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Biomedical subjects

M H Shyr

Publications and source records attributed to M H Shyr.

At least 37 records · Page 2Linked to original sources
PubMed1998

Hyperbaric oxygen pretreatment attenuates hepatic reperfusion injury.

Microcirculatory derangement, energy depletion and lipid peroxidation have been related to development of ischemia-reperfusion injury in the liver. This study investigates the effects of hyperbaric oxygen (HBO) on hepatic ischemia-reperfusion injury. Adult, male Sprague-Dawley rats were used. Three groups were evaluated: 1) sham-operated control (laparotomy only, no ischemia, no HBO), n=8; 2) ischemia control (1-h ischemia, 2-h reperfusion, no HBO), n=8; and 3) HBO pretreatment (100%, oxygen, 2.5 atm absolute, 90 min) plus ischemia (1-h ischemia, 2-h reperfusion), n=8. An in vivo microscope was used to investigate hepatic microcirculation. Tissue malondialdehyde (MDA) and adenosine triphosphate (ATP) were determined. In comparison with the ischemia control group, HBO significantly improved harmful insults following ischemia-reperfusion. HBO lessened adherent leukocyte count (6.00+/-1.31 cells/200 microm vs 11.38+/-2.88 cells/200 microm), and improved flow velocity (1.72+/-0.26 mm/s vs 0.83+/-0.19 mm/s) in post-sinusoidal venules. HBO also reduced MDA (1.04+/-0.24 nmol/mg protein vs 2.24+/-0.49 micromol/g protein), and increased ATP (2.03+/-0.17 micromol/g wet wt vs 0.73+/-0.11 micromol/g wet wt) levels. This study demonstrates that HBO before ischemia may ameliorate the ischemia-reperfusion injury of the liver in the rat model.

Adenosine Triphosphate↗
PubMed1998

Softened endothracheal tube reduces the incidence and severity of epistaxis following nasotracheal intubation.

BACKGROUND: Many complications were reported to be related with nasotracheal intubation. Various chemical or mechanical techniques have been proposed to decrease hemorrhage and trauma associated with nasotracheal intubation but the results remain controversial. We conducted a prospective, randomized, single-blind study to elucidate the effect of an endotracheal tube softened with warm water before use on the incidence and severity of epistaxis following nasotracheal intubation. METHODS: Sixty-two healthy, (ASA class I or II) patients scheduled for elective surgery were randomly assigned into two groups. Patients in the treatment group were intubated with a softened endotracheal tube made possible by heating it in warm water while those in the control group were intubated with unsoftened (intact) tube. Epistaxis was evaluated immediately after intubation and its severity was graded as none, mild, moderate and severe. The use of Magill forceps and postoperative nasal morbidity were also recorded. RESULTS: The total incidence of epistaxis in the "unsoftened" group was significantly higher than that of "softened" group (76.7% vs. 43.8%, P = 0.0002). The severity of nasal hemorrhage was also significantly lightened in the "softened" group. No technical difficulty was encountered in intubation with a softened endotracheal tube by prewarming. The morbidity referable to nasal intubation, however, did not differ in both groups. CONCLUSIONS: In conclusion, our study shows that using an endotracheal tube softened by warm water could reduce the incidence and severity of epistaxis during the act of nasotracheal intubation. It is an effective way and worth a try.

Adolescent↗
PubMed1998

Hyperbaric oxygen therapy attenuates pancreatic microcirculatory derangement and lung edema in an acute experimental pancreatitis model in rats.

This study was designed to investigate hyperbaric oxygen (HBO) therapy as a treatment for managing animals with induced acute pancreatitis. Forty-five anesthetized male Sprague-Dawley rats were studied. A severe acute pancreatitis model was established by combining an intravenous infusion of cerulein (15 microg/kg/h) and an intraductal injection of 0.1 ml of glycodeoxycholic acid (5 mM). Pathology, serum amylase level, pancreatic malondiadehyde levels and water content of the lungs and the pancreas were used to evaluate the severity of disease. Moreover, an in vivo microscopic technique was used to investigate microcirculatory derangement in the pancreas, i.e., flow velocity and leukocytes sticking in postcapillary venules. HBO was delivered in three regimens, i.e., 100% oxygen at 2.5 absolute atmospheric pressure (AAP), 40% oxygen at 2.5 AAP, and 100% oxygen at 1 AAP, 6 h after the initiation of induction of acute pancreatitis. All animals survived until the end of the experiments. HBO significantly improved the pathologic conditions and pancreatic malondiadehyde levels. Concomitantly, it also significantly lessened the severity of lung edema and improved the microcirculatory environment in the pancreas. Our results support the findings that HBO therapy has a beneficial effect on pancreatic microcirculation and lung edema during acute pancreatitis in rats.

3,4-Methylenedioxyamphetamine↗
PubMed1997

Propofol anesthesia increases dopamine and serotonin activities at the somatosensory cortex in rats: a microdialysis study.

We sought to estimate the activities of dopamine and serotonin in animals receiving propofol anesthesia. The in vivo microdialysis technique was used in Sprague-Dawley rats (n = 6) to measure the major metabolites of dopamine and serotonin, i.e. 3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (4-hydroxy-3-methyphenylacetic acid; HVA) and 5-hydroxy indole acetic acid (5-HIAA) in the somatosensory cortex. We also measured the levels of propofol in the brain and blood by microdialysis sampling in another group of rats (n = 6). During the experiment, the rat was infused intravenously (IV) with propofol at a rate of 10 mg x kg(-1) x h(-1) for 60 min and 60 mg x kg(-1) x h(-1) for 40 min. We found that IV infusion of propofol at a rate of 60 mg x kg(-1) x h(-1) significantly increased DOPAC, HVA, and 5-HIAA. We also determined that these changes correlated well with propofol levels in the brain and blood. We concluded that anesthetic doses of propofol increased the functional activities of dopamine and serotonin in the cortex. These increases correlate well with propofol levels in the cortex and blood.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1997

Gabexate mesilate improves pancreatic microcirculation and reduces lung edema in a rat model of acute pancreatitis.

We evaluated the effects of a protease inhibitor on the progression of acute pancreatitis in rats. The model was selected and modified to mimic an intermediate stage of the disease. The degree of microcirculatory derangement in the pancrease and of lung edema was determined to assess the effects of gabexate mesilate (ethyl-4-(6-guanidinohexanoyloxy) benzoate methane sulfonate), a synthetic antiprotease, in acute pancreatitis. Male Sprague-Dawley rats (225-275 g) were used. Experimental pancreatitis was established by four intramuscular injections of cerulein (50 micrograms/kg) at 1 hour intervals. Lipopolysaccharide (10 mg/kg) was injected intraperitoneally as an acute septic challenge. Gabexate mesilate was infused intravenously 6 hours after the initiation of induction of acute pancreatitis at doses of 0.01, 0.1, 1, or 10 mg/kg/h. Microcirculatory changes in the pancreas were studied using in vivo microscopy. All animals survived until the end of the experiments. Gabexate mesilate significantly improved pathologic criteria and decreased serum lipase levels at doses of 1 and 10 mg/kg/h. It significantly lessened the severity of lung edema and improved the microcirculatory environment in the pancreas by increasing flow velocity and reducing leukocyte sticking. These results indicate the beneficial effects of gabexate mesilate on pancreatic microcirculation and lung edema in the progression of acute pancreatitis with septic challenge in rats.

Acute Disease↗
PubMed1997

Low-flow anesthesia in adult orthotopic liver transplantation: a preliminary clinical experience.

BACKGROUND: Anesthesia in orthotopic liver transplantation (OLT) may carry with complex hemodynamic, body temperature, and metabolic alterations. Although OLT cases increased in recent years in Taiwan, experiences remained limited. Notable advantage of low flow anesthesia may include reduced consumption of anesthetic gases and vapors, reduced environmental pollution and cost-saving. This study investigated patient profiles and the feasibility of low-flow rebreathing technique for adult orthotopic liver transplantation. METHODS: Since June 1996, there were six OLT patients who received low flow anesthesia with isoflurane. All patients received hepatic veno-venal anastmosis (so-called piggy back procedure). Two patients were excluded from this study because of different surgical procedure (total occlusion of inferior vena cava and inferior vena cava veno-venal anastmosis). During maintenance of anesthesia, isoflurane was carried by a mixture of oxygen and air at a total fresh gas flow of 0.6 L/min. Alongside with the standard anesthesia machine and physiologic monitors, a newly designed Swan-Ganz catheter was introduced to measure and record cardiac output, systemic vascular resistance, pulmonary artery pressure, central venous pressure, and core temperature in a real-time manner. Blood samples were collected at 6 predetermined time-points in each patient for analysis of arterial blood gases, electrolytes, lactate and glucose concentrations. RESULTS: The anesthetic time was 916 +/- 26 min (900 to 930 min). All patients regained their consciousness within 30 min after completion of surgery. The hemodynamics were relatively stable except after reperfusion of the liver. There was a significant decrease in mean arterial blood pressure, which occurred with accompaniment of a reduction of systemic vascular resistance and increased cardiac output. Arterial blood gas, electrolyte, and glucose were, however, maintained within acceptable limits. Blood lactate was progressively increased and reached its peak after reperfusion of the liver until the end of surgery. The core temperature was well maintained above 34 degrees C. No patient developed hypoxia or hypercapnia. CONCLUSIONS: Low-flow rebreathing anesthetic technique maintained acceptable patient profiles and good body temperature preservation in orthotopic liver transplantation. These characteristics make it a promising method in maintenance of anesthesia for OLT.

Adult↗
PubMed1997

Propofol anesthesia in a patient with Isaacs syndrome--report of a case and literature review.

Isaacs syndrome is an unusual lower motor neuron disease characterized by myokymia (muscle twitching), muscular stiffness, and decreased tendon reflexes. We reported a patient who was affected with this rare disease, with manifestation of involuntary muscular contractions and required general anesthesia for bilateral tonsillectomies. Understanding the presentation and characterization of this unusual disease may be helpful in making choice of anesthetics or anesthetic techniques. Its possible mechanisms of action and its specific considerations in anesthesia in the literature are reviewed and discussed.

Adult↗
PubMed1996

Video-assisted mitral valve operations.

BACKGROUND: Video-assisted endoscopy has been applied frequently in the management of a variety of surgical diseases. However, it has rarely been applied in mitral valve surgery. METHODS: We report 2 patients who received emergency operations for thrombosis of a mitral prosthesis (patient 1, a 68-year-old man) and acute mitral regurgitation due to rupture of anterior chordae (patient 2, a 75-year-old woman). They both had severe congestive heart failure. Cardiogenic shock was noted in patient 2. The mitral valve was approached through a right anterior minithoracotomy with the aid of an endoscope by means of projected images on the video monitor under femorofemoral cardiopulmonary bypass. The aorta was not cross-clamped, and the myocardium was protected by continuous coronary perfusion with hypothermic fibrillatory arrest. The left atrium was entered posterior to the interatrial groove. Thrombectomy and mitral valve repair were performed successfully. RESULTS: The duration of extracorporeal circulation was 204 and 147 minutes, respectively. Both patients recovered from the operation rapidly with uneventful postoperative courses. CONCLUSIONS: Our preliminary results suggest that video-assisted endoscopic cardiac surgery is technically feasible and could be performed in the milieu of open heart surgery.

Aged↗
PubMed1996

Peritoneal nitric oxide is a marker of peritonitis in patients on continuous ambulatory peritoneal dialysis.

Nitric oxide plays an important role in mediating the inflammatory process. The aim of this study was to evaluate if nitric oxide production was increased during peritonitis in patients receiving continuous ambulatory peritoneal dialysis (CAPD), and the association with the prognosis. The study population comprised 21 patients with 22 episodes of peritonitis. Fifteen patients without peritonitis were controls. Nitrate was measured by HPLC and nitrite by the Griess method, to reflect nitric oxide production. Peritoneal dialysate effluent and plasma were collected from six patients during peritonitis and 1 week after treatment to study changes in dialysate:plasma ratio. In 15 patients, nitrite was measured during peritonitis and every 3 days for 2 weeks or until normalized for evolutional changes. The dialysate:plasma ratios of nitrate and nitrite during peritonitis were reduced 26% and 41.5%, respectively, after 1 week of treatment, indicating the peritoneal production of nitric oxide during peritonitis. In the evolutional study, a 5.1-fold increase of peak nitrite levels in bacterial peritonitis (n = 13) and a 2.5-fold increase in fungal peritonitis (n = 3) were observed compared to controls. Nitrite gradually declined to control levels (9.3 +/- 7.2 days) after effective antibiotic treatment, but took longer than to normalize leukocyte count in the peritoneal dialysate effluent (3.9 +/- 1.9 days). In four patients with refractory peritonitis (Candida infection in three, Acinetobacter infection in one), the nitrite levels remained elevated 2-fold despite treatment, and the catheters were removed. It is concluded that nitrite levels in peritoneal dialysate effluent may serve as a marker to assess treatment efficacy in CAPD patients with peritonitis.

Acinetobacter Infections↗
PubMed1996

Participation of AT1 and AT2 receptors in the differential interaction between angiotensin II or III and alpha-2 adrenoceptors in the nucleus reticularis gigantocellularis in cardiovascular regulation and antinociception in rats.

We evaluated possible interactions between angiotensin II (AII) or angiotensin III (AIII) and the alpha-2 adrenoceptors of the nucleus reticularis gigantocellularis (NRGC) in the medulla oblongata that are involved in cardiovascular regulation and antinociception, as well as the angiotensin receptor subtypes involved, using Sprague-Dawley rats that were anesthetized with pentobarbital sodium. The efficacy of guanabenz, which acts on the alpha-2 adrenoceptors in the NRGC to elicit hypotension, bradycardia and antinociception, based on tail-flick responses to noxious thermal stimuli (50 degrees C), was used as our experimental index. Bilateral microinjection of AII or AIII into the NRGC, at equimolar doses (40 pmol) that did not alter base-line systemic arterial pressure, heart rate or tail-flick latency, significantly and site-specifically attenuated the cardiovascular suppression elicited by guanabenz (100 micrograms/kg i.v.). This attenuation was appreciably antagonized by coadministration of the AT2 receptor antagonist PD-123319 (1.6 nmol). Concomitant examination of tail-flick responses revealed discernible inhibition by AII (40 pmol), but potentiation by AIII (40 pmol), of guanabenz-induced antinociception. These differential modulating effects of AII and AIII were, however, antagonized by comicroinjection of losartan (1.6 nmol) into the bilateral NRGC. Our results suggest that both AII and AIII produced a reduction, via AT2 receptors, of the activity of alpha-2 adrenoceptors in the NRGC that are involved in central cardiovascular regulation. On the other hand, antinociception induced by activation of alpha-2 adrenoceptors in the NRGC was suppressed by AII and potentiated by AIII, although AT1 receptors may play a major role in both interactions.

Analgesia↗
PubMed1996

Propofol anesthesia in a patient with myasthenia gravis--a case report.

Experience with the use of propofol for induction and maintenance of anesthesia in patients with myasthenia gravis is limited in the literature. We report, in this case, the well prepared and successful use of continuous propofol infusion without conventional neuromuscular blocking agents in a patient with Ossermann stage IIb of myasthenia gravis undergoing laparoscopic cholecystectomy.

Anesthesia, Intravenous↗
PubMed1995

Concentration and regional distribution of propofol in brain and spinal cord during propofol anesthesia in the rat.

We evaluated the pharmacokinetics and regional distribution of propofol in the brain and spinal cord during propofol anesthesia in Sprague-Dawley rats, using high-performance liquid chromatographic determination of propofol concentration in brain, whole blood and plasma. We found that the concentration of propofol in the brain increased and decreased expeditiously during and after a 15-min and 30-min period of i.v. infusion of an anesthetic dose (60 mg/kg per h) of propofol. Furthermore, propofol was evenly distributed in the brain and spinal cord during infusion, with a significant inter-individual variation. Upon the establishment of anesthesia 15 and 30 min following intravenous infusion of propofol, the concentration of propofol in the brain, whole blood and plasma was respectively 15.7 +/- 1.9 and 39.4 +/- 2.7 micrograms/g, 4.5 +/- 1.2 and 13.6 +/- 1.3 micrograms/ml and 1.8 +/- 0.5 and 5.1 +/- 0.9 micrograms/ml (mean +/- SEM, n = 6 or 7). These high brain/blood and brain/plasma ratios during anesthesia suggest that propofol manifests a pharmacokinetic profile that is different from at least thiopental.

Anesthesia↗
PubMed1995

Effects of propofol on nociceptive response and power spectra of electroencephalographic and systemic arterial pressure signals in the rat: correlation with plasma concentration.

We applied simultaneous spectral analysis of electroencephalographic (EEG) and systemic arterial pressure signals in Sprague-Dawley rats to monitor the status of consciousness and cardiovascular functions during intravenous anesthesia with propofol and to assess their correlations with plasma propofol concentration. Our results support the hypothesis that a 'threshold' plasma concentration (1.7-1.8 micrograms/ml) exists for propofol anesthesia. This threshold level, we further showed, may be attained by both i.v. bolus injection and continuous infusion, although the pharmacokinetic profiles, as well as EEG and hemodynamic correlates, may be different. Continuous, on-line power spectral analysis of EEG signals revealed that the degree of reduction in the power density of the theta and delta bands and root mean square value paralleled the level of anesthesia. Significant suppression of both alpha and beta components occurred only concomitant with EEG burst suppression. At the subanesthetic dose, i.v. infusion of propofol increased preferentially the power density of the theta and delta bands, suggesting the validity of including sedation as a nonhypnotic therapeutic application of propofol. We also found that appreciable cardiovascular suppression took place only upon anesthetic doses of propofol. Power spectral analysis of systemic arterial pressure signals indicated that this was accompanied by a progressive depression of spectral parameters that signify peripheral vascular resistance and baroreceptor reflex response.

Analgesics↗
PubMed1993

Power spectral analysis of the electroencephalographic and hemodynamic correlates of propofol anesthesia in the rat: intravenous infusion.

Based on the tail-flick response to noxious thermal stimuli, we determined in the present study that effective antinociception could be achieved in adult male Sprague-Dawley rats 15 min after intravenous infusion of propofol at 60 mg/kg/h. Simultaneous power spectral analysis of the electroencephalographic (EEG) and systemic arterial pressure signals further revealed a concomitant depression of the activity of all EEG frequency bands (delta, theta, alpha, beta), alongside hypotension, negative inotropic and chronotropic actions, and attenuated baroreceptor reflex and vasomotor activity. These effects were congruent with a plasma concentration of propofol in the arterial blood of 1.70 +/- 0.13 micrograms/ml, as determined by high-performance liquid chromatography.

Anesthesia↗
PubMed1993

Power spectral analysis of the electroencephalographic and hemodynamic correlates of propofol anesthesia in the rat: intravenous bolus administration.

Based on the tail-flick response to noxious thermal stimuli, we determined in the present study that the minimal effective antinociceptive dose of propofol in adult, male Sprague-Dawley rats, given in an intravenous bolus manner, was 10 mg/kg. Simultaneous power spectral analysis of the electroencephalographic (EEG) and systemic arterial pressure signals further revealed a concomitant transient suppression of the EEG activity, primarily in the theta and sigma bands, alongside minor hypotensive and negative inotropic and chronotropic actions, but with maintained vasomotor tone. These alterations followed a time course that paralleled the plasma concentration of propofol in the arterial blood, as detected by high-performance liquid chromatography.

Anesthesia, Intravenous↗
PubMed1991

Comparison of inguinal nerve block and intravenous fentanyl in relieving postinguinal herniorrhaphy pain for pediatric outpatients.

The purpose of this study was to compare the effects of ilioinguinal/iliohypogastric (IG/IH) nerve block and intravenous fentanyl for pain control following inguinal herniorrhaphy in pediatric outpatients. Seventy-five ASA physical status I and II children (aged 1 to 10 yr) with unilateral inguinal herniorrhaphy under general anesthesia were randomly divided into three groups. Group A received IG/IH nerve block, using 0.25% bupivacaine (1 mg/kg) immediately after induction. Group B received intravenous fentanyl (1 microgram/kg) immediately after induction. Group C received only general anesthesia as control. At postanesthetic care unit (PACU), we recorded the degree of pain/or discomfort at 5, 15, 30, 45 and 60 min using modified Hannallah's scoring system after the patient was fully awake. The degree of recovery was also evaluated using Steward's scoring system. After discharge, the parents were interrogated about the condition of child within 24 h by telephone. Follow-up items raised included vomiting, drowsiness, pain and shivering. Our results showed that children in both study groups had lower pain score than those in the control group, and in the fentanyl group children had lower pain score than in the nerve block group during the first 30 min at PACU. The recovery time was also longer in the fentanyl group. There was no significant difference among the three groups regarding the raised items over telephone interrogation. In sum, inguinal nerve block was effective for postoperative pain relief in children undergoing inguinal herniorraphy. We also suggested that small dose of intravenous fentanyl would serve as an easy, simple and effective means for relieving postinguinal herniorrhaphy pain during the first 30 min of the initial postoperative period.

Child, Preschool↗
PubMed1990

Low concentration of caudal bupivacaine for postoperative analgesia in elective pediatric surgery.

This report summarizes [corrected] our experiences in 0.125% bupivacaine caudal analgesia in 70 pediatric patients with age ranging from 3 months to 7 years undergoing routine surgical procedures including herniorrhaphies, orchiopexies, and circumcision. The local anesthetic chosen was 0.125% bupivacaine with epinephrine (1:200,000) being added and the dosage administered [corrected] varied from 0.5-1.0 ml/kg depending upon the sites of the surgical procedures. In the recovery room, patients were observed and accessed using the modified Hannallah's pain/discomfort scoring system. Patients who achieved a score of four or more during a 30 min observation period were given codeine 1 mg/kg intramuscularly and the blocks were rated as uneffective. Our result was that 0.125% bupivacaine caudal analgesia was effective. The rate of success was 79%. The duration of analgesia was 4-8 hours. No delay or difficulty in urination was found. Most of the patients could move their lower extremities but could not bear their weight. Telephone follow-up failed to reveal any analgesia-related complication.

Analgesia, Epidural↗