What Are Postoperative Nausea and Vomiting?
Postoperative nausea and vomiting (PONV) are frequent complications occurring within the first 24-48 hours after surgical procedures under general or regional anesthesia. They affect 30% of surgical patients overall and up to 80% of high-risk patients.
PONV is consistently ranked by patients as one of the most undesirable side effects of surgery — many consider it worse than postoperative pain itself. Beyond the discomfort, it can cause complications such as dehydration, suture dehiscence, pulmonary aspiration, and prolonged hospitalization.
Effective prevention and treatment of PONV are priorities in modern anesthesiology, with a multimodal approach based on individual patient risk stratification.
Frequent Complication
Affects 30% of surgical patients overall and up to 80% of high-risk patients. It is the second most common cause of postanesthetic dissatisfaction.
Vomiting Center
PONV results from activation of the vomiting center in the brainstem by multiple afferent pathways: vestibular, vagal, pharyngeal, and the chemoreceptor trigger zone.
Multimodal Prevention
The modern approach combines risk stratification, reduction of triggering factors, and stepwise pharmacologic prophylaxis.
Pathophysiology
Vomiting is a complex protective reflex coordinated by the vomiting center, located in the lateral reticular formation of the medulla. This center receives afferents from multiple sources: chemoreceptor trigger zone (area postrema), vestibular system, visceral vagal nerves, and higher cortical centers.
In PONV, the main stimuli include the action of anesthetics and opioids on the chemoreceptor trigger zone (rich in dopaminergic D2, serotonergic 5-HT3, and neurokinin NK1 receptors), vagal stimulation by surgical manipulation, and vestibular activation by position changes.
Risk Factors
The Apfel score is the most widely used risk-stratification system, including four independent factors: female sex, nonsmoker status, history of PONV or motion sickness, and use of postoperative opioids. Each factor present increases risk by approximately 20%.
Anesthetic factors include the use of inhalational anesthetics, nitrous oxide, and neostigmine. Surgical factors include longer surgeries, laparoscopic, otologic, gynecologic, and strabismus surgeries.
Symptoms
PONV typically manifests in the first 24 hours after surgery, with peak incidence in the first 2-4 hours. Nausea may occur in isolation or precede vomiting episodes. In some patients, symptoms may persist for 48-72 hours.
PONV Manifestations
- 01
Postoperative nausea
Subjective sensation of gastric discomfort and the urge to vomit. Can be as debilitating as vomiting itself.
- 02
Vomiting and retching
Forced expulsion of gastric contents. Retching consists of rhythmic contractions of the abdominal musculature without expulsion of contents.
- 03
Early vs late PONV
Early PONV (0-2h) is related to anesthetics; late PONV (2-24h) is more associated with opioids and patient factors.
- 04
Sialorrhea and pallor
Excessive salivation, pallor, and cold sweats frequently accompany intense nausea.
- 05
Dehydration
Repeated vomiting can cause dehydration, electrolyte disturbances, and delay in resumption of oral intake.
Diagnosis and Risk Stratification
Diagnosis of PONV is clinical and obvious. The most relevant aspect is preoperative risk stratification, which allows planning of adequate prophylaxis. The simplified Apfel score classifies patients into low, moderate, and high risk.
It is important to rule out mechanical causes of postoperative vomiting, such as bowel obstruction or paralytic ileus, especially in abdominal surgeries. Vomiting persisting after 48 hours should be investigated.
APFEL SCORE AND MANAGEMENT
| RISK FACTORS | ESTIMATED RISK | PROPHYLACTIC STRATEGY |
|---|---|---|
| 0 factors | ~10% | No routine prophylaxis |
| 1 factor | ~20% | Consider 1 antiemetic |
| 2 factors | ~40% | Prophylaxis with 1-2 antiemetics |
| 3 factors | ~60% | Multimodal prophylaxis (2-3 agents) |
| 4 factors | ~80% | Aggressive multimodal prophylaxis + TIVA |
DIAGNÓSTICO DIFERENCIAL
Diagnóstico Diferencial
Anesthetic-Drug-Induced Nausea
- Opioids and nitrous oxide are risk factors
- Positive Apfel score
- Immediate postoperative context
Testes Diagnósticos
- Apfel score for PONV
Postoperative Paralytic Ileus
- Absence of bowel sounds
- Abdominal distention
- No passage of flatus
Testes Diagnósticos
- Abdominal radiograph
- CT if obstruction is suspected
Upper Gastrointestinal Bleeding
- Vomiting with blood or hematemesis
- Hypotension
- Previous abdominal surgery
- Postoperative hematemesis = urgent endoscopy
Testes Diagnósticos
- Urgent endoscopy
- Complete blood count
Postoperative Bowel Obstruction
- Postsurgical adhesions and bands
- Distention and abdominal pain
- No passage of flatus/stool
- Obstruction = urgent surgery
Testes Diagnósticos
- Abdominal CT
Hyponatremia
- Nausea + headache + postoperative confusion
- Excessive hypotonic fluids
- Serum sodium < 135
- Severe hyponatremia = urgent slow correction
Testes Diagnósticos
- Serum electrolytes
Paralytic Ileus and Bowel Obstruction: Serious Surgical Complications
Postoperative paralytic ileus is the most common cause of persistent nausea after abdominal surgery. It results from temporary inhibition of intestinal motility by neuroendocrine reflexes, surgical manipulation, and opioid use. The bowel does not propel food and gas normally — absence of bowel sounds, abdominal distention, and inability to pass flatus are the characteristic signs. It generally resolves in 3-5 days with fasting, early ambulation, and pain control with opioids minimized.
Bowel obstruction from postsurgical adhesions (bands) is a more serious complication that requires intervention. Nausea and vomiting with progressive abdominal distention, complete absence of gas and stool passage, and persistent colicky pain point to mechanical obstruction. Contrast-enhanced abdominal CT is the test of choice to differentiate paralytic ileus from mechanical obstruction and to determine the need for urgent surgery.
Gastrointestinal Bleeding and Hyponatremia: Emergencies That May Mimic PONV
Postoperative upper gastrointestinal bleeding — from stress ulcer, anastomotic dehiscence, or surgical-stump bleeding — may initially manifest as nausea and vomiting. The presence of hematemesis (vomiting with blood), hypotension, tachycardia, or a drop in hematocrit are alarm signs that require urgent upper gastrointestinal endoscopy. Patients undergoing major abdominal surgery, especially with NSAID use in the perioperative period, are at increased risk.
Hyponatremia is a metabolic cause of postoperative nausea that can be confused with simple PONV. Excessive administration of hypotonic solutions, postoperative syndrome of inappropriate ADH secretion (SIADH), and electrolyte losses are frequent mechanisms. Nausea associated with headache, mental confusion, and muscle weakness in the postoperative context should prompt immediate electrolyte measurement. Severe hyponatremia (sodium < 125 mEq/L) can cause seizures and is a clinical emergency.
Risk Stratification: The Apfel Score as a Diagnostic Tool
The Apfel score is the instrument most widely used to stratify the risk of PONV before surgery, with four factors: female sex, nonsmoker, prior history of PONV or motion sickness, and postoperative opioid use. The score (0-4) determines the intensity of antiemetic prophylaxis — from no intervention (score 0) to aggressive multimodal prophylaxis (score 3-4). Identification of preoperative risk is an essential part of diagnosis and management.
Beyond the Apfel score, anesthetic factors contribute significantly: inhalational anesthesia with volatile agents (sevoflurane, desflurane) versus total intravenous anesthesia (propofol); use of nitrous oxide; duration of surgery; and type of surgery (laparoscopy, gynecologic, and otorhinolaryngologic surgeries carry higher risk). The anesthesiologist should document and communicate these factors to the medical team that will follow the postoperative course.
Treatment
The modern approach to PONV is multimodal, combining reduction of baseline risk factors (total intravenous anesthesia, opioid minimization) with stepwise pharmacologic prophylaxis and complementary therapies.
Baseline Risk Reduction
Total intravenous anesthesia (TIVA) with propofol, avoidance of nitrous oxide and inhalational anesthetics, opioid minimization with multimodal analgesia, adequate hydration.
Pharmacologic Prophylaxis
Dexamethasone 4-8 mg at induction, ondansetron 4 mg at the end of surgery. In high risk: add droperidol or transdermal scopolamine.
Rescue Treatment
Use an antiemetic of a class different from prophylaxis. If prophylaxis included ondansetron, use droperidol or promethazine as rescue.
Complementary Therapies
Acupuncture/acupressure at point PC-6, ginger, isopropyl alcohol aromatherapy. May be associated with pharmacotherapy.
Acupuncture as Treatment
Acupuncture at point PC-6 (Neiguan) is one of the interventions with the highest level of evidence in all of medical acupuncture. The Cochrane Collaboration published a systematic review demonstrating significant efficacy of PC-6 stimulation in the prevention and treatment of PONV.
Point PC-6 is located on the anterior aspect of the forearm, between the tendons of the palmaris longus and flexor carpi radialis muscles, two finger-widths above the wrist crease. Its stimulation can be performed by needles, acupressure (wristbands), electroacupuncture, or transcutaneous electrical stimulation.
Proposed mechanisms include vagal modulation, regulation of emetic centers in the brainstem, release of endorphins, and modulation of serotonergic receptors. Systematic reviews describe that PC-6 stimulation, when used as an adjunct, has a magnitude of effect close to that of pharmacologic antiemetics in PONV prevention — the indication, however, is complementary and does not replace the pharmacologic prophylaxis prescribed by the anesthesiologist.
Prognosis
PONV is a self-limited condition in the great majority of cases, resolving within 24-48 hours. With adequate prophylaxis based on risk stratification, incidence can be reduced from 80% to 10-20% in high-risk patients.
Severe complications are rare but include pulmonary aspiration (especially in patients with reduced level of consciousness), severe dehydration, abdominal suture dehiscence, and pneumomediastinum from vigorous emetic effort.
Patients with a history of PONV in previous surgeries are at elevated risk in future procedures. Detailed documentation of PONV occurrence and the strategies that worked is essential for planning subsequent surgeries.
Myths and Facts
Myth vs. Fact
Postoperative nausea is inevitable after general anesthesia
With adequate multimodal prophylaxis, the incidence can be reduced significantly. Total intravenous anesthesia with propofol and multimodal analgesia can reduce risk by more than 50%.
A single medication resolves PONV in all patients
No single antiemetic is sufficient for all patients. The multimodal approach — combining agents from different classes — is more effective, since it acts on multiple receptors involved in emesis.
Prolonged fasting before surgery prevents PONV
Prolonged fasting beyond what is necessary does not reduce PONV and may even worsen it through dehydration and hypoglycemia. Current guidelines recommend clear liquids until 2 hours before anesthesia.
Acupressure wristbands are just placebo
The Cochrane review demonstrated that PC-6 stimulation (used by the wristbands) is superior to placebo for preventing PONV. The mechanism involves vagal modulation and modulation of cerebral emetic centers.
When to Seek Help
Mild nausea in the first 24 postoperative hours is common. However, persistent or severe symptoms require medical attention for adequate treatment and exclusion of complications.
Frequently Asked Questions about Postoperative Nausea and Vomiting
PONV (Postoperative Nausea and Vomiting) is a common complication of anesthesia and surgery, affecting 20-30% of all operated patients and up to 70-80% of high-risk patients (high Apfel score). It occurs in the first 24 hours after surgery and results from activation of the vomiting center in the brainstem by multiple stimuli: volatile anesthetic agents, opioids, gastrointestinal manipulation, hypotension, and pain. It is one of the most common causes of dissatisfaction with surgery and delayed hospital discharge.
The Apfel score identifies the four main risk factors: female sex (doubles the risk), nonsmoker, prior history of PONV or motion sickness, and use of postoperative opioids. Additional factors include: inhalational anesthesia with volatile agents, use of nitrous oxide (N₂O), prolonged surgeries (>1h), type of surgery (laparoscopy, gynecologic, otorhinolaryngologic), history of elevated anxiety, and prolonged preoperative fasting.
Yes. Acupressure and electroacupuncture at point PC-6 (Neiguan, located on the wrist) have robust evidence and are recognized by the Cochrane review as effective adjuncts for reducing postoperative nausea — with a magnitude of effect of an order comparable to that of antiemetics such as ondansetron in some studies. In practice, they are used as a complement to the pharmacologic antiemetic prophylaxis prescribed by the anesthesiologist, not as a substitute. Point PC-6 modulates the nucleus of the solitary tract and the vagus, reducing the nauseous reflex.
Opioids stimulate μ receptors in the chemoreceptor trigger zone (CTZ) of the brainstem, which directly activate the vomiting center. They also delay gastric emptying, cause orthostatic hypotension (which amplifies nausea), and increase vestibular sensitivity. Morphine, fentanyl, and tramadol are the most emetogenic. Reducing the opioid dose — using multimodal analgesia with NSAIDs, dipyrone, and regional blocks — is one of the most effective strategies for reducing PONV.
First-line antiemetics include: ondansetron and other 5-HT3 antagonists (excellent for prophylaxis and rescue); dexamethasone 4-8 mg IV (very effective at anesthetic induction); droperidol and haloperidol (dopaminergic blockers); and dimenhydrinate/promethazine (antihistamines). For high risk (Apfel 3-4), multimodal prophylaxis — combining two or three agents — is recommended by SAMBA guidelines. PC-6 acupuncture/acupressure can be added as a fourth component.
Yes, especially intense vomiting in the immediate postoperative period. Complications include: dehydration and electrolyte imbalance (especially in prolonged surgeries); pulmonary aspiration of gastric contents (greater risk with reduced consciousness); abdominal suture dehiscence from repeated effort; increased intracranial pressure (contraindicated in neurosurgery); tension on the anastomosis after gastrointestinal surgery; and significant delay in recovery and hospital discharge. Prophylactic management is preferable to rescue.
Yes, significantly. Propofol, the main TIVA agent, has intrinsic antiemetic properties — it reduces PONV by 20-30% compared to inhalational agents. TIVA eliminates exposure to volatile agents (halogenated) and to nitrous oxide, the main anesthetic risk factors for PONV. In high-risk patients (Apfel ≥2), TIVA is recommended as the preferred strategy by international anesthesia guidelines.
Most cases of PONV resolve within 24-48 hours. Nausea in the first 2-6 hours is more related to the acute effect of anesthetics; late nausea (6-24h) is more influenced by opioids and by the return of gastrointestinal motility. In high-risk patients without adequate prophylaxis, symptoms may persist for 48-72 hours. With adequate multimodal prophylaxis, incidence is reduced by 70-80% and duration of episodes is significantly shorter.
Yes. Prolonged fasting (>8h for liquids) causes hypoglycemia, relative dehydration, and increases preoperative anxiety — all factors that amplify nausea. Modern anesthesia guidelines recommend ingestion of clear liquids (water, pulp-free juice, tea) until 2 hours before surgery, and solids until 6 hours before. This approach (liberal fasting) reduces PONV incidence without increasing aspiration risk and improves patient comfort and recovery.
Always inform the medical and anesthesia team about your PONV history before any surgical procedure — this information is critical for planning. The anesthesiologist may opt for: total intravenous anesthesia (TIVA) with propofol; multimodal antiemetic prophylaxis (ondansetron + dexamethasone + droperidol); minimization or elimination of opioids with multimodal analgesia; and preventive PC-6 acupressure/electroacupuncture. The combination of these strategies significantly reduces recurrence.
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