OBJECTIVE To determine the onset, duration, and extent of regional nerve blocks performed by administration of lidocaine or lidocaine-bupivacaine into the infraorbital canal in dogs.
ANIMALS 6 healthy hound-type dogs.
PROCEDURES Under general anesthesia, stimulating needles were inserted into the gingiva dorsolateral to both maxillary canine (MC) teeth and the maxillary fourth premolar (MPM4) and second molar (MM2) teeth on the treatment side. A reflex-evoked muscle potential (REMP) was recorded from the digastricus muscle after noxious electrical stimulation at each site. After baseline measurements, 1 mL of 2% lidocaine solution or a 2% lidocaine-0.5% bupivacaine mixture (0.5 mL each) was injected into the infraorbital canal (at approx two-thirds of the canal length measured rostrocaudally). The REMPs were recorded for up to 7 hours. The REMP data for the contralateral (untreated control) canine tooth were used to normalize results for all stimulation sites.
RESULTS With both treatments, nerve block for MC teeth on the treated side was achieved by 5 (n = 5 dogs) or 10 (1) minutes after injection, but nerve block for ipsilateral MPM4 and MM2 teeth was successful for only 3 dogs and 1 dog, respectively. Mean duration of nerve blocks for MC teeth was 120 and 277 minutes following injection of lidocaine and lidocaine-bupivacaine, respectively.
CONCLUSIONS AND CLINICAL RELEVANCE Local anesthesia, as performed in this study, successfully blocked innervation of MC teeth, but results for MPM4 and MM2 teeth were inconsistent. This specific technique should not be used during tooth extractions caudal to the MC teeth.
Objective—To compare cardiovascular effects of
equipotent infusion doses of propofol alone and in
combination with ketamine administered with and
without noxious stimulation in cats.
Procedure—Cats were anesthetized with propofol
(loading dose, 6.6 mg/kg; constant rate infusion [CRI],
0.22 mg/kg/min) and instrumented for blood collection
and measurement of blood pressures and cardiac
output. Cats were maintained at this CRI for a further
60 minutes, and blood samples and measurements
were taken. A noxious stimulus was applied for 5 minutes,
and blood samples and measurements were
obtained. Propofol concentration was decreased to
0.14 mg/kg/min, and ketamine (loading dose, 2
mg/kg; CRI, 23 µg/kg/min) was administered. After a
further 60 minutes, blood samples and measurements
were taken. A second 5-minute noxious stimulus
was applied, and blood samples and measurements
Results—Mean arterial pressure, central venous
pressure, pulmonary arterial occlusion pressure,
stroke index, cardiac index, systemic vascular resistance
index, pulmonary vascular resistance index,
oxygen delivery index, oxygen consumption index,
oxygen utilization ratio, partial pressure of oxygen in
mixed venous blood, pH of arterial blood, PaCO2, arterial
bicarbonate concentration, and base deficit values
collected during propofol were not changed by the
addition of ketamine and reduction of propofol.
Compared with propofol, ketamine and reduction of
propofol significantly increased mean pulmonary arterial
pressure and venous admixture and significantly
Conclusions and Clinical Relevance—Administration
of propofol by CRI for maintenance of anesthesia
induced stable hemodynamics and could prove
to be clinically useful in cats. (Am J Vet Res 2003;64:913–917)
Objective—To determine the minimum infusion rate
(MIR50) for propofol alone and in combination with
ketamine required to attenuate reflexes commonly
used in the assessment of anesthetic depth in cats.
Procedure—Propofol infusion started at 0.05 to 0.1
mg/kg/min for propofol alone or 0.025 mg/kg/min for
propofol and ketamine (low-dose [LD] constant rate
infusion [CRI] of 23 µg/kg/min or high-dose [HD] CRI
of 46 µg/kg/min), and after 15 minutes, responses of
different reflexes were tested. Following a response,
the propofol dose was increased by 0.05 mg/kg/min
for propofol alone or 0.025 mg/kg/min for propofol
and ketamine, and after 15 minutes, reflexes were
Results—The MIR50 for propofol alone required to
attenuate blinking in response to touching the medial
canthus or eyelashes; swallowing in response to
placement of a finger or laryngoscope in the pharynx;
and to toe pinch, tetanus, and tail-clamp stimuli were
determined. Addition of LD ketamine to propofol significantly
decreased MIR50, compared with propofol
alone, for medial canthus, eyelash, finger, toe pinch,
and tetanus stimuli but did not change those for laryngoscope
or tail-clamp stimuli. Addition of HD ketamine
to propofol significantly decreased MIR50, compared
with propofol alone, for medial canthus, eyelash,
toe pinch, tetanus, and tail-clamp stimuli but did
not change finger or laryngoscope responses.
Conclusions and Clinical Relevance—Propofol
alone or combined with ketamine may be used for
total IV anesthesia in healthy cats at the infusion rates
determined in this study for attenuation of specific
reflex activity. ( Am J Vet Res 2003;64:907–912)
Objective—To determine the incidence and type of alterations in heart rate (HR), peak systolic blood pressure (PSBP), and serum biochemical variables (total bilirubin, BUN, and creatinine concentrations) associated with IV administration of ionic-iodinated contrast (IIC), nonionic-iodinated contrast (NIC), and gadolinium dimeglumine (GD) contrast media in anesthetized dogs.
Procedures—HR and PSBP were recorded at 5-minute intervals for 20 minutes for untreated control dogs and dogs that received IIC, NIC, or GD contrast medium. The development of an HR of < 60 beats/min or > 130 beats/min that included a ≥ 20% change from baseline was considered a response. The development of PSBP of < 90 mm Hg or > 160 mm Hg that included a ≥ 20% change from baseline was considered a response. Pre- and postcontrast serum biochemical values were recorded.
Results—Of dogs receiving IIC medium, 3% (3/91) had a response in HR and 4% (4/91) had a response in PSBP at ≥ 1 time points. None of the dogs receiving NIC medium had a response in HR; 1 of 16 had a response in PSBP. Of dogs receiving GD contrast medium, 1% (1/92) had a response in HR and 4% (4/92) had a response in PSBP. Of control dogs, 2% (2/81) had a response in HR and 4% (3/81) had a response in PSBP. No serum biochemical alterations were observed.
Conclusions and Clinical Relevance—IV administration of contrast media in anesthetized dogs caused moderate bradycardia, tachycardia, hypotension, or hypertension.
Objective—To determine effects of epidural administration of morphine and buprenorphine on the minimum alveolar concentration of isoflurane in cats.
Animals—6 healthy adult domestic shorthair cats.
Procedures—Cats were anesthetized with isoflurane in oxygen. Morphine (100 μg/kg diluted with saline [0.9% NaCl] solution to a volume of 0.3 mL/kg), buprenorphine (12.5 μg/kg diluted with saline solution to a volume of 0.3 mL/kg), or saline solution (0.3 mL/kg) was administered into the epidural space according to a Latin square design. The minimum alveolar concentration (MAC) of isoflurane was measured in triplicate by use of the tail clamp technique. At least 1 week was allowed between successive experiments.
Results—The MAC of isoflurane was 2.00 ± 0.18%, 2.13 ± 0.11%, and 2.03 ± 0.09% in the morphine, buprenorphine, and saline solution groups, respectively. No significant difference in MAC was detected among treatment groups.
Conclusions and Clinical Relevance—A significant effect of epidural administration of morphine or buprenorphine on the MAC of isoflurane in cats could not be detected. Further studies are needed to establish whether epidural opioid administration has other benefits when administered as a component of general anesthesia in cats.
Objective—To determine whether opioids with varying
interactions at receptors induce a reduction in
minimum alveolar concentration (MAC) of isoflurane
Animals—12 healthy, female, spayed cats.
Procedure—Cats were anesthetized with isoflurane
and instrumented to allow collection of arterial blood
and measurement of arterial blood pressure. Each
drug was studied separately, and for each drug cats
were randomly allocated to receive 2 doses. The
drugs studied were morphine (0.1 or 1.0 mg/kg),
butorphanol (0.08 or 0.8 mg/kg), buprenorphine
(0.005 and 0.05 mg/kg), and U50488H (0.02 and 0.2
mg/kg). All drugs were diluted in 5 ml of saline (0.9%
NaCl) solution and infused IV for 5 minutes. The MAC
of isoflurane was determined in triplicate, the drug
administered, and the MAC of isoflurane redetermined
for a period of 3 hours.
Results—All drugs had a significant effect on MAC
over time. With morphine only, the effect on MAC
over time was different between doses. The greatest
mean (± SD) reductions in MAC of isoflurane in
response to morphine, butorphanol, buprenorphine,
and U50488H administration were 28 ± 9, 19 ± 3, 14
± 7, and 11 ± 7%, respectively.
Conclusions and Clinical Relevance—Morphine (1.0
mg/kg) and butorphanol (0.08 and 0.8 mg/kg) induced
significant reductions in MAC of isoflurane that were
considered clinically important. Although significant,
reductions in MAC of isoflurane induced by morphine
(0.1 mg/kg), buprenorphine (0.005 and 0.05 mg/kg),
and U50488H (0.02 and 0.2 mg/kg) were not considered
clinically relevant because they fell within the
error of the measurement technique. Administration
of morphine or butorphanol decreases the need for
potent inhalant anesthetics in cats and could potentially
be beneficial in combination with inhalants.
(Am J Vet Res 2002;63:1198–1202)
Objective—To determine the incidence and type of alterations in heart rate (HR), peak systolic blood pressure (PSBP), and serum biochemical variables (serum total bilirubin, BUN, and creatinine concentrations) associated with IV administration of ionic-iodinated contrast (IIC), nonionic-iodinated contrast (NIC), and gadolinium (GD) contrast media in anesthetized cats.
Procedures—HR and PSBP were recorded at 5-minute intervals for 20 minutes for untreated control cats and cats that received IIC, NIC, or GD contrast medium. The development of HR < 100 beats/min or > 200 beats/min that included a ≥ 20% change from baseline was considered a response. The development of PSBP of < 90 mm Hg or > 170 mm Hg that included a ≥ 20% change from baseline was considered a response. Pre- and postcontrast serum biochemical values were recorded.
Results—Of cats receiving IIC medium, 2% (1/60) had a response in HR at ≥ 1 time point. Of cats receiving IIC medium, 7% (4/60) had a response in PSBP. None of the cats receiving NIC medium had a response in HR; 2 of 12 had a response in PSBP. Of cats receiving GD contrast medium, 6% (5/83) had a response in HR and 8% (7/83) had a response in PSBP. None of the control cats had a response in HR or PSBP. No serum biochemical alterations were observed.
Conclusions and Clinical Relevance—IV administration of iodine and GD contrast media in anesthetized cats was associated with changes in HR and PSBP.
Case Description—Acute severe systemic reactions developed during IV administration of an ionic iodinated contrast agent (iothalamate meglumine) in 2 dogs undergoing contrast-enhanced computed tomography.
Clinical Findings—Both dogs developed marked changes in heart rate and systolic arterial blood pressure during or immediately after IV administration of the contrast agent. The first dog became profoundly hypertensive and bradycardic with poor oxygenation, apparent bronchospasm, and prolonged diarrhea. The second dog became hypotensive and tachycardic with erythema on the ventral aspect of the abdomen and pelvic limbs, periocular edema, and diarrhea.
Treatment and Outcome—Both dogs were treated for shock by means of IV fluid administration, and anesthesia was discontinued. The first dog was placed on a ventilator to improve oxygenation but was hypertensive and unresponsive for 6.5 hours following contrast agent administration. Bloody diarrhea persisted once consciousness was regained. The dog was discharged 3 days after contrast agent administration, and diarrhea resolved 15 days later. The second dog responded to phenylephrine administration, but urine output appeared low immediately following recovery from anesthesia. Urine output was normal the following day, and the dog was released 36 hours after contrast administration with no residual adverse effects.
Clinical Relevance—Findings highlighted the potential risk for severe reactions associated with IV administration of ionic iodinated contrast agents in dogs. Both hypertensive and hypotensive responses were seen. Supportive care for systemic manifestations was effective in these 2 dogs, and extended hospitalization was not necessary.
To compare the efficacy and duration of desensitization of oral structures following injection of various volumes of lidocaine-bupivacaine via an infraorbital approach in dogs.
6 healthy adult hound-type dogs.
In a randomized crossover study, each dog received 1, 2, and 3 mL of a 2% lidocaine-0.5% bupivacaine mixture (50:50 vol/vol) injected within and near the caudal aspect of the infraorbital canal with a 14-day washout period between treatments. Dogs were anesthetized, and each treatment was administered through a 22-gauge, 4.5-cm-long catheter, which was fully inserted through and then withdrawn 2 cm to the caudal aspect of the infraorbital canal. The reflex-evoked motor potential was measured for the maxillary canine tooth (MC), fourth premolar tooth (MPM4), second molar tooth (MM2), and hard palate mucosa ipsilateral to the injected treatment and for the contralateral MC (control) at predetermined times before and for 6 hours after treatment administration or until the block was no longer effective. For each oral structure, the proportion of dogs with desensitization (efficacy) and time to onset and duration of desensitization were compared among the 3 treatments (injectate volumes).
Treatment was not associated with efficacy, time to onset, or duration of desensitization. Regardless of treatment, MC and MPM4 were more frequently desensitized and mean durations of desensitization for MC and MPM4 were longer, compared with those for MM2 and the hard palate.
CONCLUSIONS AND CLINICAL RELEVANCE
The volume of local anesthetic used for an infraorbital nerve block had no effect on block efficacy or duration.