Effect of intravenous propofol and remifentanil on heart rate, blood pressure and nociceptive response in acepromazine premedicated dogs

ObjectiveTo investigate the cardiorespiratory, nociceptive and endocrine effects of the combination of propofol and remifentanil, in dogs sedated with acepromazine.Study designProspective randomized, blinded, cross-over experimental trial.AnimalsTwelve healthy adult female cross-breed dogs, mean weight 18.4 ± 2.3 kg.MethodsDogs were sedated with intravenous (IV) acepromazine (0.05 mg kg^?1) followed by induction of anesthesia with IV propofol (5 mg kg^?1). Anesthesia was maintained with IV propofol (0.2 mg kg^?1 minute^?1) and remifentanil, infused as follows: R1, 0.125 μg kg^?1 minute^?1; R2, 0.25 μg kg^?1 minute^?1; and R3, 0.5 μg kg^?1 minute^?1. The same dogs were administered each dose of remifentanil at 1-week intervals. Heart rate (HR), mean arterial pressure (MAP), respiratory rate (f_R), end tidal CO₂ (Pe′CO₂), arterial hemoglobin O₂ saturation, blood gases, and rectal temperature were measured before induction, and 5, 15, 30, 45, 60, 75, 90, and 120 minutes after beginning the infusion. Nociceptive response was investigated by electrical stimulus (50 V, 5 Hz and 10 ms). Blood samples were collected for plasma cortisol measurements. Statistical analysis was performed by anova (p < 0.05).ResultsIn all treatments, HR decreased during anesthesia with increasing doses of remifentanil, and increased significantly immediately after the end of infusion. MAP remained stable during anesthesia (72–98 mmHg). Antinociception was proportional to the remifentanil infusion dose, and was considered satisfactory only with R2 and R3. Plasma cortisol concentration decreased during anesthesia in all treatments. Recovery was smooth and fast in all dogs.Conclusions and clinical relevanceInfusion of 0.25–0.5 μg kg^?1 minute^?1 remifentanil combined with 0.2 mg kg^?1 minute^?1 propofol produced little effect on arterial blood pressure and led to a good recovery. The analgesia produced was sufficient to control the nociceptive response applied by electrical stimulation, suggesting that it may be appropriate for performing surgery.     

The effect of remifentanil infusion on sevoflurane minimum alveolar concentration–no movement (MACNM) and bispectral index in dogs

ObjectiveTo determine the effect of remifentanil infusion on the minimum alveolar concentration of sevoflurane preventing movement (SEVOMAC_NM) and bispectral index (BIS) in dogs.Study designProspective, unmasked study.AnimalsA total of 10 adult Beagle dogs weighing 9.0 ± 1.1 kg.MethodsDogs were anesthetized with sevoflurane and baseline SEVOMAC_NM was determined. Remifentanil was infused at 5, 10 and 20 μg kg^–1 hour^–1, in sequence, with 20 minutes washout between infusions. Variables monitored throughout anesthesia included heart rate (HR), oscillometric blood pressure, end-tidal partial pressure of carbon dioxide, end-tidal sevoflurane concentration (Fe′Sevo) and BIS. SEVOMAC_NM after remifentanil infusion (SEVOMAC_NM-REMI) determination started 20 minutes after the start of each infusion. Venous blood samples were collected for plasma remifentanil concentration determination at baseline, SEVOMAC_NM-REMI determination time points, and 20 minutes after each infusion was stopped. A mixed model analysis was used to determine the effect of remifentanil infusion on response variables. The relationships between BIS and Fe′Sevo, plasma remifentanil concentrations and the percentage decrease in baseline SEVOMAC_NM were evaluated (p < 0.05).ResultsThe overall SEVOMAC_NM at baseline was 2.47 ± 0.11%. Addition of remifentanil at all infusion rates significantly decreased SEVOMAC_NM, but the medium and high doses resulted in significantly greater decreases in SEVOMAC_NM than the lower dose. There was no difference in SEVOMAC_NM percentage change between infusions 10 and 20 μg kg^–1 hour^–1. Plasma remifentanil concentrations were significantly different in all infusion rates. Baseline BIS value was 70 ± 1 and was lower than the BIS values recorded during all remifentanil infusions. BIS values were not significantly different among infusion rates. HR was lower and mean arterial pressure was higher during remifentanil infusions than at baseline.Conclusions and clinical relevanceAll remifentanil infusions decreased SEVOMAC_NM in dogs. Remifentanil infusion at any rate studied did not reduce BIS values.     

A comparison of recovery times and characteristics with sevoflurane and isoflurane anaesthesia in horses undergoing magnetic resonance imaging

Objective To compare recovery times and quality following maintenance of anaesthesia with sevoflurane or isoflurane after a standard intravenous induction technique in horses undergoing magnetic resonance imaging (MRI). Study design Prospective, randomised, blinded clinical study. Animals One hundred ASA I/II horses undergoing MRI. Materials and methods Pre‐anaesthetic medication with intravenous acepromazine and romifidine was followed by induction of anaesthesia with diazepam and ketamine. The animals were randomised into two groups to receive either sevoflurane or isoflurane in oxygen. Horses were subjectively scored (0–5) for temperament before sedation, for quality of sedation, induction and maintenance and anaesthetic depth on entering the recovery area. Recoveries were videotaped and scored by an observer, unaware of the treatment, using two scoring systems. Times to the first movement, head lift, sternal recumbency and standing were recorded along with the number of attempts to achieve sternal and standing positions. Variables were compared using a Student t‐test or Mann–Whitney U‐test (p < 0.05), while the correlation between subjective recovery score and other relevant variables was tested calculating the Spearman Rank correlation coefficient and linear regression modelling performed when significant. Results Seventy‐seven horses entered the final analysis, 38 received isoflurane and 39 sevoflurane. Body mass, age and duration of anaesthesia were similar for both groups. There were no differences in recovery times, scoring or number of attempts to achieve sternal recumbency and standing between groups. Weak, but significant, correlations were found between the subjective recovery score for the pooled data from both groups and both temperament and time in sternal recumbency. Conclusions No differences in recovery times or quality were detected following isoflurane or sevoflurane anaesthesia after intravenous induction. Clinical relevance Sevoflurane affords no obvious advantage in recovery over isoflurane following a standard intravenous induction technique in horses not undergoing surgery.     

Pharmacokinetics of dexmedetomidine in isoflurane-anesthetized New Zealand White rabbits

Objective

To characterize the pharmacokinetics of dexmedetomidine when administered as a short intravenous (IV) infusion to isoflurane-anesthetized rabbits.

Uterine torsion diagnosed in a mare at 515 days' gestation

A pregnant mare with a history of prolonged gestation (～515 days) and suspected diagnosis of fetal mummification was examined. Rectal palpation revealed that the left broad ligament of the uterus was dorsal and medial to the right uterine ligament and it was not possible to observe the cervix during vaginal examination. Transabdominal ultrasound revealed fluid in the uterus, fetal membranes and the uterine walls defined and thickened. Free fluid was not seen in the peritoneal cavity. Laboratory tests (blood cell count and clinical chemistry) were normal. Based on clinical history, physical examination and ultrasound findings, a chronic uterine torsion with fetal death was diagnosed and the mare was subjected to exploratory celiotomy. The uterus was strongly adhered to the peritoneum of the ventral abdominal wall and there were multiple adhesions to the colon. Hysterotomy was performed to remove the fetus and to permit repositioning of the uterus. When the fetus was removed, a large devitalised grey tissue area of the right ventral uterine horn was observed. Multiple adhesions prevented a rescue hysterectomy and euthanasia of the patient was performed. During the necropsy, a 180° cranial cervix clockwise uterine torsion was observed. This rare case of uterine torsion appears to be the most chronic case reported in the equine literature.     

THE EFFECTS OF REGIONAL PERINEURAL ANESTHESIA ON SOFT TISSUE AND BONE PHASE SCINTIGRAPHY IN THE HORSE

Soft tissue phase scintigrams were acquired from 7 normal horses before and over a 17-day period after palmar digital, abaxial sesamoid, low palmar and high palmar nerve blocks. Bone phase scintigrams were acquired from 4 additional horses prior to performing similar regional anesthesia and over a 14-day period postanesthesia. Images were evaluated subjectively and quantitatively for increased activity in nerve block regions. On soft tissue phase scintigrams, palmar digital and abaxial sesamoid blocks resulted in increases in activity which were relatively mild, of short duration, and subjectively had little or no effect on image interpretation. Low palmar and high palmar blocks resulted in obvious focal accumulation of activity during the soft tissue phase. Such increases in activity were usually greatest at 1 day postanesthesia and persisted up to 17 days postanesthesia. On bone phase scintigrams, abnormal accumulation of activity was not evident.     

THE EFFECTS OF INTRA-ARTICULAR ANESTHESIA ON SOFT TISSUE-AND BONE-PHASE SCINTIGRAPHY IN THE HORSE

Soft tissue- and bone-phase scintigrams were acquired from 4 normal horses before and over a 14-day period after metacarpophalangeal, antebrachiocarpal, tarsocrural and tarsometatarsal joint blocks. Images were evaluated subjectively and quantitatively for increased activity in these regions. The antebrachiocarpal block resulted in obvious focal accumulation of activity on soft tissue-phase scintigrams. This increased activity was greatest 2 to 4 days postanesthesia and persisted up to 14 days postanesthesia. On quantitative analysis of soft tissue-phase images, similar trends were noted after the metacarpophalangeal and tarsocrural blocks, but these increases were relatively mild and were not evident on subjective evaluation of the images. Abnormal soft tissue-phase activity was not associated with the tarsometatarsal block. On bone-phase scintigrams, increased activity was not present following any of these joint blocks.