Search Results

Abstract

Objective—To identify factors associated with short-term (30-day) and overall survival rates in cats that underwent renal transplantation surgery (RTS).

Design—Retrospective cohort study.

Animals—94 cats that underwent RTS from 1998 through 2010.

Procedures—Data obtained from the medical records pertinent to RTS included cat signalment; anesthetic agents, techniques, and timings; supportive treatment; perioperative physiologic findings; and surgery and warm ischemia times. Associations with short-term and overall survival rates were investigated.

Results—Median survival time was 653 days (range, 2 to 4,580 days). Prolonged anesthesia (median, 300 minutes; range, 225 to 445 minutes) reduced overall survival rate but did not influence short-term survival rate. No associations were identified between survival rates and anesthetic agent used, amount and type of fluid administered IV, physiologic abnormalities, and blood product administration. All cats that received μ-opioid receptor antagonists at anesthetic recovery to reverse the effects of μ-opioid receptor agonists survived for at least 30 days. High Hct at the end of anesthesia was also associated with an increase in short-term survival rate. Two cats had an intraoperative hemoglobin oxygen saturation < 90%, and both died within 7 days after surgery. Cats > 12 years old had a lower overall survival rate than did younger cats.

Conclusions and Clinical Relevance—Minimization of total anesthesia time, reversal of μ-opioid receptor agonists at the end of anesthesia, and prevention of intraoperative decreases in blood oxygen saturation and postoperative decreases in Hct appeared to help maximize postsurgical survival time in cats undergoing RTS.

Abstract

Objective—To compare analgesic efficacy of preoperative epidural anesthesia with efficacy of femoral and sciatic nerve blockade in dogs undergoing hind limb orthopedic surgery.

Design—Prospective randomized blinded clinical study.

Animals—22 dogs requiring stifle joint surgery.

Procedures—Dogs were premedicated with acepromazine and morphine, and anesthesia was induced with diazepam and propofol and maintained with sevoflurane in oxygen. Prior to surgery, a combination of 1.0% lidocaine solution with 0.25% bupivacaine solution was administered either into the lumbosacral epidural space (11 dogs) or perineurally along the femoral and sciatic nerves (11). Intraoperative nociception was assumed if heart rate or systolic blood pressure increased by > 10% from baseline, in which case fentanyl (2 μg/kg [0.9 μg/lb], IV) was administered as rescue analgesia. Following recovery from anesthesia, signs of postoperative pain were assessed every 30 minutes for 360 minutes from the time of local anesthetic administration via the modified Glasgow pain scale. Patients with scores > 5 (scale, 0 to 20) received hydromorphone (0.1 mg/kg [0.05 mg/lb], IV) as rescue analgesia and were then withdrawn from further pain scoring.

Results—Treatment groups did not differ significantly in the number fentanyl boluses administered for intraoperative rescue analgesia. Time to administration of first postoperative rescue analgesia was comparable between groups. Furthermore, there was no significant difference between groups in baseline pain scores, nor were there significant differences at any other point during the postoperative period.

Conclusions and Clinical Relevance—Femoral and sciatic nerve blocks provided intraoperative antinociception and postoperative analgesia similar to epidural anesthesia in dogs undergoing stifle joint surgery.

Abstract

Objective—To compare the cardiopulmonary effects of anesthesia maintained by continuous infusion of ketamine and propofol with anesthesia maintained by inhalation of sevoflurane in goats undergoing magnetic resonance imaging.

Animals—8 Saanen goats.

Procedures—Goats were anesthetized twice (1-month interval) following sedation with midazolam (0.4 mg/kg, IV). Anesthesia was induced via IV administration of ketamine (3 mg/kg) and propofol (1 mg/kg) and maintained with an IV infusion of ketamine (0.03 mg/kg/min) and propofol (0.3 mg/kg/min) and 100% inspired oxygen (K-P treatment) or induced via IV administration of propofol (4 mg/kg) and maintained via inhalation of sevoflurane in oxygen (end-expired concentration, 2.3%; 1X minimum alveolar concentration; SEVO treatment). Cardiopulmonary and blood gas variables were assessed at intervals after induction of anesthesia.

Results—Mean ± SD end-expired sevoflurane was 2.24 ± 0.2%; ketamine and propofol were infused at rates of 0.03 ± 0.002 mg/kg/min and 0.29 ± 0.02 mg/kg/min, respectively. Overall, administration of ketamine and propofol for total IV anesthesia was associated with a degree of immobility and effects on cardiopulmonary parameters that were comparable to those associated with anesthesia maintained by inhalation of sevoflurane. Compared with the K-P treatment group, mean and diastolic blood pressure values in the SEVO treatment group were significantly lower at most or all time points after induction of anesthesia. After both treatments, recovery from anesthesia was good or excellent.

Conclusions and Clinical Relevance—Results suggest that ketamine-propofol total IV anesthesia in goats breathing 100% oxygen is practical and safe for performance of magnetic resonance imaging procedures. (Am J Vet Res 2005;66:2135–2141)

Abstract

Objective—To evaluate pharmacokinetics of ketamine and norketamine enantiomers after constant rate infusion (CRI) of a subanesthetic dose of racemic ketamine or S-ketamine in ponies.

Animals—Five 6-year-old Shetland pony geldings that weighed between 101 and 152 kg.

Procedures—In a crossover study, each pony received a CRI of racemic ketamine (loading dose, 0.6 mg/kg; CRI, 0.02 mg/kg/min) and S-ketamine (loading dose, 0.3 mg/kg; CRI, 0.01 mg/kg/min), with a 1-month interval between treatments. Arterial blood samples were collected before and at 5, 15, 30, 45, and 60 minutes during drug administration and at 5, 10, 30, and 60 minutes after discontinuing the CRI. Plasma ketamine and norketamine enantiomers were quantified by use of capillary electrophoresis. Individual R-ketamine and S-ketamine concentration-versus-time curves were analyzed by use of a monocompartmental model. Plasma disposition curves for R-norketamine and S-norketamine were described by estimating the area under the concentration-versus-time curve (AUC), maximum concentration (Cmax), and time until Cmax.

Results—Plasma concentrations of S-ketamine decreased and biodegradation products increased more rapidly after S-ketamine CRI, compared with results after racemic ketamine CRI. The R-norketamine was eliminated faster than was the S-norketamine. Significant differences between treatments were found for the AUC of S-ketamine and within the racemic ketamine CRI for the AUC and Cmax of norketamine isomers.

Conclusions and Clinical Relevance—CRI of S-ketamine may be preferable over CRI of racemic ketamine in standing equids because the S-enantiomer was eliminated faster when infused alone instead of as part of a racemic mixture.

Abstract

Objective—To compare anesthesia recovery quality after racemic (R-/S-) or S-ketamine infusions during isoflurane anesthesia in horses.

Animals—10 horses undergoing arthroscopy.

Procedures—After administration of xylazine for sedation, horses (n = 5/group) received R-/S-ketamine (2.2 mg/kg) or S-ketamine (1.1 mg/kg), IV, for anesthesia induction. Anesthesia was maintained with isoflurane in oxygen and R-/S-ketamine (1 mg/kg/h) or S-ketamine (0.5 mg/kg/h). Heart rate, invasive mean arterial pressure, and end-tidal isoflurane concentration were recorded before and during surgical stimulation. Arterial blood gases were evaluated every 30 minutes. Arterial ketamine and norketamine enantiomer plasma concentrations were quantified at 60 and 120 minutes. After surgery, horses were kept in a padded recovery box, sedated with xylazine, and video-recorded for evaluation of recovery quality by use of a visual analogue scale (VAS) and a numeric rating scale.

Results—Horses in the S-ketamine group had better numeric rating scale and VAS values than those in the R-/S-ketamine group. In the R-/S-ketamine group, duration of infusion was positively correlated with VAS value. Both groups had significant increases in heart rate and mean arterial pressure during surgical stimulation; values in the R-/S-ketamine group were significantly higher than those of the S-ketamine group. Horses in the R-/S-ketamine group required slightly higher end-tidal isoflurane concentration to maintain a surgical plane of anesthesia. Moderate respiratory acidosis and reduced oxygenation were evident. The R-norketamine concentrations were significantly lower than S-norketamine concentrations in the R-/S-ketamine group.

Conclusions and Clinical Relevance—Compared with R-/S-ketamine, anesthesia recovery was better with S-ketamine infusions in horses.

Abstract

Objective—To evaluate the use of the oxygen content–based index, Fshunt, as an indicator of venous admixture (s/t) at various fractions of inspired oxygen (Fio ₂s) in anesthetized sheep undergoing Flung or 2-lung ventilation.

Animals—6 healthy adult female sheep.

Procedures—Sheep were anesthetized and administered 5 different Fio ₂s (0.21, 0.40, 0.60, 0.80, and 1.00) in random order during 2-lung mechanical ventilation. Arterial and mixed venous blood samples were obtained at each Fio ₂ after a 15-minute stabilization period. Vital capacity alveolar recruitment maneuvers were performed after blood collection. The previously used Fio ₂ sequence was reversed for sample collection during Flung ventilation. Blood samples were analyzed for arterial, pulmonary end-capillary, and mixed venous oxygen content and partial pressure and for hemoglobin concentration. Oxygen hemoglobin saturation, s/t, Fshunt, and oxygen tension–based indices (OTIs; including Pao ₂:Fio ₂, alveolar-arterial difference in partial pressure of oxygen [Pao ₂ – Pao ₂], [Pao ₂ – Pao ₂]:Fio ₂, [Pao ₂ – Pao ₂]:Pao ₂, and Pao ₂:Pao ₂) were calculated at each Fio ₂; associations were evaluated with linear regression analysis, concordance, and correlation tests. Intermethod agreement between s/t and Fshunt was tested via Bland-Altman analysis.

Results—Strong and significant associations and substantial agreement were detected between Fshunt and s/t. Relationships between OTIs and s/t varied, but overall correlations were weak.

Conclusions and Clinical Relevance—Whereas OTIs were generally poor indicators of s/t, Fshunt was a good indicator of s/t at various Fio ₂s, regardless of the magnitude of s/t, and could be potentially used as a surrogate for s/t measurements in healthy sheep.

Abstract