High concentration versus incremental induction of anesthesia with sevoflurane in children: a comparison of induction times, vital signs, and complications. Comparison of three techniques for induction of anaesthesia with sevoflurane in children. Effect of smoking on induction of anaesthesia with sevoflurane. Apnea during induction of anesthesia with sevoflurane is related to its mode of administration. Comparison of inhalation induction with 2%, 4%, 6%, and 8% sevoflurane in nitrous oxide for pediatric patients. Induction characteristics with 3% and 8% sevoflurane in adults: an evaluation of the second stage of anaesthesia and its haemodynamic consequences. Randomized comparison between sevoflurane anaesthesia and unilateral spinal anaesthesia in elderly patients undergoing orthopaedic surgery. Conventional stepwise vs. vital capacity rapid inhalation induction at two concentrations of sevoflurane. Efficient inspired concentration of sevoflurane for vital capacity rapid inhalation induction (VCRII) technique.
To compare sevoflurane induction times and complications in children during a high concentration, primed-circuit method and an incremental induction technique.
                Randomized, prospective open-label study.
                Academic university hospital.
                40 unpremedicated ASA physical status I and II children age 4 months to 15 years undergoing elective surgical procedures with general anesthesia.
                Patients were randomized to one of two study groups. In the high concentration group, the anesthesia circuit was primed with 8% sevoflurane in a 2:1 nitrous oxide:oxygen (N2O:O2) mixture. Patients breathed this gas mixture spontaneously until loss of the eyelash reflex. In the incremental group, the face mask was applied and 1% sevoflurane in a 2:1 N2O:O2 mixture was administered. In this group, the sevoflurane concentration was increased by 1% every 2 to 3 breaths. Gas flows of 6 L/min were administered to both groups during the study period. Following loss of the eyelash reflex, the sevoflurane concentration was decreased to 5% until a depth of anesthesia sufficient to start an intravenous catheter was achieved.
                Induction cooperation, induction time (face mask application to loss of the eyelash reflex), one-minute vital signs [blood pressure, heart rate, oxygen saturation via pulse oximetry (SpO2)], induction complications. Induction of anesthesia was faster in the high concentration group than in the incremental group (mean (SD) 42 (9) sec vs. 66 (12) sec, respectively; p < 0.001). Induction complications were minor and occurred with similar frequencies (4/20 patients vs. 3/20 patients). There were no significant intergroup heart rate, blood pressure, or SpO2 differences during induction. No patients required treatment for hypotension or bradycardia.
                In healthy pediatric patients undergoing mask induction of general anesthesia with sevoflurane, the induction time can be significantly shortened without an increase in the frequency of airway or vital sign complications using a high concentration, primed circuit technique compared with a conventional, incremental induction method. This study was designed to evaluate the clinical characteristics of three induction techniques using sevoflurane in children scheduled for tonsillectomy: incremental induction with sevoflurane(2,4,6,7%) in 100% O2 (group IC-O2; n=23); induction with high concentration of sevoflurane in 100% O2 (group HC-O2; n=22); and induction with high concentration of sevoflurane in a mixture of O2:N2O(50:50) (group HC-N2O; n=20). Induction was well accepted and well tolerated in most children. The addition of nitrous oxide resulted in faster loss of consciousness (P< 0.001) compared to the other induction techniques and in a tendency for reduced excitement compared with the same rapid technique without nitrous oxide (P=0.053). Time to tracheal intubation was identical in the three groups and intubation conditions were scored as good in most children. During the early induction phase, an increase in SAP and HR was observed in the three groups. Changes were maximal at two min after the beginning of induction in the three groups. SAP and HR values were back to baseline values at the time of tracheal intubation. In conclusion, the addition of nitrous oxide to a high sevoflurane concentration decreases the time to loss of eyelash reflex, tends to reduce the incidence of excitement and is not associated with an increased incidence of respiratory complications even in patients with obstructive airway. Inhalational induction with sevoflurane has been shown to be a viable alternative to intravenous induction; however, studies have focused mainly on healthy patients or volunteers. Airway complications in patients with potential airway irritability have not been studied. Sixty smokers undergoing general anaesthesia were randomly assigned to one of three groups: group 1, vital capacity breathing with 8% sevoflurane; group 2, tidal breathing with 8% sevoflurane; and group 3, tidal breathing with step-up of sevoflurane (sevoflurane concentration increased by increments of 2% every 10 s until 8%). Step-up induction was significantly slower to induce loss of consciousness than a vital capacity breath or tidal breathing at 8% (p < 0.05). Step-up induction produced more complications than tidal breathing at 8% (p = 0.05). All patients had acceptable induction of anaesthesia with no patient having an oxygen saturation below 96% at any time. Blood pressure and heart rate decreased gradually over time in all groups (p < 0.001), but there were no significant differences between groups. Patient satisfaction with the techniques was high with 59 of 60 patients willing to have the same technique again. Inhalational induction with sevoflurane can be used safely as an induction technique in smokers. In common with other patient groups, use of a high initial concentration reduces induction time without causing additional airway or cardiovascular complications. The incidence and duration of apnea during sevoflurane anesthesia have not been fully characterized. We hypothesized that sevoflurane at slowly increasing concentrations reduces incidence and shortens the duration of apnea compared to administration of a highly concentrated anesthetic mixture.
                131 women were randomly assigned to receive 35% oxygen in air and sevoflurane at: incremental concentrations of 1%, from 1% to 8% (group 1-8%, n = 42); decremental-incremental concentrations of 2%, from 8% to 4% and then from 4% to 8% (group 8-4-8%, n = 36); or fixed concentrations of 8% for induction of anesthesia (group 8%, n = 53). A blinded investigator observed whether and for how long patients stopped breathing.
                All groups reached 2.5 minimum alveolar concentration of end-tidal sevoflurane. Although apnea was observed in all groups, it was more frequent in the 8% group than in 1 to 8% (68% vs 21%, P < 0.05) or 8 to 4 to 8% groups (68% vs 20%, P < 0.05). Duration of apnea was also more pronounced in the 8% group than in 1 to 8% and 8 to 4 to 8% groups ( 58 +/- 25 s vs 32 +/- 18 sec, P < 0.05 and vs 35 +/- 16 sec, P < 0.05, respectively).
                Sevoflurane induces apnea more frequently and for longer duration at a fixed high concentration compared to incremental or decremental-incremental concentrations. Decremental-incremental concentrations offer the additional advantage of a speed of induction similar to that elicited by the 8% concentration. Sevoflurane is almost the idealest volatile anesthetic agent regarding inhalation induction of general anesthesia. Previous studies have established a role of sevoflurane in high concentration primed in the circuit for inhalation induction in pediatric patients. However, which concentration of sevoflurane is suitable has not yet been reported. This study was designed to compare the efficiency of different concentration of sevoflurane i.e. 2%, 4%, 6%, and 8% and with N2O in 50% oxygen for induction of anesthesia in pediatric patients and at the same time to evaluate the tolerance of patients.
                One hundred and twenty children who were 3 to 10 years old, of ASA class I, were randomly assigned to receive either 2%, 4%, 6%, and 8% sevoflurane and N2O in 50% O2 for induction of anesthesia. The time to loss of eyelash reflex, responses of airway reflex, involuntary movement, and hemodynamic responses were recorded.
                Ninety-nine children completed the study. The times to loss of eyelash reflex with 2% in sequence to 8% sevoflurane were 114 +/- 21 s, 87 +/- 11 s, 75 +/- 6 s, and 48 +/- 8 s respectively. Incidence of airway reflex response including coughing, laryngospasm, and breath holding was the highest in the 8% group (P < 0.05). Inhalation induction with sevoflurane significantly decreased systolic as well as diastolic blood pressure compared with baseline blood pressure in all the four groups. The extent of decrease of blood pressure was within 20% range of baseline blood pressure in all groups. Significant increase of heart rate was only observed in the 4% and 6% groups.
                Sevoflurane 6% for inhalation induction apparently caused low incidence of adverse effects and hastened induction. We suggest that 6% sevoflurene is a concentration more practical for inhalation induction in pediatric patients. 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. This prospective, randomized study was conducted to compare unilateral spinal block using small doses of hyperbaric bupivacaine and single-agent anaesthesia with sevoflurane in elderly patients undergoing hip surgery.
                Thirty patients (> 65 yr) undergoing hip fracture repair were randomly allocated to receive unilateral spinal anaesthesia with hyperbaric bupivacaine 7.5 mg 0.5% (Group Spinal, n = 15) or volatile induction and maintenance anaesthesia with sevoflurane (Group SEVO, n = 15). General anaesthesia was induced by increasing the inspired concentration to 5%. A laryngeal mask airway was placed without muscle relaxants, and the end-tidal concentrations of sevoflurane were adjusted to maintain cardiovascular stability. Hypotension (decrease in systolic arterial pressure > 20% from baseline), hypertension or bradycardia (heart rate < 50 beats min(-1)) requiring treatment, and the length of stay in the postanaesthesia care unit was recorded. Cognitive functions were evaluated the previous day, and 1 and 7 days after surgery with the Mini Mental State Examination test.
                Hypotension occurred in seven patients of Group Spinal (46%) and in 12 patients of Group SEVO (80%) (P = 0.05). Phenylephrine was required to control hypotension in three spinal patients (21%) and four SEVO patients (26%) (n.s.). SEVO patients had lower heart rates than spinal patients from 15 to 60 min after anaesthesia induction (P = 0.01). Bradycardia was observed in three SEVO patients (22%). Discharge from the postanaesthesia care unit required 15 (range 5-30) min in Group Spinal and 55 (15-80) min in Group SEVO (P = 0.0005). Eight patients in Group Spinal (53%) and nine patients in Group SEVO (60%) showed cognitive decline (Mini Mental State Examination test decreased > or = 2 points from baseline) 24 h after surgery (n.s.). Seven days after surgery, confusion was still present in one patient of Group Spinal (6%) and in three patients of Group SEVO (20%) (n.s.).
                In elderly patients undergoing hemiarthroplasty of the hip, induction and maintenance with sevoflurane provide a rapid emergence from anaesthesia without more depression of postoperative cognitive function compared with unilateral spinal anaesthesia. This technique represents an attractive option when patient refusal, lack of adequate co-operation or concomitant anticoagulant therapy contraindicate the use of spinal anaesthesia. A multicentre study was conducted to compare three methods of inhalation induction with sevoflurane in adult premedicated patients.
                One-hundred-and-twenty-five adult patients of ASA I-II were scheduled for short elective surgical procedures (< 90 min) under general anaesthesia with spontaneous ventilation of the lungs via a laryngeal mask airway. Patients were randomly assigned to one of three groups: conventional stepwise inhalation induction group (Group C) or vital capacity rapid inhalation induction groups at 4.5% (Group VC4.5) or at 8% sevoflurane (Group VC8). Before anaesthetic induction, fentanyl 1 micro kg(-1) was given and the face mask applied with the anaesthetic breathing system primed with sevoflurane 4.5% or 8% in the respective vital capacity groups. Loss of eyelash reflex, time to cessation of finger tapping, laryngeal mask insertion, side-effects and adequacy of induction were recorded.
                The time to loss of eyelash reflex was significantly shorter in both vital capacity groups vs. the control group: VC8: 68 +/- 7 s; and VC4.5: 94 +/- 6.5 s vs. C: 118 +/- 6.4s (P < 0.0001). Significant differences were found in all pairwise comparisons for time to cessation of tapping: Group VC8 (62 +/- 7 s), Group VC4.5 (85 +/- 6 s) and Group C (116 +/- 6 s; P < 0.0001). The time to laryngeal mask insertion was significantly shorter in the Group VC8 (176 +/- 13 s) compared with the other two groups, Group VC4.5 (219 +/- 13 s) and Group C (216 +/- 9 s). There were no significant differences in the incidence of side-effects between the three groups.
                Inhalation induction of anaesthesia with sevoflurane with the three techniques tested is safe, reliable and well accepted by the patients. The vital capacity rapid inhalation group primed with sevoflurane 8% was the fastest method with no relevant side-effects. To evaluate the efficient inspired concentration of sevoflurane for a vital capacity rapid inhalation induction (VCRII) technique with respect to induction time, characteristics, and acceptability.
                Prospective study.
                Medical college hospital.
                68 unpremedicated healthy adult volunteers were assigned to one of four groups in order of sequential entry of informed consent.
                3%, 4.5%, 6%, or 7.5% concentrations of sevoflurane were administered for 5 minutes (3% and 4.5%) or 3 minutes (6% and 7.5%) using a single breath technique.
                The mean induction time required with 3%, 4.5%, 6%, or 7.5% sevoflurane was 120 +/- 26 sec, 79 +/- 18 sec, 52 +/- 15 sec, or 47 +/- 17 seconds, respectively. Each induction time was significantly different from the others (p < 0.05) except for that between 6% and 7.5%. There appeared to be a direct inverse relationship between the mean induction time and the logarithm of inspired concentration of sevoflurane, but this relationship did not extend beyond concentrations above 6%. Blood pressure decreased by approximately 18% from baseline at the end of inhalation of the drug, and heart rate remained constant in all groups. Except of one subject in the 7.5% group, no coughing was observed and laryngospasm, breath-holding, and secretions were not seen in any subjects. Slight limb movement was observed in a few subjects in each group. All subjects except one in the 3% group would accept undergoing a similar procedure again.
                Sevoflurane 6% can be recommended for VCRII, but increasing the concentration higher than this does not markedly shorten the induction time and thus seems to add little benefit.
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.