Recognizing and managing pain in small mammals (Proceedings)

Physiologic "Stress" Response to Pain

      - Vasoconstriction

      -Increased Heart Rate and Stroke Volume

      -Decreased GI & Urinary Tone

      -Physiologic "Stress" Response to Pain:

      -Endocrine Responses

      -Nociceptive Stimulation of Brain

      - Enhance Reflex Sympathetic Responses

      -Immune Suppression

      -Impaired Wound Healing

      -Decreased Food & Water Intake

      -Secondary Medical Problems

      -Gastric ulcers GI Stasis

      -Shock

      -Death

• Higher rate of anesthetic death in exotics?

• Higher rate of death postoperatively?

How is this related to inadequate use of pre, intra & postoperative analgesics in prey species????? Stress???

Behaviors Associated with Pain in Small Mammals

      -Predators such as ferrets are more likely to show overt signs of pain

      -Prey species such as rabbits and guinea pigs are less likely to show overt signs of pain

      -Half-closed/dull/unfocused eyes

      -Aggressive when normally docile

      -Pressing abdomen on the floor

      -Immobility/Lethargy/Isolation

      -Fewer, smaller or no fecal pellets

      -Vocalization (squeal may be fear in rabbits)

      -Increased frequency and depth of respirations or rapid shallow breathing

      -Polyuria/Polydipsia (especially w/GI pain)

      -Teeth grinding (bruxism)                                          Lameness/Ataxia

      -Reluctance to curl when sleeping (ferrets)                 Anorexia

      -Stretching w/back arched                                        Hunched posture

      -Tucked appearance                                               Chewing at affected site

      -Strained facial expression w/bulging eyes                Piloerection

      -Head extended and elevated                                   Stiff movements

      -Stinting on palpation                                               Self-mutilation

      -Porphyrin secretion (stress)                                      Squinting (especially ferrets)

Painful Disease Processes

Pain Management Considerations

      - Pre-emptive analgesia

      -Neuropathic Pain

      -Inflammatory Pain

      -Decreases dose of maintenance anesthetic

      -Care with injectable anesthetics

      -Individualize treatment and provide Multimodal Pain Therapy

      -Numerous pain pathways

      -Synergistic effect

      -Analgesics often used at lower doses

      -Anxiety lowers the pain threshold

      -The effects of illness, restraint and environmental changes w/hospitalization increase the level of stress experienced.

      -Never discount the owners concern - familiarity w/daily behavior is important in assessing pain.

      -Train your staff to recognize pain in exotics

      -Assign staff member to monitor patient throughout their hospitalization

NSAID's

      -Don't use with renal and hepatic impairment, bleeding disorders, enteritis, gastritis, gastric ulcers hypotension or hypovolemia

      -Don't combine with corticosteroids

      -Use lower doses with ferrets

      -Use with caution for prolonged use in herbivores, use gastric protectants

      -Hypotension is often seen as an anesthetic complication in small mammals – use pre-op NSAIDS w/caution

Opioids

      -Avoid use in hypotensive patients

      -Short duration of action

      -Decrease need for isoflurane

      -Administer during lighter plane when also using injectable anesthesia

      -Butorphanol – least potent and shortest duration

      -Buprenorphine – intermediate strength and longest duration (6-8 hrs.)

      -Morphine – most potent and intermediate duration

      -Oral buprenorphine (transmucosal) has been found pharmacologically effective in cats and more recently dogs (abstract from ACVA mtg). Clinically effective in rabbits and ferrets.

      -Pica has been noted in rats on buprenorphine

      -Ferrets can be prone to side effects including hypotension, sedation and respiratory depression

      -Guinea pigs, rabbits, chinchillas can be prone to side effects associated with the GI tract.

Analgesics for Small Mammals

NSAIDS

      -Acetylsalicylic Acid - 50 to 100 mg/kg q 8 - 24 h PO

      -Carprofen - 1 to 4 mg/kg q 12 to 24 h PO, SQ, IM

      -Flunixin meglamine - 0.1 to 2 mg/kg q 12 -24 h SQ, IV, IM (herbivores)

      -Piroxicam – 0.2 mg/kg PO q 8 h

      -Ibuprofen - 2 to 7.5 mg/kg q 4 to 24 h IM, PO

      -Ketoprofen - 1 to 3 mg/kg IM, SQ, PO q 24 h

      -Meloxicam - 0.1 to 0.2 mg/kg q 24 hr SQ, PO

      -Meloxicam (Metacam)

      -6 to 8 hrs to reach blood levels so use well before procedure for post-op pain

      -Possibly d/t rapid metabolism higher doses may be needed in rabbits/rodents

      0.3 mg/kg/day PO in rabbits (Turner, et al)

      1-2 mg/kg pre-op in rats (to achieve post-op pain) (Roughan and Flecknell)

      -Ferrets can be more sensitive to NSAID side effects so be more cautious w/dose (similar to cats)

      -Do not use in ferrets if ulcers are suspected or if vomiting/diarrhea or melena are present

      -Bloodwork to R/O liver/kidney disease

Opioids

      -Butorphanol - 0.1 to 0.5 mg/kg q 4-6 h SQ, IV, IM

      -Buprenorphine - 0.01 to 0.1 mg/kg q 6 to 12 h SQ, IM, IV

      -Tramadol (syn. Analogue of codeine) – less side effects than opiods.

      -Pharmacological studies indicated 10 mg/kg safe in rabbits (TBB uses 3 mg/kg)

      -Can decrease blood glucose levels

      -Morphine - 1.25 to 5 mg/kg q 2-4 h SQ, IM

      -Oxymorphone 0.05 to 0.2 mg/kg q 4-12 h SQ, IM

           Combining NSAIDS and Opiods provides multimodal analgesia (usually at lower dosages) with less side effects.

Local Analgesia

      -Lidocaine 2% - 1 mg/kg (can be used in combo with bupivicaine for longer analgesia)

      -Bupivicaine 0.5% - 1 mg/kg (can be used in combo with lidocaine for longer analgesia)

      -Cetacaine on wounds from maggots and on incisions if chewing postoperatively

Nerve Blocks

Epidural Analgesia

Lidocaine 1.5% 0.4 ml/kg

Fentanyl

     • 0.0074 mg/kg IV

     • 0.15 to 0.44 ml/kg IM (can cause muscle necrosis)

Fentanyl Patches

     • Rabbits: 1/3 to 1/2 patch per 3 kg rabbit X 3 days

Alternative Approaches to Pain Management

      -Acupuncture

      -Massage Therapy

      -Chiropractic

      -Physiotherapy

      -Cranioelectrical Stimulation (CES)

      -Alpha Stim TM

      -Uses a biphasic square electrical wave

      -Rx for pain, anxiety, depression and insomnia

      -Current studies in amputees & breast cancer patients

      -Pain, Wound Healing, Anxiety in animals

      -Alternative Approaches to Pain Management

      -Produces the alpha state within the body's electrical activity pattern

      -Calmness, mental focus, pain control

      -Disregulation of firing patterns in the brain responsible for behavioral anomalies:

      -depression, anxiety, insomnia. addictions, OCD, etc.

Microcurrent Electrical Therapy (MET)

      -Electrical current stimulates healing and growth and regeneration

      -Initiates and sustains chemical & electrical relations in the healing process

      -Bacteria do not like the microcurrent

      Injury causes a change in polarity that is reestabished with MET

Assessment of Response to Analgesics

      Return to Normal Behavior:

          • Eating

          • Sleeping

          • Stretching

          • Grooming

Always sedate or preferably anesthetize small mammals before euthanasia