Effects of intravenous administration of tiletamine-zolazepam, alfaxalone, ketamine-diazepam, and propofol for induction of anesthesia on cardiorespiratory and metabolic variables in healthy dogs before and during anesthesia maintained with isoflurane

Hemodynamic effects in dogs anesthetized with the combination tiletamine-zolazepam-ketamine-xylazine

This was a prospective, experimental study, that evaluated the hemodynamic effects in dogs administered the combination tiletamine-zolazepam-ketamine-xylazine (TKX). Six healthy, adult dogs, with an average weight of 13.9 ± 1.3 kg, were anesthetized with propofol and sevoflurane for placement of an arterial and a thermodilution catheter. After instrumentation, sevoflurane was discontinued and approximately 60 min were allowed before baseline data was recorded. Dogs were then administered TKX at a dosage of 0.032 mL/kg, corresponding to 1.6 mg/kg of tiletamine, 1.6 mg/kg of zolazepam, 2.56 mg/kg of ketamine and 0.64 mg/kg of xylazine. Assessments were repeated at 15, 30 and 45 min after TKX administration (T15, T30 and T45). Comparisons between T15-T45 and the baseline were performed by one-way ANOVA followed by a Dunnett's test or a Friedman's test followed by a Dunn's test (p < 0.05). Administration of TKX decreased heart rate (27-43%), cardiac index (48-55%), stroke index (21-28%), oxygen delivery index (49-56%) and oxygen consumption index (41-44%), and increased mean arterial pressure (26-43%), systemic vascular resistance index (211-234%) and oxygen extraction ratio (17-28%). Respiratory rate decreased by as much as 41% without significantly affecting blood gases. It was concluded that TKX administration resulted in cardiovascular depression in dogs, characterized by decreased heart rate, cardiac index and oxygen delivery index. Despite respiratory rate decreased, blood gases were unchanged. These cardiorespiratory effects were well tolerated by healthy dogs. Nonetheless, the findings of this study should not be extrapolated to dogs with compromised health conditions.

Effects of hydromorphone alone and combined with medetomidine-vatinoxan or dexmedetomidine on alfaxalone induction dose and mean arterial pressure in dogs anesthetized with sevoflurane

OBJECTIVE

To evaluate the dose of alfaxalone needed for induction of anesthesia following sedation with medetomidine-vatinoxan plus hydromorphone (MVH), dexmedetomidine plus hydromorphone (DH), or hydromorphone (H) alone. A secondary objective included evaluating selected cardiopulmonary variables before, during, and after sedation and general anesthesia with sevoflurane in healthy dogs.

STUDY DESIGN

Prospective, randomized, masked, crossover.

ANIMALS

Eight healthy Beagle dogs, 3-4 years old.

METHODS

All dogs received three intramuscular (IM) treatments: H (0.1 mg kg-1), DH (0.005 mg kg-1 + 0.1 mg kg-1, respectively), or MVH (0.01 mg kg-1 + 0.2 mg kg-1 + 0.1 mg kg-1, respectively) at least 6 days apart. General anesthesia was induced with alfaxalone 20 minutes after treatment administration and maintained for 60 minutes with 2.8% sevoflurane (expired). Sedation scores, selected cardiopulmonary variables, and recovery scores were measured before, during, and after anesthesia at selected timepoints. Mixed-effects ANOVA and ANOVA on ranks were used to evaluate differences between treatments, time, and their interaction, and Tukey-Kramer method was used for post hoc analysis (p < 0.05). Data are presented as mean ± SD or median (range).

RESULTS

Dogs given MVH required a lower dose of alfaxalone for induction of anesthesia (0.77 ± 0.4 mg kg-1) compared to DH and H (1.16 ± 0.34 mg kg-1; p = 0.02, 1.13 ± 0.18 mg kg-1; p = 0.02), and had a higher incidence (50%; p = 0.038) and longer duration [median; 10 (0-35) minutes] of hypotension during sevoflurane anesthesia compared to H [0%; 0 (0-0) minutes; p = 0.040] but not DH (p = 0.272).

CONCLUSIONS AND CLINICAL RELEVANCE

Premedication with MVH provided the greatest alfaxalone-sparing effect. However, this treatment was associated with lower arterial pressures and clinically relevant hypotension. Off-label use of medetomidine-vatinoxan before sevoflurane-based anesthesia should be used with caution due to a high incidence of hypotension.

The effect of age on the induction dose of propofol for general anesthesia in dogs

OBJECTIVE

In people, the dose of propofol (DOP) required for procedural sedation and anesthesia decreases significantly with age. The objective of this study was to determine if the DOP required to perform endotracheal intubation decreases with age in dogs.

STUDY DESIGN

Retrospective case series.

ANIMALS

1397 dogs.

METHODS

Data from dogs anesthetized at referral center (2017-2020) were analyzed with three multivariate linear regression models with backward elimination using a combination of either absolute age, physiologic age, or life expectancy (ratio between age at the time of anesthetic event and expected age of death for each breed obtained from previous literature) as well as other factors as independent variables, and DOP as the dependent variable. The DOP for each quartile of life expectancy (<25%, 25-50%, 50-75%, 75-100%, >100%) was compared using one-way ANOVA. Significance was set at alpha = 0.025.

RESULTS

Mean age was 7.2 ± 4.1 years, life expectancy 59.8 ± 33%, weight 19 ± 14 kg, and DOP 3.76 ± 1.8 mg kg-1. Among age models, only life expectancy was a predictor of DOP (-0.37 mg kg-1; P = 0.013) but of minimal clinical importance. The DOP by life age expectancy quartile was 3.9 ± 2.3, 3.8 ± 1.8, 3.6 ± 1.8, 3.7 ± 1.7, and 3.4 ± 1.6 mg kg-1, respectively (P = 0.20). Yorkshire Terrier, Chihuahua, Maltese, mixed breed dogs under 10 kg, and Shih Tzu required higher DOP. Status of neutered male, ASA E, and Boxer, Labrador and Golden Retriever breeds decreased DOP, along with certain premedication drugs.

CONCLUSIONS AND CLINICAL RELEVANCE

In contrast to what is observed in people, an age cut-off predictive of DOP does not exist. Percentage of elapsed life expectancy along with other factors such as breed, premedication drug, emergency procedure, and reproductive status significantly alter DOP. In older dogs, the dose of propofol can be adjusted based on their elapsed life expectancy.

Intraocular pressure and cardiovascular effects of dexmedetomidine premedication and tiletamine-zolazepam for anesthetic induction in dogs

Background and Aim

The effect of anesthetic drugs on intraocular pressure (IOP) is an important concern in ophthalmic surgery. The impact of dexmedetomidine (DEX) combined with tiletamine-zolazepam on IOP is scarcely studied. This study aimed to evaluate IOP and cardiovascular effects in dogs after premedication with 5 μg/kg (DEX5) or 10 μg/kg (DEX10) of intramuscular DEX followed by intravenous tiletamine-zolazepam administration for induction of anesthesia in healthy dogs.

Materials and Methods

Eighteen dogs, American Society of Anesthesiologists I or II, without ocular abnormality were investigated. All dogs were randomly divided into the DEX5 (n = 9) and DEX10 groups (n = 9). The IOP, heart rate (HR), systolic blood pressure (SBP), oxygen saturation, and sedation scale were measured before premedication (baseline), after premedication at 5, 10, 15, and 20 min, after tiletamine-zolazepam administration, after endotracheal intubation, and post-operative.

Results

There were no significant differences between the groups at any time point. The DEX5 and DEX10 groups had significantly decreased HR values at 10 min compared with baseline. The IOP at 20 min was significantly lower compared to the baseline in the DEX10 group. Moreover, the DEX10 group showed increased IOP, HR, SBP, and sedation scale values after induction and intubation compared with 20 min, but these values did not differ significantly from baseline. All parameters of both groups did not change significantly between post-operative and baseline.

Conclusion

Intramuscular DEX (10 μg/kg) is an appropriate premedication in ophthalmic examination or surgical procedures. Moreover, it could be combined with tiletamine-zolazepam for generalized anesthesia in dogs with an ophthalmic problem, as it had no clinically significant effects on IOP or cardiovascular values.

Comparison of cardiorespiratory and anesthetic effects of ketamine-midazolam-xylazine-sufentanil and tiletamine-zolazepam-xylazine in miniature pigs

Effective and adequate anesthesia is conducive to better restrain for pigs during surgical or diagnostic procedures This study aimed to evaluate cardiorespiratory and anesthetic effects of ketamine-midazolam-xylazine-sufentanil or tiletamine-zolazepam-xylazine as general anesthetics in miniature pigs. In phase 1, one of the combinations was administered intramuscularly to miniature pigs. The KMXS protocol combined 10 mg kg^-1 ketamine, 0.5 mg kg^-1 midazolam, and 2 mg kg^-1 xylazine with 2 μg kg^-1 sufentanil. The TZX protocol combined 2.2 mg kg^-1 tiletamine, 2.2 mg kg^-1 zolazepam, and 1.4 mg kg^-1 xylazine. After treatment, the mean arterial pressure, systolic arterial pressure, diastolic arterial pressure, heart rate, respiratory rate, peripheral hemoglobin oxygen saturation, rectal temperature, and anesthesia quality were recorded. In phase 2, the feasibility of KMXS and TZX as general anesthetics were evaluated for pig castration. In phase 1, both drug combinations provided smooth induction with similar anesthetic effects. The KMXS protocol provided moderate anesthesia for 60–70 minutes in pigs, while the TZX protocol provided 30–45 minutes. In phase 2, castration was completed smoothly in all pigs with little fluctuation in physiological variables. The KMXS protocol is better for medium-term anesthesia, while the TZX protocol is preferable for short-term anesthesia in pigs.

Reduction of greenhouse gases emission through the use of tiletamine and zolazepam

Isoflurane is an anaesthetic gas widely used in both human and veterinary medicine. All currently used volatile anaesthetics are ozone-depleting halogenated compounds. The use of total intravenous anaesthesia (TIVA) allows to induce the effect of general anaesthesia by administering drugs only intravenously without the use of anaesthetic gases. This allows you to create a protocol that is safe not only for the patient, but also for doctors and the environment. However, so far, no anaesthetic protocol based on induction of anaesthesia with tiletamine-zolazepam without the need to maintain anaesthesia with anaesthetic gas has been developed. Our study showed that the use of this combination of drugs for induction does not require the use of additional isoflurane to maintain anaesthesia. Thanks to Dixon's up-and-down method we proved that with the induction of anaesthesia with tiletamine-zolazepam at a dose of 5 mg/kg the use of isoflurane is not needed to maintain anaesthesia in minimally invasive surgical procedures. Until now, this dose has been recommended by the producer for more diagnostic than surgical procedures or for induction of general anaesthesia. The maintenance was required with anaesthetic gas or administration of another dose of the tiletamine-zolazepam. The results obtained in this study will allow for a significant reduction in the consumption of isoflurane, a gas co-responsible for the deepening of the greenhouse effect, having a negative impact on patients and surgeons. These results are certainly the first step to achieving a well-balanced and safe TIVA-based anaesthetic protocol using tiletamine-zolazepam, the obvious goal of which will be to maximize both the safety of the patient, people involved in surgical procedures, and the environment itself. Being aware of the problem of the greenhouse effect, we are committed to reducing the consumption of anaesthetic gases by replacing them with infusion agents.

Clinicophysiological and hematobiochemical effect of dexmedetomidine or diazepam with ketamine and propofol in total intravenous anesthesia in goats

Background

Total intravenous anesthesia (TIVA) is a well-documented anesthetic concept for some animal species, including dogs and horses; however, information about TIVA protocols in goats is currently inadequate. Therefore, this study aimed to compare the clinicophysiological and hematobiochemical effects of dexmedetomidine (DEX) and diazepam premedication with ketamine and propofol.

Result

The DEX-treated group showed a significantly decreased heart rate compared with the diazepam-treated group. Onset of anesthesia and sedation in group I was significantly faster than that in group II (0.33 ± 0.08 and 0.25 ± 0.08 min vs. 3.33 ± 1.53 and 2.0 ± 1.0 min, respectively). Duration of anesthesia and sedation in group I was significantly longer than that in group II (66.67 ± 7.64 and 161.3 ± 43.3 min vs. 37.0 ± 5.19 and 60.33 ± 7.57 min, respectively). The total recovery period in group II was significantly shorter than that in group I (47.0 ± 7.21 vs. 98.33 ± 15.27 min).

Smooth induction and recovery occurred in all goats in group I, whereas most goats in group II exhibited slightly prolonged induction with mild excitation and presence of swallowing reflex and prolonged struggling during recovery.

Conclusion

In TIVA, premedication with DEX produces excellent quality anesthesia, analgesia, sedation, and muscle relaxation. Furthermore, it produces a longer duration of anesthesia, sedation, and analgesia than premedication with diazepam. For these reasons, DEX is more suitable for long surgical procedures, whereas diazepam can be used in minor surgical procedures in goats. Both drug combinations produce hemodynamic stability.

Clinical review of the pharmacological and anaesthetic effects of alfaxalone in dogs

This clinical review summarises the pharmacological and anaesthetic properties of alfaxalone in the dog. Available pharmacokinetic-pharmacodynamic data and factors affecting the induction dose have been reported. Furthermore, quality of induction and recovery after alfaxalone administration, the use of alfaxalone for total intravenous anaesthesia, and its effects on the cardio-respiratory system, on laryngeal motion, on intraocular pressure and tear production have been evaluated. Finally, the use of alfaxalone in dogs undergoing caesarean section and the effect of intramuscular alfaxalone administration have been considered.

Cardiopulmonary (No Ventilation) and Anesthetic Effects of Dexmedetomidine-Tiletamine in Dogs

The aim of the present study was to evaluate the anesthetic and cardiopulmonary effects of dexmedetomidine in combination with tiletamine (without zolazepam) as a general anesthetic. The study was divided into two phases. In Phase 1, 18 adult healthy mixed-breed dogs were randomly allocated into three groups: Group TD8 (4.5 mg kg⁻¹ tiletamine and 8 μg kg⁻¹ dexmedetomidine), Group TD10 (4.5 mg kg⁻¹ tiletamine and 10 μg kg⁻¹ dexmedetomidine), or Group TD12 (4.5 mg kg⁻¹ tiletamine and 12 μg kg⁻¹ dexmedetomidine). After drug administration, the heart rate (HR), respiratory rate (f_R), mean arterial pressure (MAP), systolic arterial pressure (SAP), diastolic arterial pressure (DAP), peripheral hemoglobin oxygen saturation (SpO₂), behavioral score, quality of induction and recovery, extent of ataxia, the time taken for induction, and the duration of anesthesia were recorded. The recovery time and quality were recorded after administration of atipamezole (50 μg kg⁻¹) after 60 min. In phase 2, the feasibility of combining dexmedetomidine (10 μg kg⁻¹) and tiletamine (4.5 mg kg⁻¹) as general anesthetics for orchiectomy was evaluated in dogs (n = 6). HR, f_R, MAP, SAP, DAP, temperature, SpO₂, behavioral scores, and adverse reactions were recorded during each surgical procedure. In phase 1, the dogs were anesthetized for 5 min after administration of drugs and achieved a maximum behavioral score in TD10 and TD12 after 10 min. Although HR, MAP, SAP, DAP, and NIBP decreased in all three groups, they still maintained within the normal range. In phase 2, orchiectomy was completed smoothly in all dogs with little fluctuation in the physiological variables. We found that a combination of tiletamine (4.5 mg kg⁻¹) and dexmedetomidine (10 μg kg⁻¹) intramuscularly induced moderate anesthesia in dogs and could be utilized for short-term anesthesia and minor surgery.

Effect of Xylazine-Tiletamine-Zolazepam on the Local Field Potential of the Rat Olfactory Bulb

Neural oscillations of the mammalian olfactory system have been studied for decades. This research suggests they are linked to various processes involved in odor information analysis, depending on the vigilance state and presentation of stimuli. In addition, the effects of various anesthetics, including commonly used ones like chloral hydrate, pentobarbital, ketamine, and urethane, on the local field potential (LFP) in the olfactory bulb (OB) have been studied. In particular, the combination of xylazine and tiletamine-zolazepam has been shown to produce steady anesthesia for an extended period and relatively few adverse effects; however, their effects on the LFP in the OB remain unknown. To study those effects, we recorded the LFP in the OB of rats under xylazine-tiletamine-zolazepam anesthesia. During the period of anesthesia, the spectral powers of the 1-4, 9-16, 31-64, 65-90 frequency bands increased significantly, and that of 91-170 Hz frequency band decreased significantly, whereas no significant changes were observed in the 5-8 and 17-30 Hz ranges. These results reveal dynamic changes in the time and frequency characteristics of the LFP in the OB of rats under xylazine-tiletamine- zolazepam anesthesia and suggest that this combination of anesthetics could be used for studying oscillatory processes in the OB of rats.

Recovery characteristics of dogs following anesthesia induced with tiletamine-zolazepam, alfaxalone, ketamine-diazepam, or propofol and maintained with isoflurane

OBJECTIVE To compare characteristics of recovery from isoflurane anesthesia in healthy nonpremedicated dogs after anesthetic induction by IV administration of tiletamine-zolazepam with those observed after induction by IV administration of alfaxalone, ketamine-diazepam, or propofol. DESIGN Prospective, randomized crossover study. ANIMALS 6 healthy adult hounds. PROCEDURES Each dog underwent the 4 treatments in random order with a ≥ 7-day washout period between anesthetic episodes. Anesthesia was induced by IV administration of the assigned induction drug or combination (each to effect in 25% increments of calculated dose) and maintained with isoflurane in oxygen for 60 minutes. Cardiorespiratory variables and end-tidal isoflurane concentration (ET_ISO) were measured just before isoflurane administration was discontinued. Dogs were observed and video recorded during recovery. Recovery characteristics were retrospectively scored from recordings by 3 raters. Interrater and intrarater reliability of scoring was assessed by intraclass correlation coefficient calculation. Linear and mixed ANOVAs were used to compare extubation times, recovery scores, and body temperature among treatments. RESULTS Most cardiorespiratory variables, body temperature, ET_ISO, and time to extubation did not differ between tiletamine-zolazepam and other induction treatments. Recovery scores were lower (indicating better recovery characteristics) with propofol or alfaxalone than with tiletamine-zolazepam but did not differ between tiletamine-zolazepam and ketamine-diazepam treatments. Anesthetic episode number and ET_ISO had no effect on extubation time or recovery score. Intrarater and interrater correlations for recovery scores were excellent. CONCLUSIONS AND CLINICAL RELEVANCE Recovery of healthy dogs from anesthesia with isoflurane after induction with tiletamine-zolazepam was uncomplicated and had characteristics comparable to those observed following induction with ketamine-diazepam. However, recovery characteristics were improved when anesthesia was induced with propofol or alfaxalone.

Clinical and pharmacokinetic interactions between oral fluconazole and intravenous ketamine and midazolam in dogs

OBJECTIVE

To evaluate drug interactions between fluconazole and the intravenous (IV) anesthetic induction agents, ketamine and midazolam.

STUDY DESIGN

Randomized parallel study.

ANIMALS

A group of 12 adult healthy Beagle dogs.

METHODS

Dogs were randomly allocated to two groups of six dogs. Dogs in group KM were administered IV ketamine (7 mg kg^-1) and IV midazolam (0.25 mg kg^-1), and dogs in group KMF were administered fluconazole (5 mg kg^-1) orally 12 and 24 hours prior to ketamine-midazolam using the same doses as KM. Sedation scores (0-4) were assigned by investigators unaware of group assignment. Heart rate (HR) and times to sternal and standing were obtained and compared between groups for differences with p < 0.05 considered statistically significant. Blood was obtained and plasma drug concentrations were measured using liquid chromatography-mass spectrometry.

RESULTS

The times to sternal, mean 32.3 and 24.6 minutes, for groups KMF and KM, respectively, were not different between the groups. The time to standing, 73 and 36 minutes in groups KMF and KM, respectively, was significantly different (p = 0.002). The duration of elevated HR compared with baseline was longer in KMF (110 minutes) than in KM (25 minutes) (p < 0.05). In group KMF, one dog developed hyperthermia (40.6 °C), which resolved spontaneously. The clearance of ketamine and midazolam was significantly slower (approximately 50%) and the area under the curves were significantly higher (two-fold) in group KMF (p = 0.02).

CONCLUSIONS AND CLINICAL RELEVANCE

A significant interaction between oral fluconazole and IV ketamine-midazolam occurred, but the effects appear minor in healthy dogs. Based on these data, a single dose of ketamine-midazolam is not contraindicated in dogs treated with fluconazole, but the duration of effects and pharmacokinetics are altered.

Alfaxalone total intravenous anaesthesia in dogs: pharmacokinetics, cardiovascular data and recovery characteristics

OBJECTIVE

To evaluate the cardiovascular effects, pharmacokinetic (PK) data and recovery characteristics of an alfaxalone constant rate infusion (CRI) of different duration in dogs at manufacturer's recommended dose rate.

STUDY DESIGN

Experimental, prospective, randomized, crossover study.

ANIMALS

Six intact female Beagles.

METHODS

Following an intravenous alfaxalone bolus (3 mg kg^-1), anaesthesia was maintained using an alfaxalone CRI at 0.15 mg kg^-1 minute^-1 for 90 (short CRI) or 180 minutes (long CRI). Venous blood samples were collected to determine the PK profile. Cardiovascular variables and recovery characteristics were evaluated. Recovery was scored on a scale ranging from 0, excellent to 4, bad. A mixed-model statistical approach was used to compare the cardiovascular parameters (global α = 0.05). An analysis of variance was performed to compare PK parameters and recovery times between treatments.

RESULTS

No significant difference was noted between protocols for any PK parameter. Volume of distribution at steady state (935.74 ± 170.25 versus 1119.15 ± 190.65 mL kg^-1), elimination half-life (12 ± 2 versus 13 ± 3 minutes), clearance from the central compartment (26.02 ± 4.41 versus 27.74 ± 5.65 mL kg^-1 minute^-1) and intercompartmental clearance (8.47 ± 4.06 versus 12.58 ± 7.03 mL kg^-1 minute^-1) were comparable for short CRI and long CRI. Cardiovascular variables remained within physiological limits. Mechanical ventilation was necessary (short CRI: n = 1, long CRI: n = 4). The manufacturer's recommended dose rate resulted in a light plane of anaesthesia. No significant differences in recovery times and scores were observed between treatments. The quality of recovery was scored as very poor with both protocols.

CONCLUSIONS AND CLINICAL RELEVANCE

PK data were similar between long and short infusions of alfaxalone at the manufacturer's recommended dose, with acceptable cardiovascular conditions. Nevertheless, both protocols resulted in a superficial plane of general anaesthesia with poor recovery characteristics.