Changes in echocardiographic indices and left ventricular strain values by two-dimensional speckle-tracking echocardiography following pre-anesthetic oral pimobendan administration compared with intravenous pimobendan in dogs

Introduction

The effects of pre-anesthetic single-dose oral pimobendan during inhalational anesthesia, including the comparison with the effects of single intravenous pimobendan under anesthesia, remain unexplored. Therefore, this study aimed to determine changes in hemodynamic and echocardiographic parameters induced by pre-anesthetic administration of oral pimobendan under isoflurane general anesthesia and to compare them with those induced by intravenous pimobendan.

Methods

Thirteen clinically normal dogs (4 laboratory and 9 client-owned dogs) with no clinical signs and not on any medical treatment were included. Anesthesia was performed three times: no pimobendan (Control), oral pimobendan (PIMO PO, 0.3 mg/kg), and intravenous pimobendan (PIMO IV, 0.15 mg/kg). Echocardiographic and hemodynamic parameters were monitored at 30-min intervals in all groups.

Results

Compared to the Control group, end-systolic volume index (ESVI) and normalized left ventricular internal diameter at end-systole (LVIDSN) were significantly lower, and fractional shortening (FS) and ejection fraction (EF) were significantly higher in the PIMO PO and IV groups (p < 0.001). Global radial strain (GRS) was significantly higher in the PIMO PO and IV groups (p = 0.015).

Conclusion

Under general anesthesia, oral pimobendan preserved LV systolic and myocardial function in a manner comparable to intravenous pimobendan. Pre-anesthetic administration of oral pimobendan can be used to compensate for cardiac systolic function in dogs who require therapeutic and diagnostic procedures under general anesthesia with potential risk of circulatory failure.

The Bioequivalence of Emulsified Isoflurane With a New Formulation of Emulsion: A Single-Center, Single-Dose, Double-Blinded, Randomized, Two-Period Crossover Study

Background: Emulsified isoflurane is a novel intravenous general anesthetic obtained by encapsulating isoflurane molecules into emulsion. The formulation of emulsion has been improved according to the latest regulations of the China Food and Drug Administration. This study was designed to compare the bioequivalence of the new and previous formulation emulsion of isoflurane.

Methods: In a single-center, single-dose, double-blinded, randomized, two-period crossover study, healthy volunteers received intravenous injection of 30 mg/kg of isoflurane with either previous formulation of emulsion isoflurane (PFEI) or new formulation of emulsion isoflurane (NFEI). Arterial and venous blood samples were obtained for geometric mean test/reference ratios of C_max, AUC_0-t, and AUC_0-∞, as well as their 90% confidence interval (CI90) as the primary outcome. The secondary outcomes were safety measurements such as vital signs, 12-lead electrocardiography, adverse effects, and laboratory tests; and anesthesia efficacy was assessed by Modified Observer’s Assessment of Alertness/Sedation (MOAA/S) score, bispectral index (BIS), and loss/recovery of eyelash reflex.

Results: 24 subjects were eligible, of which 21 completed the whole experiment (NFEI n = 21, PFEI n = 23). Arterial geometric mean test/reference ratios of C_max, AUC_0-t, and AUC_0-∞ were 104.50% (CI90 92.81%–117.65%), 108.23% (94.51%–123.96%), and 106.53% (93.94%∼120.80%), respectively. The most commonly seen adverse effects for NFEI and PFEI were injection pain (38.1% vs. 34.8%), hypotension (19.0% vs. 13.0%), apnea (14.3% vs. 17.4%), and upper airway obstruction (14.3% vs. 13.0%). No severe adverse effect was observed. The effectiveness of general anesthesia was similar between the two formulations.

Conclusion: The CI90 of C_max, AUC_0-t, AUC_0-∞, NFEI, and PFEI were within the range of 80%–125%, suggesting bioequivalence between NFEI and PFEI. The safety and anesthesia effectiveness were also similar.

Anesthetic Potency of Intravenous Infusion of 20% Emulsified Sevoflurane and Effect on the Blood-Gas Partition Coefficient in Dogs

BACKGROUND

Intravenous (IV) infusions of volatile anesthetics in lipid emulsion may increase blood lipid concentration, potentially altering the anesthetic agent's blood solubility and blood-gas partition coefficient (BGPC). We examined the influence of a low-lipid concentration 20% sevoflurane emulsion on BGPC, and the anesthetic potency of this emulsion using dogs.

METHODS

We compared BGPC and anesthetic characteristics in 6 dogs between the IV anesthesia of emulsion and the sevoflurane inhalation anesthesia in a randomized crossover substudy. Minimum alveolar concentrations (MACs) were determined by tail-clamp stimulation by using the up-and-down method. Blood sevoflurane concentration and partial pressure were measured by gas chromatography; end-tidal sevoflurane concentration was measured using a gas monitor. The primary outcome was BGPC at the end of IV anesthesia and inhalation anesthesia. Secondary outcomes were time to loss/recovery of palpebral reflex, finish intubation and awakening, MAC, blood concentration/partial pressure at MAC and awakening, correlation between blood partial pressure and gas monitor, and the safety of emulsions.

RESULTS

BGPC showed no difference between IV and inhaled anesthesia (0.859 [0.850-0.887] vs 0.813 [0.791-0.901]; P = .313). Induction and emergence from anesthesia were more rapid in IV anesthesia of emulsion than inhalation anesthesia. MAC of emulsion (1.33% [1.11-1.45]) was lower than that of inhalation (2.40% [2.33-2.48]; P = .031), although there was no significant difference in blood concentration. End-tidal sevoflurane concentration could be estimated using gas monitor during IV anesthesia of emulsion. No major complications were observed.

CONCLUSIONS

IV anesthesia with emulsion did not increase the BGCP significantly compared to inhalation anesthesia. It was suggested that the anesthetic potency of this emulsion may be equal to or more than that of inhalation.

The Effectiveness and Stability of a 20% Emulsified Sevoflurane Formulation for Intravenous Use in Rats

BACKGROUND

Halogenated volatile anesthetics can be safely and rapidly administered to animals and humans using emulsion formulations. However, they must be administered simultaneously with a high dose of lipids. Increasing the concentration of volatile anesthetics may solve this clinical issue. Moreover, careful observation is needed when the emulsion is injected because anaphylactic reactions have been reported.

METHODS

We prepared a 20% sevoflurane lipid emulsion and administered it to 69 male Sprague-Dawley rats via the tail vein. The median effective dose (ED50) for the loss of righting reflex and the median lethal dose (LD50) were determined. ED50 and LD50 values were calculated using nonlinear regression, and data were fitted with a cumulative Gaussian model using GraphPad Prism. Measurements of vital signs and evaluation of the presence of adverse effects associated with continuous infusion of emulsions were verified. Stability of the emulsion was assessed by measuring particle size at 365 days and sevoflurane concentrations after opening the vial at 180 minutes.

RESULTS

The ED50 and LD50 were 0.47 mL/kg (95% confidence interval [CI], 0.46-0.48) and 1.13 mL/kg (95% CI, 1.07-1.18), respectively. The therapeutic index (LD50/ED50) was 2.41 (95 CI%, 2.23-2.59), which compares favorably with therapeutic index of a fluoropolymer-based emulsion of sevoflurane, propofol, and thiopental. There were no adverse effects associated with the continuous infusion of emulsions. Particle size of the emulsion at 365 days after preparation was 78.9 ± 3.8 nm (±SD), and sevoflurane concentration at 180 minutes after opening the vial was 19.0% ± 0.6% (±SD).

CONCLUSIONS

We prepared a 20% sevoflurane lipid emulsion using caprylic triglyceride (i.e., medium-chain triglyceride). In rats, this emulsion was an effective anesthetic and was not associated with adverse events. The emulsion was stable after consecutive evaluation for 365 days and for 180 minutes after the vial was opened.

General anesthesia with an injectable 8% v/v sevoflurane lipid emulsion administered intravenously to dogs

OBJECTIVE

To evaluate the potential of an intravenous (IV) sevoflurane formulation for maintenance of general anesthesia in dogs.

STUDY DESIGN

Prospective crossover design.

ANIMALS

Six healthy, mature, mixed-breed dogs, four males and two females, weighing 11.7 ± 3.4 kg.

METHODS

Anesthesia was induced and maintained with propofol IV for instrumentation. Baseline measurements were recorded before administration of either sevoflurane in oxygen (Sevo-Inh) or lipid-emulsified sevoflurane 8% v/v in 30% Intralipid IV (Sevo-E), 0.5 mL kg(-1) over 5 minutes followed by an infusion at 0.1-0.3 mL kg(-1)  minute(-1) . Dogs were breathing spontaneously. The 'up-and-down' technique was used to determine the minimum alveolar concentration (MAC) of sevoflurane. Over 120 minutes, a tail clamp was applied every 15 minutes and sevoflurane administration was adjusted depending on the response. End-tidal sevoflurane concentration and variables were recorded at 30, 60, 90, and 120 minutes: heart rate (HR), systemic arterial pressure (sAP), respiratory rate (fR ), end-tidal carbon dioxide tension, hemoglobin oxygen saturation (SaO2 ), arterial pH and blood gases, blood urea nitrogen, alanine aminotransferase, creatine kinase, gamma-glutamyl transferase, and aspartate aminotransferase.

RESULTS

There were no significant differences between treatments for HR, sAP, fR , SaO2 , and biochemical variables (p > 0.05). pH and HCO3-were significantly decreased, and PaCO2 increased from baseline in Sevo-E (p < 0.05). MAC was significantly lower for Sevo-E than for Sevo-Inh, although the required dose of sevoflurane (g hour(-1) ) to maintain general anesthesia was not significantly different between treatments.

CONCLUSIONS AND CLINICAL RELEVANCE

Administration of 8% v/v sevoflurane lipid emulsion IV was effective in maintaining general anesthesia in dogs, but resulted in moderate cardiopulmonary depression, metabolic and respiratory acidosis. The amount of sevoflurane (g hour(-1) ) required to maintain general anesthesia was significantly lower for inhaled than for IV sevoflurane.