Effect of Cricoid Pressure Compared With a Sham Procedure in the Rapid Sequence Induction of Anesthesia: The IRIS Randomized Clinical Trial.

Importance: The use of cricoid pressure (Sellick maneuver) during rapid sequence induction (RSI) of anesthesia remains controversial in the absence of a large randomized trial. Objective: To test the hypothesis that the incidence of pulmonary aspiration is not increased when cricoid pressure is not performed. Design, Setting, and Participants: Randomized, double-blind, noninferiority trial conducted in 10 academic centers. Patients undergoing anesthesia with RSI were enrolled from February 2014 until February 2017 and followed up for 28 days or until hospital discharge (last follow-up, February 8, 2017). Interventions: Patients were assigned to a cricoid pressure (Sellick group) or a sham procedure group. Main Outcomes and Measures: Primary end point was the incidence of pulmonary aspiration (at the glottis level during laryngoscopy or by tracheal aspiration after intubation). It was hypothesized that the sham procedure would not be inferior to the cricoid pressure. The secondary end points were related to pulmonary aspiration, difficult tracheal intubation, and traumatic complications owing to the tracheal intubation or cricoid pressure. Results: Of 3472 patients randomized, mean (SD) age was 51 (19) years and 1777 (51%) were men. The primary end point, pulmonary aspiration, occurred in 10 patients (0.6%) in the Sellick group and in 9 patients (0.5%) in the sham group. The upper limit of the 1-sided 95% CI of relative risk was 2.00, exceeding 1.50, failing to demonstrate noninferiority (P = .14). The risk difference was -0.06% (2-sided 95% CI, -0.57 to 0.42) in the intent-to-treat population and -0.06% (2-sided 95% CI, -0.56 to 0.43) in the per protocol population. Secondary end points were not significantly different among the 2 groups (pneumonia, length of stay, and mortality), although the comparison of the Cormack and Lehane grade (Grades 3 and 4, 10% vs 5%; P <.001) and the longer intubation time (Intubation time >30 seconds, 47% vs 40%; P <.001) suggest an increased difficulty of tracheal intubation in the Sellick group. Conclusions and Relevance: This large randomized clinical trial performed in patients undergoing anesthesia with RSI failed to demonstrate the noninferiority of the sham procedure in preventing pulmonary aspiration. Further studies are required in pregnant women and outside the operating room. Trial Registration: ClinicalTrials.gov Identifier: NCT02080754.

Prediction of difficult tracheal intubation: time for a paradigm change.

BACKGROUND: It has been suggested that predicting difficult tracheal intubation is useless because of the poor predictive capacity of individual signs and scores. The authors tested the hypothesis that an accurate prediction of difficult tracheal intubation using simple clinical signs is possible using a computer-assist model. METHODS: In a cohort of 1,655 patients, the authors analyzed the predictive properties of each of the main signs (Mallampati score, mouth opening, thyromental distance, and body mass index) to predict difficult tracheal intubation. They built the best score possible using a simple logistic model (SCOREClinic) and compared it with the more recently described score in the literature (SCORENaguib). Then they used a boosted tree analysis to build the best score possible using computer-assisted calculation (SCOREComputer). RESULTS: Difficult tracheal intubation occurred in 101 patients (6.1%). The predictive properties of each sign remain low (maximum area under the receiver operating characteristic curve 0.70). Using receiver operating characteristic curve, the global prediction of the SCOREClinic (0.74, 95% CI: 0.72-0.76) was greater than that of the SCORENaguib (0.66, 95% CI: 0.60-0.72, P<0.001) but significantly lower than that of the SCOREComputer (0.86, 95% CI: 0.84-0.91, P<0.001). The proportion of patients in the inconclusive zone was 71% using SCORENaguib, 56% using SCOREClinic, and only 32 % using SCOREComputer (all P<0.001). CONCLUSION: Computer-assisted models using complex interaction between variables enable an accurate prediction of difficult tracheal intubation with a low proportion of patients in the inconclusive zone. An external validation of the model is now required.

Oxygen delivery during transtracheal oxygenation: a comparison of two manual devices.

BACKGROUND: The Manujet™ and the ENK Oxygen Flow Modulator™ (ENK) deliver oxygen during transtracheal oxygenation. We sought to describe the ventilation characteristics of these 2 devices. METHODS: The study was conducted in an artificial lung model consisting of a 15-cm ringed tube, simulating the trachea, connected via a flow analyzer and an artificial lung. A 15-gauge transtracheal wire reinforced catheter was used for transtracheal oxygenation. The ENK and Manujet were studied for 3 minutes at respiratory rates of 0, 4, and 12 breaths/min, with and without the artificial lung, in a totally and a partially occluded airway. Statistical analysis was performed using analysis of variance followed by a Fisher exact test; P < 0.05 was considered significant. RESULTS: Gas flow and tidal volume were 3 times greater with the Manujet than the ENK (approximately 37 vs 14 L · min(-1) and 700 vs 250 mL, respectively) and were not dependent on the respiratory rate. In the absence of ventilation, the ENK delivered a 0.6 ± 0.1 L · min(-1) constant gas flow. In the totally occluded airway, lung pressures increased to 136 cm H(2)O after 3 insufflations with the Manujet, whereas the ENK, which has a pressure release vent, generated acceptable pressures at a low respiratory rate (4 breaths/min) (peak pressure at 27.7 ± 0.7 and end-expiratory pressure at 18.8 ± 3.8 cm H(2)O). When used at a respiratory rate of 12 breaths/min, the ENK generated higher pressures (peak pressure at 95.9 ± 21.2 and end-expiratory pressure at 51.4 ± 21.4 cm H(2)O). In the partially occluded airway, lung pressures were significantly greater with the Manujet compared with the ENK, and pressures increased with the respiratory rate with both devices. Finally, the gas flow and tidal volume generated by the Manujet varied proportionally with the driving pressure. DISCUSSION: This study confirms the absolute necessity of allowing gas exhalation between 2 insufflations and maintaining low respiratory rates during transtracheal oxygenation. In the case of total airway obstruction, the ENK may be less deleterious because it has a pressure release vent. Using a Manujet at lower driving pressures may decrease the risk of barotrauma and allow the safe use of higher respiratory rates.

Comparison of single-use and reusable metal laryngoscope blades for orotracheal intubation during rapid sequence induction of anesthesia: a multicenter cluster randomized study.

BACKGROUND: Single-use metal laryngoscope blades are cheaper and carry a lower risk of infection than reusable metal blades. The authors compared single-use and reusable metal blades during rapid sequence induction of anesthesia in a multicenter cluster randomized trial. METHODS: One thousand seventy-two adult patients undergoing general anesthesia under emergency conditions and requiring rapid sequence induction were randomly assigned on a weekly basis to either single-use or reusable metal blades (cluster randomization). After induction, a 60-s period was allowed to complete intubation. In the case of failed intubation, a second attempt was performed using the opposite type of blade. The primary endpoint was the rate of failed intubation, and the secondary endpoints were the incidence of complications (oxygen desaturation, lung aspiration, and/or oropharynx trauma) and the Cormack and Lehane score. RESULTS: Both groups were similar in their main characteristics, including the risk factors for difficult intubation. The rate of failed intubation was significantly decreased with single-use metal blades at the first attempt compared with reusable blades (2.8 vs. 5.4%, P < 0.05). In addition, the proportion of grades III and IV in Cormack and Lehane score were also significantly decreased with single-use metal blades (6 vs. 10%, P < 0.05). The global complication rate did not reach statistical significance, although the same trend was noted (6.8% vs. 11.5%, P = not significant). An investigator survey and a measure of illumination pointed that illumination might have been responsible for this result. CONCLUSIONS: The single-use metal blade was more efficient than a reusable metal blade in rapid sequence induction of anesthesia.

Modification of the hepatic hemodynamic response to acute changes in PaCO2 by nitric oxide synthase inhibition in rabbits.

BACKGROUND: Hypercapnia has been reported to modify liver circulation. The vascular regulations implicated in this response remain partly unknown. METHODS: Using anesthetized and ventilated rabbits, we designed this study to evaluate the hepatic artery and portal vein blood flow velocity adjustments (20 MHz pulsed Doppler) after changes in PaCO2 (by varying the inspiratory fraction of CO2 and to assess the proper role of pH, independent of PaCO2 changes, the role of portal vein CO2, and the effect of nitric oxide synthase inhibition on CO2-induced modifications of hepatic hemodynamics. RESULTS: Increasing PaCO2 from 30.9 +/- 5 mm Hg to 77 +/- 11 mm Hg increased arterial blood pressure by 20% (P < 0.01) and hepatic artery blood flow velocity by 90% (P < 0.05) and decreased aortic blood flow velocity by 15% and portal vein blood flow velocity by 40% (both P < 0.05). Changes in pH (1 mL of 0.1 N hydrochloric acid infusion) or isolated changes in portal vein CO2 at constant PaCO2 induced by CO2 insufflation in an open abdomen had no effect on hepatic hemodynamics. Pretreatment with a nitric oxide synthase inhibitor, N(omega)-nitro-L-arginine (2.5 mg/kg), blunted the systemic response to hypercapnia, whereas the portal modifications persisted, with a largely attenuated hepatic artery blood flow increase. CONCLUSIONS: CO2 per se acts on hepatic blood flow by its systemic effect, probably via chemoreflexes. Nitric oxide does not mediate hepatosplanchnic hemodynamic modifications to acute changes in PaCO2 but may play a permissive role by regulating the amplitude of hepatic vascular response.

Effects of various osmolarity on human red blood cells in terms of potassium efflux and hemolysis induced by free radicals.

OBJECTIVES: To study in an in vitro model of erythrocytes exposed to free radicals the effects of hyperosmolarity and hypoosmolarity on the induced potassium efflux and hemolysis. DESIGN SETTING: Erythrocytes were separated from plasma and suspended in 3 different phosphate buffer solutions (HYPO, ISO, and HYPER) containing, respectively, 100, 150 and 200 mmol/l of Na. Free radicals were generated from 2,2'-azobis(2-amidinopropane) hydrochloride (AAPH). Potassium efflux (flame photometry) and hemolysis (Drabkin method) were measured. Measurements were expressed in % (versus total) and area under % versus time curves were calculated (% min). An ANOVA was used for statistical analysis. RESULTS: In presence of AAPH, hemolysis was significantly greater in HYPO (732.45+/-40% min) and lower in HYPER (578.97+/-15% min) as compared to ISO (608.30+/-42% min). Potassium efflux was significantly increased in HYPER (7508.04+/-85% min) as compared with HYPO (5308.74+/-62% min) and ISO (6561.39+/-62% min). DISCUSSION: Our data suggest that hyperosmolarity increases the resistance of the red blood cells when exposed to free radicals as shown by the decreased hemolysis. In such conditions, the potassium efflux analysis appears to be inappropriate to evaluate the free radical effects on erythrocytes.

A comparison of two emergency cricothyroidotomy kits in human cadavers.

BACKGROUND: We compared two emergency cricothyroidotomy kits designed to avoid lesions during insertion, one based on the Seldinger technique (ST), the other based on the concept of a mechanical detection of the posterior wall of the larynx, with regard to insertion time, success rate, and complication rate. METHODS: Cricothyroidotomy was performed under fiberoptic control in 40 human cadavers embalmed according to Thiel's technique. The set chosen for use was randomized: new technique (NT) or ST. Duration of the procedure, success rates, and incidence of laryngeal injuries were compared. Traumatic lesions observed with the fiberoptic bronchoscope were anatomically confirmed after dissection. RESULTS: The two groups had comparable epidemiological and anatomical records. Cricothyroidotomy was performed faster with the NT than with the ST (median 54 vs 71 s, P = 0.01). Failure rates were comparable between groups (4 vs 1, P = 0.34), and there were fewer major complications in the posterior tracheal wall with the ST (0 vs 8, P = 0.003). In the ST group, only minor punctiform lesions of the posterior trachea wall were observed in four cases. CONCLUSIONS: In this model, despite a shorter insertion time, the NT produced more lesions and more failures than the ST.

Comparison of three methods for oxidative stress-induced potassium efflux measurement.

The aim of the study was to compare the potassium efflux measurements (flame photometry (FP), specific electrode (SE) and atomic absorption photometry (AAP)) using a model of erythrocytes exposed to an oxidative stress in various conditions of osmolarity. Human erythrocytes were incubated in 3 different values of osmolarity and in the presence of 50mM AAPH, potassium efflux was measured by FP, SE and AAP at t=0 and every 30min for 2h. These methods were similar for the measurement of global potassium efflux. However, SE detected important amounts of potassium at the beginning of the experiment or in absence of AAPH in comparison with AAP and FP. It is noteworthy that these different methods of measurements were not altered by the osmolarity. FP and AAP make it possible to study the potassium efflux during oxidative stress while SE should be used only for global measurements.

Anaphylactic shock: the advantages of intra aortic balloon counter pulsation for the treatment of heart failure.

The authors report a patient with a history of angina pectoris who developed anaphylactic shock that was complicated by a heart failure due to focal heart ischaemia. Early coronary angiography confirmed the diagnosis of localised coronary hypoperfusion. Intra aortic balloon counter pulsation succeeded in the restoration of coronary blood flow and haemodynamic stability. The authors discuss the opportunity of such treatment when a focal coronary hypoperfusion is diagnosed.

Rapid sequence induction: a survey of practices in three French prehospital mobile emergency units.

OBJECTIVES: This prospective study was conducted in three mobile emergency and intensive care units. METHODS: The patients were over 15 years of age and were not in cardiac arrest. The study was to compare practices in the three units with the guidelines drawn up by the Commission of Experts so as to define the main parameters for quality assurance. All of the patients involved were considered to have full stomachs and required rapid sequence induction. RESULTS: This procedure comply the guidelines only in 45% of cases; in the other cases succinylcholine should have been administered (mobile emergency and intensive care unit A) and the Sellick manoeuvre should have been used (mobile emergency and intensive care unit A and B). Notwithstanding, these two centres treated more traumatized patients than mobile emergency and intensive care unit C, and use of the Sellick manoeuvre in such circumstances is questionable. CONCLUSIONS: More training and greater diffusion of the protocols are required, especially with regard to doctors who intervene intermittently.

Comparison of two techniques for retrograde tracheal intubation in human fresh cadavers.

BACKGROUND: During retrograde tracheal intubation, the short distance existing between the cricothyroid membrane and vocal cords may be responsible for accidental extubation. The insertion of a catheter into the trachea before the removal of the guide wire may help to cope with this problem. This work was conducted to study the impact of such a modification on the success rate and the duration of the procedure. METHODS: Procedures of retrograde tracheal intubation following the classic and modified techniques were randomly performed in cadavers (n = 70). The duration of the procedure from the puncture of the cricothyroid membrane to the inflation of the balloon of the endotracheal tube was measured, and, at the end of the procedure, the position of the endotracheal tube was checked under laryngoscopy. The procedure was considered to have failed if it had taken more than 5 min or when the endotracheal tube was not positioned in the trachea. RESULTS: The mean time to achieve tracheal intubation was similar in both groups (123 +/- 51 vs. 127 +/- 41 s; not significant), but intubation failed significantly more frequently with the classic technique (22 vs. 8 failures; P < 0.05). All failures were related to incorrect positioning of the endotracheal tube. In four cases, both techniques failed. CONCLUSIONS: This efficient, simple modification of the technique significantly increases the success rate of the procedure, without prolonging its duration. These data should be confirmed in clinical conditions but may encourage a larger use of the retrograde technique in cases of difficult intubation.

Effects of an oxidative stress on human hemoglobin: a multiwavelength visible spectrometry study.

This study was carried out to investigate hemoglobin behavior and the role of cell membrane during oxidative stress of human red blood cells induced by a water-soluble radical initiator, 2,2'-azobis(amidino-propane) hydrochloride (AAPH) and compare the observed data to the one obtained with purified human haemoglobin solution. The different forms of hemoglobin were identified and quantified by multiwavelength visible spectrometry using multiple linear regression analysis. Hemolysis was quantified by the Drabkin method. Oxidative stress on purified hemoglobin solutions induced an early formation of Hb(+). In intact erythrocytes, no modified form of haemoglobin was found. Only the hemoglobin released by hemolysis in the extracellular medium was notified in the same way as purified haemoglobin. Thus, the cell membrane appears to protect intraerythrocytic hemoglobin toward an extracellular oxidative stress. Oxidative stress-induced by hemolysis does not seem to be due to changes in intraerythrocytic hemoglobin forms.

The influence of extracorporeal circulation on the susceptibility of erythrocytes to oxidative stress.

Extracorporeal circulation (ECC), a necessary and integral part of cardiac surgery, can itself induce deleterious effects in patients. The pathogenesis of diffuse damage of several tissues is multifactorial. It is believed that circulation of blood extracorporeally through plastic tubes causes a whole body inflammatory response and a severe shear stress to blood cells. The aim of this study was to evaluate the level of oxidative stress and its deleterious effect on red blood cell (RBC) before (pre-ECC), immediately after (per-ECC) and 24 h after an ECC (24 h post-ECC). Several indicators of extracellular oxidative status were evaluated. The ascorbyl free radical (AFR) was directly measured in plasma using electron spin resonance (ESR) spectroscopy and expressed with respect to vitamin C levels in order to obtain a direct index of oxidative stress. Allophycocyanin assay was also used to investigate the plasma antioxidant status (PAS). Indirect parameters of antioxidant capacities of plasma such as vitamin E, thiol and uric acid levels were also quantified. RBC alterations were evaluated through potassium efflux and carbonyl levels after action of AAPH, a compound generating carbon centered free radicals. No changes in plasma uric acid and thiols levels were observed after ECC. However, vitamin E levels and PAS were decreased in per-ECC and 24h post-ECC samples. Vitamin C levels were significantly lower in 24 h post-ECC and the AFR/ vitamin C ratio was increased. Differences in results had been noted when measurements took account of hemodilution. Increases of uric acid and thiols levels were observed after ECC. Vitamin E levels were not modified. However after hemodilution correction a significant decrease of vitamin C level was noted in 24 h post-ECC samples as compared to per-ECC sample. Whatever the way of measurement, vitamin C levels decreased suggesting the occurrence of ECC induced-oxidative stress. Concerning RBC, in the absence of AAPH, extracellular potassium remained unchanged between pre-, per- and 24 h post-ECC. AAPH induced a significant increase in extracellular potassium and carbonyls levels of RBC membranes, which was not modified by ECC. These results suggest the absence of alterations of RBC membrane during ECC despite the occurrence of disturbances in PAS. Such protection is of particular importance in a cell engaged in the transport of oxygen and suggests that RBC are equipped with mechanisms affording a protection against free radicals.

The protective effects of lidocaine on human erythrocytes stored for seven days at 04 degrees C.

Erythrocyte storage may result in cell damage due to an alteration of membrane integrity, which results in potassium efflux and hemolysis. Lidocaine has been shown to protect erythrocytes from oxidative stress by a possible membrane effect. We conducted this study to examine the effects of lidocaine on human erythrocyte storage. Erythrocytes were kept for seven days at 04 degrees C in the absence or in presence of plasma, and of lidocaine at 36.9 and 221.6 microM. Cell damage was assessed by measuring potassium efflux in the supernatant after seven days, and studying potassium efflux and hemolysis induced by oxidative stress. As expected, erythrocyte storage in the presence of plasma was less deleterious. Lidocaine decreased potassium efflux after 7 days' storage. Resistance toward oxidative stress was greater when the erythrocytes had been kept in the presence of plasma. Considering that lidocaine is widely used in various clinical situations, this data may be of clinical relevance.

Lidocaine has better antioxidant potential than ropivacaine and bupivacaine: in vitro comparison in a model of human erythrocytes submitted to an oxidative stress.

BACKGROUND: Local anesthetic agents may exert antioxidant properties in various models. The aim of this work was to compare the antioxidant properties of lidocaine, bupivacaine and ropivacaine using an in vitro model of human erythrocytes submitted to an oxidative stress. METHODS: Blood was obtained from healthy volunteers. After separation, erythrocytes were suspended in phosphate buffer. Oxidative stress was induced by incubation with 2,2'-azobis (2-amidinopropane) hydrochloride (AAPH). (1) Effects of four different concentrations (50, 100, 300 and 600 microg ml(-1)) of lidocaine, bupivacaine and ropivacaine were studied in absence or presence of AAPH (20 mM). Potassium efflux was assessed by flame photometry. (2) Effects of 50 and 600 microg ml(-1) of lidocaine, bupivacaine and ropivacaine on AAPH (50 mM) induced hemolysis were also studied. (3) The oxygen radical absorbing capacity of lidocaine, bupivacaine and ropivacaine at the four concentrations was evaluated by the analysis of the allophycocyanin fluorescence. RESULTS: In absence of AAPH, neither extracellular potassium nor hemolysis was noted. AAPH (20 mM) induced a significant increase in extracellular potassium that was reduced by all local anesthetic agents, with greater effects for lidocaine. AAPH-induced hemolysis was significantly decreased by all the local anesthetic agents at higher concentration, but only by lidocaine at 50 microg ml(-1). Finally, none of the local anesthetic agents modified the allophycocyanin fluorescence. CONCLUSION: In this model, lidocaine was proved more effective than bupivacaine and ropivacaine in protecting human erythrocytes submitted to an oxidative challenge. This was not due to a free radical scavenging effect.

Massive chloroquine intoxication: importance of early treatment and pre-hospital treatment.

Chloroquine intoxication, despite therapeutic improvements, remains a potentially serious condition. We report a case of a 25-year-old patient, having ingested 10 g of chloroquine, a dose commonly considered to be lethal. Thanks to appropriate early medical treatment, this patient's outcome was favourable. To our knowledge, the literature contains no other report of survival of a patient after such an intake. This report emphasises the need to use a pre-designed medical care protocol to implement appropriate therapy as rapidly as possible.