Basic Monitoring During Anesthesia: Standards and Mandatory Monitoring Parameters
Analysis of basic monitoring standards during anesthesia. Mandatory parameters of oxygenation, ventilation, and hemodynamics for patient safety.
Postoperative Nausea and Vomiting: Definition of Risk Groups and Prevention Principles
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Postoperative nausea and vomiting (PONV) is one of the most common postoperative complications in the early postoperative period after the patient emerges from anesthesia or after surgical intervention. Preventing PONV has significant clinical importance because this complication leads to reduced patient satisfaction with treatment, extended hospital stays, dehiscence of postoperative sutures, dehydration, aspiration of gastric contents, and increased intra-abdominal or intraocular pressure, as well as electrolyte imbalances.
Mechanism of PONV occurrence
Five main neurotransmitter receptors are involved in the occurrence of nausea and vomiting:
- Muscarinic, M1;
- Dopaminergic, D2;
- Histaminergic, H1;
- Serotonergic 5-hydroxytryptamine, 5-HT3;
- Neurokinin-1 (NK1): substance P receptors.
Receptor stimulation can be divided into three groups:
- Central mechanism
During the perioperative period, nausea can be triggered by signals from the brain, such as fear, anxiety, pain, and irritation of the vestibular apparatus (e.g., ear interventions) through stimulation of H1 and M1 receptors. These stimuli activate centers in the brainstem, which include the “vomiting” reflex.
- Peripheral mechanism
In this pathway, PONV is provoked by intestinal surgeries and blood in the gastrointestinal tract: irritation of the stomach and intestines leads to the release of substance P and serotonin from enterochromaffin cells, thereby activating 5-HT3 receptors of the vagus and splanchnic nerves, whose afferent fibers transmit the signal to the chemoreceptor zone of the brainstem.
- Influence of medications
The molecular mechanisms of vomiting induced by medications and toxins are not yet fully understood, but one of the pathways of reaction initiation is the stimulation of the area postrema at the base of the fourth ventricle in the medulla oblongata, which interacts with central pattern generators through dopaminergic and serotonergic receptors.
Understanding the mechanisms of PONV and the role of key neurotransmitter receptors allows for the development and rational application of drugs targeting these sites for the prevention and treatment of postoperative nausea and vomiting.
Predictors of risk for postoperative nausea and vomiting
Patient-dependent risk factors
- Female sex (the strongest overall prognostic factor for PONV);
- History of postoperative nausea and vomiting in the past, seasickness, and motion sickness;
- Non-smoker status;
- Young age (in children, early age has a protective effect: PONV is rare in children under 3 years, increases with age, and then decreases with puberty);
- Family history in pediatric patients (PONV reported in siblings or parents).
Surgical risk factors
- Bariatric surgery;
- Laparoscopic surgery;
- Gynecological surgery;
- Cholecystectomy;
- Strabismus surgery, adenotonsillectomy, otoplasty (considered pediatric age risk factors);
- Duration of surgical intervention > 60 min (> 30 min for pediatric scores).
Anesthesiological risk factors
- Inhalational Anesthetics;
- Nitrous oxide;
- Postoperative opioids.
Predictive models for assessing PONV risk
A number of predictive models or systems have been developed to assess the risk of postoperative nausea and vomiting. The simplified Apfel risk assessment scale for preoperative assessment of adult patients is the most widespread, including four high-prognostic risk factors:
- Female sex is one of the main risk factors.
- Non-smoker status increases the likelihood of developing symptoms.
- Medical history: presence of motion sickness or PONV in the history.
- Opioids: expected use of postoperative opioids.
The presence of 0, 1, 2, 3, and 4 of these risk factors corresponds to a risk of postoperative nausea and vomiting of 10, 20, 40, 60, and 80%, respectively. The Koivuranta risk score, which additionally includes factors such as age and surgery duration, is also widely used.
Risk assessment scales used for adult patients are not applicable to children. The fourth consensus recommendations of 2020 for the treatment of PONV established by ASER (American Society of Enhanced Recovery) and SAMBA (Society for Ambulatory Anesthesia) suggest using an assessment system that includes the following groups of factors:
- Preoperative: age over 3 years, PONV history, family history, postpubertal girls.
- Intraoperative: strabismus surgery, adenotonsillectomy, otoplasty, surgery duration over 30 minutes, inhalation anesthetics, and anticholinergic drugs.
- Postoperative: postoperative administration of opioids.
This scale divides pediatric patients into three risk groups: low (absence of factors), medium (1–2 factors), and high (3 or more factors).
Principles of PONV prevention
PONV prevention is based on two strategies:reducing baseline risk and multimodal pharmacoprophylaxis (antiemetics).
Reducing baseline risk
Approaches to reducing initial PONV risk:
- Use of total intravenous anesthesia with propofol as the main anesthetic;
- Limiting the use of inhalation anesthetics;
- Preferential use of regional anesthesia,when possible;
- Minimizing the use of opioids in the perioperative period by applying multimodal analgesia techniques (using NSAIDs and COX-2 inhibitors [paracetamol, acetaminophen], and α2-agonists [clonidine or dexmedetomidine] reduces opioid consumption);
- Adequate hydration of patients (minimizing preoperative fasting time and additional intravenous fluid administration to maintain normovolemia).
Multimodal pharmacoprophylaxis
Modern consensus recommendations suggest using multimodal prophylaxis for patients with one or more risk factors, meaning the use of at least two antiemetics, and for high-risk patients, the combination of different classes. When using more than one antiemetic, choose medications from different classes, as the beneficial effects of antiemetics acting on different receptors are additive.
Main classes of medications used for PONV prevention
Various antiemetic agents acting through different mechanisms are used for PONV prevention. The choice of agents is based on the side effect profile and the patient’s previous experience. In pediatric practice, as in adults, combined therapy is the most effective.
The most commonly used antiemetic agents and categories include the following:
- 5-HT3 receptor antagonists (ondansetron, granisetron, dolasetron, tropisetron, ramosetron, palonosetron). Agents of this class are the “gold standard” for managing PONV, as they have sufficient antiemetic effects both when used alone and in combination. Almost all medications of this class are recommended for use at the end of surgery/anesthesia, except for palonosetron, which should be used during anesthesia induction, as it is a long-acting agent.
- Glucocorticosteroids (dexamethasone). Such an agent should be administered after induction into anesthesia. Used as one of the components of multimodal prophylaxis.
- Transdermal scopolamine. It is recommended to be applied the day before or several hours (at least 2 hours) before anesthesia and removed after 24 hours. Side effects include dry mouth, dizziness, and visual disturbances. As a component of multimodal prophylaxis with prolonged effect.
- Neurokinin-1 receptor antagonists (aprepitant, fosaprepitant). Relevant for high-risk patients, used in the preoperative period. It should be remembered that aprepitant and fosaprepitant may reduce the effectiveness of hormonal contraceptives. They belong to long-acting agents.
- Antihistamines (dimenhydrinate or diphenhydramine). Used in combination.
- Antidopaminergic agents (droperidol, haloperidol, amisulpride, metoclopramide). It is recommended to administer them at the end of anesthesia, except for amisulpride, which is used at the induction of anesthesia. Effective in combinations but have limitations in certain patients due to prolongation of the PQ interval.
- Other antiemetics include gabapentinoids (gabapentin and pregabalin; their disadvantages are sedation, dizziness, and headache), midazolam (reduces PONV symptoms when used during induction), and ephedrine (reduces PONV risk when administered at the end of surgery; should not be used in patients at risk of coronary ischemia).
Combined therapy
Below are the most popular combinations:
- 5-HT3 agonists in combination with dexamethasone;
- 5-HT3 agonists in combination with droperidol;
- 5-HT3 agonists in combination with aprepitant;
- Aprepitant in combination with dexamethasone.
If PONV prophylaxis fails, patients should receive antiemetic therapy with medications from a different group than those used for prophylaxis.
Non-pharmacological prophylaxis
Acupuncture stimulation of points PC6 (located on the forearm 2-3 fingerbreadths proximal to the wrist crease in the groove between the tendons along the palmar surface midline of the forearm) and L14 (located on the dorsal side of the hand in the “webbing” between the thumb and index finger) is considered a low-risk adjuvant to standard prophylaxis. Point L14 should not be used during pregnancy due to its potential to stimulate uterine contractility.
PONV prevention algorithm for adults
| Section | Details and recommendations |
|---|---|
| Risk factors | Patient-related: • Female sex • Young age • Non-smoking status • History of PONV or motion sickness (seasickness) Clinical: • Type of surgery • Use of opioid analgesics |
| Risk reduction | Minimization strategies: • Limit use of nitrous oxide, inhalational (volatile) anesthetics, and high doses of neostigmine • Consider regional anesthesia • Use opioid-sparing/multimodal analgesia (as part of Enhanced Recovery After Surgery protocols, ERAS) |
| Risk stratification | Quantitative assessment of risk factors for strategy selection: • 1–2 risk factors: prescribe 2 agents • > 2 risk factors: prescribe 3-4 agents |
| Prevention | Classes of agents and methods: • 5-HT3 receptor antagonists • Corticosteroids (dexamethasone) • Antihistamines • Dopamine antagonists • Propofol-based anesthesia (Total Intravenous Anesthesia, TIVA) • NK-1 receptor antagonists • Acupuncture • Anticholinergics |
| Treatment of developed PONV | Strategies and medications: Use an antiemetic from a pharmacological group different from that used for prophylaxis |
PONV prevention algorithm in children
| Section | Details and recommendations |
|---|---|
| Risk factors | Preoperative: • Age ≥ 3 years • History of PONV (vomiting) or motion sickness (seasickness) • Family history of PONV • Female sex (post-pubertal age) Intraoperative: • Strabismus surgery • Adenotonsillectomy (removal of adenoids and tonsils) • Otoplasty (plastic surgery of the ear) • Duration of surgery ≥ 30 minutes • Use of inhalational (volatile) anesthetics • Use of anticholinergics Postoperative: • Use of long-acting opioids |
| Risk stratification | Risk assessment: • No risk factors: low risk • 1-2 risk factors: medium risk • ≥ 3 risk factors: high risk Important note: Consider multimodal analgesia to minimize opioid use |
| Prevention | Strategy depending on risk: • Low risk: prevention is not required, or monotherapy (5-HT3 antagonist or dexamethasone) • Medium risk: combination therapy (5-HT3 antagonist + dexamethasone) • High risk: 5-HT3 antagonist + dexamethasone + consider total intravenous anesthesia (TIVA) |
| Treatment of developed PONV | Strategies and medications: • Use an antiemetic from a class different from that used for prophylaxis • Medication options: droperidol, promethazine, dimenhydrinate, metoclopramide • Acupuncture or acupressure can also be considered |
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Postdischarge nausea and vomiting (PDNV)
This is a common complication of outpatient surgery that occurs after discharge and significantly affects the quality of recovery. PDNV risk factors are the same as those for PONV, considering early discharge.
Preventive methods are based on reducing the baseline risk (most importantly by selecting appropriate anesthesia and limiting opioid use) and multimodal antiemetic prophylaxis, and at high risk—including long-acting agents and mandatory patient education about therapy during home stay.
FAQ
1. What is PONV and why is it dangerous?
PONV refers to postoperative nausea and/or vomiting in the first 24 hours; it worsens well-being, delays discharge, and can lead to dehydration, electrolyte imbalances, and rare but serious complications (aspiration, wound dehiscence).
2. Who is in the high-risk group?
Most often, women, non-smokers, patients with a history of PONV/motion sickness, and young people are affected; inhalational anesthetics, nitrous oxide, and postoperative opioids increase the risk.
3. How to quickly assess the risk in an adult patient?
The Apfel score is convenient: 4 factors (female sex, PONV/motion sickness history, non-smoking status, postoperative opioids). The more factors, the higher the risk.
4. Why combine antiemetics instead of prescribing just one?
PONV is triggered by multiple receptor pathways, so a combination of agents from different classes provides more effective prophylaxis than monotherapy.
5. How many medications are needed for prophylaxis?
For moderate and high risk, 2 medications from different classes are usually used; for very high risk, 3 or more in combination with reducing baseline risk.
6. What non-pharmacological measures really work?
Reducing baseline risk: total intravenous anesthesia with propofol as the main anesthetic, minimizing inhalational anesthetics and nitrous oxide, reducing opioid consumption (regional techniques, multimodal analgesia), adequate infusion; as an adjuvant—PC6 point stimulation.
7. What to do if PONV occurs despite prophylaxis?
Use rescue drugs from a different class than was used for prophylaxis, and simultaneously eliminate precipitating factors (pain, hypotension, reduce dosage of opioids or discontinue them).
8. When to think about PDNV (nausea/vomiting after discharge) and how to prevent it?
If there is a high risk and outpatient surgery is planned, it is advisable to preselect regimens with a prolonged effect (e.g., the addition of scopolamine/NK1 antagonist as indicated) and minimize opioids; provide the patient with instructions for the home period.
References
1.
VOKA 3D Anatomy & Pathology – Complete Anatomy and Pathology 3D Atlas [Internet]. VOKA 3D Anatomy & Pathology.
Available from: https://catalog.voka.io/
2.
Gan T.J., Belani K.G., Bergese S. (2020). Fourth Consensus Guidelines for the Management of Postoperative Nausea and Vomiting/ Anesthesia & Analgesia.131(2):411-448. doi: 10.1213/ANE.0000000000004833.
3.
Feinleib J., Kwan L.H., Yamani A.N. Postoperative nausea and vomiting. In: Post TW, ed. UpToDate [Internet]. Waltham (MA): UpToDate; 2025 [updated 2025 Apr 30; cited 2026 Jan].
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