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Biomedical subjects

M O Columb

Publications and source records attributed to M O Columb.

30 records · Page 2Linked to original sources
PubMed2000

Thromboelastography identifies sex-related differences in coagulation.

UNLABELLED: Thromboelastography is an in vitro, point-of-care monitor of whole blood coagulation. Thromboelastography studies have demonstrated a hypercoagulable state during pregnancy. Perhaps the hypercoagulability is attributable to female sex hormones. The aim of the study was to determine if sex, in addition to pregnancy, affected thromboelastography variables by studying male and female (pregnant and nonpregnant) volunteers. Thromboelastography showed significant (P:<0.01) differences in sex, with a significant (P: < 0. 0001) trend of increasing whole blood coagulability from men through nonpregnant to pregnant women. The thromboelastograph, used as a diagnostic tool, shows that women have more whole blood coagulability than men. IMPLICATIONS: The thromboelastograph, used as a diagnostic tool, shows that women have more whole blood coagulability than men.

Adult↗
PubMed2000

Effect of intravenous versus epidural fentanyl on the minimum local analgesic concentration of epidural bupivacaine in labor.

BACKGROUND: The minimum local analgesic concentration (MLAC) has been defined as the median effective local analgesic concentration (EC50) in a 20-ml volume for epidural analgesia in the first stage of labor. The aim of this study was to determine the relative local anesthetic sparing efficacies of intravenous and epidural fentanyl by comparison of their effects on the MLAC of bupivacaine. METHODS: In this double-blind, randomized, prospective study, 84 parturients at < or = 7-cm cervical dilation who requested epidural analgesia were allocated to one of two groups. After lumbar epidural catheter placement, 20 ml bupivacaine (n = 44) or bupivacaine with 3 microg/ml (60 microg) fentanyl (n = 40) was administered. The plain bupivacaine group then received 60 microg intravenous fentanyl. The bupivacaine-fentanyl group received intravenous saline. The concentration of bupivacaine was determined by the response of the previous patient in that group to a higher or lower concentration using up-down sequential allocation. Analgesic efficacy was assessed using 100-mm visual analog pain scores, with < or = 10 mm within 30 min define as effective. RESULTS: The MLAC of bupivacaine-intravenous fentanyl was 0.064% wt/vol (95% confidence interval, 0.049-0.080), and the MLAC of bupivacaine-epidural fentanyl was 0.034% wt/vol (95% confidence interval, 0.017-0.050). Epidural fentanyl significantly increased the analgesic potency of bupivacaine by a factor of 1.88 (95% confidence interval, 1.09-3.67) compared with intravenous fentanyl. The epidural fentanyl group demonstrated significantly higher dermatomal spread (P = 0.0064) and increased pruritus (P = 0. 01). CONCLUSIONS: Epidural fentanyl significantly reduced the MLAC of bupivacaine when compared with intravenous fentanyl for the parturients in this study. The significantly enhanced local anesthetic sparing, dermatomal level, and pruritus with epidural fentanyl suggest a primarily spinal site of action.

Adult↗
PubMed1999

Relative analgesic potencies of ropivacaine and bupivacaine for epidural analgesia in labor: implications for therapeutic indexes.

BACKGROUND: The minimum local analgesic concentration (MLAC) has been defined as the median effective local analgesic concentration in a 20-ml volume for epidural analgesia in the first stage of labor. The aim of this study was to assess the relative analgesic potencies of epidural bupivacaine and ropivacaine by determining their respective minimum local analgesic concentrations. METHODS: Seventy-three parturients at < or = 7 cm cervical dilation who requested epidural analgesia were allocated to one of two groups in this double-blinded, randomized, prospective study. After a lumbar epidural catheter was placed, 20 ml of the test solution was given, either ropivacaine (n = 34) or bupivacaine (n = 39). The concentration of local anesthetic was determined by the response of the previous patient in that group to a higher or lower concentration using up-down sequential allocation. Analgesic efficacy was assessed using 100-mm visual analog pain scores with < or = 10 mm within 30 min defined as effective. An effective result directed a 0.01% wt/vol decrement for the next patient. An ineffective result directed a 0.01% wt/vol increment. RESULTS: The minimum local analgesic concentration of ropivacaine was 0.111% wt/vol (95% confidence interval, 0.100-0.122), and the minimum local analgesic concentration of bupivacaine was 0.067% wt/vol (95% confidence interval, 0.052-0.082). Ropivacaine was significantly less potent than bupivacaine, with a potency ratio of 0.6 (95% confidence interval, 0.49-0.74). No difference in motor effects was observed. CONCLUSION: Ropivacaine was significantly less potent than bupivacaine for epidural analgesia in the first stage of labor.

Adult↗
PubMed1998

Dose-dependent reduction of the minimum local analgesic concentration of bupivacaine by sufentanil for epidural analgesia in labor.

BACKGROUND: The minimum local analgesic concentration (MLAC) has been defined as the median effective local analgesic concentration in a 20-ml volume for epidural analgesia in the first stage of labor. The aim of this study was to determine the local anesthetic-sparing efficacy of epidural sufentanil by its effect on the MLAC of bupivacaine. METHODS: In this double-blind, randomized, prospective study, 147 parturients at < or = 7 cm cervical dilation who requested epidural analgesia were allocated to one of four study groups. After a lumbar epidural catheter was placed, study participants received 20 ml bupivacaine (n = 38), bupivacaine with sufentanil 0.5 microg/ml (n = 38), bupivacaine with sufentanil 1 microg/ml (n = 33), or bupivacaine with sufentanil 1.5 microg/ml (n = 38). The concentration of bupivacaine was determined by the response of the previous patient using up-down sequential allocation. The analgesic efficacy was assessed using 100-mm visual analog pain scores, with < or = 10 mm within 30 min defined as effective. RESULTS: The MLAC of bupivacaine alone was 0.104% wt/vol (95% CI, 0.090-0.117). The addition of sufentanil at doses of 0.5 microg/ml, 1 microg/ml, and 1.5 microg/ml resulted in significant reductions (P < 0.0001) in the MLAC of bupivacaine to 0.048% wt/vol (95% CI, 0.030- 0.065), 0.021% wt/vol (95% CI, 0-0.055), and 0.009% wt/vol (95% CI, 0-0.023), respectively. CONCLUSIONS: This study showed a significant (P < 0.0001) dose-dependent reduction in the MLAC ofbupivacaine by sufentanil.

Analgesia, Epidural↗
PubMed1997

Determination of the minimum local analgesic concentration of epidural chloroprocaine hydrochloride in labor.

The aim was to determine the effective concentration in 50% of patients (EC(50)) of chloroprocaine in the first stage of labor. A constant dose modification of a model where EC(50) was previously defined as the minimum local analgesic concentration (MLAC) was used. Parturients (n = 36) requesting epidural analgesia in labor, at cervical dilatation not exceeding 7 cm, were enrolled into this prospective, double-blinded study. After placing a lumbar epidural catheter, chloroprocaine 150 mg diluted to the concentration being evaluated was given. The concentration was determined by up-down sequential allocation. The volume of the bolus ranged from 15 to 50 ml. Efficacy was assessed using 100 mm visual analogue pain scores with 10 mm or less within 30 min defined as effective. MLAC (95%CI) was 0.42%w/v (0.34 to 0.5) using the formula of Dixon & Massey and as a sensitivity test was 0.4%w/v (0.35 to 0.46) using probit regression analysis. In conclusion, MLAC of chloroprocaine was 0.42%w/v in these parturients, equivalent to 14 millimolar solution. This study confirmed that concentration rather than dose could be used as a measure of efficacy in this constant dose model.

Journal Article↗
PubMed1996

Effect of propofol and thiopentone on free radical mediated oxidative stress of the erythrocyte.

Propofol has free radical scavenging properties similar to those of recognized phenol-based antioxidants. We have examined these properties in an in vitro model of radical-induced cellular injury, comparing its activity with that of thiopentone (which has also been shown to have radical scavenging activity). Haemolysis of human erythrocytes was induced using the azo compound 2,2'-azo-bis(2-amidinopropane) dihydrochloride (ABAP). This was achieved by incubating a 10% suspension of erythrocytes with ABAP 100 mmol litre-1 at 37 degrees C. For propofol, at concentrations of 12.5, 25 and 50 mumol litre-1, the times to achieve 50% haemolysis were mean 126 (SEM 7) min (95% confidence interval 108-144 min), 150 (8) (129-170) min and 182 (12) (160-180) min, respectively (Intralipid control 107 (7) (90-125) min, ANOVA P < 0.0001). For thiopentone, at concentrations of 62.5, 125 and 250 mumol litre-1, the values were 117 (2) (112-121) min, 126 (3) (119-133) min and 138 (2) (132-144) min, respectively (saline control 109 (2) (104-113) min, ANOVA P < 0.0001). Spectroscopic analysis in the visible and ultraviolet spectra demonstrated a steady increase in the proportion of methaemoglobin during haemolysis, with the highest concentrations in the propofol-containing flasks. The formation of methaemoglobin was preceded by the generation of ferrylhaemoglobin (a Fe4+ haemoglobin species). Further experiments examining oxidation of purified methaemoglobin to ferrylhaemoglobin by hydrogen peroxide suggested that propofol, but not Intralipid or thiopentone, reduced ferrylhaemoglobin back to the met- state, and thereby explained the higher concentrations of methaemoglobin in the propofol-containing erythrocyte suspensions. We conclude that propofol is a more potent free radical scavenger in this model of oxidant stress than thiopentone, and that reduction of high oxidation states of haemoglobin may contribute to such activity.

Adult↗
PubMed1996

The effect of epidural fentanyl on the minimum local analgesic concentration of epidural chloroprocaine in labor.

The minimum local analgesic concentration (MLAC) has been defined as the median effective local analgesic concentration (EC50) in a 20-mL volume in the first stage of labor. The aim of this study was to determine the local anesthetic sparing efficacy of epidural fentanyl by its effect on the MLAC of chloroprocaine. Fifty-six parturients, not exceeding 7 cm cervical dilation, who requested epidural analgesia were allocated to one of two groups in this double-blind, randomized, prospective study. After placing a lumbar epidural catheter, 20 mL of the solution being tested was given: chloroprocaine (n = 28) or chloroprocaine with fentanyl 3 micrograms/mL (60 micrograms) (n = 28). The concentration of chloroprocaine was determined by the response of the previous patient to a higher or lower concentration using up-down sequential allocation. Analgesic efficacy was assessed using 100-mm visual analog pain scores with 10 mm or less within 30 min defined as effective. The MLAC of chloroprocaine was reduced from 0.43% wt/vol to 0.26% wt/vol by fentanyl (P = 0.023). Thus, the addition of epidural fentanyl 3 micrograms/mL (60 micrograms resulted in a significant 40% reduction in the MLAC of chloroprocaine in the first stage of labor.

Adult↗
PubMed1995

Determination of the minimum local analgesic concentrations of epidural bupivacaine and lidocaine in labor.

The aim of this study was to devise a clinical model to determine the effective concentrations in 50% of patients (EC50) for bupivacaine and lidocaine in the first stage of labor and define EC50 as the minimum local analgesic concentration (MLAC). This should allow the determination of relative analgesic potency and, subsequently, the local anesthetic sparing efficacy of other epidural analgesics. Parturients not exceeding 5 cm cervical dilation who requested epidural analgesia were enrolled. The two studies involved 81 women (bupivacaine n = 41, lidocaine n = 40). After a lumbar epidural catheter was placed, 20 mL of the concentration of local anesthetic being tested was given. The concentration was determined by the response of the previous patient to a higher or lower concentration using double-blinded, up-down sequential allocation. Efficacy was assessed using 100-mm visual analog pain scores with less than 10 mm within 1 h defined as effective. MLAC was determined using the formula of Dixon and Massey. Results show MLAC bupivacaine 0.065% (95% confidence interval [CI] 0.045-0.085), MLAC lidocaine 0.37% (95% CI 0.32-0.42), equivalent to 2 and 14 mmol solutions, respectively. Thus bupivacaine was 5.7 times more potent than lidocaine in weighted and 7 times more potent in molar ratios at analgesic EC50, in the volume of local anesthetic studied.

Adult↗