Sung-Sik Park

Reactive oxygen species in rats with chronic post-ischemia pain

Background: An emerging theme in the study of the pathophysiology of persistent pain is the role of reactive oxygen species (ROS). In the present study, we examined the hypothesis that the exogenous supply of antioxidant drugs during peri‐reperfusion would attenuate pain induced by ischemia/reperfusion (IR) injury. We investigated the analgesic effects of three antioxidants administered during peri‐reperfusion using an animal model of complex regional pain syndrome‐type I consisting of chronic post‐ischemia pain (CPIP) of the hind paw.

Reduction of pain on injection of propofol: combination of pretreatment of remifentanil and premixture of lidocaine with propofol

Backgrounds and objective: There is a high incidence of pain following intravenous injection of propofol, and many studies have been conducted to find a way of reducing this. The administration of lidocaine and, recently, remifentanil has also been used for this purpose, but it is only partially effective. Thus, the purpose of this study was to investigate the analgesic effect of a combination of pretreatment with remifentanil and premixture of lidocaine with propofol and to compare either treatment alone during propofol injection in dorsal hand‐veins. Methods: In a prospective, randomized, double‐blinded trial, we studied 141 adult patients scheduled for elective surgery. The combination of pretreatment of remifentanil (0.35 &mgr;g kg−1 min−1) and a premixture of lidocaine with propofol (mixture of propofol 1% and lidocaine 1% in a 10 : 1 ratio) was compared with either treatment alone in the prevention of pain on propofol injection. Pain was assessed on a four‐point scale (0 = none, 1 = mild, 2 = moderate, 3 = severe) during propofol injection. Patients in Group B received remifentanil (0.35 &mgr;g kg−1 min−1) 30 s before the injection of propofol. Results: The reduction of pain on propofol injection was similar in both the remifentanil pretreatment and lidocaine premixture groups (62.2% vs. 62.2%). Combination therapy was associated with a higher incidence of patients without pain (91.3%) than either treatment alone (P < 0.001). On analysing the injection pain scores, we found a significant reduction of the score in the remifentanil and lidocaine Group C compared with the lidocaine Group A (P < 0.001) and the remifentanil Group B (P < 0.001). Conclusions: The combination of pretreatment of remifentanil and premixture of lidocaine with propofol was more effective in reducing the incidence of pain on injection of propofol than either treatment alone.

Can intravenous patient-controlled analgesia be omitted in patients undergoing laparoscopic surgery for colorectal cancer?

PURPOSE Opioid-based intravenous patient-controlled analgesia (IV-PCA) is a popular method of postoperative analgesia, but many patients suffer from PCA-related complications. We hypothesized that PCA was not essential in patients undergoing major abdominal surgery by minimal invasive approach. METHODS Between February 2013 and August 2013, 297 patients undergoing laparoscopic surgery for colorectal cancer were included in this retrospective comparative study. The PCA group received conventional opioid-based PCA postoperatively, and the non-PCA group received intravenous anti-inflammatory drugs (Tramadol) as necessary. Patients reported their postoperative pain using a subjective visual analogue scale (VAS). The PCA-related adverse effects and frequency of rescue analgesia were evaluated, and the recovery rates were measured. RESULTS Patients in the PCA group experienced less postoperative pain on days 4 and 5 after surgery than those in the non-PCA group (mean [SD] VAS: day 4, 6.2 [0.3] vs. 7.0 [0.3], P = 0.010; and day 5, 5.1 [0.2] vs. 5.5 [0.2], P = 0.030, respectively). Fewer patients in the non-PCA group required additional parenteral analgesia (41 of 93 patients vs. 53 of 75 patients, respectively), and none in the non-PCA group required rescue PCA postoperatively. The incidence of postoperative nausea and vomiting was significantly higher in the non-PCA group than in the PCA group (P < 0.001). The mean (range) length of hospital stay was shorter in the non-PCA group (7.9 [6-10] days vs. 8.7 [7-16] days, respectively, P = 0.03). CONCLUSION Our Results suggest that IV-PCA may not be necessary in selected patients those who underwent minimal invasive surgery for colorectal cancer.

Contrasting Development of the Latest Quaternary Slope Failures and Mass-Transport Deposits in the Ulleung Basin, East Sea (Japan Sea)

In order to understand how the variations in shelf morphology and sediment supply to the shelf within a basin can change the occurrence styles of slope failures and mass-transport deposits (MTDs), this chapter details dimensions and morphology of the latest Quaternary slope failures and MTDs on the western and southern margins of the Ulleung Basin. On the western margin, the slides and slumps have relatively small dimensions with a few small, scoop-shaped scars and gullies deeper than 700 m water depth. The downslope mass-flow deposits occur as small, solitary lobes restricted at the base-of-slope. On the western margin, the small sediment input to the shelf and the prominent Hupo Bank and Hupo Trough blocking sediment delivery to the slope probably caused relatively low accumulation of muddy sediments in the slope, most likely resulting in the small dimensions of slope failures, and the restricted occurrence of small MTDs at the base-of-slope. In contrast, the southern margin is characterized by large dimensions of gullied scars with huge slides and slumps deeper than 250 m water depth. These catastrophic failures evolved into extensive mass flows, which travelled downslope for several tens of kilometers. On the southern margin, the flat, broad shelf and the high sediment supply to the shelf during the last glacial period probably caused relatively high accumulation of mixed muddy and sandy sediments in the upper slope. These conditions could have promoted large-scale slope failures along the entire upper slope, forming the extensive occurrence of MTDs in the middle to lower slopes. This study provides an example that the variations in shelf morphology and sediment supply to the shelf within a basin can affect the styles of slope failures and MTDs by controlling sediment input and sediment types to the slope.

Prediction of hypotension in spinal anesthesia

According to recent government statistics report [1], people over 65 years of age comprised 11.8% of the Korean population in the year 2012 and will comprise more than 15% of the total Korean population before the year 2020. In addition, the percentage of the population aged over 65 years is expected to double to ~32.3% by the year 2040 compared with the year 2020. The rate of population aging in Korea is now the highest worldwide [2]. On the other hand, advances in surgical and anesthetic techniques have enabled aged people to more safely undergo surgical operations. Accordingly, elderly patients will become a large proportion of anesthetic practice, and anesthesiologists thus need to be familiar with age-related physiological changes. Although there is debate surrounding which anesthetic methods are best for elderly patients, most anesthesiologists prefer spinal anesthesia, especially for orthopedic, genitourinary, and gynecological surgeries. However, the limited cardiovascular reservoirs of elderly patients sometimes make anesthesia more complicated than expected. High-level blockade (≥ T5) and old age (≥ 40 years) are the two main factors in hypotensive complication after spinal anesthesia, which has an incidence of 15.3 to 33% [3,4]. Therefore, in elderly patients who are scheduled to undergo surgery under spinal anesthesia, prediction of hypotension is important for proper anesthetic management. In an article published in this issue of Korean Journal of Anesthesiology, Kweon et al. [5] concluded that heart rate variability (HRV) is not a reliable predictor of hypotension after spinal blockade in hypertensive patients. As the authors mentioned in the article, differences in patient samples and anesthetic methods might have resulted in the negative predictive value of HRV, contrary to the findings of other studies [6,7]. Many factors can affect HRV in various ways. Elderly people usually have higher sympathetic activity than younger people. In addition, Abhishekh et al. [8] showed that females have a significantly lower sympathetic tone than that of males in healthy volunteers. Liao et al. [9] showed lower HRV, including the low-frequency (LF) and high-frequency (HF) components, in patients with hypertension, excluding the LF/HF ratio. The lower HRV of patients with hypertension reflects reduced cardiac autonomic control due to various underlying pathophysiological factors. In addition, patients with diabetes mellitus (DM) complicated by cardiovascular autonomic neuropathy may develop abnormalities in heart rate control with central and peripheral vascular dysfunction [10]. When patients have concurrent hypertension and DM, a significant graded decrease in HRV indices may occur. According to these data, it is reasonable that patient age, sex and coexisting diseases should be considered together for patient selection for HRV studies. As Kweon et al. [5] mentioned, other factors that affect HRV could contribute to negative results. Various antihypertensive medications could change the cardiovascular responses to spinal anesthesia [11]. Physicians prefer antihypertensive drugs that do not increase sympathetic nervous system (SNS) activity or even lower SNS activity. In addition, we must consider the block level. When compared with the study by Hanss et al. [6], the level of spinal blockade in the study by Kweon et al. is too broad (T1-T10), and resulted in diverse sympathetic blockade. In conclusion, although the study by Kweon et al. showed no changes in HRV, we should be aware of various factors that can affect the activity of the autonomic nervous system and be prepared for potential hypotensive events in elderly patients with hypertension scheduled to undergo spinal anesthesia.

Postoperative nausea and vomiting after thyroidectomy: a comparison between dexmedetomidine and remifentanil as part of balanced anesthesia

Background Postoperative nausea and vomiting (PONV) is the major complication related to general anesthesia, occurring in 60–80% of patients after thyroidectomy. The objective of this study was to compare the effects of an intraoperative dexmedetomidine infusion with remifentanil, as anesthetic adjuvants of balanced anesthesia, on PONV in patients undergoing thyroidectomy. Methods Eighty patients scheduled for thyroidectomy were randomized into the following two groups: 1) The dexmedetomidine group (Group D), who received an initial loading dose of dexmedetomidine (1 µg/kg over 10 min) during the induction of anesthesia, followed by a continuous infusion at a rate of 0.3–0.5 µg/kg/h; 2) the remifentanil group (group R), who received remifentanil at an initial target effect site concentration of 4 ng/ml during the induction of anesthesia, followed by a target effect site concentration of 2–3 ng/ml. PONV was assessed during the first 24 hours in 2 time periods (0–2 h and 2–24 h). The pain intensity, sedation score, extubation time, and hemodynamics were also assessed. Results During the 2 time periods, the incidence and severity of PONV in group D were significantly lower than in group R. In addition, the need for rescue antiemetics was significantly lower in group D than in group R. The effect of dexmedetomidine on postoperative pain relief (2–24 h) was superior to that of remifentanil. The hemodynamics were similar in both groups, whereas eye opening and extubation time were delayed in group D. Conclusions Adjuvant use of intraoperative dexmedetomidine infusion may be effective for the prevention of PONV.

Methods for Calcium Carbonate Content Measurement of Biocemented Soils

AbstractRecently, a new soil improvement method to use a microbially induced calcium carbonate precipitation (MICP) process to generate biocementation in sand has been developed. In this method, th...

Effect of Specimen Size on Undrained and Drained Shear Strength of Sand

Failure of granular soils can be defined by a friction angle that can be obtained from direct shear tests or triaxial tests. The results of triaxial tests can be influenced by various experimental conditions such as confining pressure, shearing rate, end constraint, and specimen size. In this study, the effect of specimen size on the undrained and drained shearing behavior of Nakdong River sand was investigated using loose (Dr = 40%) and dense (Dr = 80%) specimens 5 and 10 cm in diameter. Friction angles such as the undrained total stress friction angle, undrained effective stress friction angle, and drained friction angle obtained from Mohrs stress circle decreased slightly as the diameter of the specimen increased, regardless of relative densities. The difference between friction angles caused by different specimen sizes was at most 2.6° for an undrained total stress friction angle of dense sand. In most cases, there was little difference between the friction angles of large and small specimens (less than 1°). The difference between an effective friction angle from undrained tests and a drained friction angle from drained tests was up to 7° for loose sand, but was negligible for dense sand.

Shear behavior of waste rock materials in drained and undrained ring shear tests

The denudation processes in abandoned mines pose environmental and social problems. Insufficient remediation and cleanup modify the physicochemical properties near the mine sites. In addition, large amounts of sediment and debris can flow downward due to heavy rainfall. Here, the shear characteristics of mine deposits are presented rather than their chemical contaminants, which include heavy metals. Drained and undrained ring shear tests were performed on waste rock materials that were collected from pyrophyllite mine deposits in the mountainous region of Korea. These samples were classified as gravelly sandy soils (i.e., with an effective grain size of D10 = 0.3 mm and a uniformity coefficient of cu = 5). The following three tests were performed: (i) shear stress measurement with shearing time for a given shear velocity (i.e., 0.1 mm/sec), (ii) shear stress as a function of shear velocity, and (iii) shear stress as a function of normal stress. The fully saturated samples were subjected to different normal stresses (i.e., 25 and 100 kPa) and shear velocities (i.e., 0.01, 0.1, 1, and 100 mm/sec). The waste materials exhibited a strain-softening behavior regardless of the drainage and shear velocity condition. In addition, the shear stress was strongly influenced by the shear velocity and increased with increasing shear velocity and normal stress in the post-failure stage. Using grain size distribution analyses, we show that significant grain crushing occurs in the shear zone during shearing. Under relatively high shear velocity conditions (i.e., >;100 mm/sec), the grain crushing effect is more significant and results in rapid mass movements.

Beneficial Role of Hydrogen Sulfide in Renal Ischemia Reperfusion Injury in Rats

Purpose Hydrogen sulfide (H2S) is an endogenous gaseous molecule with important physiological roles. It is synthesized from cysteine by cystathionine γ-lyase (CGL) and cystathionine β-synthase (CBS). The present study examined the benefits of exogenous H2S on renal ischemia reperfusion (IR) injury, as well as the effects of CGL or CBS inhibition. Furthermore, we elucidated the mechanism underlying the action of H2S in the kidneys. Materials and Methods Thirty male Sprague-Dawley rats were randomly assigned to five groups: a sham, renal IR control, sodium hydrosulfide (NaHS) treatment, H2S donor, and CGL or CBS inhibitor administration group. Levels of blood urea nitrogen (BUN), serum creatinine (Cr), renal tissue malondialdehyde (MDA), and superoxide dismutase (SOD) were estimated. Histological changes, apoptosis, and expression of mitogen-activated protein kinase (MAPK) family members (extracellular signal-regulated kinase, c-Jun N-terminal kinase, and p38) were also evaluated. Results NaHS attenuated serum BUN and Cr levels, as well as histological damage caused by renal IR injury. Administration of NaHS also reduced oxidative stress as evident from decreased MDA, preserved SOD, and reduced apoptotic cells. Additionally, NaHS prevented renal IR-induced MAPK phosphorylation. The CGL or CBS group showed increased MAPK family activity; however, there was no significant difference in the IR control group. Conclusion Exogenous H2S can mitigate IR injury-led renal damage. The proposed beneficial effect of H2S is, in part, because of the anti-oxidative stress associated with modulation of the MAPK signaling pathways.