Effect of nebulized lignocaine on airway irritation and haemodynamic changes during induction of anaesthesia with desflurane

This study was designed to assess the effect of nebulized lignocaine or saline given before induction on the quality of induction of anaesthesia with desflurane in unpremedicated, young, adult males. Of the first six patients, five developed laryngospasm, breath-holding, coughing and increased secretions. In four patients oxygen saturation decreased to 92% or less. Significant tachycardia and hypertension occurred in four patients, and bradyarrhythmia after induction occurred in three patients. Hiccups and bronchospasm occurred in one patient. Because of the unacceptably high incidence of complications, the study was discontinued. The incidence and severity of complications were not decreased by administration of nebulized lignocaine and were higher than those reported by other workers. We conclude that in unpremedicated, young, adult males, induction of anaesthesia with desflurane and nitrous oxide in oxygen was associated with a high incidence of respiratory irritant effects, tachycardia, hypertension and post-induction bradyarrhythmia. We also found that lignocaine, as used in this study, did not appear to obtund the cardiovascular and respiratory complications during inhalation induction using desflurane.      

The site of airway irritation during induction of anaesthesia

The aim of this investigation was to study the role of the nasal airway in mediating upper airway reflexes during induction of anaesthesia when the commonly used irritant inhalational anaesthetic agent enflurane is used. In a prospective randomised study, 40 ASA 1 & 2 day-case patients undergoing body surface surgery were recruited. Following intravenous induction using propofol, 20 patients received enflurane administered via a laryngeal mask airway (LMA), the anaesthetic vapour therefore bypassing the nasal airway. In the other group, 20 patients received enflurane anaesthesia administered using a face mask, the nasal airway therefore being exposed to inhalation anaesthetic. We were unable to demonstrate any significant (p < 0.05) differences between the two groups in relation to upper airway complications (cough, breath holding, laryngeal spasm, bronchospasm and excitement). Previous work has identified the nose as a possible important reflexogenic site for upper airway reflexes in humans during anaesthesia. We have been unable to demonstrate any difference in upper airway complications when the nasal airway was included or excluded from exposure to irritant anaesthetic vapours, when administered in a clinical setting.     

Memory priming during light anaesthesia with desflurane and remifentanil anaesthesia

Background: Previous studies of memory priming during anaesthesia with EEGmonitoring have observed implicit memory effects for words presentedduring light and deep anaesthesia with and without surgicalstimulation. We hypothesized that memory priming occurs undereach of five different combinations of anaesthesia and surgery,and no significant differences occur in memory priming amongthe five conditions or between the two test points such as,12 vs 24 h after surgery. Methods: Forty gynaecological patients (aged between 28 and 66 yr, median44.5 yr) were included in the study. They received propofoland remifentanil induction followed by desflurane and remifentanilanaesthesia in conjunction with neuromuscular blocking agents.Each patient was exposed to 60 of 120 nouns in a double-blindrandomized design. These 60 nouns were divided into 5 groupsof 12 words, presented under one of the five different conditions,namely, intubation, skin incision, deep anaesthesia and moderateanaesthesia (both during surgery), and light anaesthesia duringthe emergence phase. The depth of anaesthesia was measured usingthe EEG monitor, Narcotrend^TM. Results: No explicit memories were observed in a free recall or in ayes–no recognition test. A word-stem completion test revealeda significant implicit priming only for light anaesthesia (P< 0.01). No significant differences were detected among thefive conditions. An overall implicit memory effect occurredfor the second test point (P < 0.05). Conclusions: Our hypotheses could not be verified. Implicit memory primingoccurred only under light anaesthesia, when the patients weremost probably conscious. Priming effects may be enhanced afternight's sleep.     

地氟醚对罗库溴铵肌松作用的影响

目的 研究新型吸入药地氟醚对罗库溴铵肌松作用的影响。方法 ２０例ＡＳＡⅠ－Ⅱ病人随机分为两组，每组１０例。两组均采用表麻下慢诱导插管，吸入５０％氧化亚氮及静注芬太尼，羟丁酸钠维持麻醉，对照组静脉注射罗库溴铵０．６ｍｇ．ｋｇ＾－１；地氟醚组在吸入３％地氟醚３０分钟后，静脉注射胃库溴铵０．６ｍｇ．ｋｇ＾－１。     

Laryngeal mask airway can be inserted with inhaled desflurane induction

Purpose In this prospective, randomized, controlled trial, we investigated the reliability of laryngeal mask airway (LMA) insertion with inhaled desflurane.Methods Eighty patients undergoing elective surgery were randomized into two groups to receive either 2.5mg·kg^–1 propofol (n = 40) or tidal breath desflurane (n = 40) induction followed by LMA insertion. All patients received fentanyl 1µg·kg^–1 2min before induction. Inhalation of desflurane was started at 3% and increased by 3% every 3–5 breaths up to settings of 12%.Results Insertion of the LMA was faster in the propofol group (131.8s versus 228.6s, P < 0.01). The number of patients in whom the jaw opening was described as good (95% versus 72.5%, P = 0.27, for the desflurane and propofol groups, respectively) and the ease of LMA insertion described as good (87.5% versus 72.5%, P = 0.6) were comparable. The LMA was inserted in a single attempt in the majority of patients in both groups (80% versus 77.5%, P = 0.90). There were more complications at insertion in the propofol group than in the desflurane group (2.5% versus 19.5%, P < 0.01), especially for apnea (7.5% versus 70%, P < 0.01) and excitatory movements (2.5% versus 25%, P < 0.01). There were significant decreases in the mean arterial pressure in the propofol group compared to baseline data over the first 5min of induction. Mean arterial pressure, heart rate, and S_{p O 2} remained stable during the same period in the desflurane group.Conclusion We demonstrated that inhaled desflurane when used with caution in a controlled manner provided acceptable conditions for LMA insertion.     

Intravenous ketamine attenuates arterial pressure changes during the induction of anaesthesia with propofol

BACKGROUND AND OBJECTIVE: To investigate whether the administration of ketamine before induction with propofol produces a smaller decrease in arterial pressure. METHODS: Twenty-two patients were assigned to one of two groups to receive either propofol with ketamine (n = 11) or propofol alone (n = 11, control). Anaesthesia was induced with 2 mg kg-1 propofol and 0.5 mg kg-1 ketamine or 2 mg kg-1 propofol alone. Ketamine was administered 1 min prior to induction with propofol. Immediately after induction with propofol, vecuronium (0.15 mg kg-1) was administered. Four minutes after administration of vecuronium, tracheal intubation was performed. Anaesthesia was maintained using sevoflurane (0.5%) in 66% nitrous oxide until 3 min after intubation. Systolic, diastolic and mean arterial pressure and heart rate were recorded on arrival, directly before induction with propofol, prior to tracheal intubation, immediately after intubation and at 3 min after intubation. RESULTS AND CONCLUSIONS: Administration of ketamine before induction with propofol preserved haemodynamic stability compared with induction with propofol alone.     

Low-flow anaesthesia with desflurane: kinetics during clinical procedures

BACKGROUND AND OBJECTIVE: Low-flow anaesthesia is economical and less polluting. The purpose of this study was to determine the inspired and end-tidal desflurane concentrations during anaesthesia with a vaporizer setting maintained at 5%, during low-flow anaesthesia after 120 min with fresh gas inflows of 1.0 and 2.0 L min-1. METHODS: The study was both prospective and randomized, including 56 patients (28 patients in each group) scheduled for elective surgery of an expected anaesthesia time of at least 120 min. Inspired and end-tidal concentrations of desflurane were measured during low-flow anaesthesia with fresh gas inflows of 1.0 and 2.0 L min-1. The vaporizer setting was fixed at 5% desflurane. RESULTS: The inspired and end-tidal concentrations of desflurane in the 1.0 L min-1 group after 120 min were 4.54% vs. 4.37% (P < 0.001). In the 2.0 L min-1 group, the inspired and end-tidal concentrations of desflurane were 4.76% vs. 4.58% (P < 0.001). The estimated end-tidal/inspired ratios at 120 min of anaesthesia were 0.96 in both groups. At a fresh gas flow of 1.0 L min-1, the end-tidal concentration was 0.87 of the vaporizer setting. Increasing the fresh gas flow to 2.0 L min-1 increased the end-tidal value by 0.05. CONCLUSION: There is a significant difference between the inspired and end-tidal concentrations of desflurane when fresh gas inflows were 1.0 and 2.0 L min-1, but not for the ratio of inspired/end-tidal.     

Effect of desflurane/remifentanil anaesthesia on glucose metabolism during surgery: a comparison with desflurane/epidural anaesthesia

BACKGROUND: The aim of this study was to investigate the effect of general anaesthesia combined with remifentanil or epidural blockade on glucose metabolism during surgery. METHODS: We randomly assigned patients undergoing elective colorectal surgery to receive either desflurane anaesthesia supplemented with intravenous remifentanil (n = 7) or desflurane anaesthesia supplemented with epidural bupivacaine (n = 7). Plasma concentrations of glucose, lactate, free fatty acids (FFA), insulin, glucagon and cortisol were measured before and after 2 h of surgery. Pre- and intraoperative whole body glucose production and glucose clearance, an indicator of glucose uptake, were determined by an isotope dilution technique using [6,6-2H2]glucose. RESULTS: In both groups intraoperative glucose production ( P< 0.05) and uptake ( P< 0.05) decreased. Plasma glucose concentrations ( P< 0.05) increased during surgery but did not exceed the normal range (remifentanil group: 5.7 +/- 0.7 mmol l-1, epidural group: 5.8 +/- 0.4 mmol l-1). The plasma concentrations of lactate, FFA, insulin and glucagon remained unchanged during the operation. The plasma cortisol concentration in both groups increased intraoperatively (P< 0.05). CONCLUSION: Both desflurane/remifentanil and desflurane/epidural anaesthesia decrease the intraoperative rate of whole body glucose production, thereby attenuating the hyperglycaemic response to colorectal surgery.     

Waste gas exposure during desflurane and isoflurane anaesthesia

Background : Currently, there are no data available concerning the occupational exposure to desflurane during general anaesthesia. This prospective, randomized study reports on occupational exposure to desflurane, compared to isoflurane, in a modern operation theatre (OT).
Methods : The study was performed in an OT equipped with a modern air-conditioning system and with a low-leakage anaesthesia machine connected to a central scavenging system. Trace concentrations of the anaesthetics were measured continuously by means of a photoacoustic infrared spectrometer during general anaesthesia in 30 patients undergoing eye surgery. Values were obtained within the breathing zone of the anaesthetist, the surgeon, the auxiliary nurse and at the mouth of the patient.
Results : Desflurane and isoflurane were administered with median (range) endtidal concentrations of 4.7 (3.8–10.3) vol% and 0.9 (0.6–1.4) vol%, respectively. The personnel-related median values of the average trace concentrations of desflurane and isoflurane were 0.5 (0.01–7.5) ppm and 0.2 (0.01–1.6) ppm, respectively.
Conclusions : Occupational exposure to desflurane is low in the environment of a modern OT, even though it has to be administered in approximately 5-fold higher concentrations compared to isoflurane.     

The effect of humidification and smoking habit on the incidence of adverse airway events during deepening of anaesthesia with desflurane

The effect of two levels of humidification on the incidence of adverse airway events was studied in 58 adult female patients during deepening of anaesthesia using up to 12% desflurane. Humidification was provided by a breathing system filter with either low moisture-conserving performance (17.2 mg x l(-1) at 0.5 1 tidal volume, Group L) or high moisture-conserving performance (33.5 mg x l(-1) at 0.5 1 tidal volume, Group H). Forty-eight per cent of patients smoked and there were more smokers in Group L than in Group H. Adverse airway events consisted of coughing and laryngospasm. For coughing, the dominant explanator was smoking. When both humidity and age were included in the analysis, there was a significant smoking-humidity interaction (p < 0.05), such that high humidity decreased the incidence of coughing in nonsmokers but not in smokers. The incidence of laryngospasm was significantly lower in Group H than in Group L (p < 0.05). We conclude that when patients inspire high concentrations of desflurane during induction of anaesthesia, increasing humidification to the levels achieved in this study decreases the incidence of coughing among nonsmokers and of laryngospasm in both smokers and nonsmokers.     

Midlatency auditory evoked potentials during anaesthesia with increasing endexpiratory concentrations of desflurane

Background. Under general anaesthesia with the volatile anaesthetics halothane, enflurane and isoflurane, midlatency auditory evoked potentials (MLAEP) are suppressed dose-dependently. Therefore, MLAEP have been used to measure depth of anaesthesia and to indicate intraoperative awareness. Desflurane is a new volatile anaesthetic and its effects on MLAEP have not been studied previously.
Methods. We have studied MLAEP during general anaesthesia with increasing endexpiratory concentrations of desflurane in 12 patients scheduled for elective gynaecological surgery. Auditory evoked potentials were recorded in the awake state and during anaesthesia with endexpiratory steady state concentrations of 1.5, 3.0, 4.5 and 6.0 vol %, of desflurane on vertex (positive) and mastoids on both sides (negative). Latencies of the peaks V, Na, Pa, Nb, Pl (ms) and amplitudes Na/Pa, Pa/Nb and Nb/Pl (μV) were measured.
Results. In the awake state, MLAEP had high peak-to-peak amplitudes and a periodic waveform. During general anaesthesia with increasing endexpiratory concentration of desflurane, the latency of the brainstem response V increased only slightly. In contrast, MLAEP showed a marked dose-dependent and statistically significant increase in latencies of Na, Pa, Nb and Pl and decrease in amplitudes of Na/Pa, Pa/Nb and Nb/Pl. Under 6.0 vol % of desflurane MLAEP were severely attenuated or even abolished.
Conclusion. Based on these observations, endexpiratory concentrations of ≥4.5 vol % desflurane should suppress awareness phenomena such as auditory perceptions during anaesthesia.     

ED50 of desflurane for laryngeal mask airway removal in anaesthetised adults

Previous estimates for the end‐tidal concentration of desflurane that allows removal of the laryngeal mask airway in 50% of anaesthetised adults (ED50) have ranged from 2.1% to 5.3%. To assess which value is correct, we studied 32 female patients (aged 30–50 years) undergoing intracavity caesium implants for cervical carcinoma under general anaesthesia. Anaesthesia was induced with propofol 2–3 mg.kg^?1 and maintained with desflurane in a 50% nitrous oxide‐oxygen mixture. At the end of surgery, a predetermined target end‐tidal desflurane concentration (starting at 4%) was maintained for 10 min using Dixon’s up‐down method and the laryngeal mask airway was removed. The target end‐tidal concentration in the next patient was increased or decreased by 0.5% depending upon the response of the previous patient. Removal of the laryngeal mask airway without coughing, clenching, biting, movement or any adverse airway event during or within 1 min after removal was considered to be successful. We found that the laryngeal mask airway can be successfully removed in 50% (ED50) and 95% (ED95) of the anaesthetised adults at end‐tidal desflurane concentrations of 2.4% (95% CI 1.3–2.9) and 3.8% (3.1–9.6), respectively.