Fear, stress and pain-what about nausea?

Compensating for nausea in your postop patients can lead to a dreamy recovery. (Shutterstock.com)We care about how our patients feel when they are under our care.

The veterinary profession is trying to make the hospital experience better for our furry friends. In the last decade, prevention of patient discomfort has received increasingly more attention in veterinary medicine. Stress-free handling techniques and fear-reduction protocols for dogs and cats are sweeping the nation. Pain management of our veterinary patients is a routine topic in lectures, workshops and symposia. Pain scoring systems and pain management standards have been developed and have become standards of care. Across the board, in all types of practices, veterinarians are doing a fantastic job of incorporating stress, pain and fear prevention into their medical, procedural and surgical protocols. Postoperative nausea, on the other hand, has received much less attention than pain.

So are we forgetting something here?

Nausea is an enormous consideration in the human surgical experience. Postoperative nausea and vomiting in people undergoing surgery and anesthesia, which even has its own moniker-PONV, or postoperative nausea and vomiting-is a perpetually hot topic in human medicine, with new studies or articles about the treatment or prevention of it being published almost monthly. One article states that human “patients have reported that [the] avoidance of PONV is of greater concern than avoiding postoperative pain.”1

Routinely used perioperative opiates are famously emetogenic.2 Additionally, though muddied by the use of opiates, there appears to be a linked-if not a causal-relationship between the level of nausea and the degree of reported pain in human patients in one direction or both.3-5 This could mean that pain (and opiates) can cause nausea, or nausea can worsen a human patient's experience of pain. In people, there are many study-based suggestions and protocols for preventing nausea using antiemetics, antihistamines and single-dose corticosteroids; avoiding certain opiates; and avoiding opiates altogether for patients at high risk for nausea.

PONV risk factors have been analyzed-the type and dose of opiates, patient gender, history of motion sickness in general, duration of anesthesia and type of procedure have been found to be among the risk factors for problematic PONV in humans.6 Because of these analytics, human hospitals can identify high-risk patients and appropriately prevent nausea in these surgical patients.7

Why don't we care about this in veterinary medicine?

We do.

Why don't we know the risk factors for animals for PONV? Well, because we can't.

The difficulty lies in the age-old conundrum in our profession: animals can't clearly convey to us how they feel. Nausea and pain can be notoriously subclinical. As veterinarians, we are stuck subjectively interpreting clinical signs, extrapolating from human medicine and human experiences, and designing studies that attempt to grade or objectify experiences like pain and nausea, using indirect but measurable parameters like respiratory rate and heart rate, food intake and vomiting. We know for certain that animals are experiencing nausea if they vomit. We can make an inference that they are nauseated if they drool or lip smack. We might suppose that they are nauseated if they refuse to eat, but there are many other reasons that dogs, and especially cats, may refuse food in the hospital, or even drool or lip smack. Since we routinely use opiates in most of our elective and emergency anesthetic and pain management protocols, we might reasonably assume that some of our patients will be nauseated because of this.

Maropitant's dual role

Motion sickness

“Perhaps as many as 30% of dogs are subject to motion sickness,” says Dr. Harvey. This is regardless of a surgical procedure or opiate administration. He stresses that this may not just go away once arriving at the hospital. With motion sickness “[you] can feel lousy for hours after [you] get [your] feet back on solid ground,” he says. Dogs learn, and those dogs that get motion sickness will likely associate this bad experience with a veterinary hospital. “This is an aversive experience for the animal, and we can now deal with this-we can prevent this,” Dr. Harvey says.

Pain relief

Maropitant blocks substance P, published data documents the pain relief properties,1 and it's used extralabel for pain in veterinary medicine. More studies are needed, but pain relief may be another consideration in its use as a perioperative medication. Veterinary patients appear to be less painful after surgery and have been found to have a statistically significant reduction in the amount of inhaled anesthetic needed during surgery after receiving maropitant.2

References

1. Marquez M, Boscan P, Weir H, et al. Comparison of NK-1 receptor antagonist (maropitant) to morphine as a pre-anaesthetic agent for canine ovariohysterectomy. PLOS ONE 2015 10(10): e0140734. Available at: https://doi.org/10.1371/journal.pone.0140734

2. Boscan P, Monnet E, DVM, PhD; Mama K, et al. Effect of maropitant, a neurokinin 1 receptor antagonist, on anesthetic requirements during noxious visceral stimulation of the ovary in dogs. Am J Vet Res 2011;72(12):1576-1579.

So what do we do?

Ralph C. Harvey, DVM, MS, DACVAA, an associate professor of anesthesiology at the University of Tennessee, recommends the prevention of nausea as part of our routine preanesthetic protocols in all of our surgical or opiate-sedated patients. He recommends it for both cats and dogs, although dogs dominate the current studies. Dr. Harvey is well-known as an advocate for discomfort-free medicine. His motivation is “focusing on the well-being of the animal” and identifying, addressing and preventing as much discomfort as possible in veterinary patients, including pain, fear (Fear-Free initiative), stress and nausea.

Dr. Harvey recently lectured at the 2017 International Veterinary Emergency and Critical Care Symposium in Nashville, where he recommended the prophylactic use of antiemetics in cats and dogs in any veterinary situation in which patients might become nauseated. Specifically, he strongly recommended standard perioperative use of maropitant (Cerenia-Zoetis; 1 mg/kg injectable or 2 mg/kg orally) for both dogs and cats in all of our preanesthetic protocols, including for spays and neuters.

Maropitant is a very powerful antiemetic that acts on both peripheral (e.g. vagal stimulation) and central receptors (chemoreceptor trigger zone) to prevent vomiting. In studies, it exceeds the efficacy of all other antiemetics used in veterinary medicine. It also blocks nausea from motion sickness, such as that car ride over to your clinic. Additionally, it blocks the binding of substance P to NK1 receptors, so it may have some analgesic properties.

What the studies say

Dr. Harvey describes a student lab study in which 31 dogs in a spay-neuter lab were given morphine as a preanesthetic medication and were divided into two groups: one group received a maropitant injection 45 minutes prior to the opiate and the other group received a placebo.8 After the morphine, vomiting events and food intake over 20 hours were measured. None of the dogs receiving maropitant vomited, while 90% of the placebo dogs receiving a placebo vomited-over half of these vomited more than once. By hour 20, 42% of the placebo dogs were eating, but over 80% of the maropitant dogs were eating. The dogs receiving maropitant were perceived to have less postoperative pain. Additionally, these dogs were eating five times more food than the placebo dogs.

“That's good medicine!” Dr. Harvey says. “And you know something else? Food is love! Our dogs and cats are eating machines, and our clients want them to eat!” By hour 20, they are already at home, and the owners see that they are eating and feel good about it. When the owners offer food at home and the patient refuses, they hear: If you loved me, you would have never taken me to the veterinarian. “So it's so nice to get them eating again,” Dr. Harvey says. “It reinforces the human-animal bond, gets them in a positive nitrogen balance, and supports gut function.”

Does it hurt to presume that our patients might become nauseated as a result of our anesthetic or surgical protocol and preemptively treat?

It seems that added cost is the only downside to adding antiemetics to our anesthetic protocol. Bonnie Hay Kraus, DVM, DACVS, DACVAA, Iowa State University College of Veterinary Medicine, addressed this by performing a survey of clients that asked: “If we could do something to prevent nausea and vomiting in your animal, would you want us to?”9 The answer was a resounding: Oh, yes, please! “How much would you be willing to pay for this?” The median figure written on the questionnaire was $50. (Note that her demographic was not very wealthy.)

“That will buy you a lot of maropitant,” Dr. Harvey says. It only costs us about 1.5 times as much as a carprofen (Rimadyl-Zoetis) injection. Most clients are willing to pay for this because they are searching for value. It is “value added” in the way that sedation for lower stress, higher quality, and less (technician) time-consuming radiographs is “value added.” It is “value added” in the way pain prevention is.

A more comfortable conclusion

Vomiting and nausea is stressful for an animal-probably as stressful as it is for humans. Because our patients can't talk, we as veterinarians need to take preventive measures to ensure comfort. The use of antiemetics should be strongly considered as an addition to our routine anesthetic and sedation protocols. Just like pain, fear and stress reduction is important to clients, the added value of preventing nausea appears to outweigh the added cost for most clients.

If low cost is a necessity in your hospital, consider having owners pick up an oral dose of maropitant (2 mg/kg) prior to the scheduled surgery date to be given at home the morning of surgery or even the night before. And don't forget to tell your clients why you are doing this. Communication often adds more value than skill or discounts do. You may end up with generally happier clients, and, as we all know, happy clients make our jobs easier.

References

1. Rahman MH, Beattie J. Post-operative nausea and vomiting. Pharm J 2008. Available at: http://www.pharmaceutical-journal.com/learning/learning-article/post-operative-nausea-and-vomiting/10030469.article

2. Smith HS, Smith JM, Seidner P. Opioid-induced nausea and vomiting. Ann Palliat Med 2012;1(2):121-129. Available at: http://apm.amegroups.com/article/view/1038/1264

3. Odom-Forren J, Rayens MK, Gokun Y, et al. The relationship of pain and nausea in postoperative patients for 1 week after ambulatory surgery. Clin J Pain 2015;31(10):845-851.

4. Chatterjee S, Rudra A, Sengupta S. Current concepts in the management of postoperative nausea and vomiting. Anesthesiol Res Pract Vol 2001. Available at: https://www.hindawi.com/journals/arp/2011/748031/

5. Mandelcorn M, Taback N, Mandelcorn E, et al. Risk factors for pain and nausea following retinal and vitreous surgery under conscious sedation. Can J Ophthalmol 1999;34(5):281-285.

6. Sinclair DR, Chung F, Mezei G. Can post-operative nausea and vomiting be predicted? Anesthesiology 7 1999;91:109-118. Available at: http://anesthesiology.pubs.asahq.org/article.aspx?articleid=1946288

7. Muchatuta NA, Paech MJ. Management of postoperative nausea and vomiting: focus on palonosetron. Ther Clin Risk Manag 2009; 5: 21-34 Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2697527/

8. Ramsey D, Fleck T, Berg T, et al. Cerenia prevents perioperative nausea and vomiting and improves recovery in dogs undergoing routing surgery. Intern J App Res Vet Med 2014;12(3):229-238. Available at: http://www.jarvm.com/articles/Vol12Iss3/Vol12%20Iss3McCall.pdf

9. Kraus B, Cazlan C. Assessment of dog owner concern regarding perioperative nausea and vomiting and willingness to pay for antiemetic treatment [abstract]. In Proceedings of the International Veterinary Emergency and Critical Care Symposium, Sept 18-22, 2015, Washington, D.C.

Carla Johnson, DVM, practices emergency medicine at Berkeley Dog and Cat Hospital in Berkeley, California, and general practice at Cameron Veterinary Hospital in Sunnyvale, California. Her nonveterinary loves are writing, Dressage with her Iberian warmblood mare, Synergy; watercolor painting on yupo; vinyasa yoga; and running with her dog Tyson. Try as she might, her curly-coated Scottish Fold, Hootie, refuses to go jogging with her.