Development of a New Method for Evaluating Heat-and-Moisture Exchanger Performance.

BACKGROUND: A model system described in International Organization for Standardization 9360 is the standard method for estimating the humidifying performance of heat-and-moisture exchangers (HMEs). However, there are no reliable bedside methods for evaluating the ongoing humidification performance of HMEs. Therefore, this study aimed to develop 2 clinically applicable methods for estimating the ongoing humidifying performance of HMEs and to evaluate their reliability in a model system. METHODS: Physiologically expired gas was simulated using a heated humidifier, and ventilation was delivered using a ventilator with constant flow through 3 different types of HMEs. Relative humidity (RH) was measured using a capacitive-type moisture sensor. Water content lost during expiration was calculated by integrating absolute humidity (AH), instantaneous gas flow measured at the expiratory outlet of the ventilator, and time. We also calculated the water content released and captured by the HMEs during tidal ventilation by integrating the difference in AH across the HMEs, instantaneous gas flow, and time. RESULTS: We found that the RH, temperature, and AH were almost constant on the expiratory outlet of the ventilator but rapidly varied near the HMEs. The water content lost by the 3 HMEs was associated with the manufacturer-reported values and inversely correlated with the calculated values of the water content exchanged by the HMEs. The water content released and captured by HMEs was closely correlated with the difference in HME weight measured at the end of inspiration and expiration; however, the water content captured by HMEs seemed to be overestimated. CONCLUSIONS: Our results demonstrated that our system was able to detect the differences in the performance of 3 models of HMEs and suggest that our method for calculating water loss is reliable for estimating the water retention performance of HMEs during mechanical ventilation, even in the presence of a constant flow.

Effects of volume-targeted pressure-controlled inverse ratio ventilation on functional residual capacity and dead space in obese patients undergoing robot-assisted laparoscopic radical prostatectomy.

Background: The effect of inverse inspiration:expiration (I:E) ratio on functional residual capacity (FRC) during pneumoperitoneum is unclear. We hypothesised that volume-targeted pressure-controlled inverse ratio ventilation (vtPC-IRV) would increase FRC by increasing the level of auto-PEEP in low respiratory compliance situations. Methods: During robot-assisted laparoscopic radical prostatectomy, 20 obese patients were sequentially ventilated with four different settings for 30 min in each setting: (1) control, I:E ratio of 1:2 and baseline airway pressure (BAP) of 5 cm H2O; (2) IRV2, I:E ratio of 2:1 and BAP off; (3) IRV3, I:E ratio of 3:1 and BAP off; and (4) IRV4, I:E ratio of 4:1 and BAP off. The changes in FRC were identified and compared among these settings. Results: The FRC significantly increased as the I:E ratio increased. The FRC values expressed as median (inter-quartile range) during control, IRV2, IRV3, and IRV4 were 1149 (898-1386), 1485 (1018-1717), 1602 (1209-1775), and 1757 (1337-1955) ml, respectively. Auto-PEEP increased significantly as the I:E ratio increased and correlated with FRC (rho=0.303; P=0.006). Shunt and physiological dead space were significantly lower in all IRV groups than in the control group; however, there were no significant differences among the IRV groups. Conclusions: vtPC-IRV with shortened expiratory time and increased auto-PEEP effectively increases FRC during robot-assisted laparoscopic radical prostatectomy in obese patients. FRC increases progressively as the I:E ratio increases from 1:2 to 4:1; however, an I:E ratio higher than 2:1 does not further improve the dead space. Clinical trial registration: UMIN000038989.

Changes in dead space components during pressure-controlled inverse ratio ventilation: A secondary analysis of a randomized trial.

BACKGROUND: We previously reported that there were no differences between the lung-protective actions of pressure-controlled inverse ratio ventilation and volume control ventilation based on the changes in serum cytokine levels. Dead space represents a ventilation-perfusion mismatch, and can enable us to understand the heterogeneity and elapsed time changes in ventilation-perfusion mismatch. METHODS: This study was a secondary analysis of a randomized controlled trial of patients who underwent robot-assisted laparoscopic radical prostatectomy. The inspiratory to expiratory ratio was adjusted individually by observing the expiratory flow-time wave in the pressure-controlled inverse ratio ventilation group (n = 14) and was set to 1:2 in the volume-control ventilation group (n = 13). Using volumetric capnography, the physiological dead space was divided into three dead space components: airway, alveolar, and shunt dead space. The influence of pressure-controlled inverse ratio ventilation and time factor on the changes in each dead space component rate was analyzed using the Mann-Whitney U test and Wilcoxon's signed rank test. RESULTS: The physiological dead space and shunt dead space rate were decreased in the pressure-controlled inverse ratio ventilation group compared with those in the volume control ventilation group (p < 0.001 and p = 0.003, respectively), and both dead space rates increased with time in both groups. The airway dead space rate increased with time, but the difference between the groups was not significant. There were no significant changes in the alveolar dead space rate. CONCLUSIONS: Pressure-controlled inverse ratio ventilation reduced the physiological dead space rate, suggesting an improvement in the total ventilation/perfusion mismatch due to improved inflation of the alveoli affected by heterogeneous expansion disorder without hyperinflation of the normal alveoli. However, the shunt dead space rate increased with time, suggesting that atelectasis developed with time in both groups.

CLP290 promotes the sedative effects of midazolam in neonatal rats in a KCC2-dependent manner: A laboratory study in rats.

Immature neurons dominantly express the Na+-K+-2Cl- cotransporter isoform 1 (NKCC1) rather than the K+-Cl- cotransporter isoform 2 (KCC2). The intracellular chloride ion concentration ([Cl-]i) is higher in immature neurons than in mature neurons; therefore, γ-aminobutyric acid type A (GABAA) receptor activation in immature neurons does not cause chloride ion influx and subsequent hyperpolarization. In our previous work, we found that midazolam, benzodiazepine receptor agonist, causes less sedation in neonatal rats compared to adult rats and that NKCC1 blockade by bumetanide enhances the midazolam-induced sedation in neonatal, but not in adult, rats. These results suggest that GABA receptor activation requires the predominance of KCC2 over NKCC1 to exert sedative effects. In this study, we focused on CLP290, a novel KCC2-selective activator, and found that midazolam administration at 20 mg/kg after oral CLP290 intake significantly prolonged the righting reflex latency even in neonatal rats at postnatal day 7. By contrast, CLP290 alone did not exert sedative effects. Immunohistochemistry showed that midazolam combined with CLP290 decreased the number of phosphorylated cAMP response element-binding protein-positive cells in the cerebral cortex, suggesting that CLP290 reverted the inhibitory effect of midazolam. Moreover, the sedative effect of combined CLP290 and midazolam treatment was inhibited by the administration of the KCC2-selective inhibitor VU0463271, suggesting indirectly that the sedation-promoting effect of CLP290 was mediated by KCC2 activation. To our knowledge, this study is the first report showing the sedation-promoting effect of CLP290 in neonates and providing behavioral and histological evidence that CLP290 reverted the sedative effect of GABAergic drugs through the activation of KCC2. Our data suggest that the clinical application of CLP290 may provide a breakthrough in terms of midazolam-resistant sedation.

Comparison of polyurethane tracheal tube cuffs and conventional polyvinyl chloride tube cuff for prevention of ventilator-associated pneumonia: A systematic review with meta-analysis.

BACKGROUND: The aim of this meta-analysis with trial sequential analysis (TSA) was to evaluate the effect of a polyurethane (PU) tracheal tube cuff on the prevention of ventilator-associated pneumonia (VAP). METHODS: We performed a systematic search using the MEDLINE database through PubMed, Cochrane Central Register of Controlled Trial, SCOPUS, and Web of Science.Randomized controlled trials comparing the incidence of VAP and clinically relevant outcomes between PU cuff tubes and polyvinyl chloride (PVC) cuff tubes in adult patients. Two authors independently extracted study details, patient characteristics, and clinical outcomes such as incidence of VAP, bacterial colonization of tracheal aspirate, duration of mechanical ventilation, ICU stay, and ICU mortality. RESULTS: From 309 studies identified as potentially eligible, six studies with 1226 patients were included in this meta-analysis. All studies compared the incidence of VAP between PU cuffs and PVC cuffs. Use of a PU cuff was not associated with a reduction in VAP incidence (RR = 0.68; 95% CI, 0.45-1.03) with significant statistical heterogeneity (I2 = 65%). The quality of evidence was "very low." According to the TSA, the actual sample size was only 15.8% of the target sample size, and the cumulative Z score did not cross the trial sequential monitoring boundary for benefit. No positive impact was reported for the other relevant outcomes for PU cuffs. CONCLUSIONS: The use of a PU cuff for mechanical ventilation did not prevent VAP. Further trials with a low risk of bias need to be performed.

Lung-protective properties of expiratory flow-initiated pressure-controlled inverse ratio ventilation: A randomised controlled trial.

BACKGROUND: Expiratory flow-initiated pressure-controlled inverse ratio ventilation (EF-initiated PC-IRV) reduces physiological dead space. We hypothesised that EF-initiated PC-IRV would be lung protective compared with volume-controlled ventilation (VCV). METHODS: Twenty-eight men undergoing robot-assisted laparoscopic radical prostatectomy were enrolled in this randomised controlled trial. The EF-initiated PC-IRV group (n = 14) used pressure-controlled ventilation with the volume guaranteed mode. The inspiratory to expiratory (I:E) ratio was individually adjusted by observing the expiratory flow-time wave. The VCV group (n = 14) used the volume control mode with a 1:2 I:E ratio. The Mann-Whitney U test was used to compare differences in the serum cytokine levels. RESULTS: There were no significant differences in serum IL-6 between the EF-initiated PC-IRV (median 34 pg ml-1 (IQR 20.5 to 63.5)) and VCV (31 pg ml-1 (24.5 to 59)) groups (P = 0.84). The physiological dead space rate (physiological dead space/expired tidal volume) was significantly reduced in the EF-initiated PC-IRV group as compared with that in the VCV group (0.31 ± 0.06 vs 0.4 ± 0.07; P<0.001). The physiological dead space rate was negatively correlated with the forced vital capacity (% predicted) in the VCV group (r = -0.85, P<0.001), but not in the EF-initiated PC-IRV group (r = 0.15, P = 0.62). Two patients in the VCV group had permissive hypercapnia with low forced vital capacity (% predicted). CONCLUSIONS: There were no differences in the lung-protective properties between the two ventilatory strategies. However, EF-initiated PC-IRV reduced physiological dead space rate; thus, it may be useful for reducing the ventilatory volume that is necessary to maintain normocapnia in patients with low forced vital capacity (% predicted) during robot-assisted laparoscopic radical prostatectomy.

Effect of endotracheal tube lubrication on cuff pressure increase during nitrous oxide exposure: a laboratory and prospective randomized controlled trial.

BACKGROUND: We previously demonstrated that lubrication of an endotracheal tube (ETT) cuff with K-Y™ jelly strongly and significantly inhibited the increase in cuff pressure during nitrous oxide (N2O) exposure in vitro. However, in our previous study, we identified critical differences between some influential factors, such as the amount of lubricant retained on the cuff, and studied temperature differences between laboratory and clinical conditions. Therefore, it remained unclear whether this effect holds true in clinical settings. METHODS: We first sought to study how changes in the amount of K-Y™ jelly and temperature influence the inhibitory effects of the lubricant on the increase in N2O-induced cuff pressure in vitro. Furthermore, we aimed to determine whether the application of K-Y™ jelly inhibits the increase in ETT cuff pressure during general anesthesia using N2O in adult patients. RESULTS: In the laboratory studies, we found that K-Y™ jelly inhibited the cuff pressure increase dose-dependently when the dose of K-Y™ jelly was varied (P = 0.02), and that such an inhibitory effect decreased with an increase in the studied temperature (P = 0.019). In the clinical study, lubrication with K-Y™ jelly slightly, but significantly, delayed the increase in ETT cuff pressure during general anesthesia with N2O (P = 0.029). However, the inhibitory effect in the clinical settings was smaller than that in vitro. CONCLUSIONS: Lubrication of the ETT cuff with K-Y™ jelly may delay the increase in cuff pressure during general anaesthesia with N2O. However, the clinical significance of this effect may be limited. TRIAL REGISTRATION: UMIN Clinical Trials Registry: UMIN000031377 on March 1, 2019.

Intravenous ephedrine abolished suspected bronchoconstriction during general anesthesia in a patient undergoing beta-adrenergic blocker therapy for hypertension.

We report a case of intravenous ephedrine administration that abolished suspected bronchoconstriction during general anesthesia in a patient undergoing beta-adrenergic blocker therapy for hypertension and who was subsequently diagnosed postoperatively as having bronchial asthma. A 54-year-old man who had childhood asthma was scheduled for laparoscopic cholecystectomy at our institution. The preanesthetic interview suggested full resolution of his childhood asthma. His capnogram showed an airway obstructive pattern immediately after the initiation of mechanical ventilation. However, after administration of ephedrine due to low blood pressure during surgery, his obstructive capnogram reverted to normal. On postoperative day 3, he was diagnosed as having bronchial asthma. Furthermore, we found that small airway obstruction as indicated in his preoperative pulmonary function test (PFT) had been overlooked. Two important points arise from this case. First, the use of beta-blockers for the treatment of hypertension in patients potentially having obstructive lung disease should be avoided. Second, clinicians should carefully check the preoperative PFT results in detail to ensure that nothing has been overlooked.

Perioperative management of a pediatric patient with suspected type 1 von Willebrand disease undergoing tonsillectomy: a case report.

BACKGROUND: Von Willebrand disease (VWD) is the most common inherited bleeding disorder in humans. Coagulopathies such as VWD are evidently risk factors for post-surgical bleeding. Perioperative management of patients with VWD remains controversial and is a major clinical concern. CASE PRESENTATION: A 5-year-old girl was scheduled for tonsillectomy under general anesthesia. Preoperative laboratory tests revealed prolongation of activated partial thromboplastin time and a mild decrease in von Willebrand factor (VWF) activity. Prophylactic administration of desmopressin or VWF was not performed. During tonsillectomy, oozing from the surgical wound was uncontrollable by conventional hemostasis techniques, but complete hemostasis was ensured by plasma-derived coagulation factor VIII concentrate containing VWF. CONCLUSION: Pediatric patients with mild abnormalities in preoperative laboratory tests may have coagulopathies. Prophylactic intervention and/or the preparation of a sufficient amount of coagulation factor VIII concentrate containing VWF may be required in patients suspected of having VWD or with mild VWF deficiency.

K-Y™ jelly inhibits increase in endotracheal tube cuff pressure during nitrous oxide exposure in vitro.

BACKGROUND: The increase in endotracheal tube cuff pressure due to nitrous oxide diffusion is a well-known risk during general anesthesia using nitrous oxide. We hypothesized that lubricating endotracheal tube cuffs with K-Y™ Jelly might inhibit the increase in cuff pressure that occurs during exposure to nitrous oxide. METHODS: We used two types of endotracheal tube cuffs: one made from ultrathin polyurethane (PU) and another made from conventional polyvinyl chloride (PVC). Using a pediatric trachea model, which consisted of an acrylic cylinder with an internal diameter of 12 mm, we measured changes in the cuff pressure during nitrous oxide exposure in size 5.0-mm internal diameter endotracheal tubes with each type of cuff, with and without lubrication with K-Y™ Jelly. RESULTS: During nitrous oxide exposure, the increase in cuff pressure was significantly lower in the lubricated cuffs than in the non-lubricated cuffs in both types of cuffs (PVC, P < 0.0001; PU, P < 0.0001). However, the cuff compliance in the trachea model was unaffected by lubrication in both types of cuffs. CONCLUSIONS: Lubrication of endotracheal tube cuffs with K-Y™ Jelly may effectively delay the increase in cuff pressure that occurs during general anesthesia using nitrous oxide.

Supraglottic airway device versus a channeled or non-channeled blade-type videolaryngoscope for accidental extubation in the prone position: A randomized crossover manikin study.

BACKGROUND: It is very rare but challenging to perform emergency airway management for accidental extubation in a patient whose head and neck are fixed in the prone position when urgently turning the patient to the supine position would be unsafe. The authors hypothesized that tracheal intubation with a videolaryngoscope would allow effective airway rescue in this situation compared with a supraglottic airway device and designed a randomized crossover manikin study to test this hypothesis. METHODS: The authors compared airway rescue performances of the 3 devices-the ProSeal laryngeal mask airway (PLMA; Teleflex Medical, Westmeath, Ireland) as a reference; the Pentax AWS (AWS; Nihon Kohden, Tokyo, Japan) as a channeled blade-type videolaryngoscope; and the McGRATH videolaryngoscope (McGRATH; Medtronic, Minneapolis, MN) as a nonchanneled blade type in a manikin fixed to the operating table in the prone position. Twenty-one anesthesiologists performed airway management on the prone manikin with the 3 devices, and the time required for intubation/ventilation and the success rates were recorded. RESULTS: The median (range) intubation/ventilation times with the PLMA, AWS, and McGRATH were 24.5 (13.5-89.5) s, 29.9 (17.1-79.8) s, and 46.7 (21.9-211.7) s, respectively. There was no significant difference in intubation/ventilation times between the PLMA and AWS. The AWS permitted significantly faster tracheal intubation than did the McGRATH (P = 0.006). The success rates with the PLMA (100%) and AWS (100%) were significantly greater than that with the McGRATH (71.4%). Airway management performance of the PLMA and AWS was comparable between devices and better than that of the McGRATH in the prone position. CONCLUSIONS: Considering that tracheal intubation can provide a more secure airway and more stable ventilation than the PLMA, re-intubation with a channeled blade-type videolaryngoscope such as the AWS may be a useful method of airway rescue for accidental extubation in patients in the prone position.

Effect of pressure-controlled inverse ratio ventilation on dead space during robot-assisted laparoscopic radical prostatectomy: A randomised crossover study of three different ventilator modes.

BACKGROUND: Pressure-controlled inverse inspiratory to expiratory ratio ventilation (PC-IRV) is thought to be beneficial for reducing the dead space volume. OBJECTIVE: To investigate the effects of PC-IRV on the components of dead space during robot-assisted laparoscopic radical prostatectomy (RLRP). DESIGN: A randomised crossover study of three different ventilator modes. SETTING: A single university hospital from September 2014 to April 2015. PATIENTS: Twenty consecutive study participants undergoing RLRP. INTERVENTIONS: Patients were ventilated sequentially with three different modes in random order for 30 min: volume control ventilation (VCV; inspiratory to expiratory ratio 0.5), pressure control ventilation (PCV; inspiratory to expiratory ratio 0.5) and PC-IRV. Inverse inspiratory to expiratory ratio was adjusted individually by observing the expiratory flow-time wave to prevent the risk of dynamic pulmonary hyperinflation. MAIN OUTCOME MEASURES: The primary outcome included physiological dead space (VDphys), airway dead space (VDaw), alveolar dead space (VDalv) and shunt dead space (VDshunt). VDphys was calculated by Enghoff's method. We also analysed respiratory dead space (VDresp) and VDaw using a novel analytical method. Then, VDalv and VDshunt were calculated by VDalv = VDresp - VDaw and VDshunt = VDphys - VDresp, respectively. RESULTS: The VDphys/expired tidal volume (VTE) ratio in PC-IRV (29.2 ±â€Š4.7%) was significantly reduced compared with that in VCV (43 ±â€Š8.5%) and in PCV (35.9 ±â€Š3.9%). The VDshunt/VTE in PC-IRV was significantly smaller than that in VCV and PCV. VDaw/VTE in PC-IRV was also significantly smaller than that in VCV but not that in PCV. There was no significant change in VDalv/VTE. CONCLUSION: PC-IRV with the inspiratory to expiratory ratio individually adjusted by the expiratory flow-time wave decreased VDphys/VTE in patients undergoing RLRP. TRIAL REGISTRATION: University Hospital Medical Information Network in Japan 000014004.

Effects of lubrication on air-sealing performance of a pediatric cuffed tracheal tube.

BACKGROUND: Lubrication of cuffed tracheal tubes (CTTs) reduces liquid leakage. However, it is not clear how cuff lubrication influences air leakage. We aimed to test the hypothesis that pretreatment with K-Y jelly, a water-soluble lubricant, would improve the air-sealing performance of pediatric CTTs in a model study. METHODS: We placed Parker Flex-Tip™ CTT with 4.0- and 5.0-mm internal diameter (ID) into a tracheal model with 9- and 12-mm ID. The tracheal model was connected to a test lung ventilated in pressure control mode. We compared three cuff lubrication conditions: none (N), water (W), and K-Y jelly (KY). We measured the leak airway pressure (LAWP), defined as the lowest peak airway pressure (PAWP) at which leakage was detected, with the fixed cuff pressure (CP) at 20 cmH2O and varied PAWP. We also measured the leak CP (LCP), defined as the highest CP at which leakage was detected, with fixed PAWP at 25 cmH2O and varied CP. We confirmed air leakage when an apparent elevation of oxygen concentration was detected above the cuff after changing the inspiratory gas from air to oxygen. RESULTS: For both 4.0-mm ID and 5.0-mm ID endotracheal tubes, the KY group showed significantly higher LAWP and lower LCP than the other two groups. For the 4.0-mm ID, median values and ranges of LAWP and LCP were K-Y group: 25 (25) and 15 (15); N group: 5 (5) and 35 (35): and W group: 5 (5) and 35 (15-35) cmH2O. For the 5.0-mm ID, median values and ranges of LAWP and LCP were K-Y group: 25 (15-25) and 15 (15-35); N group: 5 (5) and 35 (35); and W group: 5 (5) and 35 (15-35) cmH2O. Water application did not change these outcomes compared with the N group. CONCLUSION: Pre-treatment of the cuff with K-Y jelly significantly improved the air-sealing performance of a pediatric CTT in our model study.

Bumetanide, an Inhibitor of NKCC1 (Na-K-2Cl Cotransporter Isoform 1), Enhances Propofol-Induced Loss of Righting Reflex but Not Its Immobilizing Actions in Neonatal Rats.

Gamma-aminobutyric acid (GABA) has been shown to induce excitation on immature neurons due to increased expression of Na+-K+-2Cl- co-transporter isoform 1 (NKCC1), and the transition of GABAergic signaling from excitatory to inhibitory occurs before birth in the rat spinal cord and spreads rostrally according to the developmental changes in cation-chloride co-transporter expression. We previously showed that midazolam activates the hippocampal CA3 area and induces less sedation in neonatal rats compared with adolescent rats in an NKCC1-dependent manner. In the present study, we tested the hypothesis that propofol-induced loss of righting reflex (LORR) but not immobilizing actions are modulated by NKCC1-dependent mechanisms and reduced in neonatal rats compared with adolescent rats. We estimated neuronal activity in the cortex, hippocampus and thalamus after propofol administration with or without bumetanide, an NKCC1 inhibitor, by immunostaining of phosphorylated cyclic adenosine monophosphate-response element binding protein (pCREB). We studied effects of bumetanide on propofol-induced LORR and immobilizing actions in postnatal day 7 and 28 (P7 and P28) rats. The pCREB expression in the cortex (P = 0.001) and hippocampus (P = 0.01) was significantly greater in the rats receiving propofol only than in the rats receiving propofol plus bumetanide at P 7. Propofol-induced LORR or immobilizing effects did not differ significantly between P7 and P28. Bumetanide significantly enhanced propofol-induced LORR (P = 0.031) but not immobilization in P7 rats. These results are partially consistent with our hypothesis. They suggest that propofol may activate the rostral but not caudal central nervous system dependently on NKCC1, and these differential actions may underlie the different properties of sedative and immobilizing actions observed in neonatal rats.

Effect of head position on the success rate of blind intubation using intubating supraglottic airway devices.

BACKGROUND: To evaluate the effect of head position on the performance of intubating supraglottic airway devices, we compared the success rate of blind intubation in the head-elevated and the pillowless head positions with the LMA Fastrach and the air-Q, and the change of glottic visualization through the air-Q. METHODS: We assigned 193 patients to two groups according to the device used and subgrouped by head position used for intubation: Fastrach/pillowless, Fastrach/head-elevated, air-Q/pillowless, and air-Q/head-elevated. Blind intubation through the Fastrach or the air-Q was attempted up to twice after induction of general anesthesia. Before the attempt at blind intubation with the air-Q, the percentage of glottic opening (POGO) score was also fiberscopically evaluated at the outlet of the device in both head positions in a cross-over fashion. RESULTS: The Fastrach significantly facilitated blind intubation compared with the air-Q in both the pillowless and head-elevated positions: 87.2% in Fastrach/pillowless vs 65.9% in air-Q/pillowless (P=.048), 90% in Fastrach/head-elevated vs 53.7% in air-Q/head-elevated (P<.001). The head-elevated position did not significantly affect the success rate of blind intubation for either device (P=.97 in Fastrach, P=.37 in air-Q). Although the head-elevated position significantly improved the POGO score from the median (10-90 percentile) 60% (0-100%) in the pillowless position to 80% (0-100%) (P=.008), it did not contribute to successful blind intubation with the air-Q. CONCLUSION: Although the head-elevated position improved glottic visualization in the air-Q, the head position had minimal influence on the success rate of blind intubation with either the Fastrach or the air-Q.

Effects of sniffing position for tracheal intubation: a meta-analysis of randomized controlled trials.

BACKGROUND: The purpose of this meta-analysis was to validate the efficacy of the sniffing position in the performance of intubation with direct laryngoscopy. METHODS: We searched MEDLINE, the Cochrane Central Register of Controlled Trials, Embase, and Web of Science. Six randomized controlled trials comprising 2759 adult participants were analyzed. The DerSimonian-Laird method was used to calculate pooled relative risk (RR) and the 95% confidence interval (CI) of Cormack-Lehane classification, Intubation Difficulty Scale, success rate of the first intubation, and weighted mean difference of intubation time. RESULTS: Compared with the other head positions, the sniffing position did not improve glottic visualization, success rate of the first intubation, or intubation time. However, the sniffing position was significantly associated with better Intubation Difficulty Scale compared with the simple head extension position. (RR,1.28; 95% CI, 1.15-1.42; p<0.0001) CONCLUSIONS: Although patients do not benefit from the sniffing position in terms of glottic visualization, success rate of the first intubation, or intubation time, the sniffing position can still be recommended as the initial head position for tracheal intubation because the sniffing position provides easier intubation conditions.

Effects of gas composition on the delivered tidal volume of the Avance Carestation.

BACK GROUND: Measurements with various flowmeters are affected by changes in gas mixture density. The Avance Carestation incorporates ventilator feedback controlled by a built-in flowmeter with a variable orifice sensor. We hypothesised that changes in the composition of delivered gas may cause changes in the delivered tidal volume by affecting the flow measurement unless appropriate corrections are made. METHODS: We used 100 % O2, 40 % O2 in N2 and 40 % O2 in N2O as carrier gases with/without sevoflurane and desflurane. We measured delivered tidal volume using the FlowAnalyzer™ PF 300 calibrated with the corresponding gas mixtures during volume control ventilation with 500-ml tidal volume using the Avance Carestation connected to a test lung. RESULTS: Change of carrier gas and addition of sevoflurane and desflurane significantly altered delivered tidal volume. Desflurane 6 % reduced delivered tidal volume by 7.6, 3.6 and 16 % of the pre-set volume at 100 % O2, 40 % O2 in N2 and 40 % O2 in N2O, respectively. Importantly, the Carestation panel indicator did not register these changes in measured expired tidal volume. Ratios of delivered tidal volume to 500 ml correlated inversely with the square root of the delivered gas density. CONCLUSIONS: These results support our hypothesis and suggest that changing gas composition may alter delivered tidal volume of anesthesia machines with built-in ventilators that are feedback-controlled by uncorrected flowmeters due to changes in gas mixture density.

Comparison of intubation performance between the King Vision and Macintosh laryngoscopes in novice personnel: a randomized, crossover manikin study.

PURPOSE: The King Vision laryngoscope is a newly developed video laryngoscope. We conducted a simulation study to evaluate the efficacy of the King Vision in novice personnel. METHODS: Thirty-one registered nurses with no previous experience with tracheal intubation were enrolled. Participants made 6 consecutive attempts at intubation of the manikin's trachea with a Macintosh laryngoscope (MAC) and the King Vision with channeled blade (KVC) and non-channeled blade (KVNC) in a randomized cross-over fashion. The Grading Scale of Intubation Difficulty (GSID) was rated on a 5-point scale. RESULTS: Overall median (range) intubation times (sec) were 16.9 (8.0-60.0) with the MAC, 20.5 (7.2-60.0) with the KVC, and 60.0 (11.0-60.0) with the KVNC. The KVNC required significantly longer intubation time compared with the MAC or the KVC (p < 0.001). Success rate with the KVNC was 47.3 %, which was significantly inferior to that with the MAC (91.4 %) or KVC (86.6 %). Median GSID was 2 (range 1-5) with the KVC and 3 (1-4) with the MAC, which were both significantly lower than the 4 (2-5) with the KVNC (p < 0.001). Esophageal intubation with the MAC occurred in 18 of 186 attempts, whereas no incidents of esophageal intubation occurred with the KVC or KVNC. CONCLUSION: The KVC facilitated intubation by novice personnel without incidence of esophageal intubation. However, intubation times, success rates, and GSID scores were similar to the values obtained with the MAC. These findings suggest that the KVC, but not the KVNC, could be used as an alternative device for intubation by novice personnel.

Bumetanide, an inhibitor of cation-chloride cotransporter isoform 1, inhibits γ-aminobutyric acidergic excitatory actions and enhances sedative actions of midazolam in neonatal rats.

BACKGROUND: It has been shown that γ-aminobutyric acid exerts excitatory actions on the immature brain due to the increased expression of Na(+)-K(+)-2Cl(-) cotransporter isoform 1. The authors sought to clarify whether midazolam, a γ-aminobutyric acid-mimetic hypnotic agent, causes neuronal excitation that can be blocked by bumetanide, a selective inhibitor of Na(+)-K(+)-2Cl(-) cotransporter isoform 1. Furthermore, the authors examined whether bumetanide potentiates the sedative effects of midazolam in neonatal rats. METHODS: The authors measured the effects of midazolam with or without bumetanide on the cytosolic Ca(2+) concentration ([Ca](2+)(i)) in hippocampal slices (n=3 in each condition) from rats at postnatal days 4, 7, and 28 (P4, P7, and P28) using fura-2 microfluorometry. Neuronal activity in the hippocampus and thalamus after intraperitoneal administration of midazolam with or without bumetanide was estimated by immunostaining of phosphorylated cyclic adenosine monophosphate-response element-binding protein (n=12 in each condition). Furthermore, the authors assessed effects of bumetanide on the sedative effect of midazolam by measuring righting reflex latency (n=6 in each condition). RESULTS: Midazolam significantly increased [Ca](2+)(i) in the CA3 area at P4 and P7 but not at P28. Bumetanide inhibited midazolam-induced increase in [Ca](2+)(i). Midazolam significantly up-regulated phosphorylated cyclic adenosine monophosphate-response element-binding protein expression in a bumetanide-sensitive manner in the hippocampus at P7 but not P28. Bumetanide enhanced the sedative effects of midazolam in P4 and P7 but not P28 rats. CONCLUSION: These results suggest that γ-aminobutyric acid A receptor-mediated excitation plays an important role in attenuated sedative effects of midazolam in immature rats.