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In order to investigate the influence of decoupling charge structure on rock blasting, explosion experiments were carried out in the laboratory with cement mortar models and air-decoupling charge with different diameters. The sizes of blasting fragments were screened and the explosive strain was statistically analyzed. Different charge structures were used to numerically simulate the forming process of the cracks and crushing circles during the propagation of explosive stress wave. Experimental results indicate that, compared with coupling charge, air-decoupling charge structure could improve the distribution of fragment size and increase the utilization ratio of explosive energy. Numerical simulation also illustrates that the gap between charge and the wall of borehole could change the stress wave loading rate on the wall, prolong the action time of stress wave and gas, decrease obviously the thickness of crush zone, and lead to the improvement of blasting effect. [ABSTRACT FROM AUTHOR]

Astrocytes, the major component of blood-brain barriers, have presented paradoxical profiles after cerebral ischemia and reperfusion in vivo and in vitro. Our previous study showed that sevoflurane preconditioning improved the integrity of blood-brain barriers after ischemia and reperfusion injury in rats. This led us to investigate the effects of sevoflurane preconditioning on the astrocytic dynamics in ischemia and reperfusion rats, in order to explore astrocytic cell-based mechanisms of sevoflurane preconditioning. In the present study, 2,3,5-triphenyltetrazolium chloride staining and Garcia behavioral scores were utilized to evaluate cerebral infarction and neurological outcome from day 1 to day 3 after transient middle cerebral artery occlusion surgery. Using immunofluorescent staining, we found that sevoflurane preconditioning substantially promoted the astrocytic activation and migration from the penumbra to the infarct with microglial activation from day 3 after middle cerebral artery occlusion. The formation of astrocytic scaffolds facilitated neuroblasts migrating from the subventricular zone to the lesion sites on day 14 after injury. Neural networks increased in the infarct of sevoflurane preconditioned rats, consistent with decreased infarct volume and improved neurological scores after ischemia and reperfusion injury. These findings demonstrate that sevoflurane preconditioning confers neuroprotection, not only by accelerating astrocytic spatial and temporal dynamics, but also providing astrocytic scaffolds for neuroblasts migration to ischemic regions, which facilitates neural reconstruction after brain ischemia., Competing Interests: None

Objective: Our objective was to examine whether prior tetanic stimulation of cranial nerves enhances the amplitudes of transcranial motor-evoked potentials (MEPs)., Methods: Thirty patients undergoing elective craniotomy under propofol-fentanyl anesthesia with partial neuromuscular blockade were enrolled. Both control and posttetanic MEPs (c-MEPs and p-MEPs) monitoring were performed with a train of five pulses delivered to C3 or C4. c-MEPs were recorded from target muscles and p-MEPs were obtained 1 s after tetanic stimulation to the ulnar nerves and facial nerves. The amplitudes of paired MEPs were compared with Wilcoxon's signed rank test., Results: When tetanic stimulation was separately applied to the facial nerves, amplitudes of p-MEPs from abductor pollicis brevis, orbicularis oculi or oris were similar with those of c-MEPs. When tetanic stimulations were separately applied to the ulnar nerves, the amplitudes of p-MEPs from the abductor pollicis brevis but not orbicularis oculi or oris were significantly enlarged compared with c-MEP., Conclusions: We found that only prior tetanic stimulation of ulnar nerve but not facial nerve could enlarge the amplitudes of trancranial hand MEPs. Augmentation of MEP amplitude via prior tetanic stimulation of peripheral nerve seems to originate from the subcortical level but not motor cortex.

Objective: To evaluate the preoperative effects of acute hypervolemic hemodilution (AHH) on intracranial pressure, cerebral oxygen supply-demand balance and cardiovascular functions of neurosurgical patients., Methods: Approved by hospital ethics committee, a total of 80 ASA grade I/II patients at our hospital during 2009, of either gender aged 18-60 yrs, undergoing elective craniotomy were recruited. The subjects were randomly divided equally into 2 groups: group H (hemodilution) and group C (control) (n = 40 each). After induction, 6% hydroxyethyl starch solution was infused at the rate of 24 ml×kg(-1)×h(-1) in group H, while patients in group C received compound electrolyte solution at the rate of 6 ml×kg(-1)×h(-1). Central venous pressure (CVP), cardiac output index (CI), stroke volume variation (SVV) and cerebral spinal fluid pressure (CSFP) were recorded at the following time points: T(Base) (before induction), T(0) (after induction and hemodynamic stabilization), T(30) (after infusion for 30 min) and T(60) (after infusion for 60 min). Blood samples from radial artery and jugular bulb were collected and calculated for systemic vascular resistance index (SVRI) and cerebral oxygen uptake rate (CERO(2)). The dosing frequency of vasoactive drugs was also recorded., Results: CI in group H was significantly higher than that in group C (P < 0.01). No significant difference was found in both SjvO(2) and CERO(2) between groups and among different points of time (P > 0.05). At the end of AHH, CVP and CSFP were (12 ± 2.2) mm Hg and (20.0 ± 2.1) mm Hg respectively. They were significantly higher than that in group C (P < 0.01)., Conclusion: Preoperative AHH in craniotomy will increase CI and maintain the balance of cerebral oxygen supply. But its clinical application is limited in the patient with high intracranial pressure due to the simultaneous increases in CVP and CSFP.

Objective: To evaluate the efficacy of multiple cranial nerves monitoring under partial Seventy elective neuromuscular relaxation during cerebellopontine angle (CPA) tumor resection., Methods: patients undergoing CPA tumor resection via microneurosurgery were randomly allocated to 2 equal groups: Group FN receiving intraoperative facial nerve (NF) monitoring and Group MN receiving monitoring of multiple nerves: trigeminal nerve, glossopharyngeal nerve, accessory nerve or hypoglossal nerve other than the FN which were considered at risk by the neurosurgeon preoperatively. The manipulation procedure were modified according to cranial nerves monitoring and neuromuscular relaxation was maintained at train of four stimulation (TOF)=3 by continuous vencronium infusion during the acoustic neuroma resection. The function of the cranial nerves monitored were evaluated preoperatively and 8 days postoperatively., Results: Discernable and legible images of electromyographic wave complex were obtained during cranial nerve mapping and monitoring under intraoperative partial neuromuscular relaxation form all the patients. The facial nerve function of 4 patients exacerbated (from H-B grade I-II to grade III-IV) in both groups, and one new glossopharyngeal nerve function deficiency was found in Group FN, and one new hypoglossal nerve function deficiency was found in Group MN postoperatively., Conclusion: Intraoperative cranial nerves monitoring under partial neuromuscular relaxation is feasible. Multiple cranial nerves combined with facial nerve monitoring seems unable to increase the short-term protective effects of nerve function after CPA tumor resection.

Objective: To study the feasibility of using non-depolarizing relaxant in intraoperative facial nerve monitoring (IFNM) during total intravenous anesthesia (TIVA)., Methods: Thirty adult patients, aged 37 (20-50), with ASA class I or II, without disorder of facial nerve, underwent IFNM during TIVA, using fentanyl, midazolam, and propofol, to record the compound muscle action potentials (CMAPs) of the facial nerve. Train of four (TOF) pattern was used to evaluate the degree of peripheral neuromuscular blockade. The relationship between the TOF value and CMAP was studied., Results: When the TOP value was 1 the wave amplitude of the CMAP of facial nerve was 0.19 +/- 0.08 mv, significantly lower than that when no muscle relaxant was used (2.72 +/- 0.34 mv, P < 0.01), however, when the TOF values were > or = 2 there were no statistically significant differences in the amplitude of the CMAP of facial nerve. In addition, clear graph of CMAP could be obtained when the TOF values were > or = 2., Conclusion: IFNM can be safely and efficaciously performed when neuromuscular blockade is monitored carefully during TIVA.

Objective: To determine the optimal target plasma concentration of propofol required to induce EEG burst suppression administered by TCI in order to decrease cerebral metabolic rate and increase tolerance to cerebral ischemia and hypoxia., Methods: One hundred and fifty ASA I-II patients(aged 18-55 years-old, BMI < 30, Mallampati Score I-II) scheduled for elective surgery undergoing general anesthesia were enrolled in this study. Patients with systemic diseases or other factors effecting the electrical activity of brain were excluded. ECG, IBP, SpO2, PetCO2, Temperature and EEG (two-channel referential montage system) were continuously monitored during the procedure. Patients were induced with TCI propofol (the target plasma concentration was initially set at 5.4 microg/ml), After induction and intubation, target plasma concentration was increased by 0.3 microg/ml increment and sustained 15 minutes until EEG burst suppression appeared(stable burst suppression waveform and BSR > 50%), and this target concentration was recorded., Results: The mean target plasma concentration of propofol with TCI required to induce EEG burst suppression was 6.1 +/- 0.6 microg/ml with 95% confidence interval of 5.99-6.19 microg/ml. There was no significant difference between the genders., Conclusions: The target plasma concentration of propofol reached 6.2 microg/ml can induce EEG burst suppression, which is better for intraoperative cerebral protection.

Objective: Stimulating lateral or posterior cord may produce different anesthesia extent because of different anatomical position of the two plexus at the infraclavicular region. We To explore the difference in the efficacy of infraclavicular brachial plexus block by stimulating different cords of the infraclavicular brachial plexus., Methods: 70 patients of the ASA physical status class I - II, aged 14 - 64, scheduled for elective surgical procedures below elbow underwent infraclavicular brachial plexus block with the Wilson's approach via the point 2 cm medial and caudal to the coracoid process guided by nerve stimulator, to simulate the lateral cord (n = 32) or posterior cord (n = 38). 30 ml of 0.5% ropivacaine was injected after the stimulation of the lateral or posterior cords. Anesthesia was assessed 5, 10, 20, and 30 min after the local anesthetic injection. A successful blockade was defined as analgesia in all dermatomes of the five nerves (median nerve, musculocutaneous nerve, radial nerve, ulnar nerve, and medial antebrachial cutaneous nerve)., Results: Stimulating the posterior cord provided complete blockade in 30 patients (78.9%) and stimulating the lateral cord provided complete blockade in 17 patients (53.1%)., Conclusion: Stimulating the posterior cord guided by nerve stimulator increases the efficacy of infraclavicular brachial plexus block compared with stimulating the lateral cord.

Objective: To investigate if low minimal stimulating current used in nerve stimulator localizing is associated with a greater likelihood of infraclavicular block success., Methods: 188 patients, aged 14 to 64, of ASA physical status class I - II, and scheduled for surgical procedures below elbow were assigned to low current group (Group A, n = 118) or regular current group (Group B, n = 70) according to the last figure of admission number. The infraclavicular plexus block was performed using the Wilson's approach 2 cm medial and caudal to the coracoid process guided by nerve stimulator with 30 ml of 0.5% ropivacaine after eliciting distal motor responses. The minimal stimulating current (I) was adjusted to 0.1 mA < or = I < 0.3 mA in Group A or 0.3 mA < or = I < 0.5 mA in Group B. The 2 groups were further sub-divided into 2 subgroups: lateral cord subgroup when motor responses of wrist and finger-flexion and pronation of forearm were induced, and posterior subgroup when extension of wrist and finger was induced. Anesthesia efficacy was assessed 5, 10, 20 and 30 min after the local anesthetic injection. A successful blockade was defined as analgesia in all dermatomes of the five nerves (median nerve, musculocutaneous nerve, radial nerve, ulnar nerve, and medial antebrachial cutaneous nerve)., Results: The success rate of Group A was 84.7%, significantly higher than that of Group B (67.1%, P < 0.05). When divided into posterior and lateral cord subgroups, The success rate of the posterior subgroup of Group A was 96.5%, significantly higher than that of the posterior subgroup of Group B (78.9%, P < 0.05)., Conclusion: Minimal stimulating current lower than 0.3 mA, significantly lower than the recommended value (0.5 mA), improves the efficacy of infraclavicular brachial plexus block, especially when the posterior cord is stimulated.

Objective: To improve the anesthetic environment in monitoring short-latency somatosensory evoked potentials (SSEP) during operation, we compared the effects of different anesthetics on SSEP and Bispectral index (BIS), which aim to select suitable anesthetics and their doses used intraoperatively., Methods: 60 ASA I-II patients undergoing elective neurosurgery were randomly allocated into three groups: enflurane, isoflurane and desflurane group. The concentration of each volatile anesthetic was increased step by step from 0 to end-tidal 0.3, 0.5, 0.75, 1.0 and 1.5 MAC. The changes of cortical SSEP component N20 were recorded as well as Bispectral index (BIS) monitoring. The effects of three volatile anesthetics in various concentrations on short-latency SSEP and BIS were investigated., Results: All three volatile anesthetics significantly decreased N20 amplitude and prolonged N20 latency. The N20 waveform disappeared in some patients when the end-tidal concentration of enflurane reached 1.0 MAC, it occurred when that of isoflurane or desflurane was at 1.5 MAC. BIS monitoring showed BIS values were all under 60 when at 1.0 MAC in three group. For some patients in enflurane group and desflurane group, BIS values were above 60 (45-64, 44-61, respectively) when at 0.75 MAC, while those in isoflurane group were still less than 60 (39-58). And the amplitude or latency of cortical SSEP correlated poorly with BIS., Conclusion: The effects of three volatile anesthetics on SSEP and BIS are significant in dose-dependent manner. Anesthetic regimen of 0.75 MAC isoflurane for intraoperative cortical SSEP monitoring may be optimal. It seemed that the correlation between BIS and short-latency SSEP was poor, although both are associated with the effects of anesthetics on cerebral cortex.

Objective: To compare the relation between the preoperative functional magnetic resonance imaging (fMRI) with blood oxygen level dependent (BOLD) technique and intraoperative motor evoked potential (MEP) monitoring for cortical mapping of primary motor cortex in patients with tumors near the central area. And to determine whether non-invasive preoperative fMRI can provide results equivalent to those achieved with the invasive neurosurgical "gold standard"., Methods: A prospective study of 16 patients with various pathological tumors of the central area was conducted. Preoperative fMRI scans using the BOLD contrast technique in each patient were performed. An activation scan was achieved by using a motor task paradigm, which consisted of simple flexion-extension finger movements and finger-to-thumb touching in a repeating pattern. The anatomical structure was delineated by the T(1)-weighted three-dimensional fast spoiled gradient recalled sequence (3D/FSPGR) immediately afterward. The BOLD images were overlaid on the T(1)-weighted 3D/FSPGR images, and then co-registered to the neuronavigation system. The fMRI activations were documented by using a neuronavigation system in sequence, and compared to standardized intraoperative MEP monitoring, which included direct cortical electrical stimulation (DCES) or transcranial cortical electrical stimulation (TCES) or their combination. The compound muscle action potentials of forearm flexor and hand muscle responses were recorded during either TCES or DCES. Two techniques were compared to determine the accuracy for cortical mapping of primary motor areas with fMRI., Results: Overall, the intraoperative MEP monitoring showed good correlation with fMRI activation in 92.3% of cases. The coincidence rate, however, was 100.0% between TCES and fMRI, and 66.7% between DCES and fMRI respectively. There was no statistically difference between two cortical mapping techniques, chi-square test of paired comparison of enumeration data, P < 0.01., Conclusion: BOLD fMRI was a high sensitive and reliable technique to locate the position of the primary motor areas and their spatial relation with adjacent tumor, especially for the presurgical planning in patients with central area brain tumor.

Objective: To choose suitable general anesthetics dosages when short-latency somatosensory evoked potentials (SLSEP) is monitored during operation., Methods: 150 ASA I-II neurosurgical patients undergoing elective operations were randomly divided into intravenous anesthesia group of 90 patients and inhalation anesthesia group of 60 patients. The intravenous anesthesia group was further divided into 9 subgroups of 10 patients treated with different anesthetics of different dosages: propofol (1.5 mg/kg, 2 mg/kg, and 3 mg/kg), midazolam (0.2 mg/kg, 0.3 mg/kg, and 0.4 mg/kg), and etomidate (0.15 mg/kg, 0.3 mg/kg, and 0.4 mg/kg). The intravenous anesthetics were given and upper limb SLSEP was monitored continuously. The inhalation anesthesia group was further divided into enflurane, isoflurane and desflurane subgroups of 20 patients each. The inhalational anesthetics were given at the concentrations corresponding to the end-expiratory concentrations of 0 to 0.3, 0.5, 0.75, 1.0 and 1.5 MAC. The changes of N(14), N(20) and central conduction time (CCT) were recorded. In addition to SLSEP, EKG, NIBP, SpO(2), P(ET) CO(2) were monitored as well as end-tidal anesthetic concentration. During the experiment SpO(2) was maintained > 95% and P(ET) CO(2) was maintained at the range of 35 - 45 mmHg by mask oxygen or assisted ventilation., Results: The intravenous anesthetic propofol significantly decreased N(20) amplitude and produced less effect on the latency of N(14), N(20) and CCT. Midazolam significantly decreased the N(20) amplitude and prolonged the latency of N(20) and CCT. Etomidate significantly increased the N(20) amplitude, and the change did not recover when the patients had opened their eyes 10 minutes after medication. All three inhalational anesthetics significantly decreased the N(20) amplitude and prolonged the N(20) latency and CCT. N(20) amplitude disappeared in some patients treated with enflurane when the end-expiratory concentration was 1.0 MAC, while disappeared in some patients treated with isoflurane and desflurane when the end-expiratory concentration was 1.5 MAC for these 2 drugs., Conclusion: When using SLSEP monitoring, the most suitable general anesthetic is etomidate during the induction stage and isoflurane and desflurane during the maintenance stage with the end-expiratory concentration below 1.0 MAC.