CASE DESCRIPTION A 9-year-old 7.5-kg (16.5-lb) castrated male Dachshund was referred for emergency evaluation of pelvic limb paraplegia of < 24 hours' duration.
CLINICAL FINDINGS A spinal cord lesion between T3 and L3 was suspected given the dog's history and neurologic examination results. Computed tomography and myelography spanning T3 through L4 identified an extradural compressive lesion at the L3-4 disk space. Hemilaminectomy was performed, and disk material adhered to and compressing the spinal cord was identified. However, because the material appeared to have been present for an extended period, postoperative CT of the cervicothoracic region was performed, which revealed extrusion of disk material from the T1-2 space and marked spinal cord compression.
TREATMENT AND OUTCOME A sternotomy of the manubrium and ventral slot decompression of the T1-2 disk space were performed successfully without entering the thoracic cavity. A large amount of disk material was removed from the spinal canal. No loss of intrathoracic negative pressure was appreciated, and intraoperative complications included only mild hemorrhage. The dog maintained pelvic limb pain sensation postoperatively and regained motor function 2 days after surgery.
CLINICAL RELEVANCE Intervertebral disk disease is rare at T1-2 in Dachshunds. Typically, a dorsal approach has been used to decompress the spinal cord, but findings for this dog suggested that a ventral approach may also be appropriate. Consideration should be given to include the T1-2 disk space when performing advanced imaging in dogs because of the inconsistent ability to identify lesions at this location by means of neurologic examination.
Procedure—Anesthesia was induced by administering
sevoflurane or isoflurane through a face mask.
Time to intubation was recorded. After induction of
anesthesia, minimal alveolar concentration (MAC)
was determined with a tail clamp method while dogs
were mechanically ventilated. Apneic concentration
was determined while dogs were breathing spontaneously
by increasing the anesthetic concentration
until dogs became apneic. Anesthetic index was calculated
as apneic concentration divided by MAC.
Results—Anesthetic index of sevoflurane (mean ±
SEM, 3.45 ± 0.22) was significantly higher than that
of isoflurane (2.61 ± 0.14). No clinically important differences
in heart rate; systolic, mean, and diastolic
blood pressures; oxygen saturation; and respiratory
rate were detected when dogs were anesthetized
with sevoflurane versus isoflurane. There was a significant
linear trend toward lower values for end-tidal
partial pressure of carbon dioxide during anesthesia
with sevoflurane, compared with isoflurane, at
increasing equipotent anesthetic doses.
Conclusions and Clinical Relevance—Results suggest
that sevoflurane has a higher anesthetic index in
dogs than isoflurane. Sevoflurane and isoflurane
caused similar dose-related cardiovascular depression,
but although both agents caused dose-related
respiratory depression, sevoflurane caused less respiratory
depression at higher equipotent anesthetic
doses. (J Am Vet Med Assoc 2004;225:700–704)