1)     AGENTS

a)      Lidocaine

i)        General

(1)   Local anesthetic with quick onset and short duration of action

(a)    Onset = few seconds to a few minutes

(b)   Duration = 1 to 2 hours

ii)      Dose

(1)   Dogs

(a)    1.0 to 5 mg/kg (0.5 to 2.5 mg/lb)

(2)   Cats

(a)    1.0 to 2.5 mg/kg (0.5 to 1.0 mg/lb)

iii)    Precautions

(1)   Potential CNS toxicity

(a)    Usually manifests as seizure activity

iv)    Cost

(1)   Low

b)      Mepivacaine

i)        General

(1)   Local anesthetic with quick onset and moderate duration of action

(a)    Onset = 5 to 10 minutes

(b)   Duration = 2 to 3 hours

ii)      Dose

(1)   Dog

(a)    5 mg/kg (2.5 mg/lb) in dogs

(2)   Cat

(a)    2.5 mg/kg (1.0 mg/lb)

iii)    Precautions

(1)   IV use is not currently recommended

iv)    Cost

(1)   Low

c)      Bupivacaine

i)        General

(1)   Local anesthetic with slower onset and longer duration of action

(a)    Onset = 20 to 30 minutes

(b)   Duration = 3 to 5 hours

ii)      Dose

(1)   Dog and cat

(a)    1.0 to 2.0 mg/kg (0.5 to 1.0 mg/lb)

iii)    Precautions

(1)   Never give bupivacaine IV

(2)   Potentially fatal cardiac toxicity

(a)    Calculate doses carefully and aspirate carefully to guard against intravascular administration

(3)   There is some debate about the use of intrapleural bupivacaine if a pericardiectomy has been performed due to the increased potential for cardiac toxicity

iv)    Cost

(1)   Moderate

2)     APPLICATIONS

a)      First, consider adding an opioid to the local anesthetic

i)        Both 0.075 mg/kg (0.035 mg/lb) morphine and 0.003 mg/kg (0.0015 mg/lb) buprenorphine have been shown to effectively double the analgesic duration when combined with lidocaine and bupivacainein humans ^1,2 

b)      Outpatient/awake patient use

i)        Mix 0.9 cc Lidocaine, 0.1 cc sodium bicarbonate, and 2 cc of sterile water

(1)   Reduced sting

(2)   Volume is more important than concentration

(3)   Increasing the bicarbonate percentage above 10% is not recommended as it will lead to precipitation of the drug

c)      Splash block

i)        Drip on or in SubQ space at closure of skin wound

ii)       The effectiveness of splash blocks is in question

d)      Ring blocks

i)        Mix 1.0 mg/kg (0.5 mg/lb) bupivacaine with 1.0 mg/kg (0.5 mg/lb) lidocaine and:

(1)   Either 0.075 mg/kg (0.035 mg/lb) morphine or 0.003 mg/kg (0.0015 mg/lb) buprenorphine to effectively double the duration of analgesia ^1,2

(2)   Sterile water q.s., if needed, to total 1 cc volume for cats less than 2.5 kg (5 lb).

(3)   Sterile water q.s., if needed, to total 2 cc volume for cats 2.5 kg (5 lb) and over.

ii)       Inject subcutaneously at the three sites demonstrated below:

iii)     You may drop the lidocaine if given prior to spay (gives bupivacaine time to take effect)

iv)     Bupivacaine has significant potential to cause cardiac toxicity

(1)   Calculate dose carefully

v)   DO NOT USE EPINEPHRINE CONTAINING AGENTS

v)      Click here for an MS Excel Ring Block dose calculator

e)      Intra-testicular blocks

i)        This is a very effective, low-cost application of local anesthetic agents

ii)       Mix 1.0 mg/kg (0.5 mg/lb) bupivacaine with 1.0 mg/kg (0.5 mg/lb) lidocaine and:

(1)   Either 0.075 mg/kg (0.035 mg/lb) morphine or 0.003 mg/kg (0.0015 mg/lb) buprenorphine to effectively double the duration of analgesia^1,2

iii)     Use a 25g 5/8” needle for most cats and a 22g 1 to 1 ½“ needle for dogs

iv)     Place the needle through the testicle starting from the caudal pole aiming for the spermatic cord

v)      It is OK, even desirable, for the needle to exit the testicle proximally as it is the spermatic cord that will receive the direct clamp stimulation

vi)     ASPIRATE BEFORE INJECTING

(1)    Inject, expecting firm backpressure, while withdrawing the needle

(2)   Expect to use about 1/3 to ½ of the drug volume per testicle leaving the organ firmly turgid

vii)   Repeat for other testicle

viii)  The left over drug can/should be used to place a dermal incisional block

ix)     The total time for this procedure should be 1 to 2 minutes

x)      Drugs costs:

(1)   3 kg cat = $0.04

(2)   55 kg dog = $0.65

xi)     Videos

IT Block in 16 kg canine	Incisional block in 16 kg canine

f)     Intra-articular Injections

i)        Lidocaine

(1)   2 mg/kg (1 mg/lb)

(a)    With epinephrine prior to arthrotomy to help control hemorrhage

(b)   Without epinephrine after joint closure

ii)       Bupivacaine

(1)   1.0 mg/kg (0.5 mg/lb) after closure

iii)     Generally, 4 - 6 ml fills a stifle

iv)     Place in joint after closure or place lidocaine w/epinephrine in joint before arthrotomy, wait 5 minutes, then proceed with surgery

g)       Mandibular Block

i)        Palpate foramen digitally from oral cavity to guide needle

ii)       Use 0.5 to 1.5 ml total volume

iii)     Effective coverage includes:

(1)   Lower teeth

(2)   Skin and mucosa of lower lip

h)      Maxillary Block

i)        1.5 cm caudal to medial canthus

ii)       Just ventral to zygomatic arch and ahead of the ramus

iii)     Use 1.0 to 1.5 ml total volume

iv)     Effective coverage includes:

(1)   Maxilla and upper teeth

(2)   Nose and upper lip

i)      Intercostal blocks

i)        Block 2 spaces ahead and behind intercostals incision

ii)       Place 0.25 to 1.0 ml per site along the caudal border of each rib near the level of the intervertebral foramen

(1)   Do not exceed the dose guidelines above

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