Gastric Myoelectric and Motor Activity in Dogs After Isoflurane Anesthesia

To characterize the effects of isoflurane on gastric motility, gastric electrical and contractile activities were assessed in six healthy adult dogs before and after recovery from anesthesia. Baseline recordings (fasting and fed state) were obtained in unanesthetized dogs 8 days after implantation of serosal electrodes and strain-gauge force transducers. After an overnight fast, dogs were anesthetized with 1.3 minimum alveolar concentration (MAC) isoflurane for 4.5 hours (approximately 6 MAC hours). No other anesthetic or sedative drugs were administered. During anesthesia, ventilation was mechanically controlled to maintain arterial carbon dioxide tension at 36 ± 4 mm Hg. Gastric electrical and contractile activities (fasting and fed state) were recorded again 18 hours after recovery from isoflurane anesthesia. Recordings were analyzed to determine gastric slow-wave frequency, presence of slow-wave dysrhythmias, slow-wave propagation velocity, coupling of contractions to slow waves, a motility index based on relative contractile amplitudes, and onset and duration of contractions after a standardized meal. The only variable that was significantly decreased 18 hours after 6 MAC hours of isoflurane anesthesia was the gastric motility index during fasting-state phase III. This decrease was not apparent in the fed-state test periods. Our results suggest that, with the exception of gastric motility index during fasting-state phase III, variables for gastric electrical and contractile activities in dogs are unaffected by isoflurane 18 hours after anesthesia.     

Assessment of cardiac troponin I and C-reactive protein concentrations associated with anesthetic protocols using sevoflurane or a combination of fentanyl, midazolam, and sevoflurane in dogs

ObjectiveTo report serum cardiac troponin I (cTnI) and C-reactive protein (CRP) concentrations in dogs anesthetized for elective surgery using two anesthetic protocols.Study designProspective, randomized clinical study.AnimalsTwenty client-owned dogs presenting for elective ovariohysterectomy or castration.MethodsThe dogs were randomized into two groups. All dogs were premedicated with glycopyrrolate (0.011 mg kg^?1) and hydromorphone (0.1 mg kg^?1) IM approximately 30 minutes prior to induction of anesthesia. Anesthesia in dogs in group 1 was induced with propofol (6 mg kg^?1) IV to effect and in dogs in group 2 with diazepam (0.2 mg kg^?1) IV followed by etomidate (2 mg kg^?1) IV to effect. For maintenance of anesthesia, group 1 received sevoflurane (adjustable vaporizer setting 0.5–4%) and group 2 received a combination of fentanyl (0.8 μg kg^?1 minute^?1) and midazolam (8.0 μg kg^?1 minute^?1) IV plus sevoflurane (adjustable vaporizer setting 0.5–4%) to maintain anesthesia. Serum cTnI and CRP concentrations were measured at baseline and 6, 18, and 24 hours post-anesthetic induction. Biochemical analysis was performed at baseline. Lactate was obtained at baseline and 6 hours post-anesthetic induction. Heart rate and mean arterial blood pressure were measured intra-operatively.ResultsBaseline serum cTnI and CRP concentrations were comparable between groups. A significant difference in serum cTnI or CRP concentrations was not detected post-operatively between groups at any time point. Serum CRP concentrations were significantly increased post-anesthetic induction in both groups, which was attributed to surgical trauma.Conclusions and clinical relevanceThere was no significant difference in serum cTnI and CRP concentrations between anesthetic protocols. Further investigation in a larger number of dogs is necessary to confirm the current findings.     

Evaluation of the analgesic effect of fentanyl–ketamine and fentanyl–lidocaine constant rate infusions in isoflurane-anesthetized dogs undergoing thoracolumbar hemilaminectomy

ObjectiveTo evaluate anesthetic conditions and postoperative analgesia with the use of intraoperative constant rate infusions (CRIs) of fentanyl–lidocaine or fentanyl–ketamine in dogs undergoing thoracolumbar hemilaminectomy.Study designProspective, randomized, blinded, clinical study.AnimalsA total of 32 client-owned dogs.MethodsDogs were premedicated with fentanyl (5 μg kg^–1) administered intravenously (IV), anesthesia was induced with IV alfaxalone and maintained with isoflurane. Fentanyl (0.083 μg kg^–1 minute^–1) was infused IV with either ketamine (0.5 mg kg^–1; then 40 μg kg^–1 minute^–1; group KF) or lidocaine (2 mg kg^–1; then 200 μg kg^–1 minute^–1; group LF) assigned randomly. Heart rate, noninvasive arterial pressures, respiratory rate, esophageal temperature, end-tidal partial pressure of carbon dioxide and isoflurane concentration were recorded throughout anesthesia. Maintenance of anesthesia, recovery and postoperative pain (Glasgow Composite Pain Scale) were scored. Cardiopulmonary data were analyzed using a two-way anova with repeated measures, demographics of the two groups with a t test, and scores with Mann–Whitney U test, with p < 0.05.ResultsAll dogs recovered from anesthesia without complications. No significant difference was found between groups for cardiopulmonary variables, total anesthesia time, sedation score and requirement for postoperative sedation or for rescue analgesia. Anesthetic maintenance score was of lower quality in KF than in LF [median (interquartile range): 0 (0–0.5) versus 0 (0–0); p = 0.032)], but still considered ideal. Recovery score was higher and indicative of less sedation in LF than in KF [1 (1–1.5) versus 0.5 (0–1); p < 0.0001]. Pain score was higher in KF than in LF [2 (1–3) versus 1 (1–2); p = 0.0009].Conclusions and clinical relevanceBoth CRIs of KF and LF provided adequate anesthetic conditions in dogs undergoing thoracolumbar hemilaminectomy. Based on requirement for rescue analgesia, postoperative analgesia was adequate in both groups.     

The effect of a pre‐anesthetic infusion of amino acids on body temperature,venous blood pH,glucose, creatinine,and lactate of healthy dogs during anesthesia

ObjectiveTo evaluate the effect of preanesthetic, intravenous (IV) amino acids on body temperature of anesthetized healthy dogs.Study designRandomized, experimental, crossover study.AnimalsEight mixed-breed dogs approximately 2 years of age weighing 20.7 ± 2.1 kg.MethodsDogs received 10% amino acid solution (AA) or 0.9% saline (SA) IV at 5 mL kg⁻¹ over 60 minutes. Body temperature (BT) was recorded at 5 minute intervals during infusions. Dogs were then anesthetized with sevoflurane for 90 minutes. BT was recorded at 5 minute intervals during anesthesia. Jugular blood samples were analyzed for pH, glucose, creatinine, and lactate concentrations at baseline, after infusion, after anesthesia and after 24 hours.ResultsBT at conclusion of infusion decreased -0.34 ± 0.42 °C in group AA and -0.40 ± 0.38 °C in group SA and was not different between groups (p = 0.072). BT decreased 2.72 ± 0.37 °C in group AA and 2.88 ± 0.26 °C in group SA after anesthesia and was different between groups (p < 0.05). Creatinine in group AA was increased immediately after infusion (p < 0.0001) and at 24 hours (p < 0.0001). There were no differences between groups for other parameters. Values for both groups were never outside the clinical reference ranges.Conclusions and clinical relevanceIn healthy dogs, preanesthetic IV infusion of amino acids attenuated heat loss compared to controls, however, the amount attenuated may not be clinically useful. Further studies are warranted to determine if nutrient-induced thermogenesis is beneficial to dogs undergoing anesthesia.     

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.     

Determination of acute tolerance and hyperalgesia to remifentanil constant rate infusion in dogs undergoing sevoflurane anaesthesia

ObjectiveTo determine if acute opioid tolerance (AOT) or opioid-induced hyperalgesia (OIH) could develop and limit the remifentanil-induced reduction in the sevoflurane minimum alveolar concentration (MAC). The response to mechanical nociceptive threshold (MNT) was evaluated and related to OIH.Study designA crossover, randomized, experimental animal study.AnimalsA total of nine Beagle dogs.MethodsThe dogs were anaesthetized with sevoflurane in 50% oxygen. Baseline sevoflurane MAC was measured (MACb1). Remifentanil (0.3 μg kg^–1 minute^–1) or 0.9% saline constant rate infusion (CRI) was administered intravenously (IV). Sevoflurane MAC was determined 20 minutes after CRI was initiated (MACpostdrug1), 30 minutes after MACpostdrug1 determination (MACpostdrug2) and after 1 week (MACb2). The MNT was determined at baseline (before anaesthesia), 3 and 7 days after anaesthesia. An increase of MACpostdrug2 ≥0.25% compared to MACpostdrug1 was considered evidence of AOT. A decrease in MNT at 3 and 7 days or an increase in MACb2 or both with respect to MACb1 were considered evidence of OIH.ResultsRemifentanil CRI reduced sevoflurane MACpostdrug1 by 43.7% with respect to MACb1. MACpostdrug2 was no different from MACpostdrug1 with the saline (p = 0.62) or remifentanil (p = 0.78) treatments. No significant differences were observed in the saline (p = 0.99) or remifentanil (p = 0.99) treatments between MACb1 and MACb2, or for MNT values between baseline, 3 and 7 days.Conclusion and clinical relevanceIn dogs, under the study conditions, remifentanil efficacy in reducing sevoflurane MAC did not diminish in the short term, suggesting remifentanil did not induce AOT. Hyperalgesia was not detected 3 or 7 days after the administration of remifentanil. Contrary to data from humans and rodents, development of AOT or OIH in dogs is not supported by the findings of this study.     

Computed tomographic features of gastric and esophageal content in dogs undergoing CT myelography and factors influencing the presence of esophageal fluid

BackgroundGastroesophageal reflux (GER) has been reported to be a common finding in dogs under general anesthesia.ObjectivesThe aim of this retrospective study was to assess the esophageal and gastric contents in a population of dogs undergoing computed tomographic myelography (myelo-CT) examination and to evaluate the factors influencing the presence of esophageal fluid (gastric content, duration of anesthesia, body position, and intrinsic factors).MethodsEsophageal and gastric contents of 83 non-brachycephalic dogs were retrospectively assessed based on plain and myelo-CT scans. Age, weight, breed, sex, and the time between the 2 computed tomography [CT] scans were included.ResultsEsophageal fluid was present in 19% (16/83) of the animals, and 14% (12/83) and 46% (37/83), respectively, had fluid or food material in their stomachs. The frequency of observing esophageal fluid on myelo-CT scans was significantly increased compared with plain CT scans (p = 0.006). The presence of gastric fluid was significantly associated with an increased frequency of observing esophageal fluid compared to other gastric contents (p = 0.049; odds ratio, 3.1). The presence of esophageal fluid was not correlated with alimentary gastric contents (p = 0.17). Increased body weight and duration of anesthesia were significantly associated with an increased frequency of observing esophageal fluid (p = 0.022, p = 0.021).ConclusionsUnlike alimentary gastric contents, fluid gastric contents were correlated with the presence of esophageal fluid upon myelo-CT. The observation of fluid in the esophagus may be consistent with GER. This study provides data additional to pH monitoring studies of GER and may support previous studies recommending shorter pre-anesthetic fasting periods in dogs.     

Effects of constant rate infusions of dexmedetomidine,remifentanil and their combination on minimum alveolar concentration of sevoflurane in dogs

ObjectiveTo evaluate the effects of constant rate infusions (CRIs) of dexmedetomidine and remifentanil alone and their combination on minimum alveolar concentration (MAC) of sevoflurane in dogs.Study designRandomized crossover experimental study.AnimalsA total of six (three males, three females) healthy, adult neutered Beagle dogs weighing 12.6 ± 1.4 kg.MethodsAnesthesia was induced with sevoflurane in oxygen until endotracheal intubation was possible and anesthesia maintained with sevoflurane using positive-pressure ventilation. Each dog was anesthetized five times and was administered each of the following treatments: saline (1 mL kg^–1 hour^–1) or dexmedetomidine at 0.1, 0.5, 1.0 or 5.0 μg kg^–1 loading dose intravenously over 10 minutes followed by CRI at 0.1, 0.5, 1.0 or 5.0 μg kg^–1 hour^–1, respectively. Following 60 minutes of CRI, sevoflurane MAC was determined in duplicate using an electrical stimulus (50 V, 50 Hz, 10 ms). Then, CRI of successively increasing doses of remifentanil (0.15, 0.60 and 2.40 μg kg^–1 minute^–1) was added to each treatment. MAC was also determined after 30 minutes equilibration at each remifentanil dose. Isobolographic analysis determined interaction from the predicted doses required for a 50% MAC reduction (ED₅₀) with remifentanil, dexmedetomidine and remifentanil combined with dexmedetomidine, with the exception of dexmedetomidine 5.0 μg kg^–1 hour^–1, obtained using log-linear regression analysis.ResultsThe sevoflurane MAC decreased dose-dependently with increasing infusion rates of dexmedetomidine and remifentanil. Remifentanil ED₅₀ values were lower when combined with dexmedetomidine than those obtained during saline–remifentanil. Synergistic interactions between dexmedetomidine and remifentanil for MAC reduction occurred with dexmedetomidine at 0.5 and 1.0 μg kg^–1 hour^–1.Conclusions and clinical relevanceCombined CRIs of dexmedetomidine and remifentanil synergistically resulted in sevoflurane MAC reduction. The combination of dexmedetomidine and remifentanil effectively reduced the requirement of sevoflurane during anesthesia in dogs.     

The effect of epidural injection speed on epidural pressure and distribution of solution in anesthetized dogs

ObjectiveTo determine the effect of injection speed on epidural pressure (EP), injection pressure (IP), epidural distribution (ED) of solution, and extent of sensory blockade (SB) during lumbosacral epidural anesthesia in dogs.Study designProspective experimental trial.AnimalsTen healthy adult Beagle dogs weighing 8.7 ± 1.6 kg.MethodsGeneral anesthesia was induced with propofol administered intravenously and maintained with isoflurane. Keeping the dogs in sternal recumbency, two spinal needles connected to electrical pressure transducers were inserted into the L6-L7 and the L7-S1 intervertebral epidural spaces for EP and IP measurements, respectively. Bupivacaine 0.5% diluted in iohexol was administered epidurally to each dog via spinal needle at L7-S1 intervertebral space, at two rates of injection (1 and 2 mL minute^?1 groups), with a 1-week washout period. Epidural distribution was verified with computed tomography, and SB was evaluated after arousal by pinching the skin with a mosquito hemostatic forceps over the vertebral dermatomes. The results were analyzed according to each injection speed, using paired t- and Wilcoxon signed-rank tests.ResultsMean ± SD of baseline EP and IP values were 2.1 ± 6.1 and 2.6 ± 7.1 mmHg, respectively. Significant differences were observed between 1 and 2 mL minute^?1 groups for peak EP (23.1 ± 8.5 and 35.0 ± 14.5 mmHg, p = 0.047) and peak IP (68.5 ± 10.7 and 144.7 ± 32.6 mmHg, p <0.001). However, the median (range) of the ED, 11.5 (4–22) and 12 (5–21) vertebrae, and SB, 3.5 (0–20) and 1 (0–20) dermatomes, values of the two groups were not related to injection speed.Conclusions and clinical relevanceThe EP profile during injection was measured by separating the injection and pressure monitoring lines. The increase in epidural injection speed increased the EP, but not the ED or the SB in dogs.     

Assessing the influence of mechanical ventilation on blood gases and blood pressure in rattlesnakes

ObjectiveTo characterize the impact of mechanical positive pressure ventilation on heart rate (HR), arterial blood pressure, blood gases, lactate, glucose, sodium, potassium and calcium concentrations in rattlesnakes during anesthesia and the subsequent recovery period.Study designProspective, randomized trial.AnimalsTwenty one fasted adult South American rattlesnakes (Crotalus durissus terrificus).MethodsSnakes were anesthetized with propofol (15 mg kg⁻¹) intravenously, endotracheally intubated and assigned to one of four ventilation regimens: Spontaneous ventilation, or mechanical ventilation at a tidal volume of 30 mL kg⁻¹ at 1 breath every 90 seconds, 5 breaths minute⁻¹, or 15 breaths minute⁻¹. Arterial blood was collected from indwelling catheters at 30, 40, and 60 minutes and 2, 6, and 24 hours following induction of anesthesia and analyzed for pH, PaO₂, PaCO₂, and selected variables. Mean arterial blood pressure (MAP) and HR were recorded at 30, 40, 60 minutes and 24 hours.ResultsSpontaneous ventilation and 1 breath every 90 seconds resulted in a mild hypercapnia (PaCO₂ 22.4 ± 4.3 mmHg [3.0 ± 0.6 kPa] and 24.5 ± 1.6 mmHg [3.3 ± 0.2 kPa], respectively), 5 breaths minute⁻¹ resulted in normocapnia (14.2 ± 2.7 mmHg [1.9 ± 0.4 kPa]), while 15 breaths minute⁻¹ caused marked hypocapnia (8.2 ± 2.5 mmHg [1.1 ± 0.3 kPa]). Following recovery, blood gases of the four groups were similar from 2 hours. Anesthesia, independent of ventilation was associated with significantly elevated glucose, lactate and potassium concentrations compared to values at 24 hours (p < 0.0001). MAP increased significantly with increasing ventilation frequency (p < 0.001). HR did not vary among regimens.Conclusions and clinical relevanceMechanical ventilation had a profound impact on blood gases and blood pressure. The results support the use of mechanical ventilation with a frequency of 1–2 breaths minute⁻¹ at a tidal volume of 30 mL kg⁻¹ during anesthesia in fasted snakes.     

Comparison of noninvasive cardiac output measurements by transthoracic bioimpedance, partial carbon dioxide rebreathing, and transesophageal echocardiography with the thermodilution technique in beagle dogs

Most methods for determining cardiac output (CO) have limited application in clinical practice due to the invasive techniques required. This study compared the thermodilution technique (TDCO) with three noninvasive methods for determining CO in anesthetized dogs: transthoracic bioimpedance (BICO), partial CO₂ rebreathing (NICO), and transesophageal echocardiography (TEECO). TDCO was compared to BICO, NICO, and TEECO in six adult sevoflurane anesthetized beagle dogs (9.1–13.0 kg). All dogs were administered midazolam [0.3 mg kg^?1, intravenously (IV)] and butorphanol (0.1 mg kg^?1 IV), followed by ketamine (5.0 mg kg^–1 IV) and sevoflurane in nitrous oxide (1 L minute^–1) and oxygen (1 L minute^–1) and mechanically ventilated. Dogs were maintained at 2.2% end‐tidal sevoflurane (ETsev) concentration for instrumentation and baseline measurements. Low (5.0% ETsev), intermediate (3.3% ETsev), and high cardiac output values were achieved by varying the end‐tidal sevoflurane concentration and the administration of dobutamine (3–10 g kg^–1 minute^–1 and 2.2% ETsev). A minimum of thirty data sets was obtained for each comparison. The correlation coefficients when compared to TDCO were 0.684 for BICO (p < 0.0001), 0.883 for NICO (p < 0.0001), and 0.991 for TEECO (p < 0.0001). Cardiac output values ranged 50–444 mL kg^–1 minute^–1 for TDCO, 100–253 mL kg^–1 minute^–1 for BICO, 64–214 mL kg^–1 minute^–1 for NICO, and 52–401 mL kg^–1 minute^–1 for TEECO. The differences when compared to TDCO ranged – 62–235 mL kg^?1minute^?1 for BICO, 18–220 mL kg^?1 minute^?1 for NICO, and – 35–32 mL kg^–1 minute^–1 for TEECO. Differences were maximum at the highest CO in BICO and NICO. In conclusion, this study demonstrated that BICO and NICO underestimate CO in sevoflurane anesthetized dogs. TEECO is a viable noninvasive method for determining CO in sevoflurane anesthetized dogs.     

Combined effects of dexmedetomidine and vatinoxan infusions on minimum alveolar concentration and cardiopulmonary function in sevoflurane-anesthetized dogs

ObjectiveTo evaluate the effects of combined infusions of vatinoxan and dexmedetomidine on inhalant anesthetic requirement and cardiopulmonary function in dogs.Study designProspective experimental study.MethodsA total of six Beagle dogs were anesthetized to determine sevoflurane minimum alveolar concentration (MAC) prior to and after an intravenous (IV) dose (loading, then continuous infusion) of dexmedetomidine (4.5 μg kg^–1 hour^–1) and after two IV doses of vatinoxan in sequence (90 and 180 μg kg^–1 hour^–1). Blood was collected for plasma dexmedetomidine and vatinoxan concentrations. During a separate anesthesia, cardiac output (CO) was measured under equivalent MAC conditions of sevoflurane and dexmedetomidine, and then with each added dose of vatinoxan. For each treatment, cardiovascular variables were measured with spontaneous and controlled ventilation. Repeated measures analyses were performed for each response variable; for all analyses, p < 0.05 was considered significant.ResultsDexmedetomidine reduced sevoflurane MAC by 67% (0.64 ± 0.1%), mean ± standard deviation in dogs. The addition of vatinoxan attenuated this to 57% (0.81 ± 0.1%) and 43% (1.1 ± 0.1%) with low and high doses, respectively, and caused a reduction in plasma dexmedetomidine concentrations. Heart rate and CO decreased while systemic vascular resistance increased with dexmedetomidine regardless of ventilation mode. The co-administration of vatinoxan dose-dependently modified these effects such that cardiovascular variables approached baseline.Conclusions and clinical relevanceIV infusions of 90 and 180 μg kg^–1 hour^–1 of vatinoxan combined with 4.5 μg kg^–1 hour^–1 dexmedetomidine provide a meaningful reduction in sevoflurane requirement in dogs. Although sevoflurane MAC-sparing properties of dexmedetomidine in dogs are attenuated by vatinoxan, the cardiovascular function is improved. Doses of vatinoxan >180 μg kg^–1 hour^–1 might improve cardiovascular function further in combination with this dose of dexmedetomidine, but beneficial effects on anesthesia plane and recovery quality may be lost.     

Postoperative analgesic effects of either a constant rate infusion of fentanyl,lidocaine, ketamine,dexmedetomidine, or the combination lidocaine‐ketamine‐dexmedetomidine after ovariohysterectomy in dogs

ObjectiveTo evaluate the postoperative analgesic effects of a constant rate infusion (CRI) of either fentanyl (FENT), lidocaine (LIDO), ketamine (KET), dexmedetomidine (DEX), or the combination lidocaine-ketamine-dexmedetomidine (LKD) in dogs.Study designRandomized, prospective, blinded, clinical study.AnimalsFifty-four dogs.MethodsAnesthesia was induced with propofol and maintained with isoflurane. Treatments were intravenous (IV) administration of a bolus at start of anesthesia, followed by an IV CRI until the end of anesthesia, then a CRI at a decreased dose for a further 4 hours: CONTROL/BUT (butorphanol 0.4 mg kg⁻¹, infusion rate of saline 0.9% 2 mLkg⁻¹ hour⁻¹); FENT (5 μg kg⁻¹, 10 μg kg⁻¹hour⁻¹, then 2.5 μg kg⁻¹ hour⁻¹); KET (1 mgkg⁻¹, 40 μg kg⁻¹ minute⁻¹, then 10 μg kg⁻¹minute⁻¹); LIDO (2 mg kg⁻¹, 100 μg kg⁻¹ minute⁻¹, then 25 μg kg⁻¹ minute⁻¹); DEX (1 μgkg⁻¹, 3 μg kg⁻¹ hour⁻¹, then 1 μg kg⁻¹ hour⁻¹); or a combination of LKD at the aforementioned doses. Postoperative analgesia was evaluated using the Glasgow composite pain scale, University of Melbourne pain scale, and numerical rating scale. Rescue analgesia was morphine and carprofen. Data were analyzed using Friedman or Kruskal–Wallis test with appropriate post-hoc testing (p < 0.05).ResultsAnimals requiring rescue analgesia included CONTROL/BUT (n = 8), KET (n = 3), DEX (n = 2), and LIDO (n = 2); significantly higher in CONTROL/BUT than other groups. No dogs in LKD and FENT groups received rescue analgesia. CONTROL/BUT pain scores were significantly higher at 1 hour than FENT, DEX and LKD, but not than KET or LIDO. Fentanyl and LKD sedation scores were higher than CONTROL/BUT at 1 hour.Conclusions and clinical relevanceLKD and FENT resulted in adequate postoperative analgesia. LIDO, CONTROL/BUT, KET and DEX may not be effective for treatment of postoperative pain in dogs undergoing ovariohysterectomy.     

Effects of pre‐operative administration of medetomidine on plasma insulin and glucose concentrations in healthy dogs and dogs with insulinoma

ObjectiveTo investigate the effect of medetomidine on plasma glucose and insulin concentrations in dogs with insulinoma and in healthy dogs undergoing anesthesia and surgery.AnimalsTwenty–five dogs with insulinoma and 26 healthy dogs.MethodsIn dogs with insulinoma, medetomidine (5 μg kg^?1) was randomly included (n = 12) or omitted (n = 13) from the pre–anesthetic medication protocol, which typically contained an opioid and an anticholinergic. Healthy dogs received medetomidine (5 μg kg^?1; n = 13) or acepromazine (0.04 mg kg^?1; n = 13) plus an opioid (morphine 0.5 mg kg^?1) and an anticholinergic (atropine 0.04 mg kg^?1) as pre–anesthetic medications. Pre–anesthetic medications were given intramuscularly. Plasma glucose and insulin concentrations were measured before (sample 1) and 30 minutes after pre–anesthetic medication (sample 2), and at the end of surgery in dogs with insulinoma or at 2 hours of anesthesia in healthy dogs (sample 3). Glucose requirement to maintain intra–operative normoglycemia in dogs with insulinoma was quantified and compared. Data were analyzed with anova and Bonferroni post–test, t–tests or chi–square tests as appropriate with p < 0.05 considered significant. Data are shown as mean ± SD.ResultsMedetomidine significantly decreased plasma insulin concentrations and increased plasma glucose concentrations in healthy dogs and those with insulinoma. These variables did not change significantly in the dogs not receiving medetomidine. In the dogs with insulinoma, intra–operative glucose administration rate was significantly less in the animals that received medetomidine compared to those that did not.ConclusionsPre–anesthetic administration of medetomidine significantly suppressed insulin secretion and increased plasma glucose concentration in dogs with insulinoma and in healthy dogs undergoing anesthesia and surgery.Clinical relevanceThese findings support the judicious use of medetomidine at low doses as an adjunct to the anesthetic management of dogs with insulinoma.     

Evaluation of nalbuphine,butorphanol and morphine in dogs during ovariohysterectomy and on early postoperative pain

ObjectiveTo evaluate the effects of nalbuphine, butorphanol and morphine combined with acepromazine on intraoperative and early postoperative pain management in dogs anesthetized for ovariohysterectomy.Study designProspective, randomized blinded clinical study.AnimalsA total of 48 healthy female dogs of different breeds, aged 1–6 years, weighing (mean ± standard deviation) 14.5 ± 4.8 kg.MethodsDogs were randomly assigned into four groups to be intravenously administered nalbuphine (0.5 mg kg^–1; group N0.5), nalbuphine (1.0 mg kg^–1; group N1.0), butorphanol (0.4 mg kg^–1; group B0.4) or morphine (0.2 mg kg^–1; group M0.2) combined with acepromazine (0.02 mg kg^–1) prior to propofol and isoflurane for anesthesia. Heart rate (HR), respiratory rate, systolic arterial pressure and rectal temperature (RT) were recorded at time points during anesthesia. A dynamic interactive visual analog scale applied in three phases (DIVAS I, II and III) and the modified Glasgow composite measure pain scale were used to assess pain before premedication and 1, 2, 3, 4, 5 and 6 hours after extubation. Administration of rescue analgesia was recorded.ResultsAt the left ovarian pedicle ligation, HR was higher in N1.0 than in B0.4 (p = 0.020). RT decreased significantly by the end of surgery in N0.5 (p = 0.043) and B0.4 (p = 0.010). Rescue analgesia was administered postoperatively over 6 hours to eight, seven, nine and 10 dogs in N0.5, N1.0, B0.4 and M0.2, respectively (p = 0.57). DIVAS II was higher in B0.4 than in N1.0 at 2 and 3 hours (p = 0.038 and p = 0.002, respectively) and N0.5 at 3 hours (p = 0.003).Conclusions and clinical relevanceAt the doses used, all premedication protocols provided insufficient intraoperative analgesia, with minimal clinical differences between groups. No premedication provided satisfactory analgesia in the first 6 hours postoperatively.     

The effect of ketamine on the MACBAR of sevoflurane in dogs

ObjectiveTo determine the effect of intravenous ketamine on the minimum alveolar concentration of sevoflurane needed to block autonomic response (MAC_BAR) to a noxious stimulus in dogs.Study designRandomized, crossover, prospective design.AnimalsEight, healthy, adult male, mixed-breed dogs, weighing 11.2–16.1 kg.MethodsDogs were anesthetized with sevoflurane on two occasions, 1 week apart, and baseline MAC_BAR (B-MAC_BAR) was determined on each occasion. MAC_BAR was defined as the mean of the end-tidal sevoflurane concentrations that prevented and allowed an increase (≥15%) in heart rate or invasive mean arterial pressure in response to a noxious electrical stimulus (50 V, 50 Hz, 10 ms). Dogs then randomly received either a low-dose (LDS) or high-dose series (HDS) of ketamine, and treatment MAC_BAR (T-MAC_BAR) was determined. The LDS had an initial loading dose (LD) of 0.5 mg kg^?1 and constant rate infusion (CRI) at 6.25 μg kg^?1 minute^?1, followed, after T-MAC_BAR determination, by a second LD (1 mg kg^?1) and CRI (12.5 μg kg^?1 minute^?1). The HDS had an initial LD (2 mg kg^?1) and CRI (25 μg kg^?1 minute^?1) followed by a second LD (3 mg kg^?1) and CRI (50 μg kg^?1 minute^?1). Data were analyzed with a mixed-model anova and are presented as LSM ± SEM.ResultsThe B-MAC_BAR was not significantly different between treatments. Ketamine at 12.5, 25, and 50 μg kg^?1 minute^?1 decreased sevoflurane MAC_BAR, and the maximal decrease (22%) occurred at 12.5 μg kg^?1 minute^?1. The percentage change in MAC_BAR was not correlated with either the log plasma ketamine or norketamine concentration.Conclusions and clinical relevanceKetamine at clinically relevant doses of 12.5, 25, and 50 μg kg^?1 minute^?1 decreased sevoflurane MAC_BAR, although the reduction was neither dose-dependent nor linear.     

Delivery of sevoflurane to dogs using a Stephens anaesthetic machine

ObjectiveTo investigate the sevoflurane concentrations produced within the Stephens anaesthetic machine circuit (vaporizer in-circle system) at different fresh gas flow rates (FGFRs), temperatures, vaporizer settings and vaporizer sleeve positions when used to anaesthetize dogs of different body sizes.Study designExperimental non-blinded studies.AnimalsEighteen mixed breed dogs, weights 4–39 kg.MethodsAnaesthetic induction with propofol was followed by maintenance with sevoflurane in oxygen via the Stephens anaesthetic machine. In study 1, the vaporizer setting, temperature and circuit FGFRs were altered with the vaporizer sleeve down (n = 3), or in separate experiments, up (n = 3). Delivered (Fi’SEVO) and expired sevoflurane concentrations were recorded. Study 2 determined the vaporizer settings (sleeve up) required to achieve predetermined multiples of minimal alveolar concentration (MAC) of Fi’SEVO when sevoflurane was delivered to dogs (n = 12) of different bodyweights and at different FGFRs.ResultsDelivered concentrations of sevoflurane were sufficient to maintain anaesthesia in all dogs, regardless of bodyweight, FGFR, vaporizer temperature and sleeve position. Fi’SEVO increased with increasing temperature, when the vaporizer sleeve was down, when vaporizer setting was increased and when FGFR was decreased. As the FGFR increased or the dog’s bodyweight decreased, higher vaporizer settings were required to produce the same Fi’SEVO. The median Stephens vaporizer settings to achieve an Fi’SEVO of 1.3 MAC ranged from 4.3 to 5.0 for a small dog (1–10 kg), 2.5 to 5.6 for a medium dog (15–25 kg) and 2.5 to 3.5 for a large dog (30–40 kg), depending on the FGFR.Conclusion and clinical relevanceThe Stephens anaesthetic machine can deliver to dogs, weighing 4 kg and above, concentrations of sevoflurane sufficient or in excess of that required to maintain anaesthesia, at temperatures from 10 to 35 °C, FGFRs of 1 to 5 times the patient’s estimated metabolic oxygen requirement and at any vaporizer sleeve position.     

Bispectral index in dogs at three intravenous infusion rates of propofol

ObjectiveTo establish the correlation between the bispectral index (BIS) and different rates of infusion of propofol in dogs.Study designProspective experimental trial.AnimalsEight adult dogs weighing 6–20 kg.MethodsEight animals underwent three treatments at intervals of 20 days. Propofol was used for induction of anesthesia (10 mg kg⁻¹ IV), followed by a continuous rate infusion (CRI) at 0.2 mg kg⁻¹ minute⁻¹ (P2), 0.4 mg kg⁻¹ minute⁻¹ (P4) or 0.8 mg kg⁻¹ minute⁻¹ (P8) for 55 minutes. The BIS values were measured at 10, 20, 30, 40, and 50 minutes (T10, T20, T30, T40, and T50, respectively) after the CRI of propofol was started. Numeric data were submitted to analysis of variance followed by Tukey test (p < 0.05).ResultsThe BIS differed significantly among groups at T40, when P8 was lower than P2 and P4. At T50, P8 was lower than P2. The electromyographic activity (EMG) in P2 and P4 was higher than P8 at T40 and T50.ConclusionsAn increase in propofol infusion rates decreases the BIS values and EMG.     

Procedural sedation combined with locoregional anesthesia for orthopedic surgery of the pelvic limb in 10 dogs: case series

HistoryTen dogs weighing 36 (21.4–75) kg [median (min–max)] and aged 3 (1–9) years scheduled for orthopedic surgery involving the stifle and structures distal to it.Physical ExaminationPatients were classified as ASA I or II based on physical examination and basic hematology and biochemistry.ManagementEach dog was managed using combined femoral and sciatic nerve blocks and procedural sedation with an intravenous infusion of propofol (0.07–0.15 mg kg^?1 minute^?1) and dexmedetomidine (1 μg kg^?1 hour^?1). None of the patients required conversion to general anesthesia as a result of response to surgical stimulation. The level of sedation was considered adequate in all patients and was characterized by occasional head lifting, thoracic limb stretching, yawning, lingual movements and swallowing. The eye position ranged from central to partial ventromedial rotation and was accompanied by spontaneous blinking. Intra-operative cardiovascular and ventilatory variables were considered within acceptable limits. Muscle relaxation at the surgical field was adequate and surgical conditions were indistinguishable from those produced by general anesthesia. Intraoperatively, no additional analgesics were considered necessary. The quality of the recoveries was considered excellent in all cases.Follow upNo additional pain relief was required in any of the dogs within the 10 hours following blockade. All dogs ate 5.5 (3.5–12) hours after recovery. Ambulation occurred at 4 (2–6) hours. No evidence of esophagitis or aspiration pneumonitis has been reported during a period of 1 year after the procedures in any of the dogs.ConclusionWhen combined with femoral and sciatic nerve blocks, procedural sedation has the potential of being an alternative to general anesthesia for orthopedic surgery involving the stifle and structures distal to it in the dog.