by 60%.
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