Veterinary Anesthesia & Analgesia Support Group
Practical Information for the Compassionate Veterinary Practitioner
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  Pain Management Basics
  Bob Stein
  December, 2004


a)      General Approach

i)        Pain management is an integral part of any thorough anesthetic program. Patient comfort improves and morbidity is reduced with effective pain relief.

ii)       Key facts:

(1)   Pre-emptive analgesic use is the most effective.

(a)    Central and peripheral sensitization are most effectively managed preemptively

(2)   Strategic analgesic use requires anticipation of patient need. We are not as effective when we wait for the symptoms of increasing pain before employing added analgesics.

(a)    An understanding of currently held opinions regarding duration of analgesic effect is critical

(b)   Developing a familiarity with techniques that provide sustained analgesia is critical

(3)   Analgesics should not be reserved for severe pain. They should be employed during any procedure that is associated with stress and discomfort. By more effectively limiting patient anxiety and pain, we create a patient population that is much less fearful about future visits to our facilities. This can enhance the enjoyment for client, patient, and veterinary staff alike.

(a)    We extend this concern over patient stress to include the collection of pre-anesthetic screening tests. If it is deemed appropriate by the anesthetist, an analgesic/sedative may be given to help facilitate patient comfort and reduce the struggle associated with sample collection.

(i)      Few tests are directly influenced by analgesic/sedative medications but these influences can include:

1.      Decreased PCV – Acepromazine can decrease the PCV by 30 %.

2.      Blood pressure – Acepromazine can decrease systemic blood pressure.

3.      Opioid agents can decrease heart rate and decrease ventilation.

4.      Alpha-2 agonists can dramatically lower heart rate.

a.       Blood pressure may remain normal.

iii)     Duration of effect

(1)   30 minutes

(a)    Fentanyl injectable

(2)   30 to 60 minutes

(a)    Butorphanol in dogs

(3)   1 to 3 hours                        

(a)    Butorphanol in cats

(b)   Buprenorphine at 0.006 mg/kg

(4)   4 to 6 hours

(a)    Morphine, hydromorphone, oxymorphone

(b)   Buprenorphine at 0.010 mg/kg

(c)    Medetomidine

(5)   6 to 8 hours

(a)    Buprenorphine at 0.020 mg/kg

(6)   8 to 10 hours

(a)    Buprenorphine at 0.030 mg/kg

(7)   10 to 12 hours at high end of dose range

(a)    Buprenorphine at 0.040 mg/kg

(b)   Epidural oxymorphone

(8)   12 to 18 hours

(a)    Epidural hydromorphone

(b)   Epidural morphine

(c)    Epidural buprenorphine

(d)   Ketoprofen

(i)      To avoid GI side-effects, limit to single dose use

(ii)    F

(e)    3 to 5 days

(9)   Indefinite duration

(a)    Sustained effect during CRI administration

(b)   No specific limitation

(c)    Agents

(i)      Ketamine

1.      Should be preceded by an opioid agent

(ii)    Fentanyl

(iii)   Morphine

(iv)  Lidocaine

b)      Pre-anesthetic Medications

i)        Medetomidine, acepromazine, opioids, and benzodiazepines are utilized based upon patient status and need.

ii)       Remember that Fentanyl patches take 12 – 18 hours to develop adequate Fentanyl blood levels, possibly up to 24 hours in dogs

c)      Induction

i)        Effective pain management will lead to a reduction in induction anesthetic need

d)      Maintenance

i)        Effective pain management will lead to a reduction in maintenance anesthetic need

ii)       Intraoperative fentanyl, hydromorphone, or oxymorphone boluses or increasing the CRI analgesic rate can help a patient through a particularly painful portion of a procedure and help avoid the need for higher levels of maintenance anesthetic

e)      Post-op

i)        Repeat analgesics as needed or continue CRI

(1)   Anticipate patient need – do not wait for patient to act painful before redosing

f)       Support

i)        Constant rate infusion (CRI) – the following dose schedules are intended for use during the perioperative period with planned flow rates of 10 to 20 ml/kg/hr (5 to 10 ml/lb/hr) - See CRI specific heading for alternatives

(1)   Ketamine

(a)    Add 60 mg Ketamine (0.6 cc) to 1 liter fluid bag

(i)      Affix high visibility sticker itemizing added medications

(b)   Administer 10 ml/kg/hr (5 ml/lb/hr) to begin with

(i)      Provides 0.6 mg/kg/hr (0.3 mg/lb/hr)

(ii)    Rate can be doubled if needed

(c)    Bolus 0.15 to 0.25 mg/lb IV at the start of the infusion if ketamine or telazol was not already given in the induction protocol

(d)   Ketamine CRI should always be preceded by an opioid agent

(2)   Morphine Sulfate CRI recipe

(a)    Add 15 mg Morphine (1.0 cc) to 1 liter fluid bag

(i)      Affix high visibility sticker itemizing added medications

(b)   Administer 10 ml/kg/hr (5 ml/lb/hr) to begin with

(i)      Provides 0.15 mg/kg/hr (0.075 mg/lb/hr)

(ii)    Rate can be doubled if needed

(c)    If on drip for over 24 hours, plan gradual reduction over 12 to 24 hours to avoid cold turkey withdrawal

(3)   Lidocaine

(a)    Add 30 mg Lidocaine (1.5 cc)  to 1 liter fluid bag

(i)      Affix high visibility sticker itemizing added medications

(b)   Administer 10 ml/kg/hr (5 ml/lb/hr) to begin with

(i)      Provides 0.3 mg/kg/hr (0.15 mg/lb/hr)

(ii)    Rate can be doubled if needed

(iii)   Use very cautiously in cats



a)      General

i)         Benzodiazepines are not analgesics

ii)       Acepromazine is not an analgesic

iii)     Ketoprofen should be limited to single use only - dose should not be repeated

(1)   Potential for undesirable effects is extremely small if limited to single use only but potential for undesirable effects increases substantially when Ketoprofen is repeated

iv)     Ketamine use is generally discouraged in seizure patients and head trauma patients

v)      Remember that narcotic antagonists will reverse opioid analgesic effect as they reverse sedative effect.

(1)   Most pure Mu opioid agonists have a longer duration than naloxone. If you are serious about reversing a narcotic effect, you should consider redosing naloxone as needed until you are confident the agonist effect has worn off.

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