The effect of autonomic manipulation on heart rate variability in dogs

Beat‐to‐beat variation of heart rate is reflective of autonomic balance and has been used to assess pain and stress in human beings. The purpose of this investigation was to pharmacologically manipulate the autonomic nervous system and to determine the effect of these manipulations on heart rate variability (HRV) in dogs. Four adult male hound dogs (27 ± 1 kg) were used in the investigation. Each dog was given five treatments: Parasympathetic blockade (glycopyrrolate; 0.01 mg kg^–1 IV and 0.01 mg kg^–1 IM), parasympathetic stimulation (phenylephrine; 0.005 mg kg^–1 IV + 0.05 mg kg^–1hour^–1), sympathetic blockade (propranolol; 0.11 mg kg^–1 IV), sympathetic stimulation propranolol; 0.01 μg kg^–1 minute^–1), and saline control. At least 48 hours were allowed between treatments. ECG recordings were obtained using an ambulatory ECG monitor. A 5‐minutes period of continuous recording obtained ~30 minutes after initiation of drug administration was used for data analysis. Changes in HRV were evaluated by time and frequency‐domain analysis. The standard deviation of normal R‐R intervals (SDNN), as well as the standard deviation of successive differences in RR intervals (SDSD) were assessed for each treatment. Low frequency (LFP; 0.05–0.15 Hz), high frequency (HFP; 0.15–0.35 Hz), and total (TP; 0.017–0.5 Hz) spectral power were also determined. The LFP:HFP ratio was also evaluated. A two‐way anova with a Tukey's test was used to detect differences (p < 0.05). Administration of glycopyrrolate or isoproterenol increased HR and decreased SDNN and SDSD below control levels. Phenylephrine or propranolol administration were without effect. LFP was diminished by glycopyrrolate and isoproterenol, but was unaffected by phenylephrine and propranolol. HFP, TP, and LFP:HFP were unaffected by treatment. Both branches of the autonomic nervous system influence SDNN and LFP. SDSD, in contrast, is altered primarily by parasympathetic activity. Thus, it appears that parasympathetic activity modulates HRV in the resting dog, as either withdrawal of parasympathetic influence or accentuated sympathetic activity led to significant changes in these measures of HRV. Conversely, augmentation of parasympathetic activity or withdrawal of sympathetic tone minimally affected HRV.     

Cardiovascular,respiratory, electrolyte and acid–base balance during continuous dexmedetomidine infusion in anesthetized dogs

ObjectiveTo evaluate the cardiovascular, respiratory, electrolyte and acid–base effects of a continuous infusion of dexmedetomidine during propofol–isoflurane anesthesia following premedication with dexmedetomidine.Study designProspective experimental study.AnimalsFive adult male Walker Hound dogs 1–2 years of age averaging 25.4 ± 3.6 kg.MethodsDogs were sedated with dexmedetomidine 10 μg kg^?1 IM, 78 ± 2.3 minutes (mean ± SD) before general anesthesia. Anesthesia was induced with propofol (2.5 ± 0.5 mg kg^?1) IV and maintained with 1.5% isoflurane. Thirty minutes later dexmedetomidine 0.5 μg kg^?1 IV was administered over 5 minutes followed by an infusion of 0.5 μg kg^?1 hour^?1. Cardiac output (CO), heart rate (HR), ECG, direct blood pressure, body temperature, respiratory parameters, acid–base and arterial blood gases and electrolytes were measured 30 and 60 minutes after the infusion started. Data were analyzed via multiple linear regression modeling of individual variables over time, compared to anesthetized baseline values. Data are presented as mean ± SD.ResultsNo statistical difference from baseline for any parameter was measured at any time point. Baseline CO, HR and mean arterial blood pressure (MAP) before infusion were 3.11 ± 0.9 L minute^?1, 78 ± 18 beats minute^?1 and 96 ± 10 mmHg, respectively. During infusion CO, HR and MAP were 3.20 ± 0.83 L minute^?1, 78 ± 14 beats minute^?1 and 89 ± 16 mmHg, respectively. No differences were found in respiratory rates, PaO₂, PaCO₂, pH, base excess, bicarbonate, sodium, potassium, chloride, calcium or lactate measurements before or during infusion.Conclusions and clinical relevanceDexmedetomidine infusion using a loading dose of 0.5 μg kg^?1 IV followed by a constant rate infusion of 0.5 μg kg^?1 hour^?1 does not cause any significant changes beyond those associated with an IM premedication dose of 10 μg kg^?1, in propofol–isoflurane anesthetized dogs. IM dexmedetomidine given 108 ± 2 minutes before onset of infusion showed typical significant effects on cardiovascular parameters.     

Comparison between three dosages of intramuscular alfaxalone and a ketamine–dexmedetomidine–midazolam–tramadol combination in golden-headed lion tamarins (Leontopithecus chrysomelas)

ObjectivesTo characterize the cardiopulmonary and anesthetic effects of alfaxalone at three dose rates in comparison with a ketamine–dexmedetomidine–midazolam–tramadol combination (KDMT) for immobilization of golden-headed lion tamarins (GHLTs) (Leontopithecus chrysomelas) undergoing vasectomy.Study designProspective clinical trial.AnimalsA total of 19 healthy, male, wild-caught GHLTs.MethodsTamarins were administered alfaxalone intramuscularly (IM) at 6, 12 or 15 mg kg^–1, or KDMT, ketamine (15 mg kg^–1), dexmedetomidine (0.015 mg kg^–1), midazolam (0.5 mg kg^–1) and tramadol (4 mg kg^–1) IM. Immediately after immobilization, lidocaine (8 mg kg^–1) was infiltrated subcutaneously (SC) at the incision site in all animals. Physiologic variables, anesthetic depth and quality of immobilization were assessed. At the end of the procedure, atipamezole (0.15 mg kg^–1) was administered IM to group KDMT and tramadol (4 mg kg^–1) SC to the other groups; all animals were injected with ketoprofen (2 mg kg^–1) SC.ResultsA dose-dependent increase in sedation, muscle relaxation and immobilization time was noted in the alfaxalone groups. Despite the administration of atipamezole, the recovery time was longer for KDMT than all other groups. Muscle tremors were noted in some animals during induction and recovery with alfaxalone. No significant differences were observed for cardiovascular variables among the alfaxalone groups, whereas an initial decrease in heart rate and systolic arterial blood pressure was recorded in KDMT, which increased after atipamezole administration.Conclusions and clinical relevanceAlfaxalone dose rates of 12 or 15 mg kg^–1 IM with local anesthesia provided good sedation and subjectively adequate pain control for vasectomies in GHLTs. KDMT induced a deeper plane of anesthesia and should be considered for more invasive or painful procedures. All study groups experienced mild to moderate hypothermia and hypoxemia; therefore, the use of more efficient heating devices and oxygen supplementation is strongly recommended when using these protocols.     

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 tumescent local anesthesia in cats undergoing unilateral mastectomy

ObjectiveTo evaluate the analgesic efficacy and safety of tumescent local anesthesia (TLA) in cats undergoing unilateral mastectomy.Study designProspective clinical trial.AnimalsA total of 12 ovariohysterectomized female cats.MethodsAll animals were premedicated with pethidine (4 mg kg^–1) intramuscularly (IM), followed by induction of anesthesia with propofol (5 mg kg^–1) intravenously and maintenance with isoflurane in oxygen. A refrigerated TLA solution (15 mL kg^–1, 8 °C) was injected using a Klein cannula. The solution was composed of 0.5 mL of epinephrine (1 mg mL^–1) and 40 mL of 2% lidocaine added to 210 mL lactated Ringer’s solution (final lidocaine concentration 0.32%). Heart and respiratory rates, systolic arterial blood pressure, temperature and oxygen saturation were measured during anesthesia. Blood samples were collected from the jugular vein for measurement of plasma lidocaine concentration using high performance liquid chromatography. Postoperative pain scores were evaluated hourly for 6 hours. Analgesic rescue was performed with tramadol (2 mg kg^–1) IM and meloxicam (0.15 mg kg^–1) subcutaneously.ResultsPlasma lidocaine concentration peaked at 90 minutes after injection of TLA, but no concentration considered toxic for the species was measured. The median postoperative analgesia time was 6 hours after injection of TLA.ConclusionsThis study found that TLA prevented sympathetic response to noxious stimuli during anesthesia and provided satisfactory postoperative analgesia in cats submitted to total unilateral mastectomy, with no apparent signs of toxicity.Clinical relevanceTLA can prevent sympathetic stimulation resulting from noxious stimuli during anesthesia, promoting good intraoperative conditions, proving to be a viable addition to analgesia in cats submitted to a total unilateral mastectomy.     

Comparison of tramadol and morphine for pre-medication of dogs undergoing general anesthesia for orthopedic surgery

Tramadol is a centrally acting analgesic with opioid and monoaminergic actions. Its clinical effects have been well characterized in humans, where it has been in use for many years, but little is known for veterinary species. This study evaluated the sedative, emetic, thiopental‐sparing and intraoperative respiratory and hemodynamic effects of tramadol in comparison to morphine for pre‐medication of dogs undergoing orthopedic surgery under halothane anesthesia. Sixteen adult, healthy, mixed breed dogs (8.0 ± 2.6 kg) were studied. Eight dogs were pre‐medicated with tramadol (1.0 mg kg^‐1 IM) and the other eight with morphine (1.0 mg kg^–1 IM). After 20 minutes, anesthesia was induced with thiopental and subsequently maintained with halothane in oxygen using a Bain system, with spontaneous respiration. Degree of sedation and occurrence of emesis were evaluated after pre‐anesthetic medication. Dose of thiopental necessary for tracheal intubation was compared between the two groups. Arterial blood gas analyzes were done before pre‐medication and at 60 minutes of anesthesia. Heart rate and noninvasive arterial blood pressure were recorded before pre‐medication and every 10 minutes during anesthesia. Observer was blinded of the treatment given for each dog. Tramadol produced no visible sedation and no vomiting, while morphine induced a moderate degree of sedation in all dogs and vomiting in 62% of them. Dogs pre‐medicated with tramadol required significantly more thiopental (17 ± 3.8 mg kg^–1) for induction of anesthesia than those pre‐medicated with morphine (12 ± 1.8 mg kg^–1). Pre‐medication with morphine was associated with significantly higher PaCO₂ and lower pH at 60 minutes of anesthesia. The remaining respiratory parameters and the hemodynamic variables were similar between the two groups. In conclusion, dogs pre‐medicated with tramadol at 1 mg kg^–1 IM do not become visibly sedated and require a greater amount of thiopental for induction of anesthesia than pre‐medication with morphine. As intraoperative respiratory function is better preserved with tramadol, it may be useful for pre‐medication of respiratory compromised patients.     

Effect of pre-medication on gastroduodenoscopy in isoflurane-anesthetized cats

The pre‐medicant chosen may influence the ease with which gastroduodenoscopy (GD) is performed. The purpose of this study was to evaluate the relative ease of GD in cats under ketamine and isoflurane anesthesia after IM injection of hydromorphone (H, 0.1 mg kg^?1), hydromorphone plus glycopyrrolate (HG, 0.1 mg kg^?1 (H), 0.01 mg kg^?1 (G)), medetomidine (M, 0.03 mg kg^?1), or butorphanol (B, 0.4 mg kg^?1). Eight cats were assigned randomly to receive each treatment in a cross‐over design with at least 7 days between treatments. Twenty minutes after pre‐medication, medetomidine produced greater (p = 0.001) sedation than the other treatments when assessed, using a subjective ordinal scale. The cats were injected with ketamine (10 mg kg^?1 IM), orotracheally intubated, connected to a pediatric circle breathing system, and allowed to spontaneously breathe isoflurane in oxygen. Once end‐tidal isoflurane concentration was stable at 1.4% for 15 minutes, endoscopy was started. A single endoscopist (REG), who was unaware of the treatment used, performed all endoscopies. The endoscopist scored the difficulty of endoscopy subjectively (0–3). The significance of differences between treatments was evaluated using Friedman's test. Time for entering the stomach was 9.4 (4.7–15.9) (median (minimum–maximum)), 6.6 (5.2–11.7), 8.4 (6.3–16.5), and 7.7 (5.1–14.7) seconds and for entering the duodenum from the stomach was 20.5 (13.8–40.9), 18.2 (10.3–39.8), 20.2 (16.2–119.5), and 22.2 (11.8–83.8) seconds for H, HG, M, and B treatments, respectively. There were no significant differences in the time for, or difficulty of, endoscopy. We conclude that any of these drugs can be used satisfactorily at the doses and combinations tested to pre‐medicate cats prior to general anesthesia for GD.     

Comparison of two injectable anesthetic regimes in feral cats at a large-volume spay clinic

Same‐day mass sterilization of feral cats requires rapid onset, short‐duration anesthesia. The purpose of this study was to compare our current anesthetic protocol, Telazol–ketamine–xylazine (TKX) with medetomidine–ketamine–buprenorphine (MKB). Feral female cats received either IM TKX (n = 68; 0.25 mL cat^?1; tiletamine 12.5 mg, zolazepam 12.5 mg, K 20 mg, and X 5 mg per 0.25 mL) or MKB (n = 17; M 40 µg kg^?1, K 15 mg kg^?1, and B 10 µg kg^?1). Intervals measured included time from injection to recumbency, time to surgery, duration of surgery, and time from reversal of anesthesia (TKX: yohimbine 0.50 mg cat^?1 IV; MKB: atipamezole 0.50 mg cat^?1 IM) to sternal recumbency. Following instrumentation (Vet/Ox 4403 and Vet/BP Plus 6500), physiological measurements were recorded at 5‐minute intervals, and included rectal temperature, heart rate (HR), respiratory rate (RR), SpO₂ (lingual or rectal probes), and indirect mean arterial blood pressure (MAP) (oscillometric method). Nonparametric means were compared using Mann–Whitney U‐tests. Parametric means were compared using a two‐factorial anova with Bonferroni's t‐tests. The alpha‐priori significance level was p < 0.05. Values were mean ± SD. Body weight (TKX: 2.9 ± 0.5 kg, MKB: 2.7 ± 0.7 kg), time to recumbency (TKX: 4 ± 1 minutes, MKB: 3 ± 1 minutes), time to surgery (TKX: 28 ± 7 minutes, MKB: 28 ± 5 minutes), and duration of surgery (TKX: 11 ± 7 minutes, MKB: 8 ± 5 minutes) did not differ between groups. In contrast, MKB cats required less time from reversal to sternal recumbency (TKX: 68 ± 41 minutes, MKB: 7 ± 2 minutes) and were recumbent for shorter duration (TKX: 114 ± 39 minutes, MKB: 53 ± 6 minutes). Temperature decreased during the study in both groups, but overall temperature was higher in MKB cats (38.0 ± 0.95 °C) than in TKX cats (37.5 ± 0.95 °C). RR, HR, and SpO₂ did not change during the study in either group. However, overall HR and RR were higher in TKX cats (RR: 18 ± 8 breaths minute^?1, HR: 153 ± 30 beats minute^?1) compared to MKB cats (RR: 15 ± 7 breaths minute^?1, HR: 128 ± 19 beats minute^?1). In contrast, overall SpO₂ was lower in the TKX group (90 ± 6%) compared to the MKB group (94 ± 4%). MAP was also lower in the TKX group (112 ± 29 mm Hg) compared to that in the MKB group (122 ± 20 mm Hg). However, MAP increased in the TKX group during surgery compared to pre‐surgical values, but did not change in the MKB group. The results of this study suggested that MKB might be more suitable as an anesthetic for the purpose of mass sterilization of feral female cats.     

Effects of dissociative anesthesia opioid-free protocols combined with local anesthesia,with or without flumazenil or atipamezole postoperatively,for orchiectomy in cats

ObjectiveTo evaluate the anesthetic effects of two drug combinations with local anesthesia, with or without postoperative antagonists, for orchiectomy in cats.Study designProspective, randomized blinded clinical study.AnimalsA total of 64 healthy cats.MethodsCats were assigned to four equal groups: ketamine (5 mg kg^–1) and dexmedetomidine (10 μg kg^–1) were administered intramuscularly (IM), followed postoperatively with intravenous (IV) saline (5 mL; group KDS) or atipamezole (50 μg kg^–1; group KDA); and ketamine (14 mg kg^–1) with midazolam (0.5 mg kg^–1) and acepromazine (0.1 mg kg^–1) IM, with postoperative IV saline (5 mL; group KMAS) or flumazenil (0.1 mg kg^–1; group KMAF). Lidocaine (2 mg kg^–1) was divided between subcutaneous and intratesticular injection. Physiologic variables were recorded at time points during anesthesia. Ketamine rescue dose was recorded. The degree of sedation and the quality of recovery were evaluated postoperatively.ResultsTime to loss of pedal reflex was longer in groups KMAS and KMAF than in groups KDS and KDA (p = 0.010). Total rescue dose of ketamine was higher in KMAS and KMAF than in KDS and KDA (p = 0.003). Heart rate (HR) during anesthesia was higher in KMAS and KMAF than in KDS and KDA (p = 0.001). Times to head up (p = 0.0005) and to sternal recumbency (p = 0.0003) were shorter in KDA than in KDS, KMAS and KMAF. Lower sedation scores were assigned sooner to KDA than KDS, KMAS and KMAF (p < 0.001). Recovery quality scores were good in all groups.Conclusions and clinical relevanceBoth anesthetic protocols allowed the performance of orchiectomy. Groups KMAS and KMAF required higher rescue doses of ketamine before injecting lidocaine. HR and oscillometric systolic pressure were minimally changed in groups KD and tachycardia was recorded in groups KMA. Only atipamezole shortened the anesthetic recovery.     

Analgesic effect of pre-operative etodolac and butorphanol administration in dogs undergoing ovariohysterectomy

The analgesic, bleeding, and renal effects of dogs pre‐medicated with etodolac with and without butorphanol were evaluated. Twenty‐four 1‐year‐old healthy dogs, weighing 19 ± 3 kg (mean ± SD) were randomly assigned to four treatment groups (n = 6): control (C), etodolac (E), butorphanol (B), and etodolac with butorphanol (EB). Etodolac (12–14 mg kg^?1 PO) was given 1 hour before propofol induction and isoflurane maintenance anesthesia. Butorphanol (0.4 mg kg^?1 IV) was given immediately following endotracheal intubation. Control dogs received only propofol (8 mg kg^?1 to effect) and isoflurane anesthesia. All dogs were mechanically ventilated to maintain Pe ′CO₂ between 35 and 45 mm Hg (4.7–6.0 kPa). Lactated Ringer's solution was given at 10 mL kg^?1 hour^?1 during anesthesia. Plasma cortisol concentrations were assessed 1 day prior to surgery (baseline), immediately prior to anesthesia induction, and every 30 minutes until 5 hours following extubation, and 1 day after surgery. Total duration of anesthesia was 50 minutes and total surgery duration was 30 minutes. Isoflurane concentration area under the curve (AUC) over time during the anesthesia was compared among treatment groups. Buccal mucosal bleeding time (BMBT) was assessed 1 day before E administration and during surgery. Urine GGT to urine creatinine ratio, BUN, and plasma creatinine were taken daily from 1 day before to 3 days after surgery. Behavioral pain scores (numerical rating scale) were assessed by two observers blinded to the treatment during the 5‐hour recovery period at 30 minute intervals until 3 hours, and again at 5 hours after extubation. All data were analyzed using anova . Multiple comparisons were performed if the anova was significant. Alpha value was set at 0.05. Plasma cortisol concentrations significantly increased from time of extubation in all the treatment groups. They did not return to the baseline until 5, 2.5, 1.5, and 1.5 hours after extubation in the C, B, E, and EB groups, respectively. Isoflurane AUC was not significantly different among treatment groups. Dogs treated with EB had significantly less behavioral pain than all other groups throughout the 5‐hour recovery period. No significant difference was found between treatment groups or within treatment groups over time in BMBT, or any renal variables. This study demonstrated that (i) pre‐operative administration of E provides profound analgesia during the post‐operative period without renal or bleeding side‐effects in dogs undergoing OHE; and (ii) a combination of butorphanol–etodolac provides the best analgesic effect during the post‐operative period based on the behavioral pain score.     

Electrocardiographic and cardiopulmonary effects of intramuscular administration of glycopyrrolate and romifidine in conscious beagle dogs

Objective To determine the electrocardiographic and cardiopulmonary effects of IM administration of romifidine with and without prior administration of glycopyrrolate in conscious dogs. Study design Prospective randomized study. Animals Twelve healthy, adult beagles. Materials and methods Dogs were assigned at random to each of three treatments with glycopyrrolate (six dogs), and to each of three treatments without glycopyrrolate (six dogs). Baseline data were recorded, and saline solution or glycopyrrolate (10 µg kg^–1) was given IM. After 15 minutes, saline solution (control) or romifidine (20 or 40 µg kg^–1) was given IM. An ECG, heart rate (HR), systemic blood pressures, and respiratory rate (RR) were recorded before and 2.5, 5, 10, 15, 30, 45, 60, 75, 90, 105 and 120 minutes after romifidine administration. Rectal temperature (RT), pH, PaCO₂, PaO₂, hematocrit and plasma protein were determined before and 15, 30, 60 and 120 minutes after romifidine administration. Data were analyzed using analysis of variance for repeated measures and Tukey multiple comparison tests. Results Without glycopyrrolate, HR (beats minute^–1) decreased to minimum values (mean ± SD) of 52 ± 7 and 49 ± 12 (control 89 ± 20) 45 minutes after administration of romifidine at doses of 20 and 40 µg kg^–1, respectively. Sinus bradycardia (HR < 60 beats minute^–1), which persisted for up to 120 minutes, was observed in five of six and six of six dogs given romifidine at doses of 20 and 40 µg kg^–1, respectively. With glycopyrrolate, decreases in HR were prevented and mean arterial pressure (mm Hg) increased to maximum values of 139 ± 25 and 173 ± 17 (control 113 ± 11) 30 minutes after administration of romifidine at doses of 20 and 40 µg kg^–1, respectively. With and without glycopyrrolate, RR did not change appreciably, RT decreased, and pH, PaCO₂, PaO₂, hematocrit and plasma protein did not change after administration of romifidine. Conclusions and clinical relevance In healthy conscious beagles, IM administration of romifidine at doses of 20 and 40 µg kg^–1 causes sinus bradycardia which persists for up to 120 minutes. Administration of glycopyrrolate 15 minutes before administration of romifidine, prevents sinus bradycardia and induces moderate increases in arterial pressure.     

Total intravenous anesthesia in domestic chicken (Gallus gallus domesticus) with propofol alone or in combination with methadone,nalbuphine or fentanyl for ulna osteotomy

ObjectiveTo compare the propofol infusion rate and cardiopulmonary effects during total intravenous anesthesia with propofol alone and propofol combined with methadone, fentanyl or nalbuphine in domestic chickens undergoing ulna osteotomy.Study designProspective, randomized, experiment trial.AnimalsA total of 59 healthy Hissex Brown chickens weighing 1.5 ± 0.2 kg.MethodsAnesthesia was induced with propofol (9 mg kg^–1) administered intravenously (IV) and maintained with propofol (1.2 mg kg^–1 minute^–1) for 30 minutes. Birds were intubated and supplemented with 100% oxygen through a nonrebreathing circuit under spontaneous ventilation. Thereafter, each animal was randomly assigned to one of four groups: group P, no treatment; group PM, methadone (6 mg kg^–1) intramuscularly (IM); group PN, nalbuphine IM (12.5 mg kg^–1); and group PF, fentanyl IV (30 μg kg^–1 loading dose, 30 μg kg^–1 hour^–1 constant rate infusion). During the osteotomy surgery, the propofol infusion rate was adjusted to avoid movement of birds and provide adequate anesthesia. Pulse rate, invasive blood pressure, respiratory frequency, end-tidal carbon dioxide partial pressure (Pe′CO₂) and hemoglobin oxygen saturation (SpO₂) were recorded.ResultsData were available from 58 chickens. The mean ± standard deviation propofol infusion rate (mg kg^–1 minute^–1) for the duration of anesthesia was: group P, 0.81 ± 0.15; group PM, 0.66 ± 0.11; group PN, 0.60 ± 0.14; and group PF, 0.80 ± 0.07. Significant differences were P versus PM (p = 0.042), P versus PN (p = 0.002) and PF versus PN (p = 0.004). Pulse rate, blood pressure and SpO₂ remained acceptable for anesthetized birds with minor differences among groups. Values of Pe′CO₂ >60 mmHg (8 kPa) were observed in all groups.Conclusions and clinical relevanceMethadone and nalbuphine, but not fentanyl, decreased the propofol infusion rate required for anesthesia maintenance, but resulted in no obvious benefit in physiological variables.     

Medetomidine/midazolam/ketamine anaesthesia in ferrets: effects on cardiorespiratory parameters and evaluation of plasma drug concentrations

ObjectiveTo evaluate the cardiorespiratory effects and plasma concentrations of medetomidine-midazolam-ketamine (MMK) combinations administered by intramuscular (IM) or subcutaneous (SC) injection in sable ferrets (Mustela putorius furo).Study designProspective randomized experimental study.AnimalsEighteen adult ferrets: weight median 1.19 (range 0.81–1.60) kg.MethodsAnimals were allocated to one of three groups: group IM07 received 20 μg kg^?1 medetomidine, 0.5 mg kg^?1 midazolam and 7 mg kg^?1 ketamine IM; group IM10 20 μg kg^?1 medetomidine, 0.5 mg kg^?1 midazolam and 10 mg kg^?1 ketamine IM; and group SC10 20 μg kg^?1 medetomidine, 0.5 mg kg^?1 midazolam and 10 mg kg^?1 ketamine SC. Following instrumentation, cardiorespiratory parameters and plasma drug concentrations were measured every 5 minutes (T5–T30) for 30 minutes Ferrets were then euthanased. Data were analysed using anova for repeated measures. p < 0.05 was considered significant.ResultsResults are mean ± SD. Induction of anaesthesia (minutes) in IM07 and IM10 [2 (1)] was significantly faster than in SC10 [5 (2)]. All groups demonstrated the following: results given as groups IM07, IM10 and SC10 respectively. Mean arterial blood pressures (mmHg) were initially high [186 (13); 174 (33) and 174 (9) at T5] but decreased steadily. Pulse rates were initially 202 (20), 213 (17) and 207 (33) beats minute^?1, decreasing with time. PaO₂ (mmHg) was low [54.0 (8), 47.7 (10) and 38.5 (1)] at T5, although in groups IM07 and IM10 it increased over time. Plasma concentrations of all drugs were highest at T5 (36, 794 and 8264 nmol L^?1 for medetomidine, midazolam and ketamine, respectively) and decreased thereafter: for both midazolam and ketamine, concentrations in IM07 and IM10 were higher than SC10.Conclusions and clinical relevanceMMK combinations containing either 7 or 10 mg kg^?1 ketamine and given IM are suitable combinations for anaesthetising ferrets, although the observed degree of hypoxaemia indicates that oxygen administration is vital.     

Total intravenous anesthesia with propofol and S(+)‐ketamine in rabbits

ObjectiveTo evaluate total intravenous anesthesia with propofol alone or in combination with S(+)-ketamine in rabbits undergoing surgery.Study designProspective, randomized, blinded trial.AnimalsNine 6-month-old New Zealand white rabbits, weighing 2.5–3 kg.MethodsAnimals received acepromazine (0.1 mg kg^?1) and buprenorphine (20 μg kg^?1) IM, and anesthesia was induced with propofol (2 mg kg^?1) and S(+)-ketamine (1 mg kg^?1) IV. Rabbits received two of three treatments: propofol (0.8 mg kg^?1 minute^?1) (control treatment, P), propofol (0.8 mg kg^?1 minute^?1) + S(+)-ketamine (100 μg kg^?1 minute^?1) (PK100) or propofol (0.8 mg kg^?1 minute^?1) + S(+)-ketamine (200 μg kg^?1 minute^?1) (PK200). All animals received 100% O₂ during anesthesia. Heart rate, mean arterial pressure, hemoglobin oxygen saturation and respiratory rate were measured every 5 minutes for 60 minutes. Blood-gas parameters were measured at zero time and 60 minutes. Additional propofol injections, if necessary, and recovery time were recorded.ResultsAn increase in heart rate was observed in P and PK200 up to 10 minutes after induction of anesthesia. Blood pressure decreased from baseline values during the first 10 minutes in P and PK200, and during the first 15 minutes and between 45 and 55 minutes in PK100. A reduction in respiratory rate was observed after 5 minutes in all treatments. Respiratory acidosis was observed in all treatments. Six (2.8) [median (interquartile range)] further propofol injections were necessary in P, which differed statistically from PK100 [1 (0.2)] and PK200 [2 (0.6)]. Recovery time was shorter in P compared with PK100 and PK200, being [7.5 minutes (4.11)], [17.5 minutes (10.30)], and [12 minutes (10.30)], respectively.Conclusions and clinical relevanceS(+)-ketamine potentiates propofol-induced anesthesia in rabbits, providing better maintenance of heart rate. All of these techniques were accompanied by clinically significant respiratory depression.     

Evaluation of the perioperative stress response from dexmedetomidine infusion alone,with butorphanol bolus or remifentanil infusion compared with ketamine and morphine infusions in isoflurane-anesthetized horses

ObjectiveTo evaluate perioperative stress-related hormones in isoflurane-anesthetized horses administered infusions of dexmedetomidine alone or with butorphanol or remifentanil, compared with ketamine–morphine.Study designRandomized, prospective, nonblinded clinical study.AnimalsA total of 51 horses undergoing elective surgical procedures.MethodsHorses were premedicated with xylazine, anesthesia induced with ketamine–diazepam and maintained with isoflurane and one of four intravenous infusions. Partial intravenous anesthesia (PIVA) was achieved with dexmedetomidine (1.0 μg kg^–1 hour^–1; group D; 12 horses); dexmedetomidine (1.0 μg kg^–1 hour^–1) and butorphanol bolus (0.05 mg kg^–1; group DB; 13 horses); dexmedetomidine (1.0 μg kg^–1 hour^–1) and remifentanil (3.0 μg kg^–1 hour^–1; group DR; 13 horses); or ketamine (0.6 mg kg^–1 hour^–1) and morphine (0.15 mg kg^–1, 0.1 mg kg^–1 hour^–1; group KM; 13 horses). Infusions were started postinduction; butorphanol bolus was administered 10 minutes before starting surgery. Blood was collected before drugs were administered (baseline), 10 minutes after ketamine–diazepam, every 30 minutes during surgery and 1 hour after standing. Mean arterial pressure (MAP), pulse rate, end-tidal isoflurane concentration, cortisol, nonesterified fatty acids (NEFA), glucose and insulin concentrations were compared using linear mixed models. Significance was assumed when p < 0.05.ResultsWithin D, cortisol was lower at 120–180 minutes from starting surgery compared with baseline. Cortisol was higher in KM than in D at 60 minutes from starting surgery. Within all groups, glucose was higher postinduction (except DR) and 60 minutes from starting surgery, and insulin was lower during anesthesia and higher after standing compared with baseline. After standing, NEFA were higher in KM than in DB. In KM, MAP increased at 40–60 minutes from starting surgery compared with 30 minutes postinduction.Conclusions and clinical relevanceDexmedetomidine suppressed cortisol release more than dexmedetomidine–opioid and ketamine–morphine infusions. Ketamine–morphine PIVA might increase catecholamine activity.     

A comparison of two combinations of xylazine-ketamine administered intramuscularly to alpacas and of reversal with tolazoline

ObjectiveTo evaluate the anesthetic and cardiorespiratory effects of two doses of intramuscular (IM) xylazine/ketamine in alpacas, and to determine if tolazoline would reduce the anesthetic recovery time.Study designProspective randomized crossover study.AnimalsSix castrated male alpacas.MethodsEach alpaca received a low dose (LD) (0.8 mg kg⁻¹ xylazine and 8 mg kg⁻¹ ketamine IM) and high dose (HD) (1.2 mg kg⁻¹ xylazine and 12 mg kg⁻¹ ketamine IM) with a minimum of one week between trials. Time to sedation, duration of lateral recumbency and analgesia, pulse rate, respiratory rate, hemoglobin oxygen saturation, arterial blood pressure, blood-gases, and the electrocardiogram were monitored and recorded during anesthesia. With each treatment three alpacas were randomly selected to receive tolazoline (2 mg kg⁻¹ IM) after 30 minutes of lateral recumbency.ResultsOnset of sedation, lateral recumbency and analgesia was rapid with both treatments. The HD was able to provide ≥30 minutes of anesthesia in five of six alpacas. The LD provided ≥30 minutes of anesthesia in three of six alpacas. Respiratory depression and hypoxemia occurred with the HD treatment during the first 10 minutes of lateral recumbency: two animals were severely hypoxemic and received nasal oxygen for 5 minutes. Heart rate decreased, but there were no significant changes in arterial blood pressure. Tolazoline significantly shortened the duration of recumbency with the HD.ConclusionsThe HD provided more consistent clinical effects in alpacas than the LD. Intramuscular tolazoline shortened the duration of lateral recumbency in alpacas anesthetized with the HD combination.Clinical relevanceBoth doses of the combination were effective in providing restraint in alpacas and the duration of restraint was dose dependent. Supplemental oxygen should be available if using the HD and IM administration of tolazoline will shorten the recovery time.     

The cardiopulmonary effects of anesthetic induction with isoflurane,ketamine‐diazepam or propofol‐diazepam in the hypovolemic dog

ObjectiveTo evaluate and compare the cardiopulmonary effects of induction of anesthesia with isoflurane (Iso), ketamine–diazepam (KD), or propofol–diazepam (PD) in hypovolemic dogs.Study designProspective randomized cross–over trial.AnimalsSix healthy intact, mixed breed, female dogs weighing 20.7 ± 4.2 kg and aged 22 ± 2 months.MethodsDogs had 30 mL kg^?1 of blood removed at a rate of 1.5 mL kg^?1 minute^?1 under isoflurane anesthesia. Following a 30–minute recovery period, anesthesia was reinduced. Dogs were assigned to one of three treatments: isoflurane via facemask using 0.5% incremental increases in the delivered concentration every 30 seconds, 1.25 mg kg^?1 ketamine and 0.0625 mg kg^?1 diazepam intravenously (IV) with doses repeated every 30 seconds as required, and 2 mg kg^?1 propofol and 0.2 mg kg^?1 diazepam IV followed by 1 mg kg^?1 propofol increments IV every 30 seconds as required. Following endotracheal intubation all dogs received 1.7% end–tidal isoflurane in oxygen. Cardiopulmonary variables were recorded at baseline (before induction) and at 5 or 10 minute intervals following endotracheal intubation.ResultsInduction time was longer in Iso (4.98 ± 0.47 minutes) compared to KD (3.10 ± 0.47 minutes) or PD (3.22 ± 0.45 minutes). To produce anesthesia, KD received 4.9 ± 2.3 mg kg^?1 ketamine and 0.24 ± 0.1 mg kg^?1 diazepam, while PD received 2.2 ± 0.4 mg kg^?1 propofol and 0.2 mg kg^?1 diazepam. End–tidal isoflurane concentration immediately following intubation was 1.7 ± 0.4% in Iso. Arterial blood pressure and heart rate were significantly higher in KD and PD compared to Iso and in KD compared to PD. Arterial carbon dioxide partial pressure was significantly higher in PD compared to KD and Iso immediately after induction.Conclusions and clinical relevanceIn hypovolemic dogs, KD or PD, as used in this study to induce anesthesia, resulted in less hemodynamic depression compared to isoflurane.     

Anaesthesia with medetomidine,midazolam and ketamine in six gorillas after premedication with oral zuclopenthixol dihydrochloride

ObjectiveTo evaluate the effects of medetomidine, midazolam and ketamine (MMK) in captive gorillas after premedication with oral zuclopenthixol.Study designCase series.AnimalsSix gorillas, two males and four females, aged 9–52 years and weighing 63–155 kg.MethodsThe gorillas were given zuclopenthixol dihydrochloride 0.2 ± 0.05 mg kg^?1 per os twice daily for 3 days for premedication. On the day of anaesthesia the dose of zuclopenthixol was increased to 0.27 mg kg^?1 and given once early in the morning. Anaesthesia was induced with medetomidine 0.04 ± 0.004 mg kg^?1, midazolam 0.048 ± 0.003 mg kg^?1 and ketamine 4.9 ± 0.4 mg kg^?1 intramuscularly (IM). Upon recumbency, the trachea was intubated and anaesthesia was maintained on 1–2% isoflurane in oxygen. Physiological parameters were monitored every 10 minutes and arterial blood gas analysis was performed once 30–50 minutes after initial darting. At the end of the procedure, 42–115 minutes after initial darting, immobilisation was antagonized with atipamezole 0.21 ± 0.03 mg kg^?1 and sarmazenil 5 ± 0.4 μg kg^?1 IM.ResultsRecumbency was reached within 10 minutes in five out of six animals. One animal required two additional darts before intubation was feasible. Heart rate ranged from 60 to 85 beats minute^?1, respiratory rate from 17 to 46 breaths minute^?1 and temperature from 36.9 to 38.3 °C. No spontaneous recoveries were observed and anaesthetic level was stable. Blood gas analyses revealed mild respiratory acidosis, and mean PaO₂ was 24.87 ± 17.16 kPa (187 ± 129 mmHg) with all values being above 13.4 kPa (101 mmHg). Recovery was smooth and gorillas were sitting within 25 minutes.Conclusion and clinical relevanceThe drug combination proved to be effective in anaesthetizing captive gorillas of various ages and both sexes, with minimal cardio-respiratory changes.     

Comparison of blind and endoscopic-guided orotracheal intubation on laryngeal and tracheal damage in domestic rabbits (Oryctolagus cuniculus)

ObjectiveTo compare blind and endoscopic-guided techniques for orotracheal intubation in rabbits and the number of intubation attempts with laryngeal/tracheal damage.Study designProspective, randomized experimental study.AnimalsA total of 24 healthy, intact female New Zealand White rabbits, weighing 2.2 ± 0.2 kg (mean ± standard deviation).MethodsRabbits were randomly assigned to blind (group B) or endoscopic-guided (group E) orotracheal intubation with a 2.0 mm internal diameter uncuffed tube. Intramuscular (IM) alfaxalone (7 mg kg^–1), hydromorphone (0.1 mg kg^–1) and dexmedetomidine (0.005 mg kg^–1) were administered, and additional IM alfaxalone (3–5 mg kg^–1) and dexmedetomidine (0.025 mg kg^–1) were administered to rabbits with strong jaw tone. An intubation attempt was defined as the advancement of the endotracheal tube from the incisors to the laryngeal entrance. Tracheal intubation was confirmed via capnography and anesthesia was maintained with isoflurane for 2 hours. Following euthanasia, laryngeal and tracheal tissues were submitted for histopathology. Quality of anesthesia for orotracheal intubation, intubation procedure and tissue damage were numerically scored. Data were analyzed using Poisson regression, Spearman’s correlation, t test, mixed anova, Mann–Whitney U test, Friedman and Chi square tests as appropriate.ResultsMedian (range) intubation attempts were 2 (1–8) and 1 (1–3) for groups B and E, respectively. More rabbits in group E (91.6%) required additional alfaxalone and dexmedetomidine than in group B (16.7%). Median (range) cumulative histopathology scores were 6 (3–10) and 6 (2–9) for groups B and E, respectively. Scores were highest in the cranial trachea, but there was no difference between groups and no correlation between laryngeal/tracheal damage and the number of intubation attempts.Conclusions and clinical relevanceBoth orotracheal intubation techniques were associated with laryngeal/tracheal damage. Although blind orotracheal intubation was associated with a higher number of attempts, the tissue damage was similar between groups.