Alfentanil modifies the neurocirculatory responses to desflurane

Effect-site concentration of remifentanil for smooth inhalational induction with desflurane

Objective To determine the effect-site concentration (Ce) of remifentanil target-controlled infusion required for a smooth inhalational induction without airway irritation using desflurane in a stepwise incremental manner for 50% of patients (EC₅₀) and 95% of patients (EC₉₅). Methods Patients with an American Society of Anesthesiologists physical status I and II, aged 19-60 years undergoing elective surgery were enrolled in this study. When target Ce of remifentanil was reached, desflurane was inhaled at 4 vol% initially and then it was increased to 8 and 12 vol% at intervals of 30 s. Smooth induction was regarded as an absence of airway irritation signs and excitatory movements. The EC₅₀ and EC₉₅ values for remifentanil were determined using a modified Dixon's up-and-down method as well as an isotonic regression method with a bootstrapping approach. Results The EC₅₀ and EC₉₅ of remifentanil for smooth induction during inhalation of desflurane were 3.40 ng/ml (95% confidence interval [CI] 2.42, 4.38 ng/ml) and 4.31 ng/ml (95% CI 2.15, 5.98 ng/ml), respectively. Conclusion Prior administration of remifentanil could provide smooth inhalational induction with desflurane in a stepwise increment.

Effect-site concentration of remifentanil for minimizing cardiovascular changes by inhalation of desflurane

PURPOSE

This study aims to investigate the most appropriate effect-site concentration of remifentanil to minimize cardiovascular changes during inhalation of high concentration desflurane.

MATERIALS AND METHODS

Sixty-nine American Society of Anesthesiologists physical status class I patients aged 20-65 years were randomly allocated into one of three groups. Anesthesia was induced with etomidate and rocuronium. Remifentanil was infused at effect-site concentrations of 2, 4 and 6 ng/mL in groups R2, R4 and R6, respectively. After target concentrations of remifentanil were reached, desflurane was inhaled to maintain the end-tidal concentration of 1.7 minimum alveolar concentrations for 5 minutes (over-pressure paradigm). The systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), heart rate (HR) and end-tidal concentration of desflurane were measured for 5 minutes.

RESULTS

The end-tidal concentration of desflurane increased similarly in all groups. The SBP, DBP, MAP and HR within group R4 were not significantly different as compared with baseline values. However, measured parameters within group R2 increased significantly 1-3 minutes after desflurane inhalation. The MAP within group R6 decreased significantly at 1, 2, 4, and 5 minutes (p<0.05). There were significant differences in SBP, DBP, MAP and HR among the three groups 1-3 minutes after inhalation (p<0.05). The incidence of side effects such as hyper- or hypo-tension, and tachy- or brady-cardia in group R4 was 4.8% compared with 21.8% in group R2 and 15.0% in group R6.

CONCLUSION

The most appropriate effect-site concentration of remifentanil for blunting hemodynamic responses by inhalation of high concentration desflurane is 4 ng/mL.

Desflurane - revisited

The search for an ideal inhalational general anesthetic agent continues. Desflurane, which was recently introduced in the Indian market, possesses favorable pharmacokinetic and pharmacodynamic properties and is closer to the definition of an ideal agent. It offers the advantage of precise control over depth of anesthesia along with a rapid, predictable, and clear-headed recovery with minimal postoperative sequelae, making it a valuable anesthetic agent for maintenance in adults and pediatric patients in surgeries of all durations. The agent has advantages when used in extremes of age and in the obese. Its use may increase the direct costs of providing anesthetic care. Methods or techniques, such as low-flow anesthesia, to reduce the overall cost and along with minimal environmental implications must be followed.

Optimal effect-site concentration of remifentanil for preventing development of hypertension during tracheal intubation with inhaled desflurane induction

BACKGROUND

The aim of the present study was to determine the effect-site concentration of remifentanil needed to prevent haemodynamic instability during tracheal intubation with inhaled desflurane induction.

METHODS

One hundred American Society of Anesthesiologists I and II female patients were randomized to receive an effect-site concentration of remifentanil of 0, 1, 2, 3, or 4 ng/ml. Induction of anaesthesia was started with intravenous injection of propofol 2 mg/kg. Ninety seconds after the completion of propofol injection, rocuronium (0.8 mg/kg) and remifentanil were administered simultaneously with 3% desflurane inhalation. Tracheal intubation was attempted 150 sec after the commencement of remifentanil administration.

RESULTS

A probit model of remifentanil concentration was predictive of successful intubation without development of hypertension (P for goodness-of-fit = 0.419). The effect-site concentration of remifentanil needed to achieve successful intubation without development of hypertension in 95% of the patients was 3.3 ng/ml (95% confidence interval, 2.6-4.8 ng/ml).

CONCLUSIONS

The effect-site concentration of remifentanil of 3.3 ng/ml is effective in blunting the haemodynamic response in 95% of the patients when 2.0 mg/kg of propofol induction was followed by 3% desflurane inhalation.