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Biomedical subjects

L C Tsen

Publications and source records attributed to L C Tsen.

At least 19 recordsLinked to original sources
PubMed2001

Can estrogen influence the response to noxious stimuli?

STUDY OBJECTIVES: To evaluate estrogen-induced alternations in noxious stimuli response. DESIGN: Randomized, prospective, double-blind study. SETTINGS: Tertiary-care academic medical center. PATIENTS: 40 ASA physical status I and II women at the beginning and conclusion of an in vitro fertilization stimulation cycle. INTERVENTIONS: Stimuli were applied to the fingers of the dominant hand via a Basile Analgesy-Meter, which applied increasing pressure (g/cm(2)) in a continuous fashion, and ice water immersion. MEASUREMENTS: Serum hormonal concentrations and responses to noxious (pressure and cold thermal) stimuli were studied. MAIN RESULTS: Estrogen and progesterone concentrations changed from 377 +/- 323.42 pg/mL to 2078.05 +/- 1175.92 pg/mL (p < 0.001) and 1.20 +/- 0.56 to 1.03 +/- 0.35 ng/mL (p = NS), respectively. Although no significant difference was noted in the response to pressure (16.92 +/- 4.41 to 17.85 +/- 4.95 g/cm(2)), a significant reduction in the tolerance to ice water immersion (34.18 +/- 28.29 to 24.05 +/- 23.02 s) was observed. CONCLUSIONS: High estrogen concentrations are associated with significantly lower tolerance to cold, but not pressure stimuli.

Adult↗
PubMed2001

Transcutaneous electrical nerve stimulation does not augment epidural labor analgesia.

STUDY OBJECTIVE: To evaluate whether transcutaneous electrical nerve stimulation (TENS) can increase the quality and duration of an initiation dose of bupivacaine used for the establishment of epidural labor analgesia. DESIGN: Randomized, double-blind study. SETTING: Tertiary-care academic medical center. PATIENTS: 40 ASA physical status I and II parturients in early, active spontaneous labor with a singleton, vertex term fetus, and requesting analgesia. INTERVENTIONS: A standardized epidural technique with either an active or inactive TENS unit was performed. Before epidural placement, TENS intensity thresholds were determined with electrodes placed over the paraspinus muscles at T(10)-L(1), and S(2)-S(4); TENS settings for mode, cycle, and pulse width were standardized. MEASUREMENTS: Data were collected at timed intervals on pain as measured by visual analog scale (VAS), sensory level (pinprick), motor blockade (Bromage score), cervical dilation, and duration of analgesia. MAIN RESULTS: The duration of analgesia produced by the initial dose of epidural bupivacaine did not differ between groups (TENS turned off 82.3 +/- 26 [mean +/- SD] vs. TENS activated 80.7 +/- 40 min, p = 0.88). Kaplan-Meier survival analysis and Mantel-Cox log rank analysis showed no difference between the two treatments (p = 0.75). No difference in the quality of analgesia was observed between the two groups. CONCLUSIONS: In healthy laboring parturients, the application of a TENS unit did not alter the quality or duration of an initiation dose of bupivacaine utilized for the establishment of epidural labor analgesia.

Adult↗
PubMed2001

The mask avenger?

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Anesthesia, Conduction↗
PubMed2000

Transcutaneous electrical nerve stimulation does not augment combined spinal epidural labour analgesia.

PURPOSE: The spinal portion of the combined spinal epidural technique (CSE) provides dramatic but limited labour analgesia. Transcutaneous Electrical Nerve Stimulation (TENS) has been noted to modulate pain, in part by the frequency of stimulation chosen. Because nerve action potentials are blocked by local anesthetics in a frequency dependent manner, we speculated that a TENS unit could increase the quality and duration of the spinal portion of a CSE. METHODS: Forty parturients in active spontaneous labour, with a singleton, vertex, term fetus, requesting analgesia were enrolled in a randomized, double blind fashion to receive a standardized CSE with either an active or inactive TENS unit. Prior to CSE placement, TENS intensity thresholds were determined with electrodes placed on the paraspinus muscles at T10-L1, and S2-4; TENS settings for mode, cycle, and pulse width were standardized. Data were collected at timed intervals on pain (VAS), sensory level (pinprick), motor blockade (Bromage), cervical dilatation, and duration of analgesia, and at delivery on fetal and neonatal outcome. RESULTS: The duration of the spinal portion of the CSE did not differ between groups (TENS off 91.1+/-33 [mean +/- SD] vs. TENS on 83.1+/-28 min, P = .42). Kaplan-Meier survival analysis and Mantel-Cox log rank analysis showed no difference between the two treatments (P = .28). Analgesia was comparable throughout the first hour of spinal analgesia. CONCLUSION: In healthy labouring parturients, the application of a TENS unit did not alter the quality or duration of labour analgesia provided by the spinal portion of CSE analgesia.

Adult↗
PubMed2000

Hemodynamic effects of simultaneous administration of intravenous ephedrine and spinal anesthesia for cesarean delivery.

STUDY OBJECTIVE: To evaluate the hemodynamic effects of an intravenous (IV) ephedrine bolus given simultaneously with spinal anesthesia for cesarean delivery. DESIGN: Randomized, prospective, double-blind study. SETTING: Tertiary-care academic medical center. PATIENTS: 40 ASA physical status I and II nonlaboring women undergoing elective cesarean delivery of term, uncomplicated, singleton pregnancies. INTERVENTIONS: After a 10 mL/kg IV lactated Ringers bolus given over 15 minutes, patients simultaneously received an IV dose of 2 mL (10 mg) ephedrine or 2 mL saline, and an intrathecal dose of 12 mg (1.6 mL 0.75%) bupivacaine with 10 microg of fentanyl. Hypotension, defined as a 20% decrease in mean arterial pressure (MAP), was treated with 10-mg IV doses of ephedrine. MEASUREMENTS: Hemodynamic (heart rate and MAP) and non-invasive thoracic impedance (cardiac index, stroke index, and systemic vascular resistance index) measurements at baseline and at 1-minute intervals until the time of delivery. Total fluid, supplemental ephedrine, and Apgar scores were recorded. Data were evaluated using analysis of variance (ANOVA), ANOVA for repeated measures, and Mann-Whitney U-tests where appropriate, with p < 0.05 considered significant. MAIN RESULTS: Significant changes from baseline in MAP, systemic vascular resistance index, heart rate, and cardiac index were observed in both groups after spinal anesthesia. However, there were no differences between the ephedrine and saline groups in the incidence and severity of change from the baseline. The overall incidence of hypotension was 70% in both groups. No difference in total fluid or supplemental ephedrine use was observed. CONCLUSIONS: 10 mg of IV ephedrine given at the time of spinal anesthesia, and after a 10 mL/kg lactated Ringers fluid bolus, does not diminish the incidence or severity of hypotension in parturients undergoing cesarean delivery.

Adult↗
PubMed2000

Alternative medicine use in presurgical patients.

BACKGROUND: A dramatic increase in the use of complementary and alternative medicines has been observed. The use of such remedies in the presurgical population has implications for the anesthesiologist because of the potential for drug interactions, side effects, and medical liability. This study was undertaken to quantify the use of herbal remedies and vitamins in the presurgical population of a large tertiary care center. METHODS: A one-page questionnaire was distributed to all patients presenting for evaluation in the preoperative clinic over an 11-week period. Patients answered questions regarding use of prescription and nonprescription medications, herbal remedies, and vitamins. RESULTS: Twenty-two percent of presurgical patients reported the use of herbal remedies, and 51% used vitamins. Women and patients aged 40-60 yr were more likely to use herbal medicines. Over-the-counter medication use was strongly associated with herbal preparation use. The most commonly used compounds, from highest to lowest, included echinacea, gingko biloba, St. John's wort, garlic, and ginseng. CONCLUSIONS: Alternative medicine use is common in the preoperative period.

Adult↗
PubMed1999

Anesthesia for in vitro fertilization: the addition of fentanyl to 1.5% lidocaine.

UNLABELLED: Ultrasonically guided transvaginal oocyte retrieval is relatively short procedure that is performed on an out-patient basis. The optimal anesthetic technique should allow good surgical anesthesia with minimal side effects, a short recovery time, and, if possible, a high rate of successful pregnancy. Spinal anesthesia is often used in this institution, as well as many others, for this procedure. The addition of fentanyl may be effective for both intraoperative and postoperative pain relief. We assessed the effect of adding fentanyl to 1.5% lidocaine in women undergoing ultrasonically guided oocyte retrieval. Seventy-eight women were randomized to receive 45 mg of hyperbaric 1.5% lidocaine with or without 10 microg of fentanyl. Visual analog scale (VAS) pain scores were lower in the operating room (OR) (P < 0.05) and postanesthesia care unit (PACU) (P < 0.0005) for the group that received fentanyl. In addition, the amount of narcotic required in the PACU was less in the fentanyl group (P < 0.005). There was no difference in VAS scores the evening of or 24 h after the procedure. The amount of analgesics and narcotics required after discharge was the same for both groups. Timed variables, such as time to urination, ambulation, and discharge, were the same for both groups of women. The addition of fentanyl to lidocaine for transvaginal oocyte retrieval results in a more comfortable patient in the OR and PACU. IMPLICATIONS: This study demonstrates that when fentanyl is added to a local anesthetic, lidocaine, with spinal anesthesia for egg retrieval procedures, patients are more comfortable during the procedure compared with those who receive lidocaine alone. In addition, the narcotic requirements of patients are less in the postanesthesia care unit.

Adult↗
PubMed1999

Measurements of maternal protein binding of bupivacaine throughout pregnancy.

UNLABELLED: Pregnancy-related decreases in protein binding may contribute to altered effects of local anesthetics in the parturient. Previous studies have measured protein binding of bupivacaine in term parturients; the current study defines the ratio of bound-to-free bupivacaine throughout gestation at both therapeutic and toxic systemic concentrations of bupivacaine. Venous samples were obtained from 81 women, including 70 parturients, ranging from 7 to 42 wk of gestation and 11 nonpregnant controls. The percent bound bupivacaine at a fixed concentration was determined for each sample at both therapeutic (1 microg/mL) and toxic (5 microg/mL) concentrations using an ultrafiltration technique. Albumin and alpha-1-glycoprotein levels were also measured. Linear regression analysis showed a significant increase in concentration of free bupivacaine throughout gestation at the 5-microg/mL concentration, corresponding to a decrease demonstrated in both albumin and alpha-1-glycoprotein levels. A similar correlation was not found at the 1-microg/mL concentration. Although the relative magnitude of these changes is small, the relative change in free drug throughout gestation is large. Protein binding is only one of several mechanisms that may influence the susceptibility to local anesthetic toxicity in the parturient; however, its relative importance remains unclear. IMPLICATIONS: When venous samples taken from pregnant women were mixed with 5 microg/ml bupivacaine and analyzed, an increase in the free fraction of drug was seen with increasing gestational age, corresponding to decreases in alpha-1-glycoprotein and albumin.

Analysis of Variance↗
PubMed1999

Clinical effects and maternal and fetal plasma concentrations of 0.5% epidural levobupivacaine versus bupivacaine for cesarean delivery.

BACKGROUND: Bupivacaine exists as a mixture of two enantiomers, levobupivacaine and dexbupivacaine. Data suggest that levobupivacaine has equal local anesthetic potency, with reduced potential for central nervous system and cardiovascular toxicity. The present study compares the efficacy of 0.5% levobupivacaine with 0.5% bupivacaine for epidural anesthesia in parturients undergoing elective cesarean delivery. METHODS: Sixty healthy obstetric patients undergoing elective cesarean delivery with epidural anesthesia completed the study. Patients were randomized to receive 30 ml of either 0.5% levobupivacaine or 0.5% bupivacaine in a double-blind fashion. The efficacy endpoint measures included onset, offset, and quality of anesthesia. Neonatal blood gas analyses, Apgar score determinations, and neurobehavioral examinations were performed. Venous samples for pharmacokinetic studies and serial electrocardiograms were obtained in 10 patients in each group. RESULTS: Levels of sensory block, motor block, muscle relaxation, and overall quality of anesthesia did not differ between groups. The frequency of hypotension was 84.4% in the levobupivacaine group and 100% for the bupivacaine group (P < or = 0.053). No significant difference in observed maximum concentration of drug after dosing or area under the plasma drug concentration versus time curve were seen. The maximum concentrations were 1.017 and 1.053 microg/ml, and the areas were 4.082 and 3.765 h(microg/ml) for the levobupivacaine and bupivacaine groups, respectively. Umbilical vein-to-maternal vein ratios were 0.303 for the levobupivacaine group and 0.254 for the bupivacaine group. CONCLUSIONS: The use of epidural 0.5% levobupivacaine for cesarean delivery results in equally efficacious anesthesia compared with 0.5% bupivacaine. Pharmacokinetic parameters were similar in the two groups.

Adult↗
PubMed1999

Is combined spinal-epidural analgesia associated with more rapid cervical dilation in nulliparous patients when compared with conventional epidural analgesia?

BACKGROUND: The combined spinal-epidural technique provides rapid onset of labor analgesia and, anecdotally, is associated with labors of shorter duration. Epidural analgesia, by contrast, has been suggested to prolong labor modestly. It is unclear, however, whether more rapid cervical dilation in patients who receive combined spinal-epidural analgesia is a physiologic effect of the technique or an artifact of patient selection. The authors hypothesized that anesthetic technique may influence the rate of cervical dilation, and we compared the effects of combined spinalepidural with those of epidural analgesia on the rate of cervical dilation. METHODS: One hundred healthy nulliparous parturients in spontaneous labor with singleton, vertex, full-term fetuses were enrolled in a double-blinded manner when their cervical dilation was less than 5 cm. The patients were randomly assigned to receive analgesia via a standardized combined spinal-epidural (n = 50) or epidural (n = 50) technique. Data were collected on cervical dilation, pain, sensory level, and motor blockade. RESULTS: When regional analgesia was induced in comparable groups at a mean of 3 cm cervical dilation, the mean initial cervical dilation rates were significantly faster in the combined spinal-epidural group (mean values, 2.1 +/- 2.1 cm/h vs. 1 +/- 1 cm/h; P = 0.0008). Five parturients in the combined spinal-epidural group had a very rapid (> 5 cm/h) rate of mean initial cervical dilation, compared with none of the women in the epidural group. Overall mean cervical dilation rates in patients who achieved full cervical dilation were 2.3 +/- 2.6 cm/h and 1.3 +/- 0.71 cm/h (P = 0.0154) in the combined spinal-epidural and epidural groups, respectively. CONCLUSIONS: In healthy nulliparous parturients in early labor, combined spinal-epidural analgesia is associated with more rapid cervical dilation compared with epidural analgesia. Further study is needed to elicit the cause and overall effect of this difference.

Adult↗
PubMed1997

Estrogen-induced changes in protein binding of bupivacaine during in vitro fertilization.

BACKGROUND: Patients having in vitro fertilization (IVF) procedures that use gonadotropin-releasing hormone agonist down-regulation undergo hormonal manipulation of estrogen concentrations to induce oocyte maturation. After achieving minimal estrogen concentrations (baseline), stimulation increases estrogen concentrations to supraphysiologic levels, leading to egg retrieval. The isolated effect of estrogen on protein binding has not previously been reported. This study was conducted to measure the effect of estrogen concentrations on protein binding of two concentrations of bupivacaine, 1 microg/ml and 5 microg/ml, corresponding, respectively, to systemic concentrations expected after administration of epidural anesthesia and associated with bupivacaine toxicity. Serum proteins were measured to address the mechanism. METHODS: Twenty-nine healthy women undergoing IVF procedures were enrolled and venous samples were drawn at times of minimal and maximal estrogen concentrations. The percentage of free bupivacaine was determined at fixed concentrations of 1 and 5 microg/ml. Serum albumin and alpha1-acid glycoprotein concentrations were measured at baseline and at retrieval in a group of 24 women. RESULTS: The percentage of free bupivacaine increased between times of minimal and maximal serum estrogen concentrations, corresponding to decreased protein binding. Concentrations of serum albumin and alpha1-acid glycoprotein decreased between baseline and retrieval times. CONCLUSIONS: Patients undergoing IVF procedures demonstrate a decrease in protein binding of bupivacaine from baseline concentrations. These changes may be explained by a decrease in albumin and alpha1-acid glycoprotein. During anesthesia for egg retrieval, clinicians should consider the implications of increased free fraction of drug, especially for highly protein-bound agents.

Anesthetics, Local↗