PONV: Postoperative Nausea and Vomiting, A Common Side Effect of Anesthesia
PONV: Postoperative Nausea and Vomiting
Postoperative nausea and vomiting (PONV) occurs as the most common side effect of anesthesia. As an after-effect of general anesthetics, it causes discomfort and distress for millions of people every year. About 33% of all people undergoing surgery, and 70% of people identified as high risk, will suffer this side effect of anesthesia.
How do you know if you are at risk for this complication—and what can you, your surgeon, and your anesthesiologist do to prevent and treat this ailment?
Many hospitals, anesthesia departments, and surgery centers use a scoring system to evaluate your particular risk for PONV. They will then use the score to determine which agents to use to prevent it.
Surgical Risk Factors for PONV
- Abdominal surgery
- Gynecologic surgery
- Eye surgery
- Ear, nose, and throat surgery
- Breast surgery
- Any surgery lasting over 30 minutes
Patient Risk Factors for PONV
- Young age
- History of motion sickness
- History of prior postoperative nausea and vomiting
- Family history of PONV
Risk Factors for PONV: Surgical Factors
While PONV can strike anyone having surgery, some people—and some types of surgery and anesthesia—have higher risk than others.
Some surgeries lead to a higher risk of PONV, according to most data. It's probably no surprise that surgeries on the digestive system, and others inside the abdomen (intra-abdominal surgery), cause a high incidence of nausea and vomiting. Manipulating the digestive organs causes them to be "stunned" after surgery. In addition, serotonin is released, which also contributes to postoperative nausea and vomiting. General anesthesia slows down the digestive system as well as contributing to nausea and vomiting by its activity on the vomiting centers in the brain (more on that later).
In addition to the obvious, other surgeries are also more likely to lead to PONV. By the time you read through the list, though, you may wonder which surgeries do not lead to more nausea and vomiting.
Breast surgery is well-known to have a high incidence of PONV, and is postulated to be related to the "emotional load" and possibly hormonal disruption associated with this surgery. Surgery in the ear disturbs the vestibular centers, leading to dizziness and nausea. Surgery of the tonsils, adenoids, and other mouth and throat structures causes blood to be swallowed, a strong stimulus for vomiting. Hysterectomies trigger part of the nervous system that can predispose to nausea and vomiting after surgery. The list goes on and on.
There are so many other factors (like anesthesia, pain medication, and patient issues) that can lead to PONV that it is assumed that any surgery is a risk for postoperative nausea and vomiting.
Risk Factors for PONV: Patient Factors
Women are more prone, in general, to PONV than males. There is even some preliminary evidence that the risk fluctuates with the day of the menstrual cycle, being highest around day five and lowest around day 19, based on a small study of women having laparoscopic surgery. It seems more data needs to be collected to substantiate this finding.
Women in their child-bearing years are at particular risk. The risk for these women and for everyone is amplified by a previous history of motion-sickness or postoperative nausea and vomiting in the past. Non-smokers have a higher risk than smokers. More painful surgeries induce more nausea and vomiting than less invasive procedures.
What to Expect from Anesthesia - Types of Anesthesia
Risk Factors for PONV: Anesthesia Factors
The type and duration of the anesthetic administered also affects the outcome regarding PONV. General anesthesia is more likely to lead to this after effect of anesthesia than local or regional anesthesia. General anesthesia means you are unconscious for your surgery through a combination of IV and inhaled medications. With the brain as the site of action of general anesthesia medicines, side effects such as PONV are more likely. For a great number of surgeries, though, general anesthesia is the best or only choice.
Strong, narcotic pain medications are are often used as part of the anesthetic and narcotics are well-known to lead to gastrointestinal distress. An interesting characteristic of narcotic pain medications (morphine, dilaudid, etc) is that at low doses, they stimulate the vomiting center in the brain stem, but at very high doses, like those used for open heart surgery and long spine surgeries, they suppress the vomiting center. Unfortunately, using high doses of narcotic pain medication also causes the breathing rate, heart rate and blood pressure to drop, so they must be used with care and cannot be administered in large doses to avoid the PONV problem.
Anesthesia gases, by themselves also cause nausea and vomiting. Luckily, the gases we use now, while still leading to PONV, are better in this regard than the gases used even 20 years ago.
Unfortunately, anesthesia factors, like patient and surgical factors, sometimes are unavoidable. The anesthesia can be manipulated to some degree by altering which medications are used as the predominant agent, but the risk cannot be completely eliminated. The intravenous drug, propofol (yes, the Michael Jackson drug) has some anti-emetic properties, meaning it 'fights' nausea and vomiting and can be used as a continuous infusion during general anesthesia. Of course, it has issues of its own, so this is not always an option.
Prevention and treatment of postoperative nausea and vomiting are pretty effective in a great many people, though.
Prevention of PONV
So what can you do to minimize your risk of PONV?
- Tell your doctors if you have a history of motion sickness or previous PONV
- Follow all instructions about when to stop eating and drinking. Do not have hard candy or gum either after this time, as the act of sucking or chewing stimulates digestive enzymes increasing secretions in the stomach. Stay hydrated up to the point you were told to stop eating or drinking.
- If you have any experience with acupressure bands decreasing nausea and vomiting for motion sickness, bring one with you and ask if you can apply it before or after surgery. Some hospitals have these to apply in the recovery room, but as you can guess, the charge will be many times higher buying through the hospital than bringing your own.
- When you get home, have some ginger tea, ginger soda (a little flat is better), or ginger hard candy. Ginger is a very old, and sometimes effective anti-emetic (decreases vomiting).
What Can Your Anesthesiologist Do to Prevent PONV?
If your anesthesiologist knows of your risk for, or concern regarding, PONV, there are measures they can take to minimize the risk.
- Preventive Medicines - Intravenous medicines such as metoclopramide (Reglan) and ondansetron (Zofran) can be used before the anesthesia is given. I give these medicines to nearly 100% of my patients before their anesthesia, unless there is a contraindication (reason why it shouldn't be given). There are some side effects, but they are very rare.
- Motion Sickness Patch - The scopolamine patch, usually used for preventing motion sickness, is another preventive tactic. The patch is applied behind the ear before surgery. It takes several hours to "kick in", so hopefully by the time the surgery and recovery are over, and the other medications are wearing off, this patch will be working. This definitely provides benefit but has side effects such as sedation, dry mouth, blurry or double vision. Some people also have rebound nausea and vomiting after the patch is removed (it can be left on for 3 days).
- Hydration - Anesthesiologists are responsible for administering IV fluids during surgery. Maintaining hydration helps prevent nausea. Of course, there are some times that it is not advisable to give IV fluids in large amounts, but your anesthesiologist will do what they can with IV fluids to prevent PONV.
- Manipulate Anesthetic Agents - Sometimes anesthesiologists can decrease the amount of narcotic or gas used and use more propofol as part of the anesthesia. Sometimes, for various reasons, this is not a possibility, however.
Treatment for PONV
If PONV occurs despite preventive measures, other therapies provide relief for a great many people. Most of these therapies are IV medications, such as metoclopramide, ondansetron, Compazine (prochlorperazine), and even the steroid Decadron (dexamethasone). Decadron is sometimes used as a premedication as well, if there is no surgical reason not to do it (the fear is that it leads to extra bleeding and difficulty healing).
Acupuncture has shown mixed results. Some studies show that it decreased nausea but not vomiting. It is difficult to find a hospital with an acupuncturist to provide therapy, but there are some (I worked in one). One of the most unexpected remedies that does work (my experience only), is sniffing an alcohol pad. The effect is short-lived, but helps with those waves of nausea until medications become active.
Whether you are staying in the hospital or going home after your surgery, ask your surgeon to prescribe something for nausea along with the pain medicine (Zofran tablets work great and there's a variety that dissolves under the tongue so you don't even have to swallow it). Take the nausea medicine about 30 minutes before the pain medication.