Comparison of sevoflurane with propofol for laryngeal mask airway insertion in adults

We performed a prospective, randomized, controlled trial to compare the quality and ease of laryngeal mask airway (LMA) insertion after either rapid inhaled sevoflurane or i.v. propofol induction of anesthesia. Seventy-six unpremedicated ASA physical status I or II patients were anesthetized with either a single vital capacity breath of sevoflurane 8% or i.v. propofol 3 mg/kg, which produced equally rapid loss of consciousness (40.5 +/- 13.9 vs 37.7 +/- 9.9 s; P > 0.05). The LMA was inserted more rapidly in patients in the propofol group (74 +/- 29 vs 127 +/- 35 s; P < 0.01) and required fewer attempts (1.2 vs 1.6; P < 0.05) than the sevoflurane group. There was a greater incidence of initially impossible mouth opening in the sevoflurane group (45% vs 21%; P < 0.05). Once mouth opening was possible, the degree of attenuation of laryngeal reflexes was similar. The overall incidence of complications related to LMA insertion, especially apnea (32% vs 0%; P < 0.01), was more frequent in the propofol group (82% vs 26%; P < 0.01). There were four failures of LMA insertion in the propofol group and none in the sevoflurane group. Both groups had stable hemodynamic profiles and good patient satisfaction. We conclude that sevoflurane vital capacity breath induction compares favorably with i.v. propofol induction for LMA insertion in adults. However, prolonged jaw tightness after the sevoflurane induction of anesthesia may delay LMA insertion. Implications: In this randomized, controlled trial, we compared the ease of insertion of the laryngeal mask airway in adults after induction of anesthesia with either a sevoflurane vital capacity breath technique or propofol i.v.. We conclude that sevoflurane compares favorably with propofol, although prolonged jaw tightness may delay laryngeal mask airway insertion.     

脑电双频指数指导下不同麻醉诱导方式对喉罩插入条件的影响

目的 观察脑电双频指数(BIS)指导下不同麻醉诱导方式对喉罩插入条件的影响.方法 60例择期行宫腔镜手术患者,ASAⅠ或Ⅱ级,根据诱导方式的不同随机均分为三组:七氟醚复合丙泊酚组(SP组)、七氟醚组(S组)及丙泊酚组(P组).SP组肺活量法吸入七氟醚,待患者意识消失后静脉注射丙泊酚;S组以肺活量法吸入七氟醚;P组静脉泵注丙泊酚.BIS值稳定于40～50超过20 s后插入喉罩.记录诱导开始至成功插入喉罩的时间及成功率;评估下颌松弛度评分和喉罩插入后咳嗽及肢体运动评分.结果 诱导至喉罩插入时间S组＞SP组＞P组(P＜0.05).呼吸暂停发生率P组(40％)明显高于SP和S组(均为0)(P＜0.05).不自主肢体运动发生率P组高于SP和S组(35％ vs 5％和10％,P＜0.05).结论 BIS指导下七氟醚复合丙泊酚诱导较丙泊酚或七氟醚诱导能提供更好的喉罩插入条件.     

A comparison of sevoflurane-propofol versus sevoflurane or propofol for laryngeal mask airway insertion in adults

In a prospective, randomized study, we investigated the incidence of successful insertion of laryngeal mask airway (LMA) at the first attempt and the incidence of side effects after LMA insertion using the combination of sevoflurane and propofol as compared with either sevoflurane or propofol alone for induction of anesthesia. Eighty-three unpremedicated ASA physical status I-II patients were anesthetized with a single vital capacity breath (VCB) of sevoflurane 8% supplemented with IV propofol 1.5 mg/kg, a single VCB of sevoflurane 8%, or IV propofol 3 mg/kg. The coinduction technique was associated with the most frequent incidence of successful LMA insertion at the first attempt (93.5%) than either sevoflurane alone (46%) or propofol alone (61.5%) (P < 0.001). Propofol-induced induction of anesthesia allowed the fastest insertion of LMA and was associated with the least frequent incidence of postoperative nausea and vomiting. However, this advantage of propofol was offset by a frequent incidence of pain on injection (69%) and the occurrence of movements during insertion of the LMA (50% in the propofol group versus 19% and 26% in the sevoflurane and sevoflurane-propofol groups, respectively; P < 0.05), as well as a more frequent incidence of apnea (84% in the propofol group versus 7% and 16% in the sevoflurane and sevoflurane-propofol groups, respectively; P < 0.001). The report shows that induction of anesthesia with sevoflurane-propofol combined provides a frequent incidence of successful LMA insertion at the first attempt that is associated with an infrequent incidence of apnea.     

Vital capacity and patient controlled sevoflurane inhalation result in similar induction characteristics

PURPOSE: To compare patient controlled inhalational induction (PCI) with the most commonly used sevoflurane induction technique, vital capacity inhalational induction (VCI). METHODS: Following approval of the Research Ethics Board, 124 outpatients undergoing knee arthroscopy were randomly assigned to receive either PCI or VCI sevoflurane followed by laryngeal mask airway (LMA) insertion and sevoflurane maintenance. In the PCI group, the circle circuit was not primed. The patients were asked to hold the facemask themselves and breathe normally with sevoflurane 8% in oxygen at a flow rate of 4 L x min(-1). In the VCI group, the circle circuit was primed and patients were asked to take vital capacity breaths with sevoflurane 8% at an oxygen flow rate of 8 L x min(-1). The LMA was inserted as soon as the patient's jaw was relaxed. Time from induction to LMA insertion was recorded and insertion conditions rated. The amount of sevoflurane used for LMA insertion was calculated. Vital signs were monitored at one-minute intervals until ten minutes after LMA insertion. RESULTS: Demographic data were comparable. There were no differences with respect to LMA insertion time (PCI - 3.4 min vs VCI - 3.3 min), laryngospasm (PCI - 7% vs VCI - 5%), mean arterial pressure, heart rate, SaO(2) as well as patient's overall satisfaction. CONCLUSION: PCI was comparable to VCI in sevoflurane induction with respect to the speed of induction, side effects during induction and patient satisfaction. However, PCI requires no special training and is widely applicable to all patient populations.     

Multiple-deep-breath inhalation induction with 5% sevoflurane and 67% nitrous oxide: comparison with intravenous injection of propofol

Purpose. To evaluate the clinical characteristics of multiple-deep-breath inhalation induction with sevoflurane and nitrous oxide followed by the same inhalational anesthetics for maintenance, we compared the technique with intravenous propofol anesthesia. Methods. Forty patients scheduled for ophthalmic surgery under general anesthesia with a laryngeal mask airway (LMA) were assigned to two groups. Anesthesia was induced with multiple-deep-breath inhalation of 5% sevoflurane and 67% nitrous oxide in oxygen (group S: n = 20) or intravenous injection of 1% propofol at the rate of 1200 ml·h⁻¹ with spontaneous inhalation of 67% nitrous oxide in oxygen until the patient lost consciousness or received propofol up to 2 mg·kg⁻¹ (group P: n = 20). We attempted to insert an LMA when the patient's jaw relaxation was adequate. We compared induction times, recovery times, occurrence of adverse events, and patient satisfaction between the two groups. Results. The mean time to insertion of the LMA was significantly shorter in group P (209 ± 118 s) than in group S (302 ± 102 s; P < 0.05). The recovery times did not differ significantly between the groups. There were no serious side effects during the induction and recovery period in either group. Significantly more patients in group P than in group S wanted to have the same anesthetic method (90% vs 50%; P < 0.05). Conclusion. Multiple-deep-breath inhalation induction with 5% sevoflurane and 67% nitrous oxide followed by the same inhalational anesthetics for maintenance was safely performed without serious adverse events. However, the induction time was shorter and patient satisfaction was higher in propofol group than in the inhalational group. Received: April 11, 2001 / Accepted: November 6, 2001     

The use of remifentanil to facilitate the insertion of the laryngeal mask airway

Propofol is often used as an IV induction drug for anesthesia and the insertion of a laryngeal mask airway (LMA). As a sole anesthetic, it may be associated with undesirable airway responses such as coughing and gagging. We conducted a randomized, double-blinded study to compare the conditions during insertion of the LMA in 120 patients who received normal saline (Group P), remifentanil 0.25 microg/kg (Group R1), or remifentanil 0.5 microg/kg (Group R2) before the induction of anesthesia with IV propofol. The addition of remifentanil significantly improved the conditions of insertion; in Group R1, 82.5% (33 of 40 patients), and in Group R2, 85.0% (34 of 40 patients) had excellent insertion conditions as compared with the Control group P, 32.5% (13 of 40 patients). Patients in Group P were apneic for a mean (SD) time of 85 (38) s, 186 (75) s in group R1, and 284 (130) s in group R2. There was a lesser decrease in mean arterial blood pressure in group R1. We conclude that remifentanil 0.25 microg/kg, when administered after IV propofol 2.5 mg/kg, provides excellent conditions for insertion of the LMA with minimal hemodynamic disturbances. IMPLICATIONS: Small-dose remifentanil can provide excellent conditions for laryngeal mask airway insertion with minimal hemodynamic disturbances.     

Coasting after overpressure induction with sevoflurane

STUDY OBJECTIVE: To evaluate the clinical feasibility of using a coasting technique to temporarily maintain anesthesia after overpressure induction with sevoflurane. STUDY DESIGN: Prospective clinical study. SETTING: Large teaching hospital. PATIENTS: 12 ASA physical status I, II, and III patients receiving general anesthesia for a variety of peripheral procedures. INTERVENTIONS: After overpressure induction of anesthesia with sevoflurane (8%) in an O(2)/N(2)O mixture, the fresh gas flow (FGF) was lowered to 0.5 L/min and the vaporizer was turned off (coasting). MEASUREMENTS AND MAIN RESULTS: After priming a circle system with sevoflurane (8% sevoflurane vaporizer setting in 6 L/min O(2)/N(2)O [33%/66%] for 30 s), patients took several vital capacity breaths from the mixture until loss of consciousness. After 3.4 +/- 0.7 min, depth of anesthesia was considered adequate for laryngeal mask airway (LMA) insertion, and FGF was reduced to 0.5 L/min (33% O(2), 66% N(2)O) and the sevoflurane vaporizer was turned off. The end-expired sevoflurane concentration (Et(sevo)) decreased from 5.8 +/- 1.3% just before insertion of the LMA to 0.97 +/- 0.22% at 20 minutes. CONCLUSIONS: After overpressure induction with sevoflurane, coasting during minimal flow anesthesia (FGF 0.5 L/min) is a simple technique that can maintain anesthesia for short procedures (less than 15 to 20 min), or can be used as a bridge or an adjunct to other low-flow techniques.     

Sevoflurane versus propofol for induction and maintenance of anaesthesia with the laryngeal mask airway in children

We compared patient outcomes for propofol vs sevoflurane with the laryngeal mask airway (LMA) using either spontaneous breathing (SB) or pressure controlled ventilation (PCV). One hundred and twenty children undergoing minor surgery below the umbilicus were randomly assigned to receive either (1) propofol 3 mg.kg-1 followed by a maintenance infusion of 5 mg.kg-1.h-1, or (2) induction with sevoflurane 7% followed by maintenance with 1.7%. Following LMA insertion, patients were given atracurium and underwent PCV if surgery was expected to last > or = 30 min. The following assessments were made: time to LMA insertion/removal, airway problems, cardiorespiratory effects and recovery characteristics. The first time insertion success rates were similar, but insertion time was shorter with sevoflurane (115 +/- 67 s vs 252 +/- 107 s, P < 0.0001). One patient coughed during placement, but there were no other problems during any phase of anaesthesia in any group. Heart rate was higher in the sevoflurane group following insertion, during maintenance and emergence (all P < 0.03). There were no differences in blood pressure and oxygen saturation among groups PECO2 in the SB group was unaffected by the agent used. Emergence was more rapid (232 +/- 104 s vs 348 +/- 127 s, P < 0.0001) and postoperative agitation more common (15% vs 0%, P = 0.02) with sevoflurane. There were no differences in the Aldrete scores among groups. Patient outcome was similar for the SB and PCV groups. We concluded that the techniques described here using propofol and sevoflurane are equally suitable for induction and maintenance of anaesthesia with the LMA in children undergoing minor surgery below the umbilicus. Emergence is more rapid, but postoperative agitation more common with sevoflurane.     

Sevoflurane as a single anesthetic and physostigmine failure to enhance arousal

AIM: Sevoflurane is recommended for inhalational induction of anesthesia. Physostigmine may antagonize general anesthetics. The study investigates sevoflurane as a single anesthetic and its possible antagonism by physostigmine. METHODS: In 60 women scheduled for breast lump excision, anesthesia was induced with 8% sevoflurane. After 3 min of sevoflurane inhalation, a laryngeal mask airway (LMA) was inserted. Anesthesia was maintained with spontaneous ventilation at end tidal sevoflurane 3%. Systolic and diastolic blood pressure, heart rate and end tidal CO(2) were recorded intraoperatively. After skin closure and at end tidal sevoflurane 0.9%, physostigmine 2 mg or normal saline was given. After 2 min systolic, diastolic blood pressure, heart rate and end tidal CO(2) were recorded and sevoflurane was discontinued. Time to eyes opening, LMA removal and verbal response was recorded. Patients were also assessed for orientation, sedation, sitting ability and the 'picking up matches' test at 0, 15 and 30 min after LMA removal. RESULTS: Systolic, diastolic blood pressure and heart rate increased after laryngeal mask placement (P=0.0001, P=0.0001 and P=0.0001, respectively). Orientation, sitting ability and 'picking up' matches were similar in the 2 groups. Sedation at 15 min was less in the control group (P=0.004). CONCLUSIONS: Sevoflurane can be used as a single anesthetic but its recovery is not enhanced by physostigmine.     

Conditions for insertion of the laryngeal mask airway: comparisons between sevoflurane and propofol using fentanyl as a co-induction agent. A pilot study

BACKGROUND AND OBJECTIVE: To compare the conditions for insertion of the laryngeal mask airway using sevoflurane or propofol plus fentanyl. We evaluated the haemodynamic changes and cost of induction of anaesthesia in both groups. METHODS: Sixty patients were equally and randomly divided into two groups. Both groups received fentanyl 1 microg kg(-1). Patients in the sevoflurane group were induced with 8% sevoflurane and those in the propofol group with propofol 2.5 mg kg(-1). Conditions for insertion were graded on a three-point scale using six variables. Overall, conditions were assessed as excellent, satisfactory or poor based on the total score in each group. Systolic and diastolic arterial pressure and heart rate were recorded for 6 min after mask insertion. The financial cost of induction in both groups was calculated. RESULTS: The mean (+/- SD) time taken from induction to successful laryngeal mask insertion was significantly shorter with propofol (68.70 +/- 22.60 s) compared with sevoflurane (149.83 +/- 55.25 s). Excellent or satisfactory conditions were observed in 30 (100%) patients in the propofol group and in 29 (96.66%) in the sevoflurane group. Systolic and diastolic arterial pressures were significantly lower in the propofol group. The cost of sevoflurane used was 3.95 euros +/- 1.48 (Rs 216.23 +/- 64.66) (P < 0.05) compared with that of propofol, which was 3.23 euros +/- 0.65 (Rs 141.00 +/- 28.20). CONCLUSIONS: Although there was a faster induction with propofol-fentanyl, conditions for insertion of the laryngeal mask airway were similar in both groups. Haemodynamic stability was better with sevoflurane-fentanyl. The propofol-fentanyl combination was more cost-effective.     

Sevoflurane versus propofol for anesthetic induction: a meta-analysis

We performed this meta-analysis to compare the characteristics of sevoflurane and propofol for the induction of routine anesthesia and for laryngeal mask airway (LMA) insertion. The variables assessed were 1) time to loss of consciousness, 2) incidence of apnea during induction, 3) induction complications, 4) time for successful LMA insertion, 5) success with LMA insertion on first attempt, 6) patient dissatisfaction, and 7) postoperative nausea and vomiting. MEDLINE, Embase, and the Cochrane library databases between January 1992 and October 1999 were reviewed for randomized, controlled trials comparing anesthetic induction between sevoflurane/nitrous oxide and propofol. Data from the 12 randomized, controlled studies were used for the meta-analysis. Sevoflurane induction was associated with a trend toward higher patient dissatisfaction and higher first-time success with LMA. Apnea was less common in the sevoflurane group. The incidence of postoperative nausea and vomiting was significantly more frequent in the sevoflurane group (P < 0.05). This effect was still present when all other variables, except the induction methods, were controlled. The other pooled variables did not show a significant difference between sevoflurane and propofol. Sevoflurane and propofol had similar efficacy for anesthetic induction. However, for routine outpatient surgery, propofol may still be the preferred induction anesthetic because of its favorable induction of anesthesia characteristics, high patient satisfaction, and less frequent incidence of postoperative nausea and vomiting. IMPLICATIONS: Sevoflurane and propofol had similar efficacy for anesthetic induction. However, for routine outpatient surgery, propofol may still be the preferred induction anesthetic because of its favorable induction of anesthesia characteristics, high patient satisfaction, and less frequent incidence of postoperative nausea and vomiting.     

Oral clonidine premedication reduces minimum alveolar concentration of sevoflurane for laryngeal mask airway insertion in children

BACKGROUNDS: Sevoflurane is widely employed for inhalational induction in children. Clonidine deepens volatile anesthetics and reduces several types of MAC of sevoflurane. Laryngeal mask airway is a useful device for pediatric anesthesia. The aim of the current study was to determine whether oral clonidine premedication can reduce MAC of sevoflurane for an LMA insertion in children. METHODS: Fifty-six ASA physical status I patients (3-11 years) scheduled for general anesthesia were randomly divided into two groups of 28 patients each. One group (clonidine group) received clonidine 4 microg x kg(-1) approximately 100 min before anesthesia, and the other (control) group did not. Anesthesia was induced with sevoflurane. Each concentration of sevoflurane, at which an LMA insertion was attempted, was predetermined according to the modification of Dixon's up-and-down method with 0.25% as a step size and held constant for at least 20 min before the trial. All responses ('movement' or 'no movement') to an LMA insertion were assessed. RESULTS: Minimum alveolar concentration values of sevoflurane for an LMA insertion were lower in the clonidine group (1.31% +/- 0.18% [mean +/- sd]) than in the control group (2.00% +/- 0.16%). Logistic regression analysis revealed that sevoflurane EC95 values were 1.79% and 2.49% in the clonidine and control groups, respectively. CONCLUSIONS: Oral clonidine premedication reduced the MAC (EC50) and EC95 values of sevoflurane for LMA insertion by 38% and 28%, respectively.     

Desflurane Enhances Reactivity during the Use of the Laryngeal Mask Airway

Background: Desflurane and sevoflurane have markedly different pungencies. The tested hypothesis was that patients breathing equivalent concentrations of desflurane or sevoflurane through a laryngeal mask airway (LMA) would have similar responses.

Methods: After institutional review board approval and informed consent were obtained, 60 patients were enrolled and given intravenous midazolam (14 [mu]g/kg) and fentanyl (1 [mu]g/kg) 5 min before induction of anesthesia. The LMA was inserted at loss of consciousness after 2 mg/kg propofol. When spontaneous breathing returned, a randomly assigned volatile anesthetic was started at an inspired concentration of either 1.8% sevoflurane or 6% desflurane at a fresh gas flow of 6 l/min in air:oxygen (50:50). After 5 min, a controlled movement of the LMA took place. Three minutes later, the inspiratory anesthetic concentration was changed to either 3.6% sevoflurane or 12% desflurane for 3 min. A blinded observer recorded movements and airway events during the start of anesthetic, LMA movement, deepening of the anesthetic, and emergence before LMA removal.

Results: There were no differences at anesthetic start and LMA movement. Desflurane titration to 12% increased heart rate, increased mean arterial blood pressure, and initiated frequent coughing (53% vs. 0% sevoflurane) and body movements (47% vs. 0% sevoflurane). During emergence, there was a twofold greater incidence of coughing and a fivefold increase in breath holding in the desflurane group.     

Desflurane enhances reactivity during the use of the laryngeal mask airway

BACKGROUND: Desflurane and sevoflurane have markedly different pungencies. The tested hypothesis was that patients breathing equivalent concentrations of desflurane or sevoflurane through a laryngeal mask airway (LMA) would have similar responses. METHODS: After institutional review board approval and informed consent were obtained, 60 patients were enrolled and given intravenous midazolam (14 microg/kg) and fentanyl (1 microg/kg) 5 min before induction of anesthesia. The LMA was inserted at loss of consciousness after 2 mg/kg propofol. When spontaneous breathing returned, a randomly assigned volatile anesthetic was started at an inspired concentration of either 1.8% sevoflurane or 6% desflurane at a fresh gas flow of 6 l/min in air:oxygen (50:50). After 5 min, a controlled movement of the LMA took place. Three minutes later, the inspiratory anesthetic concentration was changed to either 3.6% sevoflurane or 12% desflurane for 3 min. A blinded observer recorded movements and airway events during the start of anesthetic, LMA movement, deepening of the anesthetic, and emergence before LMA removal. RESULTS: There were no differences at anesthetic start and LMA movement. Desflurane titration to 12% increased heart rate, increased mean arterial blood pressure, and initiated frequent coughing (53% vs. 0% sevoflurane) and body movements (47% vs. 0% sevoflurane). During emergence, there was a twofold greater incidence of coughing and a fivefold increase in breath holding in the desflurane group. CONCLUSIONS: When airway responses to sevoflurane and desflurane were compared in elective surgical patients breathing through an LMA, there were significantly more adverse responses with desflurane at 12% concentrations and during emergence.     

Conventional stepwise vs. vital capacity rapid inhalation induction at two concentrations of sevoflurane

BACKGROUND AND OBJECTIVE: A multicentre study was conducted to compare three methods of inhalation induction with sevoflurane in adult premedicated patients. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.     

Propofol causes less postoperative pharyngeal morbidity than thiopental after the use of a laryngeal mask airway

The insertion of a laryngeal mask airway (LMA) may result in postoperative sore throat. The choice of induction drug on airway morbidity after LMA insertion may be important. We performed this study to compare the incidence of postoperative pharyngeal morbidity after the insertion of a LMA in 340 patients administered either 2 mg/kg propofol (group P) or thiopental 5 mg/kg (group T) for induction of anesthesia. Patients were maintained at 1-2 minimum alveolar anesthetic concentration sevoflurane in 50% oxygen/air. Spontaneous or assisted spontaneous ventilation was maintained. An investigator blinded to group allocation visited patients at 2, 12, and 24 h postoperatively. Adverse responses were noted (yes/no) at each time point including sore throat, sore mouth, sore jaw, hoarseness, dysphonia, and dysphagia. At 2 h postoperatively, the incidence of sore throat, dysphagia, and postoperative nausea and vomiting in group T was higher than in group P (24% vs 13% for sore throat, 15% vs 3% for dysphagia, 20% vs 11% for nausea, 14% vs 6% for vomiting, P < 0.05). The number-needed-to-treat to prevent sore throat and dysphagia was 10 and 8, respectively (95% confidence intervals, 5-43). We concluded that, when propofol, rather than thiopental, is used for the induction of anesthesia, it results in a lower incidence of early pharyngeal morbidity and postoperative nausea and vomiting after the insertion of a LMA.     

The effect on intraocular pressure of tracheal intubation or laryngeal mask™ insertion during sevoflurane anaesthesia in children without the use of muscle relaxants

BACKGROUND: We studied the effects of sevoflurane on intraocular pressure after induction in children undergoing either tracheal tube (TT) or laryngeal mask airway (LMA) insertion without a muscle relaxant METHODS: The study included 38 children. Anaesthesia was induced (8%) and maintained (3-4%) with sevoflurane in 100% O2. No muscle relaxant was used. A TT was inserted in group I (n=20), and an LMA in group II (n=18). IOPs were measured after induction, insertion of TT or LMA and at 1, 2 and 3 min thereafter. The heart rate, mean arterial pressures were also recorded. RESULTS: Intraocular pressures increased significantly in group I after TT (P < 0.01) and remained high until after 3 min. The pressures were similar in the LMA group at all measurements. CONCLUSION: Sevoflurane does not prevent the increase in IOP after intubation without muscle relaxants. LMA does not increase IOP in children after sevoflurane induction.     

Induction of Anesthesia and Tracheal Intubation with Sevoflurane in Adults

Background: The speed, quality, and cost of mask induction of anesthesia and laryngeal mask airway insertion or tracheal intubation were studied in young non-premedicated volunteers given high inspired concentrations of sevoflurane (6 to 7%).

Methods: Twenty healthy persons who were 19 to 32 years old participated three times, received 6 l/min fresh gas flow, and were randomized to receive 6 to 7% sevoflurane in 66% nitrous oxide/28% oxygen by face mask until tracheal intubation (treatment 1) or until laryngeal mask airway insertion (treatment 3), or 6 to 7% sevoflurane without nitrous oxide to tracheal intubation (treatment 2). Participants exhaled to residual volume and took three vital capacity breaths of the gas mixture; thereafter ventilation was manually assisted. The time of exposure to the inhaled gas was varied for consecutive participants. It was either increased or decreased by 30-sec increments based on the failure or success of the preceding volunteer's response to laryngoscopy and intubation after a preselected exposure time. Failure was defined as poor jaw relaxation, coughing or bucking, or inadequate vocal cord relaxation.

Results: Loss of the lid-lash reflex in unpremedicated young volunteers was achieved in 1 min and did not differ among groups. Average time (and 95% confidence interval) for acceptable conditions for LMA insertion was achieved in 1.7 (0.7 to 2.7) min, and all participants had an immediate return of spontaneous ventilation. The time for acceptable tracheal intubating conditions after manual hyperventilation by mask was 4.7 (3.7 to 5.7) min and 6.4 (5.1 to 7.7) min in treatments 1 and 2, respectively. There were no cases of increased secretions or laryngospasm. The incidence of breath holding and expiratory stridor ("crowing") was 7.5% and 25%, respectively, during treatment 1 and 15% and 40%, respectively, during treatment 2.     

Optimal end-tidal sevoflurane concentration for the removal of the laryngeal mask airway in anesthetized adults

Sevoflurane provides smooth and rapid emergence from anesthesia and can be used when the removal of a laryngeal mask airway (LMA) is required in anesthetized patients. We sought to determine the optimal end-tidal concentrations of sevoflurane required for the removal of LMA in anesthetized adults. We studied 35 adults, aged 22-64 years old with an ASA physical status I or II, who were undergoing perineal surgery. General anesthesia was induced with thiopental, and the LMA was then inserted. Anesthesia was maintained with sevoflurane, oxygen, and air. After the surgery, the target concentration was maintained for at least 10 min, and then the LMA was removed. Each target concentration at the time of removal was predetermined by the Dixon up-down method (with 0.1% as a step size) starting at 1.7% end-tidal concentration of sevoflurane. The LMA removal was considered successful when there was no coughing, clenching of teeth, or gross purposeful movements during or within 1 min after removal and also if there was no breath holding, laryngospasm, or desaturation after removal. The end-tidal concentration of sevoflurane to achieve successful LMA removal in 50% of adults was 0.99% +/- 0.09% (mean +/- SD) and in 95% of adults was 1.18% (95% confidence limits, 1.07%-1.79%). In conclusion, we have determined that LMA removal in 50% and 95% of anesthetized adults can be safely accomplished without coughing, moving, or any other airway complications at 0.99% and 1.18% end-tidal concentrations of sevoflurane. IMPLICATIONS: Because the removal of the laryngeal mask airway (LMA) in the anesthetized state is required in some clinical situations, we sought to determine the end-tidal concentration of sevoflurane to safely remove the LMA in anesthetized adults.     

A comparison of the laryngeal tube with the laryngeal mask airway during routine surgical procedures

The laryngeal mask airway (LMA; Laryngeal Mask Company, Henley-on-Thames, UK) is an established airway device, whereas the laryngeal tube (LT) is relatively new and therefore not as well investigated. Therefore, the purpose of the present prospective, randomized, controlled trial was to compare the LT with the LMA in routine clinical practice. In 50 patients undergoing general anesthesia for minor routine surgery, standardized anesthesia was induced and maintained with alfentanil and propofol. Patients were randomized to controlled ventilation (fraction of inspired oxygen = 0.4; fraction of inspired nitrous oxide = 0.6; tidal volume = 7 mL/kg; respiratory rate = 10 breaths/min) with the LT (n = 25) or the LMA (n = 25). Oxygen saturation was recorded before the induction of anesthesia and after the administration of oxygen. After 2 and 10 min of ventilation with the LT or LMA, oxygen saturation, end-expiratory carbon dioxide, expiratory tidal volume, and peak airway pressure were recorded. Capillary blood gas samples were taken before the induction of anesthesia and after 10 min of ventilation. Time of insertion and airway leak pressure of each device were measured. The time of insertion was comparable with both devices (LT versus LMA, median 21 s versus 19 s; P = not significant). Blood gas samples and ventilation variables revealed sufficient ventilation and oxygenation with either device (P = not significant). Peak airway pressure (LT, 17 +/- 3 cm H(2)O; LMA, 15 +/- 3 cm H(2)O) and airway leak pressure (LT, 36 +/- 3 cm H(2)O; LMA, 22 +/- 3 cm H(2)O) were significantly (P < 0.05) higher when using the LT compared with the LMA. In conclusion, using the LT and LMA resulted in comparable ventilation and oxygenation variables in this model of ASA physical status I and II patients undergoing routine surgical procedures. The newly developed LT may be a simple alternative device to secure the airway. IMPLICATIONS: The laryngeal tube, a newly developed airway device, and the laryngeal mask airway were used to ventilate patients in the operating room. Both airway devices proved to be effective and safe; however, the laryngeal tube allowed greater airway pressure during ventilation.