OBJECTIVE To compare the effectiveness of an ultrasound-guided paravertebral nerve blockade technique (UGPNB) with distal and proximal paravertebral nerve blockade techniques without ultrasound guidance (DPNB and PPNB, respectively) in calves.
ANIMALS 4 calf cadavers and 7 healthy calves.
PROCEDURES A suitable acoustic window was identified to facilitate access to the T13, L1, and L2 spinal nerves in cadavers and live calves. In cadavers, nerves were injected with dye under ultrasound guidance. In calves, the UGPNB, DPNB, and PPNB were performed in random order at 10-day intervals by injection of an anesthetic solution containing 2% lidocaine hydrochloride. Nociceptive withdrawal responses were assessed to determine the effects of the blockades.
RESULTS In cadavers, nerve staining success rates (ie, ≥ 2-cm-long dye path) achieved with ultrasound guidance were 88% (T13 [ventral branch]), 75% (T13 and L1 [dorsal branches] and L1 and L2 [ventral branches]), and 38% (L2 [dorsal branch]). The nerves were each identified as a hyperechoic band in a longitudinal plane. In calves, the UGPNB, DPNB, and PPNB reduced the withdrawal response to the noxious stimulus, mainly in the dorsal-cranial, dorsal-caudal, and ventral-cranial areas of the flank. Overall, the UGPNB resulted in a better nociceptive cumulative score, administering only one half of the local anaesthetic dose, compared with findings for the DPNB and PPNB. However, time to perform the UGPNB was longer.
CONCLUSIONS AND CLINICAL RELEVANCE The UGPNB evaluated may be an improved alternative to the DPNB and PPNB for provision of anesthesia for flank surgery in calves. However, effectiveness of the UGPNB should be evaluated in a clinical setting and in adult cattle.
Objective—To evaluate the influence of epidural
administration of xylazine hydrochloride on the minimum
alveolar concentration of isoflurane (MACISO)
and cardiopulmonary system in anesthetized dogs.
Animals—6 clinically normal dogs.
Procedure—Dogs were anesthetized with isoflurane
in oxygen after randomly being assigned to receive 1
of the following 4 treatments: epidural administration
of saline (0.9% NaCl) solution or xylazine at a dose of
0.1, 0.2, or 0.4 mg·kg–1. Experiments were performed
on 5 occasions with at least a 1-week interval
between experiments; each dog received all 4 treatments.
Following instrumentation, the concentration
of isoflurane was maintained constant for 15 minutes
at the MACISO that had been determined for each dog,
and data on heart rate, arterial blood pressure, respiratory
rate, tidal volume, minute volume, arterial partial
pressure of oxygen, arterial partial pressure of carbon
dioxide, and arterial pH were collected. The
epidural treatment was administered, and 30 minutes
later, data were again collected. From this point on,
determination of the MACISO following epidural treatment
(ie, MACISO + EPI) was initiated. Cardiopulmonary
data were collected before each electrical supramaximal
stimulus during MACISO + EPI determinations.
Results—The mean (± SD) MACISO was 1.29 ±
0.04%. The epidural administration of xylazine at
doses of 0.1, 0.2, and 0.4 mg·kg−1 decreased the
MACISO, respectively, by 8.4 ± 2.4%, 21.7 ± 4.9%,
and 33.4 ± 2.64%. Cardiopulmonary effects were limited.
Conclusions and Clinical Relevance—Epidural
administration of xylazine decreases the MACISO in a
dose-dependent manner and is associated with few
cardiopulmonary effects in anesthetized dogs. (Am J
Vet Res 2004;65:854–859)