The pharmacology of inhaled anesthetics

Comparative study of a modified double-lumen tube ventilation control connector and traditional connector in clinical use: a randomised-controlled trial

Background

A Y-shaped rotatable connector (YRC) for double-lumen tubes (DLT) is invented and compared with the traditional connector (Y-shaped connector, YC).

Methods

Sixty patients with ASA grade I-III, aged ≥ 18 years, who needed to insert a DLT for thoracic surgery were recruited and assigned into the YRC group (n = 30) and the YC group (n = 30) randomly. The primary endpoints included the inhaled air concentration (Fi) and the exhaled air concentration (Et) of sevoflurane before and after the switch between two-lung ventilation and one-lung ventilation at different times, positioning time, and switching time. The secondary endpoints were the internal gas volume of the two connectors, airway pressure, and the sputum suction time.

Results

The Et and Fi of the YRC group and the YC group were significantly different (all p < 0.05) at 5s, 10s, and 30s after the patient switched from two-lung ventilation to one-lung ventilation. The positioning time of the YRC group was less than YC group (89.75 ± 14.28 s vs 107.80 ± 14.96 s, p < 0.05), as well as the switching time (3.60 ± 1.20 s vs 9.05 ± 2.53 s, p < 0.05) and the internal gas volume (17.20 ml vs 24.12 ml). There was no difference in airway pressure and the sputum suction time in two groups.

Conclusion

Compared with YC, YRC was beneficial for maintaining depth of anesthesia, improves efficiency for the switch between one-lung and two-lung ventilation, and shortens the tube positioning time.

1. YRC was beneficial to maintain the stability of anesthesia depth.

2. YRC improves the conversion efficiency for one-lung and two-lung ventilation.

3. YRC shortens the positioning time.

Combined effects of dexmedetomidine and vatinoxan infusions on minimum alveolar concentration and cardiopulmonary function in sevoflurane-anesthetized dogs

OBJECTIVE

To evaluate the effects of combined infusions of vatinoxan and dexmedetomidine on inhalant anesthetic requirement and cardiopulmonary function in dogs.

STUDY DESIGN

Prospective experimental study.

METHODS

A total of six Beagle dogs were anesthetized to determine sevoflurane minimum alveolar concentration (MAC) prior to and after an intravenous (IV) dose (loading, then continuous infusion) of dexmedetomidine (4.5 μg kg^-1 hour^-1) and after two IV doses of vatinoxan in sequence (90 and 180 μg kg^-1 hour^-1). Blood was collected for plasma dexmedetomidine and vatinoxan concentrations. During a separate anesthesia, cardiac output (CO) was measured under equivalent MAC conditions of sevoflurane and dexmedetomidine, and then with each added dose of vatinoxan. For each treatment, cardiovascular variables were measured with spontaneous and controlled ventilation. Repeated measures analyses were performed for each response variable; for all analyses, p < 0.05 was considered significant.

RESULTS

Dexmedetomidine reduced sevoflurane MAC by 67% (0.64 ± 0.1%), mean ± standard deviation in dogs. The addition of vatinoxan attenuated this to 57% (0.81 ± 0.1%) and 43% (1.1 ± 0.1%) with low and high doses, respectively, and caused a reduction in plasma dexmedetomidine concentrations. Heart rate and CO decreased while systemic vascular resistance increased with dexmedetomidine regardless of ventilation mode. The co-administration of vatinoxan dose-dependently modified these effects such that cardiovascular variables approached baseline.

CONCLUSIONS AND CLINICAL RELEVANCE

IV infusions of 90 and 180 μg kg^-1 hour^-1 of vatinoxan combined with 4.5 μg kg^-1 hour^-1 dexmedetomidine provide a meaningful reduction in sevoflurane requirement in dogs. Although sevoflurane MAC-sparing properties of dexmedetomidine in dogs are attenuated by vatinoxan, the cardiovascular function is improved. Doses of vatinoxan >180 μg kg^-1 hour^-1 might improve cardiovascular function further in combination with this dose of dexmedetomidine, but beneficial effects on anesthesia plane and recovery quality may be lost.

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.