To determine the cardiopulmonary effects of IV administration of fentanyl to cats anesthetized with isoflurane and during anesthetic recovery with concurrent administration of acepromazine or dexmedetomidine.
6 healthy adult cats.
Cats received an IV bolus (5 μg/kg) followed by an IV infusion (5 μg/kg/h) of fentanyl for 120 minutes during isoflurane anesthesia and for 30 minutes after discontinuing isoflurane. Cats were randomly assigned in a crossover study to receive acepromazine (0.05 mg/kg) or dexmedetomidine (2.5 μg/kg), IV, when isoflurane was discontinued. Cardiopulmonary data were obtained during anesthesia and for 30 minutes during the anesthetic recovery period.
The administration of fentanyl during isoflurane anesthesia resulted in a transient increase in arterial blood pressure, mean pulmonary artery pressure, and oxygen delivery. Compared with values during isoflurane anesthesia, administration of dexmedetomidine during anesthetic recovery resulted in significant decreases in cardiac index, stroke index, and oxygen delivery and significant increases in arterial, central venous, and mean pulmonary artery pressures; systemic vascular resistance index; and oxygen extraction ratio. Administration of acepromazine resulted in increases in heart rate, cardiac index, oxygen uptake, and oxygen extraction ratio. Oxygen extraction ratio did not differ between acepromazine and dexmedetomidine.
CONCLUSIONS AND CLINICAL RELEVANCE
Fentanyl transiently improved indices of cardiopulmonary performance when administered to healthy cats anesthetized with isoflurane. The cardiovascular effects of acepromazine and dexmedetomidine in healthy cats receiving fentanyl during recovery from isoflurane anesthesia differed, but measured cardiopulmonary parameters remained within acceptable limits.
Objective—To determine the cardiovascular effects
of 60 minutes of abdominal insufflation with CO2 to
an intra-abdominal pressure of 15 mm Hg in standing
horses receiving a constant rate infusion of detomidine.
Procedure—Horses were randomly allocated into
treatment or control groups. A washout period of a
minimum of 7 days separated the 2 experimental
periods of the crossover study. Catheters were
placed into the right atrium, pulmonary artery, jugular
vein, and right transverse facial artery after lidocaine
infiltration. All horses were sedated with detomidine
(8.54 µg/kg/h, IV). Horses in the treatment
group received abdominal insufflation with CO2 via
a laparoscopic cannula to a final and constant intraabdominal
pressure of 15 mm Hg for 60 minutes.
Systemic arterial pressure, right atrial pressure,
heart rate, cardiac output, core body temperature,
and the pH and gas tensions of arterial and mixed
venous blood were obtained. Cardiac index and systemic
vascular resistance were calculated. Data
were collected in 3 stages: preinsufflation (–10 and
–5 minutes), insufflation (0, 15, 30, 45, and 60 minutes),
and postinsufflation (70 and 80 minutes). The
quality of sedation and level of analgesia were
Results—The PaO2 of horses in the treatment group
was significantly higher after 60 minutes of pneumoperitoneum
than in the control group. Core body
temperature decreased significantly from baseline in
Conclusions and Clinical Relevance—A 60-minute
period of abdominal insufflation to an intra-abdominal
pressure of 15 mm Hg did not induce significant cardiovascular
abnormalities in healthy horses. ( Am J Vet Res 2004;65:357–362)
Objective—To evaluate cardiopulmonary effects of anesthetic induction with diazepam and ketamine or xylazine and ketamine, with subsequent maintenance of anesthesia with isoflurane, in foals undergoing abdominal surgery.
Animals—17 pony foals.
Procedures—Foals underwent laparotomy at 7 to 15 days of age and laparoscopy 7 to 10 days later. Foals were randomly assigned to receive diazepam, ketamine, and isoflurane (D/K/Iso; n = 8) or xylazine, ketamine, and isoflurane (X/K/Iso; 9) for both procedures.
Results—During anesthesia for laparotomy, cardiac index, and mean arterial blood pressure ranged from 110 to 180 mL/kg/min and 57 to 81 mm Hg, respectively, in the D/K/Iso group and 98 to 171 mL/kg/min and 50 to 66 mm Hg, respectively, in the X/K/Iso group. Cardiac index, heart rate, and arterial blood pressures were significantly higher in the D/K/Iso group, compared with the X/K/Iso group. During anesthesia for laparoscopy, cardiac index and mean arterial blood pressure ranged from 85 to 165 mL/kg/min and 67 to 83 mm Hg, respectively, in the D/K/Iso group, and 98 to 171 mL/kg/min and 48 to 67 mm Hg, respectively, in the X/K/Iso group. Heart rates and arterial blood pressures were significantly higher in the D/K/Iso group, compared with the X/K/Iso group. There were no significant differences between groups during either experimental period for percentage end-tidal isoflurane, arterial blood gas partial pressures, or pH values.
Conclusions and Clinical Relevance—Anesthesia of foals for abdominal surgery with D/K/Iso was associated with less hemodynamic depression than with X/K/Iso.
Objective—To determine the effects of meloxicam and butorphanol on minimum alveolar concentration of isoflurane (MACISO) in rabbits.
Animals—10 healthy young adult female rabbits.
Procedure—Rabbits were anesthetized with isoflurane on 3 occasions in a blinded, randomized complete block design to determine the MACISO associated with administration of meloxicam (0, 0.3, or 1.5 mg/kg, PO) and butorphanol (0.4 mg/kg, IV). The MACISO was determined by use of a paw clamp technique as the end-tidal concentration of isoflurane halfway between the values that allowed or inhibited purposeful movement. Rectal temperature, end-tidal CO2 concentration, heart rate, oxygen saturation, and arterial blood pressure were measured to evaluate cardiopulmonary function.
Results—Mean ± SE MACISO in saline (0.9% NaCl) solution–treated rabbits was 2.49 ± 0.07% and was not significantly different from that associated with administration of meloxicam at 0.3 mg/kg (2.56 ± 0.07%) or 1.5 mg/kg (2.66 ± 0.07%). Butorphanol significantly reduced the MACISO to 2.30 ± 0.07% when administered with saline solution alone, 2.27 ± 0.07% when administered with 0.3 mg of meloxicam/kg, and 2.33 ± 0.07% when administered with 1.5 mg of meloxicam/kg. The percentage reduction in MACISO was significantly greater for rabbits that received butorphanol and meloxicam at either dose, compared with butorphanol and saline solution.
Conclusions and Clinical Relevance—Results indicated that meloxicam does not have a direct isoflurane-sparing effect and does not interfere with the anesthetic-sparing effect of butorphanol in rabbits.
Objective—To evaluate the use of a lithium dilution
cardiac output (LiDCO) technique for measurement of
CO and determine the agreement between LiDCO and
thermodilution CO (TDCO) values in anesthetized cats.
Animals—6 mature cats.
Procedure—Cardiac output in isoflurane-anesthetized
cats was measured via each technique. To
induce different rates of CO in each cat, anesthesia
was maintained at > 1.5X end-tidal minimum alveolar
concentration (MAC) of isoflurane and at 1.3X endtidal
isoflurane MAC with or without administration of
dobutamine (1 to 3 µg/kg/min, IV). At least 2 comparisons
between LiDCO and TDCO values were made
at each CO rate. The TDCO indicator was 1.5 mL of
5% dextrose at room temperature; with the LiDCO
technique, each cat received 0.005 mmol of
lithium/kg (concentration, 0.015 mmol/mL). Serum
lithium concentrations were measured prior to the
first and following the last CO determination.
Results—35 of 47 recorded comparisons were analyzed;
via linear regression analysis (LiDCO vs TDCO
values), the coefficient of determination was 0.91.
The mean bias (TDCO-LiDCO) was –4 mL/kg/min (limits
of agreement, –35.8 to +27.2 mL/kg/min). The concordance
coefficient was 0.94. After the last CO
determination, serum lithium concentration was < 0.1
mmol/L in each cat.
Conclusions and Clinical Relevance—Results indicated
a strong relationship and good agreement
between LiDCO and TDCO values; the LiDCO
method appears to be a practical, relatively noninvasive
method for measurement of CO in anesthetized
cats. (Am J Vet Res 2005;66:1639–1645).
Objective—To evaluate the cardiopulmonary and sedative effects of the peripheral α2-adrenoceptor antagonist MK 0467 when administered IM or IV concurrently with medetomidine in dogs.
Animals—8 adult dogs.
Procedures—Dogs received 20 μg of medetomidine/kg, IM, alone or concurrently with MK 0467 (0.4 mg/kg, IM), and 10 μg of medetomidine/kg, IV, alone or concurrently with MK 0467 (0.2 mg/kg, IV), in a randomized crossover study. Sedation characteristics were scored and hemodynamic measurements and arterial and mixed-venous blood samples for blood gas analysis were obtained before (time 0; baseline) and for 90 minutes after treatment.
Results—Heart rate (HR), mixed-venous partial pressure of oxygen (Pvo2), and cardiac index (CI) were significantly lower and mean arterial blood pressure (MAP), systemic vascular resistance (SVR), and oxygen extraction ratio (ER) were significantly higher after administration of medetomidine IM or IV, compared with baseline values. Administration of medetomidine and MK 0467 IM caused a significantly higher heart rate, CI, and Pvo2 and significantly lower MAP, SVR, and ER for 60 to 90 minutes than did IM administration of medetomidine alone. Administration of medetomidine and MK 0467 IV caused a significantly higher CI and Pvo2 and significantly lower MAP, SVR, and ER for 45 to 90 minutes than did IV administration of medetomidine alone. There was no significant difference in sedation scores among treatments.
Conclusions and Clinical Relevance—In dogs, MK 0467 administered concurrently with medetomidine IV or IM reduced the cardiovascular effects of medetomidine but had no detectable effect on sedation scores.
Objective—To assess the sedative and cardiopulmonary effects of medetomidine and xylazine and their reversal with atipamezole in calves.
Procedures—A 2-phase (7-day interval) study was performed. Sedative characteristics (phase I) and cardiopulmonary effects (phase II) of medetomidine hydrochloride and xylazine hydrochloride administration followed by atipamezole hydrochloride administration were evaluated. In both phases, calves were randomly allocated to receive 1 of 4 treatments IV: medetomidine (0.03 mg/kg) followed by atipamezole (0.1 mg/kg; n = 6), xylazine (0.3 mg/kg) followed by atipamezole (0.04 mg/kg; 7), medetomidine (0.03 mg/kg) followed by saline (0.9% NaCl; 6) solution (10 mL), and xylazine (0.3 mg/kg) followed by saline solution (10 mL; 6). Atipamezole or saline solution was administered 20 minutes after the first injection. Cardiopulmonary variables were recorded at intervals for 35 minutes after medetomidine or xylazine administration.
Results—At the doses evaluated, xylazine and medetomidine induced a similar degree of sedation in calves; however, the duration of medetomidine-associated sedation was longer. Compared with pretreatment values, heart rate, cardiac index, and PaO2 decreased, whereas central venous pressure, PaCO2, and pulmonary artery pressures increased with medetomidine or xylazine. Systemic arterial blood pressures and vascular resistance increased with medetomidine and decreased with xylazine. Atipamezole reversed the sedative and most of the cardiopulmonary effects of both drugs.
Conclusions and Clinical Relevance—At these doses, xylazine and medetomidine induced similar degrees of sedation and cardiopulmonary depression in calves, although medetomidine administration resulted in increases in systemic arterial blood pressures. Atipamezole effectively reversed medetomidine- and xylazine-associated sedative and cardiopulmonary effects in calves.
Objective—To compare laparoscopic dissection withlaparoscopic
dissection combined with abdominal
instillation of ferric hyaluronate gel for the treatment
of experimentally induced adhesions in pony foals.
Animals—12 healthy pony foals.
Procedure—A serosal abrasion method was used to
create adhesions at 4 sites on the jejunum (day 0). At
day 7, laparoscopy was performed and the adhesions
observed in each foal were recorded. In group-1 foals
(n = 6), the adhesions were separated laparoscopically
(treatment 1). In group-2 foals (n = 6), 300 mL of
0.5% ferric hyaluronate gel was infused into the
abdomen after the adhesions were separated laparoscopically
(treatment 2). At day 24, terminal
laparoscopy was performed and the adhesions
observed were recorded. Total number of adhesions
within each group was compared between day 7 and
24. Data were analyzed to determine whether an
association existed between the number of adhesions
on day 24 and treatment type.
Results—At day 24, the number of adhesions was
significantly decreased within each group, compared
with the number of adhesions at day 7 (group-1 foals,
10 vs 22 adhesions; group-2 foals, 3 vs 20 adhesions).
Treatment 1 was associated with a significantly higher
number of adhesions at day 24, compared with
treatment 2 (odds ratio, 4.54; 95% confidence interval,
1.03 to 23.02).
Conclusions and Clinical Relevance—Abdominal
instillation of 0.5% ferric hyaluronate gel after laparoscopic
dissection was a more effective technique
than laparoscopic dissection alone to treat experimentally
induced adhesions in pony foals.
Laparoscopic adhesiolysis following abdominal
surgery in foals is a safe and effective technique. ( Am J Vet Res 2004;65:681–686)
Objective—To determine the relationship between
epidural cranial migration and injectate volume of an
isotonic solution containing dye in laterally recumbent
foal cadavers and evaluate the cranial migration and
dermatome analgesia of an epidural dye solution during
conditions of laparoscopy in foals.
Animals—19 foal cadavers and 8 pony foals.
Procedure—Foal cadavers received an epidural
injection of dye solution (0.05, 0.1, 0.15, or 0.2 mL/kg)
containing 1.2 mg of new methylene blue (NMB)/mL
of saline (0.9% NaCl) solution. Length of the dye column
and number of intervertebral spaces cranial and
caudal to the injection site were measured.
Anesthetized foals received an epidural injection of
dye solution (0.2 mL/kg) containing saline solution or
2% mepivacaine. Foals were placed in a 10o headdown
position, and pneumoperitoneum was induced.
Dermatome analgesia was determined by use of a
described electrical stimulus technique. Foals were
euthanatized, and length of the dye column was measured.
Results—Epidural cranial migration of dye solution in
foal cadavers increased with increasing volume injected.
No significant difference was found in epidural
cranial migration of a dye solution (0.2 mL/kg)
between anesthetized foals undergoing conditions of
laparoscopy and foal cadavers in lateral recumbency.
Further craniad migration of the dye column occurred
than indicated by dermatome analgesia.
Conclusions and Clinical Relevance—Epidural cranial
migration increases with volume of injectate. On
the basis of dermatome analgesia, an epidural injection
of 2% mepivacaine (0.2 mL/kg) alone provides
analgesia up to at least the caudal thoracic dermatome
and could permit caudal laparoscopic surgical
procedures in foals. ( Am J Vet Res 2005; 66:1324–1329)
Objective—To determine reasons for epidural catheter
placement among horses examined at a veterinary
teaching hospital, efficacy of epidural administration of
analgesics, duration of catheter placement, reasons for
catheter removal, and complications encountered.
Procedure—Medical records were reviewed.
Results—A total of 50 epidural catheters were placed
in the 43 horses. Underlying conditions included fractures,
lacerations, septic arthritis, myositis, perineal
injuries, and cellulitis. Horses ranged from 2 to 21 years
old and weighed between 365 and 795 kg (803 and
1,749 lb). Median duration of catheter placement was
96 hours (range, 1.5 to 480 hours). The response to
epidural drug administration was reported as positive in
34 horses and negative in 4. There was no apparent
response in 2 horses, and response could not be determined
in 3. Three temporary patient-related complications
associated with epidural catheter administration
were observed. Technical problems associated with
the epidural catheters included dislodgement of the
catheter itself (7 catheters) or of the adapter or filter (5),
obstruction (5), and leakage (5). Twenty-two catheters
were removed because of resolution of the underlying
condition, and 10 were removed because of complications.
For 6 catheters, the reason for catheter removal
was not recorded. The remaining 12 catheters were in
place when the horses were euthanatized .
Conclusions and Clinical Relevance—Results suggest
that epidural catheterization can be used successfully
for repeated epidural delivery of analgesics and
anesthetics in horses with various clinical conditions.
Complications associated with epidural catheters or
epidural drug administration were infrequent and transient.
(J Am Vet Med Assoc 2003;222:1394–1398)