Efficient inspired concentration of sevoflurane for vital capacity rapid inhalation induction (VCRII) technique

Ventilator-assisted priming of an anaesthesia circuit (VAP technique): An exploratory study

Background and Aims

The speed of inhalational induction depends on a variety of factors, of which priming the breathing circuit with volatile anaesthetics plays a vital role. This study compared ventilator-assisted priming (VAP) and a passive priming technique using different fresh gas flows (FGFs) in neonatal, paediatric, and adult anaesthetic circuits.

Methods

In both techniques, FGF with 100% oxygen and 8% sevoflurane vaporiser concentration were set at 2 Lmin^-1, 4 Lmin^-1, and 8 Lmin^-1, representing three groups FGF-2, FGF-4, and FGF-8, respectively. The time taken to achieve 6% sevoflurane concentration at the patient end of the circuit was measured. In addition to this, we explored various combinations of tidal volumes and respiratory rates in the VAP technique and recorded the priming time with each combination. The amount of sevoflurane consumed for priming in both techniques was also calculated.

Results

VAP was three times faster than passive priming in all the FGF groups in the three circuits. In the VAP technique, the shortest priming times were similar for FGF-4 and FGF-8 (P > 0.05) but were significantly higher for FGF-2 (P = 0.001) in the three circuits. Sevoflurane consumption did not differ in FGF-2 and FGF-4 groups, whereas it doubled in the FGF-8 group using the VAP technique in all three circuits.

Conclusion

The VAP technique provides a quick and effective method for priming to achieve a high anaesthetic concentration within the breathing circuit for inhalational induction.

Arrhythmia incidence and associated factors during volatile induction of general anesthesia with sevoflurane: a retrospective analysis of 950 adult patients

BACKGROUND

Sevoflurane has been used to induce anaesthesia in adults due to its suitability for airway management and haemodynamic stability. Few studies have reported arrhythmia during volatile induction with sevoflurane in adults. Here, we investigated the incidence of arrhythmia and risk factors associated with its occurrence during sevoflurane induction of anaesthesia in adults.

PATIENTS AND METHODS

We retrospectively analysed 950 adult patients who underwent elective ear nose and throat surgery with volatile induction using sevoflurane between May and December 2015. The incidence of arrhythmia and the factors associated with its development were analysed.

RESULTS

Arrhythmia was observed in 164 (17.3%) of 950 adult patients. The most frequently observed arrhythmia was sinus tachycardia (heart rate > 120 bpm) (77 patients, 47.0%). The multivariable logistic analysis showed four independent risk factors: age (odds ratio [OR] = 0.984, 95% confidence interval [CI] = 0.973-0.996, p = 0.006), coronary artery disease (OR = 3.749, 95% CI = 1.574-8.927, p = 0.003), maximal concentration (8 vol%) of sevoflurane from the start of induction (OR = 2.696, 95% CI = 1.139-6.382, p = 0.024), and maintenance of 8 vol% sevoflurane concentration after eyelash reflex loss (OR = 1.577, 95% CI = 1.083-2.296, p = 0.018). The risk of hypotension was greater in patients in whom arrhythmia occurred, although blood pressure recovered to baseline after the concentration of sevoflurane was adjusted.

CONCLUSIONS

We recommend that the sevoflurane concentration be gradually increased with continuous and vigilant electrocardiogram and blood pressure monitoring. The sevoflurane concentration should be adjusted after sufficient unconsciousness is reached.

High initial concentration versus low initial concentration sevoflurane for inhalational induction of anaesthesia

BACKGROUND

Sevoflurane induction for general anaesthesia has been reported to be safe, reliable and well accepted by patients. Sevoflurane induction uses either low or high initial concentrations. The low initial concentration technique involves initially administering a low concentration of sevoflurane and gradually increasing the concentration of the dose until the patient is anaesthetized. The high initial concentration technique involves administering high concentrations from the beginning, then continuing with those high doses until the patient is anaesthetized. This review was originally published in 2013 and has been updated in 2016.

OBJECTIVES

We aimed to compare induction times and complication rates between high and low initial concentration sevoflurane anaesthetic induction techniques in adults and children who received inhalational induction for general anaesthesia. We defined 'high' as greater than or equal to and 'low' as less than a 4% initial concentration.

SEARCH METHODS

For the updated review, we searched the following databases: Cochrane Central Register of Controlled Trials (CENTRAL; 2016, Issue 2), MEDLINE (1950 to February 2016), EMBASE (1980 to February 2016), Latin American Caribbean Health Sciences Literature (LILACS) (1982 to February 2016) and the Institute for Scientific Information (ISI) Web of Science (1946 to February 2016). We also searched the reference lists of relevant articles and conference proceedings and contacted the authors of included trials. The original search was run in September 2011.

SELECTION CRITERIA

We sought all published and unpublished, randomized controlled trials comparing high versus low initial sevoflurane concentration inhalational induction. Our primary outcomes included two measures of anaesthesia (time to loss of the eyelash reflex (LOER) and time until a weighted object held in the patient's hand was dropped), time to successful insertion of a laryngeal mask airway (LMA) and time to endotracheal intubation. Other outcomes were complications of the technique.

DATA COLLECTION AND ANALYSIS

We used standardized methods for conducting a systematic review as described in the Cochrane Handbook for Systematic Reviews of Interventions. Two review authors independently extracted details of trial methods and outcome data from reports of all trials considered eligible for inclusion. We conducted all analyses on an intention-to-treat basis, when possible. We estimated overall treatment effects by using a fixed-effect model when we found no substantial heterogeneity, whereas we applied the random-effects model in the presence of considerable heterogeneity.

MAIN RESULTS

We reran the searches and included one new study (100 participants) in this updated review. In total, we included 11 studies with 829 participants, although most analyses were based on data from fewer participants and evidence of low quality. We noted substantial heterogeneity in the included trials. Thus, our results should be read with caution. It was not possible to combine trials for the primary outcome (LOER), but individual trials reported faster induction times (typically 24 to 82 seconds faster, 41 seconds (31.37 to 50.62)) with high initial concentration sevoflurane (six studies, 443 participants, low-quality evidence). Apnoea appeared to be more common in the high initial concentration sevoflurane group (risk ratio (RR) 3.14, 95% confidence interval (CI) 1.72 to 5.7, two studies, 160 participants, low-quality evidence). We found no evidence of differences between the two groups in the incidence of cough (odds ratio (OR) 1.23, 95% CI 0.53 to 2.81, eight studies, 589 participants, low-quality evidence), laryngospasm (OR 1.59, 95% CI 0.16 to 15.9, seven studies, 588 participants, low-quality evidence), breath holding (OR 1.16, 95% CI 0.47 to 2.83, five studies, 389 participants, low-quality evidence), patient movement (RR 1.14, 95% CI 0.69 to 1.89, five studies, 445 participants, low-quality evidence) or bradycardia (OR 0.8, 95% CI 0.22 to 2.88, three studies, 199 participants, low-quality evidence), and the overall incidence of complications was low.

AUTHORS' CONCLUSIONS

A high initial concentration sevoflurane technique probably offers more rapid induction of anaesthesia and a similar rate of complications, except for apnoea, which may be more common with a high initial concentration. However, this conclusion is not definitive because the included studies provided evidence of low quality.

High initial concentration versus low initial concentration sevoflurane for inhalational induction of anaesthesia

BACKGROUND

Sevoflurane induction for general anaesthesia has been reported to be safe, reliable and well accepted by patients. Sevoflurane induction uses either low or high initial concentrations. The low initial concentration technique involves initially administering a low concentration then gradually increasing the dose until the patient is anaesthetized. The high initial concentration technique involves administering high concentrations from the beginning, continuing until the patient is anaesthetized.

OBJECTIVES

We aimed to compare the induction times and complications between high and low initial concentration sevoflurane induction in patients who received inhalational induction for general anaesthesia. We defined 'high' as greater and 'low' as less than a 4% initial concentration.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2011, Issue 9); MEDLINE (1950 to September 2011); EMBASE (1980 to September 2011); LILACS (1982 to September 2011) and ISI Web of Science (1946 to September 2011). We also searched the reference lists of relevant articles, conference proceedings; and contacted the authors of included trials.

SELECTION CRITERIA

We sought all published and unpublished, randomized controlled trials comparing high versus low initial sevoflurane concentration inhalational induction. Our primary outcomes were two measures of anaesthesia (time to loss of the eyelash reflex (LOER) and time until a weighted object held in the patient's hand was dropped), time to successful insertion of a laryngeal mask airway (LMA), and time to endotracheal intubation. Other outcomes were complications of the technique.

DATA COLLECTION AND ANALYSIS

We used the standardized methods for conducting a systematic review as described by the Cochrane Handbook for Systematic Reviews of Interventions. Two authors independently extracted details of trial methodology and outcome data from reports of all trials considered eligible for inclusion. All analyses were made on an intention-to-treat basis, where possible. The overall treatment effects were estimated by using a fixed-effect model when there was no substantial heterogeneity, whereas the random-effects model was applied in the presence of considerable heterogeneity.

MAIN RESULTS

We used data from 10 studies with 729 participants in the review, though most analyses were based on data from fewer participants. There was substantial heterogeneity in the trials. Thus, our results should be read with caution. It was not possible to combine the trials for the primary outcome (LOER) but individual trials found faster induction times (typically 24 to 82 seconds faster) with high initial concentration sevoflurane. Apnoea appeared to be more common in the high initial concentration sevoflurane group (two trials,160 participants). There was no evidence of a difference in the incidence of cough, laryngospasm, breath holding, bradycardia, salivation and hypotension between the two groups, with the overall incidence of complications being low.

AUTHORS' CONCLUSIONS

A high initial concentration sevoflurane technique probably offers more rapid induction of anaesthesia and a similar rate of complications except for apnoea, which may be more common with a high initial concentration. However, this conclusion is not definitive.

The target concentration of remifentanil to suppress the hemodynamic response to endotracheal intubation during inhalational induction with desflurane

Background

Anesthesia induction with desflurane is troublesome because of the frequent sympathetic hyperactivity during desflurane administration. We thought that a low concentration of desflurane combined with a target-controlled infusion (TCI) of remifentanil would eliminate the desflurane-related complications and provide hemodynamic stability during desflurane induction. An up-and-down study was planned to find the target effect-site concentration of remifentanil to block the hemodynamic response to endotracheal intubation, the highest level of stimulus, during anesthesia induction with administering desflurane at 1 MAC.

Methods

Remifentanil TCI was initiated before desflurane administration. When the preset target was achieved, spontaneous inhalation of desflurane 1 MAC was performed until the patients became unconscious. Laryngoscopic tracheal intubation was facilitated with rocuronium injection. The starting concentration of remifentanil and the test space were 5 and 1 ng/ml, respectively. The criteria for up-and-down was a 20% increase of the mean arterial pressure or heart rate after intubation. The median effective concentration (EC₅₀) of remifentanil was calculated from 6 independent pairs. The complications related with remifentanil and desflurane were assessed during the study.

Results

We studied 20 patients using 2-5 ng/ml of the effect-site concentrations of remifentanil. The EC₅₀ of remifentanil was 3.7 ng/ml. Loss of consciousness was achieved at 125 ± 22 s after desflurane inhalation and this was irrespective of the combined remifentanil concentrations. Any remifentanil-related complication was not observed. Transient cough was seen in one patient who received 2 ng/ml of remifentanil.

Conclusions

We demonstrated that uncomplicated induction with desflurane was possible by the use of target-controlled remifentanil. The EC₅₀ of remifentanil to block the hemodynamic response to tracheal intubation was 3.7 ng/ml during inhalational induction with 1 MAC desflurane.

Onset Time for Sevoflurane/Nitrous Oxide Induction in Adults Is Prolonged with Increasing Age

Inhaled induction of anesthesia is occasionally used in adults. Using a modified vital capacity sevoflurane/nitrous oxide (N2O) inhaled induction, we evaluated the effect of increasing age on the onset time of anesthesia. Twenty patients, aged 26-65 yr, performed a vital capacity breath followed by regular tidal breathing from an anesthesia circuit primed with sevoflurane 8%/N2O/O2. The following values were recorded: time to loss of eyelash reflex (LOER); time to bispectral index < or =60 (BIS < or =60); expired fraction of sevoflurane at the time of induction, LOER and BIS < or =60. The mean times and 95% confidence intervals to LOER and BIS < or =60 were 54 s (37-70 s) and 175 s (143-207 s), respectively, and were significantly prolonged by aging (r = 0.65; P = 0.002). Times to LOER and BIS < or =60, predicted from the regression line, were 3.9 and 2 times longer in a 60-yr-old than in a 30-yr-old patient. The expired fraction of sevoflurane measured at time to LOER and BIS < or =60 decreases with increase in age. We conclude that inhaled induction with sevoflurane/N2O is dramatically prolonged with increased age.

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.

Rapid sevoflurane induction compared with thiopental

STUDY OBJECTIVES

To examine whether the speed of induction of anesthesia with sevoflurane/nitrous oxide (N2O) utilizing a 10-second vital capacity rapid inhalation induction (VCRII) followed by tidal breathing was similar or faster than cautious intravenous (i.v.V) thiopental induction with inhaled N2O.

DESIGN

Prospective, randomized, double-blinded study.

SETTING

Veterans Affairs Medical Center.

PATIENTS

50 male ASA physical status I, II, and III patients scheduled for general anesthesia.

INTERVENTIONS

Patients were randomized to receive either 8% sevoflurane or i.v. thiopental. Patients were allocated to one of two groups of 25 patients each. In both groups, the breathing circuit was initially primed for 5 minutes with (4 L/min) and O2 (2 L/min), while the Y-piece was occluded. In the sevoflurane group, the circuit was additionally primed with 8% sevoflurane. Patients were trained to perform a vital capacity breath. After maximal exhalation, the occluding plug was rapidly removed from the Y-piece and connected to the facemask. The patient then inspired to vital capacity, held his breath for 10 seconds, and then was allowed to breathe normally. At the end of the 10-second breathhold, and as the patient started normal breathing, either thiopental (thiopental group) or normal saline (sevoflurane group) was injected at a rate of 4 mL every 10 seconds.

MEASUREMENTS

A study-blinded observer recorded the time to induction, as defined by the time to loss of eyelash reflex, and noted the occurrence of side effects.

MAIN RESULTS

The speed of induction was the same for both groups (p > 0.05). An average of eight breaths was required before loss of eyelash reflex. Side effects occurred in 36% of the patients in the thiopental group, and 32% in the sevoflurane group (p > 0.05); these were minor and did not affect induction.

CONCLUSION

Sevoflurane/N2O VCRII as used in this investigation is an effective inhalation technique; it resulted in an induction time similar to that of slow i.v. thiopental with inhaled N2O.

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

Sevoflurane is a non-pungent volatile anaesthetic agent with a low blood-gas solubility coefficient. It has been studied in concentrations of up to 8% for induction of anaesthesia. Previous work has suggested that there may be a ceiling effect with increasing concentration of sevoflurane above 6%, but there are no published studies using 12% sevoflurane. This study compared 8 and 12% sevoflurane to induce anaesthesia in adults. Sevoflurane was administered using two adapted datum vaporisers with the interlock removed. Induction with 12% sevoflurane compared to 8% sevoflurane produced a significant decrease in the time to achieve central pupils, corresponding to surgical anaesthesia and the third part of Guedel's stage 3 of anaesthesia (mean time (SD) 201 s (81) and 247 s (39), respectively, p < 0.05). Twelve-percent sevoflurane produced a similar stable cardiovascular profile to 8% sevoflurane, and there was no increase in respiratory complications.

Bispectral monitoring during vital capacity rapid inhalation induction with sevoflurane

STUDY OBJECTIVE

To evaluate the variables of bispectral index (BIS) values during vital capacity rapid inhalation induction (VCRII) with sevoflurane.

DESIGN

Randomized, prospective study.

SETTING

University hospital.

PATIENTS

40 ASA physical status I and II patients scheduled for elective orthopedic surgery with general anesthesia.

INTERVENTIONS

Patients was divided into two groups, both of which received intravenous (IV) injection of propofol 2 mg/kg followed by inhalation of sevoflurane 3% (Group P), or vital capacity inhalation induction with sevoflurane 8% (Group S). After loss of consciousness, tracheal intubation was performed with vecuronium 0.1 mg/kg.

MEASUREMENTS AND MAIN RESULTS

The induction times in Group P were significantly shorter than those in Group S (p < 0.01). In Group S, BIS values were gradually decreased and maintained the adequate hypnotic levels were maintained during induction. In Group P, although BIS values were rapidly decreased, the values remained higher compared with Group S. The BIS value before intubation in Group S was significantly lower than that in Group P (25 +/- 9 and 38 +/- 7, respectively; p < 0.01). Five of 20 Group P patients had BIS values exceeding 60 before tracheal intubation, but no patient in Group S had a BIS value as high. Mean arterial pressure immediately after intubation in Group S was significantly lower than that in Group P (p < 0.05).

CONCLUSION

VCRII with a high concentration of sevoflurane provided adequate BIS values during induction, suggesting that it may allow smoother transition from anesthesia induction to maintenance, and also maintain an adequate hypnotic level in readiness for certain stimuli such as laryngoscopy and tracheal intubation.

Tracheal intubation conditions and cardiovascular effects after modified rapid-sequence induction with sevoflurane-rapacuronium versus propofol-rapacuronium

STUDY OBJECTIVES

To compare intubation conditions and hemodynamic effects resulting from rapid-sequence induction of anesthesia with sevoflurane-rapacuronium and propofol-rapacuronium.

DESIGN

Randomized, blinded study.

SETTING

Operating suites of a large university-affiliated medical center.

PATIENTS

40 ASA physical status I and II adult patients without airway abnormalities who were scheduled for elective surgery requiring endotracheal intubation.

INTERVENTIONS

Patients were randomly allocated to receive either sevoflurane inhalational induction (Group 1) or propofol (2 mg/kg) intravenous induction (Group 2). Group 1 patients were coached on how to perform vital capacity breathing and the anesthesia machine was primed with sevoflurane 8%, N2O:O2 3.5:1.5 L/min. In both groups, when loss of consciousness was established, rapacuronium 1.5 mg/kg was administered. After 50 seconds, an anesthesiologist blinded to the study entered the room and attempted laryngoscopy and intubation.

MEASUREMENTS

Intubation conditions were graded as excellent, good, poor, or impossible according to Good Clinical Research Practice (GCRP) criteria. Arterial blood pressure and heart rate changes accompanying both induction techniques were also monitored and recorded.

MAIN RESULTS

All patients were successfully intubated within 60 seconds. Clinically acceptable intubating conditions (excellent or good scores) were obtained in 19 of 20 Group 1 patients and in 19 of 20 Group 2 patients. Moderate tachycardia was encountered in both groups and mild systolic hypotension in the Group 2 patients. There were no complications.

CONCLUSIONS

Modified rapid-sequence inhalational induction using sevoflurane and rapacuronium produced clinically acceptable intubation conditions within 60 seconds of muscle relaxant administration. The intubation conditions were similar to those produced after intravenous propofol and rapacuronium.

Comparison of sevoflurane-nitrous oxide anaesthesia with the conventional intravenous-inhalational technique using bispectral index monitoring

Ninety-one patients were randomly allocated to one of two groups. Group A was induced with a single vital capacity breath of 6% (end-tidal) sevoflurane in nitrous oxide-oxygen (2 : 1 l.min-1), whereas group B was induced with intravenous fentanyl 1 microg.kg-1 + propofol 2 mg.kg-1 followed by nitrous oxide-oxygen (2 : 1 l.min-1) and sevoflurane. Induction was considered to have been achieved when the bispectral index value decreased to below 70. Mean induction time in group A (95.2 s, 95% CI 88.5-101.9 s) was longer than group B (70.3 s, 95% CI 66.3-74.3 s; p < 0.0001). Mild coughing was more common in group A, but relative hypotension was more common in group B. There was no difference in the emergence times. Thirty minutes after emergence, there was no difference in the incidence of adverse effects, with the exception of essentially mild abdominal pain which was more frequent in group A.

High concentration sevoflurane induction of anesthesia accelerates onset of vecuronium neuromuscular blockade

PURPOSE

To investigate neuromuscular block using accelography after administration of vecuronium under sevoflurane 8% induction and maintenance with sevoflurane 2% in adults.

METHODS

Patients were allocated to three groups: (1) group I: anesthesia was induced and maintained with propofol and fentanyl (n= 15), (2) group II: anesthesia was induced with propofol and maintained with N2O(66%)-O2-sevoflurane 2% (n = 15), (3) group III: anesthesia was induced with sevoflurane 8% using a vital capacity inhalation induction and maintained with N2O(66%)-O2-sevoflurane 2% (n = 15). 0.1 mg x kg(-1) vecuronium was used for paralysis three minutes after anesthetic induction and reversed using intravenous 0.04 mg x kg(-1) neostigmine with 0.02 mg kg atropine when the train-of-four (TOF) ratio returned to 25%.

RESULTS

The onset time from initial administration of vecuronium to maximal block in the group III was shorter than that in the groups I and II (139 +/- 35, 193 +/- 35 and 188 +/- 47s, respectively: P < 0.05). The clinical duration from maximal block to 25% recovery of TOF ratio in group II and III was longer than that in the group I (47 +/- 15, 48 +/- 14 and 36 +/- 10 min, respectively: P < 0.05). The reversal times from administration of neostigmine to 75% of TOF ratio in groups II and III were longer than that in the group I (196 +/- 53, 208 +/- 64 and 136 +/- 28s, respectively: P < 0.05).

CONCLUSIONS

Vital capacity inhalation induction of anesthesia with sevoflurane accelerates onset and prolongs duration of vecuronium neuromuscular block compared with propofol-fentanyl anesthesia.

Sevoflurance: approaching the ideal inhalational anesthetic. a pharmacologic, pharmacoeconomic, and clinical review

Sevoflurane is a safe and versatile inhalational anesthetic compared with currently available agents. Sevoflurane is useful in adults and children for both induction and maintenance of anesthesia in inpatient and outpatient surgery. Of all currently used anesthetics, the physical, pharmacodynamic, and pharmacokinetic properties of sevoflurane come closest to that of the ideal anesthetic (200). These characteristics include inherent stability, low flammability, non-pungent odor, lack of irritation to airway passages, low blood:gas solubility allowing rapid induction of and emergence from anesthesia, minimal cardiovascular and respiratory side effects, minimal end-organ effects, minimal effect on cerebral blood flow, low reactivity with other drugs, and a vapor pressure and boiling point that enables delivery using standard vaporization techniques. As a result, sevoflurane has become one of the most widely used agents in its class.

Induction characteristics with 3% and 8% sevoflurane in adults: an evaluation of the second stage of anaesthesia and its haemodynamic consequences

The second stage of anaesthesia was examined during 3 and 8% sevoflurane induction to see if any shortening of its duration was at the expense of cardiovascular stability. Fourteen volunteers underwent consecutive, randomly ordered inductions. Pupil size, skin sympathetic activity, plasma catecholamines, blood pressure and heart rate were measured. Eight per cent sevoflurane produced significantly shorter times to loss of consciousness (mean 68 s (SD 18) vs. mean 150 s (SD38)) and durations of second stage (mean 58 s (SD 38) vs. mean 91 s (SD 46)). Blood pressure, heart rate and sympathetic nerve responses were the same in both groups. Compared with baseline, skin sympathetic activity was greatest during pre-oxygenation (not significant) and unaltered during second stage. Both groups showed significantly increased plasma norepinephrine and heart rate and decreased blood pressure from baseline. Eight per cent sevoflurane induction produced a shorter second stage than 3% with equal cardiovascular stability and the same sympathetic response.

Fentanyl supplementation of sevoflurane induction of anaesthesia

Sevoflurane induction of anasthesia has been examined extensively, but little is known about the usefulness of other drugs as adjuncts to hasten and smooth the process. Sixty patients, undergoing surgery of a type suitable for a spontaneous respiration, laryngeal mask airway anasthetic technique, were randomly allocated to receive 1.0 microgram.kg-1 intravenous fentanyl or the equivalent volume of normal saline, 30 s prior to triple-breath induction with sevoflurane. The study was double-blind. There were no differences between the groups for the times to loss of eyelash reflex, jaw relaxation, insertion of the laryngeal mask airway or regular settled breathing. However, there was a difference in the incidence of adverse airway events (breath-holding, coughing and laryngospasm) between the two groups (16.5% in the fentanyl group and 40% in the placebo group); this did not reach statistical significance. Both groups were haemodynamically stable throughout induction, although the fentanyl group had a statistically significant decrease in systolic blood pressure at 4 min compared with the placebo group, which was not considered clinically relevant. We conclude that fentanyl has no significant influence over the speed and quality of sevoflurane induction.

Hemodynamic response to tracheal intubation after vital capacity rapid inhalation induction (VCRII) with different concentrations of sevoflurane

STUDY OBJECTIVE

To evaluate the blood pressure (BP) and heart rate (HR) response to tracheal intubation after vital capacity rapid inhalation induction (VCRII) with four concentrations of sevoflurane followed by nitrous oxide (N2O) 50% and sevoflurane in concentrations administered by clinical judgment.

DESIGN

Prospective, randomized study.

SETTING

University teaching hospital.

PATIENTS

60 unpremedicated, ASA physical status I and II adult patients undergoing surgery with general anesthesia.

INTERVENTIONS

After fentanyl 3 micrograms/kg, VCRII was accomplished with four concentrations of sevoflurane in O2: Group 1 (n = 15): sevoflurane 3%; Group 2 (n = 15): sevoflurane 4%; Group 3 (n = 15): sevoflurane 5%; and Group 4 (n = 15): sevoflurane 6%. At loss of consciousness, rocuronium 0.6 mg/kg was given, and intubation was performed 90 seconds later. Thereafter, anesthesia continued with N2O 50% and sevoflurane.

MEASUREMENTS AND MAIN RESULTS

BP and HR measurements were made at the ward (baseline), at loss of consciousness, and just prior to, and each minute after, tracheal intubation during a 5-minute period. The hemodynamic profile among groups was similar, with a slight hypertensive and tachycardic response to intubation.

CONCLUSION

VCRII with sevoflurane 3% to 6% following fentanyl 3 micrograms/kg can be considered for blunting the hemodynamic response to tracheal intubation in healthy patients.

Comparison of the hemodynamic effects of sevoflurane anesthesia induction and maintenance vs TIVA in CABG surgery

PURPOSE

To compare the hemodynamic effects of sevoflurane when used for induction and maintenance of anesthesia with a total intravenous technique in patients with known coronary artery disease (CAD).

METHODS

Thirty patients undergoing elective coronary artery bypass graft (CABG) were randomly allocated to receive either sevoflurane (S group, n = 15) at a minimal concentration of 4% in oxygen for induction and at 0.5-2 MAC end-tidal concentration for maintenance, or a total intravenous technique (T group, n = 15) consisting of midazolam for induction and propofol for maintenance. In both groups, anesthesia was supplemented with sufentanil and muscle relaxation with cis-atracurium. Hemodynamic measurements included systemic and pulmonary pressures, heart rate, mixed venous oxygen saturation and cardiac output at the following times: pre-induction, 7 and 25 min post-induction, chest closure, one hour after surgery and pre and post tracheal extubation.

RESULTS

More patients in the S group (8/15) presented bradycardia in the induction period (T:2/15) (P = 0.05). During maintenance of anesthesia, treatment of hypertension was more frequent in the T group (12/15) than in the S group (6/15) (P = 0.025). All other parameters were comparable.

CONCLUSION

Induction of anesthesia in patients with CAD, VCRII with sevoflurane supplemented by sufentanil provided hemodynamic responses comparable with those of TIVA although bradycardia was observed more often with sevoflurane. Intraoperative control of systemic blood pressure was achieved with fewer interventions with a sevoflurane/sufentanil maintenance than with a propofol/sufentanil technique in CABG surgery.