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Biomedical subjects

S S Liu

Publications and source records attributed to S S Liu.

At least 55 records · Page 3Linked to original sources
PubMed1998

The effect of epinephrine on small-dose hyperbaric bupivacaine spinal anesthesia: clinical implications for ambulatory surgery.

UNLABELLED: The effect of adding epinephrine to small doses of spinal bupivacaine on the duration of sensory motor block has not been carefully investigated. Twelve volunteers underwent hyperbaric bupivacaine spinal anesthesia (7.5 mg) with and without epinephrine (0.2 mg) in a randomized, double-blind, cross-over fashion. Sensory block was assessed with pinprick, transcutaneous electrical stimulation (TES) equivalent to surgical stimulation (at umbilicus, pubis, knee, and ankle), and tolerance of a pneumatic thigh tourniquet. Motor block was assessed with isometric force dynamometry. Discharge criteria were defined as return of pinprick sensation to dermatome S2, ability to ambulate, and ability to urinate. Extent of sensory block to pinprick over time was unaffected by the addition of epinephrine. However, epinephrine prolonged tolerance of TES at the pubis, knee, and ankle (33-48 min, P < 0.05) and of thigh tourniquet (30 min, P < 0.01). Motor block was prolonged by epinephrine at the quadriceps and gastrocnemius muscles (by 23 and 51 min, respectively, P < 0.002). Achievement of discharge criteria was prolonged by 48 min by the addition of epinephrine (P < 0.01). Thus, epinephrine may prolong surgical anesthesia for lower abdominal and lower extremity surgery and delay time until patients achieve discharge criteria. IMPLICATIONS: Using a cross-over study design, 12 volunteers underwent bupivacaine spinal anesthesia with and without epinephrine. This study suggests that adding epinephrine to bupivacaine may prolong surgical anesthesia and also delay patients' discharge.

Adult↗
PubMed1998

Premedication with fentanyl and midazolam decreases the reliability of intravenous lidocaine test dose.

UNLABELLED: This study was performed to determine whether premedication with midazolam and fentanyl prevents reliable detection of an i.v. lidocaine test dose. Thirty ASA physical status I or II patients received either 3 mL of saline or 1.5 mg of midazolam (1.5 mL) plus 75 microg of fentanyl (1.5 mL) i.v. in a randomized, double-blind fashion. Five minutes later, lidocaine 1 mg/kg was injected i.v. At 1.5 min before and every minute after lidocaine administration, each subject was questioned regarding the presence of four symptoms of systemic lidocaine toxicity. Any new tinnitus, perioral numbness, metallic taste, or light-headedness within 5 min after lidocaine administration was considered a positive response. All 15 patients in the saline group (100% sensitivity) had a positive response to i.v. lidocaine, but only 9 of 15 patients in the sedation group had a positive response (60% sensitivity; P = 0.017). We conclude that midazolam and fentanyl premedication decreases the reliability of subjective detection of i.v. lidocaine. IMPLICATIONS: Anesthesiologists often rely on subjective symptoms to prevent local anesthetic toxicity while performing regional anesthesia. Sedatives are often administered during the administration of regional anesthesia. This study demonstrates that typical sedation decreases the reliability of detection of local anesthetic toxicity by subjective symptoms.

Adult↗
PubMed1998

Quantitative analysis of respiratory, motor, and sensory function after supraclavicular block.

UNLABELLED: The incidence and clinical significance of hemidiaphragmatic paresis after supraclavicular block of the brachial plexus is unknown. Eight healthy volunteers received a supraclavicular block with a standard technique using 30 mL of 1.5% lidocaine. Respiratory function was assessed with ultrasound of the diaphragm, respiratory inductive plethysmography (RIP), and pulmonary function tests (PFT) every 20 min. Sensory block was assessed with pinprick and motor block with isometric force dynamometry every 20 min. Four of eight subjects demonstrated hemidiaphragmatic paresis on both ultrasound and RIP. No subject experienced changes in PFT values or subjective symptoms of respiratory difficulty. Motor and sensory blockade outlasted hemidiaphragmatic paresis. These results are contrasted to the often symptomatic, 100% incidence of hemidiaphragmatic paresis seen after interscalene block. In this study of healthy volunteers, supraclavicular block was associated with a 50% incidence (95% confidence interval 14-86) of hemidiaphragmatic paresis that was not accompanied by clinical evidence of respiratory compromise. IMPLICATIONS: Interscalene block is always associated with diaphragmatic paralysis and respiratory compromise. The significance of these side effects after supraclavicular block is unknown. Using sensitive measures of respiratory function, we determined that diaphragmatic paralysis occurs less often with the supraclavicular approach and is not associated with respiratory difficulties in healthy subjects.

Adult↗
PubMed1998

Peripheral nerve blocks improve analgesia after total knee replacement surgery.

UNLABELLED: Total knee replacement (TKR) produces severe postoperative pain. Peripheral nerve blocks can be used as analgesic adjuncts for TKR, but the efficacy of femoral nerve blocks alone is controversial. The sciatic nerve innervates posterior regions of the knee; thus, performance of both sciatic and femoral nerve blocks may be necessary to improve analgesia after TKR. We performed this study to determine whether peripheral nerve blocks improve analgesia after TKR. In a randomized, double-blind fashion, 36 patients undergoing TKR received either femoral, sciatic-femoral, or sham nerve blocks after a standardized spinal anesthetic. Further postoperative analgesia was provided by patient-controlled i.v. morphine and ketorolac. Pain at rest and with physical therapy, morphine use, nausea, pruritus, sedation, and patient satisfaction were assessed. Patients receiving peripheral nerve blocks reported better analgesia at rest for at least 8 h after transfer to the hospital ward (P < 0.05). Morphine use was decreased by approximately 50% in the peripheral nerve block groups until the second postoperative day (P < 0.02). Side effect profiles and patient satisfaction were similar between groups. We conclude that femoral nerve blocks improve analgesia and decrease morphine use after TKR. The addition of a sciatic nerve block to the femoral nerve block did not further improve analgesic efficacy. IMPLICATIONS: Performance of femoral nerve blocks improves analgesia and decreases the need for morphine after total knee replacement surgery. The addition of a sciatic nerve block to the femoral nerve block does not provide additional benefits.

Aged↗
PubMed1998

Patient-controlled epidural analgesia with bupivacaine and fentanyl on hospital wards: prospective experience with 1,030 surgical patients.

BACKGROUND: The efficacy and safety of patient-controlled epidural analgesia (PCEA) for postoperative analgesia on hospital wards was studied. METHODS: Postoperative analgesia was provided for 1,030 patients with PCEA using 0.05% bupivacaine and fentanyl, 4 microg/ml, in a standardized manner. Patients were seen at least twice a day by the staff of the anesthesia pain management service. Prospectively gathered data included verbal pain scores at rest and activity (0-10); consumption of bupivacaine and fentanyl; and incidences of pruritus, nausea, sedation, hypotension, motor block, and respiratory depression. Descriptive statistics were used. Risk factors for side effects were determined using logistic regression. RESULTS: The study included 552 women and 477 men who underwent a median (mode) of 3 (2) days of PCEA. Their mean age was 59 +/- 16 yr and their mean weight was 76 +/- 19 kg. There were 454 abdominal, 165 gynecologic, 126 urologic, 108 vascular, 90 thoracic, 83 orthopedic, and 4 plastic surgical procedures. Median (mode) pain scores were 1 (0) at rest and 4 (5) with activity on postoperative day 1. Incidences of side effects were 16.7% (pruritus), 14.8% (nausea), 13.2% (sedation), 6.8% (hypotension), 2% (motor block), and 0.3% (respiratory depression). Reasons for termination of PCEA were elective (82%), displaced epidural catheter (12%), anticoagulation (3%), infection (1%), side effects (1%), inadequate analgesia (1%), and other (<1%). Risk factors for side effects were female sex, patient weight <73 kg, patient age <58 yr, bupivacaine and fentanyl consumption >9 ml/h, use of analgesic adjuncts, and lumbar placement of epidural catheters. CONCLUSION: Patient-controlled epidural analgesia provides effective and safe postoperative analgesia on hospital wards.

Analgesia, Epidural↗
PubMed1998

Lumbosacral cerebrospinal fluid volume is the primary determinant of sensory block extent and duration during spinal anesthesia.

UNLABELLED: BACKGROUND. Injection of local anesthetic into cerebrospinal fluid (CSF) produces anesthesia of unpredictable extent and duration. Although many factors have been identified that affect the extent of spinal anesthesia, correlations are relatively poor and the extent of spread remains unpredictable. This study was designed to determine whether variability in the volume of lumbosacral CSF among individuals is a contributing factor in the variability of spinal anesthesia. METHODS: Spinal anesthesia was administered to 10 healthy volunteers with 50 mg lidocaine in 7.5% dextrose. The technique was standardized to minimize variability in factors known to affect the distribution of spinal anesthesia. The extent of sensory anesthesia was assessed by pin-prick and by transcutaneous electrical stimulation. Motor blockade was assessed in the quadriceps and gastrocnemius muscles by force dynamometry. Duration of anesthesia was assessed by pinprick, transcutaneous electrical stimulation, and duration of motor blockade. Lumbosacral CSF volumes were calculated from low thoracic, lumbar, and sacral axial magnetic resonance images obtained at 8-mm increments. Volumes of CSF were correlated with measures of extent and duration of spinal anesthesia using the Kendall rank correlation test. RESULTS: Lumbosacral CSF volumes ranged from 42.7 to 81.1 ml. Volumes of CSF correlated with pin-prick assessments of peak sensory block height (P = 0.02) and duration of surgical anesthesia (as assessed by the duration of tolerance to transcutaneous electrical stimulation at the ankle (P < 0.05). CONCLUSIONS: Variability in lumbosacral CSF volume is the most important factor identified to date that contributes to the variability in the spread of spinal sensory anesthesia.

Adult↗
PubMed1997

Prevalence of HPV infection in esophageal squamous cell carcinoma in Chinese patients and its relationship to the p53 gene mutation.

Human papillomavirus (HPV), in particular types 16 and 18, is positively associated with anogenital cancers and may be an important etiologic factor in their pathogenesis. The goal of our study was to investigate the role of HPV infection in the pathogenesis of esophageal squamous cell carcinoma (ESCC) and its relationship with the p53 mutation. We have examined ESCC collected from Sichuan, China, for the presence of HPV infection and p53 mutation. The presence of HPV DNA was detected by PCR-Southern analysis while the p53 mutation was analyzed by PCR-SSCP. High-risk HPV (types 16 and 18) DNA was detected in 32 out of 152 cases of ESCC examined. In contrast, HPV DNA was not detected in normal esophageal tissues excised from the distant end (tumor free) of resected ESCC. Mutation of the p53 gene was detected in 22 out of 55 cases of ESCC. The distribution of the 22 p53 mutation was: 5 in exon 5, 1 in exon 6, 5 in exon 7, 10 in exon 8 and 1 in exon 10. The p53 mutation was detected at a significantly lower rate in ESCC with HPV infection. Our results support a role of HPV infection in the pathogenesis of ESCC from a high-incidence area.

Adult↗
PubMed1997

Distribution of tumor necrosis factor receptor messenger RNA in normal and herpes simplex virus infected trigeminal ganglia in the mouse.

PURPOSE: to investigate the distribution of p55 and p75 tumor necrosis factor (TNF) receptor mRNA in normal murine trigeminal ganglia, and in murine trigeminal ganglia acutely infected with McKrae strain herpes simplex virus (HSV). METHODS: in situ hybridization with antisense 35S-labeled riboprobes for mRNA encoding both the p55 and p75 TNF receptor (TNFR) subtypes was used in normal and HSV-infected murine trigeminal ganglia. Sense riboprobes were used as controls. RESULTS: in situ hybridization with both p55 and p75 riboprobes produced a strong autoradiographic signal over many, but not all, trigeminal sensory neurons. Signal for mRNA encoding both TNFR subtypes was also present over the arachnoid layers surrounding trigeminal ganglia. Acute ocular HSV infection was accompanied by an intense leukocytic infiltrate into the ophthalmic portion of the trigeminal ganglia, and, in this setting, increased p55 and p75 mRNA signal was closely related to the location and number of infiltrating white blood cells. The distribution and number of trigeminal sensory neurons expressing mRNA for the two TNFR subtypes did not appear to change following infection. Signal over control sections hybridized with sense p55 and p75 TNFR cRNA probes was comparable to background. CONCLUSIONS: the observed distribution of p55 and p75 TNFR mRNA over trigeminal sensory neurons and over the arachnoid layers surrounding trigeminal ganglia supports suggestions that TNF has a direct effect on neurons, either as a neuromodulator or neurotrophic factor, and that TNF may play a central role in blood-brain barrier regulation. Increased signal for TNFR mRNA in acutely infected trigeminal ganglia appears to reflect infiltration by receptor-bearing white blood cells.

Animals↗
PubMed1997

Generating, partitioning, targeting and functioning of superoxide in mitochondria.

Recently, we proposed a hypothetical model of coexistence of "Reactive oxygen cycle" with Q cycle and H+ cycle in mitochondrial respiratory chain to combine both processes of univalent electron leak for production of superoxide and of proton leak across inner mitochondrial membrane. This review presents a more detailed description of this model and summaries the supporting experimental evidence obtained.

Animals↗
PubMed1997

Differential sensory block after spinal bupivacaine in volunteers.

We performed this study to determine whether differential sensory block to touch, pinprick, and cold after spinal bupivacaine could be used to predict the dermatomal level of block to transcutaneous electrical stimulation (TES) equivalent to surgical stimulation, onset of tourniquet pain, or magnitude of hemodynamic depression. Eight subjects per group were randomized to receive 3.75, 7.5, or 11.25 mg of 0.75% bupivacaine with 8.25% dextrose in a double-blind fashion. Sensory block was assessed with touch, pinprick, cold, TES at T-12, L-2, S-1, and thigh tourniquet pain. Differential extent of sensory block to touch, pinprick, and cold occurred at the time of offset of tolerance to TES (P < 0.03) and at the time of tourniquet pain (P < 0.05). However, the extent of differential sensory block to touch, pinprick, and cold varied up to 10 dermatomes (2 SD) cephalad to block to TES and up to 7 dermatomes (2 SD) cephalad to the thigh tourniquet at the time of intolerable tourniquet pain. Sensory block to cold did not correlate with hemodynamic depression. Differential sensory block occurs after bupivacaine spinal anesthesia, but is a poor predictor for surgical anesthesia, tourniquet pain, and hemodynamic depression.

Adult↗
PubMed1997

Comparison of lidocaine and saline for epidural top-up during combined spinal-epidural anesthesia in volunteers.

This study was designed to determine the efficacy of saline as an epidural top-up to prolong spinal anesthesia during combined spinal-epidural anesthesia (CSEA). Eight volunteers received three separate CSEAs with intrathecal lidocaine (50 mg). After two-segment regression, each subject received either a saline (10 mL), lidocaine 1.5% (10 mL), or control sham (0.5 mL saline) epidural injection in a randomized, double-blind, triple cross-over fashion. Sensory block was assessed by pinprick and tolerance to transcutaneous electrical stimulation (TES) equivalent to surgical stimulation at the knee and ankle. Motor strength was assessed with iso-metric force dynamometry. Data were analyzed with a repeated measures analysis of variance and a paired t-test. Sensory block to pinprick was prolonged in the thoracolumbar dermatomes only by lidocaine (P < 0.05). Neither lidocaine nor saline prolonged the duration of tolerance to TES at the tested sites. Instead, saline decreased the duration of tolerance to TES by 20 and 24 min at the knee and ankle (P < 0.05). Recovery from motor block at the quadriceps was prolonged by an epidural injection of lidocaine (P < 0.05). We conclude that when 10 mL of epidural saline is administered after two-segment regression, it is an ineffective top-up and may decrease the duration of spinal anesthesia during CSEA.

Adult↗
PubMed1997

The efficacy of epinephrine test doses during spinal anesthesia in volunteers: implications for combined spinal-epidural anesthesia.

Epinephrine test doses may be administered during combined spinal-epidural anesthesia to determine intravascular placement of epidural catheters. This study was designed to determine systolic blood pressure (SBP) and heart rate (HR) responses to intravenous injection of epinephrine (15 microg) during spinal anesthesia. Twelve volunteers received three spinal anesthetics (lidocaine 100 mg, tetracaine 15 mg, and bupivacaine 15 mg) in a randomized, double blind, cross-over fashion. Epinephrine was administered prior to spinal anesthesia (control), 30 min after injection of spinal anesthesia, and at regression of sensory block to T-10. SBP was measured with a radial arterial catheter and HR with an electrocardiogram. Positive responses were defined as peak increase in SBP > or = 15 mm Hg or HR > or = 20 bpm after injection of epinephrine. Compared with control, peak SBP responses decreased by a mean of 12 mm Hg during spinal anesthesia with tetracaine and bupivacaine (P < 0.05). Peak HR responses decreased by 11 bpm during all three spinal anesthetics (P < 0.05). Incidences of detection of intravenous injection by positive SBP and HR responses ranged from 50% to 100% and were not significantly affected by spinal anesthesia. Spinal anesthesia reduces hemodynamic responses to intravenous epinephrine injection but is unlikely to reduce detection by positive SBP and HR criteria.

Adult↗
PubMed1997

Effects of concentration and volume of 2-chloroprocaine on epidural anesthesia in volunteers.

BACKGROUND: Effect of local anesthetic concentration and volume on the spread and density of epidural anesthesia is unclear. This study was performed to delineate effects of a threefold difference in concentration and volume of 2-chloroprocaine on epidural anesthesia. METHODS: Twelve healthy volunteers underwent lumbar epidural anesthesia with 300 mg of 2-chloroprocaine as a 3% (10 ml) and a 1% (30 ml) solution in a randomized, double-blind, balanced, crossover fashion. Sensory block was assessed with pinprick, touch (calibrated plastic filament), cold, and electrical stimulation. Motor block was assessed at the quadriceps and gastrocnemius muscles with isometric force dynamometry. Differences between solutions were assessed with repeated measures analysis of variance followed by post hoc testing. RESULTS: The number of dermatomes blocked to pinprick, touch, and cold was significantly greater with the 1% concentration (2 dermatomes greater than the 3% concentration on average, P < 0.05). Similar intensity of sensory block to electrical stimulation developed at the hip and knee and was unaffected by concentration of 2-chloroprocaine. Similar intensity of motor block developed at the quadriceps with both concentrations. CONCLUSIONS: Intensity of sensory and motor block from epidural anesthesia with 2-chloroprocaine appears to depend primarily on total milligram dose.

Adult↗
PubMed1997

Abnormal expression and mutation of p53 in cervical cancer--a study at protein, RNA and DNA levels.

OBJECTIVES: The objectives of this study are to document the status of p53 expression and mutation in cervical cancer at protein, RNA and DNA levels and to relate this to the presence of HPV. MATERIALS AND METHODS: Biopsy specimens from one hundred and three squamous cell carcinoma of the cervix and histologically normal ectocervix were analysed. Fresh tissues were extracted for protein, RNA and DNA and flash frozen tissue cryostat sectioned for immunohistochemical staining. HPV DNA status was determined by PCR using L1 consensus primers and typed for HPV 16 and 18 with E6 specific primers. p53 expression was determined at the protein level by Western blotting on protein extracts and at RNA level by Northern blotting. RESULTS: There was no p53 overexpression or mutation detectable in the protein extracts. Three of 65 (4.6%) of the carcinomas were positive for p53 by immunostaining with the polyclonal antibody CM1. Overexpression at the RNA level was detected in 2 of 32 (6.3%) carcinomas. p53 mutation was screened for by PCR/SSCP (single strand conformation polymorphism) followed by sequencing to define the site of mutation. Two of the cervical cancers (2.0%) showed mutation in p53 in exons 7 or 8. The mutation rate in HPV positive tumours was 1.2% (1/81) and in HPV negative tumours was 5.2% (1/19). CONCLUSION: p53 overexpression or mutation does not seem to play a significant role in cervical carcinomas.

Blotting, Northern↗
PubMed1997

Localization of tumor necrosis factor receptor messenger RNA in normal and herpes simplex virus-infected mouse eyes.

PURPOSE: To investigate the distribution of p75 and p55 tumor necrosis factor receptor (TNFR) mRNA in normal mouse eyes and in mouse eyes acutely infected with McKrae strain herpes simplex virus (HSV). METHODS: In situ hybridization with antisense 35S-labeled riboprobes for p55 and p75 TNFR subtypes was used in uninfected and HSV-infected mouse eyes. Controls included the use of sense riboprobes and corneas inoculated with vehicle alone. RESULTS: In uninfected and infected mouse eyes, in situ hybridization produced an autoradiographic signal for mRNA, encoding both p75 and p55 over the corneal endothelium, iris, ciliary body, choroid, and arachnoid layers of the optic nerve sheath. In addition, the signal was observed over scattered cells at the vitreoretinal interface. Signal for p75, but not p55, was observed over cells in the retinal ganglion cell layer. Acute HSV infection was accompanied by an intense leukocytic infiltrate in the conjunctiva, the corneal subepithelium and stroma, the anterior and posterior chambers, the iris root and ciliary body, and the vitreous cavity. In this setting, increased p75 and p55 mRNA signal was correlated closely with the number and location of receptor-bearing white blood cells. Signal over control sections hybridized with sense p75 and p55 TNFR cRNA probes was comparable to background. Signal over control eyes inoculated with sterile vehicle showed slight increased signal in the immediate vicinity of the traumatic keratitis, but otherwise it was comparable to that observed in uninfected animals. CONCLUSIONS: The observed distribution of p75 and p55 TNFR mRNA in normal and acutely infected mouse eyes, and particularly over the heavily vascularized uveal tract and over cells at the vitreoretinal interface, supports a role for TNF as a mediator of intraocular inflammation, perhaps as a key regulator of the blood-ocular barrier.

Acute Disease↗
PubMed1996

The effects of electrical stimulation at different frequencies on perception and pain in human volunteers: epidural versus intravenous administration of fentanyl.

The study was performed to determine whether epidural fentanyl produced segmental sensory changes to electrical stimulation at different frequencies. Eight healthy volunteers received fentanyl 1 microgram/kg both intravenously and epidurally in a randomized, double-blind, cross-over fashion. Perception thresholds and amount of current required to elicit a predetermined level of moderate pain (Cmp) at 5,250, and 2000 Hz stimulation were measured at ipsilateral dermatomes C2 and L2 at 0, 5, 15, 30, 45, and 60 min after injection. Perceptions to 5,250, and 2000 Hz stimulation were unaffected by either intravenous or epidural fentanyl (P > 0.08). Intravenous fentanyl increased Cmp at both 5 and 250 Hz at both dermatomes (P < 0.004) and thus did not produce segmental analgesia. In contrast, epidural fentanyl increased Cmp only at the L2 dermatome and only at 5 Hz (P = 0.005). We conclude that an epidural bolus of fentanyl results in segmental spinal analgesia to transcutaneous electrical stimulation only at specific frequencies. Furthermore, pain produced by stimulation at 5 Hz may have a different pharmacology than pain produced by 250 Hz stimulation.

Adult↗