• Hero Banner
  • ACVCACVC
  • DVM 360
  • Fetch DVM 360Fetch DVM 360
DVM 360
dvm360 | Veterinary News, Veterinarian Insights, Medicine, Pet Care
dvm360 | Veterinary News, Veterinarian Insights, Medicine, Pet Care
By Role
AssociatesOwnersPractice ManagerStudentsTechnicians
Subscriptions
dvm360 Newsletterdvm360 Magazine
News
All News
Association
Breaking News
Education
Equine
FDA
Law & Ethics
Market Trends
Medical
Products
Recalls
Regulatory
Digital Media
dvm360 LIVE!™
Expert Interviews
The Vet Blast Podcast
Medical World News
Pet Connections
The Dilemma Live
Vet Perspectives™
Weekly Newscast
dvm360 Insights™
Publications
All Publications
dvm360
Firstline
Supplements
Top Recommended Veterinary Products
Vetted
Clinical
All Clinical
Anesthesia
Animal Welfare
Behavior
Cardiology
CBD in Pets
Dentistry
Dermatology
Diabetes
Emergency & Critical Care
Endocrinology
Equine Medicine
Exotic Animal Medicine
Feline Medicine
Gastroenterology
Imaging
Infectious Diseases
Integrative Medicine
Nutrition
Oncology
Ophthalmology
Orthopedics
Pain Management
Parasitology
Pharmacy
Surgery
Toxicology
Urology & Nephrology
Virtual Care
Business
All Business
Business & Personal Finance
Buying or Selling a Practice
Hospital Design
Leadership & Personal Growth
Personnel Management
Practice Finances
Practice Operations
Technology
Wellbeing & Lifestyle
Continuing Education
Conferences
Live Conferences
Conference News
Conference Proceedings
Resources
CBD in Pets
Contests
Veterinary Heroes
Partners
Spotlight Series
Team Meeting in a Box
Toolkit
Top Recommended Veterinary Products
Vet to Vet
  • Contact Us
  • Fetch DVM360 Conference
  • Terms and Conditions
  • Privacy
  • Do Not Sell My Information
  • About Us

© 2023 MJH Life Sciences and dvm360 | Veterinary News, Veterinarian Insights, Medicine, Pet Care. All rights reserved.

Advertisement
By Role
  • Associates
  • Owners
  • Practice Manager
  • Students
  • Technicians
Subscriptions
  • dvm360 Newsletter
  • dvm360 Magazine
  • Contact Us
  • Fetch DVM360 Conference
  • Terms and Conditions
  • Privacy
  • Do Not Sell My Information
  • About Us
  • MJHLS Brand Logo

© 2023 MJH Life Sciences™ and dvm360 | Veterinary News, Veterinarian Insights, Medicine, Pet Care. All rights reserved.

Pain Assessment with the Rat Grimace Scale

June 23, 2017
JoAnna Pendergrass, DVM

The rat grimace scale is a reliable way to determine pain levels in rats following surgical experimental procedures.

In a recent study, a team of Romanian researchers reported preliminary results demonstrating that the rat grimace scale (RGS) can assess pain levels in rats reliably following surgical experimental procedures.

The 3 R’s of animal research—replace, reduce, refine—were developed over 50 years ago to ensure humane laboratory animal care. Pain control, wrote the current study’s researchers, is “one of the most important refinement strategies” in laboratory animal research. Unfortunately, only about 20% of laboratory rats undergoing surgical experimental procedures receive postoperative analgesia.

Effective pain control in laboratory animals relies on accurate quantification of pain. Traditional pain assessment methods evaluate physiologic and behavioral changes, which may not adequately reflect pain intensity.

The face grimace scale, originally developed to assess pain in nonspeaking humans, was recently validated for pain assessment in several laboratory animals, including rats.

The RGS rates pain from 0 (no pain) to 2 (severe pain) based on changes in 4 facial expression categories:

Advertisement
  • Orbital tightening
  • Cheek/nose flattening
  • Ear changes (position, orientation, shape)
  • Whisker changes (position, orientation)

Study Design

Researchers assessed pain in 5 healthy female laboratory rats. Four rats were ovariectomized (OVX) under general anesthesia and assigned to 1 of 4 treatment groups (1 rat/treatment group):

  • OVX without analgesia
  • OVX + preoperative tramadol 25 mg/kg
  • OVX + postoperative tramadol 25 mg/kg
  • OVX + postoperative tramadol 50 mg/kg

One rat served as control and did not undergo surgery or receive tramadol. Tramadol was selected because it is commonly used to relieve postoperative pain in animals. In this study, tramadol was administered subcutaneously.

Pain was assessed at 0, 2, 4, and 6 hours after surgery by recording the rats in glass cages for 10 minutes at each time point.

Results

Overall, pain was most severe (1.5—2) for OVX without analgesia. Preoperative 25 mg/kg tramadol provided only short-term analgesia, with moderate to severe pain (1–1.5) beginning 2 hours after OVX. Postoperative tramadol dosed at 25 mg/kg resulted in moderate pain (0.5–1.25). Postoperative tramadol at 50 mg/kg resulted in the least severe pain (0.25).

For each facial expression category, researchers observed variable pain levels in the treatment groups across time points:

  • Orbital tightening: Throughout the study period, pain was severe (eyes tightly closed) for OVX without analgesia. For OVX with analgesia, the pain was moderate at most time points, with postsurgical analgesia resulting in no observable pain at 6 hours after surgery.
  • Nose/cheek flattening: Pain was severe (nose elongated and cheeks absent) immediately after surgery for OVX without analgesia and 25 mg/kg tramadol (pre- and postoperative). Starting 2 hours after surgery, pain was moderate for each treatment group.
  • Ear position: Pain was severe (ears curled and angled outward) for most treatment groups immediately after surgery. Starting 2 hours after surgery, the pain tapered to a moderate level for each treatment group.
  • Whisker position: OVX without analgesia led to pain that was severe (whiskers angled outward and bunched together) immediately after surgery and moderate thereafter. OVX with analgesia resulted in moderate pain throughout the study period.

Discussion

These preliminary results indicate the reliability of the RGS in assessing postoperative pain in laboratory rats. In particular, the scores suggest that, in ovariectomized rats, 25 mg/kg tramadol provides inadequate analgesia and 50 mg/kg tramadol provides optimal analgesia.

Because of the study’s small sample size, further research will be needed to determine the dose and administration of tramadol needed to achieve optimal analgesia in laboratory rats undergoing surgical procedures.

Dr. JoAnna Pendergrass received her Doctor of Veterinary Medicine degree from the Virginia-Maryland College of Veterinary Medicine. Following veterinary school, she completed a postdoctoral fellowship at Emory University’s Yerkes National Primate Research Center. Dr. Pendergrass is the founder and owner of JPen Communications, a medical communications company.

Related Content:

Pain Management
Managing pain in the postoperative patient
Managing pain in the postoperative patient
Most important advice this veterinarian received in rehabilitative medicine
Most important advice this veterinarian received in rehabilitative medicine
3 Must-reads from the Directions in Veterinary Medicine symposium
3 Must-reads from the Directions in Veterinary Medicine symposium

Advertisement

Latest News

Drug for acute onset of canine pancreatitis is launched on the US market

New Automatic 2-in-1 Pet Feeder and Water Dispenser launched

PetHub launches AI tools for pet owners

Prairie dog pups emerge from underground at Maryland Zoo

View More Latest News
Advertisement