Tinsley, Mary H. RN, ADN; Barone, Claudia P. EdD, RN, LNC, CPC, CCNS-BC, APN
For surgical patients, postoperative nausea and vomiting (PONV) is one of the most undesired complications of anesthesia and surgery.1–3
PONV has been identified as a surgical problem since 1848, shortly after the introduction of anesthesia.4 Vomiting also can lead to serious complications, including pulmonary aspiration, dehydration, and dysrhythmias secondary to electrolyte imbalances.4 About 10% of surgical patients develop PONV in the postanesthesia care unit (PACU), and up to 30% of surgical patients develop PONV within the first 24 hours.5 PONV also poses dangers for ambulatory surgery patients, who may go home before symptoms develop.6
The many variables that contribute to PONV, including type of surgery, anesthesia selection, opioid use, and patient preexisting conditions, make prevention and treatment a challenge.7 Treatment has improved with the advent of newer anesthetic drugs as well as newer antiemetic drugs.8,9 But despite these advances, PONV remains difficult to understand as well as treat.
Defining the problem
Nausea is a subjective and unpleasant sensation associated with the conscious awareness of the urge to vomit. Usually felt in the back of the throat and epigastrium, nausea is accompanied by the loss of gastric tone, contractions of the duodenum, with reflux of the intestinal contents into the stomach.2
Retching is rhythmic and spasmodic contractions of the respiratory muscles, diaphragm, chest wall, and abdominal muscles, without the expulsion of gastric contents. The patient's mouth and glottis are closed. Gastric contents flow back and forth between the stomach and esophagus as the antral portion of the stomach contracts and the proximal portion relaxes. The diaphragm doesn't relax and intra-abdominal pressure increases and intrathoracic pressure decreases.2
Vomiting, or emesis, is the forceful expulsion of gastric contents from the mouth, and is brought about by coordinated motor changes involving muscles of the respiratory and gastrointestinal (GI) systems.10 Excessive distension or irritation of the duodenum provides an especially strong stimulus for vomiting. Impulses are transmitted by vagal and sympathetic afferents to the vomiting center of the medulla, prompting the automatic motor reactions that cause vomiting (see Physiologic events involved in vomiting). The motor impulses are transmitted from the vomiting center through the fifth, seventh, ninth, and 12th cranial nerves to the upper GI tract and through the spinal nerves to the diaphragm and abdominal muscles.11
The hiatal portion of the diaphragm relaxes and intra-abdominal pressure is transferred to the thorax. The rectus abdominis and external oblique muscles of the anterior abdominal wall contract, the esophageal sphincter relaxes, reverse peristalsis occurs, and the glottis and mouth open as gastric contents are expelled.11
Emesis can be divided into three phases:
Figure. Physiologic ...Image Tools
* The preejection phase is characterized by the symptom of nausea as well as the autonomic signs of increased salivation, swallowing, pallor, diaphoresis, and tachycardia.
* The ejection phase consists of retching and vomiting.
* The postejection phase consists of relaxation of respiratory and abdominal muscles and cessation of nausea.6
The vomiting center can be stimulated by several sources. These include afferent neurons from the pharynx, GI tract, and mediastinum, as well as afferents from the higher cortical centers (including the visual center and the vestibular portion of the eighth cranial nerve). Rapid position changes and motion in patients with vestibular disturbances can trigger vomiting and can be a profound problem in any PACU setting, but especially in the ambulatory care setting.10
Another cause of vomiting is the chemoreceptor trigger zone (CTZ) at the base of the fourth ventricle in the area postrema, a medullary structure in the brain. The CTZ is highly vascularized; the vessels terminate in fenestrated capillaries surrounded by large perivascular spaces. Without an effective blood-brain barrier, the CTZ can be stimulated by chemicals received in the blood (such as drugs) and cerebrospinal fluid.11,12 However, direct electrical stimulation of the CTZ doesn't result in vomiting.11
The vomiting center can also be activated indirectly when afferent pathways are stimulated by specific neurotransmitters—dopamine, serotonin, acetylcholine, and histamine—that activate the CTZ.4,13 Antiemetic drugs that block specific neurotransmitter receptors are used to prevent or treat PONV.4,13
Lastly, the practice of fasting a patient overnight before surgery may lead to dehydration, and in combination with anesthetic agents and surgical blood loss can cause a state of transient ischemia in the GI system due to mesenteric hypoperfusion, one of the identified causes of PONV.13,14
Risk factors for PONV
Not all surgical patients will experience PONV or experience it to the same degree. Understanding and identifying risk factors can help clinicians decide whether the patient should receive prophylaxis or later treatment for PONV (see Rating an adult's risk for PONV).5 Causes of PONV include the patient and his or her associated risk factors, the underlying disease process that prompted the surgery, the type of surgery, and the anesthetic technique.15
* Patient age. Children under age 3 experience the lowest incidence of PONV; patients between ages 3 and 50 are most at risk.16,17 PONV typically decreases after the age 50, although older patients undergoing spinal surgery or joint replacement have a greater incidence of PONV, due to length of anesthesia and reduced ability to clear these medications.11
* Gender. Among adults and adolescents, women are two to four times more likely to experience PONV than men, possibly due to varying levels of female hormones.15 Differences in PONV due to gender aren't found in preadolescents or patients age 80 or older.18
* Obesity. A positive correlation has been found in obese patients and the incidence of PONV. One of the reasons used to explain this relationship is that adipose tissue acts as a reservoir for inhaled anesthetic agents, prolonging their half-lives so that the drugs continue to be released into the bloodstream during the recovery phase.5 Other explanations include a larger gastric volume, esophageal reflux, and airway difficulties that result in more gastric inflation.18
* History of PONV or motion sickness. Patients with a history of either motion sickness or PONV are believed to have a lower threshold of tolerance, thereby increasing their risk of future episodes of PONV by two to three times.3,11 A history of motion sickness or prior PONV are considered independent predictors of PONV; the presumption is the patient has already established a reflex arc (an established pathway for nerve impulses) for vomiting.16
* • Type of surgery. Surgeries that are associated with a higher incidence of PONV include breast augmentation or other plastic surgery, strabismus repair or procedures associated with ophthalmology, otolaryngology, gynecology (especially with a laparoscopic approach), orthopedic and abdominal surgery, mastectomies and lumpectomies.5 Whether this is due to the type of surgical procedure, the length of the procedure, or the anesthetic agent used is unclear.11
* Length of surgery. PONV and length of surgery are strongly correlated.5 In a patient with a surgical procedure taking less than 30 minutes, the risk of PONV is 28%; for a procedure that lasts 151 to 180 minutes, the risk of PONV is 46.2%.11 Longer surgeries may result in the patient receiving potentially emetogenic anesthetic agents over a longer time frame, resulting in the increased percentage of patients with PONV.18
* Medications. Chloroform and ether, although no longer used for anesthesia, had the highest probability of causing PONV.10 Newer anesthetic agents such as propofol, and the use of patient-controlled analgesia, spinal opioid administration, and total I.V. anesthesia (TIVA), have reduced the incidence of PONV to about 30%, compared with 80% during the era in which ether was used.12 However, nitrous oxide and volatile anesthetic agents such as isoflurane and enflurane, are all highly emetogenic, and general anesthesia causes more PONV than regional anesthesia. The use of opioids postoperatively about doubles the patient's risk for PONV.16
* Tobacco use. Nonsmokers are at higher risk of developing PONV than smokers. The chemicals in cigarette smoke increase the metabolism of several drugs used in anesthesia, reducing the risk of PONV.16
A patient with one risk factor has a 10% to 21% chance of developing PONV, compared with an 80% chance in patients with two or more risk factors.5
Early and effective management of PONV is critically important for many reasons, such as patient satisfaction and safety, improved surgical outcomes, and reducing medical costs. If the patient is at risk for PONV, here are some steps for reducing that risk:
* Consider regional anesthesia instead of general anesthesia whenever possible. Don't use fentanyl in combination with nitrous oxide in patients who have a history of PONV or motion sickness.6
* Consider I.V. agents such as propofol instead of inhaled volatile anesthetic agents when possible.
* As appropriate, manage pain with nonsteroidal medications and regional blocks instead of opioids. If opioids are needed, use the lowest effective dose, and administer an antiemetic as prescribed and needed.6
* Provide adequate presurgical hydration with crystalloids or colloids, which has been shown to reduce the incidence of PONV on the first postoperative day.5
* Provide 100% oxygen intraoperatively (via endotracheal tube or laryngeal mask airway) and 80% oxygen therapy for 30 minutes postoperatively, which may reduce the incidence of PONV by helping to clear anesthetic gases.5
Nonpharmacologic interventions are also available and can be used in selected patients. Because the mechanisms of PONV are triggered by neurochemicals, there's a strong mind-body link, and nondrug therapies work well in anxious patients.4 Two such interventions include acupressure and aromatherapy.19 Acupressure wrist bands have been shown to be effective when applied before anesthesia in patients undergoing short surgical procedures such as hysterectomy, tonsillectomy, or adenoidectomy.5 A meta-analysis of 19 studies on acupuncture, electroacupuncture, transcutaneous electrical nerve stimulation, acupoint stimulation, and acupressure found that these techniques were similar to pharmacologic agents in preventing early and late vomiting.5
Few studies have investigated the use of aromatherapy for PONV. A study of 33 surgical patients concluded that aromatherapy using isopropyl alcohol or essential oil of peppermint is effective in reducing nausea in surgical patients, but this may be due to controlled breathing patterns rather than the scents used in the trial.5 Commonly used aromatherapy scents include essential oil of ginger, essential oil of peppermint, and isopropyl alcohol.7 The scents are thought to affect the neurotransmitters that activate the CTZ.20
Drugs for prevention and management
Various drugs can be used to prevent PONV or manage it once it occurs (see Effects of some antiemetic drugs). Rescue antiemetic therapy should be initiated as soon as the patient has been assessed for other contributing factors to PONV such as opioid use, abdominal obstruction, or surgical complications. Patients who were given selective 5-HT3 receptor antagonists as prophylaxis should be treated with a drug from another class if PONV develops.5
Although its mechanism of action isn't clearly understood, dexamethasone, a corticosteroid, has been successfully used to manage PONV, and administering it during anesthesia induction may delay PONV.19 Few studies have focused on combination therapy for PONV, but the combination of dexamethasone and a selective 5-HT3 antagonist has been found more effective than the use of either agent alone.3
Selective 5-HT3 receptor antagonists such as ondansetron, granisetron, and dolasetron are approved to prevent PONV and treat PONV in patients who didn't receive prophylactic therapy.5 In randomized placebo studies with high-risk PONV patients, ondansetron was shown to be more effective in treating vomiting than in treating nausea.5 Studies indicate no significant difference between single-dose treatments of dolasetron and ondansetron. Granisetron is an effective treatment for PONV in patients undergoing abdominal or vaginal hysterectomy.5 Selective 5-HT3 receptor antagonists may prolong the QT interval, and there have been postmarketing reports of torsades de pointes. These drugs should be avoided in patients with congenital long QT syndrome.
Phenothiazines such as promethazine and prochlorperazine are more effective than ondansetron in preventing postoperative nausea, but no difference was noted in the treatment of vomiting.5 Phenothiazines may cause extrapyramidal symptoms (EPS) such as dystonia, tardive dyskinesia, and akathisia, which can be disturbing to the patient. (Symptoms typically resolve when the drug is discontinued.) Diphenhydramine can be administered with prochlorperazine to reduce the chance of akathisia, but this can increase the risk of sedation.5
Table Effects of som...Image Tools
Anticholinergic agents such as scopolamine, which block muscarinic receptors in the vestibular system, also can be used to treat PONV. Scopolamine is available as a transdermal patch that should be applied the night before surgery (onset of action is 2 to 4 hours) and should remain in place for at least 24 hours postoperatively.5 Scopolamine is contraindicated in patients with angle-closure glaucoma.4
Antihistamines are the drugs of choice for preventing PONV in patients undergoing middle ear surgeries because of the high concentration of histamine and muscarinic cholinergic receptors within the vestibular system.5 Hydroxyzine and dimenhydrinate are two commonly used antihistamines. Hydroxyzine is anxiolytic, has bronchodilatory effects, has a long duration of action, and isn't associated with circulatory or respiratory compromise. Hydroxyzine also supplements the analgesic effects of opioids. Dimenhydrinate was found to be as effective as ondansetron in preventing PONV in a random prospective trial of patients undergoing laparoscopic cholecystectomy.5 In a meta-analysis of 18 trials involving more than 3,000 patients, dimenhydrinate was as effective as 5-HT3 receptor antagonists and droperidol in preventing PONV.5
Droperidol, a centrally acting antidopaminergic agent, prevents PONV and treats opioid-induced nausea and vomiting, and is as effective as ondansetron and promethazine with no significant differences related to adverse events.3,21–23 However, use of droperidol has significantly decreased since 2001, when the FDA issued a black box warning about the drug's potential for causing prolonged QT intervals and potentially fatal cardiac dysrhythmias such as torsades de pointes.4,5
Metoclopramide is another drug that's no longer used as routinely for PONV because of its adverse effects (including a black box warning that the drug may cause tardive dyskinesia) and the availability of more effective treatment.5 Metoclopramide acts centrally in the CTZ and peripherally in the GI tract to increase lower esophageal sphincter tone and promote gastric motility. The drug is as effective as ondansetron in treating postoperative nausea but isn't as effective with postoperative vomiting.5 Metoclopramide crosses the blood-brain barrier and has centrally mediated adverse effects causing somnolence, reduced mental acuity, anxiety, depression, and EPS in young children and older adults.
Aprepitant, the first substance P and neurokinin-1 receptor antagonist approved by the FDA for prevention of PONV, is an oral drug administered 3 hours before induction of general anesthesia. Aprepitant also is used to treat nausea and vomiting associated with chemotherapy.10
Complications associated with PONV
In addition to dehydration and electrolyte disturbances that can lead to cardiac dysrhythmias, complications of PONV include transient changes in intraocular pressure that can impair vision. (Report these changes to the anesthesia provider.)
Pulmonary complications are often due to aspiration, and are commonly seen in patients who wake up slowly from anesthesia or are unable to protect their airway. Position the patient in Fowler or semi-Fowler position (unless contraindicated) to reduce the risk of aspiration. If the patient can't sit up, position him or her on one side to prevent aspiration.
PONV can also lead to wound dehiscence in surgical patients, and, rarely, esophageal rupture. Patients should be taught to splint their wounds when coughing, retching, or vomiting.24
Severe PONV can cause hematoma development, especially in patients undergoing thyroidectomy. Monitor the surgical site for edema and airway compression (difficult breathing). Administer prophylactic antiemetics as prescribed, to help the patient avoid retching and vomiting.25
PONV has a negative effect on patient satisfaction and quality of life and also delays the patient's discharge from the PACU.26
For hospitalized patients, PONV can delay discharge from the PACU and significantly increase the cost of medical care.25 Direct costs of PONV are those associated with the cost of drugs, nursing time, and delays in PACU discharge. Indirect costs include hospital readmission for ambulatory surgery patients who develop PONV after returning home, delays in discharge, and loss of income for patients who can't return to work as soon as they'd expected.
By identifying patients at risk for PONV and taking steps to prevent and manage it, you can help patients have the best outcomes.
Rating an adult's risk for PONV1
Risk factor (each worth one point)
* Female gender
* History of PONV or motion sickness
* Intraoperative or postoperative opioid therapy
Prophylactic PONV therapy based on the patient's score:
* 0 to 1 point—no intervention, or transdermal scopolamine patch preoperatively; or preoperative dexamethasone; or TIVA; or prochlorperazine given I.V. or I.M. at the end of surgery.
* 2 points—one or two of the following drugs: transdermal scopolamine patch preoperatively, I.V. dexamethasone preoperatively, TIVA, or prochlorperazine given I.V. or I.M. at the end of surgery.
* 3 or 4 points—three of the following drugs: transdermal scopolamine patch preoperatively, I.V. dexamethasone preoperatively, TIVA, prochlorperazine given I.V. or I.M. at the end of surgery, or dolasetron I.V. at the end of surgery.
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