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Biomedical subjects

C B Collier

Publications and source records attributed to C B Collier.

36 records · Page 2Linked to original sources
PubMed1989

The disposition and placental transfer of diazepam in cesarean section.

The disposition parameters and placental transfer of diazepam were determined from blood and both plasma total and free concentration data in five women who had not undergone labor and who received diazepam (5 mg intravenously for 2 minutes) 1 1/2 to 3 hours before cesarean section at term. All patients exhibited smooth log plasma free concentration-time profiles. In contrast, marked increases in plasma total (approximate 50% increase) and blood (approximate 40% increase) diazepam concentrations occurred at delivery. The plasma total and blood concentration fluctuations were associated with reciprocal variations in diazepam percent free in plasma. For each patient there was a substantial increase in plasma nonesterified fatty acid (NEFA) concentration during the surgical period. There was a significant correlation (p less than 0.02) between diazepam percent free and plasma NEFA concentration on the day of delivery, suggesting that the fluctuations in percent free, and hence plasma total and blood diazepam concentrations, were mediated in part by variations in plasma NEFA concentration. Disposition parameters were calculated for four of the patients; the mean free plasma clearance of diazepam was 42.5 ml/min/kg, similar to the mean value reported previously for nonpregnant women of comparable age. For each mother-infant pair at delivery the ratio of total plasma diazepam concentration in umbilical vein plasma to that in maternal vein plasma was considerably greater than unity (mean +/- SD = 1.73 +/- 0.47), whereas the corresponding ratio for free plasma diazepam concentration was near unity (0.92 +/- 0.09).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1983

Differential transplacental binding of diazepam: causes and implications.

Diazepam plasma binding was determined in 17 matched pairs of maternal and foetal plasma, collected at delivery. Diazepam % free was higher (p less than 0.001) in maternal (mean 3.24%) than in either umbilical venous (mean 1.50%) or umbilical arterial (mean 1.24%) plasma. The data from in vitro dialysis studies were consistent with the reported higher diazepam concentrations in infants than in mothers at delivery. Plasma nonesterified fatty acids (NEFA) concentrations were higher (p less than 0.001) in maternal (mean = 643 microM) than in matched umbilical venous plasma (means = 211 microM) and there was a significant correlation (p less than 0.01) between diazepam % free and corresponding plasma NEFA concentration for pooled data (r = 0.871, n = 34). Multiple and partial regression analysis indicates that transplacental differences in albumin, bilirubin and total protein concentrations made a minimal contribution to diazepam binding differences between mother and foetus and that approximately 76% of the variability in diazepam % free was accounted for by plasma NEFA concentration. The binding of diazepam to human serum albumin (HSA) was markedly perturbed by the presence of NEFA but not by bilirubin and there was no apparent cooperativity between bilirubin and NEFA on diazepam-HSA binding. Moreover, our findings provide further evidence that substantial differences in binding affinities exist between foetal and maternal plasma albumins.

Adult↗
PubMed1983

Disposition of betamethasone in parturient women after intravenous administration.

The pharmacokinetics of betamethasone and its phosphate ester are described in nine women in late pregnancy who each received a bolus intravenous dose of 10.6 mg betamethasone phosphate. Both compounds were measured by high-performance liquid chromatography with ultra-violet detection using sample handling methods which prevent in vitro hydrolysis of the ester. The plasma clearance of betamethasone phosphate (mean = 980 ml/min) and its apparent distribution volume (mean = 5.61) were both higher than previously found for nonpregnant subjects, but its half-life (mean = 4.6 min) was unchanged. Plasma concentrations of betamethasone reached a peak 5-37 min after dosing with betamethasone phosphate, then declined biexponentially with a mean terminal half-life of 262 min. Plasma clearance in pregnant patients (mean = 287 ml/min) was higher than previously reported for nonpregnant subjects. Evidence from urinary excretion and plasma binding measurements and the previously reported transplacental plasma concentration gradient indicated that the increase in clearance was due to increased metabolism possibly by the placental/fetal unit. Plasma binding of beta-methasone was higher in maternal than fetal plasma; binding to alpha 1-acid glycoprotein was more important than binding to albumin as a determinant of this difference. In pregnant patients the decline of endogenous cortisol concentrations in maternal venous plasma was less marked and slower than in nonpregnant subjects. The data now available allows comparison of pharmacokinetic properties between betamethasone and its stereoisomer dexamethasone with respect to their use in preventing neonatal respiratory distress syndrome.

Adult↗
PubMed1981

Epidural morphine.

Explore the source record for details and available documents.

Anesthesia, Epidural↗
PubMed1980

Suxamethonium fasciculations: a topographical study.

It has been found in a group of 455 gynaecological patients that not all the voluntary muscles of the body respond to suxamethonium in the same way. One group of muscles (e.g. biceps) which is sensitive to suxamethonium, responds by fasciculating in almost every individual. A second, resistant, group of muscles (e.g. pectoralis major) is almost totally unresponsive to suxamethonium. A third muscle group (e.g. triceps) shows fasciculations in about 60% of cases and appears intimately associated with the development of suxamethonium pains, for if fasciculations do occur then suxamethonium pains are likely to ensure, but not necessarily involving all the fasciculating muscles. A theory to account for these different groups has been proposed involving the known variation in distribution of red and white muscle fibres throughout the body.

Adolescent↗
PubMed1979

Dantrolene and suxamethonium. The effect of pre-operative dantrolene on the action of suxamethonium.

A single oral dose of dantrolene (100--150 mg) given at least 2 hr pre-operatively has been found to reduce significantly the strength of muscular fasciculations, the hyperkalaemia and the incidence of muscle pains following suxamethonium (from 56 to 4%) in a series of forty-eight patients compared with controls. The biceps EMG of the fasciculations was unchanged by dantrolene; the incidence of troublesome side effects was low (9%) and there did not appear to be any alteration in the duration of action of suxamethonium.

Adult↗
PubMed1978

Suxamethonium pains and early electrolyte changes.

Significant changes in the plasma electrolytes were found in a group of ninety-two female patients in the first 5 min following suxamethonium administration. The plasma potassium rose to a higher level in those patients who developed suxamethonium pains than in those who did not; the plasma calcium decreased in the former group, but increased in the latter. The plasma sodium decreased early in most patients, with the greatest reduction in those patients who did not develop symptoms. A decrease in the level of plasma calcium at 1 min correlated well with the incidence of 'the pains'. There were significant differences in the electrolyte changes, depending on whether thiopentone or Althesin was used for induction, but there was no difference in the incidence of suxamethonium pains. Suxamethonium pains are attributed to damaged muscle-spindles with enhanced calcium release playing an important part.

Adolescent↗
PubMedDate not supplied

Epidural catheters for obstetrics. Terminal hole or lateral eyes?

BACKGROUND AND OBJECTIVES: Controversy exists over the choice of the ideal epidural catheter for obstetric use, particularly whether the catheter should have a single terminal hole or three lateral eyes. METHODS: A randomized single-blind study of 200 obstetric patients undergoing epidural block for analgesia in labor or for cesarean delivery was undertaken, using either a catheter with a terminal hole or three lateral eyes. The extent and quality of the block was recorded, as well as the presence of any complications. RESULTS: The study was abandoned after 102 patients had been assessed, as the incidence of unsatisfactory blocks with terminal eye catheters was found to be unacceptably high (32%), when compared with the lateral eye catheters (12%) (P < .05). Four of the terminal eye catheters (8%) had to be resited compared with one of the lateral eye catheters (2%). One case of intravascular injection (2%) occurred through a terminal eye catheter, despite repeated negative attempts at aspiration. CONCLUSIONS: The use of terminal eye epidural catheters in our obstetric patients has led to an unacceptably high incidence of both unsatisfactory blocks and catheter replacement. Lateral eye catheters produced better results in our circumstances.

Analgesia, Epidural↗