Procedure—Guaifenesin (150 mg/kg of body weight,
IV) was administered during a 5-minute period. Using
a 2-channel referential electrode configuration, electroencephalograms
were recorded before, during,
and after infusion of guaifenesin. Changes in spectral
edge frequency 95% (SEF), median frequency (MED),
and total power were evaluated.
Results—After administration of guaifenesin, SEF
decreased significantly, and total power increased significantly;
however, MED did not change significantly.
Analysis of the data did not reveal differences
between pigs on the basis of sex.
Conclusions and Clinical Relevance—We concluded
that guaifenesin synchronized the patterns of electroencephalograms.
This is a strong indication that the
drug has a sedative effect in pigs. (Am J Vet Res
Objective—To assess the efficacy of a commercially available topical vapocoolant spray in reducing responses to arthrocentesis of the middle carpal (MC) and metacarpophalangeal (MCP) joints and jugular vein catheterization in unsedated horses.
Animals—8 healthy research horses.
Procedures—Arthrocentesis of both MC and MCP joints and bilateral jugular vein catheterization were performed in each horse. Immediately prior to skin penetration, 1 randomly selected MC joint, MCP joint, and jugular vein were sprayed with a vapocoolant liquid (intervention product), and the contralateral MC joint, MCP joint, and jugular vein were sprayed with water (placebo). An observer blinded to the type of spray treatment used evaluated the horses' responses to needle or catheter placement procedures by use of a 6-point categorical scale and a 100-mm visual analog scale.
Results—Responses evaluated via the visual analog scale were significantly reduced after application of the intervention product, compared with responses after application of the placebo, for the MC and MCP joints; no difference in responses to jugular vein catheterization was detected between the 2 treatments.
Conclusions and Clinical Relevance—Vapocoolant spray was safe and effective in reducing horses' responses to arthrocentesis. The use of such products prior to joint injections may reduce procedural nociception and pain anticipation in unsedated horses and may improve the safety of personnel performing such procedures.
Objective—To evaluate the effect of intratesticular administration of lidocaine on cardiovascular responses and cremaster muscle tension during castration of isoflurane-anesthetized stallions.
Animals—28 healthy stallions (mean ± SD age, 4.2 ± 2.8 years) with no testicular abnormalities that were scheduled for castration.
Procedure—Each horse was given acepromazine (20 μg/kg, IM), romifidine (50 μg/kg, IV), and butorphanol (20 μg/kg, IV). Anesthesia was induced with ketamine (2.5 mg/kg, IV) and midazolam (50 μg/kg, IV) and maintained with isoflurane (1.7% end-tidal concentration). After 10 minutes at a stable anesthetic plane, a needle was placed in each testicle and either no fluid or 15 mL of 2% lidocaine was injected; 10 minutes after needle placement, surgery was commenced. Pulse rate and arterial blood pressures were measured invasively at intervals from 5 minutes prior to castration (baseline) until 5 minutes after the left spermatic cord was clamped. The surgeon subjectively scored the degree of cremaster muscle tension. In 2 horses, lidocaine labeled with radioactive carbon (C14) was used and testicular autoradiograms were obtained.
Results—Compared with baseline values, castration significantly increased blood pressure measurements; intratesticular injection of lidocaine decreased this blood pressure response and cremaster muscle tension. In 2 horses, autoradiography revealed diffuse distribution of lidocaine into the spermatic cord but poor distribution into the cremaster muscle.
Conclusions and Clinical Relevance—In isoflurane-anesthetized stallions, intratesticular injection of lidocaine prior to castration appeared to decrease intraoperative blood pressure responses and cremaster muscle tension and may be a beneficial supplement to isoflurane anesthesia.