A comparison of 8% and 12% sevoflurane for inhalation induction in adults

Bispectral Index Guided Timing of Intubation without Neuromuscular Blockade during Sevoflurane Induction of Anaesthesia in Adults

The aim of this study was to assess the effectiveness of bispectral index monitoring (BIS) as a guide to the timing of intubation during sevoflurane induction of anaesthesia without the use of neuromuscular blocking agents in adults, and specifically, whether a target BIS value of 25 provides better intubating conditions than a target BIS of 40.

Forty patients were randomized into one of two groups, a target BIS 25 (n=21) or a target BIS 40 (n =19). Patients received premedication with midazolam 20 μg/kg and fentanyl 0.5 μg/kg. Sevoflurane induction of anaesthesia was initiated and titrated to reach the target BIS value and maintained within the target range for two minutes. The trachea was then intubated, with intubating conditions being assessed using a standardized scale.

The BIS 25 group had a superior median intubating score of 4 (range 3–9, [IQR 4–5]) vs the BIS 40 group with a median of 7 (5–10, [6–9], P<0.001).

The time to reach target BIS values was not statistically different (BIS 25 group 6.6 min, BIS 40 group 5.1 min, P=0.054). End-tidal sevoflurane concentration upon reaching the target BIS was higher in the BIS 25 group (5.3%±1.2%) vs the BIS 40 group (3.5% ±0.95) (P<0.001). There was no statistical difference in haemodynamic parameters between groups.

A target BIS value of 25 provides good to excellent intubating conditions and better intubating conditions than a target BIS of 40 during sevoflurane induction of anaesthesia without the use of neuromuscular blocking agents.

Safety Evaluation of Sevoflurane as Anesthetic Agent in Mouse Model of Myocardial Ischemic Infarction

The selection of anesthetics for patients with myocardial infarction is critically challenging. Sevoflurane is a volatile anesthetic gradually used in recent years. The intraoperative hemodynamic stability of sevoflurane was supported by several studies with some suggestions for its use for patients with cardiac events. The present study was undertaken to investigate the effect of sevoflurane on mice with myocardial infarction to evaluate the safety issue of this agent for possible application in patients with myocardial infarction. Mice of 7-12 weeks old were subjected to left anterior descending artery ligation to introduce acute myocardial infarction. The effect of sevoflurane on the hemodynamics was examined in comparison with that of currently available agent etomidate at low and moderate doses. The results showed that sevoflurane caused unstable hemodynamic changes in mice with myocardial infarction at both low and moderate inhaled concentrations relative to low and moderate doses of etomidate. In addition, the relative safety margin estimated from therapeutic index was decreased by 50 % when sevoflurane was used for mice with myocardial infarction relative to control mice, but only decreased by 20 % for etomidate. These analyses indicate that in comparison with currently available agent etomidate, sevoflurane should not be applied to patients with myocardial infarction or other cardiac events.

Tracheal intubation with volatile induction and target bispectral index of 25 versus 40: A randomized clinical trial

Background and Aims:

A target bispectral index (BIS) value of 40 is considered adequate for depth of anesthesia, but no consensus exists regarding BIS value for tracheal intubation without neuromuscular blocking drugs. The aim of this randomized, double-blinded study was to compare the total duration from sevoflurane induction to tracheal intubation at a BIS value of 25 or 40.

Material and Methods:

This study was a prospective, randomized and observer-blinded clinical trial. After approval of the Institutional Ethics Committee and written informed consent, 80 patients of American Society of Anesthesiologists physical status I-II, aged 20-60 years, of either sex, requiring general anesthesia with tracheal intubation were enrolled. The patients were randomized to either Group BIS₄₀-intubation at a target BIS value of 40 ± 5 or group BIS₂₅-intubation at a target BIS value of 25 ± 5. The intubating conditions, hemodynamic, and adverse effects were observed in both the groups.

Results:

This study showed that the total time required from induction to tracheal intubation was 4.9 ± 0.9 min in group BIS₄₀ as compared to 6.3 ± 0.5 min in group BIS₂₅ (P = 0.001) using two-tailed sample t-test. The mean intubation score was 6.5 ± 0.9 in group BIS_40, and 5.1 ± 0.7 in group BIS₂₅ (P = 0.001) using Mann-Whitney U-test.

Conclusion:

The time to achieve target BIS value of 25 was greater as compared to target BIS value of 40 during sevoflurane induction but provided better intubating conditions in the absence of neuromuscular agents.

Sevoflurane (12% and 8%) inhalational induction in children

BACKGROUND

Sevoflurane induction of anesthesia is frequently used in children. Rapidly performed inhalational induction may reduce excitation during early anesthesia. Increasing the total anesthetic MAC delivered to patients can be achieved by increasing volatile concentration or adding nitrous oxide. The latter reduces inspired oxygen concentration delivered, which may not be desirable. Even 8% sevoflurane induction is associated with excitation. A system capable of delivering 12% sevoflurane using two tandem vaporizers has been developed.

METHODS

A randomized double blind study was undertaken to assess whether 12% sevoflurane offered any advantage over 8% in time and quality of induction. Sixty children aged 5-10 years were recruited and received either 12 or 8% sevoflurane. Time to loss of eyelash reflex, central pupils, incidence of adverse events, induction quality, systolic blood pressure and heart rate were recorded.

RESULTS

Twelve percent sevoflurane reduced time to loss of eyelash reflex compared with 8% [mean (sd): 35 (12) and 46 (14) P<0.05], but the reduction was only 10% higher than the error in the measurement (assessment every 10 s). Twelve percent sevoflurane offered significantly better quality of induction (P<0.05). There was no difference in cardiovascular stability between groups, although heart rate rose significantly in both groups. Maintaining sevoflurane at 12% for 4 min caused significant amounts of apnea (69% with 12% and 38% with 8%, P<0.05).

CONCLUSION

Twelve percent sevoflurane offers a smoother anesthesia induction than 8% in children of this age with no additional consequences for the cardiovascular system.