Diagnostic performance of qualitative ultrasound assessment for the interpretation of point-of-care gastric ultrasound to detect high gastric fluid volume: A prospective randomized crossover study.

STUDY OBJECTIVE: This study aimed to assess whether elevating the head of the bed to 45° was associated with sensitivity >90% of the qualitative ultrasound assessment for the diagnosis of gastric fluid volume > 1.5 ml.kg-1. We also assessed the performance of qualitative assessment, composite ultrasound scale, and clinical algorithm, for the diagnosis of fluid volume > 1.5 ml.kg-1 according to whether the head of the bed was elevated to 45° or not. DESIGN: Prospective randomized observer-blind crossover trial. SETTING: Hospices Civils de Lyon, France. PATIENT: Healthy adult volunteers. INTERVENTIONS: Two separate study sessions in fasting volunteers: with and without head-of-bed elevation to 45°, in a randomized order. Each session consisted of three tests, each corresponding to a randomized and different volume of water (either 0, 50, 100, 150 or 200 ml); the same volumes were used in both sessions and in a randomized order. Gastric ultrasounds were performed three minutes after the ingestion of water by an investigator blinded to the volume ingested. MEASUREMENTS: Diagnostic performance of each approach for the diagnosis of gastric fluid volume > 1.5 ml.kg-1. MAIN RESULTS: Twenty volunteers were included, and 120 measurements were analyzed. The sensitivity of the qualitative assessment for the diagnosis of gastric fluid volume > 1.5 ml.kg-1 with and without head-of-bed elevation was 91% (95%CI: 75-98) and 75% (95%CI: 57-89), respectively. The clinical algorithm with head-of-bed elevation had significantly better sensitivity than the qualitative assessment with no head-of-bed elevation; there was no significant difference for other comparisons. CONCLUSIONS: The results suggest that qualitative examination of gastric antrum in the supine position with head-of-bed elevation to 45° can discriminate between low and high gastric fluid volume with high sensitivity, while neither the composite ultrasound scale nor the clinical algorithm improved the diagnostic performance of gastric ultrasound for the diagnosis of gastric fluid volume > 1.5 ml.kg-1.

Technics to put on and remove personal protective equipment before surgical or obstetrical procedure in suspected or infected COVID-19 patients (with video).

Coronavirus pandemic is widely changing our professional daily practice and preventive measures must be taken and taught. Before any planned gynaecological or obstetric surgery, specific technics to put on and safely remove personal protective equipment should be implemented in order to avoid any contamination for both patients and healthcare workers.

Ventilation in pediatric anesthesia: A French multicenter prospective observational study (PEDIAVENT).

INTRODUCTION: Protective ventilation is now a standard of care in adults. However, management of ventilation is heterogeneous in children and little is known regarding the mechanical ventilation parameters actually used during pediatric anesthesia. AIM: The aim of the study was to assess current ventilatory practices during pediatric anesthesia in France and to compare them with pediatric experts' statements, with a specific focus on tidal volume. PATIENTS AND METHODS: We conducted a prospective multicenter observational study, regarding the ventilatory management and the mechanical ventilation parameters, over two days (21 and 22 June 2017) in 29 pediatric centers in France. All children undergoing general anesthesia during these 2 days were eligible; those who required extracorporeal circulation or one-lung ventilation were excluded. RESULTS: A total of 701 children were included; median [IQR] age was 60 [24-120] months. Among the patients in whom controlled ventilation was used, 254/515 (49.3%) had an expired tidal volume >8 mL/kg and 44 children (8.8%) an expired tidal volume ≥10 mL/kg. Lower weight and use of a supraglottic airway device were significantly associated with provision of a tidal volume ≥10 mL/kg (odds ratio 0.94, 95% confidence interval [0.92; 0.97], P < .001 and 2.28 [1.20; 4.31], P = .012, respectively). The positive end-expiratory pressure was set at a median [IQR] of 4 [3-5] cmH2 O; it was <3 cmH2 O in 15.7% of children and not used in 56/499 (9.3%). Among intubated children, 57 (18.3%) received a tidal volume < 10 mL/kg with a positive end-expiratory pressure ≥3 cmH2 O in association with recruitment maneuvers. CONCLUSIONS: Ventilatory practices in children were heterogenous, and a large proportion of children were not ventilated as it is currently recommended by some experts.

Does a two-minute mini-fluid challenge predict fluid responsiveness in pediatric patients under general anesthesia?

BACKGROUND: Very little evidence for predictive markers of fluid responsiveness has been reported in children as compared to adults. The impact of hypovolemia or hypervolemia on morbidity has driven interest in the fluid challenge titration strategy. AIM: The objective of this study was to explore the ability of a 3 mL kg-1 mini-fluid challenge over 2 minutes to predict fluid responsiveness in children under controlled ventilation. METHODS: Children scheduled for surgery under general anesthesia were included and received a fluid challenge of 15 mL kg-1 of crystalloid prior to incision administered over 10 minutes in two steps: 3 mL kg-1 over 2 minutes then 12 mL kg-1 over 8 minutes. Fluid responsiveness was defined as a change of ≥10% in cardiac output estimated by left ventricular outflow tract velocity time integral (VTI) as measured by transthoracic ultrasound before and after the fluid challenge of 15 mL kg-1 . RESULTS: Of the 55 patients included in the analysis, 43 were fluid responders. The increase in the VTI after the mini-fluid challenge (ΔVTIminiFC ) predicted fluid responsiveness with an area under the receiver operating characteristic curve of 0.77; 95% CI (0.63-0.87), P = .004. Considering the least significant change which was 7.9%; 95% CI (6-10), the threshold was 8% with a sensitivity of 53%; 95% CI (38-68); and a specificity of 77%; 95% CI (54-100). CONCLUSION: ΔVTIminiFC weakly predicted the effects of a fluid challenge of 15 mL kg-1 of crystalloid in anesthetized children under controlled mechanical ventilation.

Simulation of difficult airway management for residents: prospective comparative study / Simulação de manejo de via aérea difícil para residentes: estudo comparativo prospectivo

Abstract Background and objectives Procedural simulation training for difficult airway management offers acquisition opportunities. The hypothesis was that 3 hours of procedural simulation training for difficult airway management improves: acquisition, behavior, and patient outcomes as reported 6 months later. Methods This prospective comparative study took place in two medical universities. Second-year residents of anesthesiology and intensive care from one region participated in 3 h procedural simulation (intervention group). No intervention was scheduled for their peers from the other region (control). Prior to simulation and 6 months later, residents filled-out the same self-assessment form collecting experience with different devices. The control group filled-out the same forms simultaneously. The primary endpoint was the frequency of use of each difficult airway management device within groups at 6 months. Secondary endpoints included modifications of knowledge, skills, and patient outcomes with each device at 6 months. Intervention cost assessment was provided. Results 44 residents were included in the intervention group and 16 in the control group. No significant difference was observed for the primary endpoint. In the intervention group, improvement of knowledge and skills was observed at 6 months for each device, and improvement of patient outcomes was observed with the use of malleable intubation stylet and Eschmann introducer. No such improvement was observed in the control group. Estimated intervention cost was 406€ per resident. Conclusions A 3 h procedural simulation training for difficult airway management did not improve the frequency of use of devices at 6 months by residents. However, other positive effects suggest exploring the best ratio of time/acquisition efficiency with difficult airway management simulation. ClinicalTrials.gov Identifier NCT02470195.

Resumo Justificativa e objetivos O treinamento em simulação para o manejo de via aérea difícil oferece oportunidades de aprendizagem. A hipótese foi que um treinamento em simulação de procedimentos de três horas, para o manejo de via aérea difícil, melhoraria o aprendizado, o comportamento e os resultados dos pacientes, conforme relatado seis meses após o treinamento. Métodos Este estudo comparativo prospectivo foi realizado em duas universidades médicas. Residentes do segundo ano de anestesiologia e terapia intensiva de uma região participaram de um curso de três horas em simulação de procedimentos (grupo intervenção). Nenhuma intervenção foi programada para seus pares da outra região (grupo controle). Antes da simulação e seis meses após, os residentes preencheram a mesma ficha de autoavaliação sobre sua experiência com diferentes dispositivos. O grupo controle preencheu os mesmos formulários simultaneamente. O desfecho primário foi a frequência de uso de cada dispositivo para o manejo de via aérea difícil dentro dos grupos aos seis meses. Os pontos de corte secundários incluíram modificações em relação ao conhecimento, às habilidades e aos resultados dos pacientes com cada dispositivo aos seis meses. A avaliação do custo da intervenção foi registrada. Resultados Foram incluídos no grupo intervenção 44 residentes e 16 no grupo controle. Nenhuma diferença significativa foi observada para o ponto de corte primário. No grupo intervenção, a melhoria do conhecimento e das habilidades foi observada aos seis meses para cada dispositivo e a melhoria dos desfechos dos pacientes foi analisada com o uso de estilete maleável e do introdutor de Eschmann para intubação. Nenhuma melhoria foi observada no grupo controle. O custo da intervenção estimado foi de 406€ por residente. Conclusões Um treinamento simulado de três horas para o manejo de via aérea difícil não melhorou a frequência do uso de dispositivos pelos residentes aos seis meses. No entanto, outros efeitos positivos sugerem a exploração da melhor relação tempo/eficiência de aquisição de conhecimento com a simulação do manejo de via aérea difícil. ClinicalTrials.gov Identifier NCT02470195.

Ultrasound assessment of the prevalence of increased gastric contents and volume in elective pediatric patients: A prospective cohort study.

BACKGROUND: Though pulmonary aspiration of gastric contents occurs mainly in the setting of emergency surgery, it may also occur in children scheduled for elective surgery without any obvious clinical risk factor. Increased gastric content volume is one the predisposing factors for pulmonary aspiration that could affect such children and may be identified using ultrasound examination of the gastric antrum. AIMS: We aimed to assess the prevalence of "at-risk stomach" defined by ultrasound visualization of any solid content in the antrum and/or by calculated gastric fluid volume > 1.25 mL/kg, in children scheduled for elective surgery. METHODS: Children scheduled for elective surgery were consecutively included into this prospective cohort study. Preoperative ultrasound examination of the antrum was performed in both the supine and the right lateral decubitus positions. Gastric fluid content was assessed using a 0-2 qualitative grading scale. The antral cross-sectional area was also measured in both the supine and the right lateral decubitus positions, allowing the calculation of the gastric fluid volume according to a formula previously described. RESULTS: We analyzed 200 elective children. Median duration of fasting was 4 hours for liquids and >13 hours for solids. None of the children included in this study had evidence of solid content. Six (3%) children had a Grade 2 antrum (fluid content seen in both the supine and the right lateral decubitus positions). Two children had a gastric fluid volume >1.25 mL/kg. The prevalence of "at-risk stomach" was 1% (95% confidence interval: 0.2%-3.9%). CONCLUSION: According to our results, only 1% of elective children had potentially increased risk for pulmonary aspiration. Further studies should be performed in order to define the target population of elective children for which ultrasound assessment of gastric content should be performed prior to general anesthesia.

Suprasternal notch echocardiography: a potential alternative for the measurement of respiratory variation in aortic blood flow peak velocity in mechanically ventilated children.

We conducted a prospective, observational study to investigate the relationship between the respiratory variation in aortic blood flow peak velocity (ΔVPeak) measured by echocardiography in the proximal ascending aorta from the suprasternal notch window and the ΔVPeak measured at the level of the aortic annulus from the classical apical five-chamber view. We studied children aged from 1 to 10 years referred for surgery under general anesthesia with positive pressure ventilation, after induction of general anesthesia. Twenty-two children (mean age = 5 ± 3 years) were recruited. There was a significant relationship between the ΔVPeak recorded via the suprasternal notch view and the ΔVPeak recorded via the apical five-chamber view (r = 0.62 [95% confidence interval 0.25-0.84], P = 0.003). The ΔVPeak measured using the suprasternal notch route could be considered to predict fluid responsiveness in children under mechanical ventilation, notably when the access to the chest wall is limited during surgery.

Predictive factors of maternal hypothermia during Cesarean delivery: a prospective cohort study.

PURPOSE: Although perioperative hypothermia may increase maternal morbidity, active warming is infrequently performed to maintain normothermia during Cesarean delivery (CD). The aim of this prospective observational study was to determine the factors associated with maternal hypothermia in this setting. METHODS: Women scheduled for elective or emergency CD were consecutively included in this study from November 2014 to October 2015. Maternal temperature was measured using an infrared tympanic thermometer on the patient's arrival in the operating room, at skin incision, and at the end of skin suture. Maternal hypothermia was defined by tympanic temperature < 36°C at the end of skin suture. Univariate analysis was performed, followed by multivariate logistic regression analysis, in order to determine the factors associated with maternal hypothermia at the end of the surgery. RESULTS: Three hundred fifty-nine women were included and analyzed during this study. The incidence of hypothermia was 23% (95% confidence interval, 18 to 27) among the total population included. According to multivariate analysis, obesity, oxytocin augmentation of labour, and use of active forced-air warming were associated with a decreased risk of maternal hypothermia, while maternal temperature < 37.1°C on arrival in the operating room, maternal temperature < 36.6°C at skin incision, and an infused volume of fluids > 650 mL were significantly associated with maternal hypothermia. Both goodness of fit and predictive value of multivariate analysis were high. CONCLUSION: Several predictive factors for maternal hypothermia during CD were identified. These factors should be taken into account to help prevent maternal hypothermia during CD.

Intravenous Amisulpride for the Prevention of Postoperative Nausea and Vomiting: Two Concurrent, Randomized, Double-blind, Placebo-controlled Trials.

BACKGROUND: Two essentially identical, randomized, double-blind, placebo-controlled, parallel-group phase III studies evaluated the efficacy of intravenous amisulpride, a dopamine D2/D3 antagonist, in the prevention of postoperative nausea and vomiting in adult surgical patients. METHODS: Adult inpatients undergoing elective surgery during general anesthesia and having at least two of the four Apfel risk factors for postoperative nausea and vomiting were enrolled at 9 U.S. and 10 European sites. A single 5-mg dose of amisulpride or matching placebo was given at induction of anesthesia. The primary endpoint was complete response, defined as no vomiting/retching and no use of antiemetic rescue medication in the 24-h postoperative period. Nausea incidence was a secondary endpoint. RESULTS: Across the two studies, 689 patients were randomized and dosed with study medication, of whom 626 were evaluable per protocol. In the U.S. study, 46.9% (95% CI, 39.0 to 54.9) of patients achieved complete response in the amisulpride group compared to 33.8% (95% CI, 26.2 to 42.0) in the placebo group (P = 0.026). In the European study, complete response rates were 57.4% (95% CI, 49.2 to 65.3) for amisulpride and 46.6% (95% CI, 38.8 to 54.6) for placebo (P = 0.070). Nausea occurred less often in patients who received amisulpride than those who received placebo. There was no clinically significant difference in the safety profile of amisulpride and placebo; in particular, there were no differences in terms of QT prolongation, extrapyramidal side effects, or sedation. CONCLUSIONS: One of the two trials demonstrated superiority, while pooling both in a post hoc change to the plan of analysis supported the hypothesis that amisulpride was safe and superior to placebo in reducing the incidence of postoperative nausea and vomiting in a population of adult inpatients at moderate to high risk of postoperative nausea and vomiting.

Fortuitous diagnosis of "full stomach" made by using ultrasonographic examination of the antrum in two elective patients.

We report two cases of patients presenting for elective surgery, in whom significant gastric contents were identified by performing fortuitous ultrasound examination of their antral area. The first patient presented for a day-case surgery scheduled under regional anesthesia. With his consent, ultrasound examination of the antral area was by chance performed within the context of training for this technique, showing significant solid contents in the stomach. The patient admitted that he had not respected preoperative fasting. The second patient was scheduled for an elective ophthalmologic surgery. Ultrasound examination of the antrum showed that the antrum was dilated, with significant solid and liquid gastric contents. This case may be related to a strongly delayed gastric emptying. These two cases demonstrate that some elective patients may present with significant gastric contents exposing them to the risk of pulmonary aspiration in the case of general anesthesia.

Risk factors for intraoperative allogeneic blood transfusion during craniotomy for brain tumor removal in children.

BACKGROUND: Several clinical and surgical factors can influence the occurrence of allogeneic blood transfusion (ABT) during oncologic neurosurgery. OBJECTIVES: To identify the potential predictive factors of ABT during craniotomy for the removal of brain tumors in children and the potential impact of intraoperative ABT on early postoperative outcome. METHODS: A retrospective study was performed in all pediatric patients younger than 18 years who underwent craniotomy for brain tumor removal from December 2009 to December 2012 in our institution. Pre-, intra-, and postoperative data were collected from medical and stored electronic anesthesia records. The predictors of intraoperative ABT were determined using multivariate logistic regression. RESULTS: A total of 110 patients were included. Twenty-seven patients (25%) received intraoperative ABT with a volume of 16 ± 8 ml·kg(-1) . On multivariate analysis, an age <4 years, a duration of surgery >270 min, and a preoperative hemoglobin <12.2 g·dl(-1) were independently associated with the need for intraoperative ABT. We did not show any significant difference concerning postoperative early outcome and length of stay between the transfused and non-transfused patients except for the duration of postoperative mechanical ventilation that was significantly higher in the transfused group (P = 0.04). CONCLUSION: In children, craniotomy for brain tumor removal is at risk of intraoperative ABT. An age <4 years, a duration of surgery >270 min, and a preoperative hemoglobin <12.2 g·dl(-1) are the main factors associated with intraoperative ABT during this surgery.

Impact of sevoflurane anesthesia on brain oxygenation in children younger than 2 years.

OBJECTIVE/AIM: To assess the impact of sevoflurane and anesthesia-induced hypotension on brain oxygenation in children younger than 2 years. BACKGROUND: Inhalational induction with sevoflurane is the most commonly used technique in young children. However, the effect of sevoflurane on cerebral perfusion has been only studied in adults and children older than 1 year. The purpose of this study was to assess the impact of sevoflurane anesthesia on brain oxygenation in neonates and infants, using near-infrared spectroscopy. METHODS: Children younger than 2 years, ASA I or II, scheduled for abdominal or orthopedic surgery were included. Induction of anesthesia was started by sevoflurane 6% and maintained with an expired fraction of sevoflurane 3%. Mechanical ventilation was adjusted to maintain an endtidal CO2 around 39 mmHg. Brain oxygenation was assessed measuring regional cerebral saturation of oxygen (rSO2 c), measured by NIRS while awake and 15 min after induction, under anesthesia. Mean arterial pressure (MAP) variation was recorded. RESULTS: Hundred and ninety-five children were included. Anesthesia induced a significant decrease in MAP (-27%). rSO2 c increased significantly after induction (+18%). Using children age for subgroup analysis, we found that despite MAP reduction, rSO2 c increase was significant but smaller in children ≤ 6 months than in children >6 months (≤ 6 months: rSO2 c = +13%, >6 months: rSO2 c = +22%; P < 0.0001). Interindividual comparison showed that, during anesthesia at steady-state with comparable CMRO2, rSO2 c values were significantly higher when MAP was above 36 mmHg. And the higher the absolute MAP value during anesthesia was, the higher the rSO2 c was. We observed a rSO2 c variation ≤ 0 in 21 patients among the 195 studied, and the majority of these patients were younger than 6 months (n = 19). No increase or decrease of rSO2 c during anesthesia despite reduction of CMRO2 can be explained by a reduction of oxygen supply. Using the ROC curves, we determined that the threshold value of MAP under anesthesia, associated with rSO2 c variation ≤ 0%, was 39 mmHg in all the studied population (AUC: 0.90 ± 0.02; P < 0.001). In children younger than 6 months, this value of MAP was 33 mmHg, and 43 mmHg in children older than 6 months. CONCLUSION: Despite a significant decrease of MAP, 1 MAC of sevoflurane induced a significant increase in regional brain oxygenation. But subgroup analysis showed that MAP decrease had a greater impact on brain oxygenation, in children younger than 6 months. According to our results, MAP value during anesthesia should not go under 33 mmHg in children ≤6 months and 43 mmHg in children >6 months, as further changes in MAP, PaCO2 or hemoglobin during anesthesia may be poorly tolerated by the brain.

Impact of sevoflurane anesthesia on cerebral blood flow in children younger than 2 years.

OBJECTIVE/AIM: To assess the impact of sevoflurane and anesthesia-induced hypotension on cerebral blood flow (CBF) in children younger than 2 years. BACKGROUND: Inhalational induction with sevoflurane is the most commonly used technique in young children. However, the effect of sevoflurane on cerebral perfusion has been only studied in adults and children older than 1 year. The purpose of this study is to assess the impact of sevoflurane anesthesia on CBF in neonates and infants, using transcranial Doppler (TCD) sonography. METHODS: Children younger than 2 years, ASA I or II, for abdominal or orthopedic surgery were included. Induction of anesthesia was started by sevoflurane 6% and maintained with an expired fraction of sevoflurane 3%. Mechanical ventilation was controlled to maintain an end tidal CO(2) around 39 mmHg. CBF was assessed by measuring the velocities (systolic velocity SVmca, diastolic velocity DVmca and mean velocity MVmca) in the proximal segment of the middle cerebral artery (mca) in children awake and then 15 min after induction. Mean arterial pressure (MAP) variation was noted. RESULTS: One hundred and thirteen children were included. We observed a significant decrease in MAP (-30%). DVmca decreased and pulsatility index increased significantly after induction. Subgroup analysis according to age showed that in infants older than 6 months, despite a significant reduction in MAP, there was no change in CBF velocity (CBFV) as measured by TCD sonography, until MAP dropped below 40% of baseline. In infants younger than 6 months, a significant decrease in MAP was observed which was associated with a significant variation in CBFV. In this population, when CBFV start to decrease, MAP under sevoflurane anesthesia was 38 mmHg or -20% from baseline value. CONCLUSION: Our results are in favor of a reduction in CBF after induction with sevoflurane in children younger than 6 months. This population is more sensitive to MAP decrease than older children because of a lower limit of cerebral autoregulation, and this limit may be 38 mmHg with sevoflurane anesthesia.

Intravenous buspirone for the prevention of postoperative nausea and vomiting.

RATIONALE: Buspirone, a partial 5HT(1A) agonist and D2 and D3 antagonist, has shown promising antiemetic efficacy when given parenterally in animal models, but its efficacy for the prevention of postoperative nausea and vomiting (PONV) is unknown. OBJECTIVE: To study the efficacy and dose-responsiveness of intravenous buspirone for the prevention of PONV. METHODS: A randomised, double-blind, placebo-controlled study was performed in adults at moderate to high PONV risk undergoing surgery with a general anaesthetic. Patients were randomised to receive an intravenous dose of buspirone (0.3, 1.0, 2.0, 3.0 mg) or placebo at the end of surgery. The primary endpoint was the cumulative 24-h PONV incidence (i.e. any nausea and/or vomiting). Vomiting included retching. Nausea was defined as a score of ≥ 4 on an 11-point verbal rating scale running from zero (no nausea) to ten (the worst nausea imaginable). RESULTS: A total of 257 patients received the study drug and fulfilled the criteria for inclusion in the primary efficacy and safety analyses. With placebo, the mean 24-h PONV incidence was 49.0 % (90 % confidence interval [CI] 37.5-60.5 %). With buspirone, that incidence ranged from a mean of 40.8 % (29.3-52.4 %) in the 1 mg arm to 58.0 % (46.5-69.5 %) in the 0.3 mg arm (P > 0.05 for all comparisons). There was no difference between placebo and buspirone at any dose for any other efficacy endpoint, nor in the number or severity of adverse events or any other safety measures. CONCLUSION: We were unable to show that intravenous single-dose buspirone, at the tested dose-range, was effective at preventing PONV in surgical adult patients. The present study emphasises the difficulty in extrapolating from animal models of emesis to clinical efficacy in PONV.

What is the optimal remifentanil dosage for providing excellent intubating conditions when coadministered with thiopental? A prospective randomized dose-response study.

BACKGROUND AND OBJECTIVE: The aim of the present study was to determine the dosage of remifentanil that must be added to thiopental 5 mg kg(-1) to provide excellent intubating conditions in 95% of patients. METHODS: Sixty-eight premedicated female American Society of Anesthesiologists class 1 and 2 patients were randomly allocated to four remifentanil dose groups (3, 4, 5 or 6 microg kg(-1)). Induction of anaesthesia was performed with a blinded dose of remifentanil infused over 60 s, simultaneously coadministered with thiopental 5 mg kg(-1) infused over 20 s; and tracheal intubation was attempted 150 s after the beginning of induction. The intubating conditions were assessed with the Copenhagen score, according to jaw relaxation, resistance to laryngoscope, vocal cord position and movements and reaction to cuff inflation. A probit analysis was performed to calculate the intubating efficient doses (IEDs) of remifentanil in 50 and 95% of patients (IED50 and IED95). Haemodynamic tolerance was also analysed. RESULTS: The IED95 of remifentanil was 7.8 microg kg(-1) (95% confidence interval 5.9-10.9). Although the maximum decrease in heart rate and mean arterial pressure was less than 30% during induction of anaesthesia, the haemodynamic tolerance of such a relaxant-free protocol for anaesthesia providing excellent intubating conditions in 95% of patients when using remifentanil and thiopental could not be assessed, as the IED95 of remifentanil was more than 6 microg kg(-1). CONCLUSION: The dosage of remifentanil providing excellent intubating conditions in 95% of patients when coadministered with thiopental 5 mg kg(-1) in healthy premedicated female patients undergoing elective surgery was more than 7 microg kg(-1). Our results question the feasibility of using thiopental for a relaxant-free protocol for anaesthesia.

Optimal remifentanil dose for laryngeal mask airway insertion when co-administered with a single standard dose of propofol.

PURPOSE: This dose-response study aimed to determine the optimal dose of remifentanil combined with propofol 2.5 mg.kg(-1) iv in order to achieve excellent conditions for laryngeal mask airway (LMA) insertion in 95% of adult female patients. METHODS: Sixty-eight adult premedicated female patients, American Society of Anesthesiologists (ASA) physical status I and II requiring anesthesia for ambulatory surgery, were randomly allocated to one of four remifentanil dose groups (0.25, 0.5, 1, or 2 microg.kg(-1)). Induction of anesthesia was achieved with one of the four blinded doses of remifentanil infused over 60 sec and simultaneously co-administered with propofol 2.5 mg.kg(-1) iv infused over 45 sec. Insertion of the LMA was attempted 150 sec after the beginning of the induction sequence. Insertion conditions were assessed using a six-category score according to resistance to mouth opening and insertion, swallowing, coughing and gagging, movement, and laryngospasm. A probit analysis was performed to calculate the effective dose for insertion of the LMA in 95% of patients (efficient dose [ED](95)). The changes in heart rate (HR) and mean arterial blood pressure (MAP) in response to LMA insertion were recorded and compared as secondary outcome variables. RESULTS: The ED(95) of remifentanil was 1.32 (95% confidence interval [CI] 0.99-2.46) microg.kg(-1). Changes in heart rate and mean arterial pressure were modest and similar over time across groups, with maximum decreases in heart rate and mean arterial pressure < 30% each during induction of anesthesia. CONCLUSIONS: The required dose of remifentanil is 1.32 (95% CI 0.99-2.46) microg.kg(-1) to achieve excellent LMA insertion conditions in 95% of patients when co-administered with propofol 2.5 mg.kg(-1) in healthy premedicated female patients undergoing elective ambulatory surgery.