Shingo Sugioka

Sevoflurane enhances ethanol-induced cardiac preconditioning through modulation of protein kinase C, mitochondrial KATP channels, and nitric oxide synthase, in guinea pig hearts.

BACKGROUND:Volatile anesthetics and regular ethanol consumption induce cardioprotection mimicking ischemic preconditioning. We investigated whether sevoflurane enhances ethanol preconditioning and whether inhibition of protein kinase C (PKC) and mitochondrial KATP channels attenuated this enhanced cardioprotection. The effects of regular ethanol consumption on expression of inducible (iNOS) and endothelial (eNOS) nitric oxide synthase were determined. METHODS:Isolated perfused guinea pig hearts underwent 30-min global ischemia and 120-min reperfusion (Control: CTL). The ethanol group (EtOH) received 2.5% ethanol in their drinking water for 6 wk. Anesthetic preconditioning was elicited by 10-min exposure to sevoflurane (1 minimum alveolar anesthetic concentration; 2%) in ethanol (EtOH + SEVO) or nonethanol (SEVO) hearts. PKC and mitochondrial KATP channels were inhibited with chelerythrine and 5-hydroxydecanoate pretreatment, respectively. Contractile recovery was assessed by monitoring of left ventricular developed and end-diastolic pressures. Infarct size was determined by triphenyltetrazolium chloride staining. Expression of iNOS and eNOS were determined by Western blot analysis. RESULTS:After ischemia-reperfusion, hearts from the EtOH, sevoflurane (SEVO), and EtOH + SEVO groups had higher left ventricular developed pressure and lower left ventricular end-diastolic pressure compared with CTL. Infarct size was reduced in EtOH and SEVO hearts compared with CTL (27% and 23% vs 45%, respectively, P < 0.001). Sevoflurane further reduced infarct size in EtOH hearts (27% vs 15%, P < 0.001). Chelerythrine and 5-hydroxydecanoate abolished cardioprotection in both SEVO and EtOH cardioprotected hearts. iNOS expression was reduced and eNOS expression was increased in EtOH hearts. CONCLUSIONS:Sevoflurane enhances cardiac preconditioning induced by regular EtOH consumption. This effect is mediated in part by modulation of PKC and mitochondrial KATP channels, and possibly by altered modulation of NOS expression.

The influence of head and neck position on ventilation with the i-gel airway in paralysed, anaesthetised patients.

Context and objective We hypothesised that head and neck position could affect the effectiveness of ventilation with the i-gel airway. To test this hypothesis, we investigated the influence of different head and neck positions on oropharyngeal sealing pressures and ventilation scores during ventilation with i-gel. Methods A single, experienced supraglottic airway device user inserted the i-gel in 20 paralysed, anaesthetised patients who were scheduled for oral surgery. Oropharyngeal leak pressures and ventilation scores were measured with the head and neck in the neutral position, flexed, extended or rotated to the right. Ventilation was scored from 0 to 3 based on three criteria (no leakage with an airway pressure of 15 cmH2O, bilateral chest excursion and a square wave capnogram; each item scoring 0 or 1 point). Results Compared with the neutral position (25.8 ± 5.2 cmH2O), oropharyngeal leak pressure was significantly higher with flexion (28.5 ± 3.4 cmH2O, P = 0.015) and lower with extension (23.0 ± 4.2 cmH2O, P = 0.015), but similar with rotation (26.7 ± 5.1 cmH2O, P = 0.667). Flexion of the head and neck [2 (1–3)] adversely affected the ventilation score compared with the neutral position [3 (2–3), P = 0.004]. Conclusion Effective ventilation with an i-gel can be performed in patients in whom the head and neck is extended or rotated, whereas flexion of the head and neck adversely affects ventilation. Clinically, flexion of the head and neck should be avoided during ventilation with the i-gel.

Aprotinin Abolishes Sevoflurane Postconditioning by Inhibiting Nitric Oxide Production and Phosphorylation of Protein Kinase C-δ and Glycogen Synthase Kinase 3β

Background:It remains controversial whether aprotinin use during cardiac surgery is cardioprotective or detrimental. In contrast, volatile anesthetics may offer cardioprotection perioperatively. Increased nitric oxide, protein kinase C activation, and glycogen synthase kinase 3β inhibition play a role in sevoflurane-induced cardioprotection. The authors investigated whether aprotinin affects sevoflurane postconditioning. Methods:Isolated guinea pig hearts underwent 30 min of global ischemia and 120 min of reperfusion (control [CTL]). Postconditioning was elicited with sevoflurane (2%) for 2 min at reperfusion onset (POST). Aprotinin (250 kallikrein inhibitor units/ml) was administered for 5 min at reperfusion onset (POST + APRO and CTL + APRO). In additional experiments, both sevoflurane and aprotinin were given before ischemia and throughout the reperfusion period (SEVO + APRO (throughout)) to mimic clinical conditions. Left ventricular developed and end-diastolic pressures and infarct size were measured. Western blot analysis determined phosphorylated protein kinase C-&dgr;, protein kinase C-&dgr;, Akt, and glycogen synthase kinase 3β expression. Nitric oxide production during reperfusion was measured by nitric oxide sensor. Results:After ischemia–reperfusion, POST had significantly higher left ventricular developed (56 ± 11 vs. 26 ± 8 mmHg [mean ± SD]) and lower end-diastolic pressures (20 ± 9 vs. 47 ± 15 mmHg) and reduced infarct size (15 ± 3% vs. 41 ± 10%) versus CTL. Aprotinin abolished these improvements. Expressions of phospho-Akt (activated), phospho–protein kinase C-&dgr; (activated), and phospho–glycogen synthase kinase 3β (inhibited) were significantly increased in POST. Aprotinin attenuated these increased expressions. Nitric oxide production after reperfusion was higher in POST than in CTL, but not in POST + APRO. Conclusions:Aprotinin abolishes sevoflurane postconditioning, associated with inhibited phosphorylation of Akt, protein kinase C-&dgr;, and glycogen synthase kinase 3β and reduced nitric oxide production.

Acute memory phase of sevoflurane preconditioning is associated with sustained translocation of protein kinase C-α and ε, but not δ, in isolated guinea pig hearts

Background and objective Anaesthetic preconditioning (APC) exerts cardioprotective effects by reducing infarct size and improving recovery of contractile function after ischaemia–reperfusion. The interval between brief exposure to volatile anaesthetic and sustained ischaemia, the acute memory phase, is dependent on intracellular signalling mediating this cardioprotection. Intramyocyte translocation of protein kinase C (PKC) is known to be a key mediator in APC. We examined the relationship between the time frame of the acute memory phase of sevoflurane preconditioning and intramyocyte translocation of PKC-α, δ and ϵ to the particulate fraction. Methods Isolated perfused guinea pig hearts were subjected to 30 min ischaemia and 120 min reperfusion. APC was elicited with one minimum alveolar concentration sevoflurane for 10 min. Washout times of 10, 30, 60 and 90 min were studied. Contractile recovery was assessed by monitoring left ventricular developed pressures. Infarct size was determined by triphenyltetrazolium chloride staining. Translocation of PKC was examined by western blot analysis. Results After ischaemia–reperfusion, left ventricular developed pressure recovered to a greater degree with APC compared with control for washout times of 10 and 30 min, but not 60 and 90 min. Similarly, infarct size was reduced for washout times of 10 and 30 min, but not 60 and 90 min. Sustained translocation of PKC-α and ϵ, but not δ, was associated with the time frame of the acute memory phase. Conclusion The acute memory phase of sevoflurane preconditioning is limited to less than 60 min. Sustained translocation of PKC-α and ϵ, but not δ, correlates with this acute memory phase of sevoflurane preconditioning.

Effect of cerebral venous congestion on the pressure-volume index in the evaluation of intracranial pressure dynamics.

&NA; Translocation of cerebrospinal fluid (CSF) between the intracranial and spinal subarachnoid space was blocked by ligating the cervical spinal core in eight cats under pentobarbital and nitrous oxide anesthesia, and the effects of cerebral venous congestion on the pressure‐volume index (PVI), a measure relating the change in intracranial volume, and the logarithm of intracranial pressure (ICP) were evaluated. The changes in the volume‐pressure response (VPR), a measure of intracranial elastance, were calculated simultaneously. Cerebral venous congestion was induced by lowering the head relative to the level of the heart by tilting the trunk of the animals to 20° below horizontal. The presence of venous congestion was confirmed by an increase in the sagittal sinus pressure (SSP). The body position was shifted from horizontal prone (H1 group) to head‐down tilt (D1 group) in four animals (group 1) and from headdown tilt (D2 group) to horizontal prone (H2 group) in the other four animals (group 2), and PVI and VPR were determined in each group. The changes in ICP and SSP with change of body position in group 1 were not significantly different from those in group 2, with both pressures changing by 7‐8 mm Hg. PVI showed no significant differences between the H1 group and H2 group or between the D1 group and D2 group. The mean (±SEM) PVI for all measurements in the head‐down tilt position (D1 and D2 groups) was significantly higher (0.50 ± 0.02 ml; p < 0.01) than in the horizontal position (H1 and H2 groups; 0.35 ± 0.02 ml). In contrast, VPR showed a positive linear relationship with ICP in both the horizontal and head‐down tilt positions. These results show that, when ICP is increased due to cerebral venous congestion, VPR correctly indicates increased intracranial elastance; however, PVI paradoxically indicates an increase in the pressure‐buffering ability as ICP is increased. The authors conclude that PVI is greatly affected by the cerebral venous volume and must be interpreted cautiously.

Optimal Degree of Mouth Opening for Laryngeal Mask Airway Function During Oral Surgery

PURPOSE This study was performed to determine the optimal degree of mouth opening in anesthetized patients requiring laryngeal mask airway (LMA) during oral surgery. PATIENTS AND METHODS A single, experienced LMA user inserted the LMA in 15 patients who were scheduled for elective oral surgery. Oropharyngeal leak pressure, intracuff pressure, and fiberoptic assessment of the LMA position were sequentially documented in 5 mouth conditions-opening of 1.4 (neutral position), 2, 3, 4, and 5 cm-and any resulting ventilatory difficulties were recorded. RESULTS Oropharyngeal leak pressure with the mouth open 4 cm (21.8 ± 3.2 cm H(2)O, P = .025) and 5 cm (27.3 ± 7.2 cm H(2)O, P < .001) was significantly higher than in the neutral position (18.1 ± 1.5 cm H(2)O), as was intracuff pressure (neutral position, 60.0 ± 0 cm H(2)O; 4 cm, 72.6 ± 5.1 cm H(2)O [P < .001]; and 5 cm, 86.9 ± 14.4 cm H(2)O [P < .001]). LMA position, observed by fiberoptic bronchoscopy, was unchanged by mouth opening, being similar in the 5 mouth conditions (P = .999). In addition, ventilation difficulties (abnormal capnograph curves or inadequate tidal volume) occurred in 2 of 15 patients (13%) and 7 of 15 patients (53%) (P < .001) with the mouth opening of 4 and 5 cm, respectively. CONCLUSIONS This study showed that a mouth opening over 4 cm led to substantial increases in oropharyngeal leak pressure and intracuff pressure of the LMA, warranting caution, because gastric insufflation, sore throat, and ventilation difficulties may occur. A mouth opening of 3 cm achieves acceptable airway conditions for anesthetized patients requiring LMA.

The Influence of Mouth Opening on Oropharyngeal Leak Pressure, Intracuff Pressure, and Cuff Position With the Laryngeal Mask Airway

PURPOSE The aim of this study was to investigate the influence of mouth opening on oropharyngeal leak pressure, intracuff pressure, and cuff position of the laryngeal mask airway (LMA). PATIENTS AND METHODS Fifteen patients who were scheduled for elective oral surgery were recruited into this study. A single, experienced LMA user inserted the LMA according to the manufacturers recommended technique. Oropharyngeal leak pressure, intracuff pressure, and fiberoptic assessment of the LMA position were documented under 3 mouth conditions: neutral position (1.4-cm distance between upper and lower incisors), mouth open (5- to 6-cm distance between upper and lower incisors), and return to the neutral position. Any ventilation difficulties under the 3 mouth conditions were recorded. RESULTS Oropharyngeal leak pressure with the mouth open was higher than in the neutral position (P < .001). Compared with the neutral position, intracuff pressure was also higher with the mouth open (P < .001). Both measurement values returned to control levels when the neutral position was once again assumed. The LMA position observed by fiberoptic bronchoscopy was unchanged by mouth opening and was similar in the 3 mouth conditions (P = .998). Although ventilatory difficulties occurred after mouth opening in 8 of 15 patients (P < .001), it did not occur when the neutral position was reassumed. CONCLUSIONS This study showed that mouth opening led to substantial increases in oropharyngeal leak pressure and intracuff pressure of the LMA, warranting caution because gastric insufflation, sore throat, and ventilation difficulties may occur.

Comparison of Metal Stylet, Small Tracheal Tube and Combined Introducer-Aided Insertions of the Flexible Reinforced Laryngeal Mask Airway with the Conventional Method: a Manikin Study

Purpose: The present study compared the conventional method (without any adjunct) and three different adjunct-aided methods (a metal stylet, a small tracheal tube, and a combined introducer) with regard to the time required for insertion of the flexible reinforced laryngeal mask airway (FLMA). We also surveyed participants’ views on the ease of FLMA insertion with each method. Methods: Thirty dental students inserted the FLMA in a manikin by each method and the times required for insertion were measured. Subjects were asked to rate the ease of insertion with each method using a 100-mm visual analogue scale (VAS; from 0 mm = extremely easy to 100 mm = extremely difficult). Results: Insertion time was significantly shorter with the small tracheal tube compared with the conventional method. However, insertion times with the metal stylet-aided insertion and the combined introducer-aided insertion were not significantly different as compared to the conventional method. With regard to the ease of insertion as rated using the 100-mm VAS, the dental students rated tracheal tube-aided insertion and combined introducer-aided insertion as being significantly easier, and the metal stylet-aided insertion as significantly more difficult than the conventional method. Conclusions: The small tracheal tube-aided insertion and the combined introducer-aided insertion each appear to possess advantages over the conventional method. The small tracheal tube-aided insertion seems overall more favorable in terms of ease and time to insertion.

Effect of sevoflurane on intracranial pressure, sagittal sinus pressure, and the intracranial volume-pressure relation in cats.

The effect of sevoflurane on intracranial pressure (ICP), sagittal sinus pressure (SSP), and the intracranial volume-pressure (V-P) relation was examined in cats. In experiment 1, on nine cats, changes in ICP and SSP were studied for 180 min during anesthesia with 1 MAC sevoflurane (2.6%, inspired) and 50% nitrous oxide (N2O) in oxygen (O2). ICP significantly (p <0.01) increased from 8.4 +/- 3.8 cm H2O (mean +/- SD), the control level to 10.6 +/- 5.1 cm H2O immediately after the administration of sevoflurane. ICP was unchanged for the subsequent 120 min but then increased significantly (p <0.05) 140 min after administration, being 15.5 +/- 9.0 cm H2O at 180 min. There were no changes in SSP or blood gases. In experiment 2, the rapid injection technique of mock cerebrospinal fluid was used to determine the intracranial V-P relation in ten cats. Measures of V-P relationships included (a) ICP before volume injection (Po), (b) peak ICP caused by volume injection (Pp), (c) intracranial compliance (C) calculated as the ratio of change of intracranial volume Delta V) to change of ICP (Delta P), and (d) the pressure volume index (PVI) calculated as the ratio of Delta V to log Pp/Po. The subjects were divided into two groups, one administered 2.6% sevoflurane and 50% N2O in O2 (n = 6) and the other 50% N2O in O2 (n = 4). Each cat in both groups was given two bolus injections into the lateral ventricle at 180 min after the start of anesthesia. Then, C and PVI were calculated. C and PVI in the group treated with sevoflurane were significantly (p <0.05) lower than in the other group. These findings suggest that prolonged use of sevoflurane increases the intracranial elastance.

Comparison of insertion of the modified i-gel airway for oral surgery with the LMA Flexible: a manikin study.

We previously modified the i-gel airway to enable its use in the field of oral and maxillofacial surgery and reported its fabrication methods. In general, the standard i-gel airway is quick to insert and has a high success rate, but the modified i-gel airway has yet to be assessed for these attributes. We, therefore, set out to compare the ease of insertion of the modified i-gel airway with the LMA Flexible to investigate the usefulness of the modified i-gel airway. The study participants, who included 20 new interns with no experience using either the LMA Flexible or the modified i-gel airway, inserted each device 3 times into an intubation practice manikin. The variables measured in this study were insertion time and rate of successful insertions. Mean insertion time over 3 attempts was significantly shorter for the modified i-gel™ airway (18.9 ± 4.7 seconds) than the LMA Flexible (24.9 ± 5.1 seconds, P < .001). The rate of successful insertions as a total of all 3 attempts was significantly higher for the modified i-gel airway (56/60 times, 93.3%) than the LMA Flexible (45/60 times, 75%; P = .012). When used by an inexperienced operator, the modified i-gel™ airway is faster and has a higher success rate than the LMA Flexible, suggesting that it can be easily manipulated during insertion.