Effect of lidocaine on the minimum alveolar concentration of sevoflurane in dogs

Objective  To investigate the effects of a low-dose constant rate infusion (LCRI; 50 μg kg⁻¹ minute⁻¹) and high-dose CRI (HCRI; 200 μg kg⁻¹ minute⁻¹) lidocaine on arterial blood pressure and on the minimum alveolar concentration (MAC) of sevoflurane (Sevo), in dogs.
Study design  Prospective, randomized experimental design.
Animals  Eight healthy adult spayed female dogs, weighing 16.0 ± 2.1 kg.
Methods  Each dog was anesthetized with sevoflurane in oxygen and mechanically ventilated, on three separate occasions 7 days apart. Following a 40-minute equilibration period, a 0.1-mL kg⁻¹ saline loading dose or lidocaine (2 mg kg⁻¹ intravenously) was administered over 3 minutes, followed by saline CRI or lidocaine LCRI or HCRI. The sevoflurane MAC was determined using a tail clamp. Heart rate (HR), blood pressure and plasma concentration of lidocaine were measured. All values are expressed as mean ± SD.
Results  The MAC of Sevo was 2.30 ± 0.19%. The LCRI reduced MAC by 15% to 1.95 ± 0.23% and HCRI by 37% to 1.45 ± 0.21%. Diastolic and mean pressure increased with HCRI. Lidocaine plasma concentration was 0.84 ± 0.18 for LCRI and 1.89 ± 0.37 μg mL⁻¹ for HCRI. Seventy-five percent of HCRI dogs vomited during recovery.
Conclusion and clinical relevance  Lidocaine infusions dose dependently decreased the MAC of Sevo, did not induce clinically significant changes in HR or arterial blood pressure, but vomiting was common during recovery in HCRI.     

Differences in need for hemodynamic support in horses anesthetized with sevoflurane as compared to isoflurane

OBJECTIVE: To study whether hemodynamic function in horses, particularly mean arterial blood pressure (MAP), is better maintained with sevoflurane than isoflurane, thus requiring less pharmacological support. STUDY DESIGN: Prospective randomized clinical investigation. Animals Thirty-nine racehorses undergoing arthroscopy in lateral recumbency. METHODS: Horses were assigned to receive either isoflurane (n = 20) or sevoflurane (n = 19) at 0.9-1.0 minimum alveolar concentration (MAC) for maintenance of anesthesia. Besides routine clinical monitoring, cardiac output (CO) was measured by lithium dilution. Hemodynamic support was prescribed as follows: when MAP decreased to <70 mmHg, patients were to receive infusion of 0.1% dobutamine, which was to be discontinued at MAP >85 mmHg or heart rate >60 beats minute(-1). Statistical analysis of results, given as mean +/- SD, included a clustered regression approach. RESULTS: Average inhalant anesthetic time [91 +/- 35 (isoflurane group) versus 97 +/- 26 minutes (sevoflurane group)] and dose (in MAC multiples), volume of crystalloid solution infused, and cardiopulmonary parameters including CO were similar in the two groups, except heart rate was 8% higher in isoflurane than sevoflurane horses (p < 0.05). To maintain MAP >70 mmHg, isoflurane horses received dobutamine over a significantly longer period (55 +/- 26 versus 28 +/- 21% of total anesthetic time, p < 0.01) and at a 51% higher dose than sevoflurane horses (41 +/- 19 versus 27 +/- 23 microg kg(-1) MAC hour(-1); p = 0.058), with 14/20 isoflurane animals and only 9/19 sevoflurane horses being infused with dobutamine at >30 microg kg(-1) MAC hour(-1) (p < 0.05). Dobutamine infusion rates were consistently lower in the sevoflurane as compared to the isoflurane group, with differences reaching significance level during the 0-30 minutes (p < 0.01) and 61-90 minutes periods (p < 0.05). CONCLUSIONS AND CLINICAL RELEVANCE: Horses under sevoflurane anesthesia may require less pharmacological support in the form of dobutamine than isoflurane-anesthetized horses. This could be due to less suppression of vasomotor tone.     

Effects of intravenous lidocaine, ketamine, and the combination on the minimum alveolar concentration of sevoflurane in dogs

ObjectiveTo evaluate the effects of intravenous lidocaine (L) and ketamine (K) alone and their combination (LK) on the minimum alveolar concentration (MAC) of sevoflurane (SEVO) in dogs.Study designProspective randomized, Latin-square experimental study.AnimalsSix, healthy, adult Beagles, 2 males, 4 females, weighing 7.8 – 12.8 kg.MethodsAnesthesia was induced with SEVO in oxygen delivered by face mask. The tracheas were intubated and the lungs ventilated to maintain normocapnia. Baseline minimum alveolar concentration of SEVO (MAC_B) was determined in duplicate for each dog using an electrical stimulus and then the treatment was initiated. Each dog received each of the following treatments, intravenously as a loading dose (LD) followed by a constant rate infusion (CRI): lidocaine (LD 2 mg kg⁻¹, CRI 50 μg kg⁻¹minute⁻¹), lidocaine (LD 2 mg kg⁻¹, CRI 100 μgkg⁻¹ minute⁻¹), lidocaine (LD 2 mg kg⁻¹, CRI 200 μg kg⁻¹ minute⁻¹), ketamine (LD 3 mg kg⁻¹, CRI 50 μg kg⁻¹ minute⁻¹), ketamine (LD 3 mgkg⁻¹, CRI 100 μg kg⁻¹ minute⁻¹), or lidocaine (LD 2 mg kg⁻¹, CRI 100 μg kg⁻¹ minute⁻¹) + ketamine (LD 3 mg kg⁻¹, CRI 100 μg kg⁻¹ minute⁻¹) in combination. Post-treatment MAC (MAC_T) determination started 30 minutes after initiation of treatment.ResultsLeast squares mean ± SEM MAC_B of all groups was 1.9 ± 0.2%. Lidocaine infusions of 50, 100, and 200 μg kg⁻¹ minute⁻¹ significantly reduced MAC_B by 22.6%, 29.0%, and 39.6%, respectively. Ketamine infusions of 50 and 100 μg kg⁻¹ minute⁻¹ significantly reduced MAC_B by 40.0% and 44.7%, respectively. The combination of K and L significantly reduced MAC_B by 62.8%.Conclusions and clinical relevanceLidocaine and K, alone and in combination, decrease SEVO MAC in dogs. Their use, at the doses studied, provides a clinically important reduction in the concentration of SEVO during anesthesia in dogs.     

The effect of cannabidiol on sevoflurane minimum alveolar concentration reduction produced by morphine in rats

ObjectiveTo investigate the effect of cannabidiol (CBD) on sevoflurane minimum alveolar concentration (MAC_SEV) reduction produced by morphine in rats.Study designRandomized, blinded trial.AnimalsA total of 75 male Wistar Han rats weighing 276 ± 23 g (mean and standard deviation), aged 3 months.MethodsCannabidiol (CBD) was prepared in an ethanol-solutol-saline vehicle. Animals were randomly divided into 15 groups and given an intraperitoneal bolus of 1, 3, 5, 6.5, 7.5 or 10 mg kg^?1 of CBD alone (CBD1, CBD3, CBD5, CBD6.5, CBD7.5 and CBD10 respectively) or combined with 5 mg kg^?1 of morphine (MOR+CBD1, MOR+CBD3, MOR+CBD5, MOR+CBD6.5, MOR+CBD7.5 and MOR+CBD10). While three controls groups: MOR+saline, MOR+vehicle and vehicle were given an intraperitoneal bolus of morphine with saline, morphine with vehicle or vehicle alone respectively. The MAC_SEV was determined from alveolar gas samples at the time of tail clamp application. The MAC_SEV reduction was analyzed using a one-way ANOVA followed by Tukey’s test. Additionally, Kruskal-Wallis test for non-normally-distributed data was performed. Data are presented as mean ± standard deviation. P < 0.05ResultsThe mean MAC_SEV was not reduced by the action of CBD administered alone, but the addition of morphine to the different doses of CBD significantly reduced the MAC_SEV. That reduction was greatest in the MOR+CBD1, MOR+CBD7.5 and MOR+CBD10 groups (29 ± 5%, 32 ± 5% and 30 ± 6% respectively), less in MOR+CBD3 and MOR+CBD6.5 groups (24 ± 3% and 26 ± 4% respectively) and least in MOR+CBD5 group (17 ± 2%). However, only the MOR+CBD5 group was statistically significantly different from MOR+CBD1, MOR+CBD7.5 and MOR+CBD10 groups.Conclusions and clinical relevanceMAC_SEV in rat was unaltered by the action of CBD alone, the reduction in MAC_SEV produced by morphine was not enhanced by the addition of CBD at the doses studied.     

Effects of a constant‐rate infusion of dexmedetomidine on the minimal alveolar concentration of sevoflurane in ponies

Reasons for performing study: Dexmedetomidine has been administered in the equine as a constant‐rate infusion (CRI) during inhalation anaesthesia, preserving optimal cardiopulmonary function with calm and coordinated recoveries. Inhalant anaesthetic sparing effects have been demonstrated in other species, but not in horses. Objectives: To determine the effects of a CRI of dexmedetomidine on the minimal alveolar concentration (MAC) of sevoflurane in ponies. Methods: Six healthy adult ponies were involved in this prospective, randomised, crossover, blinded, experimental study. Each pony was anaesthetised twice (3 weeks washout period). After induction with sevoflurane in oxygen (via nasotracheal tube), the ponies were positioned on a surgical table (T0), and anaesthesia was maintained with sevoflurane (expired sevoflurane fraction 2.5%) in 55% oxygen. The ponies were randomly allocated to treatment D (dexmedetomidine 3.5 µg/kg bwt i.v. [T10–T15] followed by a CRI of dexmedetomidine at 1.75 µg/kg bwt/h) or treatment S (bolus and CRI of saline at the same volume and rate as treatment D). After T60, MAC determination, using a classic bracketing technique, was initiated. Stimuli consisted of constant‐current electrical stimuli at the skin of the lateral pastern region. Triplicate MAC estimations were obtained and averaged in each pony. Monitoring included pulse oximetry, electrocardiography, anaesthetic gas monitoring, arterial blood pressure measurement and arterial blood gases. Normocapnia was maintained by mechanical ventilation. Analysis of variance (treatment and period as fixed factors) was used to detect differences between treatments (α= 0.05). Results: An intravenous (i.v.) dexmedetomidine CRI decreased mean ± s.d. sevoflurane MAC from 2.42 ± 0.55 to 1.07 ± 0.21% (mean MAC reduction 53 ± 15%). Conclusions and potential relevance: A dexmedetomidine CRI at the reported dose significantly reduces the MAC of sevoflurane.     

Performance of a new carbon dioxide absorbent,Yabashi lime? as compared to conventional carbon dioxide absorbent during sevoflurane anesthesia in dogs

In the present study, we compare a new carbon dioxide (CO₂) absorbent, Yabashi lime^® with a conventional CO₂ absorbent, Sodasorb^® as a control CO₂ absorbent for Compound A (CA) and Carbon monoxide (CO) productions. Four dogs were anesthetized with sevoflurane. Each dog was anesthetized with four preparations, Yabashi lime^® with high or low-flow rate of oxygen and control CO₂ absorbent with high or low-flow rate. CA and CO concentrations in the anesthetic circuit, canister temperature and carbooxyhemoglobin (COHb) concentration in the blood were measured. Yabashi lime^® did not produce CA. Control CO₂ absorbent generated CA, and its concentration was significantly higher in low-flow rate than a high-flow rate. CO was generated only in low-flow rate groups, but there was no significance between Yabashi lime^® groups and control CO₂ absorbent groups. However, the CO concentration in the circuit could not be detected (≤5ppm), and no change was found in COHb level. Canister temperature was significantly higher in low-flow rate groups than high-flow rate groups. Furthermore, in low-flow rate groups, the lower layer of canister temperature in control CO₂ absorbent group was significantly higher than Yabashi lime^® group. CA and CO productions are thought to be related to the composition of CO₂ absorbent, flow rate and canister temperature. Though CO concentration is equal, it might be safer to use Yabashi lime^® with sevoflurane anesthesia in dogs than conventional CO₂ absorbent at the point of CA production.     

Comparison of three different inhalant anesthetic agents (isoflurane, sevoflurane, desflurane) in red-tailed hawks (Buteo jamaicensis)

Objective To compare isoflurane, sevoflurane and desflurane for inhalant anesthesia in red‐tailed hawks (Buteo jamaicensis) in terms of the speed and characteristics of induction; cardiovascular and respiratory parameters while anesthetized; and speed and quality of recovery. Study design Prospective, cross over, randomized experimental study. Animals 12 healthy adult red‐tailed hawks. Methods Anesthesia was induced with isoflurane, sevoflurane or desflurane in oxygen via face mask in a crossover, randomized design with a 1 week washout period between each treatment. Hawks were tracheally intubated, allowed to breathe spontaneously, and instrumented for cardiopulmonary monitoring. Data collected included heart rate, respiratory rate, end‐tidal CO₂, inspired and expired agent, SpO_2, temperature, systolic blood pressure, time to intubation and time to recovery (tracking). Recovery was subjectively scored on a 4 point scale as well as a summary evaluation, by a single blinded observer. Results No significant difference in time to induction and time to extubation was noted with the administration of isoflurane, sevoflurane or desflurane. Time to the ability of the bird to follow a moving object with its eyes (tracking) was significantly faster with the administration of sevoflurane and desflurane. All recoveries were scored 1 or 2 and were assessed as good to excellent. No significant difference was noted in heart rate, blood pressure and temperature among the three inhalants. Administration of isoflurane resulted in lower respiratory rates. Conclusions and clinical relevance Overall, although isoflurane remains the most common inhaled anesthetic in avian practice, sevoflurane and desflurane both offer faster time to tracking, while similar changes in cardiopulmonary function were observed with each agent during anesthesia of healthy red‐tailed hawks.     

The effects of age, isoflurane and sevoflurane on atracurium in lambs

ObjectiveTo determine the effects of age, sevoflurane and isoflurane on atracurium-induced neuromuscular blockade in 3–16 week-old lambs.Study designProspective randomized experimental trial.AnimalsTwenty-six Scottish blackface ewe-lambs were anaesthetized for spinal surgery when either 3–6 (mean age 4.6 weeks; n = 18) or 12–16 weeks (mean age 13.7 weeks; n = 15) of age; seven animals were anaesthetized at both ages.MethodsAfter intramuscular injection of medetomidine (10 μg kg^?1) anaesthesia was induced in the younger lambs either with isoflurane or sevoflurane in oxygen delivered by mask, and in the older lambs with ketamine (4 mg kg^?1), and midazolam (0.2 mg kg^?1) administered intravenously (IV). In both groups anaesthesia was maintained with fixed end-tidal concentrations of either sevoflurane (2.8%) or isoflurane (1.8%) delivered in oxygen. Before surgery meloxicam (0.6 mg kg^?1), morphine (0.5 mg kg^?1) and ketamine (1 mg kg^?1 followed by 10 μg kg^?1 minute^?1) were administered IV. The lungs were ventilated mechanically to maintain normocapnia. Neuromuscular block was achieved with a loading dose (LD) of atracurium (0.5 mg kg^?1 IV). The peroneal nerve was stimulated (train-of-four every 12 seconds). Evoked responses in the digital extensor muscles were evaluated by palpation and observation. Maintenance doses (MD) of atracurium (0.17 mg kg^?1 IV) were administered when the first twitch (T1) returned. The onset and duration of LD action (T1 absent) and the duration of MD were recorded. Data were analysed using Student's t test, Mann–Whitney U test, repeated–measures anova, Wilcoxon's matched pairs test or Pearson correlation coefficient as relevant (p < 0.05).ResultsOnset of LD action developed significantly (p < 0.05) more rapidly in isoflurane compared with sevoflurane-anaesthetized lambs (55 ± 18 cf. 80 ± 37 seconds). Duration of action of LDs and MDs was longer (p < 0.05) in lambs aged 12–16 than 3–6 weeks (33 ± 5.4 cf. 25 ± 6.4 and 26 ± 4.2 cf. 18 ± 5.5 minutes) but were independent of the anaesthetic used.Conclusions and clinical relevanceThe effect of atracurium is age-dependent in lambs being prolonged in older animals. The onset of neuromuscular blockade is more rapid in isoflurane compared with sevoflurane-anaesthetized lambs.     

Prolonged anesthesia using sevoflurane,remifentanil and dexmedetomidine in a horse

HistoryA 10–year old Arabian mare had a slow–growing mass on the lower right mandible and required a large partial mandibulectomy.Physical examinationNo abnormalities were detected apart from the mass.ManagementA temporary tracheostomy was performed pre–operatively. Anesthesia was induced with xylazine followed by ketamine and diazepam. For 13 hours, anesthesia was maintained using sevoflurane, dexmedetomidine and remifentanil infusions, with the exception of surgical preparation time. Intra–operatively, ventilation was delivered through the cuffed tracheotomy tube. Heart and respiratory rates, ECG, arterial pressures, inspired and expired gases, pulse oximetry values and body temperature were monitored. Dobutamine and whole blood were necessary, and romifidine was used to control recovery. Post–operatively, phenylbutazone and buprenorphine given systemically and bupivacaine administered through a wound soaker catheter were used to provide analgesia. Head–shaking from buprenorphine was controlled with acepromazine and detomidine once standing after 87 minutes in recovery. For 3 days after surgery, analgesia was provided with butorphanol, phenylbutazone and bupivacaine. The mare recovered well, appeared comfortable and started eating the following day with no signs of ileus.Follow–upSeven months later, the mare was doing well.ConclusionsSevoflurane, dexmedetomidine and remifentanil infusions were suitable for a long and invasive procedure.     

Investigation on the Stabilization of Flame and Control of Fuel-oil Splitting Decomposition Spray by Anti-flow

On the basis of trial and theory, this paper advances an effective preventive measure to solve the problem of producing black smoke during fuel oil thermolysis and polluting the atmosphere in the process of combustion. It provides valuable references to protect the environment,save energy and solve the problem of clean combustion of high-hydrocarbon fuel, especially fuel oils such as kerosene, diesel oil, heavy oil etc.