Intracranial pressure during induction of anaesthesia and tracheal intubation with etomidate-induced EEG burst suppression

This study was designed to determine if induction of anaesthesia with etomidate titrated to an early EEG burst suppression pattern would produce minimal changes in cerebral perfusion pressure, and prevent increases in intracranial pressure (ICP) associated with tracheal intubation. Eight patients, 18-71 yr, with intracranial space-occupying lesions, were studied. In each patient ICP was monitored via a lateral ventriculostomy catheter placed preoperatively. In the operating room, an ECG, a radial arterial line, and a two-channel computerized EEG were placed. Control (awake) measurements of MAP (mmHg), ICP (mmHg), CPP (mmHg), heart rate (HR-bpm), EEG power (picowatts-pW), and spectral edge frequency (SEF, Hz) were obtained. Anaesthesia was induced with etomidate, 0.2 mg.kg-1 iv, followed immediately by an etomidate infusion, 20 mg.min-1, iv, and vecuronium 0.2 mg.kg-1 iv. When early burst suppression was achieved, the etomidate infusion was stopped and tracheal intubation performed. The etomidate dose (bolus plus infusion) required to reach burst suppression was 1.28 +/- 0.11 mg.kg-1. Compared with awake control values (mean +/- SE), the period from induction to burst suppression was associated with a 50% decrease in ICP (22 +/- 1 vs 11 +/- 1 mmHg, P less than 0.01), but there were no changes in MAP, CPP, or HR. The decrease in ICP was maintained during the first 30 sec and the following 60 sec after intubation as MAP and HR remained unchanged. Our results suggest that when etomidate was administered to early burst suppression pattern on EEG, minimal changes in CPP occurred during induction of anaesthesia and a marked reduction in ICP was maintained following tracheal intubation.     

The effect of intravenous lidocaine on QT changes during tracheal intubation

Laryngoscopy and tracheal intubation may provoke changes of cardiac repolarisation. The aim of this study was to assess the effect of intravenous lidocaine on the ECG changes induced by laryngoscopy and tracheal intubation. Forty-three female patients were randomly allocated to receive lidocaine (1.5 mg.kg⁻¹) or placebo immediately after induction of anaesthesia and changes in the ECG and arterial blood pressure were recorded. Correction of QT interval was calculated using Bazett's formula (QTcb), Fridericia's correction (QTcf), and Framingham formula (QTcF). Transmural dispersion of repolarisation (TDR) was determined as Tpeak-Tend time. There were no changes in the QTc value in the lidocaine group. In the placebo group, significant increases in QTcb, QTcf and QTcF values were observed after intubation compared to either control measurements or to comparative measurements in the lidocaine group. There were no significant differences in TDR either between or within the groups. Lidocaine diminishes prolongation of QTc, induced by tracheal intubation but there is no effect of intubation on TDR.     

Failed tracheal intubation during obstetric general anaesthesia: a literature review

We reviewed the literature on obstetric failed tracheal intubation from 1970 onwards. The incidence remained unchanged over the period at 2.6 (95% CI 2.0 to 3.2) per 1000 anaesthetics (1 in 390) for obstetric general anaesthesia and 2.3 (95% CI 1.7 to 2.9) per 1000 general anaesthetics (1 in 443) for caesarean section. Maternal mortality from failed intubation was 2.3 (95% CI 0.3 to 8.2) per 100 000 general anaesthetics for caesarean section (one death per 90 failed intubations). Maternal deaths occurred from aspiration or hypoxaemia secondary to airway obstruction or oesophageal intubation. There were 3.4 (95% CI 0.7 to 9.9) front-of-neck airway access procedures (surgical airway) per 100 000 general anaesthetics for caesarean section (one procedure per 60 failed intubations), usually carried out as a late rescue attempt with poor maternal outcomes. Before the late 1990s, most cases were awakened after failed intubation; since the late 1990s, general anaesthesia has been continued in the majority of cases. When general anaesthesia was continued, a laryngeal mask was usually used but with a trend towards use of a second-generation supraglottic airway device. A prospective study of obstetric general anaesthesia found that transient maternal hypoxaemia occurred in over two-thirds of cases of failed intubation, usually without sequelae. Pulmonary aspiration occurred in 8% but the rate of maternal intensive care unit admission after failed intubation was the same as that after uneventful general anaesthesia. Poor neonatal outcomes were often associated with preoperative fetal compromise, although failed intubation and lowest maternal oxygen saturation were independent predictors of neonatal intensive care unit admission.     

Dose-dependent suppression of the neutrophil respiratory burst by lidocaine

Background : Oxygen radical production is thought to be fundamental to the pathogenesis of post-ischaemic reperfusion injury which is routinely managed with lidocaine. Attention has, therefore, focused on the suppression of the neutrophil respiratory burst with a therapeutic endpoint. The widest application of lidocaine remains in local analgesia.
Methods : A standard chemiluminescence technique was used to assess the human neutrophil leukocyte response to increasing doses of lidocaine in the presence or absence of particulate hydroxyapatite.
Results : No reduction of oxygen radical production was seen at the drug concentration of 1 mg/ml. A clear, concentration-dependent inhibition was seen at 2 mg/ml, 3 mg/ml, 4 mg/ml and 8 mg/ml concentrations. These drug concentrations may be reached at or near the site of injection in local anaesthetic use.
Conclusion : Lidocaine showed profound anti-inflammatory action in this experimental system. Controlled studies in the clinical setting would identify the optimal analgesic and anti-inflammatory dosage, whilst preserving host defence without compromising tissue repair.     

Heart rate and arterial pressure changes during fibreoptic tracheal intubation under general anaesthesia

The cardiovascular responses to fibreoptic orotracheal intubation under general anaesthesia were compared with those in a control group in whom tracheal intubation was effected with a Macintosh laryngoscope. The patients received a standard anaesthetic and were allocated randomly to either group immediately before intubation. Fibreoptic intubation took significantly longer to perform. There were significant increases in heart rate and arterial pressure in both groups compared with pre-induction values. The tachycardia in the fibreoptic group was significantly greater than that in the control group during the second minute after intubation, and the increase in systolic pressure was sustained for a longer period in the fibreoptic group. The maximum increases in systolic and diastolic pressures above pre-intubation values were significantly greater in the fibreoptic group. The cardiovascular responses associated with fibreoptic intubation under general anaesthesia appear to be more severe than those which follow intubation effected with a Macintosh laryngoscope.     

The effect of tracheal intubation and surgical stimulation on median nerve somatosensory evoked potentials during anaesthesia

This study was designed to determine whether alterations in the median nerve somatosensory evoked potentials occur during the stimuli of tracheal intubation and skin incision. Twenty-two patients scheduled for elective surgery and who required tracheal intubation were studied. Median nerve somatosensory evoked potentials were recorded, analysed and stored approximately every 40 seconds. Anaesthesia was induced with thiopentone and vecuronium used for neuromuscular blockade; the trachea was intubated 2 minutes after induction. Fentanyl 1.5 micrograms/kg was administered subsequently. Evoked potential monitoring was continued until at least 2 minutes after surgical incision. Induction of anaesthesia was associated with an increase in evoked potential latency of 0.8 msec and reduction in amplitude of 1.7 microV. Small, statistically insignificant changes occurred between induction of anaesthesia and tracheal intubation. Surgical incision was accompanied by a statistically significant mean decrease in evoked potential latency of 0.5 msec and a statistically significant increase in evoked potential amplitude of 0.6 microV. The fact that surgical stimulation produced an activating effect on evoked potentials suggests that they may be used as a measure of the neurophysiological effects of anaesthesia.     

听觉诱发电位指数用于诱导插管期间麻醉深度监测的临床评价

目的 观察听觉诱发电位指数在全麻诱导插管期间的变化，评价其用于临床麻醉深度监测的有效性。方法 ASAⅠ-Ⅱ级，全麻下行择期手术的病人40例。依次给予咪唑安定0.06mg/kg，芬太尼4μg/kg，丙泊酚0.5mg/kg，维库溴铵0.1mg/kg诱导后，行气管插管，观察诱导前，气管插管前，插管时及插管后1-5分钟等8个时点的AEPI，BIS，HRV，SEF及MAP，HR和RPP的变化。结果 诱导后各观察指标较诱导前的基础值均有所降低，插管后BIS，HRV，SEF等指标均在5分钟内回复至插管前水平，AEP在第3分钟即可回复至插管前水平，插管前后几项观察指标变化趋势相一致。结论 AEPI，BIS，HRV，SEF均能有效反映插管的应激反应。AEPI较其他几项指标更为迅速灵敏，可作为麻醉深度监测的有效指标。     

Isoflurane waste gas exposure during general anaesthesia: the laryngeal mask compared with tracheal intubation

We have compared exposure to isoflurane while using the laryngeal mask airway (LMA) during anaesthesia under positive pressure ventilation with exposure while using tracheal intubation. Trace concentrations of isoflurane were measured directly using a highly sensitive photoacoustic infrared spectrometer (Bruel and Kjaer 1302, Denmark) during general anaesthesia in 20 eye surgery procedures. Measurements were made at six locations (three personnel-related, three leakage- related) in the operating theatre. Despite some high isoflurane values (greater than 2000 ppm at one leakage-related measurement point) all measured values at the personnel-related points were low (the majority were less than isoflurane 2 ppm). In the LMA group, mean trace concentrations were slightly higher than in the tracheal tube (ET) group. Mean exposure to isoflurane, expressed as median (range) related to anaesthetic administration, was highest for the auxiliary nurse (0.64 (0.22-26.89) ppm for the LMA compared with 0.31 (0.02-1.07) ppm for the tracheal tube), followed by the anaesthetist (0.50 (0.28-2.28) ppm for the LMA compared with 0.35 (0.02-0.73) ppm for the tracheal tube) and the surgeon (0.36 (0.20-3.93) ppm for the LMA compared with 0.29 (0.01-0.50) ppm for the tracheal tube). We conclude that the use of the LMA in patients undergoing ventilation is not associated necessarily with high concentrations of isoflurane in a modern working environment.      

The optimal bolus dose of alfentanil for tracheal intubation during sevoflurane induction without neuromuscular blockade in day-case anaesthesia

Background: The purpose of this study was to determine the optimal bolus dose of alfentanil required to provide successful intubating conditions following inhalation induction of anaesthesia using 5% sevoflurane and 60% nitrous oxide without neuromuscular blockade in adult day-case anaesthesia.
Methods: Twenty-four adults, aged 18–60 years, undergoing general anaesthesia for short ambulatory surgery were enroled into the study. After vital capacity induction, with sevoflurane 5% and 60% nitrous oxide in oxygen, pre-determined dose of alfentanil was injected over 30 s. The dose of alfentanil was determined by modified Dixon's up-and-down method (2 μg/kg as a step size). Ninety seconds after the end of bolus administration of alfentanil, the trachea was intubated. Systolic blood pressure, heart rate and SpO₂ were recorded at anaesthetic induction, before, 1 min and 3 min after intubation.
Results: The bolus dose of alfentanil for successful tracheal intubation was 10.7±2.1 μg/kg in 50% of patients during inhalation induction. From probit analysis, 50% effective dose (ED₅₀) and ED₉₅ values (95% confidence limits) of alfentanil were 10.7 μg/kg (8.0–12.9 μg/kg) and 14.9 μg/kg (12.9–31.1 μg/kg), respectively.
Conclusions: Using the modified Dixon's up-and-down method, the bolus dose of alfentanil for successful tracheal intubation was 10.7±2.1 μg/kg in 50% of adult patients during inhalation induction using 5% sevoflurane and 60% nitrous oxide in oxygen without neuromuscular blocking agent in day-case anaesthesia.     

曲吗多静脉诱导时对心血管反应的影响

采用经食管无创伤超声血流测定仪监测４５例择期手术病例，随机分三组：巨组，安定０．４ｍｇ／ｋｇ； Ⅱ组，咪唑安定０．３ｍｍ／ｋｍ；Ⅲ组，依托咪酯０． ３ｍｍ／ｋｍ。三组病例均静注曲吗多４ｍｇ／ｋｇ、阿曲可林０．５ｍｇ／ ｋｇ，观察插管前、插管时、插管后心排血量（ＣＯ）、心脏指数（ＣＩ）、周围血管阻力（ＳＶＲ）、平均动脉压（ＭＡＰ）、心率（ＨＲ）的变化。结果表明用曲吗多后 ＨＲ减慢， Ⅰ、Ⅱ组 ＣＯ、ＣＩ、ＭＡＰ下降，Ⅲ组 ＭＡＰ、ＣＯ、ＣＩ、无明显变化，插管时，插管后ＣＯ、ＣＩ、ＭＡＰ、ＨＲ无显著变化（Ｐ＞０．０５）。提示曲吗多有预防插管时的心血管副反应作用。     

Electroencephalographic arousal response during tracheal intubation and laryngeal mask airway insertion after induction of anaesthesia with propofol

Laryngoscopy and tracheal intubation, or insertion of a laryngeal mask airway may lead to an arousal response on the electroencephalogram. We studied whether more intense stimulation (laryngoscopy and tracheal intubation) causes a greater arousal response than less intense stimulation (laryngeal mask airway insertion). Thirty-four patients (ASA I-II) were anaesthetised with propofol 3 mg.kg-1, followed by vecuronium 0.15 mg.kg-1 and a propofol infusion of 10 mg.kg-1.h-1. Three minutes after induction of anaesthesia, either laryngoscopy and tracheal intubation (n = 18), or laryngeal mask airway insertion (n = 16) was performed. Laryngoscopy and tracheal intubation caused a significantly greater increase in blood pressure (but not heart rate) than laryngeal mask airway insertion (p < 0.05). Electroencephalogram responses were not different. More intense stimulation does not cause a greater arousal response during propofol anaesthesia.     

Bolus dose remifentanil for control of haemodynamic response to tracheal intubation during rapid sequence induction of anaesthesia

The effect of three bolus doses of remifentanil on the pressor response to laryngoscopy and tracheal intubation during rapid sequence induction of anaesthesia was assessed in a randomized, double-blind, placebo- controlled study in four groups of 20 patients each. After preoxygenation, anaesthesia was induced with thiopental 5-7 mg kg-1 followed immediately by saline (placebo) or remifentanil 0.5, 1.0 or 1.25 micrograms kg-1 given as a bolus over 30 s. Cricoid pressure was applied just after loss of consciousness. Succinylcholine 1 mg kg-1 was given for neuromuscular block. Laryngoscopy and tracheal intubation were performed 1 min later. Arterial pressure and heart rate were recorded at intervals until 5 min after intubation. Remifentanil 0.5 microgram kg-1 was ineffective in controlling the increase in heart rate and arterial pressure after intubation but the 1.0 and 1.25 micrograms kg-1 doses were effective in controlling the response. The use of the 1.25 micrograms kg-1 dose was however, associated with a decrease in systolic arterial pressure to less than 90 mm Hg in seven of 20 patients.      

Takotsubo syndrome during induction of general anaesthesia

A 77-year-old female was admitted in our hospital for uterine prolapse surgery. She developed ventricular tachycardia during induction of general anaesthesia and after initial symptomatic measures, she was transferred to the coronary care unit. Heart failure persisted and electrocardiographic changes mimicking acute myocardial infarction appeared. Coronary angiography was normal and left ventriculography revealed akinesis of the apical region of the left ventricle and apical ballooning during systole, with relative sparing of the base of the heart. Complete recovery of left ventricular function occurred 8 days after the initial onset of symptoms. A diagnosis of Takotsubo syndrome was made on the basis of consistent clinical and laboratory findings, typical echocardiography and angiography findings, and reversible course. This case emphasises the importance of being aware of uncommon causes of cardiac dysfunction in stressful situations, especially during induction of general anaesthesia.