Comparison of the effectiveness of lidocaine/bupivicain infused Gelfoam® to the
effectiveness of the injection of local anesthetic into the retrobulbar space as postoperative analgesia following an eye enucleation in dogs.
Objective – To compare the effectiveness of lidocaine/bupivicain infused Gelfoam® to the effectiveness of
an injection of local anesthetic into the retrobulbar space as post-operative analgesia following an eye
enucleation in dogs.
Design – Randomized controlled trial
Methods and Materials – Client-owned dogs admitted to VCA Aurora Animal Hospital for routine eye
enucleation were enrolled with the owner consent and randomly assigned to a treatment group
(lidocaine/bupivicaine infused Gelfoam®) or control group (0.9% saline infused Gelfoam®). Baseline
subjective pain scores were recorded using a pain scale developed from a previous study using previously
published pain scales (Myrna et al, 2010). Anesthesia consisted of hydromorphone (0.2 mg/kg, IM),
midazolam (0.2 mg/kg, IM), glycopyrrolate (0.007 mg/kg, IM) and isoflorane in oxygen for maintenance.
Patients were also perioperatively given cefazolin (22 mg/kg, IV) and meloxicam (0.2 mg/kg, IV).
Transpalpebral eye enucleation was performed. The amount of liquid injected into the Gelfoam®
depended on weight of the animal. For dogs weighing < 15kg received 1.0ml of bupivacaine and 1.0ml of
lidocaine or 2mls of saline was used. For dogs weighing > 15kg received 1.5mls bupivacaine and 1.3mls of
lidocaine or 3mls of 0.9% saline was used to infuse the Gelfoam®. In order to avoid local anesthetic
toxicosis a < 2mg/kg dose was used. Pain scores were then recorded at 15 and 30 minutes 1, 2, 4, 6, 8, and
24 hours after extubation (time 0) by trained observers masked to treatment groups. Dogs were given
hydromorphone (0.2mg/kg, IM or IV) as rescue analgesia if the subjective pain score ≥6/24 or ≥ 9/18 (or a
score of three in any individual category at any point in time) with their respective pain scales.
Animals – Number to be determined; Patients were excluded from the study if their contralateral remaining
eye was painful, they were being treated by systemic administration of pain medication for a chronic
condition, or they had any other clinically detectable source of pain not attributed to the affected globe.
Procedures – All dogs underwent initial complete ophthalmic and physical examinations. Dogs were
evaluated subjectively to obtain a baseline pain score. Preoperative diagnostic evaluations, including CBC,
serum biochemical analysis, and diagnostic imaging (eg, thoracic radiography or abdominal
ultrasonography), were preformed as indicated by signalment, historical and clinical findings, and
underlying systemic conditions.
Prior to anesthesia, all dogs were premedicated with hydromorphone (0.2 mg/kg [0.09 mg/lb],
midazolam (0.2 mg/kg, IM), and glycopyrrolate (0.007 mg/kg, IM). Twenty minutes later, and IV catheter
was placed in the cephalic or lateral saphenous vein and anesthesia was induced by IV administration of
propofol to effect. Anesthesia was then maintained with isoflurane in oxygen after endotracheal intubation.
cefazolin (22 mg/kg, IV) and meloxicam (0.2 mg/kg, IV) were also given perioperatively. Transpalpebral
eye enucleation, with or without placement of an intraorbital silicone prosthesis, was preformed.
Dogs were randomly allocated to 1 or 2 treatment groups as follows: a 0.9% saline solution
control group and a lidocaine/bupivicaine treatment group. Patients were randomly assigned to
treatment groups. Personnel in the VCA Ophthalmology department provided the lidocaine/bupivicaine
or saline solution in an unlabeled syringe, such that personnel performing pain scoring were masked to
treatment. Dogs were administered the infused Gelfoam® (control or treatment) after the enucleation and
hemostasis was controlled.
Dogs were monitored at a set time points post-operatively and pain scored at set time points postoperatively by one of two trained, blinded veterinarians. Rescue analgesia, hydromorphone (0.2 mg/kg, IV
or IM, q 2 to 4 h), was administered as needed throughout the 24-hour postoperative period on the basis of
a cumulative participant pain score of 6/24 or ≥ 9/18 (or a score of three in any individual category at any
point in time) with their respective pain scales. The pain scores were recorded using a pain scale from a
published study which adapted their pain scale from previously published pain scales (Myrna et al, 2010).
This was done in order to allow for better comparison between the two studies. Subjective pain score
measurements were obtained by assessment at the time of initial admission (12 to 24 hours before surgery
at the time of ophthalmic examination), before premedication, at extubation, and 15 and 30 minutes and 1,
2, 4, 6, 8, and 24 hours after surgery. Post operative medications included: meloxicam (0.2mg/kg PO
q24hrs), tramadol (3mg/kg PO q8hrs), and cefpodoxime (5mg/kg PO q24hrs).
Statistical Analysis – To be determined
Results – To be determined
Eye Enucleation Pain Score Assessment System
Date: ___________
Patient: ____________________________
Client/Patient#: ____________________________
Time: 12-24 hours prior to surgery / premedication / at extubation / Post Op: 15min /
30min / 1 / 2 / 4 / 6 / 8 / 24 hours (Circle one)
Observation
Comfort
Final Score
Score
0
1
2
3
4
Criteria
Dog asleep or calm
Awake; interested in surroundings
Mild agitation or depressed; uninterested in surroundings
Moderate agitation, restless, and uncomfortable
Extremely agitated and thrashing
Movement
0
1
2
3
Quiet
1-2 position changes/min
2-6 position changes/min
Continuous position changes
Appearance
0
1
2
3
4
Too sedate to evaluate
Normal
Allows, but then moves away when operated eye touched
Will not allow operated eye to be touched
Will no allow head to be touched
Behavior
(unprovoked)
0
1
2
3
4
Too sedate to evaluate
Normal
Minor changes
Moderately abnormal (less mobile or alert than normal; unaware of surroundings or very restless)
Markedly abnormal (very restless, vocalization, self-mutilation, grunting, or facing back of the
cage)
Vocalization
0
1
2
3
Quiet
Crying, but responds to quiet voice and stroking
Intermittent crying, no response to quiet voice and stroking
Constant crying (unusual for this individual); no response to stroking or voice.
Heart Rate
Comments:______________________________________________________________________________________________________
______________________________________________________________________________________________________________________
_____________________________________________________________________________________________________________________
Eye Enucleation Random Assignment Form
Date
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35
Patient Name
Client Name
Patient
Number
Client Number
Control/Treatment
Control
Treatment
Control
Treatment
Control
Treatment
Control
Treatment
Control
Treatment
Control
Treatment
Control
Treatment
Control
Treatment
Control
Treatment
Control
Treatment
Control
Treatment
Control
Treatment
Control
Treatment
Control
Treatment
Control
Treatment
Control
Treatment
Control
Treatment
Control
Reason for
Enucleation
Eye Enucleation Random Assignment Form
Date
Patient Name
Client Name
Patient
Number
36
37
38
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Client Number
Control/Treatment
Control
Treatment
Control
Treatment
Control
Treatment
Control
Treatment
Control
Treatment
Control
Treatment
Control
Treatment
Control
Treatment
Control
Treatment
Control
Treatment
Control
Treatment
Control
Treatment
Control
Treatment
Control
Treatment
Control
Treatment
Control
Treatment
Control
Treatment
Control
References:
Reason for
Enucleation
1. Tranquilli, WJ., Thurmon, JC., Grimm KA. Lumb and Jones’ Veterinary Anesthesia
and Analgesia: 4th Edition. Blackwell Publishing, 2007.
2. Myrna KE, Bentley E, Smith, Lesley JS. Effectiveness of Injection of Local
Anesthetic into the Retrobulbar Space for Postoperative Analgesia Following Eye
Enucleation in Dogs. JAVMA 2010;237:174-177.
3. Plumbs DC., Plumb’s Veterinary Drug Handbook: 6th edition. Stolkholm, Wis.
PharmVet, 2008.
4. Ripart J., Lefant JY, et al. Peribulbar versus Retrobulbar Anesthesia for Ophthalmic
Surgery. Anesthesiology 2001; 94:56-62.
5. Nouvellon E., Cuvillon P., et al. Regional Anesthesia and Eye Surgery.
Anesthesiology 2010; 113:1236-42.
6. Ripart J., Lefrant JY., et al. Opthalmic Regional Anesthesia: Medical Canthus
Episcleral (Sub-Tenon) Anesthesia Is More Efficient than Peribulbar Anesthesia.
Anesthesiology 2000; 92:1278-85.
7. Kumar, C., Dowd, T. Ophthalmic Regional Anesthesia. Current Opinion in
Anaesthesiology 2008; 21:632-637.