Comparison of methohexital and propofol as induction agents for evaluation of laryngeal function in healthy dogs

Electroencephalographic and Cardiovascular Changes Associated with Propofol Constant Rate of Infusion Anesthesia in Young Healthy Dogs

This study aimed to evaluate electroencephalography (EEG) and cardiovascular changes associated with propofol constant rate of infusion (CRI) anesthesia in dogs. Six dogs were each given propofol CRI to induce different anesthetic phases including induction (1 mg/kg/min for 10 min), and decremental maintenance doses of 2.4 mg per kg per min, 1.6 mg per kg per min, and 0.8 mg per kg per minute over 45 min. Processed EEG indices including patient state index (PSI), (burst) suppression ratio (SR), and spectral edge frequency (95%) were obtained continuously until the dogs recovered to sternal recumbency. The dogs were intubated and ventilated. Cardiovascular and EEG index values were compared between anesthetic phases. The PSI, SR, mean arterial blood pressure, and subjective anesthetic depth scores were highly correlated throughout anesthetic depth changes. The PSI decreased from 85.0 ± 17.3 at awake to 66.0 ± 29.0 at induction, and then sharply reduced to 19.7 ± 23.6 during maintenance and returned to 61.5 ± 19.2 at extubation. The SR increased from 15.4 ± 30.9% at induction to 70.9 ± 39.8% during maintenance and decreased to 3.4 ± 8.9% at extubation. We concluded that EEG indices can be used to aid in tracking ongoing brain state changes during propofol anesthesia in dogs.

Comparison between propofol and alfaxalone anesthesia for the evaluation of laryngeal function in healthy dogs utilizing computerized software

Laryngeal paralysis is a well-documented cause of upper respiratory tract obstruction in canines. Diagnosis of laryngeal paralysis is usually made by visual evaluation of laryngeal motion whilst patients are under a light-plane of anesthesia. However, in human studies of laryngeal function evaluation, it has been shown that subjective scoring can lead to significant interobserver variance, which may cause false diagnosis. In this study, we propose to introduce a more objective method of assessing laryngeal function using GlotAnTools and Tracker software to directly measure laryngeal motion in anaesthetized patients. Additionally, two anesthetic agents, alfaxalone and propofol, were compared in this study to assess their relative effect on laryngeal motion and thus their suitability for use in this diagnostic process. This study was a two-stage, cross-over, 1:1 randomization, with two active treatment arms. Ten beagles (10–18 months, five males and five females) were exposed to both anesthetic agents and laryngeal motion was recorded using videoendoscopy. GlotAnTools and Tracker software were applied to the recorded images to measure glottal gap area (A) and length (L). A normalized measure of laryngeal function–computed as A/L–was created, representing the "elongatedness" of the rima glottidis. The glottal gap area was significantly reduced in dogs receiving alfaxalone. This study objectively establishes that alfaxalone impacted laryngeal motion significantly more than propofol and confirms the capability of these computational methods to detect differences in laryngeal motion.

Effect of doxepin on quality of life in Labradors with laryngeal paralysis: A double-blinded, randomized, placebo-controlled trial

Background

Laryngeal paralysis commonly affects older Labrador retrievers. Currently, dogs with severe disease require surgical intervention, most commonly arytenoid lateralization. Anecdotally, doxepin has been proposed to help dogs with laryngeal paralysis.

Hypothesis

Doxepin will improve quality of life measures assessed by owners of Labrador retrievers with laryngeal paralysis not requiring emergency surgery.

Animals

Twenty‐two Labrador retrievers with laryngeal paralysis.

Methods

Dogs were randomized to receive doxepin (3‐5 mg/kg q12h PO) or placebo for 28 days. Owners completed quality‐of‐life assessments before and after completing the study. Data were compared between groups using Rank‐Sum tests or Fisher's exact tests.

Results

The 2 groups of dogs did not differ at baseline except for owner‐perceived degree of ataxia (owners of dogs receiving doxepin considered them more ataxic than owners of dogs receiving placebo). After 28 days, owner‐assessed quality of life measures did not differ between dogs receiving doxepin or placebo (dogs worsening: doxepin = 2, placebo = 1; dogs unchanged: doxepin = 6, placebo = 7; dogs improved: doxepin = 4, placebo = 2; P = .84). Dogs receiving placebo had a greater improvement in client‐assessed overall health than dogs receiving doxepin (mean ranks: doxepin = 4.36, placebo = 6.64; P = .04). The study was terminated at this interim analysis.

Conclusions and Clinical Importance

Doxepin did not appear to improve any measures of owner‐assessed quality of life in Labrador retrievers with laryngeal paralysis.

Laryngeal function in normal dogs administered isoflurane following partial clearance of alfaxalone or propofol

OBJECTIVE

To assess laryngeal function in normal dogs administered isoflurane following partial clearance of alfaxalone or propofol.

STUDY DESIGN

Randomized experimental crossover study.

ANIMALS

A group of 12 purpose-bred, male Beagle dogs.

METHODS

Dogs were randomly assigned to one of two treatments: alfaxalone-isoflurane (ALF-ISO) or propofol-isoflurane (PRO-ISO) and anesthetized for three video laryngoscopy examinations. The alternate treatment occurred after ≥ 14 days interval. Examinations were performed after induction of anesthesia (LS-A), after 20 minutes of breathing isoflurane via a facemask (LS-B) and after a further 20 minutes of isoflurane (LS-C). Parameters of objective laryngeal function included inspiratory rima glottidis surface area (RGSA-I), expiratory rima glottidis surface area (RGSA-E) and % RGSA increase, calculated from three consecutive respiratory cycles in the final 15 seconds of each video laryngoscopy examination. The % RGSA increase was calculated using [(RGSA-I - RGSA-E)/RGSA-E] × 100. Subjective laryngeal function was evaluated independently by two experienced surgeons blinded to treatment.

RESULTS

The % RGSA increase within each treatment was greater for LS-B and LS-C than for LS-A (ALF-ISO: p = 0.03, PRO-ISO: p = < 0.001). There was no difference within each treatment from LS-B compared with LS-C. RGSA-I increased within each treatment from LS-A to both LS-B and LS-C (ALF-ISO: p = 0.002) and to LS-C (PRO-ISO: p = 0.006). Subjective laryngeal function scores improved from LS-A to LS-C.

CONCLUSIONS AND CLINICAL RELEVANCE

Laryngeal function improved from postinduction examination following either 20 or 40 minutes of anesthesia with isoflurane via facemask. This study demonstrates that isoflurane may have a lesser effect on arytenoid abduction activity compared with more commonly used intravenous induction anesthetics (alfaxalone and propofol).

Effects of propofol and sevoflurane on tumor killing activity of peripheral blood natural killer cells in patients with gastric cancer

Objective

This study aimed to investigate the effects of propofol and sevoflurane on cytotoxicity of natural killer (NK) cells in patients with gastric cancer.

Methods

Patients with gastric cancer were anesthetized by propofol or sevoflurane. Peripheral blood NK cells were isolated and co-cultured with BGC-823 gastric cancer cell culture supernatant, and the rate of apoptosis and effector molecules were analyzed by flow cytometry. Effects of propofol and sevoflurane on NK cell function and SMAD4 protein expression were investigated.

Results

Cytotoxicity of NK cells in patients with gastric cancer was inhibited before surgery, but it was enhanced in patients who were anesthetized by propofol compared with those who had sevoflurane. In vitro co-culture with BGC-823 cells significantly inhibited the cytotoxicity of NK cells, which was abolished by treatment of propofol or transforming growth factor (TGF)-β1. SMAD4 protein expression in the NK cell nucleus was significantly downregulated by TGF-β1 treatment and BGC-823 supernatant co-culture, and this expression could be restored by propofol.

Conclusions

Cytotoxicity of NK cells in patients with gastric cancer is low, but it can be promoted by propofol. Propofol regulates cytotoxicity in NK cells by promoting SMAD4, thereby affecting cellular function.

The Influence of Anaesthetic Drugs on the Laryngeal Motion in Dogs: A Systematic Review

Simple Summary

Laryngeal paralysis is secondary to a loss of normal function of the larynx. Older dogs are particularly affected, with normal breathing becoming difficult. A successful diagnosis typically relies on the visualisation of either, complete, or partially absent, laryngeal movements. The use of anaesthesia drugs to provide sedation and stress relief is most commonly necessary during the diagnosis of laryngeal paralysis. While, the excessive administration of anaesthesia drugs may result in absent movements, the ideal anaesthesia regime remains unknown, and the use of sedation is questionable, given the potential for absent laryngeal movements, even in healthy dogs. In this systematic review, we found a potential benefit from using sedation during the evaluation of laryngeal function when compared to injectable anaesthetics only. The respiratory stimulant doxapram was effective in differentiating normal dogs from dogs with laryngeal paralysis but has associated safety hazards.

Abstract

Anaesthetic drugs are commonly used during the evaluation of laryngeal function in dogs. The aim of this review was to systematically analyse the literature describing the effects of anaesthetic drugs and doxapram on laryngeal motion in dogs and to determine which drug regime provides the best conditions for laryngeal examination. PubMed, Google Scholar, and EMBASE databases were used for the literature search up to November 2019. Relevant search terms included laryngeal motion, anaesthetic drugs and dogs. Studies were scored based on their level of evidence (LoE), according to the Oxford Centre for Evidence-based Medicine, and the quality was assessed using the risk-of-bias tool and SIGN-checklist. In healthy dogs, premedication before laryngeal examination provided better examination conditions and maintained overall adequate laryngeal motion in 83% of the studies. No difference in laryngeal motion between induction drugs was found in 73% of the studies but the effects in dogs with laryngeal paralysis remain largely unknown. Doxapram increased laryngeal motion in healthy dogs without serious side effects, but intubation was necessary for some dogs with laryngeal paralysis. Methodological characteristics varied considerably between studies, including the technique and timing of evaluation, number of assessors, study design, drug dose, combinations, route and speed of administration.

Examination of laryngeal function of healthy dogs by using sedation protocols with dexmedetomidine

OBJECTIVE

To determine the ability to evaluate laryngeal function under sedation with dexmedetomidine alone or in combination with opioids.

STUDY DESIGN

Randomized, crossover, blinded study.

ANIMALS

Eight adult research hounds weighing 8 to 22.5 kg.

METHODS

Dogs were sedated with propofol, dexmedetomidine, dexmedetomidine and butorphanol, or dexmedetomidine and hydromorphone. Digital images were collected with video laryngoscopy before and after doxapram administration. Maximal inspiratory normalized glottal gap (GGA_n ) and laryngeal motion were compared between and within protocols before and after doxapram by using a difference of least squares mean.

RESULTS

Normal laryngeal function was confirmed in all dogs with all protocols except propofol, which resulted in two false positive results. No difference between protocols was detected for predoxapram GGA_n . Postdoxapram GGA_n was greater than predoxapram GGA_n for all four sedation protocols (P ≤ .0030). Compared with propofol, postdoxapram GGA_n was greater for all three dexmedetomidine protocols (P ≤ .0420).

CONCLUSION

Dexmedetomidine alone or in combination with opioids was an effective sedation protocol for laryngeal examination, producing sufficient immobilization to prevent jaw motion and without affecting arytenoid abduction.

CLINICAL SIGNIFICANCE

Dexmedetomidine sedation does not inhibit normal laryngeal motion. Laryngeal examination with propofol alone can produce false positive results.

Comparison of methohexital and propofol as induction agents for evaluation of laryngeal function in healthy dogs

Objective

To determine the influence of propofol or methohexital, with and without doxapram, on the examination of laryngeal function in dogs.

Study design

Experimental study.

Animals

Forty healthy dogs randomly assigned to 4 groups: propofol with saline (n = 10), propofol with doxapram (n = 10), methohexital with saline (n = 10), or methohexital with doxapram (n = 10).

Methods

Propofol and methohexital were administered to effect. Investigators examined laryngeal function (initial) simultaneously with video laryngoscopy. Doxapram or saline was administered, and laryngeal function was reevaluated (second). Laryngeal motion, quality of laryngeal exposure, and the degree of swallowing, laryngospasm, and jaw tone were scored at each evaluation. Adverse events were recorded. Initial and second videos were evaluated by a masked observer, and still images obtained from both evaluations were evaluated for change in rima glottidis size by 2 masked observers.

Results

Administration of doxapram and saline was delayed with propofol (P = .001). Laryngeal function did not differ between dogs receiving propofol or methohexital, irrespective of doxapram administration. Doxapram improved breathing scores in both groups (P < .001). Jaw tone increased with propofol during the second evaluation (P = .049). Swallowing was more prevalent at initial examination (P = .020). Methohexital resulted in an increased heart rate (P < .001) compared with propofol. Twenty‐five percent of dogs receiving methohexital developed seizure‐like activity (n = 5/20).

Conclusion

Evaluation of laryngeal function did not differ between healthy dogs anesthetized with propofol or methohexital. Methohexital provided shorter examination times with less jaw tone but was associated with adverse events.

Clinical significance

This study provides evidence to recommend propofol over methohexital as an induction agent for laryngeal function examination.